Leaching method and device for rare earth in ionic rare earth ore

Abstract

The invention provides a leaching method and device for rare earth in ionic rare earth ore, and relates to the technical field of rare earth extraction.The leaching device comprises a plate-and-frame filter press used for pressing ionic rare earth ore slurry into a filter cake and leaching rare earth-containing leaching liquid from the filter cake under the action of a rare earth leaching agent; the sedimentation tank is used for collecting the rare earth-containing immersion liquid and carrying out sedimentation treatment on the rare earth-containing immersion liquid to obtain rare earth concentrate; according to the method, the plate-and-frame filter press is used for leaching the rare earth, the rare earth ore concentrate can be efficiently extracted from the ionic rare earth ore in an environment-friendly mode through the rare earth leaching mode, and the method has a good large-scale application prospect.

Description

Technical Field

[0001] This invention relates to the field of rare earth extraction technology, and in particular to a method and apparatus for leaching rare earths from ion-type rare earth ores. Background Technology

[0002] Ion-adsorption rare earth ore leaching processes can be classified into pond leaching, heap leaching, and in-situ leaching according to the leaching method.

[0003] Currently, in-situ leaching is encouraged by the state. Compared with pond leaching and heap leaching, it has advantages such as less damage to vegetation in the mining area and no off-site tailings storage, and is considered the best process for ion-adsorption rare earth mining. This technology uses ammonium sulfate as the leaching agent, which is directly injected into the ore body. The leachate is then pumped into a purification and sedimentation tank, where ammonium bicarbonate is used for purification and sedimentation. To avoid rare earth loss and ammonium sulfate leakage, this technology requires high bedrock conditions in the mine. However, when the bottom plate of the ore body fails to act as a flow barrier or the impermeable rock layer is far from the bottom of the ore body, ammonium sulfate leaching agent will inevitably leak from the bottom or side into the groundwater system and surface water bodies during the mining process, causing ammonia nitrogen or salt pollution in the mining area and surrounding small watersheds. At the same time, after the in-situ leaching is completed, the ammonia nitrogen adsorbed in the ore body is slowly released, causing long-term ammonia nitrogen pollution in the small watersheds. Therefore, continuous investment in remediation is required, which has disadvantages such as high difficulty and long time. In addition, improper injection may also lead to landslides, destroy farmland, and pose serious safety hazards.

[0004] Heap leaching is a simple and economical method for processing low-grade ores. It was initially used for leaching gold, silver, copper, uranium, and nickel, and later applied to the mining of ion-adsorption rare earth elements, using ammonium sulfate as the leaching agent and ammonium bicarbonate as the precipitant. The heap leaching process involves first arranging an impermeable layer on the heap, along with collection ditches, collection pipes, and diversion pipes to collect the leachate. The ion-adsorption rare earth ore is then placed on top of the collection system, and the leaching agent is injected into the top of the heap. The leachate is collected through the collection system at the bottom of the heap. Typically, the heap bottom area is 40–1000 m². 2 The heaps are 1.5 to 5 meters high, with a volume of 60 to 5000 tons. The bottom of the heap typically consists of a seepage barrier and a runoff channel. Compared with in-situ leaching, heap leaching solves the problem of rare earth loss and achieves a higher rare earth recovery rate, making it valuable for the mining of low-grade ion-adsorption rare earth deposits.

[0005] Pond leaching is the earliest industrialized method for mining ion-adsorption rare earth minerals. It requires the construction of leaching ponds, typically small in volume, with the bottom sloping along the direction of liquid collection. The leachate flows towards a collection pond along this slope. An artificial bottom plate and filter media are installed at the bottom of the leaching pond. The smaller, higher-grade rare earth ore particles are piled on top of the artificial bottom plate. A leaching agent (sodium chloride solution) is injected into the rare earth ore to obtain leachate and tailings. The mother liquor, with a lower leaching concentration, is recycled for further leaching. The resulting leachate is then precipitated using a precipitant (oxalic acid) to obtain rare earth concentrate. This process is a small-scale stirred leaching method and cannot be used for large-scale production. Furthermore, in order to ensure the rare earth yield, the pool leaching process requires the use of a large amount of sodium chloride, that is, the liquid-solid ratio of the leaching agent to the rare earth ore must be greater than 2.5 to ensure the completion of leaching. This necessitates the construction of a large number of stirred tanks for leaching. At the same time, the use of a large amount of leaching agent means that the entire system needs to use a large amount of washing water to wash the large amount of leachate remaining in the tailings, resulting in a serious problem of leachate swelling and an overall water imbalance.

[0006] In commonly used ion-adsorption rare earth ore extraction processes such as pond leaching, stirred leaching, and heap leaching, the off-site dumping of topsoil, tailings, and low-grade ore can have a significant impact on the mine's ecosystem. Furthermore, leaching agents remaining in the tailings, if left untreated, can be washed into the surrounding mining area soil by rainwater, leading to excessive levels of ammonia nitrogen and sulfate in nearby water bodies. Therefore, addressing the environmentally harmful residual leaching agents in tailings from off-site leaching processes is a necessary follow-up remediation step.

[0007] Therefore, in the field of rare earth extraction technology, how to achieve large-scale mining and ensure high rare earth yield while avoiding the use of large amounts of leaching agents during the ion-adsorption rare earth ore leaching process remains an urgent problem to be solved in the future. Summary of the Invention

[0008] To address the aforementioned problems, in a first aspect, the present invention provides a leaching apparatus for rare earth elements in ion-adsorption rare earth ores, the leaching apparatus comprising: Plate and frame filter press is used to press ion-type rare earth mineral slurry into filter cake and leach the filter cake with rare earth leaching solution under the action of rare earth leaching agent. A sedimentation tank is used to collect rare earth-containing leachate and to perform sedimentation treatment on the rare earth-containing leachate to obtain rare earth concentrate.

