(190c) Preparation of Nano Silica-Sol From Siliceous Mudstone In Korea

Nano silica sol which has high surface area and excellent surface properties are chemically stable inorganic materials and used for various applications in industry. Since the reserve of siliceous mudstone is abundant in Korea, the process development of preparation of silica sol from mudstone economically is needed. Therefore this work was focused on utilizing the abundant but less used minerals such as siliceous mudstone to synthesize nano silica sol. Sodium silicate solution from siliceous mudstone by NaOH leaching was used as precursor, and the formation of silica sol from sodium silicate solution was investigated in this study. The SiO2 content of 2% in sodium silicate solution was proper to oxidize sodium silicate with sulfuric acid. After the removal of sodium ions in sodium silicate solution, the pH of silicate solution had to be controlled above 9 for a stable silicate solution. The condensation between silicic acid species and silica nuclei surfaces has been studied at 20°80°C and pH 10°11 in silicate solutions with silica nuclei. From the results of FT-IR analysis, the intensity of silanol bond and hydrate bond decreased with increasing reaction temperature. As reaction temperature increased up to 80°C, the intensity of silanol bond decreased and the intensity of siloxane bond increased. The silica sol prepared at 80°C included hydrate, and anhydrous silica particles was not formed in this study. Zeta potential of silica sol prepared at each condition was -40°-60 mV and it could be known that silica sol in this study was well dispersed. The silica sol, which size was about 5°10 nm, could be prepared by heating the mixed solution of sodium silicate and silicate solution removed sodium ions.