Cyclodextrin-enhanced solubilization of organic contaminants with implications for aquifer remediation

Reagents that enhance the aqueous solubility of nonaqueous phase organic li quid (NAPL) contaminants are under investigation for use in enhanced subsur face remediation technologies. Cyclodextrin, a glucose-based molecule, is s uch a reagent. In this paper, laboratory experiments and numerical model si mulations are used to evaluate and understand the potential remediation per formance of cyclodextrin. Physical properties of cyclodextrin solutions suc h as density, viscosity, and NAPL-aqueous interfacial tension are measured. Our analysis indicates that no serious obstacles exist related to fluid pr operties that would prevent the use of cyclodextrin solutions for subsurfac e NAPL. remediation. Cyclodextrin-enhanced solubilization for a large suite of typical ground water contaminants is measured in the laboratory, and th e results al-e related to the physicochemical properties of the organic com pounds. The most-hydrophobic contaminants experience a larger relative solu bility enhancement than the less-hydrophobic contaminants but have lower aq ueous-phase apparent solubilities. Numerical model simulations of enhanced- solubilization flushing of NAPL-contaminated soil demonstrate that the more -hydrophilic compounds exhibit the greatest mass-removal rates due to their greater apparent solubilities, and thus are initially more effectively rem oved from soil by enhanced-solubilization-flushing reagents. However, the r elatively more hydrophobic contaminants exhibit a greater improvement in co ntaminant mass-removal (compared with water flushing) than that exhibited f or the relatively hydrophilic contaminants.