[0009] Optionally, the plate and frame filter press is provided with a pressing plate and at least one pressing assembly, the pressing assembly including a filter plate and a filter frame; the ion-type rare earth mineral slurry entering the pressing assembly is pressurized and dewatered under the action of the pressing plate to obtain filter cake and filtered water.

[0010] Optionally, the bottom of the plate and frame filter press is provided with a collection tank for collecting the washing liquid and filtrate flowing out of the plate and frame filter press.

[0011] Secondly, the present invention provides a method for leaching rare earth elements from ion-adsorption rare earth ores, the method being applicable to the leaching apparatus described in the first aspect above, the method comprising: Ion-type rare earth mineral slurry is injected into a plate and frame filter press for pressure dewatering to obtain filter cake and filtered water. A rare earth leaching agent is continuously injected into the filter cake fixed on the plate and frame filter press at a pressure of 0.05 MPa to 1.5 MPa to exchange and leach rare earth ions in the filter cake for 0.1 h to 2 h, obtaining a rare earth-containing leachate and a salt-containing filter cake; the amount of the rare earth leaching agent is 30% to 60% of the mass of the filter cake. The rare earth-containing leachate is transferred to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate.

[0012] Optionally, the rare earth leaching agent is one or more of ammonium sulfate, magnesium sulfate, and sodium chloride.

[0013] Optionally, the concentration of the rare earth leaching agent is 5 g / L-50 g / L.

[0014] Optionally, in the ionic rare earth slurry, the liquid-solid mass ratio of water to ionic rare earth ore is 2.5:1 to 20:1.

[0015] Optionally, the method further includes: reusing the filtrate to prepare the rare earth leaching agent, including: The pH of the filtrate is adjusted to 2-3 using an acid containing the anion of the leaching agent, and then reused as the rare earth leaching agent.

[0016] Optionally, the method further includes: washing the salt-containing filter cake to obtain washing liquid and washed filter cake; the washed filter cake is discharged after purging and piled up as tailings; the washing liquid is collected through the collection tank and used for secondary washing.

[0017] Optionally, the step of transferring the rare earth-containing leachate to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate includes: The rare earth-containing leachate is precipitated and filtered in the sedimentation tank using an alkaline precipitant to obtain rare earth concentrate and the filtrate; or The rare earth-containing leachate is precipitated directly in the sedimentation tank using oxalic acid to obtain rare earth oxalate and the filtrate; the rare earth oxalate is then calcined to obtain rare earth concentrate.

[0018] Optionally, the alkaline precipitant is one or more of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, and sodium carbonate.

[0019] Compared with the prior art, the present invention has the following advantages: This invention provides a method and apparatus for leaching rare earth elements from ion-adsorption rare earth ores, relating to the field of rare earth extraction technology. The leaching apparatus includes: a plate and frame filter press for pressing ion-adsorption rare earth ore slurry into a filter cake, and leaching the filter cake with a rare earth-containing leachate under the action of a rare earth leaching agent; a sedimentation tank for collecting the rare earth-containing leachate and performing sedimentation treatment on the rare earth-containing leachate to obtain rare earth concentrate. In this invention, the ion-adsorption rare earth ore slurry is injected into the plate and frame filter press for pressurized dewatering to obtain a filter cake and filtered water; a rare earth leaching agent is continuously injected into the filter cake fixed on the plate and frame filter press at a pressure of 0.05 MPa to 1.5 MPa to exchange and leach the rare earth ions in the filter cake for 0.1 h to 2 h. h, obtaining rare earth-containing leachate and salt-containing filter cake; washing the salt-containing filter cake to obtain washing liquid and washed filter cake; transferring the washing liquid to a collection tank for collection; unloading the washed filter cake after purging and stockpiling it as tailings; transferring the rare earth-containing leachate to a sedimentation tank for precipitation treatment to obtain rare earth concentrate and filtrate. Using the method provided by this invention, rare earth leaching is carried out using a plate and frame filter press. This rare earth leaching method can efficiently and environmentally extract rare earth concentrate from ion-adsorption rare earth ores, and has good prospects for large-scale application.

[0020] The rare earth leaching method provided in this invention differs from heap leaching, stirred leaching, or pool leaching processes. In this invention, a plate and frame filter press is used for rare earth extraction during the leaching process of ion-adsorption rare earth ores. A measured amount of rare earth leaching agent is injected into the plate and frame filter press, followed by pressurized leaching. This pressurized ion exchange method extracts rare earth elements. On one hand, pressurized ion exchange leaching under a certain high pressure (0.05 MPa~1.5 MPa) can improve the leaching yield and leaching rate of ion-adsorption rare earths, accelerating the mining and utilization of rare earth resources and improving rare earth efficiency. On the other hand, the plate and frame filter press artificially divides the leaching exchange process into multiple zones, increasing ion exchange efficiency and avoiding runoff or channeling. The production efficiency and rare earth yield are higher than those of in-situ leaching or heap leaching, which can further reduce the boundary grade of rare earth ores and increase the amount of rare earth resources. This achieves efficient, green, and controllable extraction of rare earth elements from ion-adsorption rare earth ores, yielding rare earth concentrate. Therefore, the method provided by this invention eliminates the need for a high liquid-to-solid ratio to improve rare earth yield and ensure leaching efficiency. This avoids the problems associated with maintaining a large amount of leaching agent in the filter cake, requiring extensive washing with large amounts of washing water, and the need for large stirring tanks that occupy significant space. Furthermore, since the key equipment used in the rare earth leaching process is a plate and frame filter press that can be mass-produced, the plate and frame filter press, composed of individual filter frames and plates, can be reused multiple times through skid-mounted installation, eliminating the difficulties associated with developing dedicated pressurized ion exchange equipment. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the plate and frame filter press in an embodiment of the present invention; Figure 2 A flowchart of a method for leaching rare earth elements from ion-adsorption rare earth ores provided in an embodiment of the present invention; Figure 3 This is a flow chart of a rare earth leaching process in another ion-type rare earth ore provided in an embodiment of the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0024] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0025] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0026] In the description of this invention, it should be understood that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0027] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] Plate and frame filter presses are a well-established industrial device for solid-liquid separation, widely used in chemical, pharmaceutical, food, and environmental protection industries. They form a filtration chamber by stacking plate and frame components, applying pressure to achieve solid-liquid separation—that is, separating suspended solids from a liquid. This process purifies the liquid, recovers slurry, and ultimately yields the desired solid and liquid products. Through rational structural design and operational control, plate and frame filter presses can efficiently process slurry, improve material utilization, and reduce environmental pollution. They also boast advantages such as simple structure, convenient operation, and excellent filtration effect, thus finding widespread application in industrial production.

