Surfactant enhanced solubilization of residual trichloroethene: an experimental and numerical analysis

The ability of an aqueous polyoxyethylene (20) sorbitan monooleate solution to solubilize a residual trichloroethene (TCE) saturation, present as a trapped dense non-aqueous phase liquid (DNAPL), was studied in a series of column experiments. Different flow regimes and stopflow scenarios were applied. No mobilization of the DNAPL was observed, leading to the assumption that the only recovery mechanism was a surfactant enhanced micellar solubilization of the TCE molecules. The solubilization of TCE by the surfactant solution was observed to be rate-limited under the applied conditions and the exchange rate depended on pore water velocity and volumetric DNAPL content. A phenomenological power-law model between the mass transfer rate and the pore water velocity and volumetric DNAPL content was implemented in a numerical model to describe DNAPL dissolution, advection and dispersion in the water phase. The applied model accounts for non-flow dissolution. The obtained mass transfer rate parameters provide a good fit to the experimental data also for no-flow conditions. Compared to other mass transfer rate models the obtained relationship predicts lower mass transfer rates and an intercept in case of zero flow.