A high-purity molybdenum disulfide and its preparation method

Abstract

This application relates to the field of molybdenum disulfide preparation technology, specifically disclosing a high-purity molybdenum disulfide and its preparation method. The preparation method includes the following steps: (1) plasma treatment of molybdenum concentrate followed by ultrasonic dispersion to obtain pretreated molybdenum concentrate; (2) adding the pretreated molybdenum concentrate to an acidic solution for oxidation reaction, followed by the sequential addition of hydroxyethylidene diphosphate and hexafluorophosphate for reaction, vacuum filtration, washing, and drying to obtain high-purity molybdenum disulfide. This application combines plasma and ultrasonic pretreatment of molybdenum concentrate. The combined effect of these two methods, utilizing the physical field enhancement effect, significantly improves the removal rate of iron and silicon dioxide, thereby increasing the purity of the obtained molybdenum disulfide.

Description

Technical Field

[0001] This application relates to the field of molybdenum disulfide preparation technology, and more specifically, to a high-purity molybdenum disulfide and its preparation method. Background Technology

[0002] Molybdenum disulfide (MoS2), as a typical layered transition metal sulfide, has a unique graphene-like layered structure. The layers are bonded by strong covalent bonds within the layers and connected by weak van der Waals forces between the layers. This structure endows it with excellent mechanical, electrical, optical and chemical properties, and it has great application prospects in the fields of superlubricants, sensors, batteries, photocatalysts, hydrogen storage and nanocomposite materials.

[0003] With the rapid development of high-end equipment manufacturing, semiconductor chips, quantum devices, and other fields, higher purity requirements have been placed on molybdenum disulfide. Existing methods for preparing high-purity molybdenum disulfide include chemical synthesis and physical purification. Chemical synthesis is further divided into pyrometallurgical sulfidation synthesis and wet sulfidation synthesis; physical purification methods include shear flocculation-flotation and flotation-chemical leaching. The main steps of pyrometallurgical sulfidation synthesis for producing high-purity molybdenum disulfide include oxidative roasting, sublimation purification, pyrometallurgical sulfidation, and pyrolysis. The main steps of wet sulfidation synthesis for producing high-purity molybdenum disulfide include oxidative roasting, ammonia leaching, leaching solution purification, wet sulfidation, and roasting pyrolysis. Although the molybdenum disulfide obtained by chemical synthesis has high purity, its lubricating properties are inferior to those of natural molybdenum disulfide. Furthermore, the synthesis process is lengthy, costly, and has a low molybdenum recovery rate. While physical purification does not destroy the natural lattice of molybdenum disulfide, the product purity is lower, and the chemical leaching process is complex.

[0004] Patent application CN109095501A discloses a method for one-step impurity removal from molybdenum concentrate to prepare high-purity molybdenum disulfide. The method involves adding an auxiliary agent to hydrochloric acid to form a homogeneous solution, then adding the molybdenum concentrate, heating under normal pressure and stirring to ensure a complete reaction, followed by vacuum filtration, washing with deionized water, drying, and pulverizing to obtain high-purity molybdenum disulfide with an iron content of less than 0.1% (1000 ppm), a silica content of less than 0.05% (500 ppm), and a purity greater than 99.5%. However, the embodiments in this application show that the iron content of the final molybdenum disulfide is 690-820 ppm and the silica content is 250-330 ppm, which are still relatively high. Iron impurities reduce the lubrication, wear resistance, and electronic conductivity of molybdenum disulfide; silica blocks the interlayer gaps of molybdenum disulfide, weakening its lamellar sliding characteristics or catalytic active sites. Therefore, it is necessary to further improve the removal efficiency of iron and silica to increase the purity of the obtained molybdenum disulfide. Summary of the Invention

[0005] In order to improve the removal of impurities from iron and silicon dioxide and thus increase the purity of the obtained molybdenum disulfide, this application provides a high-purity molybdenum disulfide and its preparation method.

[0006] In a first aspect, this application provides a method for preparing high-purity molybdenum disulfide, employing the following technical solution:

[0007] A method for preparing high-purity molybdenum disulfide includes the following steps:

[0008] (1) The molybdenum concentrate was subjected to plasma treatment and then ultrasonic dispersion to obtain pretreated molybdenum concentrate;

[0009] (2) After adding the pretreated molybdenum concentrate to an acidic solution for oxidation, hydroxyethylidene diphosphate and hexafluorophosphate are added in sequence for reaction. The mixture is then vacuum filtered, washed, and dried to obtain high-purity molybdenum disulfide.

[0010] By adopting the above technical solution, this application pre-treats molybdenum concentrate. The high-energy particles of plasma can reduce the activation energy of FeS2 and SiO2, promote their decomposition and complexation under acidic conditions, and reduce impurity residues caused by incomplete reactions. At the same time, the ultrasonic cavitation effect breaks the diffusion limitation of the solid-liquid interface, making it easier for chemical reagents to penetrate into the interior of molybdenum concentrate particles, solving the problem of "sufficient surface reaction and internal impurity residue" in traditional leaching. The two work together to overcome the problems of traditional chemical leaching by utilizing the physical field enhancement effect, significantly improving the removal rate of iron and silica, thereby improving the purity of the obtained molybdenum disulfide.

