Method for synchronously removing cerium from cerium-containing rare earth solution and recovering cerium

Abstract

The invention relates to a method for removing cerium and synchronously recovering cerium from a cerium-containing rare earth solution. The method comprises the following steps: mixing the cerium-containing rare earth solution, an oxidizing agent and a transforming agent, and reacting to remove cerium in the cerium-containing rare earth solution, wherein the oxidizing agent comprises potassium permanganate; the transforming agent comprises any one or a combination of at least two of divalent cation carbonate, rare earth carbonate or rare earth hydroxide; according to the method, the cerium in the cerium-containing rare earth solution is efficiently removed under the mild condition, the primary removal rate of the cerium is preferably as high as 93.89% or above, and the secondary removal rate of the cerium is preferably as high as 99.98% or above; meanwhile, the coprecipitation phenomenon of cerium is greatly reduced, the purity of cerium enrichment is improved to 73.40% or above, meanwhile, when the method is used for a cerium-containing rare earth solution of a chlorine salt system, generation of harmful gas Cl2 is avoided, and the method is environmentally friendly.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, and in particular to a method for removing cerium from a cerium-containing rare earth solution and simultaneously recovering cerium. Background Art

[0002] Rare earth elements are known as "vitamins of industry" and have unique and excellent physical properties such as light, electricity, magnetism and heat. They play a great role in improving product performance, increasing product variety and improving production efficiency. They are widely used in metallurgy, military, petroleum, chemical industry, glass ceramics, agriculture and new materials. Rare earth elements have their electrons filled into the 4f sublayer, and the 4f electron cloud is diffuse, which cannot completely shield the increased nuclear charge, resulting in an increase in effective nuclear charge and a reduction in atomic radius, thus causing similar electronic layer structures and the rare earth "lanthanide contraction" phenomenon, resulting in similar ion radii between rare earth elements, which determines the similarity of the physical and chemical properties of rare earth elements, thus making it difficult to separate rare earth elements.

[0003] At present, the mainstream rare earth separation process includes solvent extraction. The raw materials are mainly raw ores or rare earth secondary resources. The raw ores are mainly northern fluorocarbon cerium ore and southern ionic rare earth ore, and the rare earth secondary resources are mainly NdFeB waste, phosphor waste and rare earth smelting slag. Since the radii of cerium and praseodymium ions are very close, separation is very difficult. The solvent extraction method requires hundreds or even thousands of extraction tanks to achieve separation between the two. In addition, cerium is a variable valence element. It is inevitable that a small amount of tetravalent cerium will enter the extraction phase with praseodymium and neodymium during the extraction process. Over time, it may cause organic phase poisoning, and will also cause the cerium content in the stripping phase to exceed the standard, greatly reducing the purity of single rare earth products and affecting product quality. Based on this, researchers are committed to studying new methods to remove cerium from rare earth feed solutions.

[0004] For example, CN111996396A discloses a method for removing cerium and non-rare earth impurities from a rare earth liquid. The method uses hydrogen peroxide as a redox agent to oxidize trivalent cerium to tetravalent cerium, and precipitates tetravalent cerium by adding rare earth carbonate or rare earth hydroxide as an adsorbent. The method is only for rare earth liquids with a cerium content of less than 0.3wt%, and has a low cerium removal rate. In addition, hydrogen peroxide is a redox agent in the method, which can easily reduce the precipitated tetravalent cerium to trivalent cerium and dissolve it back into the liquid, increasing the consumption of hydrogen peroxide. In addition, during the precipitation of cerium, other rare earth elements in the liquid co-precipitate, and the higher the concentration of other rare earth elements, the greater the amount of co-precipitation, which increases the burden of recovering rare earths from the precipitate.

[0005] CN115232965A discloses a method for removing cerium from a high-cerium praseodymium-neodymium rare earth liquid. In this method, hydrogen peroxide is used to oxidize trivalent cerium to tetravalent cerium. In the process, a large amount of hydrogen ions are present. A buffer is used to absorb the hydrogen ions, reduce the acidity, and precipitate cerium to complete the removal of cerium from the high-cerium praseodymium-neodymium liquid. However, this method still cannot reduce the co-precipitation phenomenon and cannot achieve selective cerium removal. In addition, this method also has the problem that hydrogen peroxide is used as a reducing agent to reduce the precipitated tetravalent cerium to trivalent cerium and dissolve it back into the liquid.

[0006] In view of this, how to develop a method for selectively and efficiently removing cerium from a cerium-containing rare earth solution and simultaneously recovering cerium, and how to achieve a high cerium removal rate under mild conditions are currently difficult problems that need to be solved urgently in this field. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a method for removing cerium from a cerium-containing rare earth solution and simultaneously recovering cerium, which can selectively and efficiently remove cerium ions in the cerium-containing rare earth solution under mild conditions, and no harmful gases are generated in the whole process. The co-precipitation phenomenon of other rare earth elements except cerium in the cerium-containing rare earth solution is relatively small; in addition, the method has the advantages of wide application range, simple operation, low energy consumption and green environmental protection.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for removing cerium from a cerium-containing rare earth solution and simultaneously recovering cerium, the method comprising the following steps:

[0010] Mixing a cerium-containing rare earth solution, an oxidant, and a conversion agent to react to remove cerium from the cerium-containing rare earth solution;

[0011] Wherein, the oxidant includes potassium permanganate; the conversion agent includes any one of divalent cation carbonate, rare earth carbonate or rare earth hydroxide, or a combination of at least two of them, wherein typical but non-limiting combinations include a combination of divalent cation carbonate and rare earth carbonate, a combination of divalent cation carbonate and rare earth hydroxide, or a combination of rare earth carbonate and rare earth hydroxide, etc.

[0012] The method of the present invention selectively removes cerium ions in the cerium-containing rare earth solution under mild conditions by selecting a specific oxidant and a specific conversion agent, and the two act synergistically without generating harmful gas Cl2; wherein the oxidant converts Ce in the cerium-containing solution to 3+ Fully oxidized to Ce 4+ , and the conversion agent is mainly alkaline (or weakly alkaline) conversion agent, which helps to produce a small amount of hydroxide ions. sp ≈10 -21 , tetravalent rare earth hydroxide Ksp ≈10 -47.7 In an acidic solution with a pH value greater than 1.5, tetravalent cerium will preferentially react with hydroxide to form tetravalent cerium hydroxide precipitate (as shown in formula (1) to formula (4)), while only a small amount of other rare earth ions will co-precipitate with tetravalent cerium hydroxide (as shown in formula (5)), while most of them will stably exist in the acidic solution; that is, the oxidant will react with Ce 3+ Oxidized to Ce 4+ At the same time, the conversion agent simultaneously converts the Ce 4+ The oxidation process and the conversion process promote each other, and the cerium ions in the cerium-containing rare earth solution are efficiently removed, while the co-precipitation phenomenon is reduced to a certain extent. Therefore, the synergistic effect of the specific oxidant and the specific conversion agent of the present application achieves the purpose of selectively precipitating cerium while other rare earth ions are stably present in the solution.

[0013] Among them, formula (1) to formula (5) are as follows:

[0014] 3Ce 3+ +MnO4 - +4H + →3Ce 4+ +MnO 2(s) +2H2O (1)

[0015] CaCO3+H2O→Ca 2+ +HCO3 - +OH - (2)

[0016] Ce 4+ +4OH - →Ce(OH) 4(s) (3)

[0017] Ce 4+ +4HCO3 - →Ce(HCO3) 4(s) (4)

[0018] RE 3+ +3OH - →RE(OH)3(s) (5)

[0019] Among them, RE is a rare earth element.

[0020] Preferably, the cerium content in the cerium-containing rare earth solution is ≥ 0.025wt%, for example, it can be 0.025wt%, 1wt%, 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, 90wt% or 100wt%, etc.

[0021] It is worth noting that the method of the present invention is applicable to both low-cerium rare earth solutions and high-cerium rare earth solutions, and a higher cerium removal rate can be achieved by simply selecting the amount of oxidant and converter added according to the cerium content.

[0022] Preferably, the cerium ions in the cerium-containing rare earth solution include Ce 3+ and Ce 4+ .

[0023] Because Ce 4+ It is unstable in a solution with a pH of 1 to 7 or an acidic solution containing chlorate, so the cerium ions in the cerium rare earth solution mainly exist in the form of Ce 3+ .

[0024] Preferably, the rare earth elements other than cerium in the cerium-containing rare earth solution include any one or a combination of at least two of La, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu or Y, wherein typical but non-limiting combinations include a combination of Nd, La and Pr, a combination of Pr, Gd, Tb and Dy, or a combination of Nd, La, Pr, Gd, Tb and Dy, etc.

[0025] Preferably, the anions in the cerium rare earth solution include Cl - 、SO4 2- or NO3 - Any one or a combination of at least two of the following, wherein typical but non-limiting combinations include Cl - and SO4 2- Combination of Cl - and NO3 - Combination or Cl - 、SO4 2- and NO3 - combinations of etc.

[0026] Preferably, the initial pH of the cerium rare earth solution is 0.1-7.0, for example, 0.1, 0.3, 0.5, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5 or 7.0.

[0027] Preferably, the divalent cation carbonate comprises any one of calcium carbonate, magnesium carbonate or magnesium calcium carbonate or a combination of at least two thereof, wherein typical but non-limiting combinations include a combination of calcium carbonate and magnesium carbonate, a combination of calcium carbonate and magnesium calcium carbonate, or a combination of magnesium carbonate and magnesium calcium carbonate, etc.

[0028] Preferably, the rare earth element in the rare earth carbonate and the rare earth element in the rare earth hydroxide are each independently any one of La, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu or Y, or a combination of at least two of them, wherein typical but non-limiting combinations include a combination of Nd, La and Pr, a combination of La, Pr, Gd and Tb, or a combination of Nd, La, Pr, Gd, Tb and Dy, etc., preferably the same element as the rare earth element other than cerium in the cerium-containing rare earth solution.

[0029] The present invention further prefers that the rare earth elements in the rare earth carbonate and the rare earth elements in the rare earth hydroxide are the same as the rare earth elements in the cerium-containing rare earth solution except cerium, so as to avoid the introduction of impurities and reduce the burden for the subsequent recovery of the cerium enrichment and the separation of the rare earth elements in the filtrate.

[0030] In order to minimize the co-precipitation of other rare earth ions, this can be achieved by controlling the amount of added oxidant and converter. For example, if the amount of calcium carbonate added is controlled to be less than the theoretical amount, there will be no co-precipitation of other rare earth ions. The specific reaction equation is shown in formula (6).

[0031] 4RE(OH) 3(s) +3Ce 4+ →3Ce(OH) 4(s) +4RE 3+ (6);

[0032] Among them, RE is a rare earth element.

[0033] Preferably, the molar ratio of the oxidant to the cerium element in the cerium-containing rare earth solution is (0.1-1):1, for example, it can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1, etc., and is preferably (0.35-0.55):1.

[0034] The present invention further preferably has a molar ratio of the oxidant to the cerium element in the cerium-containing rare earth solution of (0.35-0.55):1, which is beneficial to the Ce in the cerium-containing rare earth solution. 3+ Fully oxidized to Ce 4+ , which is beneficial to the subsequent 4+ The process of converting to precipitation by the converting agent is carried out, thereby improving the cerium removal rate; if the molar ratio of the oxidant to the cerium element in the cerium-containing rare earth solution is too small, it will cause Ce in the cerium-containing rare earth solution 3+ If the oxidation is not sufficient and the cerium removal rate is reduced, the cerium removal needs to be repeated, which reduces the cerium removal efficiency; if the molar ratio of the oxidant to the cerium element in the cerium-containing rare earth solution is too large, the removal rate cannot be significantly improved, but instead causes a waste of reagents.

[0035] Preferably, the molar ratio of the conversion agent to the cerium element in the cerium-containing rare earth solution is (0.8-3.0):1, for example, it can be 0.8:1, 1:1, 1.3:1, 1.5:1, 1.8:1, 2.0:1, 2.3:1, 2.5:1, 2.8:1 or 3.0:1, etc.

[0036] Preferably, when the conversion agent is a divalent cation carbonate, the molar ratio of the conversion agent to the cerium element in the cerium-containing rare earth solution is (1.3-2.0):1, for example, it can be 1.3:1, 1.4:1, 1.42:1, 1.48:1, 1.50:1, 1.55:1, 1.85:1 or 2.0:1, etc.

