Effect of structure of N,N dialkyl amides on the extraction of U(VI) and Th(IV): a thermodynamic study

Abstract

The temperature effect on the extraction behaviour of U(VI) and Th(IV) from 3 M HNO3 employing 1 M solutions of N,N diallkyl amides with varying alkyl substituents on the Cα atom viz. di(2-ethylhexyl)acetamide (D2EHAA), di(2-ethylhexyl)propionamide (D2EHPRA), di(2-ethylhexyl)isobutyramide (D2EHIBA) and di(2-ethylhexyl)pivalamide (D2EHPVA) in n-dodecane has been investigated. These studies indicate that the extraction reactions of U(VI) and Th(IV) are enthalpy stabilised while the entropy factor counteracts the extraction. An attempt has been made to correlate the thermodynamic parameters with the structure of the extractant molecules.