Process for the separation and purification of rare earth elements

Abstract

The application discloses a rare earth element separation and purification method, comprising the following steps: adsorbing a solution containing target rare earth metal ions on a first chromatographic column, eluting the first chromatographic column with first acid liquid with a concentration of 0.02mol / L-0.1mol / L, and connecting a second chromatographic column in series with the outlet of the first chromatographic column when target rare earth metal ions are detected in the eluate of the first chromatographic column, eluting the first chromatographic column and the second chromatographic column connected in series with second acid liquid with a concentration of 0.02mol / L-0.1mol / L, and decoupling the second chromatographic column when target rare earth metal ions are detected in the eluate of the second chromatographic column; eluting the decoupled second chromatographic column with third acid liquid with a concentration of 0.3mol / L-0.6mol / L; collecting the eluate of the second chromatographic column, and sequentially performing precipitation and calcination on the eluate to obtain target rare earth element oxide. The method can shorten the time consumption and improve the production efficiency.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, and in particular to a method for the separation and purification of rare earth elements. Background Technology

[0002] Rare earth elements share similar chemical properties, making individual separation of each element extremely difficult. Traditional solvent extraction methods require multiple stages of countercurrent extraction, back-extraction, saponification, and washing, resulting in numerous steps, large equipment footprints, and operation cycles lasting several days or even weeks. Traditional chromatography methods, to achieve a certain degree of separation, necessitate longer columns or slower flow rates, leading to extremely long single-session runs, sometimes exceeding 40 hours, high eluent consumption, and low production efficiency. Summary of the Invention

[0003] Therefore, it is necessary to provide a method for the separation and purification of rare earth elements that can shorten the time required, reduce the amount of leachate used, and improve production efficiency.

[0004] One aspect of the present invention provides a method for separating and purifying rare earth elements, comprising the following steps S10-S50.

[0005] S10, to adsorb the solution containing the target rare earth metal ions onto the first chromatographic column;

[0006] S20. The first chromatographic column obtained in step S10 is eluted with a first acid solution with a concentration of 0.02mol / L-0.1mol / L, and when the target rare earth metal ions are detected in the eluent of the first chromatographic column, a second chromatographic column is connected in series at the outlet of the first chromatographic column.

[0007] S30. Elute the first and second chromatographic columns connected in series with a second acid solution of concentration of 0.02mol / L-0.1mol / L, and decouple the second chromatographic column when the target rare earth metal ions are detected in the eluent of the second chromatographic column.

[0008] S40. Elute the decoupled second chromatographic column separately with a third acid solution at a concentration of 0.3 mol / L to 0.6 mol / L;

[0009] S50. Collect the eluent from the second chromatographic column in S40, and precipitate and calcine the eluent sequentially to obtain the target rare earth element oxide.

[0010] The rare earth element separation and purification method described in this application eliminates the complex steps of multi-stage countercurrent extraction, back-extraction, and saponification in traditional solvent extraction. It only requires an adsorption-washing-decoupling-washing operation to obtain a solution rich in the target rare earth metal ion segment. Through dual-column series / decoupling and precise acid gradient control, gradient washing with different acidities of the first, second, and third acid solutions serves as the driving force for the chemical separation of the target rare earth metal ions. The target rare earth metal ions are directionally eluted under high-concentration acid washing with narrow-band burst desorption, thereby achieving a highly efficient, low-consumption, and high-yield purification process. This method can significantly simplify traditional rare earth separation steps, significantly shorten process time and reagent consumption, and improve separation and purification efficiency.

[0011] In some embodiments, in S20 and S30, the detection of target rare earth metal ions includes detection using a colorimetric reagent; and / or,

[0012] In S20 and S30, the series connection and decoupling of the first chromatographic column and the second chromatographic column are controlled by a solenoid valve; optionally, the solenoid valve is linked to the result of the colorimetric reagent detection, and the response time of the colorimetric reagent color development and the valve being connected in series or decoupled is ≤5s.

