RECOVERY OF VOCS FROM SURFACTANT SOLUTIONS BY PERVAPORATION

Surfactant-based processes are emerging as promising technologies to e nhance conventional pump-and-treat methods for remediating soils conta minated with nonaqueous phase liquids (NAPLs), primarily due to the po tential to significantly reduce the remediation time. In order to reus e the surfactant, thereby making the process more economical, the NAPL s must be separated from the surfactant solution. Pervaporation was id entified as a potential technology for removing volatile NAPLs from su rfactant solutions. Initial tests with 1,1,1 -trichloroethane (TCA) in an aqueous solution of the non-ionic surfactant Triton X-100 showed t hat the surfactant had a negligible effect on both flux and selectivit y at concentrations of up to four times the critical micelle concentra tion (4 x CMC). Further tests with a 40 x CMC surfactant solution yiel ded moderately lower TCA fluxes and selectivities than comparable aque ous solutions without surfactant. The reduced pervaporation performanc e at higher surfactant and TCA concentrations were found to result fro m two effects: (1) increases in the viscosity of the solution, which i ncreases the liquid-side boundary layer mass transfer resistance and ( 2) partitioning of TCA into the micelles, thereby reducing the effecti ve extramicellar concentration. Despite these reductions in performanc e, pervaporation was found to be quite capable of removing this volati le NAPL from the surfactant solutions.