[0011] Preferably, in step (1), the specific process of plasma treatment is as follows: the crushed molybdenum concentrate is placed into the plasma reaction chamber, the chamber is closed and a vacuum is drawn; the activated molybdenum concentrate is obtained by treating it with an argon-oxygen mixture of volume ratio of (8-9):(1-2) at a power of 100-200W for 5-15 minutes.

[0012] By adopting the above technical solution and optimizing the volume ratio of argon to oxygen, a balance is achieved between physical etching and chemical activation. + Breaking the surface inert layer, •O free radicals selectively oxidize iron sulfides without damaging MoS2, thus improving Fe during subsequent acid leaching. 2+ The dissolution rate is increased while avoiding molybdenum loss due to excessive oxidation.

[0013] Optimize the power during plasma processing to stabilize plasma discharge. + The moderate bombardment energy can form uniform micropores on the surface of molybdenum concentrate, increasing the specific surface area; the O radical depth is sufficient to oxidize the exposed iron sulfides on the surface without causing deep oxidation of the molybdenum concentrate, thereby reducing the activation energy and reaction rate of the subsequent leaching reaction.

[0014] The plasma treatment duration was optimized to ensure that the plasma depth covered the main impurity areas on the surface of the molybdenum concentrate particles, and the iron sulfide oxidation rate was high enough to ensure sufficient contact for subsequent acid leaching.

[0015] Preferably, in step (1), the specific process of ultrasonic dispersion is as follows: after adding deionized water to the plasma-treated molybdenum concentrate, it is placed in an ultrasonic cleaner and ultrasonically dispersed for 20-40 minutes at a power of 150-250W to obtain pretreated molybdenum concentrate.

[0016] By employing the above technical solution and optimizing the power during ultrasound, a stable cavitation effect can be generated, which can disperse molybdenum concentrate agglomerates into single particles or small agglomerates. This allows iron sulfides and silicon impurities to be fully exposed on the particle surface, facilitating subsequent acidic oxidation leaching. 2+ The dissolution rate was improved, and the chelating agent had a better effect on Fe. 3+ The chelation rate is higher; during fluorine complexation for silicon removal, SiO2 and F... - The increased contact area leads to the formation of SiF6. 2- The reaction is more thorough. In addition, the loose filter cake formed by proper dispersion is easier to wash, reduces the amount of soluble impurities, and improves the purity of the final product.

[0017] Optimizing the ultrasonic treatment time allows the molybdenum concentrate particles to be dispersed as much as possible, maximizing the exposure area of ​​iron sulfides and silicon impurities. During the acidic oxidation leaching stage, Fe... 2+ It can be dissolved and oxidized to Fe. 3+ During the fluorine complexation desiliconization reaction, the impurity removal rate is high. At the same time, the fully dispersed filter cake has a loose structure, which can quickly wash away residual chelates and complex ions during washing. The final residual rate of iron and silicon impurities is reduced, thus improving the purification effect.

[0018] Preferably, in step (2), the acidic solution is prepared by adding sodium hypochlorite complex salt to 20-25 wt% hydrochloric acid and stirring until completely dissolved; the mass ratio of sodium hypochlorite complex salt to hydrochloric acid is 1:(8-10); the sodium hypochlorite complex salt is a mixture of sodium hypochlorite and sodium chloride with a mass ratio of 1:1.

[0019] By adopting the above technical solution, optimizing the hydrochloric acid concentration can provide sufficient H+. + This allows iron sulfides to dissolve rapidly while ensuring that hypochlorite ions exist primarily in the form of HClO. The strong oxidizing property of HClO can dissolve Fe... 2+ Efficient oxidation to Fe 3+ At the same time, the acidity is moderate, which avoids the reduction of chelating sites due to excessive protonation of the chelating agent caused by strong acidity, and also inhibits Fe. 3+Hydrolysis produces Fe(OH)3 precipitate, avoiding co-precipitation with MoS2 and ensuring the chelating agent's effect on Fe. 3+ The chelation rate is high; silicon impurities are rapidly converted into active silicic acid under these acidic conditions, providing sufficient reaction substrates for subsequent fluorine complexation reactions and reducing the amount of residual silicon.

[0020] Optimize the mass ratio of hydrochloric acid to sodium hypochlorite complex salt to make ClO - Concentration matching Fe 2+ Oxidation requirement, at this time H in the system + With ClO - The ratio is balanced to ensure that iron sulfides are fully dissolved while avoiding ClO - Excessive MoS2 oxidation leads to a decrease in molybdenum loss and a reduction in residual iron and silicon impurities.

[0021] By optimizing the mass ratio of sodium hypochlorite and sodium chloride, it is possible to ensure that Fe 2+ It achieves efficient oxidation while minimizing MoS2 loss, thus improving purification efficiency.

[0022] In summary, by optimizing the hydrochloric acid concentration, the mass ratio of hydrochloric acid to sodium hypochlorite composite salt, and the mass ratio of sodium hypochlorite to sodium chloride, the impurity removal efficiency in the oxidative acid leaching stage can be improved, and the purity of the final product can be increased.

[0023] Preferably, in step (2), the oxidation reaction specifically involves placing the pretreated molybdenum concentrate into an acidic solution and performing an oxidation reaction under ultrasonic treatment.

