Patent ID: 7462337

Claim:
A method of recovering titanium dioxide from a titanium dioxide bearing material, comprising the steps of: a) grinding a material containing 22-32% by weight titanium dioxide to form a particulate raw feed material; b) contacting the particulate raw feed material with an up to 96% sulphuric acid solution in a fusion reactor and introducing a non-aqueous reaction initiator including a gas consisting of pre-heated air into the fusion reactor to heat the fusion reactor to a reaction temperature at which a reaction takes place to produce a cake material containing titanyl sulphate; c) dissolving the cake material by contacting the cake material with a sufficient quantity of water, and optionally sulphuric acid, and by introducing air with the water, in order to facilitate agitation to dissolve the cake, forming a solution which contains the titanyl sulphate; d) filtering and collecting the solution containing the titanyl sulphate; e) hydrolysing the solution by contacting the solution with at least one of 1) water, which has first been seeded with an appropriate amount of rutile and heated, or 2) a portion of previously hydrolysed solution containing hydrated titanium dioxide; and heating the solution to a boiling point to precipitate out hydrated titanium dioxide; one of f) washing the hydrated titanium dioxide with an ammonium sulphate solution to remove residual sulphate as ammonium sulphates followed by filtering off the hydrated titanium dioxide or g) filtering the hydrated titanium dioxide followed by washing with sodium hydroxide, ammonium hydroxide, water, phosphoric acid and/or diluted sulphuric acid; and h) calcining the hydrated titanium dioxide to drive off any residual acid and water of crystallisation to produce titanium dioxide.