Desalinization of Kaolin Soil Using Radial Electromigration and Electroosmosis

The storage and management of road salt piles can cause contamination of drinking water aquifers owing to precipitation runoff that ultimately contaminates the groundwater. Such sites can be remediated using direct current (DC) electric fields in conjunction with relatively inexpensive direct-push wells. When soil and groundwater are subjected to DC electric fields, the pore water moves toward the cathode via electroosmosis while cations also migrate to the cathode and anions migrate toward the anode by electromigration. A series of anode and cathode wells placed in the soil can be used to separate and remove chloride ($\mathrm{Cl}-$) and sodium ($\mathrm{Na}+$), respectively. To accommodate the use of well-based electrodes on a large scale basis, a two-dimensional model, approximating a cylinder, was developed to simulate the electromigration and electroosmosis aspects of sodium and chloride transport in soil with a center cathode surrounded by anodes. To validate the model, a small pilot-sized experiment was conducted, and sodium was used as the primary monitored ion owing to its conservativeness and stability at the cathode. The model predicted a sodium transport time of 4 days for sodium ions to travel the 20.3 cm (8-in.) distance and reach the cathode. The actual sodium flow into the cathodes was elevated and steady for about 5 days followed by the steady drop-off out to day 14 as expected. On the basis of whole hexagon and background soil samples, 80% of the sodium was removed. Sodium removal was significant owing to the removal at the cathode wells while chloride accumulated at the anode where some was oxidized. On the basis of this model, cost for a full scale implementation can be estimated.