阅读说明：本技术 一种钕铁硼合金废料的绿色回收方法 (Green recovery method of neodymium iron boron alloy waste ) 是由 张军 许轩 贾晓峥 于 2021-09-18 设计创作，主要内容包括：本申请公开了一种钕铁硼合金废料的绿色回收方法,至少包括以下步骤：(1)前处理：将钕铁硼合金油泥/磨泥废料去除油污和非磁性杂质；(2)填充：将阳极置于滤袋中,步骤(1)中得到的钕铁硼油泥/磨泥废料填充于滤袋与阳极之间；(3)电解：将步骤(2)中的带有滤袋的阳极和阴极在酸性电解液中进行电解,所述钕铁硼油泥/磨泥废料表面的金属氧化物被溶解,暴露出高导电性的钕铁硼合金,稀土元素以离子形式进入电解液；(4)沉淀：向所述电解液中添加Na-(2)SO-(4),使稀土元素沉淀；过滤回收稀土元素。本申请中的电化学回收方法具有绿色、简便、成本低等优点。(The application discloses a green recovery method of neodymium iron boron alloy waste, which at least comprises the following steps: (1) pretreatment: removing oil stains and nonmagnetic impurities from the neodymium iron boron alloy oil sludge/mill mud waste; (2) filling: placing an anode in a filter bag, and filling the neodymium iron boron oil sludge/mill mud waste obtained in the step (1) between the filter bag and the anode; (3) electrolysis: electrolyzing the anode and the cathode with the filter bags in the step (2) in an acid electrolyte, dissolving the metal oxide on the surface of the neodymium iron boron oil sludge/mill mud waste material to expose the high-conductivity neodymium iron boron alloy, and allowing rare earth elements to enter the electrolyte in an ion form; (4) and (3) precipitation: adding Na to the electrolyte 2 SO 4 To make rare earth elementsPrecipitating; filtering and recovering rare earth elements. The electrochemical recovery method has the advantages of being green, simple, convenient, low in cost and the like.)

1. The green recycling method of the neodymium iron boron alloy waste is characterized by at least comprising the following steps:

1) pretreatment: removing oil stains and nonmagnetic impurities from the neodymium iron boron alloy oil sludge/mill mud waste;

2) filling: placing an anode in a filter bag, and filling the neodymium iron boron oil sludge/mill mud waste obtained in the step 1) between the filter bag and the anode;

3) electrolysis: electrolyzing the anode and the cathode with the filter bags in the step 2) in an acid electrolyte, dissolving the metal oxide on the surface of the neodymium iron boron oil sludge/mill mud waste material to expose the high-conductivity neodymium iron boron alloy, and allowing rare earth elements to enter the electrolyte in an ion form;

4) sink with a metal plateAnd (2) precipitation: adding Na to the electrolyte₂SO₄Precipitating the rare earth elements; filtering and recovering rare earth elements.

2. The green recycling method of neodymium iron boron alloy waste materials according to claim 1, characterized in that in step 1), the rare earth permanent magnet alloy oil sludge/mill mud waste materials are placed into a degreasing tank, petroleum ether is added to remove oil stains in the waste materials, the waste materials are dried, and then nonmagnetic impurities are removed through magnetic separation.

3. The green recycling method of neodymium iron boron alloy waste materials according to claim 1, characterized in that the thickness of neodymium iron boron alloy oil sludge/grinding sludge waste materials filled around the anode in the filter bag in the step 2) is 1-50 mm.

4. The green recycling method of neodymium iron boron alloy waste materials according to claim 1, characterized in that the pH of the electrolyte is maintained to be 2.0-4.0 in the electrolysis process in the step 3).

5. The green recycling method of neodymium iron boron alloy waste according to claim 1, characterized in that the mixed solution containing 0.6M ammonium ferrous sulfate, 0.1M citric acid and 0.4M boric acid is used as electrolyte in the step 3).

6. The green recycling method of neodymium iron boron alloy waste material according to claim 1, characterized in that during the electrolysis in step 3), the cathode current density is 10-20 mA-cm^-2Anode current density of 30-50 mA-cm^-2。

7. The green recycling method of neodymium iron boron alloy waste materials according to claim 1, characterized in that Na is added in the step 4)₂SO₄And carrying out post-heating reaction to generate a precipitate, wherein the heating temperature is 40-90 ℃.

