Switchable Surfactants for Soil Remediation
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Soil remediation requires technologies to restore contaminated soil to a state that is environmentally acceptable. In most cases, while the soil can be remediated the contaminant itself cannot be reclaimed. Soil washing involves cleaning contaminated soil with a wash solution, generally an aqueous solution of a surfactant. It was proposed that using switchable surfactants for washing oil-contaminated soil will not only help remove the oil from soil, but also aid in the recovery of the oil contaminant from the wash mixture. Six surfactants were evaluated for their ability to wash Ottawa Sand artificially contaminated with North Sea crude oil. A water wash solution was used as a control. Two commercial surfactants, sodium dodecyl sulfate (SDS) and Triton X-100, and four switchable surfactants, N'-octyl-N,N-dimethylamidine (C8), sodium octyl 4-hydroxy-3-nitrobenzoate (SAS1), sodium 4-(octyoxy) benzoate (SAS2) and sodium laurate (SAS3) were studied. The surfactants were assessed based on their ability to remove oil from the sand and their ability to separate the crude oil from the wash mixture after CO2 treatment. Oil removal from sand was determined by gravimetric analysis. Oil content in the wash mixture was determined using Solid Phase Extraction and gravimetric analysis. It was determined that switchable surfactants are able to remove North Sea crude oil from sand as well or better than the commercial surfactants and have the added feature of oil separation and recovery from the wash mixture after CO2 treatment.