Synthesis of biohybrid magnetic chitosan-polyvinyl alcohol/MgO nanocomposite blend for remazol brilliant blue R dye adsorption: solo and collective parametric optimization

Facile preparation of cucurbituril-modified magnetic chitosan microspheres for efficient removal of Cr(VI) and MB from wastewater: Adsorption experiments, statistical optimization, and mechanistic insights

In this study, a magnetic microsphere (CB/MCS) based on magnetic chitosan and cucurbituril (CB) was successfully prepared for efficient removal of methylene blue (MB 2968.6 mg/g) and hexavalent chromium (Cr(VI) 297.3 mg/g) from water. CB/MCS combined the fast magnetic separation performance of magnetic chitosan and the excellent adsorption capacity of CB to realize the efficient removal of MB and Cr(VI), and it is noteworthy that the adsorption capacity of Cr(VI) was significantly enhanced in the presence of MB. The synthesis conditions of CB/MCS were optimized by response surface methodology and Box-Behnken Design experimental design. The results of the adsorption experiments showed that the adsorption process of CB/MCS on MB and Cr(VI) conformed to the quasi-secondary kinetic model and Langmuir isotherm model, indicating that the adsorption process was mainly controlled by chemisorption and there was a strong interaction between the adsorbent and adsorbate. In addition, CB/MCS demonstrated excellent removal efficiencies in different aqueous environments, reaching 93.2 % and 91.4 % for Cr(VI) and MB, respectively, even in complex industrial wastewater. The results of the cycling experiments further confirmed the stability and reusability of CB/MCS. In summary, CB/MCS can be used as an excellent adsorbent for the removal of Cr(VI) and MB from wastewater.

Guanylated chitosan derivatives for the adsorption of anionic dyes: Performance and mechanism

Chitosan is an emerging adsorbent in pollution management, but its solubility in acidic aqueous solutions and its weak affinity towards pollutants limit its adsorption performance. The development of novel cationic chitosan containing guanidinium groups, has facilitated the advancement of various applications. This work presents a comprehensive methodology for chitosan guanylation through the reaction of neat chitosan with carbodiimide reagents in ionic liquid media. The resulting two guanidinium chitosan derivatives, guanidinium chitosan containing dicyclohexyl and guanidinium chitosan containing dimethylaminopropyl hydrochloride were thoroughly characterized by FT-IR, XRD, thermogravimetry, solid-state NMR and scan electron microscopy, and then investigated as adsorbents for anionic dyes, i.e. methyl orange. The impact of pH, contact time, dye concentration and temperature on the adsorption of methyl orange dye were explored. Both materials showed high adsorption efficiency of 274 and 320 mg/g, respectively. Due to the lower acidity of the guanidinium groups, the gunaylated materials display efficient anion exchange properties even at basic pH. Furthermore, the guanylation leads to decreased solubility via the construction of intermolecular hydrogen bonds. The adsorption properties of cationic chitosan derivatives are outstanding, displaying a high degree of recyclability. The utilization of guanylated chitosan derivatives presents new opportunities in the field of water purification.

Cellulose nanofiber-reinforced carboxymethyl chitosan/polyvinyl alcohol composite gels: Physicochemical characterization and acid blue dye adsorption performance

Composite gels of carboxymethyl chitosan (CMCS), polyvinyl alcohol (PVA), and cellulose nanofibers (CNF) are promising for environmental remediation and materials science. This study examines how varying CNF content affects the structural, thermal, and adsorption properties of CMCS/PVA/CNF gels. The results show that CNF enhances the storage modulus and thermal stability of the gels. The PCF composite gel with 0.4 % CNF content exhibited the highest thermal stability, maintaining stability up to 600 °C. The microstructure of the composite gels displayed a porous structure, favorable for dye adsorption. FTIR analysis revealed that the hydrogen bonding interactions between CNF, CMCS, and the PVA matrix increased with higher CNF content. XRD results indicated that these interactions reduced the crystallinity of the composite gels. As CNF content rose, the swelling ratio decreased from 1124.4 % to 973.3 %, and the gel fraction increased from 75.8 % to 83.5 %. Dye adsorption followed the pseudo-second-order kinetic model and the Langmuir isotherm. The maximum adsorption capacity for Acid Blue dye at 25 °C was 940.6 mg/g. The adsorption process was chemical, spontaneous, endothermic, and entropically favorable, indicating strong interactions between the gel and dye molecules. This study highlights the potential of CMCS/PVA/CNF gels for environmental applications and efficient dye removal.

Glutaraldehyde-crosslinked magnetic chitosan nanocomposite for efficient Cr(VI) removal: A sustainable approach to aquatic remediation

Hexavalent chromium (Cr(VI)) is a highly toxic pollutant in aquatic environments, posing serious threats to ecosystems and human health. This study aims to develop an effective adsorbent for the removal of Cr(VI) from water. A novel magnetic chitosan-based nanocomposite (Fe₃O₄@MCS) was synthesized by in situ embedding of Fe₃O₄ nanoparticles into a chitosan matrix, crosslinked with glutaraldehyde, and further modified with ammonia via a Schiff base reaction. The material was thoroughly characterized using FTIR, XPS, XRD, SEM, TEM, EDX, and VSM. Adsorption experiments showed that Fe₃O₄@MCS achieved a maximum Cr(VI) uptake of 221.4 mg/g under optimal conditions (pH 4.0, 25 °C, 10 mg dosage, 120 min contact time), with 100 % removal efficiency at initial concentrations up to 50 ppm within just 15 min. The adsorption followed pseudo-second-order kinetics and fitted well with the Langmuir isotherm model (R2 = 0.999), indicating monolayer adsorption behavior. The removal mechanism involves electrostatic interactions between HCrO₄- and protonated amine/hydroxyl groups, followed by Cr(VI) reduction to Cr(III), as confirmed by FTIR and XPS analyses. Fe₃O₄@MCS also demonstrated excellent magnetic separability and reusability, maintaining over 90 % removal efficiency after five adsorption-desorption cycles. These findings highlight Fe₃O₄@MCS as a highly promising adsorbent for Cr(VI) remediation in water treatment applications.

