Stability of Silicate Coatings on Pyrite Surfaces in a Low pH Environment
Publication: Journal of Environmental Engineering
Volume 131, Issue 9
Abstract
The suppression of pyrite oxidation due to the formation of stable coatings of –silica and/or –hydroxy–silica complexes over pyrite surfaces in near-neutral and neutral solution pHs is well documented. On the contrary, there is currently no convincing experimental evidence that proves the existence of such a coating under low pH environments. Aqueous continuous flow kinetic experiments were conducted using coating solutions containing and at pH 6, 4, 3, and 2. Results showed that at pH 2, pyrite oxidation in the presence of silica is pseudofirst order and oxidation is not inhibited by silica. At pH 6, silica significantly reduced pyrite oxidation via a pseudofirst-order reaction that takes on several stages related to changes in the relative contributions of and . Iron speciation data suggests a surface adsorption mechanism at pH 6 and an electrochemical mechanism at pH 2 for pyrite oxidation. Scanning electron microscopy and energy dispersive x-ray spectroscopy also support the kinetic model and showed the absence of any significant silica coating at pH 2.
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Acknowledgments
This work is sponsored in part by a grant from the United States Environmental Protection Agency (USEPA). The writers wish to thank the many individuals who helped with the experimental setup, analysis of the data, and review of the manuscript. Dr. Daniel Strongin of the Chemistry Department provided very useful comments and made available to them his many laboratory resources, without which this paper may not have been possible. Also any mention of trade names is for identification purposes only and does not imply endorsement by the writers or the USEPA.
References
Backes, C. A., Pulford, I. D., and Duncan, H. J. (1987). “Studies on the oxidation of pyrite in colliery spoil. II. Inhibition of the oxidation by amendment treatments.” Reclam. Reveg. Res., 6(1), 1–11.
Bonnissel-Gissinger, P., Alnot, M., Ehrhardt, J.-J., and Behra, P. (1998). “Surface oxidation of pyrite as a function of pH.” Environ. Sci. Technol., 32, 2839–2845.
Davis, A., and Ashenberg, D. (1989). “The aqueous geochemistry of the Berkeley Pit, Butte, Montana, U.S.A.” Appl. Geochem., 4, 23–26.
Eggleston, C., Ehrhardt, M. J., and Stumm, W. A. M. (1996). “Surface structural controls on pyrite oxidation kinetics: an XPS-UPS, STM and modeling study.” Am. Mineral., 81, 1036–1056.
Elsetinow, A., Borda, M., Schoonen, M. A., and Strongin, D. R. (2003). “Suppression of pyrite oxidation in acidic aqueous environments using lipids having two hydrophobic tails.” Adv. Environ. Res., 7, 969–974.
Elsetinow, A., Strongin, D. R., and Schoonen, M. A. (2001). “An aqueous geochemical and surface science investigation of the effect of phosphate on pyrite oxidation.” Environ. Sci. Technol., 35, 2252–2257.
Evangelou, V. P. (1995a). “Potential microencapsulation of pyrite by artificial inducement of ferric phosphate coatings.” J. Environ. Qual., 24, 535–542.
Evangelou, V. P. (1995b). Pyrite oxidation and its control, CRC, Boca Raton, Fla.
Fytas, K., and Bousquet, P. (2002). “Silicate micro-encapsulation of pyrite to prevent acid mine drainage.” CIM Bulletin 95, 1063–1063.
Fytas, K., Bousquet, P., and Evangelou, V. P. (1999). “Application of silicate coatings on pyrite to prevent acid mine drainage.” Proc., Sudbury’99-Mining and Environment II Conf., CANMET, Laurentian Univ. and Inco, Sudbury, Ont., Canada, 1199–1207.
Fytas, K., Evangelou, V. P., and Bordeleau, D. (1998). “Coating Pyrite to prevent AMD.” Int. J. Surf. Min. Reclam, 2, 101–104.
