Hydrothermally Enhanced Electrochemical Oxidation of High Concentration Refractory Perfluorooctanoic Acid

详细信息    查看全文

• 作者：Hanshuang Xiao ; Baoying Lv ; Guohua Zhao ; Yujing Wang ; Mingfang Li ; Dongming Li
• 刊名：Journal of Physical Chemistry A
• 出版年：2011
• 出版时间：December 1, 2011
• 年：2011
• 卷：115
• 期：47
• 页码：13836-13841
• 全文大小：812K
• 年卷期：v.115,no.47(December 1, 2011)
• ISSN：1520-5215

文摘

A green hydrothermally enhanced electrochemical oxidation (HTEO) technique is developed to treat the high concentration refractory perfluorooctanoic acid (PFOA) wastewater on boron-doped diamond (BDD) film electrode. Results show that HTEO can demonstrate higher degradation efficiency for PFOA than the normal electrochemical oxidation (EO) process, with the removal of PFOA, total organic carbon (TOC), and organic fluorine in the HTEO process increasing by 1.1, 1.8, and 2.1 times, respectively. The kinetics study indicates that the degradation of PFOA follows a first-order reaction in the HTEO process with the apparent reaction rate constant 3.1 times higher than that in the EO process. The higher degradation efficiency of PFOA is due to the hydrothermal enhancement in electrochemical properties of the electrode and solution. Compared with EO, during the HTEO process, the conductivity and ionic migration rate of the solution is improved by 540% and 60%, respectively. In addition, the Tafel slope is increased to 343 from 279 mV dec^鈥?, indicating an inhibition effect of oxygen evolution reaction and a more effective oxidation of PFOA. In particular, the hydrothermal condition promotes a high formation rate of hydroxyl radical with the concentration almost 2 times of that in EO, which is considered the inner factor leading to the higher degradation efficiency. The density functional theory simulations demonstrate that the nonterminal C鈥揅 bonds in the main carbon chain can be easily destructed in the hydrothermal condition, as confirmed by the experimental detection of intermediates of C₅F₁₁COOH, C₄F₉COOH, C₃F₇COOH, C₂F₅COOH, CF₃COOH, and some dicarboxylic acids. As a result, a reaction pathway is tentatively proposed.