Method for separating molybdenum in the preparation process of high-purity ammonium vanadate

Abstract

The application provides a method for separating molybdenum in the preparation process of high-purity ammonium vanadate, which comprises the following steps: (1) a vanadium-containing leaching solution is subjected to pH adjustment and oxidation reaction in sequence to obtain an oxidized solution; (2) ammonium salt is mixed with the oxidized solution in step (1) to carry out vanadium precipitation by ammonium salt, and solid-liquid separation is carried out to obtain crude ammonium polyvanadate; (3) the crude ammonium polyvanadate in step (2) is subjected to a purification reaction by an organic acid, and solid-liquid separation is carried out to obtain a molybdenum-containing solution and a high-purity ammonium vanadate product. The method can control the molybdenum content in ammonium vanadate to be less than 0.005%, and the molybdenum resource can be recycled in the form of molybdic acid, the internal circulation of the medium is realized, no wastewater is generated, the method can be carried out at normal pressure and low temperature, and is easy to be industrialized.

Description

Technical Field

[0001] The present invention relates to the technical field of vanadium products, and particularly to a method for separating molybdenum during the preparation of high-purity ammonium metavanadate. Background Art

[0002] Vanadium is an important strategic metal. Due to its excellent physical and chemical properties such as high hardness, oxidation resistance, fatigue resistance, and multi-valent redox reaction characteristics, it is widely used in fields such as steel, chemical industry, aerospace, and new energy, and is known as the "vitamin of modern industry" and the "future energy material". V2O5 with a purity of 98% is the current mainstream industrial-grade vanadium product. High-purity V2O5 refers to vanadium pentoxide products with a purity above 99%, which are mainly used in all-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 is similar in properties to vanadium. In natural vanadium-containing minerals, vanadium and molybdenum easily coexist. Especially in secondary vanadium-containing resources such as waste HDS catalysts, vanadium and molybdenum are usually recovered as valuable resources. After being extracted into the solution through processes such as sodium roasting - water leaching or acid leaching, vanadium and molybdenum are then separated to obtain separate products of vanadium and molybdenum. Since the molybdenum content requirement in some high-purity vanadium products is relatively high, trace molybdenum is often difficult to separate, which easily causes the product quality to fail to meet the standards. The methods for separating and recovering vanadium and molybdenum usually utilize the solubility differences of ammonium metavanadate and ammonium molybdate under specific pH conditions. First, vanadium is precipitated by ammonium salts, and then molybdenum is enriched and extracted; or molybdenum is first enriched by extraction or ion exchange methods, and then vanadium is separated. Taking the extraction of molybdenum as an example, usually, the initial pH value of the leaching solution is adjusted to about 2 with nitric acid, sulfuric acid, or hydrochloric acid, and then an amine extractant is used to separate molybdenum. The extraction efficiency of molybdenum is mainly affected by the complexing ability of the extractant at different pH values. When the solution pH value is less than 1, Mo mainly exists in the form of MoO2 2+ , and tertiary amine (alamine336) is the most efficient extractant for extracting MoO2 2+ . In addition, within the weak alkaline range (8 < pH < 9), Aliquat336 can be used to extract vanadium from molybdenum ion solutions. AG1-x8 resin can be used to recover 98% of Mo and 95% of V respectively, and the metal-loaded resin is eluted with NaOH. The purity of the eluted V and Mo solutions is as high as 99%. Finally, AG1-x8 can be regenerated by converting from hydroxide to chloride form.

[0004] CN1062785A discloses a method for deep removal of vanadium from vanadium-molybdate using a strongly alkaline resin. Patent CN105692698B discloses a method for efficient separation of vanadium and molybdenum under acidic conditions. This method selectively reduces V(V) in solution to V(IV), utilizing the property that anion exchange resins or alkaline extractants can only selectively enrich Mo(IV) in solution and cannot adsorb V(IV), thus achieving 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 vanadium-molybdenum separation process requires the introduction of reducing agents, extractants / ion exchange resins, etc., resulting in a complex system composition. Furthermore, reducing Mo and V to lower valence states for separation necessitates re-oxidation to higher valence states in subsequent product preparation stages, leading to complex operations and low separation efficiency. Therefore, it is necessary to develop a method for separating molybdenum during the preparation of high-purity ammonium vanadate, achieving efficient and clean separation of molybdenum. Summary of the Invention

