Monovalent ion selectivity electrodialysis device and preparation method of lithium chloride concentrated liquor

Abstract

The invention discloses a monovalent ion selectivity electrodialysis device and a method for preparing lithium chloride concentrated liquor through the monovalent ion selectivity electrodialysis device. A high-magnesium solution containing Li+ serves as a raw material, monovalent ion selectivity of a membrane stack in the monovalent ion selectivity electrodialysis device is utilized, a mixed solution of NaNO3 and HNO3 serves as electrode liquor, Li+ is concentrated and enriched, Mg2+, SO42-, boric acid radicals and the like are intercepted, therefore, efficient separation of Li+ and impurity ions such as Mg2+, SO42- and boric acid radicals and concentration of Li+ are achieved, the concentration of Mg2+ and Cl- in electrode circulating liquor and the pH value of the electrode circulating liquor are controlled, and the lithium chloride concentrated liquor is obtained. Generation of Mg(OH)2 precipitates can be avoided, the cycle period of the electrode liquor can be effectively prolonged, losses of polar membranes can be reduced, and the parking maintenance cost can be reduced.

Description

technical field [0001] The invention belongs to the technical field of inorganic salt preparation, and in particular relates to a monovalent ion selective electrodialysis device and a method for preparing lithium chloride concentrated solution by using the monovalent ion selective electrodialysis device. Background technique [0002] As an important strategic resource for human beings in the new era, new energy lithium metal has been widely used in many fields such as lithium battery, glass and ceramics, lithium-based grease, refrigeration, medicine, metallurgy and nuclear industry. In recent years, the explosive growth of lithium batteries in the application fields of electronic products, new energy vehicles, and large-scale energy storage has driven rapid changes in the demand for basic lithium salt and alkali products such as lithium carbonate, lithium chloride, and lithium hydroxide at home and abroad. Lithium mainly exists in nature in two forms of solid ore and liquid ...

AI Technical Summary

Problems solved by technology

However, since most of the natural lithium-containing solutions are chloride systems, Cl - During the electrodialysis process, it will pass through the electrode membrane and enter the electrode solution, resulting in the Cl produced by the anode reaction 2 gradually increased, and the H produced by the anode + will be less than the OH produced by the cathode - , causing the pH of the electrode solution to increase; in addition, the high magnesium solution (referring to the Mg in it 2+ content reached a non-negligible level) Mg in 2+ It will also enter the electrode solution through the polar membrane, when Mg 2+ When the concentration reaches a certain concentration, the same as the OH produced by the cathode - Combine to form Mg(OH) 2 Precipitation, affecting long-term operation of electrodialysis

[0010] But, adopt sulfate (such as Na in the prior art 2 SO 4 ) solution as the technical solution of the electrode solution also has certain problems, such as in the process of electrodialysis, the SO in the electrode solution 4 2- It will enter the concentrated solution through the polar membrane as ions with the same name, resulting in the SO in the LiCl concentrated solution 4 2- content increased, given that Li 2 CO 3 LiCl concentrate is used as an intermediate product in the preparation process of high-purity lithium salts such as LiOH, LiOH, etc., so it will lead to the need to add SO at the back end of electrodialysis 4 2- The steps such as removal have increased the difficulty of the preparation process of these high-purity lithium saline

[0011] At present, some documents have also reported the method of extracting lithium from high-magnesium-lithium ratio salt lake brine by electrodialysis, such as: (1) a method of electrodialysis extracting lithium from high-magnesium solution, using 0.25mol / LNa 2 SO 4 solution as the electrode solution, and in the process of electrodialysis by adding H 2 SO 4 Keep its pH value at about 2, and keep the Cl in the electrode solution by continuously replenishing new electrode solution - The content is not higher than 4g / L, thus avoiding the Mg(OH) 2 Precipitation and Cl 2 (2) A method of concentrating lithium in the eluent of adsorption lithium extraction by conventional electrodialysis, which also uses 0.25mol / L Na 2 SO 4 The solution is used as the electrode solution, but the control of the pH value is not mentioned

[0012] In addition, there are also some literature reports that use HCl solution with a pH of 2, H 2 SO 4 solution or HNO 3 The solution is used as the electrode solution, and the pH is kept at 2 by adding the corresponding acid during the electrodialysis process, but the electrode solution is not suitable for processing high-magnesium solutions. At this time, Mg(OH) is generated on the cathode side 2 There is a high risk of precipitation

[0013] How to control the cathode side Mg when extracting lithium salt from high magnesium solution 2+ and OH - The concentration is very important. Too low salinity or acidity may cause water decomposition in the cathode chamber or the membrane surface near the cathode to generate a large amount of Mg(OH) 2 Precipitation, forcing the equipment to stop, greatly increasing maintenance costs; and using sulfate solution as the electrode solution will lead to SO in the concentrated solution 4 2- The content is high, which is not conducive to the process back-end Li 2 CO 3 , LiOH and other high-purity lithium saline production

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