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Mineralogical Transformations in Altasteel Electric Arc Furnace Dust Roasted with Na2CO3 and Secondary Ferrite-Forming Additives

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ABSTRACT
The effect of secondary additives, such as CaCO3 and MnCO3, on the mineralogical transformations in Altasteel EAF dust (9.4% Zn, 31.9% Fe) during roasting with Na2CO3, and metal extractions during hot water and H2SO4 leaching of the roasted residues, was studied using a combination of techniques, including Design of Experiments testing, x-ray diffraction, scanning electron microscope/energy dispersive xray analysis and chemical analysis. The research objective was to promote the formation of acid insoluble metal ferrites during roasting to try to lower iron extractions during acid leaching. Neither additive was effective in reducing iron extractions due to the unexpected mineralogical changes caused during roasting by the addition of these secondary additives to this poorly crystalline EAF dust. Low CaCO3 or MnCO3 additions promoted the formation of manganese rich iron oxides (e.g., Mn2FeO4), instead of MnFe2O4, which caused more iron to be available to react with Na2CO3 during roasting to form acid soluble NaFeO2. Increased CaCO3 additions further increased iron extractions, by further increasing the formation of Mn2FeO4 ferrites, but increased MnCO3 additions at roasting temperatures above 950°C led to the formation of a ZnFe2O4-MnFe2O4 solid solution. While this resulted in lower iron extractions, lower overall zinc recoveries during acid leaching were also observed.
 
Cite this paper
P. Holloway and T. Etsell, "Mineralogical Transformations in Altasteel Electric Arc Furnace Dust Roasted with Na2CO3 and Secondary Ferrite-Forming Additives," Journal of Minerals and Materials Characterization and Engineering, Vol. 7 No. 1, 2008, pp. 1-26.
 
References
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[2]Xia, D. K. and Pickles, C. A., 1998, “Extraction of nonferrous metals from electric arc furnace dust”, In: Waste Processing and Recycling in Mineral and Metallurgical Industries III, pp.221-245, (Rao, S. R., Ed.) Montreal, QC Canadian Institute of Mining, Metallurgy and Petroleum.
 
[3]Liebman, M., 2000, “The current status of electric arc furnace dust recycling in North America”, International Symposium on Recycling of Metals and Engineered Materials, 4th , pp.237-250, (Stewart, D. L. Jr., Daley, J. C. and Stephens, R. L. Eds.), Warrendale, Pa, Minerals, Metals & Materials Society.
 
[4]Zunkel, A. D., 2000, “Recovering zinc and lead from electric arc furnace dust: a technology status report”, International Symposium on Recycling of Metals and Engineered Materials, 4th, pp.227-236, (Stewart, D. L. Jr., Daley, J. C. and Stephens, R. L. Eds.), Warrendale, Pa, Minerals, Metals & Materials Society.
 
[5]Zunkel, A. D., 1997, “Electric arc furnace dust management: a review of technologies”, Iron and Steel Eng., Vol. 74, No. 3, pp.33-38.
 
[6]Mager, K., Meurer, U., Garcia-Egocheaga, B., Goicoechea, N., Rutten, J., Saage, W., and Simonetti, F., 2000, “Recovery of zinc oxide from secondary raw materials: new developments of the Waelz process”, International Symposium on Recycling of Metals and Engineered Materials, 4th, pp.329-344, (Stewart, D. L.Jr., Daley, J. C. and Stephens, R. L. Eds.), Warrendale, Pa, Minerals, Metals & Materials Society.
 
[7]Holloway, P.C. and Etsell, T.H., “Roasting of Altasteel Electric Arc Furnace Dust with Na2 CO3,” submitted to Metall. Trans. B.
 
[8]Holloway, P.C. and Etsell, T.H., “The Use of Secondary Additives to Control the Iron Dissolution during Na2CO3 Roasting of La Oroya Zinc Ferrite,” submitted to Metall. Trans. B.
 
[9]Johannsen, R., 2006, Private communication, Altasteel, Edmonton, AB, Canada.
 
[10]Holloway, P.C. and Etsell, T.H., “Roasting of La Oroya Ferrite with Na2 CO3”,submitted to Metall. Trans. B.
 
[11]Eschenfelder, A. H., 1958, “Ionic valences in manganese-iron spinels”, J. Appl. Phys., Vol. 29, pp.378-80.
 
[12]Holloway, P.C., 2006, “Application of Transformational Roasting to the Treatment of Metallurgical Wastes,” Ph.D. Thesis, University of Alberta                                                                                          eww150204lx
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