Method for preparing ultra-pure lanthanum oxide by utilizing chromatographic single-column method

Abstract

The invention discloses a preparation method for preparing ultra-pure lanthanum oxide by utilizing a chromatographic single-column method, and particularly relates to the field of preparation methods of ultra-pure rare earth oxides. Comprising the following steps: filling a chromatographic column with the phosphonic acid functionalized levextrel resin, enabling feed liquid to flow through the chromatographic column under the action of a pump under a certain condition, preferentially adsorbing trace rare earth impurities except Th, U, Fe and La in the feed liquid, enabling La to flow out along with the feed liquid, realizing high-efficiency separation of La and impurity elements, treating effluent with oxalic acid to obtain lanthanum oxalate precipitate, washing, drying and firing to obtain the high-purity lanthanum oxalate. The ultra-pure lanthanum oxide is obtained, the content of radioactive elements (Th and U) is lower than 0.01 ppm, and the removal rate of rare earth impurity ions is as high as 97%. The method is characterized in that purified feed liquid flows out along with feed liquid, and impurities in the feed liquid can be efficiently removed after the feed liquid passes through a column once. By adopting the technical scheme provided by the invention, the problems of complex process and poor stability of the existing ultra-pure lanthanum oxide preparation method are solved, and the method has the advantages of simplicity and high efficiency.

Description

Technical Field

[0001] The present invention relates to the field of preparation methods of ultra-high purity rare earth oxides, and particularly relates to a preparation method of ultra-high purity lanthanum oxide by using a single-column chromatography method. Background Art

[0002] Due to the special electronic layer structure, rare earths have excellent physical and chemical properties such as magnetism, optics, and electricity, and are known as the treasure house of industrial materials. China is a major rare earth country, providing about 70% of the global rare earth production and about 90% of the rare earth separation capacity. At present, China can mass-produce rare earths with a purity of 99% - 99.999% through the extraction method. However, China is still in a weak position in the preparation of ultra-high purity rare earths (rare earth purity of 99.9999% and above). With the development of technology and the application of rare earths in high-tech fields such as new-generation electronics, communications, and optics, the demand for ultra-high purity rare earths is increasing day by day, and the requirements for sensitive impurities among them are becoming more and more stringent.

[0003] Rare earths are usually associated with radioactive elements such as uranium (U) and thorium (Th). During the rare earth smelting process, most of the radioactive elements uranium and thorium in rare earths can be effectively removed. However, trace amounts of uranium (U) and thorium (Th) may still remain in rare earth products, and the high-energy particles continuously released by the decay of radioactive impurities may affect the performance of products in the high-end optoelectronic field.

[0004] Lanthanum (La) is one of the most abundant rare earth elements in the earth's crust, and its output accounts for 15% - 20% of the rare earth output. In high-tech fields such as high-end optical glass, scintillation crystals, laser crystals, and gate insulating film materials for ultra-large scale integrated circuits, high requirements are placed on the purity of La and its sensitive impurity elements.

[0005] At present, common wet separation and purification methods for rare earth elements mainly include solvent extraction method, ion exchange method, emulsion liquid membrane method, etc. The solvent extraction method is widely used in industrial production due to its advantages of high efficiency and low cost, but the purity produced is difficult to meet the requirements of high-purity rare earth functional materials. The ion exchange method is widely used as an effective method for purifying single rare earths. However, the ion exchange also has disadvantages such as poor selectivity and high resin regeneration cost. The membrane separation method has received extensive attention due to its advantages of strong selectivity, high efficiency, and environmental protection. However, factors such as its complex production process and poor stability make it not commonly used in the preparation of a large amount of ultra-high purity rare earths.

[0006] Therefore, developing a preparation method of ultra-high purity lanthanum oxide with ultra-low radioactivity helps to simplify the production process, improve production efficiency, and reduce the content of associated radioactive elements in lanthanum oxide. Summary of the Invention

[0007] The present invention aims to provide a preparation method for preparing ultra-high purity lanthanum oxide by a single-column chromatography method, which solves the problems of complex process and poor stability in the existing preparation methods for ultra-high purity lanthanum oxide.

