Synthesis of hydrophobically modified, rice husk-derived spherical silica particles

Rice husks are a renewable source of silicon because of their high silica content. In this study, hydrophobic spherical silica particles, which are widely used in several industries, were synthesized using rice husk-derived silica. Silica was extracted as sodium silicate using a one-pot alkali hydrothermal treatment and ball milling equipment. Spherical particles of silica were synthesized by the precipitation of sodium silicate using acetic acid and a polyethylene glycol additive; subsequently they were modified with triethoxyvinylsilane to obtain hydrophobic silica particles. The presence of C-H on the surface of the silica particles was confirmed by Fourier-transform infrared spectroscopy, which revealed the hydrophobicity of the particles. The contact angle of the modified spherical silica particles was 159 degrees, whereas that of the unmodified silica particles was 0 degrees. The hydrophobicity was confirmed by dispersing the particles in water. This study thus demonstrated that rice husk-derived silica can serve as an alternative to chemically derived silica; moreover, the material can be integrated into existing silica processes and used as a polymer filler.