On the reaction of carbonate radical with uranyl ion in aqueous medium: flash photolytic and pulse radiolytic studies

Abstract

During steady state and flash photolysis (λ > 248 nm), the uranyl ion in aqueous carbonate medium was observed to exhibit photochromic behaviour. Formation of a radical complex, UO 2(CO 3) 2(C 3) 4−, with a lifetime of approximately 4.2 ms or greater is postulated to account for this observation. Flash excitation with UV light produced a carbonate radical and a permanent product, in addition to photochromism. The carbonate radical is shown to result exclusively from the photoionization of free bicarbonate or carbonate ions in the solution. The permanent product was identified as a peroxy complex, {UO 2(CO 3) 2OOH} 3−; a reaction mechanism involving CO 3 ∓− and UO 2(CO 3) 2(C 3) 4− is proposed to explain its formation. Pulse radiolytic studies do not support the occurrence of the reaction, CO 3 ∓− + UV VI→products, which has been reported in the literature.