FT-IR Technique for Monitoring the Interfacial Interactions of a Surfactant Solution and a Solid Hydrocarbon

Abstract

A cylindrical internal reflection element (IRE) has been used as a support for a solid hydrocarbon-aqueous nonionic surfactant interface. Time-resolved FT-IR spectra of the interface during the removal of the hydrocarbon from the IRE surface by the detergent action of flowing surfactant solutions have been recorded. Qualitative comparisons of the detergency of different surfactants can be made. With the use of subtraction techniques, the spectra of interfacially adsorbed and aqueous surfactant can be obtained for comparison. Significant adsorption of a relatively hydrophobic ethoxylated alcohol (Neodol 25–3) at the interface was detected. The ether group bands of the adsorbed surfactant were different from those in the spectrum of an aqueous dispersion of the surfactant. The removal of hydrocarbon from the IRE by the Neodol 25–3 was much slower than that caused by a more hydrophilic material, Neodol 23–6.5.