Preliminary assessment of imidazolium-based room-temperature ionic liquids for extraction of organic contaminants from soils

Alternative solvents known as room-temperature ionic liquids (RTILs) were considered for extraction of organic soil contaminants. A hydrophobic RTIL, 1-butyl-3-methyl imidazolium hexafluorophosphate (bmim]PF6), and a hydrophilic RTIL, 1-butyl-3-methyl imidazolium chloride (bmim]Cl), were selected as representative imidazolium-based RTILs to assess the extraction of several organic contaminants (OCs) from two model soils. The two soils were montmorillonite (clay minerals, high surface area, and no organic matter) and glacial till (organic matter). The soils were spiked separately with DDT, dieldrin, hexachlorobenzene, and pentachlorophenol. With the exception of DDT, extractions of OCs from montmorillonite using bmim]PF6 (79-92%) were nearly as effective as extractions with acetone and ethanol (85-100%). The extraction of OCs from glacial till with RTILs (15-61%) was less effective than extraction with organic solvents (59-100%). The bmim]Cl was as efficient as bmim]PF6 for extraction of OCs from glacial till, while bmim]PF6 was more efficient than bmim]Cl for extraction of OCs from montmorillonite. The two RTILs were most effective for the extraction of dieldrin (the heaviest OC) from both soils. The extraction results for glacial till showed dependence of OC extraction on the viscosity and melting point of RTILs.