Dual-Mode Solution Plasma Processing for the Production of Chitosan/Ag Composites with the Antibacterial Effect.

The development of novel biocompatible and biodegradable materials for medical applications has been drawing significant interest in the scientific community for years. Particularly, chitosan loaded with silver nanoparticles (Ag NPs) has a strong antimicrobial potential and could be applied, for example, as wound dressing material. In this work, chitosan/Ag NP composites were produced utilizing a single-step plasma-solution process, which is simple and environmentally friendly. An acetic solution of chitosan containing AgNO3 was treated by the direct current (DC) atmospheric pressure glow discharge, with the liquid serving as either cathode or anode. The plasma-solution system with liquid anode is more useful for the production of Ag NPs. Nevertheless, the NP size is comparable for both cases. The plasma treatment with both polarities led to chitosan degradation. The cleavage of glucosidic chains mostly occurred in the system with the liquid cathode, whereas the side oxidation reactions took place when the solution served as the anode. The oxidation processes were possibly induced by the hydrogen peroxide H2O2 efficiently formed in the last case. The composite materials produced with both polarities of liquid electrode demonstrated the bactericidal action against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus, and Gram-positive Bacillus subtilis.

Adsorption removal of anionic dyes from aqueous solutions by chitosan nanoparticles deposited on the fibrous carrier.

The synthesis, characterization and environmental application of chitosan based material stable in acidic media for adsorption of anionic dyes were investigated. The adsorption material is chitosan nanoparticles immobilized on a fibrous carrier (CPF). The choice of optimal conditions for the preparation of chitosan particles and their immobilization on a chemically activated polyethylene terephthalate (PET) fiber is justified. Immobilized nanoparticles showed high adsorption rates and dye binding capacity (300-1050 mg g-1) depending on the dye type. Anionic phthalocyanine dyes having different molecular sizes, different nature and number of anionic groups were used as model adsorbates. The experimental isotherm data and a linear correlation coefficients (rL2 > 0.99) have shown that the dyes adsorption on CPF is best predicted by the Langmuir isotherm. The adsorption rate has been found to conform to pseudo-second-order kinetics with a good correlation (R2 > 0.99) with intra-particle diffusion as one of the rate determining steps. It has been is established that the sorption rate and the limiting sorption capacity decrease with the increment in the dye molecule size. The process of adsorption of the dyes on the CPF is pH-insensitive in the pH range of 2-8. The adsorption saturated CPF could be effectively regenerated by a simple alkaline washing.