Date of Award

8-2013

Degree Name

Master of Science

Department

Geological and Environmental Sciences

First Advisor

Dr. Carla M. Koretsky

Second Advisor

Dr. R.V. Krishnamurthy

Third Advisor

Dr. Alan Kehew

Keywords

absorption, Cr(vi), modeling, mixtures, minerals

Access Setting

Masters Thesis-Open Access

Abstract

Hexavalent chromium (Cr(VI)) is a waste product of many anthropogenic processes. Because it is highly mobile, the improper disposal of Cr(VI) has caused widespread contamination. Because reduction and adsorption reactions may reduce the bioavailability and mobility of Cr(VI) in environmental systems, a better understanding of Cr(VI) adsorption behavior will improve remediation efforts.

Subsurfaces and soils are heterogeneous, however most studies focus on single sorbate/sorbent interactions to develop surface complexation models (SCM) for prediction of heavy metal adsorption. Theoretically, combining the SCMsdeveloped for single sorbate/sorbent systems should yield accurate predictions of adsorption in more complex systems (i.e., the component additivity approach of Davis et al., 1998).

To assess this hypothesis, Cr(VI) adsorption on mineral assemblages of goethite, kaolinite, montmorillonite, y-alumina, hydrous manganese oxide (HMO), and hydrous ferric oxide (HFO) in equal surface areas, measured as a function of pH, ionic strength and pC02 were conducted. Double layer models (DLMs) developed for Cr(VI) adsorption on the pure solids were used to predict Cr(VI) adsorption in the mixed solid systems and compared with measured edges for the various mineral assemblages.

This study found that the simple additivity approach did not accurately predict adsorption in various conditions. Additional research is required to determine if particle-particle interactions or lack of robust single solid DLMs is more likely the cause.

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