[0008] To achieve the above object, the technical solution of the present invention is as follows: A preparation method for preparing ultra-high purity lanthanum oxide by a single-column chromatography method, comprising the following steps:

[0009] S1. Dissolve the lanthanum compound with an appropriate amount of nitric acid under heating conditions, then add ultrapure water and control the lanthanum concentration at 1 g / L - 150 g / L, and adjust the acidity of the solution to pH ≥ 2 with sodium hydroxide to obtain a feed solution;

[0010] S2. Fully dissolve the phosphonic acid extractant in a sufficient amount of dichloromethane, then transfer it to a flask in proportion with the carrier and mix evenly. Subsequently, perform a water bath or oil bath treatment on the flask, and reduce the air pressure in the flask to below 500 hPa to completely volatilize solvents such as dichloromethane, and dry it in a vacuum drying oven to obtain a phosphonic acid-functionalized extraction resin;

[0011] S3. Immerse the extraction resin in ultrapure water and perform a degassing treatment, then fill it into a separation column. After filling, perform an acid balance treatment on the separation column with a nitric acid solution of pH ≥ 2 to make the acidity in the separation column consistent with that of the feed solution;

[0012] S4. Add the feed solution from one end of the chromatography column and let it flow out from the other end. Collect the effluent and detect the concentrations of Ce, Pr, and Nd. When the concentration of any rare earth element among Ce, Pr, and Nd reaches or exceeds 10% of the concentrations of Ce, Pr, and Nd in the feed solution, stop adding the feed solution. The above-collected solution is a lanthanum purification solution, and analyze the concentrations of La, Ce, Pr, and Nd in it;

[0013] S5. Use a sulfuric acid solution to desorb the adsorbed impurity elements in step S4, collect the effluent and detect the concentrations of Ce, Pr, and Nd. When the concentration of any element among Ce, Pr, and Nd is lower than 20% of the corresponding element concentrations of Ce, Pr, and Nd in the feed solution, stop adding the sulfuric acid solution for acid adjustment treatment, and the solution is to be used for subsequent processes;

[0014] S6. Add an oxalic acid solution to the lanthanum purification solution obtained in step S4, heat it at 50 - 100 °C for 1 - 10 h, and perform a solid-liquid separation treatment to obtain lanthanum oxalate precipitate. After washing and drying, calcine it at 800 - 1100 °C for 1 h - 24 h to obtain ultra-low radioactive ultra-high purity lanthanum oxide with a purity greater than 99.9999%.

[0015] Furthermore, the purity of the lanthanum compound is 4N or above, and the lanthanum compound includes lanthanum oxide and lanthanum nitrate.

[0016] Furthermore, the phosphonic acid extractant is P507 or a mixture of P507 and 5%-50% TBP.

[0017] Furthermore, in step S2, the carrier includes any one of porous silicon-based polymers and macroporous adsorption resin D101.

[0018] Furthermore, the ratio of the extractant to the carrier is 1:1 - 5.

[0019] Through the above settings, the organic matter loading rate can be effectively increased, and the separation effect can be improved.

[0020] Furthermore, in step S4, the column length of the chromatographic column is 30 - 100 cm, and the diameter: column length = 1:5 - 60.

[0021] Through the above settings, different column sizes have different separation effects, which can improve the product yield.

[0022] Furthermore, in step S7, the molar ratio of oxalate ions to lanthanum ions is 1:1.5 - 2.1.

[0023] Through the above settings, different ratios of oxalate ions to lanthanum ions will obtain lanthanum oxalate with different qualities during precipitation, and an appropriate ratio will increase the yield of lanthanum oxalate.

[0024] Furthermore, ethanol and ultrapure water are alternately used to wash the lanthanum oxalate precipitate obtained in step S6.

[0025] Compared with the prior art, the beneficial effects of this solution are as follows:

[0026] 1. In the present invention, by not adsorbing or weakly adsorbing the target element and strongly adsorbing the impurity elements, the purified feed liquid flows out with the feed liquid, and the lanthanum purified feed liquid can be obtained without going through the desorption stage. Since the impurity elements are present in small amounts compared to the lanthanum element, the use efficiency of the adsorbent is greatly improved. Obtaining ultra-high purity lanthanum feed liquid through a single chromatographic column greatly simplifies the purification process and improves the production efficiency.

[0027] 2. The relative purity of the lanthanum oxide obtained by this solution is greater than 99.9999%, and at the same time, the contents of key metals Fe and Mn are lower than 1 ppm, and the contents of associated radioactive elements Th and U are lower than 0.01 ppm, and the product quality is excellent.

