Method for determining trace thallium in ammonium rhenate

Abstract

The invention relates to a method for determining trace thallium in ammonium rhenate. The method comprises the following steps: preparing a thallium standard solution; digesting the ammonium rhenate sample by adopting a nitric acid solution; on an inductively coupled plasma emission spectrometer, the ammonium rhenate digestion solution and the thallium standard solution simultaneously measure the count of elements to be measured in the solution, the thallium standard series solution is measured, a calibration curve is drawn and serves as a working curve, and the mass concentration of thallium in the ammonium rhenate sample is calculated on the working curve. The sample can be effectively decomposed by directly dissolving the sample with nitric acid, and matrix rhenium does not need to be separated; 351.924 nm is selected as the analysis spectral line of thallium, the linear correlation coefficient of a standard curve is greater than 0.999, the detection limit of the method is 0.0006 mu g / m, the quantitation limit of the method is 0.0019 mu g / mL, the operation is simple and convenient, the detection efficiency is high, the accuracy is high, the precision is good, the detection limit is low, the analysis and detection requirements of trace thallium in ammonium rhenate are met, and the detection blank of trace thallium in ammonium rhenate is filled.

Description

Technical Field

[0001] The invention relates to the technical field of methods for determining trace amounts of thallium, and in particular to a method for determining trace amounts of thallium in ammonium rhenate. Background Art

[0002] Ammonium rhenate (NH 4 R 4 ) is one of the main industrial compounds of rhenium, usually used to prepare metallic rhenium through hydrogenation reduction, and its performance quality directly affects the purity of metallic rhenium. Recovering and preparing ammonium rhenate from the waste acid system of copper smelting flue gas is currently one of the main ways to recover rhenium, and precipitants such as sulfides and polysulfides are used to precipitate and enrich rhenium. However, other toxic elements such as thallium will be enriched from the waste acid in the form of thallium sulfides during the rhenium precipitation and enrichment process, and cannot be effectively selectively separated during the oxidation leaching-extraction-stripping process, forming Tl(ReO 4 ) 3 With NH 4 R 4 The co-crystallization enters the ammonium rhenate crystal, making the thallium content in the ammonium rhenate prepared by this process as high as 0.5%, far exceeding the 4N grade requirement, thus affecting the performance quality of ammonium rhenate and further affecting the purity of metallic rhenium. In addition, thallium is a highly toxic and harmful substance, its toxicity far exceeds that of arsenic, mercury, and cadmium, and has a great toxic effect on the human body. Therefore, whether from the perspective of ammonium rhenate product quality control or thallium environmental pollution control, accurate determination of the thallium content in ammonium rhenate is of great significance.

[0003] Among the industry standard analytical methods, the only one for the determination of thallium in ammonium rhenate is "Chemical Analysis Methods for High Purity Rhenium and Ammonium Rhenate - Determination of Beryllium, Sodium, Magnesium, Aluminum, Potassium, Calcium, Titanium, Chromium, Manganese, Iron, Cobalt, Nickel, Copper, Zinc, Arsenic, Molybdenum, Cadmium, Indium, Tin, Antimony, Barium, Tungsten, Platinum, Thallium, Lead, and Bismuth - Inductively Coupled Plasma Mass Spectrometry" (YS / T 902-2013), with a determination range of 0.0001% to 0.0050%, and there is no national standard analytical method, which cannot meet the detection needs of trace thallium in ammonium rhenate. In addition, there are no relevant standard analytical methods and literature reports on the determination of trace thallium in ammonium rhenate so far. At present, the main analytical test methods for thallium in samples include inductively coupled plasma emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry, etc.

