Method for analyzing abundance of lithium isotope in crown ether-ionic liquid sample

Abstract

The invention provides a method for analyzing abundance of lithium isotopes, and particularly relates to a method for analyzing abundance of lithium isotopes in complex-state lithium salt in crown ether-ionic liquid. A lithium-containing crown ether-ionic liquid sample is mixed with a stripping agent for reverse extraction, so that lithium ions are transferred to a water phase, and the stripping agent is HNO3 with the concentration of 0.16 mol / L-0. 48 mol / L; the water phase is subjected to digestion, in the digestion process, HNO3 with the concentration being 14 mol / L to 16 mol / L and H2O2 with the concentration being 30% are adopted for treating the water phase, and a solution to be detected is obtained; and analyzing the abundance of the lithium isotope in the sample to be detected. According to the analysis method disclosed by the invention, the abundance of the lithium isotope in the crown ether-ionic liquid is accurately measured by different isotope analysis methods, and the detection result is reliable and accurate.

Description

Technical Field

[0001] The invention belongs to the field of analysis and testing research, and specifically relates to an analysis method for lithium isotope abundance in crown ether-ionic liquid. Background Art

[0002] Lithium (Li) has two stable isotopes 6 Li and 7 Li, whose natural abundance is 7.52% and 92.48% respectively. 6 Li is an essential fuel for nuclear fusion reactors; 7 Li can be used as a molten salt medium for thorium reactors, and as a coolant and heat carrier for nuclear fusion reactors. Therefore, the separation of the two stable isotopes of lithium in nature plays a vital role in national defense and economic construction. Compared with the current industrialized amalgam method, the extraction and separation method using crown ether as an extractant and ionic liquid as a solvent is a green and efficient lithium isotope separation technology. Shu Yuzhen et al. established an efficient lithium isotope separation method using crown ether as an extractant and ionic liquid as a solvent. This method is based on 6 Li and 7 Li is separated and enriched during the exchange process between the organic phase and the aqueous phase. 6 Li is enriched in the crown ether-ionic liquid, while 7 Li is enriched in the aqueous phase. In this method, lithium isotope abundance is the most important analytical data. It provides technical parameters in the process research stage to ensure the normal operation of the process. At the same time, as an important nuclear material, the lithium isotope abundance of the final product needs to be accurately determined. The current reports are all methods for separating lithium isotopes using crown ether-ionic liquids, and there is no analytical method for the lithium isotope abundance in crown ether-ionic liquids. Therefore, it is necessary to establish an accurate and reliable analytical method for determining the lithium isotope abundance in crown ether-ionic liquids. Summary of the invention

[0003] In view of this, the main purpose of the present invention is to provide an accurate and reliable analysis method for lithium isotope abundance in crown ether-ionic liquids, so as to achieve accurate analysis of lithium isotope abundance in complex lithium salts in crown ether-ionic liquids by different analysis methods.

[0004] To this end, the present invention provides a method for analyzing lithium isotope abundance in a crown ether-ionic liquid sample, the method comprising the following steps:

[0005] A lithium-containing crown ether-ionic liquid sample is mixed with a stripping agent for stripping, so that lithium ions are transferred to an aqueous phase, wherein the stripping agent is 0.16mol / L-0.48mol / L HNO3; the aqueous phase is digested, wherein the digestion uses 14mol / L-16mol / L HNO3 and 30% H2O2 to treat the aqueous phase to obtain a solution to be tested; and the lithium isotope abundance in the sample to be tested is analyzed.

[0006] In some embodiments, the volume ratio of the crown ether-ionic liquid sample to the stripping agent is 1:10 to 1:30.

[0007] In some embodiments, the stripping comprises mixing the crown ether-ionic liquid sample and the stripping agent at a oscillation frequency of 160 rpm to 180 rpm for 20 to 40 min, and centrifugally separating to obtain the aqueous phase.

[0008] In some embodiments, the centrifugation is performed at 2000 rpm to 3000 rpm for 1 to 3 min; more preferably, the back extraction is performed 2 to 3 times.

