A palladium ion extractant material and a method of making the same

Abstract

The application provides a palladium ion extractant material and a preparation method thereof, and the pyridine-oxadiazole ligand is used as the extractant, most Pd 2+ in the aqueous phase can be extracted into the organic phase in a short time, and has a very high extraction rate; selective extraction separation of Pd 2+ under acidic conditions can be realized, the applicable range of acidity is wide, and excellent extraction capacity is achieved in the range of 0.2-4M nitric acid concentration; the extractant has excellent selectivity to Pd 2+ in the aqueous phase containing various metal ions; the pyridine-oxadiazole extractant has a good application prospect in the separation and recovery of Pd 2+ in high-level radioactive waste; the m-nitro-trifluorotoluene is used as a diluent of the extraction system, has good solubility to the organic ligand and the extractant, and the 2-bromohexanoic acid can increase the lipophilicity of the extractant.

Description

Technical Field

[0001] This invention relates to the field of extractant technology, and in particular to a palladium ion extractant material and its preparation method. Background Technology

[0002] Palladium, as a precious metal, has the characteristics of corrosion resistance, high temperature resistance and strong ductility, and therefore has a wide range of applications in medical devices, pharmaceutical engineering, fuel cells, jewelry and automotive catalytic converters.

[0003] Over the past few decades, various technologies have been used to recover palladium produced by nuclear fission from radioactive solutions. Among them, liquid-liquid extraction is currently the most widely used separation method for treating high-level radioactive waste liquids due to its advantages such as high efficiency, low cost, and ease of operation. High-level radioactive waste liquid systems are extremely complex and possess strong radioactivity and acidity, posing significant challenges to the structural stability and selectivity of the extractant. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a palladium ion extractant material and its preparation method.

[0005] The technical solution of this invention is: a palladium ion extractant material, wherein the extractant is a pyridine-oxadiazolium ligand, and the pyridine-oxadiazolium ligand is used for highly selective complexation of Pd. 2+ The extractant has the following structural formula:

[0006]

[0007] Where R is a C4 to C8 hydrocarbon group.

[0008] As a preliminary selection, the structural formula of R in the structural formula of the pyridine-oxadiazazole ligand is one of the following:

[0009]

[0010] Preferably, the present invention also provides a method for preparing a palladium ion extractant material, comprising the following steps:

[0011] S1) Synthesis of 2-aminooxime-6-cyano-4-alkoxypyridine

[0012] S11) Methyl 4-alkoxypyridine-2,6-dicarboxylate was added to a methanol solution, and then NH4OH was added dropwise. The resulting mixture was stirred vigorously at room temperature for 24 hours. The white precipitate formed was filtered, washed with ice-cooled water, and dried under vacuum to give 4-alkoxypyridine-2,6-dicarboxyamide in the form of a white solid.

[0013] S12) Under a nitrogen atmosphere, 4-alkoxypyridine-2,6-dicarboxamide was added to anhydrous dichloromethane, followed by the addition of pyridine to the suspension and the slow addition of trifluoroacetic anhydride; the mixture was stirred at room temperature for 18 hours, and then water was added to the resulting mixture; the organic phase was collected, and the aqueous phase was extracted with dichloromethane; the combined organic phases were dried over anhydrous Na2SO4 and concentrated under reduced pressure.

[0014] The residue was purified by silica gel rapid chromatography to give a white, oily 2,6-dicyano-4-alkoxypyridine.

[0015] S13) Add 50% by weight of an aqueous solution of hydroxylamine to an ethanolic solution of 2,6-dicyano-4-alkoxypyridine; then stir the solution at room temperature for 24 hours; evaporate the solvent under vacuum and purify the product on silica gel to give 2-aminooxime-6-cyano-4-alkoxypyridine.

[0016] S2), Synthesis of 4-alkoxypyridine-2,6-dicarboxylic acid chloride intermediate

[0017] Oxaloyl chloride was added to a solution of 4-alkoxypyridine-2,6-dicarboxylic acid in anhydrous dichloromethane and stirred for 1 hour. The solvent was evaporated under vacuum to obtain 4-alkoxypyridine-2,6-dicarboxylic acid intermediate.

