Quantitative detection method for thallium content in converter graphite ball

Abstract

A quantitative detection method of thallium content in converter graphite ball, steps include: 1) the pretreatment of converter graphite ball; 2) the preparation of standard solution series; 3) the detection of thallium content in converter graphite ball.The application finds that the suitable pretreatment method of converter graphite ball is carbon removal by burning, and then high-chloric acid and dilute nitric acid are used to dissolve salt, by which the converter graphite ball can be completely dissolved, thereby the stability of quantitative determination of thallium content in converter graphite ball is improved, the pretreatment method is simple, fast and operable; the method is suitable for the quantitative detection of thallium content in converter graphite ball with thallium content not less than 0.0062 μg / L, the recovery rate of thallium is as high as 99.1%, the analysis accuracy is high, the detection lower limit is as low as ppb level, the sensitivity is high, and the method has the advantages of simple operation, simple analysis condition and low labor intensity.Therefore, the application has significant economic benefits and the advantages of simplicity and economy.

Description

Technical Field

[0001] This invention belongs to the field of trace detection technology, specifically relating to a quantitative detection method for thallium content in converter graphite balls. Background Technology

[0002] Thallium, a highly toxic radioactive element, can enter the human body through food, water, and respiration, causing harm to health. When the thallium concentration in the human body exceeds 12 mg / kg, it can even lead to death. Therefore, there are strict control standards for thallium emissions. Converter graphite balls, as an important raw material in steelmaking, are widely used in steelmaking, refractory materials, and conductive materials due to their advantages such as high carbon content, high temperature resistance, and good electrical conductivity. Therefore, detecting the thallium content in graphite balls is of great significance for controlling thallium content at its source.

[0003] Currently, there are no patents regarding methods for detecting and dissolving thallium in graphite spheres. Existing methods for thallium detection include graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma atomic emission spectrometry (ICP-AES), and spectrophotometry. However, these methods suffer from drawbacks such as cumbersome operation, long experimental cycles, and high detection limits, thus failing to meet the detection requirements. To monitor and control thallium in converter graphite spheres, it is essential to develop a rapid, accurate, and low-detection-limit quantitative detection method. Summary of the Invention

[0004] In order to overcome the above-mentioned shortcomings and deficiencies of the prior art, the purpose of this invention is to provide a quantitative detection method for thallium content in converter graphite balls.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for quantitatively detecting thallium content in converter graphite balls, comprising the following steps:

[0007] 1) Pretreatment of converter graphite balls: Place the converter graphite balls in a muffle furnace at 750°C. o C~850 o C. Pre-calcine for 1 hour; remove and cool, then transfer to a polytetrafluoroethylene beaker. Add 5-10 mL of hydrochloric acid, 5-10 mL of nitric acid, 2-8 mL of hydrofluoric acid and 2-5 mL of perchloric acid (analytical grade or higher) in sequence for low-temperature dissolution. After fuming, concentrate the volume, remove and cool slightly, then add dilute nitric acid to dissolve the salts. Remove, cool to room temperature, and dilute to volume with deionized water, then mix well.

[0008] 2) Preparation of standard solution series:

[0009] Preparation of thallium standard solutions: Pour dilute nitric acid to form a base, then pour different concentrations of 1000 μg / mL Tl standard stock solutions according to the dilution ratio. Dilute to volume with deionized water, shake well, and prepare concentration gradients of 0 μg / L, 0.1 μg / L, 0.3 μg / L, 0.5 μg / L, 0.7 μg / L, 1.0 μg / L, 5.0 μg / L, and 10.0 μg / L.

[0010] Preparation of indium internal standard solution: Pipette 10 μg / mL indium standard solution, dilute to volume with deionized water, and shake well to obtain 5 μg / L indium internal standard solution.

[0011] (3) Detection of thallium content in converter graphite balls: Using the indium standard solution in step (2) as an internal standard, 205Tl is used as the measuring isotope in oxygen reaction mode. The series of thallium standard solutions in step (2) and the converter graphite ball solution in step (1) are determined by inductively coupled plasma mass spectrometry. A calibration curve equation is established, and the thallium content in the converter graphite balls in the wastewater is calculated according to the standard curve equation.

