Bi-ionic systems

I.2. Interdiffusion. If a membrane separates two solutions with two different counter-ions, but the same co-ion, interdiffusion of ions takes place. The mathematical treatment of these bi-ionic systems is about the same as of the diffusion of an electrolyte across a membrane (52, 54). 

For the bi-ionic systems the agreement is generally good, except when the concentration differences at both sides of the membrane are large. 

K. Sollner, The origin of bi-ionic potentials across porous membranes of high ionic selectivity. I. The bi-ionic potential and the mechanism of its origin the various factors that determine the sign and the magnitude of the bi-ionic potential the simplest chains in which bi-ionic potentials arise systems with critical ions of the same size of different adsorbability, J. Phys. Colloid Chem., 1949, 53, 1211-1239. 

When a cation exchange membrane separates two different electrolyte solutions with different counter-ions such as AY and BY, a bi-ionic potential arises.13 The simplest system is... 

Ionic systems - less susceptible to deleterious dimerization - are accessible with a Judicious choice of ancillary ligand. The /3-diketoiminate scandium dimethyl complex (7) (Figure 11 Ar = 2,6-diisopropylphenyl), activated by B(C6Fs)3 leads to a structurally characterizable ionic complex which polymerizes ethylene. The neutral 1,4,7-triazocyclononane ligand was used to prepare a scandium trimethyl complex (8), which polymerizes ethylene when B(CeF5)3 is used as a cocatalyst. A derivative pendant amide arm leads to the yttrium bis (trimethylsilylmethyl) compound (9), which exhibits modest activity in the presence of [HNMe2Ph][B(C6F5)4l.= ... 

Nwal Amang, D., Alexandrova, S., and Schaetzel, P., Mass transfer characterization of Dorman dialysis in a bi-ionic chloride nitrate system, Chem. Eng. J., 99, 69-76, 2004. 

Despite the utility of chloroaluminate systems as combinations of solvent and catalysts in electrophilic reactions, subsequent research on the development of newer ionic liquid compositions focused largely on the creation of liquid salts that were water-stable [4], To this end, new ionic liquids that incorporated tetrafiuoroborate, hexafiuorophosphate, and bis (trifiuoromethyl) sulfonamide anions were introduced. While these new anions generally imparted a high degree of water-stability to the ionic liquid, the functional capacity inherent in the IL due to the chloroaluminate anion was lost. Nevertheless, it is these water-stable ionic liquids that have become the de rigueur choices as solvents for contemporary studies of reactions and processes in these media [5],... 

The choice of the anion ultimately intended to be an element of the ionic liquid is of particular importance. Perhaps more than any other single factor, it appears that the anion of the ionic liquid exercises a significant degree of control over the molecular solvents (water, ether, etc.) with which the IL will form two-phase systems. Nitrate salts, for example, are typically water-miscible while those of hexaflu-orophosphate are not those of tetrafluoroborate may or may not be, depending on the nature of the cation. Certain anions such as hexafluorophosphate are subject to hydrolysis at higher temperatures, while those such as bis(trifluoromethane)sulfonamide are not, but are extremely expensive. Additionally, the cation of the salt used to perform any anion metathesis is important. While salts of potassium, sodium, and silver are routinely used for this purpose, the use of ammonium salts in acetone is frequently the most convenient and least expensive approach. 

In contrast with salen ligands, ionic liquids were used earlier than fluorinated solvents for biphasic liquid systems with bis(oxazoline)-based complexes. In... 

Surfactants employed for w/o-ME formation, listed in Table 1, are more lipophilic than those employed in aqueous systems, e.g., for micelles or oil-in-water emulsions, having a hydrophilic-lipophilic balance (HLB) value of around 8-11 [4-40]. The most commonly employed surfactant for w/o-ME formation is Aerosol-OT, or AOT [sodium bis(2-ethylhexyl) sulfosuccinate], containing an anionic sulfonate headgroup and two hydrocarbon tails. Common cationic surfactants, such as cetyl trimethyl ammonium bromide (CTAB) and trioctylmethyl ammonium bromide (TOMAC), have also fulfilled this purpose however, cosurfactants (e.g., fatty alcohols, such as 1-butanol or 1-octanol) must be added for a monophasic w/o-ME (Winsor IV) system to occur. Nonionic and mixed ionic-nonionic surfactant systems have received a great deal of attention recently because they are more biocompatible and they promote less inactivation of biomolecules compared to ionic surfactants. Surfactants with two or more hydrophobic tail groups of different lengths frequently form w/o-MEs more readily than one-tailed surfactants without the requirement of cosurfactant, perhaps because of their wedge-shaped molecular structure [17,41]. 

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