INFLUENCE OF TEMPERATURE ON THE EXTRACTION OF URANIUM(VI) AND PLUTONIUM(IV) FROM NITRIC-ACID INTO NORMAL-DODECANE BY DI(2-ETHYLHEXYL)SULPHOXIDE

The influence of temperature on the extraction of uranium(VI) and plutonium(IV) from 2 M HNO3 medium into n-dodecane by di(2-ethylhexyl)sulphoxide (DESO) was investigated as a function of temperature in the range 25-50-degrees-C. The results show that the distribution ratios of both U(VI) and Pu(IV) considerably decrease with increasing temperature. From the distribution measurements, thermodynamic parameters such as the free energy (DELTA-G), enthalpy (DELTA-H) and entropy (DELTA-S) changes associated with the formation of UO2(NO3)2.2DESO and Pu(NO3)4.2DESO were evaluated. Extraction of both U(VI) and Pu(IV) from nitric acid by DESO is exothermic in nature and is mainly enthalpy controlled, with negative entropy changes for the relatively less hydrated UO2(2+) species and a small positive value for the more hydrated Pu4+ species.