WO2020215857A1

WO2020215857A1 - Method for extracting rare earth element from neodymium-iron-boron waste by means of metal lead liquid-liquid separation

Info

Publication number: WO2020215857A1
Application number: PCT/CN2020/074814
Authority: WO
Inventors: 何杰; 孙小钧; 陈斌; 赵九洲; 江鸿翔; 张丽丽; 郝红日
Original assignee: 中国科学院金属研究所
Priority date: 2019-04-22
Filing date: 2020-02-12
Publication date: 2020-10-29
Also published as: CN110066924B; CN110066924A

Abstract

Disclosed is a method for extracting a rare earth element from a neodymium-iron-boron waste by means of metal lead liquid-liquid separation, comprising first heating and melting metal lead in a crucible; then immersing the neodymium-iron-boron waste in the liquid metal lead, wherein the rare earth element in the neodymium-iron-boron waste is enriched in the liquid metal lead melt under certain temperature conditions to form a lead-rare earth alloy melt, with the remaining neodymium-iron-boron waste present in an iron-boron alloy form; and finally, separating the lead-rare earth alloy melt from the iron-boron alloy, wherein the Fe‑B iron-boron alloy can be used as an intermediate alloy material after refining, and metals such as Pb and Nd in the lead-rare earth alloy are separated out by means of vacuum evaporation or selective oxidation.

Description

Method for separating and extracting rare earth elements from NdFeB waste by metallic lead liquid-liquid separation

This application requires a Chinese patent application filed with the Chinese Patent Office on April 22, 2019, the application number is 201910325452.X, and the invention title is "a method for metal lead liquid-liquid separation and extraction of rare earth elements from neodymium iron boron waste". Priority, the entire content of which is incorporated in this application by reference.

Technical field

The invention belongs to the field of metal resource recycling and reuse, and specifically relates to a method for extracting rare earth elements from neodymium iron boron waste by metal lead liquid-liquid separation.

Background technique

Rare earth elements have unique physical and chemical properties and are widely used in the development and innovation of science and technology, and the global demand for rare earth metal resources is increasing year by year. Especially in recent years, new technologies dedicated to reducing energy consumption and developing renewable energy have become significantly more dependent on rare earth resources. Rare earth elements are widely used in new materials such as permanent magnet materials, luminescent materials, hydrogen storage alloys, nickel-hydrogen battery electrode materials, polishing and catalysts. In particular, neodymium iron boron permanent magnet materials (containing about 30wt.% of rare earths) need to consume a large amount of rare earths, and the annual consumption is close to half of my country's total rare earth consumption, resulting in extremely unbalanced utilization of rare earth resources in my country. ), praseodymium (Pr), dysprosium (Dy), terbium (Tb) and other expensive rare earth resources are increasingly scarce. From the first generation of rare earth permanent magnet samarium cobalt developed in 1967 to the third generation of rare earth permanent magnet NdFeB developed in 1983, the rare earth elements used are samarium, praseodymium, neodymium, terbium, dysprosium, lanthanum, cerium, and gadolinium , Holmium, erbium, yttrium, etc. The third-generation neodymium iron boron rare earth permanent magnet material has the advantages of light weight, small size, strong magnetism, extremely high magnetic energy, easy access to raw materials, and low price. It has developed extremely rapidly. It is the most cost-effective permanent magnet material so far. The field of magnetism is known as the "magnet king". It is widely used in hard disk drives, wind power generation, electric power steering, hybrid and electric vehicles, electric bicycles, consumer electronics and household appliances. In addition, NdFeB permanent magnet materials are still used in elevators, magnetic separation and magnetic refrigeration equipment. Currently widely used rare earth permanent magnetic materials mainly include sintered NdFeB (91.4%), bonded NdFeB (6.7%), hot-pressed/hot-deformed NdFeB (0.6%) and sintered samarium cobalt (accounting for 0.6%). 1.3%) Four categories. In 2017, the global NdFeB permanent magnet output was nearly 200,000 tons, of which China accounted for about 85%.

NdFeB waste mainly comes from: ①The waste produced during the preparation of the NdFeB material and ②The waste produced in the end of the NdFeB material due to the failure of the used device. The production and preparation process of rare earth NdFeB permanent magnet materials mainly include: batching, alloy smelting, hydrogen crushing, jet milling, magnetic field orientation forming, isostatic pressing, oil stripping, sintering, machining and other links and processes. Various processes in the production process of NdFeB permanent magnet materials will produce a certain amount of waste or waste products, mainly including: the loss of raw materials in the pretreatment process of raw materials, and the neodymium produced by severe oxidation during the induction melting process. Iron-boron waste, ultra-fine powder produced in the powdering process, powder oxidized in the powdering process, neodymium iron boron block material oxidized in the sintering process, a large amount of scrap and surface produced in the processing and forming process Substandard products produced during the processing, etc. According to statistics, in the production process of neodymium iron boron rare earth permanent magnets, the utilization rate of raw materials is only about 70%, resulting in about 30% of waste. In addition, NdFeB rare earth permanent magnet materials are widely used in new technologies and products such as hard disk drives, wind turbines, electric power steering, hybrid and electric vehicles, electric bicycles, consumer electronics and household appliances. These products have a useful life and expire when they expire. For example, the service life of voice coil motors is 8 years, the service life of hybrid/electric vehicles is 15 years, the service life of consumer motors is 15 years, and the service life of wind power motors is 20 years. In 2017, China's installed wind power capacity exceeded 188GW, and each installed capacity of 1.5MW requires approximately 1 ton of neodymium iron boron permanent magnets. Since 2000, my country's installed wind power capacity has increased year by year, especially in the past 10 years. In 2017, the total amount of scrapped rare earth NdFeB permanent magnets in the world was 50,000 to 70,000 tons, and China accounted for more than 70%, and the scrap volume increased year by year. In NdFeB rare earth permanent magnet materials, the content of rare earth elements such as praseodymium, neodymium, and dysprosium is as high as 25-30%, and the rest are mainly metallic iron, cobalt, nickel, and element boron. If a large number of waste NdFeB rare earth permanent magnets cannot be recycled efficiently and greenly, not only will they produce a large number of pollution sources and secondary pollution, but also cause waste of resources, which goes against the development of circular economy. Therefore, the recovery of metal elements from waste NdFeB rare earth permanent magnet materials not only contributes to ecological environment protection, but also alleviates the resource shortage caused by the extremely unbalanced utilization of rare earth resources, and promotes the efficient recycling and sustainable development of rare earth resources in my country . This is of great significance to environmental protection and the development of a benign recycling economy of rare earths.

