Method for lithium isotope abundance analysis in crown ether-ionic liquid samples

Abstract

The application provides a method for analyzing lithium isotope abundance, and particularly relates to a method for analyzing lithium isotope abundance in complex lithium salt in crown ether-ion liquid. A lithium-containing crown ether-ion liquid sample is mixed with a stripping agent to perform stripping, so that lithium ions are transferred to an aqueous phase, wherein the stripping agent is 0.16 mol / L-0.48 mol / L HNO3; the aqueous phase is digested, wherein the digestion adopts 14 mol / L-16 mol / L HNO3 and 30% H2O2 to treat the aqueous phase to obtain a solution to be measured; and lithium isotope abundance in the sample to be measured is analyzed. The analysis method of the application realizes accurate determination of lithium isotope abundance in crown ether-ion liquid by different isotope analysis methods, and the detection result is reliable and accurate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of analytical test research, and particularly relates to a method for analyzing lithium isotope abundance in crown ether-ion liquid. BACKGROUND

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

[0003] Therefore, the main purpose of the present application is to provide an accurate and reliable method for analyzing the lithium isotope abundance in crown ether-ionic liquid, and to realize the accurate analysis of the lithium isotope abundance in the complex lithium salt in crown ether-ionic liquid by different analysis methods.

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

[0005] mixing the lithium-containing crown ether-ionic liquid sample with a stripping agent to strip lithium ions into an aqueous phase, wherein the stripping agent is 0.16 mol / L-0.48 mol / L HNO3; digesting the aqueous phase, wherein the digestion is performed by treating the aqueous phase with 14 mol / L-16 mol / L HNO3 and 30% H2O2 to obtain a test solution; and analyzing the lithium isotope abundance in the test sample.

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

[0007] In some embodiments, the stripping includes mixing the sample of the crown ether-ionic liquid and the stripping agent at a shaking frequency of 160 rmp-180 rmp for 20-40 min, and centrifuging to obtain the aqueous phase.

[0008] In some embodiments, the centrifugation is performed at 2000 rmp-3000 rmp for 1-3 min; further preferably, the stripping is performed 2-3 times.

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

[0010] In some embodiments, the evaporation is performed at a temperature of 200℃-250℃.

[0011] In some embodiments, the volume ratio of the 30% H2O2 and the 14 mol / L-16 mol / L HNO3 is 1:5-1:10.

[0012] In some embodiments, the digestion is performed at a temperature of 200℃-250℃; preferably, the digestion is performed 3-4 times.

[0013] In some embodiments, the digestion solution is diluted and constant-volumeed with 0.32 mol / L HNO3 or water.

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

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

[0016] The application provides a method for analyzing lithium isotope abundance in crown ether / ionic liquid, which converts organic phase samples of the crown ether / ionic liquid into aqueous solution samples by using 0.16 mol / L-0.48 mol / L HNO3 as a stripping agent, the first stripping efficiency is greater than 75%, the stripping efficiency is greater than 99.7% after 2-3 times of stripping, and the lithium can be completely recovered after 2-3 times of stripping, and since the lithium isotope fractionation occurs in the stripping process 7 Li preferentially enters the aqueous phase, 6 Li is more inclined to remain in the crown ether-ionic liquid, so the lithium isotope fractionation occurs in the stripping process, and the complete recovery of lithium avoids the deviation of the measured value from the true value. Through the digestion step, the organic macromolecular lithium salt can be converted into inorganic ionic lithium salt suitable for measurement by the multi-receiving inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry, and the lithium isotope abundance in the crown ether / ionic liquid with different lithium ion concentrations can be determined. The analysis method is used for determining the actual research samples, and the analysis precision of the multi-receiving inductively coupled plasma mass spectrometry and the thermal ionization mass spectrometry is 0.2 ‰ and 0.3 ‰ respectively. The same batch of research samples is treated and measured by the multi-receiving inductively coupled plasma mass spectrometry and the thermal ionization mass spectrometry respectively, and the measurement data has good consistency, which shows that the analysis method for measuring the lithium isotope abundance in the crown ether / ionic liquid by the multi-receiving inductively coupled plasma mass spectrometry and the thermal ionization mass spectrometry is accurate and reliable. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the application will be clearly and completely described below in combination with the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0018] In the entire specification, unless otherwise specifically stated, the terms used herein are understood as having the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meanings as generally understood by those skilled in the art to which the application belongs. If there is a contradiction, the specification is preferred.

