Membrane method resource utilization method and device for neodymium iron boron permanent magnet waste material recovery waste water

Abstract

The invention belongs to the technical field of electrochemistry, and particularly relates to a membrane-method resource utilization method and device for neodymium-iron-boron permanent magnet waste recovery wastewater. A bipolar membrane electrodialysis and reverse osmosis membrane combined technology is used for neodymium iron boron waste recovery wastewater treatment; according to the principle that boron elements in water basically all exist in the form of electrically neutral boric acid (B (OH) 3) at 9.2, the electrically neutral boric acid does not diffuse to an acid chamber and an alkali chamber in the bipolar membrane electrodialysis process and is stored in a wastewater chamber, so that separation is realized, further concentration is performed through a reverse osmosis membrane, boron-rich concentrated water and fresh water are prepared, and boron in the wastewater is recovered.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater resource treatment, and in particular to a membrane method and device for resource utilization of NdFeB recovered wastewater. Background Art

[0002] Neodymium iron boron (NdFeB) permanent magnet materials are the most widely used, largest-volume, and fastest-growing rare earth products in the current rare earth materials industry due to their outstanding coercive force, magnetic energy product, and other excellent magnetic properties. They have been widely used in modern new technologies and new products such as new energy vehicles, wind turbines, hard disk drives, and household appliances. However, in the production process of NdFeB permanent magnet materials, 20% to 30% of NdFeB permanent magnet waste materials such as cutting scraps and polishing sludge will be generated. The waste powder is prone to violent oxidation and combustion reactions in the air, which poses certain safety hazards in the production and transportation process. In addition, with the use of NdFeB permanent magnet materials, a large number of expired NdFeB magnetic waste materials have been detected to contain about 20% to 40% of high-value elements such as Nd, Pr, and Dy. Therefore, NdFeB permanent magnet waste has a very considerable recycling value. How to recycle NdFeB permanent magnet waste in a green, efficient and low-cost manner is of great significance for reducing production safety risks, realizing the recycling of rare earth and iron resources, alleviating resource pressure, and promoting carbon-neutral development.

[0003] At present, the industrial recycling of NdFeB permanent magnet waste mainly adopts hydrometallurgical technology, which mainly involves: pretreatment, selective leaching, extraction separation, oxalic acid precipitation and calcination smelting and other processes. A large amount of NdFeB permanent magnet waste recycling wastewater will be generated during the treatment process. The existing wastewater treatment process is mainly for the recovery of CaCl2. For example, the recycled wastewater containing ~15% CaCl2 is coagulated and concentrated to ~30% by MVR for sale. However, there is a problem of easy scaling of MVR equipment. This is because the Ba in the wastewater 2+ Exist easily with SO4 2- In addition, the high-value B element is not recycled.

[0004] There are few reports on the recovery of boron from wastewater from NdFeB permanent magnet waste recycling in existing research. CN113816542 B document proposes an electrochemical system and method for recovering ammonia nitrogen and rare earth ions in low-concentration rare earth wastewater, which combines a bipolar membrane, an anion exchange membrane, a cation exchange membrane and a divalent cation exchange membrane to achieve the enrichment and recovery of rare earth ions in low-concentration rare earth wastewater, but the document does not involve boron recovery. Therefore, the present invention provides a method and device for recovering boron from wastewater from NdFeB permanent magnet waste recycling, which is of great significance for boron recovery. Summary of the invention

[0005] The present invention aims to propose a membrane resource utilization method and device for recycling wastewater from NdFeB permanent magnet waste, by combining bipolar membrane electrodialysis technology with reverse osmosis technology, thereby realizing boron recovery in wastewater.

[0006] The first object of the present invention is to provide: a membrane resource method for recycling wastewater from NdFeB permanent magnet waste, comprising the following steps: The wastewater recovered from NdFeB waste is treated by bipolar membrane electrodialysis to obtain acid solution, alkali solution and waste liquid, so that the boric acid is retained in the waste liquid; After the waste liquid is concentrated, the boron is recovered; The alkali solution is separated into solid and liquid to obtain solid matter and alkaline filtrate; the solid matter reacts with the acid solution to make Ca 2+ Dissolve, and concentrate the reaction solution to obtain CaCl2.

[0007] In the process of concentrating the waste liquid, reverse osmosis concentration is adopted, and the reverse osmosis is one or more than two levels; MVR concentration is adopted in the concentration of the reaction liquid; the operating pressure of the one or more than two levels of reverse osmosis is 1~40bar, preferably 20~30bar; the operating temperature is 0~45℃, preferably 20~30℃.

