Abstract

EXTRACTION OF SILICA FROM RICE HUSK USING HEATING AND CHEMICAL TREATMENT

Dr. P. Senthamilselvan*, Miss S. Priyadharsini

.

Abstract

Rice husk is an abundant agricultural by-product, and its controlled combustion produces rice husk ash (RHA), a rich source of amorphous silica (SiO₂). This study focuses on the extraction of high-purity silica from RHA through optimized chemical and thermal treatments. Raw rice husk was subjected to controlled burning at different temperatures (500–800 °C) to obtain silica-rich ash. Pre-treatment with acid was carried out to remove metallic impurities, followed by alkali leaching using sodium hydroxide (NaOH) or potassium hydroxide (KOH), which converted silica into soluble silicates. The silicate solution was then subjected to acid precipitation with sulfuric acid (H₂SO₄) or hydrochloric acid (HCl), leading to the formation of silica gel. The gel was purified through washing, drying, and calcination to obtain fine silica powder. Characterization was conducted using X- ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), confirming the amorphous nature, surface morphology, functional groups, and thermal stability of the extracted silica. The resulting material was tested for potential applications in adsorbents, catalyst supports, cementitious materials, and nanocomposites. The findings demonstrate the industrial significance of RHA-derived silica and highlight its potential as a sustainable raw material within the framework of waste valorization and green chemistry.

Keywords: Rice husk ash, silica extraction, sodium silicate, acid precipitation, amorphous silica, sustainable materials, waste valorization.