A critical review on correlating active sites, oxidative species and degradation routes with persulfate-based antibiotics oxidation

At present, numerous heterogeneous catalysts have been synthesized to activate persulfate (PS) and produce various reactive species for antibiotic degradation from water. However, the systematic summary of the correlation among catalyst active sites, PS activation pathway and pollutant degradation has not been reported. This review summarized the effect of metal-based, carbon-based and metal-carbon composite catalysts on the degradation of antibiotics by activating PS. Metal and non-metal sites are conducive to inducing different oxidation pathways (SO4 center dot-, (OH)-O-center dot radical oxidation and O-1(2) oxidation, mediated electron transfer, surface-bound reactive complexes and high-valent metal oxidation). SO4 center dot- and (OH)-O-center dot are easy to attack C=H, S=N, C=N bonds, C=C double bonds and amino groups in antibiotics. O-1(2) is more selective to the structure of the aniline ring and amino group, and also to attacking C=S, C=N and C=H bonds. Surface-bound active species can cleave C=C, S=N, C=S and C=N bonds. Other non-radical pathways may also induce different antibiotic degradation routes due to differences in oxidation potential and electronic properties. This critical review clarified the functions of active sites in producing different reactive species for selective oxidation of antibiotics via featured pathways. The outcomes will provide valuable guidance of oriented-regulation of active sites in heterogeneous catalysts to produce on-demand reactive species toward high-efficiency removing antibiotics from water.