Molecular Forces in Liquid–Liquid Extraction

Abstract

The phase transfer of ions is driven by gradients of chemical potentials rather than concentrations alone (i.e., by both the molecular forces and entropy). Extraction is a combination of high-energy interactions that correspond to short-range forces in the first solvation shell such as ion pairing or complexation forces, with supramolecular and nanoscale organization. While the latter are similar to the long-range solvent-averaged interactions in the colloidal world, in solvent extraction they are associated with lower characteristic lengths of the nanometric domain. Modeling of such complex systems is especially complicated because the two domains are coupled, whereas the resulting free energy of extraction is around k B T to guarantee the reversibility of the practical process. Nevertheless, quantification is possible by considering a partitioning of space among the polar cores, interfacial film, and solvent. The resulting free energy of transfer can be rationalized by utilizing a combination of terms which represent strong complexation energies, counterbalanced by various entropic effects and the confinement of polar solutes in nanodomains dispersed in the diluent, together with interfacial extractant terms. We describe here this ienaics approach in the context of solvent extraction systems; it can also be applied to further complex ionic systems, such as membranes and biological interfaces.

Molecular Dynamics Study of the Aggregation Behavior of N,N,N′,N′-Tetraoctyl Diglycolamide

“…Furthermore, the addition of n -octanol as a phase modifier has been shown to reduce the propensity for third phase formation and/or precipitation. 8 , 23 , 33 , 54 − 56 …”

“…The most common way to separate metals is liquid–liquid extraction. − Taking nuclear fuel recycling as an important example, spent nuclear fuel is delay-stored to reduce the effects of short-lived radioactive species and is then dissolved in nitric acid. This is contacted with an organic diluent and an appropriate ligand.…”

“…Other diluents are also used, for example, isane and odorless kerosene, of which n -dodecane is a major constituent. Furthermore, the addition of n -octanol as a phase modifier has been shown to reduce the propensity for third phase formation and/or precipitation. ,,,− …”

Martini Coarse-Grained Model for Poly(alkylimidazolium) Ionenes and Applications in Aromatic Compound Extraction

“…where R is the ideal gas constant, T is the temperature, ρ i (z) is the density profile of component i, and ρ ̅ i oil is the average density in the oil phase, obtained by integrating the average density profile in the oil phase. 56 The distribution coefficients of Oct and Bz (D Oct and D Bz ) and Bz selectivity (S) were numerically evaluated using 57…”

Liquid–liquid extraction: thermodynamics–kinetics driven processes explored by microfluidics

“…The graphs of Figure 5 give the concentration for both Yb 3+ and Fe 3+ and D-extraction/R-extraction, as a function of time of flow in the microfluidic platform. For each value of flow, one can observe first a transition period in which the concentration increases until it levels off to a plateau value which corresponds to the steady [18]. To further increase accuracy, measuring the equilibrium temperature dependence helps to determine the overall entropic contribution [19].…”