Compound for separating uranium thorium or uranium plutonium and preparation method

Abstract

The invention discloses an ionic liquid compound for separating uranium thorium or uranium plutonium and a preparation method thereof. The compound disclosed by the invention is a compound 1-(4-(bis ((2-ethylhexyl) butyl phosphate)-1-(2-ethoxyl) piperidine onium salt as shown in a formula 1. The modified phosphate extraction agent is expected to break through the limitation of a traditional system through molecular structure optimization, and efficient separation of uranium thorium or uranium plutonium under the high-acidity condition is achieved.

Description

Technical Field

[0001] The present invention relates to a compound, in particular to an ionic liquid compound which can be used for separating uranium-thorium or uranium-plutonium and a preparation method thereof. Background Art

[0002] Nuclear accidents can lead to the leakage of large amounts of radioactive elements, so it is necessary to develop analytical methods to quickly detect radioactive leakage in emergency situations. Nuclear wastewater contains a variety of radioactive nuclides, such as 134 Cs, 137 Cs, 90 Sr. 14 C. 129 I. 60 Co、 125 Sb, 106 Such as 99 Tc, 54 Mn, 106 Rh, 235 U and 239 Pu, 240 Pu, 241Ammonium and other highly toxic radioactive nuclides[1]. In order to quickly analyze the pollution caused by nuclear waste water to the environment, an element that does not exist in nature and is easy to separate and purify is usually selected for analysis. The radioactivity of plutonium in the environment is very low, so the environment can be monitored and analyzed by detecting the radioactivity level of plutonium[1,2]. However, environmental samples contain many other elements, so plutonium must be separated from other radioactive elements. Other actinides (such as uranium and americium) and lanthanides often interfere with the separation of plutonium, so there is an urgent need to develop materials for the selective separation of plutonium. Methods for separating plutonium from other actinides and lanthanides include precipitation[3], solvent extraction[4] and ion exchange[5]. The selectivity of precipitation for separating elements is too low and it is rarely used for separation[3]. Solvent extraction or ion exchange are widely used for the recovery and separation of plutonium due to their simple operation and low setup cost[6,7]. Extraction chromatography resins[8] are usually used to quickly separate low-concentration substances, so various extraction chromatography resins have been developed for the separation of radioactive substances. Horwitz et al. developed octyl-(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and tributyl phosphate (TBP) coated resins (called TRU resins) [9] and Aliquat® 336 coated resins (called TEVA resins) [10-12]. Later, UTEVA [9] resin and DGA

[13] resin were developed. Although traditional resins such as UTEVA, TRU, TEVA and DGA are simple to operate during the separation process, they not only adsorb plutonium but also other nuclides

[14] . In order to effectively separate plutonium, a combination of multiple resins is usually used. Horwitz first proposed the TEVA-UTEVA-TRU resin combination, where TEVA resin adsorbs Th and Pu, UTEVA resin adsorbs U [9], and TRU resin adsorbs Am and Pu(III), thereby selectively separating a series of actinides [9]. The combined use of resins increases the amount of radioactive waste or chemical waste, and also increases time and cost. In order to improve the separation efficiency, it is necessary to develop a new high-selectivity Pu(IV) separation method. The most stable chemical form of plutonium in low concentration HNO3 is Pu 4+ cation, and in high concentrations of HNO3, it forms a stable complex anion with nitrate, namely Pu(NO3)6 2-Americium and lanthanides do not form complex anions in nitric acid. Therefore, plutonium can be separated from lanthanides by anion exchange in high-concentration nitric acid. However, some actinides (such as uranium, neptunium, and thorium) form anions in high-concentration nitric acid solutions, which interfere with the adsorption of plutonium and hinder its specific separation [15-17]. In order to improve the selectivity of anion exchange for plutonium, it is necessary to modify the anion exchanger and add functional groups with high affinity for plutonium. Functionalized ionic liquids are traditional ionic liquids that have certain functional groups grafted onto the anions or cations to give them an affinity for certain metal ions [17-20]. Some functionalized ionic liquids can extract Pu(IV) in the form of anion exchange, and their functional groups can specifically recognize plutonium, thereby improving the efficiency of uranium-plutonium separation [21,22]. Despite significant progress in uranium-thorium (plutonium) separation technology, existing materials suffer from limitations in selectivity, acid tolerance, and engineering suitability, hindering their practical application. Modified phosphate extractants, through molecular structure optimization, are expected to overcome the limitations of traditional systems and achieve efficient separation of uranium-thorium or uranium-plutonium under high-acidity conditions. Summary of the Invention

[0003] The invention provides a piperidinium phosphate salt that can be used to prepare and separate U / Th or U / Pu, and also provides a preparation method of the compound and the application of the compound in separating uranium-thorium or uranium-plutonium from acidic radioactive wastewater.

