Large-size, high-density ammonium metavanadate and preparation method thereof

Abstract

The present invention belongs to the field of vanadium extraction technology and specifically discloses a large-size, high-density ammonium metavanadate and a preparation method thereof. The method comprises: (1) calcining and crushing vanadium slag to obtain refined vanadium slag; (2) alkali leaching, acid adjustment, and impurity removal of the refined vanadium slag to obtain a vanadium precipitation stock solution; (3) adding polyvinyl pyrrolidone and a soluble ammonium salt to the vanadium precipitation stock solution, wherein the polyvinyl pyrrolidone has a number average molecular weight of 7000-10000, and reacting the mixture at a temperature of 30-50°C for 40-80 minutes; (4) after the reaction, solid-liquid separation is performed to obtain large-size, high-density ammonium metavanadate. The present invention adds polyvinyl pyrrolidone as a surface dispersant and nucleation modifier during the vanadium precipitation process, which not only increases the bulk density of the ammonium metavanadate product, but also increases the particle size of the ammonium metavanadate, which is beneficial to the industrial application of ammonium metavanadate.

Description

Technical Field

[0001] The invention belongs to the technical field of vanadium extraction, and particularly relates to large-size and high-density ammonium metavanadate and a preparation method thereof. Background Art

[0002] Vanadium is a transition element with the symbol V, atomic number 23, and atomic weight 50.94. Pure metallic vanadium is silvery-gray in color and has high melting and boiling points at standard atmospheric pressure. Vanadium's outermost electrons can participate in bonding, combining with oxygen or other elements to form vanadium compounds of varying valence states. Depending on the valence state of vanadium, high-valence vanadium compounds are oxidizing, while low-valence vanadium compounds are reducing.

[0003] The primary natural sources of vanadium are vanadium-titanium magnetite, stone coal, and bauxite from the alumina industry. During the Bayer process or sintering process for alumina extraction, vanadium is enriched in the form of waste slag. Since the construction and commissioning of each alumina plant, vanadium has continuously accumulated in the alumina solution system. Vanadium precipitates during the seeding, transportation, and storage processes, significantly impacting the quality of the alumina product and the production process. my country possesses substantial reserves of vanadium-titanium magnetite and stone coal, with both proven reserves and mined output ranking among the highest in the world. However, whether extracting vanadium from vanadium-titanium magnetite using the sodium slag roasting and calcination processes, or from stone coal using the sodium roasting and acid leaching processes, V2O5 remains the primary product. V2O5 is typically obtained by adding ammonium salts to a vanadium-containing leachate, precipitating vanadium with the ammonium salts to produce vanadium-containing ammonium salts of various valence states, and then separating the ammonium and vanadium through calcination. Therefore, in the current mainstream vanadium production process, ammonium metavanadate is an essential intermediate in the production of V2O5. The current mainstream vanadium extraction process is the roasting process, which is the most commonly used process and accounts for more than 90% of the vanadium slag vanadium extraction capacity.

[0004] Vanadium slag contains heavy metals (such as vanadium and chromium). If improperly stored or landfilled, it can contaminate soil and groundwater through leachate, posing a threat to the ecological environment and human health. During the vanadium slag roasting process, the ammonium salt precipitation of vanadium generates large amounts of high-salt ammonia nitrogen wastewater. This wastewater is highly saline, and the main pollutants include ammonia nitrogen, oxides, and metal salts, making direct discharge highly polluting. Traditional technologies such as ammonia distillation and concentration recovery are no longer sufficient to meet the needs of industrial vanadium oxide production due to high production costs and technical difficulties in equipment operation and maintenance. Therefore, the development of new technologies to address the challenges of vanadium extraction from vanadium slag roasting is urgently needed. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention proposes a large-size and high-density ammonium metavanadate and a preparation method thereof to solve the technical problems of the existing ammonium metavanadate preparation process being relatively complex, the ammonium metavanadate particle size being small, and the density being low.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0008] (1) Roasting and crushing the vanadium slag to obtain refined vanadium slag;

[0009] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution;

