New Insights into the FeO/Peroxymonosulfate Process for Organics Removal: The Synergistic Effect of Radicals and Fe(IV)

The FeO/peroxymonosulfate (PMS) system was explored in this work for the removal of bisphenol A (BPA) as a target pollutant. FeO demonstrated the highest PMS activation ability among the common iron oxides. 95.4% of the BPA could be removed in 30 min at pH 4.0 with the addition of 300 mg/L FeO and 50 μM PMS, mostly due to heterogeneous catalysis. The coexisting inorganic anions and natural organic matter impacted BPA breakdown. In the FeO/PMS system, high-valent Fe(IV), SO₄^•–, and HO^• were produced, which collectively caused the hydroxylation of the benzene ring in the BPA molecule. Remarkably, these reactive species had distinct effects on eliminating substrates, with electron-rich pollutants more likely to experience electrophilic reactions with Fe(IV) and electron-deficient pollutants more susceptible to HO^• attack. Compared to other FeO/peroxide systems, the FeO/PMS system had a better oxidation capacity under the experimental conditions, and it continued to function effectively in real water. Additionally, in a 96 h continuous flow treatment, the FeO/PMS system demonstrated a sustained effect. As a result, this system is anticipated to be a successful advanced oxidation technique for eliminating organic micropollutants existing in water.