Method for removing silicon from high-purity yellow phosphorus

Abstract

The application discloses a silicon removal method of high-purity yellow phosphorus and belongs to the field of high-purity inorganic material purification. The method comprises the following steps: dissolving industrial yellow phosphorus in a mixed solvent of n-heptane / cyclohexane to form a homogeneous system; adding an organic fluorine source at 0-15 DEG C to slowly release F- to complex with silicon to generate [SiF6]2-; after being warmed to 20-30 DEG C, adding a metal alkoxide with a steric hindrance effect to crosslink with [SiF6]2- to form an insoluble gel; performing solid-liquid separation and distilling to recover yellow phosphorus. Through the synergistic effect of the mixed solvent pre-stripping and the steric hindrance type metal alkoxide selective gelation, one-step deep removal of silicon, arsenic, moisture and other impurities is realized, the silicon content is less than or equal to 0.1 ppm, the arsenic content is less than or equal to 0.05 ppm, the moisture content is less than or equal to 20 ppm, the method is high in safety, free of free HF, the yellow phosphorus recovery rate is greater than or equal to 99%, and the method is green and environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of high-purity inorganic material purification technology, specifically relating to a method for removing silicon from high-purity yellow phosphorus. Background Technology

[0002] High-purity yellow phosphorus is a key precursor for the preparation of electronic-grade semiconductor materials such as phosphoric acid, phosphine (PH3), indium phosphide (InP), and gallium phosphide (GaP). With the rapid development of 5G communication, lasers, high-frequency devices, and solid-state batteries, stringent requirements are placed on the purity of yellow phosphorus. According to the standards of the Semiconductor Equipment and Materials International (SEMI), electronic-grade yellow phosphorus used for compound semiconductor epitaxy must meet the following requirements: total impurities ≤ 5 ppm, silicon (Si) ≤ 0.1 ppm, and arsenic (As) ≤ 0.05 ppm. Among these, silicon impurities, due to their formation of deep-level recombination centers in the crystal lattice, significantly reduce carrier lifetime and thus become the most critical control indicator.

[0003] Industrial yellow phosphorus is mainly produced by the reduction of phosphate rock (Ca5(PO4)3F) with coke and silica (SiO2) in an electric furnace at 1400-1500℃. During this process, silicon impurities from the raw materials inevitably enter the product, existing in complex forms, mainly including: free SiO2 particles (0.1-10μm); silicate phases (such as CaSiO3, Fe2SiO4); and Si-P alloys or solid solutions. Among these multiphase silicon impurities, Si-P alloys are the most difficult to treat because they are insoluble in water, non-volatile, and stable to oxidants; conventional distillation or washing is almost ineffective.

[0004] Existing technologies mainly include the following silicon removal methods: 1. Hydrogen fluoride precipitation method: HF reacts with NH4F in CS2 to generate CaSiF6 precipitate. However, HF is highly toxic and corrosive, posing a hazardous hazard and generating fluorine-containing hazardous waste, resulting in high treatment costs.

[0005] 2. Micro-oxidation-adsorption method: Silicon is oxidized to SiO2 by a trace amount of oxygen, and then adsorbed by Al2O3. However, it is ineffective for Si-P alloys, and the silicon residue is usually >0.5ppm.

[0006] 3. Vacuum distillation: This method consumes extremely high energy and cannot remove volatile silicon.

[0007] Therefore, there is an urgent need for a safe, green, efficient, and industrially viable method for removing silicon with Si ≤ 0.1 ppm. Summary of the Invention

