An open-chain polyether ligand, a preparation method and application thereof in selective separation of strontium ions

Abstract

The application provides an open-chain polyether ligand, a preparation method and application thereof in selective separation of strontium ions, and belongs to the technical field of nuclear fuel reprocessing. The ligand is 1,14-diphenoxy-3,6,9,12-tetraoxatetradecane or 1,14-di(4-pentylphenoxy)-3,6,9,12-tetraoxatetradecane, which is prepared by nucleophilic substitution of phenol or 4-pentylphenol with p-xylene sulfonate pentanediol. The ligand and an organic solvent form a strontium ion extractant, which is used for selective complex extraction of Sr + In a strontium nitrate system. Preferred extraction conditions are as follows: pH is 5.5, the concentration of nitrate ions is 0.6 mol / L, extraction is carried out at 20 DEG C for 30-60 min. The ligand is simple in synthesis, adjustable in structure, high in extraction efficiency of Sr + , strong in selectivity, recyclable after acid stripping, and suitable for efficient separation of strontium in high-level liquid waste.

Description

Technical Field

[0001] This invention relates to the field of radionuclide separation and coordination chemistry, and particularly to an open-chain polyether ligand, its preparation method, and its application in the selective separation of strontium ions. Background Technology

[0002] Radioactive isotopes of strontium 90 Sr is one of the main high-heat fission products of uranium and plutonium fission, characterized by strong mobility, long half-life, and significant bioaccumulation effect. Because its chemical properties are similar to calcium, 90 Sr can accumulate in bone tissue over a long period through the food chain, causing severe internal radiation damage. Sr²⁺ is crucial for achieving effective nuclear fuel reprocessing, high-level radioactive waste volume reduction, and remediation of water contaminated by nuclear accidents. + Highly efficient and selective separation is a key step in reducing the environmental risks of radioactive waste.

[0003] In real high-level radioactive waste liquid, strontium is used as Sr² + It exists in high-concentration nitrate media and often interacts with Cs. + Na + UO2² + ,Th 4+ It coexists with various fission products, including lanthanides. Sr² + Strontium is a typical hard Lewis acid with high hydration energy and stable coordination structure, making it challenging to achieve high selectivity in complex aqueous systems. Existing methods for strontium ion separation mainly include solvent extraction, membrane separation, adsorption, chemical precipitation, and ion exchange. Among these, solvent extraction has attracted widespread attention in the field of strontium separation due to its advantages such as continuous operation, high throughput, and adjustable selectivity.

[0004] In the extraction and separation of strontium ions, existing solvent extraction methods often employ cyclic crown ethers (such as dicyclohexyl-18-crown-6) as extractants. However, crown ether ligands generally suffer from drawbacks such as cumbersome synthesis steps, high cost, and limited adaptability of rigid skeletons to different acidities and solvent systems, restricting their engineering applications in real nuclear waste environments. Open-chain polyether ligands (also known as "foot ethers" or "open-chain crown ethers") possess advantages such as tunable skeleton flexibility, variable number of ether oxygen donors, readily available raw materials, and simple synthesis. They can achieve induced matching with target ions by controlling chain length and terminal groups, and are considered a potential alternative to rigid crown ethers. Current research on open-chain polyether ligands mainly focuses on phase transfer catalysis of alkali metal ions or complexation extraction of transition metal ions, applying their systems to Sr² in high-salt nitric acid systems. + There are relatively few studies on selective separation, especially lacking molecular design strategies and structure-activity relationships that take into account coordination affinity, hydrophobic phase transfer ability and chemical stability.

[0005] Therefore, it is necessary to develop a class of structures with well-defined features, simple preparation methods, and effective resistance to Sr²⁺ in high-salt nitric acid systems. + Novel open-chain polyether ligands with high extraction efficiency and good selectivity are useful for promoting the extraction of nuclear waste liquids. 90 Advances in Sr separation technology have significant theoretical and practical value. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an open-chain polyether ligand, its preparation method, and its application in the selective separation of strontium ions. This ligand has a simple synthetic route, a tunable structure, and exhibits good performance in the selective separation of Sr²⁺ ions. + It exhibits excellent extraction performance and selectivity, and has good stability for repeated use.

[0007] The first aspect of the present invention provides an open-chain polyether ligand, wherein the open-chain polyether ligand is 1,14-diphenoxy-3,6,9,12-tetraoxatetradecane or 1,14-di(4-pentylphenoxy)-3,6,9,12-tetraoxatetradecane.

[0008] A second aspect of this invention provides a method for preparing an open-chain polyether ligand, wherein the open-chain polyether ligand is prepared by a nucleophilic substitution reaction of raw material A and raw material B, comprising the following steps: Raw material A, raw material B and anhydrous carbonate were added to an organic solvent and heated under reflux in an inert atmosphere. After the reaction was completed, the solvent was removed to obtain the crude product. The crude product was dissolved, acid-washed, separated by organic phase, washed with water, dried, and purified by column chromatography to obtain open-chain polyether ligands. Wherein, raw material A is phenol or 4-pentylphenol, and raw material B is p-xylenesulfonate ethylene glycol. When raw material A is phenol, the open-chain polyether ligand prepared is 1,14-diphenoxy-3,6,9,12-tetraoxatetradecane; when raw material A is 4-pentylphenol, the open-chain polyether ligand prepared is 1,14-di(4-pentylphenoxy)-3,6,9,12-tetraoxatetradecane.

[0009] Furthermore, the carbonate is one of potassium carbonate and sodium carbonate; the organic solvent is anhydrous acetonitrile; the inert atmosphere is a nitrogen atmosphere; the heating reflux temperature is 80~85℃, and the heating reflux reaction time is 20~24h.

[0010] Furthermore, the carbonate is potassium carbonate; the organic solvent is anhydrous acetonitrile; the inert atmosphere is nitrogen; the heating reflux temperature is 83°C, and the heating reflux reaction time is 24 h.