At present, the recycling of NdFeB permanent magnet waste mainly includes two treatment methods: wet method and fire method. The wet method mainly includes 4 steps: ① dissolving the waste with chemical reagents, so that the metal ions are distributed in the solution, that is, leaching; ② separating the leaching solution from the residue; ③ using ion exchange, solvent extraction or other chemical precipitation methods to make the leaching Liquid purification and separation; ④Extract compounds from the purified solution. Based on the wet recovery of rare earths, the sulfate double salt precipitation method, the sulfide precipitation method, the hydrochloric acid solution method, the hydrochloric acid solution method, and the oxalic acid precipitation method have been developed at home and abroad. Literature 1 (Lin Hecheng, Research on the Preparation of Neodymium Oxide, Rare Metals and Cemented Carbides, 03:4-7, 1997) reported the use of sulfuric acid-double salt method to recover rare earths from neodymium iron boron waste and prepare neodymium oxide products. Literature 2 (Chen Yunjin, Recovery of Rare Earth and Cobalt in NdFeB Waste Residue by Full Extraction Method, 06:10-12, 2004) reported that the NdFeB waste was dissolved in hydrochloric acid by the hydrochloric acid total solution method, and the iron was adjusted by adjusting the PH value. Separated from rare earth elements. Literature 3 (Yin Xiaowen, etc., Study on the Recovery of Rare Earth Elements in NdFeB Waste by Oxalate Precipitation Method, Rare Metals, 06:1093-1098, 2014) reported that NdFeB waste was dissolved in concentrated hydrochloric acid by the oxalic acid precipitation method. Oxalic acid is added to the leaching solution to obtain the precipitation of rare earth oxalate, which separates the rare earth from iron.

In addition, the Chinese invention patent (a method for recovering and extracting rare earth oxides from neodymium iron boron waste, publication number CN107012330A) discloses a method for recovering and extracting rare earth oxides from neodymium iron boron waste, which uses crushing-incineration-cleaning -Acid dissolution-extraction-roasting process to obtain rare earth oxides. A Chinese invention patent (a method for recovering rare earths from NdFeB waste, publication number CN106319249A) discloses a method for recovering rare earths from NdFeB waste. It uses hydrogen peroxide and oxidizing and weak acid to make NdFeB The waste is dissolved, and then N503 is used to extract the iron element in the solution first, then P507 is used to extract the rare earth elements, and finally oxalic acid and potassium carbonate are used to respectively precipitate the corresponding rare earth ions. The Chinese invention patent (Method for recovering rare earth from NdFeB waste, publication number CN103146925A) discloses a method for recovering rare earth from NdFeB waste, which includes the steps of roasting-acid dissolution-separation-burning, and the filtrate is modified Rare earth oxides are obtained after attapulgite and hydrogen peroxide treatment, centrifugal slag removal, extraction separation, precipitation separation and other processes. The Chinese invention patent (Method for recovering rare earth elements from NdFeB waste, publication number CN102011020A) discloses a method for recovering rare earth elements from NdFeB waste. The steps are: mixing NdFeB waste with water and grinding, After oxidation and grinding of NdFeB, secondary grinding of oxidation products, acid leaching, solid-liquid separation, extraction and removal of iron, rare earth chloride, extraction and separation of rare earths, extraction and removal of aluminum, precipitation and burning, etc.

Fire treatment is mainly divided into glass slag method, alloy method, chlorination method, selective oxidation method, slag finance method, etc. In 2003, Saito et al. used the glass slag method and used boron oxide as the oxidant to oxidize the rare earth elements in the NdFeB waste into neodymium oxide, and the boron oxide was reduced to boron as a simple substance and entered into the iron to form an iron-boron alloy. In 2002, Uda used FeCl ₂ as the chlorinating agent. The rare earth elements in the neodymium iron boron waste were chlorinated at 800°C, and then the rare earth chlorides were recovered by vacuum distillation. In 2014, Hua et al. proposed to use composite molten salt MgCl ₂ -KCl to selectively chlorinate rare earth elements to recover rare earths from NdFeB waste. In 2003 and 2004, Takeda et al. proposed to use metallic magnesium or silver as an extractant to extract rare earth elements from NdFeB solid waste. For the obtained magnesium neodymium alloy, distillation is used to separate the magnesium and neodymium elements in the magnesium neodymium alloy; for the silver neodymium alloy, the rare earth neodymium element is oxidized into solid neodymium oxide by selective oxidation, and then the liquid/solid separation is used to obtain neodymium oxide. And molten metallic silver. However, it is obviously difficult to realize industrial production using metallic silver. In 2018, Okabe et al. proposed to immerse solid NdFeB waste in molten MgCl ₂ at 1000°C for 3-12 hours to selectively chlorinate rare earth elements, thereby extracting rare earth elements in NdFeB solid waste. This method has a longer processing time and higher energy consumption.

