Method for preparing molybdenum disulfide-rich residues from molybdenite

Abstract

The invention discloses a method for preparing molybdenum disulfide-rich residues from molybdenite, and belongs to the technical field of metallurgical extraction. The method for preparing the molybdenum disulfide-rich residues from molybdenite comprises the following steps that molybdenite powder, sodium phosphate powder and borax powder are added into a containing cavity of a graphite crucible, and smelting raw materials are obtained; the smelting raw materials are smelted in a vacuum or argon atmosphere and then cooled, and residues are obtained; and the residues are sequentially subjected to water soaking and citric acid soaking and then washed and dried, and residues rich in molybdenum disulfide are obtained. The preparation method disclosed by the invention can avoid the generation of strong-toxicity waste liquid, and residues rich in molybdenum disulfide can be obtained in an environment-friendly and efficient manner.

Description

Technical Field

[0001] This invention relates to the field of metallurgical extraction technology, and in particular to a method for preparing molybdenum disulfide-rich residues from molybdenite. Background Technology

[0002] Molybdenum disulfide has attracted considerable attention due to its potential applications in various fields, including machinery, electronics, photocatalysts, sensors, nanocomposites, batteries, superlubricants, and hydrogen storage. High-purity molybdenum disulfide powder possesses excellent mechanical properties, unique physical properties, and stable chemical properties, and is widely recognized as the "king of solid lubricants," frequently used in high-tech fields such as aerospace, military and nuclear industries, and civil engineering.

[0003] Molybdenite is the most important molybdenum ore resource, in which various elements exist in the form or phase of MoS2, SiO2, CaO, Fe2O3, FeS, Al2O3, MgO, K2O, etc. Removing the abundant impurities SiO2 is the key to efficiently obtaining molybdenum disulfide.

[0004] However, the current technology for removing silica from molybdenite mainly uses wet leaching processes with hydrofluoric acid or mixed acids as leaching agents. These processes produce highly toxic waste liquid, are expensive to treat, and result in significant molybdenum loss. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for preparing molybdenum disulfide-rich residues from molybdenite, aiming to solve the problems of highly toxic waste liquid, high treatment costs, and severe molybdenum loss in current technologies for removing silica from molybdenite.

[0006] To achieve the above objectives, the present invention proposes a method for preparing molybdenum disulfide-rich residues from molybdenite, comprising the following steps: adding molybdenite, sodium phosphate, and borax to the cavity of a graphite crucible to obtain smelting raw materials; melting the smelting raw materials under vacuum or argon atmosphere and then cooling them to obtain residues; subjecting the residues to water leaching and citric acid leaching in sequence, followed by washing and drying to obtain molybdenum disulfide-rich residues.

[0007] In some embodiments, the method of "adding molybdenite powder, sodium phosphate powder and borax powder to the receiving cavity of the graphite crucible" includes: sequentially laying a first layer of borax powder, a uniform mixture of molybdenite and sodium phosphate powder, and a second layer of borax powder in the receiving cavity of the graphite crucible.

[0008] In some embodiments, the method of "adding molybdenite, sodium phosphate and borax to the receiving cavity of the graphite crucible" includes: spreading a uniform mixture of molybdenite, sodium phosphate and borax powder in the receiving cavity of the graphite crucible.

[0009] In some embodiments, the mass ratio of the molybdenite powder, the sodium phosphate powder, and the borax powder is 1:(0.5~2):(2~4).

[0010] In some embodiments, the molybdenite powder comprises, by mass fraction: 45-55 wt% Mo, 35-38 wt% S, 3-10 wt% SiO2, 1-6 wt% Fe, 0.2-1.5 wt% Pb, with the remainder being unavoidable impurities.

[0011] In some embodiments, the solid-liquid ratio of the water immersion is 1:(1~3).

[0012] In some embodiments, the solid-liquid ratio of the citric acid leaching is 1:(1~5); and / or, the temperature of the citric acid leaching is 70°C~100°C.

[0013] In some embodiments, the mass concentration of citric acid is 50 g / L to 200 g / L.

[0014] In some embodiments, the melting temperature is 1000°C to 1300°C under an argon atmosphere; and / or, 800°C to 1100°C under a vacuum; and / or, the melting time is 2h to 10h.

[0015] In some embodiments, the heating rate of the melting process is 1°C / min to 10°C / min.

