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

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.