[0010] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH, and reacting at a temperature of 30-50°C for 40-80 minutes; the polyvinyl pyrrolidone has a number average molecular weight of 7000-10000, and the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.006-0.03:1;

[0011] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0012] To improve production efficiency, industrial ammonium metavanadate production often involves adding an excess of ammonium salt to the solution to completely precipitate the vanadium in a short period of time. This results in a high degree of supersaturation in the vanadium precipitation reaction, and the resulting ammonium metavanadate generally has a low bulk density. This can generate a large amount of dust during workshop operations, polluting the environment and threatening worker health. Furthermore, powder volatilization can distort the batching process, hindering production. To address this issue, the present invention incorporates polyvinyl pyrrolidone (PPY) as a surface dispersant and nucleation modifier during the vanadium precipitation process. Prior art uses hydroxyl-containing surfactants such as polyvinyl alcohol (PVA) and polyethylene glycol (PEG) as modifiers (CN104973626 and CN113753952). However, PVA's strong adhesive properties not only affect the purity of the ammonium metavanadate but also hinder its particle size. The presence of both hydrophilic and lipophilic groups in the PVP molecule facilitates complexation, thereby increasing the particle size of the ammonium metavanadate. Using polyvinyl pyrrolidone with a number average molecular weight of 7,000-10,000 as a modifier not only increases the bulk density of ammonium metavanadate products, but also increases the particle size of ammonium metavanadate, which is beneficial to the industrial application of ammonium metavanadate. When the molecular weight of polyvinyl pyrrolidone is too small, it has strong mobility in aqueous solution and cannot effectively adsorb to the surface of ammonium metavanadate crystals, which cannot play a role in reducing the nucleation rate; when the molecular weight of polyvinyl pyrrolidone is too large, the viscosity is too high, which is not conducive to crystal growth and causes the crystal particles to become smaller. Furthermore, the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation solution is 0.01-0.03:1. The appropriate amount of polyvinyl pyrrolidone can fully play a role in surface modification and increase the size and density of ammonium metavanadate.

[0013] Furthermore, the blank roasting temperature in step (1) is 700-900°C. High-temperature blank roasting not only removes some impurities in the vanadium slag, but also oxidizes a small amount of low-valent vanadium in the vanadium slag into pentavalent vanadium, thereby increasing vanadium yield. The blank roasting in this process differs from conventional sodium roasting and calcification roasting processes for vanadium slag. The blank roasting method offers better environmental benefits while also increasing vanadium recovery.

[0014] Furthermore, the blank roasting time in step (1) is 1-3 h.

[0015] Furthermore, the alkali used in the alkali leaching process in step (2) is sodium hydroxide, and the acid used in the acid adjustment process is sulfuric acid. This process is relatively mature and generally adopts a high-temperature alkali leaching process. The alkali concentration is generally 20-40wt%, and the alkali leaching temperature is usually 140-200℃. The subsequent acid adjustment process can remove excess alkali, facilitating impurity removal.

[0016] Furthermore, the vanadium content in the vanadium precipitation solution in step (2) is 20-100 g / L.

[0017] Furthermore, the vanadium in the vanadium precipitation solution in step (2) exists in the form of pentavalent vanadium. Specifically, the vanadium in the vanadium precipitation solution in the present invention mainly exists in the form of sodium metavanadate.

[0018] Furthermore, the soluble ammonium salt in step (3) is one or more of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium chloride, and ammonium nitrate.

[0019] Furthermore, in step (3), the pH is adjusted to 7-10 using any one of sulfuric acid, hydrochloric acid, and nitric acid. After adding polyvinyl pyrrolidone and a soluble ammonium salt to the vanadium precipitation stock solution, the pH of the mixed solution needs to be controlled between 7-10. Excessively high or low pH will affect the nucleation and dispersion of polyvinyl pyrrolidone, making it impossible to prepare large-sized, high-density ammonium metavanadate.

