Method for determining content of elements in kaolin by alkali fusion-inductively coupled plasma emission spectrometry

Abstract

The invention relates to the technical field of fuel additive analysis, in particular to a method for determining the content of elements in kaolin by alkali fusion-inductively coupled plasma emission spectrometry, which comprises the following steps: drying and crushing kaolin to obtain a kaolin sample; carrying out melting treatment on the kaolin sample, and dissolving the molten sample to obtain a sample solution; preparing a series of standard solutions of test elements; carrying out inductively coupled plasma emission spectrum test on the series of standard solutions to obtain a standard curve of test elements; and performing inductively coupled plasma emission spectrum test on the sample solution, and determining the content of the test element in the sample solution according to the standard curve of the test element. The lithium metaborate is used for melting and decomposing the sample, the inductively coupled plasma emission spectrometer is used for determining the content of the 10 elements in the kaolin, and the method has the characteristics of convenience, rapidness and high applicability, and is of great significance for improving the detection efficiency of the kaolin.

Description

Technical Field

[0001] The invention relates to the technical field of fuel additive analysis, and is a method for determining the element content of kaolin using an alkali fusion-inductively coupled plasma emission spectrometry method. Background Art

[0002] At present, my country's power generation is mainly coal-fired, and the coal used in the Zhundong area of ​​Xinjiang Uygur Autonomous Region is mainly Zhundong coal. However, Zhundong coal contains a high level of alkali metals, which has the effect of reducing the characteristic temperature of coal ash melting. Pure combustion of Zhundong coal will cause ash accumulation and slagging in power station boilers, resulting in reduced boiler thermal efficiency and even serious boiler tube bursts, affecting the safe operation of the boiler. Kaolin is one of the effective additives for Zhundong coal. Blending Zhundong coal with kaolin can effectively capture the alkali metals in Zhundong coal and inhibit ash accumulation and slagging in boilers. Therefore, determining the chemical composition of kaolin can determine the reasonable blending ratio of Zhundong coal and kaolin.

[0003] The determination of silicon, aluminum, iron, titanium, potassium, sodium, calcium, magnesium, phosphorus and sulfur in kaolin is in accordance with the national standard GB∕T14563-2020. The principle of the method adopts the gravimetric method to measure silicon, the colorimetric method or complexometric method to measure iron, the complexometric method to measure aluminum, the spectrophotometric method to measure titanium, the complexometric method to measure calcium and magnesium, the flame photometry method to measure potassium and sodium, and the combustion method or gravimetric method to measure sulfur. This national standard analysis method requires a specific analysis method for each element. The analysis process of the elements to be measured is long, more chemical reagents are used, the output of waste acid and waste alkali is large, and the analysis cycle is long, which is difficult to meet the needs of rapid analysis. Summary of the invention

[0004] The present invention provides a method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry, which overcomes the deficiencies of the above-mentioned prior art and can effectively solve the problems of complicated detection steps and long detection time in the existing kaolin analysis method.

[0005] The technical solution of the present invention is achieved by the following measures: A method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry is carried out according to the following steps: The first step is to dry and crush the kaolin to obtain a kaolin sample; The second step is to melt the kaolin sample, and dissolve the melted sample to obtain a sample solution; The third step is to prepare a series of standard solutions of the test elements; The fourth step is to conduct inductively coupled plasma emission spectroscopy test on the series of standard solutions to obtain the standard curve of the test elements; The fifth step is to perform inductively coupled plasma emission spectroscopy test on the sample solution and determine the content of the test element in the sample solution according to the standard curve of the test element.

[0006] The following are further optimizations and / or improvements to the above technical solutions: The above test elements include: silicon, aluminum, iron, titanium, potassium, sodium, calcium, magnesium, phosphorus, and sulfur.

[0007] In the first step, the melting treatment includes: placing the kaolin sample and the lithium metaborate flux in a crucible, fully mixing the kaolin sample and the lithium metaborate, and then placing the crucible in a muffle furnace for melting.

