Electrical interfacial layer electrokinetics

It could be concluded that different assumed structures of electrical interfacial layer were not distinguished by the applied procedure. It is clear that another data are necessary for that purpose. One way would be to introduce simultaneous electrokinetic measurements and assume relationship between electrokinetic potential and the potential at the onset of diffuse layer. 

In many flotation systems, the electrical nature of the mineral/water interface controls the adsorption of collectors. The flotation behavior of insoluble oxide minerals, for example, is best understood in terms of electrical double-layer phenomena. A very useful tool for the study of these phenomena in mineral/water systems is the measurement of electrokinetic potential, which results from the interrelation between mechanical fluid dynamic forces and interfacial potentials. Two methods most commonly used in flotation chemistry research for evaluation of the electrokinetic potential are electrophoresis and streaming potential. 

The electrical double layer (edl) at the oil-water interface is a heterogeneous interfacial region that separates two bulk phases of polarized media and maintains a spatial separation of charges. EDLs at such interfaces determine the kinetics of charge transfer across phase boundaries, stability and electrokinetic properties of lyophobic colloids, mechanisms of phase transfer or interfacial catalysis, charge separation in natural and artificial photosynthesis, and heterogeneous enzymatic catalysis [1-5]. 

The electrokinetics are a class of several different interfacial effects that become important in micron and submicron dimensions. The most important and widespread categories of the electrokinetic effects are the electroosmosis and the electrophoresis. When the ionized liquids are in contact with stationary charged surfaces, counterions accumulate near the surface and buUd a layer that is called the electric double layer (EDL). The presence of an external electric field moves this layer and consequently generates the bulk flow field in the channels. This effect is named as electroosmosis and the generated flow is electroosmotic or electrokinetic flow. The external electric field also moves charged species and macromolecules in the micro- and nanochaimels which is usually referred to electrophoresis or electrophoretic effect. 

A common feature of electrokinetic phenomena is a relative motion of the charged surface and the volumetric phase of the solution. The charged surface is affected by the electric field forces, and the movement of such surfaces toward each other induces the electrical field. That is a question of slip plane between the double layer and a medium. The layer bounded by the plane at the distance d from surface (OHP) can be treated as immobile in the direction perpendicular to the surface, because the time of ion residence in the layer is relatively long. Mobilty of ions in the parallel direction to the interfacial surface should also be taken into account. However, it seems that the ions in the double layer and in the medium surrounding it constitute a rigid whole and that the layer from x = 0 to X = d is immobile also in the sense of resistance to the tangent force action. There is no reason why the boundary plane of the solution immobile layer should overlap accurately with the OHP plane. It can be as well placed deeply in the solution. The potential in the boundary plane of the solution immobile layer is called potential (. Strictly speaking it is not a potential of interface because it is created in the liquid phase. It can be considered as the difference of potentials between a point far from the surface (in the bulk solution) and that in the slip plane. 

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