Identification and quantification of the interaction mechanisms between the cationic surfactant HDTMA-Br and montmorillonite

Abstract

Using a montmorillonite and the cationic surfactant hexadecyltrimethylammonium bromide (HDTMABr), a series of organoclays were synthesized with progressively increasing surfactant loads of between 0.2 and 4.0 times the cation exchange capacity of the starting clay. Different experimental techniques were used (thermal techniques, XPS, zeta potential) for characterizing the solids. The results obtained allowed to distinguish between the fraction of surfactant adsorbed by strong interactions and the fraction adsorbed by weak interactions. Adsorption isotherms of each of these processes were constructed, and were then adjusted using the Langmuir and Dubinin-Radusquevich adsorption models. Three types of interaction between the surfactant and the clay were identified and described, qualitatively and quantitatively. Two of these interactions, strong and weak, involve the hexadecyltrimethylammonium cation (HDTMA+). The third is a weak interaction involving the ion pair HDTMA+Br-.