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ABSTRACT
The extraction behaviour of nitric acid, uranium(VI), and plutonium(IV) has been investigated using N,N-dihexyloctanamide (DHOA) in n-dodecane. Results indicate that, similar to TBP, the amide extracts HNO3, U(VI), and Pu(IV) as HNO3.DHOA, UO2(NO3)2 2DHOA and Pu(NO3)4.2DHOA, respectively, from moderately acidic solutions (3·5M HNO3). On the other hand at higher acidities (8·5 M HNO3), similar to tertiary amines, anionic species, UO2(NO3)3 − and Pu(NO3)6 2− are extracted as [UO2(NO3)− 3] [HDHOA+] and [Pu(NO3)6 2−] [HDHOA+]2, respectively, by ion-pair formation. The basicity of the amide (KH= 0·188), indicated by the equilibrium constant for the uptake of nitric acid is marginally larger than that of TBP (0·160) The third phase formation in H2O-HNO3-O·5 M DHOA-n-dodecane system occurs when nitric acid concentration in the aqueous phase approaches a value of 9 M. The equilibrium constant values (log Kex) for the formation of UO2(NO3)2 2DHOA and Pu(NO3,)4 2DHOA solvates are evaluated as 1·49 ± 0·01 and 3·55± 0·02 respectively. Preliminary data on temperature effect, extraction and stripping from fission products are also included.