[0008] The amount of the kaolin sample is 0.1 g to 0.5 g, and the amount of lithium metaborate is 0.5 g to 2 g.

[0009] The crucible is a graphite crucible, the melting temperature is 850° C. to 950° C., and the melting time is 15 min to 30 min.

[0010] In the fourth step above, the inductively coupled plasma emission spectroscopy test conditions are: RF power: 750W to 1500W; observation direction: horizontal observation; atomizing gas flow rate: 0 to 1.50L / min; auxiliary gas flow rate: 0 to 1.50L / min; peristaltic pump speed: 0 to 125rpm; integration time: short-wave exposure for 15s, then long-wave exposure for 25s.

[0011] In the above-mentioned inductively coupled plasma emission spectrometry test, the analysis spectral lines of the test elements are: silicon 288.158nm, aluminum 308.215nm, iron 238.204nm, titanium 337.280nm, potassium 766.491nm, sodium 588.995nm, calcium 317.93nm, magnesium 279.553nm, phosphorus 178.287nm, and sulfur 182.03nm.

[0012] In the first step above, the drying and crushing includes: Dry the kaolin to be tested at 105°C to 110°C and keep the weight constant; The kaolin after constant weight is crushed and ground to obtain a kaolin sample, wherein the particle size of the kaolin sample is less than or equal to 0.15 mm.

[0013] In the second step, the melted sample is dissolved in a nitric acid solution with a volume fraction of 5%.

[0014] In the third step above, the concentration range of each test element in the series of standard solutions is: silicon 8 mg / L to 32 mg / L, aluminum 5 mg / L to 20 mg / L, iron 5 mg / L to 20 mg / L, titanium 0.4 mg / L to 1.6 mg / L, potassium 1 mg / L to 4 mg / L, sodium 1 mg / L to 4 mg / L, calcium 5 mg / L to 20 mg / L, magnesium 1 mg / L to 4 mg / L, phosphorus 0.4 mg / L to 1.6 mg / L, sulfur 1 mg / L to 4 mg / L.

[0015] The invention provides a method for determining the element content of kaolin by using an alkali melting-inductively coupled plasma emission spectrometry method. The method adopts lithium metaborate to melt and decompose a sample, adds nitric acid and heats to prepare a solution, and uses an inductively coupled plasma emission spectrometer to determine the intensity of silicon, aluminum, iron, titanium, potassium, sodium, calcium, magnesium, phosphorus and sulfur in the sample to obtain the content of 10 elements in kaolin. The method of the invention is convenient, fast and highly applicable, and is of great significance for improving the detection efficiency of kaolin. DETAILED DESCRIPTION

[0016] The present invention is not limited by the following embodiments, and the specific implementation method can be determined according to the technical scheme of the present invention and the actual situation. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all chemical reagents and chemicals known and used in the prior art; unless otherwise specified, the percentages in the present invention are all mass percentages; unless otherwise specified, the solutions in the present invention are all aqueous solutions with water as the solvent, for example, hydrochloric acid solution is a hydrochloric acid aqueous solution; the normal temperature and room temperature in the present invention generally refer to a temperature of 15°C to 25°C, and are generally defined as 25°C.

[0017] The present invention will be further described below in conjunction with embodiments: Example 1: The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry is carried out according to the following steps: The first step is to dry and crush the kaolin to obtain a kaolin sample; The second step is to melt the kaolin sample, and dissolve the melted sample to obtain a sample solution; The third step is to prepare a series of standard solutions of the test elements; The fourth step is to conduct inductively coupled plasma emission spectroscopy test on the series of standard solutions to obtain the standard curve of the test elements; The fifth step is to perform inductively coupled plasma emission spectroscopy test on the sample solution and determine the content of the test element in the sample solution according to the standard curve of the test element.