[0024] By employing the above technical solution, ultrasonic assistance during oxidation utilizes cavitation to break the diffusion layer on the surface of iron sulfides and lowers the dissolution activation energy to enhance their dissolution. Microfluidic fields are used to eliminate concentration gradients and increase the reaction rate between HClO and Fe. 2+ Collision probability to accelerate Fe 2+ Oxidation, through interfacial interactions, disperses HEDP molecular clusters and inhibits Fe. 3+ Hydrolysis and aggregation to promote Fe 3+ Chelating with HEDP can also optimize the filter cake structure, reduce silicon impurity encapsulation, and improve the impurity removal rate during the oxidation and acid leaching stage.

[0025] Preferably, in step (2), when the hydroxyethylidene diphosphate is added, a chelation reaction is carried out under ultrasonic action.

[0026] By employing the above technical solution, ultrasonic assistance during chelation utilizes cavitation to break the hydrogen bonds between HEDP molecules, thereby dispersing the dimer, increasing the monomer concentration, and simultaneously enhancing Fe... 3+ The collision frequency with HEDP promotes the chelation reaction; the shear force generated by ultrasound can disperse Fe. 3+The colloidal particles formed by hydrolysis avoid adsorption on the MoS2 surface and strip away the Fe adsorbed on the particle surface. 3+ This improves the chelation rate, reduces secondary iron impurities, and ultimately lowers the iron content of the product.

[0027] Preferably, in step (2), when the hexafluorophosphate is added, a fluorine complexation reaction is carried out under ultrasonic action.

[0028] By employing the above technical solution, ultrasonic assistance during fluorine complexation generates microjets and shear forces through cavitation effects, breaking down the diffusion boundary layer on the silicon impurity surface and improving the efficiency of fluorine complexation. - The contact rate with SiO2 is increased, which in turn promotes the dissociation of hexafluorophosphate and the release of F. - Strengthening SiF6 2- The reaction generates a microfluidic field that can eliminate local concentration gradients, prevent SiO2 particle agglomeration, reduce encapsulation residue, increase silicon impurity complexation rate, and facilitate subsequent washing due to the loose filter cake structure, ultimately reducing silicon content.

[0029] Preferably, in step (2), the filter cake after vacuum filtration is washed under ultrasonic waves.

[0030] By employing the above technical solution, ultrasonic-assisted washing generates microjets and impact forces through cavitation effect, thereby stripping Fe adsorbed inside the filter cake. 3+ -HEDP chelate and SiF6 2- At the same time, it loosens the filter cake structure, enhances the penetration efficiency of the washing liquid, and improves the elution rate of soluble impurities; its shear force can disperse the ultrafine particle aggregates on the surface of the filter cake, avoid secondary adsorption of impurities, and ultimately reduce the amount of impurities remaining, thereby improving the purity of the obtained molybdenum disulfide.

[0031] Preferably, in step (2), after drying, plasma treatment is required.

[0032] By employing the above technical solution, the dried filter cake undergoes plasma treatment. Through the physical etching effect of high-energy argon ions, trace amounts of physically adsorbed silicon particles and unchelated Fe atoms are removed from the surface. 3+ The oxides simultaneously repair surface defects of MoS2 to reduce impurity re-adsorption sites; the active particles generated can also decompose residual organic chelates, reduce silicon and iron residues, and improve the purity of molybdenum disulfide.

[0033] Preferably, in step (2), after drying, ultrasonic-assisted crystallization and plasma treatment are required.

[0034] By adopting the above technical solution, the dried product undergoes ultrasonic-assisted crystallization, which promotes the regular growth of MoS2 crystals through low-frequency vibration, reduces impurity encapsulation, and accelerates the agglomeration and sedimentation of trace silicon particles, thereby improving crystal purity. Plasma treatment forms an inert nitride layer on the product surface, sealing defect sites to prevent the adsorption of moisture and impurities in the air. The two work together to improve product purity.

[0035] Secondly, this application provides a high-purity molybdenum disulfide, employing the following technical solution:

[0036] High-purity molybdenum disulfide was prepared using the method described above.

[0037] In summary, this application has the following beneficial effects:

[0038] 1. This application pre-treats molybdenum concentrate with plasma combined with ultrasonic dispersion. The two work together to overcome the problems of traditional chemical leaching by utilizing the physical field enhancement effect, significantly improving the removal rate of iron and silica, and increasing the purity of the obtained molybdenum disulfide.

[0039] 2. In this application, ultrasonic waves are used to assist in the chemical reaction process. Through cavitation effect and shear force, iron and silicon impurities can be reduced, thereby improving the purity of the obtained molybdenum disulfide.

[0040] 3. This application reduces the residual silicon and iron impurities by subjecting the dried product to plasma treatment, thereby further improving the purity of the obtained molybdenum disulfide.

[0041] 4. In this application, the dried product is subjected to ultrasonic-assisted crystallization and plasma treatment, and the synergistic effect of the two improves the purity of the obtained molybdenum disulfide. Detailed Implementation

[0042] The present application will be further described in detail below with reference to the embodiments. Unless otherwise specified, all raw materials involved in the present application can be obtained commercially.

