The biomedical and therapeutic importance of chitosan and chitosan derivatives is the subject of interdisciplinary research. In this analysis, we intended to consolidate some of the recent discoveries regarding the potential of chitosan and its derivatives to be used for biomedical and other purposes. Why chitosan? Because chitosan is a natural biopolymer that can be obtained from one of the most abundant polysaccharides in nature, which is chitin. Compared to other biopolymers, chitosan presents some advantages, such as accessibility, biocompatibility, biodegradability, and no toxicity, expressing significant antibacterial potential. In addition, through chemical processes, a high number of chitosan derivatives can be obtained with many possibilities for use. The presence of several types of functional groups in the structure of the polymer and the fact that it has cationic properties are determinant for the increased reactive properties of chitosan. We analyzed the intrinsic properties of chitosan in relation to its source: the molecular mass, the degree of deacetylation, and polymerization. We also studied the most important extrinsic factors responsible for different properties of chitosan, such as the type of bacteria on which chitosan is active. In addition, some chitosan derivatives obtained by functionalization and some complexes formed by chitosan with various metallic ions were studied. The present research can be extended in order to analyze many other factors than those mentioned. Further in this paper were discussed the most important factors that influence the antibacterial effect of chitosan and its derivatives. The aim was to demonstrate that the bactericidal effect of chitosan depends on a number of very complex factors, their knowledge being essential to explain the role of each of them for the bactericidal activity of this biopolymer.

In this paper the preparation and characterization of some chelating resins, phosphonate grafted on polystyrene−divinylbenzene supports, are reported. The resins were prepared by an Arbuzov-type reaction between chloromethyl polystyrene−divinylbenzene copolymers and triethylphosphite, yielding the phosphonate ester copolymer (resin A). This can be hydrolyzed by HCl to yield the phosphonate/phosphonic acid copolymer (resin B). The phosphonate resins A and B were characterized by determination of the phosphorus content, infrared spectrometry, and thermal analysis. The total sorption capacity of the phosphonate ester functionalized resin (A) and phosphonate/phosphonic acid functionalized resin (B) for divalent metal ions such as Ca2+, Cu2+, and Ni2+ was studied in aqueous solutions. Resin A retains ∼3.25 mg of Ca2+/g of copolymer and 2.75 mg of Cu2+/g of copolymer, but retains no Ni2+ at pH 1. On the other hand, resin B retains 8.46 mg of Ca2+/g of copolymer, 7.17 mg of Cu2+/g of copolymer, and no Ni2+ at pH 1. Efficient Ni2+ retention was observed at pH 7 only for the phosphonate/phosphonic acid functionalized resin (B) at the level of 19 mg of Ni2+/g of polymer B. Polymer A was incapable of retaining Ni2+ at pH 7.

ABSTRACT:The adsorption performance of a low-cost adsorbent (IS), viz. an iron-containing waste sludge arising during a hot-dip galvanizing process, towards the removal of As(III) ions from synthetic aqueous solutions and natural underground water was examined. The adsorption process was best described by the pseudo-second-order kinetic equation. The equilibrium adsorption data were well described by the Langmuir model. The value of the dimensional separation factor, R L , indicated favourable adsorption. The maximum adsorption capacity of IS was 625 µg As(III)/g. The variation in the extent of adsorption with temperature was used to evaluate the thermodynamic parameters for the adsorption process. The values of ∆H 0 and ∆G 0 obtained demonstrated that the adsorption process was exothermic and spontaneous. The studied material exhibited an excellent As(III) ion adsorption performance from both synthetic solutions and a natural water sample. Moreover, no secondary contaminated substances arise if the exhausted adsorbent is recycled (e.g. in glass applications).

Adsorption of rare earth metals, Eu (III) and Nd (III) was investigated on a new environmental friendly material, thiourea functionalized cellulose. Before usage, the synthesized material was characterized by Fourrier Transform Infrared spectroscopy and energy dispersive X-ray analysis. The influence of adsorption parameters (adsorbent dosage, time, temperature and initial metal concentration) on adsorption capacity was investigated. Experimental data were fitted by using the pseudo-first-order and pseudo-second-order kinetic models. Simultaneously thermodynamic and equilibrium studies have been carried out using Langmuir, Freundlich and Sips isotherm. Maximum adsorption capacities were reached in 30 minutes at 298 K having the value of 27 mg/g for Eu (III) and 73 mg/g for Nd (III).