[0029] In this invention, a plate and frame filter press is used for rare earth extraction during the leaching process of ion-type rare earth ore. After injecting a small amount of rare earth leaching agent into the plate and frame filter press, the rare earth elements are leached by pressurized ion exchange, thereby achieving efficient, green and controllable extraction of rare earth elements from ion-type rare earth ore.

[0030] In a first aspect, the present invention provides a leaching device for rare earth elements in ion-adsorption rare earth ores, the leaching device comprising: Plate and frame filter press is used to press ion-type rare earth mineral slurry into filter cake and leach the filter cake with rare earth leaching solution under the action of rare earth leaching agent. A sedimentation tank is used to collect rare earth-containing leachate and to perform sedimentation treatment on the rare earth-containing leachate to obtain rare earth concentrate.

[0031] This invention utilizes a plate and frame filter press for rare earth extraction. Ionic rare earth slurry is pressed into a filter cake by the plate and frame filter press. A measured amount of leaching agent is then injected into the filter press. Under the action of the rare earth leaching agent, the filter cake leaches out a rare earth-containing leachate. The obtained rare earth-containing leachate is transferred to a sedimentation tank for precipitation treatment to obtain rare earth concentrate. This invention uses pressurized ion exchange to leach rare earth elements. Pressurized ion exchange leaching is performed under a certain high pressure (0.05 MPa~1.5 MPa), which can improve the leaching yield and leaching rate of ionic rare earths, accelerate the mining and utilization of rare earth resources, and improve rare earth efficiency.

[0032] See Figure 1The schematic diagram of the plate and frame filter press shown illustrates that the plate and frame filter press includes a pressing plate 5 and at least one set of pressing components. The pressing components consist of filter plates 2 and filter frames 3. Each filter frame 3 and filter plate 2 has a through hole at the upper right corner, forming a channel for the flow of ion-modified rare earth slurry. Similarly, each filter frame 3 and filter plate 2 has a through hole at the upper left corner, forming a channel for the flow of washing water. Each filter plate 2 has a liquid outlet 6 at its bottom. After the pressing plate 5 is tightened, a filter chamber is formed between adjacent filter plates 2. Then, the ion-modified rare earth slurry enters the plate and frame filter press through the liquid inlet 1. After the ion-modified rare earth slurry fills the filter chamber, the feeding is completed. After the feeding is completed, the pressing plate 5 continues to apply pressure to remove the water from the ion-modified rare earth slurry. After dehydration, the ion-type rare earth slurry is squeezed into each filter chamber and automatically forms a filter cake. When no liquid is discharged or only a small amount of liquid is discharged from the outlet 6 of the plate and frame filter press, it indicates that the filter cake has been completely filled with filter residue in the filter chamber.

[0033] This invention, through the setting of multiple sets of pressing components, artificially divides the leaching exchange process into multiple areas. The pressing components can be reused multiple times by means of equipment skid mounting, eliminating the difficulties in developing dedicated pressurized ion exchange devices. This increases ion exchange efficiency, avoids runoff or channeling, and achieves higher production efficiency and rare earth yield than in-situ leaching or heap leaching. It can further reduce the boundary grade of rare earth ore and increase the amount of rare earth resources, thereby achieving efficient, green, and controllable extraction of rare earth elements from ion-adsorption rare earth ores, resulting in rare earth concentrate.

[0034] See Figure 1 The schematic diagram of the plate and frame filter press shown shows that a collection tank 7 is set at the bottom of the plate and frame filter press. During the pressing of the filter cake, the squeezed filter water flows directly out of the outlet 6 of each filter plate along the grooves of the filter plate. The outflowing filter water can be returned for the preparation of the next batch of ion-adsorption rare earth ore slurry. The obtained filter cake is subjected to a rare earth leaching operation. When obtaining the rare earth leaching solution, the remaining salt-containing filter cake can be washed to obtain washing liquid and washed filter cake. The washing liquid is collected in the collection tank 6 and reused for secondary washing. The washed filter cake is discharged after purging and stacked as tailings.

