Removing of hydrocarbon contaminated soil via air flushing enhanced by surfactant

Surfactants enhanced air sparging actually acts to displace the organic contaminant entrapped in soil pores. In this work, a comparison study was carried out between two air-flushing modes, namely, continuous air flushing and pulsed air flushing, which was conducted to remediate soil contaminated with waste-lubricant oil. Therefore, coarse sand was artificially polluted and mixed well with waste-lubricant oil at different concentrations of 10, 25 and 50 wt% to give the soil an oil blend. Then a laboratory glass column was established and backed with contaminated soil to study the effect of flow rate, pollutant and surfactant concentrations on the removal of waste-lubricant oil from soil. The contaminated soil was washed with pure water and flushed with both air-flushing modes at a pressure of 2 kPa and flow rate of 6 L min(-1). After that fixed 300 mL nonionic surfactant solutions (NPEO9.3) at concentrations of 3, 5 and 7 wt%, were poured individually along with air injection at the same pressure and flow rate. The treated soil was washed several times with pure water to eliminate the residual surfactant solutions. It was found that water washing and air injection remove 27 % of oil; however, air injection along with surfactant solutions increased the oil removal efficiency up to 90 %. Moreover, both air-flushing modes succeeded in removing the pollutant with majority to pulsed air mode over continuous mode; therefore, pulsed air flushing was applied for 25 and 50 wt% waste lubricant oils in presence of 3 wt% nonionic surfactant.