(The) effect of purging solution on electrokinetic remediation of diesel contaminated soil

Abstract

Electrokinetic (EK) remediation is a unique in situ technique that can be applied to low hydraulic conductive soil. In EK remediation, removal of hydrophobic contaminant from soil is achieved via electroosmotic flow induced by direct current. Effectiveness of petroleum oil removal mainly depends on the solubilization capacity as well as mobilization capacity of purging solution and the amount of electroosmotic flow. To enhance these capacities of purging solution, chelating agent (EDTA), cosolvent (n-propanol) and non-ionic surfactant (Tergitol 15-S-7 and Tergitol NP-10) as additives were introduced to the purging and their effect of solution on EK remediation of petroleum diesel contaminated soil was investigated. It was revealed that EDTA functions as not only electrolyte, but also effective HOCs desorbent. However, use of surfactant in combination with EDTA resulted in lower removal than the test of EDTA alone. Simultaneous use of n-propanol and EDTA enhanced removal efficiency of aromatic hydrocarbons, but high concentration of n-propanol was not effective due to reduction of electroosmotic flow. In this study, the optimum concentration of n-propanol for EK diesel removal from soil was also presented. Removal enhancement by combination of EDTA, surfactant and n-propanol was insignificant compared with the test that employed EDTA and n-propanol together. About 80% of high diesel removal efficiency was achieved in long-term(34 days) tests with 0.01M EDTA and combination of 0.01M EDTA and 20% n-propanol. In conclusion, the remediation of diesel-contaminated soil can be more effective by EK process using a proper purging solution such as EDTA and n-propanol than the case with ordinary electrolytes.