Adsorbent For Removal Of Heavy Metals Research Articles

Adsorption of mercury (II) ions on kaolinite from aqueous solutions: Isothermal, kinetic, and thermodynamic studies

AbstractDue to industrial activity, heavy metal contamination is present in water, air, and soil around the world. Due to this circumstance, serious environmental issues arise. Natural kaolin (NK) clay underwent batch processing to remove Hg2+. Scanner electron microscopy (SEM), energy dispersion spectroscopy (EDS), x‐ray diffraction (XRD), and Brunauer–Emmett–Teller (BET) were used to analyze the morphological and chemical characteristics of kaolin. Investigations were done into how adsorption is impacted by contact duration, adsorbent dosage, temperature, and solution pH. Kaolin's BET surface area was found to be 8.085 m2/g, while its pore volume was found to be 0.0537 cm3/g. The best working conditions were found to be pH 6.81 and an equilibrium period of 90 min. It was discovered that the Langmuir isotherm model was the most suitable one. At 298, 308, and 318 K, respectively, the adsorption capacities of NK were calculated to be 10.964, 10.515, and 10.101 mg/g. The pseudo‐second‐order kinetic model agreed with this. It was revealed that NK had a maximum desorption efficiency of 91.36%. Through this process, the potential of NK as an eco‐friendly adsorbent for heavy metal removal was shown.

Bentonite Clay as an Alternative Adsorbent for Removal of Heavy Metals in wastewater

This study investigates the potential of bentonite clay as an alternative adsorbent for removing heavy metals from abattoir wastewater. Laboratory experiments were conducted to evaluate the effectiveness of bentonite clay in removing six heavy metals, including Lead, Chromium, Arsenic, Cadmium, Zinc and Iron. Results show that bentonite clay effectively removed all heavy metals, with removal efficiencies ranging from 75% to 95%. The study also found that the adsorption efficiency of bentonite clay increased with increasing initial metal concentration and decreasing pH of the solution. Freundlich and Langmuir models were used to predict the adsorption process, and the R2 values for both models were similar. This suggests that both models were equally adequate or inadequate in describing the process. The study concludes that bentonite clay is a promising adsorbent for removing heavy metals from wastewater. It is recommended that the use of bentonite clay as an alternative adsorbent for heavy metal removal should be further explored and optimized, particularly in terms of operating conditions such as pH, contact time, and adsorbent dosage.

Use of biochar as a low-cost adsorbent for removal of heavy metals from water and wastewater: A review

In recent years, the removal of heavy metals from water and wastewater systems remains a challenging issue globally. Adsorption technology is widely used for the removal of heavy metals from aquatic systems due to several advantages including its simple operation, low cost and high efficiency. Biochar, which is an environmental benign and low-cost adsorbent, is increasingly used for remediation of heavy metal pollution in aquatic systems. This review critically analyzes recent developments on the biochar-based adsorptive removal of heavy metals from water and wastewater. Biochar is effective for the removal of several toxic metals (As, Cr and Mn) from groundwater and drinking water. Biochar also shows promising performance for the removal of various heavy metals (Cr, Pb, Cu, Cd and Zn) from wastewater. The heavy metal adsorption capacity of the biochar largely depends on the water/wastewater chemistry (pH, competing ions and initial concentrations of adsorbates), contact time between adsorbates and the adsorbent, adsorbent dose and environmental parameters (temperature). The adsorption isotherms and kinetics can be well explained by the Langmuir and pseudo-second order models, respectively. The key mechanisms which drive the heavy metal adsorption onto biochar include precipitation and ion exchange. Biochar-based adsorptive decontamination of heavy metal pollution is sustainable due to low environmental impacts, low energy consumption and low-costs. The key knowledge gaps and future research directions for improvement of biochar-based sorption capacities are highlighted. This review would help for the development of effective biochar-based adsorption technology for the removal of heavy metals from aquatic environments.

