Process for the purification of phosphoric acid by extraction

Claim 1

A process for purifying an aqueous phosphoric acid phase which comprises the steps of: a. contacting an unpurified aqueous phosphoric acid phase containing from 5% to about 55% P 2 O 5 by weight and at least ionic metallic impurities comprising dissolved calcium, magnesium, iron (II) and (III) and aluminum compounds with an organic extractant phase containing a water immiscible organic sulfonic acid in its H + form in the volumetric ratio of organic extractant phase to aqueous phosphoric acid phase of about 1 to 1 to about 100 to 1 at a temperature of about 20° C to about 65° C to form: i. an organic extractant phase containing the organic sulfonic acid, at least a portion of said ionic metallic impurities and extracted P 2 O 5 values, and ii. a purified aqueous phosphoric acid phase; b. separating the purified aqueous phosphoric acid phase from the organic extractant phase; c. contacting the organic extractant phase from (b) with a wash phase in the volumetric ratio of organic extractant phase to wash phase of from about 1 to 1 to about 100 to 1 at a temperature of from about 20° C to about 65° C, said wash phase consisting essentially of water or dilute phosphoric acid containing from about 10 grams/liter of P 2 O 5 , wherein said wash phase preferentially separates P 2 O 5 from the ionic metallic impurities in said extractant phase, to form i. a loaded wash phase enriched with the P 2 O 5 values extracted from the organic extractant phase, and ii. an organic phase containing the organic sulfonic acid, extracted metallic impurities and residual P 2 O 5 values; and d. separating the loaded wash phase from the organic extractant phase of step (c).