Method for measuring content of low-grade vanadium in vanadium shale by utilizing inductively coupled plasma atomic emission spectrometry

Abstract

The invention belongs to the technical field of analytical chemistry, and particularly relates to a method for measuring the content of low-grade vanadium in vanadium shale through inductively coupled plasma atomic emission spectrometry. According to the method, the alkali fusion-inductively coupled plasma emission spectrometry is adopted, the sample can be directly subjected to alkali fusion, the sample is completely fused, the solution is clear, and the defect of acid dissolution is overcome; pre-decarburization is not needed, so that a lot of time is saved. Interference introduced by a crucible material is reduced by introducing a dilution factor, interference of silicate is eliminated by ammonium fluoride, and the content of low-grade vanadium is rapidly and accurately measured by adopting a series of standard solutions with different concentration gradients, so that the method is particularly suitable for measurement of batch samples.

Description

Technical Field

[0001] The invention belongs to the technical field of analytical chemistry, and in particular relates to a method for determining the content of low-grade vanadium in vanadium shale by using inductively coupled plasma atomic emission spectrometry. Background Art

[0002] Vanadium is an important strategic rare metal element. Due to its high melting point, high hardness, low density, good corrosion resistance and stable nuclear physical properties, it is widely used in metallurgy, aerospace, nuclear industry, hydrogen storage materials and superconductivity. Vanadium shale is rich in reserves and widely distributed in my country. It is an important vanadium-containing resource unique to China. Shale vanadium extraction is an important way to develop and utilize China's vanadium resources. Therefore, it is necessary to establish an accurate determination method for the main components in vanadium shale.

[0003] There is currently no standard method for detecting vanadium in vanadium shale. The common methods for determining vanadium content in the prior art are titration and X-ray fluorescence spectrometry. Among them, the equipment for X-ray fluorescence spectrometry is relatively expensive and difficult to popularize. GB / T 6730.32-2013 "Determination of vanadium content in iron ore - Ammonium ferrous sulfate titration method" has a detection range of 0.100-1.00%, and adopts platinum crucible high temperature melting and then titration; YB / T 547.1-2014 "Determination of vanadium pentoxide content in vanadium slag - Ammonium ferrous sulfate titration method" has a detection range of 5.00-25.00%, and adopts sodium peroxide molten sulfuric acid acidification and then titration with potassium permanganate oxidation-ammonium ferrous sulfate standard solution; YB / T 5328-2009 "Vanadium pentoxide - Determination of vanadium pentoxide content - Potassium permanganate oxidation-ammonium ferrous sulfate titration method" has a detection range of >90%; GB 7315.1-87 "Chemical analysis method of vanadium pentoxide - Potassium permanganate oxidation-ammonium ferrous sulfate titration method for determination of vanadium pentoxide content" has a detection range of more than 90%, and the sample is weighed by subtraction method. The samples of the above ammonium ferrous sulfate titration method need to pass through a 125um sieve; the viscosity of sulfuric acid and phosphoric acid added during the sample dissolution process is relatively large, and the boiling solution mixed with the sample is easy to adhere to the inner wall of the beaker during the sample dissolution process, and the sample is easy to be incompletely dissolved, resulting in low test results; the oxidation reaction involving potassium permanganate needs to be completed within a limited time of 5-10 minutes, and the reduction reaction involving sodium nitrite requires 1 minute. There is a clear time limit, and the analysis can only be performed sample by sample, and the timeliness of the test results is low; because ammonium ferrous sulfate and V 5+ The reaction rate of the chemical reaction is slow, and it needs to be titrated drop by drop to the endpoint, which is labor-intensive. The samples must be decarburized in advance during the actual detection process, which is cumbersome and time-consuming. The ammonium ferrous sulfate titration method is suitable for the determination of high-grade vanadium, but not for the determination of low-grade vanadium, especially not for the rapid determination of batch samples.