Adsorptive removal of heavy metals and organic dyes by sodium alginate/coffee waste composite hydrogel

Heavy metals and dyes used in technological applications have a detrimental influence on human health and the environment. The most used methods for removing pollutants depend on high-cost materials. Therefore, this research was conducted on cost-effective alternatives derived from natural resources and food waste. Herein, we designed a composite hydrogel based on sodium alginate/coffee waste (Alg/coffee) as adsorbent for the removal of organic and inorganic pollutants from aquatic solutions. The selectivity study displayed that Alg/coffee is more effective in adsorbing Pb(II) and acridine orange dye (AO). Adsorption of Pb(II) and AO was studied at concentration range of 0–170 mgL−1 and 0–40 mgL−1. Adsorption data of Pb(II) and AO reveals their fitting to Langmuir-isotherm and pseudo-second-order-kinetic models. The findings demonstrated that Alg/coffee hydrogel are more effective than coffee powder itself with an adsorption (%) approaching 98.44 % of Pb(II) and 80.53 % of AO. Real sample analysis reveals the efficiency of Alg/coffee hydrogel beads in Pb(II) adsorption. The adsorption cycle was examined four times providing high efficiency toward Pb(II) and AO. Desorption of Pb(II) and AO was easily performed using HCl eluent. Thus, Alg/coffee hydrogel beads could be promising adsorbent for the removal of organic and inorganic pollutants.

Adsorption characteristics of U(VI) in aqueous solution by chloroacetic acid-modified MXene-CS gel microspheres

To solve the problems of the poor stability and low adsorption efficiency of MXene used as an adsorbent for heavy metal removal. In this study, the microwave-assisted novel composite of chloroacetic acid-modified MXene-chitosan gel microspheres (C-TC-CS) was prepared. The experimental results demonstrated that C-TC-CS exhibited good stability and U(VI) adsorption performance, the maximum adsorption capacity of U(VI) by C-TC-CS was up to 141.96 mg/g. Pseudo-second-order and Langmuir isotherm adsorption models fit the adsorption process well, and the thermodynamic parameters showed that the adsorption process was spontaneous and endothermic. Importantly, C-TC-CS could be easily separated and regenerated. After five cycles of regeneration, the adsorption efficiency of C-TC-CS for U(VI) remained above 74%. Spectroscopic analyses indicated that the main adsorption mechanism involved electrostatic interactions, ion exchange, and complexation. This study proved that C-TC-CS could be an effective and promising adsorbent for removing U(VI) from aqueous solution.

Arsenic and TDS removal using antibacterial/antifouling nanofiltration membranes modified by functionalized graphene oxide and copper ferrodioxide.

The intrinsic hydrophilicity of metal compounds, such as copper ferrite (CuFe2 O4 ), and organic compounds, including graphene oxide (GO) and triethylenetetramine (TETA), make them promising adsorbents for heavy metals removal. The presence of lone pairs in these compounds is observed in modified polyethersulfone (PES) membranes used for the separation of arsenic (As) and total dissolved solids (TDS), including mono and divalent salts from aqueous solutions. The objective of this study was to investigate the performance of GO-TETA-CuFe2 O4 membranes for wastewater treatment applications. The membranes were characterized for their optimal mechanical strength (tensile strength) and high negative charge (zeta potential) on the surface. Separation tests were conducted at different pressures and pH levels to evaluate the membrane's effectiveness in removing contaminants. In addition, the membranes were examined for their antibacterial properties. The modified membrane exhibited superior performance compared to the control membrane, with TDS removal rates of 93.8%, As3+ removal rates of 81.2%, and As5+ removal rates of 87.9%. The contact angle of the modified membrane was reduced, resulting in an increase in pure water flux from 13.11 to 27.87 L/m2 .h. The modified membrane also demonstrated significantly higher resistance to fouling than the control membrane, with a resistance increase from 6.78×10+12 to 2.07×10+12 m-1 . This contributed to the improved separation performance of arsenic and TDS in a cross-flow setup. The results suggest that the GO-TETA-CuFe2 O4 modified membrane has great potential for use in water treatment applications.

Isotherms and Kinetic Studies of Copper Removal from Textile Wastewater and Aqueous Solution Using Powdered Banana Peel Waste as an Adsorbent in Batch Adsorption Systems.

