Vanadium oxide activates persulfate for degradation of polycyclic aromatic hydrocarbons in aqueous system

Abstract

A novel investigation into the utilization of vanadium oxide (V2O3) as a persulfate (PS) activator in phenanthrene degradation in an aqueous system, and its subsequent pathway, was undertaken. The V2O3/PS has a high thermal degradation activity for phenanthrene at either room temperature (25 °C) or higher (35 °C and 45 °C), with a better performance (up to five times reuse) and a shorter degradation time. Phenanthrene can be effectively degraded under different pH conditions (pH 3, 5, 7, and 9), with a low PS concentration (2 mmol/L), activated by a small V2O3 loading (0.1 g/L). The electron paramagnetic resonance (EPR) technique combined with 5,5-dimethyl-1-pyrroline N-oxide (DMPO, 0.1 mol/L), captured sulfate (SO4−) and hydroxyl (OH) radical signals in the V2O3/PS system, generated from PS activation with V2O3. Free radical quenching studies revealed that both SO4− and OH contributed to phenanthrene degradation. The PS activation mechanism by V2O3 was elucidated. V2O3-activated PS produced SO4− and VO2 via electron transfer, with VO2 transferring a further electron to activate PS for SO4− and V2O5 generation, and a portion of the produced SO4− converted to OH. V2O3-activated PS generated four ion oxidation products (VO2, V2O5, V (V) and V (IV)), whereby VO2 and V2O5 actively participated in phenanthrene degradation, whereas V (V) and V (IV) provided no effective activation. A phenanthrene degradation pathway in the V2O3/PS system was proposed based on the identification of phenanthrene intermediates through liquid chromatography-mass spectrometry. These findings provide valuable insight into PS activation using a unique activator (V2O3) in the removal of environmental organic pollutants.