Simultaneous removal of ammonium, phosphate, and phenol via self-assembled biochar composites CBCZrOFe3O4 and its utilization as soil acidity amelioration

ABSTRACTHigh concentrations of ammonium, phosphate, and phenol are recognized as water pollutants that contribute to the degradation of soil acidity. In contrast, small quantities of these nutrients are essential for soil nutrient cycling and plant growth. Here, we reported composite materials comprising biochar, chitosan, ZrO, and Fe3O4, which were employed to mitigate ammonium, phosphate, and phenol contamination in water and to lessen soil acidity. Batch adsorption experiments were conducted to assess the efficacy of the adsorbents. Initially, comparative studies on the simultaneous removal of NH4, PO4, and phenol using CB (biochar), CBC (biochar + chitosan), CBCZrO (biochar + chitosan + ZrO), and CBCZrOFe3O4 (biochar + chitosan + ZrO + Fe3O4) were conducted. The results discovered that CBCZrOFe3O4 exhibited the highest removal percentage among the adsorbents (P < 0.05). Adsorption data for CBCZrOFe3O4 were well fitted to the second-order kinetic and Freundlich isotherm models, with maximum adsorption capacities of 112.65 mg/g for NH4, 94.68 mg/g for PO4 and 112.63 mg/g for phenol. Subsequently, the effect of CBCZrOFe3O4-loaded NH4, PO4, and phenol (CBCZrOFe3O4-APP) on soil acidity was studied over a 60-day incubation period. The findings showed no significant changes (P < 0.05) in soil exchangeable acidity, H+, Mg, K, and Na. However, there was a substantial increase in the soil pH, EC, available P, CEC, N-NH4, and N-NO3. A significant reduction was also observed in the available soil exchangeable Al and Fe (P < 0.05). This technique demonstrated multi-functionality in remediating water pollutants and enhancing soil acidity.

Adsorption of haem by magnetic chitosan microspheres: Optimal conditions, adsorption mechanisms and density functional theory analyses

Magnetic chitosan microspheres (Al@CTS@Fe3O4) were prepared for haem separation via chemical cross-linking of chitosan, Fe3O4 and AlCl3·6H2O. The properties of the Al@CTS@Fe3O4 microspheres were investigated through techniques including XRD, TEM, FTIR, BET analysis, SEM, TG, VSM, XPS and pHpzc analysis. The haem adsorption of Al@CTS@Fe3O4 was optimized via a Box-Behnken design (BBD) with three operating factors: Fe3O4 dose (0.5-1.3 g), AlCl3·6H2O concentration (0.25-1.25 mol/L) and glutaraldehyde dose (2-6 mL). The optimal haem adsorption effect was achieved with 1.1 g of Fe3O4, 0.75 mol/L AlCl3·6H2O, and 3 mL of glutaraldehyde. The adsorption kinetics and isotherms demonstrated that haem adsorption by the Al@CTS@Fe3O4 microspheres was best described by the pseudo-second-order model. The maximum adsorption capacity is 33.875 mg/g at pH 6. After six adsorption-desorption cycles, the removal of haem still reached 53.83 %. The surface adsorption mechanism of haem on Al@CTS@Fe3O4 can be attributed to electrostatic, hydrogen bonding, and n-π interactions. Thermodynamic calculations indicated that the adsorption process is spontaneous, with the microspheres preferentially accepting electrons and haem preferentially providing electrons. Consequently, the Al@CTS@Fe3O4 microspheres exhibit considerable potential as adsorbents for haem separation.

Developing In2S3 upon modified MgTiO3 anchored on nitrogen-doped CNT for sustainable sensing and removal of toxic insecticide clothianidin

Herein, the study introduces a novel bifunctional In2S3/MgTiO3/TiO2@N-CNT (IMTNC) nanocomposite, which is poised to revolutionize the detection and removal of clothianidin (CLD) from aquatic environments by synergistic adsorption and photodegradation. Confirmation of the material's synthesis was done using structural, optical, morphological, and chemical characterizations. An outstanding sensitivity of 2.168 μA/nM.cm2 with a linear range of 4-100 nM and a LOD of 0.04 nM, along with an exceptional elimination efficiency of 98.06 ± 0.84% for about 10 ppm CLD within 18 min was demonstrated by the IMTNC nanocomposite. Extensive studies were carried out to appraise the material's effectiveness in the presence of various interfering species, such as cations, anions, organic compounds, and different water matrices, and a comprehensive assessment of its stability throughout several cycles was made. Response Surface Methodology (RSM) study was used to determine the ideal removal conditions for improved performance. In addition, the catalytic performance in removing various other pollutants was also analyzed. Adding In2S3 and developing N-doped Carbon Nanotubes (N-CNT) increased conductivity and higher electrochemical sensing skills, improving charge transfer and increasing photocatalytic activity. This research underscores the potential of the IMTNC nanocomposite as a promising candidate for advanced environmental sensing and remediation applications.

