A method for producing crystalline cerium oxyfluoride by leaching bastnaesite

Abstract

The present invention relates to the field of rare earth production, and specifically discloses a method for producing crystalline cerium oxyfluoride by leaching bastnaesite, comprising the following steps: (1) taking oxidatively roasted bastnaesite and leaching it with an acid low-temperature wet method to obtain a rare earth leaching solution containing tetravalent cerium and a fluorine complex; (2) adding clean water to the rare earth leaching solution obtained in step (1) to dilute the rare earth leaching solution, so that Ce 4+ With F ‑ The formed complex hydrolyzes to form Ce(OH) x F y The crystalline cerium fluoride oxide is obtained by crystal precipitation, solid-liquid separation and calcination. The invention can make the rare earth leaching rate reach more than 92%, the yield of valuable elements praseodymium and neodymium is more than 95%, and the CeO2 / REO in cerium fluoride oxide is more than 95%; the method of the invention is simple, the consumption of chemical materials is low, and the fluorine, praseodymium and neodymium and cerium fluoride products in fluorocarbon cerium ore can be recovered at low cost, with significant economic and environmental benefits, and the method is more in line with market demand and enterprise needs.

Description

Technical Field

[0001] The invention relates to the field of rare earth production, and in particular to a method for producing crystalline cerium oxyfluoride by leaching bastnaesite. Background Art

[0002] Rare earth elements have excellent magnetic, optical, and electrical properties due to their unique electronic layer structure. They are indispensable strategic materials for countries around the world to transform traditional industries, develop high-tech and cutting-edge defense technologies. my country is a major producer of rare earths, providing 95% of the global rare earth market demand. Sichuan fluorocarbon cerium ore is the second largest rare earth resource in my country. Rare earths exist in the form of fluorocarbonates. After mineral processing and enrichment, the rare earth grade of the concentrate can reach 50% to 70%, and it also contains 6% to 9% fluorine and 0.2% of the radioactive element thorium.

[0003] In the 1990s, the Baotou mixed rare earth ore treatment process was introduced, and the oxidation roasting-sulfuric acid leaching process was used for smelting to obtain a rare earth sulfate solution containing fluorine and tetravalent cerium. Two double salt precipitations, alkali conversion, and acid dissolution were used to extract cerium-rich and low-cerium rare earth chlorides. The process is lengthy, with more than a dozen solid-liquid separation steps, and the rare earth yield is only about 70%. In 2000, based on the smelting process of the Monte Pass rare earth ore in the United States, the oxidation roasting-hydrochloric acid leaching chemical method was successfully developed. The main process is oxidation roasting-hydrochloric acid leaching-alkali decomposition-hydrochloric acid leaching cerium process, which can produce 98% Ce02 and low-cerium rare earth chloride. This method uses the oxidation roasting-hydrochloric acid leaching process to directly dissolve 30-35% REO (rare earth oxide) in the ore into the low-cerium rare earth chloride product, and the total yield of rare earths reaches more than 93%. However, the following technical problems exist in this method:

[0004] (1) During the treatment of bastnaesite, a large amount of high-value non-cerium rare earths still enter the cerium-rich slag, resulting in low-value utilization of high-priced elements. Therefore, it is necessary to connect the steps of alkali decomposition, washing and hydrochloric acid leaching, which is a complicated process;

[0005] (2) A large amount of water is used to wash and remove fluorine in the process. During the hydrochloric acid leaching process, fluorine enters the cerium-rich slag, and most of it enters the wastewater as the alkali is converted. Its environmental protection treatment is extremely difficult. Usually, lime or calcium hydroxide is used to treat fluorine-containing wastewater. The process will produce a large amount of calcium fluoride waste residue, which is difficult to handle later. Moreover, under strong alkaline conditions, the effect of removing fluorine from wastewater is limited. It is difficult for fluorine in wastewater to meet the discharge standards (less than 10ppm) stably. This problem has become an environmental problem that hinders the development of China's rare earth industry, especially the rare earth industry in Sichuan.

[0006] (3) The process consumes high amounts of chemical raw materials such as acids and alkalis.

[0007] Fluorine is also a valuable resource. If it can be used reasonably, it will not only solve the problem of fluorine-containing wastewater discharge, but also effectively utilize the rich fluorine resources contained in fluorocarbon cerium ore. At present, the process of recovering fluorine from alkali-converted fluorine-containing wastewater is to add calcium salt to generate calcium fluoride, or to recover fluorine by concentrating and recovering sodium fluoride products, but these two processes have long processes for recovering fluorine products, high energy consumption, and low product value.

