In situ DTSA ligand engineering of CoWO4: a robust peroxymonosulfate activator for benzophenone-3 and tetracycline degradation.

Pharmaceuticals and personal care products (PPCPs) are pervasive aquatic micropollutants that raise growing concerns due to their phytotoxic, carcinogenic and endocrine-disrupting effects. Herein, we report an in situ ligand-modulated cobalt tungstate, DTSA/CoWO4, prepared by incorporating 2,2'-dithiosalicylic acid (DTSA) into CoWO4 to regulate its interfacial coordination environment and redox behavior toward peroxymonosulfate (PMS) activation. Comprehensive characterization (SEM, XRD, XPS and FT-IR) confirms the successful construction of DTSA-modified CoWO4. Relative to pristine CoWO4, DTSA/CoWO4 exhibits markedly enhanced catalytic activity for the oxidative removal of representative PPCPs, achieving >90% degradation of benzophenone-3 (BP-3) within 30 min (k = 0.12 min-1) and 99% degradation of tetracycline (TC) within 20 min (k = 0.214 min-1), corresponding to 3.29-fold and 2.19-fold rate enhancements. Mechanistic studies, combining quenching experiments and electron paramagnetic resonance (EPR) analysis, identified superoxide anion (O2˙-) and singlet oxygen (1O2) as the dominant reactive species, whereas the involvement of sulfate radicals (SO4˙-) and hydroxyl radicals (˙OH), although suggested by quenching results, could not be directly confirmed under the current aqueous EPR conditions. LC-MS/MS analysis showed that BP-3 could be effectively converted into smaller products, and ECOSAR-based toxicity prediction indicated that the overall toxicity of the converted products was reduced after treatment. Notably, DTSA/CoWO4 retains its activity over four repeated cycles, and quantitative analysis via ICP-MS reveals that the leaching of cobalt and tungsten is negligible. These results indicate that ligand engineering of CoWO4 is an effective strategy for obtaining promising persulfate activators for the degradation of personal care products and pharmaceuticals.