Simplified Synthesis of Swelling Na-4-Mica from Diatomite

Abstract

A swelling Na-4-mica (a highly charged fluorophlogopite) has recently attracted much attention because of its unique combination of high charge (four charges per unit cell) and swelling and cation exchange properties. Synthetic mica (ideal composition of Na4Mg6Al4O20F4.xH2O) was prepared by a simplified single-step synthetic process (NaCl-melt method) from diatomite at 900 0 C for 5 h. The obtained micas were characterized by powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and 29 Si and 27 Al magic-angle-spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Powder XRD and FT-IR data showed that the swelling Na-4-mica was obtained from diatomite (which serves as a cost-effective aluminosilicate source) with a small particle size (mean 2 µm) as revealed by SEM. The 29 Si and 27 Al MAS-NMR revealed the Si and Al nearest neighbor environment as well as the presence of impurities such as glassy phase.