Hostname: page-component-586b7cd67f-g8jcs Total loading time: 0 Render date: 2024-11-25T22:12:47.423Z Has data issue: false hasContentIssue false
  • English
  • Français

Primary phases in aluminous slags produced by the aluminothermic reduction of pyrochlore

Published online by Cambridge University Press:  02 January 2018

Roger H. Mitchell  and
Anthony N. Mariano
Roger H. Mitchell*
Affiliation:
Department of Geology, Lakehead University, Thunder Bay, Ontario Canada P7B 5E1
Anthony N. Mariano
Affiliation:
48 Page Brook Road, Carlisle, Massachusetts 01741, USA
*
*E-mail: [email protected]
Get access Rights & Permissions [Opens in a new window]

Abstract

Phases present in slags from Araxá (Brazil), Oka (Quebec) and Fen (Norway) resulting from the production of ferroniobium by the aluminothermic reduction of pyrochlore-group minerals are a function of composition of the pyrochlore feed and the diverse fluxes (CaO, CaF2) added to the alumina and iron oxide used in the reduction process. Absent from all slags investigated are Fe-bearing compounds. All of the slags are modally-dominated by prismatic crystals of β-alumina or hibonite, with a wide variety of Th-Ba-Ti-Nb-Al-oxide compounds and silico-aluminate glasses occurring in the interstices between these crystals. Slag from Fen consists of a framework of β-alumina (Ba and/or CaTi varieties) with a barian titanian niobate, considered to be an highly reduced Nb3+- and Ti3+-bearing anion deficient perovskite, as the first oxide phase to crystallize. This was followed by a Zr-Ti-Th-niobate (21.7–24.1 wt.% ThO2), a Nb-rich, Thbearing zirconolite-like phase (17.7–21.2 wt.%; Nb2O5; 6.8–9.5 wt.% ThO2) and diverse Th-Nb-rich, Alpoor (< 1 wt.% Al2O3) perovskites (29.4–40.5 wt.% Nb2O5; 3.3–11.4 wt.% ThO2). The latter represents a NaNbO3–CaTiO3–Na2/3Th1/3TiO3–ThTi2O6 solid solution. Late Na-rich silicate glass contains celsian. Slag from Araxá also consists of a framework of β-alumina (Ti-poor). Interstitial compounds differ from Fen in being predominantly rare-earth element (REE)-Nb-Al-Th-perovskites belonging to a REEAlO3–Ca2AlNbO6–CaTiO3–ThTi2O6 solid solution with minor NaNbO3 and CaZrO3, and compositionally diverse barium calcium aluminates [(Ba, Ca)Al2O4] set in a F-bearing (6–7 wt.%) Na-Ba-Si-aluminate glass with minor Ba4Nb2O9, CaF2, BaF2 and NaF. Slag from Oka consists of a framework of hibonite [(Ca, REE) (Al, Ti, Mg)12O19] zoned with respect to the REE content. Interstitial compounds are CaZr4O9, Nb-Th-poor perovskites belonging to the REEAlO3–CaTiO3 series with minor CaZrO3 set in a F-bearing (5–6 wt.%) calcium aluminate glass. These data demonstrate that during ferroniobium production REE, Zr, Th, U and significant amounts of Nb are sequestered in the oxide phases in accord with their lithophile geochemical character. None of these elements are present as compounds in the siderophillic ferroniobium alloys. These data demonstrate that the aluminothermic reduction process results in the loss of significant amounts of Nb to the slag. Perovskite-group compounds are present in all of the slags but differ widely in their composition as a result of compositional differences in the feed pyrochlores and fluxes added to the smelting process. Slags originating from ferroniobium production are enriched in Th and U and could be considered as an environmental hazard if these elements are mobilized during chemical weathering of slag.

Keywords

SlagPerovskiteZirconolitePyrochloreβ-AluminaHiboniteAluminothermic ReductionOkaFenAraxá
Type
Research Article
Information
Mineralogical Magazine , Volume 80 , Issue 2 , April 2016 , pp. 383 - 397
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2016

