A pretreatment method for smelting and separation of ionic rare earth ore

Abstract

The present invention provides a pretreatment method for smelting and separating ionic rare earth ores, the pretreatment method comprising: crushing and slurrying rare earth enriched materials, acid dissolving, and then performing a first solid-liquid separation to obtain a first filter residue and an acid leaching solution; mixing the obtained acid leaching solution with a magnesium oxide slurry for reaction, and then performing a second solid-liquid separation to obtain a second filter residue and a rare earth feed liquid; extracting or precipitating the obtained rare earth feed liquid to obtain a rare earth carbonate product. The method provided by the present invention pre-treats and separates rare earth enriched materials to extract rare earth elements, and the rare earth recovery rate reaches more than 97.3%, the rare earth loss is small, and the obtained product can be directly used for the smelting and separation of rare earth products, which improves the efficiency of the overall process of mining and utilization of ionic rare earth ores, and at the same time realizes resource utilization of magnesium and aluminum impurity elements and reduces solid waste residue, reduces process costs, and improves the economic efficiency of rare earth mine development.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth smelting, and relates to a method for treating ionic rare earth ores, and in particular to a pretreatment method for smelting and separating ionic rare earth ores. Background Art

[0002] Ionic rare earth ore is a rare earth mineral resource in which ion-exchange rare earths are adsorbed on clay minerals in the form of hydration or hydroxyl hydration. The rare earth development process of ionic rare earth ore mainly includes leaching and smelting separation. When ionic rare earth ore encounters active cations, it can be exchanged and desorbed into the leachate. Based on this feature, magnesium sulfate leaching and magnesium oxide precipitation enrichment are currently the main processes for ionic rare earth ore mining, that is, magnesium sulfate is used as a leaching agent to exchange and leach the rare earth ions in the ionic rare earth ore, and the rare earth leaching mother liquor is collected, and then magnesium oxide is used as a precipitant to precipitate and enrich the rare earth ions in the rare earth leaching mother liquor, and the intermediate product of rare earth mining, rare earth enrichment, is obtained after plate and frame filtration.

[0003] Due to the single leaching selectivity of the leaching agent, ion-exchange aluminum, iron and other elements in the original ore will also be leached out simultaneously with the rare earths, resulting in an extremely high content of impurity elements in the concentrate, which will affect the purity of the rare earth products during the subsequent smelting and separation of the rare earths. The impurity elements in rare earth concentrates mainly include aluminum, silicon and magnesium. At present, companies usually use soluble carbonates such as ammonium bicarbonate and sodium bicarbonate and calcium magnesium alkaline compounds for neutralization and aluminum removal. This process not only produces a large amount of impurity removal slag, but also causes about 8% rare earth loss in the impurity removal link, increases the production process, and reduces the processing efficiency of the mine. However, if the impurity removal treatment is not performed and the rare earths are directly precipitated by a one-step precipitation method, the aluminum ions in the solution will compete with the rare earth ions during the subsequent extraction and separation in the rare earth smelting and separation plant, resulting in a serious decrease in the extraction capacity. At the same time, Al 3+ Will form Al(OH) 2+ The complex cations containing hydroxyl groups and Al(OH)3 are formed into suspended particles, which leads to emulsification of the organic phase, further reducing the extraction efficiency and increasing the extraction cost. Therefore, it is urgent to develop a treatment process for rare earth enrichment impurity removal and rare earth separation.

[0004] CN116676479A discloses a method for recovering rare earth and aluminum from ionic rare earth leaching solution, wherein rare earth enriched material is placed in a sodium hydroxide solution and stirred and washed to remove impurities, and rare earth hydroxide is separated; CN116855773A discloses a process for treating solid enriched material with low rare earth content, wherein rare earth enriched material after ball milling and slurrying is preferentially dissolved in sulfuric acid, and the pH at the end point of the reaction is adjusted to 3.5-4 to obtain a rare earth sulfate feed solution, and then the rare earth sulfate feed solution is extracted and stripped to obtain a rare earth chloride feed solution to achieve rare earth separation. This method retains components in the enriched material such as Al and Fe in the slag by preferentially dissolving them with sulfuric acid, and then extracts them. On the one hand, the purity of the rare earth feed solution for extraction is not high, which affects the extraction effect and the extraction efficiency of rare earth. On the other hand, a large amount of enriched material components are left in the slag, resulting in a waste of element resources, making it difficult to realize resource utilization, and also generating a large amount of waste slag that is difficult to handle.

[0005] CN117965915A discloses a method for extracting rare earths from magnesium salt rare earth enriched materials and acid-soluble slag, comprising the steps of adding sulfuric acid to the magnesium salt rare earth enriched materials for preferential dissolution, adjusting the pH value to 2.8-3.5, adding magnesium salt rare earth enriched materials again to adjust the pH value after solid-liquid separation, obtaining rare earth feed liquid, and preferentially dissolving the rare earth enriched materials. The rare earth production is also large, and due to incomplete acid dissolution, the rare earth content in the slag is still about 0.5% after multi-stage countercurrent washing. On the other hand, the preferential dissolution process requires continuous monitoring of pH and acid supplementation, and the process is cumbersome. When the feed liquid after preferential dissolution is filtered by plate and frame pressure, the filtration is extremely difficult (the disclosed method is to use vacuum filtration), which is not conducive to expanding production, and the subsequent impurity removal and utilization process of the sulfuric acid rare earth feed liquid is not further disclosed.