[0043] Example 1

[0044] This embodiment provides a method for preparing high-purity molybdenum disulfide, including the following steps:

[0045] (1) The molybdenum concentrate (containing 54.69wt% Mo, 2.45wt% Fe, 0.17wt% Cu, 0.09wt% Pb, 0.53wt% CaO, 1.8wt% SiO2, etc.) was crushed to a particle size ≤1mm by a jaw crusher, and then screened to below 200 mesh by a vibrating screen. The undersize material was collected for later use. 100g of the screened molybdenum concentrate was placed in the plasma reaction chamber, the chamber was closed and a vacuum was drawn to 50Pa. An argon-oxygen mixture with a volume ratio of 9:1 was passed through the chamber, and the flow rate was controlled at 5. Set the flow rate to 0 mL / min and maintain the chamber pressure at 50 Pa. Turn on the radio frequency power supply, adjust the power to 150 W, process for 10 min, then turn off the power and allow it to cool naturally to room temperature. Remove the activated molybdenum concentrate. Transfer the activated molybdenum concentrate to a 500 mL beaker, add 200 mL of deionized water, and place it in a 20 kHz ultrasonic cleaner. Set the power to 200 W and ultrasonically disperse for 30 min, stirring every 10 min to prevent particle sedimentation. After dispersion, vacuum filter using a Buchner funnel and collect the filter cake for later use.

[0046] (2) Take 100g of 30wt% concentrated hydrochloric acid and add 50g of deionized water to mix evenly to obtain a 20wt% hydrochloric acid solution. In a 500mL three-necked reaction flask, add 90g of 20wt% hydrochloric acid and turn on the mechanical stirring at 300r / min. Slowly add 5g of sodium hypochlorite and 5g of sodium chloride and stir until completely dissolved to obtain an acidic oxidation solution. Add the filter cake to the reaction flask containing the acidic oxidation solution, install the reflux condenser, place the reaction flask in a constant temperature water bath, raise the water bath temperature to 35℃, react for 60min, add 8g of hydroxyethylidene diphosphate (HEDP) to the reaction system, stir to dissolve, raise the water bath temperature to 40℃, and react for 1.5h. Then add 6g of hexafluorophosphate to the reaction system, stir evenly, maintain the water bath temperature at 40℃, and react for 1h. During this period, monitor the pH of the system with a pH meter. If the pH is >2, add a small amount of 20wt% hydrochloric acid to adjust to 1-2.

[0047] (3) After the reaction is completed, the reaction mixture is vacuum filtered using a Buchner funnel and the filter cake is collected. The filter cake is transferred to a 250 mL beaker, 100 mL of 5 wt% dilute hydrochloric acid is added, and the mixture is washed for 10 min and then filtered. The washing operation is repeated, and then 100 mL of deionized water is added. The mixture is washed for 10 min and then filtered to collect the filter cake. The washed filter cake is placed in a vacuum drying oven, the temperature is set to 100 °C, the vacuum degree is -0.09 MPa, and the mixture is dried for 2 h to obtain 88.91 g of high-purity molybdenum disulfide.

[0048] Example 2

[0049] This embodiment is basically the same as embodiment 1, except that in step (1): the molybdenum concentrate (containing Mo 54.69wt%, Fe 2.45wt%, Cu 0.17wt%, Pb 0.09wt%, CaO 0.53wt%, SiO 2 1.8wt%, etc.) is crushed to a particle size ≤1mm by a jaw crusher, and then screened to below 200 mesh by a vibrating screen, and the undersize is collected for later use; 100g of the screened molybdenum concentrate is placed in the plasma reaction chamber, the chamber is closed and a vacuum is drawn to 50Pa; an argon-oxygen mixed gas with a volume ratio of 8:2 is passed through, and the flow rate is... The flow rate was controlled at 50 mL / min, maintaining a chamber pressure of 50 Pa. The radio frequency power supply was turned on, and the power was adjusted to 100 W. After processing for 15 min, the power was turned off, and the mixture was allowed to cool naturally to room temperature. The activated molybdenum concentrate was then removed. The activated molybdenum concentrate was transferred to a 500 mL beaker, and 200 mL of deionized water was added. The beaker was then placed in a 20 kHz ultrasonic cleaner. The power was set to 150 W, and the mixture was ultrasonically dispersed for 40 min, with stirring every 10 min to prevent particle sedimentation. After dispersion, the mixture was vacuum filtered using a Buchner funnel, and the filter cake was collected for later use. Finally, 88.87 g of high-purity molybdenum disulfide was obtained.

[0050] Example 3

[0051] This embodiment is basically the same as embodiment 1, except that in step (1): the molybdenum concentrate (containing Mo 54.69wt%, Fe 2.45wt%, Cu 0.17wt%, Pb 0.09wt%, CaO 0.53wt%, SiO 2 1.8wt%, etc.) is crushed to a particle size ≤1mm by a jaw crusher, and then screened to below 200 mesh by a vibrating screen, and the undersize is collected for later use; 100g of the screened molybdenum concentrate is placed in the plasma reaction chamber, the chamber is closed and a vacuum is drawn to 50Pa; an argon-oxygen mixed gas with a volume ratio of 9:1 is passed through, and the flow rate is... The flow rate was controlled at 50 mL / min, maintaining a chamber pressure of 50 Pa. The radio frequency power supply was turned on, and the power was adjusted to 200 W. After processing for 5 min, the power was turned off, and the mixture was allowed to cool naturally to room temperature. The activated molybdenum concentrate was then removed. The activated molybdenum concentrate was transferred to a 500 mL beaker, and 200 mL of deionized water was added. The beaker was then placed in a 20 kHz ultrasonic cleaner. The power was set to 250 W, and the mixture was ultrasonically dispersed for 20 min, with stirring every 10 min to prevent particle sedimentation. After dispersion, the mixture was vacuum filtered using a Buchner funnel, and the filter cake was collected for later use. Finally, 88.83 g of high-purity molybdenum disulfide was obtained.

