A green sol–gel route for the synthesis of structurally controlled silica particles from rice husk for dental composite filler

A green sol–gel route for preparing structurally controlled non-crystalline silica particles from rice husk was developed. At optimal conditions, amorphous spherical silica particles with a surface area of ∼364 m2 g−1 and particle sizes ranging from 75 to 252 nm were synthesised through the addition of phosphoric acid into sodium silicate derived from rice husk. The powder was mesoporous with a pore size of ∼8 nm. It was observed that the degree of agglomeration of the powder was highly dependent on the sodium silicate precursor concentration, pH and solvent. TEM, SEM, N2 adsorption/desorption, XRD and FTIR techniques were used to characterise the silica powder. The route developed is simple and environmental friendly and could help solve pollution problems. The silica produced is suitable for use as a filler in dental restoration composites.