[0007] 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 ammonium vanadate. This method achieves efficient and clean separation of vanadium and molybdenum without changing the valence states of vanadium and molybdenum, ultimately obtaining high-purity ammonium vanadate product and separate molybdenum resources. Furthermore, the medium can achieve internal circulation, making it clean and environmentally friendly.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for separating molybdenum during the preparation of high-purity ammonium vanadate, the method comprising the following steps:

[0010] (1) The vanadium-containing leachate was subjected to pH adjustment and oxidation reaction in sequence to obtain the oxidized solution;

[0011] (2) Mix the ammonium salt and the oxidized liquid from step (1) to precipitate vanadium with ammonium salt, and obtain crude ammonium polyvanadate by solid-liquid separation;

[0012] (3) The crude ammonium polyvanadate described in step (2) is purified by an organic acid reaction and then separated by solid-liquid separation to obtain a molybdenum-containing liquid and a high-purity ammonium vanadate product.

[0013] The method for separating molybdenum in the preparation of high-purity ammonium vanadate provided by this invention involves complexing molybdate ions in vanadium-containing leachate into peroxymolybdate ions. The peroxymolybdate ions are then hydrolyzed to generate peroxymolybdic acid, which enters the crude ammonium polyvanadate solid phase. This peroxymolybdate then reacts with an organic acid to enter the liquid phase, achieving efficient separation of molybdenum and vanadium. The reaction equation is as follows:

[0014] MoO4 2- +H₂O₂=MoO₃(O₂) 2- +H2O

[0015] MoO3(O2) 2- +H + =H2MoO5↓

[0016] H2MoO5+2H + =Mo 2+ +2O2↑+H2O

[0017] The technical principle of the method for separating molybdenum during the preparation of high-purity ammonium vanadate provided by this invention is mainly based on the following three points:

[0018] 1) Adding an oxidant to an acidic medium can effectively complex and oxidize molybdate. In solutions with low peroxy ligand concentrations, polymolybdate can be converted into the corresponding peroxy complex.

[0019] 2) In acidic media, peroxymolybdate has low solubility at high temperatures and will combine with H+. + It precipitates as H2MoO5;

[0020] 3) In acidic 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... 16 It still exists in the form of a precipitate, thus achieving effective separation of molybdenum and ammonium vanadate.

[0021] Preferably, the vanadium-containing leachate in step (1) is a vanadium-containing leachate obtained by sequentially subjecting a vanadium source to sodium roasting and water leaching processes.

[0022] Preferably, the vanadium source includes any one or a combination of at least two of vanadium slag, vanadium-titanium magnetite, or vanadium-containing waste catalyst, wherein typical but non-limiting combinations are the combination of vanadium slag and vanadium-titanium magnetite, the combination of vanadium-containing waste catalyst and vanadium-titanium magnetite, and the combination of vanadium slag and vanadium-containing waste catalyst.

[0023] Preferably, the concentration of V in the vanadium-containing leachate in step (1), calculated as V2O5, is 2 to 40 g / L. For example, it can be 2 g / L, 7 g / L, 11 g / L, 15 g / L, 19 g / L, 24 g / L, 28 g / L, 32 g / L, 36 g / L, or 40 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the Mo concentration in the vanadium-containing leachate 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.

[0025] Preferably, the pH value after pH adjustment in step (1) is 2 to 6, for example, it can be 2, 3, 4, 5 or 6, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0026] Preferably, the pH adjusting agent includes sulfuric acid and / or hydrochloric acid.

[0027] Preferably, the oxidant in the oxidation reaction includes a peroxide.

[0028] Preferably, the peroxide comprises hydrogen peroxide and / or sodium peroxide.

[0029] Preferably, the molar ratio of peroxide ions in the oxidant to molybdenum in the vanadium-containing leachate is (1-10):1, for example, it can be 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] In this invention, the molar ratio of peroxide ions in the oxidant to molybdenum in the vanadium-containing leachate has a significant impact on the molybdenum content in ammonium vanadate. By optimally controlling the molar ratio of peroxide ions in the oxidant to molybdenum in the vanadium-containing leachate within the above-mentioned range, this invention significantly improves the purity of ammonium vanadate.

