Abstract
A two-step ammoniation was applied to neutralize the fluosilicic acid generated in the production of superphosphate 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 ratio 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 SiF 2−6 ion from the solution.
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References
Aulich, H. A., Eisenrith, K.-H. and Urbach, H.-P., “New Methods to Prepare High-purity Silica,”J. of Mat. Sci.,19, 1710 (1984).
Blake, H. E. and Stickney, W. A., “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, J.N., “Ionic Equilibrium-A Mathematical Approach,” Addison-Wesley, Reading, Massachusetts (1964).
Chemical Society, Stability Constants of Metal-ion Complexes, London (1964).
Chieng, P. C., “Method of Production of High Purity Silica and Ammonium Fluoride,” U. S. Patent 4, 981, 664 (1991).
Dragičevi’c, T. and Hraste, M., “Particle Size Distribution of Silica Produced by Neutralization of Fluosilicic Acid,”Chem. Biochem. Eng. Q.,7(2), 89 (1993).
Dragičevi’c, T. and Hraste, M., “Surface Area of Silica Produced by Neutralization of Fluosilicic Acid,”Chem. Biochem. Eng. Q.,8(3), 141 (1994).
Iler, R. K., “The Chemistry of Silica,” John Wiley and Sons, New York (1979).
Kirk, F. and Othmer, D. F., “Silica in Encyclopedia of Chemical Technology,” third ed., John Wiley & Sons, New York,30 (1982).
Min, B. H., “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, J. D. and Burkert, G. M., “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, J. J. F. and 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 P. A. and Koerner, O.,Z. Anorg. Allg. Chem.,189, 171 (1930).
Tsugeno, M., Takako, Y., Kubo, M. and Yuri, Y., “Silica Particles and Process for Producing the Same,” European Patent 435,513 (1991).
Weast, R. C. and Astle, M. J., “CRC Handbook of Chem. and Physics,” 62nd ed., CRC Press, Inc., Boca Raton, Florida (1981-1982).
Yoon, Y. R. and Ju, W. H., “Production and Application of Silica Powders (in Korean),”Chem. Industry and Tech.,16(2), 98 (1998).
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Yu, H.S., Rhee, KI., Lee, C.K. et al. Two-step ammoniation of by-product fluosilicic acid to produce high quality amorphous silica. Korean J. Chem. Eng. 17, 401–408 (2000). https://doi.org/10.1007/BF02706850
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DOI: https://doi.org/10.1007/BF02706850