[0006] Therefore, based on the shortcomings of the existing technology, it is necessary to provide a pretreatment method for smelting and separating ionic rare earth ores. Summary of the invention

[0007] The purpose of the present invention is to provide a pretreatment method for smelting and separation of ionic rare earth ores, to separate and treat the rare earth enriched product obtained by leaching the ionic rare earth ore with magnesium sulfate and precipitating magnesium oxide, to achieve effective separation of rare earth elements and other component elements in the rare earth enriched product, to achieve resource utilization through an overall process, and to solve the problem of impurity removal in rare earth smelting and separation.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a pretreatment method for smelting and separating ionic rare earth ores, the pretreatment method comprising the following steps:

[0010] (1) crushing and slurrying the rare earth enriched material, dissolving it with sulfuric acid having a concentration of ≥30%, adjusting the pH of the acid solution to 1.0-1.5, obtaining a mixed solution, controlling the rare earth concentration in the mixed solution to 15-40 g / L with water, and then performing a first solid-liquid separation to obtain a first filter residue and an acid leaching solution;

[0011] (2) slurrying the first filter residue obtained in step (1) with water, washing the slurry until the rare earth content in the wet residue produced by washing is less than 0.1%, and then performing a second solid-liquid separation to obtain a second filter residue and washing filter water, and the washing filter water is reused in step (1);

[0012] The acid leaching solution obtained in step (1) is mixed with the magnesium oxide slurry for reaction, the pH is adjusted, and then a third solid-liquid separation is performed to obtain a third filter residue and a rare earth sulfate feed solution;

[0013] When the pH is adjusted to 2.5-3.0 in step (2), the pretreatment method further comprises:

[0014] (3) extracting the rare earth sulfate solution obtained in step (2) with a first extractant saponified with magnesium oxide, wherein the saponification degree of the first extractant is 15-35%, and extracting until the rare earth concentration in the resulting raffinate is less than 0.1 g / L, thereby obtaining a rare earth-loaded organic phase and a first raffinate;

[0015] (4) stripping the rare earth-loaded organic phase obtained in step (3) to obtain a rare earth solution;

[0016] The first raffinate obtained in step (3) is adjusted to a pH of 2.5-3.0, and then extracted with a second extractant saponified with magnesium oxide, wherein the saponification degree of the second extractant is 15-30%, to obtain an aluminum-loaded organic phase and a magnesium sulfate solution;

[0017] Stripping the aluminum-loaded organic phase to obtain an aluminum salt solution;

[0018] Alternatively, when the pH is adjusted to 5.0-5.5 in step (2), the pretreatment method further comprises:

[0019] (3) mixing the rare earth sulfate solution obtained in step (2) with an ammonium bicarbonate solution for reaction, wherein the concentration of the ammonium bicarbonate solution is 5-10%, adjusting the end point pH of the reaction to ≥ 7, and then performing a fourth solid-liquid separation to obtain rare earth carbonate and a precipitate;

[0020] (4) The precipitate obtained in step (3) is subjected to ammonium recovery to obtain a magnesium sulfate solution.

[0021] The pretreatment method provided by the present invention first dissolves the rare earth enriched material with acid, and adjusts the pH of the rare earth enriched material to 1.0-1.5 for complete dissolution. Impurities in the rare earth enriched material mainly include aluminum oxide, magnesium oxide, aluminosilicate and non-ferrous metals, etc., which enter the solution after acid dissolution and can be converted into resources in subsequent processes. The generated insoluble slag contains only impurities such as aluminosilicate, and the amount of waste slag generated is small. Then, the obtained acid leaching solution is slurried with magnesium oxide slurry. The overall development process of rare earth ore adopts a magnesium salt system. The slurrying with magnesium oxide can realize the magnesium salt circulation of the overall process and improve the process efficiency. After the slurry is adjusted to a pH of 2.5-3.0, the sulfur in the solution is removed. The acid salt impurities are precipitated and converted into waste residue to obtain a rare earth feed liquid containing pure magnesium salt and aluminum salt; magnesium, aluminum and rare earth are separated by extraction to obtain a rare earth product which can be directly used for the smelting and separation of rare earths, and magnesium salt products and aluminum salt products are obtained. The magnesium salt product can be directly used for the leaching cycle of ionic rare earth ores; when the slurry is adjusted to a pH of 5.0-5.5, the aluminum sulfate in the acidolysis solution is converted into aluminum hydroxide precipitate, the precipitate can be heated with alkali to obtain a sodium aluminate product, and a feed liquid containing pure rare earth and magnesium ions is obtained. After the rare earth ions are converted into rare earth carbonate precipitates, the magnesium salt can be recovered, the rare earth in the enrichment can be efficiently extracted, and the impurities can be converted into resources.

[0022] The pretreatment process of the present invention can obtain high-purity rare earth products that can be directly used for rare earth smelting and separation, and realize the effective separation of magnesium and aluminum impurities in rare earth enrichments, realize resource utilization, solve the problem of impurity removal when ionic rare earth ores are directly used for smelting and separation after leaching, reduce the amount of waste slag, and increase resource utilization.

[0023] In the present invention, the ionic rare earth ore is leached using magnesium sulfate solution as a leaching agent to obtain a leaching mother liquor, the obtained leaching mother liquor is subjected to precipitation reaction using magnesium oxide slurry as a precipitant, and then solid-liquid separation is performed to obtain the rare earth enriched product.

[0024] In the present invention, the rare earth concentrate comprises rare earth hydroxide, magnesium oxide, magnesium hydroxide, aluminum hydroxide, silicate, sulfate and non-ferrous metals.

[0025] The rare earth content in the rare earth concentrate is ≥15wt%.

[0026] In the present invention, the concentration of sulfuric acid in step (1) is ≥30%, for example, it can be 30%, 35%, 40%, 50%, 60%, 70%, 80%, 90% or 98%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0027] In the present invention, the pH of the acid solution in step (1) is adjusted to 1.0-1.5, for example, it can be 1.0, 1.1, 1.2, 1.3, 1.4 or 1.5, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0028] In the present invention, the rare earth concentration in the mixed solution of step (1) is 15-40 g / L, for example, it can be 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L or 40 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] In the present invention, when the pH value in step (2) is adjusted to 2.5-3.0, for example, it can be 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] In the present invention, when the pH is adjusted to 2.5-3.0 in step (2), the saponification degree of the first extractant in step (3) is 15-35%, for example, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32% or 35%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0031] In the present invention, when the pH is adjusted to 2.5-3.0 in step (2), the pH of the first raffinate in step (4) is adjusted to 2.5-3.0, for example, it can be 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] In the present invention, when the pH is adjusted to 2.5-3.0 in step (2), the saponification degree of the second extractant in step (4) is 15-30%, for example, 15%, 18%, 20%, 22%, 25%, 28% or 30%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] In the present invention, when the pH value in step (2) is adjusted to 5.0-5.5, for example, it can be 5.0, 5.1, 5.2, 5.3, 5.4 or 5.5, but is not limited to the listed values. Other values ​​not listed within the numerical range are also applicable.

