Biosilica forming by sol-gel extraction method of rice husk ash

Abstract

Indonesia, as an agricultural country, produces much waste, especially from rice husk, which is a source of silica (SiO2) production. Rice husk contains about 87% - 97% SiO2 after complete combustion. SiO2 extraction from ash of rice husk is carried out using an extraction process of solid-liquid with an alkaline as a solution solvent. The solidliquid extraction process was done with 10 grams mass of rice husk ash added with 80 ml of potassium hydroxide (KOH) solution with a concentration of 10%, 15%, and 20% to extract the SiO2 content with an operating time of 60 minutes. After the extraction process is complete, the solution is added with 1 N hydrochloric acid (HCl) to precipitate the SiO2. The SiO2 formed is then separated from the rest of the solution by filtration. The drying process is carried out to remove the moisture content of the resulting SiO2. In this systematic study, HCl-washed rice husks were carried out in a muffle furnace for 60 minutes. The results showed that the samples produced SiO2 with a polycrystalline structure, as confirmed by the results of analysis of the Energy-Dispersive X-ray Spectroscopy (EDS) that could be produced by solid-liquid extraction of KOH from rice husks ash. The amorphous SiO2 has potential application as natural filler in rubber and environmentally friendly natural compounds.