Effective removal of As5+ from aqueous medium using date palm fiber biochar/chitosan/glutamine nanocomposite: kinetic and thermodynamic studies

Effective removal of As5+ from aqueous medium using date palm fiber biochar/chitosan/glutamine nanocomposite: kinetic and thermodynamic studies | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effective removal of As5+ from aqueous medium using date palm fiber biochar/chitosan/glutamine nanocomposite: kinetic and thermodynamic studies Al Isaee Khalifa, Laila M. Alshandoudi, Asaad F. Hassan, Amany G. Braish This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5256147/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 20 Jan, 2025 Read the published version in Environmental Science and Pollution Research → Version 1 posted 6 You are reading this latest preprint version Abstract In the current work, three adsorbent materials were developed; biochar derived from date palm fiber (C), date palm fiber biochar/chitosan nanoparticles (CCS), and biochar/chitosan nanoparticles composite supplemented with glutamine (CCSG). These compounds were used as solid adsorbents to remove As 5+ from polluted water. Several characterization approaches were used to investigate all the synthesized solid adsorbents, including TGA, N 2 adsorption/desorption isotherm, SEM, TEM, ATR-FTIR, and zeta potential. CCSG demonstrated good thermal stability, with a maximum specific surface area of 518.69 m 2 /g, a microporous radius of 0.97 nm, total pore volume of 0.25 cm 3 /g, an average particle size of 38 nm, and pH pzc of 6.9. To optimize the reaction conditions, various sorption factors were examined, including contact time, pH, initial As 5+ concentration, adsorbent dosage, temperature, and ionic strength. The study found that the modified samples were able to remove more As 5+ (CCS; 256.0 mg/g and CCSG; 376.0 mg/g) than unmodified ones (C; 150.5 mg/g). The As 5+ removal procedure corresponded well with Langmuir isotherm model. Thermodynamic and kinetic experiments show that the Elovich, PFO, and Van't Hoff plot with endothermic, spontaneous, and physisorption nature are the best fitted models. EDTA has the highest desorption efficiency percentage (98.8%). CCSG demonstrated enhanced reusability after six application cycles of As 5+ adsorption/desorption, with only a 4% decrease in the efficiency of adsorption. This study demonstrates that CCSG effectively remove As 5+ in wastewater and use agricultural solid waste residues (date palm fiber; DPF) for environmental remediation purposes. Date palm biochar chitosan nanocomposite adsorption arsenic Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1 Introduction The fast rise of urbanization and industrialization has led to significant heavy metal contamination of the aquatic environment. Heavy metals in wastewater, including arsenic, copper, chromium, cadmium, zinc, cobalt, nickel, manganese, iron, mercury, and lead, pose a significant threat to human health and environmental safety due to their toxicity and bioaccumulation (Mehmood et al. 2022 ). Contamination of water with arsenic (As 5+ ) is considered as a class 1 human carcinogen as classified by the International Agency for Research on Cancer (IARC(, is a growing global concern [2, 3]. Arsenic contamination can come from natural processes like rock weathering and mineral dissolution, as well as human activity like fossil fuel burning, mining, and pesticide use. Long-term usage of As 5+ -polluted water can cause several types of cancer, including lung, skin, hyperpigmentation, bladder, and hyperkeratosis (Yao et al. 2024 ). Numerous chemical, physical, and biological procedures have been used to treat As 5+ -contaminated water, such as precipitation, ion exchange, flocculation, membrane separation, reverse osmosis, solvent extraction, and biological membranes (Amen et al. 2020 ). These procedures have some limitations such as high operational costs, partial metal removal, high energy requirements, and formation of poisonous residual metal sludge. Among all the procedures, the adsorption is recognized as ideal technology for wastewater treatment technique due to its simplicity of operation, accessibility of different solid adsorbents, there is no need for a large application area, inexpensive due to the ability of solid adsorbent reusability, high efficiency, fast, and ecologically friendly as there is no toxic byproducts (Wang et al. 2024 ). Relevant research investigations have been conducted on the adsorption of As 5+ , including: Hossain et al. prepared magnetic graphene oxide for removing As 5+ , revealing a small amount of solid adsorbent, 0.14 g/L, effectively removed 98% of As 5+ in 20 min (Hossain et al. 2024 ). Furthermore, Zouli et al. fabricated an iron-titanium/carbon composite detecting a maximum adsorption capacity ( X max ) of 86 mg/g at pH 6 (Zouli 2024 ). In addition, Sugita et al. used Mg-based adsorbents to remove As 5+ from contaminated water samples and As 5+ had removal performance in the order MgCO 3 < Mg(OH) 2 <MgO (Sugita et al. 2024 ).In another investigation, Hussain et al. employed a hydrothermal approach to generate sulphur-doped copper ferrite, which effectively removed dissolved arsenic. The results indicated that one gram of S-CuFe 2 O 4 is sufficient to provide 275 gallons of arsenic-free water (Hussain et al. 2024 ). However, we believe that they are unsafe chemical substances and so unfriendly to the environment, so biomaterials should be used instead. In recent researches, various bioadsorbents have been employed for As 5+ decontamination. Hshakoor et. al . studied the removal of the As 5+ from aqueous solutions using six types of various biosorbents (water chestnut shell, egg shell, corn cob, java plum seed, pomegranate peel, and tea waste) (HShakoor et al. 2019 ). Nguyen et al. assessed the removal performance of luffa fiber as an effective bioadsorbent on the purification of water polluted by As 5+ (Nguyen et al. 2020 ). Recently, on sugarcane bagasse biochar modified with thiol and biochar based on rice husk have also been used to remove As 5+ from polluted water (Masood ul hasan et al. 2024). Biochar is substance rich with carbon made from various organic wastes, including municipal sewage sludge and wastes from agricultural works (Murtaza et al. 2024 ). Biochar garnered great interest due to its distinctive properties such as large specific surface area, stability, high cation exchange capacity, and carbon content (Sun et al. 2022 ). However, there are obstacles in recycling material, separating it from water, and regeneration. Chitosan is a cationic natural biopolymer material formed by the deacetylation of chitin via alkaline circumstances. It exhibits diverse features such as biocompatibility, biodegradability, hydrophilicity, non-toxic characteristics, and adsorption properties. The cationic heavy metals may be actively adsorbed onto chitosan by its functional groups, which include hydroxyl and amino groups. The lack of surface chemical functional active sites groups on the biochar/chitosan composite surface has limited its adsorption capacity. However, adding functional group-rich material can boost the adsorption capability of the composite. By changing surface characteristics such as specific area and surface functional groups, electron transfer capacity, zeta potential, element distribution, and cation exchange capacity, chemical modification can increase the adsorption capacity of biochar. (Enaime et al. 2020 ). These changes impact porosity and enrich the biochar surface with oxygen-containing surface functional groups, particularly carboxyl groups. Moreover, it is a technique to give certain chemical modifications like etherification, grafting, or cross-linking actions for further endowing chitosan with superior adsorption qualities (Pillai et al. 2009 ). Many studies have focused on using raw and processed biochar to remove contaminants from water systems. Glutamine is a non-toxic amino acid, having hydrophilic functional groups including carboxylic acids and amides, with a molecular formula C 5 H 10 N 2 O 3 (Kolangare et al. 2019 ). The addition of negatively charged carboxyl groups and hydrophilic to the biochar/chitosan composite surface contributes to improved adsorption characteristics and performance. In recent years, amino acids have been used as As 5+ adsorbents due to their carboxyl (-COOH) and amino (-NH 2 ) molecular structures, which allow for heavy metal ion coordination and chelation. While hydrophilic amino acids like lysine, glycine, and cysteine are commonly employed for As 5+ removal [18, 19]. However, as far as we are aware, there is no research on biochar based on date palm fiber modified with glutamine amino acid in this field was studied up to now. The fundamental purpose of the research is to identify an operative and environmentally safe adsorbent for removing As 5+ from the aquatic system. We used agricultural solid waste residues (date palm fiber; DPF) to produce biochar (C) and created biochar/chitosan as biocomposites nanoparticles (CCS), which was subsequently modified with glutamine (CCSG). We studied many parameters that impact the adsorption performance of As 5+ , such as pH, contact time, applied temperature, initial concentration, adsorbent dose, and ionic strength. Date palm pits extract (DPE) was performed as caping agent for the conversion of the fabricated solid materials into stable nanoparticles under ultrasonic grinding conditions. Several physicochemical techniques were investigated, including ATR-FTIR, TGA, SEM, TEM, point of zero charge, and N 2 adsorption/desorption. This study sheds light on the use of functionalized solid adsorbents to eliminate heavy metals cations from polluted water, paving the way for their practical implementation in wastewater treatment. Solid adsorbents reusability and sustainability was studied after several adsorption and desorption cycles. 2 Materials and methods 2.1 Materials Date palm pits and date palm fiber were obtained from Al-Wishayl special garden, Al-Rustaq, Sultanate of Oman. Sodium arsenate heptahydrate (> 98%), chitosan, sodium chloride (> 99.0%), sodium hydroxide (≥ 98%), hydrochloric acid (37%), acetic acid (96%), nitric acid (69%), ethylenediaminetetraacetic acid (99.5%), cysteine (≥ 95%), ethylene diamine (99.5%), trimethyl chloro-silane (C 11 H 17 ClO 2 SSi, > 99.5%), bis(trimethylsilyl)trifluoroacetamide (C 8 H 18 F 3 NOSi 2 , > 99.0%), diethyl ether ((CH 3 CH 2 ) 2 O, > 99.8%), pyridine (C 5 H 5 N, > 99.8%), chloroform (CHCl 3 , > 99.5%), and, ethyl acetate (CH 3 COOC 2 H 5, > 99.7%). were supplied by Sigma-Aldrich Co., USA. Stock solution of each compound was prepared using deionized water. 2.2 Date palm pits extract preparation (DPE) Date palm pits were gathered and washed manually by distilled water to remove any residual impurities. After drying, they were ground by using Retsch ZM200 titanium mill, Germany. Date palm pits extract was created as follows; 20 g of crushed date palm pits powder were added to 500 mL of distilled water and stirred continuously for 18 h using a magnetic stirrer followed by filtration. The remaining dried powder weighed 14.5 g, implying that the produced extract comprised approximately 5.5 g of the dissolved date palm pit components. The solution containing DPE was stored in clean glass bottles at 5 o C for successive uses. 2.3 Fabrication of solid adsorbents 2.3.1 Preparation of date palm fiber biochar (C) Date palm fiber was chopped into small pieces, washed with pure water to remove associated pollutants and dust, dried at 120 o C, and crushed into powder. The biochar was produced using a slow pyrolysis technique involving the powder of date palm fiber (DPF) in a muffle furnace. The temperature gradually rose to 300°C with a heating rate of 15 o C/min and kept for 1 h before being elevated to 550°C and held for 2 h. The increased temperature accelerates the pyrolysis process and improves the biochar's properties. After this duration, the system was cooled to the ambient temperature. 2.3.2 Preparation of date palm fiber biochar/chitosan nanoparticles (CCS) The chitosan-modified date palm fiber biochar was prepared by combining 1.0 g of chitosan with 2%, 100 mL of acetic acid. The solution was stirred for 6 h before adding 1.0 g of the created biochar to the chitosan solution. The previous mixture was agitated with a stirrer for 2 h to achieve a uniform suspension. The produced homogeneous solution was dropped using microsyringe into 1.0 mol/L, 200 mL of sodium hydroxide solution. The produced beads were filtered and washed numerous times with ultra-pure water until a neutral washing solution. The washed beads were dried for 24 h at 90 o C, and grinded in Retsch ZM200 titanium mill. The obtained fine powder of biochar/chitosan (0.5 g) was transferred into nanoparticles by sonication (Probe Sonicator IG-96A), for 15 min in the presence of 150 mL of the pre-prepared DPE solution which acts as a caping agent for the formed nanoparticles. Filtered via centrifugation and dried at 120 o C for 10 h [20, 21]. 2.3.3 Preparation of d biochar/chitosan nanoparticles supplemented with glutamine (CCSG) It is prepared in the same manner as before (sec.2.3.2), except for adding 0.1 g of glutamine to the previously prepared chitosan solution. 2.4 Characterization and analysis Numerous organic natural chemicals found in the recovered DPE operate as environmentally acceptable anticoagulant capping agents for nanoparticles. The 0.5 g of powdered date palm was acidified with HCl, allowed to cool, and then diethyl ether and ethyl acetate were used to extract the extract. The extracted solution was then evaporated under vacuum at 45°C. The extracted sample was resuspended in 60 µL of BSTFA (bis(trimethylsilyl)trifluoroacetamide) + TMCS (trimethylchloro-silane) 99:1 silylation reagent and 50 µL of pyridine to convert functional groups to trimethylsilyl groups (abbreviated TMS) before GC analysis. The GC-MS technique (Agilent Technologies) was set with gas chromatograph (7890B) and detector of mass spectrometer (5977A) The GC was operational with DB-5MS column (internal diameter of 30 m x 0.25 mm and 0.25 µ m as a film thickness). Analyses were carried out using H 2 as the carrier gas at 1.0 ml/min as flow rate of at a splitless, injection volume of 1 µL. The temperature program fwas adjusted to be: 60°C for 1 min; increasing to 10°C /min up to 320°C and for 10 min. At 300°C, 320°C, the injector and detector were held. Mass spectra were obtained by electron ionization (EI) at 80 eV: using a spectral range of m/z 50–800 and solvent delay 4.2 min. The mass temperature was 230°C and Quad 150°C. By comparing the spectrum fragmentation pattern with those found in Wiley and NIST Mass Spectral Library data, many natural materials might be recognized. The thermal behavior of DPF, C, CCS, and CCSG was determined using a thermoanalyzer (SDT Q600 V20.9 Build 20, UK) at a nitrogen flow rate of 20 mL/min and a heating rate of 15 o C/min up to 900 o C. Nitrogen gas adsorption/desorption was used to measure the specific area of surface (S BET , m 2 /g), pore size( \(\:\stackrel{-}{r}\) , nm), and total pore volume ( V P , cm 3 /g) of C, CCS, and CCSG using NOVA 3200e gas sorption analyzer (Quantachrome Corporation, USA). Prior to N 2 gas adsorption, the solid samples (50 mg) were degassed for 16 h at 10 − 4 Torr and 120°C. Scanning electron microscopy (JEOL JSM-6510LV model, Japan) was used to investigate the morphology of solid adsorbents (C, CCS, and CCSG). The samples were prepared via deposition on an aluminum holder covered in a carbon grid and then coated with a thin gold layer under high vacuum. The SEM was run at 15 kV as an accelerating voltage. Transmission electron microscopy employing a JEOL-JEM-2100 model from Japan is also used to study the morphology of produced adsorbent particles (C, CCS, and CCSG). The samples were sonicated for 60 min in ethanol before being transferred to a copper grid. Surface functional groups for all solid adsorbents were analyzed using Attenuated total reflectance with Fourier transform infrared (ATR -FTIR) spectroscopy at 4000–400 cm − 1 , with ten sequential scans at resolution. Zeta potentials for each adsorbent were measured to evaluate pH PZC in pH range of 2–12. The solid adsorbent material's surface is positively charged for pH values less than pH PZC and negatively charged at pH levels more than pH PZC . The measurement of pH PZC is crucial in understanding how solid adsorbents adsorb heavy metal cations. 2.5 Adsorption experiments The adsorption of As 5+ by all synthesized solid adsorbents (C, CCS, and CCSG) was investigated using a batch adsorption technique that involved shaking 25 mL of As 5+ solution with 400 mg/L and 0.025 g of adsorbent mass at pH 6, 27 o C, and for 90 min. The adsorbate solution was shaken before being centrifuged at 3000 rpm for 10 min. Then, the concentration at equilibrium C e (mg/L) of As 5+ was determined by a hydride generation-atomic absorption spectrometer (HG-AAS; AgilentAA240 with VGA–77; Australia). Three sets of measurements were made, and the average values were utilized. The percentage of removal ( R %) of As 5+ and the equilibrium sorption capacity X e (mg/g) were calculated using (Eqs. 1, 2, Table 1 ), respectively. The effects of various application settings, such as adsorbent solid dosage (0.1–2.0 g/L, mass in g/volume in L), pH (1–9), contact shaking time (5–90 min), starting As 5+ concentration (50–500 mg/L), temperature (27–47 o C), and initial solution ionic strength (µ, 0.05–0.40 mol/L), were investigated by a series of batch adsorption studies. Table 1 Applied models depict the adsorption process. Model name Models Symbols significance Number Removal percentage \(\:R\%=\frac{({C}_{i}-{C}_{e})}{{C}_{i}}\times\:100\) C i (initial conc. of As 5+ , mg/L) C e (equilibrium conc. of As 5+ , mg/L) 1 Equilibrium adsorption capacity \(\:{X}_{e}=\frac{({C}_{i}-{C}_{e})}{m}\times\:V\) X e (equilibrium sorption capacity, mg/g) V (volume of As 5+ solution, L) m (mass of solid adsorbent, g) 2 Kinetic models Adsorption capacity at certain time \(\:{X}_{t}=\frac{({C}_{i}-{C}_{t})}{m}\times\:V\) \(\:{X}_{t}\) (adsorption capacity in mg/g at time t , min) 3 Pseudo-first order \(\:{X}_{t}={X}_{exp}(1-{e}^{-{k}_{1}t})\) k 1 (PFO rate constant, min − 1 ) 4 Pseudo-second order \(\:{X}_{t}=\:\frac{{{X}_{exp}}^{2}{k}_{2}\:t}{1+\:{X}_{exp}\:{k}_{2}\:t}\) X exp (experimental adsorption capacity, mg/g) k 2 (PSO rate constant, g/mg.min) 5 Elovich \(\:{X}_{t}=\frac{1}{\beta\:}Ln(1+\alpha\:\beta\:t)\) \(\:\alpha\:\:\) (initial rate of As 5+ adsorption, mg/g.min) \(\:\beta\:\:\) (extent of surface coverage, g/mg) 6 Adsorption isotherm models Langmuir \(\:{X}_{e}=\frac{b{X}_{m}{C}_{e}}{1+b{C}_{e}}\) \(\:b\:\) (Langmuir constant, L/mg) X m (maximum Langmuir adsorption capacity, mg/g) 7 Separation factor \(\:{R}_{L}=\frac{1}{1+b{C}_{i}}\) \(\:{R}_{L}\:\) (separation factor) 8 Freundlich \(\:{X}_{e}={K}_{F}\:{C}_{e}^{\frac{1}{n}}\) n (Freundlich constant related to the adsorption intensity) K F (Freundlich constant related to the extent of adsorption, L 1/n . mg 1–1/n /g) 9 Temkin \(\:{X}_{e}\:=\frac{R\:T}{{b}_{T}}\text{ln}{K}_{T}\:{C}_{e}\) R (universal gas constant, 8.314 J/mol. K) T (absolute adsorption temperature, K) K T (equilibrium binding constant, L/g) b T (Temkin constant, J/mol) 10 Dubinin-Radushkevich \(\:{X}_{e}=\:{X}_{DR}\:{e}^{-{K}_{DR\:\:}{\epsilon\:}^{2}}\) X DR (D-R adsorption capacity, mg/g) K DR (D-R constant, mol 2 /kJ − 2 ) E DR (mean adsorption-free energy, kJ/mol) 11 Mean adsorption-free energy \(\:{E}_{DR}\:=\:\frac{1}{\sqrt{2{K}_{DR}}}\) 12 Thermodynamic studies Distribution constant \(\:{K}_{s}=\:\frac{{C}_{s}}{{C}_{e}}\) C s (surface adsorbed As 5+ , mg/g) 13 Van’t Hoff \(\:\text{ln}{K}_{s}=\:\frac{\varDelta\:S^\circ\:}{R}\:-\:\frac{\varDelta\:H^\circ\:}{RT}\) \(\:\varDelta\:S^\circ\:\:\) (entropy change, kJ/mol. K) \(\:\varDelta\:H^\circ\:\:\) (heat change, kJ/mol) 14 Gibbs free energy \(\:\varDelta\:G^\circ\:=\varDelta\:H^\circ\:-T\varDelta\:S^\circ\:\) \(\:\varDelta\:G^\circ\:\:\) (Free energy change, kJ/mol) 15 The adsorption activity was observed, and the obtained data were analyzed to provide insights into the adsorption mechanisms and the efficiency of solid adsorbent materials for As 5+ removal. Several adsorption parameters were computed using several kinetics and equilibrium nonlinear adsorption models. The kinetics investigation was conducted on As 5+ adsorption onto C, CCS, and CCSG using nonlinear expressions of pseudo-first order (PFO, Eq. 4), pseudo-second order (PSO, Eq. 5), and Elovich (Eq. 6). While nonlinear isotherm models, featuring Langmuir (Eq. 7), Freundlich (Eq. 9), Temkin (Eq. 10), and Dubinin-Radushkevich (Eq. 11) were used to analyze equilibrium data of As 5+ adsorption on C, CCS, and CCSG as given in Table 1 . Three thermodynamic parameters namely change in enthalpy, ( ΔH° , kJ/mol), change in entropy, ( ΔS° , kJ/mol.K), and Gibb’s free energy, ( ΔG° , kJ/mol) were estimated by Eqs. 14, 15 (Table 1 ). Table 1 : Applied models depict the adsorption process. 