Characterization of phosphate modified red mud based composite materials and study on heavy metal adsorption

Characterization of phosphate modified red mud based composite materials and study on heavy metal adsorption | 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 Characterization of phosphate modified red mud based composite materials and study on heavy metal adsorption Wenlou Jin, Yanzhi Yang, Jiacheng Jin, Mingchen Xu, Zhipeng Zhang, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3798495/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 21 Jun, 2024 Read the published version in Environmental Science and Pollution Research → Version 1 posted 4 You are reading this latest preprint version Abstract In this paper, Bayer red mud (RM) and lotus leaf powder (LL) were used as the main materials, and KH 2 PO 4 was added to modify the material. Under the condition of high temperature carbonization, RMLL was prepared and phosphate modified red mud matrix composite (PRMLL) was prepared based on KH 2 PO 4 modification, which can effectively remove Pb 2+ from water. The optimum preparation and application conditions were obtained by orthogonal experiment: dosage 0.1g, ratio 1:1 and temperature 600℃. The effects of PH, dosage and initial concentration on the adsorption of Pb 2+ were studied. The pseudo-first-order, pseudo-second-order and Elovich kinetic models were fitted to the experimental data, and it was found that RMLL and PRMLL were more consistent with the pseudo-second-order kinetic model and chemisorption. Langmuir, Freundlich, Timkin and Dubinin-Radushkevich isothermal adsorption models were used to fit the experimental data, and it was found that RMLL and PRMLL were more consistent with Langmuir model. In addition, the maximum adsorption capacity of RMLL and PRMLL was 188.1mg/g and 213.4mg/g respectively. Are larger than the adsorption capacity of their monomers. Therefore, the use of RMLL and PRMLL as the removal of Pb 2+ from water is a potential application material. red mud Lotus leaf Adsorption KH2PO4 Resource utilization Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Introduction Red mud is a kind of alkaline industrial hazardous waste in alumina industrial production, which contains a variety of heavy metals and other harmful substances, and is extremely difficult to dispose of. China is a big producer of alumina industry, and in 2019, its output accounted for about 64% of the world(Wei et al. 2019 ),(Wang et al. 2019 ). Therefore, China has a huge stock of red mud, and millions of tons of red mud are piled up every year. If handled improperly, it will cause immeasurable damage to the environment and even endanger human health. How to treat and utilize red mud effectively and realize resource utilization has become a difficult problem and an urgent problem to be solved by researchers all over the world. Secondly, lead is the most common toxic heavy metal, a large amount of inhalation of human body and animals and plants have great harm. For example, excessive accumulation in the human body may lead to anemia, neurological disorders and even death.According to the World Health Organization, the concentration of Pb 2+ in water should not exceed 0.001mg/L (Elebi et al. 2020 ). The main components of red mud are Fe 2 0 3 , AI 2 O 3 , CaO, TiO, Na 2 O and SiO 2 , and also contain some trace elements, such as K, Ba, Cu, Mn, Zn, S and a small amount of rare earth elements(Khairul et al. 2018 ). Red mud also has the characteristics of porous structure, very fine dispersion, high specific surface area and good adsorption properties. Therefore, red mud can not only extract some rare elements with high added value, but also be used as an adsorbent and passivator that can deal with environmental heavy metal pollution. Many scholars have done a lot of research on the application of red mud in environmental governance. For example, protonated RM is used to repair lead-arsenic contaminated soil, significantly reducing the cumulative concentration of lead and arsenic in rape, and blocking the diffusion of Pb and As to native plants(Yang et al. 2021 ).The synthesis of Fe 3 O 4 nanoparticles dissolved and precipitated iron in red mud with NaOH in aqueous solution. It was found by adsorption experiment that the removal rate of As could be improved by decreasing PH value in a certain range(Akin et al. 2012 ). Using waste wine lees and red mud, a cheap and highly adsorbent magnetic material was prepared by hydrothermal treatment. The results show that the magnetic hydrocarbon has adsorption effect on Pb 2+ in water, and the experiment shows the reusability and good adaptability of this magnetic material(Kazak &Tor 2020 ). Red mud/graphite composite (RM-CN) was synthesized from graphite carbon nitride (g-C3N4) and red mud by one-step thermal polymerization. RM-CN can absorb organic pollutants such as tetracycline (TC), chloromycin (CTC) in water(A et al.). Conversion of Fe 2 O 3 , Al and Si from waste RM to low-cost Fe 2 O 3 -ANA zeolite can effectively inhibit the migration of HM in soil and reduce the bioaccumulation concentration of HM in harvested rapeseed(Yang et al. 2022 ). There are also some studies that modified biochar with red mud can significantly improve the adsorption capacity of Cd 2+ and Cr 6+ , and the removal rate of heavy metal ions in water is as high as 99%(Wang et al. 2022 ). It was also found that calcium dihydrogen phosphate Ca(H 2 PO 4 ) 2 was added to the straw raw material at a ratio of 20% (w/w) to form biochar through pyrolysis treatment, which could effectively improve the carbon retention rate and strengthen the stability of biochar(Li et al. 2014 ). The replication decomposition of sludge with phosphate and carbonate, especially phosphate, is an effective method to prepare sludge-based biochar which immobilized toxic elements and improved the chemical stability of carbon(Xu et al. 2017 ). At the same time, phosphorus-containing materials can also effectively remove heavy metals, the mechanism is that its PO 4 3− can form phosphate precipitation with heavy metals, reduce the activity of heavy metals, and reduce its harm to the water and soil environment. The results show that red mud and biochar have a good effect on the treatment of heavy metals. Therefore, the preparation of a new type of material using red mud and easily available biochar, then modified with appropriate phosphate, has great potential for treating heavy metal pollution in water and soil(Conceio et al. 2021 , Elebi et al. 2020 , Krishnani et al. 2008 ). In view of the above research, this study prepared the composite material of carbonized red mud and lotus leaf powder, and modified it by phosphate on this basis, and evaluated its removal ability of Pb 2+ in water and environmental applicability. The effect of preparation and application parameters on the adsorption of Pb 2+ was studied. The adsorption process was studied by kinetic and isothermal adsorption models, and the adsorption mechanism was explored. Materials and methods Materials The red mud used in this study is Bayer process red mud, which is taken from an aluminum company in Zibo City, Shandong Province, China. The red mud is air-dried under natural conditions, then passed through a 100-mesh sieve, collected for use. Lotus leaves are taken from the lotus pond of the school, the lotus leaves are dried in the oven, and then crushed with a grinder, after 100 mesh sieve, collected for use.The water used for the test was deionized water, and the reagents used included HCl (37%), Pb(NO 3 ) 2 (99%), NaOH (97%), CH 3 COOH (99%) and KH 2 PO 4 (analytically pure), which were purchased from Shanghai Sinopharm Group. Chemical element analysis of raw red mud and 600℃ carbonized lotus leaves is shown in supporting document (S1). Preparation of RMLL and PRMLL materials First, the red mud and lotus leaf powder are evenly mixed according to their mass in a certain ratio, and then compacted in the crucible, and then raised to a certain temperature at 10℃/min in the pushed tube furnace, and kept for 3h. During the calcination process, nitrogen is passed through the whole process until it is cooled to room temperature. The preparation of PRMLL material is based on the best conditions for preparing RMLL material. Firstly, a certain amount of KH 2 PO 4 is evenly mixed with lotus leaf powder, dissolved in deionized water, dried in the oven at 80℃, and then collected for use after grinding through a 100-mesh sieve. Then a certain amount of red mud is added into the tube furnace for calcination, and the calcination requirements are consistent with the preparation of RMLL materials. After the material is prepared, it is cleaned with deionized water, pumped and filtered until neutral, dried and collected for use. Adsorption experiment A certain amount of Pb(NO 3 ) 2 was weighed and a Pb 2+ solution with a concentration of 1000mg/L was prepared. In subsequent experiments, the solution concentrations used were diluted from the standard solution. Specifically, 50mL of lead solution with a concentration of 500mg/L was added to a 150mL conical bottle, and then 0.1g of RMLL and PRMLL materials were added to the solution respectively. Adjust the PH to the desired value with 1% HCl or 1mol/L NaOH solution. After oscillating at 25℃ and 160r/min for 12h in a constant temperature oscillator, samples were taken and filtered, and the solubility of Pb 2+ in the adsorbed solution was determined by flame atomic spectrophotometer (AAS). See supporting document (S2) for the calculation formula of adsorption capacity(Shirzadi &Nezamzadeh-Ejhieh 2017 ). The adsorption kinetics experiment is the same as the experiment above, sampling at a specific time to measure the residual Pb 2+ concentration in the solution. The adsorption properties were studied by fitting the pseudo-first-order kinetics, pseudo-second-order kinetics and Elovich kinetics models. See supporting document (S3) for the model formula(Bagla &Khilnani 2016 , Blanchard et al. 1984 ). In the isothermal adsorption experiment, the previously configured 1000mg/L lead solution was diluted to 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000mg/L according to the needs, and 50mL of the corresponding solubility lead solution was successively added into a 150mL conical bottle. After adjusting the PH, 0.1g of RMLL and PRMLL materials were added respectively, and the oscillating rate was 160r/min at 25℃. After 12h, samples were taken respectively. The equilibrium adsorption capacity of the two materials for different initial concentrations of Pb 2+ in solution was calculated by Eq. ( 1 ).Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isothermal adsorption models were used for fitting, and their formulas are shown in supporting document (S4)(Freundlich 1906 , Langmuir 1917 ). Characteristic description Various analytical instruments (BET, XPS, SEM-EDS, AAS, XRD, FTIR) characterize the obtained materials and determine the concentration of Pb 2+ in the solution, detailed in the Supplementary material document (S6). Results and discussions Optimization of RMLL and PRMLL preparation Orthogonal experiments are designed. For details of orthogonal experiments, see supporting document (S5). The optimum preparation conditions of RMLL materials (temperature 600℃, mass ratio 1:1 and Bayer red mud) were obtained by orthogonal experiment. Then, on the basis of preparing RMLL materials, KH2PO4, which accounted for 15% of the mass of lotus leaves, was first uniformly mixed with lotus leaves, dissolved with deionized water, dried and ground, and then mixed with red mud according to the mass ratio of 1:1, and calcined at 600℃ without oxygen for 3h. Phosphate - lotus leaf - red mud composite material (0.15:1:1) was prepared. The adsorption properties of RMLL and PRMLL were compared. The specific preparation process is shown in Fig. 1. Characterization of RMLL and PRMLL materials As shown in Fig. 2 (a), the crystal phase composition of the original red mud and the modified red mud matrix composite was measured by XRD, and the results showed that the original red mud contained a high content of hematite (Fe 2 O 3 ). After calcination without oxygen at 600℃, calcite (CaCO 3 ), magnetite (Fe 3 O 4 ), quartz (TiO 2 ) and various metal-organic complexes were detected in RMLL (Li et al. 2019).It was further confirmed that a series of chemical reactions occurred between red mud and lotus leaves in the process of oxygen-free calcination, and new substances were produced. The XRD results of the phosphate-modified red mud substrate (PRMLL) are basically consistent with RMLL, and magnetite (Fe 3 O 4 ) and some phosphorous compounds are produced. The presence of these substances plays an important role in the removal of Pb 2+ . Figure 2 (b) shows the FTIR spectra of LL, RMLL and PRMLL. After carbonization of LL at 600℃, the stretching vibration peak of -OH at wave number 3415.99cm − 1 was found (Renli et al. 2019), It is probably formed by the water in the lotus leaves and a lot of cellulose expansion vibration; The wave numbers 877.4 cm − 1 , 2848.8cm − 1 , and 2918.3 cm − 1 are C-H bonds (Jian-Liang et al. 2014, Yu 2019). The wave numbers 1412.5 cm − 1 and 1577.9cm − 1 are -COO bonds, indicating that lotus leaves retain some functional groups at 600℃ carbonization, which is favorable for the adsorption of lead ions (Dinh et al. 2020). The infrared spectra of RMLL and PRMLL were basically consistent. Fe-O bonds were detected at wavelengths 441.4cm − 1 and 561.5cm − 1 , which may be the reason why Fe 3 O 4 was formed after high temperature carbonization with lotus leaf powder in Bayer red mud(Yu 2019). Compared with RMLL, PRMLL has more P-O bonds, the wave number is 1258.7cm − 1 , and there is a C = C bond at 1632.1cm − 1 (Kwon et al. 2013). It is also found that the wavelength of -OH in PRMLL is shorter than that of LL and RMLL, because the presence of C = C bond and -OH group is required for phosphate adsorption, which also indicates that the reaction may occur at high temperature carbonization, and phosphate is successfully adsorbed on the material RMLL (Zhang et al. 2019). Compared with material LL, PRMLL and RMLL have larger difference and higher peak at wavelength 1000 cm − 1 , which is formed by tensile vibration of metal bond, material LL is C-O bond, PRMLL and RML are Si(Al)-O (Jian-Liang et al. 2014, Li et al. 2020).It also shows that these metallic carbon-oxygen bonds are successfully loaded on lotus leaf biochar under the action of red mud. Figure 2. (c), (d), (e) and (f) respectively show the SEM of LL, RM, RMLL and PRMLL under different magnifications. By comparing the microscopic morphology of several different materials, it can be clearly seen that the surface of raw red mud (RM) is rough, with heterogeneous aggregates and large pore structure. After carbonization at 600℃, lotus leaves (LL) have smooth surface, block and strip distribution, compact structure, and large single volume. RMLL can clearly see that a large amount of red mud is loaded on the smooth LL surface. In the process of carbonization, adding red mud can better induce LL skeleton to form more porous structures. After the addition of phosphorus KH 2 PO 4 , the surface of the PRMLL is not only loaded with a large amount of red mud, but also some fine particles on the surface, which may be the phosphate substance loaded on the surface under the action of high temperature with the addition of KH 2 PO 4 . Figure 3. (a) shows the desorption and adsorption curves of the three materials. It can be seen from the diagram that the area enclosed by the desorption curves of RMLL and PRMLLIs is obviously larger than that enclosed by LL. It shows that the specific surface area of the monomer material has changed after composite modification, and it has expanded several times, which is more advantageous to the removal of lead ions. Figure 3 (b) is the pore size distribution diagram of the three materials. It can be seen from the figure that most of the pore sizes of the three materials are distributed between 5 and 50nm. It also shows that the three materials are mesoporous materials. The specific surface area, total pore volume and average pore diameter data of the three materials are shown in Table 1. Table 1 Specific surface area, total pore volume and pore size data tables for LL, RMLL and PRMLL Materials Specific surface area(m 2 g − 1 ) Total pore volume(cm 3 g − 1 ) Mean aperture(nm) LL 2.808 0.0275 39.216 RMLL 19.714 0.088 17.871 PRMLL 23.675 0.086 15.492 Effects of PH, dosage and initial concentration For lead, the PH level has a huge impact on it. PH has an important influence on the morphology of heavy metals and the surface charge characteristics of biochar based adsorbents. The result is shown in Fig. 4 (a). The adsorption capacity of RMLL and PRMLL for Pb 2+ increased with the increase of PH. At PH 2, the adsorption capacities of RMLL and PRMLL for Pb 2+ were 37.23mg/g and 53.82mg/g, respectively. When PH was 7, the adsorption capacities of RMLL and PRMLL were 217.63mg/g and 232.96mg/g, respectively. When PH is 6 ~ 7, the increase of adsorption capacity has gradually leveled off. PH is too low, the adsorption capacity of the material is poor, because the content of H + in the solution is high, and Pb 2+ has a competitive adsorption reason. Secondly, the two materials are based on lotus leaf biochar as the carrier and loaded with red mud as the main material. The positive charge on the surface repels the positive valence metal ion charge, which will also make the adsorption performance of the material worse (Huang et al. 2020, Yang et al. 2019). The increase of PH and the surface negative charge of the two materials are conducive to the adsorption of lead ions (Liu et al. 2022). At the same time, CO 3 2− , PO 4 3− and SO 4 2− can form precipitates with Pb 2+ , which increases the adsorption of Pb 2+ by the two materials (Luu et al. 2022). Based on the above analysis and combined with Fig. 4, the adsorption of Pb 2+ by RMLL and PRMLL was studied, and the solution PH was 7. Figure 4(b) shows the RMLL and PRMLL Zate potential plots, indicating a strong negative potential at PH 4 ~ 10,which may have strong surface charge adsorption ability for positively charged cations. As shown in Fig. 4 (c), when the dosage of RMLL and PRMLL increased from 0.05g to 0.4g, the adsorption capacity of Pb 2+ decreased from 235.98mg/g and 259.25mg/g to 62.5mg/g and 62.5mg/g, respectively. On the contrary, the removal rate of Pb 2+ increased with the increase of dosage. It may be because the dosage is at a low level, and the solubility of Pb 2+ is high, and the adsorption sites provided by the material are limited. When the dosage increased to 0.35g, the removal rate of Pb 2+ reached 100%, because with the increase of the dosage of materials, the surface functional groups and adsorption sites of the materials also increased, and the removal rate of lead ions increased. The adsorption capacity and removal rate of Pb 2+ by RMLL and PRMLL have an intersection point, and its value ranges from 0.1 to 0.125, which is basically consistent with the results of orthogonal experiment. Considering the adsorption capacity and cost of materials, the dosage of this project is set at 0.1g for subsequent research. Figure 4 (d) shows the adsorption capacity and removal rate of Pb 2+ by RMLL and PRMLL at different initial concentrations, PH 7, dosage 0.1g, and temperature 25℃. As can be seen from the figure, with the increase of the initial concentration, the removal rate of Pb 2+ of the two materials continued to decline. However, with the gradual increase of the initial concentration, the equilibrium adsorption capacity of RMLL and PRMLL materials also gradually increased, and reached an equilibrium state when the concentration was 700mg/L, and the equilibrium adsorption capacity was 181.5mg/g and 214.66mg/g, respectively. When the solution concentration is low, RMLL and PRMLL materials have more active sites and can carry out sufficient ion exchange with Pb 2+ . At the same time, with the increase of concentration, a large amount of Pb 2+ occupied the active site of the material, reaching a saturated state, inhibiting the adsorption of Pb 2+ on its surface, resulting in a decrease in the removal rate. Adsorption kinetics As shown in Fig. 5 (a), the adsorption of lead ions by RMLL and PRMLL2 materials has been increasing uniformly over time in the first 12 hours. From the 12th hour, its adsorption capacity has been in a relatively balanced state. Therefore, in the first 12 hours, the adsorption capacity of RMLL and PRMLL for lead ions has reached the adsorption equilibrium state, in which the equilibrium adsorption capacity of RMLL is 190.25mg/g, and the equilibrium adsorption capacity of PRMLL is 220.4mg/g. This is due to the fact that sufficient adsorption sites and the driving force of a large concentration gradient can lead to an initial rapid increase in adsorption capacity (Wang et al. 2020). As the adsorption site is gradually occupied, the repulsive force on the solid-liquid interface increases, the adsorption rate decreases, and finally the adsorption equilibrium is reached (Hang et al. 2019b, Lyu et al. 2021, Wei et al. 2018). Figure 5 (b) (c) (d) is the fitting diagram of pseudo-first-order, pseudo-second-order and Elovich kinetic models of RMLL and PRMLL2 materials. It can be seen that the R 2 of the pseudo-second-order kinetic model of RMLL and PRMLL are 0.9993 and 0.9994 respectively, which are higher than the R 2 of 0.99516 and 0.99607 of the first-order kinetic model. The fitted qt values of 190.25mg/g and 219.6mg/g are closer to the experimental values of 191.1mg/g and 220.4mg/g, respectively. The R 2 values fitted by Elovich kinetics are 0.987 and 0.982 respectively, which are lower than the second-order kinetics. Therefore, it can be better explained that the second-order kinetic model is more consistent with the adsorption process of Pb 2+ by RMLL and PRMLL materials, and that the adsorption process of these two materials is also a chemical adsorption process. Isothermal adsorption model Adsorption experiments were conducted at different initial Pb 2+ concentrations to obtain adsorption isotherms, and experimental data and the fitting curves of Langmuir and Freundlich isotherms were drawn, as shown in Fig. 6. Figure 6 (a) shows that the equilibrium adsorption capacity changes with the initial Pb 2+ concentration. When the concentration is below 700mg/L, the equilibrium adsorption capacity of RMLL and PRMLL for Pb 2+ shows a uniform upward trend with the increase of the concentration, and then slowly rises to the saturation state. It is possible that when the concentration is low, the amount of pollutants is much lower than the adsorption capacity of the material, and the change of the concentration gradient increases the resistance to overcome the mass transfer at the solid-liquid interface (A et al. 2019) . At high concentrations, the resistance between the adsorbent surface and the solution increases rapidly, making the equilibrium adsorption capacity increase slowly and reach the saturated adsorption capacity. Figure 6 (b) (c) shows the data fitting graphs of Langmuir, Freundlich and Temkin isothermal adsorption models of RMLL and PRMLL respectively. Figure 6 (d) is the fitting diagram of RMLL and PRML Dubinin-Radushkevich isothermal adsorption model. It can be seen that both RMLL and PRMLL materials can be well described by Langmuir, Freundlich, Temkin and D-R isothermal absorption equations. The \(R_{1}^{2}\) values of RMLL and PRMLL materials are 0.989 and 0.989, respectively, which are larger than 0.973 and 0.937 of\(R_{2}^{2}\), 0.964 and 0.961 of \(R_{3}^{2}\)and 0.898 and 0.938 of\(R_{4}^{2}\), indicating that these two materials are more consistent with Langmuir isothermal adsorption model. In the Dubinin-Radushkevich isothermal adsorption model, the E value between 8 and 16kj.mol indicates chemical adsorption, while the E value less than 8 kJ.mol indicates physical adsorption (Ecer 2018, Hang et al. 2019a, Yilmaz et al. 2018). In the D-R model fitting of RMLL and PRMLL, the E values of RMLL and PRMLL are 1.912 and 2.637, both of which are less than 8kj.mol. It is possible that the two materials in the chemical adsorption at the same time, there are physical adsorption reasons. The 1/n of RMLL and PRMLL materials are both between 0.1 and 0.5, indicating that carbonized red mud-Lotus leaf (RMLL) and phosphate-modified red mud-Lotus leaf (PRMLL) can be easily adsorbed, and the adsorption capacity of phosphate-modified red mud-lotus leaf is stronger than that of carbonized red mud-lotus leaf (Lyu et al. 2021). In addition, it can be seen from Table 3 that the \({k_L}\)value of RMLL and PRMLL2 materials is 0.11294 and 0.13636, which is between 0 and 1, which means that the adsorption process of the material is favorable (Al-Ghouti et al., Zeng et al. 2020). Relevant studies show that the adsorption capacity of red mud matrix composites is obviously better than that of some common biochar materials, aerogel, iron matrix and clay mineral composites (Zeng et al. 2020). Therefore, the removal of heavy metal ions from water by red mud matrix composite is a potential material. In addition, it can also alleviate the accumulation of red mud and reduce some problems such as environmental pollution, which is consistent with the concept of sustainable development advocated at present. Table 3 Calculated isotherm parameters for Pb 2+ absorption on RMLL and PRMLL. Models Parameters Material RMLL PRMLL Langmuir \({q_m}\)(mg/g) 189.496 218.056 \({k_L}\) 0.112 0.136 \(R_{1}^{2}\) 0.989 0.989 Freundlich \({k_F}\) 49.694 76.392 1/n 0.211 0.173 \(R_{2}^{2}\) 0.973 0.937 Temkin \({A_T}\) 0.843 3.071 \({b_T}\) 63.245 65.052 \(R_{3}^{2}\) 0.923 0.940 Dubinin-Radushkevich \({q_m}\) 178.215 214.325 \(\beta\) 1.357 7.546 1.912 2.637 \(R_{4}^{2}\) 0.898 0.938 Adsorption mechanism In order to better explore the adsorption mechanism of RMLL and PRMLL on Pb 2+ . The RMLL and PRMLL adsorbed Pb 2+ were analyzed by XRD to determine the phase composition of the materials. As shown in Fig. 7 (a), XRD patterns of RMLL and PRMLL after adsorption of Pb 2+ show diffraction peaks of PbCO 3 , Pb 3 (CO3) 2 (OH) 2 and Pb 5 (PO 4 ) 3 Cl. The results showed that Pb 2+ formed a precipitate and adsorbed on the surface of the material through chemisorption. Figure. 7 (b) shows the FTIR diagram after adsorption of Pb 2+ by RMLL and PRMLL. It is found that the characteristic peaks of carboxyl group binding with Pb 2+ are generated near 1633.43cm − 1 and 621.05cm − 1 , indicating that carboxyl group has a strong binding ability with the main group element Pb 2+ and forms an effective coordination(Luu et al. 2022). It can also be seen from the figure that after adsorption of Pb 2+ by RMLL and PRMLL, the peaks at 1415.5cm − 1 and 1003.49cm − 1 are significantly enhanced, indicating that the adsorption of Pb 2+ by RMLL and PRMLL is mainly achieved through cation exchange between carbonate and silicate, and the adsorption mechanism is consistent with that of RM(Dinh et al. 2020). Secondly, at 3426.45cm − 1 is the stretching vibration of O-H group(Huang et al. 2020, Renli et al. 2019). 621.05cm − 1 , 1003.49cm − 1 and 1122.82cm − 1 are related to the stretching and vibration of Si-O tetrahedrons or Al-O tetrahedrons, and all of them are displaced after adsorption of Pb 2+ (Ahmed et al. 2023b, Yu 2019). The peak displacement indicates that Pb 2+ is adsorbed on the surface of RMLL and PRMLL by chemisorption, which is consistent with XRD analysis. As shown in Fig. 8 (a), the total XPS spectra of RM, RMLL and RMLL and PRMLL adsorbed Pb 2+ , in which the C peak of RMLL is much higher than that of the original red mud, indicating that lotus leaf and red mud have been successfully loaded in the process of (1:1) carbonization. Compared with the O peak of the original red mud, the O peak of RMLL was shorter, which may be due to the red mud as an oxygen carrier, which promoted the further gasification of lotus leaves and produced more carbon dioxide(Haiming et al. 2015), Secondly, in the process of anaerobic calcination, Fe 2 O 3 in the original red mud reacts with C and CO respectively to produce Fe 3 O 4 , thus consuming O element. In the comparison of the total spectrum, new characteristic peaks of RMLL and PRMLL after adsorption of Pb 2+ appear around 185.6eV and 411.45eV, namely (Pb4f) and (Pb4d), which may be PbCO 3 , Pb 3 (CO 3 ) 2 (OH) 2 and Pb 5 (PO 4 ) 3 Cl after query in NTST spectrum library. This also shows that Pb 2+ is strongly adsorbed on the surface of the material through chemisorption. The Fe spectra in RM, RMLL, PRMLL and RMLL adsorbed with Pb 2+ were compared. As shown in Fig. 8 (b1), b2), b3 and (b4) (b5). The spectral peaks of RM, RMLL, PRMLL and RMLL,Fe2p 3/2 and Fe2p 1/2 after adsorption of Pb 2+ appear at 711.0 eV and 724.4eV(Geng et al. 2017). By semi-quantitative analysis of Fe2p 3/2 and Fe2p 1/2 orbits, the peak-area ratios of Fe 2 O 3 and Fe 3 O 4 are 1.8, 0.6, 0.5 and 1.2, 1.3, respectively. It shows that the red mud formed a large amount of Fe 3 O 4 after carbonization with lotus leaves at 600℃, and consumed a large amount of Fe 3 O 4 after adsorption of Pb 2+ , which is consistent with the previous XRD analysis(Yan et al. 2022). The C spectrum in RMLL after Pb 2+ adsorption is compared with that in RMLL after Pb 2 + adsorption, as shown in Fig. 8(c1), peaks appear at 284.2eV, 285.7eV and 288.6eV, which may be the functional groups of C-H/C-C, C-O and C = O. The peaks at 292.7eV are π-π transitions, which may be the result of aromatic rings(Ahmed et al. 2023a). Figure 8 (c2) In contrast, the peak area of C-H/C-C bond after