Efficient degradation of PFOA in water by persulfate-assisted and UV-activated electrocoagulation technique using Fe foam electrode

Abstract

Perfluorooctanoic acid (PFOA), as a persistent organic pollutant, has been normally present in groundwater, surface water and seawater. It has been widely studied for its persistence, immunotoxicity and bioaccumulation. However, it is extremely difficult to be degraded due to high energy of the C-F bond. In this study, PFOA was removed from simulated and real industrial wastewater with Fe foam electrode by electrocoagulation (EC) technology. To achieve better degradation, persulfate (PS) and ultraviolet (UV) light were employed in the EC technology to realize the degradation of PFOA (PEC-PS). After 60 min treatment, the PEC system showed outstanding performance in that 87.5% of PFOA was degraded and 54.6% of PFOA was defluorinated under optimal conditions with smaller energy consumption and lesser iron sludge generation. Sulfate radical (SO4•−) was generated by the activation of ferrous ions under the synergy of UV light and electric energy. In this process, •OH and SO4•− and electron transfer are crucial in the reaction with PFOA and intermediates. The degradation mechanism of PFOA was summarized according to the quenching experimental results and the contribution of various reactive substances. The potential degradation pathways of PFOA were proposed according to the intermediates obtained through the HPLC-MS. It was found that PFOA showed a decomposition with the gradual losing of −CF2− units. The PEC-PS process of using Fe foam as electrode showed high-efficiency degradation and better recoverability, indicating the great potential of PEC-PS technique in efficient and thorough cleaning of PFOA in actual industrial wastewater.