2.6 Desorption and reusability experiment Desorption of As 5+ tests are important for regenerating the three chosen adsorbents (C, CCS, and CCSG). Desorption was studied by adding 0.10 g of solid to 100 mL of 400 mg/L As 5+ at pH 6, stirring, and 27°C. After 25 min, the adsorbents were rinsed with 100 mL of 0.1 mol/L desorbing agent (dist. water, HCl, HNO 3 , ethylene diamine, cysteine, and EDTA). The desorbed concentration of As 5+ in solution was assessed using the predefined atomic absorption spectrometer. The desorption percentage was calculated using Eq. 16 to evaluate the solid nanoparticles performance after frequent application. where C d is the equilibrium metal ion (As 5+ ) concentration after desorption from adsorbents (mg/L), m is the mass of solid adsorbent (g), V is the desorbing agent volume (L), and X m is the adsorbent's greatest capacity of adsorption (mg/g). 3 Results and Discussion 3.1 Characterization techniques 3.1.2 GC-M examination of date palm pits extract The chemical content of the extract of date palm pits (DPE) was analyzed using GC-MS (gas chromatography-mass spectrometry) and the obtained data is presented in Table S1 . Figure S1 shows a chromatogram of DPE of the most active discovered chemicals. There were twenty chemical compounds found in DPE, with the most common being 9-octadecenoic acid, (E)-, TMS derivative (20.33%), dodecanoic acid, TMS derivative (15.89%), Hydroquinone, 2TMS derivative (12.41%), and palmitic acid, TMS derivative (11.64%). The data in Table S1 revealed that the extract also contained acids, alkanes, alkyl benzenes, aromatic benzene derivatives, alcohols, carboxylic acids, fatty acid derivatives, glycerides, lipids, phytosterols, terpenes, and steroids. DPE has a vital role as anticoagulant capping agent which acts as stabilizer by inhibiting nanoparticles overgrowth and preventing aggregation/coagulation because of the attendance of numerous active chemical mixtures which are rich in hydroxyl groups (Shu et al. 2020 ). So, causing the creation of nanostructures. 3.1.3. Characterization of solid adsorbents Figure 1 a shows thermal analysis curves for DPF, C, CCS, and CCSG. Weight loss of 0.9, 3.2, and 3.6% was found for C, CCS, and CCSG, respectively at 120 ℃ due to the removal of absorbed water (Gemeay et al. 2021 ). Biochar with lesser hydrophilic surface functional groups is superior to that treated with chitosan or reinforced with glutamine. The date palm fiber (DPF) mass loss occurred in four stages. The first stage up to 120°C, was due to moisture loss (vaporization), representing 6.3% of the total weight loss. From 260–340 o C, the second stage of mass loss involves the degradation of low molecular weight hemicellulose ([C 5 (H 2 O) 4 ] n ) with additional mass loss of 30.7%. The third phase of the mass loss at from 320–380°C corresponds to the heat breakdown of cellulose ([C 6 (H 2 O) 5 ] n ). The final stage is about decomposition of lignin ([C 10 H 12 O 3 ] n ) ranging from 300–580°C [24, 25]. Biochar solid sample (C) graph shows that weight loss (18.31 wt%) was occurring between 250 and 400°C. Aliphatic structures decomposed at temperatures exceeding 250°C. The discharge of volatile chemical compounds such as CO 2 was produced by the breakdown of the date palm biochar's functional groups (carboxylic acid groups and lactones) (Hadj-Otmane et al. 2024 ). The breakdown of anhydride, carbonyl, and ether operates by releasing CO and CO 2 at temperatures ~ 350°C (Wang et al. 2021 ). Over 400°C, the mass loss is connected with the dissolution of aromatic rings that exist on the surface of biochar, which occurs by liberating volatile chemicals [28, 29]. The thermal degradation for CCS and CCSG started at approximately 160°C, and continued until 450°C, with weight loss of ~ 51.88%. During the temperature between 250 ℃ to 340 ℃ in CCS thermal curve, a significant weight loss was observed due to chitosan chain decomposition and oxidation, sugar ring dehydration, and polymer degradation (Chen et al. 2022 ). At temperatures above 600 o C, which represents the ash remains, almost no mass loss was found. This result suggests the chitosan was not merely adhered on the date palm fiber biochar surface, but rather complexly linked together. Textural characterization of solid adsorbent is an important technique to describe the capacity of adsorption and way of pollutant adsorption. Figure 1 b shows the porous structure property of the produced adsorbents as measured by the N 2 adsorption/desorption isotherms. Porous structure is characterized by the specific surface area ( S BET , m 2 /g), pore volume ( V P , cm 3 /g), and average pore radius ( \(\:\stackrel{-}{r}\) , nm) which are listed in Table 2 . The prepared materials are classified as type II isotherm by the IUPAC (International Union of Pure and Applied Chemistry) with H4 hysteresis loop for C and CCS and H3 hysteresis loop for CCSG [6, 26, 31]. The specific surface area and pore volume for samples were found to be 349.09 m 2 /g, 0.21 cm 3 /g for C, 499.51 m 2 /g, 0.26 cm 3 /g for CCS, and 518.69 m 2 /g, 0.25 cm 3 /g for CCSG. The order of S BET values from the highest is: CCSG, CCS, and C. The pore volume change is comparable to that of the S BET . The results revealed that date palm fiber biochar particles improved significantly after modification in terms of pore volume and surface area. It is obvious that the insertion of biochar in the chitosan matrix followed by modification with glutamine results in a greater surface area, which may be associated to the disruption and solid structure heterogeneity. Furthermore, the average pore size for C (1.22 nm) ˃ CCS (1.05 nm) ˃ CCSG (0.97 nm) which indicates the microporous and mesoporous character of the samples. Table 2 Characterization parameters for the fabricated solid adsorbents. Parameters C CCS CCSG S BET (m 2 /g) 349.09 499.51 518.69 V P (cm 3 /g) 0.21 0.26 0.25 \(\:\stackrel{-}{\varvec{r}}\) (nm) 1.22 1.05 0.97 pH PZC 6.20 6.60 6.90 Various surface chemical functional groups of the adsorbents (C, CCS, and CCSG) were exposed to ATR-FTIR analysis in the range of 4000–400 cm − 1 as presented in Fig. 1 c. The stretching bands at about 1063 (C–O), 1438 (–CH 2 ), 1573 (C = O), 2976 (–CH), and 3373 cm − 1 (–OH) were observed from ATR-FTIR spectra of C [32]. Correspondingly, in the ATR-FTIR spectra of CCS, the chemical functional groups mentioned above were observed around the appropriate wavenumber. However, the peak at 1573 cm − 1 shifted to 1555 cm − 1 for amide I (C = O stretching), and a new peak appeared at 1656 cm − 1 for amide II (bending modes of N-H) indicated that the carboxyl groups reacted with chitosan during composite formation [33]. While CCSG has witnessed structural changes, namely the emergence of –COOH and –CONH–. At 3167, 1500, and 1407 cm − 1 , respectively, the stretching vibration peak of -OH, the stretching vibration peak of C = O, and the bending vibration absorption peak of -COOH were identified. The bending vibration peak in -NH and The C = O stretching vibration peak in -CONH- emerged at 1580 and 1675 cm − 1 , respectively, confirming the presence of -COOH and -CONH- in CCSG structure [34]. Most adsorption systems rely on electrostatic interactions between adsorbents and adsorbates. Measuring the surface charge of the adsorbent is crucial for confirming the possibility of electrostatic interactions. The zeta potential was used to evaluate the chemical surface charge as elucidated in Fig. 1 d and calculate the point of zero charge (pH PZC ) as given in Table 2 . The PZC was determined to be 6.2, 6.6, and 6.9 for C, CCS, and CCSG. At pH pH PZC , the surface charge is negative. Figure 1 : TGA curves (a), N 2 adsorption (b), ATR-FTIR spectra (c), and pH PZC (d) for C, CCS, and CCSG. In addition to TGA of date palm fiber (DPF). SEM was used to examine samples (C, CCS, and CCSG) structure and morphology, the magnification pictures given in Figs. 2 a–c. The SEM picture Fig. 2 a of the C shows stacked rocky layers structure with many pores which is a representative of biochar solid material, irregular, and a rather smooth surface [35, 36]. After modification, the surface of CCS became rough, with tiny particles holding on to the surface Fig. 2 b which might be related to the enhancement of superficial area. These tiny particles were probably chitosan. Furthermore, these microscopic particles remained on the surface of the CCSG as shown in Fig. 2 c which in turn proves the distribution of chitosan and glutamine amino acid on the CCSG surface. Figure 2 : SEM (a–c) and TEM (d–f) images for C, CCS, and CCSG, respectively. Figures 2 d–f exhibit TEM micrographs of the manufactured solid adsorbents. Figure 2 d shows that C has a layered and porous structure due to the biochar's intrinsic nature [32]. Compared to C in Fig. 2 d, the surfaces of CCS and CCSG in Figs. 2 e, 2 f showed a noticeable sparkle and clusters, indicating that the chitosan and glutamine amino acid had been constructed on the surface. It became apparent that the C, CCS, and CCSG TEM particle sizes were approximately 450, 23, and 38 nm, respectively. The resultant solid particles disperse when biochar is inserted into the biopolymer framework in CCS and CCSG, which has distinct characteristics from the two solids. Table 2 : Characterization parameters for the fabricated solid adsorbents. 3.2 Static adsorption removal of As 5+ 3.2.1 Impact of solid dose The study examined the effect of different quantities of solid adsorbents (C, CCS, and CCSG) on adsorption efficiency ( R% ) as shown in Fig. 3 a. While the Removal% of As 5+ was computed using Eq. 1. At a pH 6 and 27°C, 0.1 to 2.0 g/L of adsorbent dose was combined with 25 mL of As 5+ solution (400 mg/L) and stirred at 3000 rpm for 90 min. The adsorption efficiency increased from 21, 38, and 68% at 0.1 g/L to 43, 65, and 93% at 1.0 g/L for adsorbents (C, CCS, and CCSG), respectively. The increase in the removal percent by nearly 2.1, 1.7, and 1.4 times increase for C, CCS, and CCSG, respectively. The increase in the capacity of adsorption can be connected to the increase in active sites/As 5+ ratio. Maximum adsorption occurred at a solid sorbent dosage of 1.0 g/L on CCSG, which may be attributed to the presence of hydrophilic and negatively charged -NH 2 , -OH, and -COOH groups that provide more binding sites for As 5+ . In addition, due to the large surface area confirmed by the N 2 adsorption/desorption. High adsorbent doses resulted in poor As 5+ adsorption, possibly owing to the occurrence of unsaturated binding active sites and the absence of available As 5+ . However, fixed As 5+ concentrations reduce sorption capacity (Niazi et al. 2024 )38]. To investigate further adsorption parameters, a dosage of 1.0 g/L of all adsorbents was chosen based on these results. 3.2.2 Effect of starting solution pH The pH has a direct impact on both the adsorbent active sites and the shape of pollutant ions (As 5+ ). To test the effect of pH on solid adsorbents (C, CCS, and CCSG), the solution's pH was adjusted using either 0.1 M NaOH and/or 0.1M HCl from 1 to 9 with 0.025 g solid adsorbents, 25 mL of 400 mg/L As 5+ at 27 o C, and 90 min shaking duration as illustrated in Fig. 3 b. It is perceived that As 5+ adsorption is limited at lower and higher pH values. The highest As 5+ adsorption occurs at pH 6. It achieves adsorption capacity of 42, 63, and 92% for C, CCS, and CCSG, respectively. The removal % gradually increased from 1–6 and slightly dropped from 6 to 9. Proton ions (H 3 O + ) is more adsorbed than As 5+ at lower pH levels (< pH PZC ) due to the more ionic mobility of proton than arsenic ion forms (H 2 AsO 4 − and HAsO 4 − 2 ) [32, 39]. Figure 1 d shows that C, CCS, and CCSG had a point of zero charge (pH pzc ) of around 6.2, 6.6, and 6.9, respectively. When pH exceeds pH pzc , the surface of adsorbents acquired negative charges, which may hinder arsenic species (HAsO 4 2– ) adsorption owing to the established electrostatic repulsion (Gan et al. 2015 ). However, when the pH was higher than neutral, the adsorption effectiveness decreased due to polymer chain shrinkage caused by deprotonation of chitosan amino groups (Rahmi 2018 ). CCSG outperformed C and CCS in terms of As 5+ adsorption, suggesting that the addition of chitosan and glutamine was beneficial for As 5+ removal. It is possible that protonation of -NH 2 and -OH resulted in positively charged molecules that show considerable promise for sequestering As 5+ (in the form of AsO 4 − 3 and AsO 3 − ) via electrostatic attraction. Consequently, pH6 was nominated as the most suitable pH for As 5+ adsorption from aqueous medium onto all the investigated adsorbents. Figure 3 : The impact of adsorbent dose (a) and pH (b) on As 5+ adsorption onto C, CCS, and CCSG (Ci = 400 mg/L, T = 27 o C, and t = 90 min). 3.2.3 Kinetic studies and impact of shaking time The kinetics of As 5+ adsorption onto C, CCS, and CCSG samples was studied from 5 to 90 min at pH 6, 25 mL, 400 mg/L As 5+ , solid dose (1.0 g/L), temperature (27°C) to further determine the adsorption mechanism of the adsorbents. We evaluated the kinetic indicators of three adsorbents using PFO ( Eq. 4, Fig. 4 a), PSO ( Eq. 5, Fig. 4 b), and Elovich ( Eq. 6, Fig. 4 c) nonlinear models. Table 3 shows the model parameters for removing As 5+ metal ions on solid samples. At the beginning of adsorption time, the rapid adsorption of As 5+ on the adsorbents could be attributed to the abundance of available active sites where the ration of solid active sites/ As 5+ is higher. Then, as the adsorption sites were depleted, the adsorption capacity slowly increased until reaching equilibrium after 25 min. The time-dependent adsorption data was successfully fitted by PFO kinetic model based on correlation coefficients R 2 (0.9439–0.9730) and reduced chi-squared χ 2 (1.8681–3.4750) for all solid samples. Furthermore, the adsorbed amount of As 5+ metal ions calculated using PFO model closely corresponded to the experimental one which is derived from the Langmuir Eq. (1.99, 2.38, and 0.74% as differences in the cases of C, CCS, and CCSG, respectively). Despite R 2 values for the adsorption of As 5+ ions by PSO kinetic model are nearly high (0.8542–0.8984). However, there was a substantial discrepancy between the estimated and observed Langmuir adsorption capacities (17.28, 16.72, and 20.72% for C, CCS, and CCSG, respectively). In addition to the higher calculated reduced chi-squared χ 2 (5.1629–14.4098) proves the invalid application of PSO in comparison with PFO nonlinear model. This revealed that PSO model could not best describe the As 5+ adsorption, because the investigational adsorption capabilities did not accord with the model's hypothetical prospects. Hence, the PFO model is the beneficial kinetic model, indicating the physical adsorption process [42, 43]. The Elovich model has good applicability for As 5+ adsorption ( R 2 = 0.8926 on average). CCS and CCSG had significantly higher α values than C, indicating an increase in the primary rate of adsorption after modification. The degree of surface coverage ( β , g/mg) value, is inversely linked to the correspondence of adsorbate to adsorbent, is significantly lower for CCS and CCSG compared to C demonstrating that the modified ones (CCS and CCSG) exhibit greater affinity to As 5+ than C (Nguyen et al. 2020 ). Table 3 Kinetic, isotherm nonlinear, and thermodynamic parameters for the adsorption of As 5+ onto C, CCS, and CCSG at 27 o C. Models Parameters C CCS CCSG PFO X exp (mg/g) 147.5 249.9 373.2 k 1 (min − 1 ) 0.0840 0.0771 0.0739 R 2 0.9439 0.9688 0.9730 χ 2 1.8681 3.1290 3.4750 PSO X exp (mg/g) 176.5 298.8 453.9 k 2 (g/mg.min)×10 − 4 4.9953 2.5606 1.6013 R 2 0.8542 0.8984 0.8901 χ 2 5.1629 6.2058 14.4098 Elovich α (mg/g.min) 19.7859 33.1947 47.6115 β (g/mg) 0.0233 0.0129 0.0084 R 2 0.8827 0.8972 0.8979 χ 2 4.7160 9.9450 22.5613 Langmuir X m (mg/g) 150.5 256.0 376.0 b (L/mg) 0.11821 0.0759 0.1163 R L 0.0207 0.0319 0.0210 R 2 0.9797 0.9820 0.9910 χ 2 0.9230 3.4948 3.3513 Freundlich 1/n 0.2472 0.3477 0.2989 K F (L 1/n . mg 1 − 1/n /g) 46.6780 48.3148 95.9714 R 2 0.7603 0.8443 0.8292 χ 2 4.3942 14.3297 19.0735 Temkin b T (J/mol) 28.6213 56.1971 77.5609 K T (L/g) 1.6615 0.6723 1.1925 R 2 0.8574 0.9348 0.9165 χ 2 4.6134 5.9995 9.3233 Dubinin-Radushkevich X DR (mg/g) 148.6 251.9 361.5 K DR (kJ/mol) 0.4842 0.6264 0.4416 E DR (kJ/mol) 1.0162 0.8934 1.0641 R 2 0.9869 0.9942 0.9876 χ 2 0.2397 0.5329 1.3871 Thermodynamic parameters R 2 0.9186 0.9307 0.9264 ΔH o (kJ/mol) 4.8284 4.6216 6.4387 ΔS o (kJ/mol.K) 0.0369 0.0389 0.0320 ‒ΔG o (kJ/mol) 27 ℃ 6.2464 7.0475 3.1727 34 ℃ 6.5051 7.3198 3.3970 40 ℃ 6.7266 7.5531 3.5892 45 ℃ 6.9112 7.7476 3.7494 Figure 4 : Nonlinear PFO (a), PSO (b), and Elovich (c) nonlinear kinetic equations for the adsorption of As 5+ onto C, CCS, and CCSG (T = 27 o C, C i = 400 mg/L, dosage 1.0 g/L, pH = 6, t = 5–90 min). 