[0004] Invention patent CN101666789 "A method for rapid determination of vanadium in vanadium-containing coal mines" requires the sample to be dried for 2-3 hours, leached with hydrofluoric acid for 1-2 hours and sulfuric acid for 3-4 hours, and then fixed to volume in a 100ml volumetric flask. 1mL of the sample solution is transferred for oxidation-reduction and then titrated. The method has a long process and cumbersome operation, and is not suitable for batch determination. The 1mL sample solution has low representativeness, which affects the accuracy of the determination results.

[0005] Invention patent CN 114674810 A "A method for determining the amount of vanadium pentoxide, copper, molybdenum, nickel and zinc in stone coal vanadium ore" uses hydrochloric acid and nitric acid to heat for 1 hour, hydrofluoric acid and sulfuric acid mixed acid to stand overnight, nitric acid extraction, constant volume, take the upper clear liquid, and ICP determination. The process is complicated, the detection timeliness is too low, and it cannot guide production in a timely manner.

[0006] The above-mentioned determination methods all have certain defects.

[0007] (1) Conventional acid dissolution-ammonium ferrous sulfate titration method: The sample needs to be decarbonized before analysis, which is a cumbersome process and prone to sample loss. The acid dissolution method has high requirements for sample particle size. If the particle size is too large, the sample will not be completely dissolved, resulting in low test results. The viscosity of sulfuric acid is relatively high. During the high-temperature dissolution process, the boiling acid is easy to mix with the sample and adhere to the inner wall of the beaker, resulting in incomplete sample dissolution and low test results.

[0008] (2) Conventional alkali fusion-ammonium ferrous sulfate titration method: The sample is melted by adding a strong alkali reagent into a crucible. The strong alkali reagent corrodes the crucible severely and introduces the main components of the crucible material, making the solution unclear and interfering with the titration.

[0009] (3) Regardless of whether the sample pretreatment adopts the acid dissolution method or the alkaline fusion method, the subsequent titration with ammonium ferrous sulfate requires the completion of the oxidation reaction involving potassium permanganate and the reduction reaction involving sodium nitrite within a certain period of time. In addition, the reaction rate of pentavalent vanadium and ammonium ferrous sulfate is slow, and it is necessary to titrate drop by drop to the end point, which is labor-intensive, cumbersome, and has low timeliness of detection.

[0010] (4) When using the above method for determination, especially for the determination of low-grade vanadium, the titration method has certain restrictions. The standard titration solution has a high concentration and consumes a small titration volume, which is easy to cause excessive measurement results to be high. The standard titration solution has a low concentration, the titration end point is tailing, and the jump is not obvious, which is easy to cause the measurement result to be high.

[0011] Therefore, it is necessary to develop a method for detecting the vanadium content in vanadium shale. Summary of the invention

[0012] The purpose of the present invention is to provide a method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry, so as to solve the problems of low timeliness and low accuracy in the determination of vanadium in vanadium shale.

[0013] The implementation process of the present invention is as follows:

[0014] A method for determining the low-grade vanadium content in vanadium shale using inductively coupled plasma atomic emission spectrometry comprises the following steps:

[0015] (1) preparing a vanadium standard working solution with a vanadium standard stock solution, and preparing a vanadium series standard solution with a vanadium standard working solution;

[0016] (2) Determine the emission spectrum intensity of vanadium in a vanadium series standard solution and draw a standard curve;

[0017] (3) Determination

[0018] (3.1) Accurately weigh 0.5000-1.0000 g of vanadium shale sample and stir it evenly in a corundum crucible filled with sodium peroxide, cover the surface with a layer of sodium peroxide, melt it in a muffle furnace, take it out and cool it after melting;

[0019] (3.2) Rinse the outside of the crucible with water, place the crucible in a 400 mL beaker, add 80-100 mL of boiling water and 10-15 mL of nitric acid, wash the crucible and take out the solution, heat and boil to drive out all the hydrogen peroxide, evaporate the volume to 70-80 mL, and then take it out and cool it;

[0020] (3.3) Transfer the cooled solution to a 100 mL volumetric flask, dilute to volume with water, and shake well to obtain Solution A;

[0021] (3.4) Accurately transfer 5.00-10.00 mL of solution A into a 400 mL polytetrafluoroethylene beaker, add nitric acid and saturated ammonium fluoride solution, heat to dissolve, evaporate to dryness, and cool;