8. The green recycling method of neodymium iron boron alloy waste materials according to claim 1, characterized in that the filter bag is made of high molecular polymer, and the aperture of the filter bag is 1-50 μm.

9. The green recycling method of neodymium iron boron alloy waste materials according to claim 1, characterized in that the rare earth element precipitate is washed by acidic solution and water in sequence after being filtered in the step 4), so that the precipitate is purified.

10. The green recycling method of neodymium iron boron alloy waste materials according to claim 9, characterized in that the cleaning solution and the filtered filtrate are recycled as electrolyte.

Technical Field

The invention belongs to the technical field of resource recovery and environmental protection, and relates to a green recovery method of neodymium iron boron alloy waste.

Background

The neodymium iron boron (NdFeB) permanent magnet material has the advantages of high magnetic energy product, small volume, light weight and the like, and is widely applied to the fields of energy, transportation, machinery, medical treatment, computers and household appliances. With the rapid development of new energy automobiles, wind power generation, robots and other industries and the development trend of miniaturization and light weight of instruments and equipment, neodymium iron boron is taken as one of key materials, and the usage amount of neodymium iron boron is increased year by year. China is a big producing country of neodymium iron boron magnetic materials, according to the report of China's rare earth industry Association, the yield of China is as high as 17 million tons in 2019 years, wherein the yield of sintered neodymium iron boron is over 90 percent. In the production and processing process of sintered neodymium iron boron, 30-40% of raw materials become wastes such as blocky leftover materials, oil sludge and the like due to the working procedures such as cutting, polishing and the like. The neodymium iron boron waste material contains about 30% of rare earth elements (the content of Nd is about 90%, and the balance is Pr, Dy and Tb), and about 60% -70% of iron. As Nd contributes more than 80% of the output value of the rare earth industry, the neodymium iron boron waste is a rare earth secondary resource with high value potential. The neodymium iron boron blocky leftover materials and the scrapped blocky neodymium iron boron magnetic materials (collectively called neodymium iron boron blocky waste materials) have low oxidation degree and small pollution, and keep the inherent components and microstructure of sintered neodymium iron boron, so that the neodymium iron boron blocky leftover materials and the scrapped blocky neodymium iron boron magnetic materials can be directly utilized in the production process after simple pretreatment to produce new neodymium iron boron magnetic materials. The impurities such as cutting fluid, cooling fluid and the like in the neodymium iron boron oil sludge and the grinding mud waste are various and have high oxygen content, so that the neodymium iron boron oil sludge and the grinding mud waste cannot be directly recycled. The efficient and green comprehensive utilization of the neodymium iron boron oil sludge and the grinding sludge waste can improve the resource utilization rate, reduce the environmental pollution and have important strategic significance for maintaining the advantages of rare earth resources in China.

