A method for detecting sulfate content in high-quality potassium hydroxide produced by electrolysis

Abstract

The application relates to the technical field of product detection and analysis, and discloses a method for detecting the content of sulfate in high-quality potassium hydroxide produced by electrolysis, which comprises the following steps: preparing a sulfate standard solution, a hydrochloric acid solution and a stabilizer, and preparing a barium chloride precipitant; setting spectrophotometer determination conditions; measuring different volumes of the sulfate standard solution to prepare a standard solution system, so that sulfate ions react with barium ions to form a barium sulfate suspension and the absorbance is determined, and a standard curve is drawn; weighing potassium hydroxide samples, dissolving the samples, neutralizing the samples with hydrochloric acid, adding the stabilizer and diluting to obtain sample solutions; preparing a blank solution; determining the absorbance of the sample solution after the sample solution is reacted with the barium chloride to form a barium sulfate suspension system; and calculating the mass of the sulfate in the sample according to the standard curve. The application realizes quantitative determination of the content of the sulfate in the potassium hydroxide by combining the spectrophotometric method with the standard curve.

Description

Technical Field

[0001] This invention relates to the field of product testing and analysis technology, and in particular to a spectrophotometric method for determining the sulfate content in high-quality potassium hydroxide produced by electrolysis. Background Technology

[0002] In the electrolytic production of high-quality potassium hydroxide, sulfate content is a crucial indicator for evaluating product quality. Current technologies typically employ the industry standard HG / T3688-2010 to detect sulfate content in potassium hydroxide. This method involves reacting sulfate ions with barium ions in a hydrochloric acid medium to form a barium sulfate suspension. The sulfate content level in the sample is then determined by visually comparing it with a standard turbidimetric solution. Specifically, the sample is dissolved and adjusted to a certain acidity, then a mixed solution containing barium chloride is added to form a barium sulfate suspension. This suspension is then compared with a standard turbidimetric solution treated with different volumes of sulfate standard solution to determine whether the product meets the superior or first-class standard.

[0003] However, this method is a manual turbidimetric method, which can only determine the product grade by comparing turbidity. It is difficult to obtain the accurate content value of sulfate. Furthermore, under the condition of high-quality potassium hydroxide with low sulfate content, the difference in standard turbidity between superior and first-class products is small. The test results are easily affected by the subjective judgment of the operator, resulting in poor repeatability and accuracy. It is difficult to meet the needs of rapid, accurate and quantitative detection of sulfate content in the production process. Summary of the Invention

[0004] To solve the above-mentioned technical problems, this invention provides a method for determining sulfate content by using a glycerol-ethanol mixture to stabilize a barium sulfate suspension in hydrochloric acid medium and measuring the absorbance using a spectrophotometer. This method achieves quantitative determination of sulfate content through a standard curve, and has the advantages of high precision, good repeatability, and simple and rapid operation. The technical solution is as follows: A method for detecting sulfate content in high-quality potassium hydroxide produced by electrolysis, characterized by comprising the following steps: S1, prepare sulfate standard solution, hydrochloric acid solution and stabilizer, and prepare barium chloride precipitant; S2, Set the spectrophotometer measurement conditions, use a UV-Vis spectrophotometer, and select a 5 cm cuvette; S3. Take different volumes of sulfate standard solution into volumetric flasks, add hydrochloric acid solution and stabilizer, and dilute to volume with water. Transfer the resulting solution into a container containing barium chloride precipitant, so that sulfate ions react with barium ions to form barium sulfate suspension. After shaking and standing, measure the absorbance of each standard solution. Plot a standard curve with sulfate mass as the abscissa and absorbance as the ordinate. S4, Weigh out the potassium hydroxide sample and dissolve it in water. Add phenolphthalein indicator and neutralize with concentrated hydrochloric acid until the pink color just disappears. Then add hydrochloric acid solution and stabilizer and make up to volume to obtain the sample solution. S5. Without adding the sample, prepare a blank solution according to the same reagent composition and processing method as in step S4. The blank solution does not contain sulfate. S6. Transfer the sample solution obtained in step S4 into a container containing barium chloride precipitant, so that the sulfate ions react with the barium ions to form a barium sulfate suspension system, and shake at a speed of two revolutions per second for 2 minutes, and let it stand at room temperature for 10 minutes. S7. Using the blank solution obtained in step S5 as a reference, the absorbance of the suspension obtained in step S6 is measured under the conditions set in step S2. S8. The mass of sulfate in the sample solution is determined by using the absorbance obtained in S7 and the standard curve established in step S3.

