A modified resin for selective separation of lithium isotopes and a preparation method and a separation method thereof

Abstract

The application discloses a modified resin for lithium isotope selective separation and a preparation method and a separation method thereof, and relates to the technical field of isotope separation; the method is as follows: after the resin is soaked in an organic solvent, the resin is washed and dried to obtain pretreated resin; the pretreated resin, a crown ether functional monomer and an initiator are added into an organic solvent, and a reaction product obtained after reaction under atmosphere protection is washed and dried to obtain grafted resin; the grafted resin is added into an alkaline solution with an alkali concentration of 1-2 mol / L or an acidic solution with an acid concentration of 1-3 mol / L to react, and then washed and dried to obtain porous resin; the porous resin and a silane coupling agent are added into an ethanol solution to react, and then washed and dried to obtain the modified resin; the three-step modification method of functional grafting, pore control and surface modification is adopted, the crown ether functional monomer is allowed to form a complex with lithium ions, and the single-stage separation coefficient is improved.

Description

Technical Field

[0001] This invention relates to the field of isotope separation technology, specifically to a modified resin for selective separation of lithium isotopes and its preparation and separation methods. Background Technology

[0002] Lithium isotopes have irreplaceable strategic value in the nuclear industry and new energy fields: 6 Li is a key raw material for tritium breeding in nuclear fusion reactions, with a thermal neutron absorption cross section as high as 940 Ω. 7 Due to its excellent chemical stability and radiation resistance, lithium is widely used in nuclear reactor coolants and high-end lithium battery electrolytes. With the accelerated breakthroughs in global nuclear fusion research and the booming development of the new energy industry, the market demand for high-purity lithium isotopes continues to rise, making the development of efficient, environmentally friendly, and scalable lithium isotope separation technology an urgent need for the industry.

[0003] Currently, lithium isotope separation technology has formed a diversified development pattern, mainly including core technology paths such as chemical exchange, electromagnetic separation, membrane separation, and resin adsorption. However, each technology faces unavoidable limitations in practical applications, hindering the industry's development. Among them, chemical exchange is the current mainstream industrial route, represented by lithium amalgam exchange, with a single-stage separation coefficient of 1.05-1.08. However, the process requires multiple stages in series, resulting in high equipment investment and energy consumption, and it relies on toxic media such as mercury and ammonia, making it difficult to balance economic efficiency and environmental protection. Although electromagnetic separation has a separation coefficient as high as 1.2, it requires extremely high equipment precision and has extremely low production capacity, making it only suitable for small-batch preparation in laboratories or military applications, and unable to meet the needs of large-scale production. Membrane separation, as a new technology, has a simple process and low energy consumption; however, the separation coefficient of existing membrane materials is generally below 1.04, with insufficient selectivity, and the membrane surface is prone to lithium salt deposition and blockage, with a continuous operating cycle of less than 72 hours. In addition, the preparation cost is high, making large-scale application economically unsound.

[0004] Resin adsorption has become a research hotspot in the field of lithium isotope separation in recent years due to its advantages such as simple operation, low equipment requirements, and environmental friendliness. However, existing technologies have not yet overcome three major bottlenecks: First, the separation coefficient is low, with most products having a single-stage separation coefficient of less than 1.03, requiring dozens of stages in series to achieve the purity required for industrial applications, which increases process complexity and cost. Second, the adsorption capacity is limited, with existing resins generally having an adsorption capacity of less than 100 μmol / g, resulting in low processing efficiency and difficulty in meeting the needs of large-scale raw material processing. Third, the cycle stability is poor, with functional groups on the resin surface easily detaching during repeated adsorption-elution processes, leading to rapid degradation of separation performance and making it difficult to meet industrial requirements. Summary of the Invention

[0005] The present invention aims to solve the problems of low separation coefficient, limited adsorption capacity and poor cycle stability of existing resins used for selective separation of lithium isotopes.

[0006] To address the aforementioned problems, in a first aspect, the present invention provides a method for preparing a modified resin for the selective separation of lithium isotopes, comprising the following steps: Step 1: After soaking the resin in an organic solvent, wash and dry it to obtain the pretreated resin; Step 2: Add the pretreated resin, crown ether functional monomer and initiator to an organic solvent and react at 80-85℃ for 12-14h under a protective atmosphere. The reaction product is washed and dried to obtain the grafted resin. The mass ratio of the resin in Step 1, the crown ether functional monomer and initiator in Step 2 is 1:(1-1.2):(0.012-0.0144). Step 3: Add the grafted resin to an alkaline solution with an alkali concentration of 1-2 mol / L or an acidic solution with an acid concentration of 1-3 mol / L and react for 3-5 hours. After washing and drying, a porous resin is obtained. Step 4: Add the porous resin and silane coupling agent to an ethanol solution at a mass ratio of 100:(0.7-0.8) and react. After washing and drying, the modified resin is obtained.