[0022] (3.5) Add 5 mL of nitric acid, rinse the cup wall with water, heat for 3 to 5 minutes until the salt is completely dissolved, remove and cool, dilute to 50 to 100 mL with water in a volumetric flask, shake well, and obtain solution B to be tested; perform a blank test together with the sample;

[0023] (3.6) According to the instrument working conditions, at the selected wavelength of 290.882nm, the spectral intensity of vanadium in the blank test and the test solution B is measured respectively. A standard curve is drawn with the concentration of the series of standard solutions as the horizontal axis and the corresponding emission spectrum intensity as the vertical axis. The mass concentration of vanadium in the blank test and solution B is calculated based on the standard curve, and the vanadium content is calculated accordingly.

[0024] Furthermore, in step (1), the concentration of the vanadium standard storage solution is 1000 ug / mL.

[0025] Furthermore, the concentration of the vanadium standard working solution is 100 ug / mL; the preparation process is to accurately transfer 10.00 mL of the 1000 ug / mL vanadium standard storage solution into a 100 mL volumetric flask, dilute to volume with 5% by volume nitric acid, and shake well.

[0026] Further, vanadium series standard solutions: accurately pipette 100ug / mL vanadium standard working solution: 0, 1.00, 5.00, 10.00, 15.00, 20.00mL into a group of 100mL volumetric flasks, dilute to volume with 5% by volume nitric acid, and shake well.

[0027] Furthermore, the process of drawing the standard curve in step (2) is as follows: the standard curve is drawn with the concentration of the vanadium series standard solution as the horizontal axis and the emission spectrum intensity corresponding to the concentration of the vanadium series standard solution measured by inductively coupled plasma atomic emission spectrometry as the vertical axis.

[0028] Furthermore, in step (3.1), the volume of the corundum crucible is 30 to 50 mL; the melting temperature of the muffle furnace is 700 to 800° C.; and the melting time is 10 to 15 min.

[0029] Furthermore, the heating temperature in step (3.2) is 250-300°C.

[0030] Furthermore, the volume of nitric acid added in step (3.4) is 5-10 mL, and the volume of saturated ammonium fluoride solution added is 1 mL.

[0031] Furthermore, the blank test in step (3.5) is performed simultaneously according to steps (3.1) to (3.5) without weighing the vanadium shale sample into the corundum crucible containing sodium peroxide in step (3.1).

[0032] Further, the calculation formula of vanadium content in step (3.6) is

[0033]

[0034] Where:

[0035] W%—vanadium content, %;

[0036] C0—mass concentration of vanadium in blank test, ug / mL;

[0037] C—mass concentration of vanadium in solution B, ug / mL;

[0038] V—fixed volume of solution A, mL;

[0039] V1—volume of solution A pipetted, mL;

[0040] V2—the constant volume of solution B to be tested, mL;

[0041] m—sample mass, g.

[0042] Positive effects of the present invention:

[0043] (1) Due to the high organic content in the sample, when the acid dissolution method is used to directly digest the sample, carbonaceous residues are often left due to incomplete digestion, thus affecting the accuracy of the measurement results. Generally, it is necessary to burn and remove the carbon-containing substances in a high-temperature furnace and then add acid for treatment. The present invention does not require burning and removing carbon from the sample and directly high-temperature alkali melting for treatment. The sample solution is clear and the measurement result is accurate.

[0044] (2) In the general high-temperature alkaline fusion process, the corrosion of the sample container by strong alkali will introduce new interference. In the present invention, a corundum crucible is used. The high concentration of aluminum salt introduced by the strong alkaline flux corroding the corundum crucible causes white suspended matter to appear in the sample solution, and the solution is not clear. The sample is leached with nitric acid, which eliminates the influence of the white suspended matter on the determination.

