Method for closed-loop preparation of high-purity vanadium pentoxide from ammonium metavanadate

Abstract

The invention provides a method for closed-loop preparation of high-purity vanadium pentoxide from ammonium metavanadate, and belongs to the technical field of metallurgy. The method comprises the following steps: carrying out acid-process vanadium precipitation on an ammonium metavanadate raw material to obtain ammonium polyvanadate; carrying out alkaline vanadium precipitation on the ammonium polyvanadate to obtain high-purity ammonium metavanadate; and roasting the high-purity ammonium metavanadate to obtain the vanadium pentoxide. The existing method for producing high-purity vanadium pentoxide from ammonium metavanadate mainly adopts a pure alkali method or an acid method for purification, and has the problems of high purification cost, repeated purification, incapability of closed-loop production, low purity and the like, the acid-alkali combined secondary crystallization method is adopted, closed-loop production is realized, the cost is low, no pollution is caused, vanadium pentoxide with the purity of 99.9% can be obtained, the additional value is increased, and the method is suitable for industrial production. And the requirements of high-end vanadium markets are met.

Description

Technical Field

[0001] The present application relates to the field of metallurgical technology, and in particular to a method for preparing high-purity vanadium pentoxide from ammonium metavanadate in a closed circuit. Background Art

[0002] In recent years, with the continuous expansion of vanadium application areas, the requirements for the purity of vanadium products have become higher and higher. Vanadium aluminum alloys, vanadium batteries, vanadium catalysts, etc. are all very popular research fields. As an important raw material for these products, high-purity vanadium pentoxide has gradually become one of the most important areas with the greatest potential for future vanadium sales growth in the world. Therefore, research on the preparation process of high-purity refined vanadium is very necessary. At present, the main raw materials for vanadium extraction on the market are vanadium-titanium magnetite, vanadium slag, stone coal, waste vanadium catalyst, ammonium metavanadate, etc. The technology for extracting vanadium slag to prepare ammonium metavanadate in the Bayer process of alumina is mature, but there is a problem of low purity of ammonium metavanadate, which seriously reduces the efficiency of the enterprise and restricts the high-quality development of the enterprise. Therefore, the use of ammonium metavanadate prepared by extracting vanadium slag from the Bayer process of alumina as a raw material for vanadium extraction can increase the added value of products, improve the efficiency of enterprises, and meet market demand.

[0003] The vanadium extraction process of ammonium metavanadate generally goes through a hydrometallurgical process, which first dissolves vanadium from the raw material to obtain vanadium liquid, separates vanadium from most other components in the raw material, and then precipitates the vanadium in the solution in a certain form to obtain vanadium compounds or vanadium pentoxide. The main methods for recovering vanadium from vanadium-containing solutions are extraction, ion exchange, and precipitation. The extraction method is a method of separation using the difference in solubility of a substance in a solvent under the action of an extractant. The ion exchange method uses the exchange agent to exchange with like-charged ions in the solution, so that ions in the solution enter the exchange agent, and ions in the exchange agent enter the solution. The precipitation method is divided into calcium salt and iron salt precipitation method, hydrolysis precipitation method, and ammonium salt precipitation method according to the different precipitants used. The ammonium salt precipitation method is divided into weak alkaline ammonium salt precipitation method, weak acidic ammonium salt precipitation method, and acidic ammonium salt precipitation method depending on the acidity and alkalinity of the solution during precipitation. The vanadium product recovered by the precipitation method has stable quality and can meet the needs of different fields. Therefore, the main method for recovering vanadium from vanadium-containing solutions is to use precipitation method. However, the vanadium pentoxide prepared by the existing acid precipitation method or alkaline precipitation method has high purification cost and relatively low purity, which is mostly around 99.5%. Therefore, how to improve the purity of vanadium pentoxide prepared by ammonium metavanadate is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a method for preparing high-purity vanadium pentoxide from ammonium metavanadate in a closed circuit, in order to solve the following technical problem: how to improve the purity of vanadium pentoxide prepared from ammonium metavanadate.

