Effects of Selected Soil Characteristics on the Removal of Diesel Fuel by Supercritical Carbon Dioxide

Abstract

The role of the selected soil characteristics of natural organic matter, clay, and moisture in the removal of diesel fuel from soils by supercritical carbon dioxide (CO₂) were investigated. The range for organic matter content in the six soils studied was 0.3 to 4.1%, clay content 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 unweathered soils spiked with a known amount of diesel fuel. Recovery of diesel 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 and immediately extracted for 30 minutes at 300 atm and 50°C. Extractions of the weathered samples indicated that SFE removed the majority 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 20% did not appear to hinder removal of diesel fuel.

Keywords:

• Supercritical fluid
• remediation
• carbon dioxide
• diesel
• soil