|
Korean Journal of Chemical Engineering, Vol.17, No.4, 401-408, 2000
Two-Step Ammoniation of By-Product Fluosilicic Acid to Produce High Quality Amorphous Silica
A two-step ammoniation was applied to neutralize the fluosilicic acid generated in the production of super-phosphate fertilizer, and to recover high-quality amorphous silica in the second step. A fluosilicic acid solution at 12.6% or 25.3 wt% H2SiF6 was reacted with aqueous ammonia, precipitating silica and subsequently leaving NH4F behind in the filtrate. Based on a fixed total of 7.2 moles of ammonia per mole of H2SiF6 (120% stoichiometry) ammonia at a molar ration of ammonia to H2SiF6 of 2 to 6 was charged in the first step and the balance of 5.2-1.2 in the second step in four combination sets of ammonia addition. At a combination of 3 and 4.2 molar ratios in the respective first and second steps, amorphous silica of 99.7% purity was readily produced in the second step while a majority of the impurities were precipitated in the first step. The two-step ammoniation was near completion despite a non-equilibrium reaction. However, rapid ammoniation favored the crystallization of ammonium fluosilicate. A sharp pH change occurred between 1.5 and 2.5 NH3/H2SiF6 molar ratios, indicating the rapid disappearance of SiF62- ion from the solution.
[References]
- Aulich HA, Eisenrith KH, Urbach HP, J. Mater. Sci., 19, 1710, 1984
- Blake HE, Stickney WA, "Utilization of By-product Fluosilicic Acid," Proc. of 3rd Mineral Waste Utilization Sym. Sponsored by U.S. Bu. Min. and IIT Res. Inst., Chicago, Illinois, 179, March 14-16, 1972
- Butler JN, "Ionic Equilibrium-A Mathematical Approach," Addison Wesley, Reading, Massachusetts, 1964
- Chemical Society, Stability Constants of Metal-ion Complexes, London, 1964
- Chieng PC, "Method of Production of High Purity Silica and Ammonium Fluoride," U.S. Patent 4,981,664, 1991
- Dragicevic T, Hraste M, Chem. Biochem. Eng. Q., 7(2), 89, 1993
- Dragicevic T, Hraste M, Chem. Biochem. Eng. Q., 8(3), 141, 1994
- Iler RK, "The Chemistry of Silica," John Wiley and Sons, New York, 1979
- Kirk F, Othmer DF, "Silica in Encyclopedia of Chemical Technology," third ed., John Wiley & Sons, New York, 30, 1982
- Min BH, "Introducing a New Product of Fluosilicic Acid for Use in Preventing Teeth from Decay," a News Report of Joongang Ilbo, Seoul, Feb. 18, 1997
- Nickerson JD, Burkert GM, "Silica Pigments from Fluosilicic Acid," U.S. Pat. 3,271,107, 1966
- Private Conversation with G.P. Panasyuk of N.S. Kurnakov Inst. of General and Inorg. Chem., Moscow, March 29, 1998
- Scholten JJF, van Montfoort A, "Process for Preparing Pure Silicon Dioxide Having High Mechanical Strength, as well as Silicon Dioxide Obtained by Applying This Process," European Patent 94,138, 1983
- Spijker R, "Process for the Preparation of Pure Silicon Dioxide," European Patent 94,139, 1983
- Thiessen PA, Koerner O, Z. Anorg. Allg. Chem., 189, 171, 1930
- Tsugeno M, Takako Y, Kubo M, Yuri Y, "Silica Particles and Process for Producing the Same," European Patent 435,513, 1991
- Weast RC, Astle MJ, "CRC Handbook of Chem. and Physics," 62nd ed., CRC Press, Inc., Boca Raton, Florida, 1981
- Yoon YR, Ju WH, Chem. Ind. Technol., 16(2), 98, 1998
[Cited By]
- Hilonga A, Kim JK, Sarawade PB, Quang DV, Shao GN, Elineema G, Kim HT, Korean Journal of Chemical Engineering, 29(11), 1643, 2012
- Elineema G, Kim JK, Hilonga A, Shao GN, Kim YN, Quang DV, Sarawade PB, Kim HT, Journal of Industrial and Engineering Chemistry, 19(1), 63, 2013
|