Electroosmotic purging

An application of electrokinetics that serves to illustrate a number of chemical effects is that of electroosmotic purging of contaminated liquids from soils (Shapiro Probstein 1993). A dc electric field is applied across electrode pairs in the ground and under the action of the field, the contaminants in the liquid phase in the soil are moved by electroosmosis to one set of electrodes, typically the cathodes. The electric field simultaneously draws in a noncontaminating liquid to help wash and treat the soil to enhance the restoration process. The contaminated effluent is then removed by pumping from wells surrounding the cathodes. 

Figure 6.6.1 Comparison after removing 0.12 pore volumes of liquid between finite element calculations and experiment for electroosmotic purging of acetic acid from a cylindrical clay sample 0.5 m long, initially saturated with a 100 mol m acetic acid solution (Cq), across which 25 V is applied (A) normalized acetate concentration along sample (B) pH profile along sample (after Shapiro Probstein 1993).

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