Comparative study of silica obtained from acid leaching of rice husk and the silica obtained by thermal treatment of rice husk ash.

A comparison between silica by acid leaching of rice husk (RH) and silica obtained from thermal treatment of rice husk ash (RHA) is presented. The best leaching results were obtained using 10% hydrochloric acid followed by washing with water. The alternative method, calcination of RHA at 700 degrees C for 6 h followed by grinding for 80 min, was more effective. Silica obtained from RH was about 97% amorphous, had a 17.37 mu m mean particle size, and a specific surface area of 296 m(2)/g. On the other hand, for silica obtained from RHA the values were about 95% amorphous material 0.68 mu m, and 81 m(2)/g.