[0028] 3. All ions can be desorbed by sulfuric acid in this solution, significantly improving the resource utilization rate. At the same time, ultra-low radioactive ultra-high purity lanthanum oxide products can be produced cyclically, improving the production efficiency. Description of the Drawings

[0029] Figure 1It is the process flow diagram of a preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatography method according to the present invention;

[0030] Figure 2 It is the synthesis flow diagram of the extraction resin in the preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatography method according to the present invention;

[0031] Figure 3 It is the schematic diagram of the column separation device in the preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatography method according to the present invention. Detailed implementation manners

[0032] The present invention will be further described in detail through the following detailed implementation manners:

[0033] Example 1

[0034] As Figures 1 to 3 shown, a preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatography method includes the following steps:

[0035] S1. Preparation of the lanthanum-containing feed liquid: Use an appropriate amount of analytical reagent grade nitric acid to dissolve lanthanum compounds with a purity of 4N under heating conditions. In this example, the lanthanum compound is lanthanum oxide. As much excess nitric acid as possible is removed by heating and evaporation. Subsequently, ultrapure water is added and the concentration of lanthanum is controlled at 5 g / L. Then, analytical reagent grade or higher sodium hydroxide is used to adjust the acidity of the solution to pH 4, thereby preparing the feed liquid.

[0036] S2. Preparation of the phosphonic acid-functionalized extraction resin: The phosphonic acid-functionalized extraction resin is prepared by the vacuum impregnation method using a rotary evaporator. The specific method is as follows: The mixed extractant of P507 (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) + TBP (tributyl phosphate) (molar ratio 4:1) is fully dissolved in a sufficient amount of dichloromethane. In this solution, the mixed extraction of P507 and a certain amount of TBP can increase the recovery rate of lanthanum. Then, it is transferred into a flask with a porous silicon-based polymer carrier (SiO2-P) according to a certain mass ratio (the mass ratio of the extractant to the carrier is 1:2), and installed on the rotary evaporator to make it mix evenly. In this solution, using the porous silicon-based polymer can increase the mechanical strength, heat resistance, economy and corrosion resistance of the carrier. Subsequently, the flask is treated with a water bath or an oil bath, and the water bath or oil bath temperature is set at 38 °C. The air pressure in the flask is reduced to 500 hPa or less at a certain pressure reduction rate (such as a pressure reduction rate of 20 hPa / 20 min), and sufficient time is maintained to allow dichloromethane to volatilize as completely as possible. It is dried in a vacuum drying oven at no higher than 40 °C for 12 h, and the obtained product is the phosphonic acid-functionalized extraction resin.

[0037] S3. Separation preparation work: The separation column device in this example is as Figure 3As shown in the figure, it includes a peristaltic pump, a chromatographic column, a constant temperature control device, a liquid collection vessel for the feed solution, and pipelines. The column length is 100 cm, and the diameter: column length = 1:30. The wet packing method is adopted, that is, the extraction resin is soaked in water, and the degassing work is completed through 10 minutes of ultrasonic treatment, and then filled into the separation column. After filling, the separation column is acid-balanced with 3 bed volumes of nitric acid solution to make the acidity in the separation column consistent with that of the feed solution, where the pH of the nitric acid solution is 4.

[0038] S4. Single-column separation operation: Under the premise of normal pressure and room temperature of 25 °C, use a peristaltic pump to add the feed solution from the top of the chromatographic column at a flow rate of 0.2 bed volume / hour and flow out from the bottom of the chromatographic column. Manually collect the effluent at a flow rate of 0.2 bed volume / portion, and detect the concentrations of impurity elements Ce, Pr, and Nd in the effluent. When the concentration of any one of Ce, Pr, and Nd reaches or exceeds 10% of the concentrations of Ce, Pr, and Nd in the feed solution, stop adding the feed solution. The above-collected solution is the lanthanum purification solution, and analyze the concentrations of La, Ce, Pr, and Nd in it.

[0039] At the same time, use 2 bed volumes of nitric acid solution to flush the lanthanum-containing solution remaining in the pipeline at a flow rate of 0.2 bed volume / hour, where the pH of the nitric acid solution is 4, and collect the obtained solution and return it to the feed solution in step S1 for subsequent purification use.