[0016] The beneficial effects of this invention are as follows: The method for preparing molybdenum disulfide-rich residues from molybdenite provided by this invention, through vacuum or argon melting and the use of sodium phosphate / borax additives, successfully avoids the use of highly toxic hydrofluoric acid, significantly reduces the toxicity of waste liquid and treatment costs, and effectively reduces the dissolution loss of molybdenum disulfide during the impurity removal process, thereby greatly improving the molybdenum recovery rate. Simultaneously, this method can efficiently remove the main impurities, silica and other metal oxides, from molybdenite, ultimately obtaining a product rich in molybdenum disulfide. This achieves green, environmentally friendly, high-recovery, and low-cost silica removal, overcoming the key defects of existing wet processes. Attached Figure Description

[0017] Figure 1 This is an XRD (X-ray diffraction) pattern of molybdenum disulfide residues according to an embodiment of the present invention. The horizontal axis represents the diffraction angle, and the vertical axis represents the diffraction intensity. Figure 2 These are actual images of the residue from an embodiment of the present invention. a is an image of the residue after the experiment; b is the powder portion; c is the glass portion with a small amount of molybdenum disulfide. Figure 3 This is a photograph of the intermediate product after water immersion and citric acid immersion according to an embodiment of the present invention.

[0018] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0019] To make the technical solutions and advantages of the present invention clearer, the present invention and its beneficial effects will be described in further detail below in conjunction with specific embodiments. The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter recorded in the claims.

[0020] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0021] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0022] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0023] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0024] Molybdenite is the most important molybdenum ore resource, in which various elements exist in the form or phase of MoS2, SiO2, CaO, Fe2O3, FeS, Al2O3, MgO, K2O, etc. Removing the abundant impurities SiO2 is the key to efficiently obtaining molybdenum disulfide.

[0025] However, the current technology for removing silica from molybdenite mainly uses wet leaching processes with hydrofluoric acid or mixed acids as leaching agents. These processes produce highly toxic waste liquid, are expensive to treat, and result in significant molybdenum loss.

[0026] In view of this, this application proposes a method for preparing molybdenum disulfide-rich residues from molybdenite, comprising the following steps: S1: Add molybdenite powder, sodium phosphate powder and borax powder to the container of the graphite crucible to obtain the smelting raw materials; S2: The smelting raw material is melted under vacuum or argon atmosphere and then cooled to obtain a residue; S3: The residue is sequentially soaked in water and citric acid, then washed and dried to obtain a residue rich in molybdenum disulfide.

[0027] This solution completely avoids the use of hydrofluoric acid or fluorine-containing mixed acids as leaching agents, thus avoiding the problems of generating and treating highly toxic and corrosive fluoride waste liquids in existing technologies.

[0028] By combining vacuum or argon melting with sodium phosphate and borax additives, impurities are converted into soluble silicates and borosilicates that are easily removed by subsequent water leaching at high temperatures, rather than directly dissolving MoS2. Compared with wet processes using strong acids, this method can significantly reduce the wastewater containing fluorine compounds or strong inorganic acids and the toxic gas HF during the impurity removal process of molybdenum disulfide, thereby improving the overall recovery rate of molybdenum and the product yield.

[0029] This solution achieves green, environmentally friendly, high-recovery, and low-cost silica removal, overcoming the key shortcomings of existing wet processes.

[0030] In some embodiments, the method of "adding molybdenite powder, sodium phosphate powder and borax powder to the receiving cavity of the graphite crucible" includes: sequentially laying a first layer of borax powder, a uniform mixture of molybdenite and sodium phosphate powder, and a second layer of borax powder in the receiving cavity of the graphite crucible.

[0031] In some embodiments, the method of "adding molybdenite powder, sodium phosphate powder and borax powder to the receiving cavity of the graphite crucible" includes: spreading a uniform mixture of molybdenite, sodium phosphate and borax powder in the receiving cavity of the graphite crucible.

[0032] In some embodiments, the mass ratio of the molybdenite powder, the sodium phosphate powder, and the borax powder is 1:(0.5~2):(2~4).

[0033] Sodium phosphate (Na3PO4): Reacts with SiO2 at high temperatures to form water- or acid-soluble sodium silicate phosphates (such as Na2SiO3·Na3PO4 or more complex compounds); Borax (Na2B4O7·10H2O): Acts as a strong flux, lowering the melting temperature, promoting the reaction, and can form low-melting-point, water-soluble borosilicate glass (such as Na2O·B2O3·2SiO2) with SiO2. In some embodiments, the mass ratio of the molybdenite powder, the sodium phosphate powder, and the borax powder is preferably 1:1:3.