Heavy metals that are present in surface water and wastewater are becoming a severe environmental problem. Because of its toxicity, heavy metal removal has become the main priority for environmental concerns. Banana peels are low-cost agricultural waste that could be used for heavy metal adsorption in wastewater. The main objective of this study is to evaluate the effective powdered banana peel for the removal of copper (II) from aqueous solutions and real wastewater. The banana peels were collected from domestic waste and ground to get a particle size of 150 µm. Powdered banana peel waste adsorbent (PBPWA) contained moisture content, ash content, volatile matter, and bulk density of 3.8%, 3.5%, 37.5%, and 0.02 g/cm3, respectively. The Fourier-transform infrared spectroscopy (FTIR) results showed that the alkyne, aldehyde, and amide functional groups were dominant in the powdered banana peel surface, and the scanning electron microscope showed the morphology of the adsorbent. Physicochemical characteristics of the raw wastewater revealed that the concentration of Cu (II), Pb (II), COD, BOD5, and Cd (II) were 2.75 mg/L, 2.02 mg/L, 612.16 mg/L, 185.35 mg/L, and 0.01 mg/L, respectively. At pH 5, adsorbent dose of 2g/100 mL, initial copper (II) concentration of 80 mg/L, and contact time of 90 min, the maximum removal efficiency of synthetic wastewater was 96.8% and textile wastewater was 69.0%. The adsorption isotherm fitted well with the Langmuir isotherm model at R2 = 0.99. The kinetics of copper (II) adsorption followed the second-order kinetic model better. Finally, these studies showed that banana peel bio-adsorbent is a potential adsorbent for heavy metal removal from synthetic and textile wastewater.

Adsorptive Elimination of Heavy Metals from Aqueous Solution Using Magnetic Chitosan/Cellulose-Fe(III) Composite as a Bio-Sorbent.

Magnetic chitosan/cellulose nanofiber-Fe(III) [M-Ch/CNF-Fe(III)] composites were isolated for the elimination of Cr(VI), Cu(II), and Pb(II) from aqueous solution. Various analytical methods, such as field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction analysis (XRD), and thermogravimetric analysis (TGA) were employed to determine the morphological, physicochemical, and thermal properties of the isolated M-Ch/CNF-Fe(III) composites. It was found that the M-Ch/CNF-Fe(III) composites were porous materials, and they have the potential to be implemented as an adsorbent for heavy metals removal. The adsorption efficiency of M-Ch/CNF-Fe(III) composites was determined for Cr(VI), Cu(II), and Pb(II) elimination with changing pH (pH 1.0-8.0), adsorbent doses (0.05-1.0 g), time (15-90 min), and temperature (28-80 °C). In addition, isothermal and kinetics studies were conducted to assess the adsorption behavior and mass transfer phenomena of M-Ch/CNF-Fe(III) composites as an adsorbent for Cr(VI), Cu(II) and Pb(II) elimination from aqueous solution. The outcomes of the present study reveal that the M-Ch/CNF-Fe(III) composites could be utilized as an adsorbent for the Cr(VI), Cu(II), and Pb(II) elimination from industrial effluents.

Green synthesis of iron oxide nanobiocomposite for the adsorptive removal of heavy metals from the drinking water

The current study aimed to synthesize and characterize the Duranta erecta leaves extract-based iron oxide nanoparticles (D-Fe3O4-NPs) and chitosan biopolymer-based nanocomposites (D-Fe3O4-NC). The synthesized D-Fe3O4-NC was applied for the adsorptive removal of cadmium (Cd), chromium (Cr), and lead (Pb) from water. The nanostructure, porous, rough, crystalline structure, and different functional groups of chitosan and D-Fe3O4-NPs in D-Fe3O4-NC showed that the D-Fe3O4-NC is feasible for suitable adsorbents for quantitative removal of Cd, Cr, and Pb. Based on the batch experiments, the influences of pH, adsorption time, contents of Cd, Cr, and Pb in solution, and temperature were successfully optimized. The adsorption capacities of D-Fe3O4-NC for Cd, Cr, and Pb were observed at 74.4, 76.0, and 75.2 mg g−1, respectively. The adsorption isotherms fitted the Freundlich Model equation well, and the adsorption kinetics followed pseudo-second-order kinetics for the adsorption of these toxic metals. D-Fe3O4-NC showed an excellent recyclable efficiency up to multiple analyses (n = 20). The D-Fe3O4-NC was an excellent adsorbent for removing toxic metals from municipal and hand pump water samples (% removal >93%). Therefore, the proposed D-Fe3O4-NC is the most efficient and selective adsorbent for removing Cd, Cr, and Pb from drinking water up to recommended permissible limit.

