Environ. Sci. Technol, 1995, 29, 2936-2945
Anaerobic Corrosion of Granular Iron: Measurement and Interpretation of Hydrogen Evolution Rates ERIC
J. REARDON
Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
corrodes by the oxidative action of water itself: Fe(s) + 2H20(1)
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Introduction Interest is growing in the use of granulated iron to remediate groundwater contaminated with halogenated hydrocarbons, such as trichloromethane (TCM), tetrachloroethene (PCE), and trichloroethene (TCE) (1—6). Although the chemical mechanisms are still a subject of research, granulated iron promotes rapid dechlorination of these hydrocarbons in groundwater. Any future applications of this technology to groundwater remediation would be designed to operate under anaerobic conditions so as to prevent or inhibit corrosion of the iron by oxygen. Nevertheless, even in the absence of oxygen, iron still *
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2936
ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 29, NO. 12, 1995
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20H" + H2(g)
(1)
In this reaction, 1 mol of hydrogen gas is generated for every mole of iron corroded. The accompanying production of Fe2+ and OH" ions is of considerable importance to the geochemical design of a potential groundwater treatment system. Corrosion-produced OH" ions will increase pH and react with dissolved carbonic acid and bicarbonate species in the groundwater to produce carbonate ions: H2C03° + 20H"
Anaerobic corrosion of iron metal produces Fe2+, OH", and H2
