Photocatalytic removal of metronidazole and Cr (Ⅵ) by a novel Zn3In2S6/Bi2O3 S-scheme heterojunction: Performance, mechanism insight and toxicity assessment

Photocatalyst Zn3In2S6/Bi2O3 was prepared by hydrothermal reaction. When pH was 5, catalyst dosage was 0.5 g/L and pollutant concentration was 10 mg/L, the degradation kinetic constants of single metronidazole or hexavalent chromium (Cr (Ⅵ)) were 0.0389 and 0.05409 min−1 respectively, which were 389 (Cr (Ⅵ): 601) times and 1.81 (Cr (Ⅵ): 5.79) times that of Bi2O3 and Zn3In2S6. In the coexistence system of metronidazole and Cr (Ⅵ), the material still showed strong photocatalytic performance. At the same time, the successful preparation of the material was verified by the means of XRD, XPS and TEM. The photoelectric property of the materials was characterized by UV–Vis, DRS and PL. Finally, the UPS and in-situ XPS were used to explore the electron transfer of materials. This research not only avoids the use of precious metals, but also prepares a new photocatalyst with strong photocatalytic oxidation-reduction ability, which provides ideas for the practical application of photocatalysis and the construction of high-performance S-scheme heterojunctions.