Chromate Reduction and Retention Processes within Arid Subsurface Environments
Chromate is a widespread contaminant that has deleterious impacts on human health, the mobility and toxicity of which are diminished by reduction to Cr(III). While biological and chemical reduction reactions of Cr(VI) are well resolved, reduction within natural sediments, particularly of arid environments, remains poorly described. Here, we examine chromate reduction within arid sediments from the Hanford, WA site, where Fe(III) (hydr)oxide and carbonate coatings limit mineral reactivity. Chromium(VI) reduction by Hanford sediments is negligible unless pretreated with acid; acidic pretreatment of packed mineral beds having a Cr(VI) feed solution results in Cr(III) associating with the minerals antigorite and lizardite in addition to magnetite and Fe(II)-bearing clay minerals. Highly alkaline conditions (pH > 14), representative of conditions near high-level nuclear waste tanks, result in Fe(II) dissolution and concurrent Cr(VI) reduction. Additionally, Cr(III) and Cr(VI) are found associated with portlandite, suggesting a secondary mechanism for chromium retention at high pH. Thus, mineral reactivity is limited within this arid environment and appreciable reduction of Cr(VI) is restricted to highly alkaline conditions resulting near leaking radioactive waste disposal tanks.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
- Sponsoring Organization:
- Doe - Office Of Science
- DOE Contract Number:
- DE-AC02-98CH10886
- OSTI ID:
- 913883
- Report Number(s):
- BNL-78451-2007-JA; ESTHAG; TRN: US0801394
- Journal Information:
- Environ. Sci. Tech., Vol. 39, Issue 20; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
Similar Records
The reactivity of Fe(II) associated with goethite formed during short redox cycles toward Cr(VI) reduction under oxic conditions
Kinetics and mechanisms of metal retention/release in geochemical processes in soil. 1998 annual progress report