Method for measuring content of sulfate radicals in rare earth smelting waste gas desulfurizer

Abstract

The invention discloses a method for measuring the content of sulfate radicals in a rare earth smelting waste gas desulfurizer, which comprises the following steps: taking the desulfurizer as a sample, taking a certain amount of sample, diluting with water, and fixing the volume to prepare a sample test solution which is used as a first constant volume solution; absorbing the first constant-volume liquid, adding anaerobic acid to eliminate interference elements in the first constant-volume liquid, and diluting with water for constant volume to obtain a second constant-volume liquid; and carrying out blank and sample determination on the second constant volume solution by using a spectrophotometer, transferring a plurality of sulfate radical standard solutions into a plurality of colorimetric tubes respectively, adding a stabilizer and barium chloride respectively, measuring the absorbance by using the spectrophotometer by using the reagent blank as a reference, and calculating the concentration of sulfate radicals in the sample. Interference of impurity ions in the desulfurizing agent can be eliminated, and the stability, accuracy and applicability of the measuring method are effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth smelting detection, and in particular relates to a method for measuring sulfate content in a desulfurizer for rare earth smelting waste gas. Background Art

[0002] In the rare earth smelting and separation industry, desulfurizers are primarily used to absorb sulfur dioxide gas generated during the roasting process. Their advantages include high sulfur dioxide absorption efficiency, low cost, significant economic benefits, zero secondary pollution, and recyclable recycling. Recycled desulfurizers introduce significant amounts of impurities, including sulfur compounds, fluoride ions, chloride ions, and metal ions. The amount of these impurities significantly impacts the desulfurizer's efficiency in treating roasting exhaust gas. The presence of large amounts of sulfate ions in the desulfurizer reduces the amount of active cations within the desulfurizer, lowering desulfurization efficiency. This can lead to the formation of large amounts of suspended solids, darkening the solution color, and causing foaming. Sulfate ions combine with certain metal and non-metal ions to form scale on the interior walls of equipment, hindering heat transfer and increasing steam usage. During the desulfurizer regeneration process, sulfate ions undergo a series of side reactions, producing large amounts of sulfur, which can easily clog heat exchange equipment.

[0003] Currently, sulfate content is primarily determined using spectrophotometry, EDTA volumetric methods, and gravimetric methods. The classic gravimetric method is highly accurate and mature, but it is time-consuming and cumbersome. The EDTA volumetric method requires the addition of an excess of barium salt followed by back titration with EDTA, which is significantly affected by alkali metals. Spectrophotometry is simple to operate and highly sensitive, but has a limited detection range.

[0004] Chinese application number CN201410753891.8 discloses a method for determining sulfate in an organic amine absorption solution during a regenerative wet flue gas desulfurization process. The analysis is performed using a titration method, using alizarin red as an indicator, acetic acid to adjust the pH to 4-4.5, and barium chloride as a standard solution. The titration is performed until the color changes from yellow to pink, which is the endpoint. This method does not provide a clear endpoint, resulting in large measurement errors.

[0005] Chinese application number CN201811609993.7 discloses a method for determining sulfate content in a water sample. An excess of a barium-magnesium mixture is added to the water sample, causing the sulfate to react completely with the barium ions to form a barium sulfate precipitate. The remaining barium ions are titrated with an EDTA standard solution using Eriochrome Black T as an indicator at pH 10 in the presence of magnesium ions until the solution changes from red to blue. This method produces a large amount of white precipitate during titration, and EDTA forms a complex with the excess barium ions, making the endpoint unclear. Furthermore, interfering impurities in the desulfurizer can affect the determination.