[0009] In some embodiments, the digestion includes the following steps: evaporating the water in the aqueous phase; adding 14 mol / L to 16 mol / L HNO3 and 30% H2O2 to the evaporated product in no particular order to digest and obtain a digestion solution; diluting and fixing the digestion solution to prepare a test solution.

[0010] In some embodiments, the evaporation to dryness is performed at a temperature of 200°C to 250°C.

[0011] In some embodiments, the volume ratio of the 30% H2O2 hydrogen peroxide solution to the 14 mol / L to 16 mol / L nitric acid is 1:5 to 1:10.

[0012] In some embodiments, the digestion is performed at 200° C. to 250° C.; preferably, the digestion is performed 3 to 4 times.

[0013] In some embodiments, the digestion solution is diluted and fixed to volume with 0.32 mol / L HNO3 or water.

[0014] In some embodiments, when multi-collector inductively coupled plasma mass spectrometry is used, the lithium ion concentration in the solution to be tested is 100 μg / L to 800 μg / L, and when thermal ionization mass spectrometry is used, the lithium ion concentration in the solution to be tested is 0.5 g / L to 1 g / L.

[0015] In some embodiments, the lithium isotope abundance is determined using multi-collector inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry, respectively.

[0016] The present invention provides a method for analyzing the abundance of lithium isotopes in crown ethers / ionic liquids. The method uses 0.16 mol / L-0.48 mol / L HNO3 as a stripping agent to convert an organic phase sample of the crown ether / ionic liquid into an aqueous solution sample. The first stripping efficiency is greater than 75%, and the stripping efficiency reaches more than 99.7% after 2-3 strippings. The complete recovery of lithium can be achieved after 2-3 strippings. 7 Li preferentially enters the water phase. 6 Li is more inclined to be retained in the crown ether-ionic liquid, so the lithium isotope fractionation will occur in the stripping process, and the complete recovery of lithium avoids the deviation between the measured value and the true value. The digestion step can convert the organic macromolecular lithium salt into an inorganic ionic lithium salt suitable for multi-receiver inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry, and can realize the determination of the lithium isotope abundance in crown ethers / ionic liquids with different lithium ion concentrations. The analysis method of the present application is used to measure actual scientific research samples. The analysis precision of the analysis method of the present invention using multi-receiver inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry is 0.2‰ and 0.3‰ respectively. After the same batch of scientific research samples were processed, they were parallelly measured by multi-receiver inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry, and the measured data had a good degree of agreement, indicating that the analysis methods of multi-receiver inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry for measuring the lithium isotope abundance in crown ethers / ionic liquids are accurate and reliable. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Throughout the specification, unless otherwise specifically stated, the terms used herein should be understood as meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. In the event of a conflict, the present specification takes precedence.

[0019] It should be noted that, in the embodiments of the present invention, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a method or device including a series of elements includes not only the elements explicitly stated, but also other elements not explicitly listed, or also includes elements inherent to the implementation of the method or device. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the existence of other related elements in the method or device including the element.

[0020] It should be noted that the terms "first\second\third" involved in the embodiments of the present invention are only used to distinguish similar objects, and do not represent a specific order for the objects. It is understandable that "first\second\third" can be interchanged with a specific order or sequence where permitted. It should be understood that the objects distinguished by "first\second\third" can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those described herein.

[0021] Thermal ionization inductively coupled plasma mass spectrometry (TIMS) and multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) are commonly used analytical methods for the precise determination of isotopic abundance. Both methods are suitable for the determination of isotopic abundance in inorganic systems. However, crown ether / ionic liquid samples are an organic system with a density greater than that of water and a certain viscosity. The lithium in the sample combines with organic macromolecules to form a complex lithium salt. When the organic matrix is ​​tested by, for example, TIMS or MC-ICP-MS, it is impossible to directly inject the sample into the instrument for testing due to problems such as the inability to directly inject the sample, changes in plasma composition, and severe interference during the test process.

