Abstract
Thermal desorption (TD) is an effective physical remediation technology for polycyclic aromatic hydrocarbons (PAHs) contaminated soil. Reaction temperature is the key of TD, and the increase of the vacuum degree and addition of catalysts could improve the remediation efficiency. Therefore, testing of TD experiments (test equipment and method: Patent No. 201220468562.5) under different heating temperature and vacuum-enhanced and alkali-assisted conditions at low temperature was conducted to remediate soil contaminated by PAHs from a coking plant. The aim of the test was to improve PAHs removal efficiency and investigate its influence on physicochemical properties of contaminated soil. The results indicated that the removal efficiencies of PAHs increased with the increase of heating temperature, which reached 85.4%, 87.1%, 83.0%, and 76.2% removals of ∑PAHs, PAHs containing 2-3 benzene rings (LPAHs), PAHs containing 4 benzene rings (MPAHs), and PAHs containing 5-6 benzene rings (HPAHs) at 450°C, respectively. But the residual concentrations of Phe, BbF, and DBA were still higher than the corresponding screening levels for soil environmental risk assessment of residential land in Beijing. The vacuum-enhanced and alkali-assisted TD improved the removal of PAHs compared with the TD at 200°C, especially the vacuum-enhanced TD, which could remove almost all the available PAHs and partly unavailable PAHs owing to the lowered of melting point and increased steam flow rate by vacuumizing. Relative high-temperature TD (450°C) and vacuum-enhanced TD had a greater effect on the dissolved organic carbon, and specific surface area (SSA) of bulk soil, and volatilization of pollutant and agglomeration of particles affected the SSA during TD simultaneously, which led to the difference of removal efficiencies of PAHs probably.
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