EXTRACTION OF PHOSPHORIC ACID FROM NITRATE SOLUTIONS WITH ISOAMYL ALCOHOL

The extraction of phosphoric acid with isoamyl alcohol from aqueous solutions relevant to and produced by leaching of phosphatic iron ore by nitric acid has been studied. The results indicate that the extraction of phosphoric acid is not temperature dependent in the range 25–40°C, and that it increases with increasing the concentration of HNO3 or H2SO4. The salting-out effect of the different nitrate salts on the extraction of phosphoric acid is found to be in the order of Mg2+> Ca2+ > Na+> NH+4 K+. The presence of Fe3+ and Al3+ may reduce the extraction of phosphoric acid. Phosphoric acid can be extracted selectively against the different nitrate salts but nitric acid is coextracted. The excess coextraction of nitric acid from the aqueous phase will result in the precipitation of some phosphate complexes of Fe, Al, Ca, etc. Some tests of the continuous multistage extraction were also performed and a flowsheet for the recovery of the phosphoric acid is suggested.