Assessment of Acid Enhancement Schemes for Electrokinetic Remediation of Cd/Pb Contaminated Soil

Electrokinetic remediation technology is an effective method for treating soils contaminated by heavy metals. However, for natural soils with a high acid/base buffer capacity, the efficiency of removal decreases and the cost of treatment increase. A novel acid enhancement method that anode approaching electrokinetic remediation was investigated in this study. For assessing the new method, four types of electrokinetic remediation methods were designed for treatment of cadmium and lead contaminated soil: traditional, acetic acid pH control, citric acid pH control, and anode approaching electrokinetic remediation. The traditional method has the lowest removal rates and cost. Acid added method not only enhanced the removal of heavy metal dramatically but also increased cost correspondingly. Removal rate of the whole soil body of the anode approaching method only achieved 25.93 % for cadmium and 31.27 % for lead, which was higher than that obtained with an traditional electrokinetic method (by 17.96 and 30.40 %, respectively). However, more and more metal were forced to accumulate near the cathode in the anode approaching method so that the removal rates of cadmium and lead in the first four segments of the soil are 92.44 and 60.70 %, respectively. The cost of this treatment (primarily the cost of electricity and acid consumption) is much lower than that of the acid added method. Although the acid added method has highest removal efficiency, the anode approaching method has cost advantage. And mechanism of the new method was discussed in terms of experiment data. In addition, anode approaching method has not added other chemicals to avoid potential effect during running.