Electrokinetic effects streaming potential

Electrokinetic effects, streaming potential and current, charge formation at interfaces this provides also chemical information... 

Electrokinetic effects streaming potential and streaming current are widely used to characterise charge formation processes at the interface between planar polymer coatings... 

Streaming potentials, like other electrokinetic effects, are difficult to measure reproducibly. One means involves forcing a liquid under pressure through a porous plug or capillary and measuring E by means of electrodes in the solution on either side [6, 23, 71-73]. 

There are four related electrokinetic phenomena which are generally defined as follows electrophoresis—the movement of a charged surface (i.e., suspended particle) relative to astationaiy hquid induced by an applied ectrical field, sedimentation potential— the electric field which is crested when charged particles move relative to a stationary hquid, electroosmosis—the movement of a liquid relative to a stationaiy charged surface (i.e., capiUaty wall), and streaming potential—the electric field which is created when liquid is made to flow relative to a stationary charged surface. The effects summarized by Eq. (22-26) form the basis of these electrokinetic phenomena. 

Electrokinetic phenomena such as electroosmosis, streaming potential, and viscoelectric effects (Chapter 12)... 

Two conditions must be met to justify comparisons between f values determined by different electrokinetic measurements (a) the effects of relaxation and surface conductivity must be either negligible or taken into account and (b) the surface of shear must divide comparable double layers in all cases being compared. This second limitation is really no problem when electroosmosis and streaming potential are compared since, in principle, the same capillary can be used for both experiments. However, obtaining a capillary and a migrating particle wiih identical surfaces may not be as readily accomplished. One means by which particles and capillaries may be compared is to coat both with a layer of adsorbed protein. It is an experimental fact that this procedure levels off differences between substrates The surface characteristics of each are totally determined by the adsorbed protein. This technique also permits the use of microelectrophoresis for proteins since adsorbed and dissolved proteins have been shown to have nearly identical mobilities. 

If a liquid moves tangential to a charged surface, then so-called electrokinetic phenomena arise [101]. Electrokinetic phenomena can be divided into four categories Electrophoresis, electro-osmosis, streaming potential, and sedimentation potential [102], In all these phenomena the zeta potential plays a crucial role. The classic theory of electrokinetic effects was proposed by Smoluchowski2 [103],... 

For well-dispersed colloid systems, particle electrophoresis has been the classic method of characterization with respect to electrostatic interactions. However, outside the colloidal realm, i.e., in the rest of the known world, the measurement of other electrokinetic phenomena must be used to characterize surfaces in this respect. The term electrokinetic refers to a number of effects induced by externally applied forces at a charged interface. These effects include electrophoresis, streaming potential, and electro-osmosis. 

To characterize a surface electrokinetically involves the measurement of one of the above electrokinetic effects. With disperse colloidal systems it is practical to measure the particle electrophoretic mobility (induced particle velocity per unit applied electric field strength). However, for a nondisperse system one must measure either an induced streaming potential or an electro-osmosis fluid flow about the surface. 

A hysteresis in the electrokinetic behavior of alumina and hematite was found in [288] the absolute value of the potential at constant pH increased with T, but no return to lower potential on cooling was observed. An increase in the absolute value of the potential at constant pH with T was reported in [2370], Uptake of cations from a 1-1 electrolyte by silica and alumina at constant Gp was rather insensitive to temperature [1842], The surface potential of alumina was studied in [3057] as a function of temperature (ISFET response). The temperature effect on tlie streaming potential is reviewed in [3058], The PZCs at very high temperatures reported in [3047] were obtained by extrapolation of experimental results obtained at moderate temperatures. 

Electroosmosis is one of several electrokinetic effects that deal with phenomena associated with the relative motion of a charged solid and a solution. A related effect is the streaming potential that arises between two electrodes placed as in Figure 9.8.1 when a solution streams down the tube (essentially the inverse of the electroosmotic effect). Another is electrophoresis, where charged particles in a solution move in an electric field. These effects have been studied for a long time (37, 38). Electrophoresis is widely used for separations of proteins and DNA (gel electrophoresis) and many other substances (capillary electrophoresis). 

Finally, a third consequence of the electrokinetic effect is observed when an electrolyte is caused to flow through a capillary or porous plug by the application of a pressure difference, Ap. An electrical potential difference A, called the streaming potential, arising from the displacement of the double layer by the flowing liquid [Figure 6.8(b)], is set up. Its value is found to be given by... 

There are two types of electrokinetic phenomena, namely those in which an electric potential is generated by the mechanical notion of a surface in a liquid and those in which a particle or liquid is caused to move by an electric potential. Classically there are four major effects, i.e., streaming potentials, sedimentation potentials, electrophoresis, and electroosmosis. (There are also several secondary effects that have been noted more recently such as acoustic potentials,K effect potentials, and U effect potentials.Each of the major effects has found a niche in physical chemistry, analytical chemistry, and chemical engineering. However, the application and understanding of electrokinetic phenomena in the biological sciences has been very spotty. 

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