Microemulsion of mixed chlorinated solvents using food grade (edible) surfactants

Ground water contamination frequently consists of mixed chlorinated solvents [e.g., tetrachloroethylene (PCE), trichloroethylene (TCE), and trans-1, 2-dichloroethylene (DCE)]. In this research, mixtures of the food grade (edible) surfactants bis(2-ethylhexyl) sodium sulfosuccinate (AOT) and sodium mono- and dimethylnaphthalene sulfonate (SMDNS) were used in the formation of middle-phase microemulsions for mixed chlorinated solvents. Microemulsions of binary (e.g., PCE/TCE, PCE/DCE, DCE/ TCE) and ternary (PCE/TCE/DCE) chlorinated solvent systems were evaluated. Several empirical correlations were used for describing and/or predicting the phase behavior of the resulting middle-phase microemulsions (e.g., the ideal mixing rule or the nonideal regular mixing theory). The ideal mixing rule provided a good approximation for binary and ternary systems, but experimental deviations from the predictions were significant enough to affect the optimal surfactant system. Nonideal regular mixing theory demonstrated much better predictive capabilities than ideal mixing for the binary and ternary systems. The recognition of nonideal mixing behavior and the resulting predictive correlations will be valuable in the design of groundwater remediation scenarios when surfactants are used for remediation of mixed chlorinated solvents.