钯/铁双金属对土壤中2,2′,3,4,4′,5,5′-七氯联苯的催化脱氯研究

采用Fe⁰还原、钯催化法对土壤中2,2′,3,4,4′,5,5′-七氯联苯的的还原特性进行了实验研究.结果表明,Pd/Fe双金属能有效地进行2,2′,3,4,4′,5,5′-七氯联苯的催化脱氯.在钯化率为0.05%、钯/铁加入量1g、初始pH为5.6、反应时间5 d的条件下,钯/铁双金属对土壤中2,2′,3,4,4′,5,5′-七氯联苯去除率达54%.实验还考察了钯化率、初始pH、反应时间、钯/铁投加量、2,2′,3,4,4′,5,5′-七氯联苯初始浓度等参数对2,2′,3,4,4′,5,5′-七氯联苯脱氯效果的影响.研究表明,较高的钯化率、钯/铁加入量,较低的2,2′,3,4,4′,5,5′-七氯联苯初始浓度及弱酸性等条件更有利于Pd/Fe对2,2′,3,4,4′,5,5′-七氯联苯的还原脱氯.在Pd/Fe双金属表面,2,2′,3,4,4′,5,5′-七氯联苯的脱氯符合一级动力学反应,反应速率常数为0.014 2/h,其半衰期为49h.利用实验数据,对钯/铁双金属作用下的2,2′,3,4,4′,5,5′-七氯联苯还原脱氯的反应机制也进行了分析.

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.