Hostname: page-component-76fb5796d-r6qrq Total loading time: 0 Render date: 2024-04-30T04:47:43.969Z Has data issue: false hasContentIssue false
  • English
  • Français

Neptunium(V) Sorption on Montmorillonite: An Experimental and Surface Complexation Modeling Study

Published online by Cambridge University Press:  28 February 2024

David R. Turner ,
Roberto T. Pabalan  and
F. Paul Bertetti
David R. Turner
Affiliation:
Center for Nuclear Waste Regulatory Analyses, 6220 Culebra Road, San Antonio, Texas 78238-5166
Roberto T. Pabalan
Affiliation:
Center for Nuclear Waste Regulatory Analyses, 6220 Culebra Road, San Antonio, Texas 78238-5166
F. Paul Bertetti
Affiliation:
Cambrian Systems, Inc., 6502 Bandera Road, San Antonio, Texas 78238
Get access Rights & Permissions [Opens in a new window]

Abstract

Batch sorption experiments at fixed initial Np(V) concentration (∼1 × 10−6 M 237Np), M/V ratio (4 g L−1), and ionic strength (0.1 molal NaNO3) were conducted to determine the effects of varying pH and PCO2 on Np(V) sorption on SAz-1 montmorillonite. The results show that Np(V) sorption on montmorillonite is strongly influenced by pH and PCO2. In the absence of CO2, Np(V) sorption increases over the entire pH range examined (∼3 to ∼10), with measured sorption coefficients (KD) of about 10 mL g−1 at pH < 6 to KD ∼ 1000 mL g−1 at a pH of 10.5. However, for experiments open to atmospheric CO2 (PCO2=10−3.5atm), Np(V) sorption peaks at KD ∼ 100 mL g−1 at pH of 8 to 8.5 and decreases at higher or lower pH. A comparison of the pH-dependence of Np(V) sorption with that of Np(V) aqueous speciation indicates a close correlation between Np(V) sorption and the stability field of the Np(V)-hydroxy complex NpO2OH0 (aq). In the presence of CO2 and aqueous carbonate, sorption is inhibited at pH > 8 due to formation of aqueous Np(V)-carbonate complexes. A relatively simple 2-site Diffuse-Layer Model (DLM) with a single Np(V) surface complexation reaction per site effectively simulates the complex sorption behavior observed in the Np(V)-H2O-CO2-montmorillonite system. The good agreement between measured and DLM-predicted sorption values suggests that surface complexation models based on parameters derived from a limited set of data could be useful in extrapolating radionuclide sorption over a range of geochemical conditions. Such an approach could be used to support transport modeling and could provide a better alternative to the current use of constant KD values in performance assessment transport calculations.

Keywords

Diffuse-Layer ModelMontmorilloniteNeptuniumSorptionSurface Complexation
Type
Research Article
Information
Clays and Clay Minerals , Volume 46 , Issue 3 , June 1998 , pp. 256 - 269
Copyright
Copyright © 1998, The Clay Minerals Society