[0022] In view of this, the present invention provides a method for analyzing lithium isotope abundance, wherein a lithium-containing crown ether-ionic liquid sample is mixed with a stripping agent for stripping, so that lithium ions are transferred to an aqueous phase, wherein the stripping agent is 0.16mol / L-0.48mol / L HNO3; the aqueous phase is digested, wherein the digestion uses 14mol / L-16mol / L HNO3 and 30% H2O2 to treat the aqueous phase to obtain a solution to be tested; and the lithium isotope abundance in the sample to be tested is analyzed.

[0023] In the present invention, the lithium to be analyzed is contained in the crown ether-ionic liquid containing lithium in the form of a complex, and the method comprises the following steps: (1) mixing the crown ether-ionic liquid sample containing lithium with a stripping agent for stripping, so that the lithium ions are transferred to the aqueous phase, wherein the stripping agent is 0.16mol / L-0.48mol / L HNO3; converting the complex lithium salt in the organic phase into an organic macromolecular lithium salt in the aqueous solution by stripping, thereby avoiding the interference of the organic matrix in the crown ether-ionic liquid sample on the detection; on the other hand, when TIMS or MC-ICP-MS is used for determination, since the air entrained in the ion source already has the constituent elements of HNO3 (N, O and other elements), nitric acid as a stripping agent can avoid the inorganic medium from generating interfering ions during subsequent measurements and can prevent the occurrence of hydrolysis. Thus, the accuracy and reliability of the measurement are improved. Using the above concentration of HNO3 as the stripping agent is beneficial to improving the extraction efficiency and can recover lithium from the crown ether / ionic liquid sample with higher efficiency. After stripping 2-3 times, the stripping recovery rate of lithium reaches more than 99.7%. 7 Li preferentially enters the water phase. 6 Li prefers to be retained in the crown ether-ionic liquid, so the lithium isotope fractionation will occur during the stripping process. If the lithium cannot be completely recovered, the measurement result will deviate from the true value. (2) The organic macromolecular lithium salt in the aqueous phase solution after stripping is converted into a LiNO3 aqueous solution through digestion. The digester is 30% H2O2 and 14mol / L~16mol / L HNO3. On the one hand, the strong oxidizing properties of H2O2 and HNO3 can quickly and completely destroy organic matter and convert organic lithium salts into LiNO3 chemical forms suitable for detection, thereby realizing the determination of lithium isotope abundance by different analytical methods; on the other hand, the digester used in this application will not introduce new media, which is conducive to reducing the interference of the medium during detection and further improving the accuracy of detection. (3) This application compares the measurement results by using two different analytical methods (multi-collector inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry). The measurement data have a good degree of agreement. The precision of the measurement results of the two methods is 0.02% and 0.03%, respectively. This shows that the method is accurate and reliable.

[0024] The following is a detailed description of the lithium isotope abundance analysis method disclosed in the book through a specific embodiment. In this embodiment, the method may include the following steps:

[0025] 1) Stripping: mixing the crown ether / ionic liquid sample with a stripping agent to uniformly mix the crown ether / ionic liquid sample and the stripping agent to obtain a stripping mixed solution, wherein the stripping agent is 0.16 mol / L to 0.48 mol / L HNO3;

[0026] 2) Centrifugation: centrifuging the stripping mixed solution to separate the layers and collecting the supernatant;

[0027] 3) digestion: the supernatant is heated and evaporated to dryness, and then digested using 14 mol / L to 16 mol / L HNO3 and 30% H2O2 as digestion agents to obtain a digestion solution;

[0028] 4) Volume determination: diluting the digestion solution and adjusting the volume, and diluting the adjusted digestion solution to a suitable concentration as a test solution;

[0029] 5) Measurement: measuring the lithium isotope abundance in the solution to be tested, and calculating the lithium isotope abundance value in the crown ether / ionic liquid sample.

[0030] In the present disclosure, the crown ether / ionic liquid sample refers to a sample that has been enriched with 6 Crown ether / ionic liquid sample of Li isotope. The present application does not specifically limit the crown ether / ionic liquid system, and any crown ether / ionic liquid system that can be used to enrich lithium isotopes can be measured using the method of the present application. For example, benzo-15-crown-5 / 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt ionic liquid.