[0005] The present application provides a method for preparing high-purity vanadium pentoxide from ammonium metavanadate in a closed circuit, the method comprising:

[0006] The ammonium metavanadate raw material is subjected to acid vanadium precipitation to obtain ammonium polyvanadate; wherein the ammonium metavanadate is prepared from vanadium slag extracted from Bayer process alumina production;

[0007] subjecting the ammonium polyvanadate to alkaline precipitation of vanadium to obtain high-purity ammonium metavanadate; and

[0008] The high-purity ammonium metavanadate is roasted to obtain vanadium pentoxide.

[0009] Optionally, the step of subjecting the ammonium metavanadate raw material to acid precipitation of vanadium to obtain ammonium polyvanadate comprises:

[0010] Adding the ammonium metavanadate raw material into a solvent having a first set temperature to obtain a first mixed solution;

[0011] At a second set temperature, adjusting the pH of the first mixed solution to a first set pH to obtain a second mixed solution;

[0012] At a third set temperature, subjecting the second mixed solution to a heat preservation treatment for a first set time to precipitate vanadium, thereby obtaining a third mixed solution;

[0013] The third mixed liquid is subjected to solid-liquid separation to obtain ammonium polyvanadate and acidic circulating mother liquor.

[0014] Optionally, the first set temperature is 60° C. to 85° C.; and / or,

[0015] The second set temperature is 70°C to 90°C; and / or,

[0016] The third set temperature is 95° C. to 99° C., and the first set time is 30 min to 60 min.

[0017] Optionally, sulfuric acid is used to adjust the pH of the first mixed solution, and the first set pH is 2.5-3.5.

[0018] Optionally, the acidic circulating mother liquor is circulated for acid dissolving the ammonium metavanadate raw material to form a closed cycle; the method further comprises:

[0019] The acidic circulating mother liquor is subjected to a first purification treatment using calcium hydroxide; the temperature of the first purification treatment is 60° C. to 99° C., and the time of the first purification treatment is 60 min to 120 min.

[0020] Optionally, the step of subjecting the ammonium polyvanadate to alkaline precipitation of vanadium to obtain high-purity ammonium metavanadate comprises:

[0021] adding ammonium polyvanadate to a solvent having a fourth set temperature, and adjusting the pH to the second set pH to obtain a fourth mixed solution;

[0022] At the fourth set temperature, the fourth mixed solution is subjected to a heat preservation treatment for a second set time to dissolve the ammonium polyvanadate with alkali to obtain a fifth mixed solution;

[0023] The fifth mixed solution is cooled to a fifth set temperature and subjected to a heat preservation treatment for a third set time to precipitate ammonium metavanadate, thereby obtaining a sixth mixed solution;

[0024] The sixth mixed liquid is subjected to solid-liquid separation to obtain the ammonium metavanadate and alkaline circulating mother liquor.

[0025] Optionally, the fourth set temperature is 85° C. to 95° C., and the second set time is 15 min to 30 min; and / or,

[0026] The fifth set temperature is 20° C. to 40° C., and the third set time is 60 min to 120 min.

[0027] Optionally, the pH is adjusted to a second set pH using aqueous ammonia, and the second set pH is 8.5 to 9.5.

[0028] Optionally, the alkaline circulating mother liquor is circulated for alkali dissolution of ammonium polyvanadate to form a closed cycle; the method further comprises:

[0029] The alkaline circulating mother liquor is subjected to a second purification treatment using calcium hydroxide; the temperature of the second purification treatment is 20° C. to 80° C., and the time of the second purification treatment is 60 min to 120 min.

[0030] Optionally, the calcination temperature is 500° C. to 550° C., and the calcination time is 90 min to 150 min.