[0008] The current density of the bipolar membrane electrodialysis treatment is 4-16 mA / cm 2 .

[0009] The solids obtained by the solid-liquid separation are Ba(OH)2 precipitate, Ca(OH)2 precipitate, Mg(OH)2 precipitate and Mn(OH)2 precipitate.

[0010] Before the bipolar membrane electrodialysis treatment, citric acid buffer is added to the recovered wastewater to a concentration of 0.1-0.5% in the wastewater.

[0011] Based on the above-mentioned membrane resource utilization method of NdFeB permanent magnet waste recovery wastewater, a certain amount of NdFeB waste recovery wastewater raw water is supplied to the wastewater chamber of the bipolar membrane electrodialysis device, and a certain amount of pure water is supplied to the anode chamber, acid chamber, alkali chamber, and cathode chamber of the bipolar membrane electrodialysis device; the bipolar membrane electrodialysis device operates at a certain current density, involving the following separation processes and principles: ① H dissociated from the bipolar membrane in the anode chamber + The SO4 contained in the wastewater entering the acid chamber and the wastewater chamber 2- , Cl - 、CO3 2- OH - Under the action of the electric field, anions such as CO3 enter the acid chamber through the anion exchange membrane (AEM); 2- With H +The reaction generates CO2 and H2O, thereby removing OH - With H + The reaction generates H2O, thereby achieving removal, while H + With SO4 2- , Cl - Combine to form H2SO4 and HCl, which are stored in the acid chamber; ②OH dissociated from the bipolar membrane in the cathode chamber - The Ca in the wastewater entering the alkali room and the wastewater entering the wastewater room 2+ Mg 2+ , Mn 2+ , Ba 2+ Under the action of the electric field, cations such as OH enter the alkaline chamber through the cation exchange membrane (CEM); - Will be with Ca 2+ Mg 2+ , Mn 2+ The reaction generates suspended matter or precipitate of hydroxides such as Ca(OH)2, Mg(OH)2, and Mn(OH)2, so that the material system in the alkali chamber gradually presents a milky white, opaque suspended state and is stored in the alkali chamber; ③ The wastewater (weakly alkaline, pH 7-8) entering the wastewater chamber is electrodialyzed by bipolar membrane electrodialysis, and the anions (including OH - The cations in the wastewater chamber migrate to the acid chamber, and the cations migrate to the alkaline chamber. The pH in the wastewater chamber gradually changes from weak alkalinity to neutrality. Considering that the pH is less than 9.2 (according to the acidity equilibrium constant pK of boric acid at 25 °C), the pH in the wastewater chamber gradually changes from weak alkalinity to neutrality. A is 9.2; especially when pH≤6~8), the boron element in the water basically exists in the form of electrically neutral boric acid (B(OH)3). Therefore, the electrically neutral boric acid is stored in the wastewater chamber and does not migrate to the acid chamber and the alkali chamber. As the bipolar membrane electrodialysis continues, there is only electrically neutral boric acid in the wastewater chamber.

[0012] The alkaline filtrate is used in the pretreatment reaction of NdFeB permanent magnet waste recovery wastewater to remove Mg by precipitation. 2+ , Mn 2+ and Ca 2+ .

[0013] The pretreatment includes: using a ceramic microfiltration membrane to filter NdFeB waste to recover wastewater and remove impurities; using NaOH or Na2CO3 to precipitate the filtered clear liquid; then separating the solid and liquid to obtain a feed liquid; using HCl to adjust the pH of the feed liquid to 5-8 for subsequent bipolar membrane electrodialysis treatment.

[0014] The second object of the present invention is to provide: a membrane resource utilization device for recycling wastewater from NdFeB permanent magnet waste, comprising: Bipolar membrane electrodialysis device, used for bipolar membrane electrodialysis treatment of wastewater recovered from NdFeB permanent magnet waste; A first concentrating device, used to concentrate the boron-containing waste liquid obtained in the bipolar membrane electrodialysis device; A first solid-liquid separation device is used to perform solid-liquid separation on the alkaline solution obtained in the bipolar membrane electrodialysis device to obtain solid matter and alkaline filtrate; Reactor, used for solid matter to react with acid solution obtained from bipolar membrane electrodialysis device to make Ca 2+ Dissolve; A second solid-liquid separation device, used for filtering the reaction liquid obtained in the reactor; The second concentrating device is used to concentrate the filtrate obtained in the second solid-liquid separation device to obtain CaCl2.

