Fabrication and performance evaluation of polyaniline/N-doped graphene nanocomposite as adsorbent in removing carmine red dye from wastewater

Fabrication and performance evaluation of polyaniline/N-doped graphene nanocomposite as adsorbent in removing carmine red dye from wastewater | 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 Fabrication and performance evaluation of polyaniline/N-doped graphene nanocomposite as adsorbent in removing carmine red dye from wastewater Danial Serajedin Mirghayed, SEYYED SALAR MESHKAT, Arash Afghan, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6548482/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract One effective method for removing common dye pollutants is the use of nano-adsorbents. Among these, polymer-based nanocomposite adsorbents are gaining popularity due to their ease of fabrication and application. In this study, a polyaniline (PANI)/nitrogen-doped graphene (NG) nanocomposite was synthesized at various weight percentages using in situ polymerization and employed for the removal of carmine red dye from aqueous solutions. To analyze the properties and performance of the optimal adsorbent, several characterization techniques were utilized, including FTIR, XRD, FESEM, EDX, TEM, TGA, and BET analyses. The findings demonstrated that the PANI/NG nanocomposite with 3 wt% NG exhibited superior dye adsorption compared to those with 1 wt% and 5 wt% loadings. Thermodynamic analysis revealed that the adsorption of carmine dye onto the synthesized adsorbent was an exothermic process. Key parameters influencing the adsorption process-such as temperature, contact time, dye concentration, adsorbent dosage, and pH-were systematically investigated. The PANI/NG 3 wt% nanocomposite achieved an adsorption capacity of 23.81 mg/g. The optimal conditions for the adsorption process were determined to be a temperature of 20°C, a contact time of 30 minutes, a dye concentration of 27.5 mg/g, an adsorbent dosage of 0.03 g per 100 mL, and a pH of 7. Under these conditions, the PANI/NG 3 wt% nanocomposite removed 97.86% of carmine dye from aqueous solutions. The equilibrium data fitted well with the Freundlich isotherm model, indicating the effectiveness of this nanocomposite for dye removal from wastewater. Polyaniline Nanocomposite N-doped graphene Adsorption Carmine dye Wastewater Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 1. Introduction The removal of carmine red dye from wastewater using polymer adsorbents is a critical area of research in environmental science. Numerous studies have investigated the effectiveness of polymer-based adsorbents for dye removal from water sources. Gupta and Suhas (2009) provided a comprehensive review on the application of low-cost adsorbents for dye removal, emphasizing the importance of utilizing affordable materials to achieve efficient wastewater treatment. Agboola et al. (2021) discussed the successful application of polymer nanocomposites in membranes and adsorbents for water treatment, highlighting the effectiveness of these materials in environmental remediation. Akter et al. (2021) further summarized the use of cellulose-based hydrogels for wastewater treatment, focusing on the optimization of adsorption capacity and outlining future research directions in this field. Collectively, these studies underscore the significance of polymer adsorbents in removing dyes such as carmine red from contaminated water sources. In addition, Wang et al. (2017) focused on enhancing the decolorization ability of Bacillus amyloliquefaciens laccase for indigo carmine, illustrating the potential of enzymatic approaches in dye removal processes. Santhi et al. (2010) evaluated the removal of methyl red using activated carbon, demonstrating the crucial role of adsorbent characteristics in dye adsorption processes. Polyaniline-based nanocomposites (PANI-NCs) have emerged as a transformative solution for wastewater treatment, offering enhanced properties such as improved processability and efficiency in removing various pollutants. This innovation aligns with the urgent need to address global water pollution, as reflected by the surge in related research and advancements. The broad application spectrum of these nanocomposites, which includes the removal of metal ions, dyes, and microorganisms from water, underscores their pivotal role in advancing wastewater treatment technologies. Looking ahead, the integration of nanotechnology is expected to further enhance the effectiveness and adaptability of these systems, positioning PANI-NCs at the forefront of sustainable water purification efforts. PANI-NCs are synthesized using various methods, including chemical oxidative polymerization, electrochemical polymerization, vapor-phase polymerization, and photochemically initiated polymerization, which allow for tailoring the properties of these nanocomposites for specific applications. Polyaniline can be combined with a range of materials, such as metals, metal oxides, metal sulfides, and carbon nanomaterials, resulting in nanocomposites with superior properties and performance. These combinations broaden the application scope in wastewater treatment and other fields. Polyaniline exhibits unique properties, including tunable morphology, a porous structure, and favorable electrorheological characteristics, making it particularly effective for dye removal from wastewater. Additionally, its biodegradability and non-toxic nature ensure environmental safety. Polyaniline-based nanocomposites are recognized for their efficiency in adsorbing color pollutants from wastewater, leveraging their high surface area and the chemical properties of polyaniline to effectively bind dye molecules. The adsorption process for carmine red dye is not only highly effective but also cost-efficient, making it a preferred method in wastewater treatment technologies. The diversity of functional groups in the polyaniline structure further enhances adsorption by increasing interactions between the polymer and dye molecules. In conclusion, the utilization of polymer adsorbents for the adsorption of carmine red dye from wastewater presents a promising approach to addressing water pollution challenges. By building on insights from studies on adsorption techniques, polymer nanocomposites, and enzymatic approaches, further advancements can be achieved in developing efficient and sustainable solutions for wastewater treatment. 2. Experimental 2.1. Materials Aniline, ammonium peroxysulfate (APS), urea and camphor were purchased from Merck. Aniline was distilled under reduded pressure before use. 2.2. Instrumentation Fourier Transform Infrared Spectrometer (FTIR) was used for the determination of functional groups using KBr pellets. The pellets were analyzed with FTIR Spectrometer (Thermonicolet nexus 670) in transmittance (%) mode in the range 4000–400 cm − 1 . UV–visible spectra were taken on sp-3000 plus double beam spectrophotometer. The morphology of the prepared materials was examined on TESCAN MIRA III field emission scaning electron microscope (FESEM) and Philips CM-120 Transmission electron microscopy (TEM).Thermogravimetric analysis (TGA) was performed using SDT-Q600, measurements were carried out in N 2 atmosphere under 50 ml/min flow rate and a heating rate of 10 ° C/min from room temperature to 800 ° C. X-ray diffraction pattern was measured on XRD 6000 Shimadzu X-ray diffractometer. 2.3. Preparation of NG Nitrogen-doped graphene (NG) were prepared using camphor (C 10 H 16 O) as carbon source and urea (CO(NH 2 ) 2 ) as nitrogen source using the chemical vapor deposition (CVD) method at 1000°C. After the CVD process, for purification, the samples were kept in (18%) HCl for 24 h, then deionized water was used for washing to reach neutral pH, and then the samples were dried at 70 O C overnight (Lee and Yang 2012). 2.4. Preparation of nanocomposites based on polyaniline/NG Polyaniline-based nanocomposites were synthesized using an in situ polymerization method. Aniline was used as the monomer, while nitrogen-doped graphene (NG) acted as both a filler and reinforcing agent, enhancing the specific surface area and mechanical strength of the resulting composite. Ammonium persulfate (APS) served as the oxidant and initiator for the polymerization process. To prepare the nanocomposite, 1 g of aniline was weighed and placed in a beaker, followed by the addition of 10 mL of double-distilled water at neutral pH. Specified amounts of NG (0.01, 0.03, or 0.05 g) were then added to the mixture. The suspension was stirred at 500 rpm for 1 hour to ensure thorough dispersion of aniline and NG, allowing the aniline to intercalate within the layers of NG. Subsequently, a solution of 2.28 g APS dissolved in 20 mL of double-distilled water was prepared and added dropwise to the aniline-NG mixture under continuous stirring. Polymerization was allowed to proceed for 6 hours at 500 rpm. Upon completion, the resulting nanocomposite was collected by filtration using a Buchner funnel and washed sequentially with acetone (to remove unreacted aniline) and then with double-distilled water. The filtered material was then dried at 70°C for 12 hours to obtain the final polyaniline-based nanocomposite. 2.5. Adsorption of red carmine dye in discontinuous method In this study, the adsorption of the target dye onto the adsorbent surfaces was carried out through a batch (discontinuous) method. Following the adsorption process, the remaining dye concentration in the solution was analyzed using a spectrophotometer at the maximum absorption wavelength (λmax) of 520 nm to determine the percentage of dye removal. The PANI/NG nanocomposites with 1 wt%, 3 wt%, and 5 wt% NG loadings demonstrated dye removal efficiencies of 83.5%, 97.86%, and 97.98%, respectively, within 35 minutes. The PANI/NG 3 wt% nanocomposite emerged as the optimal adsorbent due to its balance of cost-effectiveness and performance, exhibiting a removal efficiency comparable to the 5 wt% variant while significantly outperforming the 1 wt% composite. Comparative analysis revealed distinct removal efficiencies for individual components and the nanocomposite: PANI alone: 50.5% removal NG alone: 81.23% removal PANI/NG 3 wt%: 97.86% removal This marked improvement in adsorption performance highlights the synergistic effect of combining PANI with NG, which enhances the composite's surface area and active sites. The increased surface area facilitates greater dye-polymer interactions, driven by the functional groups in PANI and the structural advantages of NG, resulting in superior adsorption capacity. 