[0031] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0032] The present application provides a method for preparing high-purity vanadium pentoxide from ammonium metavanadate in a closed circuit, the method comprising: subjecting the ammonium metavanadate raw material to acid precipitation of vanadium to obtain ammonium polyvanadate; subjecting the ammonium polyvanadate to alkaline precipitation of vanadium to obtain high-purity ammonium metavanadate; and roasting the high-purity ammonium metavanadate to obtain vanadium pentoxide. Existing ammonium metavanadate is used to produce high-purity vanadium pentoxide, mostly by simple alkaline or acid purification, which has the problems of high purification cost, multiple purifications, inability to produce in a closed circuit, and insufficient purity. The present application adopts an acid-base combined secondary crystallization method, closed-circuit production, low cost, no pollution, and can obtain 99.9% pure vanadium pentoxide, which increases added value and meets the market demand for high-end vanadium. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0034] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0035] Figure 1 A schematic diagram of a method for preparing high-purity vanadium pentoxide from ammonium metavanadate in a closed circuit provided in an embodiment of the present application;

[0036] Figure 2 A flow chart of a method for preparing high-purity vanadium pentoxide from ammonium metavanadate in a closed circuit is provided in an embodiment of the present application. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0038] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0039] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0040] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0041] Figure 1 A schematic diagram of a method for preparing high-purity vanadium pentoxide from ammonium metavanadate in a closed circuit provided in an embodiment of the present application;

[0042] Figure 2 A flow chart of a method for preparing high-purity vanadium pentoxide from ammonium metavanadate in a closed circuit is provided in an embodiment of the present application.

[0043] See also Figure 1 and Figure 2 The present application provides a method for preparing high-purity vanadium pentoxide from ammonium metavanadate in a closed circuit, the method comprising:

[0044] S1, subjecting the ammonium metavanadate raw material to acid precipitation of vanadium to obtain ammonium polyvanadate; wherein the ammonium metavanadate is prepared from vanadium slag extracted from Bayer process alumina production;

[0045] In an acidic environment, ammonium metavanadate is dissolved and converted into ammonium polyvanadate precipitation. Ammonium metavanadate is prepared from vanadium slag extracted from Bayer process alumina production. The purity of vanadium pentoxide after direct roasting of ammonium metavanadate raw material is 98% to 99%. The embodiment of the present application adopts acid-base combined secondary crystallization method to obtain vanadium pentoxide with a purity of 99.9%.

[0046] In some embodiments, the step of subjecting the ammonium metavanadate raw material to acid precipitation of vanadium to obtain ammonium polyvanadate comprises:

[0047] S101, adding an ammonium metavanadate raw material into a solvent having a first set temperature to obtain a first mixed solution;

[0048] It is understood that the solvent is usually water, but may also be other solvents that can react with ammonium metavanadate to form soluble vanadium ions. The ammonium metavanadate raw material is added to the solvent and stirred to fully mix them to form a first mixed solution.

[0049] In some embodiments, the first set temperature is 60°C to 85°C.

[0050] The first set temperature is the original temperature of the solvent, and the first set temperature is limited to 60°C to 85°C, so as to ensure that the solubility of ammonium metavanadate in the solvent is moderate, which is convenient for the subsequent vanadium precipitation reaction. Exemplarily, the first set temperature is 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, etc.

[0051] S102, adjusting the pH of the first mixed solution to a first set pH at a second set temperature to obtain a second mixed solution;

[0052] As the pH decreases, the vanadium ions in the solution are gradually converted into polyvanadate ions.

[0053] In some embodiments, the second set temperature is 70°C to 90°C.

[0054] The second set temperature is the temperature of the first mixed solution, and the second set temperature is limited to 70°C to 90°C, so as to maintain the reaction activity of the solution and promote the morphological transformation of the vanadium ions. Exemplarily, the second set temperature can be 70°C, 75°C, 80°C, 85°C, 90°C, etc.

[0055] In some embodiments, sulfuric acid is used to adjust the pH of the first mixed solution, and the first set pH is 2.5-3.5.

[0056] By adding an acid (such as sulfuric acid), the pH of the first mixed solution is adjusted to a first set pH (2.5 to 3.5). Within this pH range, the vanadium ions mainly exist in the form of polyvanadate ions, which is beneficial to the subsequent precipitation reaction. Exemplarily, the first set pH can be 2.5, 2.7, 2.9, 3.0, 3.2, 3.4, 3.5, etc.

