Abstract: The invention relates to the decontamination of wet-processed phosphoric acid with the use of organic solvents in a plurality of extraction zones, of which each is comprised of a mixing zone and a separating zone, the solvent being immiscible or partially miscible with water. Resulting organic phase and the aqueous phase are contacted countercurrently with respect to one another, the organic solvent phase being dispersed in the aqueous phase. To this end, the invention provides for the aqueous phase to be admitted to the mixing zone at the onset of the extraction, and for organic phase and aqueous phase to be continuously admitted in a volume ratio of at least 2.5:1 to the respective extracting zones in an overall quantity sufficient to provide, in the mixing zones of the extraction zones, a volume ratio of organic phase to aqueous phase of at most 1:1, which is maintained therein.

Abstract: The invention relates to a process for the purification of wet-processed phosphoric acid with the aid of organic solvents which are immiscible or only partially miscible with water, the sulfate ions being removed by addition of barium compounds. The purification is carried out in an n-stage extraction installation, where n is equal to or greater than 5. The barium compound is added to the phosphoric acid to be purified, and the resulting mixture is fed to the top of the extraction installation, in which the organic solvent phase is dispersed in the aqueous phase. The sulfuric acid is led in counter-current fashion to the phosphoric acid by adding it to one of the stages n=4 to at most n-1.

Abstract: The present invention relates to a mixer/settler-type apparatus for continuous liquid-liquid extraction. The apparatus is comprised of a separating vessel with an inclined bottom portion and an agitator-provided mixing vessel. The mixing vessel is tightly mounted to the inclined bottom portion of the separating vessel, the latter being formed with an upper outlet and a lower outlet and having a level indicator LI for determining phase boundary surface area installed therein. The lower outlet is passed through the separating vessel near its lowermost level and the upper outlet is passed therethrough near its upper end. The level indicator LI is connected to a regulator giving adjustment instructions to a structural element permitting the phase boundary surface area to be established in the separating vessel, distinctly above the upper end of the mixing vessel.

Abstract: The invention relates to the production of alkali metal phosphate solutions free of zinc, from phosphoric acid solutions contaminated with zinc. To this end, feed solution is admixed with alkali metal hydroxide or carbonate so as to establish in the resulting suspension a pH-value within the range 8 to 14. Next, resulting suspension is reacted under pressure and with thorough agitation with H.sub.2 S or an alkali metal sulfide solution; and decontaminated alkali metal phosphate solution is separated from solid matter, the pressure being maintained.

Abstract: The invention relates to a process permitting acid salt residues, hereinafter called raffinates, which are obtained in the decontamination of phosphoric acid by extraction with a solvent, to be converted to solid deposition products, wherein the raffinates are admixed with a quantity of water necessary for them to ensure, after reaction with hydrate of lime or quicklime, the formation of an aqueous filterable suspension. More particularly, the raffinates are admixed with a quantity of hydrate of lime or quicklime necessary for them to ensure, after reaction and filtration of the suspension, the formation of a filter cake having a pH-value within the range 9 to 14. The reaction suspension is filtered as soon as it has assumed a pH-value within the range 5 to 8 and the resulting filter cake is allowed to react completely and deposited.

Abstract: For extracting phosphates with alcohol in the presence of water and a strong mineral acid, with the resultant formation of an alcoholic phosphoric acid solution and an aqueous salt phase, a plurality of mixing settlors are arranged one upon another, so that the bottom outlet for the aqueous salt phase of each mixing settlor serves as the feeder for the next mixing settlor below and the outlet for the alcoholic solution of each settlor is connected with the feed pipe for this solution of the next mixing settlor above. Each mixing settlor is subdivided by means of two partitions into a mixing chamber A, a separating chamber B and a settling chamber C. The said two partitions do not extend to the bottom of the mixing settlor and are arranged so that the three chambers A, B and C communicate with one another.

Abstract: Wet-processed phosphoric acid is purified by counter-current extraction with the use of an organic solvent, in which water is partially soluble and which is capable of absorbing phosphoric acid, the organic phosphoric acid extract is separated from residual wet-processed phosphoric acid, unabsorbed by the solvent, and phosphoric acid is recovered from the separated organic phosphoric acid extract. More specifically, the wet-processed phosphoric acid is extracted with the use of a solvent containing more than 0 and less than 50% of water, based on the saturation concentration, and a mineral acid in a quantity corresponding to the quantity, in moles, of cation-bound phosphate in the crude acid.

