Use of zero-valent iron as a treatment medium for ground water remediation.

摘要

Zero-valent iron (ZVI) has been used widely as a reactive material in permeable reactive barriers (PRBs) to treat ground water contaminated by halogenated organic carbons and/or heavy metals such as hexavalent chromium and uranium via reduction. In addition to contaminants reduction, ZVI is oxidized, forming iron corrosion products (ICPs). The iron corrosion process and the formation of ICPs, mainly iron oxides, also provide other opportunities for ground water remediation in ZVI-PRB barriers. The treatment of two common ground water contaminants, arsenic and perchlorate, via ZVI-related reactions is examined in this dissertation.;The first portion of this dissertation was conducted to gain a better understanding of the ZVI corrosion process under typical ground water conditions. The effects of dissolved oxygen (DO), anion (SO42-, HCO3-/CO32- and Cl -) presence, and mass transfer conditions on ICP formation were studied using both batch and column experiments. A two-layer model was proposed for ICP formation in which ZVI is covered by an inner layer of magnetite and/or green rust, and an outer layer of ferric oxide.;The second portion of this dissertation was conducted to study the ability of ZVI to remove arsenite [As(III)] via adsorption to ICP formed from the ZVI. The effects of pH, alkalinity, and mass transfer efficiency on the removal of arsenite by ZVI were evaluated. A strong correlation between As(III) removal and increasing Reynolds number in batch testing suggests that mass transfer efficiency plays an important role in the removal of As(III) by ZVI. A diffusion-limited adsorption model was used to describe the removal of As(III) as the result of adsorption to precipitated iron oxides generated from ZVI corrosion.;In the final portion of this dissertation, the potential of using ZVI to promote perchlorate remediation via biological reduction was investigated in the laboratory. A series of experiments were performed to study the feasibility of combining ZVI and perchlorate-reducing microorganisms (PRMs) to remove perchlorate from ground water for both ex situ and in situ field scale application. H2 produced during the process of iron corrosion by water was successfully used by PRMs as an electron donor to reduce perchlorate to chloride.