An equilibrium study of the chloride and nitrate systems of praseodymium and neodymium with tributyl phosphate and acid

An equilibrium study has been made of the solvent extraction systems, Nd(NO3)3Pr(NO3)3HNO3H2OTBP and NdCl3PrCl3HClH2O TBP. Comparison of a rigorous expression for the separation factor with available data, indicates that for the nitrate system the increase in the separation factor with increasing concentration is caused by variation of the activity coefficient term. It is shown that a good correlation is obtained when the separation factor, βNdPr, is expressed as a function of the in the organic phase. The separation factor for the nitrate system was found to be a function of the ratio of the two rare earths only at very high acid concentrations and at very high mole ratios of neodymium to praseodymium. The separation factors, βNdPr, for the chloride system were less than unity, and not ratio dependent, for all concentrations and acidities used. The fact that for the system SmCl3NdCl3HClH2OTBP, the separation factor, βSmNd, was greater than unity was postulated to be the result of samarium having a lower hydration number than neodymium and praseodymium.