[0018] S3) The 2-aminooxime-6-cyano-4-alkoxypyridine prepared in step S1) is reacted with the 4-alkoxypyridine-2,6-dicarboxylic acid chloride intermediate prepared in step S2) to obtain intermediate compound T1:

[0019]

[0020] Where R is a C4 to C8 hydrocarbon group;

[0021] S4) The intermediate compound T1 is reacted with tetrabutylammonium fluoride to obtain pyridine-oxadiazol ligand T2:

[0022]

[0023] Where R is a C4 to C8 hydrocarbon group.

[0024] Preferably, in step S3), the synthesis of the intermediate compound T1 is specifically as follows:

[0025] Add a solution of 4-alkoxypyridine-2,6-dicarboxylic acid intermediate containing dichloromethane to an anhydrous dichloromethane solution containing 2-aminooxime-6-cyano-4-alkoxypyridine and diisopropylethylamine;

[0026] After stirring the resulting solution for 5 hours, the solvent was removed under vacuum. The residue was dissolved in dichloromethane, and a large amount of methanol was added under vigorous stirring to produce a large amount of white solid. The white solid was collected by filtration to obtain intermediate compound T1.

[0027] Preferably, in step S4), the synthesis of the pyridine-oxadiazolium ligand T2 is specifically as follows:

[0028] A tetrahydrofuran solution of tetrabutylammonium fluoride was added to a solution of intermediate compound T1 containing dichloromethane. After stirring the resulting solution for 24 hours, the solvent was removed under vacuum. The residue was dissolved in dichloromethane, and a large amount of methanol was added under vigorous stirring to form a large amount of white solid. The white solid was collected by filtration to obtain pyridine-oxadiazolium ligand T2.

[0029] Preferably, in step S11), the molar ratio of methyl 4-alkoxypyridine-2,6-dicarboxylate to NH4OH is 1:(20-30).

[0030] Preferably, in step S12), the molar ratio of 4-alkoxypyridine-2,6-dicarboxamide, pyridine, and trifluoroacetic anhydride is 1:(4.5-6.0):(2.4-3.2).

[0031] Preferably, in step S13), the molar ratio of 2,6-dicyano-4-alkoxypyridine to hydroxylamine is 1:(1.0 to 1.1).

[0032] Preferably, in step S2), the molar ratio of the raw materials 4-alkoxypyridine-2,6-dicarboxylic acid and oxaloyl chloride is 1:(2-3).

[0033] Preferably, in step S3), the molar ratio of 4-alkoxypyridine-2,6-dicarboxylic acid chloride, 2-aminooxime-6-cyano-4-alkoxypyridine and diisopropylethylamine is 1:2:(3-4).

[0034] Preferably, in step S4), the molar ratio of the intermediate compound T1 to tetrabutylammonium fluoride is 1:(0.2 to 0.25).

[0035] Preferably, the present invention also provides a palladium ion extraction system comprising an organic phase and an aqueous phase, wherein the volume ratio of the organic phase to the aqueous phase is 1:1; the organic phase comprises:

[0036] Extractant material: pyridine-oxadiazol ligand;

[0037] Diluent: m-nitrotrifluorotoluene;

[0038] Phase modifier: 2-bromohexanoic acid;

[0039] Wherein, the concentration of 2-bromohexanoic acid is 1M; and the concentration of the pyridine-oxadiazolium ligand is 0.1–10 mM;

[0040] The aqueous phase is a nitric acid solution containing metal ions at a concentration of 0–100 ppm, wherein the metal ions are one or more of Pd, Ni, La, Gd, Eu, Yb, Sm, Pr, Ba, Sr, Fe, Nd, Rb, Cs, Re, Mo, and Na; and the nitric acid concentration is 0.2–4 M.

[0041] The extraction system described above can remove most of the Pd in ​​the aqueous phase in a short time. 2+ The extract enters the organic phase.

[0042] The beneficial effects of this invention are as follows:

[0043] 1. This invention uses pyridine-oxadiazolium ligand as an extractant, which can remove most of the Pd in ​​the aqueous phase in a short time. 2+ It extracts Pd into the organic phase with extremely high extraction rates; it can achieve Pd extraction under acidic conditions. 2+ It exhibits selective extraction and separation with a wide applicable acidity range, demonstrating excellent extraction capability within the nitric acid concentration range of 0.2–4 M.

