KINETICS OF SURFACE-CATALYZED OXIDATION OF SULFUR(IV) BY DIOXYGEN IN AQUEOUS SUSPENSIONS OF COBALT(II) OXIDE

A comparative rate analysis of autoxidation of sulphur(IV) in CoO suspension, leachate solution and blank reaction SuggeStS the reaction to be surface catalyzed. In acetate buffers, the experimental rate law is: R(obs) = R(un) + (k3 + k4/[H+])[CoO][S(IV)][O2] where R(un) is the rate of uncatalyzed reaction. The suggested mechanism requires the adsorption of both S(IV) and O2 on the particle surface. Subsequently, the adsorbed species are activated resulting in the oxidation of sulphur(IV), probably through intervention of multiple oxidation states of cobalt.