Removal Of Hexavalent Chromium Research Articles

Optimization of batch process parameters for chromium (VI) removal from synthetic wastewater using eggshell–clay composite

In this study, a biodegradable spherical adsorbent bead was developed from eggshell (ES) and Bijoypur clay (BC) for the removal of hexavalent chromium from synthetic tannery wastewater. This Eggshell–Clay polymer composite (ES–BC) was made by incorporating them with PVA and alginate. To analyze the morphology and chemical composition of the adsorbent before and after the chromium adsorption, SEM, FTIR, XRD, and EDX were used. The impact of adsorption parameters such as adsorbent dosage (0.67–2.23 g/L), pH of the solution (1.5–9), contact time (10–240 min), initial Cr (VI) concentration (25–100 ppm), and solution temperature (25–65 °C), percentage clay in ES-BC adsorbent (0–40%) for Cr (VI) adsorption were investigated. The optimum value for adsorbent dosage, pH, contact time, initial Cr concentration, temperature, and clay to eggshell ratio was found 1.17 g/L, 1.5, 150 min, 58.2 ppm, 25 °C, and 80/20% respectively. The isotherm model was well-fitted to the Freundlich isotherm suggesting heterogeneous adsorption in multilayer on surface. The adsorption kinetics followed pseudo-second-order kinetics supporting the chemisorption process. Moreover, a decrease in enthalpy (H°) and negative Gibbs free energy (G°) with increased temperature indicated exothermic and spontaneous reaction. Therefore, this research investigated that the composite may serve as a viable option for treating Cr (VI) containing tannery effluent.

A Biotic Strategy for Enhanced Hexavalent Chromium Removal by Zero-Valent Iron under the Interference of Humic Acid

A Biotic Strategy for Enhanced Hexavalent Chromium Removal by Zero-Valent Iron under the Interference of Humic Acid

Carboxymethyl cellulose enhanced Cr(VI) removal of zero-valent iron via the coating anti-passivation mechanism

Competition for electrons from dissolved oxygen and secondary passivation resulting from the deposition of FeCr hydroxide are two challenges that impede the removal of hexavalent chromium (Cr(VI)) with zero-valent iron (ZVI). In this study, we fabricated micron-sized zero-valent iron modified with carboxymethyl cellulose (CMC-ZVI) via a mechanical ball milling process and demonstrated its improved performance up to eight times for Cr(VI) removal. Owing to the CMC protective film, the inhibition of dissolved oxygen for Cr(VI) removal, aging of ZVI in air, and secondary passivation of ZVI by the deposition of FeCr hydroxides were all inhibited. Even after a week of continuous aging, the CMC-ZVI maintained a stable Cr(VI) removal efficiency of over 50 %. The excellent hydrophilicity of CMC enhanced the interaction of CMC-ZVI with water and Cr(VI), thus improving its capacity for Cr(VI) removal. Furthermore, CMC-ZVI not only proficiently reduced and completely removed the high-mobility Cr(VI) from actual electroplating effluent, but also effectively alleviated the inhibition of Cr(VI) removal via CMC-ZVI by aeration and air aging. The efficiency of CMC-ZVI in removing Cr(VI) from actual electroplating effluent was improved by over 41 times compared to pristine ZVI. This advantage has the potential to make the storage and transportation of ZVI more affordable and convenient and increases its potential for practical applications. This study provides an efficient Cr(VI) removal strategy using ZVI for environmental remediation and a strategy for the production of highly reactive, aging-resistant, easily stored, and transported zero-valent iron with the potential for practical applications.