[0040] S5. Desorption and regeneration: Let a 5M H2SO4 solution (the H2SO4 solution is used as the desorbing solution) flow at a flow rate of 0.2 bed volume / hour to desorb the adsorbed impurity elements in step S4, manually collect the effluent at a flow rate of 0.2 bed volume / portion, and detect the concentrations of impurity elements Ce, Pr, and Nd in it. When the concentration of any one of Ce, Pr, and Nd is lower than 20% of the corresponding element concentration of Ce, Pr, and Nd in the feed solution, stop adding the sulfuric acid solution for acid adjustment treatment, and the solution is for subsequent continued use. Then, flush the pipeline with pure water at a certain flow rate (0.5 bed volume / hour) until the pH ≥ 2. The first 2 bed volumes of the collected liquid can be returned to the desorbing solution after acid adjustment for continued use.

[0041] S6. Preparation of ultra-low-radioactivity ultra-high-purity lanthanum oxide: Prepare a 1M chromatographically pure oxalic acid solution, add the oxalic acid solution to the lanthanum purification solution in step S4 according to the molar ratio of oxalate ions to lanthanum ions of 1:1.7, heat at 50 °C for 5 hours, and perform solid-liquid separation to obtain lanthanum oxalate precipitate. After washing (in this embodiment, the lanthanum oxalate precipitate is washed alternately with ethanol and ultrapure water), drying treatment, and calcination at 1000 °C for 12 hours, ultra-low-radioactivity ultra-high-purity lanthanum oxide with a purity greater than 99.9999% is obtained.

[0042] In this solution, the extractant adsorbs rare earth metal ions through the combined action of ion exchange and coordination. Due to the differences in the hydrated ionic radii of rare earth ions, the adsorption effects are different for different hydrated ionic radii. Experiments have shown that the extractant has the worst adsorption capacity for lanthanum ions among rare earth elements. Therefore, after being prepared into a resin and operated using a column separation device, other rare earth elements in lanthanum can be well removed, achieving the purpose of purifying lanthanum oxide.

[0043] Example 2

[0044] A preparation method for preparing ultra-high purity lanthanum oxide using a single-column chromatography method, comprising the following steps:

[0045] S1. Preparation of the lanthanum-containing feed solution: Use an appropriate amount of analytical reagent grade nitric acid to dissolve lanthanum compounds with a purity of 4N under heating conditions. In this example, the lanthanum compound is lanthanum oxide. Excess nitric acid is removed as much as possible by heating and evaporation. Subsequently, ultrapure water is added and the concentration of lanthanum is controlled at 5 g / L. Then, analytical reagent grade or higher sodium hydroxide is used to adjust the acidity of the solution to pH 4, thereby preparing the feed solution.

[0046] S2. Preparation of phosphonic acid-functionalized extraction resin: A phosphonic acid-functionalized extraction resin is prepared by a rotary evaporator through the vacuum impregnation method. The specific method is as follows: A mixed extractant of P507 (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) + TBP (tributyl phosphate) (molar ratio 2:1) is fully dissolved in a sufficient amount of dichloromethane, and then transferred into a flask with a porous silica-based polymer carrier (SiO2-P) according to a certain mass ratio (the mass ratio of the extractant to the carrier is 1:1), and installed on a rotary evaporator to make them mix evenly. Subsequently, the flask is subjected to a water bath or an oil bath treatment, and the water bath or oil bath temperature is set at 38 °C. The air pressure in the flask is reduced to 500 hPa or less at a certain pressure reduction rate (such as a pressure reduction rate of 20 hPa / 20 min), and sufficient time is maintained to make dichloromethane evaporate as completely as possible. It is dried in a vacuum drying oven at no higher than 40 °C for 12 h, and the obtained product is the phosphonic acid-functionalized extraction resin.

[0047] S3. Separation preparation work: The separation column device in this example is as Figure 3 shown, including a peristaltic pump, a chromatographic column, a temperature control device, a liquid collection vessel for the feed solution, and pipelines. The column length is 30 cm, and the diameter: column length = 1:60. The wet packing method is adopted, that is, the extraction resin is soaked in water, and the degassing work is completed by ultrasonic treatment for 10 minutes, and then filled into the separation column. After filling, the separation column is subjected to acid balance treatment with 3 bed volumes of nitric acid solution to make the acidity in the separation column consistent with that of the feed solution, where the pH of the nitric acid solution is 4.

