Occidental Research Corporation

Subhas K Sikdar

James H Moore

Donald E Adam

Howard Winterbottom

Hydrofluoric acid and/or other fluorine compounds are recovered by reacting fluosilicic acid with a sodium-containing compound to form an alkaline aqueous slurry comprising precipitated amorphous silica and dissolved sodium fluoride. The precipitated amorphous silica is separated from the alkaline aqueous slurry leaving an aqueous solution of sodium fluoride. The sodium fluoride solution can be used as such or reacted with other substances (such as alumina, to form synthetic cryolite). Sodium fluoride is recovered from the aqueous solution (as by evaporation or extraction) and used per se or reacted with sulfuric acid to produce hydrogen fluoride.

Process for producing fluorine compounds and amorphous silica

Hydrofluoric acid is recovered from fluosilicic acid by reacting fluosilicic acid with sodium sulfate to form sodium fluosilicate. The sodium fluosilicate is reacted with a sodium-containing compound to form an alkaline aqueous slurry comprising silica and dissolved sodium fluoride. The reaction occurs under such conditions that the slurry contains precipitated amorphous silica. The precipitated amorphous silica is separated from the alkaline aqueous slurry leaving an aqueous solution of sodium fluoride. Sodium fluoride is recovered from the aqueous solution and reacted with sulfuric acid to produce hydrogen fluoride.

Recovery of hydrofluoric acid from fluosilicic acid

In a process for purifying an aqueous phosphoric acid containing up to about 55% P.sub.2 O.sub.5 by weight and dissolved magnesium, iron and aluminum ions, wherein (a) said phosphoric acid is contacted with an organic extractant containing a water immiscible organic sulfonic acid to form: a loaded organic extractant phase containing the organic sulfonic acid, extracted ionic metallic impurities and extracted P.sub.2 O.sub.5 values, and a purified aqueous phosphoric acid; (b) the purified aqueous phosphoric acid phase is separated from the loaded organic extractant phase; (c) the separated loaded organic extractant phase is contacted with a solution phase containing calcium ions (e.g., calcium nitrate), under conditions whereby at least some of said extracted ionic metallic impurities (e.g., Mg.sup.+2, Al.sup.+3, Fe.sup.+3) are replaced by calcium and are transferred to said solution phase; and (d) the solution phase is separated from the contacted extractant phase; the improvement wherein the separated solution phase from step (d) is made basic, preferably with lime, to cause a solid precipitate to form, said solid precipitate comprising at least some of the metallic impurities and/or P.sub.2 O.sub.5 values from phosphoric acid which was entrained in the organic extractant. The separated solid precipitate is useful as a nutrient (e.g., as a fertilizer or as an animal feed supplement). Where sulfuric acid is used for the acidification, solid calcium sulfate forms, which can be separated from the 'used' acid. The sulfuric acid can be strengthened with fresh, more concentrated, acid and recycled.

Process for treating loaded extractant from purification of phosphoric

A fluosilicate material is added to a suspension of lime in water heated to a temperature at or near its boiling point to form a solid calcium fluoride product in which the silicon present in the fluosilicate material is in chemical combination with calcium. The amount of calcium in the suspension is in excess of stoichiometric for conversion of CaF.sub.2 of all of the fluorine in the fluosilicate and is sufficient to form chemical compounds of calcium and silicon from silicon in the fluosilicate.

Preparation of calcium fluoride from fluosilicic acid solutions

In a process for purifying an aqueous phosphoric acid containing up to about 55% P.sub.2 O.sub.5 by weight and dissolved magnesium, iron and aluminum ions, wherein (a) said phosphoric acid is contacted with an organic extractant containing a water immiscible organic sulfonic acid to form: an organic extractant phase containing the organic sulfonic acid, extracted ionic metallic impurities and extracted P.sub.2 O.sub.5 values, and a purified aqueous phosphoric acid; and (b) the purified aqueous phosphoric acid phase is separated from the organic extractant phase; the improvement comprising (i) contacting said separated organic extractant phase with a solution phase containing calcium ions (e.g., calcium nitrate), under conditions whereby at least some of said extracted ionic metallic impurities (e.g., Mg.sup.+2, Al.sup.+3, Fe.sup.+3) are replaced by calcium and are transferred to said solutions phase; and (ii) separating said solution phase from the contacted extractant phase. The separated extractant phase can be acidified to convert at least some of the metal form of the extractant to the hydrogen or acid form. The separated solution phase from step (ii) can be neutralized to cause a solid precipitate to form, comprising at least some of the metallic impurities and/or P.sub.2 O.sub.5 values from phosphoric acid which was entrained in the organic extractant.

Hydrofluoric acid is recovered from fluosilicic acid by reacting fluosilicic acid with sodium hydroxide to form a first slurry having a pH of from about 11 to about 14, the first slurry containing sodium metasilicate and precipitated sodium fluoride. Sodium fluoride is recovered from the first slurry leaving a first solution which is reacted with sodium fluosilicate or fluosilicic acid or both to form a second slurry comprising silica and dissolved sodium fluoride. The reaction occurs under such conditions that the second slurry contains precipitated amorphous silica. The precipitated amorphous silica is separated from the second slurry leaving a second solution of sodium fluoride. Sodium fluoride is recovered from the second solution. Recovered sodium fluoride is reacted with sulfuric acid to produce hydrogen fluoride.

Recovery of hydrofluoric acid from fluosilicic acid with high pH

Hydrofluoric acid is recovered from fluosilicic acid by reacting fluosilicic acid with sodium sulfate to form sodium fluosilicate. The sodium fluosilicate is reacted with sodium hydroxide to form a first slurry having a pH of from about 11 to about 14, the first slurry containing sodium metasilicate and precipitated sodium fluoride. Sodium fluoride is recovered from the first slurry leaving a first solution which is reacted with sodium fluosilicate or fluosilicic acid or both to form a second slurry comprising silica and dissolved sodium fluoride. The reaction occurs under such conditions that the second slurry contains precipitated amorphous silica. The precipitated amorphous silica is separated from the second slurry leaving a second solution of sodium fluoride. Sodium fluoride is recovered from the second solution. Recovered sodium fluoride is reacted with sulfuric acid to produce hydrogen fluoride.

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San Juan Capistrano, CA, United States of America

Subhas K Sikdar