Degradation of Remazol Brilliant Blue Dye Using Persulfate Activated by Fe3O4@PDA Nanoparticles: Kinetic Studies, Radical Determination, and Phytotoxicity Test

In the current research work, an advanced oxidation process was applied to the degradation of Remazol brilliant blue dye (RBBD) using a sulfate radical. Fe3O4@PDA nanoparticles were synthesized using coprecipitation and self-polymerization techniques. Nanoparticle formation was confirmed by XRD, FTIR, FESEM-EDX, VSM, and XPS analyses. The crystalline nature of the material showed that it possessed a spherical shape with an Ms value of 58 emu/g. The elemental composition and binding energy from EDX and XPS analyses showed successful doping. Batch studies were conducted, and experimental studies showed that the optimum condition for degradation of 90 ppm of RBBD was 0.3 g/L of nanomaterial, 20 mM PS at pH 3, achieving 91.35% degradation. The kinetic model suitable for this study was a pseudo-second-order kinetic model with R2 value >0.9. From the radical identification tests, sulfate radicals played a dominant role in degradation, and to confirm it, EPR analysis was conducted using DMPO. A stability test was performed for 5 cycles in which the degradation efficiency was reduced appreciably. From XPS, XRD, and EDX analyses, the elemental composition and oxidation state of the recycled material used in the fifth cycle showed variation in a negligible manner when compared to the fresh catalyst used in the first cycle of the degradation experiment. Intermediate identification was done by GCMS analysis, and it disclosed the formation of aliphatic products from the degradation of RBBD with less toxicity. Phytotoxicity analysis was conducted using green grams for 10 days, and it proved that intermediates formed in the solution were nontoxic to the plants. Additionally, TOC and COD removal % were attained to be 80.021 and 80.903%, respectively, which confirm the mineralization efficacy. Hence, this research work proved the efficient performance of the catalyst for RBBD degradation with less formation of intermediates, and therefore, this technique is most suitable for the reduction of water pollution.

Study on Adsorption Characteristics and Water Retention Properties of Attapulgite-Sodium Polyacrylate and Polyacrylamide to Trace Metal Cadmium Ion

The adsorption mechanism of superabsorbent polymer (SAP) can provide theoretical guidance for their practical applications in different environments. However, there has been limited research on the mechanism of attapulgite-sodium polyacrylate. This research aimed to compare the Cd(II) adsorption characteristics and water retention properties of organic-inorganic composite SAP (attapulgite-sodium polyacrylate, OSAP) and organic SAP (polyacrylamide, JSAP). Batch experiments were used to investigate the kinetics of Cd(II) adsorption, as well as the thermodynamic properties and factors influencing these properties. The results show that the Cd(II) adsorption capacity was directly proportional to the pH value. The maximum adsorption capacities of OSAP and JSAP were of 770 and 345 mg·g-1. The Cd(II) adsorption for OSAP and JSAP conformed to the Langmuir and the quasi-second-order kinetic model. This indicates that chemical adsorption is the primary mechanism. The adsorption process was endothermic (ΔH0 > 0) and spontaneous (ΔG0 < 0). The water adsorption ratios of OSAP and SAP were 474.8 and 152.6 in pure water. The ratio decreases with the increase in Cd(II) concentration. OSAP and JSAP retained 67.23% and 38.37% of the initial water adsorption after six iterations of water adsorption. Hence, OSAP is more suitable than JSAP for agricultural and environmental ecological restoration in arid and semi-arid regions.

Chitosan-grafted salicylaldehyde/algae composite for methyl violet dye removal: adsorption modeling and optimization

In this study, a hydrothermal approach was employed to graft chitosan (Chit)/algae (ALG) with salicylaldehyde (SA), resulting in the synthesis of a biocomposite named salicylaldehyde-based chitosan Schiff base/algae (Chit-SA/ALG). The main objective of this biocomposite was to effectively remove methyl violet (MV), an organic dye, from aqueous solutions. The adsorption performance of Chit-SA/ALG toward MV was investigated in detail, considering the effects of three factors: (A) Chit-SA/ALG dose (ranging from 0.02 to 0.1 g/100 mL), (B) pH (ranging from 4 to 10), and (C) time (ranging from 10 to 120 min). The Box-Behnken design (BBD) was utilized for experimental design and analysis. The experimental results exhibited a good fit with both the pseudo-second-order kinetic model and the Freundlich isotherm, suggesting their suitability for describing the MV adsorption process on Chit-SA/ALG. The maximum adsorption capacity of Chit-SA/ALG, as calculated by the Langmuir model, was found to be 115.6 mg/g. The remarkable adsorption of MV onto Chit-SA/ALG can be primarily attributed to the electrostatic forces between Chit-SA/ALG and MV as well as the involvement of various interactions such as n-π, π-π, and H-bond interactions. This research demonstrates that Chit-SA/ALG exhibits promising potential as a highly efficient adsorbent for the removal of organic dyes from water systems.