[0035] Specifically, the leaching device provided in this embodiment of the invention performs the leaching task as follows: the filter plate 2 and filter frame 3 are pressed together by the pressing plate 5, forming a filter chamber between adjacent filter plates 2. After pressing, the feed pump and feed valve are opened, and feed is fed from the feed port 1 through the upper right corner. Feeding is complete when the ion-type rare earth slurry fills the filter chamber. After feeding, pressure is continued to be applied to remove the water in the ion-type rare earth slurry through the filter cloth on the filter plate 2. The dewatered ion-type rare earth slurry is squeezed into each filter chamber and automatically forms a filter cake. When there is no liquid or only a small amount of liquid at the outlet of the plate and frame filter press, it indicates that the filter cake has been completely filled with filter residue in the filter chamber. The squeezed-out filtrate flows directly out from the outlet 6 of each filter plate along the grooves of the filter plate. The outflowing filtrate is returned for conditioning the next batch of ion-type rare earth slurry.

[0036] Without unloading the filter cake, a rare earth leaching agent of 30-60% of the filter cake mass is continuously pressed into the filter cake fixed on the plate and frame filter press at a pressure of 0.05 MPa to 1.5 MPa to exchange and leach the rare earth ions in the filter cake for 0.1 h to 2 h, thereby obtaining a rare earth leaching solution and a salt-containing filter cake. Washing water is introduced through the feed inlet 1 in the upper left corner to wash the salt-containing filter cake, obtaining washing liquid and washed filter cake. When no liquid is discharged or only a small amount of liquid is discharged from the liquid outlet 6 of the plate and frame filter press, it indicates that the filter chamber is completely filled and a washed filter cake has been formed. The washing liquid is collected in the collection tank 7 and used as washing water for washing the salt-containing filter cake or recycled for preparing rare earth leaching agent. The feed pump and feed valve are turned off, and the air compressor and air inlet valve are turned on to purge the washed filter cake. After purging, the air compressor and its air inlet valve are turned off. After the pressing plate is returned to its original position, the unloading button is pressed, and each filter plate 2 is pulled open in sequence to unload the material. The unloaded material is piled up as tailings. At this point, the entire solid-liquid separation, rare earth extraction, and washing work of the plate and frame filter press is completed.

[0037] The rare earth leaching solution is subjected to precipitation treatment in a sedimentation tank to obtain rare earth concentrate and filtrate. The filtrate is collected in a collection tank and used to prepare rare earth leaching agent.

[0038] In some implementations, the plate and frame filter press and the collection tank are connected in series or in parallel.

[0039] In this embodiment, a plate and frame filter press is connected in series or in parallel with multiple collection tanks to achieve large-scale production and mining.

[0040] Secondly, the present invention provides a method for leaching rare earth elements from ion-adsorption rare earth ores, the method being applicable to the leaching apparatus described in the first aspect above. Figure 2 A flowchart of the leaching method for rare earth elements in ion-type rare earth ores provided in an embodiment of the present invention is shown, as follows: Figure 2 As shown, the method includes: S1. The ion-type rare earth mineral slurry is injected into the plate and frame filter press for pressurized dewatering to obtain filter cake and filtered water; Specifically, clean water is used to prepare ion-adsorption rare earth ore into a slurry to wet the ion-adsorption rare earth ore and ensure that the ion-adsorption rare earth ore can be transported to the plate and frame filter press in slurry form; the filtered water is returned to prepare the next batch of ion-adsorption rare earth ore.

[0041] Among them, the ion-adsorption rare earth ore is the southern ion-adsorption rare earth ore. Since the extraction process provided by this invention is carried out in a plate and frame filter press, and the plate and frame filter press used in this invention can achieve efficient extraction of rare earth elements, the method provided by this invention is more suitable for small-area, low-grade rare earth ore such as southern ion-adsorption rare earth ore.

[0042] During the pressurized dewatering process, there are no specific restrictions on the operating pressure and operating time of the plate and frame filter press. When no liquid is discharged from the outlet of the plate and frame filter press or only a small amount of liquid is discharged, it proves that the filter chamber has been completely filled to form a filter cake, and the pressurized dewatering is completed at this time.

[0043] S2. A rare earth leaching agent is continuously injected into the filter cake fixed on the plate and frame filter press at a pressure of 0.05 MPa to 1.5 MPa to exchange and leach the rare earth ions in the filter cake for 0.1 h to 2 h, obtaining a rare earth leaching solution and a salt-containing filter cake; the amount of the rare earth leaching agent is 30% to 60% of the mass of the filter cake. The amount of rare earth leaching agent used is based on the moisture content of the filter cake. For example, if the moisture content of the filter cake is 32.5%, then 32.5% of the total mass of the filter cake is injected with rare earth leaching agent.

[0044] In this embodiment, the entire leaching process is carried out in a plate and frame filter press. During the leaching process, the operating pressure of the plate and frame filter press is 0.05 MPa to 1.5 MPa, which ensures the leaching yield and leaching rate of the ionic rare earth elements.

[0045] Specifically, a smaller amount of rare earth leaching agent (compared to that used in pool leaching and stirred leaching) is injected into a plate and frame filter press, followed by pressurized ion exchange leaching (0.05 MPa to 1.5 MPa) for 0.1 h to 2 h to leach rare earth elements. After the exchange leaching is completed, the rare earth concentration (calculated as the total amount of rare earth oxides REO) in the leaching solution flowing out of the plate and frame filter press is less than 0.1 g REO / L [RZH1]. At this point, the rare earth elements in the ion-adsorption rare earth ore have been basically leached into the obtained rare earth-containing leaching solution. At this point, washing water is injected to wash the salt-containing filter cake.