[0008] Patent 200610114588.9 discloses a method for decomposing bastnaesite, wherein bastnaesite and carbonate are mixed and roasted in a ratio of 1:0.5 to 1:2 of non-cerium in bastnaesite to cerium in carbonate, and a large amount of cerium carbonate is added to solidify the fluorine in the bastnaesite, and then the cerium and non-cerium rare earth are separated by acid leaching, and the fluorine is finally retained in the cerium-rich slag. This process does not recycle fluorine, and because a large amount of rare earth carbonate roasting aid is added, the amount of mineral roasting, acid dissolution, extraction separation, and rare earth precipitation process processing and the acid and alkali consumption in the processing process are increased, which increases the production cost.

[0009] Patent 200810046146.4 discloses a one-step production method of rare earth chloride and cerium fluoride with little cerium, wherein rare earth concentrate after oxidation roasting is dissolved in dilute hydrochloric acid, and strong oxidants such as sulfuric acid, nitric acid, perchloric acid or potassium permanganate are added to achieve catalytic leaching, so that cerium participates in the reaction and generates cerium fluoride with fluoride ions and enters the slag. This method avoids the subsequent steps of alkali conversion, washing, and hydrochloric acid dissolution, fixes fluorine in the slag, and suppresses or eliminates the pollution of fluorine to water. However, the addition of the above-mentioned strong oxidants will cause hydrochloric acid oxidation to release chlorine gas, pollute the environment, deteriorate production and operating conditions, and reduce the effective acid dosage of hydrochloric acid and increase acid consumption.

[0010] Patent 201010517433.6 discloses a method for leaching and decomposing bastnaesite after activation, wherein the bastnaesite is roasted and activated at a temperature below 400°C, and then leached with hydrochloric acid, and rare earth hydroxide is added to the filtrate after filtration to remove iron and thorium impurities. Since the bastnaesite is not completely decomposed when roasted at a low temperature, the leaching rate of rare earths is low. Although the fluoride content in the leached residue is greater than 95%, it is all undecomposed bastnaesite. Therefore, the leached residue is converted to sodium hydroxide-washed to remove fluorine-hydrochloric acid dissolution to recover rare earths. The fluorine-containing alkali solution needs to be evaporated to recover fluorine. The whole process involves multiple solid-liquid separations, and the process of hydrochloric acid leaching-alkali conversion-hydrochloric acid leaching is still used, which has problems such as large consumption of chemical materials, high energy consumption, and high environmental protection costs.

[0011] Patent CN106811609B heats and boils the rare earth solution after low-temperature leaching to decomplex and adjust the pH to obtain a mixed rare earth fluoride with a cerium content of 48% and a praseodymium-neodymium content of about 14%. This invention recovers fluorine while forming a large amount of high-value praseodymium-neodymium elements into rare earth fluoride. Although the purpose of recovering fluorine is achieved, it causes a waste of valuable elements praseodymium-neodymium.

[0012] Patent CN114214515A utilizes organic phase P507 to extract complex ions in the rare earth leachate, and produces cerium fluoride products with a purity of more than 99.9% through extraction, washing and hydrogen peroxide stripping. Although this invention obtains high-purity cerium fluoride products, it also has shortcomings such as a long process operation flow, the need for fractional distillation extraction, and high consumption of auxiliary materials.

[0013] Therefore, in view of the current problems of low resource utilization, serious pollution, high energy consumption, and low product value in the processing process, it is urgent to develop efficient and practical green smelting and separation processes to solve the pollution of the three wastes to the environment. At the same time, we must vigorously reduce product unit consumption and improve the comprehensive utilization rate of resources, eliminate pollution from the source of production, and realize efficient utilization of resources and clean production. Summary of the invention

[0014] In order to solve the above technical problems, the present invention uses a low-temperature wet method to leach bastnaesite after oxidation roasting, controls the rare earth concentration and acidity of the leachate, and adds clean water to dilute the solution so that the acidity of the solution reaches the acidity of hydrolysis of tetravalent cerium and fluoride ion complex ions, thereby continuously hydrolyzing the complex of tetravalent cerium and fluorine. Through XRD characterization, it is found that the hydrolysis product of the crystalline form is Ce(OH) x F y (x+y=4).