[0044] 2. For aqueous phases containing multiple metal ions, this extractant is effective against Pd. 2+ Exhibiting excellent selectivity; the pyridine-oxadiazolium extractant of the present invention separates and recovers Pd from high-level radioactive waste liquid. 2+ This aspect has good application prospects;

[0045] 3. In this invention, m-nitrotrifluorotoluene is used as a diluent in the extraction system, which has good solubility for organic ligands and extracts, and 2-bromohexanoic acid can increase the lipophilicity of the extracts. Attached Figure Description

[0046] Figure 1 The 1H NMR spectrum of pyridine-oxadiazolium ligand T2-1 prepared in Example 1 of this invention;

[0047] Figure 2 The carbon NMR spectrum of pyridine-oxadiazolium ligand T2-1 prepared in Example 1 of this invention;

[0048] Figure 3 The mass spectrum of pyridine-oxadiazolium ligand T2-1 prepared in Example 1 of this invention;

[0049] Figure 4 Pd in ​​Embodiment 2 of the present invention 2+ Extraction rate-extraction time curve;

[0050] Figure 5 Pd in ​​Embodiment 3 of the present invention 2+ Extraction rate-extractant concentration curve;

[0051] Figure 6 Pd in ​​Embodiment 4 of the present invention 2+ Extraction rate-nitric acid concentration curve;

[0052] Figure 7 This is a bar chart showing the extraction rates of various metal ions in Example 5 of the present invention. Detailed Implementation

[0053] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0054] Example 1

[0055] This embodiment provides a method for preparing a pyridine-oxadiazolium ligand with an alkyl chain of isobutyl, comprising the following steps:

[0056] S1) NH4OH (28% in water, 12.0 mL, 0.12 mol, 20.0 equivalent) was added dropwise to a methanol (50 mL) solution of compound 1 (1.6 g, 6.00 mmol). The resulting mixture was stirred vigorously at room temperature for 24 hours. The resulting white precipitate was filtered, washed with ice-cooled water, and dried under vacuum to give compound 2 (1.18 g, 83%) as a white solid. The synthetic procedure is as follows:

[0057]

[0058] S2) Under a nitrogen atmosphere, pyridine (1.02 g, 12.9 mmol, 4.5 equivalents) was added to a suspension of compound 2 (680 mg, 2.9 mmol) in anhydrous dichloromethane (100 mL), followed by the slow addition of trifluoroacetic anhydride (1.45 g, 6.89 mmol, 2.4 equivalents). After stirring the mixture at room temperature for 18 hours, water (75 mL) was added. The organic phase was collected, and the aqueous phase was extracted with dichloromethane (50 mL). The combined organic phases were dried over anhydrous Na₂SO₄ and concentrated under reduced pressure. The residue was purified by silica gel rapid chromatography (dichloromethane as eluent) to give compound 3 (480 mg, 84%) as a white oil. The synthetic procedure is as follows:

[0059]

[0060] S3) A 50% (66 mg, 1.0 mol, 1.0 equivalent) aqueous solution of hydroxylamine was added to an ethanol solution of compound 3 (201 mg, 1.0 mmol, 1 equivalent), and the solution was stirred at room temperature for 24 hours. The solvent was evaporated under vacuum, and the product was purified on silica gel (95 / 5, dichloromethane / methanol) to give compound 4 (159 mg, 68%) as a colorless solid. The synthetic procedure is as follows:

[0061]

[0062] S4) Oxaloyl chloride (274 mg, 2.16 mmol) was added to a solution of compound 5 (172 mg, 0.72 mmol) in anhydrous dichloromethane and stirred for 1 hour. The solvent was evaporated under vacuum to give compound 6 (196 mg, 99%). The synthetic procedure is as follows:

[0063]

[0064] S5) A solution of compound 6 containing dichloromethane was added to an anhydrous dichloromethane solution containing compound 4 (337 mg, 1.44 mmol) and diisopropylethylamine (280 mg, 2.16 mmol); the resulting solution was stirred for 5 hours, and the solvent was removed under vacuum; the residue dissolved in dichloromethane, and a large amount of methanol was added under vigorous stirring to produce a large amount of white solid; the white solid was collected by filtration and characterized as the target compound T1-1 (444 mg, 92%); the synthesis process is as follows:

[0065]

[0066] S6) A tetrahydrofuran solution of tetrabutylammonium fluoride (30.5 mg, 0.12 mmol) was added to a solution of T1-1 (350 mg, 0.52 mmol) in dichloromethane (30 mL); the resulting solution was stirred for 24 hours, and the solvent was removed under vacuum; the residue was dissolved in dichloromethane, and a large amount of methanol was added under vigorous stirring to form a large amount of white solid; the white solid was collected by filtration and characterized as the target compound T2-1 (320 mg, 97%). The synthetic procedure is as follows:

[0067]

[0068] Example 2

[0069] This embodiment provides a Pd 2+The extraction and separation system consists of an organic phase and an aqueous phase, each 3 mL in volume. The organic phase uses m-nitrotrifluorotoluene as a diluent, 2-bromohexanoic acid as a phase modifier, and pyridine-oxadiazolium ligand as an extractant. The concentration of 2-bromohexanoic acid is 1 M, and the concentration of pyridine-oxadiazolium ligand is 3 mM.

[0070] The aqueous phase contains Pd. 2+ A nitric acid solution; wherein, Pd 2+ The initial concentration was 100 ppm; the nitric acid concentration was 3 M.

[0071] The extraction process is as follows: 2-bromohexanoic acid and pyridine-oxadazole ligand are dissolved in m-nitrotrifluorotoluene as the organic phase, and palladium nitrate and nitric acid are dissolved in water as the aqueous phase. Then, 3 mL of each organic and aqueous phases are placed into centrifuge tubes, and the tubes are vigorously shaken at 25°C for a certain period of time. After centrifugation and phase separation, 200 μL of the aqueous phase is used for Pd detection. 2+ The remaining concentration is then taken out, along with 200 μL of organic phase, to ensure that the phase ratio remains 1 / 1 throughout the process. This process is continued until extraction equilibrium is reached.

[0072] Example 3

[0073] This embodiment provides a Pd 2+ The extraction and separation system consists of an organic phase and an aqueous phase, each 0.5 mL in volume;

[0074] The organic phase uses m-nitrotrifluorotoluene as a diluent, 2-bromohexanoic acid as a phase modifier, and pyridine-oxadiazole ligand as an extractant.

[0075] Wherein, the concentration of 2-bromohexanoic acid is 1M, and the concentration of pyridine-oxadiazolium ligand is 0.1-10mM;

[0076] The aqueous phase contains Pd 2+ A nitric acid solution, in which Pd 2+ The initial concentration was 100 ppm; the nitric acid concentration was 3 M.

[0077] The extraction process includes the following steps: 2-bromohexanoic acid and pyridine-oxadiazole ligand are dissolved in m-nitrotrifluorotoluene as the organic phase, and palladium nitrate and nitric acid are dissolved in water as the aqueous phase. Then, 0.5 mL of each of the organic and aqueous phases are placed in centrifuge tubes and vigorously shaken at 25°C for at least 8 hours. After centrifugation and phase separation, 200 μL of the aqueous phase is used for Pd detection. 2+ Remaining concentration.

[0078] Example 4

[0079] This embodiment provides a Pd 2+The extraction and separation system consists of an organic phase and an aqueous phase, each 0.5 mL in volume;

[0080] The organic phase uses m-nitrotrifluorotoluene as a diluent, 2-bromohexanoic acid as a phase modifier, and pyridine-oxadiazolium ligand as an extractant; wherein the concentration of 2-bromohexanoic acid is 1M and the concentration of pyridine-oxadiazolium ligand is 3mM.

[0081] The aqueous phase contains Pd. 2+ A nitric acid solution; wherein, Pd 2+ The initial concentration was 100 ppm; the nitric acid concentration was 0.2–4 M.

[0082] The extraction process includes the following steps: 2-bromohexanoic acid and pyridine-oxadiazole ligand are dissolved in m-nitrotrifluorotoluene as the organic phase, and palladium nitrate and nitric acid are dissolved in water as the aqueous phase. Then, 0.5 mL of each of the organic and aqueous phases are placed in centrifuge tubes and vigorously shaken at 25°C for at least 8 hours. After centrifugation and phase separation, 200 μL of the aqueous phase is used for Pd detection. 2+ Remaining concentration.

