Heterogeneous catalytic ozonation for the removal of antibiotics in water: A Review.

Abstract

Antibiotics with pseudo-persistence in water have been regarded as emerging pollutants, which have obvious biological toxicity even at trace levels. On account of high reactivity, heterogeneous catalytic ozonation has been widely applied to remove antibiotics. Among the heterogeneous catalysts, with well-developed pores and regulable surface defects, carbon-based materials can act as both adsorbents and catalysts. Metal cations, surface hydroxyl (-OH) groups and oxygen vacancies (OVs) serve as primary active sites in metal oxides. However, composites (perovskite, apatite, etc.) with special crystalline structure have more crystallographic planes and abundant active sites. The unsaturated bonds and aromatic rings which have dense structure of the electron cloud are more likely to be attacked by ozone (O3) directly. Sulfonamides (SAs) can be oxidized by O3 directly within a short time due to the structure of activated aromatic rings and double bonds. With the existence of catalysts, almost all antibiotics can attain fair removal effects. The presence of water matrix can greatly influence the removal rate of pollutants via changing the surface properties of catalysts, competing active sites with O3, etc. Correspondingly, the application of diverse heterogeneous catalysts was introduced in details, based on modification including metal/non-metal doping, surface modification and carrier composite. The degradation pathways of SAs, fluoroquinolones (FQNs), tetracyclines (TCs) and β-lactams were summarized founded on the functional group structures. Furthermore, the effects of water matrix (pH, coexisting ions, organics) for catalytic ozonation were also debated. It is expected to proffer advanced guidance for researchers in catalytic ozonation of antibiotics.