FTIR and zeta potential measurements of sepiolite treated with some organosilanes

Sepiolite has been treated with some organosilanes including dimethyloctadecylchlorosilane (DMODCS), dimethyldichlorosilane (DMDCS), and 3-aminopropyltriethoxysilane (3-APT). FTIR measurements have been used to discuss the interactions between sepiolite surface and organosilane molecules. The disappearance of OH stretching peaks of sepiolite has shown the strong interactions between the surface and organosilane molecules. H-bonds have also been indicated by the frequency shifts of OH stretching vibrations. The changes in the electrokinetic properties of the treated sepiolite samples have been investigated by following the zeta potential of the particles as a function of pH. The treatment of sepiolite with 3-APT causes a shift of isoelectronic point (IEP) from 7.8 to 9.7, to a more basic value compared to sepiolite itself. DMODCS and DMDCS-treated sepiolite samples have, however, been found to have isoelectronic points in more acidic region than that of sepiolite, which are 5.2 and 5.6, respectively.