Method for determining silicon dioxide in serpentine

Abstract

The application discloses a method for determining silicon dioxide in serpentine, which comprises the following steps: decomposing a sample with a mixed solvent, extracting with hydrochloric acid, dehydrating with perchloric acid to separate silicon dioxide from other metal ions, filtering, burning, and weighing to a constant amount, so as to determine the content of silicon dioxide. The method provides accurate data for the content of silicon dioxide in serpentine and fills the blank of determining the content of silicon dioxide in serpentine.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical analysis technology, and in particular relates to a method for determining silica in serpentine. Background Technology

[0002] Serpentine is a hydrous magnesium silicate mineral with a unique layered structure. This mineral is widely distributed in nature and is commonly used as a raw material in industries such as metallurgy and ceramics. The main chemical components of serpentine include magnesium oxide, silicon dioxide, and water, which undergo a series of complex physicochemical changes at high temperatures. In smelting, serpentine is primarily used as a flux in steelmaking, helping to remove impurities and improve slag fluidity, thereby increasing smelting efficiency. Furthermore, the silicon dioxide (SiO2) component in serpentine plays a crucial role in smelting; it reacts with alkaline oxides (such as calcium oxide) to form silicate slag, effectively lowering the melting point and promoting impurity separation. The addition of serpentine can also improve the smelting efficiency of blast furnaces. Because serpentine lowers the melting point of slag, it makes slag-iron separation easier, thus reducing energy consumption and time costs in the smelting process. Therefore, accurately determining the silicon dioxide content in serpentine is of great significance in its smelting applications.

[0003] Invention patent CN 118858053 A discloses a continuous determination and analysis method for calcium fluoride and silicon dioxide in desulfurizing agents, comprising: weighing the sample, leaching with glacial acetic acid, filtering with medium-speed quantitative filter paper, washing the precipitate several times; placing the precipitate in a crucible, igniting, removing and cooling; wetting the residue with a few drops of water, adding hydrofluoric acid, evaporating at low temperature, then adding hydrofluoric acid to evaporate to dryness at low temperature, igniting, placing in a desiccator and cooling; placing the crucible after scattering silicon dioxide in a beaker, leaching with hydrochloric acid, washing the crucible, evaporating to a certain volume on a low-temperature hot plate, adding perchloric acid and heating until fuming and dry; cooling slightly, adding hydrochloric acid to dissolve the salts, diluting to the mark for final dissolution; separating the solution, adding triethanolamine, water, hydroxylamine hydrochloride, potassium hydroxide solution, magnesium sulfate and calcein, titrating with EDTA standard solution until the fluorescent green disappears as the endpoint. The purpose of this invention is to provide an analytical method for determining the content of calcium fluoride and silicon dioxide in desulfurizing agents that is short in operation, low in cost, and highly efficient, accurate, and stable. It employs a combination of hydrofluoric acid gravimetric method and EDTA volumetric method: 1. Selective extraction and separation of calcium using glacial acetic acid; 2. Weighing after ignition of the precipitate; 3. Volatilization of SiO2 with hydrofluoric acid → SiO2 determination by weight loss method; 4. CaF2 determination by EDTA titration after dissolution of the residue. This method is a "two-component continuous analysis," not a method specifically for determining high silicon content; and the target material is completely different from the matrix. Summary of the Invention

[0004] To address the lack of a detection method for silica in serpentine, this invention aims to provide a method for determining silica in serpentine. Since there are virtually no standard samples available for detecting silica content in serpentine, a spiked recovery method is used to determine its accuracy. This method has been validated in production practice and is an effective and practical approach.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention discloses a method for determining silica in serpentine, comprising the following steps: decomposing the sample with a mixed solvent → extracting with hydrochloric acid → dehydrating with perchloric acid to separate silica from other metal ions → filtering → igniting → weighing to a constant weight, thereby determining the silica content; wherein:

[0007] The specific steps of decomposing the sample with the mixed solvent are as follows: weigh the sample into a platinum crucible pre-mixed with the mixed solvent, mix it with a glass rod, cover the surface with a small amount of the mixed solvent, melt it in a muffle furnace at 850-900℃ for 15-20 minutes, cool it and then put it into a beaker.

[0008] The steps of hydrochloric acid extraction → perchloric acid dehydration to separate silica from other metal ions specifically include: adding hydrochloric acid to the beaker to leach the molten metal, washing the crucible with hot water; concentrating the solution after hydrochloric acid extraction, adding perchloric acid, heating until the perchloric acid emits thick white fumes and refluxing for 10-15 minutes, removing and cooling slightly, adding hydrochloric acid and hot water, stirring to dissolve the salts, filtering with medium-speed quantitative filter paper, washing the beaker, washing with hot hydrochloric acid until no iron ions are present, and then washing with hot water until no chloride ions are present.

