Adsorption of surfactants on low-charged layer silicates Part II: Adsorption of non-ionic surfactants

Nonionic surfactants were adsorbed on low-charged layer silicates in the interlayers. After drying, the surfactants were arranged in densely packed double layers. However, in suspension considerably higher basal spacings are measured by x-ray diffraction which indicate that large quantities of non-ionic surfactants are adsorbed. With the aid of calorimetry, enthalpies of displacement were recorded which suggest strong interactions of the non-ionic surfactants with smectites. In analogy to tests on hydrophilic SiO₂, the adsorption of smectites is found to depend on the degree of ethoxylation of the non-ionic surfactant. The adsorption declines with increasing EO content.List of symbols n ^s adsorbed amount of surfactants (mmol/g) - n _max ^s maximal adsorbed amount of surfactants - d _L basal spacing (nm) - d _L interlayer separation because of adsorption - V _M molar volume of surfactant - V _max ^s volume of adsorbed surfactants (cm³/g) - V _int volume between the silicate layers (interlayer volume) (cm³/g) - H enthalpy of displacement (J/g) - h _max max. molar enthalpy of displacement (kJ/mol) Part I: Prog. Colloid Polymer Sci. 84, 206This paper is part of W. Röhl's doctorial dissertation at the Heinrich-Heine University, Düsseldorf