It can be seen that the above method for recovering rare earths in NdFeB waste requires pretreatment of NdFeB waste, which has long process flow, high consumption of chemical reagents, high energy consumption, secondary pollution and difficulty in iron recovery. problem.

Summary of the invention

In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a metal lead liquid-liquid separation method for extracting rare earth elements from neodymium iron boron waste, which has short process flow, high efficiency, no need for harsh chemical reagents, zero emission, and environmental protection. Friendly, using the thermodynamic properties of rare earth elements and lead and iron elements to solve the comprehensive and efficient recovery and recycling of NdFeB waste including rare earth, iron and boron elements.

The technical scheme of the present invention is:

A method for separating and extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation is carried out according to the following steps:

Step 1. Clean the dirt on the surface of the NdFeB waste material and dry it;

Step 2: Construct Fe-Pb immiscible separation system from NdFeB waste and metallic lead extractant;

Step 3. Place the NdFeB waste in a crucible for melting metallic lead, and stir the melt in the crucible to make the NdFeB waste fully contact the metallic lead liquid;

Step 4, controlling the temperature of the metal material in the crucible, the rare earth elements are enriched in the metallic lead liquid to form a lead rare earth alloy melt, and the residual NdFeB scrap is in the form of iron-boron alloy;

Step 5, separating the lead-rare earth alloy melt from the iron-boron alloy, and separating the rare earth from the lead metal in the lead-rare earth alloy by vacuum evaporation or selective oxidation.

In the method for extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation, the chemical composition of the NdFeB waste recovered in step 1 mainly includes: rare earth elements Nd, Pr, La, Ce, Dy, Tb, One or more of Gd, Ho, Er, Y, one or more of transition metal elements Fe, Ni, Co, Mn, Cu, Nb, Zn, and other elements B, Al, Sn, One or more of Ga.

In the method for extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation, the metal lead extractant used in step 2 is a lead alloy containing lead and one or more of silver, magnesium and calcium. The lead content is not less than 50wt.%.

In the method for extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation, preferably, the lead content of the metal lead extractant is not less than 98wt.%.

In the method for separating and extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation, in step 3, in the ratio of NdFeB waste and metal lead extractant, the weight ratio of NdFeB waste and metal lead is W _Nd-Fe-B /W _Pb varies from 0.1 to 10.

In the method for extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation, preferably, the weight ratio W _Nd-Fe-B /W _{Pb of} NdFeB waste to metal lead is within a range of 0.5-5.

In the method for separating and extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation, in step 3, the material of the crucible and the stirring rod for melting the metal lead is pure iron, alumina or graphite.

In the method for separating and extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation, in step 4, the heating temperature of the metal material in the crucible is between 1327°C and 1450°C.

In the method for extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation, in step 5, after the lead-rare earth alloy melt is separated from the iron-boron alloy, the iron-boron alloy is composed of transition metals with a weight percentage of not less than 97% Fe and one or more of Ni, Co, Mn, Cu, Nb, Zn, and boron B with a weight percentage of 1 to 2%, used in steel or neodymium as a master alloy after refining Production of boron permanent magnet materials.

In the method for extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation, the lead-rare earth alloy obtained by separation in step 5 uses selective oxidation to separate the metal Pb in the Pb-RE alloy from various rare earth metals; or Based on the fact that the metal Pb vapor pressure is higher than the rare earth metal at the same temperature, vacuum distillation technology is used to separate the metal Pb from the rare earth metal in the Pb-RE alloy. The remaining mixed rare earth contains one or two of Nd, Pr, Dy, and Tb Above, the intermediate alloy is used to produce NdFeB permanent magnet materials.

The design idea of the present invention is:

Based on the principle of interaction between metal atoms, the greater the absolute value of the heat of mixing between the two elements, the stronger the interaction. Normally, a positive heat of mixing means that the atoms of two elements repel each other, and a negative heat of mixing means that the atoms of the element attract each other. From the point of view of the elements in the NdFeB alloy, the heat of mixing of any two of the elements Fe, Nd, and B is ΔH _Fe-Nd =+1kJ/mol, ΔH _Fe-B =-11kJ/mol, ΔH _Nd-B = -34kJ/mol, which indicates that the elements Fe, Nd, and B are mainly attracted to each other and have good affinity. It also means that it is difficult to separate these three elements in the NdFeB alloy. When the extractant metal Pb is introduced, the heat of mixing between them and Pb is ΔH _Fe-Bi = +29kJ/mol, ΔH _Nd-Pb = -49kJ/mol, ΔH _B-Pb = +45kJ/mol. It can be seen that Pb atoms and Fe atoms and Pb atoms and B atoms strongly repel each other, but Pb atoms and Nd atoms are strongly attracted to each other. Therefore, the rare earth Nd and other elements will rapidly diffuse into the metallic Bi liquid phase to achieve clean and efficient separation of rare earth elements from iron and boron elements.