[0037] The present invention further preferably has a molar ratio of (1.3-2.0):1 when the conversion agent is a divalent cation carbonate, that is, the conversion agent is appropriately excessive, which is beneficial to convert Ce in the cerium-containing solution to 4+ It is fully converted into precipitation to improve the cerium removal rate and avoid the co-precipitation of other rare earth elements. If the converter is a divalent cation carbonate, the molar ratio of the converter to the cerium element in the cerium-containing rare earth solution is too small, resulting in the inability to fully remove the cerium ions in the cerium-containing rare earth solution. If the converter is a divalent cation carbonate, the molar ratio of the converter to the cerium element in the cerium-containing rare earth solution is too large, which will lead to the co-precipitation of more other rare earth elements in the subsequent cerium enrichment, increasing the burden of subsequent separation of cerium and other elements.

[0038] Preferably, when the converter is a rare earth carbonate and / or a rare earth hydroxide, the molar ratio of the converter to the cerium element in the cerium-containing rare earth solution is (1.3-2.8):1, for example, it can be 1.3:1, 1.55:1, 1.85:1, 2.0:1, 2.25:1, 2.45:1, 2.65:1 or 2.8:1, etc.

[0039] The present invention further preferably comprises a conversion agent which is a rare earth carbonate and / or a rare earth hydroxide, and a molar ratio of the conversion agent to the cerium element in the cerium-containing rare earth solution is (1.3-2.8):1, which is beneficial to the conversion of Ce in the cerium-containing rare earth solution. 4+ conversion, thereby improving the cerium removal rate and avoiding the co-precipitation of other rare earth elements caused by excessive conversion dosage.

[0040] Preferably, the conversion agent is a divalent cation carbonate, preferably calcium carbonate and / or magnesium carbonate.

[0041] The present invention further prefers that the conversion agent is a divalent cation carbonate, which has the following four advantages: first, in the subsequent extraction, separation and purification of rare earth elements in the filtrate, the competitive ability of divalent cations is much weaker than that of trivalent rare earth ions, so the divalent cations released by the divalent cation carbonate have almost no effect on the subsequent extraction of rare earth elements; second, due to the solubility product constant (K sp ≈10 -9 ) is much larger than rare earth hydroxide (average K sp ≈10 -21 ) and rare earth carbonate (average K sp ≈10 -33 ) so that divalent cation carbonates are more likely to ionize hydroxide ions. Therefore, tetravalent cerium ions will preferentially react with divalent cation carbonates, and the reaction time is short, and the reaction can be completed within 10 minutes. Thirdly, using divalent cation carbonates as conversion agents is conducive to the precipitation of tetravalent cerium, and the precipitate is easy to filter, while tetravalent cerium precipitated by rare earth hydroxide or rare earth carbonate is very difficult to filter, because rare earth hydroxide and tetravalent cerium precipitates are charged particles and are not easy to precipitate, while the addition of divalent cation carbonates can adsorb such particles to form large particles and precipitate together. Fourthly, divalent cation carbonates are cheap, and the price of the same molar amount of rare earth carbonate or rare earth hydroxide is many times that of divalent cation carbonate.

[0042] Preferably, the mixing comprises: a first mixing and a first reaction of the cerium-containing rare earth solution and an oxidant to obtain a mixed solution; and a second mixing and a second reaction of the mixed solution and a converter to obtain a suspension containing a cerium enrichment.

[0043] The present invention further preferably performs a first mixing of the cerium-containing rare earth solution and the oxidant, and a second mixing of the mixed solution and the converter, that is, the preferred mixing order is conducive to the conversion of trivalent cerium to tetravalent cerium.

[0044] Preferably, the first mixing process is accompanied by a first stirring.

[0045] Preferably, the first stirring rate is 600-1000 r / min, for example, 600 r / min, 700 r / min, 800 r / min, 900 r / min or 1000 r / min.

[0046] Preferably, the temperature of the first reaction is 20-100°C, for example, it can be 20°C, 23°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 70°C, 80°C, 90°C or 100°C, etc., preferably 25-45°C.

[0047] Preferably, the first reaction time is 1 to 10 min, for example, it can be 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min.

[0048] Preferably, the second mixing process is accompanied by a second stirring.

[0049] Preferably, the second stirring rate is 100-1500 r / min, for example, it can be 100 r / min, 300 r / min, 500 r / min, 800 r / min, 1000 r / min, 1200 r / min or 1500 r / min, etc., preferably 600-1000 r / min.

[0050] The present invention further preferably has the second stirring rate of 600 to 1000 r / min, which is beneficial for the conversion agent to convert Ce in the cerium rare earth solution into 4+ Timely conversion to precipitation can improve the removal rate of cerium, otherwise Ce 4+ It cannot be converted in time, and it has high oxidizability. When Cl - When Ce is not converted in time 4+ Will Cl - Oxidized to Cl2, it is harmful to the environment and experimenters.

[0051] Preferably, the temperature of the second reaction is 20-100°C, for example, it can be 20°C, 23°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 70°C, 80°C, 90°C or 100°C, etc., preferably 25-45°C.

[0052] The present invention further preferably has the first reaction temperature of 25 to 45°C and the second reaction temperature of 25 to 45°C, so as to ensure that Ce in the cerium rare earth solution is 3+ Fully oxidized to Ce 4+ , and Ce 4+ The cerium removal rate in the cerium-containing rare earth solution is improved by converting it into precipitation in time, and the conversion process and the oxidation process promote each other. However, when the cerium-containing rare earth solution contains Cl - , the temperature of the first reaction and the temperature of the second reaction are too high, the oxidizing property of the oxidant potassium permanganate is stronger, Cl - It will be oxidized into harmful gas Cl2, and the energy consumption of the whole process will increase; if the corresponding temperature is low, the oxidation process and the conversion process will be slower, reducing the cerium removal rate.

[0053] Preferably, the second reaction time is 5 to 30 min, for example, 5 min, 10 min, 15 min, 20 min, 25 min or 30 min, etc., preferably 5 to 20 min.

[0054] Preferably, the method further comprises, after the second reaction, sequentially performing a static treatment and a solid-liquid separation on the suspension containing the cerium enriched product to obtain a first cerium enriched product.

