| 摘要 |
The invention relates to a process for the removal of chloride ions from a fine-particle titanium dioxide A titanium dioxide sol containing at least 100 g/l TiO2 is mixed, at a temperature between 40.degree.C and the boiling point, with an aqueous alkaline solution up to a pH of between 4 0 and 11.0 while stirring without generating high shear, resulting essentially in a tangential to radial flow of the liquid; the fine-particle titanium dioxide is flocculated in this procedure, subsequently it is filtered and washed with an aqueous electrolyte solution The flocculated mixture has a low viscosity which results in short filtration and washing times and in an improved removal of chloride. The titanium dioxide sol can be produced by reacting titanium dioxide hydrate with alkali, decomposing the titanate formed and peptising with hydrochloric acid, the mixture washed free of sulphate or by heating and/or partially neutralizing an aqueous TiC14 solution. The invention also relates to the fine-particle titanium dioxide freed of chloride ions that is obtainable in the process of this invention and to its use as a rutilisation seed in the production of rutile from titanyl sulphate solutions, as a UV absorber and for the generation of special optical effects in paints.
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