[0018] Embodiment 2: As an optimization of the above embodiment, the test elements include: silicon, aluminum, iron, titanium, potassium, sodium, calcium, magnesium, phosphorus, and sulfur.

[0019] Example 3: As an optimization of the above example, in the first step, the melting treatment includes: placing the kaolin sample and the lithium metaborate flux in a crucible, and after the kaolin sample and the lithium metaborate are fully mixed, placing the crucible in a muffle furnace for melting.

[0020] Example 4: As an optimization of the above example, the amount of kaolin sample is 0.1g to 0.5g, and the amount of lithium metaborate is 0.5g to 2g.

[0021] Embodiment 5: As an optimization of the above embodiment, the crucible is a graphite crucible, the melting temperature is 850° C. to 950° C., and the melting time is 15 min to 30 min.

[0022] Example 6: As an optimization of the above example, in the fourth step, the inductively coupled plasma emission spectroscopy test conditions are: RF power: 750 W to 1500 W; observation direction: horizontal observation; atomizing gas flow rate: 0 to 1.50 L / min; auxiliary gas flow rate: 0 to 1.50 L / min; peristaltic pump speed: 0 to 125 rpm; integration time: short-wave exposure for 15 s, then long-wave exposure for 25 s.

[0023] Example 7: As an optimization of the above example, in the inductively coupled plasma emission spectrometry test, the analysis spectral lines of the test elements are: silicon 288.158nm, aluminum 308.215nm, iron 238.204nm, titanium 337.280nm, potassium 766.491nm, sodium 588.995nm, calcium 317.93nm, magnesium 279.553nm, phosphorus 178.287nm, sulfur 182.03nm.

[0024] Embodiment 8: As an optimization of the above embodiment, in the first step, the drying and crushing comprises: Dry the kaolin to be tested at 105°C to 110°C and keep the weight constant; The kaolin after constant weight is crushed and ground to obtain a kaolin sample, wherein the particle size of the kaolin sample is less than or equal to 0.15 mm.

[0025] Example 9: As an optimization of the above example, in the second step, the melted sample is dissolved in a nitric acid solution with a volume fraction of 5%.

[0026] Example 10: As an optimization of the above example, in the third step, the concentration range of each test element in the series of standard solutions is: silicon 8 mg / L to 32 mg / L, aluminum 5 mg / L to 20 mg / L, iron 5 mg / L to 20 mg / L, titanium 0.4 mg / L to 1.6 mg / L, potassium 1 mg / L to 4 mg / L, sodium 1 mg / L to 4 mg / L, calcium 5 mg / L to 20 mg / L, magnesium 1 mg / L to 4 mg / L, phosphorus 0.4 mg / L to 1.6 mg / L, sulfur 1 mg / L to 4 mg / L.

[0027] Compared with the prior art, the present invention has the following advantages: (1) By adopting the scheme of the present invention to prepare a kaolin sample solution, a plasma emission spectrometer can be used to directly determine 10 elements, including silicon, aluminum, iron, titanium, potassium, sodium, calcium, magnesium, phosphorus and sulfur, in the test solution, which greatly shortens the detection cycle and improves the detection efficiency. Compared with the chemical analysis method, it reduces the labor intensity of personnel, reduces the use of chemical reagents, reduces the physical harm of chemical reagents to the detection personnel, and reduces the experimental cost.

[0028] (2) The scheme of the present invention is used to determine the elements silicon, aluminum, iron, titanium, potassium, sodium, calcium, magnesium, phosphorus and sulfur in kaolin, and the test results have good accuracy, stability and reproducibility.

[0029] (3) The method of the present invention is reliable and practical, and can meet the daily determination needs of silicon, aluminum, iron, titanium, potassium, sodium, calcium, magnesium, phosphorus and sulfur in kaolin.

[0030] Example 11: The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry, the specific steps are as follows: Sample pretreatment: Dry the kaolin to be tested at 105°C to 110°C for 2 hours, remove moisture, and place in a dryer to cool to room temperature and then keep constant weight.

