Dechlorination of 2,2＇,4,4＇,5,5＇-hexachlorobiphenyl by thermal reaction with activated carbon-supported copper or zinc

Activated carbon （AC）-supported copper or zinc made from ion exchange resin （IRCu-C and IRZn-C） have an increased metal load of 557.3 mg·g^-1 and 502.8 mg·g^-1 compared to those prepared by the traditional method involving impregnation with AC and copper （II） citrate or zinc citrate solution （LaCu-C and LaZn-C） of 12.9 mg·g^-1 and 46.0 mg·g^-1 respectively. When applied to decompose 2,2＇,4,4＇,5,5＇-hexachlorobiphenyl at 250 ℃, IRCu-C achieved higher activity of 99.0% decomposition efficiency than LaCu-C of 84.7%, IRZn-C of 90.5% and LaZn-C of 62.7%. When the reaction temperature rose to 350 ℃, all the four kinds of reactants can decompose PCB- 153 with efficiency above 90%. Further, X-ray photoelec- tron spectroscopy characterization of IRCu-C before and after the reaction indicated transformation of 19.1% of Cu atoms into Cu^2＋, illustrating that Cu is the active ingredient or electron donor promoting the decomposition of PCB- 153. The mechanism underlying this process differs from a traditional H donor. However, there is no significant change on the surface of IRZn-C before and after the reaction, suggesting that Zn acts as catalyst during the process of PCB-153 decomposition.