Platinum and palladium sorption on chitosan derivatives

Chitosan is a unique biopolymer due to its cationic properties in acidic so lutions. Protonation of the amino groups induces ion-exchange properties th at can be used for anion recovery. As this sorbent is soluble in acidic med ia, it may be necessary to reinforce its chemical stability using a glutara ldehyde cross-linking treatment. Sorption properties are strongly influence d by the pH of the solution and the presence of competitor anions, especial ly sulfate anions. This competitor effect may be decreased by the grafting of sulfur derivatives on the chitosan backbone using glutaraldehyde as a li nker between the polysaccharide chains and the substituent. Several techniq ues such as FTIR and SEM-EDAX were used for the chemical characterization o f chitosan substitution and for the location of PGM sorption on the sorbent . Sorption isotherms and kinetics were investigated and compared for cross- linked materials and substituted polymers, and special attention was given to the influence of competitor anions. The grafting of sulfur compounds inc reased sorption capacities and decreased the competition of sulfate and chl oride anions. While cross-linked materials sorbed platinum and palladium th rough anion exchange, the grafting of sulfur moities gave chelating functio nalities to the ion-exchange resin.