Abstract: Due to inherent limitations such as high carrier recombination efficiency, limited active sites, and suboptimal utilization of visible light, graphite-like carbon nitride (g-C₃N₄) has constrained its widespread application in water treatment within photocatalytic systems. In addressing this issue, the present study employed acid etching and sonochemistry to fabricate a Ti₃C₂-SO₃H/g-C₃N₄ (TiCSOHCN) composite photocatalyst for the removal of tetracycline hydrochloride (TC). The amalgamation of Ti₃C₂-SO₃H (TiCSOH) with g-C₃N₄ engendered the establishment of a discernible Schottky barrier, facilitating an expedited electron transfer rate. Photocatalytic degradation experiments demonstrate that, compared to individual components, the TiCSOHCN composite photocatalyst exhibits significantly enhanced photocatalytic activity. The removal efficiency of TC reaches 75.42 % within 2 h, and even after five cycles of experimentation, the degradation efficiency remains close to 70 %, indicating excellent stability. The augmentation can be predominantly ascribed to the cooperative influence arising from the synergy between Ti₃C₂-SO₃H and g-C₃N₄. The augmentation of visible light responsiveness in g-C₃N₄, achieved through its modification with TiCSOH, resulted in the mitigation of photoelectron-hole pair recombination, consequently leading to an amelioration in the photocatalytic efficacy of the TiCSOHCN composite catalyst. Intermediate species arising from the degradation of tetracycline were discerned utilizing LC-MS, and conjectures regarding plausible degradation pathways were postulated. Evaluations of the ecotoxicological impact of tetracycline and its intermediates indicated a progressive diminution in toxicity throughout the course of the photocatalytic degradation process. Furthermore, through free radical capture and EPR tests, it was confirmed that ·O₂^- and ·OH are the primary active species responsible for the photocatalytic degradation of TC, substantiating the proposed rational photocatalytic degradation mechanism. This research provides an innovative approach to developing high-performance and stable photocatalysts.

Key words: g-C₃N₄, Ti₃C₂ -SO₃H, Tetracycline, Photocatalysis