[0052] Example 4

[0053] This embodiment is basically the same as embodiment 1, except that in step (2): 100g of 30wt% concentrated hydrochloric acid is added to 100g of deionized water and mixed evenly to obtain a 15wt% hydrochloric acid solution. In a 500mL three-necked reaction flask, 100g of 15wt% hydrochloric acid is added, and a mechanical stirrer with a speed of 300r / min is turned on. 5g of sodium hypochlorite and 5g of sodium chloride are slowly added and stirred until completely dissolved to obtain an acidic oxidation solution. The filter cake is added to the reaction flask containing the acidic oxidation solution, and a reflux cooler is installed. The reaction flask was placed in a constant temperature water bath and heated to 35°C for 60 minutes. 8g of hydroxyethylidene diphosphate (HEDP) was added to the reaction system and stirred until dissolved. The water bath temperature was then raised to 40°C and the reaction was continued for 1.5 hours. Next, 6g of hexafluorophosphate was added to the reaction system and stirred until homogeneous. The water bath temperature was maintained at 40°C, and the reaction was continued for 1 hour. During this period, the pH of the system was monitored with a pH meter. If the pH > 2, a small amount of 20wt% hydrochloric acid was added to adjust it to 1-2. Finally, 88.82g of high-purity molybdenum disulfide was obtained.

[0054] Example 5

[0055] This embodiment is basically the same as embodiment 1, except that in step (2): 100g of 30wt% concentrated hydrochloric acid is added to 20g of deionized water and mixed evenly to obtain a 25wt% hydrochloric acid solution. In a 500mL three-necked reaction flask, 80g of 25wt% hydrochloric acid is added, and a mechanical stirrer with a speed of 300r / min is turned on. 5g of sodium hypochlorite and 5g of sodium chloride are slowly added and stirred until completely dissolved to obtain an acidic oxidation solution. The filter cake is added to the reaction flask containing the acidic oxidation solution, and a reflux condenser is installed. The reaction flask was placed in a constant temperature water bath, and the water bath temperature was raised to 35℃. The reaction was carried out for 60 min. 8 g of hydroxyethylidene diphosphate (HEDP) was added to the reaction system, and after stirring to dissolve, the water bath temperature was raised to 40℃ and the reaction was carried out for 1.5 h. Then, 6 g of hexafluorophosphate was added to the reaction system, and after stirring evenly, the water bath temperature was maintained at 40℃ and the reaction was carried out for 1 h. During this period, the pH of the system was monitored with a pH meter. If the pH was >2, a small amount of 20wt% hydrochloric acid was added to adjust it to 1-2. Finally, 88.59 g of high-purity molybdenum disulfide was obtained.

[0056] Example 6

[0057] This embodiment is basically the same as embodiment 1, except that in step (2): 100g of 30wt% concentrated hydrochloric acid is added to 50g of deionized water and mixed evenly to obtain a 20wt% hydrochloric acid solution. In a 500mL three-necked reaction flask, 90g of 20wt% hydrochloric acid is added, and a mechanical stirrer with a speed of 300r / min is turned on. 5g of sodium hypochlorite and 5g of sodium chloride are slowly added and stirred until completely dissolved to obtain an acidic oxidation solution. The filter cake is added to the reaction flask containing the acidic oxidation solution, a reflux condenser is installed, and the reaction flask is placed in a constant temperature water bath. A 20kHz ultrasonic probe is turned on and inserted into the liquid surface to... The sample was placed 2 cm below the surface, the power was set to 200W, and the water bath temperature was raised to 35℃. After reacting for 30 minutes, the ultrasonic power was adjusted to 300W, and the reaction was continued in the 35℃ water bath for another 30 minutes. Then, 8g of hydroxyethylidene diphosphate (HEDP) was added to the reaction system, stirred and dissolved, and the water bath temperature was raised to 40℃. The reaction was continued for 1.5 hours. Then, 6g of hexafluorophosphate was added to the reaction system, stirred evenly, and the water bath temperature was maintained at 40℃ for 1 hour. During this period, the pH of the system was monitored with a pH meter. If the pH was >2, a small amount of 20wt% hydrochloric acid was added to adjust it to 1-2. Finally, 89.17g of high-purity molybdenum disulfide was obtained.

[0058] Example 7

[0059] This embodiment is basically the same as embodiment 6, except that in step (2): 100g of 30wt% concentrated hydrochloric acid is added to 50g of deionized water and mixed evenly to obtain a 20wt% hydrochloric acid solution. In a 500mL three-necked reaction flask, 90g of 20wt% hydrochloric acid is added, and a mechanical stirrer with a speed of 300r / min is turned on. 5g of sodium hypochlorite and 5g of sodium chloride are slowly added and stirred until completely dissolved to obtain an acidic oxidation solution. The filter cake is added to the reaction flask containing the acidic oxidation solution, a reflux condenser is installed, and the reaction flask is placed in a constant temperature water bath. A 20kHz ultrasonic probe is turned on and inserted 2cm below the liquid surface. The ultrasonic power was set at 200W, and the water bath temperature was raised to 35℃. After reacting for 30 minutes, the ultrasonic power was adjusted to 300W, and the reaction was continued in the 35℃ water bath for another 30 minutes. Then, 8g of hydroxyethylidene diphosphate (HEDP) was added to the reaction system, stirred and dissolved, and the water bath temperature was raised to 40℃. The ultrasonic power was maintained at 300W, and the reaction was carried out for 1.5 hours. Next, 6g of hexafluorophosphate was added to the reaction system, stirred evenly, and the water bath temperature was maintained at 40℃ for 1 hour. During this period, the pH of the system was monitored with a pH meter. If the pH was >2, a small amount of 20wt% hydrochloric acid was added to adjust it to 1-2. Finally, 89.03g of high-purity molybdenum disulfide was obtained.

