Method for purifying iminodipropionic acid

Abstract

The invention relates to the technical field of iminodipropionic acid production, and discloses a method for purifying iminodipropionic acid, which comprises the following steps: (1) removing an organic solvent in a mother liquor containing iminodipropionic acid, and mixing the obtained product with water to obtain a mixed aqueous solution; (2) contacting the mixed aqueous solution with anion exchange resin, eluting the anion exchange resin with a first elution solution, and eluting the anion exchange resin with a second elution solution and a third elution solution in sequence to obtain a first solution and an iminodipropionic acid solution in sequence; (3) carrying out post-treatment on the iminodipropionic acid solution to obtain iminodipropionic acid; wherein the pH value of the second elution solution is 8-9.5; the pH value of the third elution solution is 10 to 14. The method is high in recovery rate, and the purity of the iminodipropionic acid product is high; and when the mother liquor contains the beta-alanine, the beta-alanine can be recovered, and the yield of the beta-alanine is improved.

Description

Technical Field

[0001] The invention relates to the technical field of producing iminodipropionic acid, and in particular to a method for purifying iminodipropionic acid. Background Art

[0002] The distilled liquor produced during the β-alanine production process contains a significant amount of β-alanine (approximately 20 wt%) and iminomalonic acid (approximately 18 wt%). During the β-alanine production process, crystallization and filtration produce a primary crystallization mother liquor. This primary crystallization mother liquor is then concentrated, added with methanol, and then subjected to secondary crystallization and filtration to produce the distilled liquor. Currently, the distilled liquor is processed by directly recovering the solvent, then bagging and incinerating it. This is costly and leaves some β-alanine unrecovered, increasing production costs. Therefore, the high β-alanine content in the distilled liquor can be recycled and reused. The iminodipropionic acid (CAS number 505-47-5; also known as calcium pantothenate 05, calcium pantothenate Z05, calcium pantothenate impurity F, and calcium pantothenate impurity 3) impurity in the mother liquor can be used as an impurity standard or as a raw material for the production of other products, placing high demands on the purity of the iminodipropionic acid.

[0003] Therefore, there is an urgent need for a method for purifying iminodipropionic acid with safe reagents, environmentally friendly process, easy process scale-up, simple operation, low cost and high yield. Summary of the Invention

[0004] The present invention aims to overcome the problems in the prior art of low yield and low purity of the purified iminodipropionic acid, and to provide a method for purifying iminodipropionic acid. The method has a high recovery rate and the purity of the iminodipropionic acid product is high. Furthermore, when β-alanine is contained in the mother liquor, the β-alanine can be recovered, thereby improving the yield of the β-alanine.

[0005] In order to achieve the above object, the present invention provides a method for purifying iminodipropionic acid, wherein the method comprises:

[0006] (1) removing the organic solvent from the mother liquor containing iminodipropionic acid, and mixing the obtained product with water to obtain a mixed aqueous solution;

[0007] (2) after the mixed aqueous solution is brought into contact with the anion exchange resin, the anion exchange resin is eluted with a first elution solution, and then the anion exchange resin is eluted with a second elution solution and a third elution solution in sequence to obtain a first solution and an iminodipropionic acid solution in sequence;

[0008] (3) the iminodipropionic acid solution is post-treated to obtain iminodipropionic acid;

[0009] The pH value of the second eluent is 8-9.5; the pH value of the third eluent is 10-14.

[0010] Through the above technical solution, the method for purifying iminodipropionic acid provided by the present invention has the following beneficial effects.

[0011] The present invention brings a mixed aqueous solution containing iminodipropionic acid into contact with an anion exchange resin, then uses a first elution solution to elute the anion exchange resin to remove impurities, i.e., weakly bound substances. The anion exchange resin is then sequentially eluted with a second elution solution and a third elution solution to obtain a first solution and an iminodipropionic acid solution, respectively. Thus, a high-purity iminodipropionic acid product can be obtained, and the method has a high recovery rate. Furthermore, the method of the present invention has the advantages of being easily industrialized, simple to operate, low cost, and having minimal environmental damage.

