Abstract
Ethylenediaminetetracetic acid (EDTA), which was co-disposed with Pu at several US Department of Energy sites, has been reported to enhance the solubility and transport of Pu. It is generally assumed that this enhanced transport of Pu in geologic environments is a result of complexation of Pu(IV) with EDTA. However, the fundamental basis for this assumption has never been fully explored. Whether EDTA can mobilize Pu(IV) in geologic environments is dependent on many factors, chief among them are not only the complexation constants of Pu with EDTA and dominant oxidation state and the nature of Pu solids, but also (1) the complexation constants of environmentally important metal ions (e.g., Fe, Al, Ca, Mg) that compete with Pu for EDTA and (2) EDTA interactions with the geomedia (e.g., adsorption, biodegradation) that reduce effective EDTA concentrations available for complexation. Extensive studies over a large range of pH values (1 to 14) and EDTA concentrations (0.0001 to 0.01 mol⋅L−1) as a function of time were conducted on the solubility of 2-line ferrihydrite (Fe(OH)3(s)), PuO2(am) in the presence of different concentrations of Ca ions, and mixtures of PuO2(am) and Fe(OH)3(s). The solubility data were interpreted using Pitzer’s ion-interaction approach to determine/validate the solubility product of Fe(OH)3(s), the complexation constants of Pu(IV)-EDTA and Fe(III)-EDTA, and to determine the effect of EDTA in solubilizing Pu(IV) from PuO2(am) in the presence of Fe(III) compounds and aqueous Ca concentrations. Predictions based on these extensive fundamental data show that environmental mobility of Pu as a result of Pu(IV)-EDTA complexation as reported/implied in the literature is a myth rather than the reality. The data also show that in geologic environments where Pu(III) and Pu(V) are stable, the EDTA complexes of these oxidation states may play an important role in Pu mobility.
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References
Ayers, J.A.: Decontamination of Nuclear Reactors and Equipment. Ronald Press Co., New York (1970)
Piciulo, P.L., Adams, J.W., Davis, M.S., Milian, L.W., Anderson, C.I.: Release of organic chelating agents from solidified decontamination wastes. Springfield (1986)
McFadden, K.M.: Organic components of nuclear wastes and their potential for altering radionuclide distribution when released to soil. Pacific Northwest National Laboratory Richland (1980)
Freeman-Pollard, J.R., Caggiano, J.A., Trent, S.J.: Engineering evaluation of the GAO-RCED-89-157, Tank 241-T-106 vadose zone investigations (1994)
Cleveland, J.M., Rees, T.F.: Characterization of plutonium in Maxey Flats radioactive trench leachates. Science 212, 1506–1509 (1981)
Riley, R.G., Zachara, J.M., Wobber, F.J.: Chemical contaminants on DOE lands and selection of contaminant mixtures for subsurface science research. National Technical Information Service, US Department of Commerce, Springfield (1992)
Boukhalfa, H., Reilly, S.D., Smith, W.H., Neu, M.: EDTA and mixed-ligand complexes of tetravalent and trivalent plutonium. Inorg. Chem. 43, 5816–5823 (2004)
Cauchetier, P., Guichard, C.: Electrochemical and spectrophotometric study of the complexes of plutonium ions with EDTA. I. Plutonium(III) and (IV). Radiochim. Acta 19, 137–146 (1973)
Foreman, J.K., Smith, T.D.: The nature and stability of the complex ions formed ter-, quadri-, and sexa-valent plutonium ions with ethylenediaminetetraacetic acid. Part I. pH titrations and ion-exchange studies. J. Chem. Soc. 2, 1752–1758 (1957)
Foreman, J.K., Smith, T.D.: The nature and stability of the complex ions formed by ter-, quadri-, and sexa-valent plutonium ions with ethylenediamineteraacetatic acid (EDTA). Part II. Spectroscopic studies. J. Chem. Soc. 2, 1758–1762 (1957)