[0005] Furthermore, the concentration of the sulfate standard solution in the above method is 0.1 g / L, and the usage period of the sulfate standard solution is one week.

[0006] Furthermore, the concentration of the hydrochloric acid solution in the above method is 1 mol / L.

[0007] Furthermore, the stabilizer mentioned in the above method is a glycerol-ethanol mixture, wherein the volume ratio of glycerol to ethanol in the glycerol-ethanol mixture is 1:2.

[0008] Furthermore, in the above method, the volumes of the mixed standard solution taken in S3 are 0, 0.5, 1, 1.5, 2, 2.5 and 3 mL, respectively.

[0009] Furthermore, the linear correlation coefficient of the standard curve established by S3 in the above method is not less than 0.995. Furthermore, in the above method, the sulfate content in the sample described in S4 must not exceed 0.3 mg; otherwise, it must be diluted.

[0010] Furthermore, the barium chloride precipitant added in step S4 of the above method is barium chloride dihydrate, and the mass of the barium chloride dihydrate is 0.3g.

[0011] Furthermore, in the above method, the detection wavelength in step S7 is 450.0 nm.

[0012] Furthermore, in the above method, when measuring the absorbance of the suspension in step S7, the maximum absorbance value of the suspension is read as the measurement result.

[0013] Compared with existing methods for determining sulfate content in potassium hydroxide using visual turbidimetry, this invention improves the accuracy and repeatability of the detection results by stabilizing the barium sulfate suspension system in hydrochloric acid medium with a glycerol-ethanol mixture, measuring the absorbance of the suspension using a spectrophotometer, and combining this with a standard curve method to achieve quantitative analysis of sulfate content. Experimental results show that the method of this invention has a good linear relationship between absorbance and sulfate content, with a correlation coefficient of up to 0.999, a relative standard deviation of 1.47%, and a spiked recovery rate of 96.0%–102.0%, indicating that the method has high accuracy and stability, is simple to operate, and is suitable for detecting sulfate content in high-quality potassium hydroxide produced by electrolysis. Attached Figure Description

[0014] Figure 1 This is a standard curve of sulfate in an embodiment of the present invention. Detailed Implementation

[0015] The present invention will be further described below with reference to specific embodiments. It should be understood that the present invention is not limited to the parameters and conditions listed in the following embodiments. Without departing from the essence of the technical solution of the present invention, those skilled in the art can make appropriate adjustments or equivalent substitutions to the process conditions, all of which should fall within the protection scope of the present invention. Example 1:

[0016] This embodiment provides a spectrophotometric method for determining the sulfate content in high-quality potassium hydroxide produced by electrolysis, specifically including the following steps: S1, Reagent preparation: (1) Barium chloride dihydrate; (2) A glycerol-ethanol mixture is prepared at a volume ratio of 1:2; (3) Hydrochloric acid solution, concentration 1 mol / L; (4) Phenolphthalein solution, concentration 10 g / L; (5) Concentrated hydrochloric acid; (6) Sulfate standard solution: Pipette 10 mL of sulfate standard solution prepared according to HG / T 3696.2 into a 100 mL volumetric flask, dilute to the mark with water, and shake well. The concentration is 0.1 g / L, and this solution is usable for one week.

