Synthesis, characterization and using at the copper adsorption of chitosan/polyvinyl alcohol magnetic composite

Outstanding Sorption of Copper (II) Ions on Porous Phenothiazine-Imine-Chitosan Materials

The aim of this work was to investigate the ability of a solid-state material, prepared by crosslinking chitosan with a phenothiazine-based aldehyde, to remove copper (II) ions from aqueous solutions, in a fast and selective manner. The metal uptake experiments, including the retention, sensibility, and selectivity against eight different metal ions, were realized via batch adsorption studies. The capacity of the material to retain copper (II) ions was investigated by spectrophotometric measurements, using poly(ethyleneimine) complexation agent, which allowed detection in a concentration range of 5-500 µM. The forces driving the copper sorption were monitored using various methods, such as FTIR spectroscopy, X-ray diffraction, SEM-EDAX technique, and optical polarized microscopy, and the adsorption kinetics were assessed by fitting the in vitro sorption data on different mathematical models. The phenothiazine-imine-chitosan material proved high ability to recover copper from aqueous media, reaching a maximum retention capacity of 4.394 g Cu (II)/g adsorbent when using a 0.5 M copper solution, which is an outstanding value compared to other chitosan-based materials reported in the literature to this date. It was concluded that the high ability of the studied xerogel to retain Cu (II) ions was the result of both physio- and chemo-sorption processes. This particular behavior was favored on one hand by the porous nature of the material and on the other hand by the presence of amine, hydroxyl, imine, and amide groups with the role of copper ligands.

Synthesis of silver/Fe3O4@chitosan@polyvinyl alcohol magnetic nanoparticles as an antibacterial agent for accelerating wound healing

Bacterial infection causes wound inflammation and slows wound healing, posing a great threat to human health, which needs to explore more antibacterial nanobiomaterials to promote wound healing. Therefore, this study was conducted to develop low-cost silver/Fe₃O₄@Chitosan@polyvinyl alcohol (Ag/Fe₃O₄@CS@PVA) via a one-pot method to promote healing in bacteria-infected wounds. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometry (VSM) confirmed that Ag/Fe₃O₄@CS@PVA was successfully prepared. In vitro antibacterial experiments demonstrated strong antibacterial activity of Ag/Fe₃O₄@CS@PVA against Escherichia coli and Staphylococcus aureus. The Ag/Fe₃O₄@CS@PVA destroyed the bacterial cell membrane or internal structure, thus resulting in cell death for antibacterial effects. Cytotoxicity and hemolysis rate tests showed that Ag/Fe₃O₄@CS@PVA posed fine biocompatibility. In addition, in vivo assays confirmed that Ag/Fe₃O₄@CS@PVA not only promoted the healing of wound infection caused by bacteria, but also had no toxic effect on mouse organs. Therefore, the low-cost Ag/Fe₃O₄@CS@PVA nanocomposites have great potential in controlling 'bacterial' pathogen.

Enhanced adsorption of copper ions from aqueous solution by two-step DTPA-modified magnetic cellulose hydrogel beads

Copper contamination of water is one of the most pressing environmental problems which has attracted extensive concern in recent decades. In this study, a series of magnetic adsorbents were synthesized by two-step modified cellulose with N-[3-(trimethoxysilyl)propyl]ethylenediamine (KH-792) and diethylenetriaminepentaacetic acid (DTPA) using for removal of Cu(II) from aqueous solutions. Adsorption performance of Cu(II) was systematically investigated under various treatment conditions as the effect of solution pH, contact time, initial concentration and temperature. The adsorption process was found to match better with the pseudo-second-order kinetics model, and the equilibrium adsorption data were well described by Langmuir model, which meant predominant governance of monolayer chemical adsorption. The analysis of FTIR and XPS confirmed the possible adsorption mechanism between Cu(II) and the synthesized adsorbents was electrostatic attraction and the chemical coordination. Compared with MCCs and APMC, DPMC showed higher adsorption capacity of Cu(II), reaching maximum adsorption capacity of 298.62 mg·g^-1 at pH 6. Given this, ease of preparation, low cost and excellent reusability, DPMC will be promising adsorbent for application in Cu(II) removal from wastewater.

Research progress of adsorption and removal of heavy metals by chitosan and its derivatives: A review

Chitosan has received widespread attention as an adsorbent for pollutants because of its low cost and great adsorption potentials. Chitosan has abundant hydroxyl and amino groups that can bind heavy metal ions. However, it has defects such as sensitivity to pH, low thermal stability, and low mechanical strength, which limit the application of chitosan in wastewater treatment. The functional groups of chitosan can be modified to improve its performance via crosslinking and graft modification. The porosity and specific surface area of chitosan in powder form are not ideal, therefore, physical modification has been attempted to generate chitosan nanoparticles and hydrogel. Chitosan has also been integrated with other materials (e.g. graphene, zeolite) resulting in composite materials with improved adsorption performance. This review mainly focuses on reports about the application of chitosan and its derivatives to remove different heavy metals. The preparation strategy, adsorption mechanism, and factors affecting the adsorption performance of adsorbents for each type of heavy metal are discussed in detail. Recent reports on important organic pollutants (dyes and phenol) removal by chitosan and its derivatives are also briefly discussed.