Green-synthesized, biochar-supported nZVI from mango kernel residue for aqueous hexavalent chromium removal: Performance, mechanism, and regeneration

A biochar-supported green nZVI (G-nZVI@MKB) composite was synthesized using mango kernel waste with “dual identity” as reductant and biomass of biochar. The G-nZVI@MKB with a Fe/C mass ratio of 2.0 (G-nZVI@MKB2) was determined as the most favorable composite for hexavalent chromium (Cr(VI)) removal. Distinct influencing parameters were discussed, and 99.0% of Cr(VI) removal occurred within 360 min under these optimized parameters. Pseudo-second order kinetic model and intra particle diffusion model well depicted Cr(VI) removal process. The XRD, FTIR, SEM and XPS analyses verified the key roles of G-nZVI and functional groups, as well as the primary removal mechanisms involving electrostatic attraction, reduction, and complexation. G-nZVI@MKB2 exhibited a good stability and reusability with only a 16.4% decline in Cr(VI) removal after five cycles. This study offered evidence that mango kernel could be recycled as a beneficial resource to synthesize green nZVI-loaded biochar composite for efficient Cr(VI) elimination from water.

Preparation of a cationic hydrogel microsphere adsorbent for efficient removal of hexavalent chromium from aqueous solution

AbstractHerein, a cationic hydrogel microsphere (CHMS) was prepared by inverse suspension polymerization and freeze‐drying and was applied to the adsorptive removal of hexavalent chromium (Cr(VI)) from aqueous solution. Morphological characterization shows that there are lots of folds and pores on the surface of CHMS with a unique petal‐like appearance. According to the chemical structure analysis, CHMS contains plenty of functional groups such as amine and hydroxyl groups. These features give CHMS a larger specific surface area, faster adsorption rate, and higher adsorption capacity than the conventional cationic hydrogel microparticle (CHMP) adsorbent. The adsorption of Cr(VI) in water by CHMS is mainly based on the combination of electrostatic adsorption and redox reaction, with the electrostatic interaction between the protonated amine and Cr(VI) serving as the predominant adsorption mechanism. Experimental results reveal that CHMS can efficiently remove Cr(VI) from simulated wastewater in both batch and continuous adsorption modes, which is primarily due to its distinctive surface morphology and rich functional groups. Furthermore, the common coexisting metal ions in Cr(VI)‐containing wastewater have no substantial negative influence on the adsorption. Therefore, it can be concluded that CHMS has a promising application prospect in the treatment of Cr(VI)‐containing wastewater.

A promising approach for the removal of hexavalent and trivalent chromium from aqueous solution using low-cost biomaterial.

Heavy metal pollution is an enduring environmental challenge that calls for sustainable and eco-friendly solutions. One promising approach is to harness discarded plant biomass as a highly efficient environmental friendly adsorbents. In this context, a noteworthy study has spotlighted the employment of Euryale ferox Salisbury seed coat (E.feroxSC) for the exclusion of trivalent and hexavalent chromium ions. This study aims to transform discarded plant residue into a novel, environmentally friendly, and cost-effective alternative adsorbent, offering a compelling alternative to more expensive adsorption methods. By repurposing natural materials, we can contribute to mitigating heavy-metal pollution while promoting sustainable and economically viable solutions in environmental remediation. The effect of different parameters, i.e., chromium ions' initial concentration (5-25mg L-1), solution pH (2-7), adsorbent dosage (0.2-2.4g L-1), contact time (20-240min), and temperature (298-313K), were investigated. E.feroxSC proved highly effective, achieving 96.5% removal of Cr(III) ions at pH 6 and 97.7% removal of Cr(VI) ions at pH 2, with a maximum biosorption capacity of 18.33mg/g for Cr(III) and 13.64mg/g for Cr(VI), making it a promising, eco-friendly adsorbent for tackling heavy-metal pollution. The adsorption process followed the pseudo-second-order kinetic model, aligning well with the Langmuir isotherm, exhibited favorable thermodynamics, and was characterized as feasible, spontaneous, and endothermic with physisorption mechanisms. The investigation revealed that E.feroxSC effectively adsorbed Cr(VI) which could be rejuvenated in a basic solution with minimal depletion in its adsorption capacity. Conversely, E.feroxSC's adsorption of Cr(III) demanded rejuvenation in an acidic milieu, exhibiting comparatively less efficient restoration.

