Preparation of amorphous silica from a renewable agricultural waste of rice husk ash by calcination method combined with chemical activation

In the study, silica particles were synthesized from rice husk ash by the calcination method in the presence of activating agents. The parameters which are effective in the calcination method on the structure and morphology of synthesized silica particles, activating agent type (NaOH and KOH), the calcination temperature (500-850°C), the calcination time (1-3 hours), and the weight ratio of activating agent to ash (4:1 and 5:1), were investigated. The crystal structures of the silica particles were determined by XRD, agent structures by FTIR, sizes and shapes by SEM, and surface areas and porous structures by N₂ adsorption-desorption analysis. Amorphous silica particles were synthesized in all experimental conditions. Optimum weight ratio, calcination temperature, and time were determined as 4:1, 750°C, and 2 hours, respectively. The activating agent NaOH was found to be more active than KOH in the preparation of silica.