In-situ Construction of MnIn2S4/TpBpy Z‑Scheme Heterojunction Composites for Photocatalytic Reduction of U(VI)

Abstract

The photocatalytic reduction of uranium is considered as an effective method for treating nuclear wastewater. However, insufficient charge separation and rapid recombination of photogenerated carriers restrict photocatalytic applications. The construction of compact heterostructures has proven to be an effective way to realize charge separation and photocatalytic efficiency. Herein, the Z-scheme heterojunction MnIn2S4/TpBpy was engineered and fabricated to realize high-efficiency uranium(U(VI)) reduction by the synergistic adsorption-photocatalysis strategy. The experimental results showed that the U(VI) removal rate of MIS@TpBpy-30 reached 90.25% (29.26 mg/g under irradiation) and its photocatalytic reaction rate constant was 0.0103 min-1, which was 12.1 times higher than that of MnIn2S4 and 3.3 times higher than that of TpBpy, respectively, which was attributed to the construction of the Z-scheme heterojunction to enhance the absorption of visible light and promote the separation of photogenerated electrons and holes. In the photocatalytic process, U(VI) was photo-reduced to UO2 in the presence of •O2- and e- reactive species, not only that, a large amount of H2O2 was generated during the reaction, which further contributed to the deposition of U(VI) as (UO2)O2•2H2O on the photocatalyst surface. This investigation provided new possibility for the design and production of MnIn2S4-based composites as photocatalysts for the effective utilization of visible light for U(VI) resource recovery and environmental remediation.