[0015] The first concentrating device is a reverse osmosis membrane system, which is one-stage or more than two-stage.

[0016] The membrane resource utilization device for recycling wastewater from NdFeB permanent magnet waste also includes: a pretreatment tank connected to a mixing tank for reacting the NdFeB permanent magnet waste recycling wastewater with alkali solution to generate Mg 2+ , Mn 2+ and Ca 2+ and comprising a third solid-liquid separation device for separating the precipitate generated in the pretreatment tank.

[0017] The reverse osmosis membrane system is composed of a pretreatment unit, a first-stage reverse osmosis membrane assembly and / or a multi-stage reverse osmosis membrane assembly; the reverse osmosis membrane system first transports the precipitated boric acid solution from the wastewater chamber of the bipolar membrane electrodialysis device to the pretreatment unit via a first pipeline to control the reverse osmosis inlet water quality, and then further enriches it on the interception side of the first-stage reverse osmosis membrane assembly and connects it to the inlet side of the next-stage reverse osmosis membrane assembly, and sequentially connects the multi-stage reverse osmosis membrane assemblies in series.

[0018] In the bipolar membrane electrodialysis device, the anode chamber is connected to the positive electrode of the external power supply through the anode plate, and the cathode chamber is connected to the negative electrode of the external power supply through the cathode plate; the cathode plate and the anode plate are both titanium plates, preferably ruthenium-iridium-titanium plates.

[0019] The bipolar membrane, anion exchange membrane, and cation exchange membrane are purchased from commercial products and may also be modified.

[0020] Beneficial Effects Compared with the prior art, the present invention has the following beneficial effects: the bipolar membrane electrodialysis combined with the reverse osmosis membrane technology is used for the treatment of wastewater from the recovery of NdFeB waste, and the principle that the boron element in the water is basically all present in the form of electrically neutral boric acid (B(OH)3) under pH <9.2 is utilized, so that the electrically neutral boric acid does not diffuse into the acid chamber and the alkali chamber during the bipolar membrane electrodialysis process and is stored in the wastewater chamber, thereby achieving separation, and further concentrating through the reverse osmosis membrane to obtain boron-rich concentrated water, achieve boron recovery, and reuse fresh water; and the Ca is recovered by reacting the H2SO4 and HCl acid solutions generated in the acid chamber with the suspended solids generated in the alkali chamber after solid-liquid separation. 2+ , Cl - etc., and use it for subsequent MVR concentration, recovery of CaCl2 and sale, due to the generation of SO4 2- Precipitated soluble Ba 2+ It can effectively reduce the equipment scaling problem caused by the MVR concentration process; for the liquid treatment after pretreatment by a certain method, boron recovery can also be achieved. At the same time, CaCl2 can be recovered and soluble Ba can be removed. 2+ , reduce equipment scaling, and the NaOH produced during the process can be recycled to the pretreatment stage to separate Mg 2+ , Mn 2+ and Ca 2+ ; The pH balance of citrate in raw water inhibits the precipitation of boric acid on the membrane surface, maintaining the current efficiency of the electrodialysis process. At the same time, citrate is a scale inhibitor for reverse osmosis membranes, which can further reduce the surface scaling of reverse osmosis membranes during the reverse osmosis concentration process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 : Schematic diagram of the separation principle of the bipolar membrane electrodialysis (raw water is not pretreated) described in the present invention.

[0022] Figure 2 : Schematic diagram of the separation principle of the bipolar membrane electrodialysis (raw water pretreatment) described in the present invention.

[0023] Figure 3 : Schematic diagram of the membrane integrated process described in Examples 1 and 2.