[0011] Further, the crude product is subjected to dissolution, acid washing, organic phase separation, water washing, drying, and column chromatography purification to obtain the open-chain polyether ligand, including: The crude open-chain polyether ligand product was dissolved in dichloromethane, transferred to a separatory funnel, and acid-washed with hydrochloric acid aqueous solution. After separation, the organic phase was retained. The organic phase was washed with deionized water until neutral, filtered through anhydrous sodium sulfate and dried, and purified by silica gel column chromatography using a 2:1 (v / v) mixture of petroleum ether and ethyl acetate as eluent to obtain the open-chain polyether ligand.

[0012] A third aspect of the present invention provides a strontium ion extractant comprising an open-chain polyether ligand and an organic solvent; wherein the concentration of the open-chain polyether ligand in the organic solvent is 0.1 mol / L.

[0013] Furthermore, the organic solvent is chloroform.

[0014] The fourth aspect of the present invention provides the application of an open-chain polyether ligand or a strontium ion extractant in the selective separation of strontium ions, wherein the strontium ion extractant is used for the selective complexation extraction of strontium ions in a strontium-containing nitrate system.

[0015] Furthermore, the strontium-containing nitrate system contains Sr 2+ Cs + Na + Co 2+ Cu 2+ La 3+ Eu 3+ ,Th 4+ UO2 2+ One or more ions in it.

[0016] Furthermore, the extraction conditions of the strontium ion extractant meet one or more of the following requirements: the volume ratio of the organic phase in the extractant to the aqueous phase in the nitrate system is 1:1; the pH of the aqueous phase is 4.0~5.5; the initial concentration of strontium ions in the aqueous phase is 30~150 mg / L; the concentration of nitrate ions in the aqueous phase is 0.4~0.8 mol / L; the extraction temperature is 20~25℃; and the extraction time is 30~60 min.

[0017] Furthermore, the preferred extraction conditions for the strontium ion extractant are: The volume ratio of the organic phase in the extractant to the aqueous phase in the nitrate system was 1:1; the pH of the aqueous phase was 5.5; the initial concentration of strontium ions in the aqueous phase was 50-130 mg / L; the concentration of nitrate ions in the aqueous phase was 0.6 mol / L; the extraction temperature was 20℃; and the extraction time was 60 min.

[0018] Furthermore, it also includes a step of back-extracting the supported organic phase; wherein, the back-extraction step uses a 1 mol / L nitric acid solution as the back-extraction agent.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The open-chain polyether ligands provided by the present invention have a clear structure and a simple synthetic route. They can be prepared by a one-step nucleophilic substitution reaction using inexpensive and readily available phenol or 4-pentylphenol and p-xylenesulfonate ethylene glycol as raw materials, with a total yield of over 30%.

[0020] (2) The ligands of this invention use a flexible polyether chain as a backbone, and the aromatic end groups at both ends can regulate the electron cloud density of the ether oxygen atoms and the hydrophilicity / hydrophobicity of the ligand molecule. Among them, BPPT-14, due to the introduction of the pentyl substituent, has both stronger electron-donating ability and hydrophobicity, and is more effective against Sr²⁺. + Its complexing ability and phase transfer efficiency are both superior to BPht-14.

[0021] (3) The strontium ion extractant of the present invention for Sr² in nitrate medium + It exhibits good extraction performance and selectivity in the presence of Cs + Na + Co² + Cu² + La³ + Eu³ + ,Th 4+ UO2² + Sr² can still be preferentially extracted in the presence of plasma. + Furthermore, the separation factor is relatively high.

[0022] (4) The ligands and extractants of the present invention can be regenerated by simple acid back-extraction, have good recycling performance, and have potential for engineering applications.

[0023] (5) This invention relates to high-level radioactive waste liquid 90 The efficient separation of Sr provides a novel candidate extractant, which can also be used in the treatment of strontium-containing wastewater and the recovery of strontium resources. Attached Figure Description

[0024] Figure 1 Flowchart for the preparation of open-chain polyether ligands.

[0025] Figure 2 The image shows the FT-IR spectrum of BPht-14.

[0026] Figure 3 For BPht-14 1 H NMR spectrum.

[0027] Figure 4 For BPht-1413 C10 NMR spectrum.

[0028] Figure 5 The HRMS spectrum of BPht-14.

[0029] Figure 6 The image shows the FT-IR spectrum of BPPT-14.

[0030] Figure 7 For BPPT-14 1 H NMR spectrum.

[0031] Figure 8 For BPPT-14 13 C10 NMR spectrum.

[0032] Figure 9 The image shows the HRMS spectrum of BPPT-14.

[0033] Figure 10 To investigate the effects of BPht-14 and BPPT-14 on Sr under different pH conditions 2+ The graph shows the change in extraction rate.

[0034] Figure 11 The graph shows the changes in the extraction amount of strontium in the nitrate system by BPht-14 and BPPT-14 under different extraction time conditions.

[0035] Figure 12 The graph shows the changes in the extraction amount of strontium by BPht-14 and BPPT-14 under different strontium ion concentrations.

[0036] Figure 13 The graph shows the changes in the removal rate of strontium by BPht-14 and BPPT-14 under different temperature conditions.

[0037] Figure 14 BPht-14 and BPPT-14 with Sr under different nitrate concentrations 2+ A schematic diagram showing the change in the allocation coefficient (D).

[0038] Figure 15 Schematic diagrams of the selectivity of BPht-14 and BPPT-14 for coexisting ions; where (a) is a schematic diagram of the partition coefficients of coexisting ions with BPht-14 and BPPT-14; (b) is a schematic diagram of the partition coefficients of Sr² + A schematic diagram of the separation factor with other coexisting ions.

[0039] Figure 16 This diagram illustrates the back-extraction efficiency and reusability of BPht-14.

