Several detailed studies have been done on the characterization of organoclays and the type of structures developed when they interact with alkylammonium molecules. Few published contributions exist, however, on the distribution of surfactant within the organoclays and the mechanism by which they are intercalated. Also, although X-ray photoelectron spectroscopy (XPS) is a suitable technique for the study of the surface characteristics of organoclays, very few such XPS studies have been carried out. With the aim of contributing to a better understanding of the intercalation process, a series of organoclays was synthesized using a montmorillonite and the cationic surfactant hexadecyltrimethylammonium bromide (HDTMABr), with an increasing surfactant load of between 0.2 and 4.0 times the cation exchange capacity of the starting clay. By means of XPS, zeta potential, and thermal analysis techniques, distinguishing the strongly interacting fraction from the weakly interacting fraction of the adsorbed surfactant molecules was possible. Adsorption isotherms of each of these processes were constructed and 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, involved the hexadecyltrimethylammonium cation (HDTMA+). The third was a weak interaction involving the ion pair HDTMA+Br−. The results of this study may be useful for the comprehensive design of organoclays with specific physicochemical properties according to the application for which they are destined.

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The properties of the materials determine their potential applications. The aim of this article is to study the properties of the organoclays using simple and rapid technologies. Organoclays with different surfactant loadings (SL) were synthesized using an Argentine bentonite with a high content of montmorillonite (Bent) and hexadecyltrimethylammonium bromide as cationic surfactant. The samples were characterized using thermal techniques. The results revealed that the hydrophilicity of the organoclays decreases with increasing SL until the SL reaches 0.8 times the cation exchange capacity of the clay; and remains constant at a higher surfactant load. The stability of organoclays was inversely proportional to the SL of each sample. The layers showed a stabilization of approximately 40 • C for their structural transformation temperature, caused by the presence of the surfactant. In addition, at a SL <1.0 the surfactant presented a 'liquid-like' structure in the interlayer space, whereas at a SL >1.0 the structure was 'solid-like'.