Magnetic chitosan-(d-glucosimine methyl)benzaldehyde Schiff base for Pb+2 ion removal. Experimental and theoretical methods

NiFe2O4/g- C3N4 modified chitosan Schiff base composite for efficient removal of Cu(II) and Hg(II) ions from the aquatic environment and its antibacterial properties

Modification of chitosan has been achieved by the reaction of chitosan with 4- nitro-benzaldehyde via the sol-gel method, resulting in a Schiff base. A novel magnetic Graphitic Carbon Nitride/chitosan-Schiff base/NiFe2O3 (SBIV@NiFe/g-C3N4) adsorbent was synthesized by hydrothermal route for the adsorption of Cu(II) and Hg(II) ions from the aquatic environment. The synthesized SBIV@NiFe/g-C3N4 was characterized using infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), and Brunauer-Emmett-Teller (BET), with a surface area of approximately 13.657 m2/g. It was anticipated by the results that magnetic SBIV@NiFe/g-C3N4 would be effectively synthesized. On Cu(II) and Hg(II) adsorption, the impacts of significant variables, including pH solution, contact duration, metal ion concentration, adsorbent dosage, and co-existing ions, were examined. Under ideal circumstances, the optimum adsorption capacities of Cu(II) and Hg(II) ions were 889.76 mg/g and 703.21 mg/g, respectively. Furthermore, the SBIV@NiFe/g-C3N4 material exhibited the beneficial property of simple separation, permitting the continuation of high removal effectiveness for heavy metals like Cu (II) and Hg(II) despite experiencing many reuse cycles. In summary, there are a lot of opportunities for the effective elimination of Cu (II) and Hg (II) from different water sources shortly with the use of SBIV@NiFe/g-C3N4, a new adsorbent. The as-synthesized SBIV@NiFe/g-C3N4 displayed better antibacterial activity against highly lethal bacteria like S. aureus and P. vulgaris.

Synthesis and characterization of chitosan Schiff base grafted with formaldehyde and aminoethanol: As an effective adsorbent for removal of Pb(II), Hg(II), and Cu(II) ions from aqueous media

Grafted chitosan materials show the characteristics of high stability, easy separation and recovery, and good heavy metal adsorption capacity, and have received much attention in the adsorption process. Therefore, in this work, novel grafted chitosan-based adsorbent CS-EHBSB@F-AE was prepared by a one-pot reaction of chitosan (CS), 3-ethoxy-4-hydroxybenzaldehyde (EHB), formaldehyde (F) and aminoethanol (F). The microstructure and morphology of the as-prepared composite CS-EHBSB@F-AE were characterized by FT-IR, TGA, DSC, FE-SEM, and BET analyses. The adsorption performance of the as-prepared CS-EHBSB@F-AE composite on Pb(II), Hg(II), and Cu(II) ions from aqueous was investigated using batch experiment and the effects of the initial pH of the solution, contact time, and initial metal ions concentration and temperature on the adsorption efficiency were investigated and discussed. At the best conditions, CS-EHBSB@F-AE exhibited remarkable adsorption capacity of 246.7 mg/g, 203.9 mg/g, and 234.4 mg/g in absorbing Pb(II), Hg(II), and Cu(II), respectively. The adsorption equilibrium and the kinetic studies confirmed that the ions adsorption process fits well with the Langmuir isotherm and pseudo-second-order (PSO) models. Additionally, the adsorption efficiency of Pb(II), Hg(II), and Cu(II) metal ions by the composite CS-EHBSB@F-AE was reduced by increasing the temperature from 298 K to 318 K. In addition, after the sixth ads/des cycles, the as-prepared adsorbent still exhibited high removal efficiency with a decrease in adsorption efficiency of Pb(II) (5.53 %), Hg(II) (15.43 %) and Cu(II) (8.27 %). Finally, we proposed that the ions adsorption by CS-EHBSB@F-AE has happened using the coordination of active groups containing nitrogen and oxygen atoms on the surface of the adsorbent with the Pb(II), Hg(II), and Cu(II) metal ions.