[0034] In some embodiments, the molybdenite powder comprises, by mass fraction: 45-55 wt% Mo, 35-38 wt% S, 3-10 wt% SiO2, 1-6 wt% Fe, 0.2-1.5 wt% Pb, with the remainder being unavoidable impurities.

[0035] Generally, the SiO2 in fine molybdenite particles with high silicon content often coexists closely with MoS2 particles, mutually encapsulates them, or forms complex intergrowths, which can easily lead to the loss of the target product during the silicon removal process. In this solution, even if the silicon content of molybdenite is high, efficient and gentle removal can be achieved. In some embodiments, the molybdenite powder includes 8-10 wt% SiO2.

[0036] In some embodiments, the solid-liquid ratio of the water leaching is 1:(1~3). The water leaching step can effectively dissolve most of the soluble silicate products generated during the smelting process. It achieves the removal of the main impurity SiO2, yielding a residue rich in MoS2. The waste liquid from the water leaching mainly contains soluble silicates, phosphates, borates, etc.

[0037] In some embodiments, the solid-liquid ratio of the citric acid leaching is 1:(1~5); and / or, the temperature of the citric acid leaching is 70℃~100℃. Citric acid leaching further dissolves residual oxide impurities, such as CaO, Fe2O3, Al2O3, MgO, and some compounds of B, Si, and P, forming soluble citric acid complexes that are then removed. Controlling the temperature at 70~100℃ is beneficial for the forward progress of the complexation reaction.

[0038] In some embodiments, the citric acid concentration is 50 g / L to 200 g / L. These waste liquids do not contain highly toxic fluorides or strong inorganic acids, have low toxicity, and significantly reduce treatment costs. Leaching is ineffective when the concentration is below 50 g / L, and while the dissolution rate increase is limited when the concentration is above 200 g / L, the cost increases significantly. In some embodiments, the preferred concentration is 50 g / L to 100 g / L.

[0039] In some embodiments, the melting temperature is 1000℃~1300℃ under an argon atmosphere; and 800℃~1100℃ under a vacuum; the melting time is 2h~10h. 1000℃ ensures that the borax is fully melted to form a low-viscosity liquid phase, encapsulating the solid particles, significantly reducing the system viscosity, promoting mass transfer reactions, and facilitating the conversion of silica into borosilicates, silica phosphates, etc. Temperatures below 1300℃ can avoid molybdenum loss, and in a vacuum environment, temperatures below 1100℃ can effectively avoid the decomposition loss of MoS2. In some embodiments, the preferred melting temperature is 1100℃~1200℃ (argon atmosphere) or 800℃~1000℃ (vacuum atmosphere).

[0040] In some embodiments, the heating rate of the melting process is 1°C / min to 10°C / min. Controlling the heating rate of the melting process is beneficial for regulating the dehydration of the powder, the melt phase transformation, and the reaction of the silicon phase. In some embodiments, the heating rate of the melting process is preferably 1°C / min to 5°C / min.

[0041] Example 1 S1: First, place a layer of borax powder in the cavity of the graphite crucible. Then, mix molybdenite powder and sodium phosphate powder evenly and place them on top of the borax powder in the graphite crucible. Finally, place the remaining borax powder on top of the mixture. The mass ratio of molybdenite powder (SiO2 content is 8.67wt%, MoS2 content is 88.09wt%), sodium phosphate powder and borax powder is 1:1:3 to obtain the smelting raw material. S2: Cover the graphite cap, place the smelting raw material into a high-temperature quenching furnace, heat at 1150℃ for 4 hours under an argon atmosphere with a heating rate ≤2℃ / min, and then cool to obtain the residue; separate the residue into a powder portion and a glass portion. S3: The powder and glass portions were soaked in water at a solid-liquid ratio of 1:1. The residue after water soaking was then acid-leached in a solution with a citric acid concentration of 50 g / L and a solid-liquid ratio of 1:1 at 80°C. After washing and drying, a residue rich in MoS2 was obtained.

[0042] Example 2 S1: First, place a layer of borax powder in the cavity of the graphite crucible. Then, mix molybdenite powder and sodium phosphate powder evenly and place them on top of the borax powder in the graphite crucible. Finally, place the remaining borax powder on top of the mixture. The mass ratio of molybdenite powder (SiO2 content is 8.67wt%, MoS2 content is 88.09wt%), sodium phosphate powder and borax powder is 1:1.5:3 to obtain the smelting raw material. S2: Cover the graphite cap, place the smelting raw material into a high-temperature quenching furnace, heat at 1150℃ for 4 hours under an argon atmosphere with a heating rate ≤2℃ / min, and then cool to obtain the residue; separate the residue into a powder portion and a glass portion. S3: The powder and glass portions were soaked in water at a solid-liquid ratio of 1:1. The residue after water soaking was then acid-leached in a solution with a citric acid concentration of 50 g / L and a solid-liquid ratio of 1:1 at 80°C. After washing and drying, a residue rich in MoS2 was obtained.

