Evaluation of ethoxylated alkylsulfate surfactants for use in subsurface remediation

Experiments were conducted to evaluate the potential of ether sulfate surfactants with degrees of ethoxylation ranging from one to four per molecule for use in subsurface remediation. It was hypothesized that ethoxylated anionic surfactants will exhibit lower losses in the subsurface due to precipitation and sorption as a function of increasing ethoxylation while maintaining high hydrocarbon solubilization potentials. Results demonstrated that no significant precipitation of surfactant and calcium occurred where the degree of ethoxylation was two or greater. Sorption assays demonstrated that these ethoxylated anionic surfactants were less prone to sorption on soil than nonethoxylated anionic and nonionic surfactants. Furthermore, enhancements in solubilization of naphthalene were evidenced with increasing degrees of ethoxylation, and micelle-water partition coefficients were comparable with those of other high-performance surfactants. Microbial degradation assays indicated that these ethoxylated anionic surfactants served readily as substrates, raising concerns relative to their use in subsurface aerobic systems. However, they could be compatible with a treatment train concluded with a biological unit process.