Sorption of Nonionic Surfactants on Sediment Materials

The distribution of a series of nonionic surfactants between sediments and water was studied as a function of surfactant structure, ionic strength, pH value, Ca2+ concentration in solution, sediment composition, and concentration of suspended solids. The surfactants were monotridecyl ethers of poly(ethylene glycol), also known as alcohol ethoxylates, AnEx = CH3(CH2)n-1(OCH2CH2)xOH), 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 (-OCH2CH2-) 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 Ca2+ did not affect the distribution of AEs. The distribution ratios of the AEs did not correlate well with the fraction organic c...