Linear alkylbenzenesulfonates (LAS) are anionic surfactants that are used in large quantities in industrial and consumer products. They enter the environment primarily through wastewater and sludge. In this study, the sorption of LAS to the surfaces of sediment particles was investigated as a function of LAS homologue, H + concentration in solution, Ca 2+ concentration in solution, sediment properties, and concentration of solids. Evidence for both hydrophobic and specific or electrostatic interactions was seen. Isotherms were generally nonlinear and were represented well by the Freundlich and the virial (electrostatic) equations. Comparisons of apparent distribution ratios, D (L/kg), for linear portions of the isotherms showed ∆ log D/∆ log n CH2 ≈ 0.4, ∆ log D/∆ log [H + ] ≈ 0.17, and ∆ log D/∆ log [Ca 2+ ] ≈ 0.23. The value of D for different sediments seemed to correlate most closely with the organic carbon content (f oc ) of the sediments. The value of the distribution ratio increased with the concentration of solids in the system; this effect could be explained partially by the concomitant increase in Ca 2+ concentration in solution.

The distribution of a series of nonionic surfactants between sediments and water was studied as a function of surfactant structure, ionic strength, pH value, Ca 2+ concentration in solution, sediment composition, and concentration of suspended solids. The surfactants were monotridecyl ethers of poly(ethylene glycol), also known as alcohol ethoxylates, A n E x ) CH 3 (CH 2 ) n-1 (OCH 2 CH 2 ) x OH), with n ) 13 and x ) 3, 6, and 9. Isotherms were nonlinear, with the degree of nonlinearity and the extent of sorption increasing with the number of oxyethylene (-OCH 2 CH 2 -) groups. Freundlich isotherms represented the data well. The pH and ionic strength of the solution had a small effect on sorption, but the effect increased with the number of oxyethylene groups. These observations suggest that the oxyethylene chain is specifically adsorbed, presumably through a hydrogen-bond mechanism. Addition of Ca 2+ did not affect the distribution of AEs. The distribution ratios of the AEs did not correlate well with the fraction organic carbon of the sediments; the amount of swelling clay in the sediment may affect distribution ratios. The concentration of solids had no effect on the extent of sorption.