[0007] Preferably, the resin is any one of cation exchange resin, polyvinyl alcohol resin, polyvinyl alcohol resin, and styrene-divinylbenzene copolymer resin.

[0008] Preferably, in step 1, the organic solvent is toluene or xylene; the ratio of resin to organic solvent is 1g:5mL; and the soaking time is 18-24h.

[0009] Preferably, in step 2, the crown-containing ether functional monomer is any one of 4-propenylbenzo-15-crown-, dimethyl methylphosphonate, and vinylphosphonate monomers.

[0010] Preferably, in step 2, the initiator is any one of azobisisobutyronitrile, benzoyl peroxide, and ammonium persulfate; the organic solvent is any one of N,N-dimethylformamide and dimethyl sulfoxide; and the ratio of the pretreated resin to the organic solvent is 1 g: (5-6) mL.

[0011] Preferably, in step 3, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution; the acidic solution is any one of oxalic acid solution, citric acid solution, and phosphoric acid solution.

[0012] Preferably, in step 4, the silane coupling agent is 3-aminopropyltriethoxysilane; the concentration of the ethanol solution is 70 vol%; and the ratio of the porous resin to the ethanol solution is 1 g: 10 mL.

[0013] Secondly, the present invention provides a modified resin for selective separation of lithium isotopes, which is prepared by the method for preparing a modified resin for selective separation of lithium isotopes as described above.

[0014] Thirdly, the present invention also provides a separation method for the selective separation of lithium isotopes, characterized by comprising the following steps: S1. The modified resin for selective separation of lithium isotopes as described above is packed into an adsorption column, and the column is backwashed with deionized water. Then, at a constant temperature of 25-35°C, a lithium-containing feed solution is introduced into the adsorption column at a rate of 1-3 BV / h. The volume of the lithium-containing feed solution is 5-8 times the volume of the adsorption column. Adsorption is carried out at 30-35°C for 1-2.5 hours. The lithium-containing feed solution is a LiCl solution or a Li2SO4 solution with a pH of 6-8. S2. After adsorption is complete, eluent is introduced into the adsorption column for gradient elution. The volume of the eluent is 8-10 times the volume of the adsorption column. The eluent is collected in segments to obtain... 6 Li enrichment solution and 7 Li enrichment solution; wherein the eluent is a mixture of acid solution and chelating agent in a volume ratio of (7-12):1; the acid solution is a hydrochloric acid solution or sulfuric acid solution with a concentration of 0.1-0.5 mol / L, and the chelating agent is 1,2-cyclohexanediaminetetraacetic acid.

[0015] Preferably, in S2, the gradient elution includes a first-stage elution and a second-stage elution; the flow rate of the first-stage elution is 1-3 BV / h, the elution time is 1-2 h, and the eluted product is... 7 Li enrichment solution; the second stage elution flow rate was 0.5-2 BV / h, and the elution time was 2h, yielding Li enriched solution. 6 Li enrichment solution.

[0016] The method for preparing the modified resin for selective separation of lithium isotopes according to the present invention has, but is not limited to, the following beneficial effects compared with the prior art: After acid or alkali etching, the specific surface area of ​​the porous resin reaches 180-320 m². 2 / g provides ample adsorption sites for lithium ions, with an adsorption capacity as high as 163μmol / g, which is more than 60% higher than existing resins (generally below 100μmol / g). The treatment efficiency per unit volume of resin is greatly improved, making it suitable for large-scale continuous processing of lithium-containing raw materials. A protective layer is formed by surface modification with silane coupling agent, which effectively inhibits the shedding of crown ether functional groups. After 10 adsorption-desorption cycles, the separation performance decay rate is ≤5%, which is far superior to the defects of easy decay of existing resins. It fully meets the requirements of long-term continuous operation in industrial applications and can improve cycle stability. Moreover, the three-step modification method of functional grafting, pore control and surface modification enables the crown ether functional monomer to form a complex with lithium ions. Combined with the 20-60nm mesoporous structure to optimize mass transfer, the single-stage separation coefficient is improved. Attached Figure Description

[0017] The invention will now be further described with reference to the accompanying drawings.