[0045] (3) To reduce the interference introduced by the high-concentration aluminum background, since the vanadium content in the sample is low, in order to ensure the accuracy of the results, it is necessary to improve the sample quality. However, improving the sample quality will increase the content of silicate, and the analysis method must be equipped with a high-salt atomizer, otherwise the pipeline will be blocked. In order to solve the technical bottleneck formed by the above characteristics on the detection of vanadium content, the present invention can reduce the influence of the matrix effect of aluminum within a certain range by diluting the sample solution, but the concentration of the analyzed element is reduced at the same time. By adjusting the concentration of the standard working curve, the concentration of the sample solution is within the optimal linear range of the standard curve. At the same time, the influence of silicate is eliminated by ammonium fluoride under acidic conditions, overcoming the influence of high-concentration silicate produced by alkali fusion on the analysis method, and achieving accurate determination.

[0046] (4) In the standard method GB / T 6730.58-2017, the platinum crucible and silver crucible used are resistant to strong alkali corrosion, but are extremely expensive. A 30 mL platinum crucible costs about RMB 15,000, and a silver crucible costs about RMB 3,000. The present invention uses a corundum crucible, which greatly reduces the material cost. A 30 mL corundum crucible costs about RMB 8. The high aluminum background introduced by strong alkali corrosion is effectively reduced by taking effective measures, and does not affect the accuracy of the test results.

[0047] (5) The method of the present invention is accurate, rapid, and time-efficient, with a wide measurement range, high accuracy, and good precision.

[0048] (6) The standard material GBW07877 (V2O5 standard value 1.55% ± 0.03%) with similar properties to the sample was used for verification, and the results met the uncertainty requirements of the standard material certificate (V2O5 detection value 1.52-1.56%).

[0049] (7) The present invention adopts alkali fusion-inductively coupled plasma atomic emission spectrometry, and the sample can be directly alkali fused, the sample is completely melted, and the solution is clear, which overcomes the disadvantages of acid dissolution; and no pre-decarburization is required, which saves a lot of time. The interference introduced by the crucible material is reduced by introducing a dilution factor, and the interference of silicate is eliminated by ammonium fluoride. A series of standard solutions with different concentration gradients are used to achieve rapid and accurate determination of low-grade vanadium content by inductively coupled plasma atomic emission spectrometry, which is particularly suitable for the determination of batch samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The photos of sample solutions obtained in Comparative Example 1 without adding nitric acid and in Example 1 with adding nitric acid;

[0051] Figure 2 The photos of solution A obtained by the methods of comparative example 1 and example 1;

[0052] Figure 3 The photos of the sample solutions after dissolution by the methods of Comparative Example 2 and Example 1;

[0053] Figure 4 This is a photo of the solution after heating and dissolution by the methods of Comparative Example 3 and Example 1;

[0054] Figure 5 The following are photos of the test solution B obtained by the methods of Comparative Example 3 and Example 1. DETAILED DESCRIPTION

[0055] The invention will be further described below in conjunction with the embodiments.

[0056] The principle of the method of the present invention is that the sample is melted with sodium peroxide, leached with nitric acid, and the influence of silicate is eliminated with ammonium fluoride. The emission spectrum intensity of vanadium is measured in an inductively coupled plasma atomic emission spectrometer at the analytical spectrum line of 290.882nm in a 5% nitric acid medium. The detection range is 0.1-2%.

[0057] The instruments and reagents involved in the method of the present invention are as follows:

[0058] (1) Instrument

[0059] Inductively coupled plasma atomic emission spectrometer (iCAP7400). Power 1150W, observation height 12mm, carrier gas flow 0.5L / min, auxiliary gas flow 0.5L / min, cooling gas flow 0.5L / min, analysis pump speed 50r / min, analysis spectrum: 290.882nm.

[0060] (2) Reagents

[0061] Sodium peroxide (analytical grade); nitric acid (analytical grade); ammonium fluoride (analytical grade, saturated solution); 5% nitric acid (superior grade); laboratory water is ultrapure water grade I.

[0062] Example 1

[0063] The method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry described in this embodiment specifically comprises the following steps:

[0064] (1) Preparation of standard solution and drawing of standard curve

[0065] Vanadium standard stock solution: 1000ug / mL, National Nonferrous Metals Co., Ltd.

