Photocatalytic applications of heterostructure Ag2S/TiO2 nanotube arrays for U(VI) reduction and phenol degradation

The photocatalytic reduction of U(VI) is an efficient strategy for dealing with uranium-containing wastewater. Herein, a heterostructure material of Ag2S deposited in titanium dioxide nanotube arrays (Ag2S/TNTAs) was prepared by the successive ionic layer adsorption method (SILAR) and applied as an effective photocatalyst for U(VI) reduction. Compared with pure TNTAs, the Ag2S/TNTAs-7 (the number of SILAR cycles) achieved the optimal photoreduction rate of 94% for U(VI) with the rate constant of 0.0105 min−1, which was a 21-fold boost over TNTAs. Impressively, the photocatalytic reduction process of U(VI) by Ag2S/TNTs-7 could be achieved without any sacrifice agents. Furthermore, phenol was introduced to replace the action of methanol, which would not only enhance U(VI) removal efficiency, but also realize degradation of phenol. Mechanism studies have shown that photogenerated electrons and ·O2− act as the reactive species to reduce U(VI) to immobile (UO2) O2⋅2H2O. This work paves a feasible pathway for treatment of uranium-containing wastewater and also demonstrates the potential application prospect of Ag2S/TNTAs-7 in the treatment of organic pollutants.