[0040] Figure 17 This diagram illustrates the back-extraction efficiency and reusability of BPPT-14. Detailed Implementation

[0041] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0042] In one specific embodiment of this invention, an open-chain polyether ligand is prepared by a nucleophilic substitution reaction of raw material A (phenol or 4-pentylphenol) and raw material B (pentylene glycol sulfonate). A strontium ion extractant is prepared using the open-chain polyether ligand. The prepared strontium ion extractant is used for selective complexation extraction of strontium ions in a strontium-containing nitrate system. The recyclability of the synthesized open-chain polyether extractant in practical applications is analyzed through back-extraction and reusability studies. The main reagents and instruments used in subsequent experiments are shown in Tables 1 and 2. The main research contents are as follows: Table 1. Reagents required for the experiment Table 2 Main Instruments for the Experiment (1) Preparation of open-chain polyether ligands like Figure 1 As shown, the preparation process of open-chain polyether ligands is as follows: Raw material A, raw material B, and anhydrous carbonate (K2CO3 or Na2CO3) were added to an organic solvent (acetonitrile, MeCN) and refluxed under an inert atmosphere for 20–24 h at a reflux temperature of 80–85 °C. After the reaction, the solvent was removed to obtain crude open-chain polyether ligands. The crude product was dissolved, acid-washed, separated by organic phase, washed with water, dried, and purified by column chromatography to obtain pure open-chain polyether ligands. Specifically, when raw material A was phenol, the prepared open-chain polyether ligand was 1,14-diphenoxy-3,6,9,12-tetraoxatetradecane (abbreviated as BPht-14); when raw material A was 4-pentylphenol, the prepared open-chain polyether ligand was 1,14-di(4-pentylphenoxy)-3,6,9,12-tetraoxatetradecane (abbreviated as BPPT-14).

[0043] (2) Preparation and application of strontium ion extractant To expand the practical application of open-chain polyether ligands, this embodiment of the invention dissolves open-chain polyether ligands in an organic solvent to obtain a strontium ion extractant. The organic solvent in the strontium ion extractant is chloroform, and the concentration of the open-chain polyether ligand in the organic solvent is 0.05-0.20 mol / L. Preferably, the concentration of the open-chain polyether ligand in the organic solvent is 0.1 mol / L.

[0044] In this embodiment of the invention, the prepared strontium ion extractant is also applied to the selective extraction of strontium ions in a nitrate system. Optimal conditions for selective strontium ion extraction are determined through single-factor experiments setting pH, extraction time, initial strontium ion concentration, temperature, and nitrate concentration. Furthermore, the recyclability of the strontium ion extractant prepared from the open-chain polyether ligand is analyzed in practical applications through back-extraction experiments and repeat experiments.

[0045] The preparation and application of open-chain polyether ligands are described in detail below through specific examples.

[0046] Example 1 (1) Preparation of 1,14-diphenoxy-3,6,9,12-tetraoxatetradecane (BPht-14) 1.88 g (20 mmol) of phenol, 5.53 g (40 mmol) of anhydrous potassium carbonate, and 5.47 g (10 mmol) of p-xylenesulfonate ethylene glycol were added to a 250 mL three-necked round-bottom flask. Then, 200 mL of anhydrous acetonitrile was added as a solvent. Under nitrogen protection, the mixture was stirred and refluxed in an oil bath at 80–85 °C (preferably 83 °C) for 20–24 h (preferably refluxed for 24 h) to obtain a milky white suspension. After the reaction was complete, the solvent was removed by vacuum distillation using a rotary evaporator to obtain a pale yellow crude product.

[0047] The pale yellow crude product was dissolved in 270 mL of dichloromethane, transferred to a separatory funnel, and acid-washed with 300 mL of 1 mol / L hydrochloric acid solution. After separation, the organic layer was collected. The organic layer was then repeatedly washed with deionized water until neutral. The organic layer was filtered through anhydrous sodium sulfate and dried to remove excess water. The filtrate was concentrated by rotary evaporation and purified by silica gel column chromatography using a 2:1 (v / v) mixture of petroleum ether and ethyl acetate as eluent. The target component was collected, and the solvent was removed under reduced pressure to obtain a pale green oily liquid, BPht-14, with a yield of 38%.

[0048] (2) Structural characterization and analysis The structure of the target product (pale green oily liquid BPht-14) was confirmed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (¹H NMR, ¹³C NMR) and high-resolution electrospray ionization mass spectrometry (HRMS), and the specific analysis is as follows.

[0049] ① Fourier transform infrared spectroscopy (FT-IR) analysis The FT-IR spectrum of the pale green target product is as follows: Figure 2 As shown in the spectrum, the peak at 1590 cm⁻¹ is... - ¹and 1471 cm - The absorption peak near ¹ is attributed to the C=C double bond stretching vibration of the benzene ring skeleton, indicating the presence of an aromatic ring structure in the molecule; located at 1250 cm⁻¹ - The absorption peak near ¹ is attributed to the stretching vibration of the C–O bond in the aromatic ether, indicating that an arylalkyl ether bond is formed between the phenolic hydroxyl group and the polyether chain; located at 1101 cm⁻¹ - The strong absorption peak at ¹ is attributed to the stretching vibration of the C–O–C aliphatic ether bond, corresponding to the repeating ethylene oxide unit in the polyether backbone. The simultaneous appearance of the above three characteristic absorption peaks in the spectrum confirms the successful connection between the phenoxy end group and the polyether backbone in the target product, and also proves the successful synthesis of BPht-14.

[0050] ② Nuclear magnetic resonance spectroscopy (¹H NMR, ¹³C NMR) analysis The ¹H NMR spectrum (400 MHz, CDCl3) of the pale green target product is shown below. Figure 3 As shown in the spectrum, the multiplets at chemical shifts δ 7.28–7.22 and 6.95–6.89 correspond to aromatic protons (10H in total) on the terminal benzene ring; the multiplets at δ 4.12–4.08 and 3.85–3.80 belong to the methylene protons (4H each) adjacent to and next to the phenoxy group; and the multiplet at δ 3.72–3.61 corresponds to the methylene protons (12H) of the remaining ethylene oxide units in the polyether backbone. The integral ratio of aromatic protons to aliphatic ether chain protons is consistent with the theoretical structure, further confirming that the stoichiometric ratio of the phenoxy group to the pentaethylene glycol chain in the molecule is 2:1.