[0031] Preferably, the oxidation reaction in step (1) is carried out under stirring conditions.

[0032] Preferably, the stirring speed in the oxidation reaction is 100 to 400 r / min, for example, it can be 100 r / min, 135 r / min, 165 r / min, 200 r / min, 235 r / min, 260 r / min, 300 r / min, 330 r / min, 360 r / min or 400 r / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the temperature of the oxidation reaction is 30 to 70°C, for example, 30°C, 35°C, 39°C, 44°C, 48°C, 53°C, 57°C, 62°C, 66°C or 70°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the ammonium salt in step (2) includes ammonium chloride and / or ammonium sulfate.

[0035] Preferably, the molar ratio of ammonium ions in the ammonium salt to vanadium in the oxidized solution is (0.3 to 1):1, for example, it can be 0.3:1, 0.38:1, 0.46:1, 0.54:1, 0.62:1, 0.69:1, 0.77:1, 0.85:1, 0.93:1 or 1:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] 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.

[0037] Preferably, the organic acid in step (3) 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.

[0038] This invention selects these acids as purifying agents for the purification reaction, which have the advantage of selectively reacting with Mo in ammonium vanadate to dissolve and thus achieve the separation of vanadium and molybdenum. Compared with inorganic acids such as hydrochloric acid, which dissolve molybdenum at the same time as vanadium, the selectivity is poor and it is difficult to achieve the separation of vanadium and molybdenum.

[0039] Preferably, the molar ratio of molybdenum in the organic acid and crude ammonium polyvanadate in the purification 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.

[0040] 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.

[0041] Preferably, the temperature of the purification reaction in step (3) 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.

[0042] Preferably, the purification reaction time is 30 min or more, for example, it can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 70 min or 80 min, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, the molybdenum-containing solution in step (3) is recycled to the purification 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.

[0044] Preferably, the first concentration is 8 to 10 g / L, for example, it can be 8 g / L, 8.5 g / L, 8.8 g / L, 9 g / L, 9.2 g / L, 9.5 g / L, 9.8 g / L or 10 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] As a preferred technical solution of the present invention, the method includes the following steps:

[0046] (1) The pH of the vanadium-containing leachate is adjusted to 2-6, and an oxidant is added. The molar ratio of peroxide ions in the oxidant to molybdenum in the vanadium-containing leachate is (1-10):1. The oxidation reaction is carried out at 100-400 r / min and 30-70℃ to obtain the oxidized solution.

[0047] (2) Mix ammonium salt and the oxidized solution described in step (1) at a molar ratio of ammonium ions in ammonium salt to vanadium in the oxidized 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;

[0048] (3) The crude ammonium polyvanadate in step (2) is purified by organic acid at 25-70℃ for more than 30 minutes. The molar ratio of molybdenum in organic acid and crude ammonium polyvanadate is (1-20):1. After solid-liquid separation, molybdenum-containing liquid and high-purity ammonium vanadate product are obtained.

[0049] The molybdenum-containing solution is recycled to the purification 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.

[0050] 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.

[0051] 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.

[0052] Compared with the prior art, the present invention has at least the following beneficial effects:

[0053] (1) The method for separating molybdenum during the preparation of high-purity ammonium vanadate 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.

[0054] (2) The method for separating molybdenum in the preparation of high-purity ammonium vanadate provided by the present invention has high vanadium-molybdenum separation efficiency, can control the molybdenum content in the final ammonium vanadate product to below 0.005%, preferably below 0.0034%, the purity of ammonium vanadate to above 99.5%, and the vanadium recovery rate to above 97%.

[0055] (3) The molybdenum-containing liquid obtained by the method of separating molybdenum in the preparation of high-purity ammonium vanadate provided by the present invention can be returned to the purification 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, without the generation of wastewater, and realizing the accumulation and recovery of molybdenum resources. Detailed Implementation

[0056] 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.

