Ion Exchange Treatment of Cobalt Acetate Solutions to Remove Iron(III) Impurity

Abstract

The possibility of removing an iron(III) impurity from cobalt acetate solutions by sorption was examined. Among a number of tested ion exchange resins with various functional groups (Purolite С150 sulfonic cation exchange resin, Purolite А500 strongly basic anion exchange resin, complexing ion exchange resins Purolite S930 with iminodiacetate and Purolite S950 with aminomethylenephosphonic acid groups, Purolite S957 cation exchange resin containing phosphonic and sulfonic acid groups simultaneously), only the ion exchange resins containing phosphonic acid groups, namely, Purolite S950 amphoteric resin and Purolite S957 cation exchange resin, are capable of the iron(III) sorption, with the latter resin showing considerably higher performance. The iron(III) distribution coefficients in sorption on these resins reach a maximum at рН 3.8–5.1. When passed through a column packed with Purolite S957 cation exchange resin, cobalt acetate solutions containing 40.6 and 57.2 g L–1 Co and 21 and 24 mg L–1 Fe undergo deep iron removal to its residual concentration no higher than 1.0–1.5 mg L–1. The sorbed iron(III) is virtually completely eluted from the cation exchange resin with 9 column volumes of 1.5 М sulfuric acid containing 10 g L–1 ascorbic acid after the resin pretreatment with an ascorbic acid solution.