Chitosan-Based Hydrogels for the Recovery of Precious Metals

Abstract

Chitosan (an aminopolysaccharide), cross-linked with glutaraldehyde, is very efficient for Pd(II) and Pt(IV) recovery from acidic solutions (pH 2). Due to poorly porous properties, it is necessary to condition the biopolymer as hydrogels. The uncontrolled drying of hydrogels depreciates the diffusion properties of original materials. A different method (to the acidic dissolving/alkaline neutralization procedure) has been used: after chitosan dissolving in acetic acid solution, the viscous solution was dropped into an ionotropic gelling solution (polyphosphate and glutaraldehyde to form stable gel beads with improved porosity. The restriction of diffusion properties due to drying step was less drastic with the modified procedure: a few hours were sufficient for reaching equilibrium while more than two days were required for standard material