Visible-light persulfate activation by a BiOI/BiOCOOH composite photocatalyst for accelerated organic pollutant degradation

The construction of photocatalysts that can activate persulfate (PS) efficiently is the key to the removal of water pollutants. In this study, a BiOI/BiOCOOH (IB) composite photocatalyst was prepared via an ultrasound-assisted solvothermal method, which activated PS under visible light to efficiently degrade ciprofloxacin (CIP). Compared with those of pure BiOCOOH and BiOI, the photocatalytic activity of IB was significantly improved. The 0.5 IB/PS system exhibited a maximum CIP (10 mg L−1 50 mL) degradation rate of 95.10% after 90 min of irradiation, and the photoreaction rate constant was 0.0304 min−1, which was 100.7-fold that of BiOCOOH/PS, respectively. Through photolysis experiments involving different water quality and other antibiotics and dyes, the practical application potential and universal ability of the 0.5 IB/PS system were revealed. After five cycles, the degradation rate of CIP decreased by only 13.33%, which showed good cyclic stability. On the basis of a quenching experiment and electron spin resonance measurement, a stepped heterojunction photocatalytic mechanism involving charge transfer and separation was proposed. In addition, the degradation pathway of CIP was proposed based on LC–MS analysis. This work shows that the strategy of constructing a heterojunction photocatalyst to activate PS has great application potential in environmental water remediation.