A method for recovering molybdenum from ferromolybdenum smelting dust

Abstract

The present invention relates to a method for recovering molybdenum from ferromolybdenum smelting dust. The ferromolybdenum smelting dust is first pre-treated by roasting to promote the decomposition of salt substances such as lead molybdate in the dust, and to oxidize low-valent molybdenum, which is difficult to dissolve in alkali, into high-valent molybdenum (MoO3), creating conditions for molybdenum leaching. Given the high content of impurity elements in ferromolybdenum smelting dust and the tendency of salt substances such as lead molybdate to form a covering on the surface of molybdenum chalcanth during the ferromolybdenum smelting process, NaOH is used to dissolve the salt covering such as PbMoO4 at room temperature. Molybdenum trioxide (MoO3) generated during the roasting process is then leached, reacting with impurity metals to form a hydroxide precipitate. This removes some impurity metal ions from the leaching solution, prevents large amounts of impurity metals such as copper and nickel from dissolving into the leaching solution, improves the molybdenum leaching rate, and reduces the burden of the purification process. This method can be effectively applied in the field of comprehensive resource recovery to achieve resource recovery and utilization of ferromolybdenum smelting dust.

Description

Technical Field

[0001] The present invention belongs to the technical field of mineral resource recovery, and in particular relates to a method for recovering molybdenum from ferromolybdenum smelting dust, which can effectively recover molybdenum from ferromolybdenum smelting dust. Background Art

[0002] Molybdenum is a refractory rare metal with excellent physical and chemical properties. With the increasing consumption of molybdenum, the comprehensive utilization of secondary resources, such as molybdenum-containing waste, spent molybdenum-containing catalysts, and molybdenum-containing waste slag generated during the metallurgical extraction process, has received increasing attention. However, the utilization rates of these resources vary significantly, influenced by the type of secondary resources and the separation and extraction technologies used. Current research on the comprehensive recovery of molybdenum from secondary resources primarily focuses on mineral processing tailings, spent molybdenum-containing catalysts, and spent molybdenum-containing alloys. However, little research has been conducted on the comprehensive recovery of valuable molybdenum metals from smelting dust.

[0003] Ferromolybdenum smelting dust is a molybdenum-containing waste generated during the ferromolybdenum production process. It is the result of water leaching and sedimentation of the flying dust from ferromolybdenum smelting. In addition to a certain amount of molybdenum, it also contains significant amounts of quartz, silicates, iron, copper, calcium, magnesium, aluminum, and lead. Ferromolybdenum producers typically briquette or pelletize the recovered dust, or directly add a small amount of dust to each furnace for recycling. However, this dust recycling process presents several challenges: First, the dust has a low specific gravity, making its utilization efficiency low after returning to the batching system, with the majority of it being lost from the smelting system as secondary dust. Second, the dust contains high carbon and sulfur contents, so the amount added directly to the furnace should not be large, otherwise it will affect the quality of the ferromolybdenum. Therefore, as a secondary molybdenum resource that has not been fully understood and studied, ferromolybdenum smelting dust requires the development of an efficient and environmentally friendly ferromolybdenum dust utilization process.

[0004] Patent CN202011526178 discloses a method for recovering molybdenum from waste catalysts, the specific steps of which are to grind the waste catalyst with sodium carbonate, and stir and mix the ground waste catalyst with the sodium carbonate; place the mixed waste catalyst and sodium carbonate in a vacuum resistance furnace for roasting to obtain a roasted product, wherein the roasting temperature is 140-200°C; leach the roasted product with distilled water to obtain a mixture of leachate and leach residue; separate the mixture of leachate and leach residue to obtain a leachate. However, ferromolybdenum smelting smoke is formed during the high-temperature smelting of ferromolybdenum, but because of its fine particle size, high impurity content and complex composition, the high temperature causes the mineral phase of molybdenum to transform. In addition to most of the molybdenum existing in the form of molybdenum phosphate (MoO3), there are also small amounts of lead molybdate and molybdenum disulfide. If the molybdenum recovery method of patent CN202011526178 is adopted, the molybdenum iron dust is mixed with sodium carbonate and then roasted. The roasting process may generate carbonate precipitates that wrap the target components and worsen leaching. In addition, during the leaching process, Na2MoO4 is difficult to come into direct contact with distilled water, causing the molybdenum on the surface of the molybdenum iron dust to enter the alkaline leaching residue and cannot be efficiently recovered. Therefore, the above method is not suitable for the recovery of molybdenum in molybdenum iron dust. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for recovering molybdenum from ferromolybdenum smelting dust, which is leached after oxidative roasting pretreatment to solve the problem of recovering molybdenum resources in ferromolybdenum smelting dust and improve the recovery effect of molybdenum resources.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The ferromolybdenum smelting dust is pretreated by roasting to promote the decomposition of salt substances such as lead molybdate in the dust, and at the same time oxidize low-valent molybdenum into high-valent molybdenum (MoO3), which not only ensures the decomposition of salts such as lead molybdate but also prevents molybdates such as lead molybdate from forming low-melting-point eutectics with MoO3, providing a basis for the efficient leaching of molybdenum; under normal temperature conditions, sodium hydroxide is added to the roasted sand as a leaching agent for molybdenum. Sodium hydroxide dissolves lead molybdate and molybdenum trioxide generated during the roasting process, allowing more molybdenum to dissolve in the solution, preventing large amounts of metals such as copper and nickel from dissolving into the leaching solution. At the end of leaching, a molybdenum-containing precious liquid is obtained.

