A method for rapidly and accurately determining the phosphorus content in dolomite and limestone

Abstract

The application discloses a method for rapidly and accurately determining the phosphorus content in dolomite and limestone, and belongs to the technical field of raw material analysis. The method provided by the application comprises the following steps: melting a sample by using a mixed flux containing sodium carbonate and sodium peroxide, and detecting the phosphorus content by using a sodium fluoride-stannous chloride-phosphorus molybdenum blue colorimetric method. The method provided by the application can more accurately determine the phosphorus content in dolomite and limestone, the recovery rate of a standard addition recovery experiment is between 98-103%, and accurate data can be provided for the application of dolomite and limestone.

Description

Technical Field

[0001] This invention belongs to the field of raw material analysis technology, specifically relating to a rapid and accurate method for determining the phosphorus content in dolomite and limestone. Background Technology

[0002] Dolomite and limestone have a wide range of applications in the chemical, metallurgical, building materials, and other industries. In the iron and steel metallurgical industry, they are mainly used as basic refractory materials in steelmaking converters, open-hearth furnaces, and electric furnace walls. They are also used in ladle refining equipment and thermal equipment such as cement kilns. Dolomite and limestone also play a role in desulfurization and dephosphorization during steelmaking, increasing furnace viscosity and purifying molten steel. The main hazard of phosphorus in dolomite and limestone during steelmaking is that it causes cold brittleness in steel during hot working; therefore, accurate determination of its phosphorus content is of great importance.

[0003] Patent document CN117554310A (hereinafter referred to as Document 1) discloses a method for accurately determining the phosphorus content in slaked lime. This method involves melting the slaked lime sample using sodium hydroxide and sodium peroxide during sample dissolution and then leaching the melt with nitric acid. This method can accurately determine the phosphorus content in slaked lime, with a recovery rate of 98-106% in spiking experiments, demonstrating high detection accuracy. However, possibly due to differences in chemical composition and properties between slaked lime and dolomite and limestone, the accuracy of spiking experiments is lower when the method disclosed in Document 1 is used to determine the phosphorus content in dolomite and limestone. Therefore, it is necessary to develop a method for accurately detecting the phosphorus content in dolomite and limestone. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a rapid and accurate method for determining the phosphorus content in dolomite and limestone, comprising melting the sample with a mixed flux containing sodium carbonate and sodium peroxide, and detecting the phosphorus content using the sodium fluoride-stannous chloride-phosphomolybdic blue colorimetric method.

[0005] In some embodiments, the mass ratio of sodium carbonate to sodium peroxide in the mixed flux is 1:(1-3).

[0006] In some implementations, the method includes the following steps:

[0007] 1) Melt the sample with the mixed flux, then extract with nitric acid. Optionally, when manganese precipitate appears, add hydrogen peroxide dropwise. Boil the solution until no more bubbles appear, and cool it to room temperature with running water to obtain the extraction solution.

[0008] 2) Take a certain amount of the extraction solution obtained in step 1), add nitric acid, and after heating to boiling, add potassium permanganate solution dropwise. Then, add a mixture of potassium sodium tartrate and ammonium molybdate, a mixture of sodium fluoride and tin dichloride, and water in sequence to obtain the sample solution; and

[0009] 3) Determine the absorbance of the sample solution obtained in step 2), and obtain the phosphorus content in the sample through a standard curve.

[0010] In some embodiments, the temperature of melting the sample with the mixed flux in step 1) is 650-750°C and the time is 5-10 min.

[0011] In some embodiments, the acidity during extraction with nitric acid in step 1) is controlled to be 0.8-1.2 mol / L.

[0012] In some implementations, the method includes the following steps:

[0013] S1) Weigh 0.2000g of sample into a corundum crucible, add 0.5g of sodium carbonate and 1.0g of sodium peroxide, mix well, and melt in a muffle furnace at 650-750℃ until a bright red liquid appears. Remove and cool, then place in a beaker pre-filled with nitric acid for extraction. The acidity should be controlled at 0.8-1.2mol / L. When manganese precipitate appears, add hydrogen peroxide dropwise. Boil the solution until no bubbles appear, cool to room temperature under running water, and then transfer the solution to a 100mL volumetric flask. Dilute with water to the mark and shake well to obtain the extraction solution.