[0083] Example 5

[0084] This embodiment provides a Pd 2+ The extraction and separation system consists of an organic phase and an aqueous phase, each 1 mL.

[0085] The organic phase uses m-nitrotrifluorotoluene as a diluent, 2-bromohexanoic acid as a phase modifier, and pyridine-oxadiazolium ligand as an extractant; the concentration of 2-bromohexanoic acid is 1M, and the concentration of pyridine-oxadiazolium ligand is 3mM.

[0086] The aqueous phase is a nitric acid solution containing 17 metal ions. The metal ions include Pd, Ni, La, Gd, Eu, Yb, Sm, Pr, Ba, Sr, Fe, Nd, Rb, Cs, Re, Mo, and Na ions, each with an initial concentration of 100 ppm; the nitric acid concentration is 3 M.

[0087] The extraction process includes the following steps: 2-bromohexanoic acid and pyridine-oxadiazole ligand are dissolved in m-nitrotrifluorotoluene as the organic phase, and palladium nitrate and nitric acid are dissolved in water as the aqueous phase. Then, 1 mL of each of the organic phase and the aqueous phase are placed into centrifuge tubes and shaken vigorously at 25°C for more than 8 hours. After centrifugation and phase separation, 500 μL of the aqueous phase is taken to detect the residual concentration of each metal ion.

[0088] Performance Analysis:

[0089] 1. The pyridine-oxadiazolium ligand T2-1 with isobutyl as an alkyl chain prepared in Example 1 was characterized and its performance was tested.

[0090] The testing method is as follows:

[0091] Compound structure determination: A Bruker Avance III 400MHz nuclear magnetic resonance spectrometer was used, with deuterated chloroform as the solvent;

[0092] Mass spectrometry detection: T2-1 prepared in Example 1 was dissolved in dichloromethane to prepare a solution with a concentration of 1 mg / mL. Mass spectrometry was performed using a Thermo Fisher TSQ Endura ultra-high performance liquid chromatography-tandem triple quadrupole mass spectrometer.

[0093] Extraction kinetics study: Pd in ​​the aqueous phase of Example 2 after different extraction times was determined using an iCAP5110 inductively coupled plasma atomic emission spectrometer. 2+ concentration.

[0094] Extraction stoichiometry calculation: Pd in ​​the aqueous phase after extraction in Example 3 was determined using an iCAP5110 inductively coupled plasma atomic emission spectrometer. 2+ concentration.

[0095] Aqueous phase acidity on extraction performance test: Pd in ​​the aqueous phase after extraction in Example 4 was determined using an iCAP5110 inductively coupled plasma atomic emission spectrometer. 2+ concentration.

[0096] Extraction selectivity test: The concentrations of each metal ion in the aqueous phase after extraction in Example 5 were determined using an iCAP5110 inductively coupled plasma atomic emission spectrometer.

[0097] The test results are as follows:

[0098] The 1H and 1C NMR spectra of the pyridine-oxadiazolium ligand T2-1 prepared in Example 1 are as follows: Figure 1 and Figure 2 As shown. It can be seen that: 1 HNMR(400MHz,Chloroform-d)δ8.13(s,2H),8.03-7.96(m,2H),7.41-7.33(m,2H),4.05(d,J= 6.4Hz,2H),3.96(d,J=6.4Hz,4H),2.21(m,3H),1.12(d,J=6.9Hz,6H),1.09(d,J=6.6Hz,12H). 13CNMR (100MHz, Chloroform-d) δ 174.60, 167.99, 167.46, 166.68, 148.90, 145.37, 135.53, 117.90, 116.51, 114.22, 112.57, 75.69, 28.05, 19.02. The peak energies of the proton and carbon NMR spectra correspond one-to-one with the target product, and the number is reasonable; from the mass spectrum ( Figure 3 As can be seen in the figure, the relative molecular mass is 653.2944, which is similar to the synthesized T2-1 complexed NH. 4+ The relative molecular masses were consistent. Based on the above NMR and mass spectrometry results, the product obtained in Example 1 is T2-1.