[0055] Preferably, the standing treatment time is 2 to 30 min, for example, 2 min, 5 min, 10 min, 15 min, 20 min, 25 min or 30 min, etc., preferably 5 to 15 min.

[0056] It is worth noting that in the method of the present invention, Ce 4+ The effect of conversion into precipitation is better, and the precipitate can be separated without standing still. It is preferred to stand still for 5 to 15 minutes for better separation effect.

[0057] As a further preferred technical solution of the present invention, the method comprises the following steps:

[0058] The cerium-containing rare earth solution and the oxidant are first mixed under a first stirring condition of 600 to 1000 r / min, and a first reaction is carried out at 20 to 100° C. for 1 to 10 minutes to obtain a mixed solution; the mixed solution and the conversion agent are second mixed under a second stirring condition of 100 to 1500 r / min, and a second reaction is carried out at 20 to 100° C. for 5 to 30 minutes to obtain a suspension containing a cerium enriched product; the suspension containing the cerium enriched product is then allowed to stand for 2 to 30 minutes, and a first cerium enriched product is obtained by solid-liquid separation;

[0059] Wherein, the oxidant comprises potassium permanganate; the molar ratio of the oxidant to the cerium element in the cerium-containing rare earth solution is (0.1-1):1;

[0060] The conversion agent includes any one of divalent cation carbonate, rare earth carbonate or rare earth hydroxide, or a combination of at least two thereof; the molar ratio of the conversion agent to the cerium element in the cerium-containing rare earth solution is (0.8-3.0):1.

[0061] Optionally, a first filtrate is obtained after the solid-liquid separation; and the method further comprises cyclically repeating the above steps on the first filtrate to obtain a second filtrate and a second cerium-enriched product.

[0062] That is, if cerium still remains in the first filtrate, the above steps are repeated using the first filtrate as a cerium-containing rare earth solution until the filtrate contains almost no cerium, i.e., a secondary cerium removal is performed; and during the treatment process, the molar amounts of the oxidant and the converter are selected according to the content of cerium in the first filtrate, with an appropriate excess to ensure sufficient enrichment of cerium; if there is almost no cerium remaining in the first filtrate, i.e., the primary cerium removal effect is good, close to 100%, then there is no need to perform a secondary cerium removal.

[0063] In addition, if the second filtrate is purple-red, that is, potassium permanganate is excessive during the secondary cerium removal process, hydrogen peroxide is added to the second filtrate to remove the excess potassium permanganate, and then the third filtrate is obtained by filtration, which is subsequently used to separate and recover rare earth elements.

[0064] Compared with the prior art, the present invention has at least the following beneficial effects:

[0065] (1) The present invention provides a method for removing cerium from a cerium-containing rare earth solution and simultaneously recovering cerium. The method selects potassium permanganate as an oxidant and any one or a combination of at least two of divalent cation carbonates, rare earth carbonates or rare earth hydroxides as a conversion agent. The two act synergistically. Under mild conditions, the primary removal rate of cerium is preferably as high as 93.89% or more, the secondary removal rate of cerium is preferably as high as 99.98% or more, and the purity of the cerium enrichment is as high as 73.40% or more, that is, the co-precipitation of other rare earth elements in the cerium-containing rare earth solution is greatly reduced.

[0066] (2) The method for removing cerium from a cerium-containing rare earth solution and recovering cerium simultaneously provided by the present invention, wherein the method further preferably uses a divalent cation carbonate as the conversion agent, that is, potassium permanganate and the divalent cation carbonate work synergistically, and further preferably the amount of the oxidant added and the amount of the divalent cation carbonate added, further improving the cerium removal rate to more than 99.98% (secondary removal rate), and at the same time, Ce in the cerium-containing rare earth solution is reduced to 99.98%. 3+ The oxidation process of Ce 4+ The process of conversion to precipitation promotes each other, and Ce 3+ While fully oxidizing Ce 4+ Timely precipitation to avoid Ce 4+ The chloride ions in the cerium rare earth solution of the chloride salt system are oxidized into harmful gas Cl2, and the cost of removing cerium is greatly reduced. DETAILED DESCRIPTION

[0067] The technical solution of the present invention is further described below in combination with specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0068] The NdFeB hydrochloric acid superior solution used in the following Examples 3 to 5 refers to the solution obtained by the process in which the NdFeB waste is oxidized and roasted, rare earth and iron elements are converted into corresponding oxides, and then hydrochloric acid is added for superior dissolution, so that the rare earth oxides are preferentially dissolved and leached into the solution, and the NdFeB hydrochloric acid superior solution described in Examples 3 to 5 has removed the impurity iron element.

[0069] 1. Implementation

[0070] Example 1

[0071] This embodiment provides a method for removing cerium from a cerium-neodymium chloride solution and simultaneously recovering cerium, the method comprising the following steps:

[0072] Under a first stirring condition of 900 r / min, 25 mL of a cerium neodymium chloride solution with a pH of 3.0 and 51 mg of potassium permanganate are first mixed, and a first reaction is carried out at 25° C. for 1 min to obtain a mixed solution; then, under a second stirring condition of 900 r / min, the mixed solution and 120 mg of calcium carbonate are second mixed, and a second reaction is carried out at 25° C. for 10 min to obtain a suspension containing a cerium enrichment; then, the suspension containing the cerium enrichment is allowed to stand for 10 min, and then filtered to obtain a first cerium enrichment and a first filtrate;

[0073] Wherein, the molar ratio of the potassium permanganate to the cerium element in the cerium-neodymium chloride solution is 0.38:1; the molar ratio of the calcium carbonate to the cerium element in the cerium-neodymium chloride solution is 1.42:1;

[0074] After testing, it was found that there was still 43 mg / L of Ce in the first filtrate, so the above steps were repeated on the first filtrate for secondary cerium removal to obtain a second cerium enriched product and a second filtrate. Specifically, the amount of potassium permanganate used in the secondary cerium removal process was 0.5 mg, and the amount of calcium carbonate used was 1.09 mg, that is, the molar ratio of potassium permanganate to the cerium element in the first filtrate was 0.41:1; the molar ratio of calcium carbonate to the cerium element in the first filtrate was 1.42:1, and the other parameters were the same as the parameters corresponding to the above steps; then 0.03 mL of hydrogen peroxide was added to the second filtrate to remove excess potassium permanganate and filtered to obtain a third filtrate with almost no filter mud.