[0006] In the field of rare earth smelting and separation, there is currently no method for determining the sulfate content in rare earth smelting waste gas desulfurizers. In order to meet production control needs, improve product quality, reduce production costs, and improve work efficiency, it is necessary to establish a method for determining the sulfate content in rare earth smelting waste gas desulfurizers that is simple to operate, fast, stable, and accurate. Summary of the Invention

[0007] The object of the present invention is to provide a method for determining the sulfate content in a rare earth smelting waste gas desulfurizer, which can eliminate the interference of impurity ions in the desulfurizer and effectively improve the stability, accuracy and applicability of the measurement method.

[0008] To achieve the above objectives, the technical solutions used in the present invention are:

[0009] A method for determining the sulfate content in a rare earth smelting waste gas desulfurizer, comprising:

[0010] Take the desulfurizer as a sample, take a certain amount of the sample and dilute it with water to make a sample solution, which is used as the first solution.

[0011] The first volume solution is taken and added with anaerobic acid to eliminate interfering elements in the first volume solution, and the volume is diluted with water to obtain the second volume solution;

[0012] Aspirate the second volume-fixing solution, use water as reference, and use a spectrophotometer to measure the absorbance A0 of the second volume-fixing solution in a blank.

[0013] Take the second volume solution and add stabilizer and barium chloride, use the reagent blank as reference, and use a spectrophotometer to measure its absorbance A; use A-A0 to calculate the corresponding amount of sulfate ion m from the working curve;

[0014] Pipette multiple portions of sulfate standard solution into multiple colorimetric tubes, add stabilizer and barium chloride respectively, dilute to the scale with water, measure the absorbance with a spectrophotometer using a reagent blank as a reference, and draw a standard curve with the amount of sulfate as the ordinate and the absorbance as the abscissa;

[0015] Calculation formula using sulfate results: Calculate the concentration of sulfate in the sample, where V is the volume of the sample, m is the micrograms of sulfate found from the standard curve, and F is the sample extraction coefficient;

[0016] The calculation formula of the fractionation coefficient F is: Among them, V 定1 is the volume of the first constant volume, V 吸1 V is the volume of the first fixed solution absorbed. 定2 is the volume of the second constant volume, V 吸2To absorb the volume of the second fixed solution, when no aliquoting is needed, F is 1.

[0017] Furthermore, the desulfurizer is used as a sample, and the sample is thoroughly shaken for 10-30 seconds before being drawn.

[0018] Furthermore, according to the sulfate content in the sample, a certain amount of the sample was transferred to a volumetric flask, diluted to the mark with water, and shaken to prepare the first volume solution.

[0019] Furthermore, the first volume-fixing solution was taken into a beaker, and hydrochloric acid with a volume ratio of 1+1 was added. The solution was heated on an electric stove, and after cooling, the solution was transferred into a volumetric flask, diluted to the mark with water, and shaken to obtain the second volume-fixing solution.

[0020] Furthermore, hydrochloric acid is added to react with interfering impurity ions to generate gas, thereby removing the interfering impurities while avoiding the generation of sulfate radicals.

[0021] Furthermore, the sample itself brings about changes in absorbance, so a blank measurement needs to be performed on each analyzed sample. During the measurement, water is used as a reference and the absorbance is measured at a wavelength of 430nm using a spectrophotometer.

[0022] Furthermore, the stabilizer includes sodium chloride, glycerol and anhydrous ethanol.

[0023] Furthermore, the preparation of the stabilizer includes: weighing 50g of sodium chloride and dissolving it in 200mL of water, adding 8mL of hydrochloric acid, 200mL of glycerol, and 400mL of anhydrous ethanol, shaking well, and adjusting the volume in a 1000mL volumetric flask.

[0024] Furthermore, the preparation of a 250 g / L barium chloride solution includes: weighing 25 g of barium chloride that has been dried at 105° C. for 1 hour, and adding 100 mL of pure water to dissolve it clearly.

