Abstract:
The CSIR is developing a process to produce commercially pure (CP) Grade 4 titanium metal powder
via direct metallothermic reduction of TiCl4. Crude titanium produced by this method is inevitably
contaminated with unreacted reducing metal and titanium subchlorides occluded in halide salt. For the
product to meet stringent titanium industry quality requirements, the concentration of impurities must
be held to acceptably low levels. Acid leaching was identified as a suitable method for purifying the crude
reduction mass, due to the solubility of the by-products and the potential for cost-saving provided by
this method compared to vacuum distillation. However, purification by leaching poses drawbacks such
as high oxygen impurity concentrations in the product, due to the dissolution of subchlorides in water to
form insoluble hydroxides and oxychlorides that concentrate on the surface of the titanium powder. The
crude titanium was leached under different conditions using water and 1 M and 0.035 M hydrochloric
acid at a temperature below 50°C. The 1 M acid leach yielded a product with the lowest oxygen content,
demonstrating that when the pH of the media and temperature are controlled, the drawbacks associated
with acid leaching can be overcome and the process used successfully for downstream purification of
the crude product.