[0048] S4. Single-column separation operation: On the premise of normal pressure and room temperature of 25 °C, use a peristaltic pump to add the feed liquid to the top of the chromatographic column at a flow rate of 0.2 bed volume per hour and let it flow out from the bottom of the chromatographic column. Manually collect the effluent at a flow rate of 0.2 bed volume per portion, and detect the concentrations of impurity elements Ce, Pr, and Nd in the effluent. When the concentration of any one of Ce, Pr, and Nd reaches or exceeds 10% of the concentrations of Ce, Pr, and Nd in the feed liquid, stop adding the feed liquid. The above-collected solution is the lanthanum purification solution, and analyze the concentrations of La, Ce, Pr, and Nd in it.

[0049] At the same time, use 2 bed volumes of nitric acid solution to flush the lanthanum-containing solution remaining in the pipeline at a flow rate of 0.2 bed volume per hour, where the pH of the nitric acid solution is 4. Collect the obtained solution and return it to the feed liquid in step S1 for subsequent purification use.

[0050] S5. Desorption and regeneration: Let a 5M H2SO4 solution (the H2SO4 solution is used as the desorbing solution) flow at a rate of 0.2 bed volume per hour to desorb the adsorbed impurity elements in step S4. Manually collect the effluent at a flow rate of 0.2 bed volume per portion, and detect the concentrations of impurity elements Ce, Pr, and Nd in it. When the concentration of any one of Ce, Pr, and Nd is lower than 20% of the corresponding element concentration of Ce, Pr, and Nd in the feed liquid, stop adding the sulfuric acid solution for acid adjustment, and the solution is to be used continuously later. Then, flush the pipeline with pure water at a certain flow rate (0.5 bed volume per hour) until the pH ≥ 2. The first 2 bed volumes of the collected liquid can be returned to the desorbing solution after acid adjustment for continued use.

[0051] S6. Preparation of ultra-low radioactive ultra-high purity lanthanum oxide: Prepare a 1M chromatographic grade oxalic acid solution, and add the oxalic acid solution to the lanthanum purification solution in step S4 according to the molar ratio of oxalate ions to lanthanum ions of 1:1.5. Heat at 50 °C for 5 h, and after solid-liquid separation, obtain lanthanum oxalate precipitate. After washing (in this example, the lanthanum oxalate precipitate is washed alternately with ethanol and ultrapure water), drying, and then calcining at 1000 °C for 12 h, obtain ultra-low radioactive ultra-high purity lanthanum oxide with a purity greater than 99.9999%.

[0052] Example 3

[0053] A preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatography method, comprising the following steps:

[0054] S1. Preparation of lanthanum-containing feed solution: Use an appropriate amount of analytical reagent grade nitric acid to dissolve lanthanum compounds with a purity of 4N under heating conditions. In this example, the lanthanum compound is lanthanum(III) nitrate hydrate. Evaporate as much excess nitric acid as possible by heating, then add ultrapure water and control the concentration of lanthanum at 5 g / L. Then use sodium hydroxide of analytical reagent grade or higher to adjust the acidity of the solution to pH 4, thus obtaining the feed solution.

[0055] S2. Preparation of phosphonic acid-functionalized extraction resin: Use a rotary evaporator to prepare phosphonic acid-functionalized extraction resin by vacuum impregnation method. The specific method is as follows: Dissolve the mixed extractant of P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) + TBP (tributyl phosphate) (molar ratio 1:1) in sufficient dichloromethane, then transfer it into a flask with macroporous adsorption resin D101 according to a certain mass ratio (mass ratio of extractant to carrier is 1:5), and install it on the rotary evaporator to mix evenly. Then perform a water bath or oil bath treatment on the flask, and set the water bath or oil bath temperature to 38 °C. Reduce the air pressure in the flask to 500 hPa or below at a certain pressure reduction rate (such as a pressure reduction rate of 20 hPa / 20 min), and maintain for a sufficient time to make dichloromethane volatilize as completely as possible. Dry it in a vacuum drying oven at no higher than 40 °C for 12 h, and the resulting product is the phosphonic acid-functionalized extraction resin.

[0056] S3. Separation preparation work: The separation column device in this example is as Figure 3 shown, including a peristaltic pump, a chromatographic column, a temperature control device, a feed liquid collection vessel, and pipelines. The column length is 30 cm, and the diameter: column length = 1:5. Adopt the wet packing method, that is, soak the extraction resin in water, complete the degassing work through 10 minutes of ultrasonic treatment, and then fill it into the separation column. After filling, perform acid balance treatment on the separation column with 3 bed volumes of nitric acid solution to make the acidity in the separation column consistent with that of the feed liquid, where the pH of the nitric acid solution is 4.

