Method for separating molybdenum in the preparation process of high-purity vanadium product

Abstract

The application provides a method for separating molybdenum in the preparation process of high-purity vanadium products, and the method comprises the following steps: (1) mixing an ammonium salt and an acidic vanadium-molybdenum-containing solution, carrying out vanadium precipitation by the ammonium salt, and obtaining an ammonium polyvanadate crude product through solid-liquid separation; (2) carrying out a molybdenum removal reaction on the ammonium polyvanadate crude product in step (1) under the action of an organic acid, and obtaining a molybdenum-containing solution and ammonium vanadate through solid-liquid separation. The application can separate molybdenum from ammonium vanadate in the acidic vanadium-molybdenum-containing solution, realize the technical effect that the molybdenum content in the vanadium product is controlled within 0.005%, and the molybdenum resources can be recycled in the form of molybdic acid.

Description

Technical Field

[0001] This invention relates to the field of vanadium-molybdenum separation technology, and in particular to a method for separating molybdenum during the preparation of high-purity vanadium products. Background Technology

[0002] High-purity V2O5 refers to vanadium pentoxide products with a purity of over 99%. It is mainly used in vanadium redox flow batteries, aerospace-grade vanadium-aluminum alloys, vanadium-based catalysts, and the preparation of metallic vanadium. It is a key raw material that has gradually emerged with the development of strategic emerging industries such as new energy and aerospace.

[0003] Molybdenum and vanadium share similar properties and readily coexist in vanadium-containing natural minerals, particularly in vanadium-molybdenum ores and secondary vanadium resources such as spent HDS catalysts. Vanadium and molybdenum are typically recovered as valuable resources. In nature, vanadium and molybdenum usually exist in low valence states. To extract them, they need to be oxidized to higher valence states before leaching. This is usually achieved through processes such as oxidative roasting-water leaching or oxidative acid leaching to first extract vanadium and molybdenum into a solution, followed by separation to obtain separate vanadium and molybdenum products. Because some high-purity vanadium products require high molybdenum content, trace amounts of molybdenum are often difficult to separate, easily leading to substandard product quality. Methods for vanadium and molybdenum separation and recovery typically utilize the difference in solubility between ammonium vanadate and ammonium molybdate under specific pH conditions. First, vanadium is precipitated using ammonium salts, followed by molybdenum enrichment and extraction; alternatively, molybdenum is enriched using extraction or ion exchange methods before vanadium separation. Taking molybdenum extraction as an example, the initial pH of the leachate is usually adjusted to around 2 using nitric acid, sulfuric acid, or hydrochloric acid, and then molybdenum is separated using amine extractants. The extraction efficiency of molybdenum is mainly affected by the complexing ability of the extractant at different pH values. When the solution pH is less than 1, Mo mainly exists as MoO2. 2+ It exists in the form of tertiary amine (alamine336), which is used to extract MoO2. 2+ The most efficient extractant.

[0004] CN105692698B discloses a method for efficient separation of vanadium and molybdenum under acidic conditions. By selectively reducing V(V) in solution to V(IV), the method utilizes the property that anion exchange resin or alkaline extractant can only selectively enrich Mo(IV) in solution and cannot adsorb V(IV) to achieve the separation of vanadium and molybdenum.

[0005] CN115852173A discloses a method for separating vanadium and molybdenum in an acidic solution. By reducing vanadium and molybdenum to a lower valence state under acidic conditions, and utilizing the selective complexation of metals with different valence states by organic amines, vanadium remains in the solution while molybdenum forms a precipitate in the form of a complex, thus achieving the separation of vanadium and molybdenum.

[0006] In summary, the separation process of vanadium and molybdenum requires the introduction of reducing agents, extractants / ion exchange resins, etc., resulting in a relatively complex composition of the system. In addition, after reducing Mo and V to low valence states for separation, they still need to be oxidized to high valence states again in the subsequent product preparation stage to obtain the target product, which is complicated and has low separation efficiency.