Defect-Engineered MOF-801/Sodium Alginate Aerogel Beads for Boosting Adsorption of Pb(II)

Metal-organic frameworks (MOFs) are attractive adsorbents for heavy metal capture due to their superior stability, easy modification, and adjustable pore size. However, their inherent microporous structure poses challenges in achieving a higher adsorption capacity. Defect engineering is considered a simple method to create hierarchical MOFs with larger pores. Here, we employed l-aspartic acid as a mixed linker to bind Zr4+ clusters in competition with fumaric acid of MOF-801 to create defects, and the pore size was increased from 4.66 to 15.65 nm. Mercaptosuccinic acid was subsequently used as a postexchange ligand to graft the resultant MOF-801 by acid-ammonia condensation to further expand the pore size to 22.73 nm. Notably, the -NH2, -COOH, and -SH groups contributed by these two ligands increased the adsorption sites for Pb(II). The obtained defective MOF-801 with larger pores was thereafter loaded onto sodium alginate to form aerogel beads as adsorbents, and an adsorption capacity of 375.48 mg/g for Pb(II) was achieved, which is ∼51 times that of pristine MOF-801. The aerogel beads also exhibited outstanding reusability with a removal efficiency of ∼90.23% after 5 cycles of use. The adsorption mechanism of Pb(II) included ion-exchange interaction, as well as chelation interactions of Pb-O, Pb-NH2, and Pb-S. The versatile combination of defect engineering and composite beads provides novel inspirations for MOF modification for boosting heavy metal adsorption.

The role of chitosan grafted copolymer/zeolite Schiff base nanofiber in adsorption of copper and zinc cations from aqueous media

The objective of this research was to develop and assess chitosan-grafted copolymer/HZSM5 zeolite Schiff base nanofibers for Cu2+ and Zn2+ adsorption from aqueous media. Nanofibers were prepared via electrospinning and characterized using XRD, FTIR, 1H NMR, FESEM, TGA, BET, and XPS. The study evaluated the effect of unmodified HZSM5 and Schiff base functionalization on adsorption capacities. Incorporating 10.0 wt% zeolite Schiff base as the optimum content into the chitosan-grafted copolymer significantly enhanced adsorption, achieving increases of 98.2 % for Zn2+ and 42.2 % for Cu2+. Specifically, Zn2+ adsorption increased from 27.6 to 54.7 mg/g, and Cu2+ from 67.1 to 95.4 mg/g. Factors such as temperature, pH, adsorption time, and initial cation concentration were analyzed. Kinetic studies revealed a double-exponential model, and isotherm analysis indicated a good fit with the Redlich-Peterson model, showing maximum monolayer capacities of 310.1 mg/g for Cu2+ and 97.8 mg/g for Zn2+ (pH 6.0, 240 min, 45 °C). The adsorption thermodynamics indicated a spontaneous and endothermic adsorption. Reusability tests showed minimal capacity loss (4.91 % for Cu2+ and 5.59 % for Zn2+) after five cycles. The nanofiber displayed greater selectivity for Cu2+ over Zn2+ in multi-ion systems and real electroplating wastewater, highlighting its potential for targeted heavy metal removal.

Fabrication of a novel polyvinylpyrrolidone/chitosan-Schiff base/Fe2O3 nanocomposite for efficient adsorption of Pb(II) and Hg(II) ions from aqueous solution