[0013] In some embodiments, the colorimetric agent is selected from at least one of azoarsine III, p-nitroazoarsine, chlorophosphine azo I, and xylenol orange.

[0014] Optionally, the color developer is xylenol orange.

[0015] In some embodiments, the target rare earth metal ion is selected from at least one of La, Ce, Pr and Nd.

[0016] Optionally, the element of the target rare earth metal ion is Ce.

[0017] In some embodiments, a solution containing the target rare earth metal ions needs to be prepared prior to step S10, including the following steps:

[0018] Weigh the raw material containing the target rare earth metal ions, dissolve it in hydrochloric acid to obtain a pretreatment solution, concentrate the pretreatment solution to near dryness to obtain a concentrated solution, and dilute the concentrated solution to obtain a solution containing the target rare earth metal ions.

[0019] Optionally, the pH of the solution containing the target rare earth metal ions is 4-5, and the concentration of the target rare earth metal ions is 0.05mol / L-0.1mol / L.

[0020] In some embodiments, the first and second chromatographic columns packed with resin need to be pretreated before step S10, including the following steps: washing the first and second chromatographic columns with 400 mL to 1100 mL of hydrochloric acid with a concentration of 1 mol / L to 1.5 mol / L at a flow rate of 80 mL / h to 130 mL / h, and then rinsing the first and second chromatographic columns with deionized water until the outlet pH is 4 to 5.

[0021] In some embodiments, the adsorption of the target rare earth metal ion solution onto the first chromatographic column in step S10 includes the following steps: taking 50 mL to 100 mL of the solution containing the target rare earth metal ions and adsorbing it onto the first chromatographic column at a rate of 20 mL / h to 70 mL / h, wherein the static saturation capacity of the resin for the target rare earth metal ions is ≥1 g / g.

[0022] In some embodiments, the entire process from the start of rinsing in step S20 to the end of rinsing in step S50 takes 16-30 hours.

[0023] In some embodiments, in steps S20 and S30, the rinsing rate of the first acid solution and the second acid solution is 90 mL / h-140 mL / h, and the total volume of the first acid solution, the second acid solution and the third acid solution used in the entire process from the start of rinsing in step S20 to the end of rinsing in step S40 is 2000 mL-3500 mL.

[0024] In some embodiments, the first and second chromatographic columns are packed with resin, the functional groups of which are phosphate esters and / or phosphonates, the resin particle size is 80-140 mesh, and the mass content of the functional groups is 45%-60%.

[0025] Optionally, the resin is a phosphorus-based extraction resin.

[0026] Furthermore, the phosphorus-based extraction resin is a cross-linked polystyrene-divinylbenzene microsphere containing phosphate ester and / or phosphonate functional groups.

[0027] In some embodiments, the resin packing height is 430mm-470mm, and the inner diameter of the first and second chromatographic columns is 21mm-46mm.

[0028] In some embodiments, step S50 involves precipitating and calcining the obtained leachate to obtain the target rare earth element oxide, including the following steps.

[0029] Ammonia water was added dropwise to the leachate to obtain a hydroxide precipitate of the target rare earth element. Solid-liquid separation was performed to obtain a hydroxide solid.

[0030] The obtained hydroxide solid was dissolved in nitric acid to obtain a solution rich in the target rare earth element;

[0031] Oxalic acid solution is added to a solution rich in the target rare earth element to obtain an oxalate precipitate of the target rare earth element. Solid-liquid separation is performed to obtain solid oxalate.

[0032] The oxalate solid obtained by calcination yields oxides of the target rare earth element.

[0033] In some embodiments, in step S50, the concentration of the ammonia is 5 mol / L-7 mol / L, the concentration of the nitric acid is 5 mol / L-7 mol / L, and the mass fraction of the oxalic acid is 6%-8%. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating a method for separating and purifying rare earth elements according to an embodiment of this application. Detailed Implementation

[0035] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0037] Traditional chromatography often suffers from low column efficiency, slow mass transfer, and severe elution peak broadening due to limitations in resin performance and separation strategies. To achieve a certain level of resolution, longer columns or slower flow rates are used, resulting in extremely long single-run times, sometimes exceeding 40 hours, leading to low production efficiency. Furthermore, in pursuit of high purity (e.g., 6N) using traditional methods, the number of washes is often increased, leading to product loss and reduced yield.

