Sorption of two model alcohol ethoxylate surfactants to sediments

We have examined the sorption of two radiolabeled alcohol ethoxylate surfactants (AE) (C13 alcohols with exactly 3 or 9 moles of ethylene oxide (EO) per mole of alcohol) to natural sediments. Formalin was included in the sediment/surfactant/water mixtures to prevent biodegradation. Four sediments with 0.3 to 2.2 % organic carbon content were used in equilibrium experiments to determine the effect of various sediment properties and EO chain length on the sorption process. The equilibrium sorption isotherms were determined to be non-linear and described by the Freundlich model, and distribution ratios (ratio of surfactant concentration on sediment to aqueous concentration) at 1 mg/L surfactant ranged from 110 to 590 L/kg. These distribution ratios indicated that the AEs did not sorb strongly to the tested sediments. The amount of sorption was better correlated to the percent clay content of the sediment than to the percent organic carbon content of the sediment.