A novel magnetic polyvinylpyrrolidone/chitosan-Schiff base/Fe2O3 (PVP/CS-SB/Fe2O3) adsorbent was prepared by one-pot facile co-precipitation route for adsorption of Pb(II) and Hg(II) ions from aqueous solution. Fourier transform infrared-spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), vibrating sample magnetometer (VSM) and Brunauer-Emmett-Teller (BET) were used to characterize the synthesized PVP/CS-SB/Fe2O3. The results predicted that the successfully synthesis of magnetic CSSB-PVP@Fe2O3. The effects of important factors such as pH solution, contact time, concentration of metal ions, adsorbent dose and co-existing ions on Pb(II) and Hg(II) adsorption were investigated. The maximum adsorption capacities of Pb(II) and Hg(II) ions at optimal conditions were 120 mg/g and 102.5 mg/g, respectively. The kinetic studies predicted that the adsorption followed the pseudo-second-order (PSO) model as chemisorption using the coordination of active sites of PVP/CS-SB/Fe2O3 with the metal ions and also n-π interactions. Reproducibility results predicted that the excellent regeneration ability after 6 adsorption cycles. According to the results of this work, the PVP/CS-SB/Fe2O3 nanocomposite is promising for Pb(II) and Hg(II) ions adsorption and can be potential as a simple, low-cost, high-efficient adsorbent for decontamination of other heavy metal ions from aqueous solution.

Efficient removal of per/polyfluoroalkyl substances from water using recyclable chitosan-coated covalent organic frameworks: Experimental and theoretical methods

Covalent organic frameworks (COFs) demonstrate remarkable potential for adsorbing per/polyfluoroalkyl substances (PFAS). Nevertheless, the challenge of recycling powdered COFs hampers their practical application in water treatment. In this research, a quaternary amine COF with inherent positive surface charge was synthesised to adsorb perfluorooctanoic acid (PFOA) via electrostatic interactions. The COF was then combined with chitosan (CS) through a simple dissolution-evaporation process, resulting in a composite gel material termed COF@CS. The findings indicated that the adsorption capacity of COF@CS significantly surpassed that of the original COF and CS. According to the Langmuir model, COF@CS achieved a maximum PFOA capacity of 2.8 mmol g-1 at pH 5. Furthermore, the adsorption rate increased significantly to 6.2 mmol g-1 h-1, compared to 5.9 mmol g-1 h-1 for COF and 3.4 mmol g-1 h-1 for CS. Notably, COF@CS exhibited excellent removal efficacy for ten other types of PFAS. Moreover, COF@CS could be successfully regenerated using a mixture of 70% ethanol and 1 wt% NaCl, and it exhibited stable reusability for up to five cycles. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) characterisation, and theoretical calculations revealed that the quaternary amine functional group in COF served as the primary adsorption site in the composite gel material, while the protonated amino group on CS enhanced PFOA adsorption through electrostatic interaction. This study highlights the significant practical potential of COF@CS in the removal of PFAS from aqueous solution and environmental remediation.

Chitosan-based Schiff bases: Promising materials for biomedical and industrial applications

There is plenty of scope for modifying chitosan, an only polycationic natural polysaccharide, owing to its reactive functional groups, namely hydroxyl and amino groups. Although innumerable numbers of chitosan derivatives have been synthesized by modifying these groups and reported elsewhere, in this review article, an attempt has been exclusively made to demonstrate the syntheses of various chitosan-based Schiff bases (CSBs) simply by allowing the reactions of reactive amino groups of chitosan with different aldehydes/ketones of interest. Due to their very peculiar and unique characteristics, such as biodegradability, biocompatibility, metal-binding capability, etc., they are found to be very useful for diversified applications. Thus, we have also attempted to showcase their very specific biomedical fields, including tissue engineering, drug delivery, and wound healing, to name a few. In addition, we have also discussed the utilization of CSBs for industrial applications such as wastewater treatment, catalysis, corrosion inhibition, sensors, etc.