3. Results and discussion 3.1. Characterization The FT-IR spectra obtained from 3 wt% PANI/N-G nanocomposite are shown in Fig. 1 (a-c). The spectra of polyaniline and graphene doped with nitrogen can be seen in this spectrum. The analysis of the nanocomposite spectrum shows that the adsorption band of 845 cm − 1 of out-of-plane bending vibrations (C-H), the adsorption band of 1134 cm − 1 of in-plane bending vibrations (C-H), the adsorption band of 1299 cm − 1 of the second type aromatic amine stretching vibrations (C-N), adsorption bands 1487 cm − 1 and 1570 cm − 1 are related to skeletal vibrations of benzene rings (benzenoid structure) and adsorption band 3467 cm − 1 are stretching vibrations (N-H), adsorption bands 616 cm − 1 and 762 cm − 1 are vibrational bonds (NH 2 ), band Adsorption 3440 cm − 1 are symmetric stretching vibrations (N-H) and adsorption band 3870 cm − 1 are stretching vibrations (OH). The spectra achieved from FT-IR spectroscopic analysis of carmine red dye, nanocomposite 3 wt% PANI/N-G before use in the adsorption process and nanocomposite wt 3% PANI/N-G after use in the adsorption process are shown in Fig. 2 . In the red carmine color spectrum, the broad index peak centered at 3444 cm − 1 is related to OH (alcoholic and phenolic) stretching vibrations. The adsorption band appearing at 11630 cm − 1 is related to the stretching vibrations of the carbonyl group (C = O). The stretching vibration observed in the 1199 cm − 1 adsorption band is related to (C-O) bond. Due to the fact that in the saturated adsorbent, the percentage of adsorbent is insignificant, most of the color adsorption bands did not appear. But the shift observed in the adsorption bands of the adsorbed indicates the interaction of the adsorbed-adsorbate. The broad adsorption band around 3436 cm − 1 confirms the hydrogen interaction of the adsorbing-adsorbing functional groups. The XRD spectrum of graphene doped with nitrogen is observed with characteristic peaks at (002) angles of 26.1°, 37.7°, (100) 43.8°, 64.3° and (110) 77.4°. XRD analysis of polyaniline is shown with characteristic peaks at (121) 15°, (113) 19.7° and (322) 25°. In the XRD analysis of the PANI/N-G nanocomposite shown in Fig. 3 (a-c), the peaks of both polyaniline and graphene doped with nitrogen are clearly visible. the analysis of the presence and distribution of the desired elements in the synthesized samples is carried out by elemental analysis (EDX). In the Fig. 5, the distribution of elements and their presence is shown. Figure 4 shows the EDX analysis of carmine red color describes the percentage of elements present. As shown, the elements in the analysis; Aluminum, carbon and oxygen correspond to the chemical formula of red carmine color (C 22 H 15 AlCaO 13 ). As shown in Fig. 5 (a,b), the polyaniline/N-doped graphene nanocomposite has a highly porous structure and small pore size distribution which is favorable for dye adsorption. Figure. 5. FESEM image of PANI/NG 3 wt% at a) 100k b)200k magnifications As obtainable in Fig. 6 the transparency in the TEM image illustratess a few layers of the synthesized polyaniline/N-doped graphene nanocomposite. It is important to study the surface chemistry of polyaniline/N-doped graphene nanocomposite as a significant role in the removal of dye molecules. The results of TGA and DTG under argon gas flow are shown in Fig. 7 . The 3%wt PANI/NG nanocomposite has significant weight loss in three stages. In the first stage, weight loss in the temperature range of 45.47°C is related to the decomposition of water molecules trapped in the nanocomposite structure. In the second stage, the weight loss in the temperature range of 257.72°C to 627.42°C is related to the decomposition of PANI, therefore, at the temperature of 257.72°C, the decomposition of short PANI chains occurs, and at the temperature of 627.42°C, the decomposition of long PANI chains occurs. According to review, NG decomposition occurred at a temperature of about 680°C and beyond, therefore, in the third stage, weight loss from the temperature range of 759.83°C and onwards is related to NG decomposition. The results of the BET analysis for PANI, NG and related nanocomposites are shown in Table 1 , The average pore size of 40.3 nm alleged for the graphene based sheets. According to Table 1 , it can be clearly seen that the surface of nanocomposites increases with the increase of the amount of filler. Table 1 BET analysis of the synthesized adsorbent Materials a s,BET [m 2 .g − 1 ] Total pore volume [cm 3 .g − 1 ] Mean pore diameter [nm] V m [cm 3 (STP) g − 1 ] PANI 15.233 0.122 32.032 3.4999 N-G 110.66 25.424 22.7 60.6284 PANI/N-G 1 wt% 16.176 0.1683 41.619 3.7165 PANI/N-G 3 wt% 18.066 0.1985 43.958 4.1507 PANI/N-G 5 wt% 32.132 0.254 31.622 7.3825 In the following, to better examine the conditions of the synthesized adsorbent, the diagram of nitrogen adsorption and desorption in polyaniline and PANI/NG 3wt% nanocomposite is shown in Fig. 8 (a-b), respectively. Nitrogen adsorption and desorption diagram for polyaniline is considered in order to compare with synthesized PANI/NG 3wt% nanocomposite. According to Fig. 8 b, the nanocomposite adsorption and desorption diagram has hysteresis and follows the type IV isotherm, which is used for porous materials that have very narrow and capillary-type pores. The early part of the type IV isotherm is attributed to monolayer-multilayer adsorption, as the beginning of the nearly linear middle part of the isotherm is often used to indicate the stage where monolayer coverage is complete and multilayer adsorption begins. The results show that the synthesized PANI/NG 3 wt% adsorbent has mesopore distribution. 3.2. The effect of pH Due to the significant effect of pH variable, it can have a consequence on the adsorption rate. According to Fig. 9 , for PANI/NG 3wt% nanoadsorbent, pH pzc = 1.5 was obtained, which means that at pH > pH pzc , the adsorbent surface has a negative charge and at pH < pH pzc , it has a positive charge. The effect of pH on the removal of carmine color was measured by changing the pH of the reaction solution at three points 2, 7 and 12. As can be seen in Fig. 10 , with the increase in pH from 2 to 7, an increase in the removal percentage is observed, but an increase in pH from 7 to 12 causes a decrease in the removal percentage. The removal percentage for pH 2, 7 and 12 is 88.26, 98.46 and 93.5, respectively. Considering the high optimal pH compared to pH pzc (pH = 7 and pH pzc =1.5), the reason for the high removal percentage is the hydrogen bond between the adsorbent and the phenoxide and carboxylate groups of the dye. The reason for the decrease in adsorption percentage at pH = 12 can be attributed to the electrostatic repulsion of the adsorbent-adsorbate due to the deprotonation of the hydroxyl groups present in the dye. At pH = 2, due to the protonation of the basic positions of doped polyaniline-graphene, the hydrogen interaction between the adsorbent and the adsorbent decreases significantly. 3.3. The effect of the amount of adsorbent The amount of adsorbent is a key parameter influencing the adsorption capacity and efficiency in dye removal processes. In this study, the effect of varying the dose of PANI/NG 3 wt% nanocomposite (0.01, 0.03, and 0.05 g per 100 mL) on the removal of carmine red dye was evaluated. The results, as depicted in Fig. 11 , show that increasing the adsorbent dose leads to a higher percentage of dye removal. This enhancement is attributed to the greater availability of active surface sites on the adsorbent, which facilitates more interactions between dye molecules and the adsorbent surface. Such a trend is consistent with findings in the literature, where an increase in adsorbent dose generally results in improved removal efficiency due to the increased number of adsorption sites. Specifically, the removal percentages for 0.03 g and 0.05 g doses were 98.11% and 98.48%, respectively, indicating only a minor difference between these two higher doses. Given the negligible increase in removal efficiency and the consideration of economic savings, the 0.03 g/100 mL dose was selected as the optimal amount for further adsorption studies. This approach balances high removal efficiency with reduced material usage, making the process more cost-effective without compromising performance. 3.4. The effect of contact time and adsorption kinetics Contact time is one of the important parameters in the dye adsorption process. The effect of contact time on carmine dye adsorption by the 3wt% PANI/N-G adsorbent was investigated using different adsorption times in the range of 10–120 min, the results of which can be seen in Fig. 12 . It is clear that the removal rate of carmine dye increased steadily with increasing adsorption time and then stabilized. So, the removal percentage value in 120 min was 99.10%, and in 30 min, its value was 98.15%. Due to the small difference in removal percentage (approximately 1%) between 30 and 120 min time and saving time, 30 min was considered the equilibrium time. The rapid initial removal of carmine dye was attributed to the high number of active sites on the adsorbent surface available for the dye molecules. When the removal time is increased, the available active sites will steadily decrease, and the removal speed will decrease. In order to determine the kinetics of the reaction, the data obtained from the adsorption were evaluated using pseudo-first-order, pseudo-second-order, and intraparticle penetration models. Figure 13 shows the adsorption kinetics using different models. According to the results, the correlation coefficients of adsorption kinetics for pseudo-first-order, pseudo-second-order, and intraparticle penetration models were 0.744, 0.9998, and 0.9602, respectively. Among the above models, the correlation coefficient of quasi-second-order kinetics was closer to 1. This shows that PANI/N-G 3wt% nano-adsorbent followed quasi-second-order kinetics, which indicates the high number of active sites on the adsorbent. The second-order pseudo adsorption was the most fitted data for kinetic studies. The kinetic parameters of adsorption were calculated, and the values of 0.06215 and 13.84 were determined for K 2 and q e coefficients, respectively. Different kinetic models, such as pseudo-first-order, pseudo-second-order, and interparticle diffusion kinetic models, were used to evaluate linear adsorption kinetics studies. Equations 1 to 3 respectively: $$\:Ln=\left({q}_{e}-{q}_{t}\right)=\text{Ln}{q}_{e}-{k}_{1}t\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\left(1\right)$$ $$\:\frac{t}{{q}_{t}}=\frac{1}{{k}_{2}{q}_{e}^{2}}+\frac{t}{{q}_{e}}\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\left(2\right)$$ $$\:{q}_{t}={k}_{i}{t}^{\raisebox{1ex}{$1$}\!