GB725747A - Production of alkali metal fluotitanates - Google Patents

Abstract

Sodium, potassium and ammonium fluotitanates are prepared by heating a titanium dioxide containing material with an oxidic compound of calcium, barium or strontium to at least 1200 DEG C. to form an alkaline earth metal titanate, incorporating the titanate in 20-50 per cent. sulphuric or hydrochloric acid and heating the mixture to at least 90 DEG C. in the presence of an added source of fluoride ions and alkali metal ions, separating any insoluble phase while maintaining the temperature and subsequently cooling to crystallize the desired fluotitanate. Starting materials include ilmenite, brookite, rutile, titaniferous slags or sands. Of the oxidic alkaline earth compounds, calcium sulphate is preferred, but the nitrate or carbonate may be used. If the silica content of the raw titania is in excess of 5 per cent., a 10 molar excess of the alkaline earth compound should be used. If it is desired to remove iron and silicon during the pyrolytic treatment, an added carbonaceous reducing agent should be present and treatment effected at fusion point to remove the impurities as ferrosilicon. In the acid treatment of the so formed titanate, the added fluoride and alkali metal components may be present from the start of the acid treatment, but if the silica content is high, an intermediate separation of insoluble silicon and iron compounds can be effected and the fluoride and alkali metal added subsequently. The fluoride reagents may be in the form of fluorspar, hydrofluoric acid or the fluorides of the alkali metals. The alkali metals may be introduced as sulphates, chlorides or nitrates, in addition to introduction as fluorides. According to examples (1) calcium carbonate and pigment titania are treated at 1300 DEG C. for 1 hour and the ground titanate sinter is treated with sulphuric acid at 90 DEG C. To the mixture is added fluorspar and potassium chloride and the whole digested at 90-100 DEG C., then filtered hot. On cooling and the addition of a potassium fluoride solution, potassium fluotitanate crystals are formed. (5) A mixture of ilmenite ore and precipitated calcium carbonate are heated as in (1) above and the ground sinter reacted with 50 per cent. sulphuric acid, followed by digestion at 50-75 DEG C. On dilution and a short further digestion calcium sulphate and iron hydroxide are separated by filtration. Potassium fluoride is then added and after boiling and cooling, potassium fluotitanate is crystallized. (8) Calcium titanate, prepared as in (1) above, is reacted with hydrochloric acid and fluorspar, potassium chloride, potassium sulphate and sodium sulphate are added; the function of the sodium sulphate is to hold the calcium sulphate in solution. After dilution and digestion at 95 DEG C. the solution is filtered and the potassium fluotitanate crystallized.