Efficient degradation of perfluorooctanoic acid by UV–Fenton process

Decomposition of perfluorooctanoic acid (PFOA) was investigated in UV–Fenton systems. It was found that PFOA could be efficiently degraded in the UV–Fenton system, producing fluoride ions and short-chain perfluorinated carboxylic acids. The degradation of PFOA could be divided into two stages: Within reaction time of 1 h, the added PFOA was rapidly degraded, resulting in a PFOA removal of 87.9% and a defluorination efficiency of 35.8%; Beyond 1 h, the PFOA removal was slowly increased to more than 95% at reaction time of 5 h, along with the defluorination efficiency of 53.2%. This corresponded to a two-stage mechanism for the PFOA degradation process in the UV–Fenton system. The fast defluorination and degradation of PFOA at the first stage was attributed to the generation of strong oxidizing OH radicals, which accelerated PFOA decarboxylation. At the second stage, H2O2 was completely consumed, and the defluorination was mainly due to the interactions between PFOA and Fe3+ ions.