adsorption of Pb 2+ is reduced, which may be due to the metal complexation reaction. The peak area of C-O increased and the binding energy decreased, which may be involved in the adsorption of Pb 2+ . It can also be seen from the figure that after adsorption of lead, the peak area of metal carbonate increases and the binding energy decreases. The peak area of C-O increased and the binding energy decreased, which may be involved in the adsorption of Pb 2+ . It can also be seen from the figure that after adsorption of lead, the peak area of metal carbonate increases and the binding energy decreases. Figure 8 (d) shows the XPS high resolution spectrum of Pb4f after Pb 2+ adsorption by RMLL. As can be seen in the figure, the peak of Pb4f7/2 was observed at 138.17ev, indicating that Pb 2+ became a carbonate compound (PbCO 3 ) and was adsorbed on the material(Lyu et al. 2021). The results of XRD, FTIR and XPS have proved the formation of PbCO 3 . In order to better prove that RMLL and PRMLL have adsorption effect on Pb 2+ . SEM-EDS was used to characterize RMLL and PRMLL after adsorption of Pb 2+ . Figure 9 (a) and (e) are the SEM images after adsorption of Pb 2+ by RMLL and PRMLL respectively. It can be seen from the figure that Pb 2+ is deposited on the entire surface of the material in a flocculent form, indicating that the material has a good adsorption effect on Pb 2+ . Figure 9 (b) and (f) show the EDS-mapping diagram after adsorption of Pb 2+ by RMLL and PRMLL respectively, and it can be clearly seen that a large amount of Pb 2+ is adsorbed on the surface of the material. Figure 9 (d) and (h) are EDS spectra after RMLL and PRMLLPb 2+ . The presence of Pb 2+ can be clearly seen in the figure, and it is relatively high, which also indicates that the composite material has a large adsorption capacity for Pb 2+ . In summary, the results were analyzed by XRD, FTIR, XPS and SEM-EDS. The removal effect of RMLL and PRMLL on Pb 2+ in water mainly has the following three aspects. First, Na + and Ca 2+ in the composite are dissolved in solution for ion exchange, and Pb 2+ in the solution is adsorbed on the surface of the material and reacts with carbonate to form PbCO 3 and Pb 3 (CO 3 ) 2 (OH) 2 . Secondly, when CaCO 3 in the material dissolves, part of CO 3 2− will be released into the solution, which is conducive to the formation of PbCO 3 and Pb 3 (CO 3 ) 2 (OH) 2 . Second, in the process of oxygen-free high-temperature calcination of red mud and lotus leaves, Fe 2 O 3 will be reduced to Fe 3 O 4 , which also plays an important role in the adsorption of Pb 2+ . Third, the interaction between phosphate and heavy metals promotes the precipitation of stable phosphate. The modified RMLL by KH 2 PO 4 can increase the potassium in the material, and thus increase the cation exchange capacity in the material. P can enter the material polymer to form new bonds such as C-O-P (YaxinLi et al.), the adsorption site was increased. After impregnation with KH 2 PO 4 , new minerals such as potassium metaphosphate (KPO 3 ) and potassium pyrophosphate (K 4 P 2 O 7 ) are formed on the surface of the material at high temperature. Metaphosphates are formed by 2 or more phosphate groups via O-P-O bonds (straight or circular) (also known as polyphosphates) and are readily chelated with heavy metals(Wang et al. 2022). In addition, heavy metals such as Pb 2+ can form extremely insoluble precipitates by reacting with potassium pyrophosphate, such as the formation of Pb 2 P 2 O 7 and Pb 5 (PO 4 ) 3 Cl(Zhang et al. 2023). The main reactions in the adsorption process are as follows (1) (2) (Lyu et al. 2021, Zhou et al. 2017). $$P{b^{2+}}+CO_{3}^{{2 - }} \to PbC{O_3}$$ 1 $$3P{b^{2+}}+2HCO_{3}^{{2 - }}+4O{H^ - } \to P{b_3}{(C{O_3})_2}{(OH)_2}+2{H_2}O$$ 2 Conclusions RM is a kind of larger industrial waste, damage to the environment from all aspects has irreversible effects on the environment, and the huge annual emissions. At the same time, the characteristics of red mud itself is also a huge resource. In this project, red mud and lotus leaf powder were carbonized at high temperature and modified with KH 2 PO 4 to remove Pb 2+ in sewage, which received dual effects of environment and economy, and also reflected the current new idea of "resource utilization". The results show that RMLL and PRMLL have good adsorption effect on Pb 2+ . The RM based material (PRMLL) modified with KH 2 PO4 has better adsorption effect on Pb 2+ than RMLL, and its adsorption effect is increased by 15.3%. The fitting of experimental data found that the kinetics studies of RMLL and PRMLL materials showed that the two materials were more in line with pseudo-second-order kinetics, and also reflected that Pb 2+ was chemically adsorbed on the surface of the material through ion exchange. The data fitting of isothermal adsorption showed that RMLL and PRMLL were monolayer adsorption, and the K L constants of Langmuir were 0.11 and 0.13, respectively, which was conducive to the adsorption of Pb 2+ . Finally, XRD, XPS, FTIR and SEM-EDS were used to characterize the adsorbed Pb 2+ materials, which fully proved that Pb 2+ can be adsorbed by chemical adsorption. Adsorbed on the surface of the material in the form of carbonate and phosphate precipitates. In addition, RMLL and PRMLL retain some organic functional groups (-COOH) during the carbonization process, which also plays a certain role in promoting the removal of Pb 2+ . Therefore, we can speculate that the adsorption mechanism of RMLL and PRMLL on Pb 2+ may be a combination of ion exchange and chemical precipitation and complexation. Compared with the original red mud, modified red mud and some single adsorption materials, this material has a larger adsorption capacity. Moreover, red mud is a kind of industrial waste, which has dual environmental and economic benefits in terms of environmental management. Therefore, RMLL and PRMLL can be used as potential adsorbents to remove Pb 2+ from water. Declarations Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Availability of data and materials Not applicable. Competing interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service, and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled, “Characterization of phosphate modified red mud based composite materials and study on heavy metal adsorption”. Appendix A. Supplementary material document. The following are the supplementary data to this article: Supplementary document. Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Funding Not applicable Authors' contributions Wenlou Jin : Conceptualization, Data curation, Writing-original draft. Yanzhi Yang : Supervision, Resources. Jiacheng Jin: Data curation. Mingcheng Xu : Investigation, Data curation. Fan Dong : Formal analysis. Zhipeng Zhang : Data curation, Investigation. Min Shao : Conceptualization, Funding acquisition, Writing-review & editing. Yushan Wan : Conceptualization, Funding acquisition, Writing-review & editing. Acknowledgments The author sincerely thanks the Jiangsu Graduate Research and Practice Innovation Program (SJCX23-1558) for funding. Thanks to Shiyanjia Lab [www.shiyanjia.com] for its help in the XPS test. References A QW, B CZA, A ZS, C QL, D CHA, E TCZ, C JL (2019): Polyethyleneimine and carbon disulfide co-modified alkaline lignin for removal of Pb 2+ ions from water - ScienceDirect. Chemical Engineering Journal 359, 265-274 A WS, B HR, B XH, B ML, B YT, C FG Low cost red mud modified graphitic carbon nitride for the removal of organic pollutants in wastewater by the synergistic effect of adsorption and photocatalysis - ScienceDirect. Separation and Purification Technology 237 Ahmed W, Mehmood S, Mahmood M, Ali S, Shakoor A, Nunez-Delgado A, Asghar RMA, Zhao H, Liu W, Li W (2023a): Adsorption of Pb(II) from wastewater using a red mud modified rice-straw biochar: Influencing factors and reusability. Environmental Pollution Ahmed W, Mehmood S, Mahmood M, Ali S, Shakoor A, Núñez-Delgado A, Asghar RMA, Zhao H, Liu W, Li W (2023b): Adsorption of Pb(II) from wastewater using a red mud modified rice-straw biochar: Influencing factors and reusability. Environmental Pollution 326, 121405 Akin I, Arslan G, Tor A, Ersoz M, Cengeloglu Y (2012): Arsenic(V) removal from underground water by magnetic nanoparticles synthesized from waste red mud. Journal of Hazardous Materials 235-236, 62-68 Al-Ghouti MA, Da, X, Ana DA Guidelines for the use and interpretation of adsorption isotherm models: A review. Journal of Hazardous Materials 393 Bagla H, Khilnani R (2016): Kinetics of biosorption of hazardous metals by green soil supplement, Egu General Assembly Conference Blanchard G, Maunaye M, Martin G (1984): Removal of heavy metals from waters by means of natural zeolites. Water Research 18, 1501-1507 Conceio FTD, Silva MSGD, Menegário AA, Antunes MLP, Moruzzi RB (2021): Precipitation as the main mechanism for Cd(II), Pb(II) and Zn(II) removal from aqueous solutions using natural and activated forms of red mud. Environmental Advances Dinh VP, Nguyen MD, Nguyen QH, Do TTT, Tan LV (2020): Chitosan-MnO2 nanocomposite for effective removal of Cr (VI) from aqueous solution. Chemosphere 257, 127147 Ecer SS, Tekin (2018): Highly efficient Cd(II) adsorption using mercapto-modified bentonite as a novel adsorbent: an experimental design application based on response surface methodology for optimization. Water Science and Technology 78 Elebi H, Gk G, Gk O (2020): Adsorption capability of brewed tea waste in waters containing toxic lead(II), cadmium (II), nickel (II), and zinc(II) heavy metal ions. Scientific Reports 10, 17570 Freundlich HMF (1906): UBER DIE ADSORPTION IN LOSUNGEN. Geng J, Zhou M, Zhang T, Wang W, Wang T, Zhou X, Wang X, Hou H (2017): Preparation of blended geopolymer from red mud and coal gangue with mechanical co-grinding preactivation. Materials & Structures 50, 109 Haiming, Shen, Laihong (2015): Cement/CaO-modified iron ore as oxygen carrier for chemical looping combustion of coal. Applied Energy Hang Y, Si Y, Zhou Q, Yin H, Cao A (2019a): Morphology-controlled synthesis of calcium titanate particles and adsorption kinetics, isotherms, and thermodynamics of Cd(II), Pb(II), and Cu(II) cations. Journal of Hazardous Materials 380, 120789- Hang Y, Si Y, Zhou Q, Yin H, Wang A, Cao A (2019b): Morphology-controlled synthesis of calcium titanate particles and adsorption kinetics, isotherms, and thermodynamics of Cd(II), Pb(II), and Cu(II) cations. Journal of Hazardous Materials 380, 120789 Huang R, Lin Q, Zhong Q, Zhang X, Wen X, Luo H (2020): Removal of Cd(II) and Pb(II) from aqueous solution by modified attapulgite clay - ScienceDirect. Arabian Journal of Chemistry 13, 4994-5008 Jian-Liang, Cao, Zhao-Li, Yan, Qing-Fang, Deng, Yan, Wang, Zhong-Yong, Yuan (2014): Mesoporous modified-red-mud supported Ni catalysts for ammonia decomposition to hydrogen. International Journal of Hydrogen Energy Kazak O, Tor A (2020): In situ preparation of magnetic hydrochar by co-hydrothermal treatment of waste vinasse with red mud and its adsorption property for Pb(II) in aqueous solution. Journal of Hazardous Materials 393, 122391 Khairul MA, Zanganeh J, Moghtaderi B (2018): The composition, recycling and utilisation of Bayer red mud. Resources Conservation and Recycling 141, 483-498 Krishnani KK, Meng X, Christodoulatos C, Boddu VM (2008): Biosorption mechanism of nine different heavy metals onto biomatrix from rice husk. Journal of hazardous materials, 153 Kwon SM, Jang JH, Lee SH, Park SB, Kim NH (2013): Change of Heating Value, pH and FT-IR Spectra of Charcoal at Different Carbonization Temperatures. Journal of the Korean Wood Science & Technology 41 Langmuir I (1917): The Adsorption of Gases on Plane Surfaces of Glass, Mica and Platinum. Journal of the American Chemical Society 40 Li F, Cao X, Zhao L, Wang J, Ding Z (2014): Effects of Mineral Additives on Biochar Formation: Carbon Retention, Stability, and Properties. Environmental Science & Technology 48, 11211-7 Li P, Liu Z, Yan H, He Y (2019): Recover Iron from Bauxite Residue (Red Mud) Li S, Zhang J, Li Z, Liu C, Chen J (2020): Feasibility study on grouting material prepared from red mud and metallurgical wastewater based on synergistic theory. Journal of Hazardous Materials 407, 124358 Liu R, Zhang Y, Hu B, Wang H (2022): Improved Pb(II) removal in aqueous solution by sulfide@biochar and polysaccharose-FeS@ biochar composites: Efficiencies and mechanisms. Chemosphere 287, 132087- Luu T-T, Dinh V-P, Nguyen Q-H, Tran N-Q, Nguyen D-K, Ho T-H, Nguyen V-D, Tran DX, Kiet HAT (2022): Pb(II) adsorption mechanism and capability from aqueous solution using red mud modified by chitosan. Chemosphere 287, 132279 Lyu F, Niu S, Wang L, Liu R, Sun W, He D (2021): Efficient removal of Pb(II) ions from aqueous solution by modified red mud. Journal of Hazardous Materials 406, 124678 Renli, Yin, Wanqian, Guo, Huazhe, Wang, Juanshan, Du, Qinglian (2019): Singlet oxygen-dominated peroxydisulfate activation by sludge-derived biochar for sulfamethoxazole degradation through a nonradical oxidation pathway: Performance and mechanism. Chemical Engineering Journal Shirzadi H, Nezamzadeh-Ejhieh A (2017): An efficient modified zeolite for simultaneous removal of Pb(II) and Hg(II) from aqueous solution. Journal of Molecular Liquids 230, 221-229 Wang L, Sun N, Tang H, Sun W (2019): A Review on Comprehensive Utilization of Red Mud and Prospect Analysis. Minerals 9, 362 Wang L, Shi C, Pan L, Zhang X, Zou JJ (2020): Rational design, synthesis, adsorption principles and applications of metal oxide adsorbents: a review. Nanoscale 12, 4790-4815 Wang Q, C.-J. D, C.-Y. X, Z.