[0019] It should be noted that in the embodiments of the present application, the terms "comprising", "containing" or any other variant thereof are intended to cover a non-exclusive inclusion, so that a process or device including a series of elements not only includes the elements clearly listed, but also includes other elements not explicitly listed, or further includes elements inherent to the process or device. Without more limitations, the element defined by the statement "comprising a" does not exclude the presence of another related element in the process or device including the element.

[0020] It should be noted that the terms "first", "second", "third" involved in the embodiments of the present application are only to distinguish similar objects, and do not represent the specific order of the objects. Understandably, "first", "second", "third" can be interchanged in specific order or sequence as allowed. It should be understood that the objects distinguished by "first", "second", "third" can be interchanged under appropriate circumstances, so that the embodiments of the present application 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 common analysis methods for precise determination of isotope abundance. Both methods are suitable for determination of isotope abundance in inorganic systems. However, crown ether / ionic liquid samples are an organic system with a density greater than water and a certain viscosity. Lithium in the sample is combined with organic macromolecules to form complex lithium salt. When the organic matrix is tested by, for example, TIMS or MC-ICP-MS, there are problems such as inability to directly sample, change of plasma composition, serious interference, etc. during the testing process, which result in the inability to directly sample and test in the instrument.

[0022] Therefore, the present application provides an analysis method for lithium isotope abundance, wherein a crown ether-ionic liquid sample containing lithium is mixed with a stripping agent to perform stripping, so that lithium ions are transferred to an aqueous phase, wherein the stripping agent is 0.16 mol / L-0.48 mol / L HNO3; the aqueous phase is digested, wherein the digestion uses 14 mol / L-16 mol / 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 application, the lithium to be analyzed is contained in the lithium-containing crown ether-ionic liquid in the form of a complex, and the method comprises the following steps: (1) mixing the lithium-containing crown ether-ionic liquid sample with a stripping agent to perform stripping, so that lithium ions are transferred to the aqueous phase, wherein the stripping agent is 0.16 mol / L-0.48 mol / L HNO3; the complex lithium salt in the organic phase is converted 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 (N, O, etc.) of HNO3, the use of nitric acid as the stripping agent can avoid the interference of inorganic media on the generation of interfering ions during subsequent measurement, and can prevent the occurrence of hydrolysis. Thus, the accuracy and reliability of the measurement are improved. The use of HNO3 with the above concentration as the stripping agent is beneficial to improving the extraction efficiency, and can recover lithium in the crown ether / ionic liquid sample with higher efficiency. After stripping for 2-3 times, the stripping recovery rate of lithium reaches more than 99.7%. Since the stripping process is carried out in a closed system, the loss of lithium during the stripping process is very small. 7 Li preferentially enters the aqueous phase, 6 Li is more inclined to remain in the crown ether-ionic liquid, so that lithium isotope fractionation occurs during the stripping process, and if lithium cannot be completely recovered, the measurement result will deviate from the true value. (2) The organic macromolecular lithium salt in the aqueous solution after stripping is converted into LiNO3 aqueous solution by digestion, and the digestion agent is 30% H2O2 and 14 mol / L-16 mol / L HNO3. On the one hand, the strong oxidizing property of H2O2 and HNO3 can quickly and completely destroy the organic matter, and convert the organic lithium salt into a LiNO3 chemical form suitable for detection, thereby realizing the determination of lithium isotope abundance by different analysis methods; on the other hand, the digestion agent used in the present application does not introduce new media, which is beneficial to reducing the interference of the media during detection and further improving the accuracy of detection. (3) The present application compares the measurement results by using two different analysis methods (multi-receiving inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry), and the measurement data has good consistency, and the precision of the measurement results of the two methods is 0.02% and 0.03% respectively. It shows that the method is accurate and reliable.