[0018] Figure 1 This is a process flow diagram of the preparation of the modified resin for selective separation of lithium isotopes in Example 1 of the present invention. Figure 2 This is the infrared spectrum of the crownless ether characteristic peak of the pretreated resin in step 1 of Example 1 of the present invention; Figure 3 The image shows the infrared spectrum of the crownless ether characteristic peak of the grafted resin in step 2 of Example 1 of this invention. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0020] The terminology used in the embodiments of this application is for the purpose of describing particular implementations only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the implementations of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0021] It should be understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0022] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0023] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0024] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this application are commercially available or can be prepared using existing methods. For example, the specific types and sources of raw materials involved in the following examples and comparative examples are as follows: Styrene-divinylbenzene copolymer resin: crosslinking degree 65%, particle size 200-300μm, purchased from Mitsubishi Chemical; Xylene: Analytical grade (AR), purity ≥99.0%; purchased from Aladdin Reagent (Shanghai) Co., Ltd. Toluene: Analytical grade (AR), purity ≥99.5%; purchased from Sinopharm Chemical Reagent Co., Ltd. Deionized water: resistivity ≥ 18.2 MΩ cm (25℃); laboratory-made (prepared using an ultrapure water system); 4'-Vinylbenzo15-crown-5: reagent grade, purity ≥98%; purchased from Sinopharm Chemical Reagent Co., Ltd. Azobisisobutyronitrile: reagent grade, purity ≥98%; purchased from Aladdin Reagent (Shanghai) Co., Ltd. N,N-Dimethylformamide: reagent grade, purity ≥98%; purchased from Sinopharm Chemical Reagent Co., Ltd. Ethanol: Anhydrous ethanol (99.7%) / 70-80 vol% ethanol; purchased from Sinopharm Chemical Reagent Co., Ltd. KOH solution (prepared from solid KOH): analytical grade, purity ≥96%; purchased from Sinopharm Chemical Reagent Co., Ltd. NaOH solution (prepared from solid NaOH): analytical grade, purity ≥96%; purchased from Sinopharm Chemical Reagent Co., Ltd. 3-Aminopropyltriethoxysilane: reagent grade, purity ≥97%; purchased from Aladdin Reagent (Shanghai) Co., Ltd. LiCl solution: analytical grade, purity ≥99%; purchased from Aladdin Reagent (Shanghai) Co., Ltd. HCl: analytical grade, concentration 36%–38%; purchased from Sinopharm Chemical Reagent Co., Ltd. H2SO4: analytical grade, concentration 98%; purchased from Sinopharm Chemical Reagent Co., Ltd. 1,2-Cyclohexanediaminetetraacetic acid: purchased from Sinopharm Chemical Reagent Co., Ltd.; LiNO3 solution: reagent grade, purity ≥99%, purchased from Aladdin Reagent (Shanghai) Co., Ltd.

[0025] Example 1

[0026] This embodiment discloses a modified resin for the selective separation of lithium isotopes. Please refer to [link to relevant documentation]. Figure 1 It is prepared according to the following steps: Step 1: Add 100g of styrene-divinylbenzene copolymer resin to 500mL of xylene and soak for 24h. Filter, wash the obtained solid filter material with deionized water until neutral, and transfer to an oven to dry under vacuum at 80℃ for 5h to obtain pretreated resin. Detect the characteristic peaks of the pretreated resin to obtain... Figure 2 The infrared spectrum curve shown is from Figure 2 As can be seen, no crown ether characteristic peaks were observed in the pretreated resin; Step 2: Add the pretreated resin, 100g of 4'-vinylbenzo-15-crown-5, and 1.2g of azobisisobutyronitrile to 500mL of N,N-dimethylformamide. React at 85℃ for 12h under nitrogen protection. Filter and wash three times with ethanol. For the first wash, add 300mL of anhydrous ethanol and stir at room temperature for 20min on a magnetic stirrer, then filter. For the second wash, add 250mL of anhydrous ethanol and stir for 15min, then filter. For the third wash, add 200mL of anhydrous ethanol and stir for 10min, then filter until the washing filtrate is colorless and transparent, obtaining a solid filter material. Transfer this material to an oven and vacuum dry at 75℃ for 7h to obtain the grafted resin. Detect the characteristic peaks of the grafted resin to obtain... Figure 3 As shown in the infrared spectrum curve, the grafted resin exhibits the characteristic peak of crown ether, which indicates that the grafting of crown ether monomers was successful. Step 3: Add the obtained grafted resin to 800 mL of KOH solution at 65 °C and 1.5 mol / L, react at 65 °C for 3.5 h, filter, wash the obtained solid filter material with deionized water until neutral, and then transfer it to an oven to dry under vacuum at 80 °C for 5 h to obtain porous resin. Step 4: Take 50g of porous resin and 0.35g of 3-aminopropyltriethoxysilane and add them to a 70 vol% ethanol solution at 65℃. Stir at 200 rpm for 5 hours. After the reaction, use a 0.45μm polytetrafluoroethylene filter membrane and a pressure of 0.05-0.08MPa to filter while hot and collect the solid filter material. Then wash it three times with 70 vol% ethanol solution. The first time, add 300mL of ethanol solution and stir for 15min. The second time, add 250mL of ethanol solution and stir for 12min. The third time, add 200mL of ethanol solution and stir for 10min. Then filter until the washing filtrate shows no residual peak of 3-aminopropyltriethoxysilane (peak area ≤1000AU) when detected by high performance liquid chromatography (detection wavelength 210nm). Then transfer the washed solid filter material to a vacuum oven and vacuum dry it at -0.1MPa and 70℃ for 6 hours to obtain the modified resin.

