g/L. Chromate removal was also measured in columns packed with zerovalent iron filings over this same concentration range. Electrochemical measurements were made to determine the free corrosion potential and corrosion rate of the iron reactants. In both the batch and column reactors, absolute rates of chromium removal declined with increasing chromate concentration. Corrosion current measurements indicated that the rate of iron corrosion decreased with increasing Cr(VI) concentrations between 0 and 5000 g/L. At a Cr(VI) concentration of 10 000 g/L, Tafel polarization diagrams showed that chromium removal was affected by its diffusion rate through a passivating oxide film and by the ability of iron to release Fe2+ at anodic sites. In contrast, water reduction was not mass transfer limited, but chromium did decrease the exchange current for the hydrogen evolution reaction. Even at the most passivating concentration of 10 000 g/L, effluent Cr(VI) concentrations in the column reactors reached a steady state, indicating that passivation had also reached a steady state. Although chromate contributes to iron surface passivation, the removal rates are still sufficiently fast for in situ iron barriers to be effective for Cr(VI) removal at most environmentally relevant concentrations. " /> KINETICS OF SOLUBLE CHROMIUM REMOVAL FROM CONTAMINATED WATER BY ZEROVALENT IRON MEDIA: CORROSION INHIBITION AND PASSIVE OXIDE EFFECTS. (R825223) | Science Inventory | US EPA

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KINETICS OF SOLUBLE CHROMIUM REMOVAL FROM CONTAMINATED WATER BY ZEROVALENT IRON MEDIA: CORROSION INHIBITION AND PASSIVE OXIDE EFFECTS. (R825223)

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Citation:

Melitas, N., O. Chuffe, AND J. Farrell. KINETICS OF SOLUBLE CHROMIUM REMOVAL FROM CONTAMINATED WATER BY ZEROVALENT IRON MEDIA: CORROSION INHIBITION AND PASSIVE OXIDE EFFECTS. (R825223). ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 35(19):3948-3953, (2001).

Description:

Permeable reactive barriers containing zerovalent iron are being increasingly
employed for in situ remediation of groundwater contaminated with redox active
metals and chlorinated organic compounds. This research investigated the effect
of chromate concentration on its removal from solution by zerovalent iron.
Removal rates of aqueous Cr(VI) by iron wires were measured in batch experiments
for initial chromium concentrations ranging from 100 to 10 000 src="/ncer/pubs/images/mgr.gif">g/L. Chromate removal was also measured in
columns packed with zerovalent iron filings over this same concentration range.
Electrochemical measurements were made to determine the free corrosion potential
and corrosion rate of the iron reactants. In both the batch and column reactors,
absolute rates of chromium removal declined with increasing chromate
concentration. Corrosion current measurements indicated that the rate of iron
corrosion decreased with increasing Cr(VI) concentrations between 0 and 5000
g/L. At a Cr(VI) concentration of 10 000
g/L, Tafel polarization diagrams showed
that chromium removal was affected by its diffusion rate through a passivating
oxide film and by the ability of iron to release Fe2+ at anodic
sites. In contrast, water reduction was not mass transfer limited, but chromium
did decrease the exchange current for the hydrogen evolution reaction. Even at
the most passivating concentration of 10 000 src="/ncer/pubs/images/mgr.gif">g/L, effluent Cr(VI) concentrations in the
column reactors reached a steady state, indicating that passivation had also
reached a steady state. Although chromate contributes to iron surface
passivation, the removal rates are still sufficiently fast for in situ iron
barriers to be effective for Cr(VI) removal at most environmentally relevant
concentrations.

Record Details:

Record Type:DOCUMENT( JOURNAL/ PEER REVIEWED JOURNAL)
Product Published Date:10/01/2001
Record Last Revised:12/22/2005
Record ID: 68997