[0004] Among them, the determination precision of atomic absorption spectrometry is poor; ICP-MS method has serious interference of hydride polyatomic ions and rare earth compound ions on thallium. ICP-AES plays an important role in the analysis of trace metal elements in industrial compounds, ores and other samples due to its advantages such as low detection limit and simultaneous determination of multiple elements, and is also widely used to determine thallium in samples. Among them, the determination of gallium, indium and thallium in polymetallic sulfide ores by inductively coupled plasma atomic emission spectrometry (ICP-AES) established a method of decomposing samples with hydrochloric acid, nitric acid, hydrofluoric acid and sulfuric acid, extracting thallium with butyl acetate, and then extracting with 2% nitric acid and combining ICP-AES to determine thallium, and its detection limit is less than 0.50μg / g. Furthermore, Xie Xiaoyan et al. used hydrochloric acid, nitric acid, hydrofluoric acid and perchloric acid to dissolve the sample, and separated it by ion exchange under pH 1.7-2.0 conditions and combined it with ICP-AES to determine the thallium content in manganese ore. The detection limit of the method reached 1ng / mL, and the recovery rate of spiked was 90%-108%. These methods provide references for the accurate determination of thallium, but most of them are for the determination of trace thallium in ores and wastewater.

[0005] Therefore, based on the reference to the determination of thallium in other samples and the characteristics of the ammonium rhenate sample itself and the characteristics of the high-rhenium matrix, the purpose of this invention is to design a method for the determination of trace thallium in ammonium rhenate that is simple to operate, has high detection efficiency, good accuracy and precision, low detection limit, and meets the requirements of analytical detection. Summary of the invention

[0006] In view of the technical problems existing in the above-mentioned prior art, the present invention provides a method for determining trace amounts of thallium in ammonium rhenate, which can effectively solve the technical problems existing in the above-mentioned prior art.

[0007] The technical solution of the present invention is:

[0008] A method for determining trace thallium in ammonium rhenate comprises the following specific steps:

[0009] S1, preparing a series of thallium standard solutions, which are obtained by diluting a single element standard stock solution of thallium with medium nitric acid;

[0010] S2, digestion treatment of the ammonium rhenate sample, adding nitric acid solution to the prepared ammonium rhenate sample for digestion treatment to obtain an ammonium rhenate digestion solution;

[0011] S3. According to the instrument working conditions, on the inductively coupled plasma emission spectrometer, the ammonium rhenate digestion solution and the thallium standard solution are used to simultaneously measure the count of the element to be measured in the solution, and the thallium standard series solution is measured to draw a calibration curve and use it as the working curve, and the mass concentration of thallium in the ammonium rhenate sample is calculated from the working curve.

[0012] In the inductively coupled plasma emission spectrometer, 351.924 nm is selected as the analysis spectrum line of thallium.

[0013] The ammonium rhenate digestion solution in step S2 is obtained by treating the ammonium rhenate sample through a digestion method of the following specific steps:

[0014] S21, accurately weighing an ammonium rhenate sample, adding nitric acid solution I, and heating at 60-70° C. until the ammonium rhenate sample is completely dissolved and the liquid evaporates to 1 / 3-1 / 2 of the total volume, thereby obtaining an ammonium rhenate solution;

[0015] S22, cooling the ammonium rhenate solution;

[0016] S23, diluting the cooled ammonium rhenate solution to the mark with nitric acid solution II, and shaking to a fixed volume to obtain an ammonium rhenate digestion solution.

[0017] The particle size of the ammonium rhenate sample (Re>99%) prepared in step S2 is not greater than 0.1 mm, and after being dried at 100° C. to 105° C. for 1 hour, it is placed in a desiccator and cooled to room temperature for use.

[0018] Before the volume is fixed in step S23, the container wall needs to be cleaned with 5 to 7 mL of water, and then the cleaning liquid is transferred to the volumetric flask.

[0019] The nitric acid solution I in step S21 is nitric acid solution 1+2, which is obtained by mixing 1 volume of nitric acid with 2 volumes of pure water; the nitric acid solution II in step S23 is nitric acid solution 1+9, which is obtained by mixing 1 volume of nitric acid with 9 volumes of pure water.

[0020] In step S2, a blank test needs to be performed synchronously with the sample, and the count of the blank solution accompanying the sample is measured by an inductively coupled plasma emission spectrometer. The count of the element to be measured in the ammonium rhenate digestion solution needs to be deducted from the count of the blank solution accompanying the sample by difference subtraction, and then the mass concentration of thallium is calculated from the working curve.

