Efficient degradation of ciprofloxacin by a flower-spherical Bi2MoO6/BiOCl Z-type heterojunction photocatalyst enriched with oxygen vacancies

Ciprofloxacin (CIP) is difficult to degrade naturally, for example by microorganisms, and will persist in water bodies for a long period of time, seriously jeopardizing the ecological environment and human health. Photocatalysis has high practical application value as a green and efficient technology. However, the photogenerated electrons and holes of the photocatalysts are prone to complexation, which limits the degradation efficiency of photocatalysis. Therefore, in this work, spherical Bi2MoO6/BiOCl (OVs-BMO/BOC) Z-type heterojunction photocatalysts enriched with oxygen vacancies (OVs) were successfully synthesized by a hydrothermal-calcination method. A series of characterizations showed that the OVs-BMO/BOC photocatalysts could perform Z-type charge transfer, which increased the visible light response range and improved the separation efficiency of photogenerated electrons and holes, thus improving the degradation efficiency of CIP. Under visible light, the removal efficiency of OVs-BMO/BOC composites for CIP could reach 97.40% at 120 min. It has a quasi-primary rate constant of 0.03008, which is 4.1, 3.48, and 2.19 times higher than that of monomeric BOC, BMO, and BMO/BOC, respectively. Meanwhile, the good stability of OVs-BMO/BOC was verified, and its degradation efficiency could still reach 87.80% after four cycles. Finally, electron spin resonance analysis and trapping experiments were carried out, which demonstrated that a large number of OVs were produced by the BMO/BOC composite photocatalyst generated by calcination, and also identified that the OVs-BMO/BOC produced active substances (•OH, h+, and •O2−), which revealed the mechanism of degradation of CIP by the OVs-BMO/BOC. Our study provides a new way of thinking to achieve efficient elimination of antibiotics from wastewater.