Electrokinetic resistivity

If the electric field E is applied to a system of colloidal particles in a closed cuvette where no streaming of the liquid can occur, the particles will move with velocity v. This phenomenon is termed electrophoresis. The force acting on a spherical colloidal particle with radius r in the electric field E is 4jrerE02 (for simplicity, the potential in the diffuse electric layer is identified with the electrokinetic potential). The resistance of the medium is given by the Stokes equation (2.6.2) and equals 6jtr]r. At a steady state of motion these two forces are equal and, to a first approximation, the electrophoretic mobility v/E is... 

The "plug-like velocity flow profile for electrokinetically pumped capillary columns (see Figure 1) is important in minimizing resistance to mass transfer within the mobile phase (4). Hydrostatically-pumped capillaries, have parabolic flow profiles which tend to severely disperse solute bands unless extreme narrow-bore (i.d.s less than 10 pm) capillaries are employed (12). Fortunately, larger capillaries, with less stringent detector volume requirements, can be efficiently used in MECC. 

Another possible solution to this problem has been implemented by Attiya et al. [97]. The device contained a large sample introduction channel with a volume flow resistance >105-fold lower than that in the analysis microchannels. This approach enabled interfacing the large sample introduction channel with an external pump (up to 1-mL/min flow rate) for pressure-driven sample delivery without perturbing the solutions and electrokinetic manipulations within the... 

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. 

Szymczyk, A., Fievet, P., and Foissy, A., Electrokinetic characterizaton of porous plugs from streaming potential coupled with electrical resistance measurements, J. Colloid Interf. Sci., 255, 323, 2002. 

For this purpose, Li s group reported a simple multi-functional particle detection PDMS chip [17]. This chip generates liquid flow and particle motion electrokinetically, and uses two pairs of parallel optical fibers embedded in the chip to measure particle speed and size, and to count particles. More recently, a new microfluidic method was developed to counting the particles flowing through microchannels, not by the optic method as described previously, but by an electric method. This method is called the microfluidic differential resistive pulse sensor method [18]. Figure 6 below illustrates the principle of this method. 

The establishment of an exact quantitative relationship between the thermodynamic potential, (p0, or the potential of the adsorption layer (the Stern layer) potential, (pd, and the electrokinetic potential, , is an important and at present unsolved problem. Depending on the thickness of the layer with increased viscosity near the solid surface, the electrokinetic potential may either approach the value of the Stem layer potential or be lower than the latter. In some cases (e.g. for quartz), as shown in studies by D.A. Fridrikhsberg and M.P. Sidorova [10,11], the difference between the electrokinetic and thermodynamic potentials may be related to the hydration (swelling) of the solid surface and the formation of a gel-like layer resistant to deformation, within which a partial potential drop takes place. The difference between (pdand C, may also be related to microscopic surface roughness of the solids, i.e. to the presence of growth steps, dislocations and other defects (see Chapter IV). 

Grahame DC. (1952). Mathematical theory of the Faradaic admittance. I. Pseudocapacity and polarization resistance./oaraa/ of The Electrochemical Society 99 370C-385C. Hamed J, Acar YB, Gale RJ. (1991). Pb(II) Removal from kaolinite by electrokinetics. 

In order to demonstrate the effectiveness of a particular setup, the energy consumption in each cell was estimated (Table 15.2). Generally, the resistance in the electrokinetic cell, filled with soil, increases with time (Fig. 15.4, cell Cl). However,... 

Reeve J, Lynch RJ. (2007). Use of a pulsed electric field for resisting groundwater pollution. 6th Symposium on Electrokinetic Remediation (EREM 2007) (ed. C CameseUe), June 12-15. Vigo, Spain University of Vigo, pp. 19-20. 

Heating resulting from electrokinetic techniques in the subsurface involves the resistance to the passage of electrical current through soil moisture. It is this... 

There is still a lot of resistance to using this relatively unknown process. Due to the nature of electrokinetic remediation, it is frequently a remediation of last resort at difficult sites and is provided by very few organizations in Europe and the USA. As the technology gets applied more frequently, future innovations will most likely lower the cost. 

The design and dimensions of the ER system to be deployed at a site are based on and derived from the data collected during the preceding investigations and from one or more electrokinetic laboratory tests. If possible, some electrical resistivity soundings should be performed on the site in order to measure the electrical resistance of the ground. 

Test Results The electrokinetic laboratory tests are finalized with a report. This presents relevant data, such as sample preparation, analysis results, concentration decrease, type of electrolyte solutions, electrolyte conditioning, and electrical and electrokinetic parameters. The electrical parameters are voltage (V), drop in potential (V/m), current (A), current density (A/m ), electrical power (kW/m ), and resistivity (Ohmm). Conditioning parameters comprise type of add... 

---