Patent ID: 7258847

Claim:
A method of recovering titanium dioxide from a raw material containing the titanium dioxide and aluminium, comprises the steps of: a) grinding the titanium dioxide bearing material to form a particulate raw feed material; b) contacting the particulate raw feed material with a predetermined amount of sulphuric acid in a reaction vessel and raising the temperature in the reaction vessel to a predetermined temperature at which a reaction takes place to produce a cake material containing titanyl sulphate; c) contacting the cake material with a quantity of water, recovered sulphuric acid or a combination thereof, to dissolve the cake material and form a suspension which contains titanyl sulphate; d) filtering the suspension and collecting the solution containing the titanyl sulphate and, if present, optionally treating the solution to remove iron and/or calcium; e) contacting the titanyl sulphate containing solution from step d) with ammonium sulphate to produce aluminium ammonium sulphate; f) precipitating and separating the aluminium ammonium sulphate out of the titanyl sulphate containing solution from step e); g) hydrolysing the titanyl sulphate containing solution from step f) by contacting the solution from step f) with one of heated, rutile-seeded water or a portion of a previously hydrolysed solution containing hydrated titanium dioxide to form a hydrolytic solution and heating the hydrolytic solution to boiling point to precipitate out hydrated titanium dioxide; h) treating the hydrolysate from step g) by one of washing the hydrolysate from step g) with an ammonium solution to remove residual sulphates as ammonium sulphate followed by filtering the hydrated titanium dioxide, or filtering the hydrolysate from step g) followed by washing with sodium hydroxide, ammonium hydroxide, water, phosphoric acid and/or diluted sulphuric acid; and i) calcining the hydrolysate from step h) to drive off any residual acid and water of crystallisation to produce titanium dioxide.