Geochemical modeling and laboratory studies of aquifer restoration at an in situ leach uranium mine

Conference · Sat Jun 01 04:00:00 EDT 1985

OSTI ID:5353131

Martin, W J; Deutsch, W J; Serne, R J

Flow-through column experiments were performed at Pacific Northwest Laboratory to simulate aquifer restoration by contacting aquifer sediment with leaching solution (lixiviant) under anoxic conditions. The chemical composition of the effluent solutions were determined to monitor the progress of restoration. The results were used to identify chemical mechanisms in the water/sediment system that occur during aquifer restoration. The movement of uranium through the column was initially retarded as a result of interactions with the sediment. A possible mechanism to explain the behavior of uranium involves the presence of pyrite. When pyrite is oxidized, the Fe(III) produced forms ferric hydroxide minerals, which have a strong sorption affinity for uranium. Adsorption of uranium onto the ferric hydroxide and clay surfaces could lower the concentration of uranium in solution. As the lixiviant displaced the residual pore water in the column, the calcium, magnesium, and sulfate concentrations decreased and the sodium concentration and pH increased. This effect probably was caused by ion exchange between dissolved constituents and cations on the sediments' surfaces. After examining the data, we developed a conceptual chemical model of the system that incorporated the reactants and chemical processes that appeared to be important. Then, we modeled the interaction of the lixiviant with the sediment during flow through the column. The chemical processes incorporated in the model included oxidation of pyrite, the dissolution and equilibration of magnesian calcite, ion exchange, and aqueous complexation of dissolved constituents. The equilibrium geochemical computer code, MINTEQ, was used to make the necessary speciation and mass transfer calculations. The model results were then compared with the observed effluent solution compositions. 7 refs., 8 figs., 5 tabs.

• Research Organization: Pacific Northwest Labs., Richland, WA (USA)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 5353131
• Report Number(s): PNL-SA-13119; CONF-850893-2; ON: TI85017902
• Country of Publication: United States
• Language: English

Related Subjects

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11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
58 GEOSCIENCES
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BENCH-SCALE EXPERIMENTS
CHEMISTRY
COMPUTER CODES
DISSOLUTION
ENVIRONMENTAL EFFECTS
ENVIRONMENTAL QUALITY
GEOCHEMISTRY
GROUND WATER
HYDROGEN COMPOUNDS
LEACHING
M CODES
MINES
MINING
ORES
OXYGEN COMPOUNDS
ROCK-FLUID INTERACTIONS
SEDIMENTS
SEPARATION PROCESSES
SOLUTION MINING
UNDERGROUND FACILITIES
URANIUM MINES
URANIUM ORES
WATER
WATER QUALITY