Adsorption of copper(II) ions by a chitosan–oxalate complex biosorbent

Sequential removal of phosphate and copper(II) ions using sustainable chitosan biosorbent

Although adsorbents are good candidates for removing phosphorus and heavy metals from wastewater, the use of biosorbents for the sequential treatment of phosphorus and copper has not yet been studied. Porous chitosan (CS)-based biosorbents (CGBs) were developed to adsorb phytic acid (PA), a major form of organic phosphate. This first adsorbate (PA) further served as an additional ligand (P-type ligand) for the CGBs (N-type ligand) to form a complex with the second adsorbate (copper). After the adsorption of PA (the first adsorbate), the spent CGBs were recycled and used as a new adsorbent to adsorb Cu(II) ions (the second adsorbate), which was expected to have a dual coordination effect through P, N-ligand complexation with copper. The interactions and complexation between CS, PA and Cu(II) ions on the PA-adsorbed CGBs (PACGBs) were investigated by performing FTIR, XPS, XRD, and SEM-EDS analyses. The PACGBs exhibited fast and enhanced adsorption of Cu(II) ions, owing to the synergistic effect of the amino groups of CS (the original ligand, N-type) and the phosphate groups of PA (an additional ligand, P-type) on the adsorption of Cu(II) ions. This is the first time that sequential removal of phosphorus and heavy metals by biosorbents has been performed using biosorbents.

Removal of lead ions from aqueous solutions by modified cellulose

The new adsorbent was prepared by mixing cellulose with dicyclohexyl-18- crown-6 via microwave irradiation method and it was used to remove lead ions from aqueous solution. In contrast to the traditional way (in which grafted polymers are produced by using chemical-free radical producers), this method is rapid, reproducible, and gives a high-quality product. Different physicochemical techniques such as FTIR, SEM, and XRD and TGA were used for the characterization of the produced adsorbent. Based on the ANOVA statistical value, the adsorption of Pb2+ ion onto grafted cellulose has been found to be significant, with very low probability (p) values (<0.001). The pH and initial concentration were observed to be the most significant factors that affected the Pb2+ ion removal from the analysis of variance. Pseudo-second-order and Langmuir equations were applied to the adsorption of Pb2+ ion and under the optimized conditions, the maximum absorption capacity in modified cellulose of Pb2+ was 58.3 mg/g. Various factors which affect metal ion adsorption, including temperature, power of hydrogen, shaking time, adsorbent quantity, and metal ions concentration were studied. More importantly, the adsorbent could be reused by using 0.1 M nitric acid.

Novel poly (N-methacryloyl-L-alanine acid) grafted chitosan microspheres based solid-phase extraction coupled with ICP-MS for simultaneous detection of trace metal elements in food

Poly (N-methacryloyl-L-alanine acid) grafted tartaric acid-crosslinked chitosan microspheres (PNMA-TACS) were successfully synthesized and employed as a novel adsorbent for the separation and enrichment of metal ions in the food system. PNMA-TACS microspheres-based solid phase extraction (SPE) was coupled with ICP-MS for accurate quantification of trace V(V), Cr(III), As(III), Pb(II), Cd(II) and Cu(II). The obtained PNMA-TACS microspheres were characterized, and parameters influencing the method were optimized. Under optimal conditions, the calibration curves for Cu(II) and V(V) were linear within 0.01-30 μg L-1, the linear ranges of Cr(III), As(III), Pb(II) and Cd(II) were 0.01-15 μg L-1, and the detection limit of the developed approach was 1.1-3.7 ng L-1. The results were consistent with the consensus values of method validation implemented by two standards. Moreover, standard addition recovery experiments were performed in rice and milk powder, which achieved satisfactory recovery of 86.1-103.5%.