The advantages and beneficial effects of the present invention are:

1. Rare earth has the reputation of "industrial vitamin" and is widely used in the preparation of rare earth permanent magnets, polishing, hydrogen storage, catalysis and other materials. NdFeB rare earth permanent magnets are used in hard disk drives, motors, wind power generation, new energy vehicles, etc. Key material. However, in the preparation process of these rare earth materials (such as neodymium iron boron permanent magnet materials), about 30% of waste materials such as sludge and scraps are generated. In addition, these products containing key rare-earth materials (such as computers, motors, automobiles, etc.) have a useful life and expire when they expire, resulting in a large amount of waste rare-earth permanent magnets. It is reported that the annual scrap volume of NdFeB rare earth permanent magnets in my country is 30,000 to 50,000 tons, and it is increasing year by year. In the neodymium iron boron permanent magnet, the weight percentage of the rare earth element reaches about 25-35%, and the weight percentage of the iron element is about 65-75%. It can be seen that the comprehensive and efficient separation and recycling of NdFeB waste have significant economic benefits.

2. The present invention helps to reduce the pressure of waste on the ecological environment. Rare earth permanent magnet materials are widely used in electronic appliances, industrial motors, wind power generation, electric vehicles, automobiles and other products. With the continuous advancement of science and technology and the upgrading of products, these products have gradually become solid waste. If the rare earth permanent magnet waste is improperly handled in the process of recycling, the secondary pollution caused will bring great harm to the ecological environment and pose a great threat to animals, plants and humans. For example, the acidity and alkalinity of groundwater and soil are seriously exceeding the standard; a large amount of smoke and dust are generated, causing serious pollution to the atmosphere. It can be seen that exploring new technologies and processes for NdFeB waste recycling and developing the comprehensive and efficient separation and recycling of NdFeB waste has significant environmental benefits.

3. The present invention uses metallic lead to separate and extract rare earth metals in NdFeB waste, and enables various metal elements in NdFeB waste to be efficiently recycled and reused, so as to realize the recovery and reuse of NdFeB permanent magnet waste . Under environmentally friendly conditions, the one-step clean and efficient separation and extraction of rare earth elements such as neodymium and iron and boron from neodymium iron boron waste are realized. This not only can effectively alleviate the resource shortage caused by the extremely unbalanced application of rare earth elements, but also promote the efficient recycling and sustainable development of rare earth resources in my country, which has long-term strategic significance.

Description of the drawings

Figure 1(a)-(c) is a schematic diagram of the selective distribution of rare earth element RE in the liquid phase separation system (L ₁ +L ₂ ) to efficiently separate and recover rare earth elements in NdFeB waste. Among them, Figure 1 (a) shows the rare earth element RE dissolved in L ₁ in the separation system, Figure 1 (b) shows the rare earth element RE dissolved in L ₂ in the separation system, and Figure 1 (c) shows the rare earth element RE distribution Near the interface of the two separated phases L ₁ and L ₂ .

Figures 2(a)-(d) are schematic diagrams of the specific implementation process of extracting rare earth elements from neodymium iron boron waste using metallic lead. Among them, Figure 2(a) shows the liquid-liquid separation to form two liquid phases rich in Fe and Pb, and Figure 2(b) shows the lower Pb-rich lead-rare earth alloy melt is introduced into a metal crucible container through the melt diversion port. Figure 2(c) shows the upper Fe-rich iron-boron alloy melt, and Figure 2(d) shows the Fe-rich iron-boron alloy melt introduced into another metal crucible container from the melt orifice. In the figure, 1—plug rod, 2—crucible, 3—induction coil, 4—iron-boron alloy melt, 5-lead rare earth alloy melt, 6—melt diversion port, 7—metal crucible container.

Figure 3 is a schematic diagram of the vacuum distillation separation of Pb-RE alloy, that is, the saturated vapor pressure logP(Pa)-temperature T(℃) relationship diagram of metal Pb and rare earth elements Nd, Pr, Dy, Tb.

Figure 4 is a schematic diagram of the selective oxidation and separation of Pb-RE alloy, that is, the free energy of formation of metal elements Pb and rare earth elements Nd, Pr, Dy, Tb and other oxides ΔG (kJ/mol)-temperature T (℃) relationship diagram .

Figure 5 is a microstructure diagram of the lower Pb-RE alloy melt enriched with rare earth elements after cooling and solidification.

Fig. 6 shows the solidified structure morphology of the Fe-B alloy remaining after the NdFeB waste is extracted with the rare earth elements by the liquid metal Pb.

Figure 7 shows the solidification structure of the lead-rare earth alloy after the lead-rare-earth alloy melt is filled with air to selectively oxidize the rare-earth elements therein and the rare-earth elements are oxidized and floated.

Detailed ways

In the specific implementation process, the present invention provides a method for efficiently separating and recovering rare earth elements in neodymium iron boron waste materials, using the selective distribution law of rare earth elements in the separation system to achieve extraction and separation of rare earth metal elements from neodymium iron boron waste materials. As shown in Figure 1(a)-(c), generally speaking, there are three selective distributions of rare earth element RE in the separation system: ① The rare earth element RE is dissolved in L ₁ in the separation system, as shown in Figure 1(a ); ②The rare earth element RE is dissolved in L ₂ in the separation system, as shown in Figure 1(b); ③The rare earth element RE is neither dissolved in L ₁ nor dissolved in L ₂ in the separation system, but distributed Near the interface of the two separated phases L ₁ and L ₂ , see Figure 1(c).