[0034] In the present invention, when the pH is adjusted to 5.0-5.5 in step (2), the concentration of the ammonium bicarbonate solution in step (3) is 5-10%, for example, 5%, 6%, 7%, 8%, 9% or 10%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] In the present invention, when the pH is adjusted to 5.0-5.5 in step (2), the endpoint pH of the reaction is adjusted to ≥ 7 in step (3), for example, it can be 7, 7.5, 8, 8.5, 9, 10, 11, 12, 13 or 14, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the solid-liquid mass ratio of the slurry adjustment in step (1) is 1:(3-4), for example, it can be 1:3, 1:3.2, 1:3.4, 1:3.5, 1:3.6, 1:3.8 or 1:4, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the solid-liquid mass ratio of the slurry adjustment in step (2) is 1:(5-6), for example, it can be 1:5, 1:5.2, 1:5.4, 1:5.5, 1:5.6, 1:5.8 or 1:6, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the solid content of the magnesium oxide slurry in step (2) is 20-30%, for example, it can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29% or 30%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Preferably, the mixing reaction time in step (2) is 0.5-1 h, for example, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h or 1 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] Preferably, when the pH is adjusted to 2.5-3.0 in step (2), the first extractant in step (3) includes P507 and a first diluent.

[0041] Preferably, the first diluent comprises sulphonated kerosene.

[0042] Preferably, the volume ratio of P507 to the first diluent is 1:(0.9-1.1), for example, it can be 1:0.9, 1:0.95, 1:1, 1:1.05 or 1:1.1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] Preferably, when the pH is adjusted to 2.5-3.0 in step (2), the second extractant in step (4) includes P204 and a second diluent.

[0044] Preferably, the second diluent comprises sulphonated kerosene.

[0045] Preferably, the volume ratio of P204 to the second diluent is 1:(0.9-1.1), for example, it can be 1:0.9, 1:0.95, 1:1, 1:1.05 or 1:1.1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] Preferably, when the pH is adjusted to 2.5-3.0 in step (2), the rare earth concentration in the rare earth solution obtained in step (4) is ≥200 g / L, for example, it can be 200 g / L, 250 g / L, 300 g / L, 350 g / L, 400 g / L, 500 g / L or 600 g / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] Preferably, when the pH is adjusted to 5.0-5.5 in step (2), the ammonium recovery method in step (4) comprises: mixing magnesium oxide with the precipitate and performing steam stripping separation to obtain a mixed gas of ammonia and water vapor and a magnesium sulfate solution, and condensing the mixed gas to obtain aqueous ammonia.

[0048] As a preferred technical solution of the pretreatment method provided by the present invention, the pretreatment method comprises the following steps:

[0049] (1) mechanically crushing the rare earth enriched material, slurrying with water at a solid-liquid mass ratio of 1:(3-4) to obtain a slurry, acid-dissolving the obtained slurry with sulfuric acid at a concentration of ≥30%, adjusting the end point pH of the acid dissolution to 1.0-1.5 to obtain a mixed solution, controlling the rare earth concentration in the mixed solution to 15-40 g / L with water, stirring for 1-2 hours, and performing a first solid-liquid separation by plate and frame filter pressing to obtain a first filter residue and an acid leaching solution;

[0050] (2) the first filter residue obtained in step (1) is slurried with water at a solid-liquid mass ratio of 1:(5-6), stirred for 20-30 minutes, and after slurrying, subjected to countercurrent three-stage washing until the rare earth content in the wet residue produced by washing is less than 0.1%. After washing, a second solid-liquid separation is performed by plate and frame filter pressing to obtain a second filter residue and washing filtrate, and the washing filtrate is reused in step (1). If the rare earth content in the wet residue produced by washing is greater than 1%, the wet residue is returned to step (1) for secondary acid dissolution;

[0051] The acid leaching solution obtained in step (1) is mixed with magnesium oxide slurry for reaction, wherein the solid content of the magnesium oxide slurry is 20-30%, the mixing reaction time is 0.5-1h, the end point pH of the mixing reaction is adjusted to 2.5-3.0, and then a plate and frame filter press is used for a third solid-liquid separation to obtain a third filter residue and a rare earth sulfate feed liquid;

[0052] (3) After mixing the extractant P507 and the diluent sulfonated kerosene in a ratio of 1: (0.9-1.1), saponification is performed with magnesium oxide slurry, wherein the saponification degree of the saponification is 15-35%, to obtain a first saponified extractant;

[0053] Using the first saponification extractant to perform a first extraction on the rare earth sulfate solution obtained in step (2) until the rare earth concentration in the raffinate produced by the extraction is less than 0.1 g / L, thereby obtaining a rare earth-loaded organic phase and a first raffinate;

[0054] (4) stripping the rare earth-loaded organic phase obtained in step (3) using hydrochloric acid to obtain a rare earth chloride solution;

[0055] The extractant P204 and the diluent sulfonated kerosene are mixed in a ratio of 1: (0.9-1.1), and then saponified with magnesium oxide slurry, wherein the saponification degree of the saponification is 15-30%, to obtain a second saponified extractant;

[0056] After adjusting the pH of the first raffinate obtained in step (3) to 2.5-3.0, performing a second extraction with the second saponification extractant to obtain an aluminum-loaded organic phase and a second raffinate;

[0057] (5) stripping the aluminum-loaded organic phase obtained in step (4) using sulfuric acid to obtain an aluminum sulfate solution;

[0058] The second raffinate obtained in step (4) is a magnesium sulfate solution.

[0059] In the present invention, the pretreatment process for determining the rare earth content in the raffinate is: adding an oxidizing agent, lithium permanganate, to the raffinate to oxidize the thallium in the raffinate to trivalent, and then adjusting the pH of the raffinate to 6.5-7.5 with magnesium oxide and / or lime to remove the non-ferrous metals aluminum, zinc and manganese in the raffinate.