[0008] Specifically, the method for recovering molybdenum from ferromolybdenum smelting dust of the present invention comprises the following steps:

[0009] Step 1: oxidatively roasting ferromolybdenum smelting dust to decompose the lead molybdate therein to form alkali-soluble molybdenum trioxide and lead oxide, and simultaneously oxidizing the molybdenum disulfide and molybdenum dioxide therein to form alkali-soluble molybdenum trioxide; the ferromolybdenum smelting dust is molybdenum-containing waste generated in the ferromolybdenum production process;

[0010] Step 2: mixing the ferromolybdenum smelting dust after oxidative roasting with water to form a slurry, and adding a reagent to perform alkaline leaching;

[0011] Step 3: After leaching, solid-liquid separation is performed, and the resulting filtrate is molybdenum-rich noble liquid.

[0012] In one embodiment, in step 1, the ferromolybdenum smelting dust is placed into a porcelain ark and oxidized and roasted in a resistance furnace.

[0013] In one embodiment, the oxidation roasting is performed at a temperature of 600 to 670° C. and for a time of 1 to 3 hours.

[0014] In one embodiment, in step 2, the liquid-to-solid ratio of the slurry is controlled to be between 1:1 and 3:1 by weight.

[0015] In one embodiment, the agent is sodium hydroxide.

[0016] In one embodiment, in step (2), the amount of reagent added is 230-330 g / L based on the weight of ferromolybdenum smelting dust.

[0017] In one embodiment, in step (2), the leaching temperature is room temperature (10-30° C.), and the leaching time is controlled to be 3-6 hours.

[0018] In one embodiment, the unrecovered molybdenum contained in the ferromolybdenum smelting dust exists in the form of lead molybdate, molybdenum fluoride and molybdenum disulfide.

[0019] Compared with the prior art, the present invention performs alkaline room-temperature leaching on ferromolybdenum smelting dust after oxidative roasting pretreatment, thereby improving the leaching rate and leaching speed of molybdenum in the dust. After solid-liquid separation, not only can a molybdenum-containing noble liquid be obtained, but the content of metal impurities in the leaching liquid can also be reduced, thereby achieving effective recovery of molybdenum and making comprehensive use of ferromolybdenum smelting dust, which is in line with the resource sustainable development strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a process flow chart of the present invention.

[0021] Figure 2 1 is a process flow chart of Example 1 of the present invention.

[0022] Figure 3 This is a process flow chart of Example 2 of the present invention. DETAILED DESCRIPTION

[0023] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0024] The ferromolybdenum smelting dust described in the present invention is molybdenum-containing waste generated during the ferromolybdenum production process. Molybdenum exists in various phases, primarily consisting of molybdenum vanadium, lead molybdate, and molybdenum disulfide, with molybdenum vanadium being present in relatively high concentrations. As previously mentioned, prior art research on the comprehensive recovery of molybdenum from secondary resources primarily focuses on mineral processing tailings, waste molybdenum-containing catalysts, waste molybdenum-containing alloys, and the like, while there is little research on the comprehensive recovery of valuable molybdenum metals from smelting dust. Therefore, the present invention provides a method for recovering molybdenum from ferromolybdenum smelting dust, which not only adds a new source for the recovery of molybdenum resources but also solves the problem of recovering molybdenum from ferromolybdenum smelting dust, thereby enabling the resource recovery and utilization of ferromolybdenum smelting dust and reducing environmental risks.

[0025] The present invention discloses a method for recovering molybdenum from ferromolybdenum smelting dust. First, the ferromolybdenum smelting dust is pre-treated by roasting to promote the decomposition of salt substances such as lead molybdate in the dust, and to oxidize low-valent molybdenum, which is difficult to dissolve in alkali, into high-valent molybdenum (MoO3), creating conditions for the leaching of molybdenum. In view of the high content of impurity elements in ferromolybdenum smelting dust and the tendency of lead molybdate and other salt substances to form a cover on the surface of molybdenum chalcanth during the ferromolybdenum smelting process, NaOH and other reagents are used to dissolve the salt cover such as PbMoO4. Molybdenum trioxide (MoO3) generated during the roasting process is leached to simultaneously react with impurity metals to form a hydroxide precipitate, thereby removing some impurity metal ions in the leaching solution and preventing large amounts of impurity metals such as copper and nickel from dissolving into the leaching solution. This method improves the leaching rate of molybdenum and reduces the burden of the purification process. This method can be effectively applied in the field of comprehensive resource recovery to achieve resource recovery and utilization of ferromolybdenum smelting dust.