[0021] The thallium standard series solutions in step S1 are thallium standard solutions of different concentrations obtained by stepwise dilution of a single element standard stock solution of 1000 μg / mL thallium with 2% by volume nitric acid as a medium.

[0022] The thallium standard series solutions are measured by an inductively coupled plasma emission spectrometer, 351.924 nm is selected as the analysis spectrum line of thallium, and the mass concentration of the element is used as the abscissa and the net emission intensity of the element to be measured is used as the ordinate. The thallium standard series solutions are measured to draw a calibration curve, and the linear equation of the obtained standard curve is y=446.056x+1.828, and the linear correlation coefficient is greater than 0.999.

[0023] The detection limit of the method was 0.0006μg / mL, and the quantification limit of the method was 0.0019μg / mL.

[0024] Advantages of the present invention:

[0025] 1) The determination method of the present invention is aimed at trace thallium in ammonium rhenate. Through experimental research on the method, verification of spike recovery, comparison of different methods, external inspection comparison, etc., a method for determining trace thallium in ammonium rhenate by acid dissolution-inductively coupled plasma emission spectrometry is established, which fills the detection gap of trace thallium in ammonium rhenate. The method uses nitric acid to directly dissolve the sample without separating the matrix rhenium, and directly determines it on ICP-AES. Compared with the traditional method, the determination result of the method is consistent with the microwave digestion-ICP-AES method and the flame atomic absorption spectrometry. More importantly, the method is simple to operate, has high detection efficiency, high accuracy, good precision and low detection limit, which can meet the analysis and detection needs of trace thallium in ammonium rhenate.

[0026] The established acid-soluble ICP-AES method for determining thallium can also be applied to the determination of thallium in the process of recovering and preparing ammonium rhenate in the smelting flue gas waste acid system, which effectively improves the detection efficiency, fills the gap in thallium detection, and provides the necessary detection technology support for improving the quality of ammonium rhenate products.

[0027] 2) The present invention directly uses nitric acid to dissolve the ammonium rhenate sample, which can effectively decompose the sample without separating the matrix rhenium; 351.924nm is selected as the analytical spectrum of thallium, and the linear equation of the standard curve obtained is y=446.056x+1.828, the linear correlation coefficient of the standard curve is greater than 0.999, the method detection limit is 0.0006μg / m, and the method quantitative limit is 0.0019μg / mL. By measuring 6 ammonium rhenate samples with different contents, the relative standard deviation (RSD, n=7) is 1.04% to 3.56%, the spike recovery rate is 95.24% to 104.29%, and the measurement results are consistent with the microwave digestion-ICP-AES method and flame atomic absorption spectrometry, and are consistent with the measurement results of well-known domestic laboratories. It is not only simple to operate, has high detection efficiency and low detection limit, but also fills the detection gap of trace thallium in ammonium rhenate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The spectrum of thallium element at a wavelength of 190.856nm in the spectrum line test of the present invention is analyzed Figure 1 .

[0029] Figure 2 The spectrum of thallium element at a wavelength of 276.787nm in the spectrum line test of the present invention is analyzed Figure 2 .

[0030] Figure 3The spectrum of thallium element at a wavelength of 351.924nm in the spectrum line test of the present invention is analyzed Figure 3 .

[0031] Figure 4 The spectrum of thallium element at a wavelength of 377.572nm in the spectrum line test of the present invention is analyzed Figure 4 . DETAILED DESCRIPTION

[0032] In order to facilitate understanding by those skilled in the art, the structure of the present invention is further described in detail with reference to the embodiments in conjunction with the accompanying drawings:

[0033] Embodiment 1

[0034] A method for determining trace thallium in ammonium rhenate

[0035] The weighing device used in the present invention is an XS204 microbalance with a sensitivity of 0.0001 g; the heating device is a temperature-controlled electric heating plate with a maximum temperature of 250° C.; the inductively coupled plasma emission spectrometer is purchased from the ICAP PRO X inductively coupled plasma emission spectrometer of Thermo Fisher Scientific, USA, and its operating parameters are shown in Table 1:

[0036] Table 1 ICP-AES operating parameters

[0037]

[0038] The nitric acid used in the present invention is commercially available high-grade pure nitric acid; the experimental water meets the secondary water specified in GB / T 6682; and the thallium single element standard stock solution is 1000 μg / mL in accordance with the standard of the National Standard Material Center.