[0075] The elemental compositions and concentrations of the elements in the cerium-neodymium chloride solution, the first filtrate and the second filtrate in this embodiment are shown in Table 1;

[0076] Table 1

[0077]

[0078] According to the data in Table 1, the primary removal rate and secondary removal rate of each element in the cerium-neodymium chloride solution in the method are calculated respectively, and the results are shown in Table 2;

[0079] Table 2

[0080] project Ce Nd Ca Mn One-time removal rate / % 99.09 7.6 / / Secondary removal rate / % 99.99 7.7 / /

[0081] The mass content of each element in the first cerium enriched material obtained in this embodiment (measured as the mass content of the oxide of each element, except Cl, and "others" represents the content of elements with low content that are difficult to measure) is as shown in Table 3; the content of the second cerium enriched material obtained is relatively low, and no component detection was performed.

[0082] Table 3

[0083] The first cerium-enriched component <![CDATA[CeO2]]> <![CDATA[Nd2O3]]> CaO MnO Cl other Mass content / wt% 81.98 2.76 2.55 11.33 1.25 0.13

[0084] It can be seen from Tables 1 to 3 that the primary removal rate of cerium in the method described in this embodiment is as high as 99.09%, and the secondary removal rate of cerium is as high as 99.99% (close to 100%), both of which are above 99%, that is, the cerium-neodymium chloride solution contains almost no cerium after two cerium removals, and the cerium removal effect is significant; although Ca and Mn are newly added to the first filtrate and the second filtrate, since they are divalent cations, they have almost no effect on the subsequent extraction and separation process of the rare earth element neodymium. There is only a small amount of neodymium in the first cerium enriched product, which can be further separated and recovered from neodymium and cerium through subsequent treatment. Compared with the traditional cerium removal method, the co-precipitation phenomenon is greatly reduced.

[0085] Example 2

[0086] This embodiment provides a method for removing cerium from a cerium-neodymium chloride solution and simultaneously recovering cerium, the method comprising the following steps:

[0087] Under a first stirring condition of 900 r / min, 25 mL of a cerium-neodymium chloride solution with a pH of 3.0 and 73.8 mg of potassium permanganate are first mixed, and a first reaction is carried out at 25° C. for 2 min to obtain a mixed solution; then, under a second stirring condition of 900 r / min, the mixed solution and 127 mg of magnesium carbonate are second mixed, and a second reaction is carried out at 25° C. for 40 min to obtain a suspension containing a cerium enrichment; then, the suspension containing the cerium enrichment is allowed to stand for 5 min, and then filtered to obtain a first cerium enrichment and a first filtrate;

[0088] Wherein, the molar ratio of the potassium permanganate to the cerium element in the cerium-neodymium chloride solution is 0.55:1; the molar ratio of the magnesium carbonate to the cerium element in the cerium-neodymium chloride solution is 1.8:1;

[0089] After testing, it was found that there was still 22 mg / L of Ce in the first filtrate, so the above steps were repeated on the first filtrate for secondary cerium removal to obtain a second cerium enriched product and a second filtrate. Specifically, the amount of potassium permanganate used in the secondary cerium removal process was 1.41 mg, and the amount of magnesium carbonate used was 1.65 mg, that is, the molar ratio of potassium permanganate to the cerium element in the first filtrate was 0.6:1; the molar ratio of magnesium carbonate to the cerium element in the first filtrate was 2.2:1, and the other parameters were the same as the parameters corresponding to the above steps; then 0.05 mL of hydrogen peroxide was added to the second filtrate to remove excess potassium permanganate and filtered to obtain a third filtrate with almost no filter mud.

[0090] The elemental compositions and concentrations of the elements in the cerium-neodymium chloride solution, the first filtrate and the second filtrate in this embodiment are shown in Table 4;

[0091] Table 4

[0092]

[0093] According to the data in Table 1, the primary removal rate and secondary removal rate of each element in the cerium-neodymium chloride solution in the method are calculated respectively, and the results are shown in Table 5;

[0094] Table 5

[0095] project Ce Nd Mg Mn One-time removal rate / % 99.54 8.17 / / Secondary removal rate / % 99.99 8.49 / /

[0096] The mass content of each element in the first cerium enriched material obtained in this embodiment (measured as the mass content of the oxide of each element, except Cl, and "others" represents the content of elements with low content that are difficult to measure) is as shown in Table 6; the content of the second cerium enriched material obtained is relatively low, and no component detection was performed.

[0097] Table 6

[0098] The first cerium-enriched component <![CDATA[CeO2]]> <![CDATA[Nd2O3]]> MgO MnO Cl other Mass content / wt% 81.03 2.95 2.42 11.23 2.17 0.2

[0099] It can be seen from Tables 4 to 6 that the primary removal rate of cerium in the method described in this embodiment is 99.54%, and the secondary removal rate of cerium is as high as 99.99%, both of which are above 99%, that is, the cerium-neodymium chloride solution contains almost no cerium after two cerium removals, and the cerium removal effect is significant; although Mg and Mn are newly added to the first filtrate and the second filtrate, since they are divalent cations, they have almost no effect on the subsequent extraction and separation process of the rare earth element neodymium. There is only a small amount of neodymium in the first cerium enriched product, which can be further separated and recovered from neodymium and cerium through subsequent treatment. Compared with the traditional cerium removal method, the co-precipitation phenomenon is greatly reduced.

