GB873611A - A process for the manufacture of titanium dioxide - Google Patents

Abstract

In the production of titanium dioxide from a titanium ore containing more than 0.5% of chromium, by treatment with sulphuric acid to solubilize the titanium values and precipitating titanium dioxide by hydrolysis, the extent of the reaction between the sulphuric acid and the ore is so regulated that the quantity of chromium in the solution to be hydrolyzed is not greater than 0.5% of the weight of titanium in the solution. The quantity of titanium dissolved preferably does not exceed 23% by weight of the titanium originally present in the ore. The ores preferably employed do not contain more than 4% of chromium and contain at least 35% by weight of soluble titanium. The sulphuric acid employed may be from 73 to 93% strength and the reaction time is normally 10 to 70 minutes with a maximum reaction temperature of p 220 DEG C. According to Examples (1) an ilmenite ore containing 48% TiO2 and 0.85% Cr2O3 together with iron and minor amounts of manganese, vanadium, phosphorus and silica was ground and treated with 82% sulphuric acid at 160 DEG C. After one hour the dry mass formed was discharged into cold water to produce a solution containing 83% of the original titanium and 8.6% of the original chromium. The solution contained 0.18% of chromium based on the quantity of titanium in solution: titanium dioxide was subsequently precipitated by hydrolysis. (5) An ore as in (1) above was slurried in oleum and fed continuously to a pug mill in admixture with water to give a sulphuric acid concentration of 80%. The reaction temperature rose to 206 DEG C. and the mass was discharged after about 20 minutes at 160 DEG C. 92% of the titanium and 15.2% of the chromium originally present went into solution on leaching the reaction mass. The solution was hydrolysed to precipitate titanium dioxide.