Radiation-induced dissolution of chromium oxide in aqueous solutions

Gamma irradiation of suspensions of a commercial sample of α-Cr 2 O 3 in the presence of KBrO 3 in the concentration range 0.1 ≤ [BrO 3 − ] ≤ 0.4 mol dm −3 , at pH 4 and 25 °C brings about oxidative dissolution. Release of Cr(VI) to the solution proceeds at a constant rate that increases with bromate concentration, even in conditions of quantitative e aq − scavenging. A mechanism of reactions is proposed in which OH and BrO 2 radicals oxidize surface Cr(III) to Cr(IV), and ionic release is achieved by oxidation of surface Cr(IV) by bromate. The corresponding set of equations was solved by a rigid method for the integration of ordinary differential equations, using these two heterogeneous rate constants as adjustable parameters. The calculated profiles are in close agreement with the experimental data. Key words: chromium oxides, radiation-induced dissolution, oxidation dissolution.