[0100] Example 3

[0101] This embodiment provides a method for removing cerium and simultaneously recovering cerium from a NdFeB hydrochloric acid solution, the method comprising the following steps:

[0102] Under a first stirring condition of 800 r / min, 200 mL of NdFeB hydrochloric acid solution with a pH of 3.0 and 385 mg of potassium permanganate are first mixed, and a first reaction is carried out at 25° C. for 3 min to obtain a mixed solution; then, under a second stirring condition of 1000 r / min, the mixed solution and 780 mg of calcium carbonate are second mixed, and a second reaction is carried out at 25° C. for 60 min to obtain a suspension containing a cerium enrichment; then, the suspension containing the cerium enrichment is allowed to stand for 2 min, and then filtered to obtain a first cerium enrichment and a first filtrate;

[0103] Wherein, the molar ratio of the potassium permanganate to the cerium element in the NdFeB hydrochloric acid solution is 0.40:1; the molar ratio of the calcium carbonate to the cerium element in the NdFeB hydrochloric acid solution is 1.3:1;

[0104] After testing, there is still 262 mg / L of Ce in the first filtrate, so the above steps are repeated on the first filtrate for secondary cerium removal to obtain a second cerium concentrate and a second filtrate. Specifically, the amount of potassium permanganate used in the secondary cerium removal process is 30 mg, and the amount of calcium carbonate used is 65 mg, that is, the molar ratio of potassium permanganate to the cerium element in the first filtrate is 0.42:1; the molar ratio of calcium carbonate to the cerium element in the first filtrate is 1.42:1, and the other parameters are the same as the parameters corresponding to the above steps; then 0.05 mL of hydrogen peroxide is added to the second filtrate to remove excess potassium permanganate and filter to obtain a third filtrate with almost no filter mud. The elemental composition and concentration of each element in the NdFeB hydrochloric acid solution, the first filtrate and the second filtrate in this embodiment are shown in Table 7;

[0105] Table 7

[0106]

[0107] According to the data in Table 4, the primary removal rate and secondary removal rate of each element in the NdFeB hydrochloric acid solution (iron removal) in the method are calculated respectively, and the results are shown in Table 8;

[0108] Table 8

[0109]

[0110]

[0111] The mass content of each element in the first cerium enriched product and the second cerium enriched product obtained in this embodiment (measured in terms of the mass content of the oxide of each element, except Cl, "others" indicates the content of elements with low content that are difficult to measure) are shown in Tables 9 and 10, respectively;

[0112] Table 9

[0113] The first cerium-enriched component <![CDATA[CeO2]]> <![CDATA[Nd2O3]]> CaO MnO Cl other Mass content / wt% 84.59 0.51 0 11.86 2.41 0.63

[0114] Table 10

[0115] The second cerium-enriched component <![CDATA[CeO2]]> <![CDATA[Nd2O3]]> <![CDATA[Pr6O 11 ]]> MnO Cl other Mass content (%) 78.34 1.5 0.5 13.31 0.95 5.4

[0116] It can be seen from Tables 8 and 9 that when potassium permanganate is excessive and calcium carbonate is insufficient during the first cerium removal process of the NdFeB hydrochloric acid solution (iron removal) described in the method described in this embodiment, the first cerium concentrate contains almost only cerium and manganese, and other rare earth elements are co-precipitated very little, and the first cerium removal rate reaches 93.89%; It can be seen from Tables 8 and 10 that when potassium permanganate is excessive and calcium carbonate is slightly excessive during the second cerium removal, the cerium concentration in the second filtrate is only 0.9 mg / L, and the secondary cerium removal rate is as high as 99.98%, the cerium removal effect is significant, and the second cerium concentrate contains trace amounts of other rare earth element precipitates, which can be further separated and recovered from cerium and other elements through subsequent treatment.

[0117] Example 4

[0118] This embodiment provides a method for removing cerium and simultaneously recovering cerium from a NdFeB hydrochloric acid solution, the method comprising the following steps:

[0119] Under a first stirring condition of 800 r / min, 50 mL of NdFeB hydrochloric acid solution with a pH of 4.0 and 100 mg of potassium permanganate are first mixed, and a first reaction is carried out at 45° C. for 3 min to obtain a mixed solution; then, under a second stirring condition of 800 r / min, the mixed solution and 300 mg of calcium carbonate are second mixed, and a second reaction is carried out at 45° C. for 40 min to obtain a suspension containing a cerium enrichment; then, the suspension containing the cerium enrichment is allowed to stand for 10 min, and then filtered to obtain a first cerium enrichment and a first filtrate;

[0120] The molar ratio of potassium permanganate to the cerium element in the NdFeB hydrochloric acid solution is 0.42:1; the molar ratio of calcium carbonate to the cerium element in the NdFeB hydrochloric acid solution is 1.99:1. The pH and elemental composition of the NdFeB hydrochloric acid solution and the first filtrate in this embodiment and the concentration of each element are shown in Table 11;

[0121] Table 11

[0122]

[0123] The element composition and mass content of the first cerium enriched product in this embodiment (measured in terms of the content of oxides of each element, except Cl, where "others" indicates the content of elements with low content that are difficult to measure) are shown in Table 12;

[0124] Table 12

[0125] The first cerium-enriched component <![CDATA[CeO2]]> <![CDATA[Nd2O3]]> <![CDATA[Pr6O 11 ]]> <![CDATA[Gd2O3]]> <![CDATA[Dy2O3]]> CaO MnO Cl <![CDATA[Al2O3]]> other Mass content (wt%) 73.40 4.53 1.43 0.51 0.21 6.36 11.51 0.63 1.12 0.3

[0126] It can be seen from Tables 11 and 12 that the first filtrate obtained by the method described in this embodiment contains almost no cerium element, indicating that the one-time cerium removal effect is significant, with a removal rate of up to 99.99%, and no secondary cerium removal is required. Although the mass content of the remaining rare earth elements in the first cerium enriched product is relatively high, the rare earth elements and cerium elements can be recovered subsequently, and the operation is simple.

[0127] Example 5

[0128] This embodiment provides a method for removing cerium and simultaneously recovering cerium from a NdFeB hydrochloric acid solution, the method comprising the following steps:

[0129] Under a first stirring condition of 900 r / min, 50 mL of NdFeB hydrochloric acid solution with a pH of 3.0 and 100 mg of potassium permanganate are first mixed, and a first reaction is carried out at 25° C. for 2 min to obtain a mixed solution; then, under a second stirring condition of 1100 r / min, the mixed solution and 436 mg of lanthanum hydroxide are second mixed, and a second reaction is carried out at 25° C. for 60 min to obtain a suspension containing a cerium enrichment; then, the suspension containing the cerium enrichment is allowed to stand for 15 min, and then filtered to obtain a first cerium enrichment and a first filtrate;

[0130] Among them, the molar ratio of the potassium permanganate to the cerium element in the NdFeB hydrochloric acid solution is 0.42:1; the molar ratio of the lanthanum hydroxide to the cerium element in the NdFeB hydrochloric acid solution is 1.5:1.