-C. G (2022): Efficient removal of Cd(II) by phosphate-modified biochars derived from apple tree branches: Processes, mechanisms, and application. Science of the Total Environment, 819 Wei D, Jun-Hui X, Yang P, Si-Yue S, Tao C (2019): Iron Extraction from Red Mud using Roasting with Sodium Salt. Mineral Processing and Extractive Metallurgy Review, 1-9 Wei Z, Qian D, Qiulai H, Jianyang S, Shilu Z, Hongyu W, Jinping Z, Huining Z (2018): A facile synthesis of core-shell/bead-like poly (vinyl alcohol)/alginate@PAM with good adsorption capacity, high adaptability and stability towards Cu(Ⅱ) removal. Chemical Engineering Journal 351, 462-472 Xu X, Hu X, Ding Z, Chen Y (2017): Effects of copyrolysis of sludge with calcium carbonate and calcium hydrogen phosphate on chemical stability of carbon and release of toxic elements in the resultant biochars. Chemosphere 189, 76 Yan Y, Qi F, Zhang L (2022): Enhanced Cd adsorption by red mud modified bean-worm skin biochars in weakly alkali environment. Separation and Purification Technology, 297 Yang D, Wang L, Li Z, Tang X, Xu J (2019): Simultaneous adsorption of Cd(II) and As(III) by a novel biochar-supported nanoscale zero-valent iron in aqueous systems. Science of The Total Environment 708, 134823 Yang D, Deng W, Tan A, Chu Z, Wei W, Zheng R, Shangguan Y, Sasaki A, Endo M, Chen H (2021): Protonation stabilized high As/F mobility red mud for Pb/As polluted soil remediation. Journal of Hazardous Materials 404, 124143 Yang D, Wang R, Feng X, Chu Z, Li J, Wei W, Zheng R, Zhang J, Chen H (2022): Transferring waste red mud into ferric oxide decorated ANA-type zeolite for multiple heavy metals polluted soil remediation. Journal of Hazardous Materials 424, 127244- YaxinLi, XianZhang, RuiguangYang, GuiyingLi, ChangweiHu The role of H 3 PO 4 in the preparation of activated carbon from NaOH-treated rice husk residue. RSC Advances 5 Yilmaz S, Ecer U, Sahan T (2018): Modelling and Optimization of As(III) Adsorption onto Thiol-Functionalized Bentonite from Aqueous Solutions Using Response Surface Methodology Approach. Chemistry Select, 3 Yu J, LinPang, YaZeng, GuangmingWang, JiajiaDeng, YaochengLiu, YaniFeng, HaopengChen, SongRen, Xiaoya (2019): Magnetic nitrogen-doped sludge-derived biochar catalysts for persulfate activation: Internal electron transfer mechanism. Chemical engineering journal 364 Zeng Q, Huang Y, Huang L, Hu L, Sun W, Zhong H, He Z (2020): High adsorption capacity and super selectivity for Pb(Ⅱ) by a novel adsorbent: Nano humboldtine/almandine composite prepared from natural almandine. Chemosphere: Environmental toxicology and risk assessment, 253 Zhang H, Shao J, Zhang S, Zhang X, Chen H (2019): Effect of Phosphorus-Modified Biochars on Immobilization of Cu (II), Cd (II), and As (V) in Paddy Soil. Journal of Hazardous Materials 390, 121349 Zhang J, Jiang Y, Ding C, Wang S, Zhao C, Yin W, Wang B, Yang R, Wang X (2023): Remediation of lead and cadmium co-contaminated mining soil by phosphate-functionalized biochar: Performance, mechanism, and microbial response. Chemosphere 334, 138938 Zhou X, Liu W, Zhang J, Wu C, Ou X, Tian C, Lin Z, Dang Z (2017): Biogenic Calcium Carbonate with Hierarchical Organic–Inorganic Composite Structure Enhancing the Removal of Pb(II) from Wastewater. Acs Appl Mater Interfaces, acsami.7b09304 Supplementary Files Supplementarymaterialdocument.docx Cite Share Download PDF Status: Published Journal Publication published 21 Jun, 2024 Read the published version in Environmental Science and Pollution Research → Version 1 posted Reviewers agreed at journal 30 Jan, 2024 Reviewers invited by journal 30 Jan, 2024 Editor assigned by journal 07 Jan, 2024 First submitted to journal 29 Dec, 2023 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-3798495","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":270255278,"identity":"82cf1216-568a-4bfe-9dfe-e93ca472aaa0","order_by":0,"name":"Wenlou Jin","email":"","orcid":"","institution":"Changzhou University - Wujin Campus: Changzhou University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Wenlou","middleName":"","lastName":"Jin","suffix":""},{"id":270255279,"identity":"5b9796ce-98c0-4756-bce5-3c238788fabc","order_by":1,"name":"Yanzhi Yang","email":"","orcid":"","institution":"Changzhou University - Wujin Campus: Changzhou University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Yanzhi","middleName":"","lastName":"Yang","suffix":""},{"id":270255280,"identity":"4454715d-2bed-4b10-838c-094aeb2cd624","order_by":2,"name":"Jiacheng Jin","email":"","orcid":"","institution":"Changzhou University - Wujin Campus: Changzhou University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Jiacheng","middleName":"","lastName":"Jin","suffix":""},{"id":270255281,"identity":"75d80cd8-51e5-4eb6-9a83-de107a694947","order_by":3,"name":"Mingchen Xu","email":"","orcid":"","institution":"Changzhou University - Wujin Campus: Changzhou University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Mingchen","middleName":"","lastName":"Xu","suffix":""},{"id":270255282,"identity":"092e90f0-c4f2-4287-9017-90f000505ad0","order_by":4,"name":"Zhipeng Zhang","email":"","orcid":"","institution":"Changzhou University - Wujin Campus: Changzhou University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Zhipeng","middleName":"","lastName":"Zhang","suffix":""},{"id":270255283,"identity":"4eef3d03-9e79-4a67-9778-72531bb52889","order_by":5,"name":"Fan Dong","email":"","orcid":"","institution":"Changzhou University - Wujin Campus: Changzhou University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Fan","middleName":"","lastName":"Dong","suffix":""},{"id":270255284,"identity":"19f48083-a36f-4866-a006-793915e3fd5c","order_by":6,"name":"Min Shao","email":"","orcid":"","institution":"Changzhou University - Wujin Campus: Changzhou University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Min","middleName":"","lastName":"Shao","suffix":""},{"id":270255285,"identity":"8955173f-4402-4c84-83f0-2d39b4f8ec70","order_by":7,"name":"Yushan Wan","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAy0lEQVRIiWNgGAWjYPCCAwwM7I2NDz6QpoXncLPhDNK0SKS3SXMQo9bg+Nlj0jx/7sibSz5skGZgsJPTbSCk5UxemjRv2zPDnbMTG4wLGJKNzQ4Q0GJ2IMdMmrfhMOOG24kNyTMYDiRuI6jl/BszoMMO22+4ebDhMA9RWm4AbeFhO5y44QZjYzNRWuxvvDG2nNt2OHnDmcRmxhkGRPhFsj/H8MabP4dtNxw//vzHhwo7OYJagIBFAsE2IKwcBJhJSSajYBSMglEwEgEAfEJKCujRraIAAAAASUVORK5CYII=","orcid":"","institution":"Changzhou University - Wujin Campus: Changzhou University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Yushan","middleName":"","lastName":"Wan","suffix":""}],"badges":[],"createdAt":"2023-12-24 02:16:44","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3798495/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3798495/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11356-024-33969-5","type":"published","date":"2024-06-21T06:28:14+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":50582162,"identity":"4c4745a0-3984-4047-9cff-1e48e65b4064","added_by":"auto","created_at":"2024-02-02 19:56:08","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":53735,"visible":true,"origin":"","legend":"\u003cp\u003e(a) is the RMLL preparation flow chart; (b) Prepare flow charts for PRMLL.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3798495/v1/7a9a9e6b6c896539a82c0cb3.jpg"},{"id":50582166,"identity":"04cbb4c2-0e09-4368-a38e-4c7bf1334d52","added_by":"auto","created_at":"2024-02-02 19:56:08","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":161336,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XRD patterns of RM, RMLL and PRMLL, (b) FTIR spectra of LL, RMLL and PRMLL, and (c) (d) (e) (f) SEM images of LL, RM, RMLL and PRMLL, respectively.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3798495/v1/bfa22549159eb970d7078a10.jpg"},{"id":50582163,"identity":"6ba59ba8-e507-4e8e-87b4-d2a591ac404f","added_by":"auto","created_at":"2024-02-02 19:56:08","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":59003,"visible":true,"origin":"","legend":"\u003cp\u003eshows the specific surface area (a) and pore size distribution (b) of materials LL, RMLL and PRMLL.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3798495/v1/87b2b97ba5834f2f3fbe438f.jpg"},{"id":50582168,"identity":"8ca81ebe-a993-41d5-b320-d9c58ccb9642","added_by":"auto","created_at":"2024-02-02 19:56:08","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":97130,"visible":true,"origin":"","legend":"\u003cp\u003e(a) (b) (c) and (d) are the effects of PH, Zeta potentials,dosage and initial concentration on the adsorption capacity of Pb\u003csup\u003e2+\u003c/sup\u003e, respectively.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3798495/v1/a06fa16621a3fb4bd3f8b821.jpg"},{"id":50582164,"identity":"3bf821c2-2e31-4060-9d5c-c9d588505a73","added_by":"auto","created_at":"2024-02-02 19:56:08","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":65481,"visible":true,"origin":"","legend":"\u003cp\u003e(a) is the curve of Pb\u003csup\u003e2+\u003c/sup\u003e adsorption capacity of RMLL and PRMLL materials over time; (b) (c) (d) RMLL and PRMLL pseudo-first-order, pseudo-second-order and Elovich models fit data graphs (PH:7, solubility 500mg/L, temperature25 ℃, dosage 0.1g).\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3798495/v1/42b2ae8fad94b5df42308c79.jpg"},{"id":50582165,"identity":"3e17e8ea-0541-494e-85b7-84e4533233fd","added_by":"auto","created_at":"2024-02-02 19:56:08","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":53523,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Adsorption capacity of RMLL and PRMLL to initial Pb\u003csup\u003e2+\u003c/sup\u003e concentration; Figure (b) (c) is the isothermal adsorption fitting diagram of Langmuir, Freundlich and Temkin models of RMLL and PRMLL. Figure (d) is a fitting diagram of RMLL and PRMLL Dubinin-Radushkevich models (PH:7, temperature 25℃, dosage 0.1g).\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3798495/v1/a54b624d9546a554947c6a66.jpg"},{"id":50582167,"identity":"6e3da14a-47f4-4fd5-9d21-58a105573f5e","added_by":"auto","created_at":"2024-02-02 19:56:08","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":56147,"visible":true,"origin":"","legend":"\u003cp\u003e(a) XRD pattern after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e by RMLL and PRMLL and (b) FTIR pattern after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3798495/v1/f41dd3a036e6b81b5b4b1ad1.jpg"},{"id":50582318,"identity":"429cadf1-d5d0-441c-831d-c025fa9cc48e","added_by":"auto","created_at":"2024-02-02 20:04:08","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":121527,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Total XPS spectra of RM, RMLL and RMLL and PRMLL adsorbed Pb\u003csup\u003e2+\u003c/sup\u003e; (b1), (b2) and (b3) are Fe spectra of RM, RMLL and PRMLL; (b4) (b5) is the Fe spectrum after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e by RMLL and PRMLL; (c1) and (c2) are the C spectra of RMLL and Pb\u003csup\u003e2+\u003c/sup\u003e adsorption, respectively. (d) is the Pb spectrum of RMLL in the Pb4f orbit after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3798495/v1/d3d59c5bf01c4564ea6d6f7e.jpg"},{"id":50582169,"identity":"8eed95f0-0d90-47d6-aa37-8c52ac50e06c","added_by":"auto","created_at":"2024-02-02 19:56:08","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":197651,"visible":true,"origin":"","legend":"\u003cp\u003e(a) (c) is the SEM image after Pb\u003csup\u003e2+\u003c/sup\u003e adsorption by RMLL and the corresponding EDS mapping(c) and EDS energy spectrum (d). (e) (f) is the SEM image after Pb\u003csup\u003e2+\u003c/sup\u003e adsorption by PRMLL and the corresponding EDS mapping(f) and EDS energy spectrum (h);\u003c/p\u003e","description":"","filename":"9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3798495/v1/5d0bd0baea0bd11b04c5c763.jpg"},{"id":60378912,"identity":"8a67066c-8a0e-4f6d-beed-30bf41d9f6fc","added_by":"auto","created_at":"2024-07-16 06:52:20","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1593553,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3798495/v1/4887480e-5094-48d2-948a-e0afb016988a.pdf"},{"id":50582704,"identity":"d93ae8e4-3878-41e2-84aa-8dbae74332c9","added_by":"auto","created_at":"2024-02-02 20:12:08","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":75754,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarymaterialdocument.docx","url":"https://assets-eu.researchsquare.com/files/rs-3798495/v1/5bf940293c759c904cdd406f.docx"}],"financialInterests":"","formattedTitle":"Characterization of phosphate modified red mud based composite materials and study on heavy metal adsorption","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRed mud is a kind of alkaline industrial hazardous waste in alumina industrial production, which contains a variety of heavy metals and other harmful substances, and is extremely difficult to dispose of. China is a big producer of alumina industry, and in 2019, its output accounted for about 64% of the world(Wei et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2019\u003c/span\u003e),(Wang et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Therefore, China has a huge stock of red mud, and millions of tons of red mud are piled up every year. If handled improperly, it will cause immeasurable damage to the environment and even endanger human health. How to treat and utilize red mud effectively and realize resource utilization has become a difficult problem and an urgent problem to be solved by researchers all over the world. Secondly, lead is the most common toxic heavy metal, a large amount of inhalation of human body and animals and plants have great harm. For example, excessive accumulation in the human body may lead to anemia, neurological disorders and even death.According to the World Health Organization, the concentration of Pb\u003csup\u003e2+\u003c/sup\u003e in water should not exceed 0.001mg/L (Elebi et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe main components of red mud are Fe\u003csub\u003e2\u003c/sub\u003e0\u003csub\u003e3\u003c/sub\u003e, AI\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, CaO, TiO, Na\u003csub\u003e2\u003c/sub\u003eO and SiO\u003csub\u003e2\u003c/sub\u003e, and also contain some trace elements, such as K, Ba, Cu, Mn, Zn, S and a small amount of rare earth elements(Khairul et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Red mud also has the characteristics of porous structure, very fine dispersion, high specific surface area and good adsorption properties. Therefore, red mud can not only extract some rare elements with high added value, but also be used as an adsorbent and passivator that can deal with environmental heavy metal pollution. Many scholars have done a lot of research on the application of red mud in environmental governance. For example, protonated RM is used to repair lead-arsenic contaminated soil, significantly reducing the cumulative concentration of lead and arsenic in rape, and blocking the diffusion of Pb and As to native plants(Yang et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).The synthesis of Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e nanoparticles dissolved and precipitated iron in red mud with NaOH in aqueous solution. It was found by adsorption experiment that the removal rate of As could be improved by decreasing PH value in a certain range(Akin et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Using waste wine lees and red mud, a cheap and highly adsorbent magnetic material was prepared by hydrothermal treatment. The results show that the magnetic hydrocarbon has adsorption effect on Pb\u003csup\u003e2+\u003c/sup\u003e in water, and the experiment shows the reusability and good adaptability of this magnetic material(Kazak \u0026amp;Tor \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Red mud/graphite composite (RM-CN) was synthesized from graphite carbon nitride (g-C3N4) and red mud by one-step thermal polymerization. RM-CN can absorb organic pollutants such as tetracycline (TC), chloromycin (CTC) in water(A et al.). Conversion of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, Al and Si from waste RM to