Method for removing fluorine from lithium salt solution

Abstract

The invention discloses a method for removing fluorine from a lithium salt solution, and particularly relates to the technical field of lithium salt solution impurity removal, and the method comprises the following steps: S1, adding sodium hydroxide or lithium hydroxide into lithium salt solutions such as lithium sulfate and lithium chloride to adjust the lithium salt solutions to be alkaline, so that the lithium hydroxide solution can be directly used; s2, adding calcium hydrogen phosphate into the alkaline lithium salt solution, stirring, and filtering to obtain a low-fluorine lithium salt solution; compared with the prior art, the calcium hydrophosphate is innovatively selected as the fluorine removal agent for the lithium salt solution, the fluorine-removed lithium salt solution is obtained by adding the calcium hydrophosphate into the alkaline lithium salt solution, controlling the reaction time and filtering, the fluorine content of the fluorine-removed lithium salt solution is lower than 5 mg / L, the fluorine ion removal effect is good, and corrosion of fluorine ions to equipment is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of impurity removal of lithium salt solution, and more particularly to a method for removing fluorine from lithium salt solution. BACKGROUND

[0002] Lithium battery is a kind of battery using non-aqueous electrolyte solution with lithium metal or lithium alloy as positive / negative electrode material. Lithium battery can be roughly divided into two categories: lithium metal battery and lithium ion battery. Lithium ion battery does not contain metallic lithium, and is rechargeable. The safety, specific capacity, self-discharge rate and performance price ratio of lithium metal battery are superior to those of lithium ion battery. Due to the high energy density, long cycle life, no memory effect, high rated voltage and low self-discharge rate of lithium battery, it has been widely used in mobile phones, notebook computers and new energy vehicles.

[0003] There is a large amount of fluorine in lithium ore and battery disassembly recycled materials. The corrosion performance of fluorine seriously affects the normal operation of the equipment, shortens the service life of the equipment, and affects the quality of the battery. Therefore, it is necessary to remove fluorine from lithium salt.

[0004] The general fluorine removal process adopts calcium salt precipitation method, that is, lime is added to the lithium salt solution to combine fluorine ions with calcium ions to generate calcium fluoride precipitate and remove fluorine. The lime consumption is large, and the fluorine content of the treated lithium salt solution is generally not less than 20-30 mg / L. The fluorine removal effect cannot meet the production requirements.

[0005] Therefore, how to efficiently remove fluorine from lithium salt solution has become a problem to be solved in the lithium salt impurity removal technology. The present application provides a method for removing fluorine from lithium salt solution. SUMMARY

[0006] In order to overcome the above-mentioned defects of the prior art, the present application provides a method for removing fluorine from lithium salt solution, which solves the technical problems of poor fluorine ion removal effect and high corrosion of fluorine ions in the solution to the equipment in the prior art.

[0007] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a method for removing fluorine from lithium salt solution, comprising the following steps:

[0008] S1, preparing an alkaline lithium salt solution;

[0009] S2, adding calcium hydrogen phosphate to the alkaline lithium salt solution and stirring for 2-4 hours, the solution temperature is 40-70 DEG C, and the low-fluorine lithium salt solution is obtained by filtering.

[0010] Preferably, the preparation method of the alkaline lithium salt solution in step S1 is: adding lithium sulfate or lithium chloride lithium salt solution to sodium hydroxide or lithium hydroxide to make it alkaline.

[0011] Preferably, the lithium content in the alkaline lithium salt solution in step S1 is 7.33-8.94 g / L.

[0012] Preferably, the pH of the alkaline lithium salt solution in step S1 is greater than 8, so as to ensure suitable reaction conditions, and the calcium hydrogen phosphate can achieve the ideal defluorination effect under alkaline conditions.

[0013] Preferably, the calcium hydrogen phosphate is used as a defluorination agent in step S2, the calcium hydrogen phosphate can adsorb the fluorine in the lithium salt solution; the amount of calcium hydrogen phosphate is 8 g / L, the stirring time is 2-4 hours, and the solution temperature is 40-70 DEG C, so as to control the suitable material ratio, temperature and time to achieve the purpose of high-efficiency defluorination.

