Z-scheme g-C3N4/α-FOD heterojunction-assisted persulfate activation for degradation of tetracycline hydrochloride under visible light: Insights into mechanism

Tetracycline hydrochloride (TCH) as an emerging pollutant poses challenges for removal using traditional treatment methods. A new and high-efficient photocatalyst graphitic carbon nitride/α-ferrous oxalate dihydrate (g-C3N4/α-FOD) was synthesized to solve this issue, which acted as a Z-scheme heterojunction for efficient activation of persulfate (PS) degradation TCH under visible (Vis) light irradiation. A comprehensive characterization of the g-C3N4/α-FOD photocatalyst was performed to analyze the structural, morphological, optical, and electrochemical properties. The Z-scheme heterojunction enabled broader visible-light absorption and enhanced charge transfer. In g-C3N4/α-FOD/PS/Vis system, SO4−, OH, and O2− were identified as the main reactive species and contributed to the efficient degradation of TCH. The initial 100 mg/L TCH concentration can be degraded to 11.3 mg/L within 120 min, reaching a high mineralization rate of 83 %. Density functional theory calculation successfully predicted that the sites on TCH molecules with high Fukui index were preferable to be attacked by the reactive species. The ring contraction and elimination reaction were found to be two major degradation pathways of TCH. The cycling experiments confirmed the good stability and reusability of the g-C3N4/α-FOD photocatalyst. This study successfully confirms that heterojunction materials can enhance the activation potential of PS, which provides a reference for realizing the harmless degradation of environmental pollutants under visible light.