Pilot Test of the Permeable Reactive Barrier for Removing Uranium from the Gunnar Pit Runoff Water

Uranium U2020, 2020

Dexu Kong, Alexey Klyashtorin, Wenhui Xiong, Lesley McGilp and Ian Wilson

This work reports on applying the iron oxide coated sands media in an experimental permeable reactive barrier to remove uranium species from flowing water.  A field experiment was conducted at the legacy Gunnar uranium mine & mill site that was abandoned in 1960s with limited to no decommissioning. The flooded Gunnar mine pit presently contains about 3.2 million m3 of water contaminated by dissolved U (1.2 mg/l), Ra-226 (0.4 Bq/l), and minor concentrations of other contaminants (As, Se, etc.). The water is seeping over the pit rim into Lake Athabasca posing environmental and health concerns. Iron oxide coated sands can be used to immobilize uranium species through adsorption process. Methods for preparation of hydrous ferric oxide sorbents and their supported forms onto silica sands were described. Fourier transform infrared spectroscopy (FTIR), and powder X-ray diffraction (pXRD) were used to characterize physical-chemical properties of the sorbent. The monolayer uranium uptake capacity (Qm) was estimated through the Langmuir isotherm. Adsorption kinetic experiments were performed in a lab environment prior to moving to a field trial. Based on these lab results and the input on field-scale appropriate geometries, a pilot permeable reactive barrier was fabricated and a field test conducted near the Gunnar pit in July 2019. This pilot test provided technical data and information needed for designing a full-scale permeable barrier based on the iron oxide coated sands, which can be applied for in-situ water treatment at Gunnar and other legacy uranium sites.
Keywords: Adsorption, Breakthrough, Iron oxide coated sands, Permeable reactive barrier, Uranium