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).