[0043] Example 3 S1: Place a uniformly mixed molybdenite powder (SiO2 content of 8.67wt%, MoS2 content of 88.09wt%), sodium phosphate powder and borax powder in the container of a graphite crucible at a mass ratio of 1:1:3 to obtain the smelting raw materials. S2: Cover the graphite cap, put the smelting raw material into a high-temperature quenching furnace, heat it at 1150°C for 4 hours under an argon atmosphere, and then cool it after high-temperature melting at a heating rate ≤2°C / min to obtain the residue. S3: The residue was directly soaked in water with a solid-liquid ratio of 1:2. The residue after water soaking was then acid-soaked in a solution with a citric acid concentration of 50 g / L and a solid-liquid ratio of 1:1 at 80°C. After washing and drying, residue rich in MoS2 was obtained.

[0044] Example 4 S1: Place a uniformly mixed molybdenite powder (SiO2 content of 8.67wt%, MoS2 content of 88.09wt%), sodium phosphate powder and borax powder in the container of a graphite crucible at a mass ratio of 1:0.5:4 to obtain the smelting raw materials. S2: Cover the graphite cap, put the smelting raw material into a high-temperature vacuum furnace, heat it at 1000°C for 6 hours in a vacuum atmosphere, and perform high-temperature melting at a heating rate ≤5°C / min, and then cool it to obtain the residue. S3: The residue was directly soaked in water with a solid-liquid ratio of 1:1. The residue after water soaking was then acid-soaked in a solution with a citric acid concentration of 50 g / L and a solid-liquid ratio of 1:1 at 80°C. After washing and drying, residue rich in MoS2 was obtained.

[0045] Example 5 S1: Place a uniformly mixed mixture of molybdenite powder (SiO2 content of 8.67wt%, MoS2 content of 88.09wt%), sodium phosphate powder, and borax powder in the container of a graphite crucible at a mass ratio of 1:2:2 to obtain the smelting raw materials. S2: Cover the graphite cap, put the smelting raw material into a high-temperature quenching furnace, heat it at 800°C for 4 hours in a vacuum environment, and then cool it after high-temperature melting at a heating rate of ≤5°C / min to obtain the residue. S3: The residue was directly soaked in water with a solid-liquid ratio of 1:1. The residue after water soaking was then acid-soaked in a solution with a citric acid concentration of 50 g / L and a solid-liquid ratio of 1:1 at 90°C. After washing and drying, residue rich in MoS2 was obtained.

[0046] Example 6 S1: Place a uniformly mixed mixture of molybdenite powder (SiO2 content of 8.67wt%, MoS2 content of 88.09wt%), sodium phosphate powder, and borax powder in the container of a graphite crucible at a mass ratio of 1:2:2 to obtain the smelting raw materials. S2: Cover the graphite cap, put the smelting raw material into the high-temperature quenching furnace, heat it at 900°C for 4 hours under vacuum atmosphere, and perform high-temperature melting at a heating rate ≤5°C / min. After melting under vacuum atmosphere, cool it to obtain the residue. S3: The residue was directly soaked in water with a solid-liquid ratio of 1:2. The residue after water soaking was then acid-soaked in a solution with a citric acid concentration of 100 g / L and a solid-liquid ratio of 1:1 at 80°C. After washing and drying, residue rich in MoS2 was obtained.

[0047] Comparative Example 1: The method of removing SiO2 using hydrofluoric acid involves using hydrofluoric acid at a concentration of 0.5 mol / L, which has a very good removal effect. However, the removal process generates toxic HF gas and strong inorganic acid waste liquid, which are seriously harmful and have high treatment costs.

[0048] Performance testing XRD characterization and tests of silica residue and molybdenum disulfide yield were performed on the MoS2-rich residues in the examples and comparative examples. 1. The MoS2-rich residue of Example 3 was subjected to XRD testing. The method included the following steps: the washed and dried residue was pressed into a pellet, and the target material was selected as Cu Kα, λ=1.5406 Å. The scanning range was set to 5°~95°, the step size was 0.02° and the scanning speed was 5° / min~10° / min. The diffraction pattern was recorded by the detector.