[0015] The technical solution adopted by the present invention is as follows:

[0016] A method for producing crystalline cerium oxyfluoride by leaching bastnaesite, comprising the following steps:

[0017] (1) taking the oxidized and roasted bastnaesite and leaching it by acid low-temperature wet leaching to obtain a rare earth leaching solution containing tetravalent cerium and fluorine complex;

[0018] (2) Add clean water to dilute the rare earth leaching solution obtained in step (1) so that Ce 4+ With F - The formed complex hydrolyzes to form Ce(OH) x F y The crystals are precipitated, solid-liquid separated and burned to obtain Ce(OH) x F y , x+y=4.

[0019] In addition to the above-mentioned roasting and acid leaching processes, the method for comprehensive recovery of rare earth and fluorine in the process of bastnaesite treatment provided by the present invention may also include other steps known to those skilled in the art. As long as the above-mentioned steps mentioned in the present invention are used in the process of bastnaesite treatment, they all belong to the protection scope of the present invention. Of course, no other steps may be added to the method for comprehensive recovery of rare earth and fluorine in the process of bastnaesite treatment provided by the present invention. At this time, the method of the present invention is to oxidize and roast the bastnaesite, and the mixture after roasting is leached by acid. The present invention proposes to use low-temperature wet leaching, which is beneficial to improve the leaching rate of rare earths.

[0020] Cerium oxyfluoride (called white cerium oxide) is mainly used in glass clarifiers, special ceramics, polishing powders, etc. The crystalline cerium oxyfluoride obtained by the present invention can be used as a solvent or raw material for rare earth metal electrolysis, and can also be used as a polishing powder base material. It is a brand-new product.

[0021] In a specific embodiment of the present invention, the acidic solution in step (1) is selected from one of hydrochloric acid, nitric acid and sulfuric acid, and is further hydrochloric acid.

[0022] In a specific embodiment of the present invention, in step (1), the hydrochloric acid leaching temperature is 20-25° C. and the acidity is 1.5-2.0 mol / L.

[0023] In a specific embodiment of the present invention, the rare earth leaching solution obtained in step (1) has a concentration of 120-150 g / L and an acidity of 1.5-2.0 mol / L.

[0024] In a specific embodiment of the present invention, in the step (2), the hydrolysis temperature is 17 to 30°C; further, the hydrolysis temperature is 20 to 25°C.

[0025] Patent CN106811609B is to add hydrochloric acid aqueous solution with complexing agent to fluorinated bastnaesite for acid leaching, add flocculant to clarify and separate after the reaction is completed, adjust pH value to obtain fluorine-containing rare earth solution, and then heat to boiling. The complex ions formed in this process are gradually decomplexed, and fluoride ions are slowly and evenly released in the solution. Fluoride ions and rare earth ions are then homogeneously generated to form fluoride rare earth that is easy to clarify and wash, thereby obtaining mixed fluoride rare earth with cerium content of 48% and praseodymium and neodymium content of about 14%. However, this invention forms rare earth fluoride with a large amount of high-value praseodymium and neodymium elements while recovering fluorine. Although the purpose of recovering fluorine is achieved, it causes waste of valuable elements praseodymium and neodymium.

[0026] Patent CN114214515A uses organic phase P507 as an extractant to extract complex ions in the fluorocarbon cerium ore rare earth leachate, and produces a cerium fluoride product with a purity of more than 99.9% through extraction, washing and hydrogen peroxide stripping. Although this invention obtains a high-purity cerium fluoride product, it also has shortcomings such as a long process operation flow, the need for fractional distillation extraction, and high consumption of auxiliary materials.

[0027] The cerium oxyfluoride of the present invention is obtained by hydrolysis and precipitation under certain acidity conditions. Generally, the hydrolysis and precipitation of metals requires the pH value of the solution to be in the range of 1 to 14, but the acidity of the present invention needs to be lower than 1 to hydrolyze and precipitate cerium oxyfluoride. At the same time, the yield of the valuable elements praseodymium and neodymium obtained is above 95%, which solves the problem of valuable elements praseodymium and neodymium not being recovered in patent CN106811609B; at the same time, the method of the present invention has a short process flow and consumes less auxiliary materials, which can make up for the shortcomings of patent CN114214515A.

[0028] In a specific embodiment of the present invention, in the step (2), during the hydrolysis process, the solution hydrolysis acidity is maintained at 0.5-0.7 mol / L, and REO is maintained at 40-50 g / L. Within this range, the hydrolysis rate of the complex is increased.

