Enhanced photocatalytic removal of tetracycline hydrochloride and Cu2+ by the integrated CoFe2O4/g-C3N4 composite and rotating magnetic field system

Abstract

The widespread occurrence of antibiotics and heavy metals in aquatic environments poses significant risks to ecosystems and human health, yet conventional treatment methods often suffer from incomplete mineralization and limited removal efficiency. An integrated CoFe 2 O 4 /g-C 3 N 4 heterojunction and rotating magnetic field (RMF) system was developed for the efficient removal of methylene blue (MB), tetracycline hydrochloride (TCH), and copper ions (Cu 2+ ). The CoFe 2 O 4 /g-C 3 N 4 composite was synthesized via sol-gel and coprecipitation methods, and its structural, optical, and electrochemical properties were systematically characterized. The RMF (~10 mT) was employed to enhance photogenerated charge separation and particle collision, and its performance outperformed static magnetic fields. Under optimized conditions (30 wt% CoFe 2 O 4 loading, 1.0 g/L photocatalyst, pH 7), the system achieved removal efficiencies of >99.9% for MB, 93.4% for TCH, and 63.0% for Cu 2+ within 300 min. Mechanistic studies, including EPR spectroscopy, DFT calculation, and LC-MS analysis, revealed that ·O 2 − was the dominant reactive species for TCH degradation, with a degradation pathway of TCH identified as m / z 445 → 393, followed by ring opening to m / z 200 and m / z 225. Cu 2+ removal proceeded via photogenerated electron-driven reduction. The composite demonstrated excellent reusability and magnetic recoverability over four cycles. The RMF modestly suppressed recombination of photogenerated charge carriers, as reflected by the enhanced radical signals in EPR, and improved pollutant–catalyst contact. This work provided a sustainable and magnetically recoverable platform for the effective remediation of antibiotics and heavy metals in wastewater.