Highly ordered and hexagonal mesoporous silica materials with large specific surface from natural rectorite mineral

摘要

Highly ordered and hexagonal mesoporous silica materials containing aluminum were successfully synthesized from natural rectorite mineral via a novel strategy. Silicon and aluminum sources were obtained from rectorite mineral by a pretreatment method involving acid leaching, alkali leaching and strongly acidic cation exchange resins (SACERs) treating, followed by a hydrothermal reaction with hexadecyl trimethyl ammonium bromide (CTAB) as template and subsequent calcination to prepare Al-MCM-41. More importantly, Wide angle X-ray diffraction (WAXRD), fourier transform infrared spectroscopy (FT-IR) and solid-state magic-angle-spinning nuclear magnetic resonance (MAS NMR) results indicated that acid treatment did not destroy the structure of natural rectorite. Unlike other silicate minerals, natural rectorite failed to provide suitable silicon sources because of residual hydroxide from alkali leaching process. In this paper, SACERs instead of inorganic acids were adopted to neutralize residual hydroxide, which avoided excessive inorganic anions to hinder the synthesis of Al-MCM-41 by a hydrothermal reaction. The final Al-MCM-41 products were amorphous SiO2, with a surface area of 1032 m(2)/g, pore volume of 0.97 cm(3)/g and an average pore diameter of 2.6 nm. A proposed mechanism for synthesizing mesoporous silica from natural rectorite was suggested.