THERMODYNAMICS OF EXTRACTION OF AM(III) AND EU(III) FROM NITRATE AND THIOCYANATE MEDIA WITH TYL(PHENYL)-N,N-DIISOBUTYLCARBAMOYLMETHYLPHOSPHINE OXIDE

The extraction of Am(III) and Eu(III) from 1.0 M NH4NO3 and NH4SCN at pH 2.60 into tyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in n-dodecane has been studied in the temperature range 15.0 to 45.0 degrees C. Under all conditions, the species ML3.3 CMPO is the d ominant extracted complex. The extraction equilibrium constants are at least 10(3) higher in the SCN- systems than in the NO3- systems. This difference is attributed to the relative energy associated with trans fer of the anions from the aqueous to the extractant phase. Extraction enthalpies and entropies have been calculated in each system from the temperature dependence of K-ex. Enthalpies are considerably more exot hermic in the thiocyanate system for both metal ions. Comparison of De lta H-Am(SCN) with Delta H-Eu(SCN) gives a possible indication of enha nced Am-SCN bond strength in the extracted complex.