A novel Bi2WO6/BiOBr/RGO photocatalyst for enhanced degradation of ciprofloxacin under visible light irradiation: Performance, mechanism and toxicity evaluation

The residual antibiotics in pharmaceutical wastewater have a great impact on the efficiency and stability of wastewater biological treatment process, and prefer to be treated by advanced oxidation process beforehand. In this study, we synthesized a novel Bi 2 WO 6 /BiOBr/reduced graphene oxide (RGO) photocatalyst by one-step hydrothermal method and applied it to the photocatalytic oxidation of ciprofloxacin. The characterization results showed that the photocatalyst had a heterojunction structure and a broadening light absorption range. RGO in the composite effectively reduced the band gap of Bi 2 WO 6 /BiOBr and promoted the separation of photogenerated charge carriers. Neutral pH condition was favor of the adsorption and degradation of ciprofloxacin by Bi 2 WO 6 /BiOBr/RGO, and the ciprofloxacin removal efficiency could be up to 90.7 % with the optimal molar ratio of Bi 2 WO 6 to BiOBr (1:1) and RGO content (5 wt%). In the free radical quenching experiment, superoxide radicals and photogenerated holes were determined to be major contributors for the photocatalytic degradation of ciprofloxacin. Furthermore, 71.3 % of ciprofloxacin could be removed through mineralization during the photocatalysis process, and the residual pollutants did not significantly affect the biological nitrogen removal process. • A novel Bi 2 WO 6 /BiOBr/RGO photocatalyst was prepared by one-step method. • Bi 2 WO 6 /BiOBr/RGO excelled in light absorption and electron–hole pairs separation. • Ciprofloxacin could be photocatalytic degraded by Bi 2 WO 6 /BiOBr/RGO efficiently. • The degradation products of ciprofloxacin had no significant biological toxicity.