THE EFFECT OF TEMPERATURE ON THE EXTRACTION OF PLUTONIUM(VI) FROM NITRIC-ACID INTO DODECANE BY DI(2-ETHYLHEXYL) SULFOXIDE

The effect of temperature on the extraction of plutonium(VI) into dodecane by di(2-ethylhexyl)sulphoxide (DEHSO) has been investigated as a function of temperature in the range 25-50-degrees-C using a wide range of concentrations of both nitric acid as well as DEHSO. The results show that the distribution ratios of plutonium(VI) considerably decrease with increasing temperature. From the variation of the distribution ratio (D(Pu)) with temperature, the thermodynamic parameters such as the free energy (DELTA-G), enthalpy (DELTA-H), and entropy (DELTA-S) changes associated with the formation of PuO2(NO3)2.2DEHSO have been evaluated following a least squares method. Extraction of plutonium(VI) from nitric acid by DEHSO is invariably exothermic in nature and is mainly enthalpy controlled, the entropy change counteracting in all cases. Values of DELTA-H are not much affected by increase in nitric acid concentration. Negative values of DELTA-S are indicative of a smaller entropy gain due to loss of hydration water molecules compared to entropy loss due to complex formation.