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Abstract

The preparation of potassium fluorosilicate (K2SiF6) from fluorosilicic acid as an inexpensive by-product of Iraqi phosphate fertilizer plant has been investigated. The effect of molar ratio (KCl/H2SiF6), temperature and agitation on the purity and conversion were studied. The reaction was performed at different temperatures( 25-60 ºC) for 1 hr under stirring, the precipitated material was separated from reaction mixture by filtration and dried under vacuum at1*10-1 bar and 150 ºC. The results indicate that using higher molar ratio led to obtain a gelatinous form of K2SiF6 which is difficult to separate from reaction solution .Using higher reaction temperature was permitted to use higher molar ratio and getting high purity filterable product with higher conversion. Agitation was improved the conversion due to increase the crystal growth rate of K2SiF6. High purity of potassium fluorosilicate (99.25%) with a maximum conversion(71.04%) was obtained by using molar ratio(1.4),Temperature(60 ºC) ,and agitation(600rpm).The level of essential impurities (Cu ,Fe ,Ni)in the preparative material is lower than 0.05% which makes this material more suitable for using as raw material for silicon preparation by electro deposition method.

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