DOWFAX surfactant components for enhancing contaminant solubilization

Surfactant selection is critical to successful implementation of surfactant-enhanced subsurface remediation. Previous research demonstrated the favorable characteristics of commercial grade DOWFAX surfactants for enhancing contaminant solubilization. In this research we studied the effectiveness of higher purity DOWFAX components for enhancing contaminant solubilization. The DOWFAX surfactant components are mono- and di-alkylated diphenyloxide disulfonates and mono- and di-sulfonated alkyl diphenyloxides. Surfactant solubilization of phenanthrene increased as the surfactant hydrophobicity increased (increasing alkyl chain length and with dialkylation for a given chain length) and as the surfactant hydrophilicity decreased (mono- versus di-sulfonate). Surfactant sorption likewise increased with increasing surfactant hydrophobicity and for monosulfonates versus disulfonates. Surfactant sorption was reduced by a factor of 2.5 for the higher purity C-16 MADS component versus commercial grade DOWFAX 8390 (which is a mixture of C16-MADS and DADS). In soil-contaminant systems surfactant-enhanced solubilization was observed to increase dramatically for DOWFAX components with higher solubilization potential and was not significantly impacted by surfactant-media sorption (reflecting the low sorption potential of these surfactants). These results thus further our understanding of how the DOWFAX components, and mixtures thereof, impact surfactant-enhanced soil remediation.