AlMahamid, I., Becraft, K.A., Hakem, N.L., Gatti, R.C., Nitsche, H.: Stability of various plutonium valence states in the presence of NTA and EDTA. Radiochim. Acta 74, 129–134 (1996)
Reed, D.T., Wygmans, D.G., Aase, S.B., Banaszak, J.E.: Reduction of Np(VI) and Pu(IV) by organic chelating agents. Radiochim. Acta 82, 109–114 (1998)
Rusin, P.A., Quintana, L., Brainard, J.R., Strietelmeir, B.A., Trait, C.D., Ekberg, S.A., Palmer, P.D., Newton, T.W., Clark, D.L.: Solubilization of plutonium hydrous oxide by iron-reducing bacteria. Environ. Sci. Technol. 28, 1686–1690 (1994)
Rai, D., Gorby, Y.A., Fredrickson, J.K., Moore, D.A., Yui, M.: Reductive dissolution of PuO2(am): The effect of Fe(II) and hydroquinone. J. Solution Chem. 31, 433–453 (2002)
Hummel, W., Anderegg, G., Puigdomenech, I., Rao, L., Tochiyama, O.: Chemical Thermodynamics of Compounds and Complexes of U, Np, Pu, Am, Tc, Se, Ni, and Zr with Selected Organic Ligands. Elsevier, Amsterdam (2005)
Mikhailov, V.A.: Solubility of plutonium arylarsonates. Russ. J. Inorg. Chem. 14, 1119–1122 (1969)
Rai, D., Bolton, H.J., Moore, D.A., Hess, N.J., Choppin, G.R.: Thermodynamic model for the solubility of PuO2(am) in the aqueous Na+-H+-OH−-Cl−-H2O-ethylenediaminetetraacetate system. Radiochim. Acta 89, 67–74 (2001)
Guillaumont, R., Fanghanel, T., Fuger, J., Grenthe, I., Neck, V., Palmer, D.A., Rand, M.H.: Update on the Chemical Thermodynamics of Uranium, Neptunium, Plutonium, Americium, and Technetium. Elsevier, Amsterdam (2003)
Anderegg, G.: Critical Survey of Stability Constants of EDTA Complexes. IUPAC Chemical Data Series, vol. 14. Pergamon, Elmsford (1977)
Smith, R.M., Martell, A.E., Motekaitis, R.J.: NIST critically selected stability constants of metal complexes database, Version 6.0 for Windows. NIST standard reference database 46. US Department of Commerce, Gaithersburg (2001)
Schwertmann, U., Cornell, R.M.: Iron Oxides in the Laboratory. Preparation and Characterization. VCH, New York (1991)
Schramke, J.A., Rai, D., Choppin, G.R., Fulton, R.W.: Determination of aqueous plutonium oxidation states by solvent extraction. J. Radioanal. Nucl. Chem. 130, 333–346 (1989)
Cleveland, J.M.: The Chemistry of Plutonium. Gordon and Breach, New York (1970)
Pitzer, K.S.: Ion interaction approach: theory and data correlation. In: Pitzer, K.S. (ed.) Activity Coefficients in Electrolyte Solutions, pp. 75–153. CRC Press, Boca Raton (1991)
Pitzer, K.S., Mayorga, G.: Thermodynamics of electrolytes. II. Activity and osmotic coefficients for strong electrolytes with one or both ions univalent. J. Phys. Chem. 77, 2300–2308 (1973)
Felmy, A.R., Weare, J.H.: The prediction of borate mineral equilibria in natural waters: application to Searles Lake, California. Geochim. Cosmochim. Acta 50, 2771–2783 (1986)
Felmy, A.R., Rai, D., Schramke, J.A., Ryan, J.L.: The solubility of Pu(OH)3 in dilute solution and in high-ionic-strength chloride brines. Radiochim. Acta 48, 29–35 (1989)
Felmy, A.R., Mason, M.J.: An aqueous thermodynamic model for the complexation of sodium and strontium with organic chelates valid to high ionic strength. I. Ethylenedinitrilotetraacetic acid (EDTA). J. Solution Chem. 32, 283–300 (2003)
Pokrovsky, O.S., Bronikowski, M.G., Moore, R.C., Choppin, G.R.: Interaction of neptunyl(V) and U(VI) with EDTA in NaCl media: Experimental study and Pitzer modeling. Radiochim. Acta 80, 23–29 (1998)
Sterner, S.M., Felmy, A.R., Rustad, J.R., Pitzer, K.S.: Thermodynamic analysis of aqueous solutions using INSIGHT. Pacific Northwest National Laboratory Richland (1997)
Rai, D., Hess, N.J., Rao, L., Zhang, Z., Felmy, A.R., Moore, D.A., Clark, S.B., Lumetta, G.J.: Thermodynamic model for the solubility of Cr(OH)3(am) in concentrated NaOH and NaOH-NaNO3 solutions. J. Solution Chem. 31, 343–367 (2002)