[0009] Furthermore, the specific steps of decomposing the sample with the mixed solvent include: weighing 0.2500g of the sample into a platinum crucible pre-mixed with 2.5-3g of mixed solvent, mixing it with a glass rod, covering the surface with a small amount of mixed solvent, melting it in a muffle furnace at 850-900℃ for 15-20min, cooling it, and then placing it in a 400mL beaker.

[0010] Furthermore, 2.5g of crystalline aluminum chloride was added to the fluorine-containing sample.

[0011] Furthermore, the steps of hydrochloric acid extraction → perchloric acid dehydration to separate silica from other metal ions specifically include: adding 50 mL of hydrochloric acid to leach the molten metal, washing the crucible with hot water; concentrating the solution after hydrochloric acid extraction to 20-30 mL, adding 15 mL of perchloric acid, heating until the perchloric acid emits thick white fumes and refluxing for 10-15 min, removing and cooling slightly, adding 10 mL of ρ1.19 hydrochloric acid and 50 mL of hot water, stirring to dissolve the salts, filtering with medium-speed quantitative filter paper, washing the beaker, washing with hot hydrochloric acid until no iron ions are present, and then washing with hot water until no chloride ions are present.

[0012] Further, the precipitate, along with the filter paper, was transferred into a porcelain crucible, carbonized, ashed, and calcined at 1000℃ for 40 minutes. It was then removed, cooled to room temperature, and weighed.

[0013] Furthermore, the sample was repeatedly burned and weighed until a constant weight was achieved.

[0014] Further, the calculation of the analysis results

[0015]

[0016] Where: m1: mass of sample precipitate (g)

[0017] m0: Mass of blank precipitate (g)

[0018] m : Sample mass (g).

[0019] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0020] The silica content in serpentine is an important chemical indicator. Accurately determining the silica content in serpentine can improve the smelting efficiency of blast furnaces during the smelting process, thereby reducing energy consumption and time costs. Specifically, the roles of silica in serpentine in smelting include: 1. Slag formation: In steelmaking or metallurgical processes, silica, as an acidic oxide, combines with alkaline impurities in the furnace charge (such as iron oxide and magnesium oxide) to form low-melting-point silicate melts, facilitating slag-iron separation. 2. Slag property adjustment: Appropriate amounts of silica can improve slag fluidity, enhance desulfurization and dephosphorization effects, and reduce erosion of refractory materials. 3. Comprehensive resource utilization: Serpentine itself is rich in magnesium oxide and silica; direct use as a flux can reduce the need for external raw materials and realize waste resource utilization. Therefore, accurately determining its silica content is of great significance. However, there is currently a lack of relevant detection methods. This method provides accurate data on the silica content in serpentine, filling the gap in the determination of silica content in serpentine. Detailed Implementation

[0021] A method for determining silica in serpentine, comprising:

[0022] 1. Scope

[0023] This method specifies the determination of silica in serpentine using the perchloric acid dehydration method.

[0024] This method is applicable to the determination of silica content in serpentine.

[0025] 2. Method Summary

[0026] The sample was decomposed with a mixed solvent, extracted with hydrochloric acid, and dehydrated with perchloric acid to separate silica from other metal ions. Then, it was filtered, ignited, and weighed to a constant weight to determine the silica content.

[0027] 3. Reagents and Materials

[0028] 3.1 Mixed solvent: Take two parts of anhydrous sodium carbonate and one part of boric acid, grind and mix them thoroughly.

[0029] 3.2 Hydrochloric acid (ρ1.19)(1+1)(5+95)

[0030] 3.3 Perchloric acid (ρ 1.68)

[0031] 3.4 Crystalline aluminum chloride (solid)

[0032] 3.5 Silica standard solution (1000µg / mL)

[0033] 4. Analysis Steps

[0034] 4.1 Sample Size

[0035] Weigh 0.5000 g of the sample (0.2500 g for samples with a content greater than 30%).

[0036] 4.2 Blank Test

[0037] Perform a blank test along with the sample.

