| 摘要 |
<p>Titanium dioxide is obtained by treating an iron- and titanium-containing material with concentrated sulphuric acid, hydrolysing, separating the dioxide from the mother liquor and concentrating the latter to at least 60% H2SO4, separating precipitated salts and dissolving them at elevated temperature in a sulphuric acid-titanium sulphate solution having a H2SO4 concentration not exceeding 30% by wt., cooling and separating precipitated iron sulphate heptahydrate from solution, recycling at least a part of said solution to dissolve more of said salts and/or hydrolysing at least part of the solution to form titanium dioxide. The whole of the solution remaining after separation of the heptahydrate may be recycled until its titanium content is from 50 to 200 g./l. expressed as TiO2. The ratio of Fe : TiO2 in the solution remaining after separation of the heptahydrate may be from 0.25 : 1 to 1 : 1, and the ratio of H2SO4: TiO2 in the salts precipitated from the mother liquor should be less than 4 : 1. A temperature above room temperature and not higher than the boiling point of the sulphuric acid-titanium sulphate solution, preferably between 50 DEG and 80 DEG C., is used to dissolve the salts in the acid titanium sulphate solution. Iron sulphate heptahydrate is precipitated from solution at 20 DEG C. or less.</p> |
