MnO_2表面结合Fe(Ⅱ)对三氯乙烯的还原脱氯作用

Reductive dechlorination of trichloroethylene by surface-bound Fe(Ⅱ) associated with manganese dioxide

通过批量实验研究了Fe(Ⅱ)、MnO2和MnO2表面吸附Fe(Ⅱ)这3种体系对溶液中三氯乙烯的还原脱氯作用。发现Fe(Ⅱ)吸附在MnO2表面时,对三氯乙烯的脱氯作用最强,氯代降解产物为顺-二氯乙烯(cis-DCE),且反应符合准一级动力学。进一步实验表明,保持Fe(Ⅱ)浓度为1 mmol/L,反应速率常数kobs和三氯乙烯去除率随pH升高(5.0～9.0)而增加,最大值分别为1.62×10-1h-1、70.4%;固定pH=7.0,kobs和三氯乙烯去除率随其Fe(Ⅱ)浓度增加(1～3mmol/L)而增大。Fe(Ⅱ)浓度继续增加,kobs和三氯乙烯去除率反而减小。pH=7.0,Fe(Ⅱ)浓度为3 mmol/L时,kobs和三氯乙烯去除率达到最大值,分别为2.86×10-1h-1和85.7%。

The reductive dechlorination of trichloroethylene（TCE） in aqueous solution was studied by batch experiments in three different systems, i.e. Fe（Ⅱ）, MnO2 and Fe（Ⅱ） bound to the surface of MnO2, respectively. The results showed that Fe（Ⅱ）-MnO2 system was most effective for the dechlorination of TCE and the catabolite of this process is cis-dichloroethylene（cis-DCE）. The reactions followed a pseudo-first-order kinetic rate law. It was showed by further study that when Fe（Ⅱ） concentration was maintained at 1 mmol/L, the rate constant kobs and TCE removal efficiency increased with increasing pH in the range of 5.0~9.0.The maximum values were 1.62×10-1 h-1 and 70.4%, respectively. When pH value was maintained at 7.0, kobs and TCE removal efficiency increased with increasing Fe（Ⅱ） concentration in the range of 1~3 mmol/L and then decreased at higher Fe（Ⅱ） concentration. The highest kobs（2.86×10-1 h-1） and TCE removal efficiency （85.7%） were observed at 3 mmol/L Fe（Ⅱ） and pH 7.0