\left/\:\!\raisebox{-1ex}{$2$}\right.}+c\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\left(3\right)$$ where q e (mg/g) is the adsorption capacity of the adsorbent, q t (mg/g) is the adsorption capacity at time t (min), and k 1 (1/min) is the rate constant of the pseudo-first-order kinetic model. k 1 and q e can be obtained from the slope and intercept of the linear curve from the plot of ln (q e – q t ) against t, using the experimental results, as presented in Fig. 13 a. k 2 (g/mg min) is the rate constant is for the pseudo-second-order kinetic model, where k 2 and q e can be calculated separately from the distance and gradient of the linear curve, specifically t/q t versus t, as shown in Fig. 13 b. Also, k i and C are the intraparticle diffusion rate constant and the boundary layer thickness constant obtained from the slope and intercept of q e vs. t^ 0.5 which is presented in Fig. 13 c. Table 2 shows the kinetic parameters of the surface adsorption process. Table 2 The kinetic study Sample Pseudo-first-order kinetics Pseudo-second-order kinetics Intra-particle diffusion q e (mg/g) K 1 (1/min) R 2 q e (mg/g) K 2 (g/mg min) R 2 K i (mg g − 1 min − 1/2 ) C R 2 PANI/N-G 3 wt% 12.7 1.1 0.744 13.84 0.06215 0.9989 0.198 11.9 0.9602 3.5. The effect of the initial concentration and adsorption isotherm As shown in Fig. 14 , the adsorption process of carmine color was investigated in different concentrations (5, 27.5, and 50 mg/g). The percentage of carmine color removal in two concentrations of 5 mg/g and 27.5 mg/g were close to each other with a slight difference, and after increasing the concentration from 27.5 to 50 mg/g, the percentage of color removal decreased. The percentage of removals in different concentrations (5, 27.5, and 50 mg/g) was 97.94%, 97.84%, and 90.62%, respectively. The high adsorption rate in two concentrations of 5 and 27.5 mg/g was due to the accessibility of the active sites of the adsorbent synthesized at low concentrations of carmine red dye. This is because, at low concentrations, the binding sites on the surface of the PANI/NG 3 wt% adsorbent for all dye molecules available in the solution increased the adsorption capacity. Also, the decrease in removal percentage at 50 mg/g concentration was due to the availability of more dye molecules due to the increase in dye concentration, which occupied most of the available active sites during adsorption and thus left additional dye molecules in the solution. Therefore, the optimal concentration value of 27.5 mg/g was the optimal initial concentration, so compared to the concentration of 5 mg/g, it had the highest concentration value, and the removal percentage was almost similar. The results of the experiments were examined using two well-known isotherm models, Langmuir and Freundlich. The parameters of the adsorption isotherm Tahi were calculated using the line equations obtained from drawing graphs and matching them with the equations of the adsorption isotherm. Figure 15 shows different isotherms of the surface adsorption process. According to the correlation coefficients reported in Table 3 , it can be concluded that PANI/NG 3wt% nano adsorbent followed the Freundlich isotherm. This theory expresses reversible adsorption as well as multilayer and heterogeneous adsorption for the synthesized nanoadsorbent. In order to calculate the surface adsorption isotherm parameters, the n f and K f coefficients were calculated as 2.26 and 8.043 mg/g, respectively, by using the equation of the line obtained from drawing the graph and matching it with the Freundlich isotherm equation. Freundlich's constant coefficient (n f ) depends on the adsorption intensity; a numerical value greater than 1 indicates the desired adsorption process. According to the calculated value for n f (2.26), it can be concluded that the adsorption of carmine red molecules by PANI/NG 3wt% nanocomposite was desirable under the conditions used in this research. Table 3 The isotherm data Sample Langmuir Freundlich q max (mg/g) K L (L/mg) R 2 n f K f (mg/g) R 2 PANI/N-G 3 wt% 23.81 0.538 0.9723 2.26 8.043 0.9831 3.6. The effect of temperature on thermodynamics of adsorption To investigate the effect of temperature on the adsorption of carmine dye on PANI/NG 3wt% nanocomposite, adsorption experiments were performed in the temperature range of 20–60°C. The effect of temperature on carmine adsorption efficiency is shown in Fig. 16 . As can be seen, increasing the temperature from 20 to 60°C decreased the dye adsorption efficiency from 97.7–77.12%. This result shows that the adsorption process of carmine dye on 3wt% PANI/NG nanocomposite was exothermic. Figure 17 shows the thermodynamics data of adsorption process. As it is clear from Table 4 , the negative value of ΔH° showed that the adsorption of carmine dye on PANI/NG was exothermic. In addition, the low value of ΔH° (-61.386 Kj/mol) suggests a physical adsorption mechanism because ΔH°40Kj/mol reflect physical and chemical adsorption mechanisms, respectively. A negative value of ΔS° indicates a decrease at the solid-liquid interface. The negative values of ΔG° indicate that the adsorption of carmine dye on the 3wt% PANI/N-G surface was a spontaneous process at three different temperatures. Table 4 Thermodynamic data Adsorbent Temp (K) ∆G (Kj/mol) ∆H (Kj/mol) ∆S (Kj/mol. K) PANI/N-G 3 wt% 298 -76/643 -61/386 -0/129 318 -65/414 328 -57/308 4. Conclusion The suitable pH value was 7. It was optimally determined for the carmine red color. The optimal adsorbent amount was 0.3 g. Therefore, this value had a higher removal percentage than the value of 0.1 g, and the removal percentage was almost close to the value of 0.05 g. 30 min time was determined as the adsorption equilibrium time. Therefore, the removal percentage was close to higher times and was also considered from an economic point of view. The optimal concentration of carmine red color was 27.5 mg/L; this concentration had a removal percentage close to 5 mg/L and a higher removal percentage than 50 mg/L. The adsorption temperature was incresed and therefore showed the best result at 20°C. The adsorption kinetics determined according to the correlation coefficient (R 2 = 0.9998) included the pseudo-second-order model. This model expressed the high number of active sites on the adsorbent. The thermodynamics of representative adsorption included negative enthalpy (∆H < 0), including exothermic process, negative entropy (∆S < 0) with low disorder, and negative Gibbs energy (∆G < 0), showing the spontaneity of the reaction. Considering the comparison of the removal percentage of PANI, NG, and PANI/NG 3wt% nanocomposite with removal percentages of 50.5%, 81.23%, and 97.86%, respectively, it can be concluded that the formation of nanocomposite increased the surface area. Therefore, in the nanocomposite, there was a synergy of hydrogen and electrostatic interactions, as well as high porosity in NG nanoparticles, which provided a high surface for high interactions. The increase of NG could improve the removal rate to a certain extent, so 3% was optimized. In the optimal dye removal conditions such as temperature: 20°C, time: 30 min, concentration: 27.5 mg/g, amount of adsorbent: 0.3 g, and pH = 7, the removal percentage was 97.86%. Declarations Acknowledgements The authors acknowledge the Urmia University of Technology for financial supports. References Agboola O, Fayomi OSI, Ayodeji A, Ayeni AO, Alagbe EE, Sanni SE, Okoro EE, Moropeng L, Sadiku R, Kupolati KW and Oni BA (2021) A Review on Polymer Nanocomposites and Their Effective Applications in Membranes and Adsorbents for Water Treatment and Gas Separation. Membranes 11:1-33. https://doi.org/10.3390/membranes11020139 Akter M, Bhattacharjee M, Dhar AK, Rahman FBA, Haque S, Rashid TU and Kabir SMF (2021) Cellulose-Based Hydrogels for Wastewater Treatment: A Concise Review. 