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Allard, B. Olofsson, U. and Torstenfeit, B., 1984 Environmental actinide chemistry Inorg Chim Acta 94 205–221 10.1016/S0020-1693(00)88006-8.CrossRefGoogle Scholar
Allison, J.D. Brown, D.S. and Novo-Gradac, K.J., 1991 MINTEQA2/PRODEFA2, A geochemical assessment model for environmental systems: Version 3.0 user’s manual EPA/600/3-91/021 Athens, GA Environmental Protection Agency.Google Scholar
Baeyens, B. and Bradbury, M.H., 1995 A quantitative mechanistic description of Ni, Zn, and Ca sorption on Namontmorillonite Villigen, Switzerland Paul Scherrer Institute.Google Scholar
Beall, G.W. Allard, B. and Tewari, P.H., 1981 Sorption of actinides from aqueous solutions under environmental conditions Adsorption from aqueous solutions New York Plenum Pr 193–212 10.1007/978-1-4613-3264-0_10.CrossRefGoogle Scholar
Bertetti, F.P. Pabalan, R.T. Almendarez, M.G. and Jenne, E., 1998 Studies of neptunium(V) sorption on quartz, clinoptilolite, montmo-rillonite, and α-alumina Adsorption of metals by geomedia: Variables, mechanisms, and model variations New York Academic Pr 131–148 10.1016/B978-012384245-9/50005-0.CrossRefGoogle Scholar
Bidoglio, G. Tanet, G. and Chatt, A., 1985 Studies on neptunium(V) carbonate complexes under geologic repository conditions Radiochim Acta 38 21–26 10.1524/ract.1985.38.1.21.CrossRefGoogle Scholar
Bidoglio, G. Offermann, P. and Saltelli, A., 1987 Neptunium migration in oxidizing clayey sand Appl Geochem 2 275–284 10.1016/0883-2927(87)90043-6.CrossRefGoogle Scholar
Bradbury, M.H. and Baeyens, B., 1994 Sorption by cation exchange: Incorporation of a cation exchange model into geochemical computer codes. 94-07 Villigen, Switzerland Paul Scherrer Institute.Google Scholar
Danesi, P.R. Chiarizia, R. Scibona, G. and D’Alessandro, G.J., 1971 Stability constants of nitrate and chloride complexes of Np(IV), Np(V) and Np(VI) ions Inorg Nucl Che 33 3503–3510 10.1016/0022-1902(71)80672-3.CrossRefGoogle Scholar
Davis, J.A. and Leckie, J.O., 1978 Surface ionization and complex-ation at the oxide/water interface II. Surface properties of amorphous iron oxyhydroxide and adsorption of metal ions J Coll Inter Sci 67 90–107 10.1016/0021-9797(78)90217-5.CrossRefGoogle Scholar
Davis, J.A. and Kent, D.B., 1990 Surface complexation modeling in aqueous geochemistry Rev Mineral 23 177–260.Google Scholar
Dzombak, D.A. and Morel, F.M.M., 1990 Surface complexation modeling: Hydrous ferric oxide New York, NY J Wiley.Google Scholar
Fuger, J., 1992 Thermodynamic properties of actinide species relevant to geochemical problems Radiochim Acta 59 81–91.CrossRefGoogle Scholar
Gauthier, R. Ilmstadter, V. and Lieser, K.H., 1983 Simultaneous determination of the various oxidation states of neptunium at low concentrations by spectrophotometry Radiochim Acta 33 35–39.CrossRefGoogle Scholar
Grauer, R., 1994 Bentonite as a backfill material in a high-level waste repository MRS Bull 19 43–46 10.1557/S0883769400048697.CrossRefGoogle Scholar
Hardy, C.J. Scargill, D. and Fletcher, J.M., 1958 Studies on protactinium(V) in nitric acid solutions J Inorg Nucl Chem 7 257–275 10.1016/0022-1902(58)80077-9.CrossRefGoogle Scholar
Hart, K.P. Payne, T.E. van Robinson, B.J. and Iseghem, P., 1994 Neptunium uptake on Boom clay—Time dependence and association of Np with fine particle Radiochim Acta 66/67 19–22 10.1524/ract.1994.6667.special-issue.19.CrossRefGoogle Scholar
Hayes, K.F. Redden, G.G. Ela, W. and Leckie, J.O., 1991 Surface complexation models: An evaluation of model parameter estimation using FITEQL and oxide mineral titration data J Coll Interface Sci 142 448–469 10.1016/0021-9797(91)90075-J.CrossRefGoogle Scholar
Hsi, C.-K. and Langmuir, D., 1985 Adsorption of uranyl onto ferric oxyhydroxides: Application of the surface complexation site-binding model Geochim Cosmochim Acta 49 1931–1941 10.1016/0016-7037(85)90088-2.Google Scholar
Itagaki, H. Nakayama, S. Tanaka, S. and Yamawaki, M., 1992 Effect of ionic strength on the solubility of neptunium(V) hydroxide Radiochim Acta 58/59 61–66 10.1524/ract.1992.5859.1.61.CrossRefGoogle Scholar