[0024] The lithium isotope abundance analysis method of the present disclosure will be described in detail below through a specific embodiment. In this embodiment, the method can comprise 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-0.48 mol / L HNO3;

[0026] 2) centrifugation: centrifuging the stripping mixed solution to separate the organic phase and the aqueous phase, and collecting the supernatant;

[0027] 3) digestion: evaporating the supernatant to dryness by heating, and then using 14 mol / L-16 mol / L HNO3 and 30% H2O2 as a digestion agent to digest the supernatant to obtain a digestion solution;

[0028] 4) volume setting: diluting and setting the volume of the digestion solution, and diluting the digestion solution to a suitable concentration after volume setting as a to-be-measured solution;

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

[0030] In the present disclosure, the above-mentioned crown ether / ionic liquid sample refers to a crown ether / ionic liquid sample that has been enriched with 6 Li isotope. The crown ether / ionic liquid system in the present application is not particularly limited, and any crown ether / ionic liquid system that can be used to enrich lithium isotope can be measured by the method of the present application. For example, benzo-15-crown-5 / 1-hexyl-3-methyl imidazole bis(trifluoromethanesulfonyl) imide salt ionic liquid.

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

[0032] In step 1), for example, 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 any two of the above 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 1:10-1:30. 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 stripping frequency, improve the stripping efficiency, and thus reduce the deviation of the measurement results caused by incomplete recovery of lithium isotope. 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. For example, the volume ratio of the crown ether / ionic liquid sample to the stripping agent can be 1:10, 1:15, 1:20, 1:25, 1:30, or a value between any two of the above values. In some embodiments, the volume ratio of the crown ether / ionic liquid sample to the stripping agent is 1:20-1:30, preferably 1:30.

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

[0035] In some embodiments, in the step 2), the centrifugation frequency is 2000rmp-3000rmp, and the centrifugation time is 1-3min. The above centrifugation frequency and centrifugation time are conducive to the sufficient separation of the organic phase and the aqueous phase and the improvement of the efficiency of the experimental operation.

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

[0037] In the method of the present application, the step 3) evaporates the supernatant to dryness, which is conducive to the improvement of the efficiency of the subsequent digestion step. In addition, through the evaporation to dryness treatment, low-concentration samples can be stripped and concentrated multiple times, realizing the determination of lithium isotope abundance in crown ether / ionic liquid with different lithium ion concentrations.

[0038] In some embodiments, in the step 3), the evaporation to dryness is carried out at a temperature of 200℃-250℃. By heating the supernatant at the above temperature, the evaporation rate is improved, the experimental operation efficiency is improved, on the other hand, the decomposition of inorganic lithium salt in the supernatant or other side reactions at high temperature is avoided, and the accuracy of the detection is further improved. Generally, the evaporation to dryness of the supernatant makes the lithium ion concentration after constant volume reach the order of g / L.

[0039] The step 3) digests the stripped organic macromolecular lithium salt to prepare LiNO3 form suitable for measurement.

[0040] In some embodiments, the digestion agent is 30% H2O2 and 14-16 mol / L HNO3. The volume ratio of H2O2 and HNO3 in the digestion agent is 1:5-10, for example, the volume ratio of H2O2 and HNO3 in the digestion agent can be 1:5, 1:8, 1:10 or a value between any two of them. Preferably, the volume ratio of H2O2 and HNO3 in the digestion agent is 1:10. The method of the present application uses 30% H2O2 and 14-16 mol / L HNO3 for digestion. On the one hand, the strong oxidizing property of H2O2 and HNO3 can quickly and completely destroy organic matter, converting organic macromolecular lithium salt into LiNO3 chemical form suitable for detection, thereby realizing the determination of lithium isotope abundance by different analysis methods. On the other hand, the digestion agent used in the present application does not introduce new matrix components, which is beneficial to reduce the interference of impurities during detection and further improve the accuracy of detection. In the present application, H2O2 and HNO3 are added to the concentrate for digestion, and the order of addition is not limited.

[0041] In some embodiments, the digestion is performed 3-4 times. By repeating the digestion step, the organic macromolecular lithium salt can be fully converted into LiNO3 form suitable for detection, and the impurities in the sample to be detected can be reduced, thereby improving the accuracy of detection.

[0042] In some embodiments, in the step 4), the digestion solution is diluted and made constant volume with 0.32 mol / L HNO3 or water. HNO3 or water is the most optimal medium for mass spectrometric detection. Since there are already elements of HNO3 in the air, the multi-atom ions formed by H2, N2 and O2 do not increase significantly after the addition of HNO3 matrix or water, thereby avoiding the interference of impurity peaks on the detection results and improving the accuracy of detection.

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

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

[0045] In some embodiments, the step 5) is performed on a multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) or thermal ionization mass spectrometry (TIMS) in the order of lithium isotope standard solution-sample-lithium isotope standard solution. The purpose of performing the test in the above-mentioned 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 solution can be a commercially available certified reference material, such as IRMM-016, IRMM-015, GBW04432.