[0057] S4. Single-column separation operation: Under the premise of normal pressure and room temperature of 25 °C, use a peristaltic pump to add the feed liquid from the top of the chromatographic column at a flow rate of 0.2 bed volume / hour and flow out from the bottom of the chromatographic column. Manually collect the effluent at a flow rate of 0.2 bed volume / portion, and detect the concentrations of impurity elements Ce, Pr, and Nd in the effluent. When the concentration of any one of Ce, Pr, and Nd reaches or exceeds 10% of the concentration of Ce, Pr, and Nd in the feed liquid, stop adding the feed liquid. The above collected solution is the lanthanum purification solution, and analyze the concentrations of La, Ce, Pr, and Nd in it.

[0058] Meanwhile, use 2 bed volumes of nitric acid solution to flush the lanthanum-containing solution remaining in the pipeline at a flow rate of 0.2 bed volume per hour, where the pH of the nitric acid solution is 4. Collect the obtained solution and return it to the feed solution in step S1 for subsequent purification use.

[0059] S5. Desorption and regeneration: Use a 5M H2SO4 solution (the H2SO4 solution serves as the desorbing solution) to desorb the adsorbed impurity elements at a flow rate of 0.2 bed volume per hour. Manually collect the effluent at a flow rate of 0.2 bed volume per portion and detect the concentrations of the impurity elements Ce, Pr, and Nd therein. When the concentration of any one of Ce, Pr, and Nd is lower than 20% of the corresponding element concentrations of Ce, Pr, and Nd in the feed solution, stop adding the sulfuric acid solution for acid adjustment treatment, and the solution is to be used continuously later. Then, flush the pipeline with pure water at a certain flow rate (1 bed volume per hour) until the pH ≥ 2. The first 2 bed volumes of the collected liquid can be returned to the desorbing solution after acid adjustment for continued use.

[0060] S6. Preparation of ultra-low radioactive ultra-high purity lanthanum oxide: Prepare a 1M chromatographically pure oxalic acid solution, and add the oxalic acid solution to the lanthanum purification solution in step S4 according to the molar ratio of oxalate ions to lanthanum ions of 1:2.1. Heat at 50 °C for 5 h, and after solid-liquid separation, obtain lanthanum oxalate precipitate. After washing (in this embodiment, the lanthanum oxalate precipitate is washed alternately with ethanol and ultrapure water), drying treatment, and calcination at 1000 °C for 12 h, obtain ultra-low radioactive ultra-high purity lanthanum oxide with a purity greater than 99.9999%.

[0061] Example 4

[0062] A preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatography method, comprising the following steps:

[0063] S1. Preparation of lanthanum-containing feed solution: Use an appropriate amount of reagent-grade nitric acid to dissolve lanthanum compounds with a purity of 5N under heating conditions. In this embodiment, the lanthanum compound is lanthanum oxide. As much excess nitric acid as possible is removed by heating and evaporation. Subsequently, add ultrapure water and control the concentration of lanthanum at 5 g / L, and then use sodium hydroxide of reagent grade or above to adjust the acidity of the solution to pH 4, thereby preparing the feed solution.

[0064] S2. Preparation of phosphonic acid-functionalized extraction resin: The phosphonic acid-functionalized extraction resin was prepared by the vacuum impregnation method using a rotary evaporator. The specific method is as follows: The P507 (2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester) extractant was fully dissolved in a sufficient amount of dichloromethane, and then transferred into a flask with a porous silicon-based polymer carrier (SiO2-P) according to a certain mass ratio (the mass ratio of the extractant to the carrier is 1:2). It was installed on the rotary evaporator to mix evenly. Subsequently, the flask was treated in a water bath or an oil bath, and the water bath or oil bath temperature was set at 38°C. The air pressure in the flask was reduced to 500 hPa or less at a certain pressure reduction rate (such as a pressure reduction rate of 20 hPa / 20 min), and enough time was maintained to make the dichloromethane volatilize as completely as possible. It was dried in a vacuum drying oven at no higher than 40°C for 12 h, and the obtained product was the phosphonic acid-functionalized extraction resin.