Hydrogels Based on Chitosan and Nanoparticles and Their Suitability for Dyes Adsorption from Aqueous Media: Assessment of the Last-Decade Progresses

Water is one of the fundamental resources for the existence of humans and the environment. Throughout time, due to urbanization, expanding population, increased agricultural production, and intense industrialization, significant pollution with persistent contaminants has been noted, placing the water quality in danger. As a consequence, different procedures and various technologies have been tested and used in order to ensure that water sources are safe for use. The adsorption process is often considered for wastewater treatment due to its straightforward design, low investment cost, availability, avoidance of additional chemicals, lack of undesirable byproducts, and demonstrated significant efficacious potential for treating and eliminating organic contaminants. To accomplish its application, the need to develop innovative materials has become an essential goal. In this context, an overview of recent advances in hydrogels based on chitosan and nanocomposites and their application for the depollution of wastewater contaminated with dyes is reported herein. The present review focuses on (i) the challenges raised by the synthesis process and characterization of the different hydrogels; (ii) the discussion of the impact of the main parameters affecting the adsorption process; (iii) the understanding of the adsorption isotherms, kinetics, and thermodynamic behavior; and (iv) the examination of the possibility of recycling and reusing the hydrogels.

A biohybrid nanomaterial of biosynthesized TiO2 NPs from Mangrove leaf and shrimp shell-based Chitosan: ultrasonic-assisted synthesis and its application for methylene blue removal and COD reduction of real industrial wastewater

In the present study, TiO2 NPs (particle size: 25-35 nm) were biosynthesized from the Mangrove leaf extract. These nanoparticles were used to modify chitosan, and Chitosan@TiO2 biohybrid nanomaterial was synthesized and characterized using FTIR, XRD, BET, and, EDX-FE-SEM analyses. The adsorption ability of Chitosan@TiO2 nanomaterial has been investigated for Methylene blue (MB) removal from aqueous solution. The results indicated that the amount of MB removal is high in alkaline pH (optimum pH = 9). The pseudo-second-order model was able to describe the effect of contact time on the adsorption ability. The Langmuir model well described the equilibrium manner, and one gram of Chitosan@TiO2 could attract 416.66 mg of MB. Kinetic data, values of parameters of activation energy (+57.283 kJ/mol), enthalpy (-86.8148 kJ/mol), and Gibbs free energy (-27.999 to -22.8987 kJ/mol) indicate the dominance of chemical adsorption over physical adsorption. The breakthrough curves of 3 adsorption/desorption cycles showed the acceptable ability and reusability of prepared nanomaterial. Synthesized biohybrid nanomaterial can reduce 75% COD and 79% nitrate of the effluent from industrial city no.3 of Yasouj. The results of this research show the high ability of chitosan@TiO2 biohybrid to remove dyes from wastewater and reduce the pollution load of industrial wastewater.

Hydrogen bond-mediated self-assembly of Tin (II) oxide wrapped with Chitosan/[BzPy]Cl network: An effective bionanocomposite for textile wastewater remediation

A novel and efficient bionanocomposite was synthesized by incorporating SnO into chitosan (Ch) and a room-temperature ionic liquid (RTIL). The bionanocomposite was synthesized in benzoyl pyridinium chloride [BzPy]Cl to maintain the unique properties of SnO, chitosan, and the ionic liquid. Adsorption and photodegradation processes were applied to evaluate the bionanocomposite for removing azo and anthraquinone dyes and textile wastewater. SnO/[BzPy]Cl and SnO/[BzPy]Cl/Ch samples were prepared and characterized using various techniques, including FT-IR, SEM, XRD, EDAX, XPS, DSC, TGA, nitrogen adsorption/desorption isotherm, and DRS analysis. SEM analysis revealed a hierarchical roughened rose flower-like morphology for the biocomposite. The band gap energies of SnO/[BzPy]Cl and SnO/[BzPy]Cl/chitosan were found to be 3.9 and 3.3 eV, respectively, indicating a reduction in the band gap energy with the introduction of [BzPy]Cl and chitosan. SnO/[BzPy]Cl/Ch showed high removal rates (92-95 %) for Fast Red, Blue 15, Red 120, Blue 94, Yellow 160, and Acid Orange 7 dyes. The adsorption kinetics followed a pseudo-second-order model. In addition, the effect of different photodegradation parameters such as solution pH, dye concentrations, contact time, and amount of photocatalyst, was studied. Given the optimal results obtained in removing azo and anthraquinone dyes, the SnO/[BzPy]Cl/Ch nanocomposite was used as an efficient nanocomposite for removing dyes from textile wastewater. The highest removal efficiency was found to be 95.8 %, obtained under ultraviolet and visible light. Furthermore, BOD and COD reduction analysis showed significant reductions, indicating the excellent performance of the photocatalyst.

Biomagnetic chitosan-ethylene glycol diglycidyl ether/organo-nanoclay nanocomposite for azo dye removal: A statistical modeling by response surface methodology

Herein, a quadruple biomagnetic nanocomposite of cross-linked chitosan-ethylene glycol diglycidyl ether/organo-nanoclay (MCH-EGDE/ORNC) was designed for the uptake of remazol brilliant blue R (RBBR) dye from aqueous environment. The adsorption process was systematically improved via the Box-Behnken design (BBD) to determine the influence of key uptake parameters, including MCH-EGDE/ORNC dosage, pH, and time, on the RBBR removal. The highest RBBR removal of 87.5 % was achieved at the following conditions: MCH-EGDE/ORNC dosage: 0.1 g/100 mL; pH: 4.0; contact time: 25 min. The findings of the kinetics and equilibrium studies revealed an excellent fit to the pseudo-second order and the Freundlich models, respectively. The adsorption capacity of the MCH-EGDE/ORNC for RBBR was found to be 168.4 mg/g, showcasing its remarkable adsorption capability. The present work highlights the potential of MCH-EGDE/ORNC biomaterial as an advanced adsorbent and lays the foundation for future applications in water purification and environmental remediation.

