Enhanced adsorption of Congo red using chitin suspension after sonoenzymolysis

Biopolymer‑carbonaceous composites, progress, and adsorptive mitigation of water pollutants

Chitin is the second most abundant natural biopolymer, which is composed of N-acetyl glucosamine units linked by β-(1 → 4) Chitosan is an N-deacetylated product of chitin. Properties of chitosan and chitin, such as biocompatibility, non-toxic nature, and biodegradability, make them successful alternatives for energy and environmental applications. However, their low mechanical properties, small surface area, reduced thermal properties, and greater pore volume restrict the potential for adsorption applications. Multiple investigations have demonstrated that these flaws can be prevented by fabricating chitosan and chitin with carbon-based composites. This review presents a comprehensive analysis of the fabrication of chitosan/chitin carbon-based materials. Furthermore, this review examines the prevalent technologies of functionalizing chitosan/chitin biopolymers and applications of chitin and chitosan as well as chitosan/chitin carbon-based composites, in various environmental fields (mitigating diverse water contaminants and developing biosensors). Also, the subsequent regeneration and reuse of adsorbents were also discussed. Finally, we summarize a concise overview of the difficulties and potential opportunities associated with the utilization of chitosan/chitin carbon-based composites as adsorbents to remove water contaminants.

Promising adsorbent for dye detoxification: Exploring the potential of chitosan sodium carboxymethylcellulose silk fibroin aerogel

The main goal of this study is to create a CS-CMC-SF aerogel consisting of chitosan sodium carboxymethylcellulose and silk fibroin. The aerogel is designed to remove types of dyes from water while also being environmentally friendly. This innovative adsorbent has been optimized for extracting both cationic and anionic dyes from solutions. It incorporates chitosan sodium carboxymethylcellulose and silk filament fibers to enhance its strength. Experimental data illustrates that the CS-CMC-SF aerogel possesses remarkable adsorption capabilities - 5461.77 mg/g for Congo Red (CR), 2392.83 mg/g for Malachite Green (MG), and 1262.20 mg/g for Crystal Violet (CV). A kinetic study aligns with the pseudo-second-order kinetic model suggesting predominant chemisorption phenomena occur during adsorption process. Isotherm analysis further identifies multilayered adsorption occurring on irregularly shaped surfaces of the aerogel while thermodynamic assessments validate exothermic and spontaneous characteristics inherent in its absorption mechanism. Several analytical methods such as SEM, FT-IR, XRD, and XPS were employed to examine physicochemical attributes tied to this unique material design conceptually; identifying mechanisms including pore filling, π-π interactions, ion exchange activity, electrostatic connections along with hydrogen bonding inducing overall superior performance output. Furthermore substantial soil biodegradability alongside compostable features associated with our proposed CS-CMC-SF aerogels established it's potential suitability within applications demanding sustainable options thereby validating its underlying ecological credibility.

Synthesis of porous calcium-guar gum benzoate nano-biohybrids for sorptive removal of congo red and phosphates from water

This work aims to develop an eco-sound nano-bio-hybrid sorbent using sustainable materials for sorptive elimination of congo red and phosphates from aquatic environment. An amphipathic biopolymer derivative, high DS guar gum benzoate (GGBN) was used for entrapment of as synthesized calcium carbonate nanoparticles using solvent diffusion nano-precipitation technique. Designer nano-biohybrids were developed upon experimenting with various materials stoichiometry. SEM, XRD and EDX studies confirmed near-uniform impregnation of rhombohedral calcium carbonate crystals throughout the biopolymer matrix. Average pore size distribution and surface area of final product Ca-GGBNC, were estimated from NDLFT and BET methods respectively. Analysis of adsorption findings acquired at study temperature 27 ± 2 °C showed that the maximum adsorption capacity of Ca-GGBNC recorded qmax, 333.33 mg/g for congo red azo dye and that for phosphate was at 500 mg/g. Adsorptive removal was noted and both components followed pseudo second order kinetics. Intra-particle diffusion kinetics investigation disclosed that the boundary layer effect was prominent and the adsorption rates were not solely directed by the diffusion stage. Activation energy, Ea was to be estimated using Arrhenius equation at 56.136 and 47.015 KJ/mol for congo red and phosphates respectively. The calculated thermodynamic parameters(ΔG°, ΔH°, and ΔS°) revealed the spontaneous, feasible and endothermic sorption process. Owing to active surface area, spherical size, functional moiety and porous network, antibacterial properties of nanobiohybrid were persistent and MIC against E. coli and S. aureus were recorded at 200 μg/mL and 350 μg/mL respectively.

