Separation and recovery method for iron and rare earth elements in rare earth iron ore

Abstract

The invention belongs to the technical field of rare earth metallurgy and resource comprehensive utilization, and particularly relates to a method for separating and recycling iron and rare earth elements in rare earth iron ore. According to the method for separating and recycling the iron and the rare earth elements in the rare earth iron ore, the iron and the rare earth elements in the rare earth iron ore are recycled through MgO reduction roasting, and the efficient separation and extraction process of the iron and the rare earth elements is achieved by adding additives such as a reducing agent and MgO and through the procedures of reduction roasting, magnetic separation, selective leaching and selective precipitation. And comprehensive utilization of the rare earth-containing iron ore can be effectively realized.

Description

Technical Field

[0001] This invention belongs to the field of rare earth metallurgy and comprehensive resource utilization technology, specifically relating to a method for separating and recovering iron and rare earth elements in rare earth iron ore. Background Technology

[0002] Many rare, super-large polymetallic deposits, such as the Bayan Obo mine, exhibit extremely complex mineral compositions, containing over 210 mineral species, including 15 rare earth minerals. Currently, typical rare earth minerals, such as bastnaesite and monazite, are closely associated with iron minerals (mainly magnetite and hematite) and gangue minerals like fluorite and apatite, exhibiting complex intergrowth relationships and fine grain sizes. This intermingling of minerals is the fundamental reason for the difficulty in separating and extracting valuable elements and the low recovery rate.

[0003] Currently, complex combined beneficiation processes are mainly used in industrial production to process polymetallic associated rare earth iron ore. Taking Baotou Steel's beneficiation plant as an example, since 1990, a combined process of weak magnetic separation, strong magnetic separation, and flotation has been used to recover iron and rare earths from Bayan Obo ore. Years of production practice have shown that this process yields iron concentrate with a grade of 60%-61% and an iron recovery rate of 79%-80%; while the rare earth concentrate grade can reach over 60%, the recovery rate is only 18.37%, and a secondary rare earth concentrate with a grade of 39.91% can be obtained with a recovery rate of 16.7%. The overall rare earth recovery rate is less than 35%, which fully demonstrates that traditional beneficiation methods are insufficient for the efficient separation of this type of ore.

[0004] In recent years, to overcome the drawbacks of traditional mineral processing techniques, researchers have explored an innovative approach: direct reduction-magnetic separation-acid leaching. This technology converts iron oxides into magnetic metallic iron using a reducing agent, separates the iron resources via magnetic separation, enriches rare earth elements in the non-magnetic slag phase, and then recovers the rare earth elements through acid leaching. This approach is theoretically simpler and more environmentally friendly. The field anticipates the development of more processes capable of efficiently separating and extracting iron and rare earth elements, which will have a positive impact on the efficient and clean utilization of rare earth iron ore. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the comprehensive recovery of iron and rare earths from polymetallic rare earth-bearing iron ore. The process has the advantages of high rare earth recovery rate, reasonable process flow, environmental friendliness and strong equipment adaptability, and effectively solves the problems of low rare earth recovery rate, complex process flow, poor environmental performance and high equipment requirements.

[0006] To address the aforementioned technical problems, this invention provides a method for separating and recovering iron and rare earth elements from rare earth iron ore, comprising the following steps: (1) Reduction roasting: Rare earth iron ore is mixed with reducing agent and additives to obtain a mixture; the mixture is then subjected to high-temperature reduction roasting after briquetting to obtain roasted clinker; wherein, The reducing agent contains elemental carbon. The additive contains MgO; (2) Magnetic separation: The roasted clinker is crushed and subjected to magnetic separation, and the magnetic concentrate and magnetic tailings are collected separately; (3) Acid leaching: The magnetic separation tailings are added to acid solution for mixing and leaching reaction. After solid-liquid separation, leaching solution and leaching residue rich in rare earth compounds are obtained respectively. (4) Precipitation separation: Add a precipitant to the leachate and mix, and carry out a precipitation reaction. Collect the precipitate to obtain mixed rare earth precipitate.

[0007] Specifically, in the method for separating and recovering iron and rare earth elements in rare earth iron ore, in step (1), the reducing agent includes at least one of coal powder, coke powder or graphite powder; The amount of reducing agent added is 3-10 wt% of the mass of the rare earth iron ore, preferably 7-10 wt%.