Efficient adsorption of methylene blue in water by nitro-functionalized metal-organic skeleton‑calcium alginate composite aerogel

This paper presents the first investigation of the adsorption performance of methylene blue by the nitro-functionalized metal-organic framework (MIL-88B-NO2). MIL-88B-NO2 has a specific surface area of 836.0 m2/g, which is 109.8 % higher than MIL-88B. The maximum adsorption capacity of methylene blue is 383.6 mg/g, which is 68.2 % higher than that of MIL-88B. This phenomenon can be attributed to the great increase in specific surface area and the introduction of nitro-functional groups. However, its microcrystalline nature makes it difficult to remove in practical applications and quickly causes secondary pollution. Therefore, the composite of MIL-88B-NO2 and calcium alginate (CA) to form aerogel maintains the inherent properties of the two materials and makes it easy to recycle. The utmost adsorption capability of MIL-88B-NO2/CA-2 aerogel is 721.0 mg/g. Compared with MIL-88B-NO2, the adsorption performance of MIL-88B-NO2/CA-2 aerogel is further improved by 88.0 %. The higher adsorption capacity of the adsorbent may be due to the synergistic interplay of electrostatic attraction, π-π conjugation, hydrogen bonding, metal coordination effect, and physicochemical properties. Also, MIL-88B-NO2/CA-2 aerogel has good recyclability, indicating that it has broad application prospects in the removal of positive dyes in contaminated water.

Development of a chitosan/nanosilica biocomposite with arene functionalization via hydrothermal synthesis for acid red 88 dye removal

Herein, the polymer nanomatrix of chitosan/SiO2 (CHI/n-SiO2) was enriched with a π-π electron donor-acceptor system using diaromatic rings of benzil (BEZ) assisted via a hydrothermal process to obtain an effective adsorbent of chitosan-benzil/SiO2 (CHI-BEZ/n-SiO2). The polymer nanomatrix (CHI/n-SiO2) and the resulting adsorbent (CHI-BEZ/n-SiO2) were applied to remove the anionic acid red 88 (AR88) dye from aqueous media in a comparative mode. Box-Behnken design (BBD) was adopted to optimize AR88 adsorption onto CHI/n-SiO2 and CHI-BEZ/n-SiO2 with respect to variables that influence AR88 adsorption (adsorbent dose: 0.02-0.1 g/100 mL; pH: 4-10; and time: 10-90). The adsorption studies at equilibrium were conducted with a variety of initial AR88 dye concentrations (20-200 mg/L). The adsorption isotherm results reveal that the AR88 adsorption by CHI/n-SiO2 and CHI-BEZ/n-SiO2 are described by the Langmuir model. The kinetic adsorption profiles of AR88 with CHI/n-SiO2 and CHI-BEZ/n-SiO2 reveal that the pseudo-first-order model provides the best fit results. Interestingly, CHI-BEZ/n-SiO2 has a high adsorption capacity (261.2 mg/g), which exceeds the adsorption capacity of CHI/n-SiO2 (215.1 mg/g) that relates to the surface effects of SiO2 and the functionalization of chitosan with BEZ. These findings show that CHI-BEZ/n-SiO2 represents a highly efficient adsorbent for the removal of harmful pollutants from water, which outperforming the CHI/n-SiO2 system.

Magnetic Ni@C nanoadsorbents for methyl orange removal from water

In this study, Ni@C nanoparticles were produced and used as an adsorbent for removing methyl orange (MO) from an aqueous solution. The sol-gel method was utilized for the preparation of the particles. The X-ray diffraction pattern and transmission electron microscopy (TEM) were utilized to determine the phase, morphology, and size. The electron micrograph indicated the coating of carbon over Ni having size between 43 and 94 nm, and the Raman spectrum supported it. Among three, the maximum specific magnetization of the Ni@C nanocomposite was 55.78 emu/g for the N7 sample. From the BET approach, specific surface areas of 2.29 × 105, 3.66 × 105, and 5.48 × 105 cm2/g as well as average pore size of 49.30, 37.25, and 35.27 nm were observed for N5, N6, and N7, respectively. The Ni@C nanoparticles were magnetically separable and exhibited rapid adsorption of MO of different concentrations from their aqueous solutions. The N7 adsorbent displayed the highest MO adsorption capacity (~ 32 mg·g-1) along with maintaining an adsorption capacity of 81% even after 5 cycles. Adsorption isotherm and kinetic analysis gave critical inputs toward the possible adsorption mechanism.

Magnetic nanocomposite of maize offal biomass for effective sequestration of Congo red and methyl orange dyes from contaminated water: modeling, kinetics and reusability

The current study aims to use a facile and novel method to remove Congo red (CR) and Methyl Orange (MO) dyes from contaminated water with Maize offal biomass (MOB) and its nanocomposite with magnetic nanoparticles (MOB/MNPs). The MOB and MOB/MNPs were characterized with Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), BET, XRD and point of zero charge (pHPZC). The influence of initial CR and MO levels (20-320 mg/L), adsorbent dosage (1-3 g/L), pH (3-9), co-exiting ions, temperature (25-45 °C) and time (15-180 min) was estimated. The findings demonstrated that MOB/MNPs exhibited excellent adsorption of 114.75 and 29.0 mg/g for CR and MO dyes, respectively while MOB exhibited 81.35 and 23.02 mg/g adsorption for CR and MO dyes, respectively at optimum pH-5, and dose 2 g/L. Initially, there was rapid dye removal which slowed down until equilibrium was reached. The interfering/competing ions in contaminated water and elevated temperature favored the dyes sequestration. The MOB/MNPs exhibited tremendous reusability and stability. The dyes adsorption was spontaneous, and exothermic with enhanced randomness. The adsorption effects were well explained with Freundlich model, pseudo second order and Elovich models. It is concluded that MOB/MNPs showed excellent, eco-friendly, and cost-effective potential to decontaminate the water.