[0060] As a preferred technical solution of the pretreatment method provided by the present invention, the pretreatment method comprises the following steps:

[0061] (1) mechanically crushing the rare earth enriched material, slurrying with water at a solid-liquid mass ratio of 1:(3-4) to obtain a slurry, acid-dissolving the obtained slurry with sulfuric acid at a concentration of ≥30%, adjusting the end point pH of the acid dissolution to 1.0-1.5 to obtain a mixed solution, adjusting the rare earth concentration in the mixed solution to 15-40 g / L with water, stirring for 1-2 hours, and performing a first solid-liquid separation by plate and frame filter pressing to obtain a first filter residue and an acid leaching solution;

[0062] (2) the first filter residue obtained in step (1) is slurried with water at a solid-liquid mass ratio of 1:(5-6), stirred for 20-30 minutes, and after slurrying, subjected to countercurrent three-stage washing until the rare earth content in the wet residue produced by washing is less than 0.1%. After washing, a second solid-liquid separation is performed by plate and frame filter pressing to obtain a second filter residue and washing filtrate, and the washing filtrate is reused in step (1). If the rare earth content in the wet residue produced by washing is greater than 1%, the mixture is returned to step (1) for secondary acid dissolution;

[0063] The acid leaching solution obtained in step (1) is mixed with magnesium oxide slurry for reaction, wherein the solid content of the magnesium oxide slurry is 20-30%, the mixing reaction time is 0.5-1h, and the end point pH of the mixing reaction is adjusted to 5.0-5.5, and then a plate and frame filter press is used for a third solid-liquid separation to obtain a third filter residue and a rare earth sulfate feed liquid;

[0064] (3) mixing the third filter residue obtained in step (2) with sodium hydroxide and heating them to obtain sodium aluminate;

[0065] The rare earth sulfate solution obtained in step (2) is mixed with an ammonium bicarbonate solution for precipitation, wherein the concentration of the ammonium bicarbonate solution is 5-10%, and the end point pH of the mixture is adjusted to ≥ 7, and then a plate and frame filter press is used for a fourth solid-liquid separation to obtain a rare earth carbonate precipitate and a precipitate liquid;

[0066] (4) recovering ammonium from the precipitate obtained in step (3) to obtain a magnesium sulfate solution;

[0067] The rare earth carbonate precipitate obtained in step (3) is subjected to three-stage countercurrent washing to obtain a rare earth carbonate product, and the washing liquid produced by the washing is recycled to step (1).

[0068] The washing liquid produced in step (4) is recycled to step (1), and the washing liquid is used as water in step (1).

[0069] In the preferred technical scheme of the pretreatment method of the present invention, in step (2), if the rare earth content in the wet residue produced by washing is ≤1%, acid dissolution is not performed, and continuous washing is performed until the rare earth content is <0.1%.

[0070] Compared with the prior art, the present invention has the following beneficial effects:

[0071] (1) Realizing the linkage between mining and smelting and separation enterprises, successfully solving the dual problems between the two:

[0072] Adding a finished product workshop pretreatment process between the mining and smelting and separation processes not only solves the problem of excessive non-rare earth impurity aluminum in rare earth products of the traditional mining process of removing impurities before precipitation, but also avoids the storage of large amounts of impurity slag during the mining stage, and eliminates the impurity removal link at the smelting and separation enterprise, thus achieving effective linkage between mines and rare earth separation plants and solving the dual problems between the two.

[0073] (2) High rare earth recovery rate, avoiding waste of strategic mineral resources:

[0074] Experiments have shown that the rare earth precipitation rate is ≥95% when magnesium oxide is used for one-step precipitation enrichment in the mining stage; the rare earth recovery rate is ≥97% when the technical solution proposed in the present invention is used in the enrichment pretreatment stage in the finished product workshop; the overall rare earth precipitation recovery rate can reach 92%. The traditional impurity removal and then precipitation process will first cause rare earth loss with slag in the impurity removal link, with a loss rate of about 8%; and the rare earth precipitation rate is low in the subsequent precipitation link, and the rare earth content in the supernatant discharged after precipitation is still 0.03g / L, and about 10% of rare earth is lost in this stage; the overall rare earth recovery rate in the mother liquor is 82-85%. Therefore, compared with the traditional impurity removal and precipitation process, a pretreatment method for smelting and separation of ion adsorption rare earth ores greatly improves the recovery rate of rare earth resources and avoids the unnecessary waste of strategic mineral resources.

[0075] (3) Recycling of non-rare earth impurities to reduce solid waste:

[0076] Aluminum is the most abundant metal in the earth's crust, and the aluminum content in the mother liquor of mine leaching is generally 15% of the rare earth content. The main purpose of the traditional mine impurity removal-precipitation process is to remove aluminum. After impurities removal, a large amount of aluminum-rich impurity removal slag is stored. However, in order to avoid emulsification of the tank body and improve the smelting separation efficiency, rare earth separation companies require that the aluminum content in the rare earth enriched products produced by mines is ≤1.5%, which is an inevitable mandatory requirement that impurities must be removed first at the mine stage. The technical solution proposed in the present invention adopts the concept of "turning waste into treasure" for the treatment of aluminum in the rare earth mother liquor in the pretreatment stage of the finished product workshop, and produces aluminum sulfate products through stripping of aluminum in the rare earth mother liquor, which not only saves the cost and process of mine impurity removal, solves the problem of having nowhere to store a large amount of impurity removal slag, but also improves the comprehensive utilization rate of resources. The output rare earth products are of high quality and stable, and the aluminum impurity content is less than 0.3%. At the same time, the magnesium saponification extraction transformation process avoids the introduction of ammonium salts from the source, is environmentally friendly, and facilitates the recycling of magnesium. The magnesium recovery rate of extraction and precipitation pretreatment reaches more than 95%.

[0077] (4) Reduce mine production costs and extend service life:

[0078] When ionic rare earth mines are in production, they will be removed from the water by a hydrometallurgical workshop for precipitation and enrichment. In order to reduce the transportation distance of the leaching solution and the leaching agent, each rare earth mine will establish multiple hydrometallurgical workshops in different mining areas. When the mining of the ore block served by one of the hydrometallurgical workshops is completed, the workshop will be closed and production will be stopped. Therefore, if impurities are removed in the production link of the mine, each hydrometallurgical workshop needs to be equipped with an impurity removal process pool and corresponding facilities (the scale of the impurity removal process pool is consistent with the scale of the rare earth precipitation and enrichment pool), resulting in the doubling of the number of pools, the increase in the floor area of ​​the workshop industrial site, the high one-time investment cost of the mine, and the short service life of the hydrometallurgical workshop, which is not conducive to the long-term development of mining enterprises. The technical solution proposed in the present invention builds a semi-finished product processing workshop serving the entire mining area or even multiple mining areas at one time, greatly reducing the construction cost of the mine hydrometallurgical workshop, and once the semi-finished product processing workshop is built, the service life is long and is not restricted by the mining conditions of the mine. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 is a process flow chart of the pretreatment method for smelting and separating ionic rare earth ores of Example 1;

[0080] Figure 2 It is a process flow chart of the pretreatment method for smelting and separating ionic rare earth ores in Example 3. DETAILED DESCRIPTION

[0081] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0082] Example 1

[0083] This embodiment provides a Figure 1 The pretreatment method for smelting and separation of ionic rare earth ores is shown.