[0008] This invention aims to provide a method for removing silicon from high-purity yellow phosphorus in a single step, eliminating the need for free HF, complex adsorption and regeneration, supporting continuous production, and enabling simultaneous removal of multiple impurities. The core concept of this invention lies in: utilizing the differential swelling and dispersion capabilities of a mixed solvent of n-heptane and cyclohexane for silicon impurities of different forms to pre-strip the silicon impurities during the dissolution stage; subsequently, using a low-temperature slow-release of F⁻ from an organic fluorine source to precisely convert the silicon impurities into soluble [SiF6]²⁻; then, selectively coordinating and cross-linking with [SiF6]²⁻ using a sterically hindered metal alkoxide (alkoxy group is isopropoxy or tert-butoxy, central metal is aluminum, zirconium, or titanium) to form an insoluble three-dimensional gel. The steric hindrance effectively repels yellow phosphorus molecules and organic phosphorus impurities, avoiding side reactions; finally, high-purity yellow phosphorus is obtained through simple filtration and distillation recovery. Throughout the process, the pre-stripping effect of the mixed solvent, the slow-release complexation effect of the organic fluorine source, and the selective gelation effect of the sterically hindered metal alkoxide work together to not only achieve deep removal of silicon, but also simultaneously reduce the content of Group VA impurities such as arsenic, moisture, and antimony.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for removing silicon from high-purity yellow phosphorus includes the following stages: S1: Raw Material Preparation ① Raw material preparation: Prepare sufficient industrial yellow phosphorus, organic fluorine source, metal alkoxide with steric hindrance effect, anhydrous mixed solvent, and high-purity inert gas; ② Tooling and equipment preparation: Prepare industrial yellow phosphorus storage tanks, dissolving kettles, reaction kettles, metering pumps, filtration devices, solvent recovery distillation towers, and high-purity yellow phosphorus collection tanks.

[0010] S2: Pretreatment Dissolution The industrial yellow phosphorus prepared in step S1① and the anhydrous mixed solvent are added to the dissolving vessel prepared in step S1② at ​​a mass ratio of 1:2 to 4. The anhydrous mixed solvent is composed of n-heptane and cyclohexane, and the mass ratio of n-heptane to cyclohexane is 1:2 to 1:5. The mixture is stirred thoroughly at a stirring speed of 200 to 400 rpm to dissolve and form a homogeneous system.

[0011] S3: Precise Combination ①The homogeneous system obtained from S2 was kept at a temperature of 0–15℃; ② Under an inert gas atmosphere, the organic fluorine source prepared in step S1 ① is slowly added dropwise to the above homogeneous system using a metering pump. The amount of organic fluorine source added is 0.8 to 1.2 wt% of the mass of industrial yellow phosphorus. The organic fluorine source is trimethylfluorosilane, fluorinated phosphonium salt, or low-polyfluorosiloxane. The mixture is stirred thoroughly at a speed of 200 to 400 rpm for 60 to 120 minutes. The organic fluorine source slowly releases F⁻ at low temperature in the homogeneous system. F⁻ precisely complexes with silicon impurities to form [SiF6]²⁻.

[0012] S4: Gel polymerization ①The reaction system obtained from S3② is heated to 20-30℃; ② Add the sterically hindered metal alkoxide prepared in step ① of S1, the amount of which is 0.5 to 1.0 wt% of the mass of industrial yellow phosphorus. The alkoxy group of the metal alkoxide is selected from isopropoxy or tert-butoxy, and the central metal is selected from aluminum, zirconium or titanium. Stir thoroughly at a stirring speed of 200 to 400 rpm for 20 to 40 min. The metal alkoxide and [SiF6]²⁻ undergo coordination crosslinking to form an insoluble three-dimensional crosslinked gel.

[0013] S5: Solid-Liquid Separation and Recovery ① Use a filtration device to perform solid-liquid separation on the gel-containing mixture obtained in S4②, and collect the filtrate; ② The filtrate is distilled through a solvent recovery distillation tower at a distillation temperature of 60-80℃, a system pressure of 1-5kPa, and a condensation temperature of 30-40℃ to recover the solvent and obtain high-purity yellow phosphorus.

[0014] Preferably, the mass ratio of n-heptane to cyclohexane in the anhydrous mixed solvent in S2 is 1:3 to 1:4. At this ratio, the mixed solvent has the best swelling and dispersion effect on silicon impurities of different forms, such as free SiO2 particles, silicate phases, and Si-P alloys, and the pre-exfoliation efficiency is the highest.

[0015] Preferably, the sterically hindered metal alkoxide described in S4② is zirconium tert-butoxide. The significant steric hindrance of the tert-butoxy group can maximally repel yellow phosphorus molecules, resulting in a dense gel with high separation efficiency, and can simultaneously and efficiently remove arsenic and moisture.

[0016] Preferably, the metal alkoxide with steric hindrance effect described in S4② is aluminum isopropoxide or titanium isopropoxide.

