| 摘要 |
<p>Titaniferous materials, such as ilmenite or rutile, are heated with ammonium fluoride or a reaction mixture yielding it, the ammonium fluoride being substantially in excess of the amount required to convert the reactive constituents of the ore to simple fluorides, and the ammonium titanium fluorine compounds formed are recovered as a solution either directly or by leaching the reaction product, or by volatilization. At least six mols of ammonium fluoride may be present for each mol of titanium oxide, and when rutile is used, it may be preheated to 1040 DEG C., and rapidly cooled to render it reactive. The ore may be mixed with the solid fluoride or a concentrated solution thereof, and the mixture be first heated, say to 150 DEG C., till ammonia ceases to be evolved, then to 250 DEG C., until ammonium fluoride ceases to be evolved, and then above 300 DEG C., and it may be up to 500--550 DEG C., to volatilize a mixture of titanium-diaminotetrafluoride and ammonium titanofluoride. By treating the volatilized compounds with an ammoniacal aqueous solution or an ammoniacal solution of ammonium fluoride, for instance at a temperature below 34 DEG C., titanium hydrate may be obtained, but preferably the volatilized products are dissolved in water or a neutral or acid solution of ammonium fluoride, the solution purified from iron as described in Specification 456,314, and the solution treated with ammonia, when, according to the conditions, either titanium hydrate or octohedral crystals of the formula TiF4.2NH3.NH4F are obtained. The crystals, if formed, may be converted to the hydrate by treatment with water and ammonia, preferably in sequence. If the initial material contains silicon, this may be separately volatilized with the ammonium fluoride as silicon diammino fluoride at temperatures below 300 DEG C., or be volatilized together with the titanium compounds. In the first case treatment with water or ammonium fluoride solution precipitates a part of the silica, and yields ammonium silicofluoride, from which the remaining silica may be precipitated by ammonia below 34 DEG C. to give a product adapted for admixture with titanium dioxide to form a composite pigment. In the second case, the further treatment of the mixed titanium and silicon compounds gives a mixed silica-titanium oxide pigment. Alternatively the separately volatilized compounds are mixed, preferably after re-sublimation, and after treatment with water, &c., to remove a part of the silica, are treated with ammonia, &c., to precipitate a mixture of silica and titanium oxide, which has a very high tinting strength when it contains 10--12 per cent silica. The residue from the reaction with ammonium fluoride, comprising ferrous ammonium fluoride, may be heated with ammonium sulphate at 300--350 DEG C. to recover ammonium fluoride and obtain ferrous sulphate, or be heated with steam and oxygen at 400--550 DEG C. to recover ammonium bifluoride and obtain a black iron oxide, the latter being converted to a red pigment, if desired, by treating at 500--550 DEG C. with moist air.</p> |