[0025] Furthermore, drawing a standard curve includes: pipetting 0.00, 1.00, 2.00, 3.00, 4.00, and 5.00 mL of a 50 ug / mL sulfate standard solution into six 25 mL colorimetric tubes, respectively, adding 5 mL of a stabilizer and 4 mL of 250 g / L barium chloride, respectively, diluting to the scale with water, shaking, and stabilizing for 10 minutes, using a 2 cm cuvette and a reagent blank as a reference, measuring its absorbance at a wavelength of 430 nm on a spectrophotometer, and drawing a standard curve with the amount of sulfate as the ordinate and the absorbance as the abscissa; the preparation of a 50 ug / mL sulfate standard solution includes: weighing 0.1814 g of potassium sulfate dried to a constant weight at 105° C. into a 100 mL beaker, dissolving it in water, transferring it into a 2000 mL volumetric flask, diluting to the scale with water, and shaking.

[0026] The technical effects of this application include:

[0027] 1. The present application can measure the sulfate content in the desulfurizer used to treat the waste gas in the rare earth smelting and roasting process, solves the problem of no analytical method for sulfate in the desulfurizer, and enables the sulfate content in the desulfurizer to be effectively monitored.

[0028] 2. This application can reduce the impurity content of the desulfurizer, eliminate the interference of impurity ions in the desulfurizer on the determination, and effectively improve the stability, accuracy and applicability of the measurement method.

[0029] (1) This application is simple, quick to operate, has a short analysis time, low cost, and accurate and stable measurement results.

[0030] This application uses spectrophotometry-barium chloride turbidimetry for analysis to avoid unclear observation endpoints and eliminate endpoint errors.

[0031] (2) This application takes into account the change in absorbance caused by the sample itself during sulfate determination. A sample blank needs to be prepared for each analyzed sample, and water is used as a reference during the determination.

[0032] (3) This application considers that the sample contains a large amount of sulfide, which affects the sulfate determination, and adopts the method of adding hydrochloric acid and heating to remove it.

[0033] (4) This application takes into account that the sample contains a large amount of fluoride, which affects the sulfate determination, and adopts the method of adding hydrochloric acid and performing secondary heating to remove it.

[0034] (5) When adding hydrochloric acid to eliminate interference, heat it to the measuring volume to prevent the desulfurizer from changing color when the volume is too small, which will affect the determination.

[0035] (6) This application takes into account the influence of sample uniformity. Before measurement, the sample is shaken thoroughly and then pipetted into a volumetric flask. This increases the sampling volume and reduces sampling errors.

[0036] (7) The present invention adopts spectrophotometry-barium chloride turbidimetry for determination, i.e., using barium chloride as a colorimetric reagent to directly determine the amount of sulfate in the desulfurizer. After removing interfering impurities during the determination, the determination results are more accurate and more stable. The barium chloride solution used in this application should be prepared immediately before use and kept at a temperature of 70-90°C during use to improve the color development effect of barium chloride.

[0037] (8) The standard working curve of this application is drawn using a linear function, i.e., y=kx+b, and the amount of sulfate (ug) is used as the ordinate and the absorbance is used as the abscissa to draw the working curve. The working curve equation drawn by this method is very convenient to use, and data processing is completed using Excel software, which is fast and time-saving, avoids human calculation errors, and is faster for batch calculations. It greatly eliminates human errors, reduces accidental errors, simplifies the calculation process, and the analysis results are accurate and reproducible.

[0038] 3. After application, this application can not only effectively monitor the sulfate content in the desulfurizer, but also improve the rationality of process control, improve desulfurization efficiency, reduce operating costs and increase economic benefits.

[0039] The detection method provided by the present invention can not only effectively monitor the sulfate content in the desulfurizer, but also improve the monitoring capability of the desulfurization process, reduce the impurity content of the desulfurizer, improve the desulfurization efficiency, prevent the occurrence of excessive sulfate content, and ensure smooth production.

[0040] By removing interfering impurities in the desulfurizer and reducing interference, the method fills the gap in analytical methods in the field of rare earth smelting analysis and detection. The method has strong applicability, making the method more widely applicable and can be promoted and applied in rare earth hydrometallurgical enterprises and other chemical industries.