[0031] Sample preparation: After constant weight, kaolin is crushed on a disc crusher lined with high manganese steel, and all of it passes through a sample sieve with a pore size of 0.25 mm. After being fully mixed, it is reduced to 50 g by quartering. This sample is ground in an agate mortar and all of it passes through a sample sieve with a pore size of 0.15 mm to obtain a kaolin sample.

[0032] Weighing samples: Weigh 0.1g to 0.5g of kaolin sample, accurate to 0.0002g, and put it into a graphite crucible. Put part of 0.5g to 2.5g of lithium metaborate into the graphite crucible, mix well, and then cover the mixture with the remaining lithium metaborate.

[0033] Melting: Place the graphite crucible in a muffle furnace preheated to 850°C to 950°C, keep it for 15min to 30min, take it out and cool it to room temperature.

[0034] Dissolution: Place the graphite crucible in a 250ml beaker, add 50ml (5+95) nitric acid solution into the crucible, place it on a heated stirrer, keep it near boiling for 30 minutes and continue stirring.

[0035] Make up the volume: remove the beaker from the heating stirrer and cool it to room temperature, transfer the solution into a 100ml plastic volumetric flask, wash the crucible and beaker with a small amount of water, pour the washing solution into the plastic volumetric flask, make up to the scale, let it stand for 2 hours, and obtain the original solution of the sample to be tested.

[0036] Preparation of series standard solutions: Weigh 4g of lithium metaborate into a 500ml beaker and place a magnetic stirrer. Add 500ml of 5% nitric acid (concentrated nitric acid and water are 5:95) and place on a heated stirrer. Heat to near boiling, stir continuously and maintain the temperature until the lithium metaborate is dissolved, then immediately transfer the solution to a 1000ml plastic volumetric flask, cool to room temperature and dilute with deionized water for later use. The commercially available single element standard solutions are prepared into series standard solutions with gradient concentrations according to the following content ranges. The concentrations of the first group of mixed series standard solutions (iron, calcium, magnesium, sodium, potassium) are shown in Table 1, and the concentrations of the second group of mixed series standard solutions (silicon, aluminum, titanium, sulfur, phosphorus) are shown in Table 2. During preparation, the lithium metaborate solution is uniformly used to dilute to 100ml and stored in a plastic bottle.

[0037] Preparation of the test solution: Accurately pipette 1 ml to 10 ml of the original solution of the sample to be tested, transfer it to a 100 ml volumetric flask, dilute to the mark with the diluent, shake well, and obtain the sample solution; at the same time, prepare the blank solution according to the above steps.

[0038] Inductively coupled plasma emission spectrometry test: The inductively coupled plasma emission spectrometry conditions are: RF power: 750W to 1500W, observation direction: horizontal observation, atomizing gas flow rate 0 to 1.50L / min, auxiliary gas flow rate: 0 to 1.50L / min, peristaltic pump speed: 0 to 125rpm, integration time: short-wave exposure for 15s, then long-wave exposure for 25s. During the test, the analytical spectral lines of each test element were silicon 288.158nm, aluminum 308.215nm, iron 238.204nm, titanium 337.280nm, potassium 766.491nm, sodium 588.995nm, calcium 317.93nm, magnesium 279.553nm, phosphorus 178.287nm, sulfur 182.03nm. The blank solution, sample solution and series of standard solutions were tested using a plasma atomic emission spectrometer.

[0039] Calculation: According to the concentration and spectral intensity of each test element in the series of standard solutions, the standard curve of the test element is obtained; based on the standard curve of the test element, the content of each test element (in terms of oxide) in kaolin is calculated according to the following formula: Where: X AxOy is the content of the measured element in terms of oxide, %; C 1 is the concentration of the element being measured in the sample solution, mg / L; C 2 is the concentration of the element being measured in the blank solution, mg / L; N is the dilution factor of the sample solution; Yis the volume of the sample solution to be tested, mL; G The coefficient for converting the test element into oxide (see Table 3), dimensionless; m is the mass of kaolin sample, g.

