Preparation of porous silica powder via selective acid leaching of calcined tobermorite

Abstract

Tobermorite was synthesized for the producing of porous silica rods through selective acid leaching method. And the preliminary study to the leaching mechanism had been carried out. After being calcined at 300–735 °C for 2 h, the tobermorite was selectively leached in diluted hydrochloric acid: Ca cations were almost leached, while the silica skeleton was undissolved, forming the amorphous porous silica possessed the morphology similar to the tobermorite particles. The higher calcining temperature (735 °C) enabled the tobermorite to better maintain the morphology during the acid leaching. Enhancing of Ca activity was the primary cause of the selective acid leaching of the calcined tobermorite. The prepared porous silica had large specific surface area and was good at the adsorption of positively charged dyes such as methylene blue. Selective acid leaching of tobermorite can provide new method for the recycling of tobermorite-based wastes and for the convenient producing of porous silica.