Purification of wet-process phosphoric acid by solvent extraction

ABSTRACT

The purification of wet-process phosphoric acid [WPA] by di-isopropyl ether [DIPE] was studied. The partition coefficient, K, of WPA between water and DIPE at different temperatures was determined. The average value amounted to 4.7 X 10-2 at 25, decreasing as the temperature increased from 25 to 55. The extraction of WPA is apparently more favorable around room temperature. It was also found that the extraction of phosphoric acid in the organic layer increased the greater solvent/acid weight ratio. The batch-wise extraction and stripping of phosphoric acid from 200 ml crude acid yielded 39 g of pure phosphoric acid, 154.7 g of pure Na2HPO4, 7H2O and 215.2 g of pure Na3PO4, 8H2O beside 75 g of a precipitated cake during the chemical treatment of the raffinate