[0051] The ¹³C NMR spectrum (100 MHz, CDCl₃) of the pale green target product is shown below. Figure 4As shown in the spectrum, the signal peaks at chemical shifts δ158.9, 129.5, 120.9, and 114.7 are attributed to the aromatic carbon atoms of the terminal benzene ring; the signal peaks at δ70.9, 70.7, 70.6, 70.5, 69.7, and 67.5 are characteristic resonance peaks of the ether methylene carbon in the polyether backbone, confirming the successful introduction of the oligomeric polyethylene glycol segment. No sulfonate-related carbon signals were observed in the spectrum from the pentylene glycol of the starting material p-xylenesulfonate, indicating that the starting material has reacted completely.

[0052] ③ High-resolution electrospray ionization mass spectrometry (HRMS) analysis The HRMS spectrum of the pale green target product is as follows: Figure 5 As shown in the spectrum, a molecular ion peak at a mass-to-charge ratio of m / z 413.1931 was observed, corresponding to the sodium ion adduct [M+Na] of the target compound BPht-14. + Form. The measured value and the theoretical calculated value C 22 H 30 The relative error between O6Na (413.1940) and other samples was less than 3 ppm, confirming that the molecular formula of the pale green product was C6Na. 22 H 30 O6.

[0053] Based on the above FT-IR, ¹H NMR, ¹³C NMR, and HRMS characterization results, the prepared pale green oily liquid was confirmed to be the target product 1,14-diphenoxy-3,6,9,12-tetraoxatetradecane (BPht-14), with the molecular formula C2. 22 H 30 O6.

[0054] Example 2 (1) Preparation of 1,14-bis(4-pentylphenoxy)-3,6,9,12-tetraoxatetradecane (BPPT-14) 3.00 g (18.3 mmol) of 4-pentylphenol, 5.53 g (40 mmol) of anhydrous potassium carbonate, and 5.47 g (10 mmol) of p-xylenesulfonate ethylene glycol were added to a 250 mL three-necked round-bottom flask, followed by 200 mL of anhydrous acetonitrile. The mixture was stirred and refluxed in an oil bath at 83 °C for 24 h under nitrogen protection. After the reaction was completed, the solvent was removed by vacuum distillation using a rotary evaporator to obtain a pale yellow crude product.

[0055] The crude product was dissolved in 270 mL of dichloromethane and transferred to a separatory funnel. It was then washed with 300 mL of 1 mol / L hydrochloric acid solution. After separation, the organic layer was collected and washed with deionized water until neutral. The organic layer was then dried over anhydrous sodium sulfate and filtered. After concentration, the product was purified by silica gel column chromatography using petroleum ether / ethyl acetate (2:1 v / v) as eluent to obtain a pale yellow oily liquid, BPPT-14, with a final yield of 31.3%.

[0056] (2) Structural characterization and analysis The structure of the target product (pale yellow oily liquid BPPT-14) was confirmed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (¹H NMR, ¹³C NMR) and high-resolution electrospray ionization mass spectrometry (HRMS). The analytical results are as follows.

[0057] ① Fourier transform infrared spectroscopy (FT-IR) analysis The FT-IR spectrum of the pale yellow target product is as follows: Figure 6 As shown in the spectrum, 2925 cm⁻¹ - ¹and 2854cm - The strong absorption peak at ¹ is attributed to the symmetric and asymmetric stretching vibrations of the methylene group in the pentyl side chain. Its peak intensity is significantly enhanced compared to BPht-14, consistent with the increased proportion of alkyl groups in the molecule; 1612 cm⁻¹ - ¹and 1512 cm - The absorption peak at ¹ is a characteristic peak of the C=C stretching vibration of the para-substituted benzene ring skeleton, 1248 cm⁻¹. - The absorption peak at ¹ corresponds to the C–O stretching vibration of aromatic ethers, 1101 cm⁻¹ - The strong absorption peak at ¹ is due to the C–O–C stretching vibration of the polyether backbone. The above characteristic peaks together indicate that the 4-pentylphenoxy end group has been successfully introduced through the ether bond, which also proves the successful synthesis of BPPT-14.

[0058] ② Nuclear magnetic resonance spectroscopy (¹H NMR, ¹³C NMR) analysis The ¹H NMR spectrum (400 MHz, CDCl₃) of the pale yellow target product is shown below. Figure 7As shown in the spectrum, the two doublets (J=8.4Hz) at δ7.08 and 6.81 constitute the AA′BB′ coupling system, corresponding to the four aromatic protons on the para-substituted benzene ring; the signals at δ4.09–4.05 and 3.83–3.79 are the methylene protons of the ether adjacent to and next to the phenoxy group; the multiplet at δ3.70–3.59 is the methylene proton of the remaining oxyethylene unit in the polyether backbone; the triplet at δ2.54 (J=7.6Hz) belongs to the methylene proton directly connected to the benzene ring; the multiplets in the range of δ1.60–1.28 and the triplet at δ0.90 (J=6.8Hz) correspond to the remaining methylene and terminal methyl protons in the pentyl chain, respectively; and the integral ratios of each signal are consistent with the expected structure.

[0059] The ¹³C NMR spectrum (100 MHz, CDCl₃) of the pale yellow target product is shown below. Figure 8 As shown in the spectrum, the signals at δ156.8, 135.1, 129.3, and 114.5 belong to the aromatic carbons of the para-substituted benzene ring, the signal in the range of δ70.9–67.5 is the characteristic resonance of the ether methylene carbon, and the signals at δ35.0, 31.5, 31.1, 22.6, and 14.1 correspond to the five carbon atoms in the pentyl chain, respectively. No carbon signals related to the starting sulfonate were detected, indicating that the nucleophilic substitution reaction was completed.