At present, although industrial recovery of neodymium iron boron oil sludge and mill mud waste is realized, hydrometallurgical technologies such as a hydrochloric acid optimum dissolution method are mainly used at present, the consumption of industrial concentrated hydrochloric acid in the whole leaching process is about 2 times of the theoretical consumption of the waste, the leaching time is long, and waste gas, a large amount of waste water and iron-containing waste residues are discharged. In addition, in order to achieve a high leaching rate, the particle size of the raw material is generally required to be less than 300 to 500 meshes, and therefore, fine grinding of the raw material not only causes an increase in cost, but also causes environmental pollution. In recent years, the electrochemical technology can recycle the electrolyte, avoid the discharge of waste water,the method gradually receives attention in the field of neodymium iron boron recovery. The elements in the neodymium iron boron waste are completely corroded by adopting a double-anode system and converted into corresponding hydroxides, the rare earth hydroxides can be selectively leached by HCl, and iron is left in the slag. At H₂SO₄+H₂C₂O₄In the electrolyte, the massive neodymium iron boron waste is used as an anode, the anode corrosion is carried out under the constant current condition, the rare earth elements are precipitated in the form of rare earth oxalate, and Fe is remained in the electrolyte as soluble oxalate, thereby achieving the purpose of separating rare earth. The research results have important significance for recognizing the application of the electrochemical technology in selectively separating and recovering the rare earth elements in the neodymium iron boron waste material. However, these studies cannot solve the problems of discharge of wastewater and iron-containing slag, as in the hydrometallurgical process. Patent CN 112522527a discloses a method for directly dissolving neodymium iron boron bulk waste as anode oxidation by using electrochemical technology, and simultaneously electrodepositing metallic Fe at cathode. The method can maintain the relative stability of the components of the electrolyte, realize the cyclic utilization of the electrolyte and avoid the discharge of waste water. Meanwhile, the method saves the consumption of strong acid by 80 percent, has low energy consumption, avoids the generation of iron-containing waste residue, and is a green and efficient recovery technology. However, the neodymium iron boron sludge/mill mud waste exists in the form of a fluid with highly oxidized particle surfaces in the solution, and the high resistance results in that the neodymium iron boron sludge/mill mud waste cannot be used as an anode for oxidation corrosion. Therefore, the research and development of the anode form for efficiently dissolving the neodymium iron boron oil sludge/mill mud waste material is the key point for realizing the recovery of the neodymium iron boron oil sludge waste material by the electrochemical technology.

Disclosure of Invention

The invention mainly solves the technical problem that the prior electrochemical technology is difficult to recover neodymium iron boron oil sludge/mill mud waste; the problems of high acid and alkali consumption, serious environmental pollution and the like in the existing neodymium iron boron oil sludge/grinding sludge waste recovery treatment are also solved. The invention aims to provide a method for recovering rare earth and metal Fe from neodymium iron boron oil sludge/mill mud waste. According to the method, the acid electrolyte is used for dissolving the non-conductive oxide on the surface of the waste material, so that the high-conductivity rare earth alloy is exposed, and the inert anode is favorable for directly carrying out electrolytic oxidation on the rare earth alloy; the oxidation efficiency of the neodymium iron boron oil sludge/mill mud waste on the inert anode is improved by maintaining the constant accumulation thickness of the neodymium iron boron oil sludge/mill mud waste on the surface of the anode. The electrochemical recovery method of the neodymium iron boron oil sludge/mill mud waste provided by the invention has the characteristics of greenness, simplicity, low cost and the like, the leaching efficiency and the acid and alkali consumption of the neodymium iron boron oil sludge/mill mud waste can be regulated and controlled by adjusting the formula of the electrolyte, the pH value, the current/voltage and the like, the electrolyte can be recycled, and the large-scale industrial production can be realized.

In order to achieve the above purpose, the present application provides a green recycling method for neodymium iron boron alloy waste, which at least comprises the following steps:

(1) pretreatment: removing oil stains and nonmagnetic impurities from the neodymium iron boron alloy oil sludge/mill mud waste;

(2) filling: placing an anode in a filter bag, and filling the neodymium iron boron oil sludge/mill mud waste obtained in the step (1) between the filter bag and the anode;

(3) electrolysis: electrolyzing the anode and the cathode with the filter bags in the step (2) in an acid electrolyte, dissolving the metal oxide on the surface of the neodymium iron boron oil sludge/mill mud waste material to expose the high-conductivity neodymium iron boron alloy, and allowing rare earth elements to enter the electrolyte in an ion form;

(4) and (3) precipitation: adding Na to the electrolyte₂SO₄Precipitating the rare earth elements; filtering and recovering rare earth elements.

Preferably, in the step (1), the rare earth permanent magnet alloy oil sludge/mill mud waste is placed into a degreasing tank, petroleum ether is added to remove oil stains in the waste, the waste is dried, and then nonmagnetic impurities are removed through magnetic separation.

Preferably, the thickness of the neodymium iron boron alloy oil sludge/grinding sludge waste filled around the anode in the filter bag in the step (2) is 1-50 mm.

Preferably, the pH value of the electrolyte is maintained to be 2.0-4.0 in the electrolysis process in the step (3).

Preferably, in the step (3), a mixed solution containing 0.6M ammonium ferrous sulfate, 0.1M citric acid and 0.4M boric acid is used as an electrolyte.

