Department of Chemistry, Tongji University, 1239 Siping Road, 200092 Shanghai, People's Republic of China.
J Phys Chem A. 2011 Dec 1;115(47):13836-41. doi: 10.1021/jp207519j. Epub 2011 Nov 4.
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(-1), 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-C bonds in the main carbon chain can be easily destructed in the hydrothermal condition, as confirmed by the experimental detection of intermediates of C(5)F(11)COOH, C(4)F(9)COOH, C(3)F(7)COOH, C(2)F(5)COOH, CF(3)COOH, and some dicarboxylic acids. As a result, a reaction pathway is tentatively proposed.
一种绿色水热强化电化学氧化（HTEO）技术被开发用于在掺硼金刚石（BDD）薄膜电极上处理高浓度难处理的全氟辛酸（PFOA）废水。结果表明，与普通电化学氧化（EO）过程相比，HTEO 可以更有效地降解 PFOA，在 HTEO 过程中，PFOA、总有机碳（TOC）和有机氟的去除率分别提高了 1.1、1.8 和 2.1 倍。动力学研究表明，在 HTEO 过程中，PFOA 的降解遵循一级反应动力学，表观反应速率常数比 EO 过程高 3.1 倍。PFOA 的较高降解效率归因于电极和溶液电化学性能的水热增强。与 EO 相比，在 HTEO 过程中，溶液的电导率和离子迁移率分别提高了 540%和 60%。此外，Tafel 斜率从 279 mV dec(-1)增加到 343 mV dec(-1)，表明析氧反应的抑制作用和更有效地氧化 PFOA。特别是，水热条件促进了羟基自由基的高生成率，其浓度几乎是 EO 的 2 倍，这被认为是导致更高降解效率的内在因素。密度泛函理论模拟表明，在水热条件下，主碳链中的非末端 C-C 键可以很容易地被破坏，这得到了 C(5)F(11)COOH、C(4)F(9)COOH、C(3)F(7)COOH、C(2)F(5)COOH、CF(3)COOH 和一些二羧酸等中间产物的实验检测的证实。因此，提出了一种反应途径。
