Electroosmotic mobility mechanism

The mechanism of separation in NCE is based on the difference in the electrophoretic mobility of the separated species. Under NCE conditions, the migration of the separated species is controlled by the sum of the intrinsic electrophoretic mobility (fxe/)) and the electroosmotic mobility (fxeo), due to the action of electroosmotic flow (EOF). The observed mobility 0bs) of the species is related to xeo and juep by the following equation ... 

The mechanism by which analytes are transported in a non-discriminate manner (i.e. via bulk flow) in an electrophoresis capillary is termed electroosmosis. Eigure 9.1 depicts the inside of a fused silica capillary and illustrates the source that supports electroosmotic flow. Adjacent to the negatively charged capillary wall are specifically adsorbed counterions, which make up the fairly immobile Stern layer. The excess ions just outside the Stern layer form the diffuse layer, which is mobile under the influence of an electric field. The substantial frictional forces between molecules in solution allow for the movement of the diffuse layer to pull the bulk... 

Electroosmotic pumps lack mechanical parts and specific localization in the manifold, producing an even electroosmotic flow. Besides, the flow in interconnected and branched channels can be controlled by switching voltages only. Just two decades ago electroosmotic pumps were attractive and feasible ways for mobile phase flow into microfluidic devices [13] but in the 1990s the conventional pumps available showed a major problem with the high pressures... 

When a DC electric field is imposed on the soil, it will move the mobile cation shell toward the cathode and drag the fluid between the shearing surfaces by a plug flow mechanism, resulting in the electroosmotic flow of fluid from the anode toward the cathode. The shearing surface in the fluid may be taken as a plane parallel to the surface at a distance 5 (m) from it. If e (F/m) is the permittivity of the fluid between these hypothetical plates, then it is known from electrostatics that... 

In order to insure the sufficient efficiency of electrokinetic removal of multiple heavy metals from porous media, it is essential to understand the main parameters affecting the transport and electrokinetic phenomena. Such parameters can be summarized as (a) the theoretical ionic mobility related to the ionic valance and molecular diffusion coefficient of species, (b) the delaying or retardation effect caused by the affinity of heavy metals in solid matrix, and (c) the chemical forms of metal contaminants initially existing in soils. In addition, some unexpected effects especially brought about in the electrokinetic remediation of mixed metal contaminants should be considered. The electrokinetic remediation for mixed metal contaminants generally shows lower removal efficiency than that for individual metal contaminants. High concentrations of multiple metal contaminants can be related to other parameters, for example, transference number, zeta potential, electroosmotic flow, and so on, which are factors that should be taken into consideration with regard to the removal mechanisms. 

Nowadays, porous monoliths have found an extensive use in CEC of organic compounds, which represents a powerful separation tool, complementary to HPLC. CEC is a hybrid method in which the separation is performed through the phase distribution mechanisms of traditional HPLC (reversed-phase, ion exchange, etc.), while the flow of the mobile phase through column packing is affected by electroosmotic forces, as in electrophoresis. The coexistence of a stationary phase and an electric field permits separation not only of ions but also of neutral compounds, due to their different electrophoretic mobhity and different distribution between the mobile and the stationary phases. 

Evaluation of the Specific Surface Conductivity When considering the transport of an electrolyte solution, one must consider the motion of mobile ionic species in addition to the considerations of traditional fluid mechanics. The transport of ions in a capillary results in an electrical current. In electroosmotic flow, the total current is a result of three physical processes ... 

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