[0046] The method provided in this embodiment, on the one hand, improves the leaching yield and leaching rate of ion-phase rare earths by performing pressurized ion exchange leaching under a certain high pressure (0.05 MPa~1.5 MPa), thereby accelerating the mining and utilization of rare earth resources and improving rare earth efficiency. On the other hand, by using a plate and frame filter press to artificially divide the leaching exchange process into multiple zones, the ion exchange efficiency is increased, runoff or channeling is avoided, and the production efficiency and rare earth yield are higher than those of in-situ leaching or heap leaching. This can further reduce the boundary grade of rare earth ore and increase the amount of rare earth resources, thereby achieving efficient, green, and controllable extraction of rare earth elements from ion-type rare earth ores and obtaining rare earth concentrate. Therefore, by using the method provided by this invention, there is no need to consider using a high liquid-to-solid ratio to improve the rare earth yield in order to ensure the leaching effect, thus avoiding the problems of needing a large amount of washing water to wash the large amount of leaching agent remaining in the filter cake and the large area occupied by a large stirring tank due to ensuring the leaching effect.

[0047] S3. The rare earth-containing leaching solution is transferred to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate.

[0048] Rare earth concentrates include rare earth enrichments, a small amount of water, and impurities such as iron.

[0049] In order to improve the leaching yield, the existing pool leaching and stirred leaching processes use a high liquid-to-solid ratio (liquid-to-solid ratio greater than 2.5) between the leaching agent and the rare earth ore. This requires a large number of stirred tanks for leaching. At the same time, the use of a large amount of leaching agent means that the entire system needs to use a large amount of washing water to wash the large amount of leachate remaining in the filter cake, which leads to serious problems of leachate swelling and overall water imbalance.

[0050] The rare earth leaching method provided in this invention differs from heap leaching, stirred leaching, or pool leaching processes. In this invention, a plate and frame filter press is used for rare earth extraction during the leaching process of ion-adsorption rare earth ores. A measured amount of rare earth leaching agent is injected into the plate and frame filter press, followed by pressurized leaching. This pressurized ion exchange method extracts rare earth elements. On one hand, pressurized ion exchange leaching under a certain high pressure (0.05 MPa~1.5 MPa) can improve the leaching yield and leaching rate of ion-adsorption rare earths, accelerating the mining and utilization of rare earth resources and improving rare earth efficiency. On the other hand, the plate and frame filter press artificially divides the leaching exchange process into multiple zones, increasing ion exchange efficiency and avoiding runoff or channeling. The production efficiency and rare earth yield are higher than those of in-situ leaching or heap leaching, which can further reduce the boundary grade of rare earth ores and increase the amount of rare earth resources. This achieves efficient, green, and controllable extraction of rare earth elements from ion-adsorption rare earth ores, yielding rare earth concentrate. Therefore, the method provided by this invention eliminates the need for a high liquid-to-solid ratio to improve rare earth yield and ensure leaching efficiency. This avoids the problems associated with maintaining a large amount of leaching agent in the filter cake, requiring extensive washing with large amounts of washing water, and the need for large stirring tanks that occupy significant space. Furthermore, since the key equipment used in the rare earth leaching process is a plate and frame filter press that can be mass-produced, the plate and frame filter press, composed of individual filter frames and plates, can be reused multiple times through skid-mounted installation, eliminating the difficulties associated with developing dedicated pressurized ion exchange equipment.

[0051] Furthermore, the method provided by this invention accelerates the production cycle and is less affected by changes in local rainfall.

[0052] In some embodiments, the rare earth leaching agent is one or more of ammonium sulfate, magnesium sulfate, and sodium chloride.

[0053] In some embodiments, the concentration of the rare earth leaching agent is 5 g / L-50 g / L.

[0054] In some embodiments, the rare earth leaching agent is continuously pressed into the filter cake fixed in the plate and frame filter press at a pressure of 0.3 MPa to 0.5 MPa.

[0055] In some embodiments, the ionic rare earth slurry is obtained by adjusting the liquid-solid mass ratio of water to ionic rare earth ore to 2.5:1 to 20:1.

[0056] In this embodiment, a certain mass ratio of water is used to prepare the ion-adsorption rare earth ore into a slurry. This mass ratio ensures that the ion-adsorption rare earth ore is wetted and can be transported in the form of a slurry.

[0057] In some embodiments, the method further includes: washing the salt-containing filter cake to obtain a washing solution and a washed filter cake; the washed filter cake is purged and then discharged as tailings; the washing solution is collected through the collection tank and used for secondary washing or for the preparation of rare earth leaching agents. Specific preparation methods include: using an anionic acid containing the leaching agent to adjust the pH of the washing solution to 2-3, and then reusing it as a rare earth leaching agent.

[0058] In this embodiment, washing water is used to wash the salt-containing filter cake in the plate and frame filter press. When the salt concentration in the washing liquid flowing out of the outlet of the plate and frame filter press is less than 2 g / L, it indicates that the salt in the salt-containing filter cake has been basically washed out, and the injection of washing water is stopped at this time.

[0059] In some embodiments, the method further includes: reusing the filtrate to prepare the rare earth leaching agent, including: The pH of the filtrate is adjusted to 2-3 using an acid containing the anion of the leaching agent, and then reused as the rare earth leaching agent.

[0060] The acid can be sulfuric acid.

[0061] In this embodiment, the filtrate or washing solution is returned to the leaching rare earth for recycling, so as to maintain the total water balance during the leaching process, thereby making reasonable use of the process solution and which is conducive to mine environmental management.

[0062] In some embodiments, the rare earth-containing leachate is transferred to the sedimentation tank for precipitation treatment to obtain rare earth concentrate and filtrate, including: The rare earth-containing leachate is precipitated and filtered in the sedimentation tank using an alkaline precipitant to obtain rare earth concentrate and the filtrate; or The rare earth-containing leachate is precipitated directly in the sedimentation tank using oxalic acid to obtain rare earth oxalate and the filtrate; the rare earth oxalate is then calcined to obtain rare earth concentrate.