[0041] It is used in the determination of sulfate content in desulfurizers used in waste gas from rare earth smelting and roasting processes, effectively guiding production. The method is simple and fast to operate, and the results are accurate and stable, which greatly shortens analysis time, reduces labor intensity, and improves work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The present invention is a flow chart of a method for determining sulfate content in a rare earth smelting waste gas desulfurizer. DETAILED DESCRIPTION

[0043] The following description sufficiently illustrates specific embodiments of the invention to enable those skilled in the art to practice and reproduce the invention.

[0044] The present invention adopts spectrophotometry for determination, according to the Lambert-Beer law, that is, the absorbance is proportional to the product of the concentration of the solution and the thickness of the liquid layer. Taking full account of the influence of interfering impurity ions in the desulfurizer on the determination of sulfate, an oxygen-free acid (such as hydrochloric acid) is added to react with the interfering impurity ions to generate gas and remove them. For example, the sulfides (such as sulfide ions, thiosulfate, sulfite, etc.) contained in the desulfurizer react with hydrochloric acid to generate sulfur dioxide gas and are removed to avoid the generation of sulfate, which affects the determination results; the fluorides contained react with hydrochloric acid to generate hydrogen fluoride gas and are removed to eliminate interference. A glycerol-ethanol solution is used as a stabilizer, and a barium chloride solution is added to prepare a barium sulfate suspension, and its absorbance is measured using a spectrophotometer. The main chemical equations are as follows:

[0045] S2O3 2- +2H + =SO2↑+S↓+H2O

[0046] SO3 2- +H + =2SO2↑+H2O

[0047] F - +H + =HF↑

[0048] SO4 2- +Ba 2+ =BaSO4

[0049] like Figure 1 The figure shows a flow chart of the method for determining the sulfate content in the rare earth smelting waste gas desulfurizer according to the present invention.

[0050] The method for determining the sulfate content in a rare earth smelting waste gas desulfurizer comprises the following steps:

[0051] (1) Sample processing;

[0052] Take the desulfurizer as the sample. Shake the sample thoroughly before absorbing it. According to the sulfate content in the sample, transfer a certain amount of sample into a 100mL volumetric flask, dilute it to the scale with water, shake it well, and prepare the first volume solution.

[0053] (2) Eliminate interfering elements in the first volume solution;

[0054] From the volumetric flask in step (1), draw 2 mL of the first constant volume solution into a 300 mL beaker, add 10 mL of hydrochloric acid (volume ratio 1+1), heat the volume on an electric stove to 2-3 mL, then add 10 mL of hydrochloric acid (volume ratio 1+1), heat the volume on an electric stove to 2-3 mL, remove it, cool it, transfer it to a 100 mL volumetric flask, dilute it to the scale with water, shake it well, and use it as the second constant volume solution.

[0055] The impact of interfering impurity ions on sulfate determination is fully considered. By adding an oxygen-free acid (such as hydrochloric acid) to react with the interfering impurity ions to generate gas, they are removed. For example, the sulfides contained in the desulfurizer (such as sulfide ions, thiosulfate, sulfite, etc.) react with hydrochloric acid to generate sulfur dioxide gas, which is removed to avoid the formation of sulfate and affect the determination results. The fluorides contained in the desulfurizer react with hydrochloric acid to generate hydrogen fluoride gas, which is removed to eliminate interference.

[0056] (3) Perform a blank test on the second volume-fixing solution;

[0057] Pipette 1 mL of the second volume solution from the 100 mL volumetric flask in step (2) into a 25 mL colorimetric tube, dilute with water to the mark, and shake well; use a 2 cm colorimetric dish and water as a reference to measure its absorbance A0 at a wavelength of 430 nm on a spectrophotometer.