[0012] Furthermore, when the mother liquor contains β-alanine, the first solution obtained after elution with the second elution solution contains a higher content of β-alanine, which can further recover β-alanine, improve the yield of β-alanine, and the β-alanine product has a higher purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the liquid chromatography spectrum of iminodipropionic acid of Example 4. DETAILED DESCRIPTION

[0014] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0015] The present invention provides a method for purifying iminodipropionic acid, characterized in that the method comprises:

[0016] (1) removing the organic solvent from the mother liquor containing iminodipropionic acid, and mixing the obtained product with water to obtain a mixed aqueous solution;

[0017] (2) after the mixed aqueous solution is brought into contact with the anion exchange resin, the anion exchange resin is eluted with a first elution solution, and then the anion exchange resin is eluted with a second elution solution and a third elution solution in sequence to obtain a first solution and an iminodipropionic acid solution in sequence;

[0018] (3) the iminodipropionic acid solution is post-treated to obtain iminodipropionic acid;

[0019] The pH value of the second elution solution is 8-9.5; the pH value of the third elution solution is 10-14.

[0020] The present invention brings a mixed aqueous solution containing iminodipropionic acid into contact with an anion exchange resin, then uses a first elution solution to elute the anion exchange resin to remove impurities, i.e., weakly bound substances. The anion exchange resin is then sequentially eluted with a second elution solution and a third elution solution to obtain a first solution and an iminodipropionic acid solution, respectively. Thus, a high-purity iminodipropionic acid product can be obtained, and the method has a high recovery rate. Furthermore, the method of the present invention has the advantages of being easily industrialized, simple to operate, low cost, and having minimal environmental damage.

[0021] Furthermore, when the pH values of the second elution solution and the third elution solution meet the above range, impurities weakly bound to the anion exchange resin can be removed, which is beneficial to improving the purity of iminodipropionic acid; at the same time, it is beneficial to remove iminodipropionic acid bound to the anion exchange resin, thereby improving the yield of iminodipropionic acid.

[0022] In the present invention, the source of the mother liquor containing iminodipropionic acid includes, but is not limited to, the di-sperm mother liquor from the β-alanine production process, or a solution containing similar components obtained during the synthesis of other materials using β-alanine as a raw material. For example, using acrylic acid and aqueous ammonia as substrates, a crude β-alanine solution is obtained by the action of an aminotransferase. This solution is then decolorized and impurity-removed using activated carbon to obtain a high-purity β-alanine solution. After concentration and cooling, the solution is filtered to obtain a primary mother liquor. The primary mother liquor is then concentrated, methanol is added as a solvent to precipitate solids, and the secondary mother liquor is filtered to obtain a secondary mother liquor. Both the primary and secondary mother liquors can be used as the mother liquor containing iminodipropionic acid.

[0023] According to the present invention, the content of the iminodipropionic acid in the mother liquor is 10-30 wt%.

[0024] Furthermore, in the mother liquor, the content of the iminodipropionic acid is 15-25 wt%.

[0025] According to the present invention, the mother liquor further comprises β-alanine.

[0026] In the present invention, when the mother liquor contains β-alanine, the first solution obtained after elution with the second elution solution contains a higher content of β-alanine, which can further recover β-alanine, improve the yield of β-alanine, and the β-alanine product has a higher purity.

[0027] The β-alanine recovery method comprises: directly adding a solution containing β-alanine to a pre-crystallization solution, i.e., the above-mentioned crude β-alanine solution, or adding the solution to a β-alanine solution after decolorization and impurity removal by activated carbon, and concentrating and cooling the solution to obtain β-alanine.

[0028] According to the present invention, the content of β-alanine in the mother liquor is 10-30 wt%.

[0029] Furthermore, the content of β-alanine in the mother liquor is 18-28 wt%.

[0030] In the present invention, the method for removing the organic solvent in step (1) is not particularly limited, and the organic solvent can be removed by conventional technical means in the art. For example, the organic solvent in the mother liquor can be at least one of methanol, ethanol and isopropanol. Preferably, the organic solvent in the mother liquor containing iminodipropionic acid is removed by vacuum distillation. Preferably, the temperature of the vacuum distillation is 30-70°C. Preferably, the vacuum degree is 0.09-0.1MPa.

[0031] In the present invention, in step (1), the mother liquor further comprises at least one of acrylic acid, β-alanyl β-alanine and water.

[0032] In the present invention, there is no particular limitation on the contents of acrylic acid, β-alanyl-β-alanine, water, and the organic solvent in the mother liquor. Preferably, in the mother liquor, the content of acrylic acid is 5-25wt%, the content of β-alanyl-β-alanine is 0-10wt%, the content of the organic solvent is 20-50wt%, and the content of water is 0-5wt%. More preferably, in the mother liquor, the content of acrylic acid is 8-15wt%, the content of β-alanyl-β-alanine is 1-5wt%, the content of the organic solvent is 30-40wt%, and the content of water is 1-3wt%.