[0063] In some embodiments, the alkaline precipitant is one or more of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, and sodium carbonate.

[0064] In some embodiments, the method further includes: Collect the leachate around the tailings after it has been piled up, and then discharge the leachate after unified treatment.

[0065] When ammonium sulfate is used as the leaching agent, the leachate is an ammonium sulfate solution.

[0066] In this embodiment, the residual leaching agent in the washed filter cake is uniformly treated before being discharged to achieve compliant discharge, thereby solving the problem of excessive ammonium ions or increased water hardness at the interface of the small watershed caused by the conversion of groundwater to surface water due to bottom plate leakage; the specific treatment steps are not limited in this invention.

[0067] To enable those skilled in the art to better understand the present invention, the preparation method provided by the present invention will be described below through several specific embodiments.

[0068] Example 1 See Figure 3 The flowchart of the rare earth leaching process is shown. The slurry is made by mixing water and rare earth ore at a liquid-to-solid ratio of 4:1, and the slurry is an ion-type rare earth ore slurry. The rare earth ore contains 0.05% REO.

[0069] Ion-adsorption rare earth ore slurry was pressurized and dewatered using a plate and frame filter press to form a filter cake. The resulting filtrate was returned to adjust the slurry for the next batch of rare earth ore. Measurements showed that the water content in the filter cake on the plate and frame filter press was 26.5%. Under a pressure of 0.5 MPa, an ammonium sulfate solution with a concentration of 20 g / L (32.5% of the total filter cake mass) was slowly injected for exchange leaching for 0.5 h, yielding a rare earth-containing leachate and a salt-containing filter cake. Throughout the exchange leaching process, samples were continuously taken to measure the rare earth concentration, which exhibited a peak-shaped curve showing an initial low concentration followed by a high concentration, and then a gradual decrease.

[0070] After the exchange leaching is completed, the rare earth concentration in the leaching solution flowing out of the outlet is below 0.1 g / L. Washing of the salt-containing filter cake then begins, with continuous pressurized injection of washing water. When the salt concentration in the washing solution flowing out of the outlet is less than 2 g / L, the injection of washing water is stopped, yielding the washing solution and the washed filter cake. The washing solution with a high concentration of ammonium sulfate is adjusted to pH 2-3 with sulfuric acid and then reused as a leaching agent. The washing solution with a low concentration is reused as washing water. The washed filter cake is purged and then unloaded. The unloaded filter cake is stored as tailings in a tailings yard for unified treatment. The rare earth-containing leaching solution was transferred to a sedimentation tank for impurity removal, precipitation, and filtration using ammonium bicarbonate to obtain rare earth concentrate and filtrate, with a rare earth yield of 94.2%. The filtrate was then adjusted to pH 2-3 with sulfuric acid and reused as a leaching agent.

[0071] Comparative Example 1 The rare earth ore contains 0.051% REO. Under stirring, the pulverized rare earth ore was leached with ammonium sulfate at solid-liquid ratios of 2.3:1 (23 t of ammonium sulfate solution, 10 t of rare earth ore), 2:1 (20 t of ammonium sulfate solution, 10 t of rare earth ore), 1:1 (10 t of ammonium sulfate solution, 10 t of rare earth ore), and 3:1 (30 t of ammonium sulfate solution, 10 t of rare earth ore). The rare earth yields obtained from the ammonium sulfate leaching were 90%, 85%, 60%, and 91%, respectively.

[0072] Experiments have shown that only when the liquid-to-solid ratio is greater than 2.3:1 can the entire raw ore be mixed; otherwise, the mixing and leaching operation cannot be achieved.

[0073] Example 2 See Figure 3 The flowchart of the rare earth leaching process is shown. The slurry is made by mixing water and rare earth ore at a liquid-to-solid ratio of 4:1, and the slurry is an ion-type rare earth ore slurry. The rare earth ore contains 0.05% REO.

[0074] Ion-adsorption rare earth ore slurry was pressurized and dewatered using a plate and frame filter press to form a filter cake. The resulting filtrate was returned to adjust the slurry for the next batch of rare earth ore. Measurements showed that the water content in the filter cake on the plate and frame filter press was 24.5%. Under a pressure of 0.8 MPa, an ammonium sulfate solution with a concentration of 25 g / L (30% of the total filter cake mass) was slowly injected for exchange leaching for 1 hour, yielding a rare earth-containing leachate and a salt-containing filter cake. Throughout the exchange leaching process, samples were continuously taken to measure the rare earth concentration, which exhibited a peak-shaped curve showing an initial low concentration, followed by a high concentration, and then a gradual decrease.

[0075] After the exchange leaching is completed, the rare earth concentration in the leaching solution flowing out of the outlet is below 0.1 g / L. Washing of the salt-containing filter cake then begins, with continuous pressurized injection of washing water. When the salt concentration in the washing solution flowing out of the outlet is less than 2 g / L, the injection of washing water is stopped, yielding the washing solution and the washed filter cake. The washing solution with a high concentration of ammonium sulfate is adjusted to pH 2-3 with sulfuric acid and then reused as a leaching agent. The washing solution with a low concentration is reused as washing water. The washed filter cake is purged and then unloaded. The unloaded filter cake is stored as tailings in a tailings yard for unified treatment. The rare earth-containing leaching solution was transferred to a sedimentation tank for impurity removal, precipitation, and filtration using ammonium bicarbonate to obtain rare earth concentrate and filtrate, with a rare earth recovery rate of 94.8%. The filtrate was then adjusted to pH 2-3 by adding sulfuric acid and reused as a leaching agent.

[0076] Example 3 See Figure 3The flowchart of the rare earth leaching process is shown. The slurry is made by mixing water and rare earth ore at a liquid-solid ratio of 4:1, and the slurry is an ion-type rare earth ore slurry. The rare earth ore contains 0.03% REO.

