Effects of Temperature on Ilmenite During Concentration of Iron in Laterites Using Charcoal and Separation using Magnetic Separation

Abstract

Effect of temperature on ilmenite minerals found in laterites has been investigated. It was found that during reduction of iron minerals in laterites to magnetite using charcoal at temperatures of about 500-700oC, ilmenite minerals were not reduced. However when temperatures were raised to about 850-1200oC using acetylene flame, ilmenite minerals were reduce to rutile and iron. Currently, the mineral ilmenite (FeTiO3) is responsible for about 85% of the world’s titanium requirements. The methods used to upgrade ilmenite are high temperature reduction and direct acid-leaching methods. Extraction of titanium from ores containing iron still remains a challenge. Laterite soils are currently being used mainly for surfacing roads. It has been proven that laterites can be a potential source of iron. This study set out to investigate whether the heat treatment that converts hematite in laterite to magnetite is adequate to decompose ilmenite. Laterite samples were concentrated by heating charcoal/laterite mixtures in the ratios of 1:10 by mass in a slow current of air and in the temperature range of 500-700oC. Elemental analysis was carried out on both the raw laterites and the concentrated samples using Atomic Absorption Spectroscopy (AAS). The minerals present were determined using a CubiX3 Powder Diffractometer from PANanalytical Company. The results of elemental analysis showed that, raw laterites contain 28-31% iron and 1-2% titanium (IV) oxide depending on source. After the concentration, the level of iron in the heat-treated sample had increased to 55-64%, and titanium oxide increased to 3-5%. The X-ray diffraction data confirmed that, iron in the raw laterites was present predominantly as the minerals goethite, hematite and ilmenite since these are known to have diffraction peaks at angles 2θ= 21.51˚, 2θ= 54.11˚ and 2θ=32.7, respectively. After reduction (at 500-700oC), goethite and hematite peaks disappeared in the heat-treated magnet-separated samples and instead, a strong peak was observed at angle 2θ= 36˚and 2θ=32.7, which represents peaks for magnetite and ilmenite respectively. From the observation, this temperature (500-700oC), had no significant effect to ilmenite hence, was collected together with magnetite by a magnet. When reduction was done at temperature range of 850-1200oC, the ilmenite peak disappeared and a peak at 2θ=27.4, 2θ= 36˚and 2θ=44.6 appeared, attributed to rutile, magnetite and metallic iron respectively. The XRD of the tailing (non-magnetic waste) show distinct peak at 2θ=27.4 and 2θ=54.3 attributed by rutile. This shows that ilmenite minerals are reduced at high temperatures to rutile (non-magnetic) and metal iron (magnetic).