Photoreduction of the uranyl ion in aqueous solution II. Alcohols in acid solutions

Photoreduction of uranyl(VI) ion (UO22+) in acid solutions has been studied with a steady-state and time-resolved exciting light, where methanol (MeOH), ethanol (EtOH) and iso-propanol (iso-PrOH) were used as quenchers (RCH2OH) and HCIO4, H2SO4 and H3PO4 as acid solvents (S). The quantum yields, phi(U4+) of resultant U4+ and the rate constants, k(q), for the quenching of excited UO22+ (*UO22+) by RCH2OH were determined. The k(q) values increased in the order of MeOH, EtOH and iso-PrOH corresponding to the increase of phi(U4+) at [RCH2OH] up to 1.0 mol dm(-3). while at the higher [RCH2OH] the phi(U4+) reached the same maximum less than unity regardless of the kinds of RCH2OH. The photoreduction with 1.5 mol EtOH dm(-3) in the acid solutions showed that the phi(U4+) increased in the order of HClO4, H2SO4 and H3PO4 in the whole range of [S]. (C) 2002 Elsevier Science B.V. All rights reserved.