A holistic NMR framework to understand environmental impact: Examining the impacts of superparamagnetic iron oxide nanoparticles (SPIONs) in Daphnia magna via imaging, spectroscopy, and metabolomics

Superparamagnetic iron oxide nanoparticles (SPIONs) are a contaminant of emerging interest, often used in the medical field as an imaging contrast agent, with additional uses in wastewater treatment and as food additives. Although the use of SPIONs is increasing, little research has been conducted on the toxic impacts to living organisms beyond traditional lethal concentration endpoints. Daphnia magna are model organisms for aquatic toxicity testing with a well understood metabolome and high sensitivity to SPIONs. Thus, as environmental concentrations continue to increase, it is becoming critical to understand their sub-lethal toxicity. Due to the paramagnetic nature of SPIONs, a range of potential nuclear magnetic resonance spectroscopy (NMR) experiments are possible, offering the potential to probe the physical location (via imaging), binding (via relaxation weighted spectroscopy), and the biochemical pathways impacted (via in vivo metabolomics). Results indicate binding to carbohydrates, likely chitin in the exoskeleton, along with a decrease in energy metabolites and specific biomarkers of oxidative stress. The holistic NMR framework used here helps provide a more comprehensive understanding of SPIONs impacts on D. magna and showcases NMR's versatility in providing physical, chemical, and biochemical insights.

Application of carbon from pomegranate husk for the removal of ibuprofen, cadmium and methylene blue from water

The presence of pharmaceutical products, dyes, and toxic metal ions in water is a major problem worldwide. This work developed low-cost pomegranate-based materials to uptake ibuprofen, cadmium and methylene blue from water. Pomegranate husks (PPH) were carbonized at 400 °C to form carbonized pomegranate husk (CPH), and nanoparticles were loaded into the carbon surface (NPH) by co-precipitation. SEM micrographs showed that the morphology of carbon was highly porous compared to pristine pomegranate husk. The data for BET revealed that CPH and NPH, had about a 20-fold increase in surface area of 142 m2/g and 190 m2/g respectively compared with 9.27 m2/g for PPH. The composites exhibited larger pore sizes and volumes. TEM images confirmed the loading of nanoparticles. The FTIR results showed that the materials had on their surface oxygenated groups such as -OH, -C]O, -COC and other groups like -NH and -C]C which are anticipated to play an essential role in the sorption of the pollutants. It was found that removal efficiency increased when there was a progressive increase in pollutant concentration for all adsorbents. The best pH value of the solution for the sorption processes was pH 8. The recorded adsorption capacities at pH 8 for Cd(II), IBU and MB were 92.85, 39.77 and 95.89 mg/g for NPH, 72.60, 32.58 and 80.59 mg/g for CPH and 32.78, 16.12 and 40.79 mg/g for PPH. Contact time studies showed three sorption steps. Step 1: rapid increase at the initial stage. Step 2: marginal uptake. Step 3: plateau. The trends indicated that sorption was influenced by temperature variation. The data for the thermodynamic parameter △Ho suggest that all the sorption processes were endothermic; the obtained positive values indicate this. The △Ho for PPH was between (64.33-69.08 kJ/mol), 82.84-86.03 kJ/mol for CPH and 87.17-88.96 kJ/mol for NPH. For PPH, molecular interactions were physisorption, and chemisorption for CPH and NPH. The △So has positive values, showing increased freedom during the sorption. The adsorbents followed PSO based on uptake processes involving syngenetic mechanisms.

