Manufacture of pure titanium(IV) oxide by the chloride process. II. Selective extraction of titanium(IV) and iron(III) from hydrochloric acid leach liquor of ilmenite ore by tributyl phosphate.

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The selective recoveries of titanium(IV) and iron(III) from the synthetic hydrochloric acid leach liquor of ilmenite, i.e., 1.8–11 M (1 M=1 mol dm−3) hydrochloric acid solutions containing 0.25–0.57 M titanium(IV) and 0.27–0.29 M iron(III), or each single metal ion, were investigated by solvent extraction with benzene solutions of various tributyl phosphate (TBP) concentrations under the volume ratio (Org/Aq) of unit at 25 °C. Iron(III) was extracted into the TBP phase over a wide concentration range of hydrochloric acid studied, and the extraction was considerably accelerated by the salting-out effect of the coexisting titanium(IV). Since no extraction of titanium(IV) was observed at hydrochloric acid concentrations lower than 6 M, iron(III) could be recovered selectively from 3–6 M hydrochloric acid solutions under the conditions of the molar ratio [TBP]org/[Fe(III)]init aq≤3.0. On the other hand, titanium(IV) in the residual aqueous phase was also extracted as TiCl4·3TBP at a concentration range of chloride ion higher than 7 M. The coextractions of other metal ions and free hydrochloric acid could be prevented by controlling the TBP concentration in the organic phase as [TBP]org/[Ti(IV)]init aq≤3.5. The problem in applying the solvent extraction technique to actual leach liquor is discussed, as well as the recovery of free hydrochloric acid from the residual leach liquor.
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