title: Electrochemical depassivation of zero-valent iron for trichloroethene reduction.
abstract: 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.
authors.affiliation: Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences, Beijing 100083, PR China.
authors.forename: Liang
authors.initials: L
authors.lastname: Chen
authors.forename: Song
authors.initials: S
authors.lastname: Jin
authors.forename: Paul H
authors.initials: PH
authors.lastname: Fallgren
authors.forename: Norbert G
authors.initials: NG
authors.lastname: Swoboda-Colberg
authors.forename: Fei
authors.initials: F
authors.lastname: Liu
authors.forename: Patricia J S
authors.initials: PJ
authors.lastname: Colberg
mesh_terms: D055664:Electrochemical Techniques; D052918:Environmental Restoration and Remediation / Q000379:methods*; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D014241:Trichloroethylene / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D014874:Water Pollutants, Chemical; D014241:Trichloroethylene; D007501:Iron