Surfactant-enhanced nonaqueous -phase liquid contaminants removal from liquid -saturated media 机翻标题: 暂无翻译,请尝试点击翻译按钮。

Zhong, Lirong;
A combination of laboratory experiments were performed to improve our understanding on surfactant-enhanced removal of nonaqueous phase liquids (NAPLs) from liquid saturated media. The influence on surfactant type, surfactant concentration, ionic strength, pore velocity, alcohol amendments, and interfacial tension (IFT) in the removal of trichloroethylene (TCE) were characterized. The (solubilization) mass transfer rates were correlated to pore velocity, initial NAPL saturation, and surfactant concentration (manuscript 1). The kinetics of surfactant enhanced solubilization and the relative importance of processes at various scales on the nonequilibrium behavior were addressed (manuscript 2). Pore scale processes was monitored and their effects on surfactant-enhanced NAPL mass removal was evaluated (manuscript 3). Batch and column experiments were conducted to study the solubilization kinetics and the mass transfer relationships. In the batch experiments, completely mixed condition was applied while dissolved NAPL concentration in aqueous phase with time was monitored. Residual NAPL saturation was established in porous media and then solubilization was conducted while effluent NAPL concentration was recorded in the column experiments. A transport simulator was developed to estimate the parameters in the mass transfer correlation for the surfactant-NAPL systems. A physical transparent micromodel and a CCD-based digital image capture system were designed and for the pore scale visualization investigation. Mobilization and solubilization experiments were performed in the micromodel to address the influence of physical and chemical factors on the pore scale mass removal behaviors. Solubilization rates decreased with increasing in hydrocarbon tail length of the surfactant molecules and surfactant concentrations in the batch tests. For anionic surfactants the solubilization rate increased with electrolyte concentrations, while for the nonionic surfactant tested the rate exhibited negligible changes with salt concentration. Addition of alcohols to surfactant solutions increased or decreased the rate depending on the surfactant type and concentration. The solubilization rate was found to be a function of solubilization capacity. From the column experiments, mass transfer rate coefficients were determined as a function of aqueous phase pore velocity, NAPL volumetric fraction, and surfactant concentration. A correlation for predicting mass transfer rate coefficients for NAPL-surfactant system as a function of system properties was developed. Non-equilibrium conditions were found to be significant at relatively low NAPL volumetric fractions. The batch and column experiment results combined showed that the overall mass transfer rates measured in column experiments increased monotonically with the solubilization rates measured in batch tests, indicating processes at molecular/micellar scale played an important role in determining the mass transfer rate. The visualization studies showed that, at relative low capillary numbers (Nca) (<0.001) a mobilization flood under relatively lower IFT conditions resulted in a higher residual NAPL saturation than a flood under higher IFT conditions with a similar Nca. No significant differences were observed in the trapped NAPL blob size, shape, and distribution between these mobilization floods. This water-surfactant “path” dependent phenomenon was attributed to the larger number of trapped blobs resulted from lower IFT in the NAPL-surfactant systems. Dissolution fingers were observed and the fingering was found to decrease the mass removal rates. A small heterogeneity in the micromodel aperture size distribution controlled the distribution of trapped NAPL and the dissolution fingering.
Environmental engineering;Environmental science;Petroleum production
Michigan Technological University
Environmental engineeringEnvironmental sciencePetroleum production
Mayer, Alex S.