[0060] Example 8

[0061] This embodiment is basically the same as embodiment 7, except that in step (2): 100g of 30wt% concentrated hydrochloric acid is added to 50g of deionized water and mixed evenly to obtain a 20wt% hydrochloric acid solution. In a 500mL three-necked reaction flask, 90g of 20wt% hydrochloric acid is added, and a mechanical stirrer with a speed of 300r / min is turned on. 5g of sodium hypochlorite and 5g of sodium chloride are slowly added and stirred until completely dissolved to obtain an acidic oxidation solution. The filter cake is added to the reaction flask containing the acidic oxidation solution, a reflux condenser is installed, and the reaction flask is placed in a constant temperature water bath. A 20kHz ultrasonic probe is turned on and inserted 2cm below the liquid surface. The power is set to 200W, and the water bath is heated. The reaction was carried out at 35°C for 30 minutes. The ultrasonic power was then adjusted to 300W, and the reaction was continued in a water bath at 35°C for another 30 minutes. 8g of hydroxyethylidene diphosphate (HEDP) was added to the reaction system and stirred until dissolved. The water bath temperature was then raised to 40°C, and the ultrasonic power was maintained at 300W for 1.5 hours. Next, 6g of hexafluorophosphate was added to the reaction system and stirred until homogeneous. The ultrasonic frequency was switched to 40kHz, the power was adjusted to 250W, and the water bath temperature was maintained at 40°C for 1 hour. During this period, the pH of the system was monitored with a pH meter. If the pH was >2, a small amount of 20wt% hydrochloric acid was added to adjust it to 1-2. Finally, 89.27g of high-purity molybdenum disulfide was obtained.

[0062] Example 9

[0063] This embodiment is basically the same as embodiment 8, except that in step (3): after the reaction is completed, the reaction mixture is vacuum filtered using a Buchner funnel and the filter cake is collected; the filter cake is transferred to a 250mL beaker, 100mL of 5wt% dilute hydrochloric acid is added, and the mixture is washed with 20kHz ultrasonic cleaning agent. After ultrasonic washing at 200W power for 10min, the mixture is filtered. The above washing operation is repeated, and then 100mL of deionized water is added. After ultrasonic washing for 10min, the mixture is filtered and the filter cake is collected; the washed filter cake is placed in a vacuum drying oven, the temperature is set to 100℃, the vacuum degree is -0.09MPa, and the mixture is dried for 2h to obtain high-purity molybdenum disulfide; finally, 89.32g of high-purity molybdenum disulfide is obtained.

[0064] Example 10

[0065] This embodiment is basically the same as that of embodiment 9, except that in step (3): after the reaction is completed, the reaction mixture is vacuum filtered using a Buchner funnel and the filter cake is collected; the filter cake is transferred to a 250mL beaker, 100mL of 5wt% dilute hydrochloric acid is added, and the mixture is washed with 20kHz ultrasonic cleaning agent. After ultrasonic washing for 10min at 200W power, the mixture is filtered. The above washing operation is repeated, and then 100mL of deionized water is added. After ultrasonic washing for 10min, the mixture is filtered and the filter cake is collected; the washed filter cake is placed in a vacuum drying oven, the temperature is set to 100℃, the vacuum degree is -0.09MPa, and the mixture is dried for 2h; the dried product is placed in a plasma reaction chamber, the vacuum is drawn to 30Pa, and pure argon gas with a flow rate of 40mL / min is passed through to maintain a pressure of 30Pa; the power is turned on, the power is adjusted to 200W, the power is turned off after 20min, and the mixture is cooled to room temperature to obtain high-purity molybdenum disulfide; finally, 89.55g of high-purity molybdenum disulfide is obtained.

[0066] Example 11

[0067] This embodiment is basically the same as that of embodiment 10, except that in step (3): after the reaction is completed, the reaction mixture is vacuum filtered using a Buchner funnel, and the filter cake is collected; the filter cake is transferred to a 250mL beaker, 100mL of 5wt% dilute hydrochloric acid is added, and the mixture is washed with 20kHz ultrasonic cleaning agent. After ultrasonic washing at 200W power for 10min, the mixture is filtered. The above washing operation is repeated, and then 100mL of deionized water is added. After ultrasonic washing for 10min, the mixture is filtered and the filter cake is collected; the washed filter cake is placed in a vacuum drying oven, the temperature is set to 100℃, the vacuum degree is -0.09MPa, and the mixture is dried for 2h; the dried product is added to 1 The product was dissolved in 0.8 L of a 1:1 volume ratio ethanol-water mixture in a three-necked flask and heated to boiling. Ultrasonic waves were then turned on at 20 kHz and sonicated at 150 W for 30 min to completely dissolve the product. Heating was then stopped, and sonication continued at 100 W until the solution cooled to room temperature. Crystals precipitated and were collected by vacuum filtration. The crystalline product was placed in a plasma reaction chamber, evacuated to 50 Pa, and nitrogen gas was introduced at a flow rate of 30 mL / min to maintain a pressure of 50 Pa. The power supply was turned on and adjusted to 100 W for 10 min. The power supply and nitrogen gas were then turned off, and the mixture was allowed to cool naturally before being removed, yielding 89.61 g of high-purity molybdenum disulfide.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing high-purity molybdenum disulfide, comprising the following steps:

[0070] (1) The molybdenum concentrate (containing 54.69wt% Mo, 2.45wt% Fe, 0.17wt% Cu, 0.09wt% Pb, 0.53wt% CaO, 1.8wt% SiO2, etc.) is crushed to a particle size of ≤1mm by a jaw crusher, and then screened to below 200 mesh by a vibrating screen. The undersize material is collected for later use.

[0071] (2) Take 100g of 30wt% concentrated hydrochloric acid and add 50g of deionized water to mix evenly to obtain a 20wt% hydrochloric acid solution. In a 500mL three-necked reaction flask, add 90g of 20wt% hydrochloric acid and turn on the mechanical stirring at 300r / min. Slowly add 5g of sodium hypochlorite and 5g of sodium chloride and stir until completely dissolved to obtain an acidic oxidation solution. Add 100g of sieved molybdenum concentrate to the reaction flask containing the acidic oxidation solution, install a reflux condenser, place the reaction flask in a constant temperature water bath, raise the water bath temperature to 35℃, and react for 60min. Add 8g of hydroxyethylidene diphosphate (HEDP) to the reaction system, stir to dissolve, raise the water bath temperature to 40℃, and react for 1.5h. Then add 6g of hexafluorophosphate to the reaction system, stir evenly, maintain the water bath temperature at 40℃, and react for 1h. During this period, monitor the pH of the system with a pH meter. If pH>2, add a small amount of 20wt% hydrochloric acid to adjust to 1-2.

[0072] (3) After the reaction is completed, the reaction mixture is vacuum filtered using a Buchner funnel and the filter cake is collected. The filter cake is transferred to a 250 mL beaker, 100 mL of 5 wt% dilute hydrochloric acid is added, and the mixture is washed for 10 min and then filtered. The washing operation is repeated, and then 100 mL of deionized water is added. The mixture is washed for 10 min and then filtered to collect the filter cake. The washed filter cake is placed in a vacuum drying oven, the temperature is set to 100 °C, the vacuum degree is -0.09 MPa, and the mixture is dried for 2 h to obtain 87.8 g of high-purity molybdenum disulfide.

[0073] Performance testing

[0074] (1) Molybdenum disulfide purity

[0075] The high-purity molybdenum disulfide obtained in each example and comparative example was tested using the lead molybdate gravimetric method. The test results are shown in Table 1.

[0076] (2) Iron content

[0077] The high-purity molybdenum disulfide obtained in each example and comparative example was tested by atomic absorption spectrometry (AAS), and the test results are shown in Table 1.

[0078] (3) Silica content

[0079] The high-purity molybdenum disulfide obtained in each example and comparative example was tested by gravimetric method, and the test results are shown in Table 1.

[0080] Table 1 Performance test data of Examples 1-11 and Comparative Example 1

[0081]

[0082] As can be seen from Example 1 and Comparative Example 1 and Table 1, in the pretreatment of molybdenum concentrate, this application uses plasma and ultrasonic treatment. The high-energy particles of plasma can reduce the activation energy of FeS2 and SiO2, promote their decomposition and complexation under acidic conditions, and reduce the residue of impurities caused by incomplete reaction. The cavitation effect of ultrasonic waves breaks the diffusion limitation of the solid-liquid interface, making it easier for chemical reagents to penetrate into the interior of molybdenum concentrate particles, solving the problem of "sufficient surface reaction and internal impurity residue" in traditional leaching. The two work together to break through the efficiency bottleneck of traditional chemical leaching by utilizing the physical field enhancement effect, improving the removal rate of iron and silicon, thereby improving the purification rate of high-purity molybdenum disulfide.

[0083] Combining Examples 1 and 6 and referring to Table 1, it can be seen that the ultrasonic assistance during oxidation in this application breaks down the diffusion layer on the surface of iron sulfides through cavitation effect, reduces the dissolution activation energy to enhance dissolution, and utilizes a microfluidic field to eliminate concentration gradients and enhance the reaction between HClO and Fe. 2+ Collision probability to accelerate Fe 2+ Oxidation, through interfacial interactions, disperses HEDP molecular clusters and inhibits Fe. 3+ Hydrolysis and aggregation to promote Fe 3+ Chelating with HEDP can also optimize the filter cake structure, reduce silicon impurity encapsulation, and improve the impurity removal effect during the oxidation and acid leaching stage.

[0084] Referring to Examples 6 and 7 and Table 1, it can be seen that the chelation process in this application is assisted by ultrasound. Through cavitation effect and shear force, the hydrogen bonds between HEDP molecules are broken to disperse the dimer, while simultaneously strengthening Fe. 3+ The collision frequency with HEDP promotes the chelation reaction; its shear force can disperse Fe. 3+ The colloidal particles formed by hydrolysis avoid adsorption on the MoS2 surface and strip away the Fe adsorbed on the particle surface. 3+ This improves the chelation rate, reduces secondary iron impurities, and ultimately lowers the iron content of the product.

