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J Hazard Mater. 2013 Jun 15;254-255:193-205. doi: 10.1016/j.jhazmat.2013.03.059. Epub 2013 Apr 2.

Greek "red mud" residue: a study of microwave reductive roasting followed by magnetic separation for a metallic iron recovery process.

Author information

1
School of Mining and Metallurgical Engineering, Laboratory of Metallurgy, National Technical University of Athens, 9, Iroon Polytechniou Street, 157 80 Zografou, Athens, Greece. Electronic address: msamouhos@metal.ntua.gr.
2
School of Mining and Metallurgical Engineering, Laboratory of Metallurgy, National Technical University of Athens, 9, Iroon Polytechniou Street, 157 80 Zografou, Athens, Greece.
3
Greek Atomic Energy Commission (GAEC), Patriarxou Grigoriou & Neapoleos, P.O. Box 60092, 15310 Agia Paraskevi, Athens, Greece.

Abstract

The present research work is focused on the development of an alternative microwave reductive roasting process of red mud using lignite (30.15 wt.%Cfix), followed by wet magnetic separation, in order to produce a raw material suitable for sponge or cast iron production. The reduction degree of iron was controlled by both the reductive agent content and the microwave heating time. The reduction followed the Fe₂O₃ → Fe₃O₄ → FeO → Fe sequence. The dielectric constants [real (ε') and imaginary (ε″) permittivities] of red mud-lignite mixture were determined at 2.45 GHz, in the temperature range of 25-1100 °C. The effect of parameters such as temperature, intensity of reducing conditions, intensity of magnetic field and dispersing agent addition rate on the result of both processes was investigated. The phase's transformations in reduction process with microwave heating were determined by X-ray diffraction analysis (XRD) in combination with thermogravimetric/differential thermal analysis (TGA/DTA). The microstructural and morphological characterization of the produced calcines was carried out by scanning electron microscopy (SEM). At the optimum conditions a magnetic concentrate with total iron concentration of 35.15 and 69.3 wt.% metallization degree was obtained.

PMID:
23611801
DOI:
10.1016/j.jhazmat.2013.03.059
[Indexed for MEDLINE]

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