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Efficient Mineralization of Perfluorooctanoate by Electro-Fenton with H2O2 Electro-generated on Hierarchically Porous Carbon Yanming Liu, Shuo Chen, Xie Quan, Hongtao Yu, Huimin Zhao, and Yaobin Zhang Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.5b03147 • Publication Date (Web): 14 Oct 2015 Downloaded from http://pubs.acs.org on October 14, 2015
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Environmental Science & Technology
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Efficient Mineralization of Perfluorooctanoate by Electro-
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Fenton with H2O2 Electro-generated on Hierarchically
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Porous Carbon
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Yanming Liu, Shuo Chen, Xie Quan,* Hongtao Yu, Huimin Zhao, and Yaobin Zhang
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Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education,
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China), School of Environmental Science and Technology, Dalian University of Technology,
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Dalian 116024, China.
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Environmental Science & Technology
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Abstract: Perfluorochemicals are environmentally persistent, bioaccumulative and globally
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distributed contaminants, which present potential toxicity to both humans and ecosystems.
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However, rapid mineralization of perfluorochemicals with cost-effective method remains great
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challenges. Here, an electro-Fenton system was reported for efficient mineralization of
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perfluorooctanoate (PFOA), where H2O2 was electro-generated in-situ from O2 reduction on
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hierarchically porous carbon (HPC). Benefited from the high H2O2 production rate (41.2~14.0
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mM/h) of HPC, PFOA (50 mg/L) was rapidly degraded by electro-Fenton with first order kinetic
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constants of 1.15~0.69 h−1 at low potential (-0.4 V) in a wide range of pH (2~6). Meanwhile,
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PFOA was effectively mineralized, as revealed by a total organic carbon removal efficiency of
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90.7~70.4% (-0.4 V, pH 2~6, 4 h). Moreover, the current efficiency of this electro-Fenton system
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for PFOA degradation was one order of magnitude higher than those of electrochemical
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oxidation. Based on the intermediate analysis, a possible mechanism for PFOA degradation was
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proposed: PFOA lost one electron to the anode and got decarboxylated. The formed
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perfluoroalkyl radical was mainly oxidized by hydroxyl radical, resulting in the formation of
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shorter chain perfluorocarboxylic acid, which followed the same reaction cycle as PFOA until it
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was mineralized.
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Keyword: perfluorooctanoic acid; electro-Fenton; defluorination; hydrogen peroxide
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generation; porous carbon.
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Introduction
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Perfluorinated compounds have been widely used for various commercial and industrial
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products in the past decades, which results in their global distribution in environment. They have
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been becoming environmental and human health concerns due to their persistence,
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bioaccumulation and potential toxicity such as endocrine disrupting effects, neurotoxicity and
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developmental toxicity.1,2 One of the extensively used perfluorochemicals is perfluorooctanoate
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(PFOA). It has been detected in many environmental matrices including water, air, soil,
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sediment, dust, human and wildlife.3 Its concentration varied from several µg/L to mg/L in
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groundwater.4-6 Therefore, it is urgent to develop effective methods for converting PFOA to
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environmentally harmless or lower toxic species.
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PFOA is resistant to traditional advanced oxidation processes and biodegradation due to the
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stability of C-F bond (154 Kcal/mol)7 and the rigidity of its perfluoroalkyl chain, for example,
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hydroxyl radical (OH•) is ineffective for direct degradation of PFOA.8 The techniques reported
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for PFOA degradation include photolysis,9,10 photocatalysis,11 electrochemical oxidation,12-14
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sonolysis15 and catalyzed H2O2 propagation.16 Photolysis and photocatalysis can decompose
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PFOA under the condition of ultraviolet irradiation (λ