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Catalysts 7(9):275. https://doi.org/10.3390/catal7090275 Supplementary Files Highlights.docx Cite Share Download PDF Status: Posted Version 1 posted 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-6548482","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":450359481,"identity":"b1c8be39-99f1-4b8c-bffe-99f863104cd2","order_by":0,"name":"Danial Serajedin Mirghayed","email":"","orcid":"","institution":"Urmia University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Danial","middleName":"Serajedin","lastName":"Mirghayed","suffix":""},{"id":450359482,"identity":"71a4a023-9555-4a7d-90fb-7e9e18ec354d","order_by":1,"name":"SEYYED SALAR 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3 wt% PANI/N-G nanocomposite\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/59cdfe2f560490192dc9ca79.png"},{"id":82062391,"identity":"5c860954-af1e-4c99-9062-3cc9793cc9e2","added_by":"auto","created_at":"2025-05-06 11:55:40","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":106856,"visible":true,"origin":"","legend":"\u003cp\u003eFT-IR spectroscopic analysis of carmine red dye, nanocomposite 3 wt% PANI/N-G before use in the adsorption process and nanocomposite wt 3% PANI/N-G after use in the adsorption process\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/2ad32e7bb39cd5b079b75a64.png"},{"id":82062390,"identity":"5d99b323-81d5-4245-b626-6f1bf727484d","added_by":"auto","created_at":"2025-05-06 11:55:40","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":85366,"visible":true,"origin":"","legend":"\u003cp\u003eXRD analysis of the PANI/N-G nanocomposite\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/24bb9f01ccf4106f79df979a.png"},{"id":82062392,"identity":"5352dd6d-2345-4bae-a568-6d877078d023","added_by":"auto","created_at":"2025-05-06 11:55:40","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":19819,"visible":true,"origin":"","legend":"\u003cp\u003eEDX analysis of carmine red color\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/79f79f08df1594c1bd526e40.png"},{"id":82063523,"identity":"926dd16a-88cd-44cc-affb-876dad3e095c","added_by":"auto","created_at":"2025-05-06 12:11:41","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":275117,"visible":true,"origin":"","legend":"\u003cp\u003eFESEM image of PANI/NG 3 wt% at a) 100k b)200k magnifications\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/48118d3aaad726dd8ee2bb92.png"},{"id":82063519,"identity":"4dc8ee00-d37a-4923-8fa5-3699a838580e","added_by":"auto","created_at":"2025-05-06 12:11:41","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":293454,"visible":true,"origin":"","legend":"\u003cp\u003eTEM image of the synthesized adsorbent\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/7fa7247394d139e1510b0785.png"},{"id":82062705,"identity":"0683fd6d-1017-4eb0-a794-b547e6cd7778","added_by":"auto","created_at":"2025-05-06 12:03:41","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":77175,"visible":true,"origin":"","legend":"\u003cp\u003e\u0026nbsp;(a) TGA (b) DTG analysis of the synthesized adsorbent\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/73d919c89cdd38fb99dc518a.png"},{"id":82062401,"identity":"b68e3320-e8f5-4033-a0c3-e140f17f786f","added_by":"auto","created_at":"2025-05-06 11:55:41","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":35240,"visible":true,"origin":"","legend":"\u003cp\u003eNitrogen adsorption/desorption isotherms of synthesized adsorbent\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/9e75c2f8facb7fce3b76ca8f.png"},{"id":82063663,"identity":"6ec4c82d-e39e-4aa2-a306-c099d694028b","added_by":"auto","created_at":"2025-05-06 12:19:41","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":14995,"visible":true,"origin":"","legend":"\u003cp\u003epH\u003csub\u003epzc\u003c/sub\u003e for for PANI/N-G 3wt% nanoadsorbent\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/90cb6b74d59fa083919cba9c.png"},{"id":82062706,"identity":"82401728-9e42-46c2-b426-f15c102f0155","added_by":"auto","created_at":"2025-05-06 12:03:41","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":20562,"visible":true,"origin":"","legend":"\u003cp\u003eThe effect of pH\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/c2905d8f04d996568476587e.png"},{"id":82063664,"identity":"f8150d51-02e1-4cf5-b822-06299b2b989b","added_by":"auto","created_at":"2025-05-06 12:19:41","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":6942,"visible":true,"origin":"","legend":"\u003cp\u003eThe effect of the amount of adsorbent\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/4141789a4d3c3861b821f462.png"},{"id":82062405,"identity":"68466cf9-219a-4221-85e8-d665931e65c3","added_by":"auto","created_at":"2025-05-06 11:55:41","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":25823,"visible":true,"origin":"","legend":"\u003cp\u003eThe effect of the contact time\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/e03d7daf00639bf20d086c97.png"},{"id":82062407,"identity":"572a642f-2d02-4cfb-a948-c0b2c351eb10","added_by":"auto","created_at":"2025-05-06 11:55:41","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":54728,"visible":true,"origin":"","legend":"\u003cp\u003ea) pseudo first order b) pseudo second order c) intraparticle kinetic models\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/caf046eb01fb727ee075d31c.png"},{"id":82062713,"identity":"d31f9cb3-430d-4f34-b2f1-850f49322872","added_by":"auto","created_at":"2025-05-06 12:03:41","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":24636,"visible":true,"origin":"","legend":"\u003cp\u003eThe effect of dye concentration\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/4020a3355d03f9b9c427fc4b.png"},{"id":82062410,"identity":"12f3f65a-485d-49bf-bd10-86a542c22e8e","added_by":"auto","created_at":"2025-05-06 11:55:41","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":35726,"visible":true,"origin":"","legend":"\u003cp\u003eIsotherms a) Langmuir b) Frendulich\u003c/p\u003e","description":"","filename":"15.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/15d45024ae60e97d965b989e.png"},{"id":82062717,"identity":"e9c13988-81f4-4919-a989-fb92130f0623","added_by":"auto","created_at":"2025-05-06 12:03:41","extension":"png","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":21619,"visible":true,"origin":"","legend":"\u003cp\u003eThe temperature effect\u003c/p\u003e","description":"","filename":"16.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/b4cc8afb05e522f2ef41741a.png"},{"id":82062414,"identity":"9a2e5d79-0c7e-4a52-b29b-fabcb345671c","added_by":"auto","created_at":"2025-05-06 11:55:41","extension":"png","order_by":17,"title":"Figure 17","display":"","copyAsset":false,"role":"figure","size":18652,"visible":true,"origin":"","legend":"\u003cp\u003ethermodynamic data\u003c/p\u003e","description":"","filename":"17.png","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/182cbbe61eab76251b76ed1e.png"},{"id":89758627,"identity":"0003d7d5-373b-467b-bb73-834f1cad6f68","added_by":"auto","created_at":"2025-08-24 10:25:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1939651,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/8b05e2ed-efbd-4543-b3ae-78f16033810d.pdf"},{"id":82062393,"identity":"8c8eb9ab-64ec-4cdb-bc53-5ae71706cbb2","added_by":"auto","created_at":"2025-05-06 11:55:40","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":13995,"visible":true,"origin":"","legend":"","description":"","filename":"Highlights.docx","url":"https://assets-eu.researchsquare.com/files/rs-6548482/v1/e889e3b735aaa2b1a788ae62.docx"}],"financialInterests":"","formattedTitle":"Fabrication and performance evaluation of polyaniline/N-doped graphene nanocomposite as adsorbent in removing carmine red dye from wastewater","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe removal of carmine red dye from wastewater using polymer adsorbents is a critical area of research in environmental science. Numerous studies have investigated the effectiveness of polymer-based adsorbents for dye removal from water sources. Gupta and Suhas (2009) provided a comprehensive review on the application of low-cost adsorbents for dye removal, emphasizing the importance of utilizing affordable materials to achieve efficient wastewater treatment. Agboola et al. (2021) discussed the successful application of polymer nanocomposites in membranes and adsorbents for water treatment, highlighting the effectiveness of these materials in environmental remediation. Akter et al. (2021) further summarized the use of cellulose-based hydrogels for wastewater treatment, focusing on the optimization of adsorption capacity and outlining future research directions in this field. Collectively, these studies underscore the significance of polymer adsorbents in removing dyes such as carmine red from contaminated water sources. In addition, Wang et al. (2017) focused on enhancing the decolorization ability of Bacillus amyloliquefaciens laccase for indigo carmine, illustrating the potential of enzymatic approaches in dye removal processes. Santhi et al. (2010) evaluated the removal of methyl red using activated carbon, demonstrating the crucial role of adsorbent characteristics in dye adsorption processes.\u003c/p\u003e \u003cp\u003ePolyaniline-based nanocomposites (PANI-NCs) have emerged as a transformative solution for wastewater treatment, offering enhanced properties such as improved processability and efficiency in removing various pollutants. This innovation aligns with the urgent need to address global water pollution, as reflected by the surge in related research and advancements. The broad application spectrum of these nanocomposites, which includes the removal of metal ions, dyes, and microorganisms from water, underscores their pivotal role in advancing wastewater treatment technologies. Looking ahead, the integration of nanotechnology is expected to further enhance the effectiveness and adaptability of these systems, positioning PANI-NCs at the forefront of sustainable water purification efforts.\u003c/p\u003e \u003cp\u003ePANI-NCs are synthesized using various methods, including chemical oxidative polymerization, electrochemical polymerization, vapor-phase polymerization, and photochemically initiated polymerization, which allow for tailoring the properties of these nanocomposites for specific applications. Polyaniline can be combined with a range of materials, such as metals, metal oxides, metal sulfides, and carbon nanomaterials, resulting in nanocomposites with superior properties and performance. These combinations broaden the application scope in wastewater treatment and other fields. Polyaniline exhibits unique properties, including tunable morphology, a porous structure, and favorable electrorheological characteristics, making it particularly effective for dye removal from wastewater. Additionally, its biodegradability and non-toxic nature ensure environmental safety. Polyaniline-based nanocomposites are recognized for their efficiency in adsorbing color pollutants from wastewater, leveraging their high surface area and the chemical properties of polyaniline to effectively bind dye molecules. The adsorption process for carmine red dye is not only highly effective but also cost-efficient, making it a preferred method in wastewater treatment technologies. The diversity of functional groups in the polyaniline structure further enhances adsorption by increasing interactions between the polymer and dye molecules.