Synthesis and characterization of nanostructured silica powders using rice hull ash-based sodium silicate solution by precipitation and calcination

Herein, characteristics of the nanostructured silica powders (NsSP) synthesized from Philippine rice hull ash-based sodium silicate solution by precipitation (pH 2, pH 6) and calcination (600 °C, 900 °C) were presented. Characterizations confirmed that the synthesized NsSP contains high amount of SiO₂. NsSP obtained at pH 2 revealed higher mass losses by ∼ 12 % until 900 °C and higher intensities of –OH and Si–OH bonds than obtained at pH 6. Calcination of NsSP at 900 °C removes the Si–OH bond leading to a relative growth in the SiO₂ primary particles but SiO₂ structure remained amorphous. Morphology of NsSP obtained at pH 2 were cloud-like while NsSP obtained at pH 6 were bead-like and more distinct.