[0060] ③ High-resolution electrospray ionization mass spectrometry (HRMS) analysis The HRMS spectrum of the pale yellow target product is as follows: Figure 9 As shown. The spectrum reveals a [M+H] peak at m / z 531.3683. + Molecular ion peak, and C 32 H 51 The relative error of the theoretical value of O6 (531.3678) is less than 2 ppm, confirming that the molecular formula of the pale yellow target product is C. 32 H 50 O6. Based on the above characterization analysis, it is confirmed that the obtained pale yellow product is 1,14-bis(4-pentylphenoxy)-3,6,9,12-tetraoxatetradecane (BPPT-14).

[0061] Example 3 Preparation and experimental process of strontium ion extractant (1) Preparation of strontium ion extractant Accurately weigh BPht-14 or BPPT-14 respectively, and use chloroform as an organic solvent to prepare a strontium ion extractant with a ligand concentration of 0.05-0.20 mol / L. Preferably, the ligand concentration in the strontium ion extractant is 0.10 mol / L.

[0062] (2) Strontium ion extractant extraction process Step 1: Prepare an aqueous solution with an initial concentration of 30~150 mg / L of strontium nitrate. Adjust the pH of the aqueous phase to 2.0~5.5 using a certain concentration of nitric acid or sodium hydroxide solution, and adjust the nitrate ion concentration in the aqueous phase to 0~1.0 mol / L. Step 2: Take 1.5 mL of strontium ion extractant into a 5 mL centrifuge tube, and add 1.5 mL of the strontium nitrate aqueous solution prepared in Step 1 (the volume ratio of the aqueous phase in the strontium nitrate aqueous solution to the organic phase in the strontium ion extractant is 1:1). Step 3: Place the centrifuge tubes in a constant temperature shaker at 20-50℃ and shake at 120 rpm for 1-120 min. After extraction, place the mixture in a centrifuge and centrifuge at 5000 rpm for 5 min to achieve complete phase separation. After centrifugation and phase separation, determine the Sr content in the aqueous phase using inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ Concentration. The ionic strength of the aqueous phase is determined by the Sr(NO3)2 solution, and no additional background electrolyte is added unless otherwise specified. Extraction efficiency (E, %), partition coefficient (D), and extraction capacity ( The calculation formulas are shown in Equation (1), Equation (2) and Equation (3) respectively.

[0063] In the formula, E% is the extraction rate. Sr² in the aqueous phase + The initial concentration, Sr² in the aqueous phase + The remaining concentration after extraction; D is the extraction partition ratio. and These represent the volumes of the aqueous phase and the organic phase, respectively. For extraction volume, and The values ​​of Sr² in the organic and aqueous phases after extraction are respectively represented. + The concentration.

[0064] To further understand the practical application effect of strontium ion extractant, this invention determined the range of values ​​for influencing factors such as pH value, extraction time, initial strontium concentration, temperature, and nitrate ion concentration during the extraction process through single-factor experiments. The selective extraction ability and reusability of strontium ion extractant were verified through ion selectivity experiments and back-extraction experiments. The specific process is described in Examples 4 to 10.

[0065] Example 4 Effect of pH on extraction performance In this embodiment, the pH of the aqueous phase was adjusted to 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, and 5.5 using nitric acid, hydrochloric acid, or sodium hydroxide solution, respectively. The effects of different pH values ​​on the extraction of Sr² by BPht-14 and BPPT-14 were investigated. + The impact on efficiency. The specific steps are as follows: Step 1: Prepare an aqueous solution with an initial concentration of 50 mg / L of strontium nitrate. Adjust the pH of the aqueous phase to 2.0~5.5 using a certain concentration of nitric acid or sodium hydroxide solution, and adjust the nitrate ion concentration in the aqueous phase to 0.6 mol / L. Step 2: Take 1.5 mL of strontium ion extractant into a 5 mL centrifuge tube, and then add 1.5 mL of the strontium nitrate aqueous solution prepared in Step 1; Step 3: Place the centrifuge tubes in a constant temperature shaker at 20℃ and shake at 120 rpm for 60 min; after extraction, place the mixture in a centrifuge and centrifuge at 5000 rpm for 5 min to achieve complete phase separation; after centrifugation and phase separation, determine the Sr in the aqueous phase by inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ concentration.

[0066] like Figure 10 The diagram shown illustrates the changes in the extraction rate of strontium ion extractant under different pH conditions. Figure 10 As can be seen, the extraction efficiencies of both BPht-14 and BPPT-14 significantly increased with increasing pH from 2.0 to 5.5. The extraction efficiency of BPht-14 increased from 15.95% to 70.25%, and that of BPPT-14 increased from 17.24% to 81.33%, with a particularly pronounced increase in extraction efficiency within the pH range of 4.0-5.5. Furthermore, it was observed that within the investigated pH range, the extraction efficiency of BPPT-14 was consistently higher than that of BPht-14. This phenomenon can be attributed to the combined effect of the enhanced hydrophobicity of the pentyl substituent in BPPT-14 and its electron-donating inductive effect, which increases the electron density on the phenoxy oxygen atom, promoting its reaction with Sr. 2+ Stronger coordination. Analysis of the extraction rate under different pH conditions shows that the optimal extraction pH for strontium ion extractant is 4.0-5.5, with 5.5 being the optimal value.

[0067] Example 5 Effect of extraction time This example investigated the changes in the extraction amount of strontium in the nitrate system by BPht-14 and BPPT-14 at extraction times of 1 min, 5 min, 10 min, 30 min, 60 min, and 120 min. The specific steps are as follows: Step 1: Prepare an aqueous solution with an initial concentration of 50 mg / L of strontium nitrate. Adjust the pH of the aqueous phase to 5.5 using a certain concentration of nitric acid or sodium hydroxide solution, and adjust the concentration of nitrate ions in the aqueous phase to 0.6 mol / L. Step 2: Take 1.5 mL of strontium ion extractant into a 5 mL centrifuge tube and add 1.5 mL of the strontium nitrate aqueous solution prepared in Step 1; Step 3: Place the centrifuge tubes in a constant temperature shaker at 20℃ and shake at 120 rpm for 1-120 min. After extraction, place the mixture in a centrifuge and centrifuge at 5000 rpm for 5 min to achieve complete phase separation. After centrifugation and phase separation, determine the Sr content in the aqueous phase using inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ The concentration was calculated and the extraction amount of strontium was determined.

