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 triva lent americium was studied in HNO3 with thenoyl, trifluoro-acetone (HTTA)/1 -phenyl, 3-methyl, 4-benzoyl pyrazolone-5 (HPMBP) in combination with neutr al donors viz. DPSO, TBP, TOPO (mono-functional) and DBDECMP, DHDECMP, CMPO (bi-functional) with wide basicity range using benzene as diluent. A linea r correlation was observed when the equilibrium constant log Ks for the org anic phase synergistic reaction of both U(VI) and Pu(VT) with either of the chelating agents HTTA or HPMBP was plotted vs. the basicity (log Kh) of th e donor (both mono- and bi-functional) indicating bi-functional donors also behave as monofunctional. This was supported by the thermodynamic data (De lta G degrees, Delta H degrees, Delta S degrees) obtained for these systems . The organic phase adduct formation reactions were identified for the abov e systems from the thermodynamic data. In the Am(III) HTTA system log K(s)v alues of bi-functional donors were found to be very high and deviate from t he linear plot (log K-s vs. log K-h) Obtained for mono-functional donors, i ndicating that they function as bi-functional for the Am(III)/HTTA system s tudied. This was supported by high +ve Delta S degrees values obtained for this system.