A review on heavy metal biosorption utilizing modified chitosan

Heavy metal pollution in water bodies is a global concern. The prominent source of metal contamination in aqueous streams and groundwater is wastewater containing heavy metal ions. Elevated concentrations of heavy metals in water bodies can have a negative impact on water quality and public health. The most effective way to remove metal contaminants from drinking water is thought to be adsorption. A deacetylated derivative of chitin, chitosan, has a wide range of commercial uses since it is biocompatible, nontoxic, and biodegradable. Due to its exceptional adsorption behavior toward numerous hazardous heavy metals from aqueous solutions, chitosan and its modifications have drawn a lot of interest in recent years. Due to its remarkable adsorption behavior toward a range of dangerous heavy metals, chitosan is a possible agent for eliminating metals from aqueous solutions. The review has focused on the ideas of biosorption, its kinds, architectures, and characteristics, as well as using modified (physically and chemically modified) chitosan, blends, and composites to remove heavy metals from water. The main objective of the review is to describe the most important aspects of chitosan-based adsorbents that might be beneficial for enhancing the adsorption capabilities of modified chitosan and promoting the usage of this material in the removal of heavy metal pollutants.

Dietary chitooligosaccharide supplementation improves mineral deposition, meat quality and intramuscular oxidant status in broilers

BACKGROUND

The present study aimed at evaluating the in vitro adsorption capability of chitooligosaccharide (COS) with some metal elements (Fe, Zn, Cd, Pb) at different pH values along with potential effects of dietary COS supplementation on growth performance, mineral content, meat quality and oxidant status in broilers. Day-old male chicks were randomly distributed into two groups and offered a basal diet supplemented with or without 30 mg kg^-1 COS for 42 days.

RESULTS

In vitro trials demonstrated that Fe levels were higher (P < 0.001) in the COS-treated group compared with the non-treated group at pH of 2.5. However, these levels became lowered when pH values were raised to 5 (P < 0.01) or 6 (P < 0.001). Similarly, COS adsorbed more (P < 0.05) Zn at pH values of 2.5 and 6, and Cd contents at pH of 2.5 for 70 min when compared with the control. For in vivo trial, the feed-to-gain ratio, serum Cu (P < 0.01), hepatic Mn, Cr (P < 0.05) and intramuscular Cd (P < 0.01) were lower in response to COS treatment. Supplementation of COS improved (P < 0.05) meat quality of broilers in terms of lower drip loss, cooking loss and malondialdehyde content with a concomitant increase (P < 0.01) in the pH of breast meat at 24 h post mortem.

CONCLUSION

COS adsorbed heavy metal ions not only in vitro but also in broilers, and dietary supplementation with 30 mg kg^-1 COS improved growth performance, breast meat quality and oxidant status in broilers. © 2022 Society of Chemical Industry.

Facile Synthesis of chitosan-g-PVP/f-MWCNTs for application in Cu(II) ions removal and for bacterial growth inhibition in aqueous solutions

Herein in this study, chitosan-grafted-4-vinylpyridine (Cs-g-PVP) and two polymeric hybrids of Cs-g-PVP/f-MWCNTs (I and II) with 3wt% and 5wt% f-MWCNTs, respectively were prepared, characterized and used as adsorbent for the removal of Cu(II) ions from aqueous solutions in a batch process The obtained Cs-g-PVP was characterized using Fourier transform infrared spectroscopy (FT-IR) to identify its surface functional groups, in addition thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM) were performed to assess the thermal stability, the morphology and the elemental analysis of the obtained Cs-g-PVP and Cs-g-PVP/f-MWCNTs (I and II). Energy dispersive X-ray (EDX) with mapping analysis was obtained for Cs-g-PVP/Cu and Cs-g-PVP/f-MWCNTs/Cu samples that was confirming on the performance of adsorption batch process. The applicability of Langmuir adsorption isotherms was evaluated to better understand the adsorption process. Additionally, antibacterial activity of the Cs-g-PVP and the two polymeric hybrids Cs-g-PVP/f-MWCNTs (I and II) was evaluated against three Gram + ve bacteria (Staphylococcus aurous, Bacillus Subtitles and Streptococcus faecalis) and three Gram -ve bacteria (Escherichia coli, Pseudomonas aeruginosa and Neisseria gonorrhoeae. The results showed that the efficiency of Cs-g-PVP copolymer was improved after inclusion of the f-MWCNTs substrate towards adsorption of Cu(II) ions and antibacterial activity as well.

