CHARACTERISTICS OF AN ADSORBED LAYER OF HYDROCARBON AND FLUOROCARBON SURFACTANTS ON ALUMINA

The adsorption of lithium perfluorooctanesulfonate (LiFOS) and lithium dodecyl sulfate (LiDS) from mixed aqueous solutions on alpha-alumina has been investigated. The adsorption from mixed solutions is enhanced at low concentration, but is depressed at high concentration compared with that of the single surfactants. Measurements of fluorescence spectra of pyrene and of ESR spectra of 2,2,6,6-tetramethylpiperidinyl-1-oxy for the surfactant adsorbed layer indicate that the polarity of the LiFOS adsorbed layer is larger than that of the LiDS adsorbed layer and the polarity of the mixed-surfactant adsorbed layer is lower than that of the LiDS adsorbed layer below a feed mole fraction of LiFOS of 0.65, while the viscosity of the mixed-surfactant layer is increased with an increase of feed mole fraction of LiFOS, but is considerably lower than that of the single LiFOS adsorbed layer.