[0012] Preferably, the particle size of the converter graphite balls mentioned in step (1) is ≤0.125 mm.

[0013] Preferably, the amount and concentration of dilute nitric acid added in steps (1) and (2) are 20 mL and 10% to 50%.

[0014] Preferably, the volume of the 1000 μg / mL Tl standard stock solution transferred in step (2) is 0 μL, 10 μL, 30 μL, 50 μL, 70 μL, 0.1 mL, 0.5 mL, or 1 mL.

[0015] Preferably, the volume of the final volume in step (2) is 100 mL.

[0016] Preferably, the amount of indium internal standard solution transferred and the volume adjusted in step (2) are 0.5 mL and 1000 mL, respectively.

[0017] Preferably, the operating parameters of the mass spectrometer in step (3) are: auxiliary gas flow rate 0.8-0.9 L / min, nebulizing gas flow rate 0.9-1.0 L / min, cooling gas flow rate 10-20 L / min, oxygen flow rate 0.5-0.8 L / min, and power 800-1000 W.

[0018] Furthermore, the specific steps for detecting the thallium ion concentration in converter graphite balls using inductively coupled plasma mass spectrometry in step (3) are as follows:

[0019] Under optimized experimental conditions, inductively coupled plasma mass spectrometry (ICP-MS) was used to determine the intensity values ​​of the test solution of the converter graphite spheres and a series of thallium ion standard solutions, respectively, using the mass concentration of Tl element as the metric. x (%) represents the ratio of the signal strength of element Tl to the internal standard element In, with the x-axis representing the percentage. I Using (cps) as the ordinate, a calibration curve is constructed. The regression equation for the calibration curve is: I (cps) = a x (%) + b, with a linear correlation coefficient of R. In this equation, a and b are constants; then, the ratio of the signal intensity of the test liquid is substituted into the standard equation, and finally the thallium content in the test liquid is calculated.

[0020] The present invention has the following advantages and beneficial effects:

[0021] (1) This invention has discovered a suitable pretreatment method for converter graphite balls—calcination decarburization pretreatment followed by perchloric acid fuming and dilute nitrate dissolution of salts. This method can completely dissolve the converter graphite balls, thereby improving the stability of quantitative determination of thallium content in converter graphite balls. This pretreatment method is simple, fast and highly operable. This method is suitable for quantitative detection of thallium content in converter graphite balls with a thallium content of not less than 0.0062 μg / L, and the thallium recovery rate is as high as 99.1%.

[0022] (2) In the process of detecting thallium content, the present invention adopts the following methods to improve the accuracy of quantitative detection of thallium content in converter graphite balls: under optimal working conditions, carbon matrix is ​​eliminated by pre-calcination treatment and matrix mass concentration is controlled to eliminate the influence of matrix effect, oxygen reaction mode is adopted and 205Tl isotope is selected to eliminate mass spectrometry interference, and In internal standard correction is used to improve analytical accuracy.

[0023] (3) In this invention, the concentration of thallium in the test solution of the converter graphite spheres is detected by inductively coupled plasma mass spectrometry (ICP-MS). Compared with graphite furnace atomic absorption spectrometry (Graphite Furnace Atomic Absorption Spectrometry) and ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry), it has a lower detection limit, down to the ppb level, and higher sensitivity. Compared with spectrophotometry, it has the advantages of simpler operation, simpler analytical conditions, and lower labor intensity. Therefore, this invention has significant economic benefits and is simple and economical. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. For process parameters not specifically specified, conventional techniques can be referred to.

