Insight into UV-induced simultaneous photocatalytic degradation of TiCT MXene and reduction of U(VI).

With the development of MXene as the efficient adsorbent for U(VI), the tendency of MXene coming into contact with U(VI) in wastewaters increases. Motivated by UV light irradiation applied in wastewater treatments, the UV light induced photochemical co-transformation of TiCT MXene and U(VI) is studied. To clarify the role of U(VI) induced TiCT aggregation in phototransformation of TiCT, the aggregation kinetics of TiCT in the presence of various valent radioactive ions are investigated, obtaining the critical coagulation concentrations (CCC) of TiCT for Cs, Sr, UO, Eu, and Th. Besides, the colloidal stability of UV-induced TiCT as a function of standing time is discussed. The results show that the aggregation behavior of TiCT induced by radioactive ions follows the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and the Schulze-Hardy rule. The UV irradiation will change the physicochemical properties and colloidal stabilities of TiCT. Furthermore, the degradation of TiCT can be accelerated by UV irradiation and further promoted by the presence of U(VI). The removal of U(VI) is highest in the case of TiCT combined with UV irradiation via adsorption and reduction. This study provides an example demonstrating that the simultaneous transformation of TiCT (adsorbent) and U(VI) (adsorbate) to mild toxic components.