[0031] In some embodiments, the lithium ion content in the lithium-containing crown ether-ionic liquid may be 0.3 mol / L, 0.5 mol / L.

[0032] In step 1), illustratively, when HNO3 is used as the stripping agent, the concentration of HNO3 can be 0.16 mol / L, 0.32 mol / L, 0.48 mol / L, or a value between the ranges formed by any two of these values. In some embodiments, the stripping agent is 0.48 mol / L HNO3.

[0033] In some embodiments, in the step 1), the volume ratio of the crown ether / ionic liquid sample to the stripping agent is 1:10 to 1:30. When the volume ratio of the two is within the above range, it is beneficial to fully separate the organic phase and the aqueous phase, reduce the number of stripping times, and improve the stripping efficiency, thereby reducing the deviation of the measurement results caused by incomplete recovery of lithium isotopes. On the other hand, it is beneficial to reduce the sample loss caused by the dissolution of the crown ether / ionic liquid in the aqueous phase. Exemplarily, the volume ratio of the crown ether / ionic liquid sample: the stripping agent can be 1:10, 1:15, 1:20, 1:25, 1:30 or a value between the ranges consisting of any two of them. In some embodiments, the volume ratio of the crown ether / ionic liquid sample: the stripping agent is 1:20 to 1:30, preferably 1:30.

[0034] In some embodiments, in step 1), the crown ether / ionic liquid sample and the stripping agent are mixed by oscillation, with an oscillation frequency of 160 rpm to 180 rpm and an oscillation time of 20 to 40 min. The use of oscillation mixing is conducive to quickly and evenly mixing the aqueous phase and the organic phase.

[0035] In some embodiments, in step 2), the centrifugation frequency is 2000 rpm to 3000 rpm, and the centrifugation time is 1 to 3 minutes. The above centrifugation frequency and centrifugation time are conducive to fully separating the organic phase and the aqueous phase, and improving the efficiency of the experimental operation.

[0036] In some embodiments, the analysis method further comprises: before step 3), repeating step 1) and step 2) 2 to 3 times, and combining the aqueous phases. Repeating the stripping and centrifugation operations is beneficial to improving the stripping efficiency, completely recovering the lithium in the crown ether-ionic liquid, and further improving the accuracy of the detection.

[0037] In the method of the present application, the step 3) evaporates the supernatant to dryness, which is beneficial to improve the efficiency of the subsequent digestion step. In addition, through evaporation to dryness, the low-concentration sample can be stripped and concentrated multiple times to achieve the determination of lithium isotope abundance in crown ethers / ionic liquids with different lithium ion concentrations.

[0038] In some embodiments, in step 3), the evaporation is performed at a temperature of 200°C to 250°C. By heating the supernatant at the above temperature, the evaporation rate is increased, the experimental operation efficiency is improved, and on the other hand, the decomposition of the inorganic lithium salt in the supernatant at high temperature or other side reactions are avoided, thereby further improving the accuracy of the detection. Usually, the supernatant is evaporated to make the lithium ion concentration after constant volume reach the g / L level.

[0039] In the step 3), the organic macromolecular lithium salt obtained by stripping is digested to prepare a LiNO3 form suitable for measurement.

[0040] In some embodiments, the digester is 30% H2O2 and 14mol / L-16mol / L HNO3. The volume ratio of H2O2 and HNO3 in the digester is 1:5-10. For example, the volume ratio of H2O2 and HNO3 in the digester can be 1:5, 1:8, 1:10 or a value between the ranges formed by any two numbers thereof. Preferably, the volume ratio of H2O2 and HNO3 in the digester is 1:10. The method of the present application uses 30% H2O2 and 14mol / L-16mol / L HNO3 for digestion. On the one hand, the strong oxidizing properties of H2O2 and HNO3 can quickly and completely destroy organic matter and convert organic macromolecular lithium salts into LiNO3 chemical forms suitable for detection, thereby realizing the determination of lithium isotope abundance by different analytical methods; on the other hand, the digester used in the present application will not introduce new matrix components, which is conducive to reducing impurity interference during detection and further improving the accuracy of detection. In the present application, H2O2 and HNO3 are added to the concentrate for digestion respectively, and the order of addition is not limited.