Chitosan cross-linked and grafted with epichlorohydrin and 2,4-dichlorobenzaldehyde as an efficient adsorbent for removal of Pb(II) ions from aqueous solution

Epichlorohydrin-modified chitosan-Schiff base composite (CS/24Cl/ECH) prepared via the one-pot reaction as characterized by Fourier transform Infra-Red spectroscopy (FT-IR), X-ray powder diffraction (XRD), Differential scanning calorimetry (DSC) and Scanning electron microscope (SEM). Its removal ability of Pb(II) ions from aqueous solution was investigated. The adsorption of Pb(II) ions carried out at different initial pH, dose of CS/24-Cl/ECH, contact time and co-existing ions. The maximum adsorption capacity of Pb(II) ions was 170 mg/g. Finally, based on the absorption results, the adsorption of Pb(II) ions was fitted by single-layer Langmuir isotherm model and the pseudo-second-order (PSO) kinetics model. The absorption mechanism of Pb(II) ions was controlled by chemical coordination Pb(II) ions with the active sites on the surface of CS/24Cl/ECH composite. Also, CS/24Cl/ECH showed excellent recyclable efficiency up to 5 cycle and potential sorbent for other heavy metal ions.

Synthesis and characterization of pendant N,N-dimethylaminobenzaldehyde-functionalized chitosan Schiff base composite (CS@MABA) as a new sorbent for removal of Pb(II) ions from aqueous media

In this work, new pendant N,N-dimethylaminobenzaldehyde-functionalized chitosan Schiff base composite (CS@MABA) was prepared from the simple and convenient condensation reaction between chitosan (CS) and N,N-dimethylaminobenzaldehyde (MABA) in ethanol-glacial acetic acid (1:1 v/v) and characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscope (SEM). The as-prepared composite CS@MABA was applied for the removal of Pb(II) ions, due to the presence of imine, hydroxyl and phenyl groups, and the effects of important parameters such as solution pH, contact time and sorbent dosage on the removal percentage and adsorption capacity were investigated and discussed. The optimum conditions were found to be at pH 5, adsorbent dosage of 0.1 g, Pb(II) concentration of 50 mg/L and contact time of 60 min. The maximum Pb(II) removal percentage was found to be 94.28 % with the high adsorption capacity of 165 mg/g. The adsorption capacity of CS@MABA is remain 87 % after 5 adsorption-desorption cycles. The adsorption kinetic and isotherm studies indicated that the Pb(II) removal by CS@MABA follows a pseudo-first order and Langmuir models, respectively. Compared to similar compounds, the synthesized CS@MABA composite has shown a relatively high yield for removing Pb(II) ions. According to these results, the CS@MABA suggested for the sorption of other heavy metals.

Modified magnetic chitosan materials for heavy metal adsorption: a review

Magnetic chitosan materials have the characteristics of both chitosan and magnetic particle nuclei, showing the characteristics of easy separation and recovery, strong adsorption capacity and high mechanical strength, and have received extensive attention in adsorption, especially in the treatment of heavy metal ions. In order to further improve its performance, many studies have modified magnetic chitosan materials. This review discusses the strategies for the preparation of magnetic chitosan using coprecipitation, crosslinking, and other methods in detail. Besides, this review mainly summarizes the application of modified magnetic chitosan materials in the removal of heavy metal ions in wastewater in recent years. Finally, this review also discusses the adsorption mechanism, and puts forward the prospect of the future development of magnetic chitosan in wastewater treatment.

Application of new chitosan 2,4-dihydroxyacetophenone Schiff base @SrFe12O19 nanocomposite for remove of Pb(II) ion from aqueous solution

A new chitosan 2,4-dihydroxyacetophenone Schiff base @SrFe₁₂O₁₉ (Cs-SB@SrFe₁₂O₁₉) nanocomposite was successfully prepared by one-pot reaction and fully characterized for its functional groups, morphology, elemental analysis and thermal behavior by FT-IR, XRD, VSM, DSC, TGA, zeta potential, FE-SEM and EDS techniques. The VSM result showed that Cs-SB@SrFe₁₂O₁₉ has M_s of 11.81 emu/g and H_c of 5488 Oe, known as hard magnetic material. Finally, the as-prepared sample utilized as a new sorbent for the removal of Pb(II) ions from aqueous solution by using batch adsorption experiments. The adsorption of Pb(II) was carried out at different pH, contact time and initial dose of Cs-SB@SrFe₁₂O₁₉. The maximum adsorption capacity was found to be 132 mg/g (99 %) at pH 5 and the contact time of 120 min. Finally, the kinetic studies reveals that the adsorption process of Cs-SB@SrFe₁₂O₁₉ followed by the pseudo second order kinetics model. Also, the sample showed excellent recyclable efficiency up to 5 cycles.