[0084] The ionic rare earth ore is leached with a magnesium sulfate solution to obtain a leaching mother liquor, the leaching mother liquor is precipitated with magnesium oxide, and a rare earth enrichment is obtained after filter pressing.

[0085] The rare earth enriched material comprises: 17wt% rare earth hydroxide, 6wt% aluminum hydroxide, 26wt% magnesium hydroxide and magnesium oxide, 42wt% water, 5wt% silicate, 3wt% sulfate, and 1wt% non-ferrous metal.

[0086] The pretreatment method comprises the following steps:

[0087] (1) The rare earth enriched material is mechanically crushed and then added to an acid leaching stirring tank, water is added to adjust the slurry, and the solid-liquid mass ratio is controlled to be 1:3, and then 50% sulfuric acid is slowly added to dissolve it, and the reaction end point pH is controlled to be 1.0, and then the total reaction volume is adjusted with clean water so that the rare earth concentration in the solution after the reaction is 40g / L, and stirring is continued for 1 hour. The solid-liquid separation is performed using a plate and frame filter press to obtain acid leaching residue and acid leaching liquid;

[0088] (2) placing the acid leaching residue produced in step (1) into a residue washing tank, adding water to adjust the slurry, controlling the solid-liquid mass ratio to 1:5, stirring for 20 minutes, and performing three-stage countercurrent washing. The rare earth content of the wet residue after washing is measured to be 0.075%. After secondary filtration using a plate and frame filter press, the residue is centrally stacked, and the rare earth-containing washing filter water is returned to step (1) as acid leaching water;

[0089] (3) The acid leaching solution produced in step (1) is transferred to a transfer stirring tank, and magnesium oxide slurry is added to the transfer stirring tank, wherein the solid content of the magnesium oxide slurry is 20%, and stirring is continued for 0.5 hours. After the pH value of the acid leaching solution is adjusted to 2.5, a plate and frame filter press is used for solid-liquid separation, and the filter residue is placed in the slag washing tank of step (2) and washed and then centrally stacked, and the rare earth sulfate filtrate is transferred to a reserve tank for standby use;

[0090] (4) Mix the organic extractant P507 and sulfonated kerosene in a ratio of 1:1, saponify them with magnesium oxide slurry, and add them into a single-stage extraction tank with a saponification degree of 30%;

[0091] (5) adding the rare earth sulfate solution in the reserve tank to the extraction tank, and performing single-stage extraction using the organic phase saponified in step (4), during which the rare earth content in the raffinate is continuously tested. When the concentration is greater than 0.1 g / L, the raffinate is continuously returned to repeat the single-stage extraction process until the concentration is less than 0.1 g / L. The rare earth content in the raffinate is measured to be 0.08 g / L, and finally a rare earth-loaded organic phase and raffinate are obtained;

[0092] (6) stripping the rare earth-loaded organic phase with hydrochloric acid to obtain a rare earth chloride solution;

[0093] (7) Mix the organic extractant P204 and sulfonated kerosene in a ratio of 1:1, saponify them with magnesium oxide slurry, and add them into a single-stage extraction tank with a saponification degree of 15%;

[0094] (8) The pH of the raffinate produced in step (5) is adjusted to 2.5, and the raffinate is extracted with the saponified organic phase in step (7). The raffinate produced is a magnesium sulfate solution, which is used as an ionic rare earth ore leaching agent. The aluminum-loaded organic phase produced is stripped with sulfuric acid to obtain a stripping solution that is an aluminum sulfate solution.

[0095] Example 2

[0096] This embodiment provides a pretreatment method for smelting and separation of ionic rare earth ores.

[0097] The ionic rare earth ore is leached with a magnesium sulfate solution to obtain a leaching mother liquor, the leaching mother liquor is precipitated with magnesium oxide, and a rare earth enrichment is obtained after filter pressing.

[0098] The rare earth enriched material comprises: 17wt% rare earth hydroxide, 6wt% aluminum hydroxide, 26wt% magnesium hydroxide and magnesium oxide, 42wt% water, 5wt% silicate, 3wt% sulfate, and 1wt% non-ferrous metal.

[0099] The pretreatment method comprises the following steps:

[0100] (1) The rare earth enriched material is mechanically crushed and then added to an acid leaching stirring tank, water is added to adjust the slurry, and the solid-liquid mass ratio is controlled to be 1:4. Then, 30% sulfuric acid is slowly added to dissolve it, and the pH value of the reaction end point is controlled to be 1.5. Then, the total reaction volume is adjusted with clean water so that the rare earth concentration in the solution after the reaction is 30 g / L. The stirring is continued for 1 hour, and the solid-liquid separation is performed using a plate and frame filter press to obtain an acid leaching residue and an acid leaching liquid;

[0101] (2) placing the acid leaching residue produced in step (1) into a residue washing tank, adding water to adjust the slurry, controlling the solid-liquid mass ratio to 1:6, stirring for 30 minutes, and performing three-stage countercurrent washing. The rare earth content of the wet residue after washing is measured to be 0.06%. After secondary filtration using a plate and frame filter press, the residue is centrally stacked, and the rare earth-containing washing filter water is returned to step (1) as acid leaching water;

[0102] (3) The acid leaching solution produced in step (1) is transferred to a transfer stirring tank, and magnesium oxide slurry is added to the transfer stirring tank. The concentration of magnesium oxide slurry is 20%, and stirring is continued for 1 hour. After the pH of the acid leaching solution is adjusted to 3.0, a plate and frame filter press is used for solid-liquid separation. The filter residue is placed in the slag washing tank of step (2) and washed and then centrally stacked. The rare earth sulfate filtrate is transferred to a reserve tank for standby use;