[0017] Preferably, the filtration device described in S5① consists of multiple units connected in parallel, with the filter element material being polytetrafluoroethylene or polyvinylidene fluoride, the filter element pore size being 0.2 to 1.0 μm, the filtration pressure being 0.1 to 0.3 MPa, and the filtration temperature being ≤40℃.

[0018] As a preferred option, the silicon content in the final high-purity yellow phosphorus is ≤0.1ppm.

[0019] As a preferred option, the final high-purity yellow phosphorus contains arsenic content ≤0.05ppm and moisture content ≤20ppm.

[0020] The present invention has the following beneficial effects: (1) Extremely high safety, completely avoiding the risk of corrosion from free HF. This invention does not use highly toxic and corrosive fluorides such as hydrofluoric acid (HF) or ammonium bifluoride throughout the entire process. The organic fluorine source (trimethylfluorosilane, fluorinated phosphonium salt or oligomeric fluorosiloxane) slowly releases F⁻ in a low-temperature, non-aqueous system. The instantaneous HF concentration in the system is less than 0.1 ppm, and no highly corrosive vapors are generated, fundamentally eliminating safety hazards for operators and equipment corrosion problems. At the same time, the solvent system uses a low-toxicity combination of n-heptane and cyclohexane, eliminating the flammable and explosive carbon disulfide (CS2) used in traditional methods, reducing the explosion risk by more than 90%, and strictly controlling moisture, eliminating the side reaction of yellow phosphorus hydrolysis to generate highly toxic phosphine (PH3), significantly improving the safety of the workshop environment.

[0021] (2) Selective gelation technology achieves high recovery rate of yellow phosphorus and low fluorine residue. This invention uses a metal alkoxide (alkoxy group is isopropoxy or tert-butoxy) with steric hindrance effect. Its large alkoxy group generates significant steric repulsion during coordination crosslinking, and can selectively react with [SiF6]²⁻ to form a three-dimensional gel, while effectively repelling yellow phosphorus molecules and organic phosphorus impurities, avoiding yellow phosphorus from being encapsulated or adsorbed by the gel. Compared with the traditional method of using alkali metal salts (such as NaCl, KCl) to precipitate fluorosilicates, the gelation process of this invention does not cause mechanical entrainment loss of yellow phosphorus, and the yellow phosphorus recovery rate can reach more than 99% (experiments have confirmed 99.2% to 99.5%). At the same time, due to the specific binding of fluorosilicate ions by the gel, the fluorine residue in the product is less than 0.01 ppm, which meets the stringent restrictions on fluoride ions for electronic-grade materials.

[0022] (3) Multi-impact synergistic removal in one step achieves a purification effect of "killing multiple birds with one stone". The technical solution of this invention is not a simple superposition of the functions of each step, but a deep synergy between the pre-stripping of the mixed solvent, the slow-release complexation of the organic fluorine source, and the selective gelation of the sterically hindered metal alkoxide. While deeply removing silicon impurities (silicon content ≤ 0.1 ppm), it can simultaneously reduce the arsenic content to ≤ 0.05 ppm and the moisture content to ≤ 20 ppm, and can effectively remove group VA impurities such as antimony. Comparative experimental data show that when using ordinary metal alkoxides without steric hindrance (such as aluminum isopropoxide), the residual arsenic content in the product is 0.10 ppm and the moisture content is 28 ppm, which is much higher than the index of this invention. This "one-step multi-effect" synergistic purification effect cannot be achieved by using known single technical means (such as recrystallization alone, adsorption alone, etc.), which reflects outstanding substantive features and significant progress.

[0023] (4) The process is simplified and easy for continuous industrial production. This invention requires only five main unit operations: dissolution, complexation, gelation, filtration, and distillation, resulting in low equipment investment. The filtration step can utilize multiple parallel polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) filter cartridges with a pore size of 0.2–1.0 μm and a filtration pressure of 0.1–0.3 MPa. The gel cake is easily removed, the filter cartridges can be backwashed online, and the flux recovery rate is high. The distillation recovery of the solvent is carried out under mild conditions (60–80℃, 1–5 kPa), with a solvent recovery rate exceeding 98%. After drying with molecular sieves, the solvent can be recycled. The entire process supports continuous feeding and discharging, making it suitable for large-scale industrial production. It also offers a wide operating window and relatively low technical requirements for operators.