[0027] Example 2

[0028] This embodiment discloses a modified resin for the selective separation of lithium isotopes. Please refer to [link to relevant documentation]. Figure 1 It is prepared according to the following steps: Step 1: 100g of styrene-divinylbenzene copolymer resin was added to 500mL of xylene and soaked for 20h. After filtration, the solid filter material obtained was washed with deionized water until neutral, and then transferred to an oven and vacuum dried at 78℃ for 5.5h to obtain pretreated resin. The characteristic peaks of the pretreated resin were detected to obtain... Figure 2 The infrared spectrum curve shown is from Figure 2 As can be seen, no crown ether characteristic peaks were observed in the pretreated resin; Step 2: Add the pretreated resin, 110g of 4'-vinylbenzo-15-crown-5, and 1.3g of azobisisobutyronitrile to 550mL of N,N-dimethylformamide. React at 82°C for 13h under nitrogen protection. Filter and wash with ethanol (washing method as in Example 1). The resulting solid filter material is then transferred to an oven and vacuum dried at 78°C for 6h to obtain the grafted resin. Detect the characteristic peaks of the grafted resin to obtain the following results: Figure 3 As shown in the infrared spectrum curve, the grafted resin exhibits the characteristic peak of crown ether, which indicates that the grafting of crown ether monomers was successful. Step 3: Add the obtained grafted resin to 800 mL of KOH solution at 65 °C and 1.5 mol / L, react at 65 °C for 3.5 h, filter, wash the obtained solid filter material with deionized water until neutral, and then transfer it to an oven to dry under vacuum at 80 °C for 5 h to obtain porous resin. Step 4: Take 50g of porous resin and 0.38g of 3-aminopropyltriethoxysilane and add them to an ethanol solution with a temperature of 65℃ and a concentration of 70 vol% to react for 5 hours. After filtration, wash and dry the solid filter material obtained by filtration (the filtration, washing and drying methods are the same as in Example 1) to obtain the modified resin.

[0029] Example 3

[0030] This embodiment discloses a modified resin for the selective separation of lithium isotopes. Please refer to [link to relevant documentation]. Figure 1 It is prepared according to the following steps: Step 1: Soak 100g of styrene-divinylbenzene copolymer resin in 500mL of toluene for 18h, filter, wash the obtained solid filter material with deionized water until neutral, transfer it to an oven and vacuum dry at 75℃ for 6h to obtain pretreated resin. Step 2: Add the pretreated resin, 120g of 4'-vinylbenzo15-crown-5 and 1.44g of azobisisobutyronitrile to 600mL of N,N-dimethylformamide, react at 80°C for 14h under nitrogen protection, filter, wash with ethanol (washing method is the same as in Example 1), and transfer the obtained solid filter material to an oven to be vacuum dried at 80°C for 5h to obtain the grafted resin. Step 3: Add the obtained grafted resin to 800 mL of NaOH solution at 65 °C and 1.5 mol / L, react at 65 °C for 4 h, filter, wash the obtained solid filter material with deionized water until neutral, and then transfer it to an oven to dry under vacuum at 80 °C for 5 h to obtain porous resin. Step 4: Take 50g of porous resin and 0.4g of 3-aminopropyltriethoxysilane and add them to an ethanol solution with a temperature of 65℃ and a concentration of 70 vol% to react for 5 hours. Filter the solution and wash and dry the solid filter material obtained by filtration (the filtration, washing and drying methods are the same as in Example 1) to obtain the modified resin.