[0131] The pH and elemental composition of the NdFeB hydrochloric acid solution and the first filtrate described in this embodiment and the concentration of each element are shown in Table 13;

[0132] Table 13

[0133]

[0134]

[0135] The element composition and mass content of the first cerium enriched material in this embodiment (measured in terms of the content of oxides of each element, "others" indicates the content of elements with low content that are difficult to measure) are shown in Table 14;

[0136] Table 14

[0137] The first cerium-enriched component <![CDATA[La2O3]]> <![CDATA[CeO2]]> <![CDATA[Nd2O3]]> <![CDATA[Pr6O 11 ]]> <![CDATA[Gd2O3]]> <![CDATA[Dy2O3]]> MnO other Mass content (wt%) 11.31 74.00 1.21 0.25 0.31 0.15 12.15 0.62

[0138] It can be seen from Tables 13 and 14 that the first filtrate obtained by the method described in this embodiment contains almost no cerium element, indicating that the one-time cerium removal effect is significant, with a removal rate of up to 99.99%, and no secondary cerium removal is required. However, the amount of lanthanum hydroxide added is relatively large, and the cost of cerium removal is increased. In addition, since lanthanum is trivalent, the burden of subsequent extraction and separation of cerium and other trivalent rare earth elements in the first cerium enriched product is increased.

[0139] Example 6

[0140] This embodiment provides a method for removing cerium from a cerium-neodymium chloride solution and simultaneously recovering cerium. The method is the same as that of Embodiment 1 except that the molar ratio of potassium permanganate to the cerium element in the cerium-neodymium chloride solution is 0.3:1.

[0141] Example 7

[0142] This embodiment provides a method for removing cerium from a cerium-neodymium chloride solution and simultaneously recovering cerium. The method is the same as that of Embodiment 1 except that the molar ratio of potassium permanganate to the cerium element in the cerium-neodymium chloride solution is 0.6:1.

[0143] Example 8

[0144] This embodiment provides a method for removing cerium from a cerium-neodymium chloride solution and simultaneously recovering cerium. The method is the same as that of Embodiment 1 except that the molar ratio of calcium carbonate to cerium in the cerium-neodymium chloride solution is 1.2:1.

[0145] Example 9

[0146] This embodiment provides a method for removing cerium from a cerium-neodymium chloride solution and simultaneously recovering cerium. The method is the same as that of Embodiment 1 except that the molar ratio of calcium carbonate to cerium in the cerium-neodymium chloride solution is 2.2:1.

[0147] Example 10

[0148] This embodiment provides a method for removing cerium from a cerium-neodymium chloride solution and simultaneously recovering cerium. The method is the same as that of Embodiment 1 except that the conversion agent is neodymium carbonate.

[0149] Embodiment 11

[0150] This embodiment provides a method for removing cerium from a cerium-neodymium chloride solution and simultaneously recovering cerium. The method is the same as that of Embodiment 1 except that the conversion agent is neodymium hydroxide.

[0151] 2. Comparison

[0152] Comparative Example 1

[0153] This comparative example provides a method for removing cerium from a cerium-neodymium chloride solution and simultaneously recovering cerium. The method uses hydrogen peroxide as an oxidant, and the molar ratio of the added amount of hydrogen peroxide to the cerium element in the cerium-neodymium chloride solution is 2:1. Other aspects are the same as those of Example 1.

[0154] Comparative Example 2

[0155] This comparative example provides a method for removing cerium from a cerium-neodymium chloride solution and simultaneously recovering cerium. The method is the same as Example 1, except that the conversion agent is replaced by neodymium carbonate from calcium carbonate, and the molar ratio of the neodymium carbonate to the cerium element in the cerium-neodymium chloride solution is 0.5:1.

[0156] 3. Test and its results

[0157] The primary and secondary cerium removal rates, the purity of the first cerium enriched product and the second cerium enriched product (in terms of the mass content of CeO2) of the methods provided in the above embodiments and comparative examples are shown in Table 15;

[0158] Table 15

[0159] project One-time removal rate / % Secondary removal rate / % Purity of the first cerium-enriched product / % Example 1 99.09 99.99 81.98 Example 2 99.54 99.99 81.03 Example 3 93.89 99.98 84.59 Example 4 99.99 / 73.40 Example 5 99.99 / 74.00 Example 6 70.28 99.05 73.12 Example 7 99.42 99.99 82.00 Example 8 90.83 99.96 84.32 Example 9 99.21 99.99 66.30 Example 10 92.15 99.12 73.36 Embodiment 11 95.33 99.24 76.55 Comparative Example 1 84.32 90.36 65.32 Comparative Example 2 81.20 88.92 63.11

[0160] From the data in Table 15, we can see that:

[0161] (1) It can be seen from Examples 1 to 5 that the method for removing cerium from a cerium-containing rare earth solution and simultaneously recovering cerium provided by the present invention achieves highly selective removal of cerium in a cerium-containing rare earth solution at a relatively low temperature, with a primary removal rate of more than 93.89%, and after secondary removal, the cerium removal rate is more than 99.98%, even close to 100%, while ensuring that the purity of the cerium enrichment is more than 73.40%, greatly avoiding the co-precipitation of other rare earth elements in the cerium-containing rare earth solution, and at the same time, no harmful gas Cl2 is generated for the chloride salt system.

[0162] (2) Combining Example 1 and Examples 6 to 9, it can be seen that since the molar ratio of potassium permanganate to the cerium element in the cerium-neodymium chloride solution in Example 6 is relatively low, the primary cerium removal rate is reduced to 70.28%; the molar ratio of potassium permanganate to the cerium element in the cerium-neodymium chloride solution in Example 7 is relatively high, resulting in an increase in the amount of potassium permanganate used and an increase in the subsequent consumption of hydrogen peroxide, but the cerium removal effect is not significantly improved; the molar ratio of calcium carbonate to the cerium element in the cerium-neodymium chloride solution in Example 8 is relatively low, resulting in a primary removal rate of 90.83%; the molar ratio of calcium carbonate to the cerium element in Example 9 is relatively high. The molar ratio of cerium in the cerium-neodymium chloride solution is relatively high, resulting in a decrease in the purity of the first cerium enriched product to 66.30%; this indicates that the present invention further prefers that the molar ratio of the oxidant to the cerium in the cerium-containing rare earth solution is (0.35-0.55):1, and further prefers that when the converter is a divalent cation carbonate, the molar ratio of the converter to the cerium in the cerium-containing rare earth solution is (1.3-2.0):1. The synergistic effect of the two further improves the removal rate of cerium in the cerium-containing rare earth solution, while greatly reducing the co-precipitation phenomenon of other rare earth elements, thereby improving the purity of the cerium enriched product.