[0024] (5) Green and environmentally friendly, with no fluoride-containing wastewater discharge and the waste gel can be recycled. Traditional hydrogen fluoride precipitation methods generate a large amount of fluoride-containing wastewater and hazardous fluoride-containing wastewater, which are costly to treat and put great pressure on the environment. In this invention, all fluorine elements eventually enter the gel solid phase, with no F⁻ discharged into the aqueous or gas phase. The collected fluoride-containing gel (mainly composed of zirconium / aluminum / titanium fluorosilicate composites) can be converted into nano-sized M-Si-O composite oxides (M=Al, Zr, Ti) after high-temperature calcination at 550-650℃. These composite oxides can be reused as catalysts or adsorbents in the phosphorus chemical industry, realizing the resource utilization of waste. In addition, the efficient recovery and recycling of organic solvents further reduces raw material consumption and the amount of waste generated. Energy consumption is reduced by more than 85% compared with the traditional vacuum distillation method, which is in line with the concept of green chemistry and clean production. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described in detail below with reference to specific embodiments and comparative experiments. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0026] Example 1 (Standardized operation using n-heptane / cyclohexane mixed solvent and zirconium tert-butoxide) S1: Raw material preparation: Take 50 kg of industrial yellow phosphorus, which, after testing, has a silicon content of 15.2 ppm, an arsenic content of 2.6 ppm, and a moisture content of 85 ppm. The anhydrous mixed solvent is prepared by 35 kg of n-heptane and 105 kg of cyclohexane (n-heptane to cyclohexane mass ratio 1:3, total solvent 140 kg, yellow phosphorus to solvent mass ratio approximately 1:2.8). The organic fluorine source is 0.5 kg of trimethylfluorosilane (1.0 wt% of yellow phosphorus mass), and the metal alkoxide is 0.4 kg of zirconium tert-butoxide (0.8 wt% of yellow phosphorus mass). High-purity argon gas is used for protection.

[0027] S2: Pretreatment Dissolution: Industrial yellow phosphorus and the above-mentioned mixed solvent are added to a dissolving vessel, and stirring is started at 200 rpm to dissolve and form a homogeneous system at 25°C. The silicon impurities are pre-exfoliated by utilizing the differential swelling and dispersion effect of the mixed solvent on silicon impurities.

[0028] S3: Precise Complexation: Cool the system to 5°C and purge with high-purity argon for protection. Slowly add trimethylfluorosilane dropwise using a metering pump, maintaining a stirring speed of 250 rpm during the addition process, and react for 90 min. The organic fluorine source slowly releases F⁻ at low temperature, precisely complexing with silicon impurities to form [SiF6]²⁻.

[0029] S4: Selective gel polymerization: The system was heated to 25°C, zirconium tert-butoxide was added, and the mixture was stirred at 200 rpm for 30 min. Due to the large steric hindrance of its tert-butoxy group, zirconium tert-butoxide selectively coordinates and crosslinks with [SiF6]²⁻ to form a dense three-dimensional gel. At the same time, the steric hindrance effect repels yellow phosphorus molecules and organophosphorus impurities, avoiding side reactions.

[0030] S5: Solid-Liquid Separation and Recovery: Multiple parallel filtration devices (filter element material: polytetrafluoroethylene, pore size: 0.2 μm) were used to remove gel by filtration at a pressure of 0.2 MPa and a temperature of 25°C, and the filtrate was collected. The filtrate was then passed into a solvent recovery distillation column at a distillation temperature of 65°C, a system pressure of 1.5 kPa, and a condensation temperature of 35°C to recover the solvent and obtain high-purity yellow phosphorus. The recovered solvent was dried using molecular sieves and then recycled.

[0031] S6: Detection: Metal impurity content was determined by ICP-MS, and moisture content was determined by Karl Fischer method. Results: Silicon content 0.03 ppm, arsenic content 0.02 ppm, antimony content 0.01 ppm, moisture 10 ppm. Yellow phosphorus recovery rate was calculated to be 99.5% (based on the mass of yellow phosphorus fed).

