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Effect of polystyrene length for the extraction of Gd3+ and UO2 2+ ions using dicyclohexano crown ether (DCH18C6) with octanol and nitrobenzene: A molecular dynamics study
, S.H. Mir, J.K. Singh
Published in Elsevier B.V.
Volume: 271
Pages: 166 - 174
The role of polystyrene (PS) grafting to the dicyclohexano crown ether (DCHCE) in extracting the Gd3+ and UO2 2+ is evaluated for the first time using atomistic molecular dynamics (MD) simulations. The thermodynamic free-energy (ΔGBind) is calculated to understand the binding of Gadolinium (Gd3+) and Uranyl (UO2 2+) to the DCHCE in nitrobenzene (NB) and octanol (OCT) solvents. The results show that the binding free-energy is favorable for Gd3+ and UO2 2+ in NB, and unfavorable in OCT. In NB, the ΔGBind of Gd3+ and UO2 2+ increases by 2.3% and 3.1% respectively with an increase in the PS length from 0 to 3. On the contrary, in OCT, the ΔGBind of Gd3+ and UO2 2+ decreases by 2.4% and 3.4% with an increase in PS length of the grafted DCHCE. The transfer free-energy (ΔGTransfer) for both the ions viz., Gd3+ and UO2 2+, from the aqueous phase to an organic phase is also analyzed using NB and OCT as extractants. The ΔGTransfer for both ions shows encouraging extraction ability in NB while the extraction ability decreases using OCT as an extractant. The partition coefficient (log P) values show an increase with an increase in PS grafting length on the DCHCE using NB as an extractant, while an opposite behavior is observed in OCT. In particular, with increase in the PS length, for Gd3+ and UO2 2+, log P values in NB increase by 13% and 9.6% respectively; whereas log P values decrease by 27% and 10% in OCT. In the presence of acidic medium (3 M HNO3 solution) the ΔGTransfer values for both Gd3+ and UO2 2+ show ~6% and 9% increase with NB and OCT, respectively. The structural and thermodynamic solvation properties are in accordance with the observed ΔGBind, ΔGTransfer, and log P. © 2018 Elsevier B.V.
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JournalData powered by TypesetJournal of Molecular Liquids
PublisherData powered by TypesetElsevier B.V.