Patent ID: 8425872

Claim:
Process for the production of high purity phosphoric acid which comprises the steps of: (a) performing an attack of phosphate rock with a solution of hydrochloric acid to form a slurry comprising 1) an aqueous phase, containing in solution, phosphate ions, chloride ions and calcium ions and 2) an insoluble solid phase containing impurities; (b) separating the aqueous phase, comprising, in solution, phosphate ions, chloride ions and calcium ions, and the insoluble solid phase; (c) performing a neutralization of the aqueous phase by addition of a calcium compound to form calcium phosphate from the phosphate ions, said calcium phosphate being insoluble in water; (d) separating the calcium phosphate, which may be used in the process as a first phosphate salt, and the aqueous phase containing, in solution, calcium ions and chloride ions; (e) performing an attack of a first phosphate salt with a first strong acid to form a slurry of first phosphoric acid, in solution, and a first solid phase; (f) separating the first phosphoric acid from the first solid phase; (g) adding a basic compound to the first phosphoric acid to form a new slurry of a second phosphate salt, in solution, and a second solid phase containing impurities; (h) separating the second phosphate salt from the second solid phase; (i) performing a second attack of the second phosphate salt with a second, concentrated, strong acid to form a second phosphoric acid and a salt; (j) separating the second phosphoric acid from the salt; (k) extracting the second phosphoric acid with an organic solvent to form an organic extraction phase containing phosphoric acid and an aqueous extraction phase containing impurities; (l) re-extracting said organic extraction phase by an aqueous re-extraction agent to form an aqueous re-extraction phase and a phosphoric acid-lean organic phase; (m) separating the aqueous re-extraction phase which contains a third phosphoric acid and the organic phase; and (n) applying ion-exchange to the third phosphoric acid to produce a high purity phosphoric acid.