[0026] like Figure 1 As shown, the present invention mainly includes the following steps:

[0027] (1), oxidative roasting.

[0028] The ferromolybdenum smelting dust contains unrecovered molybdenum, which mainly exists in the form of lead molybdate, molybdenum fluoride and molybdenum disulfide. This step mainly uses oxidative roasting to decompose the lead molybdate into molybdenum trioxide and lead oxide that are easily soluble in alkali (the decomposition temperature is 600-800℃), and at the same time oxidizes molybdenum disulfide and molybdenum dioxide into molybdenum trioxide that is easily soluble in alkali. The main reaction formula is as follows:

[0029] PbMoO4→PbO+MoO3

[0030] 2MoO2+O2→2MoO3

[0031] 2MoS2+7O2→2MoO3+4SO2↑

[0032] In a specific embodiment of this step, oxidation roasting can be achieved using a resistance furnace. Specifically, ferromolybdenum smelting smoke can be spread flatly into a porcelain ark, which is then placed in a resistance furnace and roasted and oxidized at a temperature of 600-670° C. for 1-3 hours.

[0033] In this step, the ferromolybdenum smelting dust is pretreated by oxidative roasting to decompose lead molybdate into molybdenum trioxide and lead oxide, and at the same time, the low-valent molybdenum insoluble in alkali is oxidized into high-valent molybdenum (MoO3) soluble in alkali, which provides a basis for the leaching of molybdenum. During the oxidative roasting process, no reagents are added.

[0034] In this step, the temperature (600-670°C) must be strictly controlled to ensure the decomposition of salts such as lead molybdate and to prevent the formation of low-melting-point eutectics with MoO3, thereby creating conditions for efficient leaching of molybdenum.

[0035] (2), alkaline leaching.

[0036] After the roasted ferromolybdenum dust is cooled, it is mixed with a certain amount of water to form a slurry. Sodium hydroxide is added to the slurry and stirred for alkaline leaching. The sodium hydroxide dissolves a small amount of residual lead molybdate and the molybdenum trioxide generated during the roasting process, allowing more molybdenum to dissolve in the solution and preventing large amounts of metals such as copper and nickel from dissolving into the leaching solution. At the end of the leaching process, a molybdenum-containing noble solution is obtained.

[0037] PbMoO4+2NaOH→Na2MoO4+Pb(OH)2↓

[0038] MeMoO4+2NaOH→Na2MoO4+Me(OH)2↓(Me:Pb, Fe, Cu, etc.)

[0039] MoO3+2NaOH→Na2MoO4+H2O

[0040] In the present invention, the roasted ferromolybdenum dust can be placed in a stirring tank and prepared into a slurry. The liquid-to-solid ratio of the slurry is controlled between 1:1 and 3:1 by weight. Sodium hydroxide is used as a leaching agent to achieve efficient molybdenum recovery. The main function of sodium hydroxide is to convert the molybdenum in the roasted sand into Na2MoO4, which dissolves in the aqueous solution. Impurities such as lead, copper, iron, nickel, and zinc form hydroxides and enter the slag, thereby removing impurity ions in the solution. The leaching temperature can be controlled between 10 and 30°C, and the leaching time can be controlled between 3 and 6 hours. The amount of sodium hydroxide added is generally 230 to 330 g / L, based on the weight of the ferromolybdenum dust.

[0041] In this step, the roasted ferromolybdenum smelting dust is directly leached in a system using sodium hydroxide as a leaching agent. Sodium hydroxide can convert the molybdenum in the roasted sand into Na2MoO4 and dissolve it in the aqueous solution, while removing impurity ions in the solution.

[0042] (3), solid-liquid separation.

[0043] After leaching, solid-liquid separation is carried out and the filtrate is a molybdenum-containing noble liquid (Na2MoO4).

[0044] In summary, the present invention pre-treats the ferromolybdenum smelting smoke by roasting, which can decompose lead molybdate into molybdenum trioxide and lead oxide, and at the same time oxidize the low-valent molybdenum insoluble in alkali into high-valent molybdenum (MoO3) soluble in alkali. Roasting can promote the decomposition of salt substances and the oxidation of more molybdenum. Sodium molybdate soluble in aqueous solution can be generated during sodium hydroxide leaching, and impurity ions in the solution can also be removed, thereby better realizing the efficient recovery of molybdenum resources.

