Radiation-induced dissolution of colloidal manganese oxides

Abstract

The reductive dissolution of several well-characterized suspensions of manganese oxides (α-, δ-, γ-MnO2, and Mn5O8) under steady γ-irradiation at pH 3 has been studied. Radiolytically produced reducing radicals (e.g., (CH3)2COH, CH3CHOH, HO2, and viologen radicals) can be quantitatively captured by the oxide suspension to release Mn2+ ions into the solution. The radiolytically produced H2O2 similarly leads to quantitative dissolution of the oxide. The rate-determining step in the dissolution process is slower than the diffusion-controlled limit. The stoichiometry of the dissolution process under complete scavenging of the radicals is determined by the oxidation state of the oxide (x in MnOx)..