[0040] Example 12: The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry is specifically implemented as follows: The kaolin to be tested was dried at 107°C for 2 hours, and after removing the moisture, it was placed in a desiccator and cooled to room temperature before being weighed.

[0041] The kaolin to be tested was crushed on a disc crusher lined with high manganese steel to make it all pass through a sample sieve with an aperture of 0.25 mm, and after being fully mixed, it was reduced to 50 g by quartering. The sample was ground in an agate mortar to make it all pass through a sample sieve with an aperture of 0.15 mm and set aside.

[0042] Weigh 0.1 g of kaolin sample, accurate to 0.0002 g, and put it into a graphite crucible. Put part of 0.5 g of lithium metaborate into the graphite crucible, mix well, and then cover the mixture with the remaining lithium metaborate.

[0043] The graphite crucible was placed in a muffle furnace preheated to 850°C, kept for 15 min, and then taken out and cooled to room temperature.

[0044] Place the graphite crucible in a 250ml beaker, add 50ml (5+95) nitric acid solution into the crucible, place it on a heated stirrer, keep it near boiling for 30 minutes and continue stirring.

[0045] Remove the beaker from the heating stirrer and cool to room temperature. Transfer the solution into a 100 ml plastic volumetric flask. Wash the crucible and beaker with a small amount of water. Pour the washing solution into the plastic volumetric flask and dilute to the mark to obtain the sample solution to be tested.

[0046] Prepare a series of standard solutions.

[0047] Accurately transfer 10 ml of the sample solution to be tested into a 100 ml volumetric flask, dilute to the mark with the diluent, shake well, and obtain the sample solution. The dilution factor of this sample solution is 10. At the same time, prepare a blank solution.

[0048] The inductively coupled plasma emission spectrometry conditions are: RF power: 1150W, observation direction: horizontal observation, atomizing gas flow rate 0.6L / min, auxiliary gas flow rate: 0.5L / min, peristaltic pump speed: 50rpm, integration time: short-wave exposure for 15s, then long-wave exposure for 25s. The blank solution, sample solution and series of standard solutions were tested using a plasma atomic emission spectrometer. According to the above formula 1, the content of each element in the sample solution was measured to be 68.04% SiO2, 19.21% Al2O3, 4.73% Fe2O3, 1.08% CaO, 0.86% MgO, 1.06% TiO2, 2.26% K2O, 1.90% Na2O, 0.53% SO3 and 0.12% P2O5.

[0049] Example 13: The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry is specifically implemented as follows: The kaolin to be tested (same as in Example 12) was dried at 107°C for 2 hours to remove moisture, placed in a desiccator, cooled to room temperature, and then weighed.

[0050] The kaolin to be tested was crushed on a disc crusher lined with high manganese steel to make it all pass through a sample sieve with an aperture of 0.25 mm, and after being fully mixed, it was reduced to 50 g by quartering. The sample was ground in an agate mortar to make it all pass through a sample sieve with an aperture of 0.15 mm and set aside.

[0051] Weigh 0.1 g of kaolin sample, accurate to 0.0002 g, and put it into a graphite crucible. Put part of 1 g of lithium metaborate into the graphite crucible, mix well, and then cover the mixture with the remaining lithium metaborate.

[0052] The graphite crucible was placed in a muffle furnace preheated to 900°C, kept at this temperature for 20 min, and then taken out and cooled to room temperature.

[0053] Place the graphite crucible in a 250ml beaker, place a polytetrafluoroethylene-wrapped magnetic rotor in the crucible, add 50ml (5+95) nitric acid solution into the crucible, place it on a heated stirrer, keep it near boiling for 30 minutes and continue stirring.