Synthesis of a new magnetic Sulfacetamide-Ethylacetoacetate hydrazone-chitosan Schiff-base for Cr(VI) removal

In this study, a novel magnetic organic-inorganic composite was fabricated. Where, Chitosan, sulfacetamide and ethylacetoacetae were used to prepare a new Sulfacetamide-Ethylacetoacetate hydrazone-chitosan Schiff-base (SEH-CSB) with a variety of active sites that capable of forming coordinate covalent bonds with Cr(VI). This was followed by modification of the formed SHE-CSB with NiFe₂O₄ to obtain the magnetic Chitosan-Schiff-base (NiFe₂O₄@SEH-CSB). NiFe₂O₄@SEH-CSB was characterized using FTIR, zeta potential, SEM, VSM and XPS. Results clarified that SHE played a crucial role in the removal of Cr(VI). The removal of Cr(VI) on NiFe₂O₄@SEH-CSB was found to be more fitted to pseudo-2nd order kinetics model and Freundlich isotherm. Besides, the maximum adsorption capacity of NiFe₂O₄@SEH-CSB for Cr(VI) was found to be 373.61 mg/g. The plausible mechanism for the removal of Cr(VI) on NiFe₂O₄@SEH-CSB composite suggested coulombic interaction, outer-sphere complexation, ion-exchange, surface complexation and coordinate-covalent bond pathways. The magnetic property enabled easy recycling of NiFe₂O₄@SEH-CSB composite.

Efficient removal of Pb(II) using modified chitosan Schiff base@Fe/NiFe

A novel modified chitosan Schiff base@Fe₂O₃-NiFe₂O₄ (CsSB@Fe/NiFe) was prepared and characterized using FT-IR, XRD, SEM, EDX, TGA, DSC and VSM. FT-IR and XRD results confirm that the nanoparticles of Fe/NiFe distributed throughout the surface of CS-OH and successfully prepared CsSB@Fe/NiFe. SEM image shows that the Fe/NiFe nanoparticles were assembled in the surface and inside of CS-OH. Coercivity (H_c) of CsSB@Fe/NiFe is ≈ 110 Oe, indicated that it was kind of soft-magnetic materials with saturation magnetization (M_s) of 6.45 emu/g. In addition, CsSB@Fe/NiFe was further explored as an new sorbent for the removal of Pb(II) ion from aqueous solution and the influence of various important parameters such as solution pH, contact time, dosage of adsorbent and initial Pb(II) concentration were studied and optimized. Optimum conditions for Pb(II) removal were found to be pH 5, adsorbent dosage 0.05 g, initial Pb(II) concentration of 75 ppm and contact time of 120 min. The maximum Pb(II) removal percentage was found to be 97%. Also, CsSB@Fe/NiFe shows about 88% Pb(II) removal after five adsorption-desorption cycles. The results suggested that the sorption of Pb(II) onto CsSB@Fe/NiFe was feasible and spontaneous.

High-efficiency adsorption of phenanthrene by Fe3O4-SiO2-dimethoxydiphenylsilane nanocomposite: Experimental and theoretical study