[0033] In the present invention, the mother liquor may contain a small amount of unknown impurities, and the impurity content is less than or equal to 2 wt %, which can be ignored.

[0034] According to the present invention, in step (1), the mass ratio of the product to water is 1:2-10.

[0035] In the present invention, when the mass ratio of the product to water satisfies the above range, it is beneficial to improve the recovery rate of iminodipropionic acid and improve the purity of iminodipropionic acid.

[0036] Furthermore, in step (1), the mass ratio of the product to water is 1:3-5.

[0037] According to the present invention, in step (2), the contact conditions include: the loading flow rate of the mixed aqueous solution is 1-10 BV / h, and the loading amount of the mixed aqueous solution is 10-300 mg / mL resin based on the mass of iminodipropionic acid.

[0038] In the present invention, when the contact conditions meet the above range, it is beneficial to improve the recovery rate of iminodipropionic acid and improve the purity of iminodipropionic acid.

[0039] Furthermore, in step (2), the contact conditions include: the loading flow rate of the mixed aqueous solution is 5-9 BV / h, and the loading amount of the mixed aqueous solution is 50-150 mg / mL resin based on the mass of iminodipropionic acid.

[0040] According to the present invention, the contact temperature is 5-35°C.

[0041] Furthermore, the contact temperature is 10-25°C.

[0042] According to the present invention, in step (2), the skeleton of the anion exchange resin is a styrene-divinylbenzene copolymer and / or an acrylic acid polymer.

[0043] In the present invention, the anion exchange resin is a strongly basic anion exchange resin and / or a weakly basic anion exchange resin.

[0044] In the present invention, the anion exchange resin with a styrene-divinylbenzene copolymer as a backbone may be at least one of D202 resin, D315 resin, and D301 resin. In the present invention, the anion exchange resin with an acrylic acid as a backbone may be LX-6703 resin.

[0045] In the present invention, the pretreatment method of anion exchange resin is not particularly limited, and a pretreatment method conventional in the art can be adopted. In order to further improve the recovery rate of iminodipropionic acid and improve the purity of iminodipropionic acid, according to a preferred embodiment of the present invention, the pretreatment method comprises: after using an alkaline solution to clean the anion exchange resin, the anion exchange resin is then cleaned with water until the pH value of the water is weakly alkaline (for example, the pH value of weakly alkaline can be 7-8). Preferably, the alkali content of the alkaline solution is 3-5wt%. Preferably, the alkali in the alkaline solution is sodium hydroxide and / or potassium hydroxide.

[0046] In the present invention, the pH of the first eluent is neutral, for example, the pH may be 6.5-7.5.

[0047] Furthermore, the pH value of the second elution solution is 8.5-9.

[0048] Furthermore, the pH value of the third elution solution is 11-13.

[0049] In the present invention, when at least one of the first elution solution, the second elution solution and the third elution solution satisfies the above range, the recovery rate of iminodipropionic acid and the purity of iminodipropionic acid can be further improved.

[0050] According to the present invention, in step (2), the flow rate of the first elution solution is 1-10 BV / h.

[0051] According to the present invention, the dosage of the first elution solution is 0.5-5 BV.

[0052] According to the present invention, in step (2), the flow rate of the second elution solution is 1-10 BV / h.

[0053] According to the present invention, the usage of the second elution solution is 1-10 BV.

[0054] According to the present invention, the flow rate of the third elution solution is 1-10 BV / h.

[0055] According to the present invention, the usage of the third elution solution is 1-10 BV.

[0056] In the present invention, when the flow rate and the amount of the first elution solution, the second elution solution, and the third elution solution meet the above ranges, it is not only beneficial to improve the yield and purity of β-alanine, but also beneficial to improve the recovery rate of iminodipropionic acid and improve the purity of iminodipropionic acid.

[0057] Furthermore, in step (2), the flow rate of the first elution solution is 5-8 BV / h.

[0058] Furthermore, the dosage of the first elution solution is 1-2 BV.

[0059] Furthermore, in step (2), the flow rate of the second elution solution is 5-8 BV / h.

[0060] Furthermore, the amount of the second elution solution is 2-4 BV.

[0061] Furthermore, the flow rate of the third elution solution is 5-8 BV / h.