Simultaneous photocatalytic removal of tetracycline and hexavalent chromium by BiVO4/0.6CdS photocatalyst: Insights into the performance, evaluation, calculation and mechanism

In this study, a novel Z-scheme heterojunction on bismuth vanadium/cadmium sulfide (BiVO4/0.6CdS) was developed and evaluated for simultaneous photocatalytic removal of combined tetracycline (TC) and hexavalent chromium Cr(Ⅵ) pollution under visible light. Based on the analysis of intermediate products and theoretical calculation, the property of the intermediate products of TC degradation and the effect of built-in electric field (IEF) of composite materials on photo-generated carrier separation were illustrated. According to the experiments and evaluation results, the performance of BiVO4/0.6CdS is higher than CdS 2.83 times and 4.82 times under the visible light conditions, with the aspect of simultaneous oxidizing TC and reducing Cr(Ⅵ), respectively. The catalyst has a faster removal rate in the binary composite pollution system than the single one. Therefore, the photocatalytic degradation of TC using BiVO4/0.6CdS can reduce the toxic effect of TC on the environment. The aforementioned evaluation provides a new design strategy for Z-scheme heterojunction to simultaneous photocatalytic degradation of composite organic and inorganic pollutants.

Comparison of hexavalent chromium and cadmium removal from wastewater in constructed rapid infiltration system with layered double hydroxides (LDHs) modified maifanite substrates: Physical, chemical and microbial mechanism

In order to protect the ecological environment on which human beings depend, it is of great practical significance to prevent and control the heavy metal pollution in surface water. Cr(VI) in anionic form and Cd(II) in cationic form were selected to conduct the heavy metal purification experiments. Cr(VI) and Cd(II) removal by constructed rapid infiltration systems (CRIS) contain Zn-CO3-LDHs (ZnAl-CO3-LDHs and ZnFe-CO3-LDHs) coated maifanite substrates were compared. After ZnAl-CO3-LDHs coated, the Cr(VI) and Cd(II) removal amount increased by 87.53 % and 19.00 %, respectively. It could be inferred from XRD, FTIR, and Zeta potential results that the Cr(VI) physicochemical removal mechanism of maifanite changed to anion exchange, chemical bonding and electrostatic adsorption from electrostatic adsorption and chemical bonding after Zn-CO3-LDHs coated. By contrast, isomorphous replacement, electrostatic adsorption and chemical bonding of Cd(II) induced by Zn-CO3-LDHs replaced the electrostatic adsorption by natural maifanite. Additionally, the effective Cr(VI)/Cd(II) accumulation on Zn-CO3-LDHs modified maifanite reduced the microbial quantity, but increased EPS secretion and changed the community structure, which achieved the microbial Cr(VI)/Cd(II) removal through extracellular complexation and intracellular accumulation. This research result may provide essential reference for exploring the feasibility of heavy metal removal of CRIS with LDHs modified substrate.

Hexavalent chromium removal by green synthesized nano-size iron particles combined with iron sulfides: Effects of dissolved oxygen and phosphate

The removal of hexavalent chromium (Cr(VI)) from wastewater using the green synthesized nano-zero-valent-iron (GnZVI) has attracted great attention. However, the Cr(VI) removal capacity of GnZVI remains limited by dissolved oxygen (DO) or phosphate in wastewater. Therefore, Cr(VI) removal by GnZVI combined with iron sulfides (i.e., FeS or FeS2) impacting by DO and phosphate was investigated at pH 2.0 and 6.0. Experimental results showed that DO inhibited the Cr(VI) removal by GnZVI with FeS at pH 2.0, because high DO saturation was beneficial to Fe(II) oxidization into Fe(III). Nevertheless, DO promoted the corrosion and dissolution of FeS2 but GnZVI for Cr(VI) reduction at pH 2.0. Especially, phosphate inhibited the Cr(VI) reduction by the combination of GnZVI and iron sulfides at pH 2.0, likely because phosphate inhibited Fe(II) release from GnZVI hybrid materials during the reduction process from Cr(VI) to Cr (III). Differently, at pH 6.0, phosphate mainly promoted Cr(VI) removal by FeS compared with GnZVI via the formation of phosphate complexation, while it inhibited Cr(VI) removal using GnZVI combined with FeS2 through the competitive adsorption. This study reveals the potential inherent mechanisms and emphasizes a sustainable strategy for the effective removal of Cr(VI) using a hybrid technique that combines GnZVI and iron sulfides under complex wastewater conditions.