[0077] Ion-adsorption rare earth ore slurry was pressurized and dewatered using a plate and frame filter press to form a filter cake. The resulting filtrate was returned to adjust the slurry for the next batch of rare earth ore. Measurements showed that the water content in the filter cake on the plate and frame filter press was 25.8%. Under a pressure of 1.0 MPa, an ammonium sulfate solution with a concentration of 30 g / L (30.3% of the total filter cake mass) was slowly injected for exchange leaching for 1 hour, yielding a rare earth-containing leachate and a salt-containing filter cake. Throughout the exchange leaching process, samples were continuously taken to measure the rare earth concentration, which exhibited a peak-shaped curve showing an initial low concentration followed by a high concentration, and then a gradual decrease.

[0078] After the exchange leaching is completed, the rare earth concentration in the leaching solution flowing out of the outlet is below 0.1 g / L. Washing of the salt-containing filter cake then begins, with continuous pressurized injection of washing water. When the salt concentration in the washing solution flowing out of the outlet is less than 2 g / L, the injection of washing water is stopped, yielding the washing solution and the washed filter cake. The washing solution with a high concentration of ammonium sulfate is adjusted to pH 2-3 with sulfuric acid and then reused as a leaching agent. The washing solution with a low concentration is reused as washing water. The washed filter cake is purged and then unloaded. The unloaded filter cake is stored as tailings in a tailings yard for unified treatment. The rare earth-containing leaching solution was transferred to a sedimentation tank for impurity removal, precipitation, and filtration using ammonium bicarbonate to obtain rare earth concentrate and filtrate, with a rare earth yield of 96%. The filtrate was then adjusted to pH 2-3 by adding sulfuric acid and reused as a leaching agent.

[0079] Example 4 See Figure 3 The flowchart of the rare earth leaching process is shown. The slurry is made by mixing water and rare earth ore at a liquid-solid ratio of 4:1, and the slurry is an ion-type rare earth ore slurry. The rare earth ore contains 0.03% REO.

[0080] Ion-adsorption rare earth ore slurry was pressurized and dewatered using a plate and frame filter press to form a filter cake. The resulting filtrate was returned to adjust the slurry for the next batch of rare earth ore. Measurements showed that the water content in the filter cake on the plate and frame filter press was 27.3%. Under a pressure of 0.8 MPa, an ammonium sulfate solution with a concentration of 20 g / L (35.6% of the total filter cake mass) was slowly injected for exchange leaching for 1 hour, yielding a rare earth-containing leachate and a salt-containing filter cake. Throughout the exchange leaching process, samples were continuously taken to measure the rare earth concentration, which exhibited a peak-shaped curve showing an initial low concentration followed by a high concentration, and then a gradual decrease.

[0081] After the exchange leaching is completed, the rare earth concentration in the leaching solution flowing out of the outlet is below 0.1 g / L. Washing of the salt-containing filter cake then begins, with continuous pressurized injection of washing water. When the salt concentration in the washing solution flowing out of the outlet is less than 2 g / L, the injection of washing water is stopped, yielding the washing solution and the washed filter cake. The washing solution with a high concentration of ammonium sulfate is adjusted to pH 2-3 with sulfuric acid and then reused as a leaching agent. The washing solution with a low concentration is reused as washing water. The washed filter cake is purged and then unloaded. The unloaded filter cake is stored as tailings in a tailings yard for unified treatment. The rare earth-containing leaching solution was transferred to a sedimentation tank for impurity removal, precipitation, and filtration using ammonium bicarbonate to obtain rare earth concentrate and filtrate, with a rare earth recovery rate of 95%. The filtrate was then adjusted to pH 2-3 by adding sulfuric acid and reused as a leaching agent.

[0082] Example 5 See Figure 3 The flowchart of the rare earth leaching process is shown. The slurry is made by mixing water and rare earth ore at a liquid-to-solid ratio of 4:1, and the slurry is an ion-type rare earth ore slurry. The rare earth ore contains 0.1% REO.

[0083] Ion-adsorption rare earth ore slurry was pressurized and dewatered using a plate and frame filter press to form a filter cake. The resulting filtrate was returned to adjust the slurry for the next batch of rare earth ore. Measurements showed that the water content in the filter cake on the plate and frame filter press was 28.7%. Under a pressure of 0.6 MPa, an ammonium sulfate solution with a concentration of 25 g / L (40.5% of the total filter cake mass) was slowly injected for exchange leaching for 1 hour, yielding a rare earth-containing leachate and a salt-containing filter cake. Throughout the exchange leaching process, samples were continuously taken to measure the rare earth concentration, which exhibited a peak-shaped curve showing an initial low concentration, followed by a high concentration, and then a gradual decrease.

[0084] After the exchange leaching is completed, the rare earth concentration in the leaching solution flowing out of the outlet is below 0.1 g / L. Washing of the salt-containing filter cake then begins, with continuous pressurized injection of washing water. When the salt concentration in the washing solution flowing out of the outlet is less than 2 g / L, the injection of washing water is stopped, yielding the washing solution and the washed filter cake. The washing solution with a high concentration of ammonium sulfate is adjusted to pH 2-3 with sulfuric acid and then reused as a leaching agent. The washing solution with a low concentration is reused as washing water. The washed filter cake is purged and then unloaded. The unloaded filter cake is stored as tailings in a tailings yard for unified treatment. The rare earth-containing leaching solution was transferred to a sedimentation tank for impurity removal, precipitation, and filtration using ammonium bicarbonate to obtain rare earth concentrate and filtrate, with a rare earth yield of 96.1%. The filtrate was then adjusted to pH 2-3 with sulfuric acid and reused as a leaching agent.