Preferably, the cathode current density is 10-20 mA-cm during the electrolysis in the step (3)^-2Anode current density of 30-50 mA-cm^-2。

Preferably, Na is added in the step (4)₂SO₄And carrying out post-heating reaction to generate a precipitate, wherein the heating temperature is 40-90 ℃.

Preferably, the filter bag is made of high molecular polymer, and the aperture of the filter bag is 1-50 μm.

Preferably, the rare earth element precipitate is washed with an acidic solution and water in sequence after filtration in the step (4), so that the precipitate is purified.

Preferably, the cleaning solution and the filtered filtrate are recycled as the electrolyte.

The traditional hydrometallurgical process has high requirements on the particle size of neodymium iron boron oil sludge/mill mud waste, large acid and alkali consumption, large amount of wastewater and iron-containing waste residue discharge and other energy-saving and environment-friendly problems. According to the invention, neodymium iron boron oil sludge/grinding mud waste is fully contacted with the inert anode to realize oxidation and dissolution of the neodymium iron boron oil sludge/grinding mud waste in the anode, and oxides in the neodymium iron boron oil sludge/grinding mud waste are dissolved in the acid electrolyte to expose the high-conductivity rare earth alloy, so that the problem that the low-conductivity neodymium iron boron oil sludge/grinding mud waste is difficult to be oxidized by the anode to be leached is effectively solved. The method has no special requirement on the granularity of the leaching waste, and can directly carry out electrochemical leaching only by simple impurity removal treatment, thereby avoiding a large amount of dust and energy consumption generated in the fine grinding process of the raw materials. The method has the advantages of short process flow, simple process conditions, low acid and alkali consumption, no discharge of wastewater and iron-containing waste residues, maximized improvement of the recovery value of the neodymium iron boron waste, considerable economic, social and environmental protection benefits and capability of meeting the requirements of large-scale commercial application.

Additional aspects and advantages of the invention will be set forth in part in the examples which follow. It should be noted that the embodiment is only an example, and the invention is not limited by the example. The invention is limited only by the claims and includes variations other than the embodiments contained in the invention.

Drawings

Fig. 1 is a schematic diagram of an electrolytic cell for electrochemically treating neodymium iron boron sludge/mill mud waste in accordance with the present invention.

Wherein: 1. NdFeB oil sludge/mill mud waste; 2. a filter bag; 3. an inert anode; 4. a conductive cathode; 5. an acidic electrolyte; 6. a cathodic deposit; 7. and (4) stirring.

Detailed Description

Example 1

(1) Pretreating neodymium iron boron oil sludge/grinding sludge waste: putting the neodymium iron boron oil sludge/mill mud waste into a degreasing tank, adding petroleum ether according to the volume ratio of 1:1 to remove oil stains and impurities in the waste, drying the cleaned neodymium iron boron oil sludge/mill mud waste, and removing nonmagnetic impurities through magnetic separation to obtain the dry and clean neodymium iron boron oil sludge/mill mud waste.

(2) Filling neodymium iron boron oil sludge/mill mud waste materials: in the embodiment, a stainless steel sheet is selected as a cathode, and a commercial iridium tantalum titanium mesh material is selected as an anode. As shown in figure 1, an iridium-tantalum-titanium mesh anode is placed in the center of a filter bag, neodymium iron boron oil sludge/grinding sludge waste materials treated in the example step (1) are filled in the filter bag, and the thickness of the waste materials to the surface of the anode is 1-50 mm. The thickness of the scrap in this example is about 25 mm.

(3) Preparing electrolyte: 0.6M ferrous ammonium sulfate (Fe (NH) is prepared₄)₂·(SO₄)₂·6H₂O) + 0.1M citric acid (C)₆H₈O₇) + 0.4M boric acid (H)₃BO₃) The solution serves as an electrolyte.