[0039] S1, preparing a series of thallium standard solutions: a series of thallium standard solutions of different concentrations are prepared by stepwise dilution of a single element standard stock solution of 1000 μg / mL thallium with a medium of 2% by volume nitric acid to obtain thallium standard solutions with mass concentrations of 0, 0.10, 0.50, 1.00, 2.00, and 5.00 μg / mL.

[0040] S2, preparing ammonium rhenate samples: ammonium rhenate samples (Re>99%) are obtained by washing waste acid from copper smelting flue gas, precipitating rhenium (rhenium-rich slag), oxidative leaching (rhenium-rich solution), extraction, stripping (ammonium rhenate solution), purification and impurity removal, and evaporation concentration (ammonium rhenate). The ammonium rhenate samples are dried at 100°C for 1 hour, placed in a dryer and cooled to room temperature, and the particle size is not greater than 0.1 mm; and 6 different batches of ammonium rhenate samples are randomly selected for use;

[0041] The above ammonium rhenate sample is digested to obtain an ammonium rhenate digestion solution: accurately weigh 0.10g of ammonium rhenate sample and add it to 10mL of nitric acid solution 1+2, and heat it at 60°C on a hot plate until the ammonium rhenate sample is completely dissolved and the liquid evaporates to a volume of 5mL, then transfer it to a 100mL volumetric flask, rinse the cup wall with 5mL of water, transfer the cleaning liquid to the volumetric flask, dilute it to the scale with nitric acid solution 1+9, shake it to volume, and test it. Perform a blank test together with the sample. Among them, the ammonium rhenate sample must be weighed accurately to 0.0001g; nitric acid solution 1+2 is obtained by mixing 1 volume of nitric acid with 2 volumes of pure water; nitric acid solution 1+9 is obtained by mixing 1 volume of nitric acid with 9 volumes of pure water;

[0042] S3. According to the working conditions of the instrument, on the inductively coupled plasma emission spectrometer, the counts of the elements to be measured in the ammonium rhenate digestion solution and the thallium standard solution are measured simultaneously, and the calibration curve is drawn for the thallium standard series solution and used as the working curve. The mass concentration of thallium in the ammonium rhenate sample is calculated from the working curve. A blank test must be performed simultaneously with the sample, and the counts of the blank solution must be taken along with the sample. The counts of the elements to be measured in the ammonium rhenate digestion solution must first be deducted from the counts of the blank solution with the sample by subtraction, and then the mass concentration of thallium is calculated from the working curve.

[0043] According to the composition of the ammonium rhenate sample, the main elements present in ammonium rhenate are Re (>99%), K (0-0.05%), thallium (0-0.5%), Fe (0-0.01%), and Ni (0-0.01%). The thallium element was determined using spectral lines of 190.856nm, 276.787nm, 351.924nm, and 377.572nm. By determining the concentration of the standard series of thallium elements, and combining the linear range and regression conditions, spectral line interference and background subtraction conditions, and actual sample analysis and determination conditions, the background equivalent concentration (BEC), radial detection limit (RDL), spectral intensity, and interfering elements of each spectral line are shown in Table 2, and the spectra of each wavelength are shown in Table 2. Figures 1 to 4 :

[0044] Table 2 Linear regression equation and linear correlation coefficient of thallium standard solution

[0045]

