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Thermodynamics and Complexation Reactions of Anionic Silicate Species. Annual Report September 15, 2000 through September 14, 2001.

DE2004833629

Publication Date	2002
Personal Author	Choppin, G. R.; Felmy, A. R.
Page Count	12
Abstract	Highly basic tank wastes contain several important radionuclides, including (sup 90)Sr, (sup 99)Tc, and (sup 60)Co as well as actinide elements (isotopes of U, Pu and Am). A fraction of these wastes are known to have leaked into the vadose zone at the Hanford Site. Upon entering the sediments in the vadose zone, such highly basic solutions dissolve concentrations of silica from the silica and aluminosilicate minerals present in subsurface. These dissolution reactions alter the chemical composition of the leaking solutions, transforming them from highly basic (as high as 2 M NaOH) solution into a pore solution with dissolved silica and significantly reduced pH. This moderately basic (pH 9 to 10), high-silica solution has the potential to complex radionuclides and promote migration through the subsurface. This path of radionuclide migration currently is not a recognized transport mode in the factors that are modeled for radionuclide transport through the vadose zone beneath leaking tanks. The goal of this project is to ascertain the free monosilicic acid concentration, and the degree of polymerization as a function of pH and total concentration of silicate ions, and to use this data to measure the interaction of radionuclides of Co(II), Sr(II), Nd(III), Eu(III), Am(III), U(VI) and Th(IV) with the ionic silicate.
Keywords	Actinides Chemical composition Silicates Dissolution Polymerization Radioisotopes Radionuclide migration Sediments Silica Tanks Thermodynamics Transport Wastes
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Florida State Univ., Tallahassee.; Department of Energy, Washington, DC.; Pacific Northwest National Lab., Richland, WA.
Supplemental Notes	Prepared in cooperation with Pacific Northwest National Lab., Richland, WA. Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200512

Thermodynamics and Complexation Reactions of Anionic Silicate Species. Annual Report September 15, 2000 through September 14, 2001.

Thermodynamics and Complexation Reactions of Anionic Silicate Species. Annual Report September 15, 2000 through September 14, 2001.
DE2004833629

Publication Date	2002
Personal Author	Choppin, G. R.; Felmy, A. R.
Page Count	12
Abstract	Highly basic tank wastes contain several important radionuclides, including (sup 90)Sr, (sup 99)Tc, and (sup 60)Co as well as actinide elements (isotopes of U, Pu and Am). A fraction of these wastes are known to have leaked into the vadose zone at the Hanford Site. Upon entering the sediments in the vadose zone, such highly basic solutions dissolve concentrations of silica from the silica and aluminosilicate minerals present in subsurface. These dissolution reactions alter the chemical composition of the leaking solutions, transforming them from highly basic (as high as 2 M NaOH) solution into a pore solution with dissolved silica and significantly reduced pH. This moderately basic (pH 9 to 10), high-silica solution has the potential to complex radionuclides and promote migration through the subsurface. This path of radionuclide migration currently is not a recognized transport mode in the factors that are modeled for radionuclide transport through the vadose zone beneath leaking tanks. The goal of this project is to ascertain the free monosilicic acid concentration, and the degree of polymerization as a function of pH and total concentration of silicate ions, and to use this data to measure the interaction of radionuclides of Co(II), Sr(II), Nd(III), Eu(III), Am(III), U(VI) and Th(IV) with the ionic silicate.
Keywords	Actinides Chemical composition Silicates Dissolution Polymerization Radioisotopes Radionuclide migration Sediments Silica Tanks Thermodynamics Transport Wastes
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Florida State Univ., Tallahassee.; Department of Energy, Washington, DC.; Pacific Northwest National Lab., Richland, WA.
Supplemental Notes	Prepared in cooperation with Pacific Northwest National Lab., Richland, WA. Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200512