The purpose of this study was to identify and evaluate the efficiency of the supercritical fluid extraction (SFE) method for removing diesel from an artificially contaminated soil using a supercritical carbon dioxide and an ultrasound. Compared with SFE, ultrasound-enhanced/assisted SFE (USFE) was able to provide a 14.8% increase in the diesel removal rate from diesel-contaminated soil at the SFE conditions of 40 °C, 16 MPa, 2 mL/min CO2 flow rate and 40 min dynamic extraction time, and the ultrasound conditions of 316 W/cm2 and 20 kHz. These results showed that an ultrasound reduce the extraction time, the extraction pressure, the CO2 flow rate and the extraction temperature during the SFE process by enhancing the mass transfer from the soil to the supercritical CO2.

The purpose of this study is to identify and evaluate the extraction efficiency of 15 metal species for contaminated soils using supercritical CO 2 , a chelating agent (Cyanex 272), and ultrasound. The percent extraction of metal species showed in the ascending order of pure CO 2 < ''CO 2 + Cyanex 272'' < ''CO 2 + Cyanex 272 + ultrasound'' for most of the metals with the exception of As, Cr, Sb and Se. The supercritical fluid extraction (SFE) of metal ions by pure CO 2 was confirmed to be inefficient but the supercritical CO 2 comprising Cyanex 272 showed a higher extraction rate than that of pure CO 2 . Ultrasound enhanced/assisted SFE (USFE) with Cyanex 272 could substantially enhance the extraction efficiency from the contaminated soils by facilitating mass transport which helps to move the solubilized metal or metalloid species into the supercritical fluid phase.