Molecular Weight-Dependent Desorption of Alkanes in Low Temperature Thermal Treatment of Total Petroleum Hydrocarbon-Contaminated Soils

Thermal treatment technology is one way of remediating oil-contaminated soil using elevated temperatures and collecting contaminants using a vapor treatment system. In this study, we aimed to investigate the dynamics of hydrocarbons (C₆–C₂₆) in oil-based contaminated soils and develop a model that can eventually be used to predict the application and hydrocarbon dynamics when thermal treatment is applied to the field. The thermal desorption (TD) efficiencies for all compounds increased with temperature and treatment time. The results showed that low-molecular weight hydrocarbons (≤ C₁₂) were completely removed at 50°C while a similar removal efficiency was achieved for high molecular weight hydrocarbons (≥ C₁₈) only at higher temperature studied (200°C). Notably, the total petroleum hydrocarbon (TPH) in diesel-contaminated soil decreased below Korean residential site limit (500 mg/kg) from an initial concentration of 14,300 mg/kg within 10 min at 150‒200°C (overall > 95% efficiency), indicating a good potential of low-temperature TD technology. However, the TPH concentration remained above 2000 mg/kg when the diesel contaminated soil was treated at ≤ 100°C, suggesting insufficient efficiency at very low temperatures. The TD efficiency decreased with increasing molecular weight of hydrocarbons. The fine particles have shown less tendency to desorb the contaminants, while the presence of organic matter had minimal impact. Furthermore, the developed model accurately estimated residual contaminant concentrations based on carbon number of compounds and temperature. The findings highlight the potential of low-temperature TD (≤ 200°C) for efficient and rapid remediation, offering cost-effective and energy-saving alternative to processes requiring higher temperatures or longer timeframes.