Effect of surfactants on sorption and desorption of phenanthrene onto black carbon.

Sorption and desorption of phenanthrene onto black carbon extracted from sediment were studied in the presence of a cationic surfactant (cetyltrimethylammonium bromide [CTAB]), an anionic surfactant (sodium dodecylbenzene sulfonate [SDBS]), and a nonionic surfactant (Triton X-100 [TX100]), to examine the role of surfactants in sorption and desorption. Nonlinearity of the sorption isotherms increased in the presence of surfactants. The CTAB enhanced the sorption capacity and irreversibility of phenanthrene on black carbon. However, the presence of SDBS reduced the sorption capacity and desorption hysteresis. Unlike CTAB and SDBS, the influence of TX100 on sorption was concentration-dependent. Low levels of TX100 increased sorption, as a result of the sorption of TX100 on the black carbon surface. High levels of TX100 led to a decrease in sorption because of the solubilization of phenanthrene in TX100 solution. Our results may help to understand the different effects of surfactants on the distribution and transport of polycyclic aromatic hydrocarbons in the environment.