Electrokinetic removal of chloride and sodium from tidelands

A laboratory-scale investigation was carried out to study the characteristics of electrokinetic (EK) movement for separation of salts from tideland. The salinity of tideland material, including the sodium and chloride contents, was investigated as a function of operation time under a constant voltage gradient of 1 V/cm. As the operation period increased, the salinity of tideland material decreased gradually. However, the rate of decrease gradually diminished with an increase in the operation period. The electrical current increased gradually with the operation time. Ten days of electrokinetic operation decreased the electrical conductivity of the tideland material to 65.5% of the initial value. Sodium was removed completely, but the removal efficiency of chloride was 58.5% after 10 days. The lower removal of chloride was due to the formation of complexes with magnesium and calcium. High concentrations of chloride formed chlorine gas in the anolyte, and aqueous chlorine oxidized the circulation tube. The pH distribution after electrokinetic treatment showed a typical shape, and the change in water content was negligible. The results demonstrate that the electrokinetic process is a suitable means to remove salinity from tidelands.