[0057] Example 1

[0058] This embodiment provides a method for separating molybdenum during the preparation of high-purity ammonium vanadate, the method comprising the following steps:

[0059] (1) The vanadium-containing leachate (with a V2O5 concentration of 20 g / L and a Mo concentration of 0.5 g / L) obtained by sodium roasting-water leaching of vanadium slag as raw material was adjusted to pH 2, and hydrogen peroxide was added. The amount of hydrogen peroxide added was: the molar ratio of peroxide ions in the oxidant to molybdenum in the vanadium-containing leachate was 4:1. The oxidation reaction was carried out at a speed of 300 rpm and a reaction temperature of 70 °C to obtain the oxidized liquid.

[0060] (2) Add ammonium sulfate to the oxidized solution in step (1) and precipitate vanadium with ammonium salt at 95°C. The molar ratio of ammonium ions in ammonium sulfate to vanadium in the oxidized solution is 0.5:1. After precipitating vanadium with ammonium salt, filter the solution to obtain crude ammonium polyvanadate as the solid phase.

[0061] (3) The crude ammonium polyvanadate obtained in step (2) is purified in an acetic acid solution. The molar ratio of molybdenum in the acetic acid to that in the crude ammonium polyvanadate is 10:1. The purification reaction temperature is 70℃, and the purification reaction time is 1 hour. After purification, the mixture is filtered to obtain a molybdenum-containing solution and a high-purity ammonium vanadate product. The molybdenum-containing solution is recycled back to the purification reaction as an organic acid. After the molybdenum concentration in the molybdenum-containing solution reaches 8.5 g / L, molybdic acid is separated from the molybdenum-containing solution with a molybdenum concentration of 8.5 g / L.

[0062] Example 2

[0063] This embodiment provides a method for separating molybdenum during the preparation of high-purity ammonium vanadate, the method comprising the following steps:

[0064] (1) Vanadium-titanium magnetite was used as raw material and subjected to sodium roasting-water leaching process to obtain vanadium-containing leachate (solution V2O5 concentration is 2g / L, Mo concentration is 0.1g / L). The pH value was adjusted to 4, and hydrogen peroxide was added. The amount of hydrogen peroxide added was: the molar ratio of peroxide ions to molybdenum in vanadium-containing leachate was 8:1. Oxidation reaction was carried out at 400rpm and 60℃ to obtain oxidized solution.

[0065] (2) Add ammonium chloride to the oxidized liquid in step (1) and carry out ammonium salt precipitation of vanadium at 95°C. The reaction temperature is 100°C. The molar ratio of ammonium ions in ammonium sulfate to vanadium in the oxidized liquid is 1:1. After the ammonium salt precipitation of vanadium, filter to obtain crude ammonium polyvanadate as the solid phase.

[0066] (3) The crude ammonium polyvanadate obtained in step (2) is purified in an acetic acid solution. The molar ratio of molybdenum in the acetic acid to that in the crude ammonium polyvanadate is 20:1. The purification reaction temperature is 40℃, and the purification reaction time is at least 30 minutes. After purification, the mixture is filtered to obtain a molybdenum-containing solution and a high-purity ammonium vanadate product. The molybdenum-containing solution is recycled back to the purification reaction as an organic acid. After the molybdenum concentration in the molybdenum-containing solution reaches 9 g / L, molybdic acid is separated from the molybdenum-containing solution with a molybdenum concentration of 9 g / L.

[0067] Example 3

[0068] This embodiment provides a method for separating molybdenum during the preparation of high-purity ammonium vanadate, the method comprising the following steps:

[0069] (1) The vanadium-containing waste catalyst was used as raw material and subjected to sodium roasting-water leaching process to obtain vanadium-containing leachate (the concentration of V2O5 in the solution is 30g / L and the concentration of Mo is 5g / L). The pH value was adjusted to 3, and hydrogen peroxide was added. The amount of hydrogen peroxide added was: the molar ratio of peroxide ions to molybdenum in the vanadium-containing leachate was 5:1. The oxidation reaction was carried out at a speed of 300rpm and a reaction temperature of 50℃ to obtain the oxidized solution.

