Template-free synthesis of kaolin-based mesoporous silica with improved specific surface area by a novel approach

• A template-free process to prepare mesoporous silica (MS) from kaolin was proposed.
• The simple process consists of calcination, alkali activation and acid etching.
• MS has an improved SBET of 604 m2/g and DBJH of 4.41 nm.
• MS has a high monolayer adsorption capacity of 652.9 mg/g on methylene blue.

A novel template-free method is proposed and demonstrated to develop the facile top-down strategy of preparing mesoporous materials from natural minerals. In the process, kaolin was pre-calcined, alkali-activated and finally acid-etched into mesoporous silica (MS) of improved specific surface area (604 m2/g) and large pore size (4.41 nm) at the maximum probability. The characterizations of XRF, XRD, TG, FT-IR, SEM, TEM and N2 adsorption/desorption were carried out and the material evolution mechanism was clarified. The as-resulted MS showed favorable adsorption ability toward methylene blue with the monolayer adsorption capacity up to 652.9 mg/g, indicating its promising potential in adsorption application. The template-free method proposed may benefit not only the clay products but also the wide application of mesoporous materials cost-effectively.