\u003c/p\u003e \u003cp\u003eIn conclusion, the utilization of polymer adsorbents for the adsorption of carmine red dye from wastewater presents a promising approach to addressing water pollution challenges. By building on insights from studies on adsorption techniques, polymer nanocomposites, and enzymatic approaches, further advancements can be achieved in developing efficient and sustainable solutions for wastewater treatment.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Materials\u003c/h2\u003e \u003cp\u003eAniline, ammonium peroxysulfate (APS), urea and camphor were purchased from Merck. Aniline was distilled under reduded pressure before use.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Instrumentation\u003c/h2\u003e \u003cp\u003eFourier Transform Infrared Spectrometer (FTIR) was used for the determination of functional groups using KBr pellets. The pellets were analyzed with FTIR Spectrometer (Thermonicolet nexus 670) in transmittance (%) mode in the range 4000\u0026ndash;400 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. UV\u0026ndash;visible spectra were taken on sp-3000 plus double beam spectrophotometer. The morphology of the prepared materials was examined on TESCAN MIRA III field emission scaning electron microscope (FESEM) and Philips CM-120 Transmission electron microscopy (TEM).Thermogravimetric analysis (TGA) was performed using SDT-Q600, measurements were carried out in N\u003csub\u003e2\u003c/sub\u003e atmosphere under 50 ml/min flow rate and a heating rate of 10\u003csup\u003e\u0026deg;\u003c/sup\u003eC/min from room temperature to 800\u003csup\u003e\u0026deg;\u003c/sup\u003eC. X-ray diffraction pattern was measured on XRD 6000 Shimadzu X-ray diffractometer.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Preparation of NG\u003c/h2\u003e \u003cp\u003eNitrogen-doped graphene (NG) were prepared using camphor (C\u003csub\u003e10\u003c/sub\u003eH\u003csub\u003e16\u003c/sub\u003eO) as carbon source and urea (CO(NH\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e) as nitrogen source using the chemical vapor deposition (CVD) method at 1000\u0026deg;C. After the CVD process, for purification, the samples were kept in (18%) HCl for 24 h, then deionized water was used for washing to reach neutral pH, and then the samples were dried at 70 \u003csup\u003eO\u003c/sup\u003eC overnight (Lee and Yang 2012).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Preparation of nanocomposites based on polyaniline/NG\u003c/h2\u003e \u003cp\u003ePolyaniline-based nanocomposites were synthesized using an in situ polymerization method. Aniline was used as the monomer, while nitrogen-doped graphene (NG) acted as both a filler and reinforcing agent, enhancing the specific surface area and mechanical strength of the resulting composite. Ammonium persulfate (APS) served as the oxidant and initiator for the polymerization process. To prepare the nanocomposite, 1 g of aniline was weighed and placed in a beaker, followed by the addition of 10 mL of double-distilled water at neutral pH. Specified amounts of NG (0.01, 0.03, or 0.05 g) were then added to the mixture. The suspension was stirred at 500 rpm for 1 hour to ensure thorough dispersion of aniline and NG, allowing the aniline to intercalate within the layers of NG.\u003c/p\u003e \u003cp\u003eSubsequently, a solution of 2.28 g APS dissolved in 20 mL of double-distilled water was prepared and added dropwise to the aniline-NG mixture under continuous stirring. Polymerization was allowed to proceed for 6 hours at 500 rpm. Upon completion, the resulting nanocomposite was collected by filtration using a Buchner funnel and washed sequentially with acetone (to remove unreacted aniline) and then with double-distilled water. The filtered material was then dried at 70\u0026deg;C for 12 hours to obtain the final polyaniline-based nanocomposite.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Adsorption of red carmine dye in discontinuous method\u003c/h2\u003e \u003cp\u003eIn this study, the adsorption of the target dye onto the adsorbent surfaces was carried out through a batch (discontinuous) method. Following the adsorption process, the remaining dye concentration in the solution was analyzed using a spectrophotometer at the maximum absorption wavelength (λmax) of 520 nm to determine the percentage of dye removal.\u003c/p\u003e \u003cp\u003eThe PANI/NG nanocomposites with 1 wt%, 3 wt%, and 5 wt% NG loadings demonstrated dye removal efficiencies of 83.5%, 97.86%, and 97.98%, respectively, within 35 minutes. The PANI/NG 3 wt% nanocomposite emerged as the optimal adsorbent due to its balance of cost-effectiveness and performance, exhibiting a removal efficiency comparable to the 5 wt% variant while significantly outperforming the 1 wt% composite.\u003c/p\u003e \u003cp\u003eComparative analysis revealed distinct removal efficiencies for individual components and the nanocomposite:\u003c/p\u003e \u003cp\u003ePANI alone: 50.5% removal\u003c/p\u003e \u003cp\u003eNG alone: 81.23% removal\u003c/p\u003e \u003cp\u003ePANI/NG 3 wt%: 97.86% removal\u003c/p\u003e \u003cp\u003eThis marked improvement in adsorption performance highlights the synergistic effect of combining PANI with NG, which enhances the composite's surface area and active sites. The increased surface area facilitates greater dye-polymer interactions, driven by the functional groups in PANI and the structural advantages of NG, resulting in superior adsorption capacity.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1. Characterization\u003c/h2\u003e\n \u003cp\u003eThe FT-IR spectra obtained from 3 wt% PANI/N-G nanocomposite are shown in Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e(a-c). The spectra of polyaniline and graphene doped with nitrogen can be seen in this spectrum. The analysis of the nanocomposite spectrum shows that the adsorption band of 845 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of out-of-plane bending vibrations (C-H), the adsorption band of 1134 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of in-plane bending vibrations (C-H), the adsorption band of 1299 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e of the second type aromatic amine stretching vibrations (C-N), adsorption bands 1487 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1570 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are related to skeletal vibrations of benzene rings (benzenoid structure) and adsorption band 3467 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are stretching vibrations (N-H), adsorption bands 616 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 762 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are vibrational bonds (NH\u003csub\u003e2\u003c/sub\u003e), band Adsorption 3440 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are symmetric stretching vibrations (N-H) and adsorption band 3870 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are stretching vibrations (OH). The spectra achieved from FT-IR spectroscopic analysis of carmine red dye, nanocomposite 3 wt% PANI/N-G before use in the adsorption process and nanocomposite wt 3% PANI/N-G after use in the adsorption process are shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e. In the red carmine color spectrum, the broad index peak centered at 3444 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is related to OH (alcoholic and phenolic) stretching vibrations. The adsorption band appearing at 11630 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is related to the stretching vibrations of the carbonyl group (C\u0026thinsp;=\u0026thinsp;O). The stretching vibration observed in the 1199 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e adsorption band is related to (C-O) bond. Due to the fact that in the saturated adsorbent, the percentage of adsorbent is insignificant, most of the color adsorption bands did not appear. But the shift observed in the adsorption bands of the adsorbed indicates the interaction of the adsorbed-adsorbate. The broad adsorption band around 3436 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e confirms the hydrogen interaction of the adsorbing-adsorbing functional groups.\u003c/p\u003e\n \u003cp\u003eThe XRD spectrum of graphene doped with nitrogen is observed with characteristic peaks at (002) angles of 26.1\u0026deg;, 37.7\u0026deg;, (100) 43.8\u0026deg;, 64.3\u0026deg; and (110) 77.4\u0026deg;. XRD analysis of polyaniline is shown with characteristic peaks at (121) 15\u0026deg;, (113) 19.7\u0026deg; and (322) 25\u0026deg;. In the XRD analysis of the PANI/N-G nanocomposite shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e (a-c), the peaks of both polyaniline and graphene doped with nitrogen are clearly visible.\u003c/p\u003e\n \u003cp\u003ethe analysis of the presence and distribution of the desired elements in the synthesized samples is carried out by elemental analysis (EDX). In the Fig. 5, the distribution of elements and their presence is shown. Figure \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e shows the EDX analysis of carmine red color describes the percentage of elements present. As shown, the elements in the analysis; Aluminum, carbon and oxygen correspond to the chemical formula of red carmine color (C\u003csub\u003e22\u003c/sub\u003eH\u003csub\u003e15\u003c/sub\u003eAlCaO\u003csub\u003e13\u003c/sub\u003e).\u003c/p\u003e\n \u003cp\u003eAs shown in Fig.\u0026nbsp;5 (a,b), the polyaniline/N-doped graphene nanocomposite has a highly porous structure and small pore size distribution which is favorable for dye adsorption.\u003c/p\u003e\n \u003cp\u003eFigure. 