New insights into activation mechanisms of peroxymonosulfate by halide ions for micropollutant abatement: The generation routes and contributions of reactive radicals and hypohalous acid

Abstract

Micropollutants in aquatic environments is a pressing concern due to the risk to ecological and human health, necessitating innovative treatments. Peroxymonosulfate (PMS) activation by halide ions (X⁻ = Cl⁻, Br⁻, and I⁻) was investigated for degrading micropollutants. The PMS/Cl⁻ process could be enhanced by increased H⁺ and Cl⁻, not affected by general inorganic ions (NO₃⁻, SO₄²⁻, H₂PO₄⁻), but inhibited by natural organic matter. In real water matrices, original 5.7 mM Cl⁻ could activate 1 mM PMS to effectively degrade 99 % bisphenol A, achieving substantial reductions in the cytotoxicity. Both single-electron and two-electron transfer routes existed in the PMS/X⁻ reactions, generating radicals and HOX/X₂, and Cl⁻-contained radicals predominantly decomposed micropollutants with electron-withdrawing or methoxy groups. I⁻ with greater nucleophilicity exhibits the highest efficiency at lowest concentration in PMS/X⁻. This research provides new insights into the PMS/X⁻ system, offering a promising approach for enhancing water treatment to degrade micropollutants in X⁻-contained scenarios.