Insights into the relationships of modifying methods, structure, functional properties and applications of chitin: A review

Chitin as the second plentiful polysaccharide has arouse widely attention due to its remarkable availability and biocompatibility. While the strong inter/intra molecular hydrogen bonds and crystallinity severely restrict its applications. Recently, multiple emerging technologies are increasingly used to modify chitin structure for the sake of obtaining excellent functional properties, as well as broadening the corresponding applications. Firstly, this review systematically outlines the features of single and combined methods for chitin modification. Then, the impacts of various modifying methods on the structural characteristics of chitin, including molecular weight, degree of acetylation and functional groups, are further summarized. In addition, the effects of these structural characteristics on the functional properties as well as its potential related applications are illustrated. The conclusion of this review provides better understanding of the relationships among the modifying methods, structure, properties and applications, contributing to chitin modification for the targeted purpose in the future study.

Chitin/deacetylated chitin nanocomposite film for effective adsorption of organic pollutant from aqueous solution

Cross-linked chitin/deacetylated chitin nanocomposite films can be considered as a potential industrial adsorbent for the removal of organic pollutants for water purification. Chitin (C) and deacetylated chitin (dC) nanofibers were extracted from raw chitin and characterized using FTIR, XRD and TGA techniques. The TEM image confirmed the formation of chitin nanofibers with a diameter range of 10-45 nm. The deacetylated chitin nanofibers (DDA-46 %) having 30 nm diameter was evidenced using FESEM. Further, the C/dC nanofibers were prepared at different ratios (80/20, 70/30, 60/40 & 50/50 ratios) and cross-linked. The highest tensile strength of 40 MPa and Young's modulus of 3872 MPa was exhibited by 50/50C/dC. The DMA studies revealed that the storage modulus enhanced by 86 % for 50/50C/dC (9.06 GPa) in comparison to 80/20C/dC nanocomposite. Further, the 50/50C/dC exhibited a maximum adsorption capacity of 30.8 mg/g at pH = 4 in 30 mg/L of Methyl Orange (MO) dye within 120 min. The experimental data agreed with pseudo-second-order model indicating chemisorption process. The adsorption isotherm data was best described by Freundlich model. The nanocomposite film is an effective adsorbent can be regenerated and recycled for five adsorption-desorption cycle.

Efficient adsorption of Congo red by micro/nano MIL-88A (Fe, Al, Fe-Al)/chitosan composite sponge: Preparation, characterization, and adsorption mechanism

MIL-88A crystals with three different metal ligands (Fe, Al, FeAl) were prepared by hydrothermal method for the first time. The three materials' crystal structure and surface morphology are different, leading to different adsorption properties of Congo red (CR). The maximum adsorption capacities of MIL-88A (Fe), MIL-88A (FeAl), and MIL-88A (Al) are 607.7 mg · g^-1, 536.4 mg · g^-1, and 512.1 mg · g^-1 respectively. In addition, MIL-88A was combined with chitosan (CS) respectively, and MIL-88A/CS composite sponge was prepared by the freeze-drying method, which not only solved the defect that MIL-88A powder was difficult to recover but also further improved the removal ability of CR by the adsorbent. The maximum adsorption capacities of MIL-88A (FeAl)/CS, MIL-88A (Fe)/CS, MIL-88A (Al)/CS, and CS are 1312 mg · g^-1, 1056 mg · g^-1, 996.7 mg · g^-1, and 769.6 mg · g^-1, respectively. The structure and physicochemical properties of the materials were analyzed by SEM, FTIR, XRD, TGA, BET, and Zeta. The adsorption process of CR follows pseudo-second-order kinetics and Langmuir, Sips isotherm model. Combined with thermodynamic parameters, the adsorption behavior was described as endothermic monomolecular chemical adsorption. The removal of CR is attributed to electrostatic interactions, hydrogen bonding, metal coordination effects, and size-matching effects.

