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 °C, 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 °C, all the four kinds of reactants can decompose PCB-153 with efficiency above 90%. Further, X-ray photoelectron spectroscopy characterization of IRCu-C before and after the reaction indicated transformation of 19.1% of Cu atoms into Cu2+, 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.