Process for the production of high purity phosphoric acid

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.