Photochemical reduction of uranyl ion with triphenylphosphine

Photochemical reduction of uranyl ion with triphenylphosphine has been studied in acetone-water medium in the presence of sulphuric acid at 346nm, 400nm and 434nm wavelengths. The photochemical reduction is of second order and increases with increase in hydrogen ion concentration. Absorption spectra of uranyl ion in acidic medium and uranyl ion with triphenylphosphine do not show any ground state complex formation. The value of quantum yield increases with the wavelength of the radiation increase from 346 to 434nm. Plots of reciprocal of quantum yield for the formation of U(IV) versus reciprocal [triphenylphosphine] are linear. Products characterized by UV and visible, IR and TLC show the formation of U(IV) and triphenylphosphine oxide. On the basis of above observations mechanism of the photochemical reduction has been proposed. (author)