Kozai, N., 1994 Sorption characteristics of neptunium by smectite, in Progress report on safety research on radioactive waste management for the period April 1992 to March 1993 JAERI-M94-027 Tokai, Japan Japan Atomic Energy Research Institute 39–41.Google Scholar
LaFlamme, B.D. and Murray, J.W., 1987 Solid/solution interaction: The effect of carbonate alkalinity on adsorbed thorium Geochim Cosmochim Acta 51 243–250 10.1016/0016-7037(87)90235-3.CrossRefGoogle Scholar
Lemire, R.J., 1984 An assessment of the thermodynamic behavior of neptunium in water and model groundwaters from 25 to 150°C AECL-7817 Pinawa, Manitoba Atomic Energy of Canada Limited.Google Scholar
Lemire, R.J. and Garisto, F., 1989 The solubility of U, Np, Pu, Th, and Tc in a geologic disposal vault for used nuclear fuel AECL-10009 Pinawa, Manitoba Atomic Energy of Canada Limited.Google Scholar
Lemire, R.J. Boyer, G.D. and Campbell, A.B., 1993 The solubilities of sodium and potassium dioxoneptunium (V) carbonate hydrates at 30, 50 and 75°C Radiochim Acta 61 57–63 10.1524/ract.1993.61.2.57.CrossRefGoogle Scholar
Lieser, K.H. and Mühlenweg, U., 1988 Neptunium in the hydrosphere and in the geosphere 1. Chemistry of neptunium in the hydrosphere and sorption of neptunium from groundwaters on sediments under aerobic and anaerobic conditions Radiochim Acta 43 27–35 10.1524/ract.1988.43.1.27.CrossRefGoogle Scholar
McKinley, J.P. Zachara, J.M. Smith, S.C. and Turner, G.D., 1995 The influence of hydrolysis and multiple site-binding reactions on adsorption of U(VI) to montmorillonite Clays Clay Miner 43 586–598 10.1346/CCMN.1995.0430508.CrossRefGoogle Scholar
Nakayama, S. and Sakamato, Y., 1991 Sorption of neptunium on naturally-occurring iron-containing minerals Radiochim Acta 52/53 153–157.CrossRefGoogle Scholar
Neck, V. Runde, W. and Kim, J.I., 1995 Solid-liquid equilibria of neptunium(V) in carbonate solutions of different ionic strengths: Solubility of the solid phases J Alloys Compounds 225 295–302 10.1016/0925-8388(94)07099-7.CrossRefGoogle Scholar
Nitsche, H. Gatti, R.C. Standifer, E.M. Lee, S.C. Müller, A. Prussin, T. Deinhammer, R.S. Maurer, H. Becraft, K. Leung, S. and Carpenter, S., 1993 Measured solubilities and speciations of neptunium, plutonium, and americium in a typical groundwater (J-13) from the Yucca Mountain region milestone report 3010-WBS 1.2.3.4.1.3.1 LA-12562-MS Los Alamos, NM Los Alamos National Laboratory.Google Scholar
Nitsche, H. Roberts, K. Becraft, K. Prussin, T. Keeney, D. Carpenter, S. and Hobart, D., 1995 Solubility and speciation results from over- and undersaturation experiments on neptunium, plutonium, and americium in water from Yucca Mountain region well UE-25p#1 LA-13017-MS Los Alamos, NM Los Alamos National Laboratory.Google Scholar
Ohe, T. Tsukamoto, M. Fujita, T. Hesbol, R. and Hermansson, H.-P., 1993 Temperature and pH dependence of neptunium(V) sorption on bentonite 1993 Int Conf on Nuclear Waste Management and Environmental Remediation 1 197–205.Google Scholar
Pabalan, R.T. and Turner, D.R.. 1991. Sorption modeling for HLW performance assessment. In: Patrick, W., editor. Report on research activities for the quarter July 1, 1991 through September 30, 1991. CNWRA 91-03Q. San Antonio, Texas: Center for Nuclear Waste Regulatory Analyses. p 9–1 to 9–20.Google Scholar
Pabalan, R.T. and Turner, D.R., 1997 Uranium(6+) sorption on montmorillonite: Experimental and surface complexation modeling study Aquatic Geochem 2 203–226 10.1007/BF00119855.CrossRefGoogle Scholar
Pabalan, R.T. Turner, D.R. Bertetti, F.P. Prikryl, J.D. and Jenne, E., 1998 Ura-nium(VI) sorption onto selected mineral surfaces: Key geochemical parameters Adsorption of metals by geomedia: Variables, mechanisms, and model variations New York Academic Pr 99–130 10.1016/B978-012384245-9/50004-9.CrossRefGoogle Scholar
Pickett, D.A. Murrell, M.T. and Williams, R., 1994 Determination of femtogram quantities of protactinium in geologic samples by thermal ionization mass spectrometry Anal Chem 66 1044–1049 10.1021/ac00079a020.CrossRefGoogle Scholar
Righetto, L. Bidoglio, G. Azimonti, G. and Bellobono, I.R., 1991 Competitive actinide interactions in colloidal humic acid-mineral oxide systems Env Sci Tech 25 1913–1919 10.1021/es00023a012.CrossRefGoogle Scholar