The Utilization of Algae and Seaweed Biomass for Bioremediation of Heavy Metal-Contaminated Wastewater

The presence of heavy metals in water bodies is linked to the increasing number of industries and populations. This has serious consequences for the quality of human health and the environment. In accordance with this issue, water and wastewater treatment technologies including ion exchange, chemical extraction, and hydrolysis should be conducted as a first water purification stage. However, the sequestration of these toxic substances tends to be expensive, especially for large scale treatment methods that require tedious control and have limited efficiency. Therefore, adsorption methods using adsorbents derived from biomass represent a promising alternative due to their great efficiency and abundance. Algal and seaweed biomass has appeared as a sustainable solution for environmentally friendly adsorbent production. This review further discusses recent developments in the use of algal and seaweed biomass as potential sorbent for heavy metal bioremediation. In addition, relevant aspects like metal toxicity, adsorption mechanism, and parameters affecting the completion of adsorption process are also highlighted. Overall, the critical conclusion drawn is that algae and seaweed biomass can be used to sustainably eliminate heavy metals from wastewater.

Performance of oxalic acid-chitosan/alumina ceramic biocomposite for the adsorption of a reactive anionic azo dye

A biocomposite system was developed and tested for the removal of the azo dye Reactive Red (RR195) from wastewater. The biocomposite was synthesized using ceramic particles containing 75% alumina which were coated using chitosan cross-linked with oxalic acid. The biocomposite showed high performance at low pH (maximum adsorption capacity = 345.3mg.g^-1 at pH=2.0). The physicochemical and structure characteristics of the matrix were evaluated by Z-potential, FTIR-ATR, SEM-EDS, XRD, and porosity. Langmuir sorption isotherm and pseudosecond-order model gave the best fit. The electrostatic interaction between RR195 (due to the sulfonate groups) and the free amino groups of chitosan, enabled successive desorption/regeneration cycles. The maximum removal percentage (>80%) occurred at pH=2.0 due to the cross-linking effect. Experiments at different temperatures allowed the calculation of thermodynamic parameters (ΔG, ΔS, ΔH); adsorption was spontaneous, exothermic, and enthalpy controlled. The presence of inorganic ions ([Formula: see text] ) was analyzed during the adsorption process. This novel biocomposite can be applied as a cost-effective and environmentally friendly adsorbent for anionic azo dye removal from wastewater. The application of chitosan cross-linked with oxalic acid as a coating of the ceramic support enhanced the adsorption capacity and enabled its use under acidic conditions without solubilization.

A rapid and sensitive method for separation of Cu2+ ions from industrial wastewater sample and water samples with methacrylamide-ethylene glycol dimethacrylate: A new synthesis of molecularly imprinted polymer

In this study, new molecularly imprinted polymer particles (MIP) were synthesised to extract Cu²⁺ ions from aqueous solutions using radical polymerisation. MIP was developed using the methacrylamide‐ethylene glycol dimethacrylate (EGDMA) cross linking agent, methacrylamide monomer, and ACV initiator by the radical polymerisation method. A comparison of various cross linking agents in MIP production showed that the best cross linking agents are EGDMA and gallic acid. The template ions were removed by leaching with 0.100 M HCl. The polymer particles were characterised by FTIR spectroscopy, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The effect of different parameters such as cross linkers, pH, time, maximum adsorption capacity, and kinetic and isotherm adsorption were investigated. The best conditions were determined (pH = 8.0, t = 10 min, and q_m = 262.53 mg g⁻¹). The adsorption data were best fitted by Freundlich isotherm and pseudo second order kinetic models, as well. Due to its high adsorption capacity and multi‐layer behaviour, this method is an easy, fast and safe way to extract cations. Removal of Cu²⁺ in certified tap water and rain water was demonstrated and the industrial wastewater sample (Charmshahr, Iran) with which the MIP was developed using Methacrylamide‐ Ethylene Glycol Dimethacrylate (EGDMA) was good enough for Cu²⁺ determination in matrices containing components with similar chemical property such as Co²⁺, Zn²⁺, Fe².