Guevremont, J. M., Bebie, J., Elsetinow, A. R., Strongin, D. R., and Schoonen, M. A. A. (1998). “Reactivity of the (100) plane of pyrite in oxidizing gaseous and aqueous environments: Effects of surface imperfections.” Environ. Sci. Technol., 32(23), 3743–3748.
Holmes, P. R., and Crundwell, F. K. (2000). “The kinetics of the oxidation of pyrite by ferric ions and dissolved oxygen: an electrochemical study.” Geochim. Cosmochim. Acta, 64(2), 263–274.
Huang, X., and Evangelou, V. P. (1994). “Suppression of pyrite oxidation rate by phosphate addition.” Environmental geochemistry of sulfide, oxidation, C. N. Alpers and D. W. Blowers, eds., ACS, Washington, D.C., 562–573.
Iler, R. K. (1979). The chemistry of silica, Wiley, New York.
Kargbo, D. M., Atallah, G., and Chatterjee, S. (2004). “Inhibition of pyrite oxidation by a phospholipid in the presence of silicate.” Environ. Sci. Technol., 38(13), 3432–3441.
Kargbo, D. M., Fanning, D. S., Inyang, H. I., and Duell, R. W. (1993). “The environmental significance of acid sulfate clays as waste covers.” Environ. Geol., 22, 218–226.
Lalvani, S. B., Deneve, B. A., and Seton, A. (1991). “Prevention of pyrite dissolution in acidic media.” Corrosion (Houston), 47, 55–61.
Lalvani, S. B., Zhang, G., and Lalvani, L. S. (1996). “Coal pyrite passivation due to humic acids and lignin treatment.” Fuel Sci. Technol. Int., 14(9), 1291–1313.
McKibben, M. A. (1984). “Kinetics of aqueous oxidation of pyrite by ferric iron, oxygen, and hydrogen peroxide from pH 1–4 and .” PhD dissertation, The Pennsylvania State Univ., University Park, Pa.
McKibben, M., and Barnes, H. (1986). “Oxidation of pyrite in low temperature acidic solutions: Rate laws and surface textures.” Geochim. Cosmochim. Acta, 50, 1509–1520.
Morel, F. M. M., and Hering, J. G. (1993). Principles and applications of aquatic chemistry, Wiley, New York.
Moses, C. O., and Herman, J. S. (1991). “Pyrite oxidation at circumneutral pH.” Geochim. Cosmochim. Acta, 55, 471–482.
Nesbitt, H. W., and Muir, I. J. (1994). “X-ray photoelectron spectroscopic study of a pristine pyrite surface reacted with water vapor and air.” Geochim. Cosmochim. Acta, 58(21), 4667–4679.
Peiffer, S., and Stubert, I. (1999). “The oxidation of pyrite at pH 7 in the presence of reducing and non reducing Fe(III)-chelators.” Geochim. Cosmochim. Acta, 63(19/20), 3171–3182.
Rosso, K. M., Becker, U., and Hochella, M. F. J. (1999). “The interaction of pyrite {100} surfaces with and : Fundamental oxidation mechanisms.” Am. Mineral., 84, 1549–1561.
Stumm, W., and Morgan, J. J. (1996). Aquatic chemistry, chemical equilibria and rates in natural waters, Wiley, New York.
Williamson, M. A., and Rimstidt, J. D. (1994). “The kinetics and electrochemical rate-determining step of aqueous pyrite oxidation.” Geochim. Cosmochim. Acta, 58, 5443–5454.
Zhang, Y. L., and Evangelou, V. P. (1998). “Formation of ferric hydroxide-silica coatings on pyrite and its oxidation behavior.” Soil Sci., 163(1), 53–62.
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Published In
Journal of Environmental Engineering
Volume 131 • Issue 9 • September 2005
Pages: 1340 - 1349
Copyright
© 2005 ASCE.
History
Received: May 20, 2004
Accepted: Dec 22, 2004
Published online: Sep 1, 2005
Published in print: Sep 2005
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