Nanostructured silica from bagasse ash: the effect of synthesis temperature and pH on its properties

Bagasse ash as one of the sugar mill wastes can create a serious environmental problem. Hence, we adopted a strategy to reduce the waste by utilizing its silica content. Nanostructured silica was synthesized from bagasse ash via sodium silicate route. The effect of synthesis temperature and pH on the morphology, primary particle size, pore size, thermal properties, and agglomerate fragility were investigated. Electron microscopy analysis revealed the fractal structure of silica with the appearance of mesopores and macropores. Higher synthesis temperature and pH resulted in greater primary particle size. Nitrogen physisorption analysis showed that the addition of secondary sodium silicate solution was able to prevent the collapse of the aggregate/agglomerate structure at the drying stage. Lower bound water content and lower average diameter of the nanostructured silica aggregate/agglomerates as determined from thermal analysis and particle size analysis, respectively, were observed with increasing temperature from 60 to 90 °C and decreasing pH from 11 to 8 during the synthesis protocol. The primary particle size of the silica was on a nanoscale and the agglomerate was easily destroyed, therefore the material had the potential to be used in applications where well-dispersed particles are key, such as in rubber compounding that utilizes silica as reinforcing filler.