Thermodynamics of synergistic extraction of americium(III) with HTTA using DHDECMP(bi-functional) and TBP(mono-functional)

Synergistic extraction of Am(III) was studied with HTTA in combination with bifunctional (DHDECMP) and mono-functional (TBP) neutral donors in benzene medium at various fixed temperatures. The equilibrium constant (log Ks) for the organic phase synergistic reaction with DHDECMP was found to be higher by about two orders of magnitude as compared to that with TBP, in spite of their comparable basicities. This indicated the bi-functional behaviour of DHDECMP in contrast to the previous studies reported for Pu(VI) where DHDECMP was observed to behave as a mono-functional donor. Thermodynamic parameter viz. high + ve ΔS with DHDECMP compared to that with TBP supported this conclusion. However, the ΔH values were comparable in the two cases and this was attributed to the expenditure of more energy for the release of larger number of water molecules by DHDECMP in comparison to that by TBP. (orig.)