[0068] like Figure 11 The figure shows the changes in the extraction yield of strontium by BPht-14 and BPPT-14 under different extraction time conditions. It can be seen from the figure that within the first 30 minutes of extraction, the extraction yield of strontium by BPht-14 and BPPT-14 by the two ligands is significantly reduced. + The extraction capacity increased rapidly, and the curve stabilized around 60 min, indicating that the entire system was close to extraction equilibrium. At this point, the maximum extraction capacities of BPht-14 and BPPT-14 were 36.43 and 41.7 mg / L, respectively. Therefore, in subsequent experiments, the optimal extraction time was determined to be 30–60 min, with 60 min being the optimal value.

[0069] To comprehensively study the effect of time on extraction, a pseudo-second-order kinetic model was used to fit the experimental data. Pseudo-first-order and pseudo-second-order kinetic models were used to analyze and fit the experimental data. The pseudo-first-order extraction kinetic formula is shown in equation (4), and the pseudo-second-order extraction kinetic formula is shown in equation (5). The data fitting calculation results are shown in Table 3.

[0070] In the formula, k1 and k2 are the extraction rate parameters of the quasi-first-order kinetic model and the quasi-second-order kinetic model, respectively. and These represent time t and the amount of extraction at equilibrium, respectively.

[0071] Table 3 Kinetic parameters of the pseudo-first-stage and pseudo-second-stage extraction As can be seen from Table 3, the experimental data are in better agreement with the pseudo-second-order kinetic model, and the correlation coefficient R between BPhT-14 and BPPT-14 is [missing value]. 2The correlation coefficients reached 0.815 and 0.951, respectively, significantly higher than those of the pseudo-first-order model. Simulations using the pseudo-second-order kinetic model yielded extraction yields of 36.84 mg / L and 41.91 mg / L for strontium using BPhT-14 and BPPT-14, respectively. These values ​​are close to the experimentally measured extraction yields of 36.43 mg / L and 41.7 mg / L. Therefore, the extraction mechanism of strontium in BPhT-14 and BPPT-14 is more consistent with the pseudo-second-order kinetic model, indicating that the extraction process is primarily controlled by chemical reactions.

[0072] Example 6 Effect of initial concentration of strontium ions This example studies the extraction performance of BPht-14 and BPPT-14 for strontium at initial strontium concentrations of 30, 50, 70, 110, 130, and 150 mg / L. The specific steps are as follows: Step 1: Prepare an aqueous solution with an initial concentration of 30~150 mg / L of strontium nitrate. Adjust the pH of the aqueous phase to 5.5 using a certain concentration of nitric acid or sodium hydroxide solution, and adjust the nitrate ion concentration in the aqueous phase to 0.6 mol / L. Step 2: Take 1.5 mL of strontium ion extractant into a 5 mL centrifuge tube, and then add 1.5 mL of the strontium nitrate aqueous solution prepared in Step 1; Step 3: Place the centrifuge tubes in a constant temperature shaker at 20℃ and shake at 120 rpm for 60 min. After extraction, place the mixture in a centrifuge and centrifuge at 5000 rpm for 5 min to achieve complete phase separation. After centrifugation and phase separation, determine the Sr content in the aqueous phase using inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ The concentration was calculated and the extraction amount of strontium was determined.

[0073] like Figure 12 The diagram shows the changes in strontium extraction yield by BPht-14 and BPPT-14 under different strontium ion concentrations. Figure 12 As can be seen, with the increase of the initial concentration of strontium ions, the strontium extraction capacity gradually increases and tends to saturate. The maximum extraction capacity of BPht-14 is 48.14 mg / L, and the maximum extraction capacity of BPPT-14 is 54.64 mg / L. Under the same conditions, BPPT-14 consistently exhibits a higher extraction capacity, further demonstrating its superior extraction capacity for Sr²⁺. + It has a stronger complexing ability.

[0074] Example 7 Effects of Temperature and Analysis of Thermodynamic Parameters This embodiment investigated the effect of temperature on the extraction of strontium using BPht-14 and BPPT-14. Extraction temperatures were set at 20, 30, 40, and 50°C, and extraction experiments were conducted. The specific steps are as follows: Step 1: Prepare an aqueous solution with an initial concentration of 50 mg / L of strontium nitrate. Adjust the pH of the aqueous phase to 5.5 using a certain concentration of nitric acid or sodium hydroxide solution, and adjust the concentration of nitrate ions in the aqueous phase to 0.6 mol / L. Step 2: Take 1.5 mL of strontium ion extractant into a 5 mL centrifuge tube and add 1.5 mL of the strontium nitrate aqueous solution prepared in Step 1; Step 3: Place the centrifuge tubes in a constant temperature shaker at 20-50℃ and shake at 120 rpm for 60 min. After extraction, place the mixture in a centrifuge and centrifuge at 5000 rpm for 5 min to achieve complete phase separation. After centrifugation and phase separation, determine the Sr content in the aqueous phase using inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ concentration.

[0075] Figure 13 This diagram illustrates the changes in strontium removal rates by BPht-14 and BPPT-14 under different temperature conditions. From... Figure 13 As can be seen, the extraction rates of both BPht-14 and BPPT-14 ligands decreased with increasing reaction temperature. The extraction rate of BPht-14 decreased from 75.26% to 67.52%, and that of BPPT-14 decreased from 83.52% to 69.92%, indicating that increasing the temperature is detrimental to the extraction of strontium by BPht-14 and BPPT-14. This may be because the complex formed between strontium and the extractant is more easily dissociated at higher temperatures, leading to a decrease in extraction rate.