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

Bellatreccia, E., Della Ventura, G., Caprilli, E, Williams, C.T. and Parodi, G.C. (1999) Crystal chemistry of zirconolite and calzirtite from Jacupiranga, São Paulo (Brazil). Mineralogical Magazine, 63,649—660 CrossRefGoogle Scholar
Collin, G., Boilot, IP, Colomban, P. and Comes, R. (1986) Host lattices and superionic properties in β- and p“-alumina. I. Structures and local correlations. Physical Review, B34, 5838–5949. CrossRefGoogle Scholar
Dejene, F.B. and Kebede, M.A. (2012) Synthesis and characterization of structural and luminescence prop¬erties of blue-green BaAlxOy: Eu2+ phosphors by solution combustion methods. Central European Journal of Physics, 10,977–982 Google Scholar
Ettler, V., Johan, Z., Kríbek, B. and Nolte, H. (2009) Mineralogy of primary phases in slags and mattes from the Tsumeb smelter (Namibia). Communications Geological Survey of Namibia, 14,3—14 Google Scholar
Gasik, M.I. (2013) Handbook of Ferroalloys. Elsevier Ltd, pp. 411-419 and 435-47.Google Scholar
Gieré, R., Williams, C.T. and Lumpkin, G.R. (1998) Chemical characteristics of natural zirconolite. Schweizeriche Mineralogishe und Petrologishe Mitteilungen, 78, 433–459. Google Scholar
Glasser, F.P. and Glasser, L.S.D.. (1963) Crystal chemistry of some AB2O4 compounds. Journal of the American Ceramic Society, 46,377–380 CrossRefGoogle Scholar
Gorkunov, Y and Munter, R. (2007) Calcium-alumi-nothermal production of niobium and mineral com¬position of the slag. Proceedings of the Estonian Academy of Science Chemistry, 56,142—156.Google Scholar
Gupta, C.K. and Suri, A.K. (1993) Extractive Metalurgy of Niobium.CRC Press, 272 pp.Google Scholar
Helios-Rybicka, E. (1996) Impact of mining and metallurgical industries on the environment in Poland. Applied Geochemistry, 11,3—9 CrossRefGoogle Scholar
Juric, M., Popovic, J., Santic, A., Molcanov, K., Brnicevic, N. and Planinic, P. (2013) Single step preparation of mixed BaII-NbV oxides from a hetero-polynuclear oxalate complex. Inorganic Chemistry, 52, 1832–1842. CrossRefGoogle Scholar
Lumpkin, G.R. (2014) The role of Th-U minerals in assessing the performance of nuclear waste forms. Mineralogical Magazine, 78, 1071–1095. CrossRefGoogle Scholar
Lumpkin, G.R., Colella, M., Smith, K.L., Mitchell, R.H. and Larsen, A.O. (1998) Chemical composition, geochemical alteration, and radiation effects in natural perovskites. Pp. 207-214 in: Scientific Basis for Nuclear Waste Management XXI Materials Research Society Symposium Proceedings, 506(I.G. McKinley and C. McCombie, editors).CrossRefGoogle Scholar
MacPherson, G.J., Simon, S.B., Davis, A.M., Grossman, L. and Krot, A.N. (2005) Calcium-aluminum-rich inclusions: Major unanswered questions. Pp. 225-250 in: Chondrites and the Protoplanetary Dis. (A.N. Krot E.R.D. Scott and B. Reipurth, editors). Astronomical Society of the Pacific Conference Series, 341. San Francisco, USA.Google Scholar
Mitchell, R.H. (2002) Perovskites: Modern and Ancient. Almaz Press, Thunder Bay, Ontario, Canada.Google Scholar
Mitchell, R.H. and Chakhmouradian, A.R. (1999) Solid solubility in the syste. NaLREETi2O6-ThTi2O6(LREE, light rare earth elements): experimental and analytical data. Physics and Chemistry of Minerals, 26, 396–405. Google Scholar
Piatak, NM., Seal, R.R. and Hammarstrom, J.M. (2004) Mineralogical and chemical controls on the release of trace elements from slag produced by base- and precious-metal smelting at abandoned mine sites. Applied Geochemistry, 19, 1039–1064. CrossRefGoogle Scholar
Puziewicz, J., Zainoun, K and Bril, H. (2007) Primary phases in pyrometallurgical slags from zinc smelting waste dump, Swietochlowice, Upper Silesia, Poland. The Canadian Mineralogist, 45,1189–1200 CrossRefGoogle Scholar
Ravez, J. and Simon, A. (2000) Non-stoichiometric perovskites derived from BaTiO3 with a relaxor behaviour. Physica Status Solidi A, 178,793–797 3.0.CO;2-X>CrossRefGoogle Scholar
Ravichandran, D., Johnson, S.T., Erdei, S., Roy, R. and White, W.B. (1999) Crystal chemistry and lumines-cence of the Eu2+ activated alkaline earth aluminate phosphors. Displays, 19, 197–203. CrossRefGoogle Scholar
Ringwood, A.E. (1985) Disposal of high level nuclear wastes: geological perspectives. Mineralogical Magazine, 49, 159–176. CrossRefGoogle Scholar
Ringwood, A.E., Oversby, V.M., Kesson, S.E., Sinclair, W., Ware, N., Hibberson, W and Major, A. (1981) Immobilization of high level nuclear reactor wastes in SYNROC: a current appraisal. Nuclear and Chemical Waste Management, 2, 287–305. CrossRefGoogle Scholar
Townes, W.D., Fang, J.H. and Perrotta, A.J. (1967) The crystal structure and refinement of ferrimagnetic barium ferrite BaFe12O19. Zeitschrifte für Kristallographie, Kristallgeometrie, Kristallphysik and Kristallchemie, 125,11–23 Google Scholar
Veblen, L.A., Farthing, D., O'Donell, E. and Randall, J.D. (2004) Characterization of radioactive slags. NUREG-1703. Office of Nuclear Regulatory Research, US Nuclear Regulatory Commission, Washington, DC.Google Scholar
Wymer, D.G. (2006) Assessing the Need for Radiation Protection Measures in Work Involving Minerals and Raw Materials. International Atomic Energy Agency Zelaya Bejarano, J.M., Gama, S., Ribiero, C.A. Raw Materials. International Atomic Energy Agency Safety Reports Series, 49. International Atomic Energy Agency, Vienna.Google Scholar
Xing, D.E., Gong, M.L., Qiu, A.Q., Yang, D.J. and Cheah, K.W. (2006) A bluish-green barium aluminate phosphor for PDP applications. Materials Letters, 60, 3217–3220.CrossRefGoogle Scholar
Zelaya Bejarano, J.M., Gama, S., Ribiero, C.A. and Effenberg, G. (1993). The iron-niobium phase diagram. Zeitschrift für Metallkunde, 84, 160–164.Google Scholar
Zelaya Bejarano, J.M., Gama, S., Ribiero, C.A. and Effenberg, G. (1991). On the existence of the Fe2Nb3 phase in the Fe-Nb system.Zeitschrift für Metallkunde, 82, 615–620.Google Scholar