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, 𝐽s, 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.
Volume 42 | Issue 3