[0046] From Table 2 and Figures 1 to 4It can be seen that the wavelengths of 190.856nm and 276.787nm both have spectral interferences from the main matrix rhenium, the actual sample and the standard solution spectra are offset, and the mass concentration of the ammonium rhenate matrix in the test solution is at least 200 times the concentration of thallium; at the wavelength of 377.572nm, although there is no offset between the actual sample and the standard solution spectra, it was found that there were spectral interferences on both sides during the actual sample determination process and the emission wavelength of rhodium was completely overlapped; at the wavelength of 351.924nm, there was no obvious spectral interference, the actual sample and the standard solution spectra were not offset, and the BEC was low, which had little effect on the determination results and could effectively eliminate the influence of the matrix background. It can be seen that 351.924nm as the determination spectrum line of ICP-AES has a more beneficial effect on spectral interference, background equivalent concentration, detection limit and stability.

[0047] According to the working conditions set by the instrument in Table 1, the mass concentration of the element is used as the horizontal coordinate, and the net emission intensity of the element to be measured is used as the vertical coordinate. The calibration curve is drawn for the thallium standard series solution. The linear equation of the standard curve is y=446.056x+1.828, and the linear correlation coefficient is greater than 0.999. According to the optimized pretreatment and measurement conditions of the sample, 11 process blank samples were prepared in parallel, and the measurement results were: -0.0002μg / mL, -0.0004μg / mL, -0.0001μg / mL, 0.0001μg / mL, 0.0000μg / mL, -0.0002μg / mL, -0.0003μg / mL, -0.0004μg / mL, 0.0000μg / mL, 0.0001μg / mL, 0.0001μg / mL. The detection limit calculated by the method of calculating 3 times the standard deviation of the determination result is 0.0006 μg / mL, and the quantitative limit calculated by the method of calculating 10 times the standard deviation is 0.0019 μg / mL. The detection limit of thallium is better than the 0.006 mg / kg detection limit of thallium determined by other ICP-AES methods. It can be seen that the detection limit of the present invention is low and can meet the analytical detection of trace thallium in ammonium rhenate samples.

[0048] Ammonium rhenate (NH 4 R 4 ) is a white hexagonal cubic bipyramidal crystal, a strong oxidant, soluble in hot water and dissociated into ammonium ions (NH 4 + ) and perrhenate ion (Re O4 - ), dissolves in nitric acid to form perrhenic acid. 2 O 7 It is very volatile, subliming above 220°C, which is between the volatilization temperature of sulfuric acid at 338°C and the volatilization temperature of perchloric acid at 200°C. The digestion of ammonium rhenate samples was compared by the following different digestion methods to study the effects of the digestion method and matrix rhenium on the determination of thallium.

[0049] Comparison 1: Weigh 0.10g of ammonium rhenate sample into a quartz beaker, add a small amount of water to moisten it, add 2mL of nitric acid solution 1+1 to dissolve the sample on a hot plate, take it off and cool it slightly, add 1mL of sulfuric acid and heat it to evaporate SO 3 After the white smoke has disappeared, remove and cool, then add 1mL sulfuric acid and 0.5mL nitric acid, heat at low temperature to dissolve, then heat and evaporate to SO 3 When the white smoke is gone, repeat the operation 2-3 times until the bottom of the cup is clear and transparent with no visible matter. Remove and cool, rinse the cup wall with a small amount of water, add 2mL of nitric acid solution 1+1, heat to dissolve the soluble salts, transfer to a 100mL volumetric flask after cooling, dilute to the mark with nitric acid solution 1+9, make up to volume and shake well, and then test.

[0050] Comparison 2: Weigh 0.10g of ammonium rhenate sample into a polytetrafluoroethylene beaker, add a small amount of water to moisten it, add 2mL of nitric acid solution 1+1 to dissolve the sample on a hot plate, remove and cool it slightly, add 0.5mL of hydrofluoric acid and 1mL of perchloric acid and heat and evaporate until white smoke is gone, remove and cool it, rinse the wall of the cup with a small amount of water, add 2mL of nitric acid solution 1+1, heat to dissolve soluble salts, transfer to a 100mL volumetric flask after cooling, dilute to the scale with nitric acid solution 1+9, make up to volume and shake well for testing; wherein the above nitric acid solution 1+1 is obtained by mixing 1 volume of nitric acid with 1 volume of pure water.