Sustainable synthesis of graphene sand composite from waste cooking oil for dye removal

Waste cooking oil (WCO) appears to be a potential carbonaceous source for synthesizing graphene sand composite (GSC) adsorbent in removing pollutants. This study presents a green synthesis method of GSC using WCO as a sustainable carbon source for the synthesis of GSC through the thermal graphitization method. Characterization analysis conducted on GSCWCO verified the successful coating of WCO onto the sand surface and conversion to graphene, which possessed distinct functional groups and features of graphene materials. GSCWCO adsorbent effectiveness in removing Congo Red dye through batch adsorption was studied under the influence of different initial concentrations (20 to 100 mg/L), and the optimum pH (pH 2 to 10), contact time (5 to 240 min), and temperature (25 to 45 °C) were investigated. The GSCWCO showed removal rates of 91.5% achieved at an initial dye concentration of 20 mg L-1, 1.0 g of adsorbent dosage, a temperature of 25 °C, and 150 min of contact time. The GSCWCO exhibited a maximum capacity of 5.52 mg g-1, was well-fitted to the Freundlich isotherm model with an R2 value of 0.989 and had an adsorption mechanism that followed the pseudo-second-order kinetic model. Negative values of enthalpy (ΔH) and Gibbs free energy (ΔG) revealed that CR adsorption onto GSCWCO was a spontaneous and exothermic process. The presence of functional groups on the surface of GSCWCO with such interactions (π-π attractive forces, hydrophobic forces, and hydrogen bonding) was responsible for the anionic dye removal. Regeneration of GSCWCO adsorbent declined after four cycles, possibly due to the chemisorption of dyes with GSC that resulted in inefficient adsorption. Being a waste-to-wealth product, GSCWCO possessed great potential to be used for water treatment and simultaneously benefited the environment through the effort to reduce the excessive discharge of WCO.

3D Hierarchical Porous and N-Doped Carbonized Microspheres Derived from Chitin for Remarkable Adsorption of Congo Red in Aqueous Solution

A novel adsorbent of N-doped carbonized microspheres were developed from chitin (N-doped CM-chitin) for adsorption of Congo red (CR). The N-doped CM-chitin showed spherical shape and consisted of carbon nanofibers with 3D hierarchical architecture. There were many micro/nano-pores existing in N-doped CM-chitin with high surface area (455.703 m² g^-1). The N element was uniformly distributed on the carbon nanofibers and formed with oxidize-N graphitic-N, pyrrolic-N, and pyridinic-N. The N-doped CM-chitin showed excellent adsorption capability for CR and the maximum adsorption amount was approximate 954.47 mg g^-1. The π-π/n-π interaction, hydrogen-bond interactions, and pore filling adsorption might be the adsorption mechanisms. The adsorption of N-doped CM-chitin was considered as a spontaneous endothermic adsorption process, and which well conformed to the pseudo-second-order kinetic and Langmuir isotherm model. The N-doped CM-chitin exhibited an effective adsorption performance for dynamic CR water with good reusability. Therefore, this work provides new insights into the fabrication of a novel N-doped adsorbent from low-cost and waste biomasses.

Recent advances in polymer composite, extraction, and their application for wastewater treatment: A review

Wastewater from diverse industrial sectors, agricultural practices and other household activities causes water pollution that result in different environmental issues. The main goals of wastewater treatment are typically to enhance the purity of wastewater and to enable the disposal of domestic and industrial effluents without endangering human health or causing excessive environmental issues. There were several natural and synthetic materials which have been utilized for wastewater treatment, amongst them polymers gain more importance due to their non-toxicity, economic feasibility, abundant availability of sources, renewability, biocompatibility, biodegradability, etc. The organic polymers such as cellulose, chitin, gelatin, alginates, lignin, dextran and other starch derivatives are the most commonly used natural polymers in wastewater treatments. The unique physical and chemical characteristics of the natural polymers make them become an alternative in wastewater treatments such as membrane filtration, adsorption, coagulation, flocculation and ion-exchange process to remove harmful contaminants such as toxic metals, dyes, medicines, pesticides, and so on. The review article discusses natural polymers and related uses in wastewater treatment. This review mainly focused on the wastewater treatment using natural polymers and the techniques involved for their extraction from natural sources. The recent trends in polymer extraction from the natural sources and the scope for the future research of natural polymers in various sectors are also discussed in detail.

