Cork granules for remediation of soils contaminated with lindane

Abstract

This work aims to assess the effectiveness of an integrated approach combining surfactant-assisted soil washing (SASW) and cork granules for removing lindane from contaminated soil. It focuses on the evaluation of cork granules (raw and regranulated) as natural sorbents for lindane and on the feasibility of the combination of this physical treatment with surfactant-enhanced soil washing to face the remediation of soil polluted with this hazardous pesticide. The results demonstrate that cork can efficiently retain lindane contained in aqueous solutions and dispersions consisting of mixtures of lindane and sodium dodecylsulfate (SDS) surfactant. Performance improves when using regranulated cork because of its higher affinity for nonpolar species. For lower concentrations of lindane and without surfactant, the raw cork granules presented a sorption capacity of 3.02 mg g− 1, while the regranulated cork presented 6.52 mg g−1. When using a much higher concentration of lindane and SDS, the capacities were 1.90 and 8.21 mg g−1 for raw and regranulated cork, respectively. As well, soil washing with SDS can separate efficiently lindane from spiked soil. It was also observed that the integration of both treatments was feasible, but not as efficient as initially expected. It exhibited a non-expected antagonistic effect caused by the entrapping of the lindane into SDS micelles, which makes it not readily available for sorption. Hence, the higher the amount of SDS the lower the lindane retained by the cork. If the aim is to eliminate lindane with cork specifically, the use of low concentrations of SDS in the combined treatment is encouraged, resulting in an uptake capacity for lindane of 80% from the soil. However, better overall results are achieved when higher concentrations of SDS are used where about 91% of lindane was removed from the soil remaining mainly in the liquid phase. Dichlorination caused by interaction with hydroxyl ions is also observed, being less important in the case of using cork because it attains operation at mild conditions. The results demonstrate that the integration of processes in soil remediation does not always yield expected outcomes and they enhance the knowledge about environmental technologies and their interactions.