Earth and Planetary Sciences ETDs

Publication Date

Fall 11-15-2018

Abstract

Uranium in-situ recovery (ISR) is a subsurface aqueous mining technique used to extract uranium from sandstone roll-front deposits. After ISR mining, groundwater restoration is conducted to decrease concentrations of residual U(VI) and other contaminants leftover in the groundwater. Sodium dithionite, a strong chemical reductant, is being tested for use in groundwater restoration following uranium ISR at the Smith Ranch-Highland site in Wyoming. Sodium dithionite has been used to remediate chromium plumes by creating an in-situ permeable reactive barrier, but there has been no work using sodium dithionite for groundwater restoration following uranium ISR mining.

Laboratory batch and column experiments, and two push-pull field tests were conducted to test the reductive capacity imparted to post-mined sediments from the Smith Ranch-Highland site after treatment with sodium dithionite. In one laboratory column and batch experiment, where sediments had high uranium and organic carbon content, sodium dithionite did not impart a reductive capacity to the post-mined sediments, suggesting dithionite reacts differently with organic carbon which inhibits the reduction of U(VI) to U(IV). In laboratory batch and column experiments with post-mined sediments low in organic carbon content, and in the push-pull field tests, sodium dithionite imparted a reductive capacity to the sediments that reduced a given amount of aqueous electron acceptors. Thus, the volume of water that can be effectively treated by a dithionite deployment (the metric that mining companies most care about) will depend on the concentration (in equivalents/liter) of electron acceptors that the water contains.

Degree Name

Earth and Planetary Sciences

Level of Degree

Masters

Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Dr. Gary Weissmann

Second Committee Member

Dr. Jose Cerrato

Third Committee Member

Dr. Laura Crossey

Fourth Committee Member

Dr. Paul Reimus

Language

English

Keywords

uranium, in-situ recovery, sodium dithionite, Smith Ranch-Highland site

Document Type

Thesis

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