[0008] Preferably, the fixed carbon content of the reducing agent powder is ≥95%.

[0009] Specifically, in the method for separating and recovering iron and rare earth elements in the rare earth iron ore, in step (1), the amount of additive added is 1-10 wt% of the mass of the rare earth iron ore, preferably 7-10 wt%.

[0010] More preferably, the purity of the additive powder is ≥99.9%.

[0011] Specifically, in the method for separating and recovering iron and rare earth elements in rare earth iron ore, in step (1), the temperature of the reduction roasting step is 900-1200℃, preferably 1100-1200℃, and the reaction time is 0.5-3h, preferably 2-3h.

[0012] Specifically, in the method for separating and recovering iron and rare earth elements in rare earth iron ore, in step (2), the magnetic field strength of the magnetic separation step is 50-175mT, preferably 100-130mT.

[0013] Specifically, in the method for separating and recovering iron and rare earth elements in rare earth iron ore, step (2) includes the crushing step of crushing the roasted clinker to a particle size of less than 45 μm.

[0014] Specifically, in the method for separating and recovering iron and rare earth elements in rare earth iron ore, in step (3), the acid solution includes dilute sulfuric acid, dilute hydrochloric acid, and dilute nitric acid solution; The concentration of the acid solution is 0.5-3 mol / L, preferably 1-2 mol / L; The liquid-solid mass ratio of the acid solution to the magnetic separation tailings is 5:1-30:1; The leaching reaction temperature is 20-90℃, preferably 60-90℃, and the leaching reaction time is 10-120min, preferably 90-120min.

[0015] Specifically, in the method for separating and recovering iron and rare earth elements in the rare earth iron ore, in step (4), the precipitant includes oxalic acid solution; The pH value of the mixture of the leachate and the oxalic acid solution is 1-3; The molar ratio of oxalic acid to the rare earth compounds in the leachate is 0.5:1 to 3:1. The concentration of rare earth compounds in the mixture of the leachate and the oxalic acid solution is 1-10 g / L. The precipitation reaction is carried out at a temperature of 20-100℃, preferably 40-60℃.

[0016] Specifically, in the method for separating and recovering iron and rare earth elements in the rare earth iron ore, step (4) further includes calcining the mixed rare earth precipitate at 800-1000℃ for 1-3 hours to obtain mixed rare earth oxides.

[0017] This invention also discloses the application of the method for separating and recovering iron and rare earth elements in rare earth iron ore in the field of rare earth element recovery.

[0018] This invention discloses a method for separating and recovering iron and rare earth elements from rare earth iron ore. Specifically, it addresses the comprehensive recovery of iron and rare earth elements from polymetallic rare earth iron ore (such as the Bayan Obo mine). The method utilizes MgO reduction roasting to recover iron and rare earth elements from the ore. By adding reducing agents and MgO, the process involves reduction roasting, magnetic separation, selective leaching, and selective precipitation. Specifically, the rare earth iron ore is mixed with reducing agents and MgO powder, followed by reduction roasting. The roasted clinker is then ground and magnetically separated to obtain metallic iron powder and rare earth-rich slag. The rare earth-rich slag is then selectively leached and selectively precipitated to obtain a high-purity mixed rare earth oxide product. This process achieves efficient separation and extraction of iron and rare earth elements, effectively enabling the comprehensive utilization of rare earth iron ore. The method described in this invention has the advantages of a short process, low energy consumption, and environmental friendliness, providing a new approach for the efficient utilization of complex rare earth iron ore.

