Surface charges zeta potential, relation

Several theories relating surface charge, zeta potential, and channel size with the magnitude and the flow velocity distribution of the EOF through the channel have been described [21,22,27], The various models vary in complexity and detail, but most of the details are beyond the scope of the present discussion. 

Quantitatively, the pH determines on the solid side the value of the zeta potential related to the concentration of charged surface sites (Fig. 3). On the liquid side, it allows selection of the most abundant metal... 

Zeta potential Related closely with DLVO theory. A measure of the electrical charge on the effective particle surface. A key parameter when relying on the ionic repulsion mechanism for disper-sion/deflocculation. 

Several of the surface characteristics of manbranes such ashydrophobic/hydrophilic properties, membrane charge (zeta potential), and surface roughness are strongly related to fouling because they determine the interaction between the membrane and the foulants [20,21]. 

In order to describe the effects of the double layer on the particle motion, the Poisson equation is used. The Poisson equation relates the electrostatic potential field to the charge density in the double layer, and this gives rise to the concepts of zeta-potential and surface of shear. Using extensions of the double-layer theory, Debye and Huckel, Smoluchowski,... 

Kamo et al. [Biochim. Biophys. Acta, 367, 1 and 11 (1974)] have shown that nonionic sugars modify the zeta potential of slime mold cells. Aggregation of colloids is related to their surface charge and their surface potential. This fact shows evidence of long-range electrostatic interactions controlled by metabolic reactions taking place at the membrane and able to modify the composition of the membrane medium interface. In this process the diffusion is not relevant, as indicated by Mrs. Babloyantz. 

Following this we derive the equation for electroosmotic flow and relate it to the zeta potential of the charged surface (Section 12.6). Section 12.7 focuses on the streaming potential and compares the zeta potentials obtained by the different methods. 

The surface of shear is the location within the electrical double layer at which the various electrokinetic phenomena measure the potential. We saw in Chapter 11 how the double layer extends outward from a charged wall. The potential at any particular distance from the wall can, in principle, be expressed in terms of the potential at the wall and the electrolyte content of the solution. In terms of electrokinetic phenomena, the question is How far from the interface is the surface of shear situated and what implications does this have on the relation between measured zeta potential and the surface potential ... 

Electrokinetic phenomena are only directly related to the nature of the mobile part of the electric double layer and may, therefore, be interpreted only in terms of the zeta potential or the charge density at the surface of shear. No direct information is given about the potentials tf/0 and charge density at the surface of the material in question. 

A persistent question regarding carbon capacitance is related to the relative contributions of Faradaic ( pseudocapacitance ) and non-Faradaic (i.e., double-layer) processes [85,87,95,187], A practical issue that may help resolve the uncertainties regarding DL- and pseudo-capacitance is the relationship between the PZC (or the point of zero potential) [150] and the point of zero charge (or isoelectric point) of carbons [4], The former corresponds to the electrode potential at which the surface charge density is zero. The latter is the pH value for which the zeta potential (or electrophoretic mobility) and the net surface charge is zero. At a more fundamental level (see Figure 5.6), the discussion here focuses on the coupling of an externally imposed double layer (an electrically polarized interface) and a double layer formed spontaneously by preferential adsorp-tion/desorption of ions (an electrically relaxed interface). This issue has been discussed extensively (and authoritatively ) by Lyklema and coworkers [188-191] for amphifunctionally electrified... 

The sedimentation velocity can be corrected for repulsive forces because of the surface charge of equal sign of the floes. The relation between the reduced sedimentation velocity of the particles and their zeta-potential is, after conversion to MKSA units (10, 11) ... 

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