Photochemical defluorination of aqueous perfluorooctanoic acid (PFOA) by Fe0/GAC micro-electrolysis and VUV-Fenton photolysis
2016
Zhang, Li-hong | Cheng, Jian-hua | You, Xia | Liang, Xiao-yan | Hu, Yong-you
Perfluorooctanoic acid (PFOA) is extremely persistent and bioaccumulative in the environment; thus, it is very urgent to investigate an effective and moderate technology to treat the pollution of PFOA. In this study, a process combined iron and granular activated carbon (Fe⁰/GAC) micro-electrolysis with VUV-Fenton system is employed for the remediation of PFOA. Approximately 50 % PFOA (10 mg L⁻¹) could be efficiently defluorinated under the following conditions: pH 3.0, dosage of Fe 7.5 g L⁻¹, dosage of GAC 12.5 g L⁻¹, and concentration of H₂O₂ 22.8 mmol L⁻¹. Meanwhile, during the process, evident defluorination was observed and the concentration of fluoride ion was eventually 3.23 mg L⁻¹. The intermediates including five shorter-chain perfluorinated carboxylic acids (PFCAs), i.e., C7, C6, C5, C4, and C3, were also analyzed by high-performance liquid chromatography tandem mass spectrometry (HPLC/MS/MS) and defluorination mechanisms of PFOA was proposed, which involved photochemical of OH·, direct photolysis (185-nm VUV), and photocatalytic degradation of PFOA in the presence of Fe³⁺ (254-nm UV).
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