[0020] Furthermore, in step (3), the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation solution is 2-4:1; the reaction temperature is 35-45°C; and the reaction time is 50-65 minutes. A suitable temperature can promote the increase of density and particle size. Generally speaking, the solubility of ammonium metavanadate increases slightly with increasing temperature; too low a temperature is not conducive to the movement of polyvinyl pyrrolidone molecules and the crystallization of ammonium metavanadate. Taking all factors into consideration, a reaction temperature of 35-45°C is more suitable. As time increases, the density of ammonium metavanadate gradually increases; however, if the reaction time is too long, the ammonium metavanadate crystals will break, resulting in a decrease in density and particle size.

[0021] The present invention also provides large-size and high-density ammonium metavanadate, which is prepared by the preparation method of large-size and high-density ammonium metavanadate.

[0022] The technical solution of the present invention has the following advantages:

[0023] The present invention adds polyvinyl pyrrolidone as a surface dispersant and nucleation modifier during the vanadium precipitation process. Compared with the hydroxyl-containing surfactants such as polyvinyl alcohol and polyethylene glycol commonly used in the prior art, the polyvinyl pyrrolidone molecule has both hydrophilic groups and lipophilic groups, which can play a complexing role. Using polyvinyl pyrrolidone with a number average molecular weight of 7000-10000 as a modifier can not only improve the bulk density of the ammonium metavanadate product, but also increase the particle size of the ammonium metavanadate, which is beneficial to the industrial application of ammonium metavanadate. If the molecular weight of polyvinyl pyrrolidone is too small, it has strong mobility in aqueous solution and cannot be effectively adsorbed to the surface of the ammonium metavanadate crystal, and cannot play a role in reducing the nucleation rate; when the molecular weight of polyvinyl pyrrolidone is too large, the viscosity is too large, which is not conducive to the growth of the crystal, causing the crystal particles to become smaller. DETAILED DESCRIPTION

[0024] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0025] In the vanadium precipitation stock solution used in the following examples and comparative examples, vanadium exists in the form of pentavalent vanadium, and the V (g / L) concentration is 34.10 g / L; the soluble ammonium salt in step (3) is ammonium sulfate, and sulfuric acid is used to adjust the pH.

[0026] Example 1

[0027] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0028] (1) The vanadium slag is blank roasted and crushed to obtain refined vanadium slag; the blank roasting temperature is 850℃; the blank roasting time is 2h;

[0029] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; the alkali used in the alkaline leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid;

[0030] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH to 7.5, and reacting at a temperature of 35°C for 65 minutes; the number average molecular weight of the polyvinyl pyrrolidone is 7000, and the mass ratio of polyvinyl pyrrolidone to the vanadium atoms in the vanadium precipitation stock solution is 0.01:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 2:1;

[0031] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0032] Example 2

[0033] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0034] (1) The vanadium slag is blank roasted and crushed to obtain refined vanadium slag; the blank roasting temperature is 850℃; the blank roasting time is 2h;

[0035] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; the alkali used in the alkaline leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid;

[0036] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH to 10, and reacting at a temperature of 45°C for 50 minutes; the number average molecular weight of the polyvinyl pyrrolidone is 10,000, and the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.02:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 4:1;

[0037] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0038] Example 3

[0039] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0040] (1) The vanadium slag is blank roasted and crushed to obtain refined vanadium slag; the blank roasting temperature is 850℃; the blank roasting time is 2h;

[0041] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; the alkali used in the alkaline leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid;

[0042] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH to 10, and reacting at a temperature of 35°C for 58 minutes; the number average molecular weight of the polyvinyl pyrrolidone is 10,000, and the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.012:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 4:1;

[0043] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0044] Example 4

[0045] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0046] (1) The vanadium slag is blank roasted and crushed to obtain refined vanadium slag; the blank roasting temperature is 850℃; the blank roasting time is 2h;

[0047] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; the alkali used in the alkaline leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid;

[0048] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH to 7.5, and reacting at a temperature of 45°C for 65 minutes; the number average molecular weight of the polyvinyl pyrrolidone is 7000, and the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.028:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 2.5:1;

[0049] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0050] Example 5

[0051] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0052] (1) The vanadium slag is blank roasted and crushed to obtain refined vanadium slag; the blank roasting temperature is 850℃; the blank roasting time is 2h;

