Extraction of uranium(VI) and plutonium(IV) with some aliphatic amides

Extraction of uranium(VI) and plutonium(IV) has been studied with N,N-dibutyl derivatives of hexanamide (DBHA), octanamide (DBOA) and decanamide (DBDA) at various fixed temperatures of 20, 30, 40 and (50±0.1)°C. The equilibrium constants for the uptake of nitric acid (K_h, a measure of their relative basicities) by these amides were evaluated by the usual method. The equilibrium constants for the extraction of uranium as well as plutonium with all the three amides follow their order of basicity (K_h) viz. DBHA (0.09)<DBOA (0.10)<DBDA (0.13) with log K values of 1.31, 1.43 and 1.73 for uranium and 3.55, 3.65 and 4.17 for plutonium, respectively. It has been observed that whereas uranium(VI) is extracted as a disolvate (similar to TBP and sulfoxides), plutonium(IV) has been found to be extracted as a trisolvate. The thermodynamic parameters evaluated by the usual temperature coefficient method indicate that the extraction reactions of uranium as well as plutonium are stabilized by negative enthalpy change only.