low-cost Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e-ANA zeolite can effectively inhibit the migration of HM in soil and reduce the bioaccumulation concentration of HM in harvested rapeseed(Yang et al. \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). There are also some studies that modified biochar with red mud can significantly improve the adsorption capacity of Cd\u003csup\u003e2+\u003c/sup\u003e and Cr\u003csup\u003e6+\u003c/sup\u003e, and the removal rate of heavy metal ions in water is as high as 99%(Wang et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIt was also found that calcium dihydrogen phosphate Ca(H\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e was added to the straw raw material at a ratio of 20% (w/w) to form biochar through pyrolysis treatment, which could effectively improve the carbon retention rate and strengthen the stability of biochar(Li et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). The replication decomposition of sludge with phosphate and carbonate, especially phosphate, is an effective method to prepare sludge-based biochar which immobilized toxic elements and improved the chemical stability of carbon(Xu et al. \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). At the same time, phosphorus-containing materials can also effectively remove heavy metals, the mechanism is that its PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e can form phosphate precipitation with heavy metals, reduce the activity of heavy metals, and reduce its harm to the water and soil environment. The results show that red mud and biochar have a good effect on the treatment of heavy metals. Therefore, the preparation of a new type of material using red mud and easily available biochar, then modified with appropriate phosphate, has great potential for treating heavy metal pollution in water and soil(Conceio et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, Elebi et al. \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2020\u003c/span\u003e, Krishnani et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn view of the above research, this study prepared the composite material of carbonized red mud and lotus leaf powder, and modified it by phosphate on this basis, and evaluated its removal ability of Pb\u003csup\u003e2+\u003c/sup\u003e in water and environmental applicability. The effect of preparation and application parameters on the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e was studied. The adsorption process was studied by kinetic and isothermal adsorption models, and the adsorption mechanism was explored.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eMaterials\u003c/h2\u003e \u003cp\u003eThe red mud used in this study is Bayer process red mud, which is taken from an aluminum company in Zibo City, Shandong Province, China. The red mud is air-dried under natural conditions, then passed through a 100-mesh sieve, collected for use. Lotus leaves are taken from the lotus pond of the school, the lotus leaves are dried in the oven, and then crushed with a grinder, after 100 mesh sieve, collected for use.The water used for the test was deionized water, and the reagents used included HCl (37%), Pb(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e (99%), NaOH (97%), CH\u003csub\u003e3\u003c/sub\u003eCOOH (99%) and KH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e (analytically pure), which were purchased from Shanghai Sinopharm Group. Chemical element analysis of raw red mud and 600℃ carbonized lotus leaves is shown in supporting document (S1).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003ePreparation of RMLL and PRMLL materials\u003c/h2\u003e \u003cp\u003eFirst, the red mud and lotus leaf powder are evenly mixed according to their mass in a certain ratio, and then compacted in the crucible, and then raised to a certain temperature at 10℃/min in the pushed tube furnace, and kept for 3h. During the calcination process, nitrogen is passed through the whole process until it is cooled to room temperature. The preparation of PRMLL material is based on the best conditions for preparing RMLL material. Firstly, a certain amount of KH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e is evenly mixed with lotus leaf powder, dissolved in deionized water, dried in the oven at 80℃, and then collected for use after grinding through a 100-mesh sieve. Then a certain amount of red mud is added into the tube furnace for calcination, and the calcination requirements are consistent with the preparation of RMLL materials. After the material is prepared, it is cleaned with deionized water, pumped and filtered until neutral, dried and collected for use.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eAdsorption experiment\u003c/h2\u003e \u003cp\u003eA certain amount of Pb(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e was weighed and a Pb\u003csup\u003e2+\u003c/sup\u003e solution with a concentration of 1000mg/L was prepared. In subsequent experiments, the solution concentrations used were diluted from the standard solution. Specifically, 50mL of lead solution with a concentration of 500mg/L was added to a 150mL conical bottle, and then 0.1g of RMLL and PRMLL materials were added to the solution respectively. Adjust the PH to the desired value with 1% HCl or 1mol/L NaOH solution. After oscillating at 25℃ and 160r/min for 12h in a constant temperature oscillator, samples were taken and filtered, and the solubility of Pb\u003csup\u003e2+\u003c/sup\u003e in the adsorbed solution was determined by flame atomic spectrophotometer (AAS). See supporting document (S2) for the calculation formula of adsorption capacity(Shirzadi \u0026amp;Nezamzadeh-Ejhieh \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003cspan class=\"InlineEquation\"\u003e\u003c/span\u003e\u003c/p\u003e \u003cp\u003eThe adsorption kinetics experiment is the same as the experiment above, sampling at a specific time to measure the residual Pb\u003csup\u003e2+\u003c/sup\u003e concentration in the solution. The adsorption properties were studied by fitting the pseudo-first-order kinetics, pseudo-second-order kinetics and Elovich kinetics models. See supporting document (S3) for the model formula(Bagla \u0026amp;Khilnani \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2016\u003c/span\u003e, Blanchard et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1984\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the isothermal adsorption experiment, the previously configured 1000mg/L lead solution was diluted to 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000mg/L according to the needs, and 50mL of the corresponding solubility lead solution was successively added into a 150mL conical bottle. After adjusting the PH, 0.1g of RMLL and PRMLL materials were added respectively, and the oscillating rate was 160r/min at 25℃. After 12h, samples were taken respectively. The equilibrium adsorption capacity of the two materials for different initial concentrations of Pb\u003csup\u003e2+\u003c/sup\u003e in solution was calculated by Eq.\u0026nbsp;(\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isothermal adsorption models were used for fitting, and their formulas are shown in supporting document (S4)(Freundlich \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1906\u003c/span\u003e, Langmuir \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e1917\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eCharacteristic description\u003c/h2\u003e \u003cp\u003eVarious analytical instruments (BET, XPS, SEM-EDS, AAS, XRD, FTIR) characterize the obtained materials and determine the concentration of Pb\u003csup\u003e2+\u003c/sup\u003e in the solution, detailed in the Supplementary material document (S6).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and discussions","content":"\u003cdiv id=\"Sec8\"\u003e\n \u003ch2\u003eOptimization of RMLL and PRMLL preparation\u003c/h2\u003e\n \u003cp\u003eOrthogonal experiments are designed. For details of orthogonal experiments, see supporting document (S5). The optimum preparation conditions of RMLL materials (temperature 600℃, mass ratio 1:1 and Bayer red mud) were obtained by orthogonal experiment. Then, on the basis of preparing RMLL materials, KH2PO4, which accounted for 15% of the mass of lotus leaves, was first uniformly mixed with lotus leaves, dissolved with deionized water, dried and ground, and then mixed with red mud according to the mass ratio of 1:1, and calcined at 600℃ without oxygen for 3h. Phosphate - lotus leaf - red mud composite material (0.15:1:1) was prepared. The adsorption properties of RMLL and PRMLL were compared. The specific preparation process is shown in Fig.\u0026nbsp;1.\u003c/p\u003e\n \u003cdiv id=\"Sec9\"\u003e\n \u003ch2\u003eCharacterization of RMLL and PRMLL materials\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig.\u0026nbsp;2 (a), the crystal phase composition of the original red mud and the modified red mud matrix composite was measured by XRD, and the results showed that the original red mud contained a high content of hematite (Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e). After calcination without oxygen at 600℃, calcite (CaCO\u003csub\u003e3\u003c/sub\u003e), magnetite (Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e), quartz (TiO\u003csub\u003e2\u003c/sub\u003e) and various metal-organic complexes were detected in RMLL (Li et al. 2019).It was further confirmed that a series of chemical reactions occurred between red mud and lotus leaves in the process of oxygen-free calcination, and new substances were produced. The XRD results of the phosphate-modified red mud substrate (PRMLL) are basically consistent with RMLL, and magnetite (Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e) and some phosphorous compounds are produced. The presence of these substances plays an important role in the removal of Pb\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eFigure 2 (b) shows the FTIR spectra of LL, RMLL and PRMLL. After carbonization of LL at 600℃, the stretching vibration peak of -OH at wave number 3415.99cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was found (Renli et al. 2019), It is probably formed by the water in the lotus leaves and a lot of cellulose expansion vibration; The wave numbers 877.4 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 2848.8cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 2918.3 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are C-H bonds (Jian-Liang et al. 2014, Yu 2019). The wave numbers 1412.5 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1577.9cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are -COO bonds, indicating that lotus leaves retain some functional groups at 600℃ carbonization, which is favorable for the adsorption of lead ions (Dinh et al. 2020). The infrared spectra of RMLL and PRMLL were basically consistent. Fe-O bonds were detected at wavelengths 441.4cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 561.5cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which may be the reason why Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e was formed after high temperature carbonization with lotus leaf powder in Bayer red mud(Yu 2019). Compared with RMLL, PRMLL has more P-O bonds, the wave number is 1258.7cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and there is a C\u0026thinsp;=\u0026thinsp;C bond at 1632.1cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e(Kwon et al. 2013). It is also found that the wavelength of -OH in PRMLL is shorter than that of LL and RMLL, because the presence of C\u0026thinsp;=\u0026thinsp;C bond and -OH group is required for phosphate adsorption, which also indicates that the reaction may occur at high temperature carbonization, and phosphate is successfully adsorbed on the material RMLL (Zhang et al. 2019). Compared with material LL, PRMLL and RMLL have larger difference and higher peak at wavelength 1000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which is formed by tensile vibration of metal bond, material LL is C-O bond, PRMLL and RML are Si(Al)-O (Jian-Liang et al. 2014, Li et al. 2020).It also shows that these metallic carbon-oxygen bonds are successfully loaded on lotus leaf biochar under the action of red mud.\u003c/p\u003e\n \u003cp\u003eFigure 2. (c), (d), (e) and (f) respectively show the SEM of LL, RM, RMLL and PRMLL under different magnifications. By comparing the microscopic morphology of several different materials, it can be clearly seen that the surface of raw red mud (RM) is rough, with heterogeneous aggregates and large pore structure. After carbonization at 600℃, lotus leaves (LL) have smooth surface, block and strip distribution, compact structure, and large single volume. RMLL can clearly see that a large amount of red mud is loaded on the smooth LL surface. In the process of carbonization, adding red mud can better induce LL skeleton to form more porous structures. After the addition of phosphorus KH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e, the surface of the PRMLL is not only loaded with a large amount of red mud, but also some fine particles on the surface, which may be the phosphate substance loaded on the surface under the action of high temperature with the addition of KH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e.\u003c/p\u003e\n \u003cp\u003eFigure 3. (a) shows the desorption and adsorption curves of the three materials. It can be seen from the diagram that the area enclosed by the desorption curves of RMLL and PRMLLIs is obviously larger than that enclosed by LL. It shows that the specific surface area of the monomer material has changed after composite modification, and it has expanded several times, which is more advantageous to the removal of lead ions. Figure\u0026nbsp;3 (b) is the pore size distribution diagram of the three materials. It can be seen from the figure that most of the pore sizes of the three materials are distributed between 5 and 50nm. It also shows that the three materials are mesoporous materials. The specific surface area, total pore volume and average pore diameter data of the three materials are shown in Table\u0026nbsp;1.