Demixing of Binary Water−Chloroform Mixtures Containing Ionophoric Solutes and Ion Recognition at a Liquid−Liquid Interface:  A Molecular Dynamics Study

Abstract

We report a series of molecular dynamics simulations on the demixing of “homogeneous” binary water−chloroform mixtures containing species involved in the assisted ion extraction process. We consider an ionophore L (L = 1,3-alternate calix4arene-crown6), uncomplexed salts of Cs+ and the LCs+ and LNa+ cation complexes with a lipophilic (Pic-) and a hydrophilic (Cl-) counterion, respectively, as being solutes. In all cases, the liquids separate rapidly, leading to two solvent slabs separated by a well-defined interface. However, the final state is very different, depending on the hydrophilic/hydrophobic balance of the solutes: the Cs+ and NO3 - ions of the CsNO3 salt are completely immersed in the aqueous phase, whereas Pic- anions display a strong adsorption at the interface. The LCs+ complex and the free ligand L, although more soluble in the organic phase than in water, also display a surfactant like behavior. Similar conclusions are obtained when L, LCs+, Cs+ Pic-, and Cs+ NO3 - ions are simultaneously present in the solution. On the basis of free energy perturbation calculations on LM+ complexes, we calculate a marked Cs+/Na+ recognition by L at the interface. These results have important implications concerning the mechanism of ionophore assisted liquid−liquid ion extraction and recognition processes at the interface.

Extraction with Spinodal Decomposition – Experiment and Simulation

“…As a result of this simulation, one obtains clusters of equal molecules after 200 ps and two separated phases after 450 ps. These results are in accordance with the literature [28].…”

“…Based on concentration profiles of a DPD simulation, the three-dimensional structure of the interface can be determined to be planar, but not completely smooth, with a thickness of 5-10 Å, Fig. 6, in accordance with the literature [28], which indicates a thickness of 5-7 Å. Provided that the ratio of box lengths is constant, the interface is always formed in the y-z plane as a result of energy minimization.…”

“…While the atom based summation method is applied for Van der Waals forces, the group-based method is used for the calculation of the Coulombic interactions. As shown by simulation results of Muzet et al [28], long-range forces are not crucial for the phase separation process and the use of the (time consuming) Ewald summation method is not necessary.…”

“…Finally, the last picture of this series shows the two stabilized phase boundaries and almost no concentration differences are observed within the bulk phase. As a result of the periodical boundary conditions, two aqueous phases separated by an organic phase are obtained [28]. Based on concentration profiles of a DPD simulation, the three-dimensional structure of the interface can be determined to be planar, but not completely smooth, with a thickness of 5-10 Å, Fig.…”

Complexation of macrocyclic ligands in ionic SDS micellar solutions: A dielectric spectroscopy investigation

“…Interestingly, C222 molecule is able to decrease the effective micellar charge and the average aggregation number, as well as to increase the shell thickness. This picture has been also confirmed by molecular dynamics experiments [15].…”