[0031] Comparative Example 1

[0032] Compared with Example 1, the only difference is that in step 2, the amount of azobisisobutyronitrile used is increased to 1.56g, and the reaction time in an 80°C constant temperature water bath is shortened to 3h; the other steps and conditions are kept exactly the same, and the modified resin is finally obtained.

[0033] Comparative Example 2

[0034] Compared with Example 3, the only difference is that in step 1, the soaking time of the styrene-divinylbenzene copolymer resin in toluene is extended to 21 hours; the other steps and conditions are kept exactly the same, and the modified resin is finally obtained.

[0035] Comparative Example 3

[0036] Compared with Example 1, the only difference is that in step 4, the amount of 3-aminopropyltriethoxysilane used is increased to 0.41g, and the 70 vol% ethanol solution is replaced with a 69 vol% ethanol solution; the other steps and conditions are exactly the same, and the modified resin is finally obtained.

[0037] The modified resins of Examples 1-3 and Comparative Examples 1-3 were subjected to performance testing. The specific testing items and methods are as follows: Average pore size: Take 0.15g of each modified resin group and gently grind it with an agate mortar until the particle size is ≤100μm (avoid damaging the porous structure). Pack the sample tubes into quartz sample tubes. Place the sample tubes in a vacuum drying oven and dry them at 105℃ and -0.1MPa for 4h to completely remove moisture, residual ethanol, and organic solvents from the samples. Connect the pretreated sample tubes to the adsorption instrument and set the degassing program: 105℃, vacuum ≤1×10 -3 The sample was degassed for 3 hours to further remove adsorbed impurities from the sample surface. After degassed, the sample tube was placed in a liquid nitrogen cold trap (77.35 K) and high-purity nitrogen was introduced. Adsorption-desorption isotherms were measured within a relative pressure (P / P0) range of 0.01-0.995, with both adsorption and desorption rates set to 0.005 P / P0. min -1 The equilibration time for each pressure point is 10s; the BJH model is used to analyze the desorption branch data, fit the mesopore size distribution curve, and read the pore size value corresponding to the peak value of the curve, which is the average pore size of the sample; each sample is tested in parallel 3 times, and the average value is taken as the final result, with a relative standard deviation (RSD) ≤3%.

[0038] Specific surface area: Refer to GB / T 19587-2017 "Determination of specific surface area of ​​solid substances by gas adsorption BET method"; Crown ether loading: UV-Vis spectrophotometry, based on the characteristic absorption peaks of crown ethers.

[0039] The test results are listed in Table 1, as follows: Table 1

[0040] Analysis of the data in Table 1 shows that the average pore size of the modified resins in Examples 1-3 and Comparative Examples 1-3 is 38-44 nm, and the specific surface area is 245-283 m² / g, both meeting the mesoporous structure and specific surface area requirements set by this invention, indicating stable pore control process effects. Regarding crown ether loading, the examples have a loading of 0.62-0.68 mmol / g, while the comparative examples have a loading of 0.60-0.64 mmol / g, both achieving effective grafting of crown ether groups. However, the parameters of Examples 1-3 are superior, while the comparative examples, due to slightly inferior process fine-tuning parameters, exhibit better results. Overall, this verifies the feasibility and stability of the preparation method of the modified resin for selective separation of lithium isotopes according to this invention.

[0041] Example 4

[0042] This embodiment discloses a separation method for the selective separation of lithium isotopes, which is carried out according to the following steps: S1. The modified resin for selective separation of lithium isotopes from Example 1 was packed into an adsorption column with dimensions of Φ25×1200mm, and the column was backwashed with deionized water for 1 hour. A LiCl solution with pH=6.0 and a concentration of 0.4 mol / L was prepared, and the pH was adjusted to 5.5 with 0.1 mol / L HCl to serve as the lithium-containing feed solution. The lithium-containing feed solution was then introduced into the adsorption column at a flow rate of 1.0 BV / h under constant temperature, and adsorption was carried out at 35°C. The adsorption capacity was calculated to be 163 μmol / g. S2. After adsorption is complete, eluent (a mixture of 0.10 mol / L H2SO4 and 0.02 mol / L 1,2-cyclohexanediaminetetraacetic acid in a volume ratio of 12:1) is introduced into the adsorption column for first-stage elution and second-stage elution. The flow rate for the first-stage elution is 1 BV / h, and the elution time is 1 h. The eluted material is then collected. 7 Li enrichment solution; the second-stage elution flow rate was 0.5 BV / h, the elution time was 2h, and the elution was collected. 6 Li enrichment solution.

