S-scheme heterojunction between MOFs and Ag3PO4 leads to efficient photodegradation of antibiotics in swine wastewater

Antibiotics in swine wastewater could lead to risks to the environment and human health, and it is a competitive alternative to degrade antibiotics via photocatalysis which is green and eco-friendly. However, charge separation efficiency and light absorption capacity have been key factors limiting the technology. In this work, we synthesized the novel photocatalysts of MOF-545/Ag3PO4 via solvothermal methods, and examine the performance and mechanism for the degradation of oxytetracycline (OTC) in swine wastewater. The results showed that compared with Ag3PO4, the composite catalysts have stronger photoresponse and charge separation ability. MOF-545/Ag3PO4 could completely degrade OTC within 3.0 min with a rate constant of 3.97 min(-1) which is 12.9 times that of Ag3PO4. OTC removal was still 100% within 3.0 min after 5 cycles, which confirmed that the composite catalyst was stable. Data from free radical capture tests showed that photogenerated holes (h(+)) and superoxide radicals (center dot O-2(-)) played a dominant role in OTC degradation. In-situ X-ray photoelectron spectroscopy (XPS) spectra and electron spin resonance (ESR) spectra proved the formation of an S-scheme heterojunction in MOF-545/Ag3PO4, which greatly improves the carrier separation efficiency of catalysts. This study provides a novel MOF-based catalyst for improving photocatalytic performance.