A systematic review on carbohydrate biopolymers for adsorptive remediation of copper ions from aqueous environments-Part B: Isotherms, thermokinetics and reusability

The presence of copper in aquatic environment is a serious threat for human health and ecosystem conservation. Adsorption is a powerful, operable and economic method for remediation of copper ions from aqueous phase. Carbohydrate biopolymers have emerged as promising, effective and environmental-friendly adsorbents for copper remediation. In part A of this review, different types of carbohydrate biopolymer adsorbents were surveyed focusing on prevalent and novel synthesis and modification methods. In current work (part B of the review), isothermal, thermodynamic and kinetic aspects of the copper adsorption by carbohydrate-based adsorbents as well as the regeneration and reusability of the biopolymer adsorbents are overviewed. Adsorption capacity, time required for equilibrium (adsorption rate), thermal-sensitivity of the adsorption, favorability extent, and sustainability of the adsorbents and adsorption processes are valuable and useful outcomes, resulted from the thermokinetic and reusability investigations. Such considerations are critical for the process design and scale up regarding technical, economical and sustainability of the adsorption process.

Characterization and deployment of surface-engineered chitosan-triethylenetetramine nanocomposite hybrid nano-adsorbent for divalent cations decontamination

The latency of toxic cations in the ecosystem poses serious ecological problems due to its bioaccumulation potential and toxicity to living organisms. The effective removal of these wastewater cations releasing from multi-industries is a bottleneck issue. Therefore, an attempt has been made to design a suitable sorbent for cations sorption from the aqueous environment. The chitosan biopolymer was modified with triethylenetetramine to incorporate active sites in the polymeric sequence to boost up its cations sorption capacity. Triethylenetetramine molecule anchoring chitosan (CH-TET) was authenticated through elemental assay, Fourier-transform infrared spectroscopy and ¹³C NMR in solid-state, scanning electron microscopy and thermal analysis. The sorption of lead (1.94 mmol g^-1), copper (2.79 mmol g^-1) and nickel (1.53 mmol g^-1) was carried out using the functionalized chitosan from aqueous solution, which showed higher sorption capacity for lead and copper than the pristine chitosan in terms of Langmuir sorption isotherm. To scrutinize the mechanism of sorption and energy of interaction between sorbent and sorbate, Langmuir, Temkin, and Freundlich isotherm models were used for sorption study. The Langmuir model showed the best fitting to the results based on lower error function values and a higher correlation coefficient (R²). It can be concluded that the triethylenetetramine-modified chitosan might be considered as an effective sorbent for cations removal from industrial wastewater.

Synthesis of cross-linking chitosan-PVA composite hydrogel and adsorption of Cu(II) ions

A cross-linked chitosan-PVA spherical hydrogel (CSH) was synthesized and its structure was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The physical and chemical properties of CSH, such as acid resistance and swelling, were determined. Finally, Cu(II) ion removal by the CSH was investigated, and the effects of experimental parameters, including pH, adsorption time, and regeneration performance were examined. Results revealed that CSH has outstanding stability in strong acid solution, thus extending the useful pH range as an adsorbent material. The maximum capacity of CSH for Cu(II) was obtained to be 62.1 mg/g at 25 °C for 24 h. The adsorption process was best described by a pseudo-second-order kinetic model, while isotherm modeling revealed that the Langmuir equation better described the adsorption of Cu(II) on CSH. Moreover, the loaded CSH can be easily regenerated by the HCl-washing method and reused repeatedly for Cu(II) adsorption for up to five cycles.

Removal of Cr(VI) by modified diatomite supported NZVI from aqueous solution: evaluating the effects of removal factors by RSM and understanding the effects of pH

In this study, a novel composite of modified diatomite supported nanoscale zero-valent iron (mD-NZVI) was synthesized and characterized. The effects of four factors (mD-NZVI dose, temperature, contact time and initial pH) on the removal of Cr(VI) by mD-NZVI were studied by experimental work and analyzed by response surface methodology (RSM). A second-order polynomial equation fitted by Box-Behnken design was used as a statistical model and proved to be precise in describing the significance of four factors. The analysis results show that the effects of four factors on the removal efficiency of Cr(VI) were significant (F value is 19.83), initial pH was found to be the key factor. In addition, the effect of initial pH was further studied and the maximum removal efficiency of 89.34% was obtained at pH of 3, the decrease in removal efficiency with the increase in pH is a synergistic effect of Cr(VI) species, surface charge of mD-NZVI and OH^- amount at different pH.

Efficient removal of cadmium (II) ions from aqueous solution by CoFe2O4/chitosan and NiFe2O4/chitosan composites as adsorbents

Magnetically recoverable chitosan based spinel cobalt and nickel ferrite (CS/CoFe₂O₄ and CS/NiFe₂O₄, respectively) composites were successfully prepared in one step. A series of batch adsorption experiments indicated that the removal of toxic Cd(II) ions by the as-obtained composites as adsorbents was pH-dependent, rapid, proficient, better fitted to pseudo-second-order kinetics model and Langmuir monolayer adsorption isotherm model. Compared to the naked particles, magnetic bio-polymer composites exhibited promoted adsorption capacity. Competitive adsorption studies in binary solutions illustrated preferable selectivity of adsorbents toward Cd(II) ions in the presence of co-existing cations. More importantly, CS/CoFe₂O₄ and CS/NiFe₂O₄ had a satisfactory practical application in the removal of Cd(II) from real groundwater spiked with cadmium. The exhausted adsorbents could be regenerated efficiently by 0.5 M HNO₃. The results from this study support that CS/CoFe₂O₄ and CS/NiFe₂O₄ prove excellent adsorption behavior for the removal of Cd(II) ions from aqueous media.