Comparative assessment of chemical treatments on extraction potential of commercial grade silica from rice husk

In the present study, an attempt has been made to extract commercial grade amorphous silica nanoparticles from rice husk (RH) using four different chemicals (NaOH, KOH, Na2CO3, and K2CO3) and two washing solvents (water and ethanol). The elemental, structural, and morphological characterizations of the silica samples were carried out using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), atomic absorption spectrometry (AAS), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The combined NaOH and water treatment was found to be the most efficient method in terms of recovery of silica sample, while combined Na2CO3 and water treatment was more suitable for obtaining pure silica. No significant difference in the percentage recovery of silica was observed between the two washing treatments at p < 0.05. Scanning electron micrographs of the Na2CO3-cum-water and K2CO3-cum-water treated samples showed nonagglomerated silica nanoparticles. The XRD analysis of silica obtained from these two treatments was also free from any sharp peaks illustrating pure amorphous structure of silica. EDS and AAS study of K2CO3-cum-water treated samples showed higher mineral impurities compared to Na2CO3-cum-water treated sample. It could be inferred that silica obtained from Na2CO3 and water washing treatment can be used for extraction of metallurgical grade silicon.