Extraction process for purification of phosphoric acid

A process for the purification of phosphoric acid which comprises:

• a. contacting an aqueous phosphoric acid phase containing from 1% to about 55% P.sub.2 O.sub.5 by weight and dissolved ionic metallic impurities selected from the group consisting of calcium, magnesium, aluminum and iron (II and III) with an organic extractant phase comprising a water immiscible organic solvent containing at least one water immiscible organic sulfonic acid having at least 12 carbon atoms and at least one water immiscible mono- or di-substituted organic acid phosphate compound dissolved therein to form:
• i. a purified phosphoric acid phase;
• and
• ii. a loaded organic extractant phase containing ionic metallic impurites extracted from said aqueous phosphoric acid phase and selected from the group consisting of calcium, magnesium, aluminum and iron (II and III) and P.sub.2 O.sub.5 values;
• b. separating the loaded organic extractant phase from the purified aqueous phosphoric acid phase;
• c. contacting the loaded organic extractant phase separated from the purified phosphoric phase of (b) with a wash phase selected from the group consisting of water and a phosphoric acid phase containing from about 10 to about 300 grams per liter of P.sub.2 O.sub.5 to selectively strip the P.sub.2 O.sub.5 values from the loaded organic extractant phase to form:
• i. a selectively stripped loaded organic extractant phase containing residual ionic metallic impurities selected from the group consisting of calcium, magnesium, aluminum, and iron (II and III) and residual P.sub.2 O.sub.5 values;
• and
• ii. an enriched wash phase containing ionic metallic impurities selected from the group consisting of calcium, magnesium, aluminum, and iron (II and III) and P.sub.2 O.sub.5 values stripped from the loaded organic extractant phase;
• d. separating the selectively stripped loaded organic extractant phase from the enriched wash phase;
• e. contacting the selectively stripped loaded organic extractant phase with a mineral acid stripping phase, the mineral acid being an inorganic acid which has a ionization constant at 10.sup.-3 or larger, to form:
• i. a regenerated organic extractant phase comprising a water immiscible organic solvent containing at least one water immiscible organic sulfonic acid in its H.sup.+ form and at least one water immiscible organic acid phosphate compound in its H.sup.+ form;
• and
• ii. a waste mineral acid stripping phase comprising unused mineral acid, residual P.sub.2 O.sub.5 values and mineral acid salts of ionic metallic impurities selected from the group consisting of calcium, magnesium, aluminum, and iron (II and III);
• and
• f. separating the regenerated organic extractant phase from the waste mineral acid stripping phase.

A process for the purification of phosphoric acid which comprises:

• a. contacting an aqueous phosphoric acid phase maintained at about 20.degree. to about 77.degree. C. and containing from 1 to about 55% P.sub.2 O.sub.5 by weight and dissolved ionic metallic impurities selected from the group consisting of calcium, magnesium, aluminum and iron with an organic extractant phase comprising a water immiscible organic solvent containing at least one water immiscible organic sulfonic acid having at least 12 carbon atoms and at least one water immiscile mono- or di-substituted organic acid phosphate compound dissolved therein, the temperature of said organic extractant phase being from about 20.degree. to about 60.degree. C., in a volumetric ratio of the organic extractant phase to the aqueous phosphoric acid phase of 1 to 1 to about 50 to 1 to form:
• i. a purified phosphoric acid phase;
• and
• ii. a loaded organic extractant phase containing ionic metallic impurities extracted from said aqueous phosphoric acid and selected from the group consisting of calcium, magnesium, aluminum, and iron (II) and (III) and P.sub.2 O.sub.5 values;
• b. separating the loaded organic extractant phase from the purified aqueous phosphoric acid phase;
• c. contacting the loaded organic extractant phase separated from the purified phosphoric acid phase of (b) with a wash phase selected from the group consisting of water and a phosphoric acid phase containin from about 10 to about 300 grams per liter of P.sub.2 O.sub.5 to selectively strip the P.sub.2 O.sub.5 values from the loaded organic extractant phase;
• the loaded organic extractant phase being contacted with the wash phase in the volumetric ratio of from 1 to 1 to about 100 to 1;
• the temperature of the wash phase being from about 20.degree. to about 70.degree. C., to form:
• i. a selectively stripped loaded organic extractant phase containing residual ionic metallic impurities selected from the group consisting of calcium, magnesium, aluminum, and iron (III), and residual P.sub.2 O.sub.5 values;
• and
• ii. a wash phase containing ionic metallic impurities selected from the group consisting of calcium, magnesium, aluminum and iron (II) and (III) and P.sub.2 O.sub.5 values stripped from the loaded organic extracted phase;
• d. separating the selectively stripped loaded organic extractant phase from the enriched wash phase;
• e. contacting the selectively stripped loaded organic extractant phase with a mineral acid stripping phase, the mineral acid being an inorganic acid which has an ionization constant of 10.sup.-3 or larger, in a volumetric ratio of from 1 to 1 to about 20 or more to 1, the temperature of the mineral acid stripping phase being from about 20.degree. to about 77.degree. C., to form:
• i. a regenerated organic extractant phase comprising a water immiscible organic solvent containing at least one water immiscible organic sulfonic acid in its H.sup.+ form and at least one water immiscible organic acid phosphate compound in its H.sup.+ form;
• and
• ii. a waste mineral acid stripping phase comprising unused mineral acid, residual P.sub.2 O.sub.5 values and mineral acid salts of ionic metallic impurities consisting of calcium, magnesium, aluminum and iron (II) and (III);
• and
• f. separating the regenerated organic extractant phase from the waste mineral acid stripping phase.