[0076] The thermodynamic properties of strontium extraction by BPht-14 and BPPT-14 were further investigated by introducing thermodynamic functions. The thermodynamic parameters were calculated using the van der Hoff equation, and the ΔH for BPht-14 was -21.05 kJ·mol⁻¹. - ¹, ΔS = -58.07 J·mol - ¹·K - ¹; ΔH of BPPT-14 = -9.59 kJ·mol - ¹, ΔS = -23.46 J·mol - ¹·K - ¹. It can be seen that within the experimental temperature range, the ΔH values ​​for both ligands are less than zero, indicating that the extraction process is an exothermic reaction, which is consistent with the experimental results on the effect of temperature change on the extraction of strontium; the ΔG values ​​are both negative, indicating that the extraction is a spontaneous process, and that increasing the temperature is not conducive to its spontaneous extraction. Considering the above, the preferred extraction temperature is 20℃.

[0077] Example 8 Effect of nitrate concentration In this embodiment, nitrate concentrations of 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mol / L were set to investigate the effects of different nitrate ion concentrations on the extraction of Sr by BPht-14 and BPPT-14. 2+ The impact of behavior. The specific steps are as follows: Step 1: Prepare an aqueous solution with an initial concentration of 50 mg / L of strontium nitrate. Adjust the pH of the aqueous phase to 5.5 using a certain concentration of nitric acid or sodium hydroxide solution, and adjust the concentration of nitrate ions in the aqueous phase to 0~1 mol / L. Step 2: Take 1.5 mL of strontium ion extractant into a 5 mL centrifuge tube, followed by the strontium nitrate aqueous solution prepared in Step 1; Step 3: Place the centrifuge tubes in a constant temperature shaker at 20℃ and shake at 120 rpm for 60 min; after extraction, place the mixture in a centrifuge and centrifuge at 5000 rpm for 5 min to achieve complete phase separation; after centrifugation and phase separation, determine the Sr in the aqueous phase by inductively coupled plasma optical emission spectrometry (ICP-OES). 2+ Concentration and partition coefficient (D).

[0078] Figure 14 Two ligands and Sr under different nitrate concentrations 2+ A schematic diagram illustrating the change in the allocation coefficient (D). From Figure 14 As can be seen, within the nitrate concentration range of 0–0.6 mol / L, the partition ratio of both ligands significantly increases with increasing nitrate concentration. Specifically, the D value of BPPT-14 increases from 5.11 (at 0 mol / L) to a maximum of 16.54 (at 0.6 mol / L), and the D value of BPht-14 increases from 2.54 to a maximum of 8.48 (at 0.6 mol / L). When the nitrate concentration further increases to 1.0 mol / L, the partition ratio of Sr in BPPT-14 and BPht-14 increases significantly. 2+ The partition ratios decreased to 9.39 and 6.41, respectively, while the extraction efficiency slightly decreased. The significant increase in the partition ratio indicates that nitrate ions promote the extraction of Sr. 2+ It plays an important role in the transfer from the aqueous phase to the organic phase. Therefore, the preferred nitrate concentration range is 0.4-0.8 mol / L, with the optimum being 0.6 mol / L.

[0079] Example 9 Ion selectivity experiment In actual radioactive waste disposal scenarios 90 Sr typically coexists with other ions in complex matrices; therefore, high selectivity is a key indicator for evaluating extractant performance. To assess the effectiveness of BPht-14 and BPPT-14 in real-world systems for the extraction of Sr²⁺, this study investigated their respective properties. + Due to its selective extraction capability, this embodiment formulated a mixture containing Sr²⁺.+ Cs + Na + Co² + Cu² + La³ + Eu³ + ,Th 4+ UO2² + A mixed solution was prepared, with an initial concentration of 50 mg / L for each ion. Extraction experiments were conducted using BPht-14 and BPPT-14 under the optimized conditions obtained in Examples 4-8. After extraction, the residual concentrations of all metal ions in the aqueous phase were determined using ICP-OES, and the extraction efficiency, partition coefficient, and Sr² of each ion were calculated. + The partition coefficients (D) of BPht-14 and BPPT-14 for various metal ions are shown in the figure, relative to the separation factor (SF) of each interfering ion. Figure 15 As shown in (a), BPht-14 and BPPT-14 affect Sr² + Separation factors with common coexisting ions, such as Figure 15 As shown in (b) of the diagram.

[0080] from Figure 15 As can be seen from (a), the presence of coexisting metal ions has a certain impact on the performance of the extractant, but both ligands BPht-14 and BPPT-14 affect Sr 2+ It exhibits significant selectivity; Cs + Due to its size matching with the ligand cavity portion, the extraction rate is moderate, but it can still be obtained from Sr. 2+ Clearly distinguishable; UO2 2+ Although it possesses strong Lewis acidity, its linear rigid geometry has poor matching with the ligand cavity, and strong hydration further reduces its extraction rate, resulting in an extraction rate far lower than that of Sr. 2 + Furthermore, both extractants are effective at repelling transition metals (Co). 2+ Cu 2+ ) and high-valence ions (Th) 4+ La 3+ Eu 3+ This indicates that the ligand cavity has a certain recognition function for ionic radius and charge density.

[0081] from Figure 15 As shown in (b), both open-chain polyether ligands exhibit a clear selective separation trend. For the BPht-14 system, the separation factors for Sr / Na, Sr / Co, Sr / La, and Sr / Th reached 11.31, 17.74, 15.51, and 14.32, respectively, demonstrating a significant ability to distinguish alkali metals from some trivalent and tetravalent metal ions. For Cs...+ With UO2 2+ The separation factors were only 1.74 and 2.81, respectively, indicating relatively limited selectivity for monovalent large-radius ions. The overall separation capability of the BPPT-14 system was further improved, especially for Sr / Th (18.83), Sr / Co (17.05), and Sr / Cu (7.14). Compared with BPht-14, its separation effect for Cu²⁺ was significantly enhanced. + and Eu³ + The significantly improved distinguishing ability indicates that the introduction of the aromatic ring structure enhances the ligand electron donation capacity and spatial matching, thereby strengthening the Sr 2+ Preferential complexation with Sr. Overall, both ligands exhibit preferential complexation with Sr. 2+ It exhibits a superior complexing tendency compared to most competing ions.