[0065] S3. Separation preparation work: The separation column device in this embodiment is as Figure 3 shown, including a peristaltic pump, a chromatographic column, a temperature control device, a feed liquid collection vessel, and pipelines. The wet packing method was used, that is, the extraction resin was soaked in water, and the degassing work was completed by ultrasonic treatment for 10 minutes, and then filled into the separation column (column length 50 cm, diameter: column length = 1:50). After filling, the separation column was acid-balanced with 3 bed volumes of nitric acid solution to make the acidity in the separation column consistent with the acidity of the feed liquid, where the pH of the nitric acid solution was 4.

[0066] S4. Single-column separation operation: On the premise of normal pressure and room temperature of 25°C, the feed liquid was added to the top of the chromatographic column at a flow rate of 0.2 bed volume / hour using a peristaltic pump and flowed out from the bottom of the chromatographic column. The effluent was manually collected at a flow rate of 0.2 bed volume / portion, and the concentrations of impurity elements Ce, Pr, and Nd in the effluent were detected. When the concentration of any one of Ce, Pr, and Nd reached or exceeded 10% of the concentrations of Ce, Pr, and Nd in the feed liquid, the addition of the feed liquid was stopped. The above-collected solution was the lanthanum purification solution, and the concentrations of La, Ce, Pr, and Nd in it were analyzed.

[0067] At the same time, 2 bed volumes of nitric acid solution were used to flush the lanthanum-containing solution remaining in the pipeline at a flow rate of 0.2 bed volume / hour, where the pH of the nitric acid solution was 4. The obtained solution was collected and returned to the feed liquid in step S1 for subsequent purification use.

[0068] S5. Desorption and regeneration: Use a 5M H2SO4 solution (the H2SO4 solution serves as the desorbing solution) to desorb the adsorbed impurity elements in step S4 at a flow rate of 0.2 bed volumes per hour. Manually collect the effluent at a flow rate of 0.2 bed volumes per portion and detect the concentrations of the impurity elements Ce, Pr, and Nd therein. When the concentration of any one of Ce, Pr, and Nd is lower than 20% of the corresponding element concentration of Ce, Pr, and Nd in the feed solution, stop adding the sulfuric acid solution for acid adjustment, and the solution is to be used continuously later. Then, rinse the pipeline with pure water at a certain flow rate (2 bed volumes per hour) until the pH ≥ 2. The collected liquid of the first 2 bed volumes can be returned to the desorbing solution for continued use after acid adjustment.

[0069] S6. Preparation of ultra-low radioactive ultra-high purity lanthanum oxide: Prepare a 1M chromatographically pure oxalic acid solution, and add the oxalic acid solution to the lanthanum purification solution in step S4 according to the molar ratio of oxalate ions to lanthanum ions of 1:1.7. Heat at 50 °C for 5 h, and after solid-liquid separation, obtain lanthanum oxalate precipitate. After washing (in this example, the lanthanum oxalate precipitate is washed alternately with ethanol and ultrapure water), drying, and then calcining at 1000 °C for 12 h, ultra-low radioactive ultra-high purity lanthanum oxide with a purity greater than 99.9999% is obtained.

[0070] Perform GDMS testing on the obtained lanthanum oxide solid powder sample in Example 1 to obtain the detection report shown in Table 1 below. It can be seen that the total amount of other rare earth impurities in lanthanum is less than 1 μg / g. According to the GB / T 4154-2015 standard, it can be considered that the relative purity of this lanthanum oxide product is greater than 6N.

[0071] Table 1 GD-MS analysis and detection report

[0072] Detection element Detection result (μg / g) Detection element Detection result (μg / g) Detection element Detection result (μg / g) Li ＜0.05 As ＜0.1 Eu ＜0.1 Be ＜0.05 Se ＜0.1 Gd ＜0.05 B 0.16 Br ＜0.1 Tb ＜0.05 F 0.19 Rb ＜0.05 Dy ＜0.05 Na 15.66 Sr 0.051 Ho ＜0.05 Mg 0.20 Y ＜0.05 Er ＜0.05 AI 1.94 Zr 0.065 Tm ＜0.05 Si 18.67 Nb ＜0.05 Yb ＜0.05 P 0.65 Mo ＜0.05 Lu ＜0.05 s 14.22 Ru ＜0.05 Hf ＜0.05 CI 23.67 Rh ＜0.05 Ta ＜0.5 K 6.52 Pd ＜0.05 w ＜0.05 Ca 8.89 Ag ＜0.05 Re ＜0.05 Sc 0.14 Cd ＜0.05 Os ＜0.05 Ti 0.065 Sn ＜0.05 Ir ＜0.05 v ＜0.05 Sb ＜0.05 Pt ＜0.05 Cr ＜0.05 Te ＜0.05 Au ＜0.1 Mn 0.10 I ＜0.5 Hg ＜0.05 Fe 0.78 Cs ＜0.05 TI ＜0.05 Co ＜0.05 Ba 0.078 Pb 0.11 Ni ＜0.05 La Major element Bi 0.062 Cu ＜0.05 Ce 0.13 Th ＜0.05 Zn ＜0.05 Pr 0.050 0 ＜0.05 Ga ＜0.05 Nd ＜0.05 / / Ge ＜0.05 Sm ＜0.05 / /