[0038] 4.3 Measurement

[0039] Weigh 0.2500g of sample into a platinum crucible pre-mixed with 2.5-3g of mixed solvent, mix with a glass rod, and cover the surface with a small amount of mixed solvent. Melt in a muffle furnace at 850-900℃ for 15-20min. After cooling, place in a 400mL beaker (2.5g of crystalline aluminum chloride for fluorine-containing samples[1]), add 50mL of hydrochloric acid (1+1) to leach the melt, and wash the crucible with hot water. Concentrate the solution after hydrochloric acid extraction to 20-30ml[2], add 15ml of perchloric acid, heat until the perchloric acid emits thick white fumes and reflux for 10-15min, remove and cool slightly, add 10ml of hydrochloric acid (ρ1.19) and 50ml of hot water, stir to dissolve the salts, filter with medium-speed quantitative filter paper, wash the beaker, wash with hot hydrochloric acid (5+95) until no iron ions are present, and then wash with hot water until no chloride ions are present. The precipitate, along with the filter paper, was transferred into a porcelain crucible, carbonized [3], ashed, and ignited at 1000℃ for 40 minutes. It was then removed, cooled to room temperature, and weighed [4]. The ignition and weighing were repeated until a constant weight was achieved.

[0040] Note:

[0041] [1]: If there is no crystalline aluminum chloride, 0.3g of pure aluminum can be used instead, which should be dissolved in the acid to be used beforehand.

[0042] [2]: The temperature of the solution should not exceed 110-120℃ during evaporation to prevent salts and silica gel from splashing. In addition, when the titanium content is high, 5-10 ml of sulfuric acid should be added before adding perchloric acid to prevent titanium from being converted into oxides.

[0043] [3]: When carbonizing and burning, the furnace door should be opened and burned for 10 minutes before closing the furnace door.

[0044] [4]: Weigh immediately after cooling.

[0045] 5. Calculation of Analysis Results

[0046]

[0047] Where: m1: mass of sample precipitate (g)

[0048] m0: Mass of blank precipitate (g)

[0049] m Sample mass (g)

[0050] 6 Results and Discussion

[0051] 6.1 Precision of the Method

[0052] The same sample was measured 11 times consecutively to verify the precision of the method, as shown in Table 1.

[0053] Table 1 Method precision experiment

[0054] Sample number element Measured value % average value(%) Standard deviation S Relative Standard Deviation (%) RSD Serpentine <![CDATA[SiO2]]> 46.62，46.58.，46.55，46.56，46.63，46.58，46.57，46.62，46.55，46.57，46.60 46.58 0.029 0.062

[0055] As shown in the table above, the RSD is less than 1%, indicating good precision.

[0056] 6.2 Accuracy of the Method

[0057] This invention improves the accuracy of the spiked recovery method when a suitable standard sample is unavailable. A silicon standard solution is added when determining silicon. The corresponding amounts added are shown in Table 2.

[0058] Table 2 Method accuracy experiment

[0059] Sample name and number element Measured value of sample (%) The amount of standard solution added (%) Amount of recovered standard solution (%) Recovery rate (%) Serpentine <![CDATA[SiO2]]> 46.55 10 56.43 99.79

[0060] As can be seen from Table 2, this invention can guarantee the accuracy of the test results.

[0061] 7. Conclusion

[0062] Extensive experimental data demonstrate that this invention provides a reliable and novel analytical method for determining silica in serpentine. This method is simple to operate, easy to master, and yields accurate and precise results, fully meeting the requirements for detection and analysis, and providing accurate data on the composition of serpentine for its utilization.

[0063] This invention utilizes a sodium carbonate and boric acid mixed flux, which, when melted at 850–900°C, completely destroys the layered magnesium silicate crystal structure of serpentine, releasing all SiO2. Furthermore, this invention employs perchloric acid dehydration, achieving complete precipitation of silicic acid without loss; perchloric acid dehydration causes the silicic acid colloid to completely coagulate, and the fuming perchloric acid is refluxed → silica gel is dehydrated into insoluble SiO2, which can be 100% recovered through filtration.

[0064] 1. This invention employs a binary flux of sodium carbonate and boric acid for directional melting. While conventional methods use only sodium carbonate, this invention adds boric acid to lower the melting point and enhance its ability to break down layered silicates, allowing serpentine to completely decompose at 850–900°C. Those skilled in the art would not have considered using the weakly acidic flux boric acid to synergistically break down the layers of serpentine.

[0065] 2. In fluorine-containing serpentine, crystalline aluminum chloride is added beforehand to fix the fluorine, which will react with silicon to form SiF4 and be lost through volatilization. This invention adds crystalline aluminum chloride before leaching, causing F⁻ to form a stable complex with Al³⁺, forcibly fixing the fluorine and preventing silicon volatilization. Conventionally, only fluorine is removed without fixing it; the use of aluminum salts for in-situ complexation and fluorine fixation is not considered.

[0066] 3. Perchloric acid dehydration is strictly controlled at 110–120℃. Conventional high-temperature fume generation easily causes silica gel splashing and titanium oxide co-precipitation. This invention uses low-temperature, gentle dehydration combined with pre-addition of sulfuric acid to suppress titanium interference, resulting in pure SiO2 precipitation without impurities. While the art generally pursues "high-temperature, strong fume generation," this invention reverses this conventional low-temperature controlled dehydration, defying conventional thinking.