[0082] Example 10 Back-extraction and reusability To further evaluate the recyclability of the synthesized open-chain polyether extractant in practical applications, this example conducted back-extraction experiments and reuse tests on BPht-14 and BPPT-14. Considering H... + It can promote the release of metal ions from ligands through competitive coordination sites, and its strong hydration ability helps to improve the stripping efficiency. In this example, 1 mol / L HNO3 was selected as the stripping agent to investigate its effect on the extracted Sr. 2+ The release capacity was then assessed. Subsequently, the extraction efficiency and structural stability of the extractant were evaluated through five rounds of extraction-back-extraction cycle experiments. The specific process is as follows: The loaded organic phase after extraction equilibrium in Example 4 was collected and mixed with an equal volume of 1 mol / L ammonium nitrate at a 1:1 ratio. The mixture was shaken in a constant temperature shaker at 25°C for 30 min. After standing and phase separation, the aqueous phase was taken to determine Sr². + Concentration, calculate the back-extraction rate. The changes in back-extraction rate of BPht-14 and BPPT-14 after 5 rounds of extraction-back-extraction cycle experiments are as follows: Figure 16 , 17 As shown.

[0083] from Figure 16 and Figure 17 As can be seen, both extractants exhibited good reusability during the cycling process, with back-extraction rates remaining above 90%, but their performance trends differed. BPht-14 had an initial back-extraction rate of 95%, which decreased to 90% after 5 cycles, and the extraction rate dropped from 72% to 58%. This indicates that its rigid phenyl framework underwent irreversible structural fatigue during repeated protonation, with π-π stacking of the benzene rings leading to cavity blockage, and water molecules adsorbed at the hydrophilic interface hindering H2O. + Diffusion, residual Sr 2+Accumulated ligands further occupy active sites, leading to a gradual decline in extraction performance. In contrast, BPPT-14 achieved an initial back-extraction rate of 96%, and after 5 cycles, the back-extraction rate remained above 94%, with only a slight decrease in extraction efficiency. This indicates that BPPT-14 possesses superior stability and regeneration capabilities. This stability is mainly attributed to the pentyl substituent introduced into the BPPT-14 molecular structure, which provides stronger hydrophobic protection and spatial conformational stability, suppressing structural disturbances and loss under acidic conditions and improving the durability of the ligands.

[0084] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions conceived without inventive effort should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope defined in the claims.

[0085] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. An open-chain polyether ligand, characterized in that, The open-chain polyether ligand is 1,14-diphenoxy-3,6,9,12-tetraoxatetradecane or 1,14-di(4-pentylphenoxy)-3,6,9,12-tetraoxatetradecane.

2. A method for preparing an open-chain polyether ligand, characterized in that, The open-chain polyether ligand is prepared by a nucleophilic substitution reaction of raw material A and raw material B, including the following steps: Raw material A, raw material B and anhydrous carbonate were added to an organic solvent and heated under reflux in an inert atmosphere. After the reaction was completed, the solvent was removed to obtain the crude product. The crude product was dissolved, acid-washed, separated by organic phase, washed with water, dried, and purified by column chromatography to obtain open-chain polyether ligands. Wherein, raw material A is phenol or 4-pentylphenol, and raw material B is p-xylenesulfonate ethylene glycol. When raw material A is phenol, the open-chain polyether ligand prepared is 1,14-diphenoxy-3,6,9,12-tetraoxatetradecane; when raw material A is 4-pentylphenol, the open-chain polyether ligand prepared is 1,14-di(4-pentylphenoxy)-3,6,9,12-tetraoxatetradecane.

3. The preparation method according to claim 2, characterized in that, The carbonate is either potassium carbonate or sodium carbonate; the organic solvent is anhydrous acetonitrile; the inert atmosphere is a nitrogen atmosphere; the heating and reflux temperature is 80~85℃, and the heating and reflux reaction time is 20~24h.

4. The preparation method according to claim 2, characterized in that, The crude product is dissolved, acid-washed, separated into organic phases, washed with water, dried, and purified by column chromatography to obtain the open-chain polyether ligand, including: The crude open-chain polyether ligand product was dissolved in dichloromethane, transferred to a separatory funnel, and acid-washed with hydrochloric acid aqueous solution. After separation, the organic phase was retained. The organic phase was washed with deionized water until neutral, filtered through anhydrous sodium sulfate and dried, and purified by silica gel column chromatography using a 2:1 (v / v) mixture of petroleum ether and ethyl acetate as eluent to obtain the open-chain polyether ligand.

5. A strontium ion extractant, characterized in that, It comprises an open-chain polyether ligand and an organic solvent; wherein the concentration of the open-chain polyether ligand in the organic solvent is 0.1 mol / L.

6. The strontium ion extractant according to claim 5, characterized in that, The organic solvent is chloroform.

7. The application of the open-chain polyether ligand of claim 1 or the strontium ion extractant of claim 5 in the selective separation of strontium ions, characterized in that, The strontium ion extractant is used for the selective complexation extraction of strontium ions in strontium-containing nitrate systems.

8. The application according to claim 7, characterized in that, The strontium-containing nitrate system contains Sr 2+ Cs + Na + Co 2+ Cu 2+ La 3+ Eu 3+ ,Th 4+ UO2 2+ One or more ions in it.

9. The application according to claim 7, characterized in that, Extraction conditions for strontium ion extractants must meet one or more of the following: The volume ratio of the organic phase in the extractant to the aqueous phase in the nitrate system is 1:1; The pH of the aqueous phase is 4.0~5.5; The initial concentration of strontium ions in the aqueous phase is 30~150 mg / L; The concentration of nitrate ions in the aqueous phase is 0.4~0.8 mol / L; The extraction temperature is 20~25℃; The extraction time is 30-60 minutes.

10. The application according to claim 7, characterized in that, It also includes a step of back-extracting the supported organic phase; wherein, the back-extraction step uses a 1 mol / L nitric acid solution as the back-extraction agent.

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