[0007] Therefore, it is necessary to develop a method for separating vanadium and molybdenum from acidic vanadium-containing molybdenum solutions and preparing high-purity vanadium products, so as to achieve efficient and clean separation of molybdenum. Summary of the Invention

[0008] To address the problems of existing technologies, such as the need to introduce too many third-party additives, complex operation, and insufficient separation depth, this invention provides a method for separating molybdenum during the preparation of high-purity vanadium products. For acidic vanadium-molybdenum leaching solutions, this method can achieve efficient and clean separation of vanadium and molybdenum without changing the valence states of vanadium and molybdenum, ultimately obtaining ammonium vanadate and separate molybdenum resources. Moreover, the medium can achieve internal circulation, making it clean and environmentally friendly.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] This invention provides a method for separating molybdenum during the preparation of high-purity vanadium products, the method comprising the following steps:

[0011] (1) Mix ammonium salt and acidic vanadium-molybdenum-containing solution, precipitate vanadium with ammonium salt, and obtain crude ammonium polyvanadate by solid-liquid separation;

[0012] (2) The crude ammonium polyvanadate product described in step (1) undergoes a molybdenum removal reaction under the action of organic acid, and is then separated into solid and liquid components to obtain a molybdenum-containing liquid and ammonium vanadate.

[0013] The method for separating molybdenum during the preparation of high-purity vanadium products provided by this invention is based on the following three main technical principles:

[0014] 1) In acidic vanadate-containing molybdenum solutions, vanadate ions react with H₂V 10 O 28 4- or VO2 + It exists in forms such as molybdate, and molybdate tends to react with oxidants during leaching to form MoO3(O2). 2- MoO2(O2)2 2- It exists in the form of peroxide anions.

[0015] 2) Ammonium salt precipitation of vanadium: MoO3(O2) 2- H₂MoO₅ enters the solid state as a solid;

[0016] 3) In acidic organic media, H₂MoO₅ is more reactive than ammonium polyvanadate. Under the catalysis of organic acids, it will rapidly undergo a disproportionation reaction and enter the solution, while (NH₄)₂V₆O₅... 16It still exists in the form of a precipitate, thus achieving effective separation of molybdenum and ammonium vanadate.

[0017] Preferably, the acidic vanadium-molybdenum-containing solution in step (1) is a solution obtained by sequentially oxidizing and roasting and acid leaching with vanadium source as raw material, and / or, the acidic vanadium-molybdenum-containing solution is a solution obtained by acid leaching with an oxidant with vanadium source as raw material.

[0018] As a preferred technical solution of the present invention, the vanadium source includes vanadium-containing shale and / or vanadium-molybdenum-containing waste catalyst.

[0019] Preferably, the concentration of V in the acidic vanadium-molybdenum-containing solution in step (1), calculated as V2O5, is 1 to 20 g / L. For example, it can be 1 g / L, 4 g / L, 6 g / L, 8 g / L, 10 g / L, 12 g / L, 14 g / L, 16 g / L, 18 g / L, or 20 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Preferably, the concentration of Mo in the acidic vanadium-molybdenum-containing solution is 0.01–5 g / L, for example, it can be 0.01 g / L, 0.57 g / L, 1.12 g / L, 1.68 g / L, 2.23 g / L, 2.79 g / L, 3.34 g / L, 3.9 g / L, 4.45 g / L or 5 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0021] Preferably, the pH value of the acidic vanadium-molybdenum-containing solution in step (1) is 2 to 6, for example, it can be 2, 2.5, 2.9, 3.4, 3.8, 4.3, 4.7, 5.2, 5.6 or 6, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Preferably, the ammonium salt in step (1) includes ammonium chloride and / or ammonium sulfate.

[0023] Preferably, the molar ratio of ammonium ions in the ammonium salt to vanadium in the acidic vanadium-molybdenum solution is (0.3 to 1):1, for example, it can be 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the temperature for vanadium precipitation with ammonium salt is 90-100°C, for example, 90°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C or 100°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the organic acid in step (1) includes any one or a combination of at least two of formic acid, acetic acid or oxalic acid, wherein typical but non-limiting combinations are combinations of formic acid and acetic acid, combinations of oxalic acid and acetic acid, and combinations of formic acid and oxalic acid.