According to this principle, the rare earth element RE (Nd, Pr, Dy, etc.) in the NdFeB scrap is separated from the transition metal TM (Fe, Co, Ni, Cu, etc.) efficiently, and almost all the rare earth elements are enriched in the liquid state. Among the metal Pb, a Pb-RE alloy melt is formed.

Then, using the difference in physical properties between metallic lead and rare earth metals, vacuum distillation or selective oxidation is used to separate metallic Pb from rare earth elements RE (Nd, Pr, Dy, etc.) in the Pb-RE alloy melt. The liquid metal Pb is used to extract the rare earth elements from the NdFeB scrap to realize the separation and recovery of the rare earth elements from the Pb-RE alloy melt; in addition, after the rare earth elements in the NdFeB scrap are extracted by the liquid metal Pb, the remaining metal is eliminated Most of them are Fe and a small amount of B element. After refining, Fe-B alloy is recycled as a master alloy for the production of NdFeB permanent magnet materials or as a master alloy for the production of special steel. The method for extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation has short technological process, no need to use chemical reagents, operation time period, low energy consumption, zero emission, no secondary pollution, and metal resource recovery at the utilization rate Higher merit.

The method for separating rare earth elements in NdFeB waste with metallic lead liquid-liquid provided by the present invention is the key to constructing a liquid-liquid separation system from NdFeB waste and metallic lead extractant, that is, the metallic lead extractant and The NdFeB waste materials contact to form a liquid-liquid contact surface (rather than a liquid-solid contact surface). At the same time, under the condition of not lower than the melting point of NdFeB, the two liquid phases can be brought into huge contact by mechanical stirring. Area, the diffusion distance of rare earth elements to the metal lead extractant is reduced, and the rare earth elements are quickly and fully enriched in the metal lead extractant, so that no less than 95% of the rare earth elements are enriched in the metal lead extractant within 5-30 minutes ; Then the mechanical vibration technology is used to promote the rapid separation of the liquid iron-boron alloy and the liquid lead-rare earth alloy with the difference in density to form the upper and lower layers.

It should be noted here that if the rare earth elements in the NdFeB waste are extracted and recovered by the metal lead extractant, a liquid-solid separation system is formed between the liquid metal lead and the NdFeB waste (that is, the NdFeB waste is Solid). Specifically, under the condition of 800°C, a liquid-solid reaction interface is formed between the liquid metal lead and the solid NdFeB, and the interface is maintained at 800°C for 2 hours to cause a diffusion reaction between the two. Then, the diffusion couple was observed and analyzed. The results showed that a diffusion reaction occurred at the liquid-solid interface. The rare earth elements in the solid NdFeB diffused into the liquid metal lead. The thickness of the rare earth element diffusion layer in the solid NdFeB was about 2.5 mm. If other conditions remain unchanged, the holding time is increased from 2 hours to 5 hours. At this time, it is observed that the thickness of the rare earth element diffusion layer in the solid NdFeB is about 4.5mm, and in the thickness region of the solid NdFeB diffusion layer, the rare earth neodymium The content is still about 5-7% mass content. It can be seen that when the liquid-solid interface contact system is used to extract rare earth elements, there will be the following technical problems: 1) Long operation time and low extraction efficiency; 2) High energy consumption (time × temperature) and high cost; 3) For neodymium The size of iron-boron scrap is limited, and it is difficult for bulk scraps with larger sizes (such as larger than 5mm); 4) The extraction rate of rare earths is low and the recovery rate is not high; 5) Liquid metal lead and solid neodymium iron It is difficult to completely separate boron particles, and it is inconvenient to realize continuous industrial production; 6) The operation time is long, which easily leads to the volatilization of metallic lead. The Fe-Pb liquid-liquid separation system constructed by the present invention can solve the above-mentioned technical problems existing in the liquid-solid separation system.

The method first melts the metallic lead Pb in an induction heating furnace; then adds the NdFeB waste to the liquid metal lead, and heats it to a certain temperature so that the rare earth elements in the NdFeB waste quickly diffuse into the metal lead liquid, in order to achieve Efficient and rapid extraction of rare earth elements in NdFeB waste materials can heat up the melting of NdFeB waste materials and cause liquid-liquid separation to form two immiscible solution phases of lead-rich rare earth Pb-RE and iron-rich Fe-B; hold for a certain period of time Afterwards, the rare earth elements in the NdFeB waste are fully enriched in the liquid metal lead to form a lead-rare earth Pb-RE alloy melt, and the rare earth elements in the NdFeB waste are extracted by the metal lead liquid and the residue is iron boron Fe-B alloy; finally, based on the difference in density between the two, the Pb-RE alloy melt is separated from the Fe-B iron-boron alloy. After refining, Fe-B iron-boron alloy can be recycled as an intermediate alloy for the production of neodymium iron-boron permanent magnet materials or as an intermediate alloy for the production of special steel; the metals Pb and RE in the lead-rare earth Pb-RE alloy can be vacuum evaporated or selectively oxidized Law separation. Follow the steps below:

Step 1. Clean the dirt on the surface of the NdFeB waste material and dry it;

Step 5, separating the lead and rare earth Pb-RE alloy melt from the iron-boron Fe-B alloy, and then using vacuum evaporation or selective oxidation to separate the rare earth from the lead metal in the lead rare earth alloy.

