Fluoroquinolone antibiotics trigger selective oxidation in the trace-Cu(II)/peroxydisulfate system: The synergistic effect of dual reactive sites in chemical structure.

Research on transition metal-triggered advanced oxidation processes (TM-AOPs) has primarily focused on the regulation of catalysts and oxidants, but the alternative route that involves utilizing pollutant-derived electrons to enhance TM-AOPs has been largely overlooked. This study presents a case of selective degradation using fluoroquinolone antibiotics, with ofloxacin (OFX) selected as the model pollutant. Under the presence of PDS and trace Cu(II) (10 μM or 0.64 mg/L, below the limit of US drinking water standard), the OFX degradation rate was enhanced by 12.1 times compared to sole PDS oxidation. Notably, the system exhibited high pollutant selectivity and efficient oxidant utilization. Through various experimental methods, Cu(I) was confirmed as a crucial intermediate, while Cu(III) and •OH was identified as the predominant and secondary reactive oxidative species, respectively. The critical role of OFX was proved to be chelating with Cu(II) and facilitating the production of Cu(I). The degradation selectivity of OFX was attributed to the synergy of the chelating and oxidation sites in its chemical structure. Intramolecular single electron transfer occurred between the chelated OFX and Cu(III), leading to the Cu(III) reduction and OFX oxidation on the piperazine nitrogen atom. This study serves as a representative example of a greener pollutant-induced catalytic process based on the utilization of pollutant's electron bank, and offers novel insights into the correlation between a pollutant's chemical structure and its degradation selectivity.