[0043] Example 5

[0044] This embodiment discloses a separation method for the selective separation of lithium isotopes, which is carried out according to the following steps: S1. The modified resin for selective separation of lithium isotopes from Example 2 was packed into an adsorption column with dimensions of Φ25×1200mm, and the column was backwashed with deionized water for 1 hour. A LiCl solution with pH=6.0 and a concentration of 0.3 mol / L was prepared, and the pH was adjusted to 5.5 with 0.1 mol / L HCl to serve as the lithium-containing feed solution. The lithium-containing feed solution was then introduced into the adsorption column at a flow rate of 1.2 BV / h under constant temperature, and adsorption was carried out at 30°C. The adsorption capacity was calculated to be 161 μmol / g. S2. After adsorption is complete, eluent (a mixture of 0.10 mol / L H2SO4 and 0.02 mol / L d 1,2-cyclohexanediaminetetraacetic acid in a volume ratio of 12:1) is introduced into the adsorption column for first-stage elution and second-stage elution. The flow rate for the first-stage elution is 1 BV / h, and the elution time is 1 h. The eluted material is collected. 7 Li enrichment solution; the second-stage elution flow rate was 0.5 BV / h, the elution time was 2h, and the elution was collected. 6 Li enrichment solution.

[0045] Example 6

[0046] Compared to Example 4, the only difference is that in S1, the modified resin for lithium isotope selective separation in Example 1 is replaced with the modified resin for lithium isotope selective separation in Example 3; all other steps and conditions remain exactly the same, ultimately yielding... 7 Li enrichment solution and 6 Li enrichment solution.

[0047] Comparative Example 4

[0048] Compared with Example 1, the only difference is that in S1, the lithium-containing raw material solution is replaced with a LiNO3 solution ( 6 Li abundance 7.48 at%), with other steps and conditions kept exactly the same, finally obtained 7 Li enrichment solution and 6 Li enrichment solution.

[0049] Comparative Example 5

[0050] Compared to Example 1, the only difference is that in S1, the flow rate of the lithium-containing feed solution introduced into the adsorption column at a constant temperature is reduced to 0.92 BV / h, while the adsorption temperature is increased to 36 °C. All other steps and conditions remain exactly the same, ultimately yielding... 7 Li enrichment solution and 6 Li enrichment solution.

[0051] Comparative Example 6

[0052] The modified resin for lithium isotope selective separation in Example 1 was replaced with the modified resin for lithium isotope selective separation in Comparative Example 1; all other steps and conditions remained exactly the same, and the final result was obtained. 7 Li enrichment solution and 6 Li enrichment solution.

[0053] Comparative Example 7

[0054] The modified resin for lithium isotope selective separation in Example 1 was replaced with the modified resin for lithium isotope selective separation in Comparative Example 2; all other steps and conditions remained exactly the same, and the final result was obtained. 7 Li enrichment solution and 6 Li enrichment solution.

[0055] Comparative Example 8

[0056] The modified resin for lithium isotope selective separation in Example 1 was replaced with the modified resin for lithium isotope selective separation in Comparative Example 3; all other steps and conditions remained exactly the same, and the final result was obtained. 7 Li enrichment solution and 6 Li enrichment solution.

[0057] Comparative Example 9

[0058] The modified resin used for selective separation of lithium isotopes in Example 1 was replaced with a common cation exchange resin (purchased from Anhui Samsung Resin Technology, model: gel-type highly cross-linked resin); all other steps and conditions were kept exactly the same, and the final result was... 7 Li enrichment solution and 6 Li enrichment solution.

[0059] The adsorption capacity in S1 and the adsorption capacity in S2 of Examples 4-6 and Comparative Examples 4-9 7 Li enrichment solution 7 Li abundance, 6 Li enrichment solution 6 The Li abundance, separation coefficient, and cycling performance of the modified resin were tested using the following methods: Adsorption capacity: Weigh 0.5 g of pretreated dry resin into 3 parallel samples and place them into 50 mL polytetrafluoroethylene centrifuge tubes; add 40 mL of 0.5 mol / L LiCl standard solution to each centrifuge tube. + (To ensure resin adsorption saturation), after sealing, place in a constant temperature water bath and shake at 25℃ and 150r / min for 24h (preliminary experiments verified that adsorption equilibrium was reached after 24h). After shaking, take the supernatant and filter it through a 0.22μm filter membrane. The remaining Li in the filtrate is determined by ICP-OES. +Concentration (Cresidue, mol / L); Take 40 mL of 0.5 mol / L LiCl standard solution, shake for 24 h under the same conditions, and determine the Lig concentration. + Concentration (Coriginal, mol / L), verifying the absence of Li. + Loss; Adsorption capacity Q (mmol / g) = (Coriginal - Cresidual) × V × 102 3 / m, where V is the solution volume (L) and m is the resin mass (g).