[0057] S103, subjecting the second mixed solution to a heat preservation treatment for a first set time at a third set temperature to precipitate vanadium, thereby obtaining a third mixed solution;

[0058] During the high temperature insulation process, the polyvanadate ions combine with the ammonium ions in the solution to form ammonium polyvanadate precipitates.

[0059] In some embodiments, the third set temperature is 95° C. to 99° C., and the first set time is 30 min to 60 min.

[0060] The third set temperature is the temperature of the second mixed solution after the second set temperature is heated up, and the third set temperature is 95°C to 99°C, thereby accelerating the precipitation reaction of ammonium polyvanadate. High temperature can speed up the reaction rate and improve precipitation efficiency. The first set time is 30min to 60min, and the heat preservation treatment is to ensure that ammonium polyvanadate can be fully precipitated. Exemplarily, the third set temperature is 95°C, 96°C, 97°C, 98°C, 99°C, etc., and the first set time can be 30min, 35min, 40min, 45min, 50min, 55min, 60min, etc.

[0061] S104, performing solid-liquid separation on the third mixed liquid to obtain ammonium polyvanadate and acidic circulating mother liquor.

[0062] The ammonium polyvanadate precipitate in the third mixed solution is separated from the acidic circulating mother liquor by solid-liquid separation techniques such as filtration and centrifugation. The separated ammonium polyvanadate is the desired product. The remaining acidic circulating mother liquor contains unreacted vanadium ions and other impurities, which can be recycled in the subsequent acid-dissolving ammonium metavanadate raw material step to form a closed cycle and improve resource utilization.

[0063] In some embodiments, the acidic circulating mother liquor is circulated for acid dissolving the ammonium metavanadate raw material to form a closed cycle; the method further comprises:

[0064] The acidic circulating mother liquor is subjected to a first purification treatment using calcium hydroxide; the temperature of the first purification treatment is 60° C. to 99° C., and the time of the first purification treatment is 60 min to 120 min.

[0065] For the acid process circulating mother liquor, excessive sulfate content will lead to a significant increase in solution viscosity. High viscosity solutions will bring many difficulties in the subsequent precipitation separation steps, such as slow precipitation rate, low separation efficiency and possible product contamination. Therefore, reducing the sulfate content in the acid process circulating mother liquor through purification treatment can effectively control the viscosity of the solution, thereby optimizing the precipitation separation process and improving production efficiency.

[0066] The acidic circulating mother liquor is purified by adding calcium hydroxide, aiming to remove impurities and excess acid in the mother liquor to improve the purity and reuse efficiency of the mother liquor. At the same time, the solid products (such as calcium sulfate dihydrate) produced during the purification process can be sold as industrial products to achieve effective utilization of resources. The temperature (60°C to 99°C) and time (60min to 120min) of the purification treatment are set to ensure the purification effect. Appropriate temperature and time can promote the full reaction of calcium hydroxide with impurities and acids in the acidic circulating mother liquor. Exemplarily, the temperature of the first purification treatment can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 99°C, etc., and the time of the first purification treatment can be 60min, 70min, 80min, 90min, 100min, 110min, 120min, etc.

[0067] It is worth noting that the purification step does not need to be performed in every process. This mainly depends on factors such as the impurity content of the mother liquor, the required purity, and the reuse efficiency. When the impurity content in the mother liquor is high or the purity requirement is high, purification can be considered; when the mother liquor quality is good or the reuse efficiency is high, the purification step can be omitted to reduce costs.

[0068] S2, subjecting the ammonium polyvanadate to alkaline precipitation of vanadium to obtain high-purity ammonium metavanadate; and

[0069] The ammonium polyvanadate precipitate is redissolved in an alkaline environment, and high-purity ammonium metavanadate is obtained through a crystallization process, thereby improving the purity of the ammonium metavanadate and further improving the purity of the vanadium pentoxide product.

