Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences, Beijing 100083, PR China.
J Hazard Mater. 2012 Nov 15;239-240:265-9. doi: 10.1016/j.jhazmat.2012.08.074. Epub 2012 Sep 5.
Permeable reactive barriers (PRBs) composed of zero-valent iron (ZVI) are susceptible to passivation, resulting in substantially decreased rates of chlorinated solvent removal over time. In this study, the application of low electrical direct current (DC) to restore the reductive capacity of passivated ZVI was examined. Electrical current was applied to a laboratory column reactor filled with a mixture of pre-passivated ZVI and sand. Variable voltage settings (0-12 V) were applied through two stainless steel electrodes placed at the ends of the reactor. While only partial restoration of the reductive capacity of the passivated ZVI was observed, higher rates of trichloroethene (TCE) removal were always obtained when current was applied, and the rates of TCE removal were roughly proportional to the voltage level. Although differences were observed between the rates and extent of TCE removal within the column, it is noteworthy that TCE removal was not restricted to that region of the column where the electrons entered (i.e., at the cathode). While complete "depassivation" of ZVI may be difficult to achieve in practice, the application of DC demonstrated observable restoration of reactivity of the passivated ZVI. This study provides evidence that this approach may significantly extend the life of a ZVI PRB.
可渗透反应栅（PRB）由零价铁（ZVI）组成，易发生钝化，从而导致含氯溶剂的去除率随时间显著降低。在这项研究中，应用低直流（DC）电流来恢复钝化 ZVI 的还原能力。电流施加到充满预钝化 ZVI 和砂混合物的实验室柱式反应器中。通过放置在反应器两端的两个不锈钢电极施加可变电压设置（0-12V）。虽然仅观察到部分恢复钝化 ZVI 的还原能力，但当施加电流时，三氯乙烯（TCE）的去除率始终更高，并且 TCE 的去除率大致与电压水平成正比。尽管在柱内观察到 TCE 去除的速率和程度存在差异，但值得注意的是，TCE 去除不限于电子进入的柱的区域（即阴极）。虽然在实际中可能难以实现 ZVI 的完全“去钝化”，但 DC 的应用证明了钝化 ZVI 的反应性可以得到明显恢复。这项研究提供了证据，表明这种方法可能显著延长 ZVI PRB 的使用寿命。
