Kinetic study of the electrolytic oxidation of manganese(II) to manganese(III) in sulphuric acid

Abstract

The oxidation of manganese(II) at a rotating oxide-covered platinum disc electrode has been studied, with additional data on glassy carbon. Data for the reduction of manganese(III) at the Pt electrode are also reported. Reaction orders in [Mn^II] and [Mn^III], as well as the effect of [SO^2–₄], are reported, as is the current efficiency for the oxidation process. It is shown, using partial current values obtained by chemical analysis, that Mn^II oxidation and the concurrent oxygen evolution do not proceed independently, and attempts to determine the rate of the former by subtraction of the rate of oxygen evolution in the absence of Mn^II leads to invalid results. The oxidation kinetics of Mn^II are controlled by formation of a film at the anode surface, and the role of this process is considered.