Sorption Behavior of Polycyclic Aromatic Hydrocarbons in Soil–Water System Containing Nonionic Surfactant

Abstract

This study examined the sorption behavior of PAHs (solutes) in soil-water systems containing surfactants with the objectives of better understanding the fate of contaminants in natural systems and the feasibility of using surfactants for remediation of contaminated soils. Batch studies on the sorption of three PAHs (naphthalene, acenaphthene, and phenanthrene) from water to four different soils with and without a non-ionic surfactant, Triton X-100, were conducted. The ratio of apparent PAH sorption coefficients (K_d*), that is, when Triton X-100 is added, to the intrinsic coefficients (K_d), that is, without the surfactant, varied from greater to less than 1, depending on the system. When Triton X-100 initial concentration (X₀) is less than 2CMC (critical micelle concentration), the K_d*/K_d values for all three PAHs are larger than 1 on low-f_oc soils, which disfavors the use of Triton X-100 for surfactant-enhanced remediation (SER) of contaminated soils. However, for phenanthrene on high-f_oc soils at low to moderate X₀, K_d*/K_d < 1 occurred, showing enhancement of the PAH mobility and SER efficiency. The K_d*/K_d of a PAH with four different soils tested decreases with increasing soil f_oc, whether K_d*/K_d is greater or less than 1. The sorption coefficients of PAHs with sorbed TX-100 (K_sf) are calculated and evaluated.