5. FESEM image of PANI/NG 3 wt% at a) 100k b)200k magnifications\u003c/p\u003e\n \u003cp\u003eAs obtainable in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e the transparency in the TEM image illustratess a few layers of the synthesized polyaniline/N-doped graphene nanocomposite. It is important to study the surface chemistry of polyaniline/N-doped graphene nanocomposite as a significant role in the removal of dye molecules.\u003c/p\u003e\n \u003cp\u003eThe results of TGA and DTG under argon gas flow are shown in Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e. The 3%wt PANI/NG nanocomposite has significant weight loss in three stages. In the first stage, weight loss in the temperature range of 45.47\u0026deg;C is related to the decomposition of water molecules trapped in the nanocomposite structure. In the second stage, the weight loss in the temperature range of 257.72\u0026deg;C to 627.42\u0026deg;C is related to the decomposition of PANI, therefore, at the temperature of 257.72\u0026deg;C, the decomposition of short PANI chains occurs, and at the temperature of 627.42\u0026deg;C, the decomposition of long PANI chains occurs. According to review, NG decomposition occurred at a temperature of about 680\u0026deg;C and beyond, therefore, in the third stage, weight loss from the temperature range of 759.83\u0026deg;C and onwards is related to NG decomposition.\u003c/p\u003e\n \u003cp\u003eThe results of the BET analysis for PANI, NG and related nanocomposites are shown in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, The average pore size of 40.3 nm alleged for the graphene based sheets. According to Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e, it can be clearly seen that the surface of nanocomposites increases with the increase of the amount of filler.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eBET analysis of the synthesized adsorbent\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\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\u003ea\u003csub\u003es,BET\u003c/sub\u003e [m\u003csup\u003e2\u003c/sup\u003e.g\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\u003e.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e]\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMean pore diameter [nm]\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eV\u003csub\u003em\u003c/sub\u003e [cm\u003csup\u003e3\u003c/sup\u003e(STP) g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e]\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\u003ePANI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e15.233\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e32.032\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.4999\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eN-G\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e110.66\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e25.424\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e22.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e60.6284\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePANI/N-G 1 wt%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e16.176\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1683\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e41.619\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.7165\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePANI/N-G 3 wt%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e18.066\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.1985\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e43.958\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.1507\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePANI/N-G 5 wt%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e32.132\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.254\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e31.622\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.3825\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eIn the following, to better examine the conditions of the synthesized adsorbent, the diagram of nitrogen adsorption and desorption in polyaniline and PANI/NG 3wt% nanocomposite is shown in Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e (a-b), respectively. Nitrogen adsorption and desorption diagram for polyaniline is considered in order to compare with synthesized PANI/NG 3wt% nanocomposite.\u003c/p\u003e\n \u003cp\u003eAccording to Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003eb, the nanocomposite adsorption and desorption diagram has hysteresis and follows the type IV isotherm, which is used for porous materials that have very narrow and capillary-type pores. The early part of the type IV isotherm is attributed to monolayer-multilayer adsorption, as the beginning of the nearly linear middle part of the isotherm is often used to indicate the stage where monolayer coverage is complete and multilayer adsorption begins. The results show that the synthesized PANI/NG 3 wt% adsorbent has mesopore distribution.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2. The effect of pH\u003c/h2\u003e\n \u003cp\u003eDue to the significant effect of pH variable, it can have a consequence on the adsorption rate. According to Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e, for PANI/NG 3wt% nanoadsorbent, pH\u003csub\u003epzc\u003c/sub\u003e = 1.5 was obtained, which means that at pH\u0026thinsp;\u0026gt;\u0026thinsp;pH\u003csub\u003epzc\u003c/sub\u003e, the adsorbent surface has a negative charge and at pH\u0026thinsp;\u0026lt;\u0026thinsp;pH\u003csub\u003epzc\u003c/sub\u003e, it has a positive charge. The effect of pH on the removal of carmine color was measured by changing the pH of the reaction solution at three points 2, 7 and 12. As can be seen in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e, with the increase in pH from 2 to 7, an increase in the removal percentage is observed, but an increase in pH from 7 to 12 causes a decrease in the removal percentage. The removal percentage for pH 2, 7 and 12 is 88.26, 98.46 and 93.5, respectively. Considering the high optimal pH compared to pH\u003csub\u003epzc\u003c/sub\u003e (pH\u0026thinsp;=\u0026thinsp;7 and pH\u003csub\u003epzc\u003c/sub\u003e=1.5), the reason for the high removal percentage is the hydrogen bond between the adsorbent and the phenoxide and carboxylate groups of the dye. The reason for the decrease in adsorption percentage at pH\u0026thinsp;=\u0026thinsp;12 can be attributed to the electrostatic repulsion of the adsorbent-adsorbate due to the deprotonation of the hydroxyl groups present in the dye. At pH\u0026thinsp;=\u0026thinsp;2, due to the protonation of the basic positions of doped polyaniline-graphene, the hydrogen interaction between the adsorbent and the adsorbent decreases significantly.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3. The effect of the amount of adsorbent\u003c/h2\u003e\n \u003cp\u003eThe amount of adsorbent is a key parameter influencing the adsorption capacity and efficiency in dye removal processes. In this study, the effect of varying the dose of PANI/NG 3 wt% nanocomposite (0.01, 0.03, and 0.05 g per 100 mL) on the removal of carmine red dye was evaluated. The results, as depicted in Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e, show that increasing the adsorbent dose leads to a higher percentage of dye removal. This enhancement is attributed to the greater availability of active surface sites on the adsorbent, which facilitates more interactions between dye molecules and the adsorbent surface. Such a trend is consistent with findings in the literature, where an increase in adsorbent dose generally results in improved removal efficiency due to the increased number of adsorption sites. Specifically, the removal percentages for 0.03 g and 0.05 g doses were 98.11% and 98.48%, respectively, indicating only a minor difference between these two higher doses. Given the negligible increase in removal efficiency and the consideration of economic savings, the 0.03 g/100 mL dose was selected as the optimal amount for further adsorption studies. This approach balances high removal efficiency with reduced material usage, making the process more cost-effective without compromising performance.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4. The effect of contact time and adsorption kinetics\u003c/h2\u003e\n \u003cp\u003eContact time is one of the important parameters in the dye adsorption process. The effect of contact time on carmine dye adsorption by the 3wt% PANI/N-G adsorbent was investigated using different adsorption times in the range of 10\u0026ndash;120 min, the results of which can be seen in Fig. \u003cspan class=\"InternalRef\"\u003e12\u003c/span\u003e. It is clear that the removal rate of carmine dye increased steadily with increasing adsorption time and then stabilized. So, the removal percentage value in 120 min was 99.10%, and in 30 min, its value was 98.15%. Due to the small difference in removal percentage (approximately 1%) between 30 and 120 min time and saving time, 30 min was considered the equilibrium time. The rapid initial removal of carmine dye was attributed to the high number of active sites on the adsorbent surface available for the dye molecules. When the removal time is increased, the available active sites will steadily decrease, and the removal speed will decrease.