[0047] In some embodiments, the calculation method of lithium isotope abundance is: instrument mass discrimination correction factor = 1 / 2 (standard reference value / previous standard measurement value + standard reference value / subsequent standard measurement value). The true value of lithium isotope abundance in the sample = mass discrimination correction factor * sample measurement value.

[0048] In some embodiments, the MC-ICP-MS is Nu Plasma II, and the TIMS is Triton Plus.

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

[0050] EMBODIMENT

[0051] Feasibility test of detection method

[0052] In order to verify the feasibility of the analysis method of the present application, a crown ether / ion liquid sample with a known lithium ion concentration is detected, and the recovery rate of lithium in the processing process is calculated. The closer the recovery rate is to 100%, the closer the measurement result is to the true value. The same research sample is tested for lithium isotope abundance by different analysis methods after the same pretreatment process, and the results are compared. The smaller the difference, the higher the detection accuracy of the analysis method.

[0053] EMBODIMENT 1

[0054] 1) Stripping: Take 2 mL of a benzo-15-crown-5 / 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide salt ion 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 a shaker at a shaking frequency of 160 rmp / min for 40 min to mix the two phases uniformly.

[0055] 2) Centrifugation: Centrifuge the mixed sample at a centrifugation frequency of 2000 rmp / min for 3 min to separate the two phases, and take the supernatant in a beaker.

[0056] 3) Repeat the above stripping, 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, 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 x stripping liquid volume) ÷ theoretical mass of lithium ions in the sampling sample x 100%. The calculation results are shown in Table 1. It can be understood that when the lithium ion recovery rate is close to 100%, the stripping step does not need to be continued.

[0058] 4) Digestion: Place the beaker containing all the supernatant on a 200°C electric heating plate, heat to evaporate the water, then add 2.5mL of 16mol / L HNO3 and 0.5mL of 30% H2O2 in turn for digestion, repeat the digestion step 3 times, and obtain a digestion solution.

[0059] 5) Volumetric flask: Add 1mL of 0.32mol / L HNO3 solution to the above digestion solution, then transfer it into a 5mL volumetric flask, wash the beaker with 0.32mol / L HNO3 and transfer it into the volumetric flask. Volumetric flask with 0.32mol / L HNO3 to the mark. Dilute with 0.32mol / L HNO3 to 100μg / L and 0.5g / L of lithium ion concentration for testing.

[0060] 6) Measurement: Test the above test solution on Nu Plasma II type multi-receiving inductively coupled plasma mass spectrometer (MC-ICP-MS) according to 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] Abundance of lithium isotope:

[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] In the formula:

[0066] K - instrument mass discrimination correction factor;

[0067] R c - lithium isotope standard solution 6 Li / 7 Li standard value;

[0068] R m - Lithium Isotope Standard Solution 6 Li / 7 Measured value of Li.

[0069] To 6 Li / 7 Correct the Li isotope abundance ratio.

[0070] Corrected value of Li in the sample to be measured 6 Li / 7 Li value R 校正 According to formula (2):

[0071] R 校正 = R 测量 x K ………………………………………… (2)

[0072] In the formula:

[0073] R 校正 - Corrected value of Li in the sample to be measured 6 Li / 7 Li;

[0074] R 测量 - Measured value of Li in the sample to be measured 6 Li / 7 Li.

[0075] Examples 2-4

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

[0077] Table 1 Determination results of lithium recovery rate and lithium isotope abundance using 0.48 mol / L HNO3 as stripping agent at different stripping phase ratios

[0078]

[0079] Example 5:

[0080] 1) Stripping: Take 1 mL of a benzo-15-crown-5 / 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide salt 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 a shaker to shake at a shaking frequency of 180 rpm / min for 20 min to mix the two phases uniformly.

[0081] 2) Centrifugation: The mixed sample was placed in a centrifuge and centrifuged at a centrifugal frequency of 3000 rpm / min for 1 min to separate the two phases, and the supernatant was collected in a beaker.

[0082] 3) The back extraction and centrifugation steps were repeated twice, and the supernatant was collected in a beaker. The lithium ion concentration in the supernatant obtained after each back extraction and centrifugation was measured.

[0083] The method for testing the lithium ion concentration and the calculation of the lithium ion recovery rate were 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%, the back extraction step does not need to be continued.