Amino-modified chitosan/gold tailings composite for selective and highly efficient removal of lead and cadmium from wastewater

In this work, a novel amino-modified chitosan/tailings composite (CS-PEI-nGT) was successfully synthesized from gold tailings particle treated by ball milling (nGT), chitosan (CS) and polyethyleneimine (PEI) as raw materials, for Lead (Pb(Ⅱ)) and Cadmium (Cd(Ⅱ)) removal from aqueous solutions. The CS-PEI-nGT was characterized by using FTIR, XRD, SEM, BET, TGA and XPS techniques. The results showed that CS-PEI-nGT had maximum adsorption capacity of 192.78 mg·g^-1 and 99.46 mg·g^-1 for Pb(Ⅱ) and Cd(Ⅱ) respectively at pH 5. The adsorption kinetics was described well by pseudo-second-order kinetic adsorption model, and suggested that chemisorption as the rate-controlling step for adsorption of Pb(Ⅱ) and Cd(Ⅱ). The isotherm data was accurately explained by Langmuir model with higher correlation coefficient (R²) of 0.9911 and 0.9642 for Pb(Ⅱ) and Cd(Ⅱ) respectively. In addition, CS-PEI-nGT retained its selective adsorption capacity for Pb(Ⅱ) and Cd(Ⅱ), compared to other metals such as Zn(Ⅱ), Mn(Ⅱ), Mg(Ⅱ) and Al(Ⅲ). The mechanism of the adsorption was investigated and the results revealed that amino (-NH₂), silicon oxide groups (Si-O) and hydroxyl (-OH) functional groups on composite surface were accountable for metals adsorption, suggesting surface complexation, electrostatic interactions and ion exchange. Our work presents a promising strategy for tailings recycling and highly efficient removal of toxic metals ions from wastewater.

Historical development and prospect of intimately coupling photocatalysis and biological technology for pollutant treatment in sewage: A review

Through the synergistic effect of photocatalysis and biodegradation, intimately coupling photocatalysis and biological (ICPB) technology could improve the removal rate and mineralization rate of refractory pollutants and reduce the toxicity of intermediate products. ICPB system was characterized with the advantages of simple operation, low energy consumption and high treatment efficiency. As a new sewage treatment technology, ICPB system has shown great potential in the treatment of refractory pollutants, and has been widely concerned. In this study, the research progress of photocatalyst, carrier and biofilm in ICPB system were discussed, and the degradation mechanism was introduced. The shortcomings of the current ICPB system were pointed out, and the possible research directions of ICPB in the future were proposed. This review aimed to deepen the understanding of ICPB technology and promoted the further development of ICPB technology in the treatment of refractory pollutants.

Enhanced performance of photocatalytic treatment of Congo red wastewater by CNTs-Ag-modified TiO2 under visible light

In order to improve the treatment efficiency of printing and dyeing wastewater, the carbon nanotubes-silver-modified-titanium dioxide (CNTs-Ag-TiO₂, CAT) ternary composite was prepared by a mechanical mixing method. It was found that the morphology of the prepared CAT sample was uniformly coated with strips of CNTs, speckled Ag, and lumpy TiO₂. The (002) crystal plane of CNTs, the (101) crystal plane of TiO₂, and the (111) crystal plane of Ag were observed, which possessed functional groups such as Ti-OH and Ti-O-C, indicating that the prepared CAT sample had photocatalytic reaction sites. The visible light utilization of titanium dioxide can be improved. The treatment effect of different proportions of CNTs-Ag-TiO₂ on Congo red wastewater was tested, and the results showed that the optimum degradation effect of Congo red wastewater was CNTs: Ag = 10:1, and the doped amount of CNTs/Ag was 15%, and the removal rate of Congo red wastewater could reach 100% within 140 min. The excellent removal effect of CAT ternary composite on Congo red wastewater provided a new idea and way for the modification of TiO₂ and its composites for the potential of organic dyes degradation.

