Enhanced electrokinetic remediation of cadmium contaminated soils by chelating agents

 M. Niinae*, K. Aoki

Department of Urban and Environmental Engineering, Graduate School of Engineering, Kyoto University, Yoshida-honmachi, Sakyo-ku, Kyoto 606-8501, Japan


Accepted 22 January 2005



ABSTRACT

Electrokinetic soil remediation by electroosmosis and ionic migration is restricted to soluble substances. At a higher pH, the soil particles sorb more heavy metals than at a lower pH and the precipitation reactions of heavy metals are promoted. Both mechanisms make heavy metals immobile, rendering cleanup more difficult and electrokinetic extraction inefficient.
In this study, the effectiveness of introducing chelating agents to enhance the removal of cadmium from kaolinite in the region of neutral pH by ionic migration is examined. The chelating agents selected were ethylenediaminetetraacetic acid (EDTA) and citric acid. The investigation was carried out in a laboratory-scale column containing kaolinite contaminated with cadmium. Cadmium migrates toward the anode, indicating that cadmium is indeed solubilized by EDTA and citric acid as negatively charged chelates. The dissolved chelates migrate toward the anode by ionic migration and are successfully removed at the anode reservoir. The effectiveness of EDTA and citric acid for removing cadmium was also investigated and it was found that EDTA was more effective than citric acid.



Keywords: Electrokinetics, Soil remediation, Cadmium, EDTA, Citric acid



* Corresponding author
   E-mail : niinae@kumst.kyoto-u.ac.jp