The influence of humic acid and colloidal silica on the sorption of U(VI) onto SRS Sediments Collected from the F/H Area - 15499

Conference · Wed Jul 01 04:00:00 EDT 2015

OSTI ID:22824389

Gonzaleza, Hansell; Katsenovich, Yelena ^[1]; Denhamb, Miles ^[2]; Gudavallia, Ravi; Lagos, Leonel ^[1]

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1. Applied Research Center, Florida International University, 10555 W Flagler St., EC 2100, Miami, FL 33174 (United States)
2. Savannah River National Laboratory, Savannah River Site, Aiken, SC 29808 (United States)

Between 1955 and 1988, the F/H Area Seepage Basins located in the center of SRS received approximately 6,814,000 m{sup 3} of acidic waste solutions containing radionuclides and dissolved metals. Uranium (VI) is a key contaminant of concern in groundwater associated with the basins. The pump-and-treat water treatment unit designed and built in 1997 to remove metals and radionuclides eventually became less effective, prompting research for new remedial alternatives. The pump-and-treat system was discontinued in 2004, replaced with a funnel-and-gate system in which base solutions are injected at the gates to raise pH. To take advantage of the potential formation of uranium silicate minerals, Florida International University - Applied Research Center (FIU-ARC), in collaboration with Savannah River National Laboratory (SRNL), is conducting an investigation into a base containing sodium silicate to evaluate whether these solutions have sufficient alkalinity to correct the acidic nature of the aquifer sediments. The research was extended to investigate if U(VI) is bound to colloidal silica and if any synergy exists between humic acid (HA) and colloidal Si that would influence the removal of uranium. Humic substances (HS) are a major component of soil organic matter and are known for their abilities to influence the migration behavior and fate of heavy metals. Studies showed that HA function as an important ion exchange and metal-complexing ligand, carrying a large number of functional groups with high complexing capacity that can greatly affect the mobility behavior of actinides in natural systems. The study investigates if there are any synergistic interactions between U(VI) ions, humic acid and colloidal silica under oxidized conditions and studies the influence of HA and Si on the sorption of U(VI) onto sediments collected from the F/H Area. The experiments also evaluated the effects of different environmental variables such as pH, presence of U(VI) and varying concentrations of HA on the sorption behavior of U(VI) in multi-component batch systems in the pH range between 3 and 8. Several background sediment samples were collected at SRS from archived cores obtained during installation of the well FSB 91C and used for preparation of triplicate samples. The experimental matrix was set up as follows: - Batch 1: Si (3.5 mM) + U (VI) (0.5 ppm) (no sediments and no HA); - Batch 2: Si (3.5 mM) + U (VI) (0.5 ppm) + HA (10 ppm) (no sediments); - Batch 3: U (VI) (0.5 ppm) + HA (10 ppm) (no Si and no sediments); - Batch 4: Sediments + Si (3.5 mM) + U (VI) (0.5 ppm) (no HA); - Batch 5: Sediments + Si (3.5 mM) + U (VI) (0.5 ppm) + HA; - Batch 6: Sediments + U (VI) (0.5 ppm) + HA, (no Si); - Batch 7: Sediments + U (VI) (0.5 ppm) (no Si and no HA). All samples were prepared in triplicate 50-mL conical tubes. All control and experimental tubes were vortexed and kept on a shaker for 24 h at 100 rpm and room temperature. Results showed that the sediment-bearing batches typically exceeded the performance of non-sediment batches. Results showed that the sorption of U(VI) onto sediments was influenced by the pH and the presence of HA. At low pH 3, the addition of HA slightly enhances U(VI) sorption compared to the HA-free samples. This result is consistent with other studies; in the acidic pH range, the addition of HA slightly enhances U(VI) sorption relative to the HA-free system. Conversely, in the pH range of 4 to 7, the sorption of U(VI) on Si was reduced in the presence of HA in comparison to the system without HA. In subsequent experiments the concentration of HA will be increased to 50 ppm. (authors)

• Research Organization: WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
• OSTI ID: 22824389
• Report Number(s): INIS-US--19-WM-15499
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
ACID NEUTRALIZING CAPACITY
AQUIFERS
COLLOIDS
CONCENTRATION RATIO
GROUND WATER
HEAVY METALS
HUMIC ACIDS
ION EXCHANGE
LIQUID WASTES
ORGANIC MATTER
PH VALUE
RADIOISOTOPES
SAVANNAH RIVER
SEDIMENTS
SILICA
SILICATE MINERALS
SODIUM SILICATES
SOLUTIONS
SORPTION
TEMPERATURE RANGE 0273-0400 K
TUBES
URANIUM
URANIUM SILICATES
WATER TREATMENT