Electrokinetic Remediation of Heavy Metal Contaminated Soil Using Permeable Reactive Composite Electrodes

A new permeable reactive composite electrode (PRCE) attached with a permeable reactive layer (PRL) of Fe0 and zeolite has been developed for soil pH control and the improved removal efficiency of heavy metal ions (Cd, Ni, Pb, Cu) from soil in electrokinetic remediation process. The effects of different composite electrodes on pH control and heavy metal removal efficiency were studied, and changes in the forms of heavy metals moved onto the electrodes were analyzed. The results showed that with acidic/alkaline zeolite added and renewed in time, the composite electrodes could effectively neutralize and capture H+ and OH- produced from electrolysis of the anolyte and catholyte, avoiding or delaying the formation of acidic/alkaline front in tested soil, preventing premature precipitation of heavy metal ions and over-acidification of soil, and thus significantly improved the heavy metal removal efficiency. Fe0 in composite electrodes could deoxidize and stabilize the heavy metal ions. After that capture and immobilization of the pollutants were achieved. The results also showed that, using "Fe0 + zeolite" PRCE in the cathode with timely renewal, after 15-day remediation with a DC voltage of 1.5 V/cm, the total removal rates of Cd, Pb, Cu and Ni were 49.4%, 47.1%, 36.7% and 39.2%, respectively.