A method for recovering electrode discharge liquid in the electrodialysis lithium extraction process of high-magnesium solution

Abstract

The invention relates to a recovery method of an electrode discharge solution in a high-magnesium solution electrodialysis lithium extraction process. The method comprises the following steps: mixing the electrode discharge solution generated in the electrodialysis lithium extraction process with a NaHSO3 or Na2SO3 solution, and reacting for 2-5 minutes to obtain a dechlorinated solution of which the free chlorine content is less than 0.1 mg / L; by using the dechlorinated solution as a desalting raw solution, carrying out concentration by a one-step or two-stage ion exchange membrane electrodialysis process, obtaining concentrated produced water with the lithium content of 10-16 g / L in the concentration chamber, and obtaining desalted produced water in the desalting chamber; and finally, returning the primary desalted produced water obtained in the desalting chamber to the electrodialysis lithium extraction process to be used for preparing the electrodialysis lithium extraction raw solution. The method is simple to operate, has the advantages of small occupied area, investment saving, low cost and the like, and can implement synchronization, complete recovery and zero discharge on the lithium and water quantities in the electrode discharge solution, thereby enhancing the resource utilization efficiency and lowering the electrodialysis lithium extraction operating cost.

Description

technical field [0001] The invention relates to a method for recovering electrode discharge liquid in the electrodialysis lithium extraction process of a high-magnesium solution. Background technique [0002] When liquid lithium minerals such as high-magnesium-lithium ratio salt lakes, geothermal, and oilfield waters are used as raw materials, and ion-exchange membrane electrodialysis is used to selectively separate and extract lithium salts from them, the electrode flushing solution needs to be discharged quantitatively and collected after a certain period of circulation. Supplement new liquid to control the content of magnesium ions and chloride ions, prevent the formation of magnesium hydroxide precipitation, avoid the large amount of chlorine gas from polluting the surrounding environment, and ensure the safe and stable operation of the process. [0003] These effluents are produced by nitrate systems (such as NaNO 3 +HNO 3 ) or sulfate system (such as Na 2 SO 4 +H ...

AI Technical Summary

Problems solved by technology

Compared with electrodialysis desalination solution and concentrated solution, these electrodes discharge a small amount of liquid, but if they are not recycled, it will not only waste fresh water and expensive lithium resources, increase costs, but also cause certain damage to brine resources and the surrounding environment. Pollution

[0004] For the purpose of recycling the acidic electrode discharge liquid containing more magnesium ions and free chlorine, there is no simple and mature technology that can be applied at present. In order to avoid the corrosion of equipment, most enterprises adopt the method of direct discharge to deal with these discharge liquids. The environment has caused pollution that cannot be ignored

However, the existing disclosed lithium extraction methods in solution are not invented for the treatment of acidic electrode discharge liquid containing more magnesium ions and free chlorine, and cannot independently enrich lithium ions to 10-16g / At the same time, the amount of water in it is recycled

Chinese patent 200310122238.3 discloses a method for separating magnesium and concentrating lithium from salt lake brine with a high magnesium-lithium ratio, using monovalent ion-selective ion-exchange membrane electrodialysis to realize the separation of magnesium and lithium and the concentration of lithium at the same time, and the concentration of lithium in the concentrated solution The content can be increased to 10g / L or higher, but the patent only limits the desalination stock solution to salt lake brine with a magnesium-lithium ratio of 1-300 and the concentrated brine obtained by evaporation

In addition, the natural evaporation method can only concentrate lithium but cannot separate the magnesium in it, and cannot recover most of the water in it. Moreover, forced evaporation still has problems such as high energy consumption and uncontrollable costs; the ion exchange method can only remove magnesium, and it is difficult to remove lithium. Concentrate to more than 5g / L; the nanofiltration method has a very low interception efficiency for magnesium in the discharge liquid, and cannot concentrate the lithium in it; although the reverse osmosis method can recover part of the fresh water in the discharge liquid, it cannot remove the magnesium in it , the lithium ion in the concentrated product water is lower than 5g / L

In addition, when the free chlorine in the feed liquid is higher than 0.5mg / L, under its long-term action, it will cause the separation media such as ion exchange resins, ion exchange membranes, nanofiltration membranes, and reverse osmosis membranes to degrade or The cross-linking agent is broken and gradually damaged

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