Fundamental Study on Electrochemical Dechlorination of Dioxins

氯苯是二恶英的组成部分。研究氯苯脱氯的活性电极将有助于开发将二恶英转化为无害物质的电催化剂。在含有0.1 M TEAP和介体的乙腈溶液中，用伏安法和宏观电解法研究了氯苯的电化学脱氯。检查的电极为Pt、Ir、Rh、Pd、Au、Ag、Zn、In、Pb、Sn、Cu、Fe和Cd。以萘、二苯并呋喃、蒽和二萘嵌苯为介体。在含有氯苯和萘的溶液中，在析氢过电位高的电极上，氯苯的还原产生一个峰。还原电流的大小顺序为：Cd < Sn < In < Pb < Zn < Ag。其他电极由于氯苯的还原而不产生电流，因为由于氢析出而产生的电流超过了还原电流。二苯并呋喃得到与萘相同的结果，而蒽和二萘嵌苯对氯苯的还原没有活性。我们在0.1 M TEAP/乙腈（含10 mM氯苯和萘）中，在-2.8 V（Ag/Ag^+）下，在Ag、Zn和Pt电极上进行了宏观电解。所有电极上的主要产物均为苯：苯的电流效率Pt为38%，Ag和Zn为86%。另一种还原产物是氢气。Ag的局部电流密度最高，为12.4 mA/cm^2。该值是以前报道的用C电极和二苯并呋喃的5倍多。银电极与萘的组合对氯苯具有较高的脱氯活性。

Chlorobenzene constitutes the parts of dioxins. Studying active electrodes for dechlorination of chlorobenzene will lead to the development of electro-catalysts for transforming dioxins to harmless materials. Electrochemical dechlorination of chlorobenzene was studied using voltammograms and macro electrolysis in acetonitrile solution containing 0.1 M TEAP and mediators. Electrodes examined were Pt, Ir, Rh, Pd, Au, Ag, Zn, In, Pb, Sn, Cu, Fe, and Cd. Naphthalene, dibenzofuran, anthracene and perylene were adopted as mediators. Voltammograms in the solution containing chlorobenzene and naphthalene gave a peak arising from the reduction of chlorobenzene on the electrodes of which overpotentials for hydrogen evolution are high. The following order was obtained for the reduction current : Cd < Sn < In < Pb < Zn < Ag. The other electrodes gave no current due to the reduction of chlorobenzene, because the current due to the hydrogen evolution overwhelmed the reduction current. Dibenzofuran gave the same results as naphthalene, whereas anthracene and perylene had no activity for the reduction of chlorobenzene.We did macro electrolysis on Ag, Zn and Pt electrodes at -2.8 V (Ag/Ag^+) in 0.1 M TEAP/acetonitrile containing 10 mM of chlorobenzene and naphthalene. The main product was benzene on all the electrodes : current efficiency of benzene was 38% for Pt, 86% for Ag and Zn, respectively. Another reduction product was hydrogen. The partial current density of Ag was highest of all, 12.4 mA/cm^2. This value is more than 5 times as high as the former report using C electrode and dibenzofuran. The combination of Ag electrode and naphthalene has the high activity for the dechlorination of chlorobenzene.