[0070] In some embodiments, the step of subjecting the ammonium polyvanadate to alkaline precipitation of vanadium to obtain high-purity ammonium metavanadate comprises:

[0071] S201, adding ammonium polyvanadate to a solvent having a fourth set temperature, and adjusting the pH to a second set pH to obtain a fourth mixed solution;

[0072] The solvent is typically water, but may be other solvents that react with the ammonium polyvanadate to form soluble vanadium ions.

[0073] In some embodiments, the pH is adjusted to a second set pH using aqueous ammonia, and the second set pH is 8.5 to 9.5.

[0074] By adding ammonia water, the pH of the mixed solution is adjusted to a second set pH (8.5-9.5). Within this pH range, ammonium polyvanadate can gradually dissolve to form soluble vanadium ions. Exemplarily, the second set pH can be 8.5, 8.7, 8.9, 9, 9.2, 9.4, 9.5, etc.

[0075] S202, subjecting the fourth mixed solution to a heat preservation treatment for a second set time at the fourth set temperature to dissolve the ammonium polyvanadate with alkali to obtain a fifth mixed solution;

[0076] In some embodiments, the fourth set temperature is 85° C. to 95° C., and the second set time is 15 min to 30 min.

[0077] At the fourth set temperature, the fourth mixed solution is subjected to a second set time (15min to 30min) of insulation treatment. This step is to ensure that the ammonium polyvanadate can be fully dissolved in the alkaline solution to form soluble vanadium ions. Exemplarily, the fourth set temperature can be 85°C, 87°C, 89°C, 90°C, 92°C, 94°C, 95°C, etc., and the second set time can be 15min, 18min, 20min, 22min, 25min, 28min, 30min, etc.

[0078] As the insulation time increases, the ammonium polyvanadate gradually dissolves in the alkaline solution to form a fifth mixed solution.

[0079] S203, cooling the fifth mixed solution to a fifth set temperature, and performing a heat preservation treatment for a third set time to precipitate ammonium metavanadate, thereby obtaining a sixth mixed solution;

[0080] In some embodiments, the fifth set temperature is 20° C. to 40° C., and the third set time is 60 min to 120 min.

[0081] The fifth mixed solution is cooled to the fifth set temperature (20°C to 40°C). The purpose of cooling is to promote the morphological transformation of vanadium ions so that they gradually precipitate in the form of ammonium metavanadate. At the fifth set temperature, the mixed solution is subjected to a heat preservation treatment for the third set time (60min to 120min). This step is to ensure that ammonium metavanadate can be fully precipitated to form the sixth mixed solution. Exemplarily, the fifth set temperature can be 20°C, 25°C, 30°C, 35°C, 40°C, etc., and the third set time can be 60min, 65min, 70min, 80min, 90min, 100min, 110min, 120min, etc.

[0082] S204, performing solid-liquid separation on the sixth mixed liquid to obtain the ammonium metavanadate and alkaline circulating mother liquor.

[0083] The ammonium metavanadate precipitate in the sixth mixed solution is separated from the alkaline circulating mother liquor by solid-liquid separation techniques such as filtration and centrifugation. The separated ammonium metavanadate is the desired high-purity product. The remaining alkaline circulating mother liquor contains unreacted vanadium ions and other impurities, which can be recycled in the subsequent alkali-dissolving ammonium polyvanadate step to form a closed loop and improve resource utilization.

[0084] In some embodiments, the alkaline circulating mother liquor is circulated for alkali dissolution of ammonium polyvanadate to form a closed cycle; the method further comprises:

[0085] The alkaline circulating mother liquor is subjected to a second purification treatment using calcium hydroxide; the temperature of the second purification treatment is 20° C. to 80° C., and the time of the second purification treatment is 60 min to 120 min.