Phenanthrene (PHE), as one of representative polycyclic aromatic hydrocarbons (PAHs) can cause serious adverse effects on human health, developing effective adsorbents to alleviate PHE contamination is in urgent demand. A novel Fe₃O₄-SiO₂-Dimethoxydiphenylsilane (Fe₃O₄-SiO₂-2DMDPS) nanocomposite was fabricated from encapsulation and grafting process. Magnetic Fe₃O₄ nanoparticles were served as preliminary matrix material, SiO₂ was used to link the magnetic oxide and provide hydroxyl groups for proceeding the silane coupling reaction subsequently, and the aromatic rings in DMDPS could provide active sites for PHE adsorption via π-π interaction. SEM-EDS, TEM, BET, VSM, XRD, FTIR, Raman, Zeta potential, and XPS techniques were used to characterize magnetic nanocomposite. The prepared Fe₃O₄-SiO₂-2DMDPS exhibited an excellent adsorption performance towards PHE, it could maintain 75.97% adsorption capacity after four regeneration cycles. Homogeneous adsorption acted crucial role in the whole adsorption process and film diffusion was the rate-controlling procedure. Theoretical calculations put forward the most favorable bonding modes between Fe₃O₄-SiO₂-2DMDPS and PHE molecules, confirmed the π-π interaction was valid and it usually existed in the form of parallel-displaced. This work might aid us to develop effective modification strategy for Fe₃O₄ nanoparticles and expand its application in the PAHs removing field.

Preparation of chitosan-coated polystyrene microspheres for the analysis of trace Pb(ii) ions in salt by GF-AAS assisted with solid-phase extraction

Chitosan-coated polystyrene solid-phase extraction fillers.

Synthesis of new chitosan Schiff base and its Fe2O3 nanocomposite: Evaluation of methyl orange removal and antibacterial activity

New chitosan Schiff base (3EtO-4OH/Chit) and its 3EtO-4OH/Chit/Fe₂O₃ nanocomposite were synthesized and characterized by FTIR, ¹H NMR, XRD, TGA, DSC and SEM. The result confirmed the preparation of 3EtO-4OH/Chit and its 3EtO-4OH/Chit/Fe₂O₃ nanocomposite. The efficiency of the prepared catalysts was studied for the methyl orange (MO) removal from aqueous solution. The effect of adsorbent dose and contact time on the removal of dye has been studied. Their antibacterial activities were considered against two Gram positive (S. aureus and B. cereus) and two Gram negative (E. coli and P. aeruginosa) bacteria and the results showed that the activity of the 3EtO-4OH/Chit/Fe₂O₃ is excellent and is more than chitosan and 3EtO-4OH/Chit. Thermogravimetry studies shows that the weight loss stages and the residual value at 600 °C are different for the two compounds. DSC curve of the title compounds 3EtO-4OH/Chit and 3EtO-4OH/Chit/Fe₂O₃ is different from each other. The reason for this difference could be due to the presence of iron oxide nanoparticles in 3EtO-4OH/Chit/Fe₂O₃.

Effective removal of lead (II) using chitosan and microbial adsorbents: Response surface methodology (RSM)

The ability of chitosan (1% w/v), Bifidobacterium longum (10⁸ CFU mL-¹) and Saccharomyces cerevisiae (10⁸ CFU mL-¹) separately or in combination (chitosan/B. longum, chitosan/S. cerevisiae, B. longum/S. cerevisiae) was assessed for lead (II) removal from aqueous solutions. The results showed chitosan/B. longum adsorbent had higher adsorption percentage in comparison with other adsorbents (p < 0.05). It was selected as the most efficient adsorbent and the effect of process variables including initial metal concentration (0.01-5 mg L^-1), contact time (5-180 min), temperature (4-37 °C) and pH (3-6) on the its removal efficiency was evaluated with a Box-Behnken design. Twenty-seven test runs were performed and the optimal conditions for metal adsorption was observed at metal concentration of 2.5 mg L^-1, contact time of 180 min, temperature of 37 °C and pH 4.5. The maximum lead (II) adsorption yield under optimal conditions was 97.6%. The foreign ions didn't diminish lead (II) adsorption by chitosan/B. longum and it had high selectivity toward the lead (II). Adsorption behavior was analyzed using the Freundlich and the Langmuir isotherms. The correlation coefficients (R²) demonstrated the Langmuir model had a better description on metal adsorption process. Overall, isotherms revealed chemisorption and physisorption were probably involved in metal adsorption on adsorbent.