[0026] This invention selects these acids as substances for the molybdenum removal reaction because they have the advantage of selectively reacting with the Mo entrained in ammonium vanadate to dissolve it, thereby achieving the separation of vanadium and molybdenum. Compared with inorganic acids such as hydrochloric acid, which dissolve molybdenum along with vanadium, these acids have poor selectivity and make it difficult to achieve effective separation of molybdenum and vanadium.

[0027] Preferably, the molar ratio of molybdenum in the organic acid and crude ammonium polyvanadate during the molybdenum removal reaction is (1-20):1, for example, it can be 1:1, 4:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1 or 20:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] Generally speaking, if the amount of organic acid added is too low, it is easy to cause incomplete removal of molybdenum. If the amount of organic acid added is too high, it is not only easy to waste organic acid, but also there is a problem of excessive organic acid reacting with vanadate and causing vanadium loss.

[0029] Preferably, the temperature of the molybdenum removal reaction in step (2) is 25 to 70°C, for example, it can be 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Preferably, the molybdenum removal reaction time is 30 minutes or more, for example, it can be 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, 70 minutes or 80 minutes, etc.

[0031] Preferably, the molybdenum-containing solution in step (2) is recycled to the molybdenum removal reaction as an organic acid, and molybdic acid is separated from the molybdenum-containing solution with the molybdenum concentration of the first concentration after the molybdenum concentration in the molybdenum-containing solution reaches the first concentration.

[0032] Preferably, the first concentration is 8 to 10 g / L, for example, it can be 8 g / L, 8.2 g / L, 8.5 g / L, 8.8 g / L, 9.0 g / L, 9.2 g / L, 9.5 g / L or 10 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the method further includes: the ammonium vanadate in step (2) is calcined to obtain a high-purity vanadium pentoxide product.

[0034] Preferably, the calcination temperature is 530 to 570°C, for example, 530°C, 540°C, 545°C, 550°C, 560°C, 565°C or 570°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the calcination time is 2 to 4 hours, for example, it can be 2 hours, 2.2 hours, 2.3 hours, 2.5 hours, 2.8 hours, 3.0 hours, 3.2 hours, 3.5 hours, 3.8 hours or 4.0 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] As a preferred technical solution of the present invention, the method includes the following steps:

[0037] (1) Mix ammonium salt and acidic vanadium-molybdenum-containing solution with a molar ratio of ammonium ions in ammonium salt to vanadium in acidic vanadium-molybdenum-containing solution of (0.3~1):1, and precipitate vanadium in ammonium salt at 90~100℃, and then obtain crude ammonium polyvanadate by solid-liquid separation;

[0038] (2) The crude ammonium polyvanadate in step (1) is subjected to a molybdenum removal reaction at 25-70°C for more than 30 minutes under the action of organic acid. The molar ratio of molybdenum in the organic acid and the crude ammonium polyvanadate is (1-20):1. After solid-liquid separation, molybdenum-containing liquid and ammonium vanadate are obtained.

[0039] The molybdenum-containing solution is recycled to the molybdenum removal reaction and used as an organic acid. After the molybdenum concentration in the molybdenum-containing solution reaches 8-10 g / L, molybdic acid is separated from the molybdenum-containing solution with a molybdenum concentration of 8-10 g / L.

[0040] (3) The ammonium vanadate described in step (2) is calcined at 530-570℃ for 2-4 hours to obtain a high-purity vanadium pentoxide product.

[0041] The present invention does not impose any special restrictions on the solid-liquid separation in the above process. Any device and method known to those skilled in the art for solid-liquid separation can be used. It can also be adjusted according to the actual process. For example, it can be filtration, centrifugation or sedimentation separation, or a combination of different methods.

