Preparation and characterization of crosslinked chitosan based hydrogels

An interpenetration network (IPN) ion-imprinting membrane was synthesized using silver ions as template for adsorption and removal of silver ions from aqueous solutions. The membrane was obtained via cross linking of chitosan (CS), polyvinyl alcohol (PVA), and blend chitosan/polyvinyl alcohol using glutaraldehyde (GA) as cross linker. Non-ion imprinted membrane was also synthesized. Chitosan and polyvinyl alcohol are not very compatible in the chitosan/ polyvinyl alcohol blended hydrogel membrane and the thermostability of the membranes is enhanced by glutaraldehyde as crosslink agent. Later synthesis, the membranes were immersed in 1 M sodium hydroxide, followed by repeatability washing with deionized water to eliminate any unreacted glutaraldehyde. Quality analysis was applied on the samples by using Tollen reagent for the determination of the unreacted glutaraldehyde. The characterization with different methods (FTIR, TGA, XRD, and SEM) for non-imprinted and silver ion imprinted membrane were examined. FT-IR analysis implies that the coordinating atoms may be nitrogen atom of amino in chitosan and oxygen atom of hydroxide in polyvinyl alcohol. Morphology and properties of silver ion-imprinted membranes were studied compared with non-imprinted and chitosan. The silver-imprinted membranes can be regenerated by using ethylenediaminetetraacetic acid and thiourea in hydrochloric acid. The amounts of silver-ions were determined by the atomic absorption spectroscopic analysis. As a result, it was found that thiourea in hydrochloric acid solution had higher removal capacity for silver (I) ions when compared with ethylenediaminetetraacetic acid.