Fundamental Study on Electrochemical Dechlorination of Dioxins

氯苯是二恶英的组成部分。对氯苯脱氯活性电极的研究将促进二恶英转化为无害物质的电催化剂的发展。采用伏安法和宏电解法，在含有0.1 M TEAP和介质的乙腈溶液中研究了氯苯的电化学脱氯。电极为Pt、Ir、Rh、Pd、Au、Ag、Zn、In、Pb、Sn、Cu、Fe、Cd，介质为萘、二苯并呋喃、蒽、苝。在含有氯苯和萘的溶液中，由于氯苯在析氢过电位高的电极上的还原而产生伏安图。还原电流大小顺序为：Cd < Sn < In < Pb < Zn < Ag。另一个电极由于氯苯的还原而没有电流，因为析氢产生的电流压倒了还原电流。二苯并呋喃的还原效果与萘相同，而蒽和苝对氯苯没有还原活性。我们在0.1 M TEAP/含有10 mM氯苯和萘的乙腈中，在-2.8 V （Ag/Ag^+）下对Ag、Zn和Pt电极进行了宏观电解。所有电极上的主要产物为苯：苯对Pt的电流效率为38%，对Ag和Zn的电流效率分别为86%。另一个还原产物是氢。Ag的分电流密度最高，为12.4 mA/cm^2。这一数值是以前使用C电极和二苯并呋喃的报道的5倍以上。银电极与萘的结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.