[0029] The acidity during the hydrolysis process should reach the acidity for hydrolysis of tetravalent cerium and fluoride ion complex ions.

[0030] In a specific embodiment of the present invention, the reagent for maintaining the acidity of the solution during hydrolysis is an alkaline substance; further, a carbonate.

[0031] In a specific embodiment of the present invention, the carbonate is selected from at least one of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, sodium carbonate and potassium carbonate.

[0032] In a specific embodiment of the present invention, during the hydrolysis process, the clear solution in step (2) is taken to detect Ce 4+ When the concentration is less than 5 g / L, stop adding carbonate and continue the reaction for 0.5 to 2 hours.

[0033] In a specific embodiment of the present invention, in step (2), the burning temperature is 570-650°C.

[0034] When mass ratio or other value or parameter is represented by range, preferred range, or a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when disclosing range "1 to 5", the described range should be interpreted as including range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc. When numerical range is described in this article, unless otherwise stated, the range is intended to include its end value and all integers and fractions within the range.

[0035] Approximate terms in the specification and claims are used to modify quantities, indicating that the present invention is not limited to the specific quantity, but also includes acceptable modified parts close to the quantity without causing changes in the relevant basic functions. In the specification and claims of this application, range limits can be combined and / or interchanged, and if not otherwise stated, these ranges include all sub-ranges contained therein.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention controls the leaching temperature, acidity of the rare earth solution during hydrolysis, rare earth concentration and other condition parameters to achieve a rare earth leaching rate of more than 92%, a recovery rate of valuable elements of praseodymium and neodymium of more than 95%, and a CeO2 / REO ratio of more than 95% in cerium oxyfluoride, thereby obtaining a high-value product, making full use of the fluorine resources of the rare earth concentrate, and saving resources.

[0038] (2) The method of the present invention is simple, the process operation flow is short, the auxiliary material consumption is low, the economy of the process flow is improved, and the fluorine, praseodymium, neodymium and fluorine oxide products in fluorocarbon cerium ore can be recovered at low cost, which has significant economic and environmental benefits. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. All features disclosed in this specification, or steps in all methods or processes disclosed, except mutually exclusive features and / or steps, can be combined in any way.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0041] It should be understood that the experimental methods used in the following examples are conventional methods unless otherwise specified, and the materials, reagents, etc. used in the following examples are all commercially available unless otherwise specified.

[0042] Example 1

[0043] 1. Take 200g of Sichuan fluorocarbon cerium ore REO: 74.5% after oxidation roasting, use hydrochloric acid to wet leaching at a temperature of 20°C, the residual acidity of the reaction is 1.8mol / L, react for 30min to obtain 1000mL of rare earth leaching solution containing tetravalent cerium and fluorine complex with a rare earth concentration of 135g / L and an acidity of 1.8mol / L. The remaining crude slag is dried and weighed to 39.5g, of which the REO content is 26.9%, the rare earth leaching rate is 92.86%, and the leaching rate of valuable elements Pr+Nd is 95.6%.

[0044] 2. Add 2000 mL of clean water to the rare earth leaching solution obtained in step 1 under stirring to dilute it to an acidity of 0.6 mol / L, so that Ce 4+ With F - The formed complex begins to hydrolyze to form Ce(OH) x F y The crystalline precipitate of (x+y=4) serves as the crystal nucleus for subsequent continuous hydrolysis precipitation.

[0045] 3. After continuing to stir for 2 hours in step 2, slowly add a small amount of ammonium carbonate to the system to maintain the acidity of the solution hydrolysis so that Ce 4+ With F - The formed complex continues to hydrolyze to form Ce(OH) x F y The reaction temperature was controlled at 22°C during the entire complex hydrolysis reaction.

[0046] 4. Take the clear solution from step 3 and test Ce 4+ When the concentration is 3.8 g / L, stop adding ammonium carbonate and continue stirring the reaction for 1 hour.

[0047] 5. The system in step 4 is subjected to solid-liquid separation to obtain Ce(OH) x F y The rare earth feed liquid is a crystal precipitate and a cool and transparent rare earth feed liquid, which is then subjected to subsequent extraction and separation after being impurity-removed and concentrated.

[0048] 6. Crystalline Ce(OH) obtained in step 5 x F y Filter and wash with water, then burn at 600℃ to obtain CeO x F y Product 50g.

