Improved Adsorption Capacity of EDTA-type Chitosan for Separation of Rare Earths

Abstract

By optimizing the raw material ratio for the preparation of ethylenediaminetetraacetic acid-type chitosan (EDTA-type chitosan), the extraction efficiency of rare earth elements was improved. The synthesis with a lower concentration ratio of chitosan to acetic acid than that in the previously reported preparation method was confirmed by IR spectra that the peak assigned as the carboxyl group of EDTA was drastically decreased and the amide bond reaction between chitosan and EDTA was more facilitated. In the preparation method of this work, the amide formation was preferable to the competitive acetylation of chitosan. By the optimizing preparation conditions, the adsorption capacities for Nd, Sm, Tb, and Dy were improved about twice. On the contrary, the separation factor of rare earths was not changed, and it is suggested that other compounds having adsorption ability were not produced. EDTA-type chitosan was applied to chromatographic separation of La, Nd, Sm, Tb, and Dy. In the column method, it was confirmed that lighter rare earth sequentially eluted from the column, therefore it has been proved that adsorption of lighter rare earth was substituted by heavier rare earth.