[0051] After being processed by the three methods of the embodiment of the present invention and comparison 1 and comparison 2, the results of the determination of thallium in the ammonium rhenate sample are shown in Table 3:

[0052] Table 3 Thallium determination results in samples treated by different methods (n=3) w / %

[0053]

[0054]

[0055] The test results in Table 3 above show that the test solutions are clear and transparent after dissolution by the three methods, and all of them can dissolve the samples. The emission spectrum intensity of rhenium in the test solution measured on ICP-AES for the samples digested by Method 1 and Method 2 is close to that of the blank, indicating that the rhenium matrix can be mostly volatilized after digestion by Method 1 and Method 2. Although the pretreatment of the samples by Method 1 and Method 2 can reduce the influence of the matrix effect on the analysis process, it increases the processing time and cost of the samples. The pretreatment time is about 6h to 8h, which greatly reduces the detection efficiency and also increases the probability of contamination; in addition, sulfuric acid and perchloric acid are required in the pretreatment process of the method, which increases the safety risk. Although the matrix is ​​not eliminated in the embodiment of the present invention, the measurement results are stable, which is consistent with the test results of well-known domestic laboratories (external inspection comparison), and the pretreatment process only takes 0.5h, with high safety factor and detection efficiency. It can be seen that the method of the present invention has beneficial effects on digestion efficiency, cost, pollution, safety risk efficiency and the impact on subsequent analysis.

[0056] Spike recovery test

[0057] According to the above experimental method, each sample was measured 7 times in parallel, and a certain amount of thallium single element standard solution was added to carry out spike recovery experiment. The results are shown in Table 4. "Requirements for Validation and Internal Quality Control of Chemical Analysis Methods"

[0058] The requirements for precision in the standard (GB / T32465-2015): when the content range is 0.001% to 0.01%, the relative standard deviation is less than 5.3%; when the content range is 0.01% to 1%, the relative standard deviation is less than 3.7%. The requirements for method recovery in the standard "Guidelines for Confirmation and Validation of Chemical Analysis Methods for Conformity Assessment" (GB / T27417-2017): when the content range is 0.0001% to 0.01%, the method recovery range is 90% to 110%; when the content range is greater than 0.01%, the method recovery range is 95% to 105%:

[0059] Table 4 Method accuracy and precision

[0060]

[0061]

[0062] As shown in Table 4, when the thallium content is less than 0.01%, the RSD of the thallium determination result is 3.56%, and the recovery rate of the standard addition is between 97.14% and 107.62%; when the thallium content is 0.01% to 1%, the RSD of the thallium determination result is between 1.04% and 3.48%, and the recovery rate of the standard addition is between 95.24% and 104.29%. It can be seen that the accuracy and precision of the method of the present invention meet the analysis requirements of thallium in ammonium rhenate.

[0063] Comparison of measurement results

[0064] The results of the thallium content determined by the method established by the present invention were compared with the results of other methods, and external inspections were compared with well-known domestic laboratories. The results are shown in Table 5:

[0065] Table 5 Method comparison and inter-laboratory comparison

[0066]

[0067] It can be seen from the results in Table 5 that within the range of 0.5% thallium content in ammonium rhenate sample, the results of this method are consistent with those of microwave digestion-ICP-AES and flame atomic absorption spectrometry, and the results are good compared with those of external laboratories. However, microwave digestion-ICP-AES uses a microwave digestion instrument, which is more expensive than this method. Flame atomic absorption spectrometry requires the use of isoamyl acetate to extract thallium to separate it from interfering elements. The operation process uses organic reagents with high toxicity and the operation process is relatively cumbersome. Laboratory workers can make reasonable choices according to laboratory conditions. It can be seen that the method of the present invention has the advantages of simple operation, good accuracy and precision, and fast determination speed.