[0062] Furthermore, the dosage of the third elution solution is 3-5 BV.

[0063] According to the present invention, in step (2), the first elution solution is an inorganic salt solution.

[0064] According to the present invention, the inorganic salt in the inorganic salt solution is selected from at least one of sodium chloride, potassium chloride, sodium sulfate, potassium sulfate and ammonium sulfate.

[0065] In the present invention, when the above-mentioned inorganic salts are used, it is beneficial to wash away some of the weakly bound substances, such as removing β-alanyl β-alanine in the mother liquor.

[0066] In the present invention, there is no particular limitation on the concentration of the inorganic salt solution, as long as the pH values of the first elution solution, the second elution solution, and the third elution solution meet their respective requirements. For example, the concentration of the inorganic salt solution is 0.1 wt%-2 wt%.

[0067] Furthermore, the inorganic salt in the inorganic salt solution is sodium chloride and / or sodium sulfate.

[0068] According to the present invention, the second elution solution is selected from at least one of a tris(hydroxymethyl)aminomethane-phosphate solution, a borax-sodium hydroxide solution and a sodium carbonate-sodium bicarbonate solution.

[0069] According to the present invention, the third elution solution is sodium carbonate-sodium hydroxide, ammonia water-ammonium chloride solution, or disodium hydrogen phosphate-sodium hydroxide solution.

[0070] In the present invention, when the second elution solution and / or the third elution solution adopts the above-mentioned solution, it is beneficial to elute and separate β-alanine and iminodipropionic acid, thereby improving the recovery rate and purity of β-alanine and iminodipropionic acid.

[0071] Furthermore, the second elution solution is selected from tris-phosphate solution and / or sodium carbonate-sodium bicarbonate solution.

[0072] Furthermore, the third elution solution is an ammonia water-ammonium chloride solution and / or a disodium hydrogen phosphate-sodium hydroxide solution.

[0073] In the present invention, there is no particular limitation on the concentrations of the second and third eluents, as long as the pH values of the second and third eluents meet their respective requirements. For example, the pH value of the second or third eluents can be adjusted by adjusting the ratio of the two raw materials in the second or third eluents. For example, the concentration of the second or third eluents can each independently be 0.5-5 wt%.

[0074] In the present invention, before replacing the elution solution, the anion exchange resin can be rinsed with clean water to rinse out the residual substances in the anion exchange resin. For example, step (2) includes: after contacting the mixed aqueous solution with the anion exchange resin, washing the mixed aqueous solution remaining in the anion exchange resin with water.

[0075] According to the present invention, in step (3), the post-treatment includes adjusting the pH value of the iminodipropionic acid solution to neutral, concentrating and recrystallizing.

[0076] In the present invention, there is no particular limitation on the method for adjusting the pH value, and the pH value can be adjusted using conventional methods in the art.

[0077] According to the present invention, the solvent used in the recrystallization is a C1-C4 monohydric alcohol.

[0078] In the present invention, there is no particular limitation on the specific type of monohydric alcohol. Preferably, the solvent used in the recrystallization is selected from at least one of methanol, ethanol and isopropanol.

[0079] The present invention will be described in detail below through examples.

[0080] The content of iminodipropionic acid in the iminodipropionic acid product: dissolve the iminodipropionic acid crystals (1:10) in water, dilute 10 times, use a C18 chromatographic column as the stationary phase, a mixed solution of methanol and water as the mobile phase, and a 210nm ultraviolet wavelength detector A for analytical detection. Use commercially available iminodipropionic acid solid as the standard to quantitatively identify the content of iminodipropionic acid.

[0081] Yield of iminodipropionic acid: The mass of the prepared iminodipropionic acid crystals was weighed and the yield of iminodipropionic acid was calculated according to the following formula.

[0082]

[0083] β-Alanine yield: The mass of the prepared β-alanine crystals was weighed and the β-alanine yield was calculated according to the following formula.

[0084]

[0085] All raw materials not explicitly described in the Examples and Comparative Examples are commercially available.

