Chemiluminescence study of the photolysis of sulfuric acid solutions of UO2-+

There has been an enormous amount of investigation of the luminescence of the uranyl (UO22+) ion and its photochemical reactions. Considerable attention has been given to a study of the photochemical reduction of UO22+ by organic compounds. It was long considered that UV irradiation of aqueous solutions of uranyl not containing organic impurities did not lead to any significant change in the chemical composition of the solution. However, the high oxidation-reduction potential of UO22+ (2.7 V) permits its reaction with water. Burrows and Kemp have proposed that some portion of UO2+ and the ·OH radicals, which do not enter a geminal reaction, leave the cage and small amounts of U(IV) and H2O2 then accumulate in the solution. And the mechanism for the photochemical reduction of uranyl by water through electron transfer has found only indirect evidence by τ-metry (relative to the quenching of the photoluminescence of UO22+ by a water molecule). For a study of the radiation chemical reduction of uranium(IV) in aqueous sulfuric acid in the absence of ·OH radical acceptors, the authors proposed a chemiluminescence (CL) method based on the possibility of detecting small amounts of uranium(IV) (down to 10-9 mole/liter) on the background of a significant excess of uranium(VI)(up to 10-1 mole/liter) using the chemiluminescence of the oxidation of tetravalent uranium compounds by xenon trioxide