Study on admicellar polymerization of styrene on silica from rice husk

Abstract

Amorphous silica with high purity and high specific surface area was prepared from rice husk by calcination at 600℃ with acid leaching pretreatment. The purity of the silica obtained was 97.46% SiO2 with a yield of about 19% on a dry weight basis. The specific surface area and porosity diameter of the rice husk silica were 349 m2/g and 52.80 Å, respectively. The calcination temperature and acid leaching pretreatment were found to affect the crystallinity of the rice husk silica. Surface modification of the rice husk silica by admicellar polymerization using styrene monomer was investigated and the results were compared with those obtained from Hi-Sil®255, a commercially available or precipitated silica. Cetyl trimethylammonium bromide (CTAB) and 2,2’-azobis-2-methylpropionitrile (AIBN) were used as surfactant and initiator, respectively. The adsorption isotherm of CTAB on the rice husk silica and Hi-Sil®255 were determined. After admicellar polymerization, the decreases in specific surface area of both types of silica were measured. Polystyrene was extracted from the silica and characterized by FTER and GPC. The weight average molecular weight of polystyrene extracted from the rice husk silica and Hi-Sil.255 were 832 and 885, respectively.