Solvent Extraction of Uranium(VI), Plutonium(VI) and Americium(III) with HTTA/HPMBP Using Mono- and Bi-Functional Neutral Donors: Synergism and Thermodynamics

Synergistic extraction of hexavalent uranium and plutonium as well as trivalent americium was studied in HNO3 with thenoyl, trifluoro-acetone (HTTA)/1-phenyl, 3-methyl, 4-benzoyl pyrazolone-5 (HPMBP) in combination with neutral donors viz, DPSO, TBP, TOPO (mono-functional) and DBDECMP, DHDECMP, CMPO (bi-functional) with wide basicity range using benzene as dileunt. A linear correlation was observed when the equilibrium constant log Ks for the organic phase synergistic reaction of both U(VI) and Pu(VI) with either of the chelating agents HTTA or HPMBP was plotted vs. the basicity (log Kh) of the donor (both mono- and bi-functional) indicating bi-functional donors also behave as mono-functional. This was supported by the thermodynamic data (ΔG0, ΔH0, ΔS0) obtained for these systems. The organic phase adduct formation reactions were identified for the above systems from the thermodynamic data. In the Am(III) HTTA system log Ks values of bi-functional donors were found to be very high and deviate from the linear plot (log Ks vs. log Kh) obtained for mono-functional donors, indicating that they function as bi-functional for the Am(III)/HTTA system studied. This was supported by high +ve ΔS0 values obtained for this system.