A series of saponites (Sap) with a fixed Si/Mg ratio and varied Al contents were synthesized by using hydrothermal methods. The spectral, structural and morphology characters of the obtained products were characterized by a combination of XRD, FTIR, TG-DTG, TEM, 29Si MAS NMR, 13C NMR etc. before and after 3-aminopropyltriethoxysilane (APTES) grafting. XRD patterns showed that well-ordered Sap were obtained with starting Si/Al ratios of 5.43 and 7.89. Silylation reactions have little or no effect on the layered structure of Sap at the used dosage of APTES. The existence of the –CH2 stretching bands at around 2937 cm− 1 in IR spectra clearly showed the incorporation of silane in the grafted samples. TG–DTG curves revealed that the samples with higher crystallinity displayed higher dehydroxylation temperature, as expected. A new mass loss located at around 420 °C in silylated Sap was ascribed to the volatilization of the alkyl group in silane. The 29Si NMR spectroscopy showed a series of signals of T structures, ascribed to the different silylation modes between silane and Sap. Furthermore, silylation procedures led to a decrease of the intensity of the signals at ca. − 84 ppm along with an increase of the intensity of Q3 signals. A further increase in the silane concentration did not decrease the resonance at − 84 ppm any further. This phenomenon confirmed the coexistence of Q2 structure with Q3Si(2Al) structure, which resulted from the broken bonds at the edge surfaces of the synthesized Sap.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology