Adsorption properties of carboxymethyl-chitosan and cross-linked carboxymethyl-chitosan resin with Cu(II) as template

Chitosan is an efficient metal chelater, but its practical use is limited due to the stability in acid solutions, adsorption capacities and selectivity. In the study, we attempt to find a more effective new adsorbent based on cross-linked chitosan derivative with Cu(II) as template, so a series of N,O-carboxymethyl-chitosan (CMC) with different degree of substitution (DS) were synthesized, and the influence factors on the adsorption capacities of CMC for Cu(II) ions measured in aqueous acetate, chloride and sulfate solutions were discussed, which indicate that the CMC show higher adsorption capacities in sulfate solution than in solutions of acetate or chloride. The cross-linked CMC with Cu(II) ions in sulfate solution as template (the template CMC resin)was prepared by cross-linked with glutaraldehyde. The adsorption selectivity of the template CMC resin in metal ions mixture solution was investigated. The result indicates that the template CMC resin can selectively adsorption the Cu(II) ions from the mixed solution containing three kinds of metal ions. It was also found that the template CMC resin has good reusability and adsorption capacities for Cu(II) ions after reuse for 10 times. The IR spectra and XPS data revealed that the sorption of CMC and the template CMC resin for Cu(II) ions are a chelate process between Cu(II) and the carboxyl, amino, and hydroxyl groups, but there is difference complexes structures between CMC and the template CMC resin.