STUDIES ON THE PHOTOCHEMISTRY OF URANYL ION Ⅲ.PHOTOCHEMICAL REDUCTION OF U(Ⅵ)IN UO_2~(2+)-HCOOH-HNO_3 SYSTEM WITH AN ARGON ION LASER

The photochemical reduction of uranyl ion by formic acid is investigated using an argon ion laser at wavelength 4880 A. The effects of concentration of the formic acid, formate, nitric acid, nitrate, uranylion and of temperature on quantum yield 0 of U(Ⅳ) formed are studied. Experimental results indicate that U(Ⅵ) can be reduced photochemically to U(Ⅴ), which disproportionates to U(Ⅳ) and U(Ⅵ). Φdepends mainly on the degree of complex formation of uranyl formate a in solution. Φ increases with the increase of α. Φ reaches 0.5 when a is close to 1. The rate of U(Ⅳ) formed is proportional to HCOO-1.08 at low concentration of formate and to UO2 2+ 1.01 at low concentration of uranyl ion respectively.