[0014] S2) Take 10 mL of the extraction solution obtained in step S1), add 5 mL of nitric acid (7+3), or when the phosphorus content in the sample is greater than 0.5%, take 5 mL of the extraction solution obtained in step S1), add 5 mL of nitric acid (3+17); heat to boiling, add three drops of potassium permanganate (40 g / L), boil for another 10 seconds, remove from heat, immediately add 10 mL of potassium sodium tartrate-ammonium molybdate mixture, shake for 10 seconds, add 50 mL of sodium fluoride-tin dichloride mixture, and water, stir well, and dilute to volume to obtain the sample solution; and

[0015] S3) Determine the absorbance of the sample solution obtained in step S2), and obtain the phosphorus content in the sample through a standard curve.

[0016] In some embodiments, the linear relationship of the standard curve with absorbance as the ordinate and phosphorus percentage concentration as the abscissa is: y = 1.5866x + 0.0052, R 2 =0.9997.

[0017] The method for accurately determining the phosphorus content in dolomite and limestone based on the above technical solution involves melting the sample with a mixed flux (containing sodium carbonate and sodium peroxide in a mass ratio of 1:(1-3)). Compared to the method disclosed in Document 1, which uses a mixed flux composed of sodium hydroxide and sodium peroxide to melt the sample, this method is more conducive to the complete melting of dolomite and / or limestone samples and the accurate detection of phosphorus content in the samples. The recovery rate of the spiked recovery experiment of the method provided by this invention is between 98% and 103%, with high accuracy and rapid detection, obtaining results within 30 minutes. This can provide accurate data for the application of dolomite and limestone. Attached Figure Description

[0018] Figure 1 This is a standard curve for determining the phosphorus content in dolomite and limestone. Detailed Implementation

[0019] The present invention aims to provide a rapid and accurate method for determining the phosphorus content in dolomite and limestone.

[0020] The present invention will be described in more detail below with reference to examples. These examples are merely descriptions of the best mode of implementation of the present invention and do not limit the scope of the invention in any way.

[0021] The main instruments and reagents used in the following examples are:

[0022] 1. Sodium peroxide (solid);

[0023] 2. Sodium carbonate (solid);

[0024] 3. Nitric acid (ρ1.42)(1+3)(7+3)(3+17);

[0025] 4. Hydrogen peroxide (ρ1.11);

[0026] 5. Potassium permanganate (40 g / L);

[0027] 6. Potassium sodium tartrate solution (200 g / L);

[0028] 7. Ammonium molybdate solution (200 g / L);

[0029] 8. Potassium sodium tartrate-ammonium molybdate mixture: Before use, mix equal parts of ammonium molybdate (200g / L) and potassium sodium tartrate (200g / L) and filter.

[0030] 9. Sodium fluoride solution (24 g / L);

[0031] 10. Sodium fluoride-tin dichloride mixture: Take 1L of sodium fluoride (24g / L), add 3g of tin dichloride before use, mix well and filter;

[0032] 11. Phosphorus standard solution

[0033] 11.1 Phosphorus stock solution (50.0 μg / mL)

[0034] Weigh 0.2197g of potassium dihydrogen phosphate (GR), dissolve it in distilled water, then transfer it to a 1000mL volumetric flask, dilute with water to the mark, and shake well.

[0035] 11.2 Phosphorus standard solution (10.0 μg / mL)

[0036] Take 50.00 mL of phosphorus stock solution (50.0 μg / mL) into a 250 mL volumetric flask, dilute with water to the mark and shake well.

[0037] instrument

[0038] Intelligent high-speed analyzer

[0039] Example 1: Method for determining phosphorus content in dolomite and limestone

[0040] 1.1 Determination of phosphorus content in dolomite and limestone

[0041] Weigh 0.2000 g of sample into an alumina crucible, add a mixed flux (0.5 g sodium carbonate and 1.0 g sodium peroxide) and mix well. Melt in a muffle furnace at 650-750℃ (5-10 min) until a bright red liquid is formed. Remove and cool, then transfer to a 250 mL beaker pre-filled with 60 mL of nitric acid (1+3) (the acidity should be calculated to be 0.8-1.2 mol / L based on the amount of mixed flux and nitric acid added). Heat for extraction. Clean the crucible thoroughly (this step ensures all sample is transferred to the beaker). If manganese precipitate appears, add hydrogen peroxide. Boil the solution until no bubbles appear, then cool to room temperature under running water. Transfer the solution to a 100 mL volumetric flask and dilute to the mark with water.

