Surface Charge Ionicity

Sauce bearnaise, for example, is an O/W emulsion that is mainly stabilized by egg-yolk protein in an aqueous phase of low pH. Perram et al. [830] describe how this system is primarily stabilized by electrostatic repulsive forces, and show how DLVO theory can be used to describe the effects of pH, surface charge, ionic strength, and temperature, on the stability of this emulsion. 

Molecular structure/biospecific adsorption Surface charge/ionic binding Metals complex formation/coordination complex Molecular size and shape/size exclusion Hydrophobicity/hydrophobic complex formation... 

Bjelopavic, M., Newcombe, G., and Hayes, R. (1999). Adsorption of NOM onto activated carbon effect of surface charge, ionic strength, and pore volume distribution. J. Colloid Interface Sci., 210, 271—80. 

Figure 7 shows the dimensionless bubble translation speed Ca as a function of the surfactant (anionic surfactant since the glass capillary used has positive surface charge) ionic concentration for various electric field strengths [17]. At low concentrations, given that the Debye screening length scales as the inverse of the square root of the concentration, the electric double layer thickness becomes compa-... 

One potentially powerfiil approach to chemical imaging of oxides is to capitalize on the tip-surface interactions caused by the surface charge induced under electrolyte solutions [189]. The sign and the amount of the charge induced on, for example, an oxide surface under an aqueous solution is detenuined by the pH and ionic strength of the solution, as well as by the isoelectric point (lEP) of the sample. At pH values above the lEP, the charge is negative below this value. 

Surface charge pH, ionic concentration Resistance to liquid flowthrough the filter medium and support... 

It must be kept in mind, however, that the PIC reagents themselves will not be able to enter the pores of the reverse phase due to ion exclusion and will merely coat the external surface of the stationary phase. Nevertheless, under these circumstances ions will interact with the surface charges and materials will be retained and separated due to ionic interactions. However, at higher solvent concentrations, it has also been suggested that the PIC reagents work in an entirely different manner. 

To an extent the surface charges are determined by the pH of the solution, and by the isoelectric point of the oxide, i.e. the pH at which the oxide surface is neutral. The surface is negative at pH values below the isoelectric point and positive above it. Obviously, the charged state of the surface enables one to bind catalyst precursors of opposite charge to the ionic sites of the support. 

Studies of theadsorption of surface-active electrolytes at the oil,water interface provide a convenient method for testing electrical double-layer theory and for determining the state of water and ions in the neighborhood of an interface. The change in the surface amount of the large ions modifies the surface charge density. For instance, a surface ionic area of 100 per ion corresponds to 16 pC per square centimeter. " " ... 

FIG. 10 Distribution of the ions K and A2 in the presence (full lines) and in the absence (dashed lines) of ion pairing. In the former case, the ionic interaction parameter was taken as r = —9kT. The surface-charge density was taken as cr = 2.34/iCcm in phase 1. 

---