Process for producing titanium dioxide

There is disclosed the first step comprising bringing a sulphuric acid solution containing titanium ion together with one or more kinds of metal ions into contact with an organic solvent (a) composed of one or more extractants selected from the group consisting of oxygen-containing extractants and alkylamine extractants diluted with a petroleum hydrocarbon diluent to extract the titanium ion as a sulphuric acid complex from the sulphuric acid solution; and bringing the organic solvent (a) containing the extracted titanium in a form of a sulphuric acid complex (titanyl sulphate) into contact with an aqueous liquid having been employed for rinsing insoluble titanium hydroxide in the second step and/or an aqueous liquid having been employed for stripping in the third step to strip the titanium in a form of sulphuric acid complex into the aqueous liquid and to regenerate the organic solvent (a) for recycling for extraction, the second step comprising treating the aqueous liquid containing the titanium in a form of sulphuric acid complex stripped from the organic solvent (a) for hydrolysis to form insoluble titanium hydroxide; and washing the titanium hydroxide with dilute sulphuric acid and/or clear water, and the third step comprising bringing a part or whole of raffinate of extraction in the first step into contact with an organic solvent (b) composed of an extractant selected from the group consisting of oxygen-containing extractants and alkylamine extractants diluted with a petroleum hydrocarbon diluent to extract the titanium ion as a sulphuric acid complex from the raffinate; and bringing the organic solvent (b) containing extracted titanium in a form of sulphuric acid complex into contact with water, dilute sulphuric acid solution or a dilute titanyl sulphate solution to strip the titanium in a form of sulphuric acid complex to regenerate the organic solvent (b) for recycling the extraction.