Characterization of porous silica prepared from mechanically amorphized kaolinite by selective leaching

The structure of leached products from mechanically amorphized kaolinite was investigated by various techniques. The 29Si MAS NMR spectrum of the leached products showed peaks at −102 and −111 ppm, assigned to the silanol groups and the three-dimensional silica framework, respectively. The micropore size distribution calculated by the Horvath–Kawazoe method, using Ar gas as the adsorbate, showed a maximum at 0.9 nm, suggesting slit-shaped pores formed between the layers of the mechanically destroyed kaolinite. Longer leaching times reduce the number of micropores due to a condensation reaction.