Heavy Metal Removal from Soil by Coupled Electric‐Hydraulic Gradient

An investigation was carried out using coupled electric‐hydraulic gradient to remove heavy metal contaminants from residual wastes. A mixture of spent foundry sand and millpond sludge containing high levels of Zn, Mn, and Pb was used as the contaminated source. An electric gradient was applied, in a specially constructed decontamination cell, to generate a low pH solution by electrode reactions. Simultaneously, the low pH solution was pumped through the residual waste under a constant hydraulic gradient. Experiments were carried out under 0, 100, 150, and 200 V, with a constant hydraulic gradient producing an average flow of about 1 cc/min. At 0 V with hydraulic gradient alone, negligible amount of metals were removed. It was found that higher voltages removed higher percentages of metals of interest from the solid medium. At 200 V both Mn and Zn removal was about 72%. The removal of Pb was slower compared to Mn and Zn. At 100 V a negligible amount of Pb was removed; at 200 V only 46% Pb was removed from the solid mixture. It was demonstrated that a coupled electric‐hydraulic gradient can be effectively utilized to remove heavy‐metal contaminants from a porous medium.