Long Short-Term Memory and Bidirectional Long Short-Term Memory Modeling and Prediction of Hexavalent and Total Chromium Removal Capacity Kinetics of Cupressus lusitanica Bark

Hexavalent chromium [Cr(VI)] is a high-priority environmental pollutant because of its toxicity and potential to contaminate water sources. Biosorption, using low-cost biomaterials, is an emerging technology for removing pollutants from water. In this study, Long Short-Term Memory (LSTM) and bidirectional LSTM (Bi-LSTM) neural networks were used to model and predict the kinetics of the removal capacity of Cr(VI) and total chromium [Cr(T)] using Cupressus lusitanica bark (CLB) particles. The models were developed using 34 experimental kinetics datasets under various temperature, pH, particle size, and initial Cr(VI) concentration conditions. Data preprocessing via interpolation was implemented to augment the sparse time-series data. Early stopping regularization prevented overfitting, and dropout techniques enhanced model robustness. The Bi-LSTM models demonstrated a superior performance compared to the LSTM models. The inherent complexities of the process and data limitations resulted in a heavy-tailed and left-skewed residual distribution, indicating occasional deviations in the predictions of capacities obtained under extreme conditions. K-fold cross-validation demonstrated the stability of Bi-LSTM models 38 and 43, while response surfaces and validation with unseen datasets assessed their predictive accuracy and generalization capabilities. Shapley additive explanations analysis (SHAP) identified the initial Cr(VI) concentration and time as the most influential input features for the models. This study highlights the capabilities of deep recurrent neural networks in comprehending and predicting complex pollutant removal kinetic phenomena for environmental applications.

Adsorption of Hexavalent Chromium on KOH Activated Carbon Derived from Water Hyacinth Leaf Coated with Polyaniline/Polypyrrole

KOH-Activated carbon derived from Water Hyacinth (KOH-WHL-AC) was prepared and coated with Polyaniline-Polypyrrole (PANI/PPY) copolymer for the removal of hexavalent chromium (Cr(VI)) from wastewater. The prepared material was characterized by FT-IR and XRD. The effect of pH, contact time, dosage, and initial Cr(VI) concentrations were optimized using batch adsorption experiment. The adsorption kinetics was found to fit better to pseudo-second-order than the pseudo-first order model. Langmuir and Freundlich isotherm models were analyzed using linear fitting. It was found that the Langmuir adsorption model gives the best fit indicating that the monolayer adsorption of Cr(VI) on the KOH-WHL-AC. The highest adsorption capacity of 409.83 mg/g was achieved at pH 1.0, and equilibrium was achieved within 420 min. The reuse efficiency of the synthesized material was also found to be greater than 54% for five consecutive cycles. Thermodynamic studies have also been carried out and the adsorption was found to be spontaneous and endothermic

Experimental validation off-line a nonlinear controller for removal of chromium using non-living cells of Yarrowia lipolytica

