Ceramics-Silikáty 67, (1) 20 - 28 (2023)

Rice husk ash (RHA) from a power generation plant has not been fully utilised although this substance contains a high amount of active silica. In this research, RHA was utilised as the precursor for the extraction of nano-silica using a simple precipitation method. The extraction of nano-silica contained three main steps; pre-treatment, dissolution and neutralising precipitation. The effects of the pre-treatment conditions, types of neutralisation acid, impurity (Na and Cl) removal method, solvent modification and surfactant (Tween80) addition on the characteristic properties of the extracted nano-silica, such as the morphology, size distribution and chemical composition, have been carefully studied in detail. By pre-treatment with hot 2M HCl (90 °C), neutralisation with 2M HCl, ageing the neutralised gel for 24 h, and finally washing the precipitate with hot water (90 °C) three times, the resulting nano-silica was ∼43 nm in size and had 99.75% purity. Using the ethanol/water solvent system with an addition of 0.2-0.3% Tween80 could remove the gel ageing step with final nano-silica particles of ∼36 nm.