Calculation zeta potential

The surface potential is not accessible by direct experimental measurement it can be calculated from the experimentally determined surface charge (Eqs. 3.1 - 3.3) by Eqs. (3.3a) and (3.3b). The zeta potential, calculated from electrophoretic measurements is typically lower than the surface potential, y, calculated from diffuse double layer theory. The zeta potential reflects the potential difference between the plane of shear and the bulk phase. The distance between the surface and the shear plane cannot be defined rigorously. 

Figure 7.7 Zeta potentials (calculated from electrophoretic mobility data) relating to particles of different ionogenic character plotted as a function of pH in acetate-veronal buffer at constant ionic strength of 0.05 mol dm 3, (a) Hydrocarbon oil droplets, (b) Sulphonated polystyrene latex particles, (c) Arabic acid (carboxylated polymer) adsorbed on to oil droplets, (d) Serum albumin adsorbed on to oil droplets...

Substituting a for 7 uE/e (i.e a is the apparent zeta potential calculated from the Smoluchowski equation) gives... 

The potential of the interface facilitates the expulsion of some of the long-chain ions due to the repulsion between like charges of the neighboring groups. From the rate of solution of appropriate films one can thus calculate 4 (Davies, 34). Danielli has found that the electrokinetic or zeta potential, calculated from mobilities, is in good agreement with these other methods. Table X shows some values of 4 in different films. We are now in a position to interpret the kinetic results. 

Table 2Particle Size Distributions and Zeta Potentials Calculated...

Calculate the zeta potential for the system represented by the first open square point (for pH 3) in Fig. V-8. 

This energy maximum is calculated from the electric surface potential. An approximation of this surface potential is the zeta potential, which is experimentally deterrnined with commercial instmments. For o/w emulsions with low electrolyte content in the aqueous phase, a zeta potential of 40 mV is sufficient to bring the energy maximum to this level. 

The calculation of zeta potential from electoviscous effect measures (Rubio-Hernandez et al. 1998 and 2004), is given by the equation... 

The velocity of particle migration, v, across the field is a function of the surface charge or zeta potential and is observed visually by means of an ultramicroscope equipped with a calibrated eyepiece and a scale. The movement is measured by timing the individual particles over a certain distance, and the results of approximately 10-15 timing measurements are then averaged. From the measured particle velocity, the electrophoretic mobility (defined as v/E, where E is the potential gradient) can be calculated. 

The Hamaker constants used in these calculations were obtained from values reported in the literature [Gregory (14)]. Zeta potentials were obtained both experimentally and from the literature [Huang and Stumm (15) and Sharma ( )]. 

Initial studies were made with the Rank Bros, electrophoresis unit, using the dilute supernatant suspension over a dispersion of 3.33g of carbon black per liter of dodecane equilibrated for 24 hours with the added 0L0A-1200. The electrophoretic mobility (u) of 1-3 pm clumps of particles was observed at a field of 100 volts per centimeter. The zeta-potentials ( ) were calculated... 

Lyklema(18) considers that the slipping plane may be identified with the Stem plane so that x/ss — f. Thus, since the surface potential xj/o is inaccessible, zeta potentials find practical application in the calculation of Vr from equation 5.16. In practice, electrokinetic measurements must be carried out with considerable care if reliable estimates of f are to... 

Fig. 1. Variation of the eiectric potential near a surface in the presence of an electrolyte solution, (a) Electrical double layer at the surface of a solid positively charged, in contact with an electrolyte solution, (b) The variation of the electrical potential when the measurement is made at an increasing distance from the surface, and when the liquid phase is mobile at a given flow rate. The zeta potential [) can be calculated from the streaming potential, which can be measured according to the method described by Thubikar et al. [4].

M KCl, in the cell. The distance is calculated from the known conductivity of the solution. The average electromobility of the colloids is thus obtained and hence, using (6.53), the average zeta-potential. 

A measurement of electrophoretic mobility /v, gives x = 0.02 cm s-1, where v is the velocity observed under a field, and x the mobility. Calculate the zeta potential of the colloid concerned. (Bockris)... 

Figure 17 Formal potential of Feln/n(phosbpy)3 /10 on nanocrystalline Ti02 as a function of pH ( ), and zeta potentials on Ti02 function of pH (O). Zeta-potential variations were calculated from electrophoretic transport data contained in Ref. 81. Note the strong correlation between formal potential variations and zeta-potential variations.

Criticize or defend the following proposition Zeta potentials for three different polystyrene latex preparations were calculated by the Helmholtz-Smoluchowski equation from electrophoresis measurements made in different concentrations of KCl.f... 

Collins and Jameson11 found that for small air bubbles (20 to 100 jzm), varying the particle zeta potential from +30 mV to +60 mV resulted in an order of magnitude change in the observed rate constants for each drop size. Table 9 shows the values of the calculated and observed first-order rate constants for the data of Collins and Jameson obtained when their particles (polystyrene) had the minimum stability (zeta potential + 30 mV). The observed rate constants are much smaller than those calculated from collision theory. Their data indicate that between 1 in 40 to I in 100 collisions results in the particles sticking to bubbles. This is consistent with the particle-collision removal mechanism. 

ZETA POTENTIAL. The potential across the interface of all solids and liquids. Specifically, the potential across the diffuse layer of ions surrounding a charged colloidal particle, which is largely responsible for colloidal stability. Discharge of the zeta potential, accompanied by precipitation of the colloid, occurs by addition of polyvalent ions of sign opposite to that of the colloidal particles. Zeta potentials can be calculated from electrophoretic mobilities, i.e., the rates at which colloidal particles travel between charged electrodes placed in the solution. 

The electrical potential is a function of distance x from the interface and can be measured at a specific distance z from the interface. The electrical potential as measured by means of electrophoretic mobility is called the zeta potential ( j/z). With the zeta potential, it is possible to calculate the actual interfacial charge. However, the use of the appropriate model is essential to obtaining the correct interfacial charge and can be evaluated using... 

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