[0042] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] (1) The method for separating molybdenum in the preparation of high-purity vanadium products provided by the present invention can achieve efficient separation of vanadium and molybdenum without changing the valence state of vanadium and molybdenum in the solution. The steps are simple and easy to operate. The recovery rate of vanadium is ≥98wt%, and high-purity vanadium pentoxide products with a purity of ≥99.5% can be obtained.

[0045] (2) The method for separating molybdenum in the preparation of high-purity vanadium products provided by the present invention has high vanadium-molybdenum separation efficiency and can control the molybdenum content in the final vanadium product to below 0.005%, preferably below 0.0035%;

[0046] (3) The molybdenum-containing liquid obtained by the method of separating molybdenum in the preparation of high-purity vanadium products provided by the present invention can be returned to the molybdenum removal reaction as a circulating liquid and used as an organic acid. After circulating to a certain concentration, the molybdenum in the solution is separated in the form of molybdic acid, realizing the internal circulation of the medium, generating no wastewater, and realizing the accumulation and recovery of molybdenum resources. Detailed Implementation

[0047] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0048] Example 1

[0049] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products, the method comprising the following steps:

[0050] (1) Mix an acidic vanadium-molybdenum-containing solution (the acidic vanadium-molybdenum-containing solution is a vanadium-molybdenum-containing acid leaching solution obtained by acid leaching after oxidative roasting of vanadium-molybdenum-containing raw materials, wherein the concentration of V2O5 in the solution is 20 g / L, the concentration of Mo is 2 g / L, and the pH value of the acidic vanadium-molybdenum-containing solution is 3) and ammonium chloride, and carry out ammonium salt precipitation of vanadium at 100℃, wherein the molar ratio of ammonium ions in ammonium chloride to vanadium in the acidic vanadium-molybdenum-containing solution is 1:1. After the ammonium salt precipitation of vanadium, filter, and obtain crude ammonium polyvanadate in the solid phase and molybdenum-containing mother liquor in the liquid phase;

[0051] (2) Mix the crude ammonium polyvanadate and acetic acid solution described in step (1), wherein the molar ratio of molybdenum in acetic acid and crude ammonium polyvanadate is 2:1, and carry out a molybdenum removal reaction at 70°C for 60 min. After the molybdenum removal reaction, filter to obtain a molybdenum-containing solution and ammonium vanadate.

[0052] The molybdenum-containing solution is recycled to the molybdenum removal reaction and used as an organic acid. After the molybdenum concentration in the molybdenum-containing solution reaches 10 g / L, molybdic acid is separated from the molybdenum-containing solution with a molybdenum concentration of 10 g / L.

[0053] (3) The ammonium vanadate in step (2) is calcined at 550°C for 2 hours to obtain a high-purity vanadium pentoxide product.

[0054] Example 2

[0055] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products, the method comprising the following steps:

[0056] (1) Mix an acidic vanadium-molybdenum-containing solution (the acidic vanadium-molybdenum-containing solution is a vanadium-molybdenum-containing acid leaching solution obtained by acid leaching after oxidative roasting of vanadium-molybdenum-containing raw materials, wherein the concentration of V2O5 in the solution is 5 g / L, the concentration of Mo is 1 g / L, and the pH value of the acidic vanadium-molybdenum-containing solution is 4) and ammonium sulfate, and carry out ammonium salt precipitation of vanadium at 100℃. The molar ratio of ammonium ions in ammonium sulfate to vanadium in the acidic vanadium-molybdenum-containing solution is 1:1. After the ammonium salt precipitation of vanadium, filter the solution to obtain crude ammonium polyvanadate in the solid phase and molybdenum-containing mother liquor in the liquid phase.

[0057] (2) Mix the crude ammonium polyvanadate and acetic acid solution in step (1), wherein the molar ratio of molybdenum in acetic acid and crude ammonium polyvanadate is 2:1, and carry out a molybdenum removal reaction at 40°C for 35 min. After the molybdenum removal reaction, filter to obtain a molybdenum-containing solution and ammonium vanadate.