The removal of hexavalent chromium [Cr (VI)] using non-living cells of Yarrowia lipolytica was investigated. Batch and continuous studies on removal of Cr (VI) achieved 97% and 99% removal from aqueous phase, respectively. The specific uptake values at pH of 2 in batch process were 40.73 ± 1.3 mg/g and 30.09 ± 0.23 mg/g on non-living cells, when 100 and 200 mg/L of metal Cr (VI) concentrations were used. In order to investigate the regulation of Cr (VI) under continuous operation based on reaction volume numerically a new class of feedback controller from structure polynomial was designed. The proposed methodology was used to an experimentally kinetic model for a removal Cr (VI) from Yarrowia lipolytica biomass was showed satisfactory closed-loop performance the proposed controller. Starting from an off-line optimization performed in simulation, we present the controller implementation, focussing on the methodology required to could be suitable for implementation in real time. In our experimental results, we highlight some discrepancies between simulation and reality despite these differences, the controller managed to perform convergence to removal Cr (VI). Finally, the results validated with off-line samples suggest that the proposed control could be suitable for in application in potential scenarios for wastewater treatment.

Hybrid nanomaterials for efficient hexavalent chromium removal from waste water: activated charcoal sheet modification through polypyrrole and silver nanoparticles

Hybrid nanomaterials for efficient hexavalent chromium removal from waste water: activated charcoal sheet modification through polypyrrole and silver nanoparticles

Removal of hexavalent chromium in water by chitosan-modified Enteromorpha prolifera biochar loaded with iron-manganese oxides: Application performances and reaction mechanisms

This study successfully synthesized magnetic iron-manganese biochar (F1M3BC) and iron-manganese chitosan biochar (Chi-F1M3BC) using Enteromorpha prolifera (EP) as the raw material, aiming to efficiently remove hexavalent chromium (Cr(VI)) from water. Compared to F1M3BC, Chi-F1M3BC, after chitosan cross-linking encapsulation, exhibited significant advantages in terms of specific surface area, pH adaptability, and adsorption performance. The specific surface area of Chi-F1M3BC reached 101.47 m³/g, approximately double that of F1M3BC (52.89 m³/g), making it rich in reactive groups for Cr(VI) removal. The addition of chitosan elevated the pHpzc value of Chi-F1M3BC from 5.5 to 9, and the abundant active groups enabled it to efficiently remove Cr(VI) over a wider pH range. Under 30 °C conditions, 0.5 g/L of Chi-F1M3BC could completely remove 30 mg/L of Cr(VI) solution within 1 h. Adsorption isotherm and kinetic studies indicated that Chi-F1M3BC complied with the Langmuir model and pseudo-second-order kinetics. At 30 °C, the adsorption capacity of Chi-F1M3BC reached 104.5 mg/g, approximately twice that of F1M3BC (58.93 mg/g). Moreover, after five consecutive usage cycles, the removal efficiency of Cr(VI) by Chi-F1M3BC only slightly decreased by 3%, demonstrating its superior stable removal performance. Subsequent characterization and experimental investigations elucidated the elimination of Cr(VI) by Chi-F1M3BC, achieved through the synergistic interplay of ion exchange, electrostatic attraction involving surface hydroxyl and amino functional groups, chelation, and the reduction of iron and manganese oxides. In conclusion, the synthesized Chi-F1M3BC has demonstrated its efficiency and stable adaptability in removing Cr(VI), coupled with the additional benefit of utilizing waste Enteromorpha prolifera.

CHEMICALLY CROSSLINKED CELLULOSE-BASED HYDROGEL PREPARED FROM RICE STRAW FOR THE REMOVAL OF AQUEOUS HEXAVALENT CHROMIUM ION FROM WASTEWATER

Then, this purified cellulose was co-polymerized by the addition of acrylic acid and ammonium persulfate in the presence of N,N-methylenebisacrylamide as crosslinker to form a cellulose-based hydrogel for the removal of hexavalent chromium (Cr(VI)) from wastewater. Here, the impact of various parameters, such as pH, contact time, material dosage, and initial solution concentration, on the adsorption capacity of the hydrogel for Cr(VI) ions is systematically investigated. The experimental findings revealed that the highest adsorption capacity for the treatment of Cr(VI)-containing water reached 1.1 mg Cr(VI)/g at pH 1, contact time of 120 min, and the initial concentration in the aqueous solution of 10 mg/L for an applied adsorbent dosage of 0.2 g. In addition, the equilibrium adsorption data agreed well with the Langmuir isotherm and the maximum adsorption amount was 4.14 mg Cr(VI)/g. Additionally, this material demonstrated good reusability, supporting the notion that it can be efficiently regenerated for multiple uses, a crucial factor for its practical application towards reducing the environmental impact and increasing its economic value.