[0041] In some embodiments, the digestion times are 3 to 4. Repeating the digestion steps is beneficial to fully convert the organic macromolecular lithium salt into a LiNO3 form suitable for detection, and reduce impurities in the sample to be tested, thereby improving the accuracy of detection.

[0042] In some embodiments, in step 4), 0.32 mol / L HNO3 or water is used to dilute and fix the digestion solution. HNO3 or water is the best medium for mass spectrometry detection. Since the air already has the constituent elements of HNO3, after adding the HNO3 matrix or water, the polyatomic ions formed by H2, N2, and O2 do not increase significantly, thereby avoiding the interference of impurity peaks on the detection results and improving the accuracy of detection.

[0043] In the step 4), the constant volume digestion solution is diluted to a suitable concentration as a test solution for instrument measurement. The suitable concentration is 100 μg / L to 800 μg / L for lithium ion detection using multi-collector inductively coupled mass spectrometry (MC-ICP-MS), and 0.5 g / L to 1 g / L for lithium ion detection using thermal ionization mass spectrometry (TIMS). This enables the test method of the present application to measure and accurately calculate the lithium isotope abundance.

[0044] In some embodiments, in step 5), the measurement uses multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) and thermal ionization mass spectrometry (TIMS). The present application uses MC-ICP-MS and thermal ionization mass spectrometry (TIMS) for measurement, which can accurately determine the isotopic abundance.

[0045] In some embodiments, the step 5) is performed in the order of lithium isotope standard material-test solution-lithium isotope standard material on a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) or a thermal ionization mass spectrometer (TIMS). The purpose of testing in the above order is to calculate the instrument mass discrimination correction factor and correct the instrument signal drift.

[0046] In the present application, the lithium isotope standard material may be a commercially available certified standard material, such as IRMM-016, IRMM-015, and GBW04432.

[0047] In some embodiments, the lithium isotope abundance is calculated as follows: instrument mass discrimination correction factor = 1 / 2 (reference value of standard material / previous measurement value of standard material + reference value of standard material / later measurement value of standard material). True value of lithium isotope abundance in sample = mass discrimination correction factor * sample measurement value.

[0048] In some embodiments, the MC-ICP-MS model is Nu PlasmaⅡ, and the TIMS model is TritonPlus.

[0049] The present application will be described in detail below with reference to specific embodiments.

[0050] Example

[0051] Feasibility testing of detection methods

[0052] In order to verify the feasibility of the analytical method of the present application, crown ether / ionic liquid samples with known lithium ion concentrations were used for detection, and the recovery rate of lithium during the treatment process was calculated. The closer the recovery rate is to 100%, the closer the measurement result is to the true value. Different analytical methods were used to test the lithium isotope abundance of the same scientific research sample after the same pretreatment process, and the results were compared. The smaller the difference, the higher the detection accuracy of the analytical method.

[0053] Example 1

[0054] 1) Stripping: Take 2 mL of benzo-15-crown-5 / 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquid sample with a lithium ion concentration of 0.3 mol / L in a centrifuge tube, add 20 mL of 0.48 mol / L HNO3, and place it on an oscillator at an oscillation frequency of 160 rpm for 40 min to completely mix the two phases.

[0055] 2) Centrifugation: Place the mixed sample in a centrifuge at 2000 rpm for 3 minutes to separate the two phases, and take the supernatant into a beaker.

[0056] 3) Repeat the above stripping and centrifugation steps 3 times, and collect all the supernatant in a beaker; wherein, measure the lithium ion concentration in the supernatant obtained after each stripping and centrifugation, and calculate the lithium ion recovery rate. The lithium ion concentration is tested according to the method of JY / T0567-2020.

[0057] The lithium ion recovery rate is calculated according to the formula: (lithium ion concentration × stripping solution volume) ÷ theoretical mass of lithium ions in the sample × 100%. The calculation results are shown in Table 1. It can be understood that when the lithium ion recovery rate is close to 100%, it is not necessary to continue the stripping step.