[0058] The molybdenum-containing solution is recycled to the molybdenum removal reaction and used as an organic acid. After the molybdenum concentration in the molybdenum-containing solution reaches 8 g / L, molybdic acid is separated from the molybdenum-containing solution with a molybdenum concentration of 8 g / L.

[0059] (3) The ammonium vanadate in step (2) is calcined at 530°C for 3 hours to obtain a high-purity vanadium pentoxide product.

[0060] Example 3

[0061] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products, the method comprising the following steps:

[0062] (1) Mix an acidic vanadium-molybdenum-containing solution (the acidic vanadium-molybdenum-containing solution is a vanadium-molybdenum-containing acid leaching solution obtained by direct acid leaching with an oxidant, wherein the concentration of V2O5 in the solution is 40 g / L, the concentration of Mo is 10 g / L, and the pH value of the acidic vanadium-molybdenum-containing solution is 3) and ammonium chloride, and carry out ammonium salt precipitation of vanadium at 95°C. The molar ratio of ammonium ions in ammonium chloride to vanadium in the acidic vanadium-molybdenum-containing solution is 0.5:1. After the ammonium salt precipitation of vanadium, filter the solution to obtain crude ammonium polyvanadate in the solid phase and molybdenum-containing mother liquor in the liquid phase.

[0063] (2) Mix the crude ammonium polyvanadate and oxalic acid solution described in step (1), wherein the molar ratio of molybdenum in oxalic acid and crude ammonium polyvanadate is 8:1, and carry out a molybdenum removal reaction at 50°C for 45 min. After the molybdenum removal reaction, filter to obtain a molybdenum-containing solution and ammonium polyvanadate.

[0064] The molybdenum-containing solution is recycled to the molybdenum removal reaction and used as an organic acid. After the molybdenum concentration in the molybdenum-containing solution reaches 10 g / L, molybdic acid is separated from the molybdenum-containing solution with a molybdenum concentration of 10 g / L.

[0065] (3) The ammonium vanadate in step (2) is calcined at 570°C for 1.5 hours to obtain a high-purity vanadium pentoxide product.

[0066] Example 4

[0067] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products. The only difference between this method and Embodiment 1 is that the concentration of V2O5 in the acidic vanadium-molybdenum-containing solution is changed to 30 g / L and the concentration of Mo is 0.1 g / L.

[0068] Example 5

[0069] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products. The only difference between this method and Embodiment 1 is that the concentration of V2O5 in the acidic vanadium-molybdenum-containing solution is changed to 35 g / L and the concentration of Mo is 20 g / L.

[0070] Example 6

[0071] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products. The only difference between this method and Embodiment 1 is that the pH value of the vanadium-molybdenum-containing solution in step (1) is 6.

[0072] Example 7

[0073] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products. The only difference between this method and Embodiment 1 is that in step (2), the acetic acid solution is replaced with an equal amount of formic acid solution.

[0074] Example 8

[0075] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products. The only difference between this method and that in Embodiment 1 is that the acetic acid solution in step (2) is replaced with an equal amount of oxalic acid solution.

[0076] Example 9

[0077] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products. The only difference between this method and Example 1 is that the molar ratio of molybdenum in the crude acetic acid and ammonium polyvanadate is 22:1.

[0078] Example 10

[0079] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products. The only difference between this method and Example 1 is that the molar ratio of molybdenum in the crude acetic acid and ammonium polyvanadate is 0.5:1.

[0080] Comparative Example 1

[0081] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products. The only difference between this method and Example 1 is that the pH value of the acidic vanadium-molybdenum-containing solution in step (1) is adjusted to 8 in this comparative example.

[0082] Comparative Example 2

[0083] This embodiment provides a method for separating molybdenum during the preparation of high-purity vanadium products. The difference between this method and that in Example 1 is that the acetic acid solution is replaced with hydrochloric acid solution in this comparative example.

