Abstract
The dynamics of the transfer of electrons stored in TiO2 nanoparticles to As-III, As-V, and uranyl nitrate in water was investigated by using the stopped-flow technique. Suspensions of TiO2 nanoparticles with stored trapped electrons (e(trap)(-)) were mixed with solutions of acceptor species to evaluate the reactivity by following the temporal evolution of e(trap)(-) by the decrease in the absorbance at =600nm. The results indicate that As-V and As-III cannot be reduced by e(trap)(-) under the reaction conditions. In addition, it was observed that the presence of As-V and As-III strongly modified the reaction rate between O-2 and e(trap)(-): an increase in the rate was observed if As-V was present and a decrease in the rate was observed in the presence of As-III. In contrast with the As system, U-VI was observed to react easily with e(trap)(-) and U-IV formation was observed spectroscopically at =650nm. The possible competence of U-VI and NO3- for their reduction by e(trap)(-) was analyzed. The inhibition of the U-VI photocatalytic reduction by O-2 could be attributed to the fast oxidation of U-V and/or U-IV.