\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 1\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eSpecific surface area, total pore volume and pore size data tables for LL, RMLL and PRMLL\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMaterials\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSpecific surface area(m\u003csup\u003e2\u003c/sup\u003eg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTotal pore volume(cm\u003csup\u003e3\u003c/sup\u003eg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMean aperture(nm)\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\u003eLL\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.808\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.0275\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e39.216\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eRMLL\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e19.714\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.088\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e17.871\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003ePRMLL\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e23.675\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.086\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15.492\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\"\u003e\n \u003ch2\u003eEffects of PH, dosage and initial concentration\u003c/h2\u003e\n \u003cp\u003eFor lead, the PH level has a huge impact on it. PH has an important influence on the morphology of heavy metals and the surface charge characteristics of biochar based adsorbents. The result is shown in Fig.\u0026nbsp;4 (a). The adsorption capacity of RMLL and PRMLL for Pb\u003csup\u003e2+\u003c/sup\u003e increased with the increase of PH. At PH 2, the adsorption capacities of RMLL and PRMLL for Pb\u003csup\u003e2+\u003c/sup\u003e were 37.23mg/g and 53.82mg/g, respectively. When PH was 7, the adsorption capacities of RMLL and PRMLL were 217.63mg/g and 232.96mg/g, respectively. When PH is 6\u0026thinsp;~\u0026thinsp;7, the increase of adsorption capacity has gradually leveled off. PH is too low, the adsorption capacity of the material is poor, because the content of H\u003csup\u003e+\u003c/sup\u003e in the solution is high, and Pb\u003csup\u003e2+\u003c/sup\u003e has a competitive adsorption reason. Secondly, the two materials are based on lotus leaf biochar as the carrier and loaded with red mud as the main material. The positive charge on the surface repels the positive valence metal ion charge, which will also make the adsorption performance of the material worse (Huang et al. 2020, Yang et al. 2019). The increase of PH and the surface negative charge of the two materials are conducive to the adsorption of lead ions (Liu et al. 2022). At the same time, CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e, PO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e3\u0026minus;\u003c/sup\u003e and SO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e can form precipitates with Pb\u003csup\u003e2+\u003c/sup\u003e, which increases the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e by the two materials (Luu et al. 2022). Based on the above analysis and combined with Fig. 4, the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e by RMLL and PRMLL was studied, and the solution PH was 7. Figure 4(b) shows the RMLL and PRMLL Zate potential plots, indicating a strong negative potential at PH 4\u0026thinsp;~\u0026thinsp;10,which may have strong surface charge adsorption ability for positively charged cations.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig.\u0026nbsp;4 (c), when the dosage of RMLL and PRMLL increased from 0.05g to 0.4g, the adsorption capacity of Pb\u003csup\u003e2+\u003c/sup\u003e decreased from 235.98mg/g and 259.25mg/g to 62.5mg/g and 62.5mg/g, respectively. On the contrary, the removal rate of Pb\u003csup\u003e2+\u003c/sup\u003e increased with the increase of dosage. It may be because the dosage is at a low level, and the solubility of Pb\u003csup\u003e2+\u003c/sup\u003e is high, and the adsorption sites provided by the material are limited. When the dosage increased to 0.35g, the removal rate of Pb\u003csup\u003e2+\u003c/sup\u003e reached 100%, because with the increase of the dosage of materials, the surface functional groups and adsorption sites of the materials also increased, and the removal rate of lead ions increased. The adsorption capacity and removal rate of Pb\u003csup\u003e2+\u003c/sup\u003e by RMLL and PRMLL have an intersection point, and its value ranges from 0.1 to 0.125, which is basically consistent with the results of orthogonal experiment. Considering the adsorption capacity and cost of materials, the dosage of this project is set at 0.1g for subsequent research.\u003c/p\u003e\n \u003cp\u003eFigure 4 (d) shows the adsorption capacity and removal rate of Pb\u003csup\u003e2+\u003c/sup\u003e by RMLL and PRMLL at different initial concentrations, PH 7, dosage 0.1g, and temperature 25℃. As can be seen from the figure, with the increase of the initial concentration, the removal rate of Pb\u003csup\u003e2+\u003c/sup\u003e of the two materials continued to decline. However, with the gradual increase of the initial concentration, the equilibrium adsorption capacity of RMLL and PRMLL materials also gradually increased, and reached an equilibrium state when the concentration was 700mg/L, and the equilibrium adsorption capacity was 181.5mg/g and 214.66mg/g, respectively. When the solution concentration is low, RMLL and PRMLL materials have more active sites and can carry out sufficient ion exchange with Pb\u003csup\u003e2+\u003c/sup\u003e. At the same time, with the increase of concentration, a large amount of Pb\u003csup\u003e2+\u003c/sup\u003e occupied the active site of the material, reaching a saturated state, inhibiting the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e on its surface, resulting in a decrease in the removal rate.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\"\u003e\n \u003ch2\u003eAdsorption kinetics\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig.\u0026nbsp;5 (a), the adsorption of lead ions by RMLL and PRMLL2 materials has been increasing uniformly over time in the first 12 hours. From the 12th hour, its adsorption capacity has been in a relatively balanced state. Therefore, in the first 12 hours, the adsorption capacity of RMLL and PRMLL for lead ions has reached the adsorption equilibrium state, in which the equilibrium adsorption capacity of RMLL is 190.25mg/g, and the equilibrium adsorption capacity of PRMLL is 220.4mg/g. This is due to the fact that sufficient adsorption sites and the driving force of a large concentration gradient can lead to an initial rapid increase in adsorption capacity (Wang et al. 2020). As the adsorption site is gradually occupied, the repulsive force on the solid-liquid interface increases, the adsorption rate decreases, and finally the adsorption equilibrium is reached (Hang et al. 2019b, Lyu et al. 2021, Wei et al. 2018).\u003c/p\u003e\n \u003cp\u003eFigure 5 (b) (c) (d) is the fitting diagram of pseudo-first-order, pseudo-second-order and Elovich kinetic models of RMLL and PRMLL2 materials. It can be seen that the R\u003csup\u003e2\u003c/sup\u003e of the pseudo-second-order kinetic model of RMLL and PRMLL are 0.9993 and 0.9994 respectively, which are higher than the R\u003csup\u003e2\u003c/sup\u003e of 0.99516 and 0.99607 of the first-order kinetic model. The fitted qt values of 190.25mg/g and 219.6mg/g are closer to the experimental values of 191.1mg/g and 220.4mg/g, respectively.\u003c/p\u003e\n \u003cp\u003eThe R\u003csup\u003e2\u003c/sup\u003e values fitted by Elovich kinetics are 0.987 and 0.982 respectively, which are lower than the second-order kinetics. Therefore, it can be better explained that the second-order kinetic model is more consistent with the adsorption process of Pb\u003csup\u003e2+\u003c/sup\u003e by RMLL and PRMLL materials, and that the adsorption process of these two materials is also a chemical adsorption process.\u003c/p\u003e\n \u003cp\u003e\u003cimg src=\"data:image/png;base64,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\" width=\"573\" height=\"417\"\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\"\u003e\n \u003ch2\u003eIsothermal adsorption model\u003c/h2\u003e\n \u003cp\u003eAdsorption experiments were conducted at different initial Pb\u003csup\u003e2+\u003c/sup\u003e concentrations to obtain adsorption isotherms, and experimental data and the fitting curves of Langmuir and Freundlich isotherms were drawn, as shown in Fig. 6. Figure 6 (a) shows that the equilibrium adsorption capacity changes with the initial Pb\u003csup\u003e2+\u003c/sup\u003e concentration. When the concentration is below 700mg/L, the equilibrium adsorption capacity of RMLL and PRMLL for Pb\u003csup\u003e2+\u003c/sup\u003e shows a uniform upward trend with the increase of the concentration, and then slowly rises to the saturation state. It is possible that when the concentration is low, the amount of pollutants is much lower than the adsorption capacity of the material, and the change of the concentration gradient increases the resistance to overcome the mass transfer at the solid-liquid interface\u003csup\u003e(A et al. 2019)\u003c/sup\u003e. At high concentrations, the resistance between the adsorbent surface and the solution increases rapidly, making the equilibrium adsorption capacity increase slowly and reach the saturated adsorption capacity.\u003c/p\u003e\n \u003cp\u003eFigure 6 (b) (c) shows the data fitting graphs of Langmuir, Freundlich and Temkin isothermal adsorption models of RMLL and PRMLL respectively. Figure\u0026nbsp;6 (d) is the fitting diagram of RMLL and PRML Dubinin-Radushkevich isothermal adsorption model. It can be seen that both RMLL and PRMLL materials can be well described by Langmuir, Freundlich, Temkin and D-R isothermal absorption equations. The \\(R_{1}^{2}\\) values of RMLL and PRMLL materials are 0.989 and 0.989, respectively, which are larger than 0.973 and 0.937 of\\(R_{2}^{2}\\), 0.964 and 0.961 of \\(R_{3}^{2}\\)and 0.898 and 0.938 of\\(R_{4}^{2}\\), indicating that these two materials are more consistent with Langmuir isothermal adsorption model. In the Dubinin-Radushkevich isothermal adsorption model, the E value between 8 and 16kj.mol indicates chemical adsorption, while the E value less than 8 kJ.mol indicates physical adsorption (Ecer 2018, Hang et al. 2019a, Yilmaz et al. 2018). In the D-R model fitting of RMLL and PRMLL, the E values of RMLL and PRMLL are 1.912 and 2.637, both of which are less than 8kj.mol. It is possible that the two materials in the chemical adsorption at the same time, there are physical adsorption reasons. The 1/n of RMLL and PRMLL materials are both between 0.1 and 0.5, indicating that carbonized red mud-Lotus leaf (RMLL) and phosphate-modified red mud-Lotus leaf (PRMLL) can be easily adsorbed, and the adsorption capacity of phosphate-modified red mud-lotus leaf is stronger than that of carbonized red mud-lotus leaf (Lyu et al. 2021). In addition, it can be seen from Table\u0026nbsp;3 that the \\({k_L}\\)value of RMLL and PRMLL2 materials is 0.11294 and 0.13636, which is between 0 and 1, which means that the adsorption process of the material is favorable (Al-Ghouti et al., Zeng et al. 2020). Relevant studies show that the adsorption capacity of red mud matrix composites is obviously better than that of some common biochar materials, aerogel, iron matrix and clay mineral composites (Zeng et al. 2020). Therefore, the removal of heavy metal ions from water by red mud matrix composite is a potential material. In addition, it can also alleviate the accumulation of red mud and reduce some problems such as environmental pollution, which is consistent with the concept of sustainable development advocated at present.\u003c/p\u003e\n \u003cdiv\u003e\n \u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 3\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eCalculated isotherm parameters for Pb\u003csup\u003e2+\u003c/sup\u003eabsorption on RMLL and PRMLL.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eModels\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eParameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eMaterial\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRMLL\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePRMLL\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003eLangmuir\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\\({q_m}\\)(mg/g)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e189.496\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e218.056\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\\({k_L}\\)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.112\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.136\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\\(R_{1}^{2}\\)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.989\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.989\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003eFreundlich\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\\({k_F}\\)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e49.694\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e76.392\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/n\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.211\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.173\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\\(R_{2}^{2}\\)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.973\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.937\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003e\u003cstrong\u003eTemkin\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\\({A_T}\\)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.843\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.071\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\\({b_T}\\)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e63.245\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e65.052\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\\(R_{3}^{2}\\)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.923\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.940\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" rowspan=\"4\"\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\\({q_m}\\)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e178.215\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e214.325\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\\(\\beta\\)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.357\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e7.546\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.912\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.637\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\\(R_{4}^{2}\\)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.898\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.938\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\"\u003e\n \u003ch2\u003eAdsorption mechanism\u003c/h2\u003e\n \u003cp\u003eIn order to better explore the adsorption mechanism of RMLL and PRMLL on Pb\u003csup\u003e2+\u003c/sup\u003e. The RMLL and PRMLL adsorbed Pb\u003csup\u003e2+\u003c/sup\u003e were analyzed by XRD to determine the phase composition of the materials. As shown in Fig. 7 (a), XRD patterns of RMLL and PRMLL after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e show diffraction peaks of PbCO\u003csub\u003e3\u003c/sub\u003e, Pb\u003csub\u003e3\u003c/sub\u003e(CO3)\u003csub\u003e2\u003c/sub\u003e(OH)\u003csub\u003e2\u003c/sub\u003e and Pb\u003csub\u003e5\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003eCl. The results showed that Pb\u003csup\u003e2+\u003c/sup\u003e formed a precipitate and adsorbed on the surface of the material through chemisorption.