Preparation of high purity silica originated from rice husks by chemically removing metallic impurities

Abstract

Chemical treatments were used to synthesize high-purity silica from rice husk. A comparative study was carried out by using four chemicals: sulfuric acid, hydrogen chloride, oxalic acid, and ionic liquid (1-butyl-3-methylimidazolium hydrogen sulfate). The ash content significantly increased in sulfuric-acid and the ionic liquid treatments with the removal of both cellulose and hemicellulose. Drastic increases of silica purity were observed in samples treated with sulfuric acid and the ionic liquid at 99.6% and 99.5%, respectively. Furthermore, the ionic liquid treatment increased the surface area and pore volume by 1.9 times and 2.4 times, respectively, with respect to the sample not subjected to chemical treatment.