Determination of antimony(III) and antimony(V) in copper plant electrolyte by anodic stripping voltammetry

The concentration of antimony in copper plant electrolyte needs to be known at the ppm level. Spectroscopic techniques for trace metal determination in this electrolyte, such as atomic absorption and inductively coupled plasma (ICP) spectrometry only enable total antimony to be determined, whereas ideally the concentration of both the antimony(III) and antimony(V) oxidation states needs to be known. For the determination of antimony(III) and antimony(V) by differential pulse anodic stripping voltammetry (DPASV), the similar stripping peak potentials of -0.37 V (vs. Ag/AgCl) for copper and -0.27 V (vs. Ag/AgCl; for antimony in 5 M HCl mean that concentrations of copper greater than 6 times that of antimony cause difficulties in resolving the antimony and copper stripping peaks. In this article, a simple procedure is reported for the determination of antimony(III) and (V) in copper plant electrolyte after separation of antimony from copper by passing an ammoniacal solution of plant electrolyte through a column of Chelex-100 ion-exchange resin. Most of the copper is retained on the column so that the determination of antimony(III) and (V) by DPASV is possible after addition of hydrochloric acid to the eluent. Total antimony is determined in 5 M HCl and antimony(III) in 0.1 M HC1. Total antimony concentrations correlate well with data obtained by ICP and recoveries of antimony in both oxidation stares are > 96%.