Predicting surfactant modified soil/water distribution coefficients using micellar HPLC

Soil water/distribution coefficients (K-d) have been measured for the parti tioning of naphthalene, phenanthrene and pyrene between aqueous surfactant solutions and a clean soil. The surfactants used are ABA block copolymers c onstructed from ethylene oxide (the monomer used to synthesise the hydrophi lic A blocks) and propylene oxide (used for the manufacture of the hydropho bic B block). Three of these surfactants comprising the same size propylene oxide block but different ethylene oxide/propylene oxide ratios were inves tigated. Increasing amounts of surfactant in the system result in a progres sive decrease in the K-d values signifying an increasing tendency for the h ydrophobic solutes to be dispersed in aqueous solution due to the action of the surfactant. More significantly for equal surfactant doses the most hyd rophobic surfactant possessing the lowest ethylene oxide/propylene oxide ra tio reduces K-d by the greatest amount whereas the most hydrophilic surfact ant reduces K-d the least. Finally micellar HPLC using the above surfactant s and hydrophobic solutes was undertaken. Interpolated capacity factors eva luated for particular surfactant doses correlated well with K-d values calc ulated for the same surfactant doses. The relationship between K-d and capa city was found to be log-linear and the correlation line could be fitted to the data obtained for all three surfactants. It is therefore concluded tha t micellar HPLC may be used for preliminary evaluations of the effectivenes s of particular surfactants proposed for contaminated soils restoration sch emes. (C) 1998 Elsevier Science Ltd. All rights reserved.