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Particle surface zeta potential

A foaming agent, such as crude cresol or pine oil (soap is unsuitable, as it lowers 0 too much), is added to the suspension of ground ore and collector oil in water and the pH is adjusted to give the particles low zeta potentials and, therefore, minimise electrostatic repulsions. Air is forced through a fine sieve at the bottom of the vessel. The particles of metal ore become attached to the air bubbles, which carry them to the surface (Figure 6.7), where they collect as a metal-rich foam which can be skimmed off. [Pg.162]

The selection of polymer is critical to the performance, properties, and application of nanoparticles. Further, the physicochemical properties of the polymer will determine the surface properties of nanoparticles with polymer molecular weight, hydro-phobicity, and glass transition temperature being particularly important. The surface properties that influence their biodistribution and cellular response include particle size, zeta potential, and surface hydrophilicity. [Pg.548]

Figure 9.19. The diffuse double layer, (a) Diffuseness results from thermal motion in solution, (b) Schematic representation of ion binding on an oxide surface on the basis of the surface complexation model, s is the specific surface area (m kg ). Braces refer to concentrations in mol kg . (c) The electric surface potential, falls off (simplified model) with distance from the surface. The decrease with distance is exponential when l/ < 25 mV. At a distance k the potential has dropped by a factor of 1/c. This distance can be used as a measure of the extension (thickness) of l e double layer (see equation 40c). At the plane of shear (moving particle) a zeta potential can be established with the help of electrophoretic mobility measurements, (d) Variation of charge distribution (concentration of positive and negative ions) with distance from the surface (Z is the charge of the ion), (e) The net excess charge. Figure 9.19. The diffuse double layer, (a) Diffuseness results from thermal motion in solution, (b) Schematic representation of ion binding on an oxide surface on the basis of the surface complexation model, s is the specific surface area (m kg ). Braces refer to concentrations in mol kg . (c) The electric surface potential, falls off (simplified model) with distance from the surface. The decrease with distance is exponential when l/ < 25 mV. At a distance k the potential has dropped by a factor of 1/c. This distance can be used as a measure of the extension (thickness) of l e double layer (see equation 40c). At the plane of shear (moving particle) a zeta potential can be established with the help of electrophoretic mobility measurements, (d) Variation of charge distribution (concentration of positive and negative ions) with distance from the surface (Z is the charge of the ion), (e) The net excess charge.
Kunzelmann, U., Jacobasch, H.J., and Reinhard. G., Investigations of the influence of vapour phase inhibitors on the surface charge of iron oxide particles by zeta-potential measurements, Werkstoffe Korrosion. 40, 723, 1989. [Pg.926]

DLS instruments can be used to measure the size of particle aggregates in water, as described previously. DLS can also measure the movement of nanoparticles in an electric field to determine the zeta potential, which provides information about the surface charge on a particle. The zeta potential will affect the distribution of the nanoparticles in solution and influence surface reactive properties. The zeta potential can be calculated using the Henry equation ... [Pg.699]

The streamlines at x-y plane passes the center of the microchannel at z = 1.5 Dp show the flow pattern arotmd different types of the particles (Fig. 5a, c, e). In the case of nonconducting particle, the zeta potential at any point on the surface is tmiform and constant. Thus, the streamlines smoothly follow the surface of the nonconducting particle and pass it without distortion (Fig. 5b). [Pg.1392]

The zeta-potential can also be influenced by the absorption of specific ions from the dispersion medium onto the surface of the colloidal particle. For example, if a positively charged surfactant adsorbs onto a positively charged colloidal lyophobic particle, the zeta-potential becomes larger than the Nemst potential. [Pg.370]

With the electrostatic approach, ions or charged molecules are attracted to or dissociated from the particle surfaces to produce a system of similarly charged particles. When the repulsive double-lsiyer electrostatic forces between the particles are greater than the attractive Van der Waals forces, the particles repel to produce a dispersed system. The net Interparticle force (In aqueous solutions) can be altered by changing the type of concentration of the ionic species as well as the pH. When the particle charge approaches zero, the particles floe and eventually produce a very open network of touching particles. The zeta potential provides a convenient experimental measure of such forces. [Pg.29]

Several effects, due to the existence of the double layer on the surface of most particles suspended in Hquids, can be used to measure the so-called zeta potential. Table 1 gives a simplified summary of the effects. [Pg.390]

Fig. 8. Electrical double layer of a sohd particle and placement of the plane of shear and 2eta potential. = Wall potential, = Stern potential (potential at the plane formed by joining the centers of ions of closest approach to the sohd wall), ] = zeta potential (potential at the shearing surface or plane when the particle and surrounding Hquid move against one another). The particle and surrounding ionic medium satisfy the principle of electroneutrafity. Fig. 8. Electrical double layer of a sohd particle and placement of the plane of shear and 2eta potential. = Wall potential, = Stern potential (potential at the plane formed by joining the centers of ions of closest approach to the sohd wall), ] = zeta potential (potential at the shearing surface or plane when the particle and surrounding Hquid move against one another). The particle and surrounding ionic medium satisfy the principle of electroneutrafity.
Hydrolysis. The surfaces of metal oxides and hydroxides can take up or release or OH ions and become charged. Potentials as high as 100 mV may be sustained ia aqueous solutions. For aqueous solutions this is a function of the pH the zeta potential for the particle is positive if the solution pH is below the particle s isoelectric pH (pH ), and negative if the pH is above pH Isoelectric poiats for metal oxides are presented ia several pubheations (22,23). Reactions of hydroxyl groups at a surface, Q, with acid and base may be written as follows ... [Pg.546]

Electroultrafiltration (EUF) combines forced-flow electrophoresis (see Electroseparations,electrophoresis) with ultrafiltration to control or eliminate the gel-polarization layer (45—47). Suspended colloidal particles have electrophoretic mobilities measured by a zeta potential (see Colloids Elotation). Most naturally occurring suspensoids (eg, clay, PVC latex, and biological systems), emulsions, and protein solutes are negatively charged. Placing an electric field across an ultrafiltration membrane faciUtates transport of retained species away from the membrane surface. Thus, the retention of partially rejected solutes can be dramatically improved (see Electrodialysis). [Pg.299]

This equation is a reasonable model of electrokinetic behavior, although for theoretical studies many possible corrections must be considered. Correction must always be made for electrokinetic effects at the wall of the cell, since this wall also carries a double layer. There are corrections for the motion of solvated ions through the medium, surface and bulk conductivity of the particles, nonspherical shape of the particles, etc. The parameter zeta, determined by measuring the particle velocity and substituting in the above equation, is a measure of the potential at the so-called surface of shear, ie, the surface dividing the moving particle and its adherent layer of solution from the stationary bulk of the solution. This surface of shear ties at an indeterrninate distance from the tme particle surface. Thus, the measured zeta potential can be related only semiquantitatively to the curves of Figure 3. [Pg.533]


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See also in sourсe #XX -- [ Pg.146 , Pg.164 , Pg.172 , Pg.176 , Pg.224 ]




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