[0058] (4) Determine the sulfate content of the second volume solution;

[0059] Pipette 1 mL of the second volumetric solution from the 100 mL volumetric flask in step (2) into a 25 mL colorimetric tube, add 5 mL of stabilizer and 4 mL of barium chloride (concentration 250 g / L), dilute to the mark with water, shake well, and maintain the temperature at 70-90°C. Stabilize for 10 minutes, and measure the absorbance A at a wavelength of 430 nm using a 2 cm cuvette and a reagent blank as a reference. Calculate the corresponding sulfate amount m from the working curve using A-A0.

[0060] Preparation of stabilizer: Weigh 50g sodium chloride and dissolve it in 200mL water. Add 8mL hydrochloric acid, 200mL glycerol (propylene glycol), and 400mL anhydrous ethanol and shake well. Dose to a constant volume in a 1000mL volumetric flask.

[0061] Preparation of barium chloride solution (concentration 250g / L) (prepare as needed): weigh 25g of barium chloride that has been dried at 105℃ for 1 hour, add 100mL of pure water to dissolve it clearly.

[0062] (5) Drawing of standard curve;

[0063] Accurately pipette 0.00, 1.00, 2.00, 3.00, 4.00, and 5.00 mL of a 50 μg / mL sulfate standard solution into six 25 mL colorimetric tubes. Add 5 mL of stabilizer and 4 mL of barium chloride (250 g / L) to each tube. Dilute to the mark with water and shake well. Allow to stabilize for 10 minutes. Measure the absorbance at 430 nm using a 2 cm cuvette and a reagent blank as a reference. Plot a standard curve with the amount of sulfate (μg) as the ordinate and the absorbance as the abscissa.

[0064] Preparation of sulfate standard solution (50ug / mL): Weigh 0.1814g of potassium sulfate dried at 105℃ into a 100mL beaker, dissolve in water, transfer to a 2000mL volumetric flask, dilute to the mark with water, and shake well.

[0065] (6) Result calculation

[0066] The concentration of sulfate in the sample was calculated using the following formula:

[0067] The calculation formula of sulfate in the sample is:

[0068] Wherein, V is the volume of the sample absorbed, unit: mL; m is the micrograms of sulfate ion obtained from the standard curve, unit: ug; F is the fractionation coefficient of the sample.

[0069] The calculation formula of the fractionation coefficient F is: Among them, V 定1 is the volume of the first constant volume, V 吸1 V is the volume of the first fixed solution absorbed.定2 is the volume of the second constant volume, V 吸2 To absorb the volume of the second fixed solution, and so on. When no aliquoting is needed, F is 1.

[0070] Example 1

[0071] (1) Sample processing;

[0072] Before taking the desulfurizer (lean solution 1#) sample, shake the sample thoroughly. Pipette 10mL of desulfurizer (lean solution 1#) into a 100mL volumetric flask, dilute to the mark with water, and shake well.

[0073] (2) Eliminate interference;

[0074] From the volumetric flask in step (1), draw 2 mL of the test solution into a 300 mL beaker, add 10 mL of hydrochloric acid (1+1), and heat the volume on an electric stove to 1-2 mL. Then add another 10 mL of hydrochloric acid (1+1), and heat the volume on an electric stove to 1-2 mL. Remove the solution, cool it, transfer it to a 100 mL volumetric flask, dilute it to the mark with water, and shake well.

[0075] (3) Sample blank determination;

[0076] Transfer 1 mL of the test solution from the 100 mL volumetric flask in step (2) to a 25 mL colorimetric tube, dilute to the mark with water, and shake well. Measure the absorbance of the solution at 430 nm using a 2 cm cuvette with water as the reference on a spectrophotometer to obtain a value of 0.003.

[0077] (4) Sample determination;

[0078] 1 mL of the test solution from the 100 mL volumetric flask in step (2) was transferred to a 25 mL colorimetric tube. 5 mL of stabilizer and 4 mL of barium chloride (250 g / L) were added, and the mixture was diluted to the mark with water and shaken. The mixture was allowed to stabilize for 10 minutes. The absorbance was measured at a wavelength of 430 nm using a 2 cm cuvette and a reagent blank as a reference. The absorbance was 0.164. The corresponding sulfate content of 118.89 μg was obtained from the working curve using an absorbance value of 0.161 (derived from 0.164-0.003).