[0019] The method for separating and recovering iron and rare earth elements in rare earth iron ore described in this invention is based on the recovery of iron and rare earth elements from rare earth iron ore by MgO reduction roasting. By introducing MgO as a multifunctional additive, and utilizing the multiple synergistic effects of MgO, the entire process is optimized from improving the phase composition and promoting the reaction to environmental protection, emission reduction, and element recycling. Its synergistic effects are specifically reflected in the following aspects, including: (1) During the reduction roasting process, the added MgO adjusts the basicity of the slag system. MgO will preferentially combine with SiO2 in the raw materials, effectively inhibiting the formation of low melting point and high viscosity silicate phases such as Fe2SiO4 (ferroolitic), inhibiting the formation of ferroolitic and improving the slag phase fluidity, promoting the aggregation of iron particles and improving the iron recovery rate. On the other hand, MgO can improve the fluidity of the slag, creating favorable conditions for the aggregation and sedimentation of metallic iron, thereby improving the iron recovery rate and iron grade in the subsequent magnetic separation process. (2) The addition of MgO is crucial for rare earth recovery. It can reduce the decomposition temperature of rare earth minerals and improve the decomposition efficiency of rare earth minerals. The magnesium element in the slag will be converted into soluble magnesium salt (magnesium sulfate) during the leaching process. It will not form precipitates or complexes that interfere with the leaching of rare earth ions, thus ensuring the smooth and efficient rare earth extraction process. (3) Magnesium can combine with fluorine in slag to inhibit the formation of fluorine-containing waste gas and achieve green smelting. Under high-temperature roasting conditions, fluorine in minerals is easily released in the form of HF and SiF4. On the one hand, the addition of MgO can combine with fluoride ions to form stable compounds such as MgF2, which firmly fixes fluorine in the solid slag. On the other hand, MgO inhibits the formation of SiF4, thereby inhibiting the generation of fluorine-containing waste gas and eliminating this important environmental pollution risk from the source, making the process more environmentally friendly. (4) In the whole process, magnesium element realizes efficient "function-recovery" closed loop; the magnesium ions (such as MgSO4) that enter the leachate are in the form of soluble sulfates when sulfuric acid is leached, and do not form precipitates such as calcium sulfate that affect rare earth leaching. After the selective precipitation of rare earth by oxalic acid, they are still enriched in the mother liquor and can be recovered by mature separation methods such as crystallization. The recovered magnesium salts can be used as chemical raw materials or returned to the process for reuse, realizing the recycling of magnesium. This not only reduces the consumption of new raw materials and realizes the recycling of magnesium resources, but also avoids the discharge of magnesium element in the form of waste liquid, further improving the economy and environmental protection of the whole process.

[0020] The present invention describes a method for separating and recovering iron and rare earth elements in rare earth iron ore. Using MgO as an additive, the method employs a process of reduction roasting, magnetic separation, selective leaching, and selective precipitation to achieve efficient separation and extraction of iron and rare earth elements, thus meeting the urgent need for efficient and clean utilization of rare earth-containing iron ore such as Bayan Obo.

[0021] The method for separating and recovering iron and rare earth elements in rare earth iron ore described in this invention achieves an iron metallization rate of over 99% during the reduction roasting stage. After magnetic separation, the iron recovery rate reaches over 95%, and the iron concentrate obtained has an iron grade exceeding 85%, making it suitable for direct use as a high-quality steelmaking raw material. In rare earth extraction, the preferred embodiment achieves a rare earth leaching rate exceeding 98%, a precipitation rate exceeding 99%, and a final mixed rare earth oxide purity of 99%, with a comprehensive rare earth recovery rate of over 96% throughout the entire process. This mixed rare earth oxide product can be directly dissolved in inorganic acids and then flexibly used in rare earth extraction processes, exhibiting strong process adaptability. The entire process achieves efficient recovery and utilization of iron and rare earth resources, with no waste gas or residue emissions, forming a complete environmentally friendly resource comprehensive recovery technology system. Attached Figure Description

[0022] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein... Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] The present invention provides a method for the comprehensive recovery of iron and rare earth from rare earth-bearing iron ore containing polymetallic symbiotic deposits in the following embodiments. The process has the advantages of high rare earth recovery rate, reasonable process flow, environmental friendliness and strong equipment adaptability.

[0025] In the following embodiments of the present invention, the method for separating and recovering iron and rare earth elements from rare earth iron ore includes the following steps: (1) Reduction roasting: Rare earth iron ore is mixed with reducing agent and additives to obtain a mixture; and the mixture is briquetting and then subjected to high-temperature reduction roasting to obtain roasted clinker; (2) Magnetic separation: The roasted clinker is crushed and subjected to magnetic separation, and the magnetic concentrate and magnetic tailings are collected separately; (3) Acid leaching: The magnetic separation tailings are added to acid solution for mixing and leaching reaction. After solid-liquid separation, leaching solution and leaching residue rich in rare earth compounds are obtained respectively. (4) Precipitation separation: Add a precipitant to the leachate and mix, and carry out a precipitation reaction. Collect the precipitate to obtain mixed rare earth precipitate.