[0053] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; the alkali used in the alkaline leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid;

[0054] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH to 8, and reacting at a temperature of 38°C for 62 minutes; the polyvinyl pyrrolidone has a number average molecular weight of 8000, and the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.015:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3.5:1;

[0055] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0056] Example 6

[0057] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0058] (1) The vanadium slag is blank roasted and crushed to obtain refined vanadium slag; the blank roasting temperature is 850℃; the blank roasting time is 2h;

[0059] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; the alkali used in the alkaline leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid;

[0060] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH to 9, and reacting at a temperature of 43°C for 55 minutes; the number average molecular weight of the polyvinyl pyrrolidone is 9000, and the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.025:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3.6:1;

[0061] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0062] Example 7

[0063] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0064] (1) The vanadium slag is blank roasted and crushed to obtain refined vanadium slag; the blank roasting temperature is 850℃; the blank roasting time is 2h;

[0065] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; the alkali used in the alkaline leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid;

[0066] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH to 9, and reacting at a temperature of 30°C for 56 minutes; the polyvinyl pyrrolidone has a number average molecular weight of 8000, and the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.02:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3:1;

[0067] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0068] Example 8

[0069] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0070] (1) The vanadium slag is blank roasted and crushed to obtain refined vanadium slag; the blank roasting temperature is 850℃; the blank roasting time is 2h;

[0071] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; the alkali used in the alkaline leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid;

[0072] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH to 9, and reacting at a temperature of 50°C for 56 minutes; the number average molecular weight of the polyvinyl pyrrolidone is 8000, and the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.02:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3:1;

[0073] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0074] Example 9

[0075] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0076] (1) The vanadium slag is blank roasted and crushed to obtain refined vanadium slag; the blank roasting temperature is 850℃; the blank roasting time is 2h;

[0077] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; the alkali used in the alkaline leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid;

[0078] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH to 9, and reacting at a temperature of 40°C for 56 minutes; the number average molecular weight of the polyvinyl pyrrolidone is 8000, the mass ratio of polyvinyl pyrrolidone to the vanadium atoms in the vanadium precipitation stock solution is 0.006:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3:1;

[0079] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0080] Example 10

[0081] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0082] (1) The vanadium slag is blank roasted and crushed to obtain refined vanadium slag; the blank roasting temperature is 850℃; the blank roasting time is 2h;

[0083] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; the alkali used in the alkaline leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid;

[0084] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH to 9, and reacting at a temperature of 40°C for 80 minutes; the number average molecular weight of the polyvinyl pyrrolidone is 8000, and the mass ratio of polyvinyl pyrrolidone to the vanadium atoms in the vanadium precipitation stock solution is 0.02:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3:1;

[0085] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0086] Example 11

[0087] A method for preparing large-size and high-density ammonium metavanadate comprises the following steps:

[0088] (1) The vanadium slag is blank roasted and crushed to obtain refined vanadium slag; the blank roasting temperature is 850℃; the blank roasting time is 2h;

[0089] (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; the alkali used in the alkaline leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid;

[0090] (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH to 9, and reacting at a temperature of 40°C for 56 minutes; the number average molecular weight of the polyvinyl pyrrolidone is 8000, and the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.02:1; the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation stock solution is 3:1;

[0091] (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

[0092] Comparative Example 1

[0093] A method for preparing large-size and high-density ammonium metavanadate, the preparation process of which is basically the same as that of Example 11, except that the number average molecular weight of the polyvinyl pyrrolidone is 5000.

[0094] Comparative Example 2

[0095] A method for preparing large-size and high-density ammonium metavanadate, wherein the preparation process is basically the same as that of Example 11, except that the number average molecular weight of the polyvinyl pyrrolidone is 13,000.

[0096] Comparative Example 3

[0097] A method for preparing large-sized and high-density ammonium metavanadate, wherein the preparation process is substantially the same as that of Example 11, except that the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation solution is 0.05:1.

[0098] Comparative Example 4

[0099] A method for preparing large-size and high-density ammonium metavanadate, the preparation process of which is basically the same as that of Example 11, except that polyvinyl alcohol with a number average molecular weight of 8000 is used instead of polyvinyl pyrrolidone.

