Oxidation of sulfurous acid on a graphite anode in the presence and absence of cobalt ion during electrodeposition of copper from a acidic sulfate bath

Abstract

The electro-oxidation of sulfurous acid in the presence and absence of bivalent aqua cobalt ion on a graphite anode was studied by linear sweep voltammetry. The study shows the presence of two different distinct regions with significant increase in the anodic current density current at different potentials; one is between +0.4V- +0.8V and the other is +0.8V - +1.2V that may correspond to the probable occurrence of two different path of oxidation reactions of sulfurous acid in aqueous acidic sulfate solutions (pH 0.7). The increase in the limiting current density between +0.8 - +1.2 V is more with an increase in the initial concentration of H2SO3 than that observed for the former region. The relative decrease in the anode potential with increase in initial H2SO3 concentration is more at higher current density (>150 A/m2). The addition of Co2+ (aq) to the copper electrolyte containing H2SO3 has no effect on the anode potential. The observations are compared with the previous findings obtained with the graphite as well as platinum anodes and were discussed.