Highly Porous Hydroxyapatite/Graphene Oxide/Chitosan Beads as an Efficient Adsorbent for Dyes and Heavy Metal Ions Removal

Dye and heavy metal contaminants are mainly aquatic pollutants. Although many materials and methods have been developed to remove these pollutants from water, effective and cheap materials and methods are still challenging. In this study, highly porous hydroxyapatite/graphene oxide/chitosan beads (HGC) were prepared by a facile one-step method and investigated as efficient adsorbents. The prepared beads showed a high porosity and low bulk density. SEM images indicated that the hydroxyapatite (HA) nanoparticles and graphene oxide (GO) nanosheets were well dispersed on the CTS matrix. FT-IR spectra confirmed good incorporation of the three components. The adsorption behavior of the obtained beads to methylene blue (MB) and copper ions was investigated, including the effect of the contact time, pH medium, dye/metal ion initial concentration, and recycle ability. The HGC beads showed rapid adsorption, high capacity, and easy separation and reused due to the porous characteristics of GO sheets and HA nanoparticles as well as the rich negative charges of the chitosan (CTS) matrix. The maximum sorption capacities of the HGC beads were 99.00 and 256.41 mg g⁻¹ for MB and copper ions removal, respectively.

Novel amidinothiourea-modified chitosan microparticles for selective removal of Hg(II) in solution

Glutaraldehyde-crosslinked chitosan microparticles (CGP) prepared via the inversed-phase emulsification were successively modified by epichlorohydrin (ECH) and amidinothiourea (AT) as novel adsorbent (CGPET) for selective removal of Hg(II) in solution. FTIR, EA, XPS, SEM-EDX, TG, DTG, and XRD results indicated that CGPET had ample -NH₂ and CS, relative rough surface, mean diameter of ~40 μm, great thermal stability, and crystalline degree of 2.4%, beneficial to the uptake of Hg(II). The optimum parameters (pH 5, dosage 1 g/L, contact time 4 h, and initial concentration 150 mg/L) were acquired via batches of adsorption experiments. Adsorption behavior was well described by the Liu isothermal and pseudo-second-order kinetics models, and the maximum adsorption capacity was 322.51 mg/g, surpassing many reported adsorbents. Regeneration and coexisting-ion tests demonstrated that CGPET had outstanding reusability (R_r > 86.89% at the fifth cycle) and selectivity (R_s > 93%). Besides, its potential adsorption sites and mechanisms were proposed.

Highly Efficient Removal for Methylene Blue and Cu2+ onto UiO-66 Metal-Organic Framework/Carboxylated Graphene Oxide-Incorporated Sodium Alginate Beads

Herein, we report a new metal-organic framework (MOF)-based composite beads adsorbent made via incorporating UiO-66 MOF, carboxylated graphene oxide (GOCOOH) into sodium alginate for efficient removal of methylene blue dye, and Cu2+ ions. The successful fabrication of the synthesized UiO-66/GOCOOH@SA composite beads was confirmed by means of X-ray diffraction, Fourier transform infrared, scanning electron microscopy, zeta potential, X-ray photoelectron spectroscopy analysis, and thermogravimetric analysis and BET measurement. The incorporation of both UiO-66 and GOCOOH into SA beads greatly increased their adsorption efficiency for the removal of both MB and Cu2+ with maximum adsorption capacities of 490.72 and 343.49 mg/g, respectively. The removal process of both MB and Cu2+ follows the pseudo-second-order model and Freundlich isotherm model. A plausible adsorption mechanism was discussed in detail. Regeneration tests clarified that the removal efficiencies toward both MB and Cu2+ remained higher than 87% after five cycles. These results reveal the potentiality of UiO-66/GOCOOH@SA beads as an excellent adsorbent.

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.

