dc.description.abstract |
Mineral sand deposits represent a most promising and profitable future resource
for the country. The crude heavy minerals at Pulmudai-Sri Lanka contain about 60%
to 70% of heavy minerals having composition of 70% to 75% ilmenite (FeTiO3),
10% rutile (TiO2) and 8 to 10% zircon (ZrSiO4). Titanium dioxide is an important
inorganic chemical material, especially the best-quality white pigment.
Decomposition of ilmenite (FeTiO3) structure into TiO2 is normally done at 850 C
using 70% H2SO4. In this study, the above conversion has been carried out at a
relatively low temperature with saturated vapor pressure under hydrothermal
conditions. Ilmenite was collected from beach sands in Pulmudai and finely
powdered. The powdered material was then treated with Concentrated HCl under
hydrothermal conditions at different temperatures and pressures. Ilmenite was
decomposed completely and nano-particles of anatse phase of rutile TiO2 were
obtained directly from the autoclave with further hydrothermal treatment under
basic media, the anatse phase was converted into the rutile phase of TiO2. The effect
of pH on the size and morphology of particles in nano-powders were also
investigated. Results showed that after the hydrothermal treatment of ilmenite,
black-colored granules changed into swelled yellowish-white powder. The X-ray
powder diffraction pattern confirmed that the products were well crystalline pure
phases of rutile (TiO2) depending on the experimental conditions. The SEM-EDX and
XRF analysis confirmed the product contained 100% TiO2. The particles sizes of
nano TiO2 produced were between 85 nm to 100 nm. ICPS chemical analysis of the
final product indicated 17.50 ppb of Fe which is within the range of acceptable levels
when pure TiO2 is concerned. The leachate solution was also colored yellowish,
indicating the Fe leaching from the natural source. This phenomenon implies that
the hydrothermal treatment for natural rutile can be used not only as a reaction step
but also as a semi-purification step. The results demonstrated that the process is
inexpensive, environment friendly and promising in preparing high-purity TiO2
from ilmenite with a high content of gangues. |
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