Electrokinetic phenomena The zeta potential

In this section we deal with liquids, which flow along charged solid surfaces. In many cases the surface binds one, two, or several layers of liquid molecules and possibly ions more or less tightly. As a result the shear plane is often not directly at the interface. Only at a distance 6 away from the surface do the molecules start to move. The potential at this distance is called the zeta potential . 

The concentration of potential-determining ions at which the zeta potential is zero (C = 0) is called the isoelectric point (iep). The isoelectric point is determined by electrokinetic measurements. We have to distinguish it from the point of zero charge (pzc). At the point of zero charge the surface charge is zero. The zeta potential refers to the hydrodynamic interface while the surface charge is defined for the solid-liquid interface. 

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], 

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STARTING-POINT FOR THE ANALYSIS OF ELECTROKINETIC PHENOMENA. THE ZETA-POTENTIAL... 

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