[0086] Preparation Example

[0087] Preparation of a mother liquor containing iminodipropionic acid: The mother liquor containing iminodipropionic acid is prepared from the di-scented mother liquor from the β-alanine production process. Specifically, a crude β-alanine solution is obtained by reacting acrylic acid and ammonia with β-alanine aminotransferase, using a molar ratio of acrylic acid, ammonia, and aminotransferase of 1:2:0.001, and the reaction temperature is 35°C for 25 hours. The resulting crude β-alanine solution is decolorized with activated carbon and adsorbed with a macroporous resin to remove impurities, resulting in a β-alanine solution. After concentration and cooling, the mother liquor is filtered to obtain a single-scented mother liquor. Methanol is then added to the concentrated mother liquor to precipitate solids, which are then filtered to obtain a di-scented mother liquor containing iminodipropionic acid. In the mother liquor, the content of iminodipropionic acid is 22wt%, the content of β-alanine is 25wt%; the content of acrylic acid is 8wt%; the content of β-alanylβ-alanine is 3wt%; the content of methanol is 38wt%; the content of water is 3wt%, and the remaining content of less than 1wt% is a small amount of unknown impurities.

[0088] Example 1

[0089] (1) Methanol is removed from the mother liquor containing iminodipropionic acid by vacuum distillation (the vacuum distillation temperature is 40°C and the vacuum degree is 0.1 MPa), and the obtained product is mixed with water (the mass ratio of the product to water is 1:3) to obtain a mixed aqueous solution.

[0090] (2) D202 strong basic anion exchange resin (styrene-divinylbenzene copolymer as the backbone, anion exchange capacity of 300 mg / mL) was loaded into the column. Residual impurities in the resin were cleaned with 4 wt% sodium hydroxide, and the residual alkali was removed by washing with clean water until the pH value of the water was 8. 200 g of the mixed aqueous solution was pumped in (the mixed aqueous solution was loaded at a flow rate of 8 BV / h, the loading amount was 100 mg / mL of resin, and the temperature was 20°C). Residual mother liquor was removed by top washing with clean water.

[0091] 300 g of the first elution solution was used to remove weakly bound substances, wherein the first elution solution was a 0.3 wt % sodium sulfate solution with a pH of 7. The flow rate of the first elution solution was 6 BV / h, and the amount of the first elution solution was 1 BV of resin.

[0092] A second elution solution is used for elution to obtain a first solution (containing β-alanine); wherein the second elution solution is a 1wt% sodium carbonate-sodium bicarbonate solution with a pH of 8.5, a flow rate of the second elution solution is 7BV / h, and the amount of the second elution solution is 2BV of resin.

[0093] 200 g of a third elution solution was circulated for washing to obtain an iminodipropionic acid solution. The third elution solution was a 3 wt% ammonia-ammonium chloride solution with a pH of 13. The flow rate of the second elution solution was 6 BV / h, and the amount of the second elution solution used was 4 BV of resin. The remaining iminodipropionic acid solution was then top-washed with clean water.

[0094] (3) Hydrochloric acid (concentration of 32 wt%) was added to the iminodipropionic acid solution to adjust the pH to neutral, and after concentrating to remove 70 wt% of water, methanol solution was added to precipitate iminodipropionic acid crystals.

[0095] The content of iminodipropionic acid in the iminodipropionic acid crystals was measured to be 94 wt %, and the yield was 62%.

[0096] (4) The first solution obtained in step (2) was added to the β-alanine solution obtained in the preparation example after decolorization by activated carbon and adsorption by macroporous resin to remove impurities (the mass ratio of the first solution to the β-alanine solution was 1:10), and the mixture was concentrated and cooled to obtain β-alanine crystals. The β-alanine yield in the mother liquor was 65%, and the β-alanine content in the product was 55 wt%.

[0097] Examples 2-7

[0098] The mother liquor containing iminodipropionic acid was purified according to the method of Example 1, except that the parameters in step (2) are shown in Table 1, and the content and yield of iminodipropionic acid are shown in Table 1.

[0099] Comparative Example 1

[0100] The mother liquor containing iminodipropionic acid was purified according to the method of Example 1, except that in step (2), after 200 g of the mixed aqueous solution was pumped in, 200 g of a 4 wt% sodium hydroxide solution was directly used for circulation washing. The content and yield of iminodipropionic acid are shown in Table 1.

[0101] Comparative Examples 2-5

[0102] The mother liquor containing iminodipropionic acid was purified according to the method of Example 1, except that the parameters in step (2) are shown in Table 1, and the content and yield of iminodipropionic acid are shown in Table 1. The content and yield of iminodipropionic acid are shown in Table 1.

