Electroosmosis electrokinetic phenomena

Electrochemical Remediation Heavy metals and other contaminants can be removed from the soil and groundwater with the help of electrokinetic phenomena (electroosmosis, electrophoresis, electrolysis). In electrochemical remediation processes, a continuous electrical field is generated with electrodes that are inserted into the contaminated soil (Shapiro etal. 1989 Ottosen etal. 1995 Hansen etal. 1997). Laboratory and pilot tests have been conducted, for example, with acetic acid as cleaning solution (Renaud 1990). With elec-... 

The word electrokinetic implies the joint effects of motion and electrical phenomena. We are interested in the electrokinetic phenomena that originate the motion of a liqnid within a capillary tube and the migration of charged species within the liquid that surrounds them. In the first case, the electrokinetic phenomenon is called electroosmosis whereas the motion of charged species within the solution where they are dissolved is called electrophoresis. This section provides a brief illns-tration of the basic principles of these electrokinetic phenomena, based on text books on physical chemistry [7-9] and specialized articles and books [10-12] to which a reader interested to stndy in deep the mentioned theoretical aspects should refer to. 

It has already been noted that there is a close similarity between electroosmosis and streaming potential. Therefore we consider this additional electrokinetic phenomenon next. 

Electroosmosis is the bulk fluid flow that occurs when a voltage gradient is imposed across a charged membrane. Transport by convection allows the delivery and extraction of neutral and zwitterionic compounds and plays a major role in the movement of large, poorly mobile cations. Electroosmosis is an electrokinetic phenomenon, which may be described by nonequilibrium thermodynamics [24] ... 

An innovative technology called the "lasagna" process is based on the electrokinetic phenomenon called electroosmosis. The lasagna process was created to treat difficult wastes in low permeability, silt- and day-laden soils (40). The lasagna process is so named because it consists of a number of layered subsurface electrodes and treatment zones. These layers can be constmcted either horizontally where contaminants are forced to more upward or in vertical position where lateral contaminant movement is desired. 

Another electrokinetic phenomenon that may occur during electrofiltration is electroosmosis or the movement of liquid relative to a stationary charged surface. If the membrane itself is charged, the electrical field applied across the membrane will... 

AC electroosmosis (ACEO) is a nonlinear electrokinetic phenomenon of induced-charge elec-troosmotic flow around electrodes applying an alternating voltage. 

Electrokinetic flow covers in principle the transport of liquids (electroosmosis) and samples (electrophoresis) in respraise to an electric field. Both motions are associated with the electric double layer that is formed spraitaneously at the solid-liquid interface in which there is a net charge density. Compared to the traditional pressure-driven flow, electrokinetic flow is more suited to miniaturization due to its nearly plug-like velocity profile and much lower flow resistance. However, Joule heating is a ubiquitous phenomenon in electrokinetic flow that will affect the transport of both liquids and samples via temperature-sensitive material properties. 

It may be appreciated that electrokinetic phenomena are determined by electric properties at the plane of shear rather than at the real surface. In the following sections of this chapter, the relation between the measured property and is further analyzed. This is done for electroosmosis, electrophoresis, streaming current, and streaming potential. The sedimentation potential will not be discussed any further, because in practice this phenomenon does not play an important role. The electrokinetic charge density may then be derived from using the theory for the diffuse electrical double layer. 

Electrokinetic remediation of groundwater and soil usually involves the use of electroosmosis and electromigration. Electroosmosis describes the phenomenon of water flow induced by application of an electrical field on porous media (14). Electromigration describes the transport of ions under the influence of an electrical field (75). The electroosmotic flux, qeo, can be written as... 

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