[0084] The vanadium and molybdenum contents of the high-purity vanadium pentoxide obtained in Examples 1-10 and Comparative Examples 1-2 were determined by ICP method, and the vanadium recovery rate was calculated based on the mass of vanadium pentoxide and the vanadium content. The results are shown in Table 1.

[0085] Table 1

[0086] Example 1 99.5 99.5568 0.0032 Example 2 98 99.5665 0.0035 Example 3 98.1 99.6373 0.0027 Example 4 98.3 99.6078 0.0022 Example 5 99.6 99.655 0.0015 Example 6 94.5 99.5054 0.0046 Example 7 99.5 99.5367 0.0033 Example 8 99.5 99.4892 0.0049 Example 9 99.5 99.5474 0.0026 Example 10 99.3 99.5352 0.0048 Comparative Example 1 55.4 99.429 0.21 Comparative Example 2 67.9 99.482 0.10

[0087] The following points can be observed from Table 1:

[0088] (1) As can be seen from the comprehensive examples 1 to 3, the method for preparing high-purity vanadium pentoxide using acidic vanadium-molybdenum solution as raw material provided by the present invention can effectively recover vanadium from acidic vanadium-molybdenum solution, with a vanadium recovery rate ≥98wt%, and can obtain high-purity vanadium pentoxide product with a purity of ≥99.5%, and Mo content in vanadium pentoxide ≤0.0035%.

[0089] (2) Combining Example 1 and Comparative Example 1, it can be seen that the pH of the vanadium-containing leaching solution in Comparative Example 1 was adjusted to 8. Compared with the pH of the vanadium-containing leaching solution in Example 1, which was adjusted to 3, the recovery rate of ammonium vanadate in Comparative Example 1 was only 55.4%, and the Mo content in the vanadium pentoxide product was 0.21%. In contrast, the recovery rate of ammonium vanadate in Example 1 was 99.5%, and the Mo content in the product was 0.0032%. This shows that controlling the pH of the vanadium-containing leaching solution within a specific range in Example 1 can significantly improve the recovery rate of vanadium and reduce the Mo content in the ammonium vanadate product.

[0090] (3) It can be seen from the combined examples 1 and 9-10 that in example 1, the molar ratio of acetic acid to molybdenum is 2:1 and the Mo content in V2O5 is 0.0032%, while in examples 9-10, the molar ratio of acetic acid to molybdenum is 20:1 and 0.5:1, and the Mo content in V2O5 is 0.0026% and 0.0048%, respectively. Moreover, a lot of acetic acid was wasted in example 9. This shows that by further controlling the molar ratio of acetic acid to molybdenum within a specific range, the present invention is beneficial to reducing the Mo content in ammonium vanadate products and can save the amount of acetic acid used.

[0091] (4) As can be seen from the combined results of Example 1, Comparative Example 2 and Example 8, acetic acid was used for purification in Example 1. Compared with hydrochloric acid in Comparative Example 2 and oxalic acid solution in Example 8, the Mo content in V2O5 in Example 1 was 0.0032% and the vanadium recovery rate was as high as 99.5%. In contrast, the Mo content in Example 8 was 0.0049% and the Mo content in Comparative Example 2 was as high as 0.10% and the vanadium recovery rate was only 67.9%. This shows that the present invention significantly improves the purity of the final vanadium pentoxide product and reduces its Mo content by selecting a specific acid for the molybdenum removal reaction.

[0092] In summary, the method for separating molybdenum during the preparation of high-purity vanadium products provided by this invention can achieve efficient separation of vanadium and molybdenum without changing the valence states of vanadium and molybdenum in the solution. The steps are simple and easy to operate. The vanadium-molybdenum separation efficiency is high, and the molybdenum content in the final ammonium vanadate product can be controlled below 0.005%. The vanadium recovery rate is ≥98wt%, and a high-purity vanadium pentoxide product with a purity of over 99.5% can be obtained. The molybdenum-containing solution can be returned to the purification process as a circulating liquid for continued use. After circulating to a certain concentration, the molybdenum in the solution is separated in the form of molybdic acid, realizing internal circulation of the medium and generating no wastewater.