[0038] Please see Figure 1 One embodiment of this application provides a method for separating and purifying rare earth elements, including the following steps S10-S50.

[0039] S10, to adsorb the solution containing the target rare earth metal ions onto the first chromatographic column.

[0040] S20. The first chromatographic column obtained in step S10 is eluted with a first acid solution with a concentration of 0.02mol / L-0.1mol / L. When the target rare earth metal ions are detected in the eluent of the first chromatographic column, a second chromatographic column is connected in series at the outlet of the first chromatographic column.

[0041] This step utilizes the difference in binding ability between different ions and the resin within the chromatographic column under the low acidity environment of the first acid solution. Metal impurity ions with weaker binding affinity to the resin than the target rare earth metal ions will be eluted and removed first. When the target rare earth metal ions are detected in the eluent of the first column, a second column connected in series with the first column can capture the target rare earth metal ions that are about to migrate out of the first column, preventing loss and ensuring the yield of the target rare earth metal ions.

[0042] S30. Elute the first and second chromatographic columns connected in series with a second acid solution of concentration of 0.02mol / L-0.1mol / L, and decouple the second chromatographic column when the target rare earth metal ions are detected in the eluent of the second chromatographic column.

[0043] This step uses a second acid solution with the same low acidity to elute the first and second chromatographic columns in series, driving the target rare earth metal ions to migrate from the first column to the second column. When the target rare earth metal ions are detected in the eluent of the second column, it indicates that the leading edge of the target rare earth metal ion band has reached the end of the second column. At this point, the first and second columns are decoupled. Compared to the target rare earth metal ions, rare earth metal impurity ions with stronger binding force to the resin in the column are still mainly retained in the front part of the first and second columns, spatially separating the target rare earth metal ions from the rare earth metal impurity ions with stronger binding force.

[0044] S40. Elute the decoupled second column separately with a third acid solution at a concentration of 0.3 mol / L to 0.6 mol / L.

[0045] This step involves rinsing with a highly acidic third acid solution and a high concentration of H₂. + It competes for binding sites on the resin within the chromatographic column, thereby explosively eluting the target rare earth metal ions from the second chromatographic column, obtaining an eluent enriched with the target rare earth metal ions, improving production efficiency. Moreover, with an appropriate concentration of the third acid solution, not only can the target rare earth metal ions be completely desorbed, but rare earth metal impurity ions with stronger binding force to the resin are also firmly retained on the resin, further separating and purifying the target rare earth metal ions.

[0046] S50. Collect the eluent from the second chromatographic column in S40, and then precipitate and calcine the eluent sequentially to obtain the target rare earth element oxide.

[0047] The rare earth element separation and purification method described in this application eliminates the complex steps of multi-stage countercurrent extraction, back-extraction, and saponification in traditional solvent extraction. It only requires an adsorption-washing-decoupling-washing operation to obtain a solution rich in the target rare earth element. Through dual-column series / decoupling and precise acid gradient control, the optimal acidity window is obtained based on the difference in binding energy between the target rare earth element and other metals and resins. Then, by setting gradient rinsing with different acid concentrations as the driving force for the chemical separation of the target rare earth element, the target rare earth element is eluted directionally under high-concentration acid rinsing with narrow-band burst desorption, thereby achieving a highly efficient, low-consumption, and high-yield purification process. This method can significantly simplify the traditional rare earth separation steps and significantly shorten the process time and reagent consumption.

[0048] As an example, the concentration of the first acid solution can be 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, or any two of the above values ​​within the range, such as 0.04 mol / L-0.08 mol / L.

