PHOTOREDUCTION OF URANYL-ION IN AQUEOUS-SOLUTION .1. WITH ETHANOL IN SULFURIC-ACID-SOLUTIONS

Photoreduction of UO22+ with ethanol (EtOH) in H2SO4 solutions has bee n studied by an electrochemical quantitative analysis of U-IV formed a s a final product, The quantum yield phi(U-IV) of U-IV increased rapid ly at [EtOH] up to 0.5 mol dm(-3) and then reached a maximum phi(U-IV) under oxygenated conditions was almost one-half of that under deaerat ed conditions. In order to explain these experimental results, phi(U-I V) was expressed on the basis of both formation of an encounter comple x between excited UO22+ (UO22+) and EtOH and a successive reaction of UO22+ with alpha-hydroxyalkyl radical formed after the complex formed . Kinetic parameters for the quenching of UO22+ by EtOH were derived from a plot of phi(U-IV)(-1) vs. [EtOH](-1) and checked by the measure ments of the photon emission from UO22+ with a time-resolved laser an d steady state light excitation. It was confirmed that the proposed ph otoreduction mechanism could reproduce the experimental results.