[0045] The following are several specific embodiments of the present invention.

[0046] Example 1:

[0047] like Figure 2 As shown, an experiment of recovering molybdenum from ferromolybdenum dust of a certain molybdenum industry company in Shaanxi was conducted using the present invention.

[0048] (1) Spread the ferromolybdenum smelting dust onto a porcelain ark, place it in a resistance furnace and bake it at 600℃ for 2h.

[0049] (2) The roasted ferromolybdenum dust was placed in a stirring tank, water was added to form a slurry, the liquid-to-solid ratio of the slurry was controlled at 1.5:1, 260 g / L of NaOH was added, and leaching was carried out at a temperature of 25 °C for 4 h.

[0050] (3), solid-liquid separation, the test results are as follows:

[0051]

[0052] Under conditions where ferromolybdenum smelting dust fineness meets requirements, this invention utilizes a comprehensive resource recovery process combining pre-oxidation roasting and alkaline leaching, achieving a molybdenum leaching rate of 97.11%, an increase of 5.99% and achieving highly efficient molybdenum resource recovery. This process leverages the advantages of a combined pyrometallurgical and hydrometallurgical process, reducing reagent consumption, shortening leaching time, and significantly improving molybdenum leaching rates. It is a low-cost, high-recovery molybdenum recovery process that contributes to the sustainable development of resource strategies.

[0053] Example 2:

[0054] like Figure 3 As shown, an experiment of using the present invention to recover molybdenum from ferromolybdenum smelting dust of a molybdenum company in China was conducted.

[0055] (1) Spread the ferromolybdenum smelting dust onto a porcelain ark, place it in a resistance furnace and bake it at 650℃ for 2h.

[0056] (2) The roasted ferromolybdenum dust was placed in a stirring tank, water was added to form a slurry, the liquid-to-solid ratio of the slurry was controlled at 1.5:1, 260 g / L of NaOH was added, and leaching was carried out at a temperature of 30°C for 4 h.

[0057] (3), solid-liquid separation, the test results are as follows:

[0058]

[0059] Under conditions where ferromolybdenum smelting dust fineness meets requirements, this invention utilizes a comprehensive resource recovery process combining pre-oxidation roasting and alkaline leaching, achieving a molybdenum leaching rate of 98.42%, a 6.62% improvement in molybdenum leaching efficiency and achieving efficient molybdenum resource recovery. This process leverages the advantages of a combined pyrometallurgical and hydrometallurgical process, reducing reagent consumption, shortening leaching time, and significantly improving molybdenum leaching efficiency. It is a low-cost, high-recovery molybdenum recovery process that contributes to the sustainable development of resource strategies.

[0060] The above description is only a preferred embodiment of the invention. It should be pointed out that those skilled in the art can make changes and modifications to the invention without departing from the spirit and scope of the invention, and all changes and modifications should be within the scope defined by the appended claims.

Claims

1. A method for recovering molybdenum from ferromolybdenum smelting dust, characterized in that: The steps include: Step 1: oxidatively roasting ferromolybdenum smelting dust to decompose the lead molybdate therein to form alkali-soluble molybdenum trioxide and lead oxide, and simultaneously oxidizing the molybdenum disulfide and molybdenum dioxide therein to form alkali-soluble molybdenum trioxide; the oxidative roasting is performed at a temperature of 600-670° C. for 1-3 hours; the ferromolybdenum smelting dust is molybdenum-containing waste generated during the ferromolybdenum production process; Step 2: mixing the ferromolybdenum smelting dust after oxidation roasting with water to form a slurry, adding a reagent to perform alkaline leaching, the leaching temperature is room temperature, and the leaching time is controlled at 3 to 6 hours; Step 3: After leaching, solid-liquid separation is performed, and the resulting filtrate is molybdenum-rich noble liquid.

2. The method for recovering molybdenum from ferromolybdenum smelting dust according to claim 1, wherein In the step 1, the ferromolybdenum smelting smoke is placed in a porcelain ark and oxidized and roasted in a resistance furnace.

3. The method for recovering molybdenum from ferromolybdenum smelting dust according to claim 1, wherein In step 2, the liquid-to-solid ratio of the slurry is controlled to be between 1:1 and 3:1 by weight.

4. The method for recovering molybdenum from ferromolybdenum smelting dust according to claim 1, wherein: The medicament is sodium hydroxide.

5. The method for recovering molybdenum from ferromolybdenum smelting dust according to claim 1 or 4, characterized in that: In the step 2, the amount of the reagent added is 230 to 330 g / L based on the weight of the ferromolybdenum smelting dust.

6. The method for recovering molybdenum from ferromolybdenum smelting dust according to claim 1, characterized in that: The unrecovered molybdenum contained in the ferromolybdenum smelting dust exists in the form of lead molybdate, molybdenum fluoride and molybdenum disulfide.

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