[0068] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining trace thallium in ammonium rhenate, characterized in that: The specific steps include: S1, preparing a series of thallium standard solutions, which are obtained by diluting a single element standard stock solution of thallium with medium nitric acid; S2, digestion treatment of the ammonium rhenate sample, adding nitric acid solution to the prepared ammonium rhenate sample for digestion treatment to obtain an ammonium rhenate digestion solution; S3. According to the instrument working conditions, on the inductively coupled plasma emission spectrometer, the ammonium rhenate digestion solution and the thallium standard solution are used to simultaneously measure the count of the element to be measured in the solution, and the thallium standard series solution is measured to draw a calibration curve and use it as the working curve, and the mass concentration of thallium in the ammonium rhenate sample is calculated from the working curve.

2. The method for determining trace thallium in ammonium rhenate according to claim 1, characterized in that: In the inductively coupled plasma emission spectrometer, 351.924 nm is selected as the analysis spectrum line of thallium.

3. The method for determining trace thallium in ammonium rhenate according to claim 1 or 2, characterized in that: The ammonium rhenate digestion solution in step S2 is obtained by treating the ammonium rhenate sample through a digestion method of the following specific steps: S21, accurately weighing an ammonium rhenate sample, adding nitric acid solution I, and heating at 60-70° C. until the ammonium rhenate sample is completely dissolved and the liquid evaporates to 1 / 3-1 / 2 of the total volume, thereby obtaining an ammonium rhenate solution; S22, cooling the ammonium rhenate solution; S23, diluting the cooled ammonium rhenate solution to the mark with nitric acid solution II, and shaking to a fixed volume to obtain an ammonium rhenate digestion solution.

4. The method for determining trace thallium in ammonium rhenate according to claim 1, characterized in that: The particle size of the ammonium rhenate sample (Re>99%) prepared in step S2 is not greater than 0.1 mm, and after being dried at 100° C. to 105° C. for 1 hour, it is placed in a desiccator and cooled to room temperature for use.

5. The method for determining trace thallium in ammonium rhenate according to claim 3, characterized in that: Before the volume is fixed in step S23, the container wall needs to be cleaned with 5 to 7 mL of water, and then the cleaning liquid is transferred to the volumetric flask.

6. The method for determining trace thallium in ammonium rhenate according to claim 3, characterized in that: The nitric acid solution I in step S21 is nitric acid solution 1+2, which is obtained by mixing 1 volume of nitric acid with 2 volumes of pure water; the nitric acid solution II in step S23 is nitric acid solution 1+9, which is obtained by mixing 1 volume of nitric acid with 9 volumes of pure water.

7. The method for determining trace thallium in ammonium rhenate according to claim 1, characterized in that: In step S2, a blank test needs to be performed synchronously with the sample, and the count of the blank solution accompanying the sample is measured by an inductively coupled plasma emission spectrometer. The count of the element to be measured in the ammonium rhenate digestion solution needs to be deducted from the count of the blank solution accompanying the sample by difference subtraction, and then the mass concentration of thallium is calculated from the working curve.

8. The method for determining trace thallium in ammonium rhenate according to claim 1, characterized in that: The thallium standard series solutions in step S1 are thallium standard solutions of different concentrations obtained by stepwise dilution of a single element standard stock solution of 1000 μg / mL thallium with 2% by volume nitric acid as a medium.

9. The method for determining trace thallium in ammonium rhenate according to claim 8, characterized in that: The thallium standard series solutions are measured by an inductively coupled plasma emission spectrometer, 351.924 nm is selected as the analysis spectrum line of thallium, and the mass concentration of the element is used as the abscissa and the net emission intensity of the element to be measured is used as the ordinate. The thallium standard series solutions are measured to draw a calibration curve, and the linear equation of the obtained standard curve is y=446.056x+1.828, and the linear correlation coefficient is greater than 0.

999.

10. The method for determining trace thallium in ammonium rhenate according to claim 9, characterized in that: The detection limit of the method was 0.0006μg / mL, and the quantification limit of the method was 0.0019μg / mL.

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