Eugenia umbelliflora mediated reduction of silver nanoparticles incorporated into O-carboxymethylchitosan/y-Fe2O3: Synthesis, antimicrobial activity and toxicity.

The purpose of this study was to synthesize a new magnetic material with antimicrobial properties, incorporated into a biopolymer and containing silver nanoparticles (Ag NP) prepared extract of Eugenia umbelliflora as a reducing agent. Silver nanoparticles incorporated into magnetic nanocomposite O-carboxymethylchitosan/y-Fe2O3/Ag0 (CMAgE) composite were synthesized using an extract of E. umbelliflora. The antimicrobial activity of the pathogenic microorganism is reported here. The synthesized nanoparticles were also characterized, and quantified by Ag analysis. The minimum inhibitory concentrations (MIC) of CMAgE against Staphylococcus aureus, Escherichia coli, and Candida albicans were 16.5, 1000 and 500 µg/mL, respectively. The results show that these materials have significant synergistic effect on each other. The potential phytotoxic effect of the nanocomposites was evaluated using Cucumis sativus seeds. The positive values for seedling elongation inhibition (SEI) show that CMAgE and methanol extract of Eugenia umbelliflora (Eug) cause growth inhibition at a concentration of 1000 mg/L. The germination index (GI) values of 40% and 80% at 1000 mg/L, for CMAgE and Eug, respectively, showed inhibition of germination. CMAgE and Eug showed cytotoxic effects against Artemia salina nauplii, with LC50 values of 72.5 µL/mL and < 5.0 µL/mL respectively, after 48 h.

Nanoecotoxicology study of the response of magnetic O-Carboxymethylchitosan loaded silver nanoparticles on Artemia salina.

Magnetic silver nanoparticles (MNPAg) are interesting nanotechnology materials with borderless environmental science, that can be used to disinfect water contaminated with pathogenic bacteria. The use of MNPAg leads to increased risk of nanomaterial contamination in the environment, especially natural water sources, with harmful effects on the ecosystem. This study investigating survival and enzyme activity of magnetic O-carboxymethylchitosan loaded silver nanoparticle on Artemia salina. The results showed that mortality increased with increasing concentrations of MNPAg. O-Carboxymethylchitosan loaded silver nanoparticles were found to be more toxic, with a LC50 of 902.1 mg/L for γ-Fe2O3/Ag without reducing agent. Accumulation of silver on Artemia salina depends on the type of nanoparticle. Accumulation of nanoparticle containing polymers (carboxymethylchitosan/γ-Fe2O3/Ag without reducing agent, carboxymethylchitosan/γ-Fe2O3/Ag reduced with sucrose and carboxymethylchitosan/γ-Fe2O3/Ag reduced with NaBH4) were found to be higher than γ-Fe2O3/Ag reduced with NaBH4, γ-Fe2O3/Ag reduced with sucrose and γ-Fe2O3/Ag without reducing agent under the same experimental conditions. The antioxidant enzyme (CAT, SOD and GST) activities increased slightly following exposure, indicating that the toxic effects are related to oxidative stress. The combined results so far indicate that MNPA does not have the potential to affect aquatic organisms when released into the ecosystem.

Adsorption of hexavalent chromium by crosslinked chitosan-iron(III) in an air-lift reactor.

Column experiments were conducted in an airlift reactor containing a certain amount of crosslinked chitosan-iron(III) (Ch-Fe), to examine the effects of adsorbent mass, flow rate, and influent concentrations on Cr(VI) removal. The breakthrough time increased with an increase in Ch-Fe mass, but decreased with an increase in initial Cr(VI) concentration. The exhaustion time decreased with an increase in initial Cr(VI) concentration. The capacity at the breakthrough point increased with an increase in Ch-Fe mass, flow rate, and initial Cr(VI) concentration. The capacity at the exhaustion point increased with an increase in flow rate, but showed no specific trend with an increase in initial Cr(VI) concentration. The bed volumes at breakthrough point increased with an increase in Ch-Fe, flow rate and Cr(VI) concentration. The adsorbent exhaustion decreased with an increase in flow rate and Ch-Fe, but increased with an increase in initial Cr(VI) concentration. Columns with large amounts of Ch-Fe are preferable for obtaining optimal results during the adsorption process. The higher the flow velocity, the better the column performance. The Thomas, Clark and Yoon-Nelson models were applied to the experimental results. Good agreement was observed between the predicted theoretical breakthrough curves and the experimental results.

Adsorption of Remazol Red 198 onto magnetic N-lauryl chitosan particles: equilibrium, kinetics, reuse and factorial design.

PURPOSE: The discharge of colored effluents from industries is an important environmental issue and it is indispensable to remove the dyes before the water gets back to the rivers. The magnetic adsorbents present the advantage of being easily separated from the aqueous system after adsorption by positioning an external magnetic field. METHODS: Magnetic N-lauryl chitosan (L-Cht/γ-Fe(2)O(3)) particles were prepared and characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and vibrating sample magnetometry. Remazol Red 198 (RR198) was used as a reactive dye model for adsorption on L-Cht/γ-Fe(2)O(3). The adsorption isotherms were performed at 25°C, 35°C, 45°C, and 55°C and the process was optimized using a 2(3) factorial design (analyzed factors: pH, ionic strength, and temperature). The desorption and regeneration studies were performed in a three times cycle. RESULTS: The characterization of the material indicated that the magnetic particles were introduced into the polymeric matrix. The pseudo-second order was the best model for explaining the kinetics and the Langmuir-Freundlich was the best-fitted isotherm model. At room temperature, the maximum adsorption capacity was 267 mg g(-1). The material can be reused, but with a decrease in the amount of adsorbed dye. CONCLUSIONS: L-Cht/γ-Fe(2)O(3) is a promising material to remove RR198 and probably other similar reactive dyes from aqueous effluents.

Adsorption of As(III) on chitosan-Fe-crosslinked complex (Ch-Fe).

It was reported the adsorption of As(III) on the surface of the chitosan-Fe-crosslinked complex. Theoretical correlation of the experimental equilibrium adsorption data for As(III)/Ch-Fe system is best explained by the non-linearized form Langmuir-Freundlich isotherm model. At optimum conditions, pH 9.0, the maximum adsorption capacity, calculated using the Langmuir-Freundlich isotherm model was 13.4 mg g⁻¹. The adsorption kinetics of As(III) onto Ch-Fe are described by the pseudo-first-order kinetic equation. The results of the Mössbauer spectroscopy showed that there is no redox process on the surface of the adsorbent.