The movement of the dispersion medium through a porous material under the influence of an applied electric field is called Electro-osmosis. The sol particles are kept stationary by some suitable means. Electro-osmosis is the inverse of electrophoresis. In electrophoresis, the sol particles move and the dispersion medium remains stationary. Whereas in electro-osmosis the dispersion medium moves and the sot particles remain stationary. The apparatus used for demonstrating the phenomenon of electro-osmosis is shown in the figure 3.10.
The two diaphragms (D) and D‘) divide the apparatus into three compartments. The central compartment is filled with sot while the two-side compartments are filled with water (solvent). The electrode is also fitted in the side compartments. The diaphragms are made of porous clay. When an electric field is applied across the two electrodes, water (dispersion medium) is observed to move. The direction of flow of water depends on the charge of the particles present in the sal. The applications of electro-osmosis are as follow;
(1) Electra-osmosis is used to remove water from peat.
(2) The process is used for the removed of water moist clay.