[0042] Take 10 mL of the above solution (if the phosphorus content is greater than 0.5%, take 5 mL and add 5 mL of nitric acid (3+17)), add 5 mL of nitric acid (7+3), heat to boiling, add three drops of potassium permanganate (40 g / L), boil for another 10 seconds, remove from heat, immediately add 10 mL of potassium sodium tartrate-ammonium molybdate mixture, shake for 10 seconds, add 50 mL of sodium fluoride-tin dichloride mixture, and water, stir well, and make up to volume. Measure the absorbance using a high-speed intelligent analyzer (for example, use the dedicated channel for phosphorus determination on the high-speed intelligent analyzer, or measure the absorbance at a wavelength of 700-800 nm). Calculate the percentage phosphorus content in dolomite and limestone according to the phosphorus standard curve (perform a blank test along with the sample).

[0043] 1.2 Drawing the working curve

[0044] As shown in Table 1 below, take 0.00, 2.00, 4.00, 6.00, 8.00, and 10.00 mL of phosphorus standard solution (10.0 μg / mL), add water to make up to 10 mL, add 4 mL of nitric acid (ρ 1.42) (at this point, it can be calculated that 4 mL of concentrated nitric acid can meet the acidity of 0.8-1.2 mol / L after adding phosphorus standard solution and water), heat to boiling, add three drops of potassium permanganate (40 g / L), and then perform the same analytical operation as in 1.1 above.

[0045] Table 1: Relationship of phosphorus content in phosphorus standard solutions

[0046] label Phosphorus standard solution Phosphorus content % 1 0.00mL 0.00 2 2.00 mL (10 μg / mL) 0.10 3 4.00 mL (10 μg / mL) 0.20 4 6.00 mL (10 μg / mL) 0.30 5 8.00 mL (10 μg / mL) 0.40 6 10.00 mL (10 μg / mL) 0.50

[0047] 1.3 Plotting the Phosphorus Standard Curve

[0048] A phosphorus standard curve was plotted using Excel, with absorbance values ​​on the ordinate and phosphorus content (%) on the abscissa. The relationship between phosphorus content and absorbance values ​​(A) is shown in Table 2 below. The resulting phosphorus standard curve is shown in... Figure 1 As shown, the linear relationship is: y = 1.5866x + 0.0052, R 2 =0.9997.

[0049] Table 2: Relationship between absorbance values ​​of the standard curve and phosphorus content

[0050] label Absorbance value (A) Phosphorus content % 1 0.002 0.00 2 0.165 0.10 3 0.335 0.20 4 0.483 0.30 5 0.640 0.40 6 0.798 0.50

[0051] Example 2: Spike Recovery Experiment of the Method of the Invention

[0052] Experimental Group 1: Weigh 0.4000g of dolomite sample and divide it into two equal parts. Add 0.005% phosphorus standard solution to one part and do not add phosphorus standard solution to the other part. Perform the spiked recovery experiment according to the method (step 1.1) of this invention. Repeat three times and calculate the average value. The results are shown in Table 3 below.

[0053] Experimental Group 2: Weigh 0.4000g of limestone sample and divide it into two equal parts. Add 0.005% phosphorus standard solution to one part and do not add phosphorus standard solution to the other part. Perform the spiked recovery experiment according to the method (step 1.1) of this invention. Repeat three times and calculate the average value. The results are shown in Table 3 below.

[0054] Experimental Group 3: Weigh 0.4000g of dolomite sample and divide it into two equal parts. Add 0.005% phosphorus standard solution to one part and do not add phosphorus standard solution to the other part. Perform the spiked recovery experiment according to the method in Reference 1 (1.0g sodium hydroxide + 0.5g sodium peroxide molten sample). Repeat three times and calculate the average value. The results are shown in Table 3 below.

[0055] Experimental Group 4: Weigh 0.4000g of limestone sample and divide it into two equal parts. Add 0.005% phosphorus standard solution to one part and do not add phosphorus standard solution to the other part. Perform the spiked recovery experiment according to the method in Reference 1 (1.0g sodium hydroxide + 0.5g sodium peroxide molten sample). Repeat three times and calculate the average value. The results are shown in Table 3 below.

[0056] Table 3: Spike recovery results (%) for experimental groups 1-4

[0057]

[0058] As shown in Table 3 above, the results of the spiked recovery experiments indicate that experimental groups 1 and 2, using the method of this invention, determined the phosphorus content in dolomite and limestone, respectively, with an average recovery rate between 98% and 103%, indicating high accuracy. However, experimental groups 3 and 4, using the method described in Reference 1, melted the samples with a mixed flux containing sodium hydroxide and sodium peroxide, with average recoveries of 107.6% and 94.7%, respectively, indicating relatively low accuracy. This suggests that the method described in Reference 1 may not be suitable for accurately determining the phosphorus content in dolomite and limestone.