Sakamoto, Y. Konishi, M. Shirahashi, K. Senoo, M. and Moriyama, N., 1990 Adsorption behavior of neptunium for soil Radioactive Waste Management and the Nuclear Fuel Cycle 15 13–25.Google Scholar
Sanchez, A.L. Murray, J.W. and Sibley, T.H., 1985 The adsorption of plutonium IV and V on goethite Geochim Cosmochim Acta 49 2297–2307 10.1016/0016-7037(85)90230-3.CrossRefGoogle Scholar
Sverjensky, D.A. and Sahai, N., 1996 Theoretical prediction of single-site surface-protonation equilibrium constants for oxides and silicates in water Geochim Cosmochim Acta 60 3773–3797 10.1016/0016-7037(96)00207-4.CrossRefGoogle Scholar
Thompson, R.C., 1982 Neptunium—The neglected actinide: A review of the biological and environmental literature Radiat Res 90 1–32 10.2307/3575792.CrossRefGoogle ScholarPubMed
Torstenfeit, B. Rundberg, R.S. and Mitchell, A.J., 1988 Actinide sorption on granites and minerals as a function of pH and colloids/pseudocolloids Radiochim Acta 44/45 111–117.CrossRefGoogle Scholar
Triay, I.R. Robinson, B.A. Lopez, R.M. Mitchell, A.J. and Overly, C.M., 1993 Neptunium retardation with tuffs and groundwaters from Yucca Mountain Proc 4th Annu Int Conf on High-Level Radioactive Waste Management La Grange Park, IL Am Nuclear Soc 1504–1508.Google Scholar
TRW Environmental Safety Systems, Inc., 1995 Total System Performance Assessment—1995: An evaluation of the potential Yucca Mountain repository B00000000-01717-2200-00136, Rev. 01 Las Vegas, NV TRW Environmental Safety Systems, Inc.Google Scholar
Turner, D.R. and Sassman, S.A., 1996 Approaches to sorption modeling for high-level waste performance assessment J Contamin Hydrol 21 311–332 10.1016/0169-7722(95)00056-9.CrossRefGoogle Scholar
Turner, G.D. Zachara, J.M. McKinley, J.P. and Smithand, S.C., 1996 Surface-charge properties and UO2+ 2 adsorption of a subsurface smectite Geochim Cosmochim Acta 60 3399–3414 10.1016/0016-7037(96)00169-X.CrossRefGoogle Scholar
Waite, T.D. Davis, J.A. Payne, T.E. Waychunas, G.A. and Xu, N., 1994 Uranium(VI) adsorption to ferrihydrite: Application of a surface complexation model Geochim Cosmochim Acta 58 5465–5478 10.1016/0016-7037(94)90243-7.CrossRefGoogle Scholar
Wanner, H. Albinsson, Y. Karnl, O. Wieland, E. Wersin, P. and Charlet, L., 1994 The acid/base chemistry of montmorillonite Radiochim Acta 66/67 733–738 10.1524/ract.1994.6667.special-issue.157.CrossRefGoogle Scholar
Wescott, R.G., Lee, M.P., McCartin, T.J., Eisenberg, N.A. and Baca, R.G., eds. 1995. NRC iterative performance assessment Phase 2: Development of capabilities for review of a performance assessment for a high-level waste repository. NUREG-1464. Washington, DC: Nuclear Regulatory Commission.Google Scholar
Westall, J.C., 1982 FITEQL: A computer program for determination of chemical equilibrium constants from experimental data, Version 1.2. Rpt. 82-01 Corvallis, OR Dept of Chemistry, Oregon State Univ.Google Scholar
Westall, J.C., 1982 FITEQL: A computer program for determination of chemical equilibrium constants from experimental data, Version 2.0. Rpt. 82-02 Corvallis, OR Dept of Chemistry, Oregon State Univ.Google Scholar
Westall, J.C. and Hohl, H., 1980 A comparison of electrostatic models for the oxide/solution interface Adv Coll Interface Sci 12 265–294 10.1016/0001-8686(80)80012-1.CrossRefGoogle Scholar
White, G.N. and Zelazny, L.W., 1988 Analysis and implications of the edge structure of dioctahedral phyllosilicates Clays Clay Miner 36 141–146 10.1346/CCMN.1988.0360207.CrossRefGoogle Scholar
Wilson, M.L. Gauthier, J.H. Barnard, R.W. Barr, G.E. Dockery, H.A. Dunn, E. Eaton, R.R. Guerin, D.C. Lu, N. Martinez, M.J. Nilson, R. Rautman, C.A. Robey, T.H. Ross, B. Ryder, E.E. and Schenker, A.R., 1994 Total-system performance assessment for Yucca Mountain—SNL second iteration (TSPA-1993) volume 1 and 2 SAND93-2675 .CrossRefGoogle Scholar
Yamamoto, K. Yanagi, T. Senoo, M. and Sakamoto, Y., 1990 Sorption behavior of neptunium(V) ion on clay sorbent J Nucl Sci Tech 27 626–630 10.1080/18811248.1990.9731231.CrossRefGoogle Scholar
Zachara, J.M. and McKinley, J.P., 1993 Influence of hydrolysis on the sorption of metal cations by smectites: Importance of edge coordination reactions Aquatic Sci 55 250–261 10.1007/BF00877270.CrossRefGoogle Scholar