[0025] Example 1: A quantitative detection method for thallium content in converter graphite balls

[0026] Includes the following steps:

[0027] (1) Pretreatment of converter graphite balls: Place the converter graphite balls in a muffle furnace at 750°C. o Pre-calcine C for 1 hour, remove and cool, then transfer to a polytetrafluoroethylene beaker. Add 5 mL of hydrochloric acid and dissolve at low temperature for 10 minutes. Add 5 mL of nitric acid and 2 mL of hydrofluoric acid and dissolve at low temperature for 10 minutes. Add 2 mL of perchloric acid and heat to dissolve. After fuming, concentrate the volume to 1 mL. Remove and cool slightly. Add 20 mL of 10% dilute nitric acid to dissolve the salts. Remove and cool to room temperature. Dilute to 100 mL with deionized water and mix well.

[0028] (2) Preparation of standard solutions: Preparation of thallium standard solution series: Pour dilute nitric acid to the bottom, and then according to the dilution ratio, pour 0 μL, 10 μL, 30 μL, 50 μL, 70 μL, 0.1 mL, 0.5 mL, and 1 mL of 1000 μg / mL Tl standard stock solution, respectively. After diluting with deionized water, shake well to prepare thallium standard solutions of different concentration gradients:

[0029] Indium internal standard solution (5 μg / L): Pipette 0.5 mL of 10 μg / mL indium standard solution, dilute to 1000 mL with deionized water, and shake well.

[0030] (3) Detection of thallium content in converter graphite balls: Using indium standard solution as an internal standard, and 205Tl as the measuring isotope in oxygen reaction mode, a series of thallium standard solutions and converter graphite ball solutions were determined by inductively coupled plasma mass spectrometry (ICP-MS) to establish a calibration curve equation. The thallium content in the converter graphite balls in the wastewater was then calculated based on the standard curve equation. The operating parameters of the mass spectrometer were: auxiliary gas flow rate 0.8 L / min, nebulizing gas flow rate 0.9 L / min, cooling gas flow rate 10 L / min, oxygen flow rate 0.5 L / min, and power 800 W.

[0031] Therefore, a thallium standard curve was plotted: the mass concentration x (%) of Tl element was used as the abscissa, and the ratio of the signal intensity of Tl element to the internal standard element In was used as the ordinate. The regression equation of the calibration curve was I (cps) = 90802x (%) + 84 (R = 0.9992).

[0032] Substituting the signal intensity value of the test solution into the standard equation, the thallium concentration in the converter graphite ball test solution was calculated to be 0.0188 μg / L, and the calculated recovery rate was 97.5%.

[0033] The formula for calculating the recovery rate is:

[0034]

[0035] Eleven parallel experiments were conducted using the method described above, yielding an average thallium concentration of 0.0188 μg / L in the test solution of the converter graphite balls, a relative standard deviation (RSD) of 1.6% (n=11), and a calculated recovery rate of 97.5%. This demonstrates that the detection method of the present invention has high accuracy and precision.

[0036] Example 2: A quantitative detection method for thallium content in converter graphite balls

[0037] Includes the following steps:

[0038] (1) Pretreatment of converter graphite balls: Place the converter graphite balls in a muffle furnace at 750°C. o Pre-calcine C for 1 hour, remove and cool, then transfer to a polytetrafluoroethylene beaker. Add 5 mL of hydrochloric acid and dissolve at low temperature for 10 minutes. Add 5 mL of nitric acid and 2 mL of hydrofluoric acid and dissolve at low temperature for 10 minutes. Add 2 mL of perchloric acid and heat to dissolve. After fuming, concentrate the volume to 1 mL. Remove and cool slightly. Add 20 mL of 50% dilute nitric acid to dissolve the salts. Remove and cool to room temperature. Dilute to 100 mL with deionized water and mix well.

[0039] (2) Preparation of standard solutions:

[0040] Preparation of thallium standard solutions: Pour dilute nitric acid to the bottom, and then according to the dilution ratio, pour 0 μL, 10 μL, 30 μL, 50 μL, 70 μL, 0.1 mL, 0.5 mL, and 1 mL of 1000 μg / mL Tl standard stock solution, respectively. After diluting with deionized water, shake well to prepare thallium standard solutions of different concentration gradients.

