Purifying phosphoric acid by extraction with an aliphatic nitrile

In the process for removing at least a portion of the impurities from impure aqueous phosphoric acid solutions containing at least 30% by weight of phosphoric acid by the successive steps of:

• contacting the impure acid with a substantially water-insoluble solvent whereby a portion of the phosphoric acid is extracted into the solvent, forming a loaded solvent phase;
• separating the solvent phase from the remaining materials;
• contacting the solvent phase with water whereby a portion of the phosphoric acid is extracted into the water, forming an aqueous phosphoric acid solution of increased purity;
• and separating the aqueous acid thus formed from the remaining materials;
• wherein the improvement comprises contacting the impure acid with at least one aliphatic nitrile of from 4 to 10 carbon atoms in an amount effective to extract a portion of the phosphoric acid to form a loaded solvent phase with a smaller proportion of iron than the impure aqueous phosphoric acid solution.