3.2.4 Static adsorption isotherms and effect of initial concentration Figure 5 a–d shows the equilibrium adsorption isotherms as nonlinear Langmuir ( Eq. 7, Fig. 5 a), Freundlich ( Eq. 9, Fig. 5 b), Temkin ( Eq. 10, Fig. 5 c), and Dubinin-Radushkevich ( Eq. 11, Fig. 5 d) models. While related isotherm parameters are presented in Table 3 . These isotherms predict adsorption based on mutual interactions between adsorbate and adsorbent with different principles especially Langmuir and Freundlich with contradictory postulates. The adsorption isothermal experiment was conducted at pH 6, 1.0 g/L solid dosage, temperature (27°C), and starting As 5+ concentration (50–500 mg/L). Increasing the initial concentration of As 5+ may improve adsorption capacity since a high concentration gradient encourages As 5+ ions to diffuse towards adsorption sites of solid adsorbents (C, CCS, and CCSG) (Zhou et al. 2020 ). However, further increasing starting As 5+ concentration could not improve adsorption capability due to restricted adsorption sites in solid adsorbents (Song et al. 2018 ). The Langmuir, Dubinin-Radushkevich, and Temkin nonlinear models are more accepted than the Freundlich model due to greater coefficients of correlation ( R 2 ) and lower reduced chi square ( χ 2 ) values as shown in Table 3 . All model fits had R 2 values more than 0.8574, suggesting strong significance. The prepared adsorbents had Langmuir maximum adsorption capacities follow this sequence CCSG ˃ CCS ˃ C (376.0, 256.0, and 150.5 mg/g, respectively). This could be due to the existence of novel surface chemical functional groups on the composites' surface, in addition to their larger surface areas. The R L estimates (Eq. 8) for all the adsorbents in this investigation are 0 < R L < 1, indicating a good adsorption process. On the other hand, the correlation coefficient values produced for the nonlinear Freundlich model are lower than those calculated for the Langmuir model for all solid samples. The Langmuir model exceeded the Freundlich model in describing As 5+ sorption, demonstrating that monolayer sorption was the dominating process on all three sorbent homogenous surfaces. The Freundlich model parameter (sorption intensity, 1/n ) determines whether the process of adsorption was chemisorption in nature (for 1/n > 1) or physisorption (for 1/n < 1), based on heterogeneity (Yao et al. 2024 ). In the current study, 1/n revealed values below one, indicating the physisorption mechanism. CCS and CCSG had higher sorption intensity ( 1/n ) and K F (L 1/n / mg 1 − 1/n . g) than C, indicating a stronger capacity to adsorb As 5+ . The Temkin model effectively applies As 5+ adsorption across all samples, as evidenced by high correlation values (0.8574–0.9348). The lower Temkin isotherm constant b T values ( b T ˂ 8000 J/mol) (28.6213–77.5609 J/mol) reflect physical adsorption process between the adsorbate and adsorbent (Kamal et al. 2019 ). b T (J/mol) is inversely associated with the adsorption heat (Ao et al. 2012 ). The endothermic nature of the adsorption process is suggested by the positive values reported for b T . (Adeogun and Babu 2021 ). The R 2 values found in DR model (Dubinin-Radushkevish) isotherm model for As 5+ were among 0.9869 and 0.9942 for all three sorbents. The Dubinin-Radushkevich equation yields almost similar adsorption capacity ( X DR ) to the Langmuir model. If the E DR value is less than 8 kJ/mol, adsorption is thought to be a physical process with pore-filling as the primary mechanism (Niazi et al. 2018 ). If the E DR value is between 8.0–16.0 kJ/mol, chemical adsorption and ion exchange yield control of the process. Our data indicates that As 5+ rapidly occupies accessible adsorption sites on the solid adsorbents surface, with E DR values ranging from 0.8934 to 1.0641 kJ/mol. This suggests that physical sorption is the major mechanism. Figure 5 : Nonlinear Langmuir (a), Freundlich (b), Temkin (c), and D-R (d) fitting for As 5+ adsorption onto C, CCS, and CCSG (T = 27 o C, C i = up to 500 mg/L, solid dose 1.0 g/L, pH = 6, t = 25 min). Table 3 : Kinetic, isotherm nonlinear, and thermodynamic parameters for the adsorption of As 5+ onto C, CCS, and CCSG at 27 o C. 3.2.5 Effect of adsorbate solution ionic strength Batch tests were assumed to investigate the effect of foreign ions on adsorption system at various concentrations of NaCl to simulate real-world adsorption conditions, and the results are given in Fig. 6 a. Each NaCl solution is given at different dosage to achieve a range of ionic strength (µ, 0.05–0.40 mol/L). The As 5+ initial concentration was kept at 400 mg/L, and the solution volume was 25 mL with 1.0 g/L of adsorbent dosage (C, CCS, and CCSG) at 27 o C. Obviously, the quantity of As 5+ adsorbed decreases as the ionic strength rises from NaCl µ, 0.05–0.40 mol/L. The attachment of As 5+ ions to the surface of C, CCS, and CCSG is hampered by the interference of sodium and chloride ions (Makhlouf et al. 2024 ). Increasing the ionic strength of the adsorption solution from nearly µ ≈ 0.05 to µ ≈ 0.40 reduces As 5+ removal from 43 to 26%, 65 to 48%, and 94 to 77% for C, CCS, and CCSG, respectively (with nearly 17% decrease). External ions (Na + and Cl − ) can greatly increase the thickness of the diffuse electric double layer, which protects adsorbents and As 5+ in solution. This keeps As 5+ and adsorbent particles from coming too close together, lowering their electrostatic attraction and slowing the adsorption process. Higher electrolyte concentrations can cause electrolyte ions to block surface negative charges, reducing the overall quantity of As 5+ adsorbed. Although foreign ions have a negative impact on the adsorption efficiency, this percentage indicates that even at elevated concentrations of interferents ions, the prepared samples (C, CCS, and CCSG) exhibit accepted selectivity for the uptake of As 5+ ions. 3.2.6 Influence of adsorption temperature and thermodynamic parameters It's important to analyze the obtained parameters of thermodynamic ( ΔS° , ΔH° , and ΔG° ), which indicate changes in entropy, enthalpy, and free energy to realize the energetics of As 5+ removal by C, CCS, and CCSG. The parameters ( ΔS° and ΔH° ) were obtained using the Van’t Hoff equation (Eq. 14, Fig. 6 b), whereas ∆G° (free energy change) was calculated using Eq. 15. These values are shown in Table 3 . The adsorption followed the temperature coefficient, as seen in Fig. 6 b by the strong linear relationship between Ln (K S ) and 1/T . The higher correlation coefficients ( R 2 ) values for the Van't Hoff plot, which ranged between 0.9186 and 0.9307, demonstrate the model's applicability. It is confirmed that the adsorption process is endothermic in nature requiring additional energy based on the calculated positive value of ΔH° . This is due to the fact that solvated water molecules must be displaced by As 5+ ions. (Ananta et al. 2015 ). The heat values for physical adsorption range from 20–40 kJ/mol and chemisorption from 40–400 kJ/mol. According to our results, the values of ΔH° (4.6216–6.4387 kJ/mol) demonstrated a physical adsorption process. The increase in ΔS° values implies a rise in system entropy due to randomness at the interface between solid surface and liquid phases. This rise in entropy is caused by the displacement of water molecules by As 5+ ions to adsorb on the surface of adsorbents. Moreover, the decrease in ΔG° values suggest that As 5+ adsorption by all solid adsorbents is thermodynamically viable and spontaneous. As temperature increases, the value of ΔG° lowers, indicating that As 5+ adsorption is increasingly practicable (Mahmoud et al. 2020 ). In general, physical adsorption has a lower ∆G° (-20 to 0 kJ/mol) compared to chemical adsorption (-80 to -400 kJ/mol). As a result, the adsorption of As 5+ was classified as physical adsorption based on the negative values of ∆G° (3.1727–7.7476 kJ/mol). 3.3 Desorption and reusability of solid adsorbents An ideal adsorbent should have elevated adsorption capacity and properties of desorption efficient for purpose of reduction the treatment cost (Moslehi et al. 2024 ). This study tested the stability and reusability of adsorbents (C, CCS, and CCSG) using 0.1 mol/L desorbing agent (dist. water, HCl, HNO 3 , ethylene diamine, cysteine, and EDTA) to desorb As 5+ . Figure 6 c displays the efficiency of desorption ( D.E% , Eq. 16) of As 5+ from the C, CCS, and CCSG surface, with different solutions. EDTA is the most effective solvent for pre-adsorbed As 5+ . The removal efficacy of As 5+ by C, CCS, and CCSG reduced after the first and sixth cycles, as follows in Fig. 6 d: 43–40%, 64–58%, and 94–90% for C, CCS, and CCSG, respectively. After six cycles of sorption and desorption, the As 5+ sorption capacity of solid adsorbents reduced slightly. Higher removal rates in the first cycle of applications can be related to the presence of abundant more active sites. After the first sorption-desorption cycle, As 5+ sorption decreased slightly during the other regeneration cycles. This could be due to adsorbent binding sites saturation or a partial loss of the adsorbent's uptake sites during the cleaning phase of the adsorption-desorption test (Saning et al. 2024 ). Figure 6 : Effect of ionic strength (a), Van’t Hoff plot (b), desorption study of As 5+ (c), and reusability (d) of C, CCS, and CCSG after six adsorption/desorption cycles (T = 27 o C, C i = 400 mg/L, dosage 1.0 g/L, pH = 6, t = 25 min). 3.4 Comparing CCSG with other solid adsorbents The maximum adsorption capacity of various adsorbents in comparison with CCSG are portrayed in Table 4 (Hu et al. 2015 ; Liu et al. 2017 , 2024 ; Basu et al. 2021 ; Pervez et al. 2021 ; Sahu et al. 2022 ; Din et al. 2024 ). The outcomes in Table 4 show that CCSG has competitive As 5+ ions adsorption capability. The newly synthesized adsorbent (CCSG) is a favorable and exceptional solid adsorbent for removing As 5+ ions in a variety of applications. Table 4 Comparison of CCSG with other As 5+ biosorbents. Adsorbents X m (mg/g) Ref. Magnetic chitosan/biochar composite (MCB) 17.9 (Liu et al. 2017 ) β-FeOOH@GO 69.0 (Pervez et al. 2021 ) FeOx-GOCS-0.08 61.9 (Liu et al. 2024 ) GO-MnO 2 -Goe-Ca-Alg beads 34.2 (Basu et al. 2021 ) Eleocharis dulcis biochar loaded with CuO (EDB-CuO) 26.1 (Din et al. 2024 ) Iron-impregnated biochar 2.2 (Hu et al. 2015 ) MPAC-500 and MPAC-600 (magnetic-activated carbons synthesized from the peel of Pisum sativum pea) 0.4930 and 0.9451 respectively (Sahu et al. 2022 ) CCSG 376.0 This study 4 Conclusion Using natural solid adsorbents in wastewater treatment procedures is a prospective methodology for removing heavy metals from polluted water. Herein, As 5+ removal from aqueous medium was examined by the static batch adsorption procedures employing adsorbents such as date palm fiber biochar (C) and date palm fiber biochar/chitosan nanoparticles (CCS), which were then enhanced with glutamine (CCSG). Inserting chitosan and glutamine into date palm fiber biochar through composite matrix synthesis produced unique surface chemical functional groups on the CCSG surface. This led to increased activity at surface sites and more exterior pores. SEM analysis revealed that the adsorbents had a porous and uneven surface that facilitates As 5+ ion adsorption. Adsorption kinetic data followed pseudo-first order equation, with Langmuir isotherm model more compatible with As 5+ data. Based on the Langmuir isotherm nonlinear model, the CCSG composite had a maximum capacity of adsorption of 376.0 mg/g, with adsorption equilibrium attained after 25 min. Thermodynamic explorations indicate that the adsorption procedure is both spontaneous and endothermic. According to prior results, the adsorption of As 5+ by the produced solid materials exhibited monolayer sorption. Previous research has shown that CCSG has exceptional adsorption and unique properties for wastewater treatment. Authors should pay special attention to biopolymer materials and solid agricultural waste in environmental applications because of their natural abundance, eco friendliness, increased sustainability, and biodegradability. Declarations Author contributions All authors [ Al Isaee Khalifa, Laila M. Alshandoudi, Asaad F. Hassan, and Amany G. Braish ] contributed to the study conception and design, materials preparation, data collection and analysis. Funding: This study was funded by Ministry of Higher Education, Research and Innovation of Sultanate of Oman number BFP/GRG/EBR/2023/158. Conflict of interest: There are no conflicts to declare. Ethical approval: Not applied. This study did not involve human participants and/or animals. Consent to participate: Not applied Consent for publication: Not applied Competing interests: The authors declare no competing interests Availability of data and materials: It is available upon reasonable request. 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Prog Polym Sci 34:641–678 Rahmi M (2018) Nisfayati, Comparison of cadmium adsorption onto chitosan and epichlorohydrin cross linked chitosan/eggshell composite. Mater Sci Eng 352: Roy H, Islam MS, Arifin MT, Firoz SH (2022) Synthesis, characterization and sorption properties of biochar, chitosan and ZnO-based binary composites towards a cationic dye. Sustainability 14:14571 Sahu N, Nayak AK, Verma L, et al (2022) Adsorption of As (III) and As (V) from aqueous solution by magnetic biosorbents derived from chemical carbonization of pea peel waste biomass: Isotherm, kinetic, thermodynamic and breakthrough curve modeling studies. J Environ Manage 312:114948 Saning A, Thanachayanont C, Suksai L, et al (2024) Green magnetic carbon/alginate biocomposite beads from iron scrap waste for efficient removal of textile dye and heavy metal. Int J Biol Macromol 261:129765. https://doi.org/https://doi.org/10.1016/j.ijbiomac.2024.129765 Shaheen JF, Eniola JO, Sizirici B (2024) Adsorption of ibuprofen from aqueous solution by modified date palm biochar: Performance, optimization, and life cycle assessment. Bioresour Technol Reports 25:101696 Shu M, He F, Li Z, et al (2020) Biosynthesis and antibacterial activity of silver nanoparticles using yeast extract as reducing and capping agents. Nanoscale Res Lett 15:1–9 Song J, Huang G, Han D, et al (2023) Alpha-MnO2 nanoneedle embedded in MgO-chitosan biochar for higher removal of arsenic from groundwater: Co-effects of oxidation and adsorption. J Alloys Compd 947:169643 Song Y, Tan J, Wang G, Zhou L (2018) Superior amine-rich gel adsorbent from peach gum polysaccharide for highly efficient removal of anionic dyes. Carbohydr Polym 199:178–185 Su X, Wang X, Ge Z, et al (2024) KOH-activated biochar and chitosan composites for efficient adsorption of industrial dye pollutants. Chem Eng J 486:150387 Sugita H, Morimoto K, Saito T, Hara J (2024) Simultaneous removal of arsenate and fluoride using magnesium-based adsorbents. Sustainability 16:1774 Sun Y, Lyu H, Cheng Z, et al (2022) Insight into the mechanisms of ball-milled biochar addition on soil tetracycline degradation enhancement: Physicochemical properties and microbial community structure. Chemosphere 291:132691 Wang C, Qiao J, Yuan J, et al (2024) Novel chitosan-modified biochar prepared from a Chinese herb residue for multiple heavy metals removal: Characterization, performance and mechanism. Bioresour Technol 402:130830. https://doi.org/10.1016/j.biortech.2024.130830 Wang W, Bai J, Lu Q, et al (2021) Pyrolysis temperature and feedstock alter the functional groups and carbon sequestration potential of Phragmites australis‐and Spartina alterniflora‐derived biochars. GCB Bioenergy 13:493–506 Yao S, Jabeur F, Pontoni L, et al (2024) Sustainable removal of arsenic from waters by adsorption on blue crab, Portunus segnis (Forskål, 1775) chitosan-based adsorbents. Environ Technol Innov 33:103491. https://doi.org/10.1016/j.eti.2023.103491 Zhang MM, Liu YG, Li TT, et al Chitosan modification of magnetic biochar produced from Eichhornia crassipes for enhanced sorption of Cr (VI) from aqueous solution, RSC Adv. 5 (2015) 46955–46964 Zhou Y, Luan L, Tang B, et al (2020) Fabrication of Schiff base decorated PAMAM dendrimer/magnetic Fe3O4 for selective removal of aqueous Hg (II). Chem Eng J 398:125651 Zhu R, Zhang C, Zhu L, et al (2024) “Three-dimensional environment-friendly” amino acid functionalized chitosan: Uranium adsorption performance and mechanism research. Carbohydr Polym 343:. https://doi.org/10.1016/j.carbpol.2024.122464 Zouli N (2024) Synthesis of an iron-titanium-carbon composite from slag high in titanium for removing arsenic particles from drinking water. Desalin Water Treat 317:100104 Zubair M, Mu’azu ND, Jarrah N, et al (2020) Adsorption behavior and mechanism of methylene blue, crystal violet, eriochrome black T, and methyl orange dyes onto biochar-derived date palm fronds waste produced at different pyrolysis conditions. Water, Air, Soil Pollut 231:1–19 Supplementary Files Supplementary.docx Cite Share Download PDF Status: Published Journal Publication published 20 Jan, 2025 Read the published version in Environmental Science and Pollution Research → Version 1 posted Editorial decision: Major Revision 23 Nov, 2024 Reviewers agreed at journal 22 Oct, 2024 Reviewers invited by journal 22 Oct, 2024 Editor invited by journal 21 Oct, 2024 Editor assigned by journal 16 Oct, 2024 First submitted to journal 15 Oct, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5256147","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":369145567,"identity":"73dc18b4-86b2-4adf-9fa2-886a6fd836ee","order_by":0,"name":"Al Isaee Khalifa","email":"","orcid":"","institution":"University of Applied Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Al","middleName":"Isaee","lastName":"Khalifa","suffix":""},{"id":369145568,"identity":"c0cc147b-8af7-4813-a9e7-267ada4a52b7","order_by":1,"name":"Laila M. Alshandoudi","email":"","orcid":"","institution":"University of Applied Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Laila","middleName":"M.","lastName":"Alshandoudi","suffix":""},{"id":369145569,"identity":"6bb5f3fd-5061-4bb7-a0a8-1f5930c5fff7","order_by":2,"name":"Asaad F. Hassan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA80lEQVRIiWNgGAWjYLCCDxU2DAzMDAwSYN4BInQwzjiTRqIWZs62w2AGcVr4+08nf2Y4c96ev52B8dbNNgY5vhsJjA+/4NEicSN3g3FBxe3EGYcZmK1z2xiMJW8kMBvL4LPmBu+G5BlnbicYMDOwSQO1JG64kcAmLYFHh/z5sxsO87ads4dpqQdqYf+NT4vBgdyNzbxtBxg3QLUkGABtYfyAR4vhjdzNwEBOBvqFsdk655yE4cwzD5ul8XlF7vzZzR8+VNjZ8/cfPng7p8xGnu948sGPP/DpQQDGBgZI1DA2MPMQpwVZN5G2jIJRMApGwcgAAKioT3DBdWF6AAAAAElFTkSuQmCC","orcid":"","institution":"Damanhour University Faculty of Science","correspondingAuthor":true,"prefix":"","firstName":"Asaad","middleName":"F.","lastName":"Hassan","suffix":""},{"id":369145570,"identity":"783dd44b-14b2-4683-8666-9be65b6393c1","order_by":3,"name":"Amany G. Braish","email":"","orcid":"","institution":"Damanhour University Faculty of Science","correspondingAuthor":false,"prefix":"","firstName":"Amany","middleName":"G.","lastName":"Braish","suffix":""}],"badges":[],"createdAt":"2024-10-13 16:05:40","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5256147/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5256147/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11356-025-35896-5","type":"published","date":"2025-01-20T15:57:28+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":67376161,"identity":"00951b3a-ee25-4bab-9e51-ec1e3cc8d432","added_by":"auto","created_at":"2024-10-24 08:44:07","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":404890,"visible":true,"origin":"","legend":"\u003cp\u003eTGA curves (a), N\u003csub\u003e2\u003c/sub\u003e adsorption (b), ATR-FTIR spectra (c), and pH\u003csub\u003ePZC\u003c/sub\u003e (d) for C, CCS, and CCSG. In addition to TGA of date palm fiber (DPF).