The extraction of hexavalent uranium from nitric acid solutions by tetrabutylpyrophosphate (TBPP)

The mechanism of extraction of nitric acid and uranyl ions by tetrabutylpyrophosphate (TBPP) solutions in carbon tetrachloride, has been investigated. The solvation number for the uranyl ion, determined by both extraction and the spectrophotometric method, was one. A reaction of aggregates of the extractant species with the TBPP-uranium complex is suggested. Kinetic investigations of this reaction were carried out recording the absorbance in the PO stretch band at different times after reaching thermodynamic equilibrium for the primary extraction. The postulated reaction follows a zero order equation when the molar ratio of TBPP and uranium nitrate was 10:1.