Organically modified sepiolite: Thermal treatment and chemical and morphological properties

Abstract The modification of sepiolite is one of the aspects well established in literature aiming to broaden the range of applications of this material. Additionally, in some requests, e.g. in polymer processing to produce sepiolite-based nanocomposites, higher temperatures are a necessity. Despite that, understanding the influence of the modifier as well as its modifications and thermal stability are not broadly contemplated. So, in this work Sepiolite (Sep) was treated with tetradecyltrimethylammonium bromide (TTAB) and hexadecyltrimethylammonium bromide (CTAB), as well as a thermal treatment was performed in the modified samples. The influence on structural, thermal properties and morphology in the treated Sep with TTAB and CTAB were investigated by using N2 adsorption/desorption isotherms, zeta potential, thermogravimetric analyses (TGA), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), 29Si solid-state nuclear magnetic resonance (29Si ss-NMR), and scanning electron microscopy (SEM). It was possible to observe a decrease of the SBET and V values for the modified samples with CTAB and TTAB, in contrast to an increase of the zeta potential. The thermal analyzes results showed that the oxidative atmosphere did not accelerate the degradation reactions of the raw and modified Sep. X-ray diffractograms showed that there was no change in the crystalline structure of the Sep after the modification. On the other hand, the thermal treatment performed on the Sep samples lead to changes in its structure, due to the release of zeolitic and coordination water molecules. Although SepTTAB exhibited a slightly higher thermal stability, as well as a lower specific surface area, no significant differences were observed between SepCTAB and SepTTAB.