\u003c/p\u003e\n \u003cp\u003eIn order to determine the kinetics of the reaction, the data obtained from the adsorption were evaluated using pseudo-first-order, pseudo-second-order, and intraparticle penetration models. Figure \u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003e shows the adsorption kinetics using different models. According to the results, the correlation coefficients of adsorption kinetics for pseudo-first-order, pseudo-second-order, and intraparticle penetration models were 0.744, 0.9998, and 0.9602, respectively. Among the above models, the correlation coefficient of quasi-second-order kinetics was closer to 1. This shows that PANI/N-G 3wt% nano-adsorbent followed quasi-second-order kinetics, which indicates the high number of active sites on the adsorbent. The second-order pseudo adsorption was the most fitted data for kinetic studies. The kinetic parameters of adsorption were calculated, and the values of 0.06215 and 13.84 were determined for K\u003csub\u003e2\u003c/sub\u003e and q\u003csub\u003ee\u003c/sub\u003e coefficients, respectively. Different kinetic models, such as pseudo-first-order, pseudo-second-order, and interparticle diffusion kinetic models, were used to evaluate linear adsorption kinetics studies. Equations 1 to 3 respectively:\u003c/p\u003e\n \u003cdiv id=\"Equa\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e$$\\:Ln=\\left({q}_{e}-{q}_{t}\\right)=\\text{Ln}{q}_{e}-{k}_{1}t\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\left(1\\right)$$\u003c/div\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Equb\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e$$\\:\\frac{t}{{q}_{t}}=\\frac{1}{{k}_{2}{q}_{e}^{2}}+\\frac{t}{{q}_{e}}\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\left(2\\right)$$\u003c/div\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Equc\" class=\"Equation\"\u003e\n \u003cdiv class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e$$\\:{q}_{t}={k}_{i}{t}^{\\raisebox{1ex}{$1$}\\!\\left/\\:\\!\\raisebox{-1ex}{$2$}\\right.}+c\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\:\\left(3\\right)$$\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003ewhere q\u003csub\u003ee\u003c/sub\u003e (mg/g) is the adsorption capacity of the adsorbent, q\u003csub\u003et\u003c/sub\u003e (mg/g) is the adsorption capacity at time t (min), and k\u003csub\u003e1\u003c/sub\u003e (1/min) is the rate constant of the pseudo-first-order kinetic model. k\u003csub\u003e1\u003c/sub\u003e and q\u003csub\u003ee\u003c/sub\u003e can be obtained from the slope and intercept of the linear curve from the plot of ln (q\u003csub\u003ee\u003c/sub\u003e \u0026ndash; q\u003csub\u003et\u003c/sub\u003e) against t, using the experimental results, as presented in Fig. \u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003ea. k\u003csub\u003e2\u003c/sub\u003e (g/mg min) is the rate constant is for the pseudo-second-order kinetic model, where k\u003csub\u003e2\u003c/sub\u003e and q\u003csub\u003ee\u003c/sub\u003e can be calculated separately from the distance and gradient of the linear curve, specifically t/q\u003csub\u003et\u003c/sub\u003e versus t, as shown in Fig. \u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003eb. Also, k\u003csub\u003ei\u003c/sub\u003e and C are the intraparticle diffusion rate constant and the boundary layer thickness constant obtained from the slope and intercept of q\u003csub\u003ee\u003c/sub\u003e vs. t^ 0.5 which is presented in Fig. \u003cspan class=\"InternalRef\"\u003e13\u003c/span\u003ec. Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e shows the kinetic parameters of the surface adsorption process.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eThe kinetic study\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"10\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003ePseudo-first-order kinetics\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003ePseudo-second-order kinetics\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eIntra-particle diffusion\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eq\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003ee\u003c/strong\u003e\u003c/sub\u003e \u003cstrong\u003e(mg/g)\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eK\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/sub\u003e \u003cstrong\u003e(1/min)\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eR\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eq\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003ee\u003c/strong\u003e\u003c/sub\u003e \u003cstrong\u003e(mg/g)\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eK\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e \u003cstrong\u003e(g/mg min)\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eR\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eK\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003ei\u003c/strong\u003e\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e(mg g\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e\u0026minus;\u0026thinsp;1\u003c/strong\u003e\u003c/sup\u003e \u003cstrong\u003emin\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e\u0026minus;\u0026thinsp;1/2\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e)\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eC\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eR\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sup\u003e\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\u003ePANI/N-G 3 wt%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.744\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.06215\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.9989\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.198\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.9602\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\" class=\"Section2\"\u003e\n \u003ch2\u003e3.5. The effect of the initial concentration and adsorption isotherm\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e14\u003c/span\u003e, the adsorption process of carmine color was investigated in different concentrations (5, 27.5, and 50 mg/g). The percentage of carmine color removal in two concentrations of 5 mg/g and 27.5 mg/g were close to each other with a slight difference, and after increasing the concentration from 27.5 to 50 mg/g, the percentage of color removal decreased. The percentage of removals in different concentrations (5, 27.5, and 50 mg/g) was 97.94%, 97.84%, and 90.62%, respectively. The high adsorption rate in two concentrations of 5 and 27.5 mg/g was due to the accessibility of the active sites of the adsorbent synthesized at low concentrations of carmine red dye. This is because, at low concentrations, the binding sites on the surface of the PANI/NG 3 wt% adsorbent for all dye molecules available in the solution increased the adsorption capacity. Also, the decrease in removal percentage at 50 mg/g concentration was due to the availability of more dye molecules due to the increase in dye concentration, which occupied most of the available active sites during adsorption and thus left additional dye molecules in the solution. Therefore, the optimal concentration value of 27.5 mg/g was the optimal initial concentration, so compared to the concentration of 5 mg/g, it had the highest concentration value, and the removal percentage was almost similar.\u003c/p\u003e\n \u003cp\u003eThe results of the experiments were examined using two well-known isotherm models, Langmuir and Freundlich. The parameters of the adsorption isotherm Tahi were calculated using the line equations obtained from drawing graphs and matching them with the equations of the adsorption isotherm. Figure \u003cspan class=\"InternalRef\"\u003e15\u003c/span\u003e shows different isotherms of the surface adsorption process. According to the correlation coefficients reported in Table \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e, it can be concluded that PANI/NG 3wt% nano adsorbent followed the Freundlich isotherm. This theory expresses reversible adsorption as well as multilayer and heterogeneous adsorption for the synthesized nanoadsorbent. In order to calculate the surface adsorption isotherm parameters, the n\u003csub\u003ef\u003c/sub\u003e and K\u003csub\u003ef\u003c/sub\u003e coefficients were calculated as 2.26 and 8.043 mg/g, respectively, by using the equation of the line obtained from drawing the graph and matching it with the Freundlich isotherm equation. Freundlich\u0026apos;s constant coefficient (n\u003csub\u003ef\u003c/sub\u003e) depends on the adsorption intensity; a numerical value greater than 1 indicates the desired adsorption process. According to the calculated value for n\u003csub\u003ef\u003c/sub\u003e (2.26), it can be concluded that the adsorption of carmine red molecules by PANI/NG 3wt% nanocomposite was desirable under the conditions used in this research.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eThe isotherm data\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"7\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eSample\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eLangmuir\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"3\"\u003e\n \u003cp\u003eFreundlich\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eq\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003emax\u003c/strong\u003e\u003c/sub\u003e \u003cstrong\u003e(mg/g)\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eK\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003eL\u003c/strong\u003e\u003c/sub\u003e \u003cstrong\u003e(L/mg)\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eR\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sup\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003en\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003ef\u003c/strong\u003e\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eK\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003ef\u003c/strong\u003e\u003c/sub\u003e \u003cstrong\u003e(mg/g)\u003c/strong\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eR\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sup\u003e\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\u003ePANI/N-G 3 wt%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e23.81\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.538\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.9723\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.043\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.9831\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=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003e3.6. The effect of temperature on thermodynamics of adsorption\u003c/h2\u003e\n \u003cp\u003eTo investigate the effect of temperature on the adsorption of carmine dye on PANI/NG 3wt% nanocomposite, adsorption experiments were performed in the temperature range of 20\u0026ndash;60\u0026deg;C. The effect of temperature on carmine adsorption efficiency is shown in Fig. \u003cspan class=\"InternalRef\"\u003e16\u003c/span\u003e. As can be seen, increasing the temperature from 20 to 60\u0026deg;C decreased the dye adsorption efficiency from 97.7\u0026ndash;77.12%. This result shows that the adsorption process of carmine dye on 3wt% PANI/NG nanocomposite was exothermic.