Hostname: page-component-8448b6f56d-mp689 Total loading time: 0 Render date: 2024-04-19T22:07:03.769Z Has data issue: false hasContentIssue false
  • English
  • Français

The effect of pH on chlorite dissolution rates at 25°C

Published online by Cambridge University Press:  11 February 2011

Åsa B. Gustafsson  and
Ignasi Puigdomenech
Åsa B. Gustafsson
Affiliation:
Royal Institute of Technology, Inorganic Chemistry, Stockholm, Sweden
Ignasi Puigdomenech
Affiliation:
Swedish Nuclear Fuel & Waste Management Co., Stockholm, Sweden.
Get access

Abstract

The Swedish nuclear industry is planing to dispose spent nuclear fuel encapsulated in copper canisters in granitic bedrock at a depth of approx. 500 m. The reducing capacity of the geo-sphere is important for canister corrosion and radionuclide migration. The main inorganic reduc-tants are Fe(II)-containing minerals: biotite in the bedrock, and pyrite and chlorite in the fracture filling minerals as well as in the buffer and backfill. As a consequence, the dissolution of chlorite is an important parameter when considering the reducing capacity available to groundwaters around the repository.

The weathering rates of a chlorite sample from Taberg in central Sweden has been studied in 0.01 M NaCl media at (25±1)°C in the pH region 2–12. The chlorite was characterized before and after grinding and sieving, and was found to have a relatively low Fe-content, with the formula (Mg9.44 FeII0.72Al1.68)(Si6.47Al1.4FeIII0.13)O20(OH)16. Kinetic experiments were performed using a thin-film continuous flow-through technique with flow rates of 5 mL/h or 2.7 mL/h. This technique prevents the precipitation of secondary phases such as iron(III) hydroxides. Solution samples were taken after a reaction time of 0–30 days. The contents of released Al, Fe, Mg and Si were analyzed using an Inductively Coupled Plasma emission spectroscopy (ICP-AES) technique and then normalized to the Brunauer-Emmet-Teller (BET) surface area and flow-rate in order to obtain rates of dissolution. The dissolution rate of the chlorite studied was pH-dependent, and a minimum was observed in the neutral pH region. The dissolution rate (based on Si data) decreased from 7×10-11 mol/(m2 s) at pH=2 to 4×10-13 mol/(m2 s) at pH≈7 and then in-creased to 3×10-12 mol(m2 s) at pH=12.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 757: Symposium II – Scientific Basis for Nuclear Waste Management XXVI , 2002 , II3.16
Copyright
Copyright © Materials Research Society 2003

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

REFERENCES

1. Papp, T., Phil. Trans. R. Soc. Lond. A 319, 39 (1986);Google Scholar
Hedin, A., Nucl. Technol. 138, 179 (2002).Google Scholar
2. Bertoldi, C., Benisek, A., Cemic, L., and Dachs, E., Phys. Chem. Minerals 28, 332 (2001);Google Scholar
Bailey, S.W., Brindley, G.W., Johns, W.D., Martin, R.T., and Ross, M., Clays & Clay Minerals 64, 129 (1971).Google Scholar
3. Klein, C., The 22nd edition of the Manual of Mineral Science. (John Wiley & sons, Inc., 2002).Google Scholar
4. Nagy, K.L., in Chemical Weathering Rates of Silicate Minerals, edited by Ribbe, P.H. (Reviews in Mineralogy, 31, Mineralogical Society of America, Washington DC, 1995), p. 173.Google Scholar
5. Sverdrup, H., The Kinetics of Base Cation Release Due to Chemical Weathering. (Lund University Press, Lund, 1990).Google Scholar
6. Brandt, F., Bosbach, D., Krawczyk-Bärsch, E., Arnold, T., and Bernhard, G., Geochim. Cosmochim. Acta, (in print) (2003).Google Scholar
7. Malmström, M., Banwart, S., Lewenhagen, J., Duro, L., and Bruno, J., J. Contaminant Hydrol. 21, 201 (1996).Google Scholar
8. May, H.M., Acker, J.G., Smyth, J.R., Bricker, O.P., and Dyar, M.D., in Proc. 32nd Annual Meeting Clay Minerals Society (Baltimore, MD, 1995), p. 88 (abstract).Google Scholar
9. Rochelle, C.A., Bateman, K., MacGregor, R., Pearce, J.M., Savage, D., and Wetton, P.D., in Scientific Basis for Nuclear Waste Management XVIII, edited by Murakami, T. and Ewing, R.C. (Mat. Res. Soc. Symp. Proc., 353, Pittsburgh, PA, 1995), p. 149.Google Scholar
10. Nagy, K.L., Blum, A.E., and Lasaga, A.C., Amer. J. Sci. 291, 649 (1991).Google Scholar
11. Newman, A.C.D. and Brown, G., in Chemistry of Clays and Clay Minerals, edited by Newman, A.C.D. (Longman Scientific and Technical, Essex, 1987), p. 1.Google Scholar
12. Bruno, J., Casas, I., and Puigdomenech, I., Geochim. Cosmochim. Acta 55, 647 (1991).Google Scholar
13. Malmström, M. and Banwart, S., Geochim. Cosmochim. Acta 61, 2779 (1997).Google Scholar
14. Ganor, J., Mogollon, J.L., and Lasaga, A.C., Geochim. Cosmochim. Acta 59, 1037 (1995).Google Scholar
15. Liu, W., Water Res. 35, 4111 (2001);Google Scholar
Stumm, W. and Morgan, J.J., Aquatic Chemistry, 3rd ed. (John Wiley & Sons, New York, 1996).Google Scholar
16. Cama, J., Ganor, J., Ayora, C., and Lasaga, A.C., Geochim. Cosmochim. Acta 64, 2701 (2000).Google Scholar
17. Kalinowski, B.E. and Schweda, P., Geochim. Cosmochim. Acta 60, 367 (1996).Google Scholar
18. Ross, G.J., Clays & Clay Minerals 17, 347 (1969).Google Scholar
19. Schott, J., Berner, R.A., and Sjöberg, E.L., Geochim. Cosmochim. Acta 45, 2123 (1981).Google Scholar
20. Blum, A. and Lasaga, A., Nature 331, 431 (1988).Google Scholar
21. Lowson, R., Comarmond, M., Rajaratnam, G., and Brown, P., Geochim. Cosmochim. Acta, (submitted) (2003).Google Scholar
22. Stumm, W. and Wollast, R., Revs. Geoph. 28, 53 (1990);Google Scholar
Drever, J.I., Geochim. Cosmo-chim. Acta 58, 2325 (1994).Google Scholar