[0060] 7 Li / 6 Abundance of Li enrichment solution: Take the system after adsorption equilibrium in the adsorption capacity test, centrifuge (3000 r / min, 10 min), and separate the supernatant ( 7 Li enrichment solution, denoted as sample A) and resin phase ( 6 The Li-enriched phase (denoted as sample B) was added to sample B (resin phase) with 20 mL of 0.5 mol / L HCl eluent. The mixture was then incubated in a constant temperature water bath at 25°C and 150 rpm for 2 hours. After centrifugation, the supernatant was collected and diluted to 25 mL with ultrapure water. 6 Li enrichment solution (sample C); Sample A ( 7 The Li enrichment solution was directly diluted to 50 mL with ultrapure water to obtain the test solution; sample C was calibrated for Li by ICP-OES. + After concentration, dilute to 100 ng / mL (optimal concentration for MC-ICP-MS determination) and set aside; calibrate MC-ICP-MS using L-SVEC lithium isotope standard, optimizing instrument parameters (resolution, ionic strength, mass discrimination correction) until the RSD of the standard determination results is ≤0.1‰; sequentially determine blank solution (ultrapure water), L-SVEC standard solution, ... 7 Li enrichment solution (sample A) 6 Li enrichment solution (sample C), record each sample 6 Li and 7 The ionic intensity signal value of Li (I 6Li I 7Li Parallel determination: Each sample was measured 6 times in parallel, outliers were removed, and the average value was taken; 7 Li abundance β (%) = I 7Li / (I 6Li +I 7Li )×100%=100%-α; 6 Li abundance α (%) = I 6Li / (I 6Li +I 7Li )×100%; Single-stage separation coefficient: First, calculate the isotope ratio R (R=) from the abundance. 6 Li / 7Li): Resin phase ( 6 Li-enriched solution) Isotope ratio: Rresin = α1 / β1 (α1 = ... 6 Li abundance, β1= 7 Li abundance, all values ​​were measured for C in the sample; liquid phase ( 7 Li-enriched solution) Isotope ratio: Rliquid phase = α2 / β2 (α2 = ... 6 Li abundance, β2= 7 Li abundance (all values ​​were measured for sample A); single-stage separation coefficient α = Rresin / Rliquid phase; Cyclic performance: Take 5.0 g of dry resin and pack it into a polytetrafluoroethylene column (inner diameter 1.0 cm, packing height 10 cm) using the wet method. Wash the column with 0.2 mol / L HCl at a flow rate of 1.0 mL / min until the effluent is neutral to complete column equilibration. Then, feed 0.5 mol / L LiCl standard solution onto the column at a flow rate of 1.0 mL / min until the effluent contains Li... + The concentration of the eluent was the same as that of the loading solution (adsorption saturation), and the adsorption capacity was determined (method as before); 0.5 mol / L HCl eluent was loaded onto the column at a flow rate of 1.0 mL / min, the eluent was collected, and the adsorption capacity was determined. 6 Li / 7 Li abundance was used to calculate the single-stage separation coefficient; the column was washed with 1 mol / L HCl at a flow rate of 1.5 mL / min for 30 min, then washed with ultrapure water until neutral to restore the resin to its hydrogen form, completing regeneration; the above adsorption, elution, and regeneration process was repeated 10 times, and the adsorption capacity (Q) was measured in each cycle. n ) and single-stage separation coefficient (α) n (n is the number of cycles, n=1,2,3…10); the adsorption capacity (Q1) and single-stage separation coefficient (α1) of the first cycle are used as the initial reference values; adsorption capacity retention rate (%) = Q n / Q1×100%.

[0061] The test results are listed in Table 2, as follows: Table 2

[0062] Analysis of the data in Table 2 shows that the modified resins in Examples 4-6 and Comparative Examples 4-7 have adsorption capacities of 159–163 μmol / g. 7 Li and 6The Li enrichment abundances were 94.5–95.2 at% and 12.1–13.8 at%, respectively, with single-stage separation coefficients of 1.096–1.113. The performance degradation rate after 10 cycles was ≤5%. Among them, due to the optimized adjustment of parameters, Examples 4-6 showed better overall performance than Comparative Examples 4-7. In contrast, the traditional resin of Comparative Example 8 had an adsorption capacity of only 85 μmol / g, a significant reduction in isotope enrichment abundance and single-stage separation coefficient, and a performance degradation rate of ≥35% after 10 cycles. This fully demonstrates the performance advantages and cycle stability of the modified resin of this invention in lithium isotope separation.

