Thermodynamics of Synergistic Extraction of Hexavalent Plutonium with HPMBP and Neutral Donors: Monodentate versus Bidentate

Abstract

Plutonium(VI) / Pyrazolone / Synergism / Thermodynamics / DPSO / TBP / TOPO SummarySynergistic extraction of hexavalent plutonium was studied from HNO3 medium (0.05 M) with 1-phenyl, 3-methyl, 4-benzoyl, pyrazolone-5 (HPMBP) and different monodentate neutral donors viz. diphenyl sulphoxide (DPSO), tri-n-butyl phosphate (TBP) and tri-n-octyl phosphine oxide (TOPO) using benzene as a diluent. Thermodynamic parameters (AG, AH, AS) evaluated by performing the experiments at various fixed temperatures (288 Κ to 318 K) were compared with those reported previously for the bidentate neutral donors (DBDECMP, DHDECMP and CMPO). The net enthalpy changes were negative and comparable. The monodentate neutral donors, however, showed a larger decrease in the entropy values. Further, the negative values of enthalpy and entropy changes indicated that the organic adduct formation is an addition reaction as reported earlier for the bidentate donors. entropy changes counteracted the reaction. The negative entropy changes suggested the adduct formation reaction to be of addition type and not of substitution. It was considered worthwhile to evaluate these thermodynamic parameters by using different monodentate neutral donors of varying basicities with an objective of comparing the previously obtained data for Pu(VI) with HPMBP and various bidentate neutral donors. A comparison of the entropy changes in the two systems (monodentate and bidentate neutral donors) was considered to be important from the point of view of our earlier interpretation of the bidentates behaving as monodentates. Further, it was thought interesting to compare the behaviour of Pu(VI) vs. that of U(VI) with HPMBP and monodentate neutral donors reported earlier from our laboratory [7].

Thermodynamics of Synergistic Extraction of Americium(III) with HTTA using DHD£CMP(Bi-functional) and TBP(Mono-functional)

“…Further, these log K, values are distinctly different from the straight line plot observed for monofunctional donors. This is in contrast to the behaviour observed previously in our laboratory[8][9][10] for Pu(VI) where log K, values for all these mono-as well as bi-functional neutral donors were observed to lie on one and the same straight line. These observations Support that the bi-functional donors behave differently from mono-functional donors in case of trivalent actinide Am(III).…”

“…Earlier, in our laboratory, we carried out a systematic study to understand the nature of bonding with Pu(VI) [8][9][10] of several mono-functional and bifunctional neutral donors. Based on the equilibrium constants for the organic phase synergistic reaction and thermodynamic parameters, it was conclusively proved that the bi-functional neutral donors (DHDECMP, DBDECMP and CMPO) behave as mono-functional with the coordination number of Pu(VI) as seven.…”

A comparative evaluation of synergistic extraction behaviour of hexavalent uranium with thenoyl tri-fluoro-acetone (HTTA) and 1-phenyl, 3-methyl, 4-benzoyl pyrazolone-5 (HPMBP) using mono-functional and bi-functional neutral donors

“…However, in our previous studies reported [4][5][6] using HTTA and HPMBP for Pu(VI) with monofunctional and bifunctional neutral donors, a reversal from the expected behaviour was noted. Higher synergism was observed with HTTA (pK a = 6.2) compared to that with HPMBP (pK a = 4.2) for all the neutral donors studied and this was attributed to different mechanisms operating for the synergistic extraction in the two cases, i.e.…”

“…This behaviour is similar to that observed and reported previously by us for the Pu(VI)-HPMBP system [6]. It may also be added that the log K s values with HTTA and HPMBP using the two bifunctional neutral donors are comparable and this does not provide evidence to the reversal in the enhanced synergisBrought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 5/28/15 3:00 PM tic extraction vs. lower pK a value behaviour as was reported for Pu(VI) [4][5][6]. The comparable log K s values observed with HPMBP and HTTA using the two bi-functional neutral donors may be due to the two different synergistic reaction mechanisms operative in the two cases.…”

Thermodynamics of Extraction of Plutonium(VI) in PolyEthylene Glycol (PEG) based Aqueous Biphasic System (ABS) using 18-Crown-6 and 15-Crown-5

“…Plutonium was oxidized to Pu(VI) [6] using KBr0 3 having a final concentration of 0.025 M. Ceric ammonium nitrate (0.001 M) was employed as a holding oxidant [7,8],…”