[0103] Table 1

[0104]

[0105] Table 1

[0106]

[0107]

[0108] As can be seen from the results in Table 1, the method of the present invention is used to recover iminodipropionic acid from a mother liquor containing iminodipropionic acid. Under the premise of having a good yield, the purity of the obtained iminodipropionic acid crystals is higher. Simultaneously, when the mother liquor contains β-alanine, high-purity β-alanine can be obtained simultaneously. The method of the present invention can recycle the discarded mother liquor containing iminodipropionic acid (diprine mother liquor), thereby reducing waste of resources.

[0109] pass Figure 1 This is the liquid chromatography spectrum of the iminodipropionic acid crystals obtained in Example 4.

[0110] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A method for purifying iminodipropionic acid, characterized in that, The method comprises: (1) removing the organic solvent from the mother liquor containing iminodipropionic acid, and mixing the obtained product with water to obtain a mixed aqueous solution; (2) after the mixed aqueous solution is brought into contact with the anion exchange resin, the anion exchange resin is eluted with a first elution solution, and then the anion exchange resin is eluted with a second elution solution and a third elution solution in sequence to obtain a first solution and an iminodipropionic acid solution in sequence; (3) the iminodipropionic acid solution is post-treated to obtain iminodipropionic acid; The pH value of the second elution solution is 8-9.5; the pH value of the third elution solution is 10-14.

2. The method according to claim 1, wherein In step (1), the content of the iminodipropionic acid in the mother liquor is 10-30 wt%, preferably 15-25 wt%; Preferably, the mother solution further comprises β-alanine; Preferably, the content of β-alanine in the mother liquor is 10-30 wt%, preferably 18-28 wt%.

3. The method according to claim 1 or 2, wherein: In step (1), the mass ratio of the product to water is 1:2-10, preferably 1:3-5.

4. The method according to any one of claims 1 to 3, wherein: In step (2), the contact conditions include: the loading flow rate of the mixed aqueous solution is 1-10 BV / h, and the loading amount of the mixed aqueous solution is 10-300 mg / mL resin based on the mass of iminodipropionic acid; preferably, the loading flow rate of the mixed aqueous solution is 5-9 BV / h, and the loading amount of the mixed aqueous solution is 50-150 mg / mL resin based on the mass of iminodipropionic acid; Preferably, the contacting temperature is 5-35°C.

5. The method according to any one of claims 1 to 4, wherein: In step (2), the skeleton of the anion exchange resin is a styrene-divinylbenzene copolymer and / or an acrylic acid polymer.

6. The method according to any one of claims 1 to 5, wherein: In step (2), the pH value of the second elution solution is 8.5-9; Preferably, the pH value of the third elution solution is 11-13.

7. The method according to any one of claims 1 to 6, wherein: In step (2), the flow rate of the first elution solution is 1-10 BV / h, preferably 5-8 BV / h; Preferably, the amount of the first elution solution is 0.5-5BV, preferably 1-2BV; Preferably, in step (2), the flow rate of the second elution solution is 1-10 BV / h, preferably 5-8 BV / h; Preferably, the amount of the second elution solution is 1-10 BV, preferably 2-4 BV; Preferably, in step (2), the flow rate of the third elution solution is 1-10 BV / h, preferably 5-8 BV / h; Preferably, the amount of the third elution solution is 1-10 BV, preferably 3-5 BV.

8. The method according to any one of claims 1 to 7, wherein: In step (2), the first elution solution is an inorganic salt solution; Preferably, the inorganic salt in the inorganic salt solution is selected from at least one of sodium chloride, potassium chloride, sodium sulfate, potassium sulfate and ammonium sulfate, preferably sodium chloride and / or sodium sulfate.

9. The method according to any one of claims 1 to 8, wherein: The second elution solution is selected from at least one of a tris(hydroxymethyl)aminomethane-phosphate solution, a borax-sodium hydroxide solution, and a sodium carbonate-sodium bicarbonate solution; preferably a tris(hydroxymethyl)aminomethane-phosphate solution and / or a sodium carbonate-sodium bicarbonate solution; Preferably, the third elution solution is sodium carbonate-sodium hydroxide, ammonia water-ammonium chloride solution, disodium hydrogen phosphate-sodium hydroxide solution; preferably ammonia water-ammonium chloride solution and / or disodium hydrogen phosphate-sodium hydroxide solution.

10. The method according to any one of claims 1 to 9, wherein: In step (3), the post-treatment includes adjusting the pH value of the iminodipropionic acid solution to neutral, concentrating and recrystallizing; Preferably, the solvent used in the recrystallization is a C1-C4 monohydric alcohol.

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