Electric potential and current distribution in contaminated porous building materials under electrokinetic desalination

Electrokinetic desalination is very useful method for the removal of salt ions from porous building materials. This study investigates the influence of electric potential, electric current and pH distribution on the electrokinetic desalination of sodium chloride contaminated specimens of fired clay brick and sandstone. The measurements show that the ingress of acidic and alkaline fronts in the porous materials affects the removal of salt ions by diminishing the effect of electric field and electric current intensities. To suppress pH changes, poultices composed of kaolin clay with and without addition of buffering agents are investigated. The effective suppression of pH changes by the addition buffering agents in poultice enhanced the removal efficiency of both the Na + and Cl − ions from both the fired clay brick and sandstone specimens. In order to keep the specimen in good electrical contact with poultice and electrodes, the drying of poultices was avoided by inserting wet sponges in contact with large water reservoirs in the electrodes compartments.