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Ore rejects; chemical beneficiation; iron hydroxide; iron oxyhydroxide; ferrite.

Iron oxyhydroxides and hydroxides were synthesized from chemically beneficiated high SiO₂/Al₂O₃ low-grade iron ore (57.49% Fe₂O₃) rejects and heated to get iron oxides of 96–99.73% purity. The infrared band positions, isothermal weight loss and thermogravimetric and chemical analysis established the chemical formulas of iron-oxyhydroxides as 𝛾-FeOOH.0.3H₂O; 𝛼-FeOOH.0.2H₂O and amorphous FeOOH. The thermal products of all these were 𝛼-Fe₂O₃ excepting that of 𝛾-FeOOH.0.3H₂O which gave mainly 𝛾-Fe₂O₃ and some admixture of 𝛼-Fe₂O₃. The hydrazinated iron hydroxides and oxyhydroxides, on the other hand, decomposed autocatalytically to mainly 𝛾-Fe₂O₃. Hydrazine method modifies the thermal decomposition path of the hydroxides. The saturation magnetization, 𝐽_s, values were found to be in the range 60–71 emu g^–1 which are close to the reported values for 𝛾-Fe₂O₃. Mechanism of the 𝛾-Fe₂O₃ formation by hydrazine method is discussed.

K S Rane¹ V M S Verenkar¹ P Y Sawant¹

1. Department of Chemistry, Goa University, Goa 403 206, India

Published

June 2001

Manuscript received

13 October 2000

Manuscript revised

5 March 2001