Insight into the effect of microplastics on photocatalytic degradation tetracycline by a dissolvable semiconductor-organic framework

The presence of microplastics (MPs) in large quantities in the aqueous environment significantly affects the degradation process of water pollution. Still, the interaction between MPs and pollutants during photocatalytic degradation has not been studied. Here, a soluble BiOCl-OH semiconductor-organic framework (BOCH-SOF) was prepared from xylitol, and the polystyrene (PS) MPs' effect on the photocatalytic degradation of tetracycline (TC) was investigated. It was found that the appropriate number of PS can promote TC degradation and also change degradation products and pathways. At the same time, the presence of TC can effectively enhance PS aging and reduce the molecular weight of PS. This indicates that BOCH-SOF produces a synergistic effect in treating the combined pollution of TC and PS. Through free radical analysis and density functional theory calculations, it was proposed that PS and TC can complement each other. A certain concentration and size of PS can promote the conversion of Bi(III) to Bi and enhance charge separation and radical generation; the TC can change the interfacial charge distribution and free radical depletion, extend the light absorption in the system, and the PS and TC work together to ultimately achieve the synergistic degradation of the TC and the aging PS. This paper provides an in-depth analysis of the mechanism of the effect of MPs on the photocatalytic degradation of antibiotics, which is significant in controlling the combined pollution of MPs and associated pollutants in the water environment.