[0073] The above are only the embodiments of the present invention. Specific structures and / or common knowledge such as characteristics well known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to explain the content of the claims.

Claims

1. A preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatography method, characterized in that, It includes the following steps: S1. Dissolve the lanthanum compound with an appropriate amount of nitric acid under heating conditions, then add ultrapure water and control the lanthanum concentration at 1 g / L - 150 g / L, and adjust the acidity of the solution to pH ≥ 2 with sodium hydroxide to obtain a feed solution; S2. Dissolve the phosphonic acid extractant completely in a sufficient amount of dichloromethane, then transfer it to a flask with a carrier in proportion and mix evenly. Subsequently, perform a water bath or oil bath treatment on the flask, and reduce the air pressure in the flask to below 500 hPa to completely volatilize solvents such as dichloromethane, and dry it in a vacuum drying oven to obtain a phosphonic acid-functionalized extraction resin; S3. Immerse the extraction resin in ultrapure water and perform a degassing treatment, then fill it into a separation column. After filling, perform an acid balance treatment on the separation column with a nitric acid solution of pH ≥ 2 to make the acidity in the separation column consistent with that of the feed solution; S4. Add the feed solution from one end of the chromatographic column and let it flow out from the other end, collect the effluent and detect the concentrations of Ce, Pr, and Nd. When the concentration of any rare earth element in Ce, Pr, and Nd reaches or exceeds 10% of the concentrations of Ce, Pr, and Nd in the feed solution, stop adding the feed solution. The above-collected solution is a lanthanum purification solution, and analyze the concentrations of La, Ce, Pr, and Nd in it; S5. Use a sulfuric acid solution to desorb the adsorbed impurity elements in step S4, collect the effluent and detect the concentrations of Ce, Pr, and Nd. When the concentration of any element in Ce, Pr, and Nd is lower than 20% of the corresponding element concentrations of Ce, Pr, and Nd in the feed solution, stop adding the sulfuric acid solution for acid adjustment treatment, and the solution is to be used continuously later; S6. Add an oxalic acid solution to the lanthanum purification solution obtained in step S4, heat it at 50 - 100 °C for 1 - 10 h, and perform a solid-liquid separation treatment to obtain lanthanum oxalate precipitate. After washing and drying, calcine it at 800 - 1100 °C for 1 h - 24 h to obtain ultra-low radioactive ultra-high purity lanthanum oxide with a purity greater than 99.9999%; 2. The preparation method of ultra-high purity lanthanum oxide by using a single chromatographic column method according to claim 1, characterized in that, The purity of the lanthanum compound is 4N or above, and the lanthanum compound includes lanthanum oxide and lanthanum nitrate.

3. A preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatographic method according to claim 1, characterized in that: The phosphonic acid extractant is P507 or a mixture of P507 and 5% - 50% of TBP.

4. A preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatography method according to claim 1, characterized in that: In step S2, the carrier includes any one of porous silicon-based polymers and macroporous adsorption resin D101.

5. A preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatography method according to claim 4, characterized in that: The ratio of the extractant to the carrier is 1:1 - 5.

6. The preparation method of ultra-high purity lanthanum oxide by using a single chromatographic column method according to claim 1, characterized in that: In step S4, the column length of the chromatographic column is 30 - 100 cm, and the diameter: column length = 1:5 - 60.

7. A preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatography method according to claim 1, characterized in that: In step S7, the molar ratio of oxalate ions to lanthanum ions is 1:1.5 - 2.

1.

8. A preparation method for preparing ultra-high purity lanthanum oxide by using a single-column chromatography method according to claim 1, characterized in that: Wash the lanthanum oxalate precipitate obtained in step S6 alternately with ethanol and ultrapure water.

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