[0058] 4) Digestion: Place the beaker containing all the supernatant on an electric heating plate at 200°C, heat to evaporate the water, then add 2.5mL16mol / L HNO3 and 0.5mL 30% H2O2 in sequence for digestion, repeat the digestion steps 3 times to obtain a digestion solution.

[0059] 5) Make up the volume: Add 1mL 0.32mol / L HNO3 solution to the above digestion solution, then transfer to a 5mL volumetric flask. Rinse the beaker with 0.32mol / L HNO3 and transfer to the volumetric flask. Make up the volume to the mark with 0.32mol / L HNO3. Dilute with 0.32mol / L HNO3 to a lithium ion concentration of 100μg / L and 0.5g / L to be tested.

[0060] 6) Measurement: The above-mentioned test solution was tested on Nu Plasma II multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) in the order of lithium isotope standard solution-test solution-lithium isotope standard solution, wherein the lithium isotope standard solution is IRMM-016. The test results are shown in Table 1.

[0061] Calculation of lithium isotope abundance:

[0062] Correction factor calculation:

[0063] The instrument mass discrimination correction factor is calculated according to formula (1):

[0064] K=R c / R m ……………………………………(1)

[0065] Where:

[0066] K——Instrument mass discrimination correction factor;

[0067] R c ——Lithium isotope standard solution 6 Li / 7 Standard value of Li;

[0068] R m ——Lithium isotope standard solution 6 Li / 7 The measured value of Li.

[0069] right 6 Li / 7 The Li isotope abundance ratio was used for correction.

[0070] After calibration, the sample 6 Li / 7 Li value R 校正 Calculate according to formula (2):

[0071] R 校正 =R 测量 ×K……………………………………(2)

[0072] Where:

[0073] R 校正 ——In the sample to be tested 6 Li / 7 Correction value of Li;

[0074] R 测量 ——In the sample to be tested 6 Li / 7 The measured value of Li.

[0075] Embodiment 2-4

[0076] Example 2-4 The lithium-containing ionic liquid-crown ether sample was treated and the lithium recovery rate was tested in a similar manner to Example 1, except that the amount of the added stripping agent was adjusted so that the volume ratio of the crown ether-ionic liquid sample to the stripping agent had a value as described in Table 1. The test results are shown in Table 1.

[0077] Table 1 Determination results of lithium recovery and lithium isotope abundance under different stripping phases using 0.48 mol / L HNO3 as stripping agent

[0078]

[0079] Embodiment 5:

[0080] 1) Stripping: Take 1 mL of benzo-15-crown-5 / 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ionic liquid sample with a lithium ion concentration of 0.5 mol / L in a centrifuge tube, add 30 mL of 0.16 mol / L HNO3, and place it on an oscillator at an oscillation frequency of 180 rpm for 20 min to completely mix the two phases.

[0081] 2) Centrifugation: Place the mixed sample in a centrifuge at 3000 rpm for 1 min to separate the two phases, and take the supernatant into a beaker.

[0082] 3) Repeat the above stripping and centrifugation steps twice, and collect all the supernatant in a beaker; wherein, measure the lithium ion concentration in the supernatant obtained after each stripping and centrifugation.

[0083] The test method of lithium ion concentration and the calculation of lithium ion recovery rate are the same as those shown in Example 1, and the calculation results are shown in Table 2. It can be understood that when the lithium ion recovery rate is close to 100%, there is no need to continue the stripping step.

[0084] 4) Digestion: Place the beaker containing all the supernatant on an electric heating plate at 250°C, heat to evaporate the water, then add 3mL 14mol / L HNO3 and 0.3mL 30% H2O2 in sequence for digestion, repeat the digestion steps 3 times to obtain a digestion solution.

[0085] 5) Volume adjustment: Add 1 mL of H2O solution to the above digestion solution, then transfer to a 5 mL volumetric flask. Rinse the beaker with H2O and transfer to the volumetric flask. Use H2O to adjust the volume to the mark. Use H2O to dilute the solution to a lithium ion concentration of 800 μg / L and the original solution after volume adjustment for testing.