\u003c/p\u003e\n \u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e17\u003c/span\u003e shows the thermodynamics data of adsorption process. As it is clear from Table \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e, the negative value of \u0026Delta;H\u0026deg; showed that the adsorption of carmine dye on PANI/NG was exothermic. In addition, the low value of \u0026Delta;H\u0026deg; (-61.386 Kj/mol) suggests a physical adsorption mechanism because \u0026Delta;H\u0026deg;\u0026lt;40Kj/mol and \u0026Delta;H\u0026deg;\u0026gt;40Kj/mol reflect physical and chemical adsorption mechanisms, respectively. A negative value of \u0026Delta;S\u0026deg; indicates a decrease at the solid-liquid interface. The negative values of \u0026Delta;G\u0026deg; indicate that the adsorption of carmine dye on the 3wt% PANI/N-G surface was a spontaneous process at three different temperatures.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab4\" border=\"1\" class=\"fr-table-selection-hover\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eThermodynamic data\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAdsorbent\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTemp (K)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e∆G (Kj/mol)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e∆H (Kj/mol)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003e∆S (Kj/mol. K)\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\" rowspan=\"3\"\u003e\n \u003cp\u003ePANI/N-G 3 wt%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e298\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-76/643\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003e-61/386\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003e-0/129\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e318\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-65/414\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e328\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-57/308\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"},{"header":"4. Conclusion","content":"\u003cp\u003eThe suitable pH value was 7. It was optimally determined for the carmine red color. The optimal adsorbent amount was 0.3 g. Therefore, this value had a higher removal percentage than the value of 0.1 g, and the removal percentage was almost close to the value of 0.05 g. 30 min time was determined as the adsorption equilibrium time. Therefore, the removal percentage was close to higher times and was also considered from an economic point of view. The optimal concentration of carmine red color was 27.5 mg/L; this concentration had a removal percentage close to 5 mg/L and a higher removal percentage than 50 mg/L. The adsorption temperature was incresed and therefore showed the best result at 20\u0026deg;C. The adsorption kinetics determined according to the correlation coefficient (R\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;0.9998) included the pseudo-second-order model. This model expressed the high number of active sites on the adsorbent. The thermodynamics of representative adsorption included negative enthalpy (∆H\u0026thinsp;\u0026lt;\u0026thinsp;0), including exothermic process, negative entropy (∆S\u0026thinsp;\u0026lt;\u0026thinsp;0) with low disorder, and negative Gibbs energy (∆G\u0026thinsp;\u0026lt;\u0026thinsp;0), showing the spontaneity of the reaction. Considering the comparison of the removal percentage of PANI, NG, and PANI/NG 3wt% nanocomposite with removal percentages of 50.5%, 81.23%, and 97.86%, respectively, it can be concluded that the formation of nanocomposite increased the surface area. Therefore, in the nanocomposite, there was a synergy of hydrogen and electrostatic interactions, as well as high porosity in NG nanoparticles, which provided a high surface for high interactions. The increase of NG could improve the removal rate to a certain extent, so 3% was optimized. In the optimal dye removal conditions such as temperature: 20\u0026deg;C, time: 30 min, concentration: 27.5 mg/g, amount of adsorbent: 0.3 g, and pH\u0026thinsp;=\u0026thinsp;7, the removal percentage was 97.86%.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThe authors acknowledge the Urmia University of Technology for financial supports.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAgboola O, Fayomi OSI, Ayodeji A, Ayeni AO, Alagbe EE, Sanni SE, Okoro EE, Moropeng L, Sadiku R, Kupolati KW and Oni BA (2021) A Review on Polymer Nanocomposites and Their Effective Applications in Membranes and Adsorbents for Water Treatment and Gas Separation. \u003cem\u003eMembranes\u003c/em\u003e 11:1-33. https://doi.org/10.3390/membranes11020139\u003c/li\u003e\n \u003cli\u003eAkter M, Bhattacharjee M, Dhar AK, Rahman FBA, Haque S, Rashid TU and Kabir SMF (2021) Cellulose-Based Hydrogels for Wastewater Treatment: A Concise Review. \u003cem\u003eGels\u003c/em\u003e 7:1-28. https://doi.org/10.3390/gels7010030\u003c/li\u003e\n \u003cli\u003eGupta VK and Suhas, Application of Low-Cost Adsorbents for Dye Removal (2009) \u003cem\u003eJ Environ Manage\u003c/em\u003e 90:2313-2342. https://doi.org/10.1016/j.jenvman.2008.11.017\u003c/li\u003e\n \u003cli\u003eKhan M, Ali SW, Shahadat M and Sagadevan S (2022) Applications of polyaniline-impregnated silica gel-based nanocomposites in wastewater treatment as an efficient adsorbent of some important organic dyes. Green Process and Synth 11:617-630. https://doi.org/10.1515/gps-2022-0063\u003c/li\u003e\n \u003cli\u003eLee YC, Yang JW (2012) Self-assembled flower-like TiO2 on exfoliated graphite oxide for heavy metal removal. J Ind Eng Chem 18:1178\u0026ndash;1185. https://doi.org/10.1016/j.jiec.2012.01.005\u003c/li\u003e\n \u003cli\u003eMandal G, Bauri J, Nayak D, Kumar S, Ansari S and Choudhary RB (2023) Synthesis, Structural Study and Various Applications of Polyaniline and its Nanocomposites, in Trends and Developments in Modern Applications of Polyaniline, ed by Năstase F. Intechopen Publisher, Chaper 6. https://doi.org/10.5772/intechopen.1002227\u003c/li\u003e\n \u003cli\u003eNaseer MN, Dutta K, Zaidi AA, Asif M, Alqahtani A, Aldossary NA, Jamil R, Alyami SH and Jaafar J (2022) Research Trends in the Use of Polyaniline Membrane for Water Treatment Applications:A Scientometric Analysis. \u003cem\u003eMembranes\u003c/em\u003e 12:777. https://doi.org/10.3390/membranes12080777\u003c/li\u003e\n \u003cli\u003eNaser A and Mashkoor F (2019) Application of polyaniline-based adsorbents for dye removal from water and wastewater. Environ Sci Pollut Res Int 26:5333-5356. https://doi.org/10.1007/s11356-018-3990-y\u003c/li\u003e\n \u003cli\u003eSanthi T, Manonmani S and Smitha T (2010) Removal of methyl red from aqueous solution by activated carbon prepared from the Annona squmosa seed by adsorption. Chem Eng Res Bull 14:11-18. http://dx.doi.org/10.3329/cerb.v14i1.3767\u003c/li\u003e\n \u003cli\u003eWang J, Lu L and Feng F (2017) Improving the Indigo Carmine Decolorization Ability of a \u003cem\u003eBacillus amyloliquefaciens\u003c/em\u003e Laccase by Site-Directed Mutagenesis. \u003cem\u003eCatalysts\u0026nbsp;\u003c/em\u003e7(9):275. https://doi.org/10.3390/catal7090275\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Polyaniline, Nanocomposite, N-doped graphene, Adsorption, Carmine dye, Wastewater","lastPublishedDoi":"10.21203/rs.3.rs-6548482/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6548482/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"One effective method for removing common dye pollutants is the use of nano-adsorbents. Among these, polymer-based nanocomposite adsorbents are gaining popularity due to their ease of fabrication and application. In this study, a polyaniline (PANI)/nitrogen-doped graphene (NG) nanocomposite was synthesized at various weight percentages using in situ polymerization and employed for the removal of carmine red dye from aqueous solutions. To analyze the properties and performance of the optimal adsorbent, several characterization techniques were utilized, including FTIR, XRD, FESEM, EDX, TEM, TGA, and BET analyses. The findings demonstrated that the PANI/NG nanocomposite with 3 wt% NG exhibited superior dye adsorption compared to those with 1 wt% and 5 wt% loadings. Thermodynamic analysis revealed that the adsorption of carmine dye onto the synthesized adsorbent was an exothermic process. Key parameters influencing the adsorption process-such as temperature, contact time, dye concentration, adsorbent dosage, and pH-were systematically investigated. The PANI/NG 3 wt% nanocomposite achieved an adsorption capacity of 23.81 mg/g. The optimal conditions for the adsorption process were determined to be a temperature of 20°C, a contact time of 30 minutes, a dye concentration of 27.5 mg/g, an adsorbent dosage of 0.03 g per 100 mL, and a pH of 7. Under these conditions, the PANI/NG 3 wt% nanocomposite removed 97.86% of carmine dye from aqueous solutions. The equilibrium data fitted well with the Freundlich isotherm model, indicating the effectiveness of this nanocomposite for dye removal from wastewater.","manuscriptTitle":"Fabrication and performance evaluation of polyaniline/N-doped graphene nanocomposite as adsorbent in removing carmine red dye from wastewater","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-06 11:55:36","doi":"10.21203/rs.3.rs-6548482/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"14c22907-7c3d-4500-8836-39ca480540c4","owner":[],"postedDate":"May 6th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-08-24T10:17:22+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-06 11:55:36","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6548482","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6548482","identity":"rs-6548482","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}