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-5256147/v1/9a7c6741ec4460092b7a6a31.png"},{"id":67376157,"identity":"d8dbf7a5-f81f-4230-a902-86d6eb546bd5","added_by":"auto","created_at":"2024-10-24 08:44:06","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":766821,"visible":true,"origin":"","legend":"\u003cp\u003eSEM (a–c) and TEM (d–f) images for C, CCS, and CCSG, respectively.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-5256147/v1/1d27856ad88cc777b4a85f28.png"},{"id":67376160,"identity":"871f5917-37ad-4a63-8c98-7b8547092e02","added_by":"auto","created_at":"2024-10-24 08:44:07","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1318254,"visible":true,"origin":"","legend":"\u003cp\u003eThe impact of adsorbent dose (a) and pH (b) on As\u003csup\u003e5+\u003c/sup\u003e adsorption onto C, CCS, and CCSG (Ci = 400 mg/L, T = 27 \u003csup\u003eo\u003c/sup\u003eC, and t = 90 min).\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-5256147/v1/12c704929cf78b2f9e715e9c.png"},{"id":67376156,"identity":"843c2b1d-d280-4bc8-869b-83a6f03886c2","added_by":"auto","created_at":"2024-10-24 08:44:06","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":262759,"visible":true,"origin":"","legend":"\u003cp\u003eNonlinear PFO (a), PSO (b), and Elovich (c) nonlinear kinetic equations for the adsorption of As\u003csup\u003e5+\u003c/sup\u003e onto C, CCS, and CCSG (T = 27 \u003csup\u003eo\u003c/sup\u003eC, C\u003csub\u003ei\u003c/sub\u003e = 400 mg/L, dosage 1.0 g/L, pH = 6, t = 5–90 min).\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-5256147/v1/01cbde35a9373ccb62b44f85.png"},{"id":67376158,"identity":"5f3b1646-2155-465c-917b-00e72b271595","added_by":"auto","created_at":"2024-10-24 08:44:06","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":352776,"visible":true,"origin":"","legend":"\u003cp\u003eNonlinear Langmuir (a), Freundlich (b), Temkin (c), and D-R (d) fitting for As\u003csup\u003e5+\u003c/sup\u003e adsorption onto C, CCS, and CCSG (T = 27 \u003csup\u003eo\u003c/sup\u003eC, C\u003csub\u003ei\u003c/sub\u003e = up to 500 mg/L, solid dose 1.0 g/L, pH = 6, t = 25 min).\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-5256147/v1/5190d03695b11a12cf2b764a.png"},{"id":67376162,"identity":"4e2ba693-75ae-446d-9d72-1f3012872b7b","added_by":"auto","created_at":"2024-10-24 08:44:07","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":439251,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of ionic strength (a), Van’t Hoff plot (b), desorption study of As\u003csup\u003e5+\u003c/sup\u003e (c), and reusability (d) of C, CCS, and CCSG after six adsorption/desorption cycles (T = 27 \u003csup\u003eo\u003c/sup\u003eC, C\u003csub\u003ei\u003c/sub\u003e = 400 mg/L, dosage 1.0 g/L, pH = 6, t = 25 min).\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-5256147/v1/b9dabcea9d750515284ddd33.png"},{"id":74858579,"identity":"820996d9-4177-468c-93c8-8e96d2eba515","added_by":"auto","created_at":"2025-01-27 16:11:49","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6279951,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5256147/v1/c75dcca7-7c6a-45cf-90da-18325ee75026.pdf"},{"id":67376159,"identity":"a718dd86-6bb5-428e-a1cb-3d5d97922d91","added_by":"auto","created_at":"2024-10-24 08:44:06","extension":"docx","order_by":7,"title":"","display":"","copyAsset":false,"role":"supplement","size":272720,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementary.docx","url":"https://assets-eu.researchsquare.com/files/rs-5256147/v1/16e2755eb325516e9d532cdf.docx"}],"financialInterests":"","formattedTitle":"Effective removal of As5+ from aqueous medium using date palm fiber biochar/chitosan/glutamine nanocomposite: kinetic and thermodynamic studies","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eThe fast rise of urbanization and industrialization has led to significant heavy metal contamination of the aquatic environment. Heavy metals in wastewater, including arsenic, copper, chromium, cadmium, zinc, cobalt, nickel, manganese, iron, mercury, and lead, pose a significant threat to human health and environmental safety due to their toxicity and bioaccumulation (Mehmood et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). Contamination of water with arsenic (As\u003csup\u003e5+\u003c/sup\u003e) is considered as a class 1 human carcinogen as classified by the International Agency for Research on Cancer (IARC(, is a growing global concern [2, 3]. Arsenic contamination can come from natural processes like rock weathering and mineral dissolution, as well as human activity like fossil fuel burning, mining, and pesticide use. Long-term usage of As\u003csup\u003e5+\u003c/sup\u003e-polluted water can cause several types of cancer, including lung, skin, hyperpigmentation, bladder, and hyperkeratosis (Yao et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Numerous chemical, physical, and biological procedures have been used to treat As\u003csup\u003e5+\u003c/sup\u003e-contaminated water, such as precipitation, ion exchange, flocculation, membrane separation, reverse osmosis, solvent extraction, and biological membranes (Amen et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). These procedures have some limitations such as high operational costs, partial metal removal, high energy requirements, and formation of poisonous residual metal sludge. Among all the procedures, the adsorption is recognized as ideal technology for wastewater treatment technique due to its simplicity of operation, accessibility of different solid adsorbents, there is no need for a large application area, inexpensive due to the ability of solid adsorbent reusability, high efficiency, fast, and ecologically friendly as there is no toxic byproducts (Wang et al. \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Relevant research investigations have been conducted on the adsorption of As\u003csup\u003e5+\u003c/sup\u003e, including: Hossain \u003cem\u003eet al.\u003c/em\u003e prepared magnetic graphene oxide for removing As\u003csup\u003e5+\u003c/sup\u003e, revealing a small amount of solid adsorbent, 0.14 g/L, effectively removed 98% of As\u003csup\u003e5+\u003c/sup\u003e in 20 min (Hossain et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Furthermore, Zouli \u003cem\u003eet al.\u003c/em\u003e fabricated an iron-titanium/carbon composite detecting a maximum adsorption capacity (\u003cem\u003eX\u003c/em\u003e\u003csub\u003e\u003cem\u003emax\u003c/em\u003e\u003c/sub\u003e) of 86 mg/g at pH 6 (Zouli \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). In addition, Sugita \u003cem\u003eet al.\u003c/em\u003e used Mg-based adsorbents to remove As\u003csup\u003e5+\u003c/sup\u003e from contaminated water samples and As\u003csup\u003e5+\u003c/sup\u003e had removal performance in the order MgCO\u003csub\u003e3\u003c/sub\u003e\u0026thinsp;\u0026lt;\u0026thinsp;Mg(OH)\u003csub\u003e2\u003c/sub\u003e\u0026lt;MgO (Sugita et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).In another investigation, Hussain \u003cem\u003eet al.\u003c/em\u003e employed a hydrothermal approach to generate sulphur-doped copper ferrite, which effectively removed dissolved arsenic. The results indicated that one gram of S-CuFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e is sufficient to provide 275 gallons of arsenic-free water (Hussain et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). However, we believe that they are unsafe chemical substances and so unfriendly to the environment, so biomaterials should be used instead. In recent researches, various bioadsorbents have been employed for As\u003csup\u003e5+\u003c/sup\u003e decontamination. Hshakoor \u003cem\u003eet. al\u003c/em\u003e. studied the removal of the As\u003csup\u003e5+\u003c/sup\u003e from aqueous solutions using six types of various biosorbents (water chestnut shell, egg shell, corn cob, java plum seed, pomegranate peel, and tea waste) (HShakoor et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Nguyen \u003cem\u003eet al.\u003c/em\u003e assessed the removal performance of luffa fiber as an effective bioadsorbent on the purification of water polluted by As\u003csup\u003e5+\u003c/sup\u003e (Nguyen et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Recently, on sugarcane bagasse biochar modified with thiol and biochar based on rice husk have also been used to remove As\u003csup\u003e5+\u003c/sup\u003e from polluted water (Masood ul hasan et al. 2024). Biochar is substance rich with carbon made from various organic wastes, including municipal sewage sludge and wastes from agricultural works (Murtaza et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Biochar garnered great interest due to its distinctive properties such as large specific surface area, stability, high cation exchange capacity, and carbon content (Sun et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). However, there are obstacles in recycling material, separating it from water, and regeneration. Chitosan is a cationic natural biopolymer material formed by the deacetylation of chitin via alkaline circumstances. It exhibits diverse features such as biocompatibility, biodegradability, hydrophilicity, non-toxic characteristics, and adsorption properties. The cationic heavy metals may be actively adsorbed onto chitosan by its functional groups, which include hydroxyl and amino groups. The lack of surface chemical functional active sites groups on the biochar/chitosan composite surface has limited its adsorption capacity. However, adding functional group-rich material can boost the adsorption capability of the composite. By changing surface characteristics such as specific area and surface functional groups, electron transfer capacity, zeta potential, element distribution, and cation exchange capacity, chemical modification can increase the adsorption capacity of biochar. (Enaime et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). These changes impact porosity and enrich the biochar surface with oxygen-containing surface functional groups, particularly carboxyl groups. Moreover, it is a technique to give certain chemical modifications like etherification, grafting, or cross-linking actions for further endowing chitosan with superior adsorption qualities (Pillai et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). Many studies have focused on using raw and processed biochar to remove contaminants from water systems. Glutamine is a non-toxic amino acid, having hydrophilic functional groups including carboxylic acids and amides, with a molecular formula C\u003csub\u003e5\u003c/sub\u003eH\u003csub\u003e10\u003c/sub\u003eN\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (Kolangare et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). The addition of negatively charged carboxyl groups and hydrophilic to the biochar/chitosan composite surface contributes to improved adsorption characteristics and performance. In recent years, amino acids have been used as As\u003csup\u003e5+\u003c/sup\u003e adsorbents due to their carboxyl (-COOH) and amino (-NH\u003csub\u003e2\u003c/sub\u003e) molecular structures, which allow for heavy metal ion coordination and chelation. While hydrophilic amino acids like lysine, glycine, and cysteine are commonly employed for As\u003csup\u003e5+\u003c/sup\u003e removal [18, 19]. However, as far as we are aware, there is no research on biochar based on date palm fiber modified with glutamine amino acid in this field was studied up to now.\u003c/p\u003e \u003cp\u003eThe fundamental purpose of the research is to identify an operative and environmentally safe adsorbent for removing As\u003csup\u003e5+\u003c/sup\u003e from the aquatic system. We used agricultural solid waste residues (date palm fiber; DPF) to produce biochar (C) and created biochar/chitosan as biocomposites nanoparticles (CCS), which was subsequently modified with glutamine (CCSG). We studied many parameters that impact the adsorption performance of As\u003csup\u003e5+\u003c/sup\u003e, such as pH, contact time, applied temperature, initial concentration, adsorbent dose, and ionic strength. Date palm pits extract (DPE) was performed as caping agent for the conversion of the fabricated solid materials into stable nanoparticles under ultrasonic grinding conditions. Several physicochemical techniques were investigated, including ATR-FTIR, TGA, SEM, TEM, point of zero charge, and N\u003csub\u003e2\u003c/sub\u003e adsorption/desorption. This study sheds light on the use of functionalized solid adsorbents to eliminate heavy metals cations from polluted water, paving the way for their practical implementation in wastewater treatment. Solid adsorbents reusability and sustainability was studied after several adsorption and desorption cycles.\u003c/p\u003e"},{"header":"2 Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Materials\u003c/h2\u003e\n \u003cp\u003eDate palm pits and date palm fiber were obtained from Al-Wishayl special garden, Al-Rustaq, Sultanate of Oman. Sodium arsenate heptahydrate (\u0026gt;\u0026thinsp;98%), chitosan, sodium chloride (\u0026gt;\u0026thinsp;99.0%), sodium hydroxide (\u0026ge;\u0026thinsp;98%), hydrochloric acid (37%), acetic acid (96%), nitric acid (69%), ethylenediaminetetraacetic acid (99.5%), cysteine (\u0026ge;\u0026thinsp;95%), ethylene diamine (99.5%), trimethyl chloro-silane (C\u003csub\u003e11\u003c/sub\u003eH\u003csub\u003e17\u003c/sub\u003eClO\u003csub\u003e2\u003c/sub\u003eSSi, \u0026gt;\u0026thinsp;99.5%), bis(trimethylsilyl)trifluoroacetamide (C\u003csub\u003e8\u003c/sub\u003eH\u003csub\u003e18\u003c/sub\u003eF\u003csub\u003e3\u003c/sub\u003eNOSi\u003csub\u003e2\u003c/sub\u003e, \u0026gt;\u0026thinsp;99.0%), diethyl ether ((CH\u003csub\u003e3\u003c/sub\u003eCH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003eO, \u0026gt;\u0026thinsp;99.8%), pyridine (C\u003csub\u003e5\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eN, \u0026gt;\u0026thinsp;99.8%), chloroform (CHCl\u003csub\u003e3\u003c/sub\u003e, \u0026gt;\u0026thinsp;99.5%), and, ethyl acetate (CH\u003csub\u003e3\u003c/sub\u003eCOOC\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e5,\u003c/sub\u003e \u0026gt;\u0026thinsp;99.7%). were supplied by Sigma-Aldrich Co., USA. Stock solution of each compound was prepared using deionized water.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Date palm pits extract preparation (DPE)\u003c/h2\u003e\n \u003cp\u003eDate palm pits were gathered and washed manually by distilled water to remove any residual impurities. After drying, they were ground by using Retsch ZM200 titanium mill, Germany.\u003c/p\u003e\n \u003cp\u003eDate palm pits extract was created as follows; 20 g of crushed date palm pits powder were added to 500 mL of distilled water and stirred continuously for 18 h using a magnetic stirrer followed by filtration. The remaining dried powder weighed 14.5 g, implying that the produced extract comprised approximately 5.5 g of the dissolved date palm pit components. The solution containing DPE was stored in clean glass bottles at 5 \u003csup\u003eo\u003c/sup\u003eC for successive uses.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Fabrication of solid adsorbents\u003c/h2\u003e\n \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\n \u003ch2\u003e2.3.1 Preparation of date palm fiber biochar (C)\u003c/h2\u003e\n \u003cp\u003eDate palm fiber was chopped into small pieces, washed with pure water to remove associated pollutants and dust, dried at 120 \u003csup\u003eo\u003c/sup\u003eC, and crushed into powder. The biochar was produced using a slow pyrolysis technique involving the powder of date palm fiber (DPF) in a muffle furnace. The temperature gradually rose to 300\u0026deg;C with a heating rate of 15 \u003csup\u003eo\u003c/sup\u003eC/min and kept for 1 h before being elevated to 550\u0026deg;C and held for 2 h. The increased temperature accelerates the pyrolysis process and improves the biochar\u0026apos;s properties. After this duration, the system was cooled to the ambient temperature.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec7\" class=\"Section3\"\u003e\n \u003ch2\u003e2.3.2 Preparation of date palm fiber biochar/chitosan nanoparticles (CCS)\u003c/h2\u003e\n \u003cp\u003eThe chitosan-modified date palm fiber biochar was prepared by combining 1.0 g of chitosan with 2%, 100 mL of acetic acid. The solution was stirred for 6 h before adding 1.0 g of the created biochar to the chitosan solution. The previous mixture was agitated with a stirrer for 2 h to achieve a uniform suspension. The produced homogeneous solution was dropped using microsyringe into 1.0 mol/L, 200 mL of sodium hydroxide solution. The produced beads were filtered and washed numerous times with ultra-pure water until a neutral washing solution. The washed beads were dried for 24 h at 90 \u003csup\u003eo\u003c/sup\u003eC, and grinded in Retsch ZM200 titanium mill. The obtained fine powder of biochar/chitosan (0.5 g) was transferred into nanoparticles by sonication (Probe Sonicator IG-96A), for 15 min in the presence of 150 mL of the pre-prepared DPE solution which acts as a caping agent for the formed nanoparticles. Filtered via centrifugation and dried at 120 \u003csup\u003eo\u003c/sup\u003eC for 10 h [20, 21].\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec8\" class=\"Section3\"\u003e\n \u003ch2\u003e2.3.3 Preparation of d biochar/chitosan nanoparticles supplemented with glutamine (CCSG)\u003c/h2\u003e\n \u003cp\u003eIt is prepared in the same manner as before (sec.2.3.2), except for adding 0.1 g of glutamine to the previously prepared chitosan solution.