Patent ID: 7799303

Claim:
A method of preparing silica nanoparticles from siliceous mudstone, comprising: heat-treating siliceous mudstone to remove water; leaching the sliceous mudstone with hydrochloric acid to remove impurities, thereby forming a silica constituent; leaching the silica constituent with sodium hydroxide, thereby forming a sodium silicate aqueous solution; passing the sodium silicate aqueous solution over an ion-exchange resin at a linear velocity of 2.0 to 0.5 cm/sec to remove a sodium constituent from the sodium silicate aqueous solution, thereby producing a silicate aqueous solution having a sodium concentration of 50 ppm or less; flame spray pyrolyzing the silicate aqueous solution with a flame reactor to prepare nanoparticles from the silicate aqueous solution, the nanoparticles having an average particle dimension of 9 to 57 nm, and the flame reactor including five tubes: a first tube through which the silicate aqueous solution, which is aerosolized by high-pressure spraying a dispersed air in a proportion of 1 to 3% by volume of a flow quantity of the whole gas, is injected, a second tube into which an argon gas flows by 7 to 8%, a third tube into which a hydrogen gas flows by 3 to 14%, a fourth tube into which an oxygen gas flows by 21 to 24%, and a fifth tube into which an air flows by 55 to 63%; and controlling the average particle dimension of the silica nanoparticles by varying the pressure of the dispersed air in the first tube from 0.5 to 2.0 kgf/cm 2 .