Enhanced oxidative degradation of tetracycline by visible light-promoted g-C₃N₄ modified Cu₃(OH)₄SO₄/Cu₇S₄ composites under an air atmosphere

Herein, a simple solvothermal method was used to prepare a CuS_x/g-C₃N₄ (CSG) heterojunction as an efficient oxygen activator containing sulfur vacancies (SVs). The as-prepared catalyst can activate oxygen to effectively degrade tetracycline (TC). The degradation rate of TC (20 mg L⁻¹) reached 98.9% in 90 min over CSG (0.02 g L⁻¹) under an air atmosphere, which maintained good performance within a wide pH range of 6-10. It was almost unaffected by any light source and water quality, indicating a highly efficient oxygen activator and good stability. Moreover, the trapping experiments and EPR results revealed that the main reactive oxygen species (ROSs) were singlet oxygen (¹O₂) and hydroxyl radicals (˙OH). CSG (4 : 1) enabled the activation of oxygen-produced ROS for removing TC even in the dark, which was in accordance with the EPR results. In addition, the CSG catalyst exhibited a good removal performance in practical wastewater treatment. Our study demonstrated that the CSG catalyst had the potential to remove organic pollutants from wastewater.