[0041] Indium internal standard solution (5 μg / L): Pipette 0.5 mL of 10 μg / mL indium standard solution, dilute to 1000 mL with deionized water, and shake well.

[0042] (3) Detection of thallium content in converter graphite balls: Using indium standard solution as an internal standard, and 205Tl as the measuring isotope in oxygen reaction mode, a series of thallium standard solutions and converter graphite ball solutions were determined by inductively coupled plasma mass spectrometry (ICP-MS) to establish a calibration curve equation. The thallium content in the converter graphite balls in the wastewater was then calculated based on the standard curve equation. The operating parameters of the mass spectrometer were: auxiliary gas flow rate 0.9 L / min, nebulizing gas flow rate 1.0 L / min, cooling gas flow rate 20 L / min, oxygen flow rate 0.8 L / min, and power 1100 W.

[0043] Therefore, a thallium standard curve was plotted: the mass concentration x (%) of Tl element was used as the abscissa, and the ratio of the signal intensity of Tl element to the internal standard element In was used as the ordinate. The calibration curve was established, and the regression equation of the calibration curve was I (cps) = 11367x (%) + 9 (R = 0.9994).

[0044] Substituting the signal intensity value of the test solution into the standard equation, the thallium concentration in the converter graphite ball test solution was calculated to be 0.0113 μg / L, and the calculated recovery rate was 96.9%.

[0045] Example 3: A quantitative detection method for thallium content in converter graphite balls

[0046] Includes the following steps:

[0047] (1) Pretreatment of converter graphite balls: Place the converter graphite balls in a muffle furnace at 850°C. o Pre-calcine C for 1 hour, remove and cool, then transfer to a polytetrafluoroethylene beaker. Add 10 mL of hydrochloric acid sequentially, dissolve at low temperature for 10 minutes, then add 10 mL of nitric acid and 8 mL of hydrofluoric acid, dissolve at low temperature for 10 minutes, then add 5 mL of perchloric acid, heat to dissolve, and concentrate to 1 mL after fuming. Remove and cool slightly, add 20 mL of 50% dilute nitric acid to dissolve the salts, remove, cool to room temperature, and then dilute to 100 mL with deionized water and mix well.

[0048] (2) Preparation of standard solutions

[0049] Preparation of thallium standard solutions: Pour dilute nitric acid to the bottom, and then according to the dilution ratio, pour 0 μL, 10 μL, 30 μL, 50 μL, 70 μL, 0.1 mL, 0.5 mL, and 1 mL of 1000 μg / mL Tl standard stock solution, respectively. After diluting with deionized water, shake well to prepare thallium standard solutions of different concentration gradients.

[0050] Indium internal standard solution (5 μg / L): Pipette 0.5 mL of 10 μg / mL indium standard solution, dilute to 1000 mL with deionized water, and shake well.

[0051] (3) Detection of thallium content in converter graphite balls: Using indium standard solution as an internal standard, and 205Tl as the measuring isotope in oxygen reaction mode, a series of thallium standard solutions and converter graphite ball solutions were determined by inductively coupled plasma mass spectrometry (ICP-MS) to establish a calibration curve equation. The thallium content in the converter graphite balls in the wastewater was then calculated based on the standard curve equation. The operating parameters of the mass spectrometer were: auxiliary gas flow rate 0.9 L / min, nebulizing gas flow rate 0.9 L / min, cooling gas flow rate 15 L / min, oxygen flow rate 0.8 L / min, and power 1000 W.

[0052] Therefore, a thallium standard curve was plotted: the mass concentration x (%) of Tl element was used as the abscissa, and the ratio of the signal intensity of Tl element to the internal standard element In was used as the ordinate. The regression equation of the calibration curve was I (cps) = 67820x (%) + 48 (R = 0.9998).

[0053] Substituting the signal intensity value of the test solution into the standard equation, the thallium concentration in the converter graphite ball test solution was calculated to be 0.0378 μg / L, and the calculated recovery rate was 99.1%.