[0026] As an exemplary implementation, such as Figure 1 The process shown in the following embodiment of the present invention provides a method for separating iron and rare earth elements in rare earth-containing iron ore based on MgO reduction roasting, which includes the following steps: (1) Reduction roasting: The rare earth iron ore is mixed evenly with reducing agent powder and additive powder to obtain a mixture; the mixture is briquetting; the compacted material is reduced roasted at 900-1200℃ for 0.5-3h to obtain roasted clinker; (2) Magnetic separation: After cooling the roasted clinker obtained in step (1), crush and grind it with a mortar and pestle, and then perform magnetic separation under a magnetic field of 50-175mT. After all the slurry has flowed through the magnetic field, magnetic concentrate and magnetic tailings are obtained, dried and weighed separately for storage. (3) Sulfuric acid leaching: The magnetic separation tailings obtained in step (2) are mixed with a dilute sulfuric acid solution with a concentration of 0.5-3 mol / L and leaching reaction is carried out at 20-90℃ for 10-120 min. After that, solid-liquid separation is carried out to obtain sulfuric acid leaching solution and leaching residue rich in rare earth. (4) Oxalic acid precipitation: Add a precipitant solution to the leachate to obtain a mixed solution. The mixed solution is subjected to a precipitation reaction at 20-100℃. The precipitate is then separated by filtration to obtain a mixed rare earth precipitate.

[0027] The technical solution of the present invention will be further explained and described below with reference to specific embodiments.

[0028] Example 1 This embodiment focuses on the extraction and separation of rare earth-bearing iron ore tailings from Bayan Obo.

[0029] In this embodiment, the chemical composition of the tailings used is shown in Table 1 below, and is referred to as tailings separation and extraction.

[0030] Table 1 Chemical composition of Bayan Obo tailings (mass fraction / %)

[0031] As attached Figure 1 The flowchart shown illustrates the separation and recycling method described in this embodiment, which includes the following steps: (1) Mix 100g of tailings with 10wt% graphite powder with a fixed carbon content of 99% and 9.20wt% MgO powder with a purity of 99.9% to obtain 115g of mixture (the basicity is about 1.80 at this time); press the mixture into blocks and put them into a graphite crucible, heat it to 1200℃ in a high-temperature furnace and keep it at that temperature for 2 hours to ensure that the mixture is fully reduced; (2) Remove the graphite crucible and cool it to room temperature. Take out the roasted clinker and grind it to a particle size of less than 45 μm. Then, perform magnetic separation under a magnetic field strength of 125 mT to obtain 11.19 g of magnetic concentrate (iron powder) and 101.58 g of magnetic tailings (rare earth rich slag). (3) Weigh 20g of the magnetic separation tailings obtained in step (2), add it to a sulfuric acid solution with a concentration of 2mol / L at a liquid-to-solid ratio of 20:1, leach at 60℃ and 400r / min for 90min, and then filter to obtain a leachate rich in rare earth sulfide and magnesium sulfate and a leach residue rich in calcium fluoride and silicon dioxide. Dry the leach residue and store it. (4) Add oxalic acid solution to the leachate obtained in step (3) to obtain a mixed solution with pH 1.5. In the mixed solution, the molar ratio of oxalic acid to rare earth sulfide is 2:1 and the mass concentration of rare earth sulfide is 3g / L. The obtained mixed solution is precipitated at 40℃ and then filtered to obtain mixed rare earth oxalic acid precipitate. At this time, the main component in the leachate is magnesium sulfate. The mixed rare earth oxalic acid precipitate is calcined at 950℃ for 2 hours to obtain mixed rare earth oxides.

[0032] According to the test and calculation, in the magnetic separation part of step (2) of this embodiment, the iron element recovery rate reached 95.21% and the iron concentrate grade reached 87.52%; in the sulfuric acid leaching part of step (3), the rare earth leaching rate reached 97.15%; in the oxalic acid precipitation part of step (4), the rare earth recovery rate reached 99.53% and the rare earth purity reached 99.24%, and the overall rare earth recovery rate was 96.69%.

[0033] Example 2 This embodiment focuses on the extraction and separation of rare earth-bearing iron ore tailings from Bayan Obo.