[0032] Example 2 (using titanium isopropoxide as a sterically hindered metal alkoxide) The main body is the same as in Example 1, except that: Except for replacing the metal alkoxide with titanium isopropoxide (0.4 kg, accounting for 0.8 wt% of the yellow phosphorus mass), the operation was exactly the same as in Example 1. The final product test results were: silicon content 0.07 ppm, arsenic content 0.04 ppm, moisture 15 ppm, and yellow phosphorus recovery rate 99.2%. This also achieved one-step deep removal of multiple impurities, verifying that the steric hindrance effect of isopropoxy metal alkoxides can also achieve good selective gelation effect.

[0033] Example 3 (The ratio of mixed solvents was adjusted to 1:4) The main body is the same as in Example 1, except that: The anhydrous mixed solvent was prepared by mixing 28 kg of n-heptane and 112 kg of cyclohexane (n-heptane to cyclohexane mass ratio 1:4), and the remaining operations were the same as in Example 1. The final product test results were: silicon content 0.04 ppm, arsenic content 0.02 ppm, moisture 12 ppm, and yellow phosphorus recovery rate 99.4%. This indicates that excellent impurity removal effect can be achieved within a ratio range of 1:3 to 1:4.

[0034] Comparative Example 1 (single n-heptane solvent) Using n-heptane as the solvent (140 kg), the remaining operations were exactly the same as in Example 1. The final product test results were: silicon content 0.38 ppm, arsenic content 0.10 ppm, moisture 28 ppm, and yellow phosphorus recovery rate 97.2%. These results were significantly worse than those of Example 1, indicating that the pre-stripping effect of the mixed solvent is crucial for silicon removal efficiency and the synergistic removal of multiple impurities.

[0035] Comparative Example 2 (using common, sterically unhindered aluminum isopropoxide as a metal alkoxide) Ordinary grade aluminum isopropoxide (without significant steric hindrance) was used as the metal alkoxide, with an addition amount of 0.4 kg (equivalent to the molar amount of zirconium tert-butoxide in Example 1). The remaining operations were identical to those in Example 1. The final product test results were: silicon content 0.12 ppm, arsenic content 0.10 ppm, moisture 28 ppm, and yellow phosphorus recovery rate 97.2%. Furthermore, it was observed that the formed gel was loose and turbid, the pressure difference increased rapidly during filtration, and the filtrate was not clear. This indicates that the metal alkoxide, lacking sufficient steric hindrance, cannot achieve selective cross-linking, resulting in partial encapsulation of yellow phosphorus, a decreased recovery rate, and a significantly weakened ability to simultaneously remove arsenic and moisture.

[0036] To further demonstrate the inventiveness of this invention, the systematic comparative experimental data are summarized below.

[0037] Experimental Example 1: The Influence of Solvent System on Silicon Removal Efficiency The same batch of industrial yellow phosphorus (silicon content 15.2 ppm) was used. The subsequent complexation conditions (trimethylfluorosilane 1.0 wt%, reaction at 10℃ for 90 min) and gelation conditions (zirconium tert-butoxide 0.8 wt%, reaction at 25℃ for 30 min) were fixed. Only the type of pretreatment solvent was changed. The experimental results are shown in Table 1.

[0038]

[0039] Table 1. Effect of solvent system on silicon removal efficiency The improvement in complexation efficiency is calculated as the increase in the average silicon removal rate of the mixed solvent compared to the single solvent. It can be seen that the mixed solvent of this invention, through pre-stripping, improves the complexation efficiency by more than 67%, and the silicon content of the final product is consistently ≤0.1ppm.

[0040] Experimental Example 2: The Influence of Metal Alkoxide Steric Hindrance on Selective Gel Removal and Multi-Impurity Removal Table 2 shows the comparison results of different metal alkoxides under the same molar addition amount using mixed solvent pretreatment.

[0041]

[0042] Table 2. Effect of metal alkoxide steric hindrance on selective gelation and removal of multiple impurities.

[0043] It is evident that metal alkoxides with steric hindrance of isopropoxy or tert-butoxy can selectively gel, repel yellow phosphorus, significantly improve recovery rate, and spontaneously and simultaneously remove arsenic and moisture, achieving synergistic deep purification with effects far superior to ordinary unhindered alkoxides.