\u003c/p\u003e\n \u003cp\u003eFigure. 7 (b) shows the FTIR diagram after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e by RMLL and PRMLL. It is found that the characteristic peaks of carboxyl group binding with Pb\u003csup\u003e2+\u003c/sup\u003e are generated near 1633.43cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 621.05cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, indicating that carboxyl group has a strong binding ability with the main group element Pb\u003csup\u003e2+\u003c/sup\u003e and forms an effective coordination(Luu et al. 2022). It can also be seen from the figure that after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e by RMLL and PRMLL, the peaks at 1415.5cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1003.49cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are significantly enhanced, indicating that the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e by RMLL and PRMLL is mainly achieved through cation exchange between carbonate and silicate, and the adsorption mechanism is consistent with that of RM(Dinh et al. 2020). Secondly, at 3426.45cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is the stretching vibration of O-H group(Huang et al. 2020, Renli et al. 2019). 621.05cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 1003.49cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1122.82cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are related to the stretching and vibration of Si-O tetrahedrons or Al-O tetrahedrons, and all of them are displaced after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e (Ahmed et al. 2023b, Yu 2019). The peak displacement indicates that Pb\u003csup\u003e2+\u003c/sup\u003e is adsorbed on the surface of RMLL and PRMLL by chemisorption, which is consistent with XRD analysis.\u003c/p\u003e\n \u003cp\u003eAs shown in Fig.\u0026nbsp;8 (a), the total XPS spectra of RM, RMLL and RMLL and PRMLL adsorbed Pb\u003csup\u003e2+\u003c/sup\u003e, in which the C peak of RMLL is much higher than that of the original red mud, indicating that lotus leaf and red mud have been successfully loaded in the process of (1:1) carbonization. Compared with the O peak of the original red mud, the O peak of RMLL was shorter, which may be due to the red mud as an oxygen carrier, which promoted the further gasification of lotus leaves and produced more carbon dioxide(Haiming et al. 2015), Secondly, in the process of anaerobic calcination, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in the original red mud reacts with C and CO respectively to produce Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e, thus consuming O element. In the comparison of the total spectrum, new characteristic peaks of RMLL and PRMLL after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e appear around 185.6eV and 411.45eV, namely (Pb4f) and (Pb4d), which may be PbCO\u003csub\u003e3\u003c/sub\u003e, Pb\u003csub\u003e3\u003c/sub\u003e(CO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e(OH)\u003csub\u003e2\u003c/sub\u003e and Pb\u003csub\u003e5\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003eCl after query in NTST spectrum library. This also shows that Pb\u003csup\u003e2+\u003c/sup\u003e is strongly adsorbed on the surface of the material through chemisorption.\u003c/p\u003e\n \u003cp\u003eThe Fe spectra in RM, RMLL, PRMLL and RMLL adsorbed with Pb\u003csup\u003e2+\u003c/sup\u003e were compared. As shown in Fig. 8 (b1), b2), b3 and (b4) (b5). The spectral peaks of RM, RMLL, PRMLL and RMLL,Fe2p\u003csub\u003e3/2\u003c/sub\u003e and Fe2p\u003csub\u003e1/2\u003c/sub\u003e after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e appear at 711.0 eV and 724.4eV(Geng et al. 2017). By semi-quantitative analysis of Fe2p\u003csub\u003e3/2\u003c/sub\u003e and Fe2p\u003csub\u003e1/2\u003c/sub\u003e orbits, the peak-area ratios of Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e and Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e are 1.8, 0.6, 0.5 and 1.2, 1.3, respectively. It shows that the red mud formed a large amount of Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e after carbonization with lotus leaves at 600℃, and consumed a large amount of Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e, which is consistent with the previous XRD analysis(Yan et al. 2022). The C spectrum in RMLL after Pb\u003csup\u003e2+\u003c/sup\u003e adsorption is compared with that in RMLL after Pb\u003csup\u003e2 +\u003c/sup\u003e adsorption, as shown in Fig. 8(c1), peaks appear at 284.2eV, 285.7eV and 288.6eV, which may be the functional groups of C-H/C-C, C-O and C\u0026thinsp;=\u0026thinsp;O. The peaks at 292.7eV are \u0026pi;-\u0026pi; transitions, which may be the result of aromatic rings(Ahmed et al. 2023a). Figure 8 (c2) In contrast, the peak area of C-H/C-C bond after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e is reduced, which may be due to the metal complexation reaction. The peak area of C-O increased and the binding energy decreased, which may be involved in the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e. It can also be seen from the figure that after adsorption of lead, the peak area of metal carbonate increases and the binding energy decreases. The peak area of C-O increased and the binding energy decreased, which may be involved in the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e. It can also be seen from the figure that after adsorption of lead, the peak area of metal carbonate increases and the binding energy decreases.\u003c/p\u003e\n \u003cp\u003eFigure 8 (d) shows the XPS high resolution spectrum of Pb4f after Pb\u003csup\u003e2+\u003c/sup\u003e adsorption by RMLL. As can be seen in the figure, the peak of Pb4f7/2 was observed at 138.17ev, indicating that Pb\u003csup\u003e2+\u003c/sup\u003e became a carbonate compound (PbCO\u003csub\u003e3\u003c/sub\u003e) and was adsorbed on the material(Lyu et al. 2021). The results of XRD, FTIR and XPS have proved the formation of PbCO\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e\n \u003cp\u003eIn order to better prove that RMLL and PRMLL have adsorption effect on Pb\u003csup\u003e2+\u003c/sup\u003e. SEM-EDS was used to characterize RMLL and PRMLL after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e. Figure\u0026nbsp;9 (a) and (e) are the SEM images after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e by RMLL and PRMLL respectively. It can be seen from the figure that Pb\u003csup\u003e2+\u003c/sup\u003e is deposited on the entire surface of the material in a flocculent form, indicating that the material has a good adsorption effect on Pb\u003csup\u003e2+\u003c/sup\u003e. Figure\u0026nbsp;9 (b) and (f) show the EDS-mapping diagram after adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e by RMLL and PRMLL respectively, and it can be clearly seen that a large amount of Pb\u003csup\u003e2+\u003c/sup\u003e is adsorbed on the surface of the material. Figure 9 (d) and (h) are EDS spectra after RMLL and PRMLLPb\u003csup\u003e2+\u003c/sup\u003e. The presence of Pb\u003csup\u003e2+\u003c/sup\u003e can be clearly seen in the figure, and it is relatively high, which also indicates that the composite material has a large adsorption capacity for Pb\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eIn summary, the results were analyzed by XRD, FTIR, XPS and SEM-EDS. The removal effect of RMLL and PRMLL on Pb\u003csup\u003e2+\u003c/sup\u003e in water mainly has the following three aspects. First, Na\u003csup\u003e+\u003c/sup\u003e and Ca\u003csup\u003e2+\u003c/sup\u003e in the composite are dissolved in solution for ion exchange, and Pb\u003csup\u003e2+\u003c/sup\u003e in the solution is adsorbed on the surface of the material and reacts with carbonate to form PbCO\u003csub\u003e3\u003c/sub\u003e and Pb\u003csub\u003e3\u003c/sub\u003e(CO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e(OH)\u003csub\u003e2\u003c/sub\u003e. Secondly, when CaCO\u003csub\u003e3\u003c/sub\u003e in the material dissolves, part of CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e will be released into the solution, which is conducive to the formation of PbCO\u003csub\u003e3\u003c/sub\u003e and Pb\u003csub\u003e3\u003c/sub\u003e(CO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e(OH)\u003csub\u003e2\u003c/sub\u003e. Second, in the process of oxygen-free high-temperature calcination of red mud and lotus leaves, Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e will be reduced to Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e, which also plays an important role in the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e. Third, the interaction between phosphate and heavy metals promotes the precipitation of stable phosphate. The modified RMLL by KH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e can increase the potassium in the material, and thus increase the cation exchange capacity in the material. P can enter the material polymer to form new bonds such as C-O-P (YaxinLi et al.), the adsorption site was increased. After impregnation with KH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e, new minerals such as potassium metaphosphate (KPO\u003csub\u003e3\u003c/sub\u003e) and potassium pyrophosphate (K\u003csub\u003e4\u003c/sub\u003eP\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e) are formed on the surface of the material at high temperature. Metaphosphates are formed by 2 or more phosphate groups via O-P-O bonds (straight or circular) (also known as polyphosphates) and are readily chelated with heavy metals(Wang et al. 2022). In addition, heavy metals such as Pb\u003csup\u003e2+\u003c/sup\u003e can form extremely insoluble precipitates by reacting with potassium pyrophosphate, such as the formation of Pb\u003csub\u003e2\u003c/sub\u003eP\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e and Pb\u003csub\u003e5\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003eCl(Zhang et al. 2023). The main reactions in the adsorption process are as follows (1) (2) (Lyu et al. 2021, Zhou et al. 2017).\u003c/p\u003e\n \u003cdiv id=\"Equ1\"\u003e\n \u003cdiv id=\"FileID_Equ1\" name=\"EquationSource\"\u003e$$P{b^{2+}}+CO_{3}^{{2 - }} \\to PbC{O_3}$$\u003c/div\u003e\n \u003cdiv\u003e1\u003c/div\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Equ2\"\u003e\n \u003cdiv id=\"FileID_Equ2\" name=\"EquationSource\"\u003e$$3P{b^{2+}}+2HCO_{3}^{{2 - }}+4O{H^ - } \\to P{b_3}{(C{O_3})_2}{(OH)_2}+2{H_2}O$$\u003c/div\u003e\n \u003cdiv\u003e2\u003c/div\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eRM is a kind of larger industrial waste, damage to the environment from all aspects has irreversible effects on the environment, and the huge annual emissions.\u003c/p\u003e \u003cp\u003eAt the same time, the characteristics of red mud itself is also a huge resource. In this project, red mud and lotus leaf powder were carbonized at high temperature and modified with KH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e to remove Pb\u003csup\u003e2+\u003c/sup\u003e in sewage, which received dual effects of environment and economy, and also reflected the current new idea of \"resource utilization\". The results show that RMLL and PRMLL have good adsorption effect on Pb\u003csup\u003e2+\u003c/sup\u003e. The RM based material (PRMLL) modified with KH\u003csub\u003e2\u003c/sub\u003ePO4 has better adsorption effect on Pb\u003csup\u003e2+\u003c/sup\u003e than RMLL, and its adsorption effect is increased by 15.3%. The fitting of experimental data found that the kinetics studies of RMLL and PRMLL materials showed that the two materials were more in line with pseudo-second-order kinetics, and also reflected that Pb\u003csup\u003e2+\u003c/sup\u003e was chemically adsorbed on the surface of the material through ion exchange. The data fitting of isothermal adsorption showed that RMLL and PRMLL were monolayer adsorption, and the K\u003csub\u003eL\u003c/sub\u003e constants of Langmuir were 0.11 and 0.13, respectively, which was conducive to the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e. Finally, XRD, XPS, FTIR and SEM-EDS were used to characterize the adsorbed Pb\u003csup\u003e2+\u003c/sup\u003e materials, which fully proved that Pb\u003csup\u003e2+\u003c/sup\u003e can be adsorbed by chemical adsorption. Adsorbed on the surface of the material in the form of carbonate and phosphate precipitates. In addition, RMLL and PRMLL retain some organic functional groups (-COOH) during the carbonization process, which also plays a certain role in promoting the removal of Pb\u003csup\u003e2+\u003c/sup\u003e. Therefore, we can speculate that the adsorption mechanism of RMLL and PRMLL on Pb\u003csup\u003e2+\u003c/sup\u003e may be a combination of ion exchange and chemical precipitation and complexation. Compared with the original red mud, modified red mud and some single adsorption materials, this material has a larger adsorption capacity. Moreover, red mud is a kind of industrial waste, which has dual environmental and economic benefits in terms of environmental management. Therefore, RMLL and PRMLL can be used as potential adsorbents to remove Pb\u003csup\u003e2+\u003c/sup\u003e from water.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e\u0026nbsp;Ethics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service, and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled, \u0026ldquo;Characterization of phosphate modified red mud based composite materials and study on heavy metal adsorption\u0026rdquo;.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAppendix A. Supplementary material document.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe following are the supplementary data to this article: Supplementary document.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of Competing Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026apos; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eWenlou Jin\u003c/strong\u003e: Conceptualization, Data curation, Writing-original draft. \u003cstrong\u003eYanzhi Yang\u003c/strong\u003e: Supervision, Resources. \u003cstrong\u003eJiacheng Jin:\u003c/strong\u003e Data curation. \u003cstrong\u003eMingcheng Xu\u003c/strong\u003e: Investigation, Data curation. \u003cstrong\u003eFan Dong\u003c/strong\u003e: Formal analysis. \u003cstrong\u003eZhipeng Zhang\u003c/strong\u003e: Data curation, Investigation. \u003cstrong\u003eMin Shao\u003c/strong\u003e: Conceptualization, Funding acquisition, Writing-review \u0026amp; editing. \u003cstrong\u003eYushan Wan\u003c/strong\u003e: Conceptualization, Funding acquisition, Writing-review \u0026amp; editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe author sincerely thanks the Jiangsu Graduate Research and Practice Innovation Program (SJCX23-1558) for funding. Thanks to Shiyanjia Lab [www.shiyanjia.com] for its help in the XPS test.