UVB-activated permanganate enables rapid emerging organic contaminants decontamination through synergistic HO• and reactive manganese species.

Permanganate [Mn(VII)] has been widely used as oxidants in water treatment. However, the limited reactivity of Mn(VII) with some recalcitrant contaminants impeded its application. In this study, UVB was introduced for Mn(VII) activation, and 95.1% of diclofenac (DCF) and 92.7% of p-hydroxybenzoic acid (p-HBA) were degraded by UVB/Mn(VII) after 30 min treatment while Mn(VII) alone were 36.6% and 25.2%, respectively. Hydroxyl radical (HO•) and reactive manganese species (RMnS) were main reactive species in UVB/Mn(VII) process. The contributions of HO• and RMnS (hypomanganate [Mn(V)] and trivalent manganese [Mn(III)]) to DCF degradation were respectively 25.2% and 55.0%, while those to p-HBA were 19.7% and 67.2% at 310 nm irradiation with 200 μM Mn(VII) and pH 7.0. The dominant RMnS responsible for DCF degradation was Mn(V) while that for p-HBA was Mn(III). When the UV wavelength increased from 255 nm to 310 nm, kobs of DCF and p-HBA decreased from 0.1510 min-1 to 0.1005 min-1 and from 0.1395 min-1 to 0.0869 min-1, respectively, with the quantum yields of Mn(VII) decreased from 0.200 mol/E to 0.014 mol/E. Comparatively, kobs of DCF and p-HBA increased as Mn(VII) dosage increased from 50 μM to 400 μM. When the pH increased from 5.0 to 9.0, the degradation efficiencies of DCF and p-HBA decreased, which was due to the lower oxidation capacity and quantum yields of Mn(VII) in alkaline conditions. The contributions of HO• decreased with the increase of pH, while those of RMnS increased and played the dominant role. As RMnS were resistant to the interference of anions, Cl- and HCO3- had negligible influences on DCF and p-HBA degradation. HA as RMnS stabilizing substance enhanced the degradation of DCF and p-HBA. The removal efficiencies of DCF and p-HBA in real water backgrounds were >95% after 30 min treatment. The high adaptability of UVB/Mn(VII) in complicated environments indicated its application potential in water treatment.