Biologically-induced synthetic manganese carbonate precipitate (BISMCP) for potential applications in heavy metal removal

Heavy metal pollution of water is a burning issue of today’s world. Among several strategies involved for heavy metal remediation purpose, biomineralization has shown great potential. Of late, research has been focused on developing effective mineral adsorbents with reduced time and cost consumption. In this present paper, the Biologically-Induced Synthetic Manganese Carbonate Precipitate (BISMCP) was produced based on the biologically-induced mineralization method, employing Sporosarcina pasteurii in aqueous solutions containing urea and MnCl2. The prepared adsorbent was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), SEM-energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD) and BET surface area analyzer. EDX analysis showed the elements in the crystal BISMCP were Mn, C, and O. XRD result of BISMCP determined the crystal structure, which is close to rhodochrosite (MnCO3). Spectral peaks of FTIR at 1641.79 cm−1 confirmed the appearance of CO binding, with strong stretching of CO32− in Amide I. From the six kinds of BISMCP produced, sample MCP-6 has the higher specific surface area by BET analysis at 109.01 m2/g, with pore size at 8.76 nm and higher pore volume at 0.178 cm3/g. These specifications will be suitable as an adsorbent for heavy metal removal by adsorption process. This study presents a preliminary analysis of the possibility of BISMCP for heavy metals adsorption using ICP multi-element standard solution XIII (As, Cr, Cd, Cu, Ni, and Zn). BISMCP formed from 0.1 MnCl2 and 30 ml of bacteria volume (MCP-6) produced a better adsorbent material than others concentrations, with the adsorption efficiency of total As at 98.9%, Cr at 97.0%, Cu at 94.7%, Cd at 88.3%, Zn at 48.6%, and Ni at 29.5%. Future work could be examined its efficiency adsorbing individual heavy metals.

Thermal Recycling of Bentonite Waste as a Novel and a Low-Cost Adsorbent ‎for Heavy Metals Removal

Thermal Recycling of Bentonite Waste as a Novel and a Low-Cost Adsorbent ‎for Heavy Metals Removal

Implementation of life cycle analysis on green tea process

This study examines the life cycle analysis of the manufacturing of 1 kg of green tea using various disposal techniques, including landfill procedure, incineration, and modification of green tea waste as an adsorbent for heavy metal removal. OpenLCA is used to produce the evaluation. To identify the objectives and scope, inventory analysis, effect, and interpretation, the assessment process corresponds to ISO 14044 of 2006. AGRIBALYSE version 3 is the database used to evaluate the environmental effects. A reference unit called a DALY is used to study the environmental impact. For the LCA of green tea, there were four main effect categories that were taken into consideration: human carcinogenic toxicity, human non-carcinogenic toxicity, global warming (human health), and fine particle creation. The outcome demonstrates that processing 1 kg of green tea waste has an environmental effect that is around 63% greater than incinerating it and roughly 58% higher than dumping it in a landfill. However the ecology is more affected by the adsorption process than by landfill and incineration of green tea waste. Even yet, if the preparation is done in bulk, the process can be improved by altering the adsorption of green tea waste.

Experimental and Modeling Study on the Removal of Mn, Fe, and Zn from Fiberboard Industrial Wastewater Using Modified Activated Carbon

In this work, the use of agricultural waste from oil palm petioles (OPP) as a raw material for the production of activated carbon (AC) and its characterization were examined. By soaking these chars in nitric acid (HNO3) and potassium hydroxide (KOH) at a 10% concentration, AC with favorable high-porosity carbons was generated. To maximize AC synthesis, the AC was pyrolyzed at 460, 480, and 500 °C temperatures for 20 min. Based on micrographs of formed pores and surface functional groups, 480 °C carbonization temperature on both chemical HNO3 and KOH was shown to be the best. The FTIR measurements reveal that chemical activation successfully transformed the raw material into AC. Moreover, FESEM micrographs show the pores and cavities of the prepared AC achieve a high surface area. This is further supported by BET results of HNO3 OPP AC and KOH OPP AC with surface areas of 883.3 and 372.4 m2/g, respectively, compared with the surface area of raw OPP of 0.58 m2/g. Furthermore, the tests were revealed by an optimization model, namely response surface methodology (RSM), using a central composite design (CCD) technique. The findings showed that all three parameters (pH, time, and dose) had a substantial impact on the removal of Zn, Fe, and Mn. Analysis of variance (ANOVA) and analytical error indicated that the models were accurate, with a low error value and a high R2 > 0.9. Remarkably, the good correlation between actual and predicted removal values showed that the modified activated carbon is a promising adsorbent for heavy metal removal from wastewater.

