Establishing g-C3N4-Vn/FeIn2S4 heterostructure for in-situ H2O2 generation and activation to degrade tetracycline in photo-Fenton process under visible light.

The heterogeneous photo-Fenton catalyst has attracted much interest in wastewater remediation applications. Herein, a heterostructure (CN-Vn/FIS) between ternary chalcogenide compound (FIS) and graphitic carbon nitride with nitrogen vacancies (CN-Vn) was synthesized via hydrothermal reaction to in-situ generate H2O2 under visible light and degrade tetracycline (TC) in water. CN-Vn/FIS could achieve as high as 98.5 % TC removal efficiency which maintained at 82.3 % in the fifth recycle, and was effective in the pH range of 2.6-9.0. The optical experiment suggested that CN-Vn/FIS demonstrates a broader light absorption edge as well as a low electron transfer energy barrier. Additionally, free radical trapping and EPR experiments proved that singlet oxygen (1O2) played a prominent role in the photo-Fenton process, while competitive reaction kinetic analysis calculated 1O2 contributed to 89.7 % TC degradation in CN-Vn/FIS system, which is nearly 3 times higher than 31.5 % in CN system. The results showed that CN-Vn/FIS created a one-step pathway to generate H2O2 without the aid of the intermediate free radical •O2-. This study illustrated an efficient and green TC degradation alternative through photo-Fenton process catalyzed by CN-Vn/FIS under visible light.