Hydroxypropyl chitosan-based dual self-healing hydrogel for adsorption of chromium ions

A facile, environmentally benign approach had been developed for the preparation of dual self-healing and adsorption hydrogel through hydroxypropyl chitosan (HPCS), polyacrylamide (PAM) and polyvinyl alcohol (PVA). The self-healing capability of the hydrogels without any external stimulus was ascribed to dynamic Schiff-base bonds, borate bonds and hydrogen bonds, while the adsorption capacity of hydrogels came from the protonated amino group effect at a specific pH. It was demonstrated that the HPP DN hydrogel had a maximum equilibrium swelling ratio of 643% and a maximum compressive strength of 267 kPa. The weight loss of HPP DN hydrogel was 14.26% lower than that of HPCS/PAM single network hydrogel, furthermore, HPP DN hydrogel could achieve self-healing within 10 h. Due to the large number of active groups, the adsorption capacity of Cr⁶⁺ reached 95.31 mg/g. It could adsorb in a wide pH range of 1 to 6, and could describe by pseudo-first-order kinetic model and Langmuir adsorption isotherm model, which would provide a new idea for the adsorption and removal of heavy metal ions. In short, the prepared HPP hydrogel had dual self-healing ability, adsorption capacity and mechanical strength, which would make it a promising candidate for long-life adsorbent.

Polyaniline-Coated TiO2 Nanorods for Photocatalytic Degradation of Bisphenol A in Water

Polyaniline (PANI)-wrapped TiO₂ nanorods (PANI/TiO₂), obtained through the oxidative polymerization of aniline at the surface of hydrothermally presynthesized TiO₂ nanorods, were evaluated as photocatalysts for the degradation of Bisphenol A (BPA). Fourier-transform infrared spectroscopy analysis revealed the successful incorporation of PANI into TiO₂ by the appearance of peaks at 1577 and 1502 cm^-1 that are due to the C=C and C-N stretch of the benzenoid or quinoid ring in PANI. Brunauer-Emmett-Teller analysis revealed that PANI/TiO₂ had almost double the surface area of TiO₂ (44.8999 m²/g vs 28.2179 m²/g). Transmission electron microscopy (TEM) analysis showed that TiO₂ nanorods with different diameters were synthesized. The TEM analysis showed that a thin layer of PANI wrapped the TiO₂ nanorods. X-ray photon spectroscopy survey scan of the PANI/TiO₂ nanocomposite revealed the presence of C, O, Ti, and N. Photocatalytic activity evaluation under UV radiation through the effect of key parameters, including pH, contact time, dosage, and initial concentration of BPA, was carried out in batch studies. Within 80 min, 99.7% of 5 ppm BPA was attained using the 0.2 g/L PANI/TiO₂ photocatalyst at pH 10. The quantum yield (QY) of these photocatalysts was evaluated to be 9.86 × 10^-5 molecules/photon and 2.82 × 10^-5 molecules/photon for PANI/TiO₂ and TiO₂, respectively. PANI/TiO₂ showed better performance than as-synthesized TiO₂ with a rate constant of 4.46 × 10^-2 min^-1 compared to 2.18 × 10^-2 min^-1. The rate of degradation of PANI/TiO₂ was also superior to that of TiO₂ (150 mmol/g/h vs 74.89 mmol/g/h). Nitrate ions increased the rate of degradation of BPA, while humic acid consistently inhibited the degradation of BPA. LC-MS analysis identified degradation products with m/z 213.1, 135.1, and 93.1. The PANI/TiO₂ nanocomposite was reused up to five cycles with a removal of at least 80% in the fifth cycle. LC-MS results revealed three possible BPA degradation intermediates. LC-MS analysis identified degradation products which included protonated BPA, [C₁₄H₁₃O₂ ⁺], and [C₉H₁₁O⁺]. The PANI/TiO₂ nanocomposite demonstrated superior photocatalytic activity with respect to improved QY and figure of merit and lower energy consumption.

A systematic review on carbohydrate biopolymers for adsorptive remediation of copper ions from aqueous environments-part A: Classification and modification strategies

Copper is one of the most toxic heavy metals which must be eliminated from aqueous environments, according to the environmental standards. Carbohydrate biopolymers are promising candidates for synthesizing copper-adsorbent composites. It is due to unique properties such as having potential adsorptive functional sites, availability, biocompatibility and biodegradability, formability, blending capacity, and reusability. Different types of copper-adsorbent carbohydrate biopolymers like chitosan and cellulose with particular focus on the synthesizing and modification approaches have been tackled in this review. Composites, functionality and morphological aspects of the biopolymer adsorbents have also been surveyed. Further progress in the fabrication and application of biopolymer adsorbents would be achievable with special attention to some critical challenges such as the process economy, copolymer and/or (nano) additive selection, and the physicochemical stability of the biopolymer composites in aqueous media.