As shown in Figure 3, for the separated lead and rare earth Pb-RE alloys, the vapor pressures of the metals Pb and RE are different. According to the saturation vapor pressure-temperature diagram of metal Pb and rare earth elements Nd, Pr, Dy, Tb, the vapor pressures of Pb, Nd, Pr, Dy and other metal elements in the Pb-RE alloy melt are different at the same temperature. Vacuum is used Distillation method separates various metals, and then obtains pure metal element with a purity of more than 99wt%; or based on the highest vapor pressure of metal Pb at the same temperature, vacuum evaporation technology is used to first separate the Pb element in the Pb-RE alloy, and then the remaining mixed rare earth ( Containing Nd, Dy, Pr, etc.) to be recycled as a master alloy for the production of NdFeB permanent magnet materials. In addition, as shown in FIG. 4, the free energy of formation of oxides such as metal Pb and rare earth elements RE (Nd, Pr, Dy, Tb) is different. At the same temperature, the rare earth elements preferentially oxidize to form oxides, so that the liquid metal Pb is separated from the rare earth elements RE.

After the NdFeB waste is extracted with rare earth elements by the metal Pb liquid, the remaining NdFeB waste is an iron-boron alloy, and the rare earth elements are distributed in the metal lead Pb liquid. When the temperature is about 1350°C, the NdFeB waste material melts and forms a liquid-liquid immiscible system with the metallic lead liquid. After separation, it solidifies to form a lead rare earth alloy (Figure 5) and an iron-boron alloy (Figure 6). Analysis shows that the total mass percentage of transition metals Fe, Co, Ni, Cu, etc. in the Fe-rich metal melt is above 98%, and the total mass percentage of rare earth elements Nd, Pr, and Dy is between 0.1 to 1.5%. This shows that it is feasible to extract and recover rare earth elements in NdFeB waste using metallic Pb. The invention can comprehensively recover light rare earth elements Nd, Pr, etc., heavy rare earth elements Dy, etc., transition metals Fe, Co, Ni, etc. and boron B elements in neodymium iron boron waste in one step, so that the metal resource separation and extraction process is improved. Simplified, has the characteristics of high efficiency, energy saving, zero emission, environmental friendliness, etc., and has economic and environmental benefits.

Hereinafter, the invention will be further described in detail through embodiments.

Example 1

In this embodiment, the rare earth strong magnet neodymium iron boron scraps purchased on the market are first demagnetized, and then the surface stains are cleaned, and dried for use. Configure NdFeB waste and metallic lead Pb in a weight ratio of 1:1, weigh out 500 grams of NdFeB waste and metallic lead, for a total mixture of 1,000 grams.

As shown in Figure 2(a)-(d), first use the alumina plug 1 to close the melt diversion port 6 at the bottom of the alumina crucible 2 in the vertical direction, and then load 1000 grams of the mixture into In the alumina crucible 2 of the induction melting furnace, the mixture is heated by induction coils 3 evenly distributed on the periphery of the alumina crucible 2 under the protection of argon, and heated until the NdFeB rare earth permanent magnet scrap is melted until the alumina rod is used When stirring, feel that there is no obvious unmelted solid in the crucible. Then, the melt in the crucible 2 was kept standing at 1400°C for 7 minutes. Liquid-liquid separation forms two liquid phases rich in Fe and Pb. Because the density of the Fe-rich liquid phase is lower than that of the Pb-rich liquid phase, the Fe-rich liquid phase floats up under the action of gravity, while the Pb-rich liquid phase sinks, forming a layered structure of Fe-rich and Pb-rich liquid phases. The upper layer is neodymium iron. The boron waste is extracted by the metal Pb solution to form a Fe-rich iron-boron alloy melt 4, and the lower layer is the rare earth element enriched into the liquid metal Pb to form a Pb-rich lead rare earth alloy melt 5, as shown in Figure 2(a). Start the stopper rod 1, and move the stopper rod 1 upwards by 6-8mm. At this time, the lower Pb-rich Pb-rare earth alloy melt 5 flows out through the melt diversion port 6, and the metal crucible container 7 below the crucible 2 is used to hold the Pb-rich Lead rare earth alloy melt 5, see Figure 2(b). When the lower Pb-rich Pb-rare earth alloy melt 5 in the alumina crucible 2 flows out from the melt diversion port 6, the upper Fe-rich iron-boron alloy melt 4 is left, and the stopper rod 1 is activated to reset and guide the melt Orifice 6 is plugged, see Figure 2(c). After replacing another metal crucible container under the crucible 2, start the stopper rod 1 again to make the Fe-rich iron-boron alloy melt 4 in the alumina crucible 2 lead into another metal crucible container from the melt diversion port 6, see Figure 2(d). After the Fe-rich iron-boron alloy melt 4 in the alumina crucible 2 has flowed out, start the stopper 1 to reset, plug the melt orifice 6, add the mixture of NdFeB scrap and metal Pb in the next furnace, and start loading A batch cycle operation. After the Fe-rich and Pb-rich alloy melts are cooled and solidified, samples are taken for analysis and testing.

The results show that, in the Pb-rich alloy ingot, the weight percentage of rare earth elements (Nd, Pr, Dy) is 13.36%, the metal Pb weight percentage is 86.14%, the metal Fe weight percentage is 0.4%, and the metal Co weight percentage. The percentage content is 0.03%, and the metal Ni weight percentage is 0.07%. In Fe-rich alloy ingots, the weight percentage of rare earth elements (Nd, Pr, Dy) totals 0.28%, the weight percentage of metal Pb is 0.06%, the weight percentage of metal Fe is 94.76%, and the weight percentage of metal Co. It is 1.92%, the weight percentage of metal Ni is 1.77%, and the weight percentage of element B is 1.21%.