[0004] The compound of the present invention is a compound represented by Formula 1: 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt. .

[0005] The preparation method of 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt of the present invention is shown in Formula 2: .

[0006] Right now: 1) React 32.25 g of di(2-ethylhexyl) phosphate with 13 g of SOCl2 at 60°C for 24 hours to obtain di(2-ethylhexyl) phosphate chloride. Then, add 12 g of 4-chloro-1-butanol and 50 mL of acetonitrile as solvent, and react at 80°C for 24 hours to obtain a crude product. Finally, purify the product by column chromatography using a 3:1 ratio of petroleum ether to ethyl acetate to obtain the intermediate 4-chlorobutyl bis(2-ethylhexyl) phosphate. 2) Synthesis of 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt: 3.23 g of di(2-ethylhexyl)phosphate and 1.6 g of N-hydroxyethylpiperidine were mixed and reacted at 80°C for 24 hours to obtain the target compound, 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt.

[0007] The compound of the present invention, 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt, can be used to separate U and Th.

[0008] Through molecular structure optimization, the modified phosphate extractant of this invention is expected to overcome the limitations of traditional systems and achieve efficient separation of uranium, thorium, and plutonium under high acidity conditions. This ionic liquid synthesized in this invention features a phosphate functional group with affinity for Th / Pu(IV) grafted onto the pyridine ring. This piperidine phosphate ionic liquid can extract thorium through coordination or ion exchange. Furthermore, its functional group specifically recognizes Th / Pu(IV), potentially improving uranium, thorium, and plutonium separation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 The effect of nitric acid concentration on the extraction of U, Th and Eu by BEPHP, as well as the effect of nitric acid concentration on the separation coefficients of Th / Eu and Th / U.

[0010] Figure 2 Effect of time on the extraction performance of thorium by extractants.

[0011] Figure 3 The effect of temperature on the extraction performance of thorium and uranium. DETAILED DESCRIPTION

[0012] The present invention is explained below with reference to embodiments.

[0013] (I) Preparation of 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt 1) React 32.25 g of di(2-ethylhexyl) phosphate with 13 g of SOCl2 at 60°C for 24 hours to obtain di(2-ethylhexyl) phosphate chloride. Then, add 12 g of 4-chloro-1-butanol and 50 mL of acetonitrile as solvent, and react at 80°C for 24 hours to obtain a crude product. Finally, purify the product by column chromatography using a 3:1 ratio of petroleum ether to ethyl acetate to obtain the intermediate 4-chlorobutyl bis(2-ethylhexyl) phosphate. 2) Synthesis of 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt: 3.23 g of di(2-ethylhexyl)phosphate and 1.6 g of N-hydroxyethylpiperidine were mixed and reacted at 80° C. for 24 hours to obtain the target compound 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt as shown in Formula 1, hereinafter referred to as BEPHP.

[0014] (2) Preparing an organic solution (ionic liquid) using the compound of the present invention Dissolve 0.542 g of 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt in kerosene and transfer the mixture to a 50 mL volumetric flask to a constant volume to obtain an organic solution of 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt with a concentration of 20 mmol / L.

[0015] (III) Separation of Plutonium Using Ionic Liquids Prepared from the Compounds of the Present Invention Since plutonium is highly radiotoxic, an element with similar chemical properties and lower radiotoxicity can be selected as a substitute. Therefore, Th was used instead of Pu in the separation experiment of the present invention

[23] . The specific method is as follows: Add 5 mL of aqueous solution with different nitric acid concentrations (1-8 mol / L) (the metal ion concentration is constant at 0.1 mmol / L) and an equal volume of 20 mmol / L phosphate onium salt organic solution to each centrifuge tube. Oscillate at 25°C and 200 rpm for 20 minutes. After centrifugation, take the aqueous phase for measurement.

