| 摘要 |
PURPOSE:To obtain the the titled inexpensive and high-purity silica useful as electronic materials, substrates, etc., by dissolving cristobalite in shale with an alkali, separating the resultant slurry into a solid and liquid, drying and calcining the obtained silica gel particles. CONSTITUTION:Shale, such as rock containing 70-90wt.% SiO2 and having 60-120m<2>/g specific surface area is pulverized into powder having <=1mm particle diameter, which is then added to 0.5-3N NaOH and dissolved therein at 40-100 deg.C to provide a slurry (A) containing the silica dissolved therein. The resultant component (A) is then separated into a solid and liquid and HCl, etc., are added to the separated liquid to form silica gel, which is subsequently stirred to afford a slurry (B) consisting of particles having <=1mm particle diameter. The obtained slurry (B) is then washed under acidic condition and further separated into a solid and liquid. The resultant particles are subsequently dried and calcined to provide crude silica (C), and it is then repeatedly subjected to steps similar to those in obtaining the above-mentioned components (B) and (C). The obtained silica is then calcined at <=130 deg.C to afford the aimed high- purity silica from the shale as a raw material. |