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4 Characterization and analysis\u003c/h2\u003e\n \u003cp\u003eNumerous organic natural chemicals found in the recovered DPE operate as environmentally acceptable anticoagulant capping agents for nanoparticles. The 0.5 g of powdered date palm was acidified with HCl, allowed to cool, and then diethyl ether and ethyl acetate were used to extract the extract. The extracted solution was then evaporated under vacuum at 45\u0026deg;C. The extracted sample was resuspended in 60 \u0026micro;L of BSTFA (bis(trimethylsilyl)trifluoroacetamide)\u0026thinsp;+\u0026thinsp;TMCS (trimethylchloro-silane) 99:1 silylation reagent and 50 \u0026micro;L of pyridine to convert functional groups to trimethylsilyl groups (abbreviated TMS) before GC analysis. The GC-MS technique (Agilent Technologies) was set with gas chromatograph (7890B) and detector of mass spectrometer (5977A) The GC was operational with DB-5MS column (internal diameter of 30 m x 0.25 mm and 0.25 \u003cem\u003e\u0026micro;\u003c/em\u003em as a film thickness). Analyses were carried out using H\u003csub\u003e2\u003c/sub\u003e as the carrier gas at 1.0 ml/min as flow rate of at a splitless, injection volume of 1 \u0026micro;L. The temperature program fwas adjusted to be: 60\u0026deg;C for 1 min; increasing to 10\u0026deg;C /min up to 320\u0026deg;C and for 10 min. At 300\u0026deg;C, 320\u0026deg;C, the injector and detector were held. Mass spectra were obtained by electron ionization (EI) at 80 eV: using a spectral range of m/z 50\u0026ndash;800 and solvent delay 4.2 min. The mass temperature was 230\u0026deg;C and Quad 150\u0026deg;C. By comparing the spectrum fragmentation pattern with those found in Wiley and NIST Mass Spectral Library data, many natural materials might be recognized.\u003c/p\u003e\n \u003cp\u003eThe thermal behavior of DPF, C, CCS, and CCSG was determined using a thermoanalyzer (SDT Q600 V20.9 Build 20, UK) at a nitrogen flow rate of 20 mL/min and a heating rate of 15 \u003csup\u003eo\u003c/sup\u003eC/min up to 900 \u003csup\u003eo\u003c/sup\u003eC.\u003c/p\u003e\n \u003cp\u003eNitrogen gas adsorption/desorption was used to measure the specific area of surface (S\u003csub\u003eBET\u003c/sub\u003e, m\u003csup\u003e2\u003c/sup\u003e/g), pore size( \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{r}\\)\u003c/span\u003e\u003c/span\u003e, nm), and total pore volume (\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eP\u003c/em\u003e\u003c/sub\u003e, cm\u003csup\u003e3\u003c/sup\u003e/g) of C, CCS, and CCSG using NOVA 3200e gas sorption analyzer (Quantachrome Corporation, USA). Prior to N\u003csub\u003e2\u003c/sub\u003e gas adsorption, the solid samples (50 mg) were degassed for 16 h at 10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e Torr and 120\u0026deg;C.\u003c/p\u003e\n \u003cp\u003eScanning electron microscopy (JEOL JSM-6510LV model, Japan) was used to investigate the morphology of solid adsorbents (C, CCS, and CCSG). The samples were prepared via deposition on an aluminum holder covered in a carbon grid and then coated with a thin gold layer under high vacuum. The SEM was run at 15 kV as an accelerating voltage.\u003c/p\u003e\n \u003cp\u003eTransmission electron microscopy employing a JEOL-JEM-2100 model from Japan is also used to study the morphology of produced adsorbent particles (C, CCS, and CCSG). The samples were sonicated for 60 min in ethanol before being transferred to a copper grid.\u003c/p\u003e\n \u003cp\u003eSurface functional groups for all solid adsorbents were analyzed using Attenuated total reflectance with Fourier transform infrared (ATR -FTIR) spectroscopy at 4000\u0026ndash;400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, with ten sequential scans at resolution.\u003c/p\u003e\n \u003cp\u003eZeta potentials for each adsorbent were measured to evaluate pH\u003csub\u003ePZC\u003c/sub\u003e in pH range of 2\u0026ndash;12. The solid adsorbent material\u0026apos;s surface is positively charged for pH values less than pH\u003csub\u003ePZC\u003c/sub\u003e and negatively charged at pH levels more than pH\u003csub\u003ePZC\u003c/sub\u003e. The measurement of pH\u003csub\u003ePZC\u003c/sub\u003e is crucial in understanding how solid adsorbents adsorb heavy metal cations.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e2.5 Adsorption experiments\u003c/h2\u003e\n \u003cp\u003eThe adsorption of As\u003csup\u003e5+\u003c/sup\u003e by all synthesized solid adsorbents (C, CCS, and CCSG) was investigated using a batch adsorption technique that involved shaking 25 mL of As\u003csup\u003e5+\u003c/sup\u003e solution with 400 mg/L and 0.025 g of adsorbent mass at pH 6, 27 \u003csup\u003eo\u003c/sup\u003eC, and for 90 min. The adsorbate solution was shaken before being centrifuged at 3000 rpm for 10 min. Then, the concentration at equilibrium \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003ee\u003c/em\u003e\u003c/sub\u003e (mg/L) of As\u003csup\u003e5+\u003c/sup\u003e was determined by a hydride generation-atomic absorption spectrometer (HG-AAS; AgilentAA240 with VGA\u0026ndash;77; Australia). Three sets of measurements were made, and the average values were utilized. The percentage of removal (\u003cem\u003eR\u003c/em\u003e%) of As\u003csup\u003e5+\u003c/sup\u003e and the equilibrium sorption capacity \u003cem\u003eX\u003c/em\u003e\u003csub\u003e\u003cem\u003ee\u003c/em\u003e\u003c/sub\u003e (mg/g) were calculated using (Eqs. 1, 2, Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), respectively. The effects of various application settings, such as adsorbent solid dosage (0.1\u0026ndash;2.0 g/L, mass in g/volume in L), pH (1\u0026ndash;9), contact shaking time (5\u0026ndash;90 min), starting As\u003csup\u003e5+\u003c/sup\u003e concentration (50\u0026ndash;500 mg/L), temperature (27\u0026ndash;47 \u003csup\u003eo\u003c/sup\u003eC), and initial solution ionic strength (\u0026micro;, 0.05\u0026ndash;0.40 mol/L), were investigated by a series of batch adsorption studies. \u0026nbsp;\u003c/p\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eApplied models depict the adsorption process.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eModel name\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eModels\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSymbols significance\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNumber\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eRemoval percentage\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:R\\%=\\frac{({C}_{i}-{C}_{e})}{{C}_{i}}\\times\\:100\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003ei\u003c/em\u003e\u003c/sub\u003e (initial conc. of As\u003csup\u003e5+\u003c/sup\u003e, mg/L)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003ee\u003c/em\u003e\u003c/sub\u003e (equilibrium conc. of As\u003csup\u003e5+\u003c/sup\u003e, mg/L)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eEquilibrium adsorption capacity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{X}_{e}=\\frac{({C}_{i}-{C}_{e})}{m}\\times\\:V\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eX\u003c/em\u003e\u003csub\u003e\u003cem\u003ee\u003c/em\u003e\u003c/sub\u003e (equilibrium sorption capacity, mg/g)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eV\u003c/em\u003e (volume of As\u003csup\u003e5+\u003c/sup\u003esolution, L)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003em\u003c/em\u003e (mass of solid adsorbent, g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003e\u003cstrong\u003eKinetic models\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAdsorption capacity at certain time\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{X}_{t}=\\frac{({C}_{i}-{C}_{t})}{m}\\times\\:V\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{X}_{t}\\)\u003c/span\u003e\u003c/span\u003e(adsorption capacity in mg/g at time \u003cem\u003et\u003c/em\u003e, min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePseudo-first order\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{X}_{t}={X}_{exp}(1-{e}^{-{k}_{1}t})\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003ek\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e (PFO rate constant, min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePseudo-second order\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{X}_{t}=\\:\\frac{{{X}_{exp}}^{2}{k}_{2}\\:t}{1+\\:{X}_{exp}\\:{k}_{2}\\:t}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eX\u003c/em\u003e\u003csub\u003e\u003cem\u003eexp\u003c/em\u003e\u003c/sub\u003e (experimental adsorption capacity, mg/g)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003ek\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e (PSO rate constant, g/mg.min)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eElovich\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{X}_{t}=\\frac{1}{\\beta\\:}Ln(1+\\alpha\\:\\beta\\:t)\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\alpha\\:\\:\\)\u003c/span\u003e\u003c/span\u003e(initial rate of As\u003csup\u003e5+\u003c/sup\u003eadsorption, mg/g.min)\u003c/p\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\beta\\:\\:\\)\u003c/span\u003e\u003c/span\u003e(extent of surface coverage, g/mg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003e\u003cstrong\u003eAdsorption isotherm models\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eLangmuir\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{X}_{e}=\\frac{b{X}_{m}{C}_{e}}{1+b{C}_{e}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:b\\:\\)\u003c/span\u003e\u003c/span\u003e(Langmuir constant, L/mg)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eX\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e (maximum Langmuir adsorption capacity, mg/g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eSeparation factor\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{R}_{L}=\\frac{1}{1+b{C}_{i}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{R}_{L}\\:\\)\u003c/span\u003e\u003c/span\u003e(separation factor)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eFreundlich\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{X}_{e}={K}_{F}\\:{C}_{e}^{\\frac{1}{n}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003en\u003c/em\u003e (Freundlich constant related to the adsorption intensity)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003eF\u003c/em\u003e\u003c/sub\u003e (Freundlich constant related to the extent of adsorption, L\u003csup\u003e1/n\u003c/sup\u003e. mg\u003csup\u003e1\u0026ndash;1/n\u003c/sup\u003e/g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e9\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTemkin\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{X}_{e}\\:=\\frac{R\\:T}{{b}_{T}}\\text{ln}{K}_{T}\\:{C}_{e}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eR\u003c/em\u003e (universal gas constant, 8.314 J/mol. K)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eT\u003c/em\u003e (absolute adsorption temperature, K)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003eT\u003c/em\u003e\u003c/sub\u003e (equilibrium binding constant, L/g)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eb\u003c/em\u003e\u003csub\u003e\u003cem\u003eT\u003c/em\u003e\u003c/sub\u003e (Temkin constant, J/mol)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e10\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eDubinin-Radushkevich\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{X}_{e}=\\:{X}_{DR}\\:{e}^{-{K}_{DR\\:\\:}{\\epsilon\\:}^{2}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eX\u003c/em\u003e\u003csub\u003e\u003cem\u003eDR\u003c/em\u003e\u003c/sub\u003e (D-R adsorption capacity, mg/g)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003eDR\u003c/em\u003e\u003c/sub\u003e (D-R constant, mol\u003csup\u003e2\u003c/sup\u003e/kJ\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eDR\u003c/em\u003e\u003c/sub\u003e (mean adsorption-free energy, kJ/mol)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eMean adsorption-free energy\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{E}_{DR}\\:=\\:\\frac{1}{\\sqrt{2{K}_{DR}}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e12\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eThermodynamic studies\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\u0026nbsp;\u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eDistribution constant\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{K}_{s}=\\:\\frac{{C}_{s}}{{C}_{e}}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e (surface adsorbed As\u003csup\u003e5+\u003c/sup\u003e, mg/g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eVan\u0026rsquo;t Hoff\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\text{ln}{K}_{s}=\\:\\frac{\\varDelta\\:S^\\circ\\:}{R}\\:-\\:\\frac{\\varDelta\\:H^\\circ\\:}{RT}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\varDelta\\:S^\\circ\\:\\:\\)\u003c/span\u003e\u003c/span\u003e(entropy change, kJ/mol. K)\u003c/p\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\varDelta\\:H^\\circ\\:\\:\\)\u003c/span\u003e\u003c/span\u003e(heat change, kJ/mol)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eGibbs free energy\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\varDelta\\:G^\\circ\\:=\\varDelta\\:H^\\circ\\:-T\\varDelta\\:S^\\circ\\:\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\varDelta\\:G^\\circ\\:\\:\\)\u003c/span\u003e\u003c/span\u003e(Free energy change, kJ/mol)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eThe adsorption activity was observed, and the obtained data were analyzed to provide insights into the adsorption mechanisms and the efficiency of solid adsorbent materials for As\u003csup\u003e5+\u003c/sup\u003eremoval. Several adsorption parameters were computed using several kinetics and equilibrium nonlinear adsorption models.\u003c/p\u003e\n \u003cp\u003eThe kinetics investigation was conducted on As\u003csup\u003e5+\u003c/sup\u003e adsorption onto C, CCS, and CCSG using nonlinear expressions of pseudo-first order (PFO, Eq. 4), pseudo-second order (PSO, Eq. 5), and Elovich (Eq. 6). While nonlinear isotherm models, featuring Langmuir (Eq. 7), Freundlich (Eq. 9), Temkin (Eq. 10), and Dubinin-Radushkevich (Eq. 11) were used to analyze equilibrium data of As\u003csup\u003e5+\u003c/sup\u003e adsorption on C, CCS, and CCSG as given in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003eThree thermodynamic parameters namely change in enthalpy, (\u003cem\u003e\u0026Delta;H\u0026deg;\u003c/em\u003e, kJ/mol), change in entropy, (\u003cem\u003e\u0026Delta;S\u0026deg;\u003c/em\u003e, kJ/mol.K), and Gibb\u0026rsquo;s free energy, (\u003cem\u003e\u0026Delta;G\u0026deg;\u003c/em\u003e, kJ/mol) were estimated by Eqs. 14, 15 (Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eTable \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e: Applied models depict the adsorption process.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e\u003cstrong\u003e2.6 Desorption and reusability experiment\u003c/strong\u003e\u003c/h2\u003e\n \u003cp\u003eDesorption of As\u003csup\u003e5+\u003c/sup\u003e tests are important for regenerating the three chosen adsorbents (C, CCS, and CCSG). Desorption was studied by adding 0.10 g of solid to 100 mL of 400 mg/L As\u003csup\u003e5+\u003c/sup\u003e at pH 6, stirring, and 27\u0026deg;C. After 25 min, the adsorbents were rinsed with 100 mL of 0.1 mol/L desorbing agent (dist. water, HCl, HNO\u003csub\u003e3\u003c/sub\u003e, ethylene diamine, cysteine, and EDTA). The desorbed concentration of As\u003csup\u003e5+\u003c/sup\u003e in solution was assessed using the predefined atomic absorption spectrometer. The desorption percentage was calculated using Eq. 16 to evaluate the solid nanoparticles performance after frequent application.\u003c/p\u003e\n \u003cp\u003e\u003cimg src=\"https://myfiles.space/user_files/122228_c8a1650c59388082/122228_custom_files/img1729759257.png\"\u003e\u003cbr\u003e\u003c/p\u003e\n \u003cp\u003ewhere \u003cem\u003eC\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e is the equilibrium metal ion (As\u003csup\u003e5+\u003c/sup\u003e) concentration after desorption from adsorbents (mg/L), \u003cem\u003em\u003c/em\u003e is the mass of solid adsorbent (g), \u003cem\u003eV\u003c/em\u003e is the desorbing agent volume (L), and \u003cem\u003eX\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e is the adsorbent\u0026apos;s greatest capacity of adsorption (mg/g).\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3 Results and Discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Characterization techniques\u003c/h2\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e3.1.2 GC-M examination of date palm pits extract\u003c/h2\u003e \u003cp\u003eThe chemical content of the extract of date palm pits (DPE) was analyzed using GC-MS (gas chromatography-mass spectrometry) and the obtained data is presented in Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e. Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e shows a chromatogram of DPE of the most active discovered chemicals. There were twenty chemical compounds found in DPE, with the most common being 9-octadecenoic acid, (E)-, TMS derivative (20.33%), dodecanoic acid, TMS derivative (15.89%), Hydroquinone, 2TMS derivative (12.41%), and palmitic acid, TMS derivative (11.64%). The data in Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e revealed that the extract also contained acids, alkanes, alkyl benzenes, aromatic benzene derivatives, alcohols, carboxylic acids, fatty acid derivatives, glycerides, lipids, phytosterols, terpenes, and steroids. DPE has a vital role as anticoagulant capping agent which acts as stabilizer by inhibiting nanoparticles overgrowth and preventing aggregation/coagulation because of the attendance of numerous active chemical mixtures which are rich in hydroxyl groups (Shu et al. \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). So, causing the creation of nanostructures.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e3.1.3. Characterization of solid adsorbents\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea shows thermal analysis curves for DPF, C, CCS, and CCSG. Weight loss of 0.9, 3.2, and 3.6% was found for C, CCS, and CCSG, respectively at 120 ℃ due to the removal of absorbed water (Gemeay et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Biochar with lesser hydrophilic surface functional groups is superior to that treated with chitosan or reinforced with glutamine. The date palm fiber (DPF) mass loss occurred in four stages. The first stage up to 120\u0026deg;C, was due to moisture loss (vaporization), representing 6.3% of the total weight loss. From 260\u0026ndash;340 \u003csup\u003eo\u003c/sup\u003eC, the second stage of mass loss involves the degradation of low molecular weight hemicellulose ([C\u003csub\u003e5\u003c/sub\u003e(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e4\u003c/sub\u003e]\u003csub\u003en\u003c/sub\u003e) with additional mass loss of 30.7%. The third phase of the mass loss at from 320\u0026ndash;380\u0026deg;C corresponds to the heat breakdown of cellulose ([C\u003csub\u003e6\u003c/sub\u003e(H\u003csub\u003e2\u003c/sub\u003eO)\u003csub\u003e5\u003c/sub\u003e]\u003csub\u003en\u003c/sub\u003e). The final stage is about decomposition of lignin ([C\u003csub\u003e10\u003c/sub\u003eH\u003csub\u003e12\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e]\u003csub\u003en\u003c/sub\u003e) ranging from 300\u0026ndash;580\u0026deg;C [24, 25]. Biochar solid sample (C) graph shows that weight loss (18.31 wt%) was occurring between 250 and 400\u0026deg;C. Aliphatic structures decomposed at temperatures exceeding 250\u0026deg;C. The discharge of volatile chemical compounds such as CO\u003csub\u003e2\u003c/sub\u003e was produced by the breakdown of the date palm biochar's functional groups (carboxylic acid groups and lactones) (Hadj-Otmane et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The breakdown of anhydride, carbonyl, and ether operates by releasing CO and CO\u003csub\u003e2\u003c/sub\u003e at temperatures\u0026thinsp;~\u0026thinsp;350\u0026deg;C (Wang et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Over 400\u0026deg;C, the mass loss is connected with the dissolution of aromatic rings that exist on the surface of biochar, which occurs by liberating volatile chemicals [28, 29]. The thermal degradation for CCS and CCSG started at approximately 160\u0026deg;C, and continued until 450\u0026deg;C, with weight loss of ~\u0026thinsp;51.88%. During the temperature between 250 ℃ to 340 ℃ in CCS thermal curve, a significant weight loss was observed due to chitosan chain decomposition and oxidation, sugar ring dehydration, and polymer degradation (Chen et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). At temperatures above 600 \u003csup\u003eo\u003c/sup\u003eC, which represents the ash remains, almost no mass loss was found. This result suggests the chitosan was not merely adhered on the date palm fiber biochar surface, but rather complexly linked together.