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eA QW, B CZA, A ZS, C QL, D CHA, E TCZ, C JL (2019): Polyethyleneimine and carbon disulfide co-modified alkaline lignin for removal of Pb\u003csup\u003e2+\u003c/sup\u003e ions from water - ScienceDirect. Chemical Engineering Journal 359, 265-274 \u003c/li\u003e\n\u003cli\u003eA WS, B HR, B XH, B ML, B YT, C FG Low cost red mud modified graphitic carbon nitride for the removal of organic pollutants in wastewater by the synergistic effect of adsorption and photocatalysis - ScienceDirect. Separation and Purification Technology 237\u003c/li\u003e\n\u003cli\u003eAhmed W, Mehmood S, Mahmood M, Ali S, Shakoor A, Nunez-Delgado A, Asghar RMA, Zhao H, Liu W, Li W (2023a): Adsorption of Pb(II) from wastewater using a red mud modified rice-straw biochar: Influencing factors and reusability. Environmental Pollution\u003c/li\u003e\n\u003cli\u003eAhmed W, Mehmood S, Mahmood M, Ali S, Shakoor A, N\u0026uacute;\u0026ntilde;ez-Delgado A, Asghar RMA, Zhao H, Liu W, Li W (2023b): Adsorption of Pb(II) from wastewater using a red mud modified rice-straw biochar: Influencing factors and reusability. Environmental Pollution 326, 121405 \u003c/li\u003e\n\u003cli\u003eAkin I, Arslan G, Tor A, Ersoz M, Cengeloglu Y (2012): Arsenic(V) removal from underground water by magnetic nanoparticles synthesized from waste red mud. Journal of Hazardous Materials 235-236, 62-68 \u003c/li\u003e\n\u003cli\u003eAl-Ghouti MA, Da, X, Ana DA Guidelines for the use and interpretation of adsorption isotherm models: A review. Journal of Hazardous Materials 393\u003c/li\u003e\n\u003cli\u003eBagla H, Khilnani R (2016): Kinetics of biosorption of hazardous metals by green soil supplement, Egu General Assembly Conference\u003c/li\u003e\n\u003cli\u003eBlanchard G, Maunaye M, Martin G (1984): Removal of heavy metals from waters by means of natural zeolites. Water Research 18, 1501-1507 \u003c/li\u003e\n\u003cli\u003eConceio FTD, Silva MSGD, Meneg\u0026aacute;rio AA, Antunes MLP, Moruzzi RB (2021): Precipitation as the main mechanism for Cd(II), Pb(II) and Zn(II) removal from aqueous solutions using natural and activated forms of red mud. Environmental Advances\u003c/li\u003e\n\u003cli\u003eDinh VP, Nguyen MD, Nguyen QH, Do TTT, Tan LV (2020): Chitosan-MnO2 nanocomposite for effective removal of Cr (VI) from aqueous solution. Chemosphere 257, 127147 \u003c/li\u003e\n\u003cli\u003eEcer SS, Tekin (2018): Highly efficient Cd(II) adsorption using mercapto-modified bentonite as a novel adsorbent: an experimental design application based on response surface methodology for optimization. Water Science and Technology 78\u003c/li\u003e\n\u003cli\u003eElebi H, Gk G, Gk O (2020): Adsorption capability of brewed tea waste in waters containing toxic lead(II), cadmium (II), nickel (II), and zinc(II) heavy metal ions. Scientific Reports 10, 17570 \u003c/li\u003e\n\u003cli\u003eFreundlich HMF (1906): UBER DIE ADSORPTION IN LOSUNGEN. \u003c/li\u003e\n\u003cli\u003eGeng J, Zhou M, Zhang T, Wang W, Wang T, Zhou X, Wang X, Hou H (2017): Preparation of blended geopolymer from red mud and coal gangue with mechanical co-grinding preactivation. Materials \u0026amp; Structures 50, 109 \u003c/li\u003e\n\u003cli\u003eHaiming, Shen, Laihong (2015): Cement/CaO-modified iron ore as oxygen carrier for chemical looping combustion of coal. Applied Energy\u003c/li\u003e\n\u003cli\u003eHang Y, Si Y, Zhou Q, Yin H, Cao A (2019a): Morphology-controlled synthesis of calcium titanate particles and adsorption kinetics, isotherms, and thermodynamics of Cd(II), Pb(II), and Cu(II) cations. Journal of Hazardous Materials 380, 120789- \u003c/li\u003e\n\u003cli\u003eHang Y, Si Y, Zhou Q, Yin H, Wang A, Cao A (2019b): Morphology-controlled synthesis of calcium titanate particles and adsorption kinetics, isotherms, and thermodynamics of Cd(II), Pb(II), and Cu(II) cations. Journal of Hazardous Materials 380, 120789 \u003c/li\u003e\n\u003cli\u003eHuang R, Lin Q, Zhong Q, Zhang X, Wen X, Luo H (2020): Removal of Cd(II) and Pb(II) from aqueous solution by modified attapulgite clay - ScienceDirect. Arabian Journal of Chemistry 13, 4994-5008 \u003c/li\u003e\n\u003cli\u003eJian-Liang, Cao, Zhao-Li, Yan, Qing-Fang, Deng, Yan, Wang, Zhong-Yong, Yuan (2014): Mesoporous modified-red-mud supported Ni catalysts for ammonia decomposition to hydrogen. International Journal of Hydrogen Energy\u003c/li\u003e\n\u003cli\u003eKazak O, Tor A (2020): In situ preparation of magnetic hydrochar by co-hydrothermal treatment of waste vinasse with red mud and its adsorption property for Pb(II) in aqueous solution. Journal of Hazardous Materials 393, 122391 \u003c/li\u003e\n\u003cli\u003eKhairul MA, Zanganeh J, Moghtaderi B (2018): The composition, recycling and utilisation of Bayer red mud. Resources Conservation and Recycling 141, 483-498 \u003c/li\u003e\n\u003cli\u003eKrishnani KK, Meng X, Christodoulatos C, Boddu VM (2008): Biosorption mechanism of nine different heavy metals onto biomatrix from rice husk. Journal of hazardous materials, 153 \u003c/li\u003e\n\u003cli\u003eKwon SM, Jang JH, Lee SH, Park SB, Kim NH (2013): Change of Heating Value, pH and FT-IR Spectra of Charcoal at Different Carbonization Temperatures. Journal of the Korean Wood Science \u0026amp; Technology 41\u003c/li\u003e\n\u003cli\u003eLangmuir I (1917): The Adsorption of Gases on Plane Surfaces of Glass, Mica and Platinum. Journal of the American Chemical Society 40\u003c/li\u003e\n\u003cli\u003eLi F, Cao X, Zhao L, Wang J, Ding Z (2014): Effects of Mineral Additives on Biochar Formation: Carbon Retention, Stability, and Properties. Environmental Science \u0026amp; Technology 48, 11211-7 \u003c/li\u003e\n\u003cli\u003eLi P, Liu Z, Yan H, He Y (2019): Recover Iron from Bauxite Residue (Red Mud)\u003c/li\u003e\n\u003cli\u003eLi S, Zhang J, Li Z, Liu C, Chen J (2020): Feasibility study on grouting material prepared from red mud and metallurgical wastewater based on synergistic theory. Journal of Hazardous Materials 407, 124358 \u003c/li\u003e\n\u003cli\u003eLiu R, Zhang Y, Hu B, Wang H (2022): Improved Pb(II) removal in aqueous solution by sulfide@biochar and polysaccharose-FeS@ biochar composites: Efficiencies and mechanisms. Chemosphere 287, 132087- \u003c/li\u003e\n\u003cli\u003eLuu T-T, Dinh V-P, Nguyen Q-H, Tran N-Q, Nguyen D-K, Ho T-H, Nguyen V-D, Tran DX, Kiet HAT (2022): Pb(II) adsorption mechanism and capability from aqueous solution using red mud modified by chitosan. Chemosphere 287, 132279 \u003c/li\u003e\n\u003cli\u003eLyu F, Niu S, Wang L, Liu R, Sun W, He D (2021): Efficient removal of Pb(II) ions from aqueous solution by modified red mud. Journal of Hazardous Materials 406, 124678 \u003c/li\u003e\n\u003cli\u003eRenli, Yin, Wanqian, Guo, Huazhe, Wang, Juanshan, Du, Qinglian (2019): Singlet oxygen-dominated peroxydisulfate activation by sludge-derived biochar for sulfamethoxazole degradation through a nonradical oxidation pathway: Performance and mechanism. Chemical Engineering Journal\u003c/li\u003e\n\u003cli\u003eShirzadi H, Nezamzadeh-Ejhieh A (2017): An efficient modified zeolite for simultaneous removal of Pb(II) and Hg(II) from aqueous solution. Journal of Molecular Liquids 230, 221-229 \u003c/li\u003e\n\u003cli\u003eWang L, Sun N, Tang H, Sun W (2019): A Review on Comprehensive Utilization of Red Mud and Prospect Analysis. Minerals 9, 362 \u003c/li\u003e\n\u003cli\u003eWang L, Shi C, Pan L, Zhang X, Zou JJ (2020): Rational design, synthesis, adsorption principles and applications of metal oxide adsorbents: a review. Nanoscale 12, 4790-4815 \u003c/li\u003e\n\u003cli\u003eWang Q, C.-J. D, C.-Y. X, Z.-C. G (2022): Efficient removal of Cd(II) by phosphate-modified biochars derived from apple tree branches: Processes, mechanisms, and application. Science of the Total Environment, 819 \u003c/li\u003e\n\u003cli\u003eWei D, Jun-Hui X, Yang P, Si-Yue S, Tao C (2019): Iron Extraction from Red Mud using Roasting with Sodium Salt. Mineral Processing and Extractive Metallurgy Review, 1-9 \u003c/li\u003e\n\u003cli\u003eWei Z, Qian D, Qiulai H, Jianyang S, Shilu Z, Hongyu W, Jinping Z, Huining Z (2018): A facile synthesis of core-shell/bead-like poly (vinyl alcohol)/alginate@PAM with good adsorption capacity, high adaptability and stability towards Cu(Ⅱ) removal. Chemical Engineering Journal 351, 462-472 \u003c/li\u003e\n\u003cli\u003eXu X, Hu X, Ding Z, Chen Y (2017): Effects of copyrolysis of sludge with calcium carbonate and calcium hydrogen phosphate on chemical stability of carbon and release of toxic elements in the resultant biochars. Chemosphere 189, 76 \u003c/li\u003e\n\u003cli\u003eYan Y, Qi F, Zhang L (2022): Enhanced Cd adsorption by red mud modified bean-worm skin biochars in weakly alkali environment. Separation and Purification Technology, 297 \u003c/li\u003e\n\u003cli\u003eYang D, Wang L, Li Z, Tang X, Xu J (2019): Simultaneous adsorption of Cd(II) and As(III) by a novel biochar-supported nanoscale zero-valent iron in aqueous systems. Science of The Total Environment 708, 134823 \u003c/li\u003e\n\u003cli\u003eYang D, Deng W, Tan A, Chu Z, Wei W, Zheng R, Shangguan Y, Sasaki A, Endo M, Chen H (2021): Protonation stabilized high As/F mobility red mud for Pb/As polluted soil remediation. Journal of Hazardous Materials 404, 124143 \u003c/li\u003e\n\u003cli\u003eYang D, Wang R, Feng X, Chu Z, Li J, Wei W, Zheng R, Zhang J, Chen H (2022): Transferring waste red mud into ferric oxide decorated ANA-type zeolite for multiple heavy metals polluted soil remediation. Journal of Hazardous Materials 424, 127244- \u003c/li\u003e\n\u003cli\u003eYaxinLi, XianZhang, RuiguangYang, GuiyingLi, ChangweiHu The role of H 3 PO 4 in the preparation of activated carbon from NaOH-treated rice husk residue. RSC Advances 5\u003c/li\u003e\n\u003cli\u003eYilmaz S, Ecer U, Sahan T (2018): Modelling and Optimization of As(III) Adsorption onto Thiol-Functionalized Bentonite from Aqueous Solutions Using Response Surface Methodology Approach. Chemistry Select, 3 \u003c/li\u003e\n\u003cli\u003eYu J, LinPang, YaZeng, GuangmingWang, JiajiaDeng, YaochengLiu, YaniFeng, HaopengChen, SongRen, Xiaoya (2019): Magnetic nitrogen-doped sludge-derived biochar catalysts for persulfate activation: Internal electron transfer mechanism. Chemical engineering journal 364\u003c/li\u003e\n\u003cli\u003eZeng Q, Huang Y, Huang L, Hu L, Sun W, Zhong H, He Z (2020): High adsorption capacity and super selectivity for Pb(Ⅱ) by a novel adsorbent: Nano humboldtine/almandine composite prepared from natural almandine. Chemosphere: Environmental toxicology and risk assessment, 253 \u003c/li\u003e\n\u003cli\u003eZhang H, Shao J, Zhang S, Zhang X, Chen H (2019): Effect of Phosphorus-Modified Biochars on Immobilization of Cu (II), Cd (II), and As (V) in Paddy Soil. Journal of Hazardous Materials 390, 121349 \u003c/li\u003e\n\u003cli\u003eZhang J, Jiang Y, Ding C, Wang S, Zhao C, Yin W, Wang B, Yang R, Wang X (2023): Remediation of lead and cadmium co-contaminated mining soil by phosphate-functionalized biochar: Performance, mechanism, and microbial response. Chemosphere 334, 138938 \u003c/li\u003e\n\u003cli\u003eZhou X, Liu W, Zhang J, Wu C, Ou X, Tian C, Lin Z, Dang Z (2017): Biogenic Calcium Carbonate with Hierarchical Organic\u0026ndash;Inorganic Composite Structure Enhancing the Removal of Pb(II) from Wastewater. Acs Appl Mater Interfaces, acsami.7b09304 \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":"red mud, Lotus leaf, Adsorption, KH2PO4, Resource utilization","lastPublishedDoi":"10.21203/rs.3.rs-3798495/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3798495/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this paper, Bayer red mud (RM) and lotus leaf powder (LL) were used as the main materials, and KH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e was added to modify the material. Under the condition of high temperature carbonization, RMLL was prepared and phosphate modified red mud matrix composite (PRMLL) was prepared based on KH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e modification, which can effectively remove Pb\u003csup\u003e2+\u003c/sup\u003e from water. The optimum preparation and application conditions were obtained by orthogonal experiment: dosage 0.1g, ratio 1:1 and temperature 600℃. The effects of PH, dosage and initial concentration on the adsorption of Pb\u003csup\u003e2+\u003c/sup\u003e were studied. The pseudo-first-order, pseudo-second-order and Elovich kinetic models were fitted to the experimental data, and it was found that RMLL and PRMLL were more consistent with the pseudo-second-order kinetic model and chemisorption. Langmuir, Freundlich, Timkin and Dubinin-Radushkevich isothermal adsorption models were used to fit the experimental data, and it was found that RMLL and PRMLL were more consistent with Langmuir model. In addition, the maximum adsorption capacity of RMLL and PRMLL was 188.1mg/g and 213.4mg/g respectively. Are larger than the adsorption capacity of their monomers. Therefore, the use of RMLL and PRMLL as the removal of Pb\u003csup\u003e2+\u003c/sup\u003e from water is a potential application material.\u003c/p\u003e","manuscriptTitle":"Characterization of phosphate modified red mud based composite materials and study on heavy metal adsorption","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-02-02 19:56:03","doi":"10.21203/rs.3.rs-3798495/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2024-01-30T10:01:43+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-01-30T10:00:22+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-01-08T04:53:03+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2023-12-30T02:54:26+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":"7af5cfcb-f2fe-4d30-867e-9c58866901fc","owner":[],"postedDate":"February 2nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-07-16T06:28:14+00:00","versionOfRecord":{"articleIdentity":"rs-3798495","link":"https://doi.org/10.1007/s11356-024-33969-5","journal":{"identity":"environmental-science-and-pollution-research","isVorOnly":false,"title":"Environmental Science and Pollution Research"},"publishedOn":"2024-06-21 06:28:14","publishedOnDateReadable":"June 21st, 2024"},"versionCreatedAt":"2024-02-02 19:56:03","video":"","vorDoi":"10.1007/s11356-024-33969-5","vorDoiUrl":"https://doi.org/10.1007/s11356-024-33969-5","workflowStages":[]},"version":"v1","identity":"rs-3798495","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3798495","identity":"rs-3798495","version":["v1"]},"buildId":"7rjqhiLT3MXkJMwkYKINL","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}