Preparation of Nano Silica-Sol from Siliceous Mudstone in Korea

摘要

Nano silica sol which has high surface area and excellent surface properties are chemicallystable inorganic materials and used for various applications in industry. Since the reserve ofsiliceous mudstone is abundant in Korea, the process development of preparation of silica solfrom mudstone economically is needed. Therefore this work was focused on utilizing theabundant 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 withsulfuric acid. After the removal of sodium ions in sodium silicate solution, the pH of silicatesolution had to be controlled above 9 for a stable silicate solution. The condensation betweensilicic acid species and silica nuclei surfaces has been studied at 20～80oc and pH 10～11 insilicate solutions with silica nuclei. From the results of FT-IR analysis, the intensity of silanolbond and hydrate bond decreased with increasing reaction temperature. As reactiontemperature increased up to 80oc, the intensity of silanol bond decreased and the intensity ofsiloxane bond increased. The silica sol prepared at 80oc included hydrate, and anhydroussilica particles was not formed in this study. Zeta potential of silica sol prepared at eachcondition was -40～-60 mV and it could be known that silica sol in this study was welldispersed. The silica sol, which size was about 5～10 nm, could be prepared by heating themixed solution of sodium silicate and silicate solution removed sodium ions.