Photoelectrocatalytic selective removal of group-targeting thiol-containing heterocyclic pollutants

The removal of a class of toxic thiol-containing heterocyclic pollutants from complex water matrices has great environmental significance. In this study, a novel photoanode (Au/MIL100(Fe)/TiO₂) with dual recognition functions was designed for selective group-targeting photoelectrocatalytic removal of thiol-containing heterocyclic pollutants from various aquatic systems. The average degradation and adsorption removal efficiency of 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, and 2-mercaptobenzoxazole were still above 96.7% and 13.5% after selective treatment with Au/MIL100(Fe)/TiO₂ even coexisting with 10-fold concentration of macromolecular interferents (sulfide lignin and natural organic matters) and the same concentration of micromolecular structural analogues. While they were below 71.6% and 3.9% after non-selective treatment with TiO₂. Targets in the actual system were selectively removed to 0.9 µg L^-1, which is 1/10 of that after non-selective treatment. FTIR, XPS and operando electrochemical infrared results proved that the highly specific recognition mechanism was mainly attributable to both the size screening of MIL100(Fe) toward targets and Au-S bond formed between -SH group of targets and Au of Au/MIL100(Fe)/TiO₂. •OH are the reactive oxygen species. The degradation mechanism was further investigated via excitation-emission matrix fluorescence spectroscopy and LC-MS. This study provides new guidelines for the selective group-targeting removal of toxic pollutants with characteristic functional groups from complex water matrices.