[0070] (2) Add ammonium sulfate and other ammonium salts to the oxidized liquid in step (1) and precipitate vanadium with ammonium salts at 95°C. The molar ratio of ammonium ions in ammonium sulfate to vanadium in the oxidized liquid is 0.8:1. After precipitating vanadium with ammonium salts, filter the solution to obtain a solid phase of crude ammonium polyvanadate.

[0071] (3) The crude ammonium polyvanadate obtained in step (2) is purified in oxalic acid solution. The molar ratio of molybdenum in oxalic acid and crude ammonium polyvanadate is 8:1. The purification reaction temperature is 70℃ and the purification reaction time is more than 30 min. After purification reaction, the mixture is filtered to obtain molybdenum-containing liquid and high-purity ammonium vanadate product. The molybdenum-containing liquid is recycled to the purification reaction as an organic acid. After the molybdenum concentration in the molybdenum-containing liquid reaches 10 g / L, molybdic acid is separated from the molybdenum-containing liquid with a molybdenum concentration of 10 g / L.

[0072] Example 4

[0073] This embodiment provides a method for separating molybdenum during the preparation of high-purity ammonium vanadate. The only difference between this method and Embodiment 1 is that the pH value of the solution in step (1) is adjusted to 6 in this embodiment.

[0074] Example 5

[0075] This embodiment provides a method for separating molybdenum during the preparation of high-purity ammonium vanadate. The only difference between this method and Embodiment 1 is that in this embodiment, the amount of hydrogen peroxide added in step (1) is such that the molar ratio of peroxide ions to molybdenum is 20:1.

[0076] Example 6

[0077] This embodiment provides a method for separating molybdenum during the preparation of high-purity ammonium vanadate. The only difference between this method and Embodiment 1 is that in this embodiment, the amount of hydrogen peroxide added in step (1) is such that the molar ratio of peroxide ions to molybdenum is 1:1.

[0078] Example 7

[0079] This embodiment provides a method for separating molybdenum during the preparation of high-purity ammonium vanadate. The only difference between this method and that in Embodiment 1 is that in step (3) of this embodiment, the acetic acid solution is replaced with an equal amount of formic acid solution.

[0080] Example 8

[0081] This embodiment provides a method for separating molybdenum during the preparation of high-purity ammonium vanadate. The only difference between this method and that in Embodiment 1 is that the acetic acid solution in step (3) of this embodiment is replaced with an equal amount of oxalic acid solution.

[0082] Example 9

[0083] This embodiment provides a method for separating molybdenum during the preparation of high-purity ammonium vanadate. The only difference between this method and Example 1 is that the molar ratio of molybdenum in acetic acid and crude ammonium polyvanadate in this embodiment is 20:1.

[0084] Example 10

[0085] This embodiment provides a method for separating molybdenum during the preparation of high-purity ammonium vanadate. The only difference between this method and Example 1 is that the molar ratio of molybdenum in acetic acid and crude ammonium polyvanadate in this embodiment is 1:1.

[0086] Comparative Example 1

[0087] This comparative example provides a method for separating molybdenum during the preparation of ammonium vanadate. The only difference between this method and Example 1 is that the vanadium-containing leaching solution in step (1) of this comparative example does not undergo an oxidation reaction and directly enters the ammonium salt precipitation step in step (2).

[0088] Comparative Example 2

[0089] This comparative example provides a method for separating molybdenum during the preparation of ammonium vanadate. The only difference between this method and Example 1 is that the pH value of the vanadium-containing leaching solution in step (1) is adjusted to 8.

[0090] Comparative Example 3

[0091] This comparative example provides a method for separating molybdenum during the preparation of ammonium vanadate. The only difference between this method and Example 1 is that the pH value of the vanadium-containing leaching solution in step (1) is adjusted to 1.

[0092] Comparative Example 4

[0093] This comparative example provides a method for separating molybdenum during the preparation of ammonium vanadate. The only difference between this method and Example 1 is that the acetic acid solution in step (3) is replaced with hydrochloric acid solution in this comparative example.

