Process method for preparing lithium hydroxide from lithium phosphate

Abstract

The invention discloses a process method for preparing lithium hydroxide by using lithium phosphate, which comprises the following steps: dissolving lithium phosphate by using hydrochloric acid to obtain a mixed solution of lithium dihydrogen phosphate and lithium chloride, and carrying out membrane separation to obtain a high-purity lithium chloride solution at a water production end; after a water producing end is subjected to precipitation and impurity removal, alkali liquor is added, and a high-purity lithium hydroxide monohydrate product is obtained through the steps of concentration crystallization, washing filtration and the like; and mixing the concentrated water end with the lithium precipitation mother liquor and the washing clear liquid, adjusting the pH value by using alkali liquor to obtain lithium phosphate precipitation, and taking the lithium phosphate precipitation as a raw material again to enter the initial step. According to the invention, lithium phosphate is used as a raw material, is insoluble in water, and can be repeatedly washed to obtain high purity; lithium dihydrogen phosphate and lithium chloride are separated by adopting a membrane method, so that the energy consumption is extremely low and the recovery rate is high. According to the whole technological method, almost no lithium element is lost in the process, the recovery rate of the lithium element exceeds 99%, only acid and alkali are introduced in the process, the agent cost is low, few impurities are introduced, and the product purity is high.

Description

technical field [0001] The invention relates to the technical field of lithium hydroxide preparation, in particular to a process method for preparing lithium hydroxide from lithium phosphate. Background technique [0002] Lithium hydroxide monohydrate is an important material for the manufacture of lithium-ion batteries, and also has important applications in metallurgy, chemical industry, national defense and other fields. At present, the methods for preparing lithium hydroxide monohydrate mainly include the following methods: 1) ion exchange membrane electrolysis method: electrolyzing lithium sulfate or lithium chloride solution, the cathode obtains lithium hydroxide solution, and the anode obtains corresponding sulfuric acid or hydrochloric acid, but the electrolysis method can Consumption is higher; 2) lithium carbonate causticization method: add calcium hydroxide in lithium carbonate solution, generate calcium carbonate precipitation, and mother liquor is high-purity li...

AI Technical Summary

Problems solved by technology

The method for preparing lithium hydroxide monohydrate mainly contains the following methods at present: 1) ion-exchange membrane electrolysis method: electrolytic lithium sulfate or lithium chloride solution, negative electrode obtains lithium hydroxide solution, and anode obtains corresponding sulfuric acid or hydrochloric acid, but electrolytic method can Consumption is higher; 2) lithium carbonate causticization method: add calcium hydroxide in lithium carbonate solution, generate calcium carbonate precipitation, mother liquor is the lithium hydroxide solution of high purity, but this method relies on the raw material of lithium carbonate of high purity; 3) Preparation method from lithium chloride: add sodium hydroxide to lithium chloride solution, use lithium hydroxide and other salt solubility differences, evaporate and crystallize to obtain lithium hydroxide monohydrate, but this method depends on high-purity lithium chloride raw material

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