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

摘要

The influence factors of the pH value, the degree of substitution (DS) of carboxymethyl-chitosan (CMC) and the dosage of cross-linking agent on the adsorption for Zn(Ⅱ) ion were investigated, and then the cross-linked CMC resin with Zn(Ⅱ) as template ion was synthesized at the optimum adsorption conditions for Zn(Ⅱ) ions. The adsorption properties and selectivity for Cu(Ⅱ), Co(Ⅱ), Ni(Ⅱ), Zn(Ⅱ), Cd(Ⅱ), and Hg(Ⅱ) ion were discussed. The results showed that the adsorption capacities of the resin for above metal ions are lower than those of CMC, but the selectivity for Zn(Ⅱ) was greatly increased. The adsorption mechanisms of CMC and the resin for zinc sulfate have also been investigated by means of X-ray photoelectron spectroscopy (XPS), IR spectra and SEM. The XPS and FT-IR spectra reveal that CMC and the resin coordinated with Zn(Ⅱ) mainly through oxygen atom in the -CH_2COO- and -OH groups, and nitrogen atom in the -NH_2 group of the polymer chain. The SEM results show that the Zn(Ⅱ) distribute on the surface of the resin-Zn(Ⅱ) complex uniformly, while distribute on the surface of CMC-Zn(Ⅱ) complex in the bulk.