[0085] Referring to Examples 7 and 8 and Table 1, it can be seen that the ultrasonic-assisted fluorine complexation process in this application generates microjets and shear forces through cavitation effects, breaking the diffusion boundary layer on the silicon impurity surface and improving the fluorine concentration. - Increased contact probability with SiO2, while simultaneously promoting the dissociation of hexafluorophosphate to release F. - Strengthening SiF6 2-The reaction generates a microfluidic field that can eliminate local concentration gradients, prevent SiO2 particle agglomeration, reduce encapsulation residue, increase silicon impurity complexation rate, and facilitate subsequent washing due to the loose filter cake structure, ultimately reducing silicon content.

[0086] As can be seen from Examples 8 and 9 and Table 1, this application uses ultrasonic assistance during washing to generate microjets and impact forces through cavitation effect, thereby stripping Fe adsorbed inside the filter cake. 3+ -HEDP chelate and SiF6 2- At the same time, it loosens the filter cake structure, enhances the penetration efficiency of the washing liquid, and improves the elution rate of soluble impurities; at the same time, its shear force can disperse the ultrafine particle aggregates on the surface of the filter cake, avoid secondary adsorption of impurities, and ultimately reduce the amount of impurities remaining, thereby improving the purity of the obtained molybdenum disulfide.

[0087] Referring to Examples 9 and 10 and Table 1, it can be seen that this application performs plasma treatment on the product after drying, using the physical etching effect of high-energy argon ions to remove the trace silicon particles physically adsorbed on the surface and the unchelated Fe. 3+ The oxides simultaneously repair surface defects of MoS2 to reduce impurity re-adsorption sites; the generated active particles can also decompose residual organic chelates (such as HEDP-Fe). 3+ This reduces silicon and iron residues, thus improving the purity of the obtained molybdenum disulfide.

[0088] As can be seen from Examples 9 and 11 and Table 1, this application further performs ultrasonic-assisted crystallization and plasma treatment after drying. Ultrasonic-assisted crystallization of the dried crude product can promote the regular growth of MoS2 crystals through low-frequency vibration, reduce impurity encapsulation, and accelerate the agglomeration and sedimentation of trace silicon particles, thereby improving crystal purity. Plasma treatment forms an inert nitride layer on the surface, sealing defect sites to prevent the adsorption of moisture and impurities in the air. The two treatments work together to improve the purity of molybdenum disulfide.

[0089] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing high-purity molybdenum disulfide, characterized in that, Includes the following steps: (1) The molybdenum concentrate was subjected to plasma treatment and then ultrasonic dispersion to obtain pretreated molybdenum concentrate; (2) After adding the pretreated molybdenum concentrate to an acidic solution for oxidation, hydroxyethylidene diphosphate and hexafluorophosphate are added sequentially for reaction. The mixture is then vacuum filtered, washed, and dried to obtain high-purity molybdenum disulfide. In step (1), the specific process of plasma treatment is as follows: the crushed molybdenum concentrate is placed into the plasma reaction chamber, the chamber is closed and a vacuum is drawn; the activated molybdenum concentrate is obtained by treating it with an argon-oxygen mixture of volume ratio of (8-9):(1-2) at a power of 100-200W for 5-15 minutes. In step (2), the acidic solution is prepared by adding sodium hypochlorite complex salt to 20-25 wt% hydrochloric acid and stirring until completely dissolved; the mass ratio of sodium hypochlorite complex salt to hydrochloric acid is 1:(8-10); the sodium hypochlorite complex salt is a mixture of sodium hypochlorite and sodium chloride with a mass ratio of 1:

1.

2. The method for preparing high-purity molybdenum disulfide according to claim 1, characterized in that, In step (1), the specific process of ultrasonic dispersion is as follows: after adding deionized water to the plasma-treated molybdenum concentrate, it is placed in an ultrasonic cleaner and ultrasonically dispersed for 20-40 minutes at a power of 150-250W to obtain pretreated molybdenum concentrate.

3. The method for preparing high-purity molybdenum disulfide according to claim 1, characterized in that, In step (2), the oxidation reaction specifically involves placing the pretreated molybdenum concentrate into an acidic solution and performing an oxidation reaction under ultrasonic treatment.

4. The method for preparing high-purity molybdenum disulfide according to claim 1, characterized in that, In step (2), when the hydroxyethylidene diphosphate is added, a chelation reaction is carried out under ultrasound; when the hexafluorophosphate is added, a fluorine complexation reaction is carried out under ultrasound.

5. The method for preparing high-purity molybdenum disulfide according to claim 1, characterized in that, In step (2), the filter cake after vacuum filtration is washed under ultrasonic waves.

6. The method for preparing high-purity molybdenum disulfide according to claim 1, characterized in that, In step (2), after drying, plasma treatment is required.

7. The method for preparing high-purity molybdenum disulfide according to claim 1, characterized in that, In step (2), after drying, ultrasonic-assisted crystallization and plasma treatment are required.

8. A high-purity molybdenum disulfide, characterized in that, It is prepared by the method for preparing high-purity molybdenum disulfide according to any one of claims 1-7.

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