Dye adsorption of aluminium- and zirconium-based metal organic frameworks with azobenzene dicarboxylate linkers

The high efficiency of metal-organic-frameworks (MOFs) such as the ZIF, MIL and UiO type species in dye adsorption is well established. Recently, an emerging class of photoresponsive azobenzene-based MOFs has found suitable application in gas adsorption. However, there is a dearth of research on their use in the adsorption of dyes and other water pollutants. In this research, two microporous photoresponsive azobenzene dicarboxylate MOFs of Al³⁺ (Al-AZB) and Zr⁴⁺ (Zr-AZB) were synthesized for the adsorption of congo red (CR) dye. The surface and textural properties of the synthesized MOFs were characterized by FTIR, PXRD, SEM, TGA, BET and pore analysis. Both MOFs were crystalline, thermally stable up to 300 °C and stable in aqueous medium at room temperature. The Al-AZB displayed a higher surface area (2718 m²/g) than the Zr-AZB (1098 m²/g), which significantly impacted the higher adsorption of CR. Besides, pore volumes of 0.86 cm³/g and 0.35 cm³/g were obtained for Al-AZB and Zr-AZB, respectively. The maximum adsorption capacity of Al-AZB and Zr-AZB was 456.6 mg/g and 128.9 mg/g, respectively, with the former superior to other potent adsorbents. The pseudo-second-order and Langmuir models were well correlated with the dye uptake on the MOFs. Thermodynamics revealed random and endothermic sorption of CR dominated by chemisorption, while efficient regeneration and reuse of both MOFs were achieved using dimethylformamide as eluent. The results proved the potency of the synthesized photoresponsive MOFs, as highly efficient and reusable materials for dye adsorption.

Applications of chitin and chitosan based biomaterials for the adsorptive removal of textile dyes from water - A comprehensive review

The presence of pollutants in the water bodies deteriorate the water quality and make it unfit for use. From an environmental perspective, it is essential to develop new technologies for the wastewater treatment and recycling of dye contaminated water. The surface modified chitin and chitosan biopolymeric composites based adsorbents, have an important role in the toxic organic dyes from removal wastewater. The surface modification of biopolymers with various organics and inorganics produces more active sites at the surface of the adsorbent, which enhances dye and adsorbent interaction more reliable. Herein, the work brought in the thought of the application of various chitin and chitosan composites in wastewater remediation and suggested the versatility in composites for the development of rapid, selective and effective removal processes for the detoxification of a variety of organic dyes. It further emphasizes the existing obstruction and impending prediction for the deprivation of dyes via adsorption techniques.

Sustainable Durio zibethinus-Derived Biosorbents for Congo Red Removal from Aqueous Solution: Statistical Optimization, Isotherms and Mechanism Studies

This investigation reports on the biosorption mechanism of Congo Red dyes (CR) in aqueous solution using acid-treated durian peels, prepared for this study. The biosorbent nature was characterized using the Scanning Electron Microscopy (SEM), Fourier Transform infrared spectroscopy (FT-IR) and Brunaure-Emmet-Teller (BET). The effect of process parameters within operational range of pH (2–9), contact time (10–200 min), initial concentration (25–400 mg g−1) and temperature (25–65 °C) for the optimum removal of CR dyes was investigated using central composite design (CCD) under response surface methodology (RSM), and revealed that the optimum condition of biosorption was achieved around a pH of 5.5, contact time of 105 min at initial concentration of 212.5 mg L−1 within 45 °C temperature, which corresponds to 95.2% percent removal of CR. The experimental data fitted better to the second order polynomial model, with a correlation coefficient R2 value of 0.9917 and the Langmuir isotherm model with biosorption capacity of 107.52 mg g−1. Gibbs free energy indicated that the adsorption of CR dyes was spontaneous. The mechanism of the adsorption of CR dyes revealed that the biosorption of CR dyes investigated under different operational conditions show that under acidic pH, the adsorption efficiency of the acid treated durian peels is enhanced for the adsorption of CR dye molecules.