[0066] Vanadium standard working solution: 100ug / mL. Accurately transfer 10.00mL of vanadium standard stock solution (1000ug / mL) into a 100mL volumetric flask, dilute to volume with 5% by volume nitric acid, and shake well.

[0067] Vanadium series standard solutions: Accurately pipette 0, 1.00, 5.00, 10.00, 15.00, and 20.00 mL of vanadium standard working solution (100 ug / mL) into a group of 100 mL volumetric flasks, dilute to volume with 5% by volume nitric acid, and shake well.

[0068] The process of drawing the standard curve is as follows: the concentration of the vanadium series standard solution is used as the abscissa, and the emission spectrum intensity corresponding to the concentration of the vanadium series standard solution measured by inductively coupled plasma atomic emission spectrometry is used as the ordinate to draw the standard curve.

[0069] (2) Measurement process

[0070] (2.1) Accurately weigh 0.5000 g (m) of vanadium shale sample into a 30 mL corundum crucible containing 4 g of sodium peroxide, stir evenly with a glass rod, cover the surface with a layer of sodium peroxide, melt in a muffle furnace at 700 °C for 10 min, and take out to cool.

[0071] (2.2) Rinse the outside of the crucible with water, place the crucible in a 400mL beaker, and wash the crucible with 80mL boiling water and 10mL nitric acid to obtain a solution. Place the beaker on a 250℃ hot plate to heat and boil to drive out all the hydrogen peroxide. Evaporate the volume to 70mL, then remove and cool. The source of hydrogen peroxide is the alkaline flux sodium peroxide, which is melted at high temperature and then leached with nitric acid to generate hydrogen peroxide.

[0072] (2.3) Transfer the cooled solution to a 100 mL (V) volumetric flask, dilute to volume with water, and shake well to obtain Solution A.

[0073] (2.4) Accurately transfer 5.00 mL (V1) of solution A into a 400 mL polytetrafluoroethylene beaker, add 5 mL of nitric acid and 1 mL of saturated ammonium fluoride solution, heat to dissolve, evaporate to dryness, and cool.

[0074] (2.5) Add 5 mL of nitric acid, rinse the cup wall with water, heat for 3 minutes until the salt is completely dissolved, remove and cool. Add water to a 50 mL (V2) volumetric flask, shake well, and obtain the test solution B.

[0075] Perform a blank test with the sample: do not weigh the vanadium shale sample into the corundum crucible containing 4 g of sodium peroxide in the above step (2.1), and complete the steps (2.1) to (2.5) simultaneously.

[0076] (2.6) According to the working conditions of the instrument, the emission spectrum intensity of vanadium in the blank test and the test solution B is measured at the selected wavelength of 290.882nm, and a standard curve is drawn with the concentration of the series of standard solutions as the horizontal axis and the corresponding emission spectrum intensity as the vertical axis. The mass concentration of vanadium in the blank test (C0) and the mass concentration of vanadium in solution B (C) are calculated based on the standard curve, and the vanadium content (W%) is calculated accordingly. The experiment is repeated according to the above methods (2.1) to (2.6) to obtain the average value of the vanadium content.

[0077] (3) Calculation of vanadium content

[0078]

[0079] Where:

[0080] W%—vanadium content, %;

[0081] C0—mass concentration of vanadium in blank test, ug / mL;

[0082] C—mass concentration of vanadium in solution B, ug / mL;

[0083] V—fixed volume of solution A, mL;

[0084] V1—volume of solution A pipetted, mL;

[0085] V2—the constant volume of solution B to be tested, mL;

[0086] m—sample mass, g.

[0087] (4) Measurement results

[0088] (4.1) Method accuracy and stability experimental results

[0089] Since no standard substance with the name of vanadium shale was found, the test used the stone coal vanadium ore component analysis standard substance GBW07876, which has similar properties and content to the sample, and determined the vanadium content according to the experimental method. The results are shown in Table 1. The RSD in the table is the relative standard deviation, which is mainly used to verify the precision of the method. The smaller the RSD, the better the repeatability of the test results. The certification value W% is the certification value of the stone coal vanadium ore component analysis standard substance GBW07876.