A visible light driven photocatalyst Ag/AgBr/SrSb2O6 for removal of model organic contaminants and hexavalent chromium

A single plausible solution to multi-environmental issues is an efficient photocatalyst. The SrSb2O6 with a band gap of 2.72 eV was successfully tailored to 1.99 eV by deposition of Ag/AgBr. The synergistic effect of reduced band gap and surface plasmon resonance (SPR) effect of Ag0 could enhance the photocatalytic efficiency to a greater extent. This work attempts to explore a composite photocatalyst Ag/AgBr/SrSb2O6 for the photodegradation of organic wastes such as dyes, organic solvents, drugs, and antibiotics. In addition, the photo remediation of heavy metal waste such as Cr6+ is also investigated. The propitious results promise Ag/AgBr/SrSb2O6 to be a wide-range photocatalyst that can eliminate both organic and inorganic waste from water. The photodegradation of RhB dye, phenol, and tetracycline reached up to 80.8%, 76.8%, and 64.5%, respectively. Notably, the Ag/AgBr/SrSb2O6 catalyst effectively converted 97.3% of lethal Cr6+ to benign Cr3+. The better electron hole pair separation of the composite was evidenced by PL spectra.

Enhanced electron transfer via synergistic electric field effects in g-C3N4/MoS2 piezo-photocatalysis for hexavalent chromium removal

This study explores the significant reduction effect of g-C3N4-modified MoS2 on Cr6+ in water, attributed to its piezo-photocatalytic activity. Electrochemical tests indicate that, compared to pure MoS2, the built-in electric field formed by the g-C3N4/MoS2 heterojunction effectively promotes the transfer rate of photogenerated charge carriers, thereby enhancing the reduction efficiency of Cr6+. Furthermore, applying mechanical force further strengthens the built-in electric field of the g-C3N4/MoS2 heterojunction, accelerating the transfer rate of photogenerated charge carriers and regulating the arrangement of the semiconductor material band structure. Moreover, cytotoxicity experiments demonstrate that the Cr6+ solution at tested concentrations treated with the g-C3N4/MoS2 piezo-photocatalytic system exhibited negligible toxic effect on Hep-G2 cells compared to before reaction, making it an environmentally friendly choice for water treatment. The research results are of significant importance for designing efficient catalysts for environmental remediation, as well as for biological and medical applications.

Effective chromium removal of metal anchored alginate-chitosan binary bio-composites

Water is the most essential resource for the biotic and abiotic components of an ecosystem. Any change in the quality of this water may cause adverse impact on the ecosystem. Hexavalent chromium is one such important pollutant that gets exposed in the water mainly through anthropogenic processes. Adsorption is considered to be an effective, economic and easiest method for remediation of such pollutants. Amongst the innumerable adsorbents available, biopolymers fetch the interest due to its cost effectiveness, efficiency and biocompatibility. But, the mechanical strength and workability of such biopolymers makes it unfit to use as an adsorbent. To improve these drawbacks, synthesis of biopolymeric composites become the need of the hour. So, an attempt was made here to synthesize metal cross-linked binary bio-composites using Alginate and Chitosan polymer matrix. Synthesized bio-composites were characterised with the aid of FTIR, XPS, Thermal analysis, SEM with EDAX and subjected for hexavalent chromium removal from water. Analysis of variance (ANOVA) with 95 % confidence intervals was used to assess the significance of independent variables and their interactions. Adsorption studies were done using batch process and to achieve greater sorption, various influencing parameters were optimized one by one. While investigating one parameter, other parameters were kept unaltered. Optimization was done for the parameters like contact time, dosage of the adsorbent, pH of the medium and presence of co-ions. Contact time and dosage for all the composites was 30 mins and 0.1 g respectively. Amongst the composites, Zirconium loaded binary composite possess high sorption capacity of around 14.8 mg/g. While Calcium and Iron loaded composites exhibit sorption capacity of around 9.8 mg/g and 10.4 mg/g respectively. Presence of other co-ions in the medium doesn't affect the sorption process. Isothermal studies infer the adsorption follows Langmuir model and thermodynamic parameters concludes the endothermic and randomness of the adsorption. The bio-composites can be recycled and used upto three cycles. Field trial was conducted and the composites work well in such conditions.