[0024] In the figure: 1-bipolar membrane electrodialysis device, 11-anode chamber, 12-anode plate, 2-bipolar membrane, 21-cathode chamber, 22-cathode plate, 31-acid chamber, 34-anion exchange membrane, 41-wastewater chamber, 45-cation exchange membrane, 51-alkali chamber, 6-reverse osmosis membrane system, 60-first pipeline, 61-pretreatment unit, 62-first reverse osmosis membrane assembly, 63-secondary reverse osmosis membrane assembly, 64-delivery pump, 65-delivery pump, 7-wastewater storage tank, 70-second pipeline, 71-delivery pump, 8-pure water storage tank, 80-third pipeline, 801-branch pipeline, 802-branch pipeline, 803-branch pipeline, 804-branch pipeline, 81-delivery pump, 9-acid chamber storage tank, 90-fourth pipeline, 91-delivery pump, 10-alkali chamber storage tank, 100-fifth pipeline, 101-delivery pump. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below in conjunction with the accompanying drawings and examples. It is particularly pointed out that the following examples are only used to illustrate the present invention, but do not limit the scope of the present invention. Similarly, the following examples are only some embodiments of the present invention rather than all embodiments, and all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] like Figure 3 As shown, this scheme is a membrane integrated process and device for recovering boron in NdFeB waste to treat wastewater, which mainly includes: a bipolar membrane electrodialysis device 1, a reverse osmosis membrane system 6, a wastewater storage tank 7, a pure water storage tank 8, an acid chamber storage tank, an alkali chamber storage tank, etc.; The two sides of the bipolar membrane electrodialysis device 1 are respectively separated by a bipolar membrane 2 with an anode chamber 11 and a cathode chamber 21, the anode chamber 11 is connected to the positive pole of the external power supply through the anode plate 12, and the cathode chamber 21 is connected to the negative pole of the external power supply through the cathode plate 22; an acid chamber 31, a wastewater chamber 41, and an alkali chamber 51 are sequentially arranged in the direction from the anode chamber 11 to the cathode chamber 21, wherein an anion exchange membrane 34 is arranged between the acid chamber 31 and the wastewater chamber 41, and a cation exchange membrane 45 is arranged between the wastewater chamber 41 and the alkali chamber 51; The reverse osmosis membrane system 6 comprises a first pipeline 60, a pretreatment unit 61, a primary reverse osmosis membrane assembly 62, a secondary reverse osmosis membrane assembly 63, delivery pumps 64 and 65, etc.; The wastewater storage tank 7 includes a second pipeline 70, a delivery pump 71, etc., and is connected to the wastewater chamber 41; The pure water storage tank 8 comprises a delivery pump 81, a third pipeline 80 and its branch pipelines 801, 802, 803, 804, and is respectively connected to the anode chamber 11, the acid chamber 31, the alkali chamber 51, and the cathode chamber 21; The acid chamber storage tank 9 includes a fourth pipeline 90, a delivery pump 91, etc., and is connected to the acid chamber 31; The alkali chamber storage tank 10 includes a fifth pipeline 100 , a delivery pump 101 , etc., and is connected to the alkali chamber 51 . Example 1

[0027] In order to verify that this method can separate and enrich electrically neutral boric acid, Ca 2+ Mg 2+ , Ba 2+ , Mn 2+ , Cl -1 、SO4 2- To remove impurity ions such as B 500mg / L, Ca 2+ 0.3mg / L, Mg 2+ 0.3mg / L, Ba 2+ 1mg / L, Mn 2+ 0.3mg / L, SO4 2- 1.2mg / L, Cl - 1.44mg / L (pH=6) simulated low-concentration NdFeB wastewater system. This simulated system meets the water quality requirements of bipolar membrane electrodialysis (the total concentration of metal ions that are prone to hydroxide precipitation, such as Ca, Mg, and Mn, is less than 1mg / L), and can be directly treated with bipolar membrane electrodialysis. If the concentration of multivalent metal ions is high, the concentration of some multivalent metal ions can be reduced by pretreatment (adding alkali precipitation) before entering the bipolar membrane electrodialysis treatment. At a current density of 5mA / cm 2 Under the condition of bipolar membrane electrodialysis, SO4 2- , Cl - Anions such as Ca enter the acid chamber through the AEM, 2+ Mg 2 + , Ba 2+ , Mn 2+ Enter the alkali chamber through CEM; after 48 hours, the B content in the wastewater chamber is 512 mg / L, slightly higher than the initial concentration. This is because the migration process of impurity ions causes the volume in the wastewater chamber to decrease; the contents of the remaining impurity ions are: Ca 2+ 0.11mg / L, Mg 2+ 0.10mg / L, Ba 2+ 0.25mg / L, Mn 2+ 0.10mg / L, SO4 2- 0.23mg / L, Cl - 0.31 mg / L, the removal rates were 63%, 67%, 75%, 65%, 81% and 78% respectively; most of the Ca 2+ Mg 2+ , Ba 2+ , Mn 2+In the base compartment, most of the cations are SO4 2- , Cl - In the acid chamber, neutral boron is in the wastewater chamber. The B-containing solution (B concentration 512 mg / L) separated from the wastewater chamber of the above-mentioned bipolar membrane electrodialysis device is taken for subsequent reverse osmosis concentration. After pretreatment with an activated carbon filter, the single-stage reverse osmosis process (laboratory-made high boron removal rate reverse osmosis membrane) is used for concentration 15 times, and the concentration of boron-rich concentrated water on the concentrated side is 7.36 g / L, which has recycling value. Example 2

