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Uranium Immobilization by Hydrogen Sulfide Gaseous Treatment under Vadose Zone Conditions

^a Pacific Northwest National Lab., Richland, WA 99354
^b Univ. of Missouri, Columbia, MO 65211

View larger version (19K): [in this window] [in a new window]   Fig. 1. Soil treatment column effluent normalized H2S concentration. Q is the flow rate of the gas mixture through the column.

View larger version (14K): [in this window] [in a new window]   Fig. 2. Effluent H2S concentration and moisture from the column of soil treated with the moisturized gas mixture.

View larger version (23K): [in this window] [in a new window]   Fig. 3. (A) Effluent U(VI) and fraction of U immobilized, and (B) effluent O2 concentration in column tests. Test Col-II: untreated Hanford Site soil; Col-III: soil treated with dry H2S–N2 gas; Col-IV: soil treated with the moisturized gas mixture. Uranium(VI) in simulated groundwater (SGW) at similar concentration was used as the influent in all tests; DIW is deionized water.

View larger version (13K): [in this window] [in a new window]   Fig. 4. Sorption isotherms for U(VI) in deionized water (DIW) and in simulated grounwater (SGW) sorbed to pristine Hanford soil. The symbols are measured data and the lines are the best fit using the Freundlich model.

View larger version (23K): [in this window] [in a new window]   Fig. 5. Activity diagram illustrating stability fields of U(VI) aqueous and solid species (shaded field) for pCO2 = 10–3.5 and under oxidizing conditions in (A) deionized water and (B) simulated groundwater. Symbol indicates the location of the solution used in this work.

View larger version (19K): [in this window] [in a new window]   Fig. 6. Immobilized U concentration in sediments across column. The distance from the column influent end was measured from the center of each section. Uranium(IV) was determined based on the measured total U and U(VI) concentration.