[0103] (4) Mix the organic extractant P507 and sulfonated kerosene in a ratio of 1:1, saponify them with magnesium oxide slurry, and add them into a single-stage extraction tank with a saponification degree of 30%;

[0104] (5) adding the rare earth sulfate solution in the reserve tank to the extraction tank, and performing single-stage extraction using the organic phase saponified in step (4), continuously testing the rare earth content in the raffinate during the process, and when the concentration is greater than 0.1 g / L, the raffinate is continuously returned to repeat the single-stage extraction process until the concentration is less than 0.1 g / L, and the rare earth content in the raffinate is measured to be 0.05 g / L, thereby finally obtaining an organic phase loaded with rare earth and a raffinate;

[0105] (6) stripping the rare earth-loaded organic phase with hydrochloric acid to obtain a rare earth chloride solution;

[0106] (7) Mix the organic extractant P204 and sulfonated kerosene in a ratio of 1:1, saponify them with magnesium oxide slurry, and add them into a single-stage extraction tank with a saponification degree of 30%;

[0107] (8) The pH of the raffinate produced in step (5) is adjusted to 3.0, and the raffinate is extracted with the saponified organic phase in step (7). The raffinate produced is a magnesium sulfate solution, which is used as an ionic rare earth ore leaching agent. The aluminum-loaded organic phase produced is stripped with sulfuric acid to obtain a stripping solution that is an aluminum sulfate solution.

[0108] Example 3

[0109] This embodiment provides a Figure 2 The pretreatment method for smelting and separation of ionic rare earth ores is shown.

[0110] The rare earth concentrate comprises: 17wt% rare earth hydroxide, 6wt% aluminum hydroxide, 26wt% magnesium hydroxide and magnesium oxide, 42wt% water, 5wt% silicate, 3wt% sulfate and 1wt% non-ferrous metal.

[0111] The pretreatment method comprises the following steps:

[0112] (1) The rare earth enriched material is mechanically crushed and then added to an acid leaching stirring tank, water is added to adjust the slurry, and the solid-liquid mass ratio is controlled to be 1:3. Then, 40% sulfuric acid is slowly added to dissolve it, and the pH value of the reaction end point is controlled to be 1.5. Then, the total reaction volume is adjusted with clean water so that the rare earth concentration in the solution after the reaction is 40g / L. The stirring is continued for 1 hour, and the solid-liquid separation is performed using a plate and frame filter press to obtain an acid leaching residue and an acid leaching liquid;

[0113] (2) placing the acid leaching residue produced in step (1) into a residue washing tank, adding water to adjust the slurry, controlling the solid-liquid mass ratio to 1:5, stirring for 20 minutes, and performing three-stage countercurrent washing. The rare earth content of the wet residue after washing is measured to be 0.06%. After secondary filtration using a plate and frame filter press, the residue is centrally stacked, and the rare earth-containing washing filter water is returned to step (1) as acid leaching water;

[0114] (3) The acid leaching solution produced in step (1) is transferred to a transfer stirring tank, and magnesium oxide slurry is added to the transfer stirring tank, wherein the solid content of the magnesium oxide slurry is 30%, and stirring is continued for 0.5 hours. After the pH value of the acid leaching solution is adjusted to 5.0, a plate and frame filter press is used for solid-liquid separation, and the filter residue is placed in the slag washing tank of step (2) and washed and then centrally stacked, and the rare earth sulfate filtrate is transferred to a reserve tank for standby use;

[0115] (4) Adding a 5% ammonium bicarbonate solution to the rare earth sulfate filtrate obtained in step (3), adjusting the pH of the solution to 7, and filtering with a plate and frame filter press to obtain a rare earth carbonate precipitate, washing the precipitate to obtain a rare earth carbonate product, and returning the washing liquid produced by the washing to step (1).

[0116] Example 4

[0117] This embodiment provides a pretreatment method for smelting and separation of ionic rare earth ores.

[0118] The rare earth concentrate comprises: 17wt% rare earth hydroxide, 6wt% aluminum hydroxide, 26wt% magnesium hydroxide and magnesium oxide, 42wt% water, 5wt% silicate, 3wt% sulfate and 1wt% non-ferrous metal.

[0119] The pretreatment method comprises the following steps:

[0120] (1) The rare earth enriched material is mechanically crushed and then added to an acid leaching stirring tank, water is added to adjust the slurry, the solid-liquid mass ratio is controlled to be 1:4, and then 30% sulfuric acid is slowly added to dissolve it, the reaction end point pH is controlled to be 1.0, and then the total reaction volume is adjusted with clean water so that the rare earth concentration in the solution after the reaction is 30g / L, and stirring is continued for 1 hour. The solid-liquid separation is performed using a plate and frame filter press to obtain an acid leaching residue and an acid leaching liquid;

[0121] (2) placing the acid leaching residue produced in step (1) into a residue washing tank, adding water to adjust the slurry, controlling the solid-liquid mass ratio to 1:6, stirring for 30 minutes, and performing three-stage countercurrent washing. The rare earth content of the wet residue after washing is measured to be 0.03%. After secondary filtration using a plate and frame filter press, the residue is centrally stacked, and the rare earth-containing washing filter water is returned to step (1) as acid leaching water;

[0122] (3) The acid leaching solution produced in step (1) is transferred to a transfer stirring tank, and magnesium oxide slurry is added to the transfer stirring tank, wherein the solid content of the magnesium oxide slurry is 30%, and stirring is continued for 1 hour. After the pH value of the acid leaching solution is adjusted to 5.5, a plate and frame filter press is used for solid-liquid separation, and the filter residue is placed in the slag washing tank of step (2) and washed and then centrally stacked, and the rare earth sulfate filtrate is transferred to a reserve tank for standby use;

[0123] (4) Adding a 10% ammonium bicarbonate solution to the rare earth sulfate filtrate obtained in step (3), adjusting the pH of the solution to 7, and filtering with a plate and frame filter press to obtain a rare earth carbonate precipitate, washing the precipitate to obtain a rare earth carbonate product, and returning the washing liquid produced by the washing to step (1).

[0124] Comparative Example 1

[0125] This comparative example provides a pretreatment method for smelting and separating ionic rare earth ores. Compared with Example 1, the endpoint pH of sulfuric acid dissolution in step (1) is controlled to be 2.0, and the rest is the same as Example 1.

