Sustainable Fe³⁺ reduction by Fe₃O₄@tourmaline in Fenton-like system

To address the issue of low Fe³⁺ reduction efficiency in the traditional Fenton system, a Fe₃O₄@tourmaline (Tml) catalyst was developed. For the first time, we investigated the reduction ability of Fe³⁺ and the source of electrons for Fe³⁺ reduction in the Fe₃O₄@Tml Fenton-like system. Results showed that the magnetic catalyst could regenerate 26.17 ± 0.57 μM Fe²⁺ after stirring at 300 rpm for 60 min. The density functional theory (DFT) calculations showed that Fe³⁺ tends to get electrons from OH^– in water rather than directly from Tml, with a free energy change of −2.954 eV. The Fe₃O₄@Tml Fenton-like system could remove 96.66 ± 0.01% of sulfathiazole (STZ) after 60 min. In addition, the mechanism of STZ removal suggested that surface ·OH and free ·OH worked together to treat STZ. This study provides a novel Fenton-like catalyst for efficient degradation of STZ and presents the theoretical basis for Fe³⁺ reduction.