Production of silica nanopowder from domestic siliceous mudstone

Chemical processes for the production of silica nanopowder from domestic siliceous mudstone (SM) were developed. Silica component yield leached out from SM was as high as 83 wt% at 100 °C and 60 min in 10 wt% of sodium hydroxide solution. Aqueous solution of silicic acid was prepared from the aqueous solution of sodium silicate by an ion exchange method. As the face velocity of the aqueous solution of sodium silicate in the ion exchange column increased from 0.5 to 2.0 cm/s, the sodium ion concentration increased from 10 to 50 ppm. The silica particles were made from the aqueous solution of silicic acid using a spray flame reactor. The average particle size increased with decreasing the air pressure or increasing the concentration of silicic acid. The particles were as small as 9 nm at 2.0 kgf/cm2 and 0.25 mol/l.