[0017] S2, Set the spectrophotometer measurement conditions as follows: A UV-Vis spectrophotometer with a 5cm cuvette was used.

[0018] S3, Plotting the standard curve: Using a pipette, measure 0.0 mL, 0.5 mL, 1.0 mL, 1.5 mL, 2.0 mL, 2.5 mL, and 3.0 mL of sulfate standard solution sequentially into seven 50 mL volumetric flasks. The mass of sulfate corresponding to different volumes of sulfate standard solution is shown in Table 1.

[0019] Table 1. Sulfate content of sulfate standard solutions Add 3 mL of hydrochloric acid solution and 5 mL of glycerol-ethanol mixture to each volumetric flask, dilute to the mark with water, and mix well. Carefully transfer the solution from the volumetric flask to a dry beaker containing 0.3 g of barium chloride dihydrate, and shake at 2 revolutions per second for 2 minutes. Let stand at room temperature for 10 minutes. Using a 5 cm cuvette, adjust the zero point of the spectrophotometer to 450 nm using a blank solution, and measure the maximum absorbance of the seven solutions. Plot a standard curve with the sulfate content (mg) on ​​the x-axis and the corresponding absorbance on the y-axis, as shown below. Figure 1 As shown in the figure. The results indicate a good linear relationship between absorbance and sulfate content, with a linear regression equation of y = 0.7643x - 0.0041 and a correlation coefficient R0. 2 =0.999.

[0020] S4, Sample: Weigh 5g of potassium hydroxide sample (accurate to 0.0002g), place it in a 100ml beaker, add 25ml of water to dissolve it, add 2 drops of phenolphthalein, neutralize with concentrated hydrochloric acid until the pink color just disappears, then add 3mL of hydrochloric acid solution, transfer the whole solution to a 50mL volumetric flask, add 5mL of glycerol-ethanol mixture, dilute with water to the mark, and shake well.

[0021] S5, Blank test: Without adding any sample, perform a blank test using the exact same analytical steps, reagents, and dosages as the test sample.

[0022] S6, Reaction Processing: Carefully transfer the sample from S4 into a dry beaker containing 0.3g of barium chloride dihydrate, shake at a speed of two revolutions per second for 2 minutes, and let stand at room temperature for 10 minutes.

[0023] S7, Measurement: Under the conditions set in step S2, using a 5cm cuvette, the zero point of the spectrophotometer is adjusted with a blank solution at a wavelength of 450nm, and the absorbance of the solution is measured.

[0024] S8, Determination of sulfate mass: The absorbance obtained through S7 is based on the standard curve established in step S3. Figure 1 The mass of sulfate in the sample solution was determined.

[0025] Finally, based on the sulfate content of the sample, the sulfate (SO4) content can be determined. 2- The mass fraction ω is expressed as a percentage (%), and the result is calculated using the following formula: In the formula: m1 - The mass of sulfate in the sample obtained from the standard curve, in mg; m - Mass of the sample, in grams.

[0026] Five parallel determinations were performed on the same potassium hydroxide sample according to the method and steps proposed in this embodiment. The reproducibility and relative standard deviation of the sulfate results of the five determinations are shown in Table 2.

[0027] Table 2. Reproducibility and relative standard deviation of sulfate determination results for the sample in 5 trials. As shown in Table 2, the relative standard deviation of sulfate determination in the five tests was 1.47%, indicating that the method has high precision.