[0079] (5) Drawing of standard curve;

[0080] Accurately pipette 0.00, 1.00, 2.00, 3.00, 4.00, and 5.00 mL of 50 ug / mL sulfate standard solution into 6 25 mL colorimetric tubes, add 5 mL of stabilizer and 4 mL of barium chloride (250 g / L), dilute with water to the scale, and shake well. Stabilize for 10 minutes, use a 2 cm cuvette, and use the reagent blank as a reference to measure the absorbance at a wavelength of 430 nm on a spectrophotometer. The absorbance is: 0, 0.067, 0.135, 0.202, 0.270, 0.342, respectively. Use the amount of sulfate (ug) as the ordinate and the absorbance as the abscissa to draw a standard curve: m = 733.35A + 0.8198, R 2 =0.9999.

[0081] (6) Calculation of results.

[0082] The concentration of sulfate in the desulfurizer (lean solution 1#) is calculated using the following formula:

[0083] Calculation formula for sulfate in desulfurizer (lean liquid 1#):

[0084]

[0085] Example 2

[0086] (1) Sample processing;

[0087] Before taking the desulfurizer (lean solution 2#) sample, shake the sample thoroughly. Pipette 10mL of desulfurizer (lean solution 2#) into a 100mL volumetric flask, dilute to the mark with water, and shake well.

[0088] (2) Eliminate interference;

[0089] From the volumetric flask in step (1), draw 2 mL of the test solution into a 300 mL beaker, add 10 mL of hydrochloric acid (1+1), and heat on an electric stove until the volume reaches 2-3 mL. Then add another 10 mL of hydrochloric acid (1+1), and heat on an electric stove until the volume reaches 2-3 mL. Remove the solution, cool it, transfer it into a 100 mL volumetric flask, dilute it to the mark with water, and shake well.

[0090] (3) Sample blank determination;

[0091] Transfer 2 mL of the test solution from the 100 mL volumetric flask in step (2) to a 25 mL colorimetric tube, dilute to the mark with water, and shake well. Measure the absorbance of the solution at 430 nm using a 2 cm cuvette with water as the reference on a spectrophotometer to 0.001.

[0092] (4) Sample determination;

[0093] 2 mL of the test solution from the 100 mL volumetric flask in step (2) was transferred to a 25 mL colorimetric tube. 5 mL of stabilizer and 4 mL of barium chloride (250 g / L) were added, and the mixture was diluted to the mark with water and shaken. The mixture was allowed to stabilize for 10 minutes. The absorbance was measured at a wavelength of 430 nm using a 2 cm cuvette and a reagent blank as a reference. The absorbance was 0.222. The corresponding amount of sulfate ion, 123.13 μg, was obtained from the working curve using the absorbance value of 0.221 (derived from 0.222-0.001).

[0094] (5) Drawing of standard curve;

[0095] Accurately pipette 0.00, 1.00, 2.00, 3.00, 4.00, and 5.00 mL of 50 ug / mL sulfate standard solution into 6 25 mL colorimetric tubes, add 5 mL of stabilizer and 4 mL of barium chloride (250 g / L), dilute to the scale with water, and shake well. Stabilize for 10 minutes, use a 2 cm cuvette, and use the reagent blank as a reference to measure the absorbance at a wavelength of 430 nm on a spectrophotometer. The absorbance is: 0, 0.065, 0.125, 0.189, 0.269, and 0.333, respectively. Use the amount of sulfate (ug) as the ordinate and the absorbance as the abscissa to draw a working curve: m = 746.23A + 2.9913, R 2 =0.9982.

[0096] (6) Calculation of results.