[0094] The ammonium vanadates obtained in Examples 1-10 and Comparative Examples 1-4 were tested for vanadium and molybdenum content using the ICP method. The vanadium recovery rate was calculated based on the mass of ammonium vanadate and its vanadium content, the volume of vanadium-containing leachate and its vanadium concentration. The results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] The following points can be observed from Table 1:

[0099] (1) As can be seen from the comprehensive examples 1 to 3, the method for separating molybdenum in the preparation process of high-purity ammonium vanadate provided by the present invention can effectively remove molybdenum in the process of preparing ammonium vanadate from vanadium-containing solution. The Mo content in the high-purity ammonium vanadate product is ≤0.0034%, and the purity of ammonium vanadate is above 99.5%, and the vanadium recovery rate is above 97%.

[0100] (2) It can be seen from the combined results of Examples 1 and 4 that the pH value of the vanadium-containing leachate in Example 1 is 2, compared with the pH value of 6 in Example 4. The Mo content in the ammonium vanadate product in Example 1 is 0.003%; while the Mo content in the ammonium vanadate product in Example 4 is 0.0047%. This shows that by further controlling the pH of the vanadium-containing leachate within a specific range, the present invention is beneficial to reducing the Mo content in the ammonium vanadate product.

[0101] (3) Combining Examples 1 and Examples 9-10, it can be seen that the molar ratio of acetic acid to molybdenum in Example 1 is 10:1. Compared with the molar ratios of acetic acid to molybdenum in Examples 9-10, which are 20:1 and 1:1 respectively, the Mo content in the ammonium vanadate product in Example 1 is 0.003%; while the Mo content in the ammonium vanadate product in Example 10 is 0.0045%, and the Mo content in Example 9 is not significantly increased. This indicates that by further controlling the molar ratio of organic acid to molybdenum within a specific range, the present invention is beneficial to reducing the Mo content in the ammonium vanadate product and reducing the amount of acid used.

[0102] (4) It can be seen from the combined results of Example 1 and Comparative Example 1 that the vanadium-containing leachate in Comparative Example 1 does not undergo complexation oxidation conversion reaction. Compared with the vanadium-containing leachate in Example 1, which undergoes complexation oxidation conversion reaction, the Mo content in the ammonium vanadate product in Comparative Example 1 is 0.24%, while the Mo content in the ammonium vanadate product in Example 1 is 0.003%. This shows that the vanadium-containing leachate in Example 1, through the combination of pH adjustment and oxidation conversion reaction, can significantly reduce the Mo content in the ammonium vanadate product.

[0103] (5) Combining Example 1 and Comparative Example 2, it can be seen that in Comparative Example 2, the pH of the vanadium-containing leachate was adjusted to 8. Compared with Example 1, where the pH of the vanadium-containing leachate was adjusted to 2, the Mo content in the ammonium vanadate product in Comparative Example 2 was 0.21%, while the Mo content in the ammonium vanadate product in Example 1 was 0.003%. This indicates that controlling the pH of the vanadium-containing leachate within a specific range in Example 1 can significantly reduce the Mo content in the ammonium vanadate product. Furthermore, if the pH is too low, insufficient vanadium precipitation occurs during the ammonium salt precipitation process, resulting in a low subsequent vanadium recovery rate.

[0104] (6) Combining Example 1 and Comparative Example 3, it can be seen that in Comparative Example 3, the pH of the vanadium-containing leachate was adjusted to 1, compared to the pH of the vanadium-containing leachate in Example 1, which was adjusted to 2. The Mo content in the ammonium vanadate product in Comparative Example 3 was 0.19%, while the Mo content in the ammonium vanadate product in Example 1 was 0.003%. This indicates that controlling the pH of the vanadium-containing leachate within a specific range in Example 1 can significantly reduce the Mo content in the ammonium vanadate product. Furthermore, if the pH is too high, insufficient vanadium precipitation occurs during the ammonium salt precipitation process, resulting in a low subsequent vanadium recovery rate.

