Abstract:
Iron oxyhydroxides and hydroxides were synthesized from chemically beneficiated high SiO2/Al2O3 low-grade iron ore (57(.)49 percent Fe2O3) rejects and heated to get iron oxides of 96-99(.)73 percent purity. The infrared band positions, isothermal weight loss and thermogravimetric and chemical analysis established the chemical formulas of iron-oxyhydroxides as gamma -FeOOH .0 .3H(2)O; alpha -FeOOH .0 .2H(2)O and amorphous FeOOH. The thermal products of all these were alpha -Fe2O3 excepting that of gamma -FeOOH .0 .3H(2)O which gave mainly gamma Fe2O3 and some admixture of alpha -Fe2O3. The hydrazinated iron hydroxides and oxyhydroxides, on the other hand, decomposed autocatalytically to mainly gamma -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 gamma -Fe2O3. Mechanism of the gamma -Fe2O3 formation by hydrazine method is discussed.