[0044] As can be seen from the above embodiments and experimental examples, the method of the present invention achieves one-step efficient removal of impurities such as silicon, arsenic, and moisture through the synergistic effect of mixed solvent pre-exfoliation and sterically hindered metal alkoxide selective gelation, as well as the multifunctional characteristics of the organic fluorine source-alkoxide combination. Moreover, the operation is safe and the process is simplified, which has significant inventiveness and industrial application value.

[0045] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for removing silicon from high-purity yellow phosphorus, characterized in that, Includes the following stages: S1: Raw Material Preparation ① Raw material preparation: Prepare sufficient industrial yellow phosphorus, organic fluorine source, metal alkoxide with steric hindrance effect, anhydrous mixed solvent, and high-purity inert gas; ② Tooling and equipment preparation: Prepare industrial yellow phosphorus storage tanks, dissolving kettles, reaction kettles, metering pumps, filtration devices, solvent recovery distillation towers, and high-purity yellow phosphorus collection tanks; S2: Pretreatment Dissolution The industrial yellow phosphorus prepared in step S1① and the anhydrous mixed solvent are added to the dissolving vessel prepared in step S1② at ​​a mass ratio of 1:2 to 4. The anhydrous mixed solvent is composed of n-heptane and cyclohexane, and the mass ratio of n-heptane to cyclohexane is 1:2 to 1:

5. The mixture is stirred thoroughly at a stirring speed of 200 to 400 rpm to dissolve and form a homogeneous system. S3: Precise Combination ① The homogeneous system obtained from S2 was subjected to temperature control at 0–15℃; ② Under an inert gas atmosphere, the organic fluorine source prepared in step S1 ① is slowly added dropwise to the above homogeneous system using a metering pump. The amount of organic fluorine source added is 0.8 to 1.2 wt% of the mass of industrial yellow phosphorus. The organic fluorine source is trimethylfluorosilane, fluorinated phosphonium salt, or oligomeric fluorosiloxane. Stir thoroughly at a stirring speed of 200 to 400 rpm for 60 to 120 min. S4: Gel polymerization ① The reaction system obtained in S3② is heated to 20-30℃; ② Add the sterically hindered metal alkoxide prepared in step ① of S1, the amount of which is 0.5 to 1.0 wt% of the mass of industrial yellow phosphorus. The alkoxy group of the metal alkoxide is selected from isopropoxy or tert-butoxy, and the central metal is selected from aluminum, zirconium or titanium. Stir thoroughly at a stirring speed of 200 to 400 rpm for 20 to 40 min to form an insoluble three-dimensional cross-linked gel. S5: Solid-Liquid Separation and Recovery ① Use a filtration device to perform solid-liquid separation on the gel-containing mixture obtained in S4②, and collect the filtrate; ② The filtrate is distilled through a solvent recovery distillation tower at a distillation temperature of 60-80℃, a system pressure of 1-5kPa, and a condensation temperature of 30-40℃ to recover the solvent and obtain high-purity yellow phosphorus.

2. The method according to claim 1, characterized in that, The mass ratio of n-heptane to cyclohexane in the anhydrous mixed solvent described in S2 is 1:3 to 1:

4.

3. The method according to claim 1, characterized in that, The metal alkoxide with steric hindrance effect is zirconium tert-butoxide.

4. The method according to claim 1, characterized in that, The metal alkoxide with steric hindrance effect mentioned in S4② is aluminum isopropoxide or titanium isopropoxide.

5. The method according to claim 1, characterized in that, The filtration device described in S5① consists of multiple units connected in parallel. The filter element material is polytetrafluoroethylene or polyvinylidene fluoride, the filter element pore size is 0.2~1.0μm, the filtration pressure is 0.1~0.3MPa, and the filtration temperature is ≤40℃.

6. The method according to claim 1, characterized in that, The final high-purity yellow phosphorus has a silicon content of ≤0.1ppm.

7. The method according to claim 6, characterized in that, The final high-purity yellow phosphorus has an arsenic content of ≤0.05ppm and a moisture content of ≤20ppm.

8. The method according to claim 1, characterized in that, The organic fluorine source mentioned in S3② is trimethylfluorosilane.

Images