The Autoxidation of Co(II)/2-Aamino- 2-Hydroxymethyl-1,3-Propanediol in the Presence of Mn(II) and S(IV)

The oxidation of Co(II)/2-amino-2-hydroxymethyl-1,3-propanediol (TRIS) by dissolved oxygen is accelerated by S(IV) oxides (SO3 and HSO3-). The effectiveness of this autocatalytic process is controlled by S(IV), manganese(II) and oxygen concentrations. The synergistic effect of Mn(II) is clearly evaluated and depends on the medium acidity and TRIS concentration, it must be related to the speciation of Co(II)/Co(III) and Mn(II)/Mn(III) complexes and the S(IV) species that participate in the rate determining step. The metal ions in the trivalent oxidation state react with S(IV) to initiate a radical chain reaction in which S(IV) is oxidized to sulfate and the metal ion is reduced to the divalent state.