[0097] The concentration of sulfate in the desulfurizer (lean liquid 2#) is calculated using the following formula:

[0098]

[0099] Example 3

[0100] (1) Sample processing;

[0101] Before taking the desulfurizer (stock solution) sample, shake the sample thoroughly. Pipette 20mL of desulfurizer (stock solution) into a 100mL volumetric flask, dilute to the mark with water, and shake well.

[0102] (2) Eliminate interference;

[0103] From the volumetric flask in step (1), draw 10 mL of the test solution into a 300 mL beaker, add 10 mL of hydrochloric acid (1+1), and heat the volume on an electric stove to 2-3 mL. Then add another 10 mL of hydrochloric acid (1+1), and heat the volume on an electric stove to 2-3 mL. Remove the solution, cool it, transfer it to a 100 mL volumetric flask, dilute it to the mark with water, and shake well.

[0104] (3) Sample blank determination;

[0105] Transfer 10 mL of the test solution from the 100 mL volumetric flask in step (2) to a 25 mL colorimetric tube, dilute to the mark with water, and shake well. Measure the absorbance of the solution at 430 nm using a 2 cm cuvette with water as the reference.

[0106] (4) Sample measurement

[0107] From step (2), 10 mL of the test solution in the 100 mL volumetric flask was transferred to a 25 mL colorimetric tube. 5 mL of stabilizer and 4 mL of barium chloride (250 g / L) were added, and the mixture was diluted to the mark with water and shaken. The mixture was allowed to stabilize for 10 minutes. The absorbance was measured at a wavelength of 430 nm using a 2 cm cuvette and a reagent blank as a reference. The absorbance was 0.056. The corresponding amount of sulfate ion, 44.54 μg, was obtained from the working curve based on the absorbance value of 0.055 (derived from 0.056-0.001).

[0108] (5) Drawing of standard curve;

[0109] Accurately pipette 0.00, 1.00, 2.00, 3.00, 4.00, and 5.00 mL of 50 ug / mL sulfate standard solution into 6 25 mL colorimetric tubes, add 5 mL of stabilizer and 4 mL of barium chloride (250 g / L), dilute to the scale with water, and shake well. Stabilize for 10 minutes, use a 2 cm cuvette, use the reagent blank as a reference, and measure the absorbance at a wavelength of 430 nm on a spectrophotometer. The absorbance is: 0, 0.062, 0.123, 0.189, 0.262, and 0.321, respectively. Use the amount of sulfate (ug) as the ordinate and the absorbance as the abscissa to draw a working curve: m = 769.96A + 2.1912, R 2 =0.9988.

[0110] (6) Result calculation

[0111] The concentration of sulfate in the desulfurizer (original solution) is calculated using the following formula:

[0112]

[0113] The terms used in this invention are descriptive and exemplary, rather than restrictive. Since the present invention can be embodied in a variety of forms without departing from the spirit or essence of the technical solution, it should be understood that the above-described embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope of the appended claims. Therefore, all changes and modifications that fall within the scope of the claims or their equivalents are intended to be covered by the appended claims.

Claims

1. A method for determining the sulfate content in a rare earth smelting waste gas desulfurizer, characterized in that: include: Take the desulfurizer as a sample, take a certain amount of the sample and dilute it with water to make a sample solution, which is used as the first solution. The first volume solution is taken and added with anaerobic acid to eliminate interfering elements in the first volume solution, and the volume is diluted with water to obtain the second volume solution; Aspirate the second volume-fixing solution, use water as reference, and use a spectrophotometer to measure the absorbance A0 of the second volume-fixing solution in a blank. Take the second volume solution and add stabilizer and barium chloride, use the reagent blank as reference, and use a spectrophotometer to measure its absorbance A; use A-A0 to calculate the corresponding amount of sulfate ion m from the working curve; Pipette multiple portions of sulfate standard solution into multiple colorimetric tubes, add stabilizer and barium chloride respectively, dilute to the scale with water, measure the absorbance with a spectrophotometer using a reagent blank as a reference, and draw a standard curve with the amount of sulfate as the ordinate and the absorbance as the abscissa; Calculation formula using sulfate results: Calculate the concentration of sulfate in the sample, where V is the volume of the sample, m is the micrograms of sulfate found from the standard curve, and F is the sample extraction coefficient; The calculation formula of the fractionation coefficient F is: Among them, V 定1 is the volume of the first constant volume, V 吸1 The volume of the first fixed solution is V 定2 is the volume of the second constant volume, V 吸2 To absorb the volume of the second fixed solution, when no aliquoting is needed, F is 1.

