[Catalytic dechlorination of 2, 2', 3, 4, 4', 5, 5'- heptachlorobiphenyl in soil by Pd/Fe].

Dechlorination of 2,2′,3,4,4′,5,5′-heptachlorobiphenyl in soil was studied by using Pd/Fe bimetallic catalytic reduction.2,2′,3,4,4′,5,5′-heptachlorobiphenyl can be dechlorinated effectively by Pd/Fe bimetal.It was found that the removal efficiency of 2,2′,3,4,4′,5,5′-heptachlorobiphenyl in soil could reach 54% after 5 days of reaction with 1 g of Pd/Fe(Pd loading 0.05%) and at an initial pH of 5.6.Several important experiment parameters involved in this process were also studied,including Pd loading,initial soil pH,the reaction time,the amount of Pd/Fe used and 2,2′,3,4,4′,5,5′-heptachlorobiphenyl initial concentration.The results showed that higher Pd loading,higher dosage of Pd/Fe,lower initial concentration of 2,2′,3,4,4′,5,5′-heptachlorobiphenyl and weak acid condition were beneficial to the catalytic dechlorination of 2,2′,3,4,4′,5,5′-heptachlorobiphenyl.The degradation of 2,2′,3,4,4′,5,5′ heptachlorobiphenyl,catalyzed by Pd/Fe,followed first-order kinetics,and the rate constant was 0.014?2/h,the half life was 49 h.In addition,two possible mechanisms of the dechlorination reaction were proposed and discussed.