[0086] 6) Measurement: The above-mentioned test solutions were tested on Nu Plasma II multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) in the order of lithium isotope standard solution-test solution-lithium isotope standard solution, wherein the lithium isotope standard solution IRMM-016, 6 Li / 7 Li=0.082121±0.000087. The calculation method of the abundance of lithium isotopes is the same as that in Example 1.

[0087] Embodiment 6-8

[0088] Examples 6-8 The lithium-containing ionic liquid-crown ether sample was treated and the lithium recovery rate was tested in a similar manner to Example 5, except that the amount of the added stripping agent was adjusted so that the volume ratio of the crown ether-ionic liquid sample to the stripping agent had a value as described in Table 2. The test results are shown in Table 2.

[0089] Table 2 The recovery rate of lithium under different stripping phases using 0.16 mol / L HNO3 as stripping agent

[0090]

[0091]

[0092] Methodological validation

[0093] In order to verify the accuracy of the method, the crown ether / ionic liquid samples with known lithium ion concentrations in the above Examples 1 and 5 were treated and then tested for lithium isotope abundance on MC-ICP-MS and TIMS respectively to obtain the actual scientific research samples. 6 Li / 7 Li value, the measurement results are shown in Table 3.

[0094] Table 3 Parallel determination results of lithium isotopes of crown ether / ionic liquid samples by MC-ICP-MS and TIMS

[0095]

[0096] It can be seen that the data measured by MC-ICP-MS and TIMS are in good agreement, and the relative deviation of the measurement results of the two methods is ≤0.05%, indicating that the established MC-ICP-MS and TIMS methods for measuring lithium isotope abundance in crown ethers / ionic liquids are accurate and reliable.

[0097] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for analyzing lithium isotope abundance, characterized in that: The method comprises the following steps: A lithium-containing crown ether-ionic liquid sample is mixed with a stripping agent for stripping, so that lithium ions are transferred to an aqueous phase, wherein the stripping agent is 0.16mol / L-0.48mol / L HNO3; the aqueous phase is digested, wherein the digestion is treated with 14mol / L-16mol / L HNO3 and 30% H2O2 to obtain a solution to be tested; and the lithium isotope abundance in the sample to be tested is analyzed.

2. The analysis method according to claim 1, characterized in that The volume ratio of the crown ether-ionic liquid sample to the stripping agent is 1:10 to 1:

30.

3. The analysis method according to claim 1 or 2, characterized in that The stripping comprises mixing the crown ether-ionic liquid sample and the stripping agent at an oscillation frequency of 160 rpm to 180 rpm for 20 to 40 min, and centrifuging to obtain the aqueous phase; preferably, the centrifugation is performed at 2000 rpm to 3000 rpm for 1 to 3 min; further preferably, the stripping is performed 2 to 3 times.

4. The method according to claim 1, characterized in that: The digestion comprises the following steps: Evaporating the water in the aqueous phase to dryness; To the above evaporated product, 14 mol / L to 16 mol / L HNO3 and 30% H2O2 are added in no particular order to digest the product to obtain a digestion solution; The digestion solution is diluted and fixed to volume to prepare a test solution.

5. The analysis method according to claim 4, characterized in that The evaporation to dryness is carried out at a temperature of 200°C to 250°C.

6. The analysis method according to claim 4, characterized in that The volume ratio of the 30% H2O2 hydrogen peroxide solution to the 14 mol / L to 16 mol / L nitric acid is 1:5 to 1:

10.

7. The analysis method according to claim 1 or 4, characterized in that The digestion is carried out at 200° C. to 250° C.; preferably, the digestion is carried out 3 to 4 times.

8. The analysis method according to claim 4, characterized in that The digestion solution was diluted and fixed to volume using 0.32 mol / L HNO3 or water.

9. The analysis method according to claim 1, characterized in that When multi-collector inductively coupled plasma mass spectrometry is used, the lithium ion concentration in the solution to be tested is 100 μg / L to 800 μg / L, and when thermal ionization mass spectrometry is used, the lithium ion concentration in the solution to be tested is 0.5 g / L to 1 g / L.

10. The analysis method according to claim 1, characterized in that The lithium isotope abundance is determined by multi-collector inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry.

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