Removal of Lead from Contaminated Soils with Chelating Agents

The biodegradable chelating agents [S,S,S]-ethylenediaminedisuccinic acid (EDDS), citric acid and the low biodegradable chelating agent ethylenediaminetetraacetic acid (EDTA) were investigated for their applicability for the removal of lead from soil by soil washing and electrokinetic processing. In the soil washing tests at 298 K, the removal efficiency of lead with EDDS and EDTA was high in the pH range from 7 to 10 and the ability of lead removal with EDDS in this pH region is comparable to that with EDTA. Meanwhile, the removal efficiency of lead with citric acid was approximately 50% at pH 4 and decreased with increasing pH. Therefore, citric acid was hardly useful. Acid contribution was predominant for the removal of lead with EDDS and citric acid at pH 4 and the complexation between these chelating agents and lead were negligible. In the electrokinetic tests at ambient temparature, EDTA was more effective than EDDS and citric acid for lead transport through the soil by electrokinetic processing. [doi: 10.2320/matertrans.M-MRA2008825]