THE SEPARATION FACTORS OF THE LANTHANIDES IN THE LN(NO3)(3)-NH4NO3-TBP SYSTEM - EFFECTS OF CHANGE IN ACTIVITY-COEFFICIENTS

The change in the molar activity coefficients of the lanthanide nitrat es is determined from the extraction data in the Ln(NO3)(3)-NH4NO3-TBP system. It is concluded that at high NO3 concentrations (6-10 M) high er lanthanide nitrate complexes Ln(NO3)(n)(3-n) are formed to a remark able extent, which results in the sudden increase in the activity coef ficients in the Sm-Er range. The improvement in the separation factors of the light lanthanides with the NO3- concentration increase is obse rved for TBP, which is in contrast to the Aliquat 336+TBP system.