Extraction of Silica Nanoparticles from Rice Husk Ash and its Characterization

Silica Nanoparticles (SiNPs), due to its tunable properties and composition, meets the needs in specified applications. Rice Husk (RH), an agricultural waste, abundant in amorphous silica has its extensive application in various industrial products. However, the presence of impurities in RHs makes the extraction process difficult and optimum experimental conditions are needed to achieve maximum yield with specific properties for its specified applications. In this work, Rice Husk Ash (RHA) is prepared from RH by acid leaching followed by silica gel extraction from RHA via controlled pyrolysis at three temperatures (700 degrees C, 750 degrees C and 800 degrees C). Pyrolyzed RHA is then dried and pulverized to get SiNPs. Characterization of SiNPs is done using UV-Vis Spectroscopy, X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). UV-Vis Spectroscopy and XRD analysis shows that the SiNPs extracted from RHA at 750 degrees C exhibited the highest peak at 260 nm and 2 theta=26 degrees respectively and XRD and SEM analysis show that crystallite and particle size is in close agreement with each other. The optimum temperature being 750 degrees C, silica gel formed at a pH 6 is more stable, transparent and thicker in comparison to the silica gel formed at varied pH. Moreover, the sodium silicate sample exhibits a bright green fluorescence and the intensity of fluorescence is higher for the sodium silicate prepared at 750 degrees C range than at any other temperature.