两类不同阳极电氧化过程中的失活现象及氧化机制

Deactivation of Two Different Kinds of Anodes during the Degradation of Organics and Their Oxidative Mechanisms

利用电化学测试技术分析了两类不同阳极在电氧化降解对氯苯酚过程中的失活现象及氧化机制.结果表明,对氯苯酚在“I”类阳极Pt和“II”类阳极含氟树酯(polytetrafluoroethylene,PTFE)的β-PbO2(PTFE-β-PbO2)上可发生直接氧化反应,且两者的电催化活性均会在短时间内失活.高电位电解能使失活的PTFE-β-PbO2和Pt得到再生,但Pt电极需要更高的电解电位.常见有机溶剂(如丙酮、四氢呋喃、二甲基亚砜)的浸洗可以再生失活的Pt电极,但不能再生PTFE-β-PbO2电极.对于“I”类阳极Pt,当阳极电位大于2.0V时,除对氯苯酚的直接氧化反应外,晶格氧的氧化作用成为整个降解过程的主导因素;而对“II”类阳极PTFE-β-PbO2,当阳极电位大于1.8V时,除直接氧化反应外,羟基自由基的降解反应成为对氯苯酚去除的主要原因.

Deactivations of two different kinds of anodes during electrochemical oxidation of p-chloropbenol （p-CP） were investigated by using electrochemical measurement, and their corresponding oxidation mechanisms were also discussed. The results indicated that p-CP could be oxidized directly on both the Pt （＂Ⅰ＂ type anode） and PTFE （polytetrafluoroethylene）-β-PbO2 （＂Ⅱ＂type anode）, however, the electro-catalytic activities of both anodes lost immediately. Electrolysis at high potential could recover the electro-catalytic activities of both anodes, and Pt needed higher potential, than PTFE-β-PbO2 did. The deactivated Pt could also recover its activity by soaking it in ordinary organic solvents such as acetone, tetrahydrofuran, dimethyl sulfoxide, but deactivated PTFE-β-PbO2 could not. For Pt anode （＂Ⅰ＂）, besides the direct oxidation of p-CP, oxygen transfer reaction was the main cause for the removal of p-CP when anodic potential was higher than 2.0 V; for PTFE-β-PbO2 anode （＂.Ⅱ＂）, besides the direct oxidation reaction, the oxidative reaction of hydroxyl radical became the main cause for the removal of p-CP when anodic potential was higher than 1.8 V.