Rai, D., Moore, D.A., Hess, N.J., Rao, L., Clark, C.B.: Chromium(III) hydroxide solubility in the aqueous Na+-OH−-H2PO −4 -HPO 2−4 -PO 3−4 -H2O system: A thermodynamic model. J. Solution Chem. 33, 1213–1242 (2004)
Rai, D., Moore, D.A., Hess, N.J., Rosso, K.M., Rao, L., Heald, S.M.: Chromium(III) hydroxide solubility in the aqueous K+-H+-OH−-CO2- HCO −3 - CO 2−3 -H2O system: a thermodynamic model. J. Solution Chem. 36, 1261–1285 (2007)
Eary, L.E., Rai, D.: Chromate removal from aqueous wastes by reduction with ferrous iron. Environ. Sci. Technol. 22, 972–977 (1988)
Neck, V., Altmaier, M., Seibert, A., Yun, J.I., Marquardt, C.M., Fanghanel, T.: Solubility and redox reactions of Pu(IV) hydrous oxide: Evidence for the formation of PuO2+x (s, hyd). Radiochim. Acta 95, 193–207 (2007)
Parker, V.B., Khodakovskii, I.L.: Thermodynamic properties of the aqueous ions (2+ and 3+) of iron and the compounds of iron. J. Phys. Chem. Ref. Data 24, 1699–1745 (1995)
Harvie, C.E., Moller, N., Weare, J.H.: The prediction of mineral solubilities in natural waters: the Na-K-Mg-Ca-H-Cl-SO4-OH-HCO3-CO2-H2O system to high ionic strengths at 25 degrees C. Geochim. Cosmochim. Acta 48, 723–751 (1984)
Wesolowski, D.J.: Aluminum speciation and equilibria in aqueous solution: I. The solubility of gibbsite in the system Na-K-Cl-OH-Al(OH)4 from 0 to 100 degrees C. Geochim. Cosmochim. Acta 56, 1065–1091 (1992)
Becke, A.D.: A new mixing of Hartree-Fock and local density functional theories. J. Chem. Phys. 98, 1372–1377 (1993)
Cao, X.Y., Dolg, M.: Relativistic energy-consistent ab initio pseudopotentials as tools for quantum chemical investigations of actinide systems. Coord. Chem. Rev. 250(7–8), 900–910 (2006)
Binkley, J.S., Pople, J.A., Hehre, W.J.: Self-consistent molecular orbital methods .21. Small split-valence basis sets for 1st row elements. J. Am. Chem. Soc. 102, 939–947 (1980)
Fackler, J.P., Kristine, F.J., Mazany, M.A., Moyer, T.J., Shepherd, R.E.: The absence of a titanyl oxygen in the Ti(IV)-EDTA4− complex: [Ti(EDTA)(H2O)]. Inorg. Chem. 24, 1857–1860 (1985)
Apra, E., Windus, T.L., Straatsma, T.P., Bylaska, E.J., de Jong, W., Kowalski, K., Hackler, M.T., Hirata, S., Valiev, M., Hackler, M.T., Zhao, Y., Harrison, R.J., Dupuis, M., Smith, D.M.A., Nieplocha, J., Tipparaju, V., Krishnan, M., Auer, A.A., Brown, E., Cisneros, G., Fann, G.I., Fruchtl, H., Garza, J., Hirao, K., Kendall, R., Nichols, J.A., Tsemekhman, K., Wolinski, K., Anchell, J., Bernholdt, D., Borowski, P., Clark, T., Clerc, D., Dachsel, H., Deegan, M., Dyall, K., Elwood, D., Glendening, E., Gutowski, M., Hess, A., Jaffe, J., Johnson, B., Ju, J., Kobayashi, H., Kutteh, R., Lin, Z., Littlefield, R., Long, X., Meng, B., Nakajima, T., Niu, S., Pollack, L., Rosing, M., Sandrone, G., Stave, M., Taylor, H., Thomas, G., van Lenthe, J., Wong, A., Zhang, Z.: NWChem: A computational chemistry package designed to run on high-performance parallel supercomputers, version 4.7. Pacific Northwest National Laboratory, Richland (2005)
Allen, P.G., Veirs, D.K., Conradson, S.D., Smith, C.A., Marsh, S.F.: Characterization of aqueous plutonium(IV) nitrate complexes by extended x-ray absorption fine structure spectroscopy. Inorg. Chem. 35, 2841–2845 (1996)
Clark, D.L., Conradson, S.D., Keogh, D.W., Palmer, P.D., Scott, B.L., Tait, C.D.: Identification of the limiting species in the plutonium(IV) carbonate system. Solid state and solution molecular structure of the [Pu(CO3)5]6− ion. Inorg. Chem. 37, 2893–2899 (1998)
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Rai, D., Moore, D.A., Rosso, K.M. et al. Environmental Mobility of Pu(IV) in the Presence of Ethylenediaminetetraacetic Acid: Myth or Reality?. J Solution Chem 37, 957–986 (2008). https://doi.org/10.1007/s10953-008-9282-2
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DOI: https://doi.org/10.1007/s10953-008-9282-2