[0126] Comparative Example 2

[0127] This comparative example provides a pretreatment method for smelting and separating ionic rare earth ores. Compared with Example 1, the pH value of the acid leaching solution is adjusted to 2.0 in step (3), and the rest is the same as Example 1.

[0128] Comparative Example 3

[0129] This comparative example provides a pretreatment method for smelting and separating ionic rare earth ores. Compared with Example 1, the pH value of the acid leaching solution is adjusted to 3.5 in step (3), and the rest is the same as Example 1.

[0130] Comparative Example 4

[0131] This comparative example provides a pretreatment method for smelting and separating ionic rare earth ores. Compared with Example 3, the pH of the acid leaching solution is adjusted to 4.5 in step (3), and the rest is the same as Example 3.

[0132] The rare earth recovery rate and magnesium recovery rate were calculated based on the product amounts obtained in the embodiments and comparative examples, the aluminum content in the rare earth product was determined, the overall slag production of the pretreatment method was determined and the slag production rate was calculated. The results are listed in Table 1.

[0133] Table 1

[0134]

[0135] As can be seen from Table 1, the pretreatment method provided by the present invention is used to separate and recover rare earth elements from rare earth concentrates, with a high recovery rate, high purity of rare earth products, and low impurity content. At the same time, effective separation and recovery of magnesium and aluminum elements in the concentrates are achieved, thereby improving the utilization rate of element resources and reducing the overall slag production, which greatly solves the problem of waste slag in rare earth mining and smelting.

[0136] In Examples 1-2, the extraction method is used for element extraction. Through the dissolution and slurry adjustment of rare earth enriched materials, the rare earth recovery rate reaches more than 97.3%, the slag production rate is low, and the slag production rate is controlled below 18.4%. The impurity content in the final extracted rare earth solution is small. At the same time, the resource recovery of magnesium and aluminum elements is achieved, and the magnesium recovery rate is more than 96.5%. Compared with Example 1, the pH of the acid solution in Comparative Example 1 is controlled to 2.0, and the pH is too high, which significantly reduces the recovery effect of rare earth elements and magnesium elements, and the slag production is significantly increased. At the same time, in the actual process, the control difficulty of pH adjustment is large, the filtering difficulty is large, and it is not easy to operate. In Comparative Examples 2 and 3, when the pH of the slurry adjustment is too low or too high, the recovery rate of rare earth elements is reduced.

[0137] In Examples 3-4, the precipitation method is used for element extraction, the rare earth recovery rate reaches more than 98.3%, the impurity content in the rare earth product is small, and the magnesium recovery effect is good, and the magnesium recovery rate is more than 95.8%. Compared with Example 3, in Comparative Example 4, the pH is adjusted too high, the rare earth recovery effect is reduced, and the separation effect of magnesium and aluminum elements is significantly reduced.

[0138] In summary, the method provided by the present invention pre-treats and separates the rare earth enriched material obtained by leaching and precipitation of ionic rare earth ores, efficiently extracts rare earth elements, and has a rare earth recovery rate of more than 97.3%. The rare earth loss is small, and the obtained product can be directly used for the smelting and separation of rare earth products, thereby improving the efficiency of the overall process of ionic rare earth mining and utilization, and separating and converting the magnesium and aluminum impurity elements in the enriched material at the same time, realizing the resource utilization of non-rare earth impurities and reducing solid waste, reducing process costs, and improving the economic efficiency of rare earth mine development.

[0139] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A pretreatment method for smelting and separating ionic rare earth ores, characterized in that: The pretreatment method comprises the following steps: (1) crushing and slurrying the rare earth enriched material, dissolving it with sulfuric acid having a concentration of ≥30%, adjusting the pH of the acid solution to 1.0-1.5, obtaining a mixed solution, controlling the rare earth concentration in the mixed solution to 15-40 g / L with water, and then performing a first solid-liquid separation to obtain a first filter residue and an acid leaching solution; (2) the first filter residue obtained in step (1) is slurried with water at a solid-liquid mass ratio of 1:(5-6), stirred for 20-30 minutes, and after slurrying, subjected to countercurrent three-stage washing until the rare earth content in the wet residue produced by washing is less than 0.1%. After washing, a second solid-liquid separation is performed by plate and frame filter pressing to obtain a second filter residue and washing filtrate, and the washing filtrate is reused in step (1). If the rare earth content in the wet residue produced by washing is greater than 1%, the wet residue is returned to step (1) for secondary acid dissolution; The acid leaching solution obtained in step (1) is mixed with magnesium oxide slurry, wherein the solid content of the magnesium oxide slurry is 20-30%, and the pH is adjusted, and then a third solid-liquid separation is performed to obtain a third filter residue and a rare earth sulfate feed solution; When the pH is adjusted to 2.5-3.0 in step (2), the pretreatment method further comprises: (3) extracting the rare earth sulfate solution obtained in step (2) with a first extractant saponified with magnesium oxide, wherein the first extractant comprises P507 and a first diluent, and the saponification degree of the first extractant is 15-35%, and extracting until the rare earth concentration in the generated raffinate is less than 0.1 g / L, thereby obtaining a rare earth-loaded organic phase and a first raffinate; (4) stripping the rare earth-loaded organic phase obtained in step (3) to obtain a rare earth solution; The first raffinate obtained in step (3) is adjusted to a pH of 2.5-3.0, and then extracted with a second extractant saponified with magnesium oxide, wherein the second extractant comprises P204 and a second diluent, and the saponification degree of the second extractant is 15-30%, to obtain an aluminum-loaded organic phase and a magnesium sulfate solution, and the magnesium sulfate solution is reused for leaching ionic rare earth ores as a leaching agent; Stripping the aluminum-loaded organic phase to obtain an aluminum salt solution; Alternatively, when the pH is adjusted to 5.0-5.5 in step (2), the pretreatment method further comprises: (3) mixing the rare earth sulfate solution obtained in step (2) with an ammonium bicarbonate solution for reaction, wherein the concentration of the ammonium bicarbonate solution is 5-10%, adjusting the end point pH of the reaction to ≥ 7, and then performing a fourth solid-liquid separation to obtain rare earth carbonate and a precipitate; (4) The precipitate obtained in step (3) is subjected to ammonium recovery to obtain a magnesium sulfate solution.

