Influence of chitosan characteristics on polymer properties: II. Platinum sorption properties

The sorption of platinum on glutaraldehyde cross-linked chitosan was investigated at pH 2, using several chitosan samples prepared from different origins and characterized by different molfractions of N-acetylation (F-A). The influence of material conditioning was also tested: chitosan was dissolved and then re-precipitated and/or dried (using either oven-drying or freeze-drying). The influence of the different characteristics and treatments on both sorption isotherms and uptake kinetics was checked. Part I has studied the effect of preparation and source on sample crystallinity. Shrimp chitosan has a greater sorption affinity for platinum than fungal chitosan and squid chitosan respectively. Sorption kinetics were found comparable for fungal chitosan and shrimp chitosan, while diffusion was more restricted in squid chitosan due to the higher crystallinity. Decreasing the F-A increased sorption capacity for shrimp chitosan but decreased sorption levels for squid material. While F-A did not influence sorption kinetics for shrimp material it strongly decreased kinetics for squid chitosan. The type of drying procedure hardly affected sorption kinetics and isotherms but when a re-precipitation step was included in the preparation procedure, the material had to be freeze-dried to maintain high sorption properties. The freeze-drying did not control sorption performance, except in the case of re-precipitated material. (C) 2003 Society of Chemical Industry.