[0016] The effects of nitric acid concentration on the extraction of U, Th, and Eu by BEPHP, as well as the effects of nitric acid concentration on the separation coefficients of Th / Eu and Th / U, are shown in the table. Figure 1 and Table 1.

[0017]

[0018] The experimental results show that the best separation effect of Th / U is achieved when the concentration of nitric acid is 1 mol / L, and the separation coefficient reaches 120.30. The best separation effect of Th / Eu is achieved when the concentration of nitric acid is 2 mol / L, and the separation coefficient reaches 52134.65.

[0019] TEVA resin is a resin commonly used for the separation of actinides and lanthanides. Its functional group is Aliquat-336. Therefore, the Th / Eu and Th / U separation coefficients of piperidine phosphate extractant and Aliquat-336 at different nitric acid concentrations were compared. The results are shown in Table 2.

[0020]

[0021] The experimental results show that under the same acidity, the ability to separate Th / U follows: BEPHP > Aliquat336; the ability to separate Th / Eu follows: Aliquat-336 > BEPHP.

[0022] 2. Effect of time on the performance of extractants in extracting thorium Add 5 mL of 1 mol / L nitric acid, 0.1 mmol / L thorium nitrate aqueous solution and an equal volume of 10 mmol / L phosphate ester onium salt organic solution to a centrifuge tube, shake at 25°C, 200 r / min for different times (0-180 minutes), centrifuge and take the aqueous phase for measurement. The results are shown in Figure 2 .

[0023] The experimental results showed that the extraction was balanced when the oscillation time was 20 minutes, so 20 minutes was the optimal extraction time.

[0024] 3. Effect of temperature on the extraction performance of thorium and uranium 5 mL of 1 mol / L nitric acid, 0.1 mmol / L uranyl nitrate, and 0.1 mmol / L thorium nitrate aqueous solution and an equal volume of 10 mmol / L phosphate onium salt organic solution were added to the centrifuge tubes, and the mixture was shaken at 200 r / min for 30 minutes at different temperatures (293-333 K). After centrifugation, the aqueous phase was measured. The results are shown in the table. Figure 3 .

