CN-121974450-A - Efficient lithium resource recovery method based on displacement dialysis process

CN121974450ACN 121974450 ACN121974450 ACN 121974450ACN-121974450-A

Abstract

The invention provides a high-efficiency lithium resource recovery method based on a displacement dialysis process, which belongs to the technical field of industrial wastewater treatment and resource recovery, and relies on a four-compartment displacement dialysis device as a core to realize the lithium fluoride wastewater by combining units such as defluorination chelating purification, bipolar membrane electrodialysis in-situ alkali production, reverse osmosis/MVR coupled crystallization and the like And The method comprises the specific steps of carrying out four-compartment displacement dialysis to generate lithium chloride and sodium fluoride solution, purifying and concentrating the lithium chloride, preparing lithium hydroxide by bipolar membrane electrodialysis to recycle and adjust pH, reacting the rest with sodium carbonate to generate high-purity lithium carbonate, and carrying out pH adjustment, reverse osmosis concentration and MVR crystallization on the sodium fluoride to obtain the high-purity product. The invention creatively combines the technologies of replacement dialysis, bipolar membrane electrolysis and evaporative crystallization, so that the recovery rates of lithium and fluorine are respectively more than or equal to 98% and more than or equal to 95%, the water reuse rate is more than or equal to 90%, no exogenous alkali liquor is added in the whole process, and the invention is suitable for high-efficiency low-carbon treatment of high-fluorine wastewater in the lithium electricity industry.

Inventors

LI LU
LIU LUOFENG
WANG LIANG
XUE XIDONG
MA LAIBO
REN TINGTING
TANG GONGWEN
WANG MIN

Assignees

自然资源部天津海水淡化与综合利用研究所

Dates

Publication Date: 20260505
Application Date: 20260228

Claims (7)

1. The method is characterized in that the method adopts a lithium fluoride wastewater treatment system to treat wastewater, wherein the lithium fluoride wastewater treatment system comprises a four-compartment displacement dialysis device, a fluorine removal resin tower, a chelating resin tower, an MVR evaporation crystallizer, a lithium carbonate reaction kettle, a bipolar membrane electrodialysis unit and a reverse osmosis membrane component; The four-compartment replacement dialysis device is provided with a first compartment, a second compartment, a third compartment and a fourth compartment in turn along the water flow direction, wherein adjacent compartments are separated by a cation exchange membrane C or an anion exchange membrane A, a water outlet of the second compartment is communicated with a water inlet of a fluorine removal resin tower, a water inlet of a chelating resin tower and a water inlet of an MVR evaporation crystallizer in turn, a liquid outlet of the MVR evaporation crystallizer is communicated with a feed inlet of a lithium carbonate reaction kettle and a feed inlet of a bipolar membrane electrodialysis unit respectively, an alkali outlet of the bipolar membrane electrodialysis unit is communicated with a pH regulating liquid inlet of the first compartment, a byproduct outlet of the lithium carbonate reaction kettle is communicated with a sodium chloride supply inlet of the third compartment, a water outlet of the fourth compartment is communicated with a water inlet of a reverse osmosis membrane assembly, and a concentrated water outlet of the reverse osmosis membrane assembly is communicated with the other water inlet of the MVR evaporation crystallizer; The method further comprises the following steps: step 1, pumping lithium fluoride waste water with pH value regulated to 3-4 into a first compartment of a four-compartment displacement dialysis device, pumping sodium chloride solution into a third compartment, respectively introducing clear water into the second compartment and the fourth compartment, starting the four-compartment displacement dialysis device, applying a direct current electric field of 10-30V, and driving the first compartment under the electric field Migration to compartment two through the cation exchange membrane and migration to compartment two in compartment three Forming a lithium chloride solution in compartment one The Na+ migrates to the fourth compartment through the anion exchange membrane to form sodium fluoride solution with Na+ migrated to the fourth compartment in the third compartment; step 2, pumping the lithium chloride solution generated in the second compartment into a fluorine-removing resin tower to remove the residual solution Pumping the purified lithium chloride solution into a MVR evaporation crystallizer, evaporating and concentrating to obtain saturated lithium chloride solution with the concentration of 1.3wt.%, and recovering distilled water generated in the evaporation process as reverse osmosis produced water; step 3, dividing the saturated lithium chloride solution obtained in the step 2 into two parts, pumping one part into a bipolar membrane electrodialysis unit, preparing lithium hydroxide through bipolar membrane hydrolysis and ion migration, wherein the lithium hydroxide is reused for regulating the pH value of lithium fluoride wastewater in a compartment one in the step 1; Pumping the sodium fluoride solution generated in the fourth compartment into a pH adjusting tank, adding NaOH solution to adjust the pH to 7-8, allowing the adjusted sodium fluoride solution to enter a reverse osmosis membrane assembly, performing membrane separation and concentration for 5-10 times, allowing the concentrated sodium fluoride solution to enter an MVR evaporation crystallizer, performing evaporation crystallization at 60-80 ℃, and performing solid-liquid separation to obtain a sodium fluoride product.
2. The method for efficient recovery of lithium resources by a displacement dialysis process according to claim 1, wherein in said step 2, the resin filled in the fluorine removal resin column is A modified resin, said The particle diameter of the modified resin is 0.3-0.8mm, and the specific surface area is 80-120 。
3. The efficient lithium resource recovery method based on the displacement dialysis process according to claim 1, wherein in the step 2, the resin filled in the chelating resin tower is D418 type chelating resin, the working exchange capacity of the D418 type chelating resin is more than or equal to 1.5mmol/g, and the use temperature is less than or equal to 60 ℃.
4. The method for efficient recovery of lithium resources based on a displacement dialysis process according to claim 1, wherein in said step 1, the initial concentration of the sodium chloride solution is 15 to 20 The initial volume ratio of compartment one, compartment two, compartment three, compartment four is 4:1:1.6:1.6.
5. The method for efficient recovery of lithium resources based on a displacement dialysis process according to claim 1, wherein in step 3, the operating parameters of the bipolar membrane electrodialysis unit are: voltage of 2-5V and current density of 100-200 The temperature of the membrane stack is 25-40 A feed flow rate of 10 to 20 。
6. The method for efficiently recovering lithium resources based on a displacement dialysis process according to claim 1, wherein in the step 4, the reverse osmosis membrane module adopts an anti-pollution aromatic polyamide composite membrane, and the operating pressure is 1.5-2.5 At a temperature of 20-30 DEG C The flow rate of the water inlet is 1.0 to 1.5 。
7. The efficient lithium resource recovery method based on a displacement dialysis process according to claim 1, wherein in the step 3, the reaction temperature of the lithium carbonate reaction kettle is 60-80 Stirring rotation speed is 200-300 The addition amount of the sodium carbonate solution and the lithium chloride solution Molar ratio of (2) is 。