Enhanced adsorption for trivalent antimony by nano-zero-valent iron-loaded biochar: performance, mechanism, and sustainability

The discharge of tailing leachate and metallurgical wastewater has led to an increasing trend of water pollution. In this study, nZVI-modified low-temperature biochar was used to adsorb Sb(III) from water. The adsorption capacity and speed of nZVI-BC were better than those of BC, and the best adsorption effect was observed for 4nZVI-BC, with 93.60 mg·g-1 maximum adsorptive capacity, which was 208.61% higher than the original BC. The Langmuir and Temkin models were well fitted (R2 ≥ 0.99), and PSO was more in line with the 4nZVI-BC adsorption process, indicating that the adsorption was a monolayer physico-chemical adsorption. The combination of XRD, FTIR, and XPS characterization demonstrated that the adsorption mechanism predominantly included redox reactions, complexation, and electrostatic interactions. The thermodynamic results demonstrated that 4nZVI-BC adsorption on Sb(III) was a spontaneous endothermic process. Additionally, the order of the influence of interfering ions on 4nZVI-BC was CO32-  > H2PO4-  > SO42-  > Cl-. After three repeated uses and adsorption-desorption, the adsorption ratio of Sb(III) by 4nZVI-BC was still as high as 90% and 65%, respectively. This study provides a theoretical reference for the exploration and development of Sb(III) removal technologies for aquatic environments.

Extraction of rare earth elements from monazite leach liquor using functionalized chitosan sorbents derived from shrimp waste

With the growing need for high-purity rare-earth elements (REEs), the separation of these REEs has received much attention recently. The objective of this research is to produce chitosan from shrimp waste, then modify it with different functionality, and investigate the adsorption properties of chitosan adsorbents towards La(III) ions. First, from shrimp waste, chitosan (ch) with a significant degree of deacetylation, purity, and solubility was produced. The purified chitosan was cross-linked with epichlorohydrin (ep), and then, it was modified with 3,6,9,12-tetraazatetradecane-1,14-diamine (HA) to produce polyaminated chitosan (HA@ep@Ch). The polycarboxylated/imine chitosan (CM@HA@ep@Ch) was obtained by treating polyaminated chitosan with chloroacetic acid in isopropyl alcohol. The chitosan adsorbents were characterized and applied for lanthanum recovery from synthetic and monazite leach liquor samples. The factors controlling the recovery process were studied and discussed. The performance of the adsorbents was achieved through equilibrium, dynamic, and isothermal studies. HA@ep@Ch and CM@HA@ep@Ch showed good performance for lanthanum recovery with a maximum capacity of 114.52 and 141.76 mg/g at 330 K, respectively. The isotherm parameters refer to the monolayer of lanthanum adsorbed into the adsorbents through chelation and ion exchange mechanisms. A 0.5-M HCl solution was found effective to elute 95.8% of the adsorbed lanthanum on HA@ep@Ch, and 93.4% of the adsorbed lanthanum on CM@HA@ep@Ch. The adsorbents showed greater selectivity in extracting La, Ce, Pr, Nd, and Sm (62-75%) from REE leach liquid compared to extracting other REEs (20-41%).

A hybrid mesoporous composite of SnO2 and MgO for adsorption and photocatalytic degradation of anionic dye from a real industrial effluent water

Water pollution by synthetic anionic dyes is one of the most critical ecological concerns and challenges. Therefore, there is an urgent need to find an efficient adsorbent and photocatalyst for dye removal. In the present study, we aimed to fabricate a hybrid mesoporous composite of spongy sphere-like SnO2 and three-dimensional (3D) cubic-like MgO (SnO2/MgO) as a promising adsorbent/photocatalyst to remove the anionic sunset yellow (SSY) dye from real wastewater at neutral pH conditions. The as-synthesized SnO2 and MgO composite was investigated using XRD, SEM, EDX, TEM, XPS, BET, and zeta potential. The experimental study of the SSY removal using SnO2/MgO composite was performed at different conditions, such as pH, stirring time, dose, and temperature. More than 99% of 10 mg/L SSY was effectively adsorbed from aqueous solution using 40 mg of SnO2/MgO composite at pH 7 and a stirring time of 60 min. The SSY adsorption behavior was well fitted by pseudo-second order and the Langmuir model, indicating that the SSY was chemisorbed to the composite-active sites as a monolayer. On the other hand, photocatalytic degradation process exhibited better results in terms of speed of removal and used quantity of photocatalyst, where 20 mg of SnO2/MgO composite can be used to remove > 99% of SSY dye within 30 min. Mechanism of SSY adsorption and photocatalytic degradation was discussed. In addition, elution experiments demonstrated that the SnO2/MgO composite as an SSY adsorbent could be reused for nine cycles without considerable reduction in the SSY adsorption efficiency. Therefore, this work exhibited that the mesoporous SnO2/MgO composite can be considered an effective adsorbent/photocatalyst to remove SSY dye from real industrial effluent water at neutral pH conditions.