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTextural characterization of solid adsorbent is an important technique to describe the capacity of adsorption and way of pollutant adsorption. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb shows the porous structure property of the produced adsorbents as measured by the N\u003csub\u003e2\u003c/sub\u003e adsorption/desorption isotherms. Porous structure is characterized by the specific surface area (\u003cem\u003eS\u003c/em\u003e\u003csub\u003e\u003cem\u003eBET\u003c/em\u003e\u003c/sub\u003e, m\u003csup\u003e2\u003c/sup\u003e/g), pore volume (\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003eP\u003c/em\u003e\u003c/sub\u003e, cm\u003csup\u003e3\u003c/sup\u003e/g), and average pore radius (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{r}\\)\u003c/span\u003e\u003c/span\u003e, nm) which are listed in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The prepared materials are classified as type II isotherm by the IUPAC (International Union of Pure and Applied Chemistry) with H4 hysteresis loop for C and CCS and H3 hysteresis loop for CCSG [6, 26, 31]. The specific surface area and pore volume for samples were found to be 349.09 m\u003csup\u003e2\u003c/sup\u003e/g, 0.21 cm\u003csup\u003e3\u003c/sup\u003e/g for C, 499.51 m\u003csup\u003e2\u003c/sup\u003e/g, 0.26 cm\u003csup\u003e3\u003c/sup\u003e/g for CCS, and 518.69 m\u003csup\u003e2\u003c/sup\u003e/g, 0.25 cm\u003csup\u003e3\u003c/sup\u003e/g for CCSG. The order of \u003cem\u003eS\u003c/em\u003e\u003csub\u003e\u003cem\u003eBET\u003c/em\u003e\u003c/sub\u003e values from the highest is: CCSG, CCS, and C. The pore volume change is comparable to that of the \u003cem\u003eS\u003c/em\u003e\u003csub\u003e\u003cem\u003eBET\u003c/em\u003e\u003c/sub\u003e. The results revealed that date palm fiber biochar particles improved significantly after modification in terms of pore volume and surface area. It is obvious that the insertion of biochar in the chitosan matrix followed by modification with glutamine results in a greater surface area, which may be associated to the disruption and solid structure heterogeneity. Furthermore, the average pore size for C (1.22 nm) ˃ CCS (1.05 nm) ˃ CCSG (0.97 nm) which indicates the microporous and mesoporous character of the samples.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacterization parameters for the fabricated solid adsorbents.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCCS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eCCSG\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eS\u003c/b\u003e\u003csub\u003e\u003cb\u003eBET\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(m\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e/g)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e349.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e499.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e518.69\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eV\u003c/b\u003e\u003csub\u003e\u003cb\u003eP\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(cm\u003c/b\u003e\u003csup\u003e\u003cb\u003e3\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e/g)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\stackrel{-}{\\varvec{r}}\\)\u003c/span\u003e\u003c/span\u003e \u003cb\u003e(nm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.97\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003epH\u003c/b\u003e\u003csub\u003e\u003cb\u003ePZC\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e6.20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.90\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eVarious surface chemical functional groups of the adsorbents (C, CCS, and CCSG) were exposed to ATR-FTIR analysis in the range of 4000\u0026ndash;400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e as presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec. The stretching bands at about 1063 (C\u0026ndash;O), 1438 (\u0026ndash;CH\u003csub\u003e2\u003c/sub\u003e), 1573 (C\u0026thinsp;=\u0026thinsp;O), 2976 (\u0026ndash;CH), and 3373 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (\u0026ndash;OH) were observed from ATR-FTIR spectra of C [32]. Correspondingly, in the ATR-FTIR spectra of CCS, the chemical functional groups mentioned above were observed around the appropriate wavenumber. However, the peak at 1573 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e shifted to 1555 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for amide I (C\u0026thinsp;=\u0026thinsp;O stretching), and a new peak appeared at 1656 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for amide II (bending modes of N-H) indicated that the carboxyl groups reacted with chitosan during composite formation [33]. While CCSG has witnessed structural changes, namely the emergence of \u0026ndash;COOH and \u0026ndash;CONH\u0026ndash;. At 3167, 1500, and 1407 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, the stretching vibration peak of -OH, the stretching vibration peak of C\u0026thinsp;=\u0026thinsp;O, and the bending vibration absorption peak of -COOH were identified. The bending vibration peak in -NH and The C\u0026thinsp;=\u0026thinsp;O stretching vibration peak in -CONH- emerged at 1580 and 1675 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively, confirming the presence of -COOH and -CONH- in CCSG structure [34].\u003c/p\u003e \u003cp\u003eMost adsorption systems rely on electrostatic interactions between adsorbents and adsorbates. Measuring the surface charge of the adsorbent is crucial for confirming the possibility of electrostatic interactions. The zeta potential was used to evaluate the chemical surface charge as elucidated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed and calculate the point of zero charge (pH\u003csub\u003ePZC\u003c/sub\u003e) as given in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The PZC was determined to be 6.2, 6.6, and 6.9 for C, CCS, and CCSG. At pH\u0026thinsp;\u0026lt;\u0026thinsp;pH\u003csub\u003ePZC\u003c/sub\u003e, the surface charge of all synthesized adsorbents is positive while at pH\u0026thinsp;\u0026gt;\u0026thinsp;pH\u003csub\u003ePZC\u003c/sub\u003e, the surface charge is negative.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e: TGA curves (a), N\u003csub\u003e2\u003c/sub\u003e adsorption (b), ATR-FTIR spectra (c), and pH\u003csub\u003ePZC\u003c/sub\u003e (d) for C, CCS, and CCSG. In addition to TGA of date palm fiber (DPF).\u003c/p\u003e \u003cp\u003eSEM was used to examine samples (C, CCS, and CCSG) structure and morphology, the magnification pictures given in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea\u0026ndash;c. The SEM picture Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea of the C shows stacked rocky layers structure with many pores which is a representative of biochar solid material, irregular, and a rather smooth surface [35, 36]. After modification, the surface of CCS became rough, with tiny particles holding on to the surface Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb which might be related to the\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eenhancement of superficial area. These tiny particles were probably chitosan. Furthermore, these microscopic particles remained on the surface of the CCSG as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec which in turn proves the distribution of chitosan and glutamine amino acid on the CCSG surface.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e: SEM (a\u0026ndash;c) and TEM (d\u0026ndash;f) images for C, CCS, and CCSG, respectively.\u003c/p\u003e \u003cp\u003eFigures \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed\u0026ndash;f exhibit TEM micrographs of the manufactured solid adsorbents. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed shows that C has a layered and porous structure due to the biochar's intrinsic nature [32]. Compared to C in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed, the surfaces of CCS and CCSG in Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee, \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef showed a noticeable sparkle and clusters, indicating that the chitosan and glutamine amino acid had been constructed on the surface. It became apparent that the C, CCS, and CCSG TEM particle sizes were approximately 450, 23, and 38 nm, respectively. The resultant solid particles disperse when biochar is inserted into the biopolymer framework in CCS and CCSG, which has distinct characteristics from the two solids.\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e: Characterization parameters for the fabricated solid adsorbents.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Static adsorption removal of As\u003csup\u003e5+\u003c/sup\u003e\u003c/h2\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003e3.2.1 Impact of solid dose\u003c/h2\u003e \u003cp\u003eThe study examined the effect of different quantities of solid adsorbents (C, CCS, and CCSG) on adsorption efficiency (\u003cem\u003eR%\u003c/em\u003e) as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea. While the Removal% of As\u003csup\u003e5+\u003c/sup\u003e was computed using Eq.\u0026nbsp;1. At a pH 6 and 27\u0026deg;C, 0.1 to 2.0 g/L of adsorbent dose was combined with 25 mL of As\u003csup\u003e5+\u003c/sup\u003e solution (400 mg/L) and stirred at 3000 rpm for 90 min. The adsorption efficiency increased from 21, 38, and 68% at 0.1 g/L to 43, 65, and 93% at 1.0 g/L for adsorbents (C, CCS, and CCSG), respectively. The increase in the removal percent by nearly 2.1, 1.7, and 1.4 times increase for C, CCS, and CCSG, respectively. The increase in the capacity of adsorption can be connected to the increase in active sites/As\u003csup\u003e5+\u003c/sup\u003e ratio. Maximum adsorption occurred at a solid sorbent dosage of 1.0 g/L on CCSG, which may be attributed to the presence of hydrophilic and negatively charged -NH\u003csub\u003e2\u003c/sub\u003e, -OH, and -COOH groups that provide more binding sites for As\u003csup\u003e5+\u003c/sup\u003e. In addition, due to the large surface area confirmed by the N\u003csub\u003e2\u003c/sub\u003e adsorption/desorption. High adsorbent doses resulted in poor As\u003csup\u003e5+\u003c/sup\u003e adsorption, possibly owing to the occurrence of unsaturated binding active sites and the absence of available As\u003csup\u003e5+\u003c/sup\u003e. However, fixed As\u003csup\u003e5+\u003c/sup\u003e concentrations reduce sorption capacity (Niazi et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2024\u003c/span\u003e)38]. To investigate further adsorption parameters, a dosage of 1.0 g/L of all adsorbents was chosen based on these results.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e \u003ch2\u003e3.2.2 Effect of starting solution pH\u003c/h2\u003e \u003cp\u003eThe pH has a direct impact on both the adsorbent active sites and the shape of pollutant ions (As\u003csup\u003e5+\u003c/sup\u003e). To test the effect of pH on solid adsorbents (C, CCS, and CCSG), the solution's pH was adjusted using either 0.1 M NaOH and/or 0.1M HCl from 1 to 9 with 0.025 g solid adsorbents, 25 mL of 400 mg/L As\u003csup\u003e5+\u003c/sup\u003e at 27 \u003csup\u003eo\u003c/sup\u003eC, and 90 min shaking duration as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb. It is perceived that As\u003csup\u003e5+\u003c/sup\u003e adsorption is limited at lower and higher pH values. The highest As\u003csup\u003e5+\u003c/sup\u003e adsorption occurs at pH 6. It achieves adsorption capacity of 42, 63, and 92% for C, CCS, and CCSG, respectively. The removal % gradually increased from 1\u0026ndash;6 and slightly dropped from 6 to 9. Proton ions (H\u003csub\u003e3\u003c/sub\u003eO\u003csup\u003e+\u003c/sup\u003e) is more adsorbed than As\u003csup\u003e5+\u003c/sup\u003e at lower pH levels (\u0026lt;\u0026thinsp;pH\u003csub\u003ePZC\u003c/sub\u003e) due to the more ionic mobility of proton than arsenic ion forms (H\u003csub\u003e2\u003c/sub\u003eAsO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e and HAsO\u003csub\u003e4\u003c/sub\u003e\u0026thinsp;\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e ) [32, 39]. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed shows that C, CCS, and CCSG had a point of zero charge (pH\u003csub\u003epzc\u003c/sub\u003e) of around 6.2, 6.6, and 6.9, respectively. When pH exceeds pH\u003csub\u003epzc\u003c/sub\u003e, the surface of adsorbents acquired negative charges, which may hinder arsenic species (HAsO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026ndash;\u003c/sup\u003e) adsorption owing to the established electrostatic repulsion (Gan et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). However, when the pH was higher than neutral, the adsorption effectiveness decreased due to polymer chain shrinkage caused by deprotonation of chitosan amino groups (Rahmi \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). CCSG outperformed C and CCS in terms of As\u003csup\u003e5+\u003c/sup\u003e adsorption, suggesting that the addition of chitosan and glutamine was beneficial for As\u003csup\u003e5+\u003c/sup\u003e removal. It is possible that protonation of -NH\u003csub\u003e2\u003c/sub\u003e and -OH resulted in positively charged molecules that show considerable promise for sequestering As\u003csup\u003e5+\u003c/sup\u003e (in the form of AsO\u003csub\u003e4\u003c/sub\u003e\u0026thinsp;\u003csup\u003e\u0026minus;\u0026thinsp;3\u003c/sup\u003e and AsO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e\u0026minus;\u003c/sup\u003e) via electrostatic attraction. Consequently, pH6 was nominated as the most suitable pH for As\u003csup\u003e5+\u003c/sup\u003e adsorption from aqueous medium onto all the investigated adsorbents.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e: The impact of adsorbent dose (a) and pH (b) on As\u003csup\u003e5+\u003c/sup\u003e adsorption onto C, CCS, and CCSG (Ci\u0026thinsp;=\u0026thinsp;400 mg/L, T\u0026thinsp;=\u0026thinsp;27 \u003csup\u003eo\u003c/sup\u003eC, and t\u0026thinsp;=\u0026thinsp;90 min).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e \u003ch2\u003e3.2.3 Kinetic studies and impact of shaking time\u003c/h2\u003e \u003cp\u003eThe kinetics of As\u003csup\u003e5+\u003c/sup\u003e adsorption onto C, CCS, and CCSG samples was studied from 5 to 90 min at pH 6, 25 mL, 400 mg/L As\u003csup\u003e5+\u003c/sup\u003e, solid dose (1.0 g/L), temperature (27\u0026deg;C) to further determine the adsorption mechanism of the adsorbents. We evaluated the kinetic indicators of three adsorbents using PFO \u003cb\u003e(\u003c/b\u003eEq.\u0026nbsp;4, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea), PSO \u003cb\u003e(\u003c/b\u003eEq.\u0026nbsp;5, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb), and Elovich \u003cb\u003e(\u003c/b\u003eEq.\u0026nbsp;6, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec) nonlinear models. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the model parameters for removing As\u003csup\u003e5+\u003c/sup\u003e metal ions on solid samples. At the beginning of adsorption time, the rapid adsorption of As\u003csup\u003e5+\u003c/sup\u003e on the adsorbents could be attributed to the abundance of available active sites where the ration of solid active sites/ As\u003csup\u003e5+\u003c/sup\u003e is higher. Then, as the adsorption sites were depleted, the adsorption capacity slowly increased until reaching equilibrium after 25 min. The time-dependent adsorption data was successfully fitted by PFO kinetic model based on correlation coefficients \u003cem\u003eR\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e (0.9439\u0026ndash;0.9730) and reduced chi-squared \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e (1.8681\u0026ndash;3.4750) for all solid samples. Furthermore, the adsorbed amount of As\u003csup\u003e5+\u003c/sup\u003e metal ions calculated using PFO model closely corresponded to the experimental one which is derived from the Langmuir Eq.\u0026nbsp;(1.99, 2.38, and 0.74% as differences in the cases of C, CCS, and CCSG, respectively). Despite \u003cem\u003eR\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e values for the adsorption of As\u003csup\u003e5+\u003c/sup\u003e ions by PSO kinetic model are nearly high (0.8542\u0026ndash;0.8984). However, there was a substantial discrepancy between the estimated and observed Langmuir adsorption capacities (17.28, 16.72, and 20.72% for C, CCS, and CCSG, respectively). In addition to the higher calculated reduced chi-squared \u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e (5.1629\u0026ndash;14.4098) proves the invalid application of PSO in comparison with PFO nonlinear model. This revealed that PSO model could not best describe the As\u003csup\u003e5+\u003c/sup\u003e adsorption, because the investigational adsorption capabilities did not accord with the model's hypothetical prospects. Hence, the PFO model is the beneficial kinetic model, indicating the physical adsorption process [42, 43]. The Elovich model has good applicability for As\u003csup\u003e5+\u003c/sup\u003e adsorption (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.8926 on average). CCS and CCSG had significantly higher \u003cem\u003eα\u003c/em\u003e values than C, indicating an increase in the primary rate of adsorption after modification. The degree of surface coverage (\u003cem\u003eβ\u003c/em\u003e, g/mg) value, is inversely linked to the correspondence of adsorbate to adsorbent, is significantly lower for CCS and CCSG compared to C demonstrating that the modified ones (CCS and CCSG) exhibit greater affinity to As\u003csup\u003e5+\u003c/sup\u003e than C (Nguyen et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eKinetic, isotherm nonlinear, and thermodynamic parameters for the adsorption of As\u003csup\u003e5+\u003c/sup\u003e onto C, CCS, and CCSG at 27 \u003csup\u003eo\u003c/sup\u003eC.