[0028] Data validation was performed using a spiked recovery experiment. 125g of high-quality potassium hydroxide sample (accurate to 0.01g) was weighed and placed in a 500ml beaker. 250ml of water was added to dissolve the sample. After cooling, the solution was transferred to a 500ml volumetric flask, diluted to the mark, and shaken well. 20ml of the sample was then transferred to five 50ml volumetric flasks. Two drops of phenolphthalein were added, and the solution was neutralized with concentrated hydrochloric acid until the pink color just disappeared. 0.0ml, 1.0ml, 1.5ml, 2.0ml, and 2.5ml of 0.1mg / ml sulfate standard working solution were added to each flask, along with 3ml of hydrochloric acid solution and 5ml of glycerol-ethanol mixture. The solution was diluted to the mark with water and shaken well. The solution from each volumetric flask was carefully transferred to a dry beaker containing 0.3g of barium chloride dihydrate. The mixture was shaken at two revolutions per second for 2 minutes and allowed to stand at room temperature for 10 minutes. The sulfate content in the solution was determined, and the recovery rate was calculated. The results are shown in Table 3. The data in the table demonstrate the accuracy of the detection method provided by this invention.

[0029] Table 3 Results of Spiked Recovery Experiment As can be seen from Table 3, the recovery rate of sulfate spiked in the range of 96.0% to 102.0%, which meets the requirements for determination.

Claims

1. A method for detecting sulfate content in high-quality potassium hydroxide produced by electrolysis, characterized in that, Includes the following steps: S1, prepare sulfate standard solution, hydrochloric acid solution and stabilizer, and prepare barium chloride precipitant; S2, Set the spectrophotometer measurement conditions, use a UV-Vis spectrophotometer, and select a 5 cm cuvette; S3. Take different volumes of sulfate standard solution into volumetric flasks, add hydrochloric acid solution and stabilizer, and dilute to volume with water. Transfer the resulting solution into a container containing barium chloride precipitant, so that sulfate ions react with barium ions to form barium sulfate suspension. After shaking and standing, measure the absorbance of each standard solution. Plot a standard curve with sulfate mass as the abscissa and absorbance as the ordinate. S4, weigh out the potassium hydroxide sample and dissolve it in water. Add phenolphthalein indicator and neutralize with concentrated hydrochloric acid until the pink color just disappears. Then add the hydrochloric acid solution and stabilizer prepared in S1 and make up to volume to obtain the sample solution. S5. Without adding the sample, prepare a blank solution according to the same reagent composition and processing method as in step S4. The blank solution does not contain sulfate. S6. Transfer the sample solution obtained in step S4 into a container containing barium chloride precipitant, so that the sulfate ions react with the barium ions to form a barium sulfate suspension system, and shake at a speed of two revolutions per second for 2 minutes, and let it stand at room temperature for 10 minutes. S7. Using the blank solution obtained in step S5 as a reference, the absorbance of the suspension obtained in step S6 is measured under the conditions set in step S2. S8. The mass of sulfate in the sample solution is determined by using the absorbance obtained in S7 and the standard curve established in step S3.

2. The detection method according to claim 1, characterized in that, The concentration of the sulfate standard solution is 0.1 g / L, and the usage period of the sulfate standard solution is one week.

3. The detection method according to claim 1, characterized in that, The concentration of the hydrochloric acid solution is 1 mol / L.

4. The detection method according to claim 1, characterized in that, The stabilizer is a glycerol-ethanol mixture, wherein the volume ratio of glycerol to ethanol in the glycerol-ethanol mixture is 1:

2.

5. The detection method according to claim 1, characterized in that, The volumes of sulfate standard solution measured in S3 were 0, 0.5, 1, 1.5, 2, 2.5 and 3 mL, respectively.

6. The detection method according to claim 1, characterized in that, The linear correlation coefficient of the standard curve established by S3 is not less than 0.

995.

7. The detection method according to claim 6, characterized in that, The sulfate content in the sample described in S4 shall not exceed 0.3 mg; otherwise, it shall be diluted.

8. The detection method according to claim 7, characterized in that, The barium chloride precipitant added in step S4 is barium chloride dihydrate, and the mass of the barium chloride dihydrate is 0.3g.

9. The detection method according to claim 1, characterized in that, The detection wavelength in step S7 is 450.0 nm.

10. The detection method according to claim 9, characterized in that, In step S7, when measuring the absorbance of the suspension, the maximum absorbance value of the suspension is read as the measurement result.

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