Regulating the dominant reactive oxygen species from Fe(IV)-oxo to 1O2 by deprotonation of Fe(IV)-oxo in electro-Fe(II)/periodate system

The ferrous species (Fe(II))-periodate (PI) system employs efficient decontamination by generating ferryl species (Fe(IV)-oxo) under acidic pH conditions. However, the mechanisms by which the Fe(II)/PI system operates across a broad pH range remain elusive. In light of the rapid oxidation and consumption of Fe(II) at neutral pH, we developed an electro-Fe(II) system utilizing an iron plate anode to activate PI (E(Fe/C)/PI). Efficient sulfamethoxazole (SMX) degradation was achieved under the E(Fe/C)/PI system across a range of pH values. Quenching and chemical probe experiments revealed a transition from Fe(IV)-oxo to singlet oxygen ( 1 O 2 ) as the predominant reactive species from acidic to near-neutral pH, respectively. Density functional theory (DFT) calculations indicated that the differences in one-electron transfer capacity and hydrolysis pathways for various protonated Fe(IV)-oxo species underlie the variations in catalytic mechanisms. This study not only enhances the efficiency of the Fe(II)/PI system but also provides a comprehensive understanding of the activation mechanisms at different pH levels.