Method for preparing high purity lithium fluoride

Abstract

The invention in particular relates to a method for preparing lithium fluoride. The method for preparing the high-purity lithium fluoride is mainly characterized by comprising the following steps: (1) putting a mixture of the lithium fluoride and lithium chloride or the lithium chloride or lithium acetate in deionized water and stirring the solution so as to make the mixture sufficiently dissolve and prepare a meta acid aqueous solution of which the pH value is between 0.1 and 7; (2) under a stirring state, quickly dropping a solution of two simple substances of saturated ammonium fluoride or ammonium hydrogen fluoride or ammonia and fluorine hydride in the aqueous solution of the step (1) so as to obtain lithium fluoride precipitates, and continuing to stir for 0.5 to 1 hour and standing for 1 to 2 hours; and (3) through the step (1) and the step (2), finishing forming the lithium fluoride into the precipitates which are not dissolved in the water, filtering and drying the lithium fluoride precipitates and washing the precipitates for 3 to 5 times, and drying the obtained lithium fluoride in vacuum for 1 to 2 hours at a temperature of between 100 and 200 DEG C. The method has the advantages that the purities of the prepared lithium fluoride meet the following requirements: the purity of lithium fluoride (LiF) is more than or equal to 99.99 percent; the purity of silicon dioxide (SiO2) is less than or equal to 4ppm; the purity of heavy metal is less than or equal to that of iron of which the purity is less than or equal to 1 ppm; and the purity of the total weight of other metals (metered by Ca, Mg and Al) is less than or equal to 1 ppm.

Description

Technical field: [0001] The present invention specifically relates to a method for preparing lithium fluoride. Background technique: [0002] With the increasing demand for high-purity lithium fluoride in traditional application fields and the continuous emergence of some new application fields (such as applying it to the raw materials for the synthesis of lithium hexafluorophosphate, long-distance communication optical fiber materials, etc.), the preparation of high-purity lithium fluoride is becoming more and more important. People have paid more and more attention to it. In the late 1980s, reports on the preparation technology of high-purity lithium fluoride began to appear internationally. The methods introduced successively include direct preparation, ion exchange preparation, and extraction preparation. [0003] The direct preparation method is the main method for the early preparation of high-purity LiF, and the raw material is generally solid Li 2 CO 3 with hydrofl...

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Problems solved by technology

[0010] The ion exchange preparation method makes full use of the by-product Na of the phosphate fertilizer plant 2 SiF 6 , which effectively reduces the production cost of LiF, its main disadvantage is that the content of silicon and some transition metal impurity elements in the prepared high-purity LiF is still high, the reason may be that the Na 2 SiF 6 Insufficient pretreatment, so that the high-purity LiF prepared by this method is not suitable for fields sensitive to these impurity ions

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