REDUCTIVE-ELUTION BEHAVIOR OF CHLORO FE(I II)-COMPLEXES FROM THE ION-EXCHANGER

In order to investigate the redox reactions of metal complexes in the ion exchanger, the reductive-elution behavior of chloro Fe(III)-comple xes adsorbed in an anion-exchanger from hydrochloric acid solution to non-adsorptive Fe(II) was examined by using Sn(II) and V(III) as reduc ing agents. The current-potential curves of Fe(III)/Fe(II) in hydrochl oric 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-c omplexes formation on the redox potential were examined. The adsorptio n-elution experiments were carried out using both batch and column met hod, and the effects of reductants as well as hydrochloric acid concen tration on the elution behavior were discussed. The redox potential of Fe(III)/Fe(II) decreased with increasing hydrochloric acid concentrat ion, revealing that the reduction of Fe(III) to Fe(II) becomes difficu lt due to the formation of chloro-complexes. The Fe(III) adsorbed in t he ion-exchanger was reduced and eluted rapidly by Sn(II), while the r eductive-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 b etween Fe(III) and V(III) happened in the solution phase.