[0049] As an example, the concentration of the second acid solution can be 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, or any two of the above values ​​within the range, such as 0.04 mol / L-0.08 mol / L.

[0050] As an example, the concentration of the third acid solution can be 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, or any two of the above values ​​within a range, such as 0.4 mol / L-0.5 mol / L.

[0051] In some embodiments, in steps S20 and S30, the series / decoupling of the first and second chromatographic columns is controlled by a solenoid valve, and the detection of the target rare earth penetration includes detection with a colorimetric reagent. The solenoid valve is linked with the colorimetric reagent indicator, and the response time from color development by the colorimetric reagent to the series / decoupling of the valve is ≤5s.

[0052] The method for separating and purifying rare earth elements described in this application dynamically adjusts the series / decoupling state of the two chromatographic columns through real-time monitoring and valve linkage. Valve switching is based on real-time colorimetric signals, precisely controlling the timing of series / decoupling with a response delay of <5s, thus reducing the transition zone volume and significantly shortening the separation time. Furthermore, due to the real-time monitoring and valve linkage, the functions and roles of the first and second chromatographic columns also dynamically change. The first column transforms from an adsorption column to a light rare earth impurity stripping column and then to a target rare earth metal ion transition column; the second column transforms from an idle state to a target rare earth metal ion capture column and then to a target rare earth metal ion enrichment column, achieving multifunctional integration.

[0053] In some embodiments, the target rare earth metal ion is selected from at least one ion selected from La, Ce, Pr and Nd.

[0054] Optionally, the target rare earth ion is a Ce ion.

[0055] Furthermore, the solution containing the target rare earth metal ions contains impurity metals such as lanthanum, praseodymium, neodymium, gadolinium, terbium, erbium, thulium, ytterbium, and lutetium, as well as non-rare earth element impurities such as iron, calcium, magnesium, nickel, copper, and chromium.

[0056] In some of these embodiments, the color developer is selected from at least one of azoarsine III, p-nitroazoarsine, chlorophosphine azo I, and xylenol orange.

[0057] Optionally, the color developer is xylenol orange.

[0058] Furthermore, xylenol orange forms a stable purple-red complex with Ce ions. When an acidic eluent without Ce ions flows through the detection cell, the yellow background of xylenol orange is detected. When a solution containing a certain concentration of Ce ions flows through, xylenol orange reacts to form a purple-red complex, and the color of the solution in the detection cell changes from yellow to red or purple-red.

[0059] The detection cell is equipped with a photometer, which monitors the absorbance value of the solution in the detection cell. When xylenol orange turns red or purplish-red, the light signal of a specific wavelength becomes sharply stronger. The photometer converts the sudden change in absorbance into an electrical signal in real time. The solenoid valve receives the electrical signal and controls the valve core in the solenoid valve to open and close, thereby realizing real-time monitoring and valve linkage.

[0060] In some embodiments, prior to step S10, a solution containing the target rare earth metal ions is prepared, including the following steps:

[0061] Weigh the raw material containing the target rare earth metal ions, dissolve it in hydrochloric acid to obtain a pretreatment solution, concentrate the pretreatment solution to near dryness to obtain a concentrated solution, and dilute the concentrated solution to obtain a solution containing the target rare earth metal ions.

[0062] Optionally, the solution containing the target rare earth metal ions has a pH of 4-5 and a concentration of the target rare earth metal ions of 0.05 mol / L-0.1 mol / L.

[0063] In some embodiments, the first and second chromatographic columns packed with resin need to be pretreated before step S10, including the following steps: washing the first and second chromatographic columns with 400 mL to 1100 mL of hydrochloric acid with a concentration of 1 mol / L to 1.5 mol / L at a flow rate of 80 mL / h to 130 mL / h, and then rinsing the first and second chromatographic columns with deionized water until the outlet pH is 4 to 5.