Abstract: Alcoholic phosphoric acid solutions are produced from acid phosphates or phosphate mixtures in the presence of water and a strong mineral acid by extraction with water. To this end, an aqueous phosphate solution or suspension is contacted countercurrently and thereby mixed with a mixture of at least one alcohol having from 3 to 8 carbon atoms and a strong mineral acid, the alcohol or alcohol mixture and the phosphate solution or suspension being used in a ratio by volume of 2:1 to 20:1, and the mineral acid being used in the quantity just necessary to transform the phosphates approximately quantitatively to phosphoric acid. The alcohol or alcohol mixture, mineral acid and phosphate solution or suspension contain the quantity of water necessary to ensure the formation of a mixture consisting of an alcoholic phase and a separate flowable salt phase, which is separated from the alcoholic phase.

Abstract: Wet-processed phosphoric acid is decontaminated. To this end, the phosphoric acid and an organic solvent, which is partially miscible with water and capable of absorbing phosphoric acid, are contacted countercurrently with respect to one another. The resulting organic phosphoric acid solution is separated from contaminants unabsorbed by the solvent, termed primary raffinate, decontaminated phosphoric acid is recovered either in the form of free acid by re-extracting the organic phosphoric acid solution with water, or in the form of an alkali metal phosphate by reacting the organic phosphoric acid solution with an alkali, and the primary raffinate is treated countercurrently with a solvent containing a mineral acid.

Abstract: Alkali metal phosphate solutions (alkali metal oxide : P.sub.2 O.sub.5 - molar ratio greater than 1.9 : 1) of reduced vanadium and chromium contents are made from wet-processed phosphoric acids which are neutralized by means of an alkali metal hydroxide and/or carbonate. The alkali metal phosphate solutions contain less than 20 ppm of vanadium and less than 1 ppm of chromium and are made by stepwise neutralization. More specifically the acid is neutralized in a first step to an alkali metal oxide to P.sub.2 O.sub.5 - molar ratio of 1.0 : 1 to 1.8 : 1; resulting precipitate is separated and resulting solution is admixed with iron(II)salt at 60 to 90.degree. C. Next, the acid is neutralized in a second step to an alkali metal oxide to P.sub.2 O.sub.5 - molar ratio greater than 1.9 : 1, and resulting precipitate is separated again.

Abstract: Production of pure alkali metal phosphate solutions by neutralizing wet-processed phosphoric acid with an alkali liquor and/or carbonate. To this end, the wet-processed phosphoric acid is neutralized to a pH from 4 to 9, the resulting neutralization sludge consisting substantially of insoluble aluminum and iron phosphates is separated from the alkali metal phosphate solution and scrubbed with water, the sludge so treated is mixed with alkali liquor, alkali metal phosphate solution and water-glass so as to establish in the resulting suspension a molar ratio of SiO.sub.2 to Al.sub.2 O.sub.3 of at least 2 : 1 and a molar ratio of dissolved alkali metal oxide to dissolved P.sub.2 O.sub.5 ranging from 2.9 : 1 to 3.3 : 1, the whole is heated to temperatures from 80.degree. to 100.degree.

Abstract: Alkali metal phosphate solutions of low vanadium content are produced from wet-processed phosphoric acids contaminated with vanadium and iron. The acids containing vanadium and iron in the highest stage of oxidation are treated with a reductant to effect conversion of the vanadium and iron contaminants to a lower stage of oxidation, the resulting acids are neutralized by means of an alkaline liquor and/or alkali metal carbonate down to a pH of at least 3, and the resulting precipitate is separated. The reductant used is the sodium salt of hydroxymethane-sulfinic acid.

Abstract: Phosphoric acid is purified. To this end, it is dissolved in an organic solvent completely miscible with water. More particularly, the phosphoric acid is mixed with a solvent having a boiling point higher than that of water or higher than that of the resulting azeotrope; the resulting solution is heated to temperatures between the boiling point of water or the azeotrope and that of the solvent for as long a period as necessary to distillatively free the solution from the bulk of uncombined water therein; and the phosphoric acid solution is separated from residue.

Abstract: Contaminated wet-processed phosphoric acid is purified. To this end, the wet-processed phosphoric acid is mixed with one or more organic solvents, in which water is partially soluble, the organic solvent(s) is (are) separated from unabsorbed wet-processed phosphoric acid portions, and phosphoric acid is recovered from the organic solvent(s) so separated. The organic solvent(s) are more particularly used in the form of anhydrous material and at least in the quantity necessary to ensure dissolution (a) of the overall quantity of phosphoric acid contained in the wet-processed phosphoric acid and (b) of the free water therein.