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eModels\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eParameters\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eC\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eCCS\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eCCSG\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u003cb\u003ePFO\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003csub\u003e\u003cb\u003eexp\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(mg/g)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e147.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e249.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e373.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003ek\u003c/b\u003e\u003csub\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(min\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;1\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0840\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0771\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.0739\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eR\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9439\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.9688\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9730\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eχ\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.8681\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.1290\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.4750\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u003cb\u003ePSO\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003csub\u003e\u003cb\u003eexp\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(mg/g)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e176.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e298.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e453.9\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003ek\u003c/b\u003e\u003csub\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(g/mg.min)\u0026times;10\u003c/b\u003e\u003csup\u003e\u003cb\u003e\u0026minus;\u0026thinsp;4\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.9953\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2.5606\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.6013\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eR\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.8542\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.8984\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.8901\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eχ\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e5.1629\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e6.2058\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e14.4098\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u003cb\u003eElovich\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eα (mg/g.min)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e19.7859\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e33.1947\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e47.6115\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eβ (g/mg)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0129\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.0084\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eR\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.8827\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.8972\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.8979\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eχ\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.7160\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e9.9450\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e22.5613\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003e\u003cb\u003eLangmuir\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003csub\u003e\u003cb\u003em\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(mg/g)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e150.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e256.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e376.0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eb (L/mg)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.11821\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0759\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.1163\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eR\u003c/b\u003e\u003csub\u003e\u003cb\u003eL\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0207\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0319\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.0210\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eR\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9797\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.9820\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9910\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eχ\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9230\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3.4948\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.3513\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u003cb\u003eFreundlich\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e1/n\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.2472\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.3477\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.2989\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eK\u003c/b\u003e\u003csub\u003e\u003cb\u003eF\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(L\u003c/b\u003e\u003csup\u003e\u003cb\u003e1/n\u003c/b\u003e\u003c/sup\u003e. \u003cb\u003emg\u003c/b\u003e\u003csup\u003e\u003cb\u003e1\u0026thinsp;\u0026minus;\u0026thinsp;1/n\u003c/b\u003e\u003c/sup\u003e\u003cb\u003e/g)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e46.6780\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e48.3148\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e95.9714\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eR\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.7603\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.8443\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.8292\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eχ\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.3942\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e14.3297\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e19.0735\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"3\" rowspan=\"4\"\u003e \u003cp\u003e\u003cb\u003eTemkin\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eb\u003c/b\u003e\u003csub\u003e\u003cb\u003eT\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(J/mol)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e28.6213\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e56.1971\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e77.5609\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eK\u003c/b\u003e\u003csub\u003e\u003cb\u003eT\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(L/g)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.6615\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.6723\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.1925\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eR\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.8574\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.9348\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9165\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eχ\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.6134\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5.9995\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e9.3233\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"4\" rowspan=\"5\"\u003e \u003cp\u003e\u003cb\u003eDubinin-Radushkevich\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003csub\u003e\u003cb\u003eDR\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(mg/g)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e148.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e251.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e361.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eK\u003c/b\u003e\u003csub\u003e\u003cb\u003eDR\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(kJ/mol)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.4842\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.6264\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.4416\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eE\u003c/b\u003e\u003csub\u003e\u003cb\u003eDR\u003c/b\u003e\u003c/sub\u003e \u003cb\u003e(kJ/mol)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.0162\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.8934\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.0641\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eR\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9869\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.9942\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9876\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eχ\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.2397\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.5329\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.3871\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\" morerows=\"6\" rowspan=\"7\"\u003e \u003cp\u003e\u003cb\u003eThermodynamic\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eparameters\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eR\u003c/b\u003e\u003csup\u003e\u003cb\u003e2\u003c/b\u003e\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9186\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.9307\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9264\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eΔH\u003c/b\u003e\u003csup\u003e\u003cb\u003eo\u003c/b\u003e\u003c/sup\u003e \u003cb\u003e(kJ/mol)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.8284\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.6216\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e6.4387\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eΔS\u003c/b\u003e\u003csup\u003e\u003cb\u003eo\u003c/b\u003e\u003c/sup\u003e \u003cb\u003e(kJ/mol.K)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0369\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0389\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.0320\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003e‒ΔG\u003c/b\u003e\u003csup\u003e\u003cb\u003eo\u003c/b\u003e\u003c/sup\u003e \u003cb\u003e(kJ/mol)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e27 ℃\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.2464\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.0475\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.1727\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e34 ℃\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.5051\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.3198\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.3970\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e40 ℃\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.7266\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.5531\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.5892\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003e45 ℃\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e6.9112\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e7.7476\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.7494\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e: Nonlinear PFO (a), PSO (b), and Elovich (c) nonlinear kinetic equations for the adsorption of As\u003csup\u003e5+\u003c/sup\u003e onto C, CCS, and CCSG (T\u0026thinsp;=\u0026thinsp;27 \u003csup\u003eo\u003c/sup\u003eC, C\u003csub\u003ei\u003c/sub\u003e = 400 mg/L, dosage 1.0 g/L, pH\u0026thinsp;=\u0026thinsp;6, t\u0026thinsp;=\u0026thinsp;5\u0026ndash;90 min).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e \u003ch2\u003e3.2.4 Static adsorption isotherms and effect of initial concentration\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea\u0026ndash;d shows the equilibrium adsorption isotherms as nonlinear Langmuir \u003cb\u003e(\u003c/b\u003eEq.\u0026nbsp;7, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea), Freundlich \u003cb\u003e(\u003c/b\u003eEq.\u0026nbsp;9, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb), Temkin \u003cb\u003e(\u003c/b\u003eEq.\u0026nbsp;10, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec), and Dubinin-Radushkevich \u003cb\u003e(\u003c/b\u003eEq.\u0026nbsp;11, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed) models. While related isotherm parameters are presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. These isotherms predict adsorption based on mutual interactions between adsorbate and adsorbent with different principles especially Langmuir and Freundlich with contradictory postulates. The adsorption isothermal experiment was conducted at pH 6, 1.0 g/L solid dosage, temperature (27\u0026deg;C), and starting As\u003csup\u003e5+\u003c/sup\u003e concentration (50\u0026ndash;500 mg/L). Increasing the initial concentration of As\u003csup\u003e5+\u003c/sup\u003e may improve adsorption capacity since a high concentration gradient encourages As\u003csup\u003e5+\u003c/sup\u003e ions to diffuse towards adsorption sites of solid adsorbents (C, CCS, and CCSG) (Zhou et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). However, further increasing starting As\u003csup\u003e5+\u003c/sup\u003e concentration could not improve adsorption capability due to restricted adsorption sites in solid adsorbents (Song et al. \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). The Langmuir, Dubinin-Radushkevich, and Temkin nonlinear models are more accepted than the Freundlich model due to greater coefficients of correlation (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e) and lower reduced chi square (\u003cem\u003eχ\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e) values as shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. All model fits had \u003cem\u003eR\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e values more than 0.8574, suggesting strong significance. The prepared adsorbents had Langmuir maximum adsorption capacities follow this sequence CCSG ˃ CCS ˃ C (376.0, 256.0, and 150.5 mg/g, respectively). This could be due to the existence of novel surface chemical functional groups on the composites' surface, in addition to their larger surface areas. The \u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e estimates (Eq.\u0026nbsp;8) for all the adsorbents in this investigation are 0\u0026thinsp;\u0026lt;\u0026thinsp;\u003cem\u003eR\u003c/em\u003e\u003csub\u003e\u003cem\u003eL\u003c/em\u003e\u003c/sub\u003e \u0026lt; 1, indicating a good adsorption process. On the other hand, the correlation coefficient values produced for the nonlinear Freundlich model are lower than those calculated for the Langmuir model for all solid samples. The Langmuir model exceeded the Freundlich model in describing As\u003csup\u003e5+\u003c/sup\u003e sorption, demonstrating that monolayer sorption was the dominating process on all three sorbent homogenous surfaces. The Freundlich model parameter (sorption intensity, \u003cem\u003e1/n\u003c/em\u003e) determines whether the process of adsorption was chemisorption in nature (for \u003cem\u003e1/n\u0026thinsp;\u0026gt;\u003c/em\u003e\u0026thinsp;1) or physisorption (for \u003cem\u003e1/n\u0026thinsp;\u0026lt;\u003c/em\u003e\u0026thinsp;1), based on heterogeneity (Yao et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). In the current study, \u003cem\u003e1/n\u003c/em\u003e revealed values below one, indicating the physisorption mechanism. CCS and CCSG had higher sorption intensity (\u003cem\u003e1/n\u003c/em\u003e) and K\u003csub\u003eF\u003c/sub\u003e (L\u003csup\u003e1/n\u003c/sup\u003e/ mg\u003csup\u003e1\u0026thinsp;\u0026minus;\u0026thinsp;1/n\u003c/sup\u003e. g) than C, indicating a stronger capacity to adsorb As\u003csup\u003e5+\u003c/sup\u003e. The Temkin model effectively applies As\u003csup\u003e5+\u003c/sup\u003e adsorption across all samples, as evidenced by high correlation values (0.8574\u0026ndash;0.9348). The lower Temkin isotherm constant \u003cem\u003eb\u003c/em\u003e\u003csub\u003e\u003cem\u003eT\u003c/em\u003e\u003c/sub\u003e values (\u003cem\u003eb\u003c/em\u003e\u003csub\u003e\u003cem\u003eT\u003c/em\u003e\u003c/sub\u003e ˂ 8000 J/mol) (28.6213\u0026ndash;77.5609 J/mol) reflect physical adsorption process between the adsorbate and adsorbent (Kamal et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). \u003cem\u003eb\u003c/em\u003e\u003csub\u003e\u003cem\u003eT\u003c/em\u003e\u003c/sub\u003e (J/mol) is inversely associated with the adsorption heat (Ao et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The endothermic nature of the adsorption process is suggested by the positive values reported for \u003cem\u003eb\u003c/em\u003e\u003csub\u003e\u003cem\u003eT\u003c/em\u003e\u003c/sub\u003e. (Adeogun and Babu \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The \u003cem\u003eR\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e values found in DR model (Dubinin-Radushkevish) isotherm model for As\u003csup\u003e5+\u003c/sup\u003e were among 0.9869 and 0.9942 for all three sorbents. The Dubinin-Radushkevich equation yields almost similar adsorption capacity (\u003cem\u003eX\u003c/em\u003e\u003csub\u003e\u003cem\u003eDR\u003c/em\u003e\u003c/sub\u003e) to the Langmuir model. If the \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eDR\u003c/em\u003e\u003c/sub\u003e value is less than 8 kJ/mol, adsorption is thought to be a physical process with pore-filling as the primary mechanism (Niazi et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). If the \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eDR\u003c/em\u003e\u003c/sub\u003e value is between 8.0\u0026ndash;16.0 kJ/mol, chemical adsorption and ion exchange yield control of the process. Our data indicates that As\u003csup\u003e5+\u003c/sup\u003e rapidly occupies accessible adsorption sites on the solid adsorbents surface, with \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eDR\u003c/em\u003e\u003c/sub\u003e values ranging from 0.8934 to 1.0641 kJ/mol. This suggests that physical sorption is the major mechanism.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e: Nonlinear Langmuir (a), Freundlich (b), Temkin (c), and D-R (d) fitting for As\u003csup\u003e5+\u003c/sup\u003e adsorption onto C, CCS, and CCSG (T\u0026thinsp;=\u0026thinsp;27 \u003csup\u003eo\u003c/sup\u003eC, C\u003csub\u003ei\u003c/sub\u003e = up to 500 mg/L, solid dose 1.0 g/L, pH\u0026thinsp;=\u0026thinsp;6, t\u0026thinsp;=\u0026thinsp;25 min).