Synthesis of Al-containing mesoporous silica (KSW-2) with semi-squared channels by incorporation of Al into the framework of kanemite

Abstract

Incorporation of Al into the framework of single-layered silicate kanemite and the formation of Al-containing mesoporous silica (Al-KSW-2) with semi-squared one-dimensional channels were surveyed. Al-containing δ-Na₂Si₂O₅ was successfully obtained by thermal treatment of an aqueous sodium silicate solution (Na₂O/SiO₂ = 1 ∶ 2) containing NaAlO₂ up to 785–810 °C, depending on the amount of NaAlO₂ added. After Al-containing δ-Na₂Si₂O₅ was dispersed in distilled water, Al-containing kanemite (Al-kanemite) was obtained with tetrahedrally coordinated Al. The reaction of Al-kanemite with an aqueous solution of hexadecyltrimethylammonium (C₁₆TMA) surfactant yielded a layered C₁₆TMA–Al-kanemite complex which was converted to a mesostructured precursor of Al-KSW-2 by mild acid treatment. Tetrahedral coordination of Al was retained in the framework of Al-KSW-2 with high surface area (830 m² g⁻¹) and uniform semi-squared mesopores (2.7 nm), which increased the adsorption ability for cationic dye molecules.