Preparation of porous silica from vermiculite by selective leaching

High surface area silica was obtained by selectively leaching vermiculite. The influence of acid concentration and leaching time on the porous properties of silica was studied. Leaching with 2 M HCl at 80 °C for 2 h produced a maximum value of surface area (672 m 2/g) with total pore volume of 0.44 ml/g. The 29Si MAS NMR spectra of the leached products indicate mainly Q 3 and Q 4 structural units, assigned as layer and framework structures, respectively. The layer structure is responsible for forming micropores and the framework structure forms mesopores. The number of micropores decreased with longer leaching time, the micropores condensing to increase the framework structure. The characteristics of the porous silica obtained from vermiculite are compared with those from other clay minerals.