[0034] In this embodiment, the chemical composition of the tailings used is shown in Table 2 below, and they are collectively referred to as tailings separation and extraction.

[0035] Table 2 Chemical composition of Bayan Obo tailings (mass fraction / %)

[0036] As attached Figure 1 The flowchart shown illustrates the separation and recycling method described in this embodiment, which includes the following steps: (1) Mix 10g of tailings with 10wt% graphite powder with a fixed carbon content of 99% and 8.02wt% MgO powder with a purity of 99.9% to obtain 11.5g of mixture (the basicity at this time is about 1.70); press the mixture into blocks and put them into a graphite crucible, heat it to 1200℃ in a high-temperature furnace and keep it at that temperature for 2 hours to ensure that the mixture is fully reduced; (2) Remove the graphite crucible and cool it to room temperature. Take out the roasted clinker and grind it to a particle size of less than 45 μm. Then, perform magnetic separation under a magnetic field strength of 125 mT to obtain 1.27 g of magnetic concentrate (iron powder) and 11.34 g of magnetic tailings (rare earth rich slag). (3) Weigh 2g of the magnetic separation tailings obtained in step (2), add it to a sulfuric acid solution with a concentration of 2mol / L at a liquid-to-solid ratio of 20:1, leach at 60℃ and 400r / min for 90min, and then filter to obtain a leachate rich in rare earth sulfide and magnesium sulfate and a leach residue rich in calcium fluoride and silicon dioxide. Dry the leach residue and store it. (4) Add oxalic acid solution to the leachate obtained in step (3) to obtain a mixed solution with pH 1.5. In the mixed solution, the molar ratio of oxalic acid to rare earth sulfide is 2:1 and the mass concentration of rare earth sulfide is 3g / L. The obtained mixed solution is precipitated at 40℃ and then filtered to obtain mixed rare earth oxalic acid precipitate. At this time, the main component in the leachate is magnesium sulfate. The mixed rare earth oxalic acid precipitate is calcined at 950℃ for 2 hours to obtain mixed rare earth oxides.

[0037] According to the test and calculation, in the magnetic separation part of step (2) in this embodiment, the iron element recovery rate reached 98.28% and the iron concentrate grade reached 86.42%; in the sulfuric acid leaching part of step (3), the rare earth leaching rate reached 98.42%; in the oxalic acid precipitation part of step (4), the rare earth recovery rate reached 99.16% and the rare earth purity reached 99.08%, and the overall rare earth recovery rate was 98.15%.

[0038] Example 3 This embodiment is based on the extraction and separation of rare earth-bearing iron tailings from Bayan Obo in Example 1, and specifically includes the following steps: (1) Mix 10g of tailings with 3wt% of coke powder with a fixed carbon content of 99% and 1wt% of MgO powder with a purity of 99.9% to obtain a mixture; press the mixture into briquettes and put them into a graphite crucible, heat it to 900℃ in a high-temperature furnace and keep it at that temperature for 3 hours to ensure that the mixture is fully reduced. (2) Remove the graphite crucible and cool it to room temperature. Take out the roasted clinker and grind it to a particle size of less than 45 μm. Then, perform magnetic separation under a magnetic field strength of 50 mT to obtain magnetic concentrate (iron powder) and magnetic tailings (rare earth rich slag). (3) Weigh the magnetic separation tailings obtained in step (2), add them to a 0.5 mol / L hydrochloric acid solution at a liquid-to-solid ratio of 5:1, leach for 120 min at a stirring speed of 400 r / min at 20℃, and then filter to obtain a leachate rich in rare earth chloride and magnesium chlorate and a leach residue rich in calcium fluoride and silicon dioxide. Dry the leach residue and store it. (4) Add oxalic acid solution to the leachate obtained in step (3) to obtain a mixed solution. In the mixed solution, the molar ratio of oxalic acid to rare earth chloride is 0.5:1, and the mass concentration of rare earth chloride is 1g / L. The obtained mixed solution is precipitated at 20℃, and then filtered to obtain mixed rare earth oxalic acid precipitate. At this time, the main component in the leachate is magnesium chloride. The mixed rare earth oxalic acid precipitate is calcined at 800℃ for 3 hours to obtain mixed rare earth oxides.

