ELECTROKINETIC REMEDIATION OF MERCURY-CONTAMINATED SOILS1

A series of batch tests were conducted to investigate the relative desorption potential of mercury from kaolin and glacial till soils under the effect of three extractant agents, namely, KI, Na-EDTA and NaCl (all of them with a concentration of 0.1 M). These tests were conducted under different pH conditions (within a pH range between 2 and 12). Also batch tests using deionized water were performed for comparison purposes. The extractant agents were selected from the solutions that form strong soluble complexes with mercury. The results of the batch tests revealed that the extractant agent KI was the most effective agent for removing mercury from both soils. Na-EDTA also, but in lesser extend, exhibited mercury removal. Electrokinetic tests were conducted to evaluate the effect of the extractant agents Na-EDTA and KI. For comparison purposes, electrokinetic baseline tests using deionized water were also carried out. All of these electrokinetic tests were conducted under the same conditions of voltage gradient (1 V/cm) and extractant ion concentration (0.1 M). The results of these electrokinetic tests revealed that KI was efficient in removing mercury from soils, while Na-EDTA did not show any significant removal of mercury. Overall, 95 % removal was achieved from kaolin; however, only 77 % removal was achieved from glacial till mainly as a result of existence of insoluble mercury complexes in this soil