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.

The extraction and removal of 2,4-dinitrotoluene (2,4-DNT) from contaminated soils were evaluated using aqueous solutions of hydroxypropyl-␤-cyclodextrin (HPCD). The cyclodextrin-enhanced removal of 2,4-DNT from soils was investigated as function of soil type and concentration of HPCD solutions up to 5% HPCD (w/w). Three soils were spiked with 480 mg of 2,4-DNT per kg of soil: kaolin, a low-buffering clayey soil; montmorillonite, a soil with high specific surface area; and glacial till, a high-buffering silty soil with organic matter. The glacial till was a field soil containing 2.8% organic matter. The solubility of 2,4-DNT in 5% HPCD solution increased approximately threefold compared to solubility of 2,4-DNT in water. For kaolin, water was as effective as HPCD solutions. For montmorillonite, the 5% HPCD solution was the most effective extractant. For glacial till, the 2% HPCD solution was as effective an extractant as the 5% HPCD solution. Although the solubility of 2,4-DNT in 2% HPCD was enhanced approximately 1.7-fold, the extraction of 2,4-DNT from glacial till and montmorillonite using 2% HPCD was enhanced more than twofold in sequential extractions. Three-stage sequential extractions with 2% HPCD followed by two water rinse stages resulted in the removal of 75 and 64% of 2,4-DNT from the glacial till and montmorillonite soils, respectively, whereas five-stage sequential extractions with water alone removed 33 and 30% of 2,4-DNT from glacial till and montmorillonite, respectively. The sequential extraction results showed that the 2% HPCD solution was an effective extractant for remediation of soils with strong retention of 2,4-DNT.