Bis-amino modified magnetic molasses wastewater hydrochar adsorbent for chromium removal

The removal of hexavalent chromium (Cr(VI)) from industrial wastewater has always been an important issue in the field of environment and human health. However, there are still challenges in achieving effective adsorption of Cr(VI) by adsorbents in slightly neutral environments. The resource utilization of organic wastewater is also a current research focus and difficulty in the academic community. In this study, molasses wastewater was used as a carbon and nitrogen source to synthesize magnetic amino hydrochar (MMHC) through a hydrothermal carbonization process. In order to further enhance the adsorption performance of MMHC for Cr(VI) in slightly neutral environments, a two-step grafting strategy was employed to introduce quaternary ammonium groups with N+ sites onto the MMHC substrate, resulting in the surface modification of MMHC with dual amino groups (MMHCQA). The introduction of dual amino groups not only increases the adsorption sites on the surface of MMHCQA, but also raises the point of zero charge of MMHCQA, ensuring its excellent adsorption performance for Cr(VI) in higher pH environments. At pH 6, the adsorption capacity of MMHCQA are 3 times higher than MMHC. This work elucidated the adsorption process using adsorption kinetics, thermodynamics, and adsorption isotherms, and fitted the three major factors (pH, Cr(VI) concentration and temperature) influencing MMHCQA adsorption performance through response surface analysis, revealing that pH is the decisive factor affecting MMHCQA adsorption performance. Furthermore, MMHCQA can be stably reused for at least 5 cycles.

Polypyrrole Modified Granular Activated Carbon Nanocomposite for Treatment of Wastewater Containing Highly Toxic Hexavalent Chromium

AbstractThis study explored the fabrication of Polypyrrole (PPy) and Granular Activated Carbon (GAC) composites (PPy‐GAC) for effective removal of toxic hexavalent chromium (Cr(VI)) from aqueous solutions. Two synthesis methods are employed: (1) electrostatic deposition of PPy onto pre‐charged GAC paper and (2) in‐situ chemical polymerization of pyrrole monomer with GAC particles. Batch adsorption experiments investigated the impact of various operational parameters on Cr(VI) removal. Compared to pristine GAC (54.64 mg g−1), the PPy‐GAC composite exhibited a remarkable 3‐fold increase in equilibrium adsorption capacity, reaching 175.44 mg g−1. Pseudo‐second‐order kinetic model (R2 > 0.999) accurately described the adsorption kinetics, while the Langmuir isotherm model (R2 > 0.99) provided a good fit for the equilibrium data. Maximum adsorption capacity (qmax) increased with temperature, reaching 204.08, 243.90, and 270.27 mg g−1 at 298, 308, and 318 K, respectively. Furthermore, a fixed‐bed column experiment examined the composite's effectiveness in continuous Cr(VI) removal, demonstrating its suitability for practical applications. Notably, the PPy‐GAC composite successfully removed Cr(VI) from a real wastewater sample containing 68 µg L−1 Cr(VI) obtained from a ferrochrome industry, highlighting its potential for real‐world remediation.