Physicochemical characteristics of organophilic clays prepared using two organo-modifiers: alkylammonium cation arrangement models

The clay was modified by an ion exchange reaction with cetylpyridinium chloride CPC and hexadecyltrimethylammonium bromide HDTMA. The modified samples were studied by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The basal spacing of unmodified clay determined by XRD was 12.72 Å and, after modification, increased with increasing concentration; expressed as a function of the cation exchange capacity (CEC) of the clay; to reach 21.08 and 26 Å for clays modified with CPC and HDTMA successively for an equal concentration of 3CEC. FTIR studies revealed structural differences between modified and unmodified clay samples. Modified clay spectra showed C–N functional bands (1480 cm⁻¹) and C–H vibrations (near 2936 and 2871 cm⁻¹). The results of the SEM study reveal a difference between natural and modified clays. The purified clay has massive and curved plates. However, the modified clays show numerous small aggregate particles and plaques that become relatively flat. The arrangement of surfactants in clay is rather complicated. It depends on the nature of the surfactant molecules, the CEC of the clay and the method of preparation. According to these parameters, the inserted surfactants may be arranged in monolayer, paraffinic or admicelles structures.