Scalable TiO2/high-entropy oxide heterojunctions for synergistic photo-PMS activation toward ciprofloxacin degradation

A series of TiO 2 /high-entropy oxide (TiO 2 /HEO) heterojunction composite catalysts was fabricated via a scalable one-step ball-milling mechanochemical strategy, coupling anatase TiO 2 with a five-component equimolar high-entropy oxide (Fe–Ni–Cu–Mg–Al) to construct a synergistic photocatalytic peroxymonosulfate (PMS) activation platform. Comprehensive characterization confirmed the formation of a TiO 2 /HEO heterointerface accompanied by pronounced lattice distortion and favorable interfacial charge redistribution. The optimized TiO 2 /5HEO composite achieved 98.6% ciprofloxacin (CIP) degradation (20 mg/L) within 30 min under UV-Vis light-assisted PMS activation, outperforming its individual components. It maintained high activity across a broad pH range (3 – 9), showed strong resistance to common inorganic anions, and retained stable performance in long-term (232 h) membrane catalytic reactor operation with extremely low metal leaching. In addition, systematic mechanistic investigations via quenching experiments and electron paramagnetic resonance spectroscopy identified photogenerated holes and singlet oxygen as the dominant reactive species, conferring the system with intrinsic resistance to anion quenching. Additionally, the CIP degradation was demonstrated to yield low-toxicity products, verified by Escherichia coli antibacterial and wheat seed germination experiments. This study established a facile, one-step ball-milling synthesis method for a highly stable and scalable photo-PMS synergistic catalyst, providing a practical and feasible approach for the efficient treatment of antibiotic-containing wastewater.