[0067] 4. Rapid cooling and weighing after ignition prevents moisture absorption. The high magnesium oxide content in the serpentine system leads to SiO2 precipitation and easy moisture absorption. The present invention uses a dryer that allows for immediate weighing after cooling, significantly improving constant weight stability.

[0068] Beneficial effects:

[0069] 1. Improved dissolution rate: The layered structure of serpentine is completely destroyed, and the recovery rate is close to 100%.

[0070] 2. Fluorine interference is completely eliminated: The solid fluorine system prevents silicon from volatilizing, significantly improving stability.

[0071] 3. Extremely high precision: RSD=0.062%, far superior to conventional methods (RSD 1%~3%).

[0072] 4. Reliable even without standard: The spiked recovery rate is 99.79%, which fully meets production requirements.

[0073] 5. Filling a technological gap: The first SiO2 gravimetric method specifically for serpentine.

[0074] The key innovative features of this invention are: 1. Using a sodium carbonate + boric acid mixed flux to enhance the destructive power of layered serpentine; 2. Using crystalline aluminum chloride to fix fluorine in situ to prevent SiF4 volatilization; 3. Abandoning conventional high-temperature dehydration, adopting low-temperature controlled dehydration at 110-120℃ to reduce interference; 4. Rapid cooling and weighing for high-magnesium matrices to avoid moisture absorption.

[0075] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for determining silica in serpentine, characterized in that, The process includes the following steps: decomposing the sample with a mixed solvent → hydrochloric acid extraction → dehydration with perchloric acid to separate silica from other metal ions → filtration → ignition → weighing to a constant weight, thereby determining the silica content; wherein: The specific steps of decomposing the sample with the mixed solvent are as follows: weigh the sample into a platinum crucible pre-mixed with the mixed solvent, mix it with a glass rod, cover the surface with a small amount of the mixed solvent, melt it in a muffle furnace at 850-900℃ for 15-20 minutes, cool it and then put it into a beaker. The steps of hydrochloric acid extraction → perchloric acid dehydration to separate silica from other metal ions specifically include: adding hydrochloric acid to the beaker to leach the molten metal, washing the crucible with hot water; concentrating the solution after hydrochloric acid extraction, adding perchloric acid, heating until the perchloric acid emits thick white fumes and refluxing for 10-15 minutes, removing and cooling slightly, adding hydrochloric acid and hot water, stirring to dissolve the salts, filtering with medium-speed quantitative filter paper, washing the beaker, washing with hot hydrochloric acid until no iron ions are present, and then washing with hot water until no chloride ions are present.

2. The method for determining silica in serpentine according to claim 1, characterized in that, The specific steps for decomposing the sample with the mixed solvent are as follows: weigh 0.2500g of sample into a platinum crucible pre-mixed with 2.5-3g of mixed solvent, mix with a glass rod, cover the surface with a small amount of mixed solvent, melt in a muffle furnace at 850-900℃ for 15-20min, cool and then place in a 400mL beaker.

3. The method for determining silica in serpentine according to claim 2, characterized in that, Add 2.5g of crystalline aluminum chloride to the fluorine-containing sample.

4. The method for determining silica in serpentine according to claim 1, characterized in that, The steps of hydrochloric acid extraction → perchloric acid dehydration to separate silica from other metal ions specifically include: adding 50 mL of hydrochloric acid to leach the molten metal, washing the crucible with hot water; concentrating the solution after hydrochloric acid extraction to 20-30 mL, adding 15 mL of perchloric acid, heating until the perchloric acid emits thick white fumes and refluxing for 10-15 min, removing and cooling slightly, adding 10 mL of ρ1.19 hydrochloric acid and 50 mL of hot water, stirring to dissolve the salts, filtering with medium-speed quantitative filter paper, washing the beaker, washing with hot hydrochloric acid until no iron ions are present, and then washing with hot water until no chloride ions are present.

5. The method for determining silica in serpentine according to claim 1, characterized in that, The precipitate, along with the filter paper, was transferred into a porcelain crucible, carbonized, ashed, and calcined at 1000℃ for 40 minutes. It was then removed, cooled to room temperature, and weighed.

6. The method for determining silica in serpentine according to claim 6, characterized in that, Repeatedly ignite and weigh until constant weight is achieved.

7. The method for determining silica in serpentine according to claim 1, characterized in that, Calculation of analysis results Where: m1: mass of sample precipitate (g) m0: Mass of blank precipitate (g) m: Sample mass (g).

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