Activation of persulfate with vanadium species for PCBs degradation: A mechanistic study

In the present study, the activation of persulfate (PS) with vanadium (V) species for PCBs (2,4,4'-trichlorobiphenyl [PCB28]) degradation was investigated for the first time. It was found that V2O3 exhibited high catalytic activity toward PS decomposition for PCB28 degradation. Even under near neutral pH (7.4), PCB28 was efficiently degraded in V2O3/PS. Sulfate radical anions (SO4 center dot-) and hydroxyl radicals (center dot OH) were produced from PS activation with V2O3 for PCB28 degradation, and were characterized with electron paramagnetic resonance (EPR) technique. Free radical quenching studies showed that ethanol inhibited PCB28 degradation, while tert-butyl alcohol enhanced PCB28 degradation via reductive dechlorination with alcohol radicals. The pathway of PCB28 degradation was proposed on the basis of GC-MS analysis of intermediates of PCB28 degradation in V2O3/PS. The mechanisms of PS activation are elucidated. It was found that V(III) in V2O3 activated PS to form SO4 center dot- and V(IV) (VO2) via electron transfer process, and the formed V(IV) further transferred an electron to PS to generate SO4 center dot- and V(V) (V6O13), which were supported with XRD analysis. Furthermore, both VO2 and V2O5 can activate PS for PCB28 degradation, indicating that V(IV) would be regenerated from the reduction of V(V) by persulfate ions (S2O82-) on the surface of V2O5 particles. These findings would help to better understand the interactions between naturally occurring V minerals and PS, and provide a novel activator for PS activation to degrade contaminants. (C) 2016 Elsevier B.V. All rights reserved.