[0105] (7) As can be seen from the combined results of Examples 1 and 8 and Comparative Example 4, acetic acid was used for purification in Example 1. Compared with oxalic acid in Example 8 and hydrochloric acid in Comparative Example 4, the Mo content in the ammonium vanadate product in Example 1 was 0.003%, and the vanadium recovery rate was as high as 98%. In contrast, the Mo content in the ammonium vanadate product in Example 8 was 0.0048%, and the vanadium recovery rate was slightly lower. In Comparative Example 4, the Mo content in the ammonium vanadate product was as high as 0.1%, and the vanadium recovery rate was only 68%. Moreover, the hydrochloric acid used in Comparative Example 4 was difficult to recycle. This shows that the method for separating molybdenum in the preparation of high-purity ammonium vanadate provided by the present invention, by selecting a specific organic acid for purification reaction, not only further reduces the Mo content in the ammonium vanadate product, but also significantly improves the vanadium recovery rate. In summary, the method for separating molybdenum during the preparation of high-purity ammonium vanadate provided by this invention can control the molybdenum content in the final ammonium vanadate product to below 0.005%, preferably below 0.0034%. Moreover, 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. It can be carried out at normal pressure and low temperature, and is easy to industrialize.

[0106] 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 ammonium vanadate, characterized in that, The method includes the following steps: (1) The vanadium-containing leachate is subjected to pH adjustment to pH 2-6 and oxidation reaction to obtain an oxidized solution; the oxidant in the oxidation reaction includes peroxide; the peroxide includes hydrogen peroxide; the molar ratio of peroxide ions in the oxidant to molybdenum in the vanadium-containing leachate is (1-10):1; (2) Mix the ammonium salt and the oxidized liquid from step (1) to precipitate vanadium with ammonium salt. The precipitation temperature of the ammonium salt vanadium is 90~100℃, and crude ammonium polyvanadate is obtained by solid-liquid separation. (3) The crude ammonium polyvanadate in step (2) is purified by an organic acid reaction and then separated by solid-liquid separation to obtain a molybdenum-containing liquid and a high-purity ammonium vanadate product; the organic acid includes any one or a combination of at least two of formic acid, acetic acid or oxalic acid.

2. The method according to claim 1, characterized in that, The vanadium-containing leaching solution in step (1) is a vanadium-containing leaching solution obtained by sequentially subjecting a vanadium source to sodium roasting and water leaching processes. The vanadium source includes any one or a combination of at least two of vanadium slag, vanadium-titanium magnetite, or vanadium-containing waste catalyst.

3. The method according to claim 1 or 2, characterized in that, The concentration of V in the vanadium-containing leachate described in step (1), calculated as V2O5, is 2~40 g / L; The concentration of Mo in the vanadium-containing leachate is 0.01~5 g / L.

4. The method according to claim 1 or 2, characterized in that, The pH adjusting agents include sulfuric acid and / or hydrochloric acid.

5. The method according to claim 1 or 2, characterized in that, The oxidation reaction described in step (1) is carried out under stirring conditions; The stirring speed during the oxidation reaction is 100~400 r / min; The oxidation reaction is carried out at a temperature of 30~70℃.

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

1.

7. The method according to claim 1 or 2, characterized in that, In step (3), the molar ratio of molybdenum in the organic acid and crude ammonium polyvanadate in the purification reaction is (1~20):

1.

8. The method according to claim 1 or 2, characterized in that, The purification reaction in step (3) is carried out at a temperature of 25~70℃; The purification reaction time is more than 30 minutes; In step (3), the molybdenum-containing solution is recycled to the purification 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.

9. The method according to claim 1 or 2, characterized in that, The method includes the following steps: (1) The pH of the vanadium-containing leachate is adjusted to 2-6, and an oxidant is added. The molar ratio of peroxide ions in the oxidant to molybdenum in the vanadium-containing leachate is (1-10):

1. The oxidation reaction is carried out at 100-400 r / min and 30-70℃ to obtain the oxidized solution. (2) Mix the ammonium salt and the oxidized liquid described in step (1) with a molar ratio of ammonium ions in the ammonium salt to vanadium in the oxidized liquid of (0.3~1):1, and precipitate vanadium in the ammonium salt at 90~100℃, and then obtain crude ammonium polyvanadate by solid-liquid separation; (3) The crude ammonium polyvanadate in step (2) is purified by organic acid at 25~70℃ for more than 30 minutes. The molar ratio of molybdenum in organic acid and crude ammonium polyvanadate is (1~20):

1. After solid-liquid separation, molybdenum-containing liquid and high-purity ammonium vanadate product are obtained. The molybdenum-containing solution is recycled to the purification 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.

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