Ex situ soil washing of highly contaminated silt loam soil using core-crosslinked amphiphilic polymer nanoparticles

Non-ionic surfactants (Triton X-100 and Brij 30) and core-crosslinked amphiphilic polymer (CCAP) nanoparticles were used as extractants in the ex situ soil washing of silt loam soil contaminated with large quantities of petroleum oil, and their soil-washing performances were compared. Following washing with the surfactants, highly turbid aqueous solutions containing large numbers of soil and petroleum oil particles were produced. In contrast, the CCAP nanoparticles successfully extracted the petroleum oils from the soil samples without the formation of such a turbid aqueous solution. In addition, the CCAP nanoparticles extracted 96% of the petroleum oils, which is a significantly larger quantity than that by Brij 30 and Triton X-100 under equivalent conditions. Indeed, owing to their crosslinked micelle-like structure, the CCAP nanoparticles maintained their nanostructure even upon contact with a highly contaminated silt loam soil matrix, thereby resulting in the extraction of only the hydrophobic oily contaminants from the soil matrix and avoiding the formation of dispersions of soil particles and hydrophobic contaminants. As such, CCAP nanoparticles could be considered as suitable washing materials for highly contaminated silt loam soils.