[0099] Figure 4 Pd in ​​Example 2 2+ Extraction rate-extraction time curve. It can be seen that in the initial stage, Pd... 2+ It is rapidly extracted into the organic phase, with 68% extraction achieved in 120 minutes. Equilibrium is reached in about 360 minutes, with an extraction rate of 98%, essentially achieving quantitative extraction.

[0100] Figure 5 Pd in ​​Example 3 2+ Extraction rate versus extractant concentration curve. It can be seen that the fitted curve is a straight line with a slope close to 1.5, indicating that T2-2 and Pd may be present in the extracted organic phase. 2+ There are two cases with complexation ratios of 1:1 and 1:2, which means that the extraction stoichiometric ratio of the two is 1:1 or 1:2.

[0101] Figure 6 Pd in ​​Example 4 2+ Extraction rate-nitric acid concentration curve. It can be seen that: across the entire acidity range, the system's effect on Pd... 2+ All of them exhibited excellent extraction capabilities, and almost all of them achieved quantitative extraction.

[0102] Figure 7 The bar chart shows the extraction rates of various metal ions in Example 5. It can be seen that the system has a high extraction rate for Pd. 2+ The adsorption rate of Pd reached 98.5%, demonstrating excellent adsorption capacity, while other ions were only extracted in small amounts: Rb (11.2%), Gd (7.4%), Eu (8.2%), Yb (7.5%), Sm (8.0%), Nd (7.5%), and Re (8.4%). These results indicate that this adsorbent is effective for Pd... 2+ Its excellent selectivity further proves its good potential for practical application.

[0103] In summary, this invention uses pyridine-oxadiazolium as an extractant, which can remove most of the Pd in ​​the aqueous phase in a relatively short time. 2+ The extractant is successfully introduced into the organic phase and exhibits extremely high extraction rates. It has a wide acidity tolerance range, demonstrating excellent extraction capabilities across a nitric acid concentration range of 0.2–4 M. Even in aqueous phases containing multiple metal ions, this extractant shows good performance for Pd. 2+ It exhibits excellent selectivity. Therefore, this pyridine-oxadiazolium extractant is used to separate and recover Pd from high-level radioactive waste. 2 + It has good application prospects in this area.

[0104] The embodiments and descriptions above are merely illustrative of the principles and preferred embodiments of the present invention. Various changes and modifications may be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A palladium ion extractant material, characterized in that: The extractant is a pyridine-oxadiazolium ligand, which is used for highly selective complexation of Pd. 2+ The extractant has the following structural formula: Where R is a C4 to C8 hydrocarbon group.

2. The palladium ion extractant material according to claim 1, characterized in that: The structural formula of R in the pyridine-oxadiazazole ligand can be one of the following:

3. A method for preparing the palladium ion extractant material according to claim 1 or 2, characterized in that, Includes the following steps: S1) Synthesis of 2-aminooxime-6-cyano-4-alkoxypyridine S11) Methyl 4-alkoxypyridine-2,6-dicarboxylate was added to a methanol solution, and then NH4OH was added dropwise. The resulting mixture was stirred vigorously at room temperature for 24 hours. The white precipitate formed was filtered, washed with ice-cooled water, and dried under vacuum to give 4-alkoxypyridine-2,6-dicarboxyamide in the form of a white solid. S12) Under a nitrogen atmosphere, 4-alkoxypyridine-2,6-dicarboxamide was added to anhydrous dichloromethane, followed by the addition of pyridine to the suspension and the slow addition of trifluoroacetic anhydride; the mixture was stirred at room temperature for 18 hours, and then water was added to the resulting mixture; the organic phase was collected, and the aqueous phase was extracted with dichloromethane; the combined organic phases were dried over anhydrous Na2SO4 and concentrated under reduced pressure. The residue was purified by silica gel rapid chromatography to give a white, oily 2,6-dicyano-4-alkoxypyridine. S13) Add 50% by weight of an aqueous solution of hydroxylamine to an ethanolic solution of 2,6-dicyano-4-alkoxypyridine; then stir the solution at room temperature for 24 hours; evaporate the solvent under vacuum and purify the product on silica gel to give 2-aminooxime-6-cyano-4-alkoxypyridine. S2), Synthesis of 4-alkoxypyridine-2,6-dicarboxylic acid chloride intermediate Oxaloyl chloride was added to a solution of 4-alkoxypyridine-2,6-dicarboxylic acid in anhydrous dichloromethane and stirred for 1 hour. The solvent was evaporated under vacuum to obtain 4-alkoxypyridine-2,6-dicarboxylic acid intermediate. S3) The 2-aminooxime-6-cyano-4-alkoxypyridine prepared in step S1) is reacted with the 4-alkoxypyridine-2,6-dicarboxylic acid chloride intermediate prepared in step S2) to obtain intermediate compound T1: Wherein, R is a C4 to C8 hydrocarbon group; S4) The intermediate compound T1 is reacted with tetrabutylammonium fluoride to obtain the pyridine-oxadiazol ligand T2: Where R is a C4 to C8 hydrocarbon group.

