CuO/BiOIO3 heterojunction with persulfate for synergistic photocatalytic degradation of oxytetracycline

5CuO/BIO shows rate constants 11.04 and 5.69 times those of CuO and BIO. • The heterojunction accelerates the Cu 2+ /Cu + cycle to efficiently activating persulfate. • LSV demonstrates the electron transfer between the catalyst and PS. • Possible degradation pathways of OTC were inferred using LC-MS and DFT calculations. Persulfate-based advanced oxidation processes (AOPs) are promising for antibiotic degradation, yet efficient and sustainable persulfate (PS) activation remains challenging. Herein, a novel S-scheme heterostructure CuO/BiOIO 3 (CuO/BIO) was synthesized via an in-situ calcination method. Under illumination, the CuO/BIO heterojunction synergistically activated PS, substantially enhancing the photocatalytic degradation of oxytetracycline (OTC). The optimal 5CuO/BIO/PS system achieved an excellent degradation rate constant (k) of 0.0740 min −1 , which is 11.04 and 5.69 times higher than those of CuO/PS and BIO/PS, respectively. X-ray photoelectron spectroscopy (XPS) revealed that the synergistic interaction between CuO and BIO promotes the Cu 2+ /Cu + redox cycle. Photoluminescence (PL) and electrochemical impedance spectroscopy (EIS) demonstrated the superior charge separation capability of the CuO/BIO composite. Linear sweep voltammetry (LSV) confirmed a synergistic effect between photocatalysis and PS activation, which facilitates electron transfer from the catalyst to PS. Additionally, the OTC degradation pathway was elucidated by liquid chromatography-mass spectrometry (LC-MS) identification of intermediates combined with theoretical calculations. Collectively, this study addresses a research gap in the CuO/BIO photocatalytic synergistic PS system and provides both a theoretical basis and experimental evidence for its application in treating antibiotic-containing wastewater. Download: Download high-res image (238KB) Download: Download full-size image