Pulse radiolytic studies of aqueous Mn(CIO4)2 solutions

Using Mn(ClO4)2, the reactions of Mn2+ with CO2-, e-/sub aq/, OH, and O2- were studied at pH 6.7. The following reaction rate constants were measured: k(Mn2+ + CO2-) less than 2 x 105 M-1 s-1; k(Mn2+ + e-/sub aq/) = (9 +- 2) x 106 M-1 s-1 (ionic strength 0.15 to 0.5 M); k(Mn2+ + OH) = (3.4 +- 0.8) x 107 M-1 s-1; k(Mn2+ + O2-) = (1.1 +- 0.2) x 108 M-1 s-1 (0.01 M formate). O2- radical ions react with Mn2+ and produce Mn3+ or MnO2+ ions. The reaction was found to be reversible, and an equilibrium constant K = (1.5 +- 0.6) x 104 M-1 was measured at pH 6.7. Mn2+, however, does not catalyze the dismutation of O2-. The disproportionation of Mn(III) (as MnOH2+) and the subsequent nucleation of the product MnO2 are reported