Soil texture affects adsorption capacity and removal efficiency of contaminants in ex situ remediation by thermal desorption of diesel-contaminated soils

Five soil-size aggregate fractions, corresponding to coarse (500-840m), medium (200-350m), fine (75-200m) sand, silt (10-75m) and clay (4m), were artificially contaminated with diesel fuel, and thermally treated using a laboratory-scale apparatus to investigate the effects of soil texture on contaminant removal. Specifically, an ex situ thermal process was simulated using helium as carrier gas at a pressure of 1.0atm, a flow rate of 1.5L center dot min-1 and different temperatures (100-300 degrees C). Soil specimen and carrier gas temperature in different experimental apparatus sections were monitored. The amount of contaminant sorbed and contaminant residual concentration in soil (as n-alkanes compounds C10-C25) were determined by gas chromatography. The main results show that soil texture influences contaminant sorption phenomena and remediation processes in thermal desorption treatment. Contaminant removal was affected by soil texture (variation up to 37.1%), and fine sandy soil exhibited the highest desorption extent of diesel fuel for a thermal treatment of 30 min. Results are of practical interest and may be used in scaling-up and designing of desorption systems for preliminary cost and optimal condition assessment.