NANO-SILICA DERIVED FROM POWER GENERATION RICE HUSK ASH WASTE BY PRECIPITATION

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 nanosilica particles of ~36 nm.