[0049]

[0050] Example 2

[0051] 1. Take 200g of Sichuan fluorocarbon cerium ore REO: 81.6% after oxidation roasting, and use hydrochloric acid to wet leaching at a temperature of 22°C. The residual acidity of the reaction is 1.6mol / L. After reacting for 28min, 1000ml of rare earth leaching solution with a rare earth concentration of 148g / L and an acidity of 1.6mol / L containing tetravalent cerium and fluorine complex is obtained. The remaining crude slag is dried and weighed to 35.5g, which contains REO: 23.5%, the rare earth leaching rate is 94.89%, and the Pr+Nd leaching rate is 96.7%.

[0052] 2. Add 1900 mL of clean water to the rare earth leaching solution obtained in step 1 under stirring to dilute it to an acidity of 0.55 mol / L, so that Ce 4+ With F - The formed complex begins to hydrolyze to form Ce(OH) x F y The crystalline precipitate of (x+y=4) serves as the crystal nucleus for subsequent continuous hydrolysis precipitation.

[0053] 3. After continuing to stir for 2 hours in step 2, slowly add a small amount of ammonium carbonate to the system to maintain the acidity of the solution hydrolysis so that Ce 4+ With F - The formed complex continues to hydrolyze to form Ce(OH) x F y The reaction temperature was controlled at 25°C during the entire complex hydrolysis reaction.

[0054] 4. Take the clear solution from step 3 and test Ce 4+ When the concentration is 4.6 g / L, stop adding ammonium carbonate and continue stirring the reaction for 1 hour.

[0055] 5. The system in step 4 is subjected to solid-liquid separation to obtain Ce(OH) x F y The rare earth feed liquid is a crystal precipitate and a cool and transparent rare earth feed liquid, which is then subjected to subsequent extraction and separation after being impurity-removed and concentrated.

[0056] 6. Crystalline Ce(OH) obtained in step 5 x F y Filter and wash with water, then burn at 600℃ to obtain CeO x F y Product 53.5g.

[0057]

[0058] Example 3

[0059] 1. Take 200g of Sichuan fluorocarbon cerium ore REO: 70.5% after oxidation roasting, and use hydrochloric acid for wet leaching at a temperature of 25°C. The residual acidity of the reaction is 1.9 mol / L. After reacting for 35 minutes, 900mL of rare earth leaching solution containing tetravalent cerium and fluorine complex with a rare earth concentration of 140g / L and an acidity of 1.9 mol / L is obtained. The remaining crude slag is dried and weighed to be 65g, of which REO=19.8%, the rare earth leaching rate is 90.87%, and the Pr+Nd leaching rate is 95.6%.

[0060] 2. Add 1900 mL of clean water to the rare earth leaching solution obtained in step 1 under stirring to dilute it to an acidity of 0.68 mol / L, so that Ce 4+ With F - The formed complex begins to hydrolyze to form Ce(OH) x F y The crystalline precipitate of (x+y=4) serves as the crystal nucleus for subsequent continuous hydrolysis precipitation.

[0061] 3. After continuing to stir for 2 hours in step 2, slowly add a small amount of ammonium carbonate to the system to maintain the acidity of the solution hydrolysis so that Ce 4+ With F - The formed complex continues to hydrolyze to form Ce(OH) x F y The reaction temperature was controlled at 25°C during the entire complex hydrolysis reaction.

[0062] 4. Take the clear solution from step 3 and test Ce 4+ When the concentration is 3.2 g / L, stop adding ammonium carbonate and continue stirring the reaction for 1 hour.

[0063] 5. The system in step 4 is subjected to solid-liquid separation to obtain Ce(OH) x F y The rare earth feed liquid is a crystal precipitate and a cool and transparent rare earth feed liquid, which is then subjected to subsequent extraction and separation after being impurity-removed and concentrated.

[0064] 6. Crystalline Ce(OH) obtained in step 5 x F y Filter and wash with water, then burn at 600℃ to obtain CeO x F y Product 46.7g.

[0065]

[0066] The present invention finds through XRD characterization that the hydrolysis product of the crystalline form is Ce(OH) x F y(x+y=4), and the hydrolyzate is calcined to obtain cerium oxyfluoride. The product can be used as a co-solvent or raw material for rare earth metal electrolysis, and can also be used as a polishing powder base material. It is a brand-new product.

[0067] It can be seen from Examples 1 to 3 and their data that the present invention can achieve a rare earth leaching rate of more than 92%, a recovery rate of more than 95% for the valuable elements praseodymium and neodymium, and a CeO2 / REO ratio of more than 95% in cerium oxyfluoride by controlling the leaching temperature, the acidity of the rare earth solution during hydrolysis, the rare earth concentration and other condition parameters, thereby achieving comprehensive utilization of fluorine resources, reducing the discharge of fluorine-containing wastewater, and greatly reducing environmental protection costs. Compared with the existing process, the present invention has significant social and economic benefits.