[0028] The above-mentioned simulated low-concentration NdFeB wastewater system (B 500mg / L, Ca 2+ 0.3mg / L, Mg 2+ 0.3mg / L, Ba 2+ 1mg / L, Mn 2+ 0.3mg / L, SO4 2- 1.2mg / L, Cl - 1.44mg / L, pH=6) as influent, increasing the bipolar membrane electrodialysis current density to 16mA / cm 2 After 48 hours, the B content in the wastewater chamber was 523 mg / L, slightly higher than the initial concentration. This is because the migration process of impurity ions caused the volume in the wastewater chamber to decrease; the contents of the remaining impurity ions were: Ca 2+ 0.03mg / L, Mg 2+ 0.04mg / L, Ba 2+ 0.09mg / L, Mn 2+ 0.03mg / L, SO4 2- 0.08mg / L, Cl - 0.05 mg / L, the removal rates were 90%, 87%, 91%, 90%, 94% and 96% respectively; the separation effect was higher than that in Example 1, because a higher current density was conducive to improving the separation efficiency. At this time, most of the Ca 2+ Mg 2+ , Ba 2+ , Mn 2+ In the base chamber, most of the cations are SO4 2- , Cl - In the acid chamber, neutral boron is basically in the wastewater chamber. The B-containing solution (B concentration 523 mg / L) separated from the wastewater chamber of the above-mentioned bipolar membrane electrodialysis device was taken for subsequent reverse osmosis concentration. After pretreatment with an activated carbon filter, a three-stage reverse osmosis process (laboratory-made high-boron removal rate reverse osmosis membrane) was used for boron concentration, with a recovery rate of 89%. The concentration of the boron-rich concentrated water on the concentrated side was 5.16 g / L, which has recycling value. Example 3

[0029] In order to verify that this method can separate and enrich electrically neutral boric acid, Ca 2+ Mg 2+ , Ba 2+ , Mn 2+ , Cl -1 、SO4 2- To remove impurity ions such as B 500mg / L, Ca 2+ 0.3mg / L, Mg 2+ 0.3mg / L, Ba 2+ 1mg / L, Mn 2+ 0.3mg / L, SO4 2- 1.2mg / L, Cl - 1.44mg / L (pH=6) simulated low-concentration NdFeB wastewater system. This simulated system meets the water quality requirements of bipolar membrane electrodialysis inlet (the total concentration of metal ions that are prone to hydroxide precipitation, such as Ca, Mg, and Mn, is <1mg / L), and can be directly treated with bipolar membrane electrodialysis. If the concentration of multivalent metal ions is high, the concentration of some multivalent metal ions can be reduced by pretreatment (adding alkali precipitation) before entering the bipolar membrane electrodialysis treatment. In order to suppress the precipitation of boric acid on the membrane surface due to the pH fluctuation in the waste liquid chamber, 0.2% sodium citrate buffer salt was added to the inlet solution at a current density of 5mA / cm 2 Under the condition of bipolar membrane electrodialysis, SO4 2- , Cl - Anions such as Ca enter the acid chamber through the AEM, 2+ Mg 2+ , Ba 2+ , Mn 2+ Entering the alkali chamber through CEM; after 48 hours, the B content in the wastewater chamber is 531 mg / L, and the contents of other impurity ions are: Ca 2+ 0.12mg / L, Mg 2+ 0.12mg / L, Ba 2+ 0.27mg / L, Mn 2+ 0.11mg / L, SO4 2- 0.24mg / L, Cl - 0.33mg / L; most Ca 2+ Mg 2+ , Ba 2+ , Mn 2+ In the base compartment, most of the cations are SO4 2- , Cl -In the acid chamber, neutral boron is in the wastewater chamber; after 48 hours of operation, the current efficiency of the bipolar membrane electrodialyzer (the ratio of theoretical desalination to actual desalination) decreased from 85.3% to 82.1%, indicating that the pH balance of citrate can keep the pH of the wastewater chamber relatively balanced, inhibiting the precipitation of boric acid on the membrane surface. The B-containing solution (B concentration 531 mg / L) separated from the wastewater chamber of the above-mentioned bipolar membrane electrodialysis device was taken for subsequent reverse osmosis concentration. After pretreatment with an activated carbon filter, the single-stage reverse osmosis process (laboratory-made high boron removal rate reverse osmosis membrane) was used for concentration 15 times, and the concentration of boron-rich concentrated water on the concentrated side was 7.63 g / L, which has recycling value.

