Low-temperature thermal desorption of diesel polluted soil: influence of temperature and soil texture on contaminant removal kinetics.

Five soil size aggregate fractions, corresponding to coarse (500-840 μm), medium (200-350 μm), fine (75-200 μm) sand, silt (10-75 μm) and clay (<4 μm), were artificially contaminated with diesel, and thermally treated using a laboratory scale apparatus to investigate the effect of soil texture on contaminant adsorption and removal. Ex situ thermal process was simulated using helium as the carrier gas at a flow rate of 1.5 L min(-1), different temperatures (100-300 °C) and different treatment times (5-30 min). The amount of contaminant adsorbed on the soil and the residual amount after thermal treatment was determined by gas chromatography. Results showed that adsorption phenomena and desorption efficiency were affected by the soil texture and that temperature and time of treatment were key factors in remedial process. A temperature of 175 °C is sufficient to remedy diesel polluted sandy and silty soils, whereas a higher temperature (250 °C) is needed for clays. Thermal desorption of diesel polluted soil was shown to be governed by first-order kinetics. Results are of practical interest and may be used in scaling-up and designing desorption systems for preliminary cost and optimal condition assessment.