Modeling Sorption of Anionic Surfactants onto Sediment Materials: An a priori Approach for Perfluoroalkyl Surfactants and Linear Alkylbenzene Sulfonates

作者：Christopher P. Higgins, Richard G. Luthy · 发表于：Environmental Science & Technology · 年份：2007 · DOI：10.1021/es062449j · 被引用次数：149 · 研究领域：Per- and polyfluoroalkyl substances research、Toxic Organic Pollutants Impact、Environmental Chemistry and Analysis

A mechanistically derived model predicting the sorption of anionic surfactants to sediments was developed and evaluated for three classes of surfactants: perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and linear alkylbenzene sulfonates. The model includes both hydrophobic and electrostatic components and estimates the contribution of each to the sediment-water distribution coefficient (Kd) using Gibbs free energy terms. The hydrophobic free energy term was calculated from the aqueous solubilities of non-charged alkylbenzene or perfluoroalkane analogs and prior observations of increases in Kd values with increasing chain lengths. The electrostatic term was calculated from aqueous solution measurements using the non-ideal competitive adsorption Donnan (NICA-Donnan) model. The NICA-Donnan calculations were performed using parameters previously derived for generic humic acids. These two terms were coupled by multiplying by the fraction of organic carbon in the sediment, foc, and a single fitting parameter, Faccess, the volumetric fraction of organic carbon accessible to the sorbing surfactant. The combined model accurately predicted the sediment-water distribution coefficients for all three classes of anionic surfactants. In its current formulation, the model was unable to capture the slight degree of isotherm nonlinearity observed for these surfactants.