[0025] The references involved in the present invention are as follows 1. Jim Smith NM, Tony Irwin (2023) The risks of radioactive wastewater release. science 382:31-33 2. Ma H, Shen M, Tong Y, Wang X (2023) Radioactive WastewaterTreatment Technologies: A Review. Molecules 28. 3. Delegard CH, Peterson RA (2019) Precipitation and crystallizationprocesses in reprocessing, plutonium separation, purification, and finishing,chemical recovery, and waste treatment. In: Engineering Separations UnitOperations for Nuclear Processing. CRC Press, pp 51-143 4. Manchanda VK, Pathak P, Mohapatra PJIE, Advances SEASo (2009) Newdevelopments in thorium, uranium, and plutonium extraction. 19:65-118 5. Xiao W, Pan D, Niu Z, Fan Y, Wu S, Wu W (2022) Opportunities andchallenges of high-pressure ion exchange chromatography for nuclideseparation and enrichment. Chinese Chemical Letters 33:3413-3421. 6. Rout A (2022) Separation of Plutonium from Other Actinides andFission Products in Ionic Liquid Medium. Separation & Purification Reviews52:98-122. 7. Rout A, Venkatesan KA, Antony MP (2019) Ammonium-Based Amide-Functionalized Task-Specific Ionic Liquid for Actinide Separations. SolventExtraction and Ion Exchange 36:558-573. 8. Khairina R, Giyatmi, Makmur M, Kusdiana (2021) The Development ofa rapid method for Plutonium separation by extraction chromatography and itsapplication for environmental samples. Journal of Physics: Conference Series1882. 9. Horwitz EP, Dietz ML, Chiarizia R, Diamond H, Maxwell III SL,Nelson MRJACA (1995) Separation and preconcentration of actinides byextraction chromatography using a supported liquid anion exchanger:application to the characterization of high-level nuclear waste solutions.310:63-78 10. Philip Horwitz E, Chiarizia R, Dietz MLJSe, exchange i (1992) Anovel strontium-selective extraction chromatographic resin. 10:313-336 11. Horwitz EP, Dietz ML, Chiarizia R, Diamond H, Essling AM, GraczykDJACA (1992) Separation and preconcentration of uranium from acidic media byextraction chromatography. 266:25-37 12. Kim G, Burnett WC, Horwitz EPJAC (2000) Efficientpreconcentration and separation of actinide elements from large soil andsediment samples. 72:4882-4887 13. Vajda N, Zagyvai M, Groska J, Bokori E, Molnár Z, Braun M (2020)Determination of uranium, plutonium and americium in soil and sediment by asequential separation procedure using a single DGA column. Journal ofRadioanalytical and Nuclear Chemistry 326:695-710. 14. Maxwell III SLJJoR, Chemistry N (2006) Rapid column extractionmethod for actinides and 89 / 90 Sr in water samples. 267:537-543 15. Yadav AG, Mohapatra PK, Valsala TP, Sathe DB, Bhatt RB (2022)Highly efficient Plutonium(IV) uptake from acidic feeds using four extractionchromatography resins containing diglycolamides and ionic liquid. Journal ofChromatography A 1665. 16. Ruhela R, Panja S, Tomar BS, Singh AK, Tripathi SC, Gandhi PM,Hubli RC (2014) Liquid–liquid extraction studies for the separation andrecovery of plutonium from acidic medium with novel ligand Benzodioxodiamide(BenzoDODA). Separation and Purification Technology 124:49-53. 17. Rout A, Ramanathan N (2022) Cyphos nitrate: A potential ionicliquid for the extraction and selective separation of plutonium (IV) fromother metal ions present in nitric acid. Journal of Ionic Liquids 2. 18. Mohapatra PK (2015) Diglycolamide-Based Solvent Systems in RoomTemperature Ionic Liquids for Actinide Ion Extraction: A Review. ChemicalProduct and Process Modeling 10:135-145. 19. Venkateswara Rao C, Rout A, Boda A, Musharaf. Ali S, VenkatesanKA (2021) Anion assisted extraction of U(VI) in alkylammonium ionic liquid:Experimental and DFT studies. Separation and Purification Technology 261. 20. De Jesus K, Rodriguez R, Baek DL, Fox RV, Pashikanti S, Sharma K(2021) Extraction of lanthanides and actinides present in spent nuclear fueland in electronic waste. Journal of Molecular Liquids 336. 21. Mark P. Jensen JrN, James V. Beitz, S. Skanthakumar, and L.Soderholm (2003) Mechanisms of Metal Ion Transfer into Room-Temperature IonicLiquids: The Role of Anion Exchange. Journal of the American ChemicalSociety:15466-15473 22. Jensen MP, Neuefeind J, Beitz JV, Skanthakumar S, SoderholmLJJotACS (2003) Mechanisms of metal ion transfer into room-temperature ionicliquids: the role of anion exchange. 125:15466-15473 23. Krauskopf KB (1986) Thorium and rare-earth matals as Analogs forActinide elements. Chemical Geology 55:323-335。

Claims

1. The compound of formula 1: 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt 。 2. The method for preparing 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt according to claim 1, characterized in that As shown in formula 2, that is: 1) React 32.25 g of di(2-ethylhexyl) phosphate with 13 g of SOCl2 at 60°C for 24 hours to obtain di(2-ethylhexyl) phosphate chloride. Then, add 12 g of 4-chloro-1-butanol and 50 mL of acetonitrile as solvent, and react at 80°C for 24 hours to obtain a crude product. Finally, purify the product by column chromatography using a 3:1 ratio of petroleum ether to ethyl acetate to obtain the intermediate 4-chlorobutyl bis(2-ethylhexyl) phosphate. 2) Synthesis of bis(2-ethylhexyl)(4-(2-(2-hydroxyethyl)piperidinyl)-1-butyl phosphate: 3.23 g of bis(2-ethylhexyl)phosphate and 1.6 g of 2-hydroxyethylpiperidinyl were mixed and reacted at 80°C for 24 hours to obtain the title compound.

3. Use of the compound 1-(4-(bis((2-ethylhexyl)butyl phosphate)-1-(2-hydroxyethyl)piperidinium salt according to claim 1 for separating U / Th or U / Pu.

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