[0064] In some embodiments, step S10, in which the first chromatographic column adsorbs the solution containing the target rare earth metal ions, includes the following steps: taking 50 mL to 100 mL of the solution containing the target rare earth metal ions and adsorbing it onto the first chromatographic column at a rate of 20 mL / h to 70 mL / h, wherein the static saturation capacity of the resin for the target rare earth metal ions is ≥1 g / g.

[0065] In some embodiments, the entire process from the start of rinsing in step S20 to the end of rinsing in step S40 takes 16-30 hours.

[0066] In some embodiments, in steps S20 and S30, the rinsing rate of the first acid solution and the second acid solution is 90 mL / h-140 mL / h, and the total volume of the first acid solution, the second acid solution and the third acid solution used in the entire process from the start of rinsing in step S20 to the end of rinsing in step S40 is 2000 mL-3500 mL.

[0067] Optionally, the first acid solution, the second acid solution, and the third acid solution are selected from at least one of hydrochloric acid and nitric acid.

[0068] The method for separating and purifying rare earth elements described in this application reduces the process time for separating and purifying target rare earth metal ions and saves on the amount of leaching agent used.

[0069] In some embodiments, the first and second chromatographic columns are packed with resin, the functional groups of which are phosphate esters and / or phosphonates, the resin particle size is 80-140 mesh, and the mass content of the functional groups is 45%-60%.

[0070] Optionally, the resin is a phosphorus-based extraction resin.

[0071] Furthermore, the phosphorus-based extraction resin is a cross-linked polystyrene-divinylbenzene microsphere containing phosphate ester and / or phosphonate functional groups.

[0072] In some embodiments, the resin packing height is 430mm-470mm, and the inner diameter of the first and second chromatographic columns is 21mm-46mm.

[0073] In some embodiments, step S50 involves sequentially precipitating and calcining the leachate, including the following steps:

[0074] Ammonia solution was added dropwise to the leachate to obtain a hydroxide precipitate of the target rare earth element. Solid-liquid separation was performed to obtain a hydroxide solid.

[0075] The obtained hydroxide solid was dissolved in nitric acid to obtain a solution rich in the target rare earth element;

[0076] Oxalic acid solution is added to a solution rich in the target rare earth element to obtain an oxalate precipitate of the target rare earth element. Solid-liquid separation is performed to obtain solid oxalate.

[0077] The oxalate solid obtained by calcination yields oxides of the target rare earth element.

[0078] In some embodiments, the concentration of ammonia in step S10 is 5 mol / L-7 mol / L. In some embodiments, the concentration of nitric acid is 5 mol / L-7 mol / L.

[0079] In some embodiments, the oxalic acid solution has a mass fraction of 6%-8%.

[0080] The following are specific examples.

[0081] Example 1

[0082] Step 1: Using cerium carbonate as raw material, the purity of cerium carbonate is 99.995%, and the cerium carbonate raw material contains rare earth element impurities such as lanthanum, praseodymium, neodymium, gadolinium, terbium, erbium, thulium, ytterbium, and lutetium, as well as non-rare earth element impurities such as iron, calcium, magnesium, nickel, copper, and chromium. Weigh 20g of cerium carbonate and add it to 60mL of deionized water to prepare a suspension. Add 15mL of concentrated hydrochloric acid to the suspension to prepare a pretreatment solution. Evaporate the solution at low temperature to near dryness to obtain a concentrated solution. Add deionized water to the concentrated solution and make up to 500mL to obtain a cerium chloride solution, in which the Ce concentration is approximately 0.087mol / L and the pH is approximately 4.5.

[0083] The first and second chromatographic columns were packed with cross-linked polystyrene-divinylbenzene microspheres containing phosphate ester functional groups. The microspheres had a particle size of 100-120 mesh, a functional group mass content of 50%-53%, and a packing height of 450 mm. The inner diameter of the first and second chromatographic columns was 30 mm.

[0084] Step 2: Wash the first and second chromatographic columns with 1000 mL of 1.5 mol / L hydrochloric acid at a rate of 120 mL / h. Then wash the first and second chromatographic columns with deionized water until the outlet pH is 4.