2. The pretreatment method according to claim 1, characterized in that The solid-liquid mass ratio of the slurry preparation in step (1) is 1:(3-4).

3. The pretreatment method according to claim 1, characterized in that: The mixing reaction time in step (2) is 0.5-1h.

4. The pretreatment method according to claim 1, characterized in that: When the pH is adjusted to 2.5-3.0 in step (2), the first diluent in step (3) includes sulfonated kerosene; The volume ratio of the P507 to the first diluent is 1:(0.9-1.1).

5. The pretreatment method according to claim 1, characterized in that: When the pH is adjusted to 2.5-3.0 in step (2), the second diluent in step (4) includes sulfonated kerosene; The volume ratio of the P204 to the second diluent is 1:(0.9-1.1).

6. The pretreatment method according to claim 1, characterized in that: When the pH is adjusted to 5.0-5.5 in step (2), the ammonium recovery method in step (4) comprises: mixing magnesium oxide with the precipitate and performing steam stripping separation to obtain a mixed gas of ammonia and water vapor and a magnesium sulfate solution, and condensing the mixed gas to obtain aqueous ammonia.

7. The pretreatment method according to claim 1, characterized in that: The pretreatment method comprises the following steps: (1) mechanically crushing the rare earth enriched material, slurrying with water at a solid-liquid mass ratio of 1:(3-4) to obtain a slurry, acid-dissolving the obtained slurry with sulfuric acid at a concentration of ≥30%, adjusting the end point pH of the acid dissolution to 1.0-1.5 to obtain a mixed solution, controlling the rare earth concentration in the mixed solution to 15-40 g / L with water, stirring for 1-2 hours, and performing a first solid-liquid separation by plate and frame filter pressing to obtain a first filter residue and an acid leaching solution; (2) the first filter residue obtained in step (1) is slurried with water at a solid-liquid mass ratio of 1:(5-6), stirred for 20-30 minutes, and after slurrying, subjected to countercurrent three-stage washing until the rare earth content in the wet residue produced by washing is less than 0.1%. After washing, a second solid-liquid separation is performed by plate and frame filter pressing to obtain a second filter residue and washing filtrate, and the washing filtrate is reused in step (1). If the rare earth content in the wet residue produced by washing is greater than 1%, the wet residue is returned to step (1) for secondary acid dissolution; The acid leaching solution obtained in step (1) is mixed with magnesium oxide slurry for reaction, wherein the solid content of the magnesium oxide slurry is 20-30%, the mixing reaction time is 0.5-1h, the end point pH of the mixing reaction is adjusted to 2.5-3.0, and then a plate and frame filter press is used for a third solid-liquid separation to obtain a third filter residue and a rare earth sulfate feed liquid; (3) After mixing the extractant P507 and the diluent sulfonated kerosene in a ratio of 1: (0.9-1.1), saponification is performed with magnesium oxide slurry, wherein the saponification degree of the saponification is 15-35%, to obtain a first saponified extractant; Using the first saponification extractant to perform a first extraction on the rare earth sulfate solution obtained in step (2) until the rare earth concentration in the raffinate produced by the extraction is less than 0.1 g / L, thereby obtaining a rare earth-loaded organic phase and a first raffinate; (4) stripping the rare earth-loaded organic phase obtained in step (3) using hydrochloric acid to obtain a rare earth chloride solution; The extractant P204 and the diluent sulfonated kerosene are mixed in a ratio of 1: (0.9-1.1), and then saponified with magnesium oxide slurry, wherein the saponification degree of the saponification is 15-30%, to obtain a second saponified extractant; After adjusting the pH of the first raffinate obtained in step (3) to 2.5-3.0, performing a second extraction with the second saponification extractant to obtain an aluminum-loaded organic phase and a second raffinate; (5) stripping the aluminum-loaded organic phase obtained in step (4) using sulfuric acid to obtain an aluminum sulfate solution; The second raffinate obtained in step (4) is a magnesium sulfate solution.

8. The pretreatment method according to claim 1, characterized in that: The pretreatment method comprises the following steps: (1) mechanically crushing the rare earth enriched material, slurrying with water at a solid-liquid mass ratio of 1:(3-4) to obtain a slurry, acid-dissolving the obtained slurry with sulfuric acid at a concentration of ≥30%, adjusting the end point pH of the acid dissolution to 1.0-1.5 to obtain a mixed solution, adjusting the rare earth concentration in the mixed solution to 15-40 g / L with water, stirring for 1-2 hours, and performing a first solid-liquid separation by plate and frame filter pressing to obtain a first filter residue and an acid leaching solution; (2) the first filter residue obtained in step (1) is slurried with water at a solid-liquid mass ratio of 1:(5-6), stirred for 20-30 minutes, and after slurrying, subjected to countercurrent three-stage washing until the rare earth content in the wet residue produced by washing is less than 0.1%. After washing, a second solid-liquid separation is performed by plate and frame filter pressing to obtain a second filter residue and washing filtrate, and the washing filtrate is reused in step (1). If the rare earth content in the wet residue produced by washing is greater than 1%, the mixture is returned to step (1) for secondary acid dissolution; The acid leaching solution obtained in step (1) is mixed with magnesium oxide slurry for reaction, wherein the solid content of the magnesium oxide slurry is 20-30%, the mixing reaction time is 0.5-1h, and the end point pH of the mixing reaction is adjusted to 5.0-5.5, and then a plate and frame filter press is used for a third solid-liquid separation to obtain a third filter residue and a rare earth sulfate feed liquid; (3) mixing the third filter residue obtained in step (2) with sodium hydroxide and heating them to obtain sodium aluminate; The rare earth sulfate solution obtained in step (2) is mixed with an ammonium bicarbonate solution for precipitation, wherein the concentration of the ammonium bicarbonate solution is 5-10%, and the end point pH of the mixture is adjusted to ≥ 7, and then a plate and frame filter press is used for a fourth solid-liquid separation to obtain a rare earth carbonate precipitate and a precipitate liquid; (4) recovering ammonium from the precipitate obtained in step (3) to obtain a magnesium sulfate solution; The rare earth carbonate precipitate obtained in step (3) is subjected to three-stage countercurrent washing to obtain a rare earth carbonate product, and the washing liquid produced by the washing is recycled to step (1).

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