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

Abstract

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 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 1.0 atm, a flow rate of 1.5 L·min⁻¹ and different temperatures (100–300 °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.

Keywords:

• diesel contamination
• soil remediation
• soil texture
• thermal desorption

Acknowledgements

This research was funded by the Italian Ministry of Education, University and Research (MIUR), ‘Research Program of Relevant National Interest’, Fiscal year 2006 (Criteria and tools for environmental remediation and functional regeneration of contaminated sites) and partially by Catanzaro Costruzioni S.r.l., Italy.