GB1425779A - Recovery of titanium dioxide from ores - Google Patents

Abstract

1425779 Recovery of TiO 2 from ilmenite ONTARIO RESEARCH FOUNDATION 29 Jan 1974 [2 Feb 1973] 04138/74 Heading C1N Pigment grade TiO 2 is recovered from ilmenite by (i) contacting the ore or a concentrate thereof in particulate form with concentrated hydrochloric acid at 15‹ to 30‹ C. to leach from the ore or concentrate at least 80%, preferably at least 95%, of the titanium and iron values, the hydrochloric acid being present in such a quantity as to provide at least 2 moles of HCl per mole of ferrous iron, at least 3 moles of HCl per mole of ferric iron and at least 4 moles of HCl per mole of titanium in the ore concentrate, (ii) separating the resulting leach liquor from residual solid material, (iii) converting any ferric iron present in the leach liquor to ferrous iron to provide an aqueous solution of titanium chlorides and ferrous chloride, (iv) hydrolysing the titanium chlorides and depositing titanium oxyhydrate while inhibiting the deposition of other metal hydroxides, (v) separating the deposited titanium oxyhydrate from the mother liquor, (vi) washing and drying the separated material and (vii) converting the dried oxyhydrate to titanium dioxide. The ore or concentrate may be treated prior to leaching, e.g. by an oxidation at 600‹ to 1000‹ C. and preferably has a particle size distribution of 90 to 95%-100 mesh and less than 50%-325 mesh. The leaching is preferably performed countercurrently at 20‹ to 25‹ C. The ferric iron values are converted to ferrous iron by the use of SO 2 or by the addition of powdered metallic iron to the solution at between 50‹ and 95‹ C. When powdered iron is used a quantity sufficient to convert all the ferric iron to ferrous iron and up to 1% of the tetravalent titanium to trivalent titanium is used. The titanium chlorides are preferably hydrolysed with 1 to 3 volumes of water per volume of leach liquor and 1 to 2% of titanium oxyhydrate is preferably added as a seed. The dried titanium oxyhydrate is suitably converted to anatase or rutile titania by heating at 700‹ to 1000‹ C. The iron values may be recovered and the hydrogen chloride values recycled to the leaching step.