It can be seen that when the NdFeB scrap and metal Pb are configured in a weight ratio of 1:1, the heavy and light rare earths in the NdFeB scrap are extracted by the liquid metal Pb in a short time, and the recovery rate of rare earth elements reaches 99.6%. . This Example 1 proves the correctness of the principle of the present invention.

Example 2

In this embodiment, the rare earth strong magnet neodymium iron boron scraps purchased on the market are first demagnetized, and then the surface stains are cleaned, and dried for use. Configure NdFeB waste and metallic lead Pb in a weight ratio of 3:2, weigh 600 grams of NdFeB waste and 400 grams of metallic lead, for a total mixture of 1000 grams.

The results show that in the Pb-rich alloy ingot, the weight percentage of rare earth elements (Nd, Pr, Dy) is 32.73%, the metal Pb weight percentage is 66.68%, the metal Fe weight percentage is 0.48%, and the metal Co weight percentage is The percentage content is 0.04%, and the metal Ni weight percentage is 0.07%. In Fe-rich alloy ingots, the weight percentage of rare earth elements (Nd, Pr, Dy) is 0.93%, the weight percentage of metal Pb is 0.08%, the weight percentage of metal Fe is 94.16%, and the weight percentage of metal Co. It is 1.89%, the weight percentage of metal Ni is 1.75%, and the weight percentage of element B is 1.19%.

It can be seen that when the NdFeB scrap and metal Pb are configured in a weight ratio of 3:2, the heavy and light rare earths in the NdFeB scrap are extracted by the liquid metal Pb in a short time, and the recovery rate of rare earth elements reaches 96.1% . Compared with Example 1, when the weight ratio of iron-boron scrap and metal Pb is reduced, the separation rate of rare earth and iron-boron alloy decreases, and the recovery rate of rare earth decreases.

Example 3

In this embodiment, the rare earth strong magnet neodymium iron boron scraps purchased on the market are first demagnetized, and then the surface stains are cleaned, and dried for use. Configure NdFeB waste and metallic lead Pb in a weight ratio of 2:1, weigh 800 grams of NdFeB waste and 400 grams of metallic lead, for a total mixture of 1200 grams.

As shown in Figure 2(a)-(d), first use the alumina plug rod 1 to close the melt diversion port 6 at the bottom of the alumina crucible 2 in the vertical direction, and then load 1200 grams of the mixture into In the alumina crucible 2 of the induction melting furnace, the mixture is heated by induction coils 3 evenly distributed on the periphery of the alumina crucible 2 under the protection of argon, and heated until the NdFeB rare earth permanent magnet scrap is melted until the alumina rod is used When stirring, feel that there is no obvious unmelted solid in the crucible. Then, the melt in the crucible 2 was kept standing at 1400°C for 7 minutes. Liquid-liquid separation forms two liquid phases rich in Fe and Pb. Because the density of the Fe-rich liquid phase is lower than that of the Pb-rich liquid phase, the Fe-rich liquid phase floats up under the action of gravity, while the Pb-rich liquid phase sinks, forming a layered structure of Fe-rich and Pb-rich liquid phases. The upper layer is neodymium iron. The boron waste is extracted by the metal Pb solution to form a Fe-rich iron-boron alloy melt 4, and the lower layer is the rare earth element enriched into the liquid metal Pb to form a Pb-rich lead rare earth alloy melt 5, as shown in Figure 2(a). Start the stopper rod 1, and move the stopper rod 1 upwards by 6-8mm. At this time, the lower Pb-rich Pb-rare earth alloy melt 5 flows out through the melt diversion port 6, and the metal crucible container 7 below the crucible 2 is used to hold the Pb-rich Lead rare earth alloy melt 5, see Figure 2(b). Then, air was charged into the lead-rare earth alloy melt at a flow rate of 5 liters/min. The rare earth elements were preferentially oxidized and the rare earth oxides floated up. After being filled with air for 4 minutes, the lead-rare earth alloy melt was cooled and solidified. When the lower Pb-rich Pb-rare earth alloy melt 5 in the alumina crucible 2 flows out from the melt diversion port 6, the upper Fe-rich iron-boron alloy melt 4 is left, and the stopper rod 1 is activated to reset and guide the melt Orifice 6 is plugged, see Figure 2(c). After replacing another metal crucible container under the crucible 2, start the stopper rod 1 again to make the Fe-rich iron-boron alloy melt 4 in the alumina crucible 2 lead into another metal crucible container from the melt diversion port 6, see Figure 2(d). After the Fe-rich iron-boron alloy melt 4 in the alumina crucible 2 has flowed out, start the stopper 1 to reset, plug the melt orifice 6, add the mixture of NdFeB scrap and metal Pb in the next furnace, and start loading A batch cycle operation. After the Fe-rich and Pb-rich alloy melts are cooled and solidified, samples are taken for analysis and testing.

