Size-dependent physicochemical properties of mesoporous nanosilica produced from natural quartz sand using three different methods

Mesoporous high-surface-area silica (SiO2) nanoparticles were produced from natural quartz sand (orthoquartzite) using three processing methods namely sol-gel, sonication, and spray pyrolysis. The inexpensive precursor was extracted from the quartz sand by alkali extraction followed by acid precipitation, which was used for all the three methods. The effects of production methods were investigated by various characterization techniques. The physicochemical properties of the obtained nanoparticles were compared to explore the effect of size and porosity on their electronic, optical, mechanical, and electrical qualities. The produced SiO2 nanoparticles were found to have an amorphous high surface area in the range of 178-322 m(2) g(-1) and a uniform size distribution with the high purity and spherical morphology. These particles formed a mesoporous material with an average pore diameter of 10-26 nm. It was found that the surface area (178 < 284 < 322 m(2) g(-1)) and band gap (5.41 < 5.43 < 5.45 eV) of the particles increased with a decrease in particle size (39 > 30 > 10 nm) when the process method was changed from sol-gel to sonication and from sonication to spray pyrolysis. This study provides useful insights and guidance for the preparation of mesoporous SiO2 nanoparticles from quartz sand and throws light on how physicochemical properties are influenced by process methods and particle size.