Preparation and characterization of poly aniline modified chitosan embedded with ZnO-Fe3O4 for Cu(II) removal from aqueous solution

Poly aniline modified chitosan embedded with ZnO/Fe₃O₄ nanocomposites were synthesized using a precipitation method and applied to the removal of Cu(II) from aqueous solution. The synthesized nanocomposite was characterized by FT-IR, XRD, FESEM, TEM, EDS, TGA, BET and zeta-potential analyses. The adsorption batch experiments were conducted as a function of five effective parameters including pH, contact time, initial concentration of copper, temperature, and adsorbent dosage using a central composite design (CCD) in response surface methodology (RSM). Contour and surface plots were used to determine the interaction effects of main factors and optimum conditions of process. The regression equation coefficients were calculated and the data confirmed the validity of second-order polynomial equation for the removal of Cu(II) with novel absorbent. Analysis of variance (ANOVA) showed a high coefficient of determination value (R²) for copper removal being 0.99. The optimum level of the pH, temperature, initial concentration of copper, adsorbent dosage and contact time for maximum Cu(II) removal (94.51%) were found to be 6.5, 31 °C, 82 mg L^-1, 0.81 g L^-1, and 51 min, respectively. It was confirmed from XPS and EDS analyses that heavy metal ions were present on the surface of nanocomposite after adsorption. The adsorption equilibrium data fitted well with the Langmuir isotherm model and the adsorption process followed the pseudo-second-order and intra-particle diffusion kinetic model. The saturated adsorption capacity is found to be 328.4 mg/g. Thermodynamics analysis suggests that the adsorption process is endothermic, with increasing entropy and spontaneous in nature. Further recycling experiments show that nanocomposite still retains 95% of the original adsorption following the 5th adsorption-desorption cycle. The effects of coexist cation ions on the adsorption of Cu(II) was also investigated under optimal condition. All the results demonstrate that nanocomposite is a potential recyclable adsorbent for hazardous metal ions in wastewater.

Novel composite films of polysaccharides and glutathione capped zinc selenide (GSH@ZnSe) quantum dots for detection of Cd2+ and Cu2+

Water-soluble glutathione capped zinc selenide (GSH@ZnSe) quantum dots (QDs) were employed to develop composite films with positively charged chitosan (CS) and negatively charged xanthan gum (XG), respectively.

Effect of medium pH on chemical selectivity of oxalic acid biosynthesis by Aspergillus niger W78C in submerged batch cultures with sucrose as a carbon source

The pH of the medium is the key environmental parameter of chemical selectivity of oxalic acid biosynthesis by Aspergillus niger. The activity of the enzyme oxaloacetate hydrolase, which is responsible for decomposition of oxaloacetate to oxalate and acetate inside the cell of the fungus, is highest at pH 6. In the present study, the influence of pH in the range of 3–7 on oxalic acid secretion by A. niger W78C from sucrose was investigated. The highest oxalic acid concentration, 64.3 g dm⁻³, was reached in the medium with pH 6. The chemical selectivity of the process was 58.6% because of the presence of citric and gluconic acids in the cultivation broth in the amount of 15.3 and 30.2 g dm⁻³, respectively. Both an increase and a decrease of medium pH caused a decrease of oxalic acid concentration. The obtained results confirm that pH 6 of the carbohydrate medium is appropriate for oxalic acid synthesis by A. niger, but the chemical selectivity of the process described in this paper was high in comparison to values reported previously in the literature.