[0068] Comparative Example 1

[0069] 1. Take 200g of Sichuan fluorocarbon cerium ore REO: 81.6% after oxidation roasting, and use hydrochloric acid to wet leaching at a temperature of 22°C. The residual acidity of the reaction is 1.6 mol / L. After reacting for 28 minutes, 1000ml of rare earth leaching solution containing tetravalent cerium and fluorine complex with a rare earth concentration of 148g / L and an acidity of 1.6 mol / L is obtained. The remaining crude slag is dried and weighed to 35.5g, which contains REO: 23.5%, the rare earth leaching rate is 94.89%, and the Pr+Nd leaching rate is 96.7%.

[0070] 2. Add ammonium carbonate to the coolant obtained in step 1 until the acidity is 0.55 mol / L, and maintain the solution hydrolysis acidity so that Ce 4+ With F - The formed complex continues to hydrolyze to form Ce(OH) x F y The reaction temperature was controlled at 25°C during the entire complex hydrolysis reaction.

[0071] 3. Take the clear solution from step 2 and check the pH to be 1.0, stop adding ammonium carbonate, and continue stirring the reaction for 1 hour.

[0072] 5. The system in step 4 is subjected to solid-liquid separation to obtain Ce(OH) x F y The rare earth feed liquid is a crystal precipitate and a cool and transparent rare earth feed liquid, which is then subjected to subsequent extraction and separation after being impurity-removed and concentrated.

[0073] 6. Crystalline Ce(OH) obtained in step 5 x F y Filter and wash with water, then burn at 600℃ to obtain CeO x F y Product 58.5g.

[0074]

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for producing crystalline cerium oxyfluoride by leaching bastnaesite, characterized in that: The steps include: (1) taking the oxidized and roasted bastnaesite and leaching it by acid low-temperature wet leaching to obtain a rare earth leaching solution containing tetravalent cerium and fluorine complex; (2) Add clean water to dilute the rare earth leaching solution obtained in step (1) so that Ce 4+ With F - The formed complex hydrolyzes to form Ce(OH) x F y The crystals are precipitated, solid-liquid separated and burned to obtain Ce(OH) x F y In the equation, x+y=4; In the step (2), the hydrolysis temperature is 17 to 30°C; In the step (2), during the hydrolysis process, the solution hydrolysis acidity is maintained at 0.5-0.7 mol / L and REO is maintained at 40-50 g / L; In the step (2), the reagent for maintaining the acidity of the solution during hydrolysis is an alkaline substance.

2. The method for producing crystalline cerium oxyfluoride by leaching bastnaesite according to claim 1, characterized in that: The acid in step (1) is selected from hydrochloric acid, nitric acid and sulfuric acid.

3. The method for producing crystalline cerium oxyfluoride by leaching bastnaesite according to claim 2, characterized in that: In the step (1), the hydrochloric acid leaching temperature is 20-25° C. and the acidity is 1.5-2.0 mol / L.

4. The method for producing crystalline cerium oxyfluoride by leaching bastnaesite according to claim 1, characterized in that: The rare earth leaching solution obtained in step (1) has a concentration of 120-150 g / L and an acidity of 1.5-2.0 mol / L.

5. The method for producing crystalline cerium oxyfluoride by leaching bastnaesite according to claim 1, characterized in that: The hydrolysis temperature is 20-25°C.

6. The method for producing crystalline cerium oxyfluoride by leaching bastnaesite according to claim 1, characterized in that: The alkaline substance is carbonate.

7. The method for producing crystalline cerium oxyfluoride by leaching bastnaesite according to claim 6, characterized in that: The carbonate is selected from at least one of ammonium bicarbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, sodium carbonate and potassium carbonate.

8. The method for producing crystalline cerium oxyfluoride by leaching bastnaesite according to claim 6 or 7, characterized in that: During the hydrolysis process, the clear solution in step (2) was taken to detect Ce 4+ When the concentration is less than 5 g / L, stop adding carbonate and continue the reaction for 0.5 to 2 hours.

9. The method for producing crystalline cerium oxyfluoride by leaching bastnaesite according to claim 1, characterized in that: In step (2), the burning temperature is 570-650°C.

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