[0054] Remove the beaker from the heating stirrer and cool to room temperature. Transfer the solution into a 100 ml plastic volumetric flask. Wash the crucible and beaker with a small amount of water. Pour the washing solution into the plastic volumetric flask and dilute to the mark to obtain the sample solution to be tested.

[0055] Prepare a series of standard solutions.

[0056] Accurately transfer 5 ml of the sample solution to be tested into a 100 ml volumetric flask, dilute to scale with diluent, shake well to obtain the sample solution. At the same time, prepare a blank solution.

[0057] The inductively coupled plasma emission spectrometry conditions are: RF power: 1200W, observation direction: horizontal observation, atomizing gas flow rate 0.7L / min, auxiliary gas flow rate: 0.5L / min, peristaltic pump speed: 50rpm, integration time: short-wave exposure for 15s, then long-wave exposure for 25s. The blank solution, sample solution and series of standard solutions were tested using a plasma atomic emission spectrometer. According to the above formula 1, the content of each element in the sample solution was measured to be 68.04% SiO2, 19.21% Al2O3, 4.73% Fe2O3, 1.08% CaO, 0.86% MgO, 1.06% TiO2, 2.26% K2O, 1.90% Na2O, 0.53% SO3 and 0.12% P2O5.

[0058] Example 14: The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry is specifically implemented as follows: The kaolin to be tested (same as in Example 12) was dried at 110°C for 2 hours, and after removing the moisture, it was placed in a desiccator and cooled to room temperature before being weighed.

[0059] The kaolin to be tested was crushed on a disc crusher lined with high manganese steel to make it all pass through a sample sieve with an aperture of 0.25 mm, and after being fully mixed, it was reduced to 50 g by quartering. The sample was ground in an agate mortar to make it all pass through a sample sieve with an aperture of 0.15 mm and set aside.

[0060] Weigh 0.1 g of kaolin sample, accurate to 0.0002 g, and put it into a graphite crucible. Put part of 1.5 g of lithium metaborate into the graphite crucible, mix well, and then cover the mixture with the remaining lithium metaborate.

[0061] The graphite crucible was placed in a muffle furnace preheated to 950°C, kept at this temperature for 25 min, and then taken out and cooled to room temperature.

[0062] Place the graphite crucible in a 250ml beaker, place a polytetrafluoroethylene-wrapped magnetic rotor in the crucible, add 50ml (5+95) nitric acid solution into the crucible, place it on a heated stirrer, keep it near boiling for 30 minutes and continue stirring.

[0063] Remove the beaker from the heating stirrer and cool to room temperature. Transfer the solution into a 100 ml plastic volumetric flask. Wash the crucible and beaker with a small amount of water. Pour the washing solution into the plastic volumetric flask and dilute to the mark to obtain the sample solution to be tested.

[0064] Prepare a series of standard solutions.

[0065] Accurately transfer 2 ml of the sample solution to be tested into a 100 ml volumetric flask, dilute to scale with diluent, shake well to obtain the sample solution. At the same time, prepare a blank solution.

[0066] The inductively coupled plasma emission spectrometry conditions are: RF power: 1250W, observation direction: horizontal observation, atomizing gas flow rate 0.8L / min, auxiliary gas flow rate: 0.6L / min, peristaltic pump speed: 50rpm, integration time: short-wave exposure for 15s, then long-wave exposure for 25s. The blank solution, sample solution and series of standard solutions were tested using a plasma atomic emission spectrometer. According to the above formula 1, the content of each element in the sample solution was measured to be 68.04% SiO2, 19.21% Al2O3, 4.73% Fe2O3, 1.08% CaO, 0.86% MgO, 1.06% TiO2, 2.26% K2O, 1.90% Na2O, 0.53% SO3 and 0.12% P2O5.

[0067] It can be seen from the test results of Example 12 to Example 14 that the test results of the present invention for the same sample have good repeatability.