Heterologous Expression of a Thermostable Chitinase from Myxococcus xanthus and Its Application for High Yield Production of Glucosamine from Shrimp Shell

Glucosamine (GlcN) is a widely used food supplement. Hence, enormous attention has been concerned with enzymatic production of GlcN owing to its advantage over a chemical approach. In this study, a previously unstudied chitinase gene (MxChi) in the genome of Myxococcus xanthus was cloned, expressed in recombinant soluble form and purified to homogeneity. TLC-, UPLC-, and microplate-reader- based activity tests confirmed MxChi hydrolyzes colloidal chitin to chitobiose as sole product. The optimal catalytic pH and temperature of MxChi was identified as 7.0 and 55 °C, respectively. MxChi exhibited 80% activity after 72 h incubation at 37 °C. The site-directed mutagenesis revealed that the amino acids D323A, D325A, and E327A of MxChi were in the DXDXE catalytic motif of GH18. When coupled with β-N-acetylhexosaminidase (SnHex) and deacetylase (CmCBDA), the enzyme allowed one-pot extraction of GlcN from colloidal chitin and shrimp shell. The optimal condition was 37 °C, pH 8.0, and 1/3/16.5 (MxChi/SnHex/CmCBDA), conducted by orthogonal design for the enzymatic cascades. Under this condition, the yield of GlcN was 26.33 mg from 400 mg shrimp shell. Facile recombinant in E. coli, robust thermostability and pure product herein makes newly discovered chitinase a valuable candidate for the green recycling of chitin rich waste.

Adsorption of Crystal Violet Dye Using Activated Carbon of Lemon Wood and Activated Carbon/Fe3O4 Magnetic Nanocomposite from Aqueous Solutions: A Kinetic, Equilibrium and Thermodynamic Study

Activated carbon prepared from lemon (Citrus limon) wood (ACL) and ACL/Fe₃O₄ magnetic nanocomposite were effectively used to remove the cationic dye of crystal violet (CV) from aqueous solutions. The results showed that Fe₃O₄ nanoparticles were successfully placed in the structure of ACL and the produced nanocomposites showed superior magnetic properties. It was found that pH was the most effective parameter in the CV dye adsorption and pH of 9 gave the maximum adsorption efficiency of 93.5% and 98.3% for ACL and ACL/Fe₃O₄, respectively. The Dubinin–Radushkevich (D-R) and Langmuir models were selected to investigate the CV dye adsorption equilibrium behavior for ACL and ACL/Fe₃O₄, respectively. A maximum adsorption capacity of 23.6 and 35.3 mg/g was obtained for ACL and ACL/Fe₃O₄, respectively indicating superior adsorption capacity of Fe₃O₄ nanoparticles. The kinetic data of the adsorption process followed the pseudo-second order (PSO) kinetic model, indicating that chemical mechanisms may have an effect on the CV dye adsorption. The negative values obtained for Gibb’s free energy parameter (−20 < ΔG < 0 kJ/mol) showed that the adsorption process using both types of the adsorbents was physical. Moreover, the CV dye adsorption enthalpy (ΔH) values of −45.4 for ACL and −56.9 kJ/mol for ACL/Fe₃O₄ were obtained indicating that the adsorption process was exothermic. Overall, ACL and ACL/Fe₃O₄ magnetic nanocomposites provide a novel and effective type of adsorbents to remove CV dye from the aqueous solutions.