Reductive-elution behavior of chloro Fe(III)-complexes from the ion exchanger

Abstract

In order to investigate the redox reactions of metal complexes in the ion exchanger, the reductive-elution behavior of chloro Fe(III)-complexes adsorbed in an anion-exchanger from hydrochloric acid solution to non-adsorptive Fe (II) was examined by using Sn(II) and V(III) as reducing agents. The current-potential curves of Fe(III)/Fe(II) in hydrochloric acid solutions of concentrations ranging from 0.1 to 9.0 mol dm-3 were measured by the cyclic voltammetry and the effects of chloro-complexes formation on the redox potential were examined. The adsorption-elution experiments were carried out using both batch and column method, and the effects of reductants as well as hydrochloric acid concentration on the elution behavior were discussed. The redox potential of Fe(III)/Fe(II) decreased with increasing hydrochloric acid concentration, revealing that the reduction of Fe(III) to Fe(II) becomes difficult due to the formation chloro-complexes. The Fe(III) adsorbed in the ion-exchanger was reduced and eluted rapidly by-Sn(II), while the reductive-elution was very slow by using V(III). This is considered to result from the difference in the adsorbability of the reductants, and the experimental results suggested that the redox reaction between Fe(III) and Sn(II) occurred mainly in the ion-exchanger phase and that between Fe(III) and V(II) happened in the solution phase.