[0163] (3) Combining Example 1 with Example 10 and Example 11, it can be seen that neodymium carbonate is used in Example 10, which leads to incomplete reaction in a short time, thereby reducing the cerium removal rate and increasing the cost; neodymium hydroxide is used in Example 11, which leads to incomplete reaction in a short time, and the cerium removal rate after secondary cerium removal is 99.24%, and the filtration difficulty is increased; this shows that the present invention further prefers that the conversion agent is a divalent cation carbonate, which further improves the selective removal of cerium and ensures a high cerium removal rate.

[0164] (4) It can be seen from the combined results of Example 1, Comparative Examples 1 and 2 that, although the conversion agent in Comparative Example 1 is calcium carbonate, the oxidant is hydrogen peroxide, which results in a large consumption of hydrogen peroxide and a reduced Ce removal rate. Due to the serious co-precipitation of Nd, the purity of the Ce precipitate is greatly reduced. In Comparative Example 2, the oxidant is hydrogen peroxide and the conversion agent is neodymium carbonate, which results in a large consumption of hydrogen peroxide and a reduced Ce removal rate. Due to the serious co-precipitation of Nd, the purity of the Ce precipitate is greatly reduced. This shows that the method of the present invention uses a specific oxidant and a specific conversion agent, which work synergistically to achieve a higher cerium removal rate under mild conditions, while also greatly reducing the co-precipitation phenomenon and avoiding the generation of Cl2.

[0165] 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 method for removing cerium from a cerium-containing rare earth solution and simultaneously recovering cerium, characterized in that: The method comprises the following steps: mixing a cerium-containing rare earth solution, an oxidant and a converting agent to react to remove cerium from the cerium-containing rare earth solution; Wherein, the oxidant includes potassium permanganate; the conversion agent includes any one of divalent cation carbonate, rare earth carbonate or rare earth hydroxide, or a combination of at least two thereof.

2. The method according to claim 1, characterized in that Calculated by mass percentage, the cerium content in the cerium-containing rare earth solution is ≥ 0.025wt%; Preferably, the cerium ions in the cerium-containing rare earth solution include Ce 3+ and Ce 4+ .

3. The method according to claim 1 or 2, characterized in that: The rare earth elements other than cerium in the cerium-containing rare earth solution include any one of La, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu or Y, or a combination of at least two thereof; Preferably, the anions in the cerium rare earth solution include Cl - 、SO4 2- or NO3 - Any one or a combination of at least two of the following: Preferably, the initial pH of the cerium rare earth solution is 0.1-7.

0.

4. The method according to any one of claims 1 to 3, characterized in that: The divalent cation carbonate includes any one of calcium carbonate, magnesium carbonate or magnesium calcium carbonate or a combination of at least two thereof; Preferably, the rare earth element in the rare earth carbonate and the rare earth element in the rare earth hydroxide are each independently any one of La, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu or Y, or a combination of at least two thereof, and are preferably the same element as the rare earth element other than cerium in the cerium-containing rare earth solution.

5. The method according to any one of claims 1 to 4, characterized in that: The molar ratio of the oxidant to the cerium element in the cerium-containing rare earth solution is (0.1-1):1, preferably (0.35-0.55):1; Preferably, the molar ratio of the conversion agent to the cerium element in the cerium-containing rare earth solution is (0.8-3.0):1; Preferably, when the conversion agent is a divalent cation carbonate, the molar ratio of the conversion agent to the cerium element in the cerium-containing rare earth solution is (1.3-2.0):1; Preferably, when the conversion agent is rare earth carbonate and / or rare earth hydroxide, the molar ratio of the conversion agent to the cerium element in the cerium-containing rare earth solution is (1.3-2.8):

1.

6. The method according to any one of claims 1 to 5, characterized in that: The conversion agent is a divalent cation carbonate, preferably calcium carbonate and / or magnesium carbonate.

7. The method according to any one of claims 1 to 6, characterized in that: The mixing comprises: the cerium-containing rare earth solution and an oxidant are first mixed and reacted to obtain a mixed solution; and the mixed solution and a conversion agent are second mixed and reacted to obtain a suspension containing a cerium enrichment.

8. The method according to claim 7, characterized in that The first mixing process is accompanied by a first stirring; Preferably, the first stirring rate is 600-1000 r / min; Preferably, the temperature of the first reaction is 20 to 100°C, preferably 25 to 45°C; Preferably, the first reaction time is 1 to 10 min; Preferably, the second mixing process is accompanied by a second stirring; Preferably, the second stirring rate is 100 to 1500 r / min, preferably 600 to 1000 r / min; Preferably, the temperature of the second reaction is 20 to 100°C, preferably 25 to 45°C; Preferably, the second reaction time is 5 to 30 min, preferably 5 to 20 min.

9. The method according to claim 7 or 8, characterized in that: The method further comprises performing a static treatment and a solid-liquid separation on the suspension containing the cerium enriched product in sequence after the second reaction to obtain a first cerium enriched product; Preferably, the static treatment time is 2 to 30 minutes, preferably 5 to 15 minutes.

10. The method according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: The cerium-containing rare earth solution and the oxidant are first mixed under a first stirring condition of 600 to 1000 r / min, and a first reaction is carried out at 20 to 100° C. for 1 to 10 minutes to obtain a mixed solution; the mixed solution and the conversion agent are second mixed under a second stirring condition of 100 to 1500 r / min, and a second reaction is carried out at 20 to 100° C. for 5 to 30 minutes to obtain a suspension containing a cerium enriched product; the suspension containing the cerium enriched product is then allowed to stand for 2 to 30 minutes, and a first cerium enriched product is obtained by solid-liquid separation; Wherein, the oxidant comprises potassium permanganate; the molar ratio of the oxidant to the cerium element in the cerium-containing rare earth solution is (0.1-1):1; The conversion agent includes any one of divalent cation carbonate, rare earth carbonate or rare earth hydroxide, or a combination of at least two thereof; the molar ratio of the conversion agent to the cerium element in the cerium-containing rare earth solution is (0.8-3.0):1.

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