[0068] In summary, the method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry of the present invention overcomes the defects of complicated detection steps and long detection time in the existing kaolin analysis method, and realizes rapid analysis of the content of silicon, aluminum, iron, titanium, potassium, sodium, calcium, magnesium, phosphorus and sulfur elements in kaolin. It has simple operation and short detection cycle, greatly improves the detection efficiency, can be applied and promoted for large-scale detection of kaolin, and is conducive to industrial product quality detection.

[0069] The above technical features respectively constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry, characterized in that Follow these steps: The first step is to dry and crush the kaolin to obtain a kaolin sample; The second step is to melt the kaolin sample, and dissolve the melted sample to obtain a sample solution; The third step is to prepare a series of standard solutions of the test elements; The fourth step is to conduct inductively coupled plasma emission spectroscopy test on the series of standard solutions to obtain the standard curve of the test elements; The fifth step is to perform inductively coupled plasma emission spectroscopy test on the sample solution and determine the content of the test element in the sample solution according to the standard curve of the test element.

2. The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry according to claim 1, characterized in that The elements tested include: silicon, aluminum, iron, titanium, potassium, sodium, calcium, magnesium, phosphorus, and sulfur.

3. The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma optical emission spectrometry according to claim 1 or 2, characterized in that In the first step, the melting treatment includes: placing the kaolin sample and the lithium metaborate flux in a crucible, fully mixing the kaolin sample and the lithium metaborate, and then placing the crucible in a muffle furnace for melting.

4. The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry according to claim 3, characterized in that The amount of kaolin sample is 0.1g to 0.5g, and the amount of lithium metaborate is 0.5g to 2g.

5. The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma optical emission spectrometry according to claim 3 or 4, characterized in that The crucible is a graphite crucible, the melting temperature is 850° C. to 950° C., and the melting time is 15 min to 30 min.

6. The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma optical emission spectrometry according to any one of claims 1 to 5, characterized in that In the fourth step, the inductively coupled plasma emission spectroscopy test conditions are: RF power: 750W to 1500W; observation direction: horizontal observation; atomizing gas flow rate: 0 to 1.50L / min; auxiliary gas flow rate: 0 to 1.50L / min; peristaltic pump speed: 0 to 125rpm; integration time: short-wave exposure for 15s, then long-wave exposure for 25s.

7. The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma emission spectrometry according to claim 6, characterized in that In the inductively coupled plasma emission spectrometry test, the analysis spectral lines of the test elements are: silicon 288.158nm, aluminum 308.215nm, iron 238.204nm, titanium 337.280nm, potassium 766.491nm, sodium 588.995nm, calcium 317.93nm, magnesium 279.553nm, phosphorus 178.287nm, and sulfur 182.03nm.

8. The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma optical emission spectrometry according to any one of claims 1 to 7, characterized in that In the first step, dry pulverization includes: Dry the kaolin to be tested at 105°C to 110°C and keep the weight constant; The kaolin after constant weight is crushed and ground to obtain a kaolin sample, wherein the particle size of the kaolin sample is less than or equal to 0.15 mm.

9. The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma optical emission spectrometry according to any one of claims 1 to 8, characterized in that In the second step, the molten sample was dissolved in 5% by volume nitric acid solution.

10. The method for determining the element content of kaolin by alkali fusion-inductively coupled plasma optical emission spectrometry according to any one of claims 1 to 8, characterized in that In the third step, the concentration range of each test element in the series of standard solutions is: silicon 8mg / L to 32mg / L, aluminum 5mg / L to 20mg / L, iron 5mg / L to 20mg / L, titanium 0.4mg / L to 1.6mg / L, potassium 1mg / L to 4mg / L, sodium 1mg / L to 4mg / L, calcium 5mg / L to 20mg / L, magnesium 1mg / L to 4mg / L, phosphorus 0.4mg / L to 1.6mg / L, sulfur 1mg / L to 4mg / L.

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