Characterisation of silica derived from rice husk (Muar, Johor, Malaysia) decomposition at different temperatures

Rice husk was thermally decomposed to yield powder composed of silica (SiO₂). Temperatures of 700°C and 1000°C were chosen as the decomposition temperatures. X-Ray Diffraction (XRD), X-Ray Florescence (XRF), Fourier Transform Infrared (FTIR), and Field Emission Scanning Electron Microscope (FESEM) analyses were conducted on a synthetic silica powder (SS-SiO₂) and the rice husk ash as for the comparative characterisation study. XRD analyses clearly indicated that the decomposed rice husk yielded silica of different nature which are Crystalline Rice Husk Silica (C-RHSiO₂) and Amorphous Rice Husk Silica (A-RHSiO₂). Moreover, it was found that SS-SiO₂ was of Quartz phase, C-RHSiO₂ was of Trydimite and Cristobalite. Through XRF detection, the highest SiO₂ purity was detected in SS-SiO₂ followed by C-RHSiO₂ and A-RHSiO₂ with purity percentages of 99.60%, 82.30% and 86.30% respectively. FTIR results clearly indicated silica (SiO₂) bonding 1056, 1064, 1047, 777, 790 and 798 cm⁻¹) increased as the crystallinity silica increased. The Cristobalite phase was detected in C-RH SiO₂ at the wavelength of 620 cm⁻¹. Morphological features as observed by FESEM analyses confirmed that, SS-SiO₂ and C-RH SiO₂ showed prominent coarse granular morphology.