(4) Electrochemical leaching of neodymium iron boron oil sludge/mill mud waste: according to the scheme shown in fig. 1, the filter bag filled with the neodymium iron boron sludge/mill mud waste in the example step (2) and the cathode are placed in the electrolyte in the example step (3) for electrolysis. The electrolysis conditions were: the electrolysis temperature is 20 ℃, and the cathode current density is 25 mA-cm^-2Anode current density 40 mA cm^-2And dropwise adding concentrated sulfuric acid to maintain the pH of the electrolyte at about 3.7. The (electro) chemical (semi) reaction equation involved in this step is as follows (RE: rare earth elements):

RE₂O₃ + 6H⁺ → 4RE³⁺ + 3H₂o (1) rare earth oxide leaching reaction

Fe₂O₃ + 6H⁺ → 4Fe³⁺ + 3H₂Leaching reaction of O (2) transition metal oxide

RE₂Fe₁₄B + 37e^- → 2RE³⁺ + 14Fe²⁺ + B³⁺(3) Anodic oxidation reaction

Based on anodic oxidation reaction and waste leaching reaction, elements in the neodymium iron boron oil sludge/mill mud waste enter the electrolyte in an ion form in the electrolysis process. At the same time, iron ions (Fe) in the electrolyte²⁺And Fe³⁺) Is deposited at the cathode in the form of metallic iron:

Fe²⁺ + 2e⁻→ Fe (4) cathode reaction

Fe³⁺ + 3e⁻→ Fe (5) cathode reaction

Since the cathodic hydrogen evolution side reaction occurs simultaneously with the electrodeposition reaction of Fe, resulting in an increase in the pH of the electrolyte, concentrated H2SO4 must be added dropwise to maintain the pH of the electrolyte at around 3.7.

2H⁺ + 2e⁻ → H₂↓ (6) cathode reaction

And when the mass ratio of the oxidation leaching amount of the neodymium iron boron oil sludge/mill mud waste material at the anode to the electrolyte reaches 1:10, the electrolysis is suspended as a batch. Under the electrolysis condition, the electrodeposition efficiency of the cathode iron is about 70 percent, and the leaching efficiency of the neodymium iron boron oil sludge/mill mud waste material at the anode is close to 90 percent.

(5) Selective precipitation of rare earth elements: after the electrolysis is finished, the neodymium iron boron oil sludge/mill mud waste possibly remaining in the solution (electrolyte) is removed by a magnet. Then adding Na₂SO₄Is a rare earth precipitator and is Na according to a molar ratio₂SO₄: RE is 1:1 was added to the solution. The solution was heated to 70 ℃ and maintained for 2 h. At this time, the rare earth element in the solution is a double salt ((RE, Na) (SO) of rare earth sodium sulfate₄)₂) The following was precipitated:

RE₂(SO₄)₃ + Na₂SO₄ → 2(RE, Na)(SO₄)₂selective deposition of ↓ (7) rare earthReaction of starch

(6) Separation and purification of rare earth sodium sulfate double salt: the solution from example step (5) was filtered while hot to obtain a precipitate of a double salt of sodium rare earth sulfate and a filtrate, respectively. The precipitate was washed 3 times with a solution of ph2.0 and deionized water in sequence, and the washing solution was collected. The filtrate and rinse were recovered and returned to example step (4) for recycle as electrolyte.

Since the electrolyte and the rinse solution can be recycled, the loss of the rare earth element is almost 0. In the example, after the electrolyte and the flushing liquid are circulated for 8 times, the recovery rate of the rare earth elements in the neodymium iron boron oil sludge/mill mud waste is as high as 99.2%, and the purity of the rare earth sodium sulfate double salt is as high as 99.8%; and the energy consumption of electrochemical treatment of each kilogram of neodymium iron boron oil sludge/mill mud waste is only 3.25 kWh, the acid consumption is only 0.5 kilogram, and no alkali is consumed.

The method for recovering rare earth elements and metallic iron from neodymium iron boron oil sludge/mill mud waste has the following beneficial characteristics: the method realizes very high rare earth recovery efficiency and high-purity rare earth sodium sulfate double salt; the metal iron is synchronously recycled, so that the discharge of iron-containing waste slag is avoided; the filtrate and the flushing fluid are recycled, and the wastewater discharge is avoided. The whole process has the advantages of low acid and alkali consumption, low energy consumption, simple treatment process and obvious industrialization advantage.