Electro-Washing Technique for On-Site Remediation of Heating Oil-Contaminated Soil from Its Properties Perspective

Statistics Canada announced that approximately 27% of dwellings still use heating oil. Therefore, it is inappropriate management, accidental spills, and occasional tank leakage in backyards have led to soil pollution. Nearly, 40% of all oil spills reported to the Ministry of Environment and Climate Change Canada annually originate from indoor or outdoor residential tanks. Oil tanks that leak can pose serious fire and environmental hazards, contaminating groundwater and private wells or other nearby drinking water supplies. Several techniques have been used to remediate polluted sites; nevertheless, they were found to be ineffective in small areas. Therefore, there is still a need to find an efficient and economical method for in situ or on-site techniques, which can be applied to small-polluted sites located close to building structures. Since the highest challenge in soil remediation is its clayey fraction, the present study aimed to investigate the feasibility of the electrokinetic application to soil media, which include various fractions of clay minerals. To determine soil–water–surfactant–oil system on electrokinetic phenomena and vice-versa, a series of lab tests were conducted using 3 different voltage gradients. Three different clayey soil matrices were contaminated with heating oil above the thresholds level (3600 mg/kg after Quebec regulations) and placed in open-air electrokinetic cells. An aqueous solution of an amphoteric surfactant, transported through soil due to electrokinetic phenomena, was applied as a washing system for 4 days. Then, soil and collected catholytes and anolytes were analyzed. The results showed that water and micelles mobility due to electrokinetic phenomena mostly attributed to electroosmotic flow. There was mobility in all combinations of power and clayey soil properties; however, the flow increased with the increasing clay fraction. Furthermore, studies demonstrated that effectiveness is limited to 2 V/cm due to high electrolysis pronounced at higher voltages. Additionally, zwitterionic surfactant with oil produces micelles which permit their transport toward both the cathode and anode.