[0085] Example 6 See Figure 3 The flowchart of the rare earth leaching process is shown. The slurry is made by mixing water and rare earth ore at a liquid-to-solid ratio of 4:1, and the slurry is an ion-type rare earth ore slurry. The rare earth ore contains 0.2% REO.

[0086] Ion-adsorption rare earth ore slurry was pressurized and dewatered using a plate and frame filter press to form a filter cake. The resulting filtrate was returned to adjust the slurry for the next batch of rare earth ore. Measurements showed that the water content in the filter cake on the plate and frame filter press was 28.8%. Under a pressure of 0.5 MPa, an ammonium sulfate solution with a concentration of 25 g / L (41.9% of the total filter cake mass) was slowly injected for exchange leaching for 1 hour, yielding a rare earth-containing leachate and a salt-containing filter cake. Throughout the exchange leaching process, samples were continuously taken to measure the rare earth concentration, which exhibited a peak-shaped curve showing an initial low concentration followed by a high concentration, and then a gradual decrease.

[0087] After the exchange leaching is completed, the rare earth concentration in the leaching solution flowing out of the outlet is below 0.1 g / L. Washing of the salt-containing filter cake then begins, with continuous pressurized injection of washing water. When the salt concentration in the washing solution flowing out of the outlet is less than 2 g / L, the injection of washing water is stopped, yielding the washing solution and the washed filter cake. The washing solution with a high concentration of ammonium sulfate is adjusted to pH 2-3 with sulfuric acid and then reused as a leaching agent. The washing solution with a low concentration is reused as washing water. The washed filter cake is purged and then unloaded. The unloaded filter cake is stored as tailings in a tailings yard for unified treatment. The rare earth-containing leaching solution was transferred to a sedimentation tank for impurity removal, precipitation, and filtration using ammonium bicarbonate to obtain rare earth concentrate and filtrate, with a rare earth recovery rate of 97.3%. The filtrate was then adjusted to pH 2-3 by adding sulfuric acid and reused as a leaching agent.

[0088] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0089] For the sake of simplicity, the method embodiments are described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, as some steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0090] The above provides a detailed description of the leaching method and apparatus for rare earths in ion-type rare earth ores provided by the present invention. 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 leaching device for rare earth elements in ion-type rare earth ores, characterized in that, The leaching device includes: Plate and frame filter press is used to press ion-type rare earth mineral slurry into filter cake and leach the filter cake with rare earth leaching solution under the action of rare earth leaching agent. A sedimentation tank is used to collect rare earth-containing leachate and to perform sedimentation treatment on the rare earth-containing leachate to obtain rare earth concentrate.

2. The leaching apparatus for rare earth elements in ion-adsorption rare earth ores according to claim 1, characterized in that, The plate and frame filter press is equipped with a pressing plate and at least one pressing assembly. The pressing assembly includes a filter plate and a filter frame. The ion-type rare earth mineral slurry entering the pressing assembly is pressurized and dewatered under the action of the pressing plate to obtain filter cake and filtered water.

3. The leaching apparatus for rare earth elements in ion-adsorption rare earth ores according to claim 1, characterized in that, The bottom of the plate and frame filter press is equipped with a collection tank for collecting the washing liquid and filtered water flowing out of the plate and frame filter press.

4. A method for leaching rare earth elements from ion-adsorption rare earth ores, characterized in that, The method is applicable to any of the leaching apparatuses described in claims 1-3 above, and includes: Ion-type rare earth mineral slurry is injected into a plate and frame filter press for pressure dewatering to obtain filter cake and filtered water. A rare earth leaching agent is continuously injected into the filter cake fixed on the plate and frame filter press at a pressure of 0.05 MPa to 1.5 MPa to exchange and leach rare earth ions in the filter cake for 0.1 h to 2 h, obtaining a rare earth-containing leachate and a salt-containing filter cake; the amount of the rare earth leaching agent is 30% to 60% of the mass of the filter cake. The rare earth-containing leachate is transferred to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate.

5. The method according to claim 4, characterized in that, The rare earth leaching agent is one or more of ammonium sulfate, magnesium sulfate, and sodium chloride; The concentration of the rare earth leaching agent is 5 g / L-50 g / L.

6. The method according to claim 4, characterized in that, In the ion-type rare earth slurry, the liquid-solid mass ratio of water to ion-type rare earth ore is 2.5:1 to 20:

1.

7. The method according to claim 4, characterized in that, The method further includes: reusing the filtrate to prepare the rare earth leaching agent, including: The pH of the filtrate is adjusted to 2-3 using an acid containing the anion of the leaching agent, and then reused as the rare earth leaching agent.

8. The method according to claim 4, characterized in that, The method further includes: washing the salt-containing filter cake to obtain washing liquid and washed filter cake; the washed filter cake is discharged after purging and piled up as tailings; the washing liquid is collected through the collection tank and used for secondary washing or for the preparation of rare earth leaching agents.

9. The method according to claim 4, characterized in that, The step of transferring the rare earth-containing leachate to the sedimentation tank for sedimentation treatment to obtain rare earth concentrate and filtrate includes: The rare earth-containing leachate is precipitated and filtered in the sedimentation tank using an alkaline precipitant to obtain rare earth concentrate and the filtrate; or The rare earth-containing leachate is precipitated directly in the sedimentation tank using oxalic acid to obtain rare earth oxalate and the filtrate; the rare earth oxalate is then calcined to obtain rare earth concentrate.

10. The method according to claim 9, characterized in that, The alkaline precipitant is one or more of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, and sodium carbonate.

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