Effects of solution pH and complexing reagents on uranium and thorium desorption under saturated equilibrium conditions

Conference · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7045493

Wang, Yug-Yea; Yu, C

Three contaminated bulk surface soils were used for investigating the effect of solution pH and complexing reagents on uranium and thorium desorption. At a low solution pH, the major chemical species of uranium and thorium, uranyl UO{sub 2}{sup +2}, thorium dihydroxide Th(OH){sub 2}{sup +2}, and thorium hydroxide Th(OH){sup +3}, tend to form complexes with acetates in the solution phase, which increases the fractions of uranium and thorium desorbed into this phase. At a high solution pH, important uranium and thorium species such as uranyl tricarbonate complex UO{sub 2}(CO){sub 3}{sub 3}{sup {minus}4} and thorium tetrahydroxide complex Th(OH){sub 4} tend to resist complexation with acetates. The presence of complexing reagents in solution can release radionuclides such as uranium and/or thorium from the soil to the solution by forming soluble complexes. Sodium bicarbonate (NaHCO{sub 3}) and diethylenetriaminepentaacetic acid (DTPA) are strong complex formers that released 38% to 62% of total uranium activity and 78% to 86% of total thorium activity, respectively, from the soil samples investigated. Solutions of 0.1 molar sodium nitrate (NaNO{sub 3}) and 0.1 molar sodium sulfate (Na{sub 2}SO{sub 4}) were not effective complex formers with uranium and thorium under the experimental conditions. Fractions of uranium and thorium desorbed by 0.15g/200ml humic acid ranged from 4.62% to 6.17% and 1.59% to 7.09%, respectively. This work demonstrates the importance of a knowledge of solution chemistry in investigating the desorption of radionuclides.

• Research Organization: Argonne National Lab., IL (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 7045493
• Report Number(s): ANL/CP-75634; CONF-920851--56; ON: DE92017092
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201 -- Chemical & Physicochemical Properties
54 ENVIRONMENTAL SCIENCES
540230* -- Environment
Terrestrial-- Radioactive Materials Monitoring & Transport-- (1990-)
ACTINIDE COMPOUNDS
CHELATING AGENTS
CONTAMINATION
DESORPTION
PH VALUE
SOILS
SORPTION
THORIUM COMPOUNDS
URANIUM COMPOUNDS