The effects of bicarbonate and mineral surfaces on uranium immobilization under anaerobic conditions

For four decades, from 1940 through 1980, the U.S. Department of Energy (DoE) extensively mined and processed uranium at various sites. As a result, widespread uranium contamination exists in subsurface sediments and aquifers. In subsurface environments, uranium primarily exists as U(VI) or U(IV), oxidized and reduced species, respectively. U(VI) is highly soluble and toxic, U(IV), while relatively toxic, is insoluble which greatly reduces its exposure pathways. We seek to examine the role of ferric iron on U(VI) reduction by adsorbing U(VI) onto ferric and non-ferric mineral surfaces in the presence of a reductant. Further, we seek to understand the role that NaHCO3, a natural groundwater buffer, has in the reductive geochemical transformations of U(VI) adsorbed on ferric and non-ferric mineral surfaces. Bench top studies were performed using 100 uM U(VI) and the reductant AHQDS, in the presence and absence of Fe-Gel (amorphous ferric oxyhydroxide) and gamma-Al2O3. In the presence of a HEPES buffer at pH 8, results demonstrate direct homogeneous reduction in several hours in the absence of Fe-Gel or gamma-Al2O3, and reduction within a 48-hour period in the presence Fe-Gel or gamma-Al2O3. While adsorbed to both ferric and non-ferric mineral surfaces, U(VI) reduction is inhibited. U(VI) reduction in the presence of NaHCO3 buffer also inhibits U(VI) reduction.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Environ Engr in Civil Engr

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Jurado, Luis A.

Contributors dc:contributor

• Werth, Charles J.

• uranium
• remediation
• uranium biogeochemistry
• uranium remediation

Statement dc:rights

• Copyright 2011 Luis A. Jurado

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/26036

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/26036