[0090] Table 1 Vanadium determination results W%

[0091]

[0092] (4.2) Method comparison experimental results

[0093] Seven vanadium shale samples were randomly selected, and the vanadium content was determined according to the method of Example 1 of the present invention. The test results of the seven samples using X-ray fluorescence spectrometry and ammonium ferrous sulfate titration were compared with the test results of the method of Example 1 of the present invention. It can be seen from the test results that the test results of the method of the present invention are accurate and satisfactory. The comparison results are shown in Table 2.

[0094] Table 2 Comparison of data between the present invention method and the prior art method for determining vanadium content

[0095]

[0096]

[0097] (4.3) Detection timeliness

[0098] Take 30 samples as an example to illustrate the measurement time and cost:

[0099] Using the method of the present invention, 30 samples can be made in one batch. The sample processing process takes 3 hours, the determination takes 1 hour, and it takes 4 hours to complete the detection of 30 samples.

[0100] Using the existing ammonium ferrous sulfate titration method, it takes 2 hours to decarbonize the sample, 30 minutes to process the sample, 20 minutes to oxidize, reduce and titrate each sample one by one, and 12 hours to complete the titration of 30 samples, which is very labor-intensive.

[0101] Example 2

[0102] The method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry described in this embodiment specifically comprises the following steps:

[0103] (1) Preparation of standard solution and drawing of standard curve

[0104] Vanadium standard stock solution: 1000ug / mL, National Nonferrous Metals Co., Ltd.

[0105] Vanadium standard working solution: 100ug / mL. Accurately transfer 10.00mL of vanadium standard stock solution (1000ug / mL) into a 100mL volumetric flask, dilute to volume with 5% by volume nitric acid, and shake well.

[0106] Vanadium series standard solutions: Accurately pipette 0, 1.00, 5.00, 10.00, 15.00, and 20.00 mL of vanadium standard working solution (100 ug / mL) into a group of 100 mL volumetric flasks, dilute to volume with 5% by volume nitric acid, and shake well.

[0107] The process of drawing the standard curve is as follows: the concentration of the vanadium series standard solution is used as the abscissa, and the emission spectrum intensity corresponding to the concentration of the vanadium series standard solution measured by inductively coupled plasma atomic emission spectrometry is used as the ordinate to draw the standard curve.

[0108] (2) Measurement process

[0109] (2.1) Accurately weigh 1.0000 g (m) of vanadium shale sample into a 50 mL corundum crucible containing 5 g of sodium peroxide, stir evenly with a glass rod, cover the surface with a layer of sodium peroxide, melt in a muffle furnace at 800 °C for 15 min, and take out to cool.

[0110] (2.2) Rinse the outside of the crucible with water, place the crucible in a 400mL beaker, add 100mL boiling water and 15mL nitric acid, wash the crucible and take it out to get a solution. Place the beaker on a 300℃ hot plate to heat and boil to drive out all the hydrogen peroxide. Evaporate the volume to 80mL, remove and cool. The source of hydrogen peroxide is the alkaline flux sodium peroxide, which is melted at high temperature and then leached with nitric acid to generate hydrogen peroxide.

[0111] (2.3) Transfer the cooled solution to a 100 mL (V) volumetric flask, dilute to volume with water, and shake well to obtain Solution A.

[0112] (2.4) Accurately transfer 10.00 mL (V1) of solution A into a 400 mL polytetrafluoroethylene beaker, add 10 mL of nitric acid and 1 mL of saturated ammonium fluoride solution, heat to dissolve, evaporate to dryness, and remove to cool.

[0113] (2.5) Add 5 mL of nitric acid, rinse the cup wall with water, heat for 5 minutes until the salt is completely dissolved, remove and cool. Add water to a 100 mL (V2) volumetric flask, shake well, and obtain the test solution B.

[0114] Perform a blank test with the sample: do not weigh the vanadium shale sample into the corundum crucible containing 5 g of sodium peroxide in the above step (2.1), and complete the steps (2.1) to (2.5) simultaneously.

