Enhanced photocatalytic removal of U(vi) from water using tea waste biochar/g-C3N4/MoS2 Z-scheme composite: synthesis, performance, and mechanistic insights

Abstract

Pollution-related problems in the water environment caused by nuclear wastewater leakage has attracted widespread public attention. In this study, the strategy of treating waste with waste was adopted to prepare a tea waste-derived biochar/g-C₃N₄/MoS₂ (BgM) Z-scheme composite for the photocatalytic reduction of U(VI) in water using thermal polymerization and hydrothermal methods. Among different proportions of BGMs, 10%BgM holds the highest removal efficiency of U(VI). Approximately all U(VI) was removed by 10%BgM under air atmosphere after 2 h of light irradiation (pH = 4.5, dosage is 0.5 g L⁻¹). Furthermore, the removal efficiency of U(VI) by 10%BgM remained >80% after five cycles of tests, and it maintained a high selectivity in the presence of co-existing ions. Based on the quenching experiments and characterization analysis, photogenerated e⁻ and ˙O₂⁻ play an important role in the reduction of U(VI). The enhancement of the photoreduction activity can be attributed to the acceleration of photogenerated electron transfer by the incorporation of tea waste biochar and the formation of a Z-type charge transfer mechanism, which improved the visible light absorption capacity. This study presents a promising material and approach for the effective treatment of uranium wastewater using photocatalysis.