[0039] Example 4 This embodiment is based on the extraction and separation of rare earth-bearing iron tailings from Bayan Obo in Example 1, and specifically includes the following steps: (1) Mix 10g of tailings with 6wt% of coal powder with a fixed carbon content of 99% and 10wt% of MgO powder with a purity of 99.9% to obtain a mixture; press the mixture into blocks and put it into a graphite crucible, heat it to 1000℃ in a high-temperature furnace and keep it at that temperature for 0.5 hours to ensure that the mixture is fully reduced. (2) Remove the graphite crucible and cool it to room temperature. Take out the roasted clinker and grind it to a particle size of less than 45 μm. Then, perform magnetic separation under a magnetic field strength of 175 mT to obtain magnetic concentrate (iron powder) and magnetic tailings (rare earth rich slag). (3) Weigh the magnetic separation tailings obtained in step (2), add them to a 3 mol / L nitric acid solution at a liquid-to-solid ratio of 30:1, leach for 10 min at a stirring speed of 400 r / min at 90℃, and then filter to obtain a leachate rich in rare earth nitrate and magnesium nitrate and a leach residue rich in calcium fluoride and silicon dioxide. Dry the leach residue and store it. (4) Add oxalic acid solution to the leachate obtained in step (3) to obtain a mixed solution. In the mixed solution, the molar ratio of oxalic acid to rare earth nitrate is 3:1, and the mass concentration of rare earth nitrate is 10 g / L. The resulting mixed solution is precipitated at 100°C and then filtered to obtain mixed rare earth oxalic acid precipitate. At this time, the main component in the leachate is magnesium nitrate. The mixed rare earth oxalic acid precipitate is calcined at 1000°C for 1 hour to obtain mixed rare earth oxides.

[0040] Example 5 This embodiment is based on the extraction and separation of rare earth-bearing iron tailings from Bayan Obo in Example 1, and specifically includes the following steps: (1) Mix 10g of tailings with 7wt% graphite powder with a fixed carbon content of 99% and 7wt% MgO powder with a purity of 99.9% to obtain a mixture; press the mixture into blocks and put it into a graphite crucible, heat it to 1100℃ in a high-temperature furnace and keep it at that temperature for 2 hours to ensure that the mixture is fully reduced. (2) Remove the graphite crucible and cool it to room temperature. Take out the roasted clinker and grind it to a particle size of less than 45 μm. Then, perform magnetic separation under a magnetic field strength of 100 mT to obtain magnetic concentrate (iron powder) and magnetic tailings (rare earth rich slag). (3) Weigh the magnetic separation tailings obtained in step (2), add them to a sulfuric acid solution with a concentration of 1 mol / L at a liquid-to-solid ratio of 30:1, leach at 60℃ and 400 r / min for 90 min, and then filter to obtain a leachate rich in rare earth sulfide and magnesium sulfate and a leach residue rich in calcium fluoride and silicon dioxide. Dry the leach residue and store it. (4) Add oxalic acid solution to the leachate obtained in step (3) to obtain a mixed solution. In the mixed solution, the molar ratio of oxalic acid to rare earth sulfide is 3:1 and the mass concentration of rare earth sulfide is 10 g / L. The obtained mixed solution is precipitated at 60°C and then filtered to obtain mixed rare earth oxalic acid precipitate. At this time, the main component in the leachate is magnesium sulfate. The mixed rare earth oxalic acid precipitate is calcined at 900°C for 2 hours to obtain mixed rare earth oxides.

[0041] Comparative Example 1 The method for separating and recovering iron and rare earth elements in rare earth iron ore described in this comparative example is the same as that in Example 1, except that CaO is selected instead of MgO as the additive.

[0042] Test results show that the efficiency of separating and recovering iron and rare earth elements from rare earth iron ore based on calcium oxide is lower than that of the MgO separation process. Furthermore, although both calcium oxide and magnesium oxide can increase the alkalinity of the system, calcium oxide solution increases slag viscosity, affecting fluidity. In contrast, the magnesium oxide chosen in this invention reduces viscosity, improves slag fluidity, and promotes the aggregation and growth of reduced metallic iron particles, ultimately facilitating iron separation and recovery. Secondly, the addition of calcium oxide is detrimental to subsequent rare earth leaching. Calcium reacts with sulfuric acid during leaching to form calcium sulfate, making the leaching system more viscous. A large amount of calcium sulfate precipitate adsorbs rare earth ions, reducing the solubility of rare earth sulfate and hindering the wet separation and recovery of rare earths. Moreover, the mixing of calcium sulfate precipitate and leaching residue makes effective separation impossible and hinders recycling. Magnesium sulfate, however, is water-soluble and can be separated and extracted, enabling magnesium recycling. Therefore, this invention selects MgO as an additive, which offers the best rare earth separation efficiency and a simple and easy-to-operate process compared to other oxides.

