A comparative study of extraction of uranium and zirconium in nitric acid media with tri-iso-butyl phosphate and tri-n-butyl phosphate

This paper describes the experimental study of solvent extraction of uranium and zirconium pure solutions in nitric acid medium with tri-iso-butyl phosphate in comparison with that of tri-n-butyl phosphate. These studies revealed that when 35% of solvent in kerosene is used as a solvent the %metal extracted into the organic phase respectively for tri-n-butyl phosphate and tri-iso-butyl phosphate are 67.8 and 66.1 for uranium and 36.8 and 32.6 for zirconium. The saturated concentration of uranium in the organic phase in the case of tri-n-butyl phosphate is 141.9g l-1 while for tri-iso-butyl phosphate it is only 104.6 g l-1. Similarly, it is observed that there is no significant difference in the extractabilities of both these solvents with respect to extraction of nitric acid. These observed differences and similarities in the extraction of behaviour of tri-n- butyl phosphate and tri-iso-butyl phosphate are rationalized in terms of the steric hindrance. Other important outcome that has stemmed from this experimental study is that the organic phase obtained with tri-iso-butyl phosphate on standing slowly develops some thick solid mass probably due to the instability of the adduct formed in this case. This is another undesirable characteristic for the utilization of this solvent on industrial scale for the purpose of solvent extraction apart from its other undesirable characteristics like low extractability with respect to uranium and zirconium and possessing branched carbon chain which is always undesirable in the processing of radioactive materials. (author)