In-situ synthesis of g-C3N4/CuxO/GA for efficient tetracycline degradation via photocatalytic activation of persulfate under simulated sunlight irradiation

The primary objective of this research was to develop an efficient and stable material capable of both photocatalysis and persulfate (PDS) activation for the degradation of tetracycline (TC). To this end, a composite material, g-C 3 N 4 /Cu x O/GA (CNCuGA), was synthesized via an optimized hydrothermal assembly method. The physicochemical, microstructural, and photoelectric properties were systematically characterized, establishing a CNCuGA/SSL/PDS system to evaluate key parameters (doping rate, catalyst amount, PDS and TC concentrations, initial pH, and co-existing components) on TC degradation under simulated sunlight. Under optimal conditions (15 % doping ratio, 0.2 g·L −1 catalyst, 20 mg·L −1 PDS and 20 mg·L −1 TC), the CNCuGA-3/SSL/PDS system achieved 93.6 % (0.04223 min −1 ) TC removal within 60 min, surpassing the GA/SSL/PDS system (55.4 %, 0.00922 min −1 ) by a factor of 4.58. Mechanistic studies indicated that the enhanced performance originated from accelerated photogenerated electron transfer and prolonged electron lifetime, which promoted reactive species generation, along with the critical role of the Cu(I)/Cu(II) redox cycle in enabling persistent PDS activation. CNCuGA-3 also exhibited excellent recyclability over five cycles, with minimal metal leaching, while the treated solution showed high mineralization efficiency and low biological toxicity. These results collectively demonstrated the promise of CNCuGA-3 as a durable and effective catalyst for solar-driven antibiotic wastewater treatment.