ADSORPTION OF BINARY-MIXTURES OF HYDROCARBON AND FLUOROCARBON SURFACTANTS ON ALUMINA

Adsorption of binary mixtures of sodium dodecyl sulfate (SDS) and sodium 4-[2-heptafluoroisopropyl-1,3-bis(trifluoromethyl)-butenoxy]benzenesulfonate (NF) from their aqueous solutions on α-alumina has been studied. Total adsorption of these mixtures is lower than that of the individual surfactants of which they are composed. This decrease in the adsorption is due to unfavorable interaction between hydrocarbon and fluorocarbon chains of SDS and NF. As feed molar fraction of NF increases, the adsorption of NF increases greatly compared with that of SDS. Properties of the surfactant adsorbed layer have also been characterized using pyrene and 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO). The polarity of the mixed adsorbed layer is not so changed against feed molar fraction of NF, whereas the viscosity increases with feed molar fraction of NF. © 1991.