[0043] In summary, the method for separating and recovering iron and rare earth elements in rare earth iron ore described in this invention utilizes MgO reduction roasting to recover iron and rare earth elements from rare earth iron ore. By adding reducing agents, MgO, and other additives, and through a process of reduction roasting-magnetic separation-selective leaching-selective precipitation, a highly efficient process for separating and extracting iron and rare earth elements is achieved, which can effectively realize the comprehensive utilization of rare earth iron ore.

[0044] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for separating and recovering iron and rare earth elements from rare earth iron ore, characterized in that, Includes the following steps: (1) Reduction roasting: Rare earth iron ore is mixed with reducing agent and additives to obtain a mixture; the mixture is then subjected to high-temperature reduction roasting after briquetting to obtain roasted clinker; wherein, The reducing agent contains elemental carbon. The additive contains MgO; (2) Magnetic separation: The roasted clinker is crushed and subjected to magnetic separation, and the magnetic concentrate and magnetic tailings are collected separately; (3) Acid leaching: The magnetic separation tailings are added to acid solution for mixing and leaching reaction. After solid-liquid separation, leaching solution and leaching residue rich in rare earth compounds are obtained respectively. (4) Precipitation separation: Add a precipitant to the leachate and mix, and carry out a precipitation reaction. Collect the precipitate to obtain mixed rare earth precipitate.

2. The method for separating and recovering iron and rare earth elements from rare earth iron ore according to claim 1, characterized in that, In step (1), the reducing agent includes at least one of pulverized coal, coke powder, or graphite powder; The amount of reducing agent added is 3-10 wt% of the mass of the rare earth iron ore.

3. The method for separating and recovering iron and rare earth elements from rare earth iron ore according to claim 2, characterized in that, In step (1), the amount of additive added is 1-10 wt% of the mass of the rare earth iron ore.

4. The method for separating and recovering iron and rare earth elements from rare earth iron ore according to claim 3, characterized in that, In step (1), the temperature of the reduction calcination step is 900-1200℃, and the reaction time is 0.5-3h.

5. The method for separating and recovering iron and rare earth elements from rare earth iron ore according to any one of claims 1-4, characterized in that, In step (2), the magnetic field strength of the magnetic separation step is 50-175mT.

6. The method for separating and recovering iron and rare earth elements from rare earth iron ore according to claim 5, characterized in that, In step (2), the crushing step includes crushing the roasted clinker to a particle size of less than 45 μm.

7. The method for separating and recovering iron and rare earth elements from rare earth iron ore according to any one of claims 1-4, characterized in that, In step (3), the acid solution includes dilute sulfuric acid, dilute hydrochloric acid, or dilute nitric acid solution; The concentration of the acid solution is 0.5-3 mol / L; The liquid-solid mass ratio of the acid solution to the magnetic separation tailings is 5:1-30:1; The leaching reaction temperature is 20-90℃, and the leaching reaction time is 10-120 min.

8. The method for separating and recovering iron and rare earth elements from rare earth iron ore according to claim 7, characterized in that, In step (4), the precipitant includes an oxalic acid solution; The pH value of the mixture of the leachate and the oxalic acid solution is 1-3; The molar ratio of oxalic acid to the rare earth compounds in the leachate is 0.5:1 to 3:

1. The concentration of rare earth compounds in the mixture of the leachate and the oxalic acid solution is 1-10 g / L. The precipitation reaction is carried out at a temperature of 20-100℃.

9. The method for separating and recovering iron and rare earth elements from rare earth iron ore according to claim 8, characterized in that, Step (4) further includes calcining the mixed rare earth precipitate at 800-1000℃ for 1-3 hours to obtain mixed rare earth oxides.

10. The application of the method for separating and recovering iron and rare earth elements in rare earth iron ore as described in any one of claims 1-9 in the field of rare earth element recovery.

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