The results show that when the lead-rare earth alloy melt is not filled with air, the weight percentage of rare earth elements (Nd, Pr, Dy) in the Pb-rich alloy ingot is 37.44%, and the weight percentage of metal Pb is 61.81%. The weight percentage of metal Fe is 0.61%, the weight percentage of metal Co is 0.05%, and the weight percentage of metal Ni is 0.09%. When the lead-rare earth alloy melt is filled with air, the solidified structure of the Pb-rich alloy melt is shown in Figure 7. Comparing Figure 7 and Figure 5, it can be seen that the phase composition of the lead-rich rare earth alloy is different. Detection and analysis show that the content of rare earth in the lead-rare-earth alloy melt is greatly reduced after being filled with air. At this time, the weight percentage of rare earth elements (Nd, Pr, Dy) totaled 2.16%, the metal Pb weight percentage was 96.81%, the metal Fe weight percentage was 0.83%, and the metal Co weight percentage was 0.08%. , The weight percentage of metal Ni is 0.12%. In Fe-rich alloy ingots, the weight percentage of rare earth elements (Nd, Pr, Dy) is 1.31%, the weight percentage of metal Pb is 0.11%, the weight percentage of metal Fe is 93.62%, and the weight percentage of metal Co. It is 1.92%, the weight percentage of metal Ni is 1.84%, and the weight percentage of element B is 1.2%.

It can be seen that when the NdFeB scrap and metal Pb are configured in a weight ratio of 2:1, the heavy and light rare earths in the NdFeB scrap are extracted by the liquid metal Pb in a short time, and the recovery rate of rare earth elements reaches 94.4% . Comparing Example 3 with Examples 1 and 2, when the weight ratio of iron-boron scrap and metal Pb is reduced, the separation rate of rare earth and iron-boron alloy is further reduced, and the recovery rate of rare earth is further reduced. This shows that when metal lead liquid is used to separate and extract rare earth elements from NdFeB waste, the recovery rate of rare earth elements can be improved by reducing the weight ratio of NdFeB waste to metal lead; in addition, lead-rare earth alloy melts can be used Selective oxidation separates lead from rare earths.

Claims

A method for separating and extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation is characterized in that it is carried out according to the following steps:

Step 1. Clean the dirt on the surface of the NdFeB waste material and dry it;

Step 2: Construct Fe-Pb immiscible separation system from NdFeB waste and metallic lead extractant;

Specifically, the NdFeB waste is placed in a crucible for melting metallic lead, and the melt in the crucible is stirred to make the NdFeB waste fully contact with the metallic lead;

Step 3, controlling the temperature of the metal material in the crucible, the rare earth elements are enriched in the metallic lead liquid to form a lead rare earth alloy melt, and the residual NdFeB scrap is in the form of iron-boron alloy;

Step 4, separating the lead-rare earth alloy melt from the iron-boron alloy, and separating the rare earth from the lead metal in the lead-rare earth alloy by vacuum evaporation or selective oxidation.
The method for extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation according to claim 1, wherein the chemical composition of the NdFeB waste recovered in step 1 mainly includes: rare earth elements Nd, Pr, One or more of La, Ce, Dy, Tb, Gd, Ho, Er, Y, one or more of transition metal elements Fe, Ni, Co, Mn, Cu, Nb, and Zn, and One or two or more of the other elements B, Al, Sn, and Ga.
The method for extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation according to claim 1, wherein the metal lead extractant used in step 2 contains lead and one of silver, magnesium and calcium elements Or two or more lead alloys, in which the lead content is not less than 50wt.%.
The method for extracting rare earth elements from NdFeB waste by metallic lead liquid-liquid separation according to claim 3, characterized in that the lead content of the metallic lead extractant is not less than 98wt.%.
The method for liquid-liquid separation and extraction of rare earth elements from NdFeB waste with metallic lead according to claim 1, wherein in step 2 the ratio of NdFeB waste and metallic lead extractant, NdFeB scrap and metallic lead The weight ratio W Nd-Fe-B /W Pb varies from 0.1 to 10.
The method for separating and extracting rare earth elements from NdFeB waste from metallic lead liquid-liquid according to claim 5, wherein the weight ratio of NdFeB waste to metallic lead W Nd-Fe-B /W Pb is 0.5-5 variation range.
The method for liquid-liquid separation and extraction of rare earth elements from NdFeB waste with metallic lead according to claim 1, characterized in that the materials of the crucible and the stirring rod for melting the metallic lead in step 2 are pure iron, alumina or graphite.
The method for separating and extracting rare earth elements from neodymium iron boron waste with metallic lead liquid-liquid according to claim 1, characterized in that, in step 3, the heating temperature of the metallic material in the crucible is between 1327°C and 1450°C.
The method for extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation according to claim 1, wherein in step 4, after the lead-rare earth alloy melt is separated from the iron-boron alloy, the iron-boron alloy is divided by weight Not less than 97% of transition metal Fe and one or more of Ni, Co, Mn, Cu, Nb, Zn, and 1 to 2% by weight of boron B element composition, after refining, the middle The alloy form is used in the production of steel or NdFeB permanent magnet materials.
The method for extracting rare earth elements from NdFeB waste by metal lead liquid-liquid separation according to claim 1, characterized in that the lead rare earth alloy obtained in step 4 is selectively oxidized to remove the metal Pb in the Pb-RE alloy Separate from various rare earth metals; or, based on the higher vapor pressure of metal Pb at the same temperature than rare earth metals, vacuum distillation technology is used to separate the metal Pb from the rare earth metals in the Pb-RE alloy, and the remaining mixed rare earth contains Nd, Pr, Dy One or more than two kinds of Tb are used to produce neodymium iron boron permanent magnet materials with intermediate alloy recycling.