Micellar Partitioning and Its Effects on Henry's Law Constants of Chlorinated Solvents in Anionic and Nonionic Surfactant Solutions

• Published in: Environmental science & technology 2006-01, Vol.40 (1), p.208-214
• Main Authors: Zhang, Chunlong, Zheng, Gang, Nichols, Courtney M
• Format: Article
• Language: English
• Subjects: Anions - chemistry; Applied sciences; Breath tests; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental Pollution - prevention & control; Environmental science; Equilibrium; Exact sciences and technology; Groundwater; Groundwaters; Hydrocarbons; Hydrocarbons, Chlorinated - chemistry; Micelles; Natural water pollution; Octoxynol - chemistry; Pollution; Pollution, environment geology; Polysorbates - chemistry; Solubility; Solvents; Solvents - chemistry; Surface-Active Agents - chemistry; Surfactants; Tetrachloroethylene - chemistry; Trichloroethylene - chemistry; VOCs; Volatile organic compounds; Volatility; Volatilization; Water - chemistry; Water Supply; Water treatment and pollution
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es051387e

Micellar partitioning of volatile chlorinated hydrocarbons in surfactant solutions and its effects on vapor−liquid equilibrium is fundamental to the overall design and implementation of surfactant-enhanced aquifer remediation. Surfactant micelles greatly enhance contaminant recovery from the subsurface; however, the reduced volatility of organic compounds compromises the aboveground treatment of surfactant-laden wastewaters using air-stripping process. Batch equilibrium tests were performed to acquire micellar partition coefficients (K m) and apparent Henry's law constants (H*) of three prominent groundwater contaminants (tetrachloroethylene, trichloroethylene, cis-dichlorethylene) in the presence of two anionic surfactants (sodium dodecyl sulfate, SDS; sodium dodecylbenzene sulfonate, SDBS) and two nonionic surfactants (Triton X-100 and Tween 80). The H* values were significantly reduced in the presence of all four surfactants over their critical micelle concentrations (cmc's). On a cmc basis, the anionic surfactant SDS had the greatest effect on H*, followed by SDBS, Triton X-100, and Tween 80. Anionic surfactants decreased H* to an order of magnitude lower than nonionic surfactants, although nonionic surfactants decreased the H* at concentrations significantly lower than the anionic surfactants due to their lower cmc's. Nonionic surfactants present higher K m and molar solubilization ratio than anionic surfactants. Tetrachloroethylene has the highest K m values among three chlorinated solvents, which agrees well with the hydrophobicity (K ow) of these chemicals. An empirical correlation between log K m and log K ow is developed on the basis of data from this study and the K m values reported for a number of chlorinated and nonchlorinated hydrocarbons. Equilibrium data were also tested against three sets of models that describe the partitioning of volatile compounds in vapor−water−micelle phases. Applications of these models in experimentally determining K m from batch vapor-water equilibrium data are discussed.