Reusable granulated silica pillared clay for wastewater treatment, selective for adsorption of Ni(II)

The article presents a study on the suitability of silica pillared clay (SPC) encapsulated with biopolymers, such as alginate, chitosan, or a combination of both, for the adsorption of Ni(II) from aqueous solutions. In the current age of stringent environmental regulations, there is an urgent requirement to identify novel sorbents that can be readily commercialized and employed in large-scale systems to efficiently remove and recover metal compounds from wastewater. Therefore, the study aimed to encapsulate powdered silica pillared clay to produce stable granules via a modified solution casting method, which was confirmed through various characterization studies (FESEM, XRF, XRD, BET, and FTIR). The study found that ALG-SPC showed the best adsorption capacity, owing to its relatively high specific surface area and the negative charge of the alginate. In contrast, encapsulation with chitosan resulted in poor performance due to a significant reduction in porosity. The study also investigated the behaviour of ALG-SPC in a binary solution containing both Ni(II) and Cr(VI) and found that it exhibited selectivity for Ni(II) over Cr(VI). The presence of Cr(VI) did not negatively affect Ni(II) adsorption; in contrast, Ni(II) helped to Cr(VI) adsorption under a limited pH range. The study also conducted adsorption mechanism, kinetic, and equilibrium modelling. Recovery of adsorbed Ni(II) from saturated ALG-SPC was most effective in acidic solutions in comparison with electrolyte solution and methanol. The study's findings have important implications for the development of effective and selective adsorbents for heavy metal removal and recovery from wastewater.

Analysis of aged refuse bio adsorbent for heavy metal removal in electroplating effluent

ABSTRACT The electroplating process is a common method in the surface-finishing process that produces toxic industrial discharges containing nickel, cobalt, cadmium, chromium, lead, cyanide, copper, zinc and other chemical reagents. Without adequate treatment, the release of these harmful compounds into an aquatic environment can have major negative repercussions for biota as well as humans. Heavy metal cationic pollutants in high concentrations can cause major health problems. As a result, it is critical to effectively remove heavy metal ion pollutants from electroplating effluents. Hence, in this research, at room temperature, aged refuse has been used as an adsorbent, which is a solid waste from landfills that have stabilised after several years of placement and are treated with concentrated sulphuric acid, was investigated for metal removal efficiency. Contact time, starting ion concentration, adsorbent dosage, aqueous solution pH and agitation speed were all changed and evaluated to depict the effect they had on removal efficiency. The BET isotherms, multipoint BET and BJH pore size distribution were determined for the adsorbent during the BET analysis. From that, the surface area for the adsorbent was found to be 4.6 /g. For the experimental results, the Langmuir and Freundlich isotherm models were compared and the Freundlich isotherm model agreed on good results. Finally, the adsorbent’s response surface methods for pH, time, dosage and agitation speed were compared, and the results indicated good agreement with the actual values.

A critical review on three-dimensional cellulose-based aerogels: synthesis, physico-chemical characterizations and applications as adsorbents for heavy metals removal from water

A critical review on three-dimensional cellulose-based aerogels: synthesis, physico-chemical characterizations and applications as adsorbents for heavy metals removal from water

Low-cost modified adsorbents derived from the solid residue of Rosmarinus officinalis L. for heavy metal uptake

The current study investigates for the first time the potential of using solid residues collected from the hydrodistillation of R. officinalis, after their modification with Fe, as low-cost adsorbents to alleviate the heavy metals in aqueous solutions. Physicochemical properties and adsorptive performances of R. officinalis solid residue (RO-SR) and Fe-modified R. officinalis solid residue (Fe-RO-SR) were investigated. The Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) revealed that the iron was successfully fixed to the surface of RO-SR. Furthermore, after iron modification, the specific surface area of ROSR was increased from 36.2 to 50.4 m2/g. Kinetics and isotherms of adsorption of Co onto RO-SR and Fe-RO-SR were fitted by applying different models, though the pseudo-second-order (Adj. R2 > 0.9985) and Langmuir (Adj. R2 > 0.9532) models fitted the experimental results better, respectively. The adsorption performances of RO-SR and Fe-RO-SR for Co were 37.31 and 50.25 mg.g−1, respectively. The equilibrium adsorption capacity was reduced from 22.56 g/L to 10.67 g/L when the temperature was raised from 25 °C to 45 °C. Furthermore, after four successful cycles of adsorption-desorption, the adsorbent's adsorptive performance remained above 83.04%, and the adsorbent selectivity revealed interesting heavy metal uptake. Selectivity tests revealed that the adsorption capacities are different for the heavy metal species at the same concentrations, and the series is Fe2+ > Co2+> Cu2+ > Cr3+. Fe-RO-SR could be an interesting, inexpensive ($4.56/Kg), and attractive potential adsorbent for heavy metal removal from aqueous solutions.