[0115] (2.6) According to the working conditions of the instrument, the emission spectrum intensity of vanadium in the blank test and the test solution B is measured at the selected wavelength of 290.882nm, and a standard curve is drawn with the concentration of the series of standard solutions as the horizontal axis and the corresponding emission spectrum intensity as the vertical axis. The mass concentration of vanadium in the blank test (C0) and the mass concentration of vanadium in solution B (C) are calculated based on the standard curve, and the vanadium content (W%) is calculated accordingly. The experiment is repeated according to the above methods (2.1) to (2.6) to obtain the average value of the vanadium content.

[0116] (3) Calculation of vanadium content

[0117]

[0118] Where:

[0119] W%—vanadium content, %;

[0120] C0—mass concentration of vanadium in blank test, ug / mL;

[0121] C—mass concentration of vanadium in solution B, ug / mL;

[0122] V—fixed volume of solution A, mL;

[0123] V1—volume of solution A pipetted, mL;

[0124] V2—the constant volume of solution B to be tested, mL;

[0125] m—sample mass, g.

[0126] Comparative Example 1

[0127] The determination method and parameters are the same as those in Example 1, except that:

[0128] (2.2) Rinse the outside of the crucible with water, place the crucible in a 400 mL beaker, wash the crucible with 80 mL of boiling water, and get a solution. Place the beaker on a 250°C hot plate and heat to boil to drive out all the hydrogen peroxide. Evaporate the volume to 70 mL, then remove and cool.

[0129] In Comparative Example 1, 10 mL of nitric acid was not added, and the obtained sample solution was obviously turbid and accompanied by precipitation, while the sample solution obtained after step (2.2) in Example 1 was clear and had no precipitation. Figure 1 .

[0130] The comparison diagram of solution A obtained by the method of comparative example 1 and solution A obtained by the method of embodiment 1 is shown in Figure 2 . Figure 2 It can be seen that the solution A obtained by the method of Comparative Example 1 is obviously turbid and accompanied by precipitation, while the solution A obtained by the method of Example 1 is clear and has no precipitation.

[0131] Comparative Example 2

[0132] The determination method and parameters are the same as those in Example 1, except that:

[0133] (2.1) Accurately weigh 0.5000 g (m) of vanadium shale sample and dissolve it according to the ammonium ferrous sulfate titration method specified in YB / T 5328-2009 and GB 7315.1-87. Figure 3 .

[0134] As can be seen from the figure, the samples dissolved by the ammonium ferrous sulfate titration method in YB / T 5328-2009 and GB 7315.1-87 are not completely dissolved and have obvious particles due to the high carbon content of vanadium shale and the difference in the properties of vanadium shale samples. However, the samples dissolved by the methods of steps (2.1) and (2.2) in Example 1 have no particles, are completely dissolved, and the sample solution is clear.

[0135] Comparative Example 3

[0136] The determination method and parameters are the same as those in Example 1, except that:

[0137] (2.4) Accurately transfer 5.00 mL (V1) of solution A into a 400 mL polytetrafluoroethylene beaker, add 5 mL of nitric acid, heat to dissolve, evaporate to dryness, and cool.

[0138] When 1 mL of saturated ammonium fluoride solution was not added to the comparative example 3, the solution of the comparative example 3 was heated and dissolved, and a precipitate was found; while when 1 mL of saturated ammonium fluoride solution was added to the method of Example 1, the solution was heated and dissolved, and it was found that the solution was a transparent solution with no precipitate. Figure 4 .

[0139] The test solution B obtained by the method of comparative example 3 showed obvious suspended matter, while the test solution B obtained by the method of example 1 was clear and no suspended matter was seen. Figure 5 .

