Enhanced dissolution of multiple-component nonaqueous phase organic liquids in porous media using Cyclodextrin : theoretical, laboratory, and field investigations

Abstract

The effectiveness of a cyclodextrin (sugar-based) solution for enhancedsolubilization removal of multicomponent nonaqueous phase organic liquid (NAPL) contamination from an aquifer is tested in a pilot-scale field experiment. This effort is the first field test of this innovative technology, termed a "Complexing Sugar Flush" (CSF). The saturated zone within an enclosed cell was flushed with 8 pore volumes of 10wt% cyclodextrin solution. The cyclodextrin solution increased the aqueous concentrations of all the target contaminants to values from about 100 to more than 20,000 times the concentrations obtained during a water flush conducted immediately prior to the CSF. The degree of solubility enhancement was greater for the morehydrophobic contaminants. Conversely, the relative mass removal was greater for the less-hydrophobic compounds due to their generally higher apparent solubilities. The average reduction in NAPL mass for the target contaminants was about 41%. A relationship is developed to describe enhanced dissolution of a multiple-component NAPL, and is used to analyze the field data. The effluent concentrations for most of the target contaminants during the cyclodextrin flush were within a factor of two of the equilibrium values predicted using this theory. Deviations from ideal dissolution behavior were also observed. Finally, the cyclodextrin solution appeared to significantly enhance both the magnitude and the rate of NAPL dissolution compared to a water flush conducted prior to the cyclodextrin flush. These results contribute to a better understanding of the important physicochemical processes involved in using enhancedsolubilization agents for the remediation of multiple-component NAPLs.