[0084] 4) Digestion: The beaker containing all the supernatant was placed on a 250°C electric heating plate to evaporate the water, and then 3 mL of 14 mol / L HNO3 and 0.3 mL of 30% H2O2 were added in sequence for digestion. The digestion step was repeated 3 times to obtain a digestion solution.

[0085] 5) Volumetric adjustment: 1 mL of H2O solution was added to the above digestion solution, and then transferred into a 5 mL volumetric flask. The beaker was washed with H2O and transferred into the volumetric flask. The volume was adjusted to the mark with H2O. The solution diluted with H2O to a lithium ion concentration of 800 μg / L and the original solution after volumetric adjustment were measured.

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

[0087] Examples 6-8

[0088] Examples 6-8 were processed and tested for lithium recovery rate according to a method similar to that of Example 5, except that the amount of back extraction agent added was adjusted so that the volume ratio of the crown ether-ionic liquid sample to the back extraction agent had the values shown in Table 2. The test results are shown in Table 2.

[0089] Table 2 Lithium recovery rate determination results under different back extraction phase ratios using 0.16 mol / L HNO3 as the back extraction agent

[0090]

[0091]

[0092] Method validation

[0093] To verify the accuracy of the method, the above-mentioned examples 1 and 5 are subjected to lithium isotope abundance test on MC-ICP-MS and TIMS respectively after treatment of the crown ether / ion liquid sample with known lithium ion concentration, and the actual research sample 6 Li / 7 Li value, and the measurement results are shown in Table 3.

[0094] Table 3 MC-ICP-MS and TIMS parallel measurement results of lithium isotope of crown ether / ion liquid sample

[0095]

[0096] It can be seen that the measurement data of MC-ICP-MS method and TIMS method have good consistency, and the relative deviation of the measurement results of the two methods is ≤0.05%. It is proved that the established MC-ICP-MS method and TIMS method for measuring lithium isotope abundance in crown ether / ion liquid are accurate and reliable.

[0097] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made by using the content of the present application specification, or direct / indirect application in other related technical fields under the inventive concept of the present application are included in the patent protection scope of the present application.

Claims

1. A method of analyzing lithium isotope abundance, characterized by, The method comprises the following steps: mixing the lithium-containing crown ether-ionic liquid sample with a stripping agent to strip lithium ions into an aqueous phase, wherein the stripping agent is 0.16 mol / L-0.48 mol / L HNO3; digesting the aqueous phase, wherein the digestion is performed using 14 mol / L-16 mol / L HNO3 and 30% H2O2 to obtain a test solution; and analyzing the lithium isotope abundance in the test sample.

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 1:10-1:

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 under a shaking frequency of 160 rmp-180 rmp for 20-40 min, and centrifuging to obtain the aqueous phase.

4. The analysis method according to claim 3, characterized in that, The centrifugation is performed at 2000 rmp-3000 rmp for 1-3 min.

5. The analysis method according to claim 4, characterized in that, The stripping is performed 2-3 times.

6. The method of claim 1, wherein, The digestion comprises the following steps: evaporating water in the aqueous phase; adding 14 mol / L-16 mol / L HNO3 and 30% H2O2 to the evaporated product in no particular order to digest, to obtain a digestion solution; diluting and constant-volumeing the digestion solution to prepare a test solution.

7. The analysis method according to claim 6, characterized in that, The evaporation is performed at a temperature of 200℃-250℃.

8. The analysis method according to claim 6, characterized in that, The volume ratio of the 30% H2O2 to the 14 mol / L-16 mol / L HNO3 is 1:5-1:

10.

9. The analysis method according to claim 1 or 6, characterized by, The digestion is performed at a temperature of 200℃-250℃.

10. The analysis method according to claim 9, characterized in that, The digestion is performed 3-4 times.

11. The analysis method according to claim 6, characterized in that, The digestion solution is diluted and constant-volumeed using 0.32 mol / L HNO3 or water.

12. The analysis method of claim 1, wherein, The lithium ion concentration in the test solution is 100 µg / L-800 µg / L when using multi-receiving inductively coupled plasma mass spectrometry, and is 0.5 g / L-1 g / L when using thermal ionization mass spectrometry.

13. The analysis method of claim 1, wherein, The lithium isotope abundance is determined using multi-receiving inductively coupled plasma mass spectrometry and thermal ionization mass spectrometry, respectively.

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