[0085] Step 3: Take 100 mL of cerium chloride solution and adsorb it onto the first chromatographic column at a rate of 60 mL / h, wherein the static saturation capacity of Ce / resin is ≥1 g / g.

[0086] Step 4: Elute the first chromatographic column with a first acid solution (dilute hydrochloric acid) with a concentration of 0.08 mol / L at a elution rate of 120 mL / h, wherein the volume of the first acid solution is 2000 mL.

[0087] Step 5: When Ce penetration is detected at the outlet of the first chromatographic column, that is, when xylenol orange changes from yellow to red, connect the second chromatographic column in series at the outlet of the first chromatographic column.

[0088] Step 6: Elute the first and second chromatographic columns connected in series with a second acid solution (dilute hydrochloric acid) with a concentration of 0.08 mol / L.

[0089] Step 7: When Ce penetration is detected at the outlet of the second chromatographic column, i.e. when xylenol orange changes from yellow to red, decouple the second chromatographic column.

[0090] Step 8: Elute the decoupled second column separately with a third acid solution (dilute hydrochloric acid) with a concentration of 0.5 mol / L.

[0091] Step 9: Collect the cerium-containing eluent from the second chromatographic column in Step 8.

[0092] Step 10: Add 6 mol / L ammonia water to the leaching liquid to convert Ce ions into Ce(OH)4 precipitate. Wash with water and filter to achieve solid-liquid separation and obtain solid Ce(OH)4.

[0093] Step 11: Dissolve the obtained Ce(OH)4 solid in 6 mol / L nitric acid, dilute to 500 mL to obtain a Ce-rich solution, heat to near boiling, and add 7% oxalic acid solution while stirring to obtain Ce2(C2O4)3 precipitate. Wash with water and filter to achieve solid-liquid separation and obtain Ce2(C2O4)3 solid.

[0094] Step 12: The obtained Ce2(C2O4)3 solid was calcined at 850℃ for 2 hours to obtain CeO2 oxide.

[0095] Example 2

[0096] The preparation method of Example 2 is basically the same as that of Example 1, except that the concentrations of the first acid solution and the second acid solution are changed to 0.04 mol / L.

[0097] Example 3

[0098] The preparation method of Example 3 is basically the same as that of Example 1, except that the concentration of the third acid solution is changed to 0.4 mol / L.

[0099] Comparative Example 1

[0100] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the concentrations of the first acid solution and the second acid solution are changed to 0.08 mol / L.

[0101] The process parameters for the preparation methods of Examples 1-3 and Comparative Example 1 are listed in Table 1 below:

[0102] Table 1

[0103]

[0104] The CeO2 obtained in Examples 1-3 and Comparative Example 1 were tested. The Ce content and the content of each impurity element were measured by inductively coupled plasma mass spectrometry (ICP-MS). The product yield was calculated by mass yield, which was calculated as the actual mass of CeO2 produced / the theoretical mass of CeO2 produced × 100%.

[0105] The test results and other key process parameters are shown in Table 2 below.

[0106] Table 2

[0107]

[0108] Comparing Examples 1-3 with Comparative Example 1, it is evident that the gradient elution with acid solutions of varying acidity, coupled with a dual-column series / decoupling separation and purification mechanism, is a key factor in achieving short-process, high-yield separation and extraction of cerium. The purity of Examples 1-3 consistently reached 99.9999% (6N), and the yield remained above 85%. In Comparative Example 1, the CeO2 yield decreased to 55.0%, the process time was extended to 36 hours, and the eluent dosage increased dramatically to 4400 mL. The low concentration of the third acid solution failed to effectively desorb the Ce firmly bound to the resin, resulting in slow Ce migration within the column. Most of the Ce could not be eluted and collected in time, leading to a low yield. Furthermore, to collect sufficient Ce, a large amount of eluent and time had to be consumed. Therefore, it is evident that the explosive increase in acid concentration from the low concentration of the first acid solution, the second acid solution (0.04 mol / L-0.08 mol / L) to the third acid solution (0.4 mol / L-0.5 mol / L) is the key to achieving a short process and high yield. This ensures that Ce is rapidly and centrally desorbed, reduces the amount of eluent used, and shortens the process time.

