Photodeposition of uranium oxides onto TiO2 from aqueous uranyl solutions

Abstract

The photoreduction of uranyl solutions on illuminated TiO, suspensions and electrodes has been investigated. The photoreduction leads to the formation, on TiO, , of an uranium oxide having a stoichiometry close to U, O, .Adsorption of uranyl species in the dark was examined. It was found that the degree of adsorption depended on pH and on the formation of uranyl complexes in solution.Initial rates of photoreduction are given for the cases when propan-2-01, sodium acetate or sodium formate are used as scavengers of the photogenerated holes.With the use of microelectrode theory, it was possible to calculate the photoreduction rates from photoelectrochemical data obtained with TiO, electrodes. The reduction rates calculated in this way were from 3.5 to 4 times lower with the electrode than with the suspension, in agreement with the larger area available in the latter case.

Heterogeneous photocatalysis: state of the art and present applications In honor of Pr. R.L. Burwell Jr. (1912–2003), Former Head of Ipatieff Laboratories, Northwestern University, Evanston (Ill).

“…The cations Pb 2+ and Tl + were deposited on UV-irradiated TiO 2 powder as PbO 2 and Tl 2 O 3 [55]. Similarly, uranium was photodeposited on TiO 2 as U 3 O 8 from uranyl solutions [56].…”

Characterization of a TiO2 Photocatalyst Film Deposited by CVD and Its Photocatalytic Activity

“…[3] In many photodecomposition reaction systems, TiO 2 powders are used as the photocatalyst. [4] However, powder catalysts have several problems, such as difficulties in the separation of the catalyst from suspension after the reaction, and difficulties in the prevention of aggregation in highly concentrated suspensions. To avoid such agglomeration, the suspension must be diluted, but then the overall reaction rate tends to be slow.…”

Heterogeneous photocatalytic removal of U(VI) in the presence of formic acid: U(III) formation

“…[9], with A decreasing in the order QP > GP > QAN and k indicating a very slow initial removal, with a higher value for QAN. In the [1,9], with a predominance of U(IV). Although TXRF analysis of these deposits (not shown) confirmed the presence of uranium, XRD analysis reported only signals of TiO 2 , probably due to the low uranium concentration or to the lack of crystallinity of deposits.…”

“…Heterogeneous photocatalysis (HP) of aqueous U(VI) systems has been rather well studied [1][2][3][4][5] as an economical and simple alternative to conventional removal methods [6][7][8]. This technological approach can solve not only environmental problems but also those related to actinide valence state control for waste minimization in nuclear fuel processing.…”

“…The uranyl HP transformation in the presence of different organic compounds, formic acid (HCOOH) among them, has been studied by Amadelli et al in an early work with TiO 2 P25, and it was found that the photoelectrochemical conversion rate followed the order formate > acetate > 2-PrOH [1].…”