[0100] The performance tests of the large-scale high-density ammonium metavanadate prepared in Examples 1-11 and Comparative Examples 1-4 were carried out: the purity of ammonium metavanadate (%) was tested using a spectrometer; the bulk density of ammonium metavanadate (g / cm 3 ); and the particle size D50 (μm) of ammonium metavanadate was tested using a laser particle size analyzer.

[0101] Table 1 Performance of large-sized and high-density ammonium metavanadate prepared in Examples 1-11 and Comparative Examples 1-4

[0102]

[0103] Table 1

[0104]

[0105] As can be seen from Examples 1-11, the addition of polyvinyl pyrrolidone as a surface dispersant and nucleation modifier during the vanadium precipitation process of the present invention not only improves the bulk density and purity of the ammonium metavanadate product, but also increases the particle size of the ammonium metavanadate, facilitating its industrial application.

[0106] Comparative Examples 1-3 show that polyvinyl pyrrolidone molecular weight affects product performance. When the polyvinyl pyrrolidone molecular weight is too small, it has strong mobility in aqueous solution and cannot be effectively adsorbed onto the ammonium metavanadate crystal surface, which can not play a role in reducing nucleation rate; when the polyvinyl pyrrolidone molecular weight is too large, the viscosity is too large, which is also unfavorable for the growth of crystals, causing the crystal particles to become smaller. Meanwhile, when the polyvinyl pyrrolidone dosage is too much, it is easy to cause the solution viscosity to be too large, which is unfavorable for the growth of crystal grains. Comparative Example 4 shows that although polyvinyl alcohol has improved the ammonium metavanadate size to a certain extent, its cohesiveness is large, causing the ammonium metavanadate purity to decrease.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing large-size and high-density ammonium metavanadate, characterized in that: The following steps are involved: (1) Roasting and crushing the vanadium slag to obtain refined vanadium slag; (2) The refined vanadium slag is subjected to alkaline leaching, acid adjustment, purification and impurity removal to obtain the vanadium precipitation solution; (3) placing the vanadium precipitation stock solution in a reaction kettle, adding polyvinyl pyrrolidone and a soluble ammonium salt respectively, stirring evenly, adjusting the pH, and reacting at a temperature of 35-45°C for 40-80 minutes; the polyvinyl pyrrolidone has a number average molecular weight of 7000-10000, and the mass ratio of polyvinyl pyrrolidone to vanadium atoms in the vanadium precipitation stock solution is 0.006-0.03:1; (4) After the reaction is completed, the solid and liquid are separated, and the solid phase is washed and dried to obtain large-sized and high-density ammonium metavanadate.

2. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, wherein: The blank calcination temperature in step (1) is 700-900°C.

3. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, wherein: The blank roasting time in step (1) is 1-3h.

4. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, wherein: In step (2), the alkali used in the alkali leaching process is sodium hydroxide; the acid used in the acid adjustment process is sulfuric acid.

5. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, wherein: The vanadium content in the vanadium precipitation solution in step (2) is 20-100 g / L.

6. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, wherein: In step (2), the vanadium in the vanadium precipitation solution exists in the form of pentavalent vanadium.

7. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, wherein: In step (3), the soluble ammonium salt is one or more of ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium chloride, and ammonium nitrate.

8. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, wherein: In step (3), any one of sulfuric acid, hydrochloric acid and nitric acid is used to adjust the pH.

9. The method for preparing large-size and high-density ammonium metavanadate according to claim 8, wherein: In step (3), the pH is adjusted to 7-10.

10. The method for preparing large-size and high-density ammonium metavanadate according to claim 1, wherein: In step (3), the molar ratio of ammonium ions in the soluble ammonium salt to vanadium atoms in the vanadium precipitation solution is 2-4:1; and the reaction time is 50-65 minutes.

11. A large-size, high-density ammonium metavanadate, characterized by: The invention is prepared by the preparation method of large-size and high-density ammonium metavanadate according to any one of claims 1 to 10.

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