Study on the effect of prior oxidation on the reduction and leaching kinetics of Bangladesh ilmenite

Abstract

Bangladesh ilmenite containing 24,2% FeD, 33.0% Fe2D3 and 39.45 % TiD2 has been oxidised in the temperature range of 700'C _ 950'C for a period of upto 4 hours. X-ray diffraction and chemical analysIs have shown that oxidation in normal furnace atmosphere for a period of 1 hour at 950'C converts all but 0.5% ferrous iron to ferric state, Oxidation at 700"C resulted in the formation of pseudorutile, hematite, rutile and some unidentified phases, where as pseudobrookite was found to have formed at temperature above. SOO'C. Optical microscope and scanning electron microscope revealed the presence of cracks in the oxidised samples, Reduction by charcoal in the temperature range of 950'C to 1050DC for treatment times of upto 6 hour showed that the maximum metallic iron content of the samples reduced after oxidation were higher ( 42,1 percent) than in the samples reduced (37.S percent) in the as- received condition. Reduction of ilmenite in the oxidised conditIOn was found to proceed in two stages, the first stage is the reformation of ilmenite and the second stage is the progressive reduction of ilmenite to metallic iron and rutile. On the other hand, the reduction of as received Bangladesh ilmenite invoives: (i) conversion of pseudorutile into rutile and ilmenite and (ii) change of ilmenite into metallic iron and rutile The rate of removal of metallic iron during leaching of reduced ilmenite in 5- 15 percent HCI at temperatures upto 75"C was found to increase with an increase in temperature and also in the concentration of acid in the leaching solution. The activation energy of leaching of preoxidised, reduced and leached sample was found to be 30.4 kJlmole whereas activation energy of leaching of as received and reduced sample was found to be 42.97 kJ/mole. Total iron content after leaching was estimated at 2.45 percent in the oxidised reduced leached sample whiie the total iron content of the leached sample reduced in the as received condition was estimated at 5,2 percent