Multifunctional polysaccharide structure as green adsorbent for efficient removal and preconcentration of chlorophenols from the aqueous medium: experimental and modeling approaches

The growing concerns about water pollution have prompted researchers to explore new materials for remediating and purifying it. In recent years, there has been a focus on polysaccharides as eco-friendly polymers that exhibit high efficiency in removing chlorophenols from waste water. This study aims to develop a trifunctional polysaccharide structure using a biodegradable matrix. The chitosan/alginate-polyethyleneimine-phenyl-phosphonamidic acid (CHIT/ALG-PEIPPAA) matrix was employed for removing chlorophenols from water. The study carefully examined the impact of various physicochemical parameters such as pH, reaction time, chlorophenols concentration, temperature, and ionic strength to determine the optimal conditions for the adsorption process. Several techniques were used to confirm the morphology, physicochemical properties, structure, and functionalization of the polymer. Scanning electron microscopy (SEM) images revealed a heterogeneous morphology with agglomerates of different particle sizes, ranging from a few micrometers with irregular shapes. The FTIR spectrum and zeta potential characterization indicated the presence of hydrophilic groups and a highly positive charge (around 31.4 mV) on the surface of the CHIT/ALG-PEIPPAA adsorbent. The optimal pH for chlorophenols removal was found to be approximately 4.4. The kinetic data supported the pseudo-second-order kinetic model, which accurately described the adsorption behavior of both chlorophenol molecules. The fitting of the isotherm analysis revealed that the Langmuir model provided a better representation of the adsorption process. The maximum adsorption capacities for 4-chlorophenol and 2,4-chlorophenol were approximately 118 mg.g-1 and 249 mg.g-1, respectively. The calculated thermodynamic functions confirmed an exothermic and spontaneous adsorption process for chlorophenols, with ∆H values of -6.98 kJ.mol-1 and -2.74 kJ.mol-1 for 4-chlorophenol and 2,4-chlorophenol, respectively. The regeneration process of the CHIT/ALG-PEIPPAA adsorbent showed higher efficacy in the presence of hydrochloric acid (2.0 mol.L-1), resulting in up to 91% desorption of chlorophenols. The CHIT/ALG-PEIPPAA adsorbent demonstrated good reusability after regeneration, with only a slight decrease in extraction efficiency: 34.63% for 4-chlorophenol and 79.03% for 2,4-chlorophenol, under the same optimal conditions as the initial adsorption cycle.

The performance of a visible light-responsive material Fe3O4/Bi2WO6 cooperating with peroxymonosulfate to degrade bisphenol A

In this study, the visible light-responsive catalysts Fe3O4/Bi2WO6 were prepared and characterized by BET, SEM, EDS, XRD, XPS, and MPMS. The performances of five catalysts (0.05 Fe/Bi, 0.13 Fe/Bi, 0.17 Fe/Bi, 0.21 Fe/Bi, and 0.30 Fe/Bi) for photocatalytic degradation of bisphenol A under visible light (300-W Xe lamp) were compared. Among five catalysts, 0.17 Fe/Bi (the molar ratio of Fe3O4 to Bi2WO6 was 0.17) acquired the highest BPA photocatalytic removal of 90.2% at 120 min. With the synergistic effect between Vis/0.17 Fe/Bi and peroxymonosulfate (PMS), the BPA removal obtained was as high as 100% at 90 min ([BPA] = 100 mg/L, [0.17 Fe/Bi] = 1.25 g/L, [PMS] = 2.0 g/L, and T = 25 °C). After five times reused of 0.17 Fe/Bi, its removal of BPA dropped by 13.4% in presence of PMS, which demonstrated 0.17 Fe/Bi possessed relatively stable performance. High BPA degradation was attributed to the attacking effects of various oxide species (SO4•-, •OH, h+, O2•-) generated in the Fe3O4/Bi2WO6/PMS system under the cooperation of photocatalyst Fe3O4/Bi2WO6 and oxidizing agent PMS.

Application of Box-Behnken Design to Optimize Phosphate Adsorption Conditions from Water onto Novel Adsorbent CS-ZL/ZrO/Fe3O4: Characterization, Equilibrium, Isotherm, Kinetic, and Desorption Studies

Phosphate (PO43-) is an essential nutrient in agriculture; however, it is hazardous to the environment if discharged in excess as in wastewater discharge and runoff from agriculture. Moreover, the stability of chitosan under acidic conditions remains a concern. To address these problems, CS-ZL/ZrO/Fe3O4 was synthesized using a crosslinking method as a novel adsorbent for the removal of phosphate (PO43-) from water and to increase the stability of chitosan. The response surface methodology (RSM) with a Box-Behnken design (BBD)-based analysis of variance (ANOVA) was implemented. The ANOVA results clearly showed that the adsorption of PO43- onto CS-ZL/ZrO/Fe3O4 was significant (p ≤ 0.05), with good mechanical stability. pH, dosage, and time were the three most important factors for the removal of PO43-. Freundlich isotherm and pseudo-second-order kinetic models generated the best equivalents for PO43- adsorption. The presence of coexisting ions for PO43- removal was also studied. The results indicated no significant effect on PO43- removal (p ≤ 0.05). After adsorption, PO43- was easily released by 1 M NaOH, reaching 95.77% and exhibiting a good capability over three cycles. Thus, this concept is effective for increasing the stability of chitosan and is an alternative adsorbent for the removal of PO43- from water.

