Improved photocatalytic activation of PMS using Co-doped g-C3N4 composites for effective degradation of tetracycline: Catalyst performance, photogenerated carrier transfer and degradation mechanism

Photocatalytic coupled SO₄^•- based advanced oxidation processes (SR-AOPs) are considered as an advanced wastewater treatment technology for degrading pollutants. In this work, Co-doped g-C₃N₄ (CCN) photocatalysts were successfully designed for activation of permonosulfate (PMS) under visible light to efficiently degrade tetracycline (TC). The CCN photocatalyst exhibited enhanced degradation efficiency, removing 95.9 % of TC within 20 min, with a much higher degradation rate constant (0.1354 min^-1) than that of the photocatalytic system (0.0090 min^-1) and the SR-AOPs system (0.0538 min^-1). The separation and transport properties of photogenerated carriers were probed with the assistance of measurements including surface photovoltage and photoluminescence. The results showed that the introduction of Co promoted the effective separation of photogenerated charges in CCN, which accelerated the Co^3+/2+ cycle and realized the efficient activation of PMS. Overall, this study provides a new strategy for the development of efficient photocatalytic activation of PMS for rapid degradation of organic pollutants.