[0109] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0110] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for separating and purifying rare earth elements, characterized in that, Includes the following steps S10-S50: S10, to adsorb the solution containing the target rare earth metal ions onto the first chromatographic column; S20. The first chromatographic column obtained in the adsorption step S10 is eluted with a first acid solution with a concentration of 0.02mol / L-0.1mol / L, and when the target rare earth metal ions are detected in the eluent of the first chromatographic column, a second chromatographic column is connected in series at the outlet of the first chromatographic column. S30. Elute the first and second chromatographic columns connected in series with a second acid solution of concentration of 0.02mol / L-0.1mol / L, and decouple the second chromatographic column when the target rare earth metal ions are detected in the eluent of the second chromatographic column. S40. Elute the decoupled second chromatographic column separately with a third acid solution at a concentration of 0.3 mol / L to 0.6 mol / L; S50. Collect the eluent from the second chromatographic column in S40, and precipitate and calcine the eluent sequentially to obtain the target rare earth element oxide. The entire process, from the start of rinsing in step S20 to the end of rinsing in step S40, takes 16-30 hours. The total volume of the first acid solution, the second acid solution, and the third acid solution used during the entire process from the start of rinsing in step S20 to the end of rinsing in step S40 is 2000mL-3500mL. The target rare earth metal ion is Ce.

2. The method for separating and purifying rare earth elements as described in claim 1, characterized in that, In steps S20 and S30, the detection of target rare earth metal ions includes detection using a colorimetric reagent; and / or, In steps S20 and S30, the series connection and decoupling of the first chromatographic column and the second chromatographic column are controlled by a solenoid valve.

3. The method for separating and purifying rare earth elements as described in claim 2, characterized in that, The solenoid valve is linked to the detection result of the color developer, and the response time of the color developer's color development and the valve being connected in series or decoupled is ≤5s.

4. The method for separating and purifying rare earth elements as described in claim 2, characterized in that, The colorimetric agent is selected from at least one of azoarsine III, p-nitroazoarsine, chlorophosphine azo I, and xylenol orange.

5. The method for separating and purifying rare earth elements as described in any one of claims 1 to 4, characterized in that, In steps S20 and S30, the rinsing rate of the first acid solution and the second acid solution is 90 mL / h-140 mL / h.

6. The method for separating and purifying rare earth elements as described in any one of claims 1 to 4, characterized in that, Both the first and second chromatographic columns are packed with resin, the functional groups of which are phosphate esters and / or phosphonates, the particle size of which is 80-140 mesh, and the mass content of which is 45%-60%.

7. The method for separating and purifying rare earth elements as described in claim 6, characterized in that, The resin packing height is 430mm-470mm, and the inner diameter of the first and second chromatographic columns is 21mm-46mm.

8. The method for separating and purifying rare earth elements as described in any one of claims 1 to 4, characterized in that, In S50, the leachate is subjected to precipitation and calcination in sequence, including the following steps: Ammonia water was added dropwise to the leachate to obtain a hydroxide precipitate of the target rare earth element. Solid-liquid separation was performed to obtain a hydroxide solid. The obtained hydroxide solid was dissolved in nitric acid to obtain a solution rich in the target rare earth element; An oxalic acid solution was added to the solution rich in the target rare earth element to obtain an oxalate precipitate of the target rare earth element. Solid-liquid separation was performed to obtain solid oxalate. The oxalate solid obtained by calcination yields oxides of the target rare earth element.

9. The method for separating and purifying rare earth elements as described in claim 8, characterized in that, In step S50, the concentration of the ammonia solution is 5 mol / L-7 mol / L, and / or the concentration of the nitric acid solution is 5 mol / L-7 mol / L, and / or the mass fraction of the oxalic acid solution is 6%-8%.

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