[0140] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and the specific implementation of the present invention cannot be limited to these descriptions. For ordinary technicians in the field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for determining the low-grade vanadium content in vanadium shale using inductively coupled plasma atomic emission spectrometry, characterized in that: The steps include: (1) preparing a vanadium standard working solution with a vanadium standard stock solution, and preparing a vanadium series standard solution with a vanadium standard working solution; (2) Determine the emission spectrum intensity of vanadium in a vanadium series standard solution and draw a standard curve; (3) Determination (3.1) Accurately weigh 0.5000-1.0000 g of vanadium shale sample and stir it evenly in a corundum crucible filled with sodium peroxide, cover the surface with a layer of sodium peroxide, melt it in a muffle furnace, take it out and cool it after melting; (3.2) Rinse the outside of the crucible with water, place the crucible in a 400 mL beaker, add 80-100 mL of boiling water and 10-15 mL of nitric acid, wash the crucible and take out the solution, heat and boil to drive out all the hydrogen peroxide, evaporate the volume to 70-80 mL, and then take it out and cool it; (3.3) Transfer the cooled solution to a 100 mL volumetric flask, dilute to volume with water, and shake well to obtain Solution A; (3.4) Accurately transfer 5.00-10.00 mL of solution A into a 400 mL polytetrafluoroethylene beaker, add nitric acid and saturated ammonium fluoride solution, heat to dissolve, evaporate to dryness, and cool; (3.5) Add 5 mL of nitric acid, rinse the cup wall with water, heat for 3 to 5 minutes until the salt is completely dissolved, remove and cool, dilute to 50 to 100 mL with water in a volumetric flask, shake well, and obtain solution B to be tested; perform a blank test together with the sample; (3.6) According to the instrument working conditions, at the selected wavelength of 290.882nm, the spectral intensity of vanadium in the blank test and the test solution B is measured respectively. A standard curve is drawn with the concentration of the series of standard solutions as the horizontal axis and the corresponding emission spectrum intensity as the vertical axis. The mass concentration of vanadium in the blank test and solution B is calculated based on the standard curve, and the vanadium content is calculated accordingly.

2. The method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry according to claim 1, characterized in that: The concentration of the vanadium standard storage solution in step (1) is 1000 ug / mL.

3. The method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry according to claim 2, characterized in that: The concentration of the vanadium standard working solution is 100ug / mL; the preparation process is to accurately transfer 10.00mL of the 1000ug / mL vanadium standard storage solution into a 100mL volumetric flask, dilute to volume with 5% by volume nitric acid, and shake well.

4. The method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry according to claim 3, characterized in that: Vanadium series standard solutions: Accurately pipette 100ug / mL vanadium standard working solution: 0, 1.00, 5.00, 10.00, 15.00, 20.00mL into a group of 100mL volumetric flasks, dilute to volume with 5% by volume nitric acid, and shake well.

5. The method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry according to claim 1, characterized in that: The process of drawing the standard curve in step (2) is as follows: the standard curve is drawn with the concentration of the vanadium series standard solution as the horizontal axis and the emission spectrum intensity corresponding to the concentration of the vanadium series standard solution measured by inductively coupled plasma atomic emission spectrometry as the vertical axis.

6. The method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry according to claim 1, characterized in that: In step (3.1), the volume of the corundum crucible is 30 to 50 mL; the melting temperature of the muffle furnace is 700 to 800° C.; and the melting time is 10 to 15 min.

7. The method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry according to claim 1, characterized in that: The heating temperature in step (3.2) is 250-300°C.

8. The method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry according to claim 1, characterized in that: The volume of nitric acid added in step (3.4) is 5-10 mL, and the volume of saturated ammonium fluoride solution added is 1 mL.

9. The method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry according to claim 1, characterized in that: The blank test in step (3.5) is performed in parallel with steps (3.1) to (3.5) without weighing the vanadium shale sample into the corundum crucible containing sodium peroxide in step (3.1).

10. The method for determining the low-grade vanadium content in vanadium shale by inductively coupled plasma atomic emission spectrometry according to claim 1, characterized in that: The calculation formula for the vanadium content in step (3.6) is Where: W%—vanadium content, %; C0—mass concentration of vanadium in blank test, ug / mL; C—mass concentration of vanadium in solution B, ug / mL; V—fixed volume of solution A, mL; V1—volume of solution A pipetted, mL; V2—the constant volume of solution B to be tested, mL; m—sample mass, g.

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