Adsorption of Metal Ions on Chitosan and Chemically Modified Chitosan and Their Application to Hydrometallurgy

Abstract

Crosslinked copper(II)-complexed chitosan was prepared to avoid the dissolution in various aqueous acidic media since chitosan, as it is, dissolves in aqueous solutions of organic acids and inorganic acids in some concentration regions except for sulfuric acid solutions. Adsorption of various metal ions from aqueous ammonium nitrate solution on the crosslinked copper(II)-complexed chitosan was investigated in terms of pH dependence on the distribution coefficient of each metal ion. It was found to have much higher selectivity than a commercial iminodiacetic acid type of chelating resin for the mutual separation of metal ions; especially noticeable are: the high selectivities to gallium and indium over zinc, to aluminum and iron(III) over zinc and to nickel over cobalt. Based on these characteristic adsorption behaviors of chitosan, several practical hydrometallurgical processes were proposed for the purification of some metals.