[0059] Example 3: Precision of the method of the present invention

[0060] 3.1 The same sample (dolomite YSBC28724a-2013) was measured 10 times consecutively according to the method for determining the phosphorus content in the sample in Example 1 above to verify the precision of the method. The exemplary results are shown in Table 4. It can be seen that the RSD is less than 1%, therefore the method of the present invention has good precision.

[0061] Table 4: Method Precision Experiment

[0062]

[0063] Example 4: Accuracy of the Method of the Invention

[0064] The accuracy of the method determined using standard samples (dolomite YSBC28724a-2013 and limestone YSBC28713a-2013) in this embodiment is shown in Table 5.

[0065] Table 5: Method Accuracy Experiment

[0066]

[0067] As can be seen from Table 5, the measurement error is very small and within the error range allowed by national standards. This invention can guarantee the accuracy of the test results.

[0068] In summary, this invention provides a reliable analytical method for determining the phosphorus content in dolomite and limestone. This method is simple to operate, easy to master, and yields accurate and precise results, fully meeting the requirements for detection and analysis. It can provide accurate data for the application of dolomite and limestone.

[0069] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A rapid and accurate method for determining the phosphorus content in dolomite and limestone, comprising melting the sample with a mixed flux containing sodium carbonate and sodium peroxide, and detecting the phosphorus content using the sodium fluoride-stannous chloride-phosphomolybdic blue colorimetric method; The mass ratio of sodium carbonate to sodium peroxide in the mixed flux is 1:1 to 1:3; The method includes the following steps: 1) Melt the sample with the mixed flux, then extract with nitric acid. When manganese precipitate appears, add hydrogen peroxide dropwise. Boil the solution until no more bubbles appear, then cool it to room temperature with running water to obtain the extraction solution. The temperature for melting the sample with the mixed flux is 650-750℃, and the time is 5-10 min. The acidity during extraction with nitric acid is controlled at 0.8-1.2 mol / L. 2) Take a certain amount of the extraction solution obtained in step 1), add nitric acid, and after heating to boiling, add potassium permanganate solution dropwise. Then, add a mixture of potassium sodium tartrate and ammonium molybdate, a mixture of sodium fluoride and tin dichloride, and water in sequence to obtain the sample solution; and 3) Determine the absorbance of the sample solution obtained in step 2) and obtain the phosphorus content in the sample through a standard curve.

2. The method according to claim 1, comprising the following steps: S1) Weigh 0.2000g of sample into a corundum crucible, add 0.5g of sodium carbonate and 1.0g of sodium peroxide, mix well, and melt in a muffle furnace at 650-750℃ until a bright red liquid appears. Remove and cool, then heat in a beaker pre-filled with nitric acid for extraction, controlling the acidity at 0.8-1.2 mol / L. When manganese precipitate appears, add hydrogen peroxide dropwise. Boil the solution until no bubbles appear, cool to room temperature under running water, and transfer the solution to a 100 mL volumetric flask. Dilute with water to the mark and shake well to obtain the extraction solution. S2) Take 10 mL of the extraction solution obtained in step S1), add 5 mL of nitric acid (a nitric acid solution obtained by mixing 7 volumes of concentrated nitric acid with 3 volumes of water), or when the phosphorus content in the sample is greater than 0.5%, take 5 mL of the extraction solution obtained in step S1), add 5 mL of nitric acid (a nitric acid solution obtained by mixing 3 volumes of concentrated nitric acid with 17 volumes of water); heat to boiling, add three drops of 40 g / L potassium permanganate, boil again for 10 seconds, remove from heat, immediately add 10 mL of potassium sodium tartrate-ammonium molybdate mixture, shake for 10 seconds, add 50 mL of sodium fluoride-tin dichloride mixture, and water, stir well, and dilute to volume to obtain the sample solution; and S3) Determine the absorbance of the sample solution obtained in step S2) and obtain the phosphorus content in the sample through a standard curve.

3. The method according to claim 1 or 2, wherein the linear relationship of the standard curve with absorbance value as the ordinate and phosphorus percentage concentration as the abscissa is: y = 1.5866x + 0.0052, R 2 =0.9997.

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