Description

Efficient lithium resource recovery method based on displacement dialysis process Technical Field The invention belongs to the technical field of industrial wastewater treatment and resource recovery, and particularly relates to a lithium resource efficient recovery method based on a displacement dialysis process. Background With the rapid development of the global lithium battery industry, the yield of the lithium fluoride serving as a key raw material of lithium battery electrolyte and cathode material is continuously increased, and the discharge amount of the wastewater produced in the lithium fluoride production is increased year by year. The waste water contains high concentration(Typically 300-500 mg/L) and(Typically 1000-2000 mg/L) with concomitant use、、If the heavy metal ions are improperly treated, not only the waste of valuable resources such as lithium, fluorine and the like can be caused, but also serious soil and water pollution problems can be caused. In the existing lithium fluoride wastewater treatment process, the most widely applied method is a 'fractional precipitation method', wherein calcium chloride is firstly added into wastewater to lead the wastewater to beCalcium fluoride%) And removing the form precipitation, and adding sodium carbonate into the wastewater after defluorination to precipitate and recycle Li+ in the form of lithium carbonate. However, this process has the following problems: (1) Waste of resources and secondary pollution: The calcium fluoride is precipitated in the form of calcium fluoride, and the calcium fluoride belongs to HW32 hazardous waste, the treatment cost is up to 2000-3000 yuan/ton, the fluorine resource recovery is not realized, and the hazardous waste disposal pressure is generated; (2) High medicine consumption and high cost 、The precipitation is complete, and excessive addition of calcium chloride and sodium carbonate is needed, so that the cost of the medicament accounts for 50% of the total treatment cost, and a large amount of the medicament is introduced、Plasma impurity ions, which affect the purity of the subsequent resource recovery; (3) The water recycling rate is low, namely high-salt wastewater (the salt content is usually more than 5%) generated after precipitation needs direct evaporation treatment, the energy consumption is extremely high, and the water recycling rate is generally lower than 50%; (4) The purity of the product is low, the purity of the lithium carbonate obtained by a precipitation method is usually only 95-98%, and the requirement of the lithium battery industry on high-purity lithium carbonate (the purity is more than or equal to 99.5%) is difficult to meet. To solve the above problems, some improved processes have been proposed in the related art. For example, patent CN202111450265.8 discloses a method for extracting lithium from high-sodium lithium-containing brine, which adopts a resin adsorption method to selectively adsorb li+, but the method has two main disadvantages: (1) The regeneration of the resin needs to consume 5% -10% of hydrochloric acid and sodium hydroxide, so that secondary pollution is generated; (2) Can not be aligned with And the fluoride ions still need to be additionally treated for recycling, so that the process complexity and the cost are increased. Disclosure of Invention In order to solve the problem of synchronous recovery of lithium, fluorine and water resources in lithium fluoride wastewater, reduce medicament consumption and realize clean production, the invention provides a high-efficiency recovery method of lithium resources based on a displacement dialysis process. In order to achieve the above purpose, the present invention provides the following technical solutions: one of the technical schemes of the invention is as follows: the method adopts a lithium fluoride wastewater treatment system to treat wastewater, wherein the lithium fluoride wastewater treatment system comprises a four-compartment replacement dialysis device, a fluorine removal resin tower, a chelating resin tower, an MVR evaporation crystallizer, a lithium carbonate reaction kettle, a bipolar membrane electrodialysis unit and a reverse osmosis membrane component; The four-compartment replacement dialysis device is provided with a first compartment, a second compartment, a third compartment and a fourth compartment in turn along the water flow direction, wherein adjacent compartments are separated by a cation exchange membrane C or an anion exchange membrane A, a water outlet of the second compartment is communicated with a water inlet of a fluorine removal resin tower, a water inlet of a chelating resin tower and a water inlet of an MVR evaporation crystallizer in turn, a liquid outlet of the MVR evaporation crystallizer is communicated with a feed inlet of a lithium carbonate reaction kettle and a feed inlet of a bipolar membrane electrodialysis unit respectively, an alkali outlet of the bipolar membrane electrodialysi