[0054] The above embodiments are merely examples of several implementation methods of the present invention, and their descriptions are relatively specific and detailed. However, they should not be construed as limiting the scope of the present invention. Any technical solutions obtained by equivalent substitution or equivalent transformation should fall within the protection scope of the present invention.

Claims

1. A method for quantitatively detecting thallium content in converter graphite balls, characterized in that... Includes the following steps: 1) Pretreatment of converter graphite balls: Place the converter graphite balls in a muffle furnace at 750°C. o C~850 o Pre-calcine at C for 1 hour; remove and cool, then transfer to a polytetrafluoroethylene beaker. Add 5–10 mL of hydrochloric acid, 5–10 mL of nitric acid, 2–8 mL of hydrofluoric acid, and 2–5 mL of perchloric acid (analytical grade or higher) sequentially for low-temperature dissolution. After fuming, concentrate the volume, remove and cool slightly, then add dilute nitric acid to dissolve the salts. Remove, cool to room temperature, and dilute to volume with deionized water, then mix well. The amount and concentration of the dilute nitric acid added are 20 mL and 10%–50%, respectively. 2) Preparation of standard solution series: Preparation of thallium standard solutions: Pour dilute nitric acid as a base, then pour different concentrations of 1000 μg / mL Tl standard stock solutions according to the dilution ratio. Dilute to volume with deionized water, shake well, and prepare concentration gradients of 0 μg / L, 0.1 μg / L, 0.3 μg / L, 0.5 μg / L, 0.7 μg / L, 1.0 μg / L, 5.0 μg / L, and 10.0 μg / L. The amount and concentration of the dilute nitric acid added are 20 mL, 10%–50%. The volume of the 1000 μg / mL Tl standard stock solutions is 0 μL, 10 μL, 30 μL, 50 μL, 70 μL, 0.1 mL, 0.5 mL, and 1 mL. Preparation of indium internal standard solution: Pipette 10 μg / mL indium standard solution, dilute to volume with deionized water, and shake well to obtain 5 μg / L indium internal standard solution; the volume of indium internal standard solution transferred and the volume of dilution are 0.5 mL and 1000 mL, respectively. 3) Detection of thallium content in converter graphite balls: Using the indium standard solution in step 2) as an internal standard, 205Tl was used as the measuring isotope in oxygen reaction mode. The series of thallium standard solutions in step 2) and the converter graphite ball solution in step (1) were determined by inductively coupled plasma mass spectrometry. A calibration curve equation was established, and the thallium content in the converter graphite balls in the wastewater was calculated according to the standard curve equation. The working parameters of the mass spectrometer were: auxiliary gas flow rate 0.8-0.9 L / min, atomizing gas flow rate 0.9-1.0 L / min, cooling gas flow rate 10-20 L / min, oxygen flow rate 0.5-0.8 L / min, and power 800-1000W.

2. The method for quantitative detection of thallium content in converter graphite balls according to claim 1, characterized in that: The particle size of the converter graphite balls mentioned in step 1) is ≤0.125 mm.

3. The method for quantitative detection of thallium content in converter graphite balls according to claim 1, characterized in that: The volume to be adjusted in step 2) is 100 mL.

4. The method for quantitative detection of thallium content in converter graphite balls according to claim 1, characterized in that: In step 3), the specific steps for detecting the thallium content in converter graphite spheres using inductively coupled plasma mass spectrometry (ICP-MS) are as follows: Under optimized experimental conditions, the intensity values ​​of the converter graphite sphere solution and a series of thallium standard solutions are determined by ICP-MS, and the thallium content is expressed as the mass concentration of Tl element. x % represents the ratio of the signal strength of element Tl to the internal standard element In, with % as the horizontal axis. I Using the vertical axis as the ordinate, a calibration curve is constructed. The regression equation for the calibration curve is: I =a x %+b, the linear correlation coefficient is R; in this equation, a and b are constants; Then, the signal intensity ratio of the converter graphite ball solution is substituted into the standard equation, and finally the thallium content in the converter graphite ball solution is calculated.