Ag decorated Zn-Al layered double hydroxide for adsorptive removal of heavy metals and antimicrobial activity: Numerical investigations, statistical analysis and kinetic studies

Ag nanoparticles have been decorated with Zn-Al layered double hydroxide (LDH) using a simple synthetic procedure. The structural and morphological characterization result confirms the formation of the layered structure Ag@Zn-Al LDH. Ag@Zn-Al LDH has been evaluated for adsorptive elimination of hazardous heavy metal ions like Pb2+ and Cd2+ from an aqueous solution. pH, initial concentration, and contact time are well-studied adsorption conditions as independent variables. The Response Surface Model was used to describe the optimization of the variables (RSM). The optimal conditions for Pb2+ and Cd2+ removal under the constraints are 200 ppm heavy metal levels (concentration), pH 8.0, a reaction duration of 90 min, and a response of 98.9 % by Ag@Zn-Al LDH. With exceptional adsorption efficiencies of 537.63 and 401.62 mg/g, the Langmuir isotherm fitted the adsorption of Pb2+ and Cd2+ well. Studies on thermodynamics demonstrate the exothermic spontaneity and pseudo-second-order kinetic model was determined to be more appropriate. Ag@Zn-Al LDH exhibits more antibacterial activity than Zn-Al LDH, with MIC values that are similar to those of standard streptomycin. The examination indicates that the synthesised Ag@Zn-Al LDH has good adsorption and antibacterial activity.

Adsorptive removal of heavy metals from water using thermally treated laterite: an approach for production of drinking water from rain water

Access to clean water is still limited in a number of regions, especially country sides, rural, and mountainous areas in Vietnam. Therefore, studies on clean water production by using sustainable and affordable processes for locals to access to clean water are of great importance. In this research, we produced laterite-based adsorbents by thermal treatment of natural laterite. The produced adsorbents were characterized in terms of morphology, crystallite, chemical composition, surface functional groups, surface charges, and surface area. The adsorption processes of Ni2+ and Cu2+ onto thermally treated laterite were studied. The treated laterite was also deployed to the removal of pollutants from real rain water. Finally, treated laterite was used in a combination system to purify rain water to produce drinking water for households in Hai Dong commune, Hai Hau district, Nam Dinh province. The results showed that the adsorption of Ni2+ and Cu2+ by thermally treated laterite reached equilibrium after 40 min and followed the Langmuir sorption isotherm, with the maximum uptake of 27.6 mg/g for Cu2+ and 17.4 mg/g for Ni2+. The second-order-kinetic model described the best the adsorption of Cu2+ and Ni2+ from aqueous solution, implying chemisorption was predominant mechanism. The treated laterite was suitable for heavy metal removal but less effective for the removal of anions from water. The combination of solar heating system with treated laterite, sand, and activated carbon allowed to safely produce drinking water from rain water, which presented the water quality respecting the Vietnam national standard for drinking water (QCVN 01:09/BYT).

Using deep eutectic solvent dissolved low-value cotton linter based efficient magnetic adsorbents for heavy metal removal.

In this study, a novel magnetic bio-adsorbent was synthesized by modifying cotton linter (CL) cellulose with deep eutectic solvents (DESs) and Fe3O4 magnetic nanoparticles. The adsorption capacity of CL, Fe3O4/CL, Fe3O4/CL-oxidation, and Fe3O4/CL-DES for Cu2+ was 11.0, 66.1, 85.7, and 93.1 mg g-1, respectively, under the optimal adsorption conditions of an initial pH value of 6.0, stirring rate of 300 rpm, and a temperature of 30 °C. The presence of Fe3O4 nanoparticles increased the proportion of hydroxyl groups and thus improved the ion-exchange ability of Cu2+. The dissolution of DES significantly decreased fiber crystallinity and increased the number of hydroxyl group (amorphous regions increased), thus improving the chelation reaction of Cu2+, which was favorable for surface adsorption. In addition, we used the Langmuir and Freundlich isothermal models to simulate the adsorption behavior of Fe3O4/CL-DES, and the results indicated that Cu2+ follows a Freundlich isotherm model of multilayer adsorption. The fitting of the adsorption kinetics model indicated that the adsorption process involves multiple adsorption mechanisms and can be described by a quasi-second-order model. These results provide a potential method for the preparation of high-efficiency adsorbents from low-value cotton linter, which has broad application prospects in wastewater treatment.