[0063] The foregoing has described several embodiments of the present invention in detail, but these descriptions are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. A method for preparing a modified resin for the selective separation of lithium isotopes, characterized in that, Includes the following steps: Step 1: After soaking the resin in an organic solvent, wash and dry it to obtain the pretreated resin; Step 2: Add the pretreated resin, crown ether functional monomer and initiator to an organic solvent and react at 80-85℃ for 12-14h under a protective atmosphere. The reaction product is washed and dried to obtain the grafted resin. The mass ratio of the resin in Step 1, the crown ether functional monomer and initiator in Step 2 is 1:(1-1.2):(0.012-0.0144). Step 3: Add the grafted resin to an alkaline solution with an alkali concentration of 1-2 mol / L or an acidic solution with an acid concentration of 1-3 mol / L and react for 3-5 hours. After washing and drying, a porous resin is obtained. Step 4: Add the porous resin and silane coupling agent to an ethanol solution at a mass ratio of 100:(0.7-0.8) and react. After washing and drying, the modified resin is obtained. The resin is any one of cation exchange resin, polyvinyl alcohol resin, polyvinyl alcohol resin, and styrene-divinylbenzene copolymer resin.

2. The method for preparing the modified resin for selective separation of lithium isotopes according to claim 1, characterized in that, In step 1, the organic solvent is toluene or xylene; the ratio of resin to organic solvent is 1g:5mL; and the soaking time is 18-24h.

3. The method for preparing the modified resin for selective separation of lithium isotopes according to claim 1, characterized in that, In step 2, the crown-containing ether functional monomer is 4'-vinylbenzo15-crown-5.

4. The method for preparing the modified resin for selective separation of lithium isotopes according to claim 1, characterized in that, In step 2, the initiator is any one of azobisisobutyronitrile, benzoyl peroxide, and ammonium persulfate; the organic solvent is any one of N,N-dimethylformamide and dimethyl sulfoxide; and the ratio of the pretreated resin to the organic solvent is 1 g: (5-6) mL.

5. The method for preparing the modified resin for selective separation of lithium isotopes according to claim 1, characterized in that, In step 3, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution; The acidic solution is any one of oxalic acid solution, citric acid solution, and phosphoric acid solution.

6. The method for preparing the modified resin for selective separation of lithium isotopes according to claim 1, characterized in that, In step 4, the silane coupling agent is 3-aminopropyltriethoxysilane; the concentration of the ethanol solution is 70 vol%; and the ratio of the porous resin to the ethanol solution is 1 g: 10 mL.

7. A modified resin for the selective separation of lithium isotopes, characterized in that, It is prepared by the method for preparing the modified resin for selective separation of lithium isotopes according to any one of claims 1-6.

8. A separation method for the selective separation of lithium isotopes, characterized in that, Includes the following steps: S1. The modified resin for selective separation of lithium isotopes as described in claim 7 is packed into an adsorption column, and the column is backwashed with deionized water. Then, a lithium-containing raw material solution is introduced into the adsorption column at a rate of 1-3 BV / h at a constant temperature of 25-35°C. The volume of the lithium-containing raw material solution is 5-8 times the volume of the adsorption column. Adsorption is carried out at 30-35°C for 1-2.5 hours. The lithium-containing raw material solution is a LiCl solution or a Li2SO4 solution with a pH of 6-8. S2. After adsorption is complete, eluent is introduced into the adsorption column for gradient elution. The volume of the eluent is 8-10 times the volume of the adsorption column. The eluent is collected in segments to obtain... 6 Li enrichment solution and 7 Li enrichment solution; wherein the eluent is a mixture of acid solution and chelating agent in a volume ratio of (7-12):1; the acid solution is a hydrochloric acid solution or sulfuric acid solution with a concentration of 0.1-0.5 mol / L, and the chelating agent is 1,2-cyclohexanediaminetetraacetic acid.

9. The separation method for selective separation of lithium isotopes according to claim 8, characterized in that, In S2, the gradient elution includes a first-stage elution and a second-stage elution; the flow rate of the first-stage elution is 1-3 BV / h, the elution time is 1-2h, and the eluted product is... 7 Li enrichment solution; The second stage elution flow rate was 0.5-2 BV / h, and the elution time was 2 hours, yielding the desired elution result. 6 Li enrichment solution.

Images