OXIDATION OF MANGANESE(II) BY OZONE AND REDUCTION OF MANGANESE(III) BY HYDROGEN-PEROXIDE IN ACIDIC SOLUTION

Manganese(II) is oxidized by ozone in acid solution, k = (1.5 +/- 0.2) x 10(3) M-1 s(-1) in HClO4 and k = (1.8 +/- 0.2) x 10(3) M-1 s(-1) in H2SO4. The plausible mechanism is an oxygen atom transfer from O-3 to Mn2+ producing the manganyl ion MnO2+, which subsequently reacts rapi dly with Mn2+ to form Mn(III). No free OH radicals are involved in the mechanism. The spectrum of Mn(III) was obtained in the wave length ra nge 200-310 nm. The activation energy for the initial reaction is 39.5 kJ/mol. Manganese(III) is reduced by hydrogen peroxide to Mn(II) with k(Mn(III) + H2O2) = 2.8 x 10(3) M-1 s(-1) at pH 0-2. The mechanism of the reaction involving formation of the manganese(II)-superoxide comp lex and reaction of H2O2 with Mn(IV) species formed due to reversible disproportionation of Mn(III), is suggested. (C) 1998 John Wiley & Son s, Inc.