Integration of soil washing and cork permeable reactive barriers for the remediation of soil contaminated with polycyclic aromatic hydrocarbons

Abstract

Soil washing is a well-known technology for the remediation of soils polluted by organic contaminants, including polycyclic aromatic hydrocarbons (PAHs). This study aimed to go further by integrating soil washing and permeable reactive barriers (PRBs) made of cork granules to remove PAHs from the soil. While PAHs may be transferred from the soil to the washing solution in the soil washing step, the cork PRB may provide the removal of PAHs from the washing solution, ultimately leading to the reuse of this solution. RESULTS: The integrated approach was tested by means of packed bed column experiments in the absence and presence of cork PRBs. Two PAHs were under focus: fluorene (FLU) and phenanthrene (PHE). In soil with 0.5 mmol L−1 kgsoil−1 of FLU and PHE, the soil washing technique employing thermally treated cork granules and a solution of 70%/30% water/acetonitrile (v/v) flowing at 2.2 mL min−1 promoted the transfer of ~58% of PAHs from the soil to the washing solution, while the cork PRB retained ~98% of the PAHs from the washing solution. The acetonitrile content of the water/acetonitrile washing solutions contributed to the soil washing since it was responsible for PAH desorption and elution, however it was unfavorable for PAH sorption onto the cork as acetonitrile competed with PAHs for cork sorption sites. CONCLUSION: Cork PRBs were able to retain PAHs from soil washing solutions and provide final solutions free of PAHs, demonstrating the viability of integrating solvent-aided soil washing with cork PRBs. © 2022 Society of Chemical Industry (SCI).