Design of separable magnetic chitosan grafted-benzaldehyde for azo dye removal via a response surface methodology: Characterization and adsorption mechanism

In this study, a magnetic chitosan grafted-benzaldehyde (CS-BD/Fe₃O₄) was hydrothermally prepared using benzaldehyde as a grafting agent to produce a promising adsorbent for the removal of acid red 88 (AR88) dye. The CS-BD/Fe₃O₄ was characterized by infrared spectroscopy, surface area analysis, scanning electron microscopy-energy dispersive X-ray, vibrating sample magnetometry, powder X-ray diffraction, CHN elemental analysis, and point of zero charge (pH_PZC). The Box-Behnken design (BBD) was adopted to study the role of variables that influence AR88 dye adsorption (A: CS-BD/Fe₃O₄ dose (0.02-0.1 g), B: pH (4-10), and time C: (10-90 min)). The ANOVA results of the BBD model indicated that the F-value for the AR88 removal was 22.19 %, with the corresponding p-value of 0.0002. The adsorption profiles at equilibrium and dynamic conditions reveal that the Temkin model and the pseudo-first-order kinetics model provide an adequate description of the isotherm results, where the maximum adsorption capacity (qmax) with the AR88 dye was 154.1 mg/g. Several mechanisms, including electrostatic attraction, n-π interaction, π-π interaction, and hydrogen bonding, regulate the adsorption of AR88 dyes onto CS-BD/Fe₃O₄ surface. As a result, this research indicates that the CS-BD/Fe₃O₄ can be utilized as an effective and promising bio-adsorbent for azo dye removal from contaminated wastewater.

Magnetic Fe3O4 embedded chitosan-crosslinked-polyacrylamide composites with enhanced removal of food dye: Characterization, adsorption and mechanism

The water solubility in acid solution, relative low adsorption capacities and unsatisfactory separation performance limit application of traditional chitosan-based adsorbents in wastewater treatment. To break the limitation, a hydrophilic magnetic Fe₃O₄ embedded chitosan-crosslinked-polyacrylamide composites (abbreviated as m-CS-c-PAM) were prepared by a two-step method. The m-CS-c-PAM composites were systematically characterized using SEM, XRD, FTIR, VSM, TGA and BET. Sunset yellow (SY) was selected as model food dye to investigate adsorption kinetics and thermodynamic parameters of food dye adsorption onto m-CS-c-PAM. Compared with magnetic Fe₃O₄/chitosan, m-CS-c-PAM can adapt to a wider range of pH (2-10) and resist the presence of inorganic salts. m-CS-c-PAM was proved to have high adsorption capacity (359.71 mg g^-1) for SY dye at 298 K, much higher than magnetic Fe₃O₄/chitosan and many reported adsorbents. Moreover, m-CS-c-PAM could be rapidly and efficiently separated from treated solution within 15 s by an external magnet and regenerated by NaOH solution. With its excellent adsorption capacity, pH-independent adsorption capability for food dye, easy and convenient separation ability, satisfactory reusability, m-CS-c-PAM can be a promising material for food wastewater treatment.

The evolution of the global COVID-19 epidemic in Morocco and understanding the different therapeutic approaches of chitosan in the control of the pandemic

In 2020, Coronavirus disease (COVID-19), a new viral respiratory disease caused by a virus that belongs to Coronaviridae family, has been identified. It is a very severe flu that negatively affects the functions of the lung and other respiratory organs. COVID-19 virus can be transmitted between people either by touching an infected person or by direct contact with their respiratory droplets. Therefore, the COVID-19 virus has become a global concern due to its rapid spread and severity. Based on the World Health Organization report from 2 March 2020 to 24 October 2022, the total infected cases and deaths in Morocco are around 1,265,389 (3.46%) and 16,280 (0.04%), respectively. Recently, some scientists have found that chitosan, a polymer existed in nature, can inhibit COVID-19 infection and repair damaged tissue. Therefore, understanding chitosan mechanisms in controlling COVID-19, might lead to innovative strategies in the medical field, such as developing drugs against SARS-CoV-2, and replacing vaccines, which have negative side effects. This review aims to show the evolution of the COVID-19 pandemic worldwide, specifically in Morocco, its pathophysiology, and its ability to silence the immune system. This review also provides an overview of the treatments and measures applied to protect human beings and how chitosan acts and controls COVID-19.

Reusable kaolin impregnated aminated chitosan composite beads for efficient removal of Congo red dye: isotherms, kinetics and thermodynamics studies

In this investigation, Kaolin (K) impregnated aminated chitosan (AM-CTS) composite beads were fabricated with multi-features including low-cost, high performance, renewable and ease of separation for adsorption of anionic Congo red (CR) dye. Characterization tools such as FTIR, XRD, SEM, TGA, BET, XPS and Zeta potential were thoroughly employed to confirm the successful formulation process. The results revealed that K@ AM-CTS composite beads displayed higher specific surface area (128.52 m²/g), while the thermal stability was prominently improved compared to pure AM-CTS. In addition, the adsorption equilibrium of CR dye was accomplished rapidly and closely gotten within 45 min. The removal efficiency was significantly enriched and reached 90.7% with increasing kaolin content up to 0.75%, compared to 20.3 and 58% for pristine kaolin and AM-CTS, respectively. Moreover, the adsorption process obeyed the pseudo-first order kinetic model, while data were agreed with the Freundlich isotherm model with a maximum adsorption capacity reached 104 mg/g at pH 6. Furthermore, D–R isotherm model demonstrated the physical adsorption process of CR dye, which includes the electrostatic interactions, ion exchange and H-bonding. Thermodynamics evidenced the spontaneous and endothermic nature of the adsorption process. Interestingly, the developed K@AM-CTS composites beads showed better reusability for eight consecutive cycles, suggesting their feasible applicability for adsorptive removal anionic dyes from polluted aquatic bodies.