4. The method for preparing a palladium ion extractant material according to claim 3, characterized in that: In step S3), the synthesis of the intermediate compound T1 is specifically as follows: Add a solution of 4-alkoxypyridine-2,6-dicarboxylic acid intermediate containing dichloromethane to an anhydrous dichloromethane solution containing 2-aminooxime-6-cyano-4-alkoxypyridine and diisopropylethylamine. After stirring the resulting solution for 5 hours, the solvent was removed under vacuum. The residue was dissolved in dichloromethane, and a large amount of methanol was added under vigorous stirring to produce a large amount of white solid. The white solid was collected by filtration to obtain intermediate compound T1.

5. The method for preparing a palladium ion extractant material according to claim 3, characterized in that: In step S4), the synthesis of the pyridine-oxadiazolium ligand T2 is specifically as follows: A tetrahydrofuran solution of tetrabutylammonium fluoride was added to a solution of intermediate compound T1 containing dichloromethane. After stirring the resulting solution for 24 hours, the solvent was removed under vacuum. The residue was dissolved in dichloromethane, and a large amount of methanol was added under vigorous stirring to form a large amount of white solid. The white solid was collected by filtration to obtain pyridine-oxadiazolium ligand T2.

6. The method for preparing a palladium ion extractant material according to claim 3, characterized in that: In step S11), the molar ratio of methyl 4-alkoxypyridine-2,6-dicarboxylate to NH4OH is 1:(20-30). In step S12), the molar ratio of 4-alkoxypyridine-2,6-dicarboxamide, pyridine, and trifluoroacetic anhydride is 1:(4.5-6.0):(2.4-3.2). In step S13), the molar ratio of 2,6-dicyano-4-alkoxypyridine to hydroxylamine is 1:(1.0 to 1.1).

7. The method for preparing a palladium ion extractant material according to claim 3, characterized in that: In step S2), the molar ratio of the raw materials 4-alkoxypyridine-2,6-dicarboxylic acid and oxaloyl chloride is 1:(2-3).

8. The method for preparing a palladium ion extractant material according to claim 3, characterized in that: In step S3), the molar ratio of 4-alkoxypyridine-2,6-dicarboxylic acid chloride, 2-aminooxime-6-cyano-4-alkoxypyridine and diisopropylethylamine is 1:2:(3-4).

9. The method for preparing a palladium ion extractant material according to claim 3, characterized in that: In step S4), the molar ratio of the intermediate compound T1 to tetrabutylammonium fluoride is 1:(0.2 to 0.25).

10. A palladium ion extraction system utilizing the extractant material according to claim 1 or 2, characterized in that, It includes an organic phase and an aqueous phase, wherein the volume ratio of the organic phase to the aqueous phase is 1:1; wherein the organic phase includes: Extractant material: pyridine-oxadiazol ligand; Diluent: m-nitrotrifluorotoluene; Phase modifier: 2-bromohexanoic acid; Wherein, the concentration of 2-bromohexanoic acid is 1M; and the concentration of the pyridine-oxadiazolium ligand is 0.1–10 mM; The aqueous phase is a nitric acid solution containing metal ions at a concentration of 0–100 ppm, wherein the metal ions are one or more of Pd, Ni, La, Gd, Eu, Yb, Sm, Pr, Ba, Sr, Fe, Nd, Rb, Cs, Re, Mo, and Na; and the nitric acid concentration is 0.2–4 M. The extraction system described above can remove most of the Pd in ​​the aqueous phase in a short time. 2+ The extract enters the organic phase.

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