MICELLAR-ENHANCED ULTRAFILTRATION AND AIR STRIPPING FOR SURFACTANT CONTAMINANT SEPARATION AND SURFACTANT REUSE

Micellar-enhanced ultrafiltration (MEUF) and air stripping were evalua ted for surfactant-contaminant separation and surfactant recovery. Two linear alkyl diphenyloxide disulfonate (DPDs) surfactants were evalua ted with the contaminants naphthalene and trichlorethylene. A separati on model developed from micellar partitioning principles showed a good correlation to batch MEUF studies, whereas flux analysis highlighted concentration polarization effects in relation to hydrophobe length. M EUF effectively concentrated the surfactant-contaminant system (93 to 99 percent retention); however, this did not result in surfactant-cont aminant separation. Batch and continuous flow air stripping models wer e developed based upon air/water ratio, surfactant concentration, and micellar partitioning; model predictions were validated by experimenta l data. Sensitivity analyses illustrated the decline in contaminant-su rfactant separation with increasing surfactant concentration (e.g., TC E removal efficiency declines from 83 percent to 37 percent as C-16 DP DS concentration increases from 0 to 55 mM). This effect is greater fo r more hydrophobic contaminants (naphthalene vs. TCE) and surfactants with greater solubilization potential (C16-DPDS vs. C-12 DPDS). The re sulting design equations can account for this effect and thus properly size air strippers to achieve the desired removal efficiency in the p resence of surfactant micelles. Proper selection and design of surfact ant-contaminant separation adn surfactant recovery systems are integra l to optimizing surfactant-enhanced subsurface remediation.