Electroendosmosis

Electroendosmosis, also known as electroosmosis or electroosmotic flow (EOF), is a physicochemical phenomenon occurring in porous materials or solutions containing charged particles. It describes the movement of a liquid relative to a stationary charged solid surface when an electric field is applied. This movement arises from the interaction between the electric field and the electric double layer that forms at the interface between the charged surface and the surrounding liquid.

The charged surface, whether it's a solid material or a suspended particle, attracts ions of opposite charge from the liquid, forming a diffuse layer of counter-ions. When an electric field is applied parallel to the surface, these counter-ions are mobilized and drag the bulk of the liquid with them, resulting in bulk fluid flow. The direction and magnitude of the electroosmotic flow depend on the polarity of the surface charge, the strength of the electric field, and the properties of the liquid, such as its viscosity and dielectric constant.

Electroendosmosis finds applications in various fields. In analytical chemistry, it is a fundamental principle behind capillary electrophoresis, where it facilitates the separation of charged analytes within a capillary tube. It is also utilized in microfluidic devices for pumping and mixing fluids. In civil engineering and environmental science, electroosmosis can be employed for dewatering soils, consolidating sediments, and removing contaminants from groundwater. The phenomenon's ability to induce fluid movement without mechanical pumps makes it an attractive technique in situations where conventional methods are impractical or undesirable.