\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e: Kinetic, isotherm nonlinear, and thermodynamic parameters for the adsorption of As\u003csup\u003e5+\u003c/sup\u003e onto C, CCS, and CCSG at 27 \u003csup\u003eo\u003c/sup\u003eC.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section3\"\u003e \u003ch2\u003e3.2.5 Effect of adsorbate solution ionic strength\u003c/h2\u003e \u003cp\u003eBatch tests were assumed to investigate the effect of foreign ions on adsorption system at various concentrations of NaCl to simulate real-world adsorption conditions, and the results are given in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea. Each NaCl solution is given at different dosage to achieve a range of ionic strength (\u0026micro;, 0.05\u0026ndash;0.40 mol/L). The As\u003csup\u003e5+\u003c/sup\u003e initial concentration was kept at 400 mg/L, and the solution volume was 25 mL with 1.0 g/L of adsorbent dosage (C, CCS, and CCSG) at 27 \u003csup\u003eo\u003c/sup\u003eC. Obviously, the quantity of As\u003csup\u003e5+\u003c/sup\u003e adsorbed decreases as the ionic strength rises from NaCl \u0026micro;, 0.05\u0026ndash;0.40 mol/L. The attachment of As\u003csup\u003e5+\u003c/sup\u003e ions to the surface of C, CCS, and CCSG is hampered by the interference of sodium and chloride ions (Makhlouf et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Increasing the ionic strength of the adsorption solution from nearly \u0026micro;\u0026thinsp;\u0026asymp;\u0026thinsp;0.05 to \u0026micro;\u0026thinsp;\u0026asymp;\u0026thinsp;0.40 reduces As\u003csup\u003e5+\u003c/sup\u003e removal from 43 to 26%, 65 to 48%, and 94 to 77% for C, CCS, and CCSG, respectively (with nearly 17% decrease). External ions (Na\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e\u0026minus;\u003c/sup\u003e) can greatly increase the thickness of the diffuse electric double layer, which protects adsorbents and As\u003csup\u003e5+\u003c/sup\u003e in solution. This keeps As\u003csup\u003e5+\u003c/sup\u003e and adsorbent particles from coming too close together, lowering their electrostatic attraction and slowing the adsorption process. Higher electrolyte concentrations can cause electrolyte ions to block surface negative charges, reducing the overall quantity of As\u003csup\u003e5+\u003c/sup\u003e adsorbed. Although foreign ions have a negative impact on the adsorption efficiency, this percentage indicates that even at elevated concentrations of interferents ions, the prepared samples (C, CCS, and CCSG) exhibit accepted selectivity for the uptake of As\u003csup\u003e5+\u003c/sup\u003e ions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section3\"\u003e \u003ch2\u003e3.2.6 Influence of adsorption temperature and thermodynamic parameters\u003c/h2\u003e \u003cp\u003eIt's important to analyze the obtained parameters of thermodynamic (\u003cem\u003eΔS\u0026deg;\u003c/em\u003e, \u003cem\u003eΔH\u0026deg;\u003c/em\u003e, and \u003cem\u003eΔG\u0026deg;\u003c/em\u003e), which indicate changes in entropy, enthalpy, and free energy to realize the energetics of As\u003csup\u003e5+\u003c/sup\u003e removal by C, CCS, and CCSG. The parameters (\u003cem\u003eΔS\u0026deg;\u003c/em\u003e and \u003cem\u003eΔH\u0026deg;\u003c/em\u003e) were obtained using the Van\u0026rsquo;t Hoff equation (Eq.\u0026nbsp;14, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb), whereas \u003cem\u003e∆G\u0026deg;\u003c/em\u003e (free energy change) was calculated using Eq.\u0026nbsp;15. These values are shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The adsorption followed the temperature coefficient, as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb by the strong linear relationship between \u003cem\u003eLn (K\u003c/em\u003e\u003csub\u003e\u003cem\u003eS\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e)\u003c/em\u003e and \u003cem\u003e1/T\u003c/em\u003e. The higher correlation coefficients (\u003cem\u003eR\u003c/em\u003e\u003csup\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sup\u003e) values for the Van't Hoff plot, which ranged between 0.9186 and 0.9307, demonstrate the model's applicability. It is confirmed that the adsorption process is endothermic in nature requiring additional energy based on the calculated positive value of \u003cem\u003eΔH\u0026deg;\u003c/em\u003e. This is due to the fact that solvated water molecules must be displaced by As\u003csup\u003e5+\u003c/sup\u003e ions. (Ananta et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The heat values for physical adsorption range from 20\u0026ndash;40 kJ/mol and chemisorption from 40\u0026ndash;400 kJ/mol. According to our results, the values of \u003cem\u003eΔH\u0026deg;\u003c/em\u003e (4.6216\u0026ndash;6.4387 kJ/mol) demonstrated a physical adsorption process. The increase in \u003cem\u003eΔS\u0026deg;\u003c/em\u003e values implies a rise in system entropy due to randomness at the interface between solid surface and liquid phases. This rise in entropy is caused by the displacement of water molecules by As\u003csup\u003e5+\u003c/sup\u003e ions to adsorb on the surface of adsorbents. Moreover, the decrease in \u003cem\u003eΔG\u0026deg;\u003c/em\u003e values suggest that As\u003csup\u003e5+\u003c/sup\u003e adsorption by all solid adsorbents is thermodynamically viable and spontaneous. As temperature increases, the value of \u003cem\u003eΔG\u0026deg;\u003c/em\u003e lowers, indicating that As\u003csup\u003e5+\u003c/sup\u003e adsorption is increasingly practicable (Mahmoud et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). In general, physical adsorption has a lower \u003cem\u003e∆G\u0026deg;\u003c/em\u003e (-20 to 0 kJ/mol) compared to chemical adsorption (-80 to -400 kJ/mol). As a result, the adsorption of As\u003csup\u003e5+\u003c/sup\u003e was classified as physical adsorption based on the negative values of \u003cem\u003e∆G\u0026deg;\u003c/em\u003e (3.1727\u0026ndash;7.7476 kJ/mol).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec23\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Desorption and reusability of solid adsorbents\u003c/h2\u003e \u003cp\u003eAn ideal adsorbent should have elevated adsorption capacity and properties of desorption efficient for purpose of reduction the treatment cost (Moslehi et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). This study tested the stability and reusability of adsorbents (C, CCS, and CCSG) using 0.1 mol/L desorbing agent (dist. water, HCl, HNO\u003csub\u003e3\u003c/sub\u003e, ethylene diamine, cysteine, and EDTA) to desorb As\u003csup\u003e5+\u003c/sup\u003e. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec displays the efficiency of desorption (\u003cem\u003eD.E%\u003c/em\u003e, Eq.\u0026nbsp;16) of As\u003csup\u003e5+\u003c/sup\u003e from the C, CCS, and CCSG surface, with different solutions. EDTA is the most effective solvent for pre-adsorbed As\u003csup\u003e5+\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe removal efficacy of As\u003csup\u003e5+\u003c/sup\u003e by C, CCS, and CCSG reduced after the first and sixth cycles, as follows in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed: 43\u0026ndash;40%, 64\u0026ndash;58%, and 94\u0026ndash;90% for C, CCS, and CCSG, respectively. After six cycles of sorption and desorption, the As\u003csup\u003e5+\u003c/sup\u003e sorption capacity of solid adsorbents reduced slightly. Higher removal rates in the first cycle of applications can be related to the presence of abundant more active sites. After the first sorption-desorption cycle, As\u003csup\u003e5+\u003c/sup\u003e sorption decreased slightly during the other regeneration cycles. This could be due to adsorbent binding sites saturation or a partial loss of the adsorbent's uptake sites during the cleaning phase of the adsorption-desorption test (Saning et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e: Effect of ionic strength (a), Van\u0026rsquo;t Hoff plot (b), desorption study of As\u003csup\u003e5+\u003c/sup\u003e (c), and reusability (d) of C, CCS, and CCSG after six adsorption/desorption cycles (T\u0026thinsp;=\u0026thinsp;27 \u003csup\u003eo\u003c/sup\u003eC, C\u003csub\u003ei\u003c/sub\u003e = 400 mg/L, dosage 1.0 g/L, pH\u0026thinsp;=\u0026thinsp;6, t\u0026thinsp;=\u0026thinsp;25 min).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Comparing CCSG with other solid adsorbents\u003c/h2\u003e \u003cp\u003eThe maximum adsorption capacity of various adsorbents in comparison with CCSG are portrayed in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e (Hu et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Liu et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Basu et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Pervez et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Sahu et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Din et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The outcomes in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e show that CCSG has competitive As\u003csup\u003e5+\u003c/sup\u003e ions adsorption capability. The newly synthesized adsorbent (CCSG) is a favorable and exceptional solid adsorbent for removing As\u003csup\u003e5+\u003c/sup\u003e ions in a variety of applications.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of CCSG with other As\u003csup\u003e5+\u003c/sup\u003e biosorbents.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAdsorbents\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eX\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e (mg/g)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eRef.\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMagnetic chitosan/biochar composite (MCB)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e17.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(Liu et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2017\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eβ-FeOOH@GO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e69.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(Pervez et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2021\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eFeOx-GOCS-0.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e61.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(Liu et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2024\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eGO-MnO\u003csub\u003e2\u003c/sub\u003e-Goe-Ca-Alg beads\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e34.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(Basu et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2021\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eEleocharis dulcis\u003c/em\u003e biochar loaded with CuO (EDB-CuO)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e26.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(Din et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2024\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIron-impregnated biochar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(Hu et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2015\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMPAC-500 and MPAC-600 (magnetic-activated carbons synthesized from the peel of Pisum sativum pea)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.4930 and 0.9451 respectively\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(Sahu et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2022\u003c/span\u003e)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCCSG\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e376.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eThis study\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4 Conclusion","content":"\u003cp\u003eUsing natural solid adsorbents in wastewater treatment procedures is a prospective methodology for removing heavy metals from polluted water. Herein, As\u003csup\u003e5+\u003c/sup\u003e removal from aqueous medium was examined by the static batch adsorption procedures employing adsorbents such as date palm fiber biochar (C) and date palm fiber biochar/chitosan nanoparticles (CCS), which were then enhanced with glutamine (CCSG). Inserting chitosan and glutamine into date palm fiber biochar through composite matrix synthesis produced unique surface chemical functional groups on the CCSG surface. This led to increased activity at surface sites and more exterior pores. SEM analysis revealed that the adsorbents had a porous and uneven surface that facilitates As\u003csup\u003e5+\u003c/sup\u003e ion adsorption. Adsorption kinetic data followed pseudo-first order equation, with Langmuir isotherm model more compatible with As\u003csup\u003e5+\u003c/sup\u003e data. Based on the Langmuir isotherm nonlinear model, the CCSG composite had a maximum capacity of adsorption of 376.0 mg/g, with adsorption equilibrium attained after 25 min. Thermodynamic explorations indicate that the adsorption procedure is both spontaneous and endothermic. According to prior results, the adsorption of As\u003csup\u003e5+\u003c/sup\u003e by the produced solid materials exhibited monolayer sorption. Previous research has shown that CCSG has exceptional adsorption and unique properties for wastewater treatment. Authors should pay special attention to biopolymer materials and solid agricultural waste in environmental applications because of their natural abundance, eco friendliness, increased sustainability, and biodegradability.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor contributions\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp;All authors [\u003c/em\u003eAl Isaee Khalifa,\u0026nbsp;Laila M. Alshandoudi, Asaad F. Hassan, and Amany G. Braish\u003cem\u003e] contributed to the study conception and design, materials preparation, data collection and analysis.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e This study was funded by Ministry of Higher Education, Research and Innovation of Sultanate of Oman number BFP/GRG/EBR/2023/158.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eConflict of interest:\u0026nbsp;\u003c/strong\u003eThere are no conflicts to declare.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eEthical approval:\u0026nbsp;\u003c/strong\u003eNot applied. This study did not involve human participants and/or animals.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;Consent to participate:\u0026nbsp;\u003c/strong\u003eNot applied\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;Consent for publication:\u0026nbsp;\u003c/strong\u003eNot applied\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u0026nbsp;Competing interests:\u0026nbsp;\u003c/strong\u003eThe authors declare no competing interests\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials:\u0026nbsp;\u003c/strong\u003eIt is available upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAdeogun AI, Babu RB (2021) One-step synthesized calcium phosphate-based material for the removal of alizarin S dye from aqueous solutions: isothermal, kinetics, and thermodynamics studies. 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Water, Air, Soil Pollut 231:1\u0026ndash;19\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Date palm, biochar, chitosan, nanocomposite, adsorption, arsenic","lastPublishedDoi":"10.21203/rs.3.rs-5256147/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5256147/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn the current work, three adsorbent materials were developed; biochar derived from date palm fiber (C), date palm fiber biochar/chitosan nanoparticles (CCS), and biochar/chitosan nanoparticles composite supplemented with glutamine (CCSG). These compounds were used as solid adsorbents to remove As\u003csup\u003e5+\u003c/sup\u003e from polluted water. Several characterization approaches were used to investigate all the synthesized solid adsorbents, including TGA, N\u003csub\u003e2\u003c/sub\u003e adsorption/desorption isotherm, SEM, TEM, ATR-FTIR, and zeta potential. CCSG demonstrated good thermal stability, with a maximum specific surface area of 518.69 m\u003csup\u003e2\u003c/sup\u003e/g, a microporous radius of 0.97 nm, total pore volume of 0.25 cm\u003csup\u003e3\u003c/sup\u003e/g, an average particle size of 38 nm, and pH\u003csub\u003epzc\u003c/sub\u003e of 6.9. To optimize the reaction conditions, various sorption factors were examined, including contact time, pH, initial As\u003csup\u003e5+\u003c/sup\u003e concentration, adsorbent dosage, temperature, and ionic strength. The study found that the modified samples were able to remove more As\u003csup\u003e5+\u003c/sup\u003e (CCS; 256.0 mg/g and CCSG; 376.0 mg/g) than unmodified ones (C; 150.5 mg/g). The As\u003csup\u003e5+\u003c/sup\u003e removal procedure corresponded well with Langmuir isotherm model. Thermodynamic and kinetic experiments show that the Elovich, PFO, and Van't Hoff plot with endothermic, spontaneous, and physisorption nature are the best fitted models. EDTA has the highest desorption efficiency percentage (98.8%). CCSG demonstrated enhanced reusability after six application cycles of As\u003csup\u003e5+\u003c/sup\u003e adsorption/desorption, with only a 4% decrease in the efficiency of adsorption. This study demonstrates that CCSG effectively remove As\u003csup\u003e5+\u003c/sup\u003e in wastewater and use agricultural solid waste residues (date palm fiber; DPF) for environmental remediation purposes.\u003c/p\u003e","manuscriptTitle":"Effective removal of As5+ from aqueous medium using date palm fiber biochar/chitosan/glutamine nanocomposite: kinetic and thermodynamic studies","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-10-24 08:44:02","doi":"10.21203/rs.3.rs-5256147/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revision","date":"2024-11-23T15:22:05+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-10-22T15:52:50+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-10-22T15:09:43+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Environmental Science and Pollution Research","date":"2024-10-21T09:06:45+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-10-16T04:17:36+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2024-10-15T04:37:16+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"74805a5f-dc94-4ba1-9340-13da2a6c01d7","owner":[],"postedDate":"October 24th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-01-27T16:05:58+00:00","versionOfRecord":{"articleIdentity":"rs-5256147","link":"https://doi.org/10.1007/s11356-025-35896-5","journal":{"identity":"environmental-science-and-pollution-research","isVorOnly":false,"title":"Environmental Science and Pollution Research"},"publishedOn":"2025-01-20 15:57:28","publishedOnDateReadable":"January 20th, 2025"},"versionCreatedAt":"2024-10-24 08:44:02","video":"","vorDoi":"10.1007/s11356-025-35896-5","vorDoiUrl":"https://doi.org/10.1007/s11356-025-35896-5","workflowStages":[]},"version":"v1","identity":"rs-5256147","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5256147","identity":"rs-5256147","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}