EFFECTS OF SELECTED SOIL CHARACTERISTICS ON THE REMOVAL OF DIESEL FUEL BY SUPERCRITICAL CARBON-DIOXIDE

The role of the selected soil characteristics of natural organic matte r, clay, and moisture in the removal of diesel fuel from soils by supe rcritical carbon dioxide (CO2) were investigated. The range for organi c matter content in the six soils studied was 0.3 to 4.1%, clay conten t was 4.4 to 43.4%, and moisture was 0 to 30% by weight. Supercritical fluid extraction (SFE) with CO2 was applied to weathered and unweathe red soils spiked with a known amount of diesel fuel. Recovery of diese l fuel was accounted for by a non-specific total petroleum hydrocarbon (TPH) method using gas chromatography with flame ionization detection . Recoveries were greater than 95% for all soils spiked with diesel an d immediately extracted for 30 minutes at 300 atm and 50 degrees C. Ex tractions of the weathered samples indicated that SFE removed the majo rity of fuel remaining in the soil after the weathering processes. No correlations between increasing amounts of organic matter or clay and removal of diesel fuel by SFE were observed. Moisture contents up to 2 0% did not appear to hinder removal of diesel fuel.