Remediation of Soils Contaminated with Total Petroleum Hydrocarbons and Polycyclic Aromatic Hydrocarbons: Extraction with Supercritical Ethane

In this work two natural certified soils were extracted with supercritical ethane. One sample was polluted with total petroleum hydrocarbons (THP soil) and the second one with polycyclic aromatic hydrocarbons (PAH soil). The extraction studies were carried out using a high-pressure experimental device constructed in our laboratory. The extraction conditions for the TPH soil were 27.1 MPa and 308.15 K, whereas those for the PAH soil were 23.7 MPa and 308.15 K. Four independent extractions were performed on each test soil varying the volume of solvent: 10, 20, 30, and 40 L. Infrared spectroscopy was used to quantify the hydrocarbons in the residues after supercritical extraction of the TPH soil, whereas high-performance liquid chromatography was employed, with a photodiode array detector and a fluorescence detector, to analyze seven polycyclic aromatic hydrocarbons (PAHs) in the residues after supercritical extraction of the PAH soil. The extraction results show that there is a reduction of hydrocarbons of 76% using 10 L of ethane while the reduction is 90% using 40 L of ethane for the TPH soil sample. For the sample of PAH soil there is a reduction greater than 80% for the concentration of six of the seven PAHs studied. Naphthalene behaves as a refractory compound; hence, it presents the lowest reduction in concentration.