[0014] The technical effects and advantages of the present application are as follows:

[0015] The present application provides a method for removing fluorine from a lithium salt solution, calcium hydrogen phosphate is added to the alkaline lithium salt solution, the reaction time is controlled, and the lithium salt solution after defluorination is obtained by filtration. The fluorine content in the lithium salt solution after defluorination is less than 5 mg / L, the fluorine ion removal effect is good, and the corrosion of fluorine ions to equipment is avoided. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0017] Embodiment 1

[0018] The present application provides a method for removing fluorine from a lithium salt solution, which comprises the following steps:

[0019] S1, a lithium hydroxide solution with a lithium content of 7.68 g / L, a pH of 13 and a fluorine content of 40.10 mg / L is prepared;

[0020] S2, 8 g / L of calcium hydrogen phosphate is added to the lithium hydroxide solution in S1, the solution temperature is 40 DEG C, and the stirring time is 4 hours, then the filtrate is filtered, and the fluorine content of the filtrate is 6.5 mg / L.

[0021] Embodiment 2

[0022] The present application provides a method for removing fluorine from a lithium salt solution, which comprises the following steps:

[0023] S1, a lithium hydroxide solution with a lithium content of 7.68 g / L, a pH of 13 and a fluorine content of 40.10 mg / L is prepared;

[0024] S2, 14g / L of calcium hydrogen phosphate is added to the lithium hydroxide solution in S1, the solution temperature is 40 DEG C, after stirring for 4 hours, filtration is performed, and the fluorine content of the filtrate is 4mg / L.

[0025] Example 3

[0026] The application provides a method for removing fluorine from a lithium salt solution, which comprises the following steps:

[0027] S1, a lithium hydroxide solution with a lithium content of 7.33g / L is prepared, the pH is 13, and the fluorine content is 40.10mg / L;

[0028] S2, 14g / L of calcium hydrogen phosphate is added to the lithium hydroxide solution in S1, the solution temperature is 40 DEG C, after stirring for 4 hours, filtration is performed, and the fluorine content of the filtrate is 4mg / L.

[0029] Example 4

[0030] The application provides a method for removing fluorine from a lithium salt solution, which comprises the following steps:

[0031] S1, a lithium hydroxide solution with a lithium content of 8.94g / L is prepared, the pH is 13, and the fluorine content is 66.6mg / L;

[0032] S2, 14g / L of calcium hydrogen phosphate is added to the lithium hydroxide solution in S1, the solution temperature is 60 DEG C, after stirring for 4 hours, filtration is performed, and the fluorine content of the filtrate is 7.4mg / L.

[0033] It can be seen from the above data that the method provided by the application can efficiently remove fluorine ions in an alkaline lithium salt solution.

[0034] Finally: the above only describes the preferred embodiments of the application and is not used to limit the application, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A method for defluorination of a lithium salt solution, characterized by: The method comprises the following steps: S1, preparing a basic lithium salt solution; S2, adding calcium hydrogen phosphate into the basic lithium salt solution and stirring, and filtering to obtain a low-fluorine lithium salt solution.

2. The method of removing fluoride from a lithium salt solution of claim 1, wherein, The method for preparing the basic lithium salt solution in step S1 is as follows: adding sodium hydroxide or lithium hydroxide into a lithium sulfate or lithium chloride lithium salt solution to adjust the solution to be alkaline.

3. The method of removing fluoride from a lithium salt solution of claim 1, wherein, The lithium content in the basic lithium salt solution in step S1 is 7.33-8.94 g / L.

4. The method of removing fluoride from a lithium salt solution of claim 1, wherein, The pH of the basic lithium salt solution in step S1 is greater than 8.

5. The method of removing fluoride from a lithium salt solution of claim 1, wherein, In step S2, the amount of calcium hydrogen phosphate is 8-14 g / L, the solution temperature is 40-70 DEG C, and the stirring time is 2-4 hours.