Claims

1. A membrane method for recycling wastewater from NdFeB permanent magnet waste, characterized in that: The following steps are involved: The wastewater recovered from NdFeB waste is treated by bipolar membrane electrodialysis to obtain acid solution, alkali solution and waste liquid, so that the boric acid is retained in the waste liquid; After the waste liquid is concentrated, the boron is recovered; The alkali solution is separated into solid and liquid to obtain solid matter and alkaline filtrate; the solid matter reacts with the acid solution to make Ca 2+ Dissolve, and concentrate the reaction solution to obtain CaCl2.

2. The utilization method according to claim 1, characterized in that: In the process of concentrating the waste liquid, reverse osmosis concentration is adopted, and the reverse osmosis is one or more than two levels; MVR concentration is adopted in the concentration of the reaction liquid; the operating pressure of the one or more than two levels of reverse osmosis is 1~40bar, preferably 25~30bar; the operating temperature is 0~45℃, preferably 20~30℃.

3. The utilization method according to claim 1, characterized in that: The current density of the bipolar membrane electrodialysis treatment is 4-16 mA / cm 2 .

4. The utilization method according to claim 1, characterized in that: The solids obtained by the solid-liquid separation are Ba(OH)2 precipitate, Ca(OH)2 precipitate, Mg(OH)2 precipitate and Mn(OH)2 precipitate.

5. The utilization method according to claim 1, characterized in that: The alkaline filtrate is used in the pretreatment reaction with the wastewater of NdFeB permanent magnet waste recovery to remove Mg by precipitation. 2+ , Mn 2+ and Ca 2+ Before the bipolar membrane electrodialysis treatment, citric acid buffer is added to the recovered wastewater to a concentration of 0.1-0.5% in the wastewater.

6. The utilization method according to claim 1, characterized in that: The pre-processing includes: The wastewater recovered from NdFeB waste is filtered by ceramic microfiltration membrane to remove impurities; the filtered clear liquid is precipitated with NaOH or Na2CO3; the solid-liquid separation is then performed to obtain a feed liquid; the pH value of the feed liquid is adjusted to 5-8 with HCl for subsequent bipolar membrane electrodialysis treatment.

7. A membrane resource utilization device for recycling wastewater from NdFeB permanent magnet waste, characterized in that: include: A bipolar membrane electrodialysis device (1) is used for bipolar membrane electrodialysis treatment of wastewater recovered from NdFeB permanent magnet waste; A first concentrating device, used to concentrate the boron-containing waste liquid obtained in the bipolar membrane electrodialysis device (1); A first solid-liquid separation device, used for performing solid-liquid separation on the alkaline solution obtained in the bipolar membrane electrodialysis device (1) to obtain solid matter and alkaline filtrate; The reactor is used for reacting the solid matter with the acid solution obtained in the bipolar membrane electrodialysis device (1) to make Ca 2+ Dissolve; A second solid-liquid separation device, used for filtering the reaction liquid obtained in the reactor; The second concentrating device is used to concentrate the filtrate obtained in the second solid-liquid separation device to obtain CaCl2.

8. The device according to claim 7, characterized in that The first concentrating device is a reverse osmosis membrane system (6), which is one-stage or more than two-stage; It also includes: a pretreatment tank connected to a mixing tank for reacting the NdFeB permanent magnet waste recovery wastewater with alkali solution to generate Mg 2+ , Mn 2+ and Ca 2+ and comprising a third solid-liquid separation device for separating the precipitate generated in the pretreatment tank.

9. The device according to claim 7, characterized in that The cathode plate (22) and the anode plate (12) in the bipolar membrane electrodialysis device (1) are both made of titanium-based materials.

10. The device according to claim 9, characterized in that The titanium-based material is a ruthenium-iridium-titanium plate.

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