Iron removal and recovery in the titanium dioxide feedstock and pigment industries

Titanium and iron are closely related in nature. Therefore, for both environmental and economic reasons, the fate of iron may be very crucial for the titanium extraction industry. Smelting of ilmenite to produce titania slag allows for the recovery of iron as high purity pig iron. However, in the production of synthetic rutile from ilmenite sands, iron is returned to the mine site as a fine oxide/hydroxide residue. Some projects to recover iron from these residues never reached the industrial scale. In the titanium dioxide (TiO₂) pigment industry, iron is deported as sulfate or chloride salt, which is usually neutralized and rejected at a considerable cost. In the past few years, ferrous sulfate heptahydrate (or copperas) and iron chloride have found a few applications, but still the demand for these iron salts is not enough to cover the production volumes. The review of some new processes currently under development clearly shows that iron recovery is essential for the long-term viability of any new ilmenite upgrading or TiO₂ pigment production process.