Removal of Cu(II) from aqueous solution using synthetic poly(catechol-diethylenetriamine-p-phenylenediamine) particles

A novel poly(catechol-diethylenetriamine-pphenylenediamine)(PCEA) adsorbent was synthesized in methanol, with chelating groups supplied by catechol and diethylenetriamine, which showed a strong removal performance and efficient adsorption toward Cu(II) ions in aqueous solution. The adsorbent was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Besides, factors such as adsorbent dosage, pH, initial ionic and metal concentrations, contact time, and temperature on the adsorption of Cu(II) were studied. The data revealed that the adsorption followed a pseudo-second order kinetic model and the adsorption rate was influenced by the intra-particle diffusion. Furthermore, the adsorption process followed the Langmuir isotherm model, and the maximum adsorption capacity (Qm) was 44.2mg/g at 298K in simulated wastewater. The value of ΔG (kJ/mol) and ΔH (kJ/mol) also demonstrated that the adsorption process was spontaneous and endothermic. Studies revealed that PCEA particles were powerful and stable for the removal of Cu(II) in water, and it could be directly applied to the Cu(II)-contaminated water.

Structure characterization of the non-crystalline complexes of copper salts with native cyclodextrins

The characterization of non-crystalline complexes is very difficult when techniques like X-ray diffraction or NMR are not available. We propose a simple procedure to characterize the physicochemical properties of amorphous new coordination compounds between cyclodextrins (CD) and Cu²⁺ salts, by several techniques as TGA, FT-IR, EPR.

Antimicrobial Properties of Chitosan-Alumina/f-MWCNT Nanocomposites

Antimicrobial chitosan-alumina/functionalized-multiwalled carbon nanotube (f-MWCNT) nanocomposites were prepared by a simple phase inversion method. Scanning electron microscopy (SEM) analyses showed the change in the internal morphology of the composites and energy dispersive spectroscopy (EDS) confirmed the presence of alumina and f-MWCNTs in the chitosan polymer matrix. Fourier transform infrared (FTIR) spectroscopy showed the appearance of new functional groups from both alumina and f-MWCNTs, and thermogravimetric analysis (TGA) revealed that the addition of alumina and f-MWCNTs improved the thermal stability of the chitosan polymer. The presence of alumina and f-MWCNTs in the polymer matrix was found to improve the thermal stability and reduced the solubility of chitosan polymer. The prepared chitosan-alumina/f-MWCNT nanocomposites showed inhibition of twelve strains of bacterial strains that were tested. Thus, the nanocomposites show a potential for use as a biocide in water treatment for the removal of bacteria at different environmental conditions.

Site energy distribution analysis of Cu (Ⅱ) adsorption on sediments and residues by sequential extraction method

Many models (e.g., Langmuir model, Freundlich model and surface complexation model) have been successfully used to explain the mechanism of metal ion adsorption on the pure mineral materials. These materials usually have a homogeneous surface where all sites have the same adsorption energies. However, it's hardly appropriate for such models to describe the adsorption on heterogeneous surfaces (e.g., sediment surface), site energy distribution analysis can be to. In the present study, the site energy distribution analysis was used to describe the surface properties and adsorption behavior of the non-residual and residual components extracted from the natural aquatic sediment samples. The residues were prepared "in-situ" by using the sequential extraction procedure. The present study is intended to investigate the roles of different components and the change of site energy distribution at different temperatures of the sediment samples in controlling Cu (Ⅱ) adsorption. The results of the site energy distribution analysis indicated firstly, that the sorption sites of iron/manganese hydrous oxides (IMHO) and organic matter (OM) have higher energy. Secondly, light fraction (LF) and carbonates have little influence on site energy distribution. Finally, there was increase in site energies with the increase of temperature. Specially, low temperature (5 °C) significantly influenced the site energies of IMHO and OM, and also had obvious effect on the energy distribution of the sediments after removing target components. The site energy distribution analysis proved to be a useful method for us to further understand the energetic characteristics of sediment in comparison with those previously obtained.

Preparation of a silver nanoparticle-based dual-functional sensor using a complexation–reduction method

A dual-functional sensor based on silver nanoparticles was synthesized by a two-stage procedure consisting of a low-temperature chitosan–Ag⁺ complexation followed by a high-temperature reduction of the complex to form chitosan-capped silver nanoparticles (CS-capped Ag NPs).