Remediation of Uranium Contaminated Mine Waste

Collaborators: R. Wong, J. B. Harsh (Washington State University)


The Pacific Northwest, and in particular the states of Washington and Idaho, contain many mining facilities. Movement of uranium out of mine waste material may pose a serious environmental hazard. Leaching of uranium may pollute ground water systems and ultimately contaminate drinking water sources. It has been suggested that layers of zero-valent iron or apatite can act as an efficient barrier for uranium leaching out of waste material. The objective of the proposed research was to evaluate the efficacy of apatite to extract uranium from water contaminated by mining operations. Column experiments were used to determine reaction rate coefficients of uranium sorption/precipitation and to determine the sorption capacity of porous materials suggested as leaching barriers. The experiments comprised of an apatite column, and two solution compositions (typical ground water from the Midnite mine site near Spokane, Washington, and carbonate saturated ground water). Column outflow was analyzed for Uranium concentrations by ICP-AES and ICP-MS. Sediment samples from the column experiments were analyzed by Scanning Electron Microsopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDXS). Transport tests in columns showed that apatite is a very effective material to remove uranium from the liquid phase. In two column studies using columns of length 20 to 24 cm, uranium was not detected in the column outflow during 270 and 180 days of column throughflow. The column throughflow corresponded to about 1,600 and 11,000 pore volumes of solution passing through the columns. EDXS analyses demonstrated that uranium migrated to a depth of about 3 cm in the large column and 4 cm in the small column.

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Markus Flury
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