2. The method for determining the sulfate content in a rare earth smelting waste gas desulfurizer according to claim 1, wherein: Take the desulfurizer as the sample and shake it thoroughly for 10-30 seconds before aspirating the sample.

3. The method for determining the sulfate content in a rare earth smelting waste gas desulfurizer according to claim 1, wherein: According to the sulfate content in the sample, transfer a certain amount of sample into a volumetric flask, dilute with water to the scale, shake well, and prepare the first volume solution.

4. The method for determining the sulfate content in a rare earth smelting waste gas desulfurizer according to claim 1, wherein: Pipette the first volume-fixing solution into a beaker, add hydrochloric acid in a volume ratio of 1+1, heat on an electric stove, transfer to a volumetric flask after cooling, dilute to the scale with water, shake well, and use as the second volume-fixing solution.

5. The method for determining the sulfate content in a rare earth smelting waste gas desulfurizer according to claim 1, wherein: By adding hydrochloric acid to react with interfering impurity ions, gas is generated to remove interfering impurities while avoiding the generation of sulfate ions.

6. The method for determining the sulfate content in a rare earth smelting waste gas desulfurizer according to claim 1, wherein: The sample itself brings about changes in absorbance, so a blank measurement needs to be performed on each analyzed sample. Water is used as a reference during the measurement, and the absorbance is measured at a wavelength of 430nm using a spectrophotometer.

7. The method for determining the sulfate content in a rare earth smelting waste gas desulfurizer according to claim 1, wherein: Stabilizers include: Sodium chloride, glycerol and anhydrous ethanol.

8. The method for determining the sulfate content in a rare earth smelting waste gas desulfurizer according to claim 1, wherein: The preparation of the stabilizer includes: weighing 50g of sodium chloride and dissolving it in 200mL of water, adding 8mL of hydrochloric acid, 200mL of propylene glycol, and 400mL of anhydrous ethanol, shaking well, and making up to volume in a 1000mL volumetric flask.

9. The method for determining the sulfate content in a rare earth smelting waste gas desulfurizer according to claim 1, wherein: The preparation of 250g / L barium chloride solution includes: weighing 25g of barium chloride that has been dried at 105°C for 1 hour, adding 100mL of pure water to dissolve it clearly.

10. The method for determining the sulfate content in a rare earth smelting waste gas desulfurizer according to claim 1, wherein: The standard curve drawing includes: pipetting 0.00, 1.00, 2.00, 3.00, 4.00, and 5.00 mL of a 50 μg / mL sulfate standard solution into six 25 mL colorimetric tubes, respectively, adding 5 mL of a stabilizer and 4 mL of 250 g / L barium chloride, respectively, diluting to the scale with water, shaking, stabilizing for 10 minutes, using a 2 cm cuvette and a reagent blank as a reference, measuring its absorbance at a wavelength of 430 nm on a spectrophotometer, and drawing a standard curve with the amount of sulfate as the ordinate and the absorbance as the abscissa; The preparation of 50 μg / mL sulfate standard solution includes: weighing 0.1814 g of potassium sulfate dried at 105°C into a 100 mL beaker, adding water to dissolve it, transferring it into a 2000 mL volumetric flask, diluting it to the scale with water, and shaking it well.

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