[0049] 1. The silica residue and molybdenum disulfide yield of the MoS2-rich residues from Examples 1 to 6 were tested according to the method shown in GB / T 23271-2009.

[0050] The test results are shown in Table 1.

[0051] Table 1. Test results of the examples and comparative examples

[0052] See the instruction manual appendix Figure 1 The results of Example 3 show that XRD revealed a small amount of SiO2 remaining in the residue, but elemental analysis showed that the removal effect of SiO2 was significant.

[0053] As shown in Table 1, this method significantly improves the removal of SiO2. Compared to wet methods, this method does not produce toxic HF gas or strong inorganic acid waste liquid.

[0054] In summary, the method for preparing molybdenum disulfide-rich residues from molybdenite provided in this solution successfully avoids the use of highly toxic hydrofluoric acid through vacuum melting and the use of sodium phosphate / borax additives. This significantly reduces the toxicity of the waste liquid and treatment costs, and effectively minimizes the dissolution loss of molybdenum disulfide during the impurity removal process, thereby greatly improving the molybdenum recovery rate. Simultaneously, this method can efficiently remove the main impurities, silica and other metal oxides, from molybdenite, ultimately obtaining a product rich in molybdenum disulfide. This achieves green, environmentally friendly, high-recovery, and low-cost silica removal, overcoming the key shortcomings of existing wet processes.

[0055] Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples.

[0056] The above description is only a part or preferred embodiment of the present invention. Neither the text nor the drawings should limit the scope of protection of the present invention. All equivalent structural transformations made using the content of the present invention specification and drawings under the overall concept of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of protection of the present invention.

Claims

1. A method for preparing molybdenum disulfide-rich residues from molybdenite, characterized in that, Includes the following steps: Molybdenite powder, sodium phosphate powder, and borax powder are added to the cavity of a graphite crucible to obtain smelting raw materials; The raw materials are melted under vacuum or argon atmosphere and then cooled to obtain residues. The residue was subjected to water immersion and citric acid immersion in sequence, followed by washing and drying to obtain a residue rich in molybdenum disulfide.

2. The method for preparing molybdenum disulfide-rich residues from molybdenite according to claim 1, characterized in that, The method of "adding molybdenite powder, sodium phosphate powder and borax powder to the container cavity of the graphite crucible" includes: sequentially laying a first layer of borax powder, a uniform mixture of molybdenite and sodium phosphate powder, and a second layer of borax powder in the container cavity of the graphite crucible.

3. The method for preparing molybdenum disulfide-rich residues from molybdenite according to claim 1, characterized in that, The method of "adding molybdenite powder, sodium phosphate powder and borax powder to the cavity of a graphite crucible" includes: spreading a uniform mixture of molybdenite, sodium phosphate and borax powder in the cavity of the graphite crucible.

4. The method for preparing molybdenum disulfide-rich residues from molybdenite according to claim 1, characterized in that, The mass ratio of the molybdenite powder, the sodium phosphate powder, and the borax powder is 1:(0.5~2):(2~4).

5. The method for preparing molybdenum disulfide-rich residues from molybdenite according to any one of claims 1 to 4, characterized in that, The molybdenite powder comprises, by mass fraction: 45~55wt% Mo, 35~38wt% S, 3~10wt% SiO2, 1~6wt% Fe, 0.2~1.5wt% Pb, The rest are unavoidable impurities.

6. The method for preparing molybdenum disulfide-rich residues from molybdenite according to claim 1, characterized in that, The solid-liquid ratio of the water immersion is 1:(1~3).

7. The method for preparing molybdenum disulfide-rich residues from molybdenite according to claim 1, characterized in that, The solid-liquid ratio of the citric acid leaching is 1:(1~5); and / or, The citric acid leaching temperature is 70℃~100℃.

8. The method for preparing molybdenum disulfide-rich residues from molybdenite according to claim 7, characterized in that, The citric acid concentration is 50 g / L to 200 g / L.

9. The method for preparing molybdenum disulfide-rich residues from molybdenite according to claim 1, characterized in that, Under an argon atmosphere, the melting temperature is 1000℃~1300℃; and / or, Under vacuum, 800℃~1100℃; and / or, The smelting time is 2 hours to 10 hours.

10. The method for preparing molybdenum disulfide-rich residues from molybdenite according to claim 8, characterized in that, The heating rate of the smelting process is 1℃ / min to 10℃ / min.

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