Polyaspartic Acid-Derived Micro-/Mesoporous Carbon for Ultrahigh H2 and CH4 Adsorption

A poly(amino acid)-based approach for scalable synthesis of micro-/mesoporous carbon (PC) with high specific surface area and narrow distribution of micro- and mesopores is presented. Using cross-linked poly aspartic acid as a precursor, PC was obtained by in situ one-step carbonization without the activating agent. The resulting PC had an ultrahigh adsorption capacity for H₂ (4.43 wt %) and CH₄ (4.49 mmol g^-1). This novel method could significantly decrease the wastewater hazards caused by washout of the considerable amount of the activating agent. The PC showed promising application in gas adsorption and storage.

Uptake of Pb(II) Ions from Simulated Aqueous Solution via Nanochitosan

In this work, nanochitosan (NC) was prepared through ionic gelation using low molecular weight chitosan and maleic acid (MA). The synthesized NC was characterized by atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). During preparation, the particle size of the material depended on parameters such as concentration of chitosan and pH of the aqueous solution. After controlling the mentioned parameters, NC smaller than 100 nm was prepared. The chitosan and prepared NC were employed for the adsorption of Pb(II) from an aqueous solution in the form of a batch system. Among the sorption parameters, pH showed the strongest effect on the sorption process and removal of the maximum number of Pb(II) ions was obtained at pH value of 6. Pseudo-first-order and pseudo-second-order models were used to track the kinetics of the adsorption process. Langmuir and Freundlich’s isotherms were subjected to the absorption data to evaluate absorption capacity. NC proved to be an excellent adsorbent with a remarkable capacity to eliminate Pb(II) ions from aqueous solutions at multiple concentrations. The NC also showed better performance with a comparatively easier preparation process than in other reported work.

Efficient removal of copper ions using a hydrogel bead triggered by the cationic hectorite clay and anionic sodium alginate

Sodium alginate (SA) is a linear biopolymer, which is the nontoxic, biodegradable, and rich in carboxyl and hydroxyl groups. In the paper, the SA-based hydrogel bead was prepared by the cationic hectorite clay and anionic sodium alginate with a simple ionic gelation method under freeze-drying, and the adsorption properties were evaluated by the removal of copper ions from aqueous solutions. The composites were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption isotherm (BET), thermal analysis (TG), and Fourier transform infrared spectroscopy (FT-IR). The pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data and the Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Temkin models were applied to describe the adsorption isotherms. The results showed that the adsorption process was found to follow the Freundlich isotherm model and the maximum sorption capacity was observed to be 160.28 mg/g under the initial concentration from 10 to 700 mg/L at 45 °C. Adsorption kinetics data fitted well with pseudo-second-order rate model. The porous structure of the composite was responsible for the adsorption of Cu²⁺ ions. But the adsorption ability could be improved by pH. Finally, the adsorption mechanism was suggested. Graphical abstract.

Chitosan capped copper oxide/copper nanoparticles encapsulated microbial resistant nanocomposite films

Chitosan (CH) capped inorganic nanomaterials have been considered as significant antibacterial materials in the clinical field. This work shows the synthesis of two new different antibacterial composite films as a result of the incorporation of CH capped copper oxide (CHCuO) and copper (CHCu) nanoparticles (NPs). Here, CHCuO and CHCu NPs were achieved by a facile chemical reduction of Cu²⁺ ions using sodium hydroxide and ascorbic acid. TEM analysis revealed the morphology as rod-type nanoflakes for CHCuO and a spherical shape for CHCu NPs with ~7 ± 2 nm size. Antimicrobial activity of the developed materials was studied by the inhibition zone method, against both gram-negative and gram-positive bacteria. The antimicrobial activity revealed that the CHCuO NPs and CHCuO-CH film showed a higher inhibition zone than the other nanomaterials. The results suggested that the synthesized materials can be used in wound dressing applications.