Organic acid-enhanced electrokinetic remediation of soil contaminated with heavy metals

Abstract

The contaminated soil near a Janghang facility in Chungnam in Korea was treated by electrokinetic (EK) remediation to remove heavy metals using organic aids. Electrokinetic remediation is a one of in situ techniques that can be applied to low hydraulic conductive soil. It is applicable for saturated soil with low groundwater flow rates. Generally, in order to increase the removal efficiency of contaminants with EK, chemical agents or strongly complexing agents are used. Organic acids have been known to increase the mobility of heavy metals in soil. Its advantages are eco-friendly and biodegradable. The acidic characteristic of organic acids is able to extract of heavy metals from soil due to cation exchange with heavy metals. For this reason, organic acids were used as an electrolyte in this study to achieve high removal efficiency of heavy metals. Before the EK experiment, extraction of heavy metals from the soil using various organic acids was conducted to investigate the feasibility of organic acids and find suitable organic acids to apply for EK system. Acetic acid, citric acid, formic acid, lactic acid and oxalic acid were used washing solution on soil washing test. In soil washing test, citric acid and oxalic acid showed high removal efficiency of heavy metals from soil. In the EK experiment using citric acid and oxalic acid, it showed higher removal heavy metals than conventional EK experiment using DW, but low current density and EOF was observed. In order to overcome these drawbacks, general electrolytes of EK such as $MgSO_4$, $NaNO_3$ was added to solution of organic acid. During that EK experiments, current density was increased by general electrolytes and also electroosmosis flow was higher than EK experiments using only organic acids. After the EK experiments, mobility of heavy was observed more clearly and removal efficiency of heavy metals was high than the EK using only organic acids. About 57 % of high heavy metals removal efficiency was ac...