[0093] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for separating molybdenum during the preparation of high-purity vanadium products, characterized in that, The method includes the following steps: (1) Mix ammonium salt and acidic vanadium-molybdenum-containing solution to precipitate vanadium with ammonium salt. The precipitation temperature of ammonium salt vanadium is 90~100℃. After solid-liquid separation, crude ammonium polyvanadate is obtained. The acidic vanadium-molybdenum-containing solution is a solution obtained by acid leaching with an oxidant using vanadium source as raw material. In the acidic vanadium-molybdenum-containing solution, molybdenum exists in the form of peroxy acid ions; (2) The crude ammonium polyvanadate in step (1) undergoes a molybdenum removal reaction under the action of organic acid, and is then separated into solid and liquid components to obtain a molybdenum-containing liquid and ammonium vanadate; the organic acid includes any one or a combination of at least two of formic acid, acetic acid or oxalic acid; the molar ratio of molybdenum in the organic acid and the crude ammonium polyvanadate in the molybdenum removal reaction is (1~20):1; The ammonium vanadate in step (2) is calcined to obtain a high-purity vanadium pentoxide product.

2. The method according to claim 1, characterized in that, The vanadium source mentioned in step (1) includes vanadium-containing shale and / or vanadium-molybdenum-containing spent catalyst.

3. The method according to claim 1 or 2, characterized in that, The concentration of V, calculated as V₂O₅, in the acidic vanadium-molybdenum-containing solution described in step (1) is 1~20 g / L; The concentration of Mo in the acidic vanadium-molybdenum-containing solution is 0.01~5 g / L.

4. The method according to claim 1 or 2, characterized in that, The pH value of the acidic vanadium-molybdenum-containing solution in step (1) is 2 to 6.

5. The method according to claim 1 or 2, characterized in that, The ammonium salt mentioned in step (1) includes ammonium chloride and / or ammonium sulfate; The molar ratio of ammonium ions in the ammonium salt to vanadium in the acidic vanadium-molybdenum solution is (0.3~1):

1.

6. The method according to claim 1 or 2, characterized in that, The temperature for the molybdenum removal reaction in step (2) is 25~70℃; The molybdenum removal reaction takes more than 30 minutes.

7. The method according to claim 1 or 2, characterized in that, In step (2), the molybdenum-containing solution is recycled to the molybdenum removal reaction and used as an organic acid. After the molybdenum concentration in the molybdenum-containing solution reaches the first concentration, molybdic acid is separated from the molybdenum-containing solution with the first molybdenum concentration. The first concentration is 8~10g / L.

8. The method according to claim 1 or 2, characterized in that, The method further includes: The calcination temperature is 530~570℃; The calcination time is 2-4 hours.

9. The method according to claim 1 or 2, characterized in that, The method includes the following steps: (1) Mix ammonium salt and acidic vanadium-molybdenum-containing solution with a molar ratio of ammonium ions in ammonium salt to vanadium in acidic vanadium-molybdenum-containing solution of (0.3~1):1, precipitate vanadium in ammonium salt at 90~100℃, and then obtain crude ammonium polyvanadate by solid-liquid separation; (2) The crude ammonium polyvanadate in step (1) is subjected to a molybdenum removal reaction at 25~70℃ for more than 30 minutes under the action of organic acid. The molar ratio of molybdenum in the organic acid and the crude ammonium polyvanadate is (1~20):

1. After solid-liquid separation, molybdenum-containing liquid and ammonium vanadate are obtained. The molybdenum-containing solution is recycled to the molybdenum removal reaction and used as an organic acid. After the molybdenum concentration in the molybdenum-containing solution reaches 8~10 g / L, molybdic acid is separated from the molybdenum-containing solution with a molybdenum concentration of 8~10 g / L. (3) The ammonium vanadate in step (2) is calcined at 530~570℃ for 2~4h to obtain high-purity vanadium pentoxide product.