Aqueous Ion Solvation at the Interface

In 2002, dos Santos and Gomes published a study on calcium ion transfer across the HjO-NB interface [26]. They observed a monotonous increase in the potential of mean force, that is, the solvation energy as the ion crosses the interface, and the process was found to be nonactivated. During the transfer from water to nitrobenzene, the first hydration shelf remains intact, whereas the second hydration shell loses its water molecules. 

In a recent publication by Wick and Dang [27], the excess concentration of cations (i.e., Na and Cs+) and of anions (i.e., chloride) at the H20-1,2-DCE interface has been studied, showing that these cations have a positive excess concentration 

Back in 1983, the concept of mixed solvent layer [16] resulted from the determination of water surface excess concentrations at different interfaces by interfacial tension measurements that showed that, in the case of the H2O-DCE interface, and unlike the liquid water-vapor or the water-heptane interfaces, the water excess concentration was less than a monolayer as expected for aqueous 1 1 electrolyte. The molecular dynamics results of Wick and Dang seem therefore to corroborate this early concept of interfacial structure in the presence of electrolytes in the aqueous phase. 

One should also mention the work of Jorge et al. who have studied ion solvation at the H2O-NPOE interface [28]. 

---