[0086] For the alkaline circulating mother liquor, when the sulfate content is higher than 20g / L, it will have an adverse effect on the dissolution of polyvanadic acid. Specifically, the alkaline circulating mother liquor with a high sulfate content will lead to incomplete dissolution of polyvanadic acid, which will not only reduce the recovery rate of vanadium, but also reduce the purity of the final product due to the undissolved polyvanadic acid residue. Therefore, purifying the alkaline circulating mother liquor to reduce the sulfate content is crucial to ensure the complete dissolution of polyvanadic acid and improve the recovery rate and purity of vanadium.

[0087] The alkaline circulating mother liquor is subjected to a second purification treatment using calcium hydroxide, which can remove some impurities and excess alkali in the solution. The temperature (20°C to 80°C) and time (60min to 120min) of the purification treatment are set to ensure the purification effect. Appropriate temperature and time can promote the full reaction of calcium hydroxide with impurities and alkali in the alkaline circulating mother liquor. The solid product (such as calcium sulfate dihydrate) produced during the purification process can be sold as an industrial product or subjected to other treatments. Exemplarily, the temperature of the second purification treatment can be 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, etc., and the time of the second purification treatment can be 60min, 70min, 80min, 90min, 100min, 110min, 120min, etc.

[0088] It is worth noting that the purification step does not need to be performed in every process. This mainly depends on factors such as the impurity content of the mother liquor, the required purity, and the reuse efficiency. When the impurity content in the mother liquor is high or the purity requirement is high, purification can be considered; when the mother liquor quality is good or the reuse efficiency is high, the purification step can be omitted to reduce costs.

[0089] Therefore, the process of the present application includes two closed-loop processes, an acid method and an alkaline method for vanadium precipitation. In the acid method for vanadium precipitation, the acidic circulating mother liquor is produced by the acid method of ammonium metavanadate to produce ammonium polyvanadate, and the alkaline method for vanadium precipitation mother liquor is the alkaline circulating mother liquor. The two circulating mother liquors are purified by adding calcium hydroxide. The purification does not need to be carried out in each process. The purified solid is mainly calcium sulfate dihydrate, which can be sold as an industrial product.

[0090] S3, roasting the high-purity ammonium metavanadate to obtain vanadium pentoxide.

[0091] High-purity ammonium metavanadate is converted into vanadium pentoxide by calcination.

[0092] In some embodiments, the calcination temperature is 500° C. to 550° C., and the calcination time is 90 min to 150 min.

[0093] The roasting temperature is limited to 500°C to 550°C, and ammonium metavanadate can be fully decomposed to ensure the high efficiency of the conversion process. At the same time, unnecessary side reactions are reduced to avoid the generation of other impurities. In addition, it can ensure the high efficiency of the reaction and avoid excessive energy consumption. The roasting time is limited to 90min to 150min to ensure that ammonium metavanadate is completely decomposed and converted into vanadium pentoxide. At the same time, it helps to reduce the impurity content and improve the purity of the product. Exemplarily, the roasting temperature can be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, etc., and the roasting time can be 90min, 100min, 110min, 120min, 130min, 140min, 150min, etc.

[0094] This application uses an acid-base combined method to prepare high-purity vanadium pentoxide, which shows significant advantages in many aspects compared to traditional processes. The following is a detailed explanation of these advantages:

[0095] 1. Through precise acid-base control, temperature regulation, time setting and purification of circulating mother liquor, this method can produce vanadium pentoxide with a purity of up to 99.9%. This high purity meets the strict requirements of the high-end market and improves the market competitiveness and added value of the product.

[0096] Second, this method adopts a closed-loop production mode, that is, both the acidic circulating mother liquor and the alkaline circulating mother liquor can be recycled in the subsequent vanadium precipitation process. This design not only reduces resource waste, but also reduces production costs. At the same time, due to the adoption of a closed-loop production mode, almost no harmful emissions are generated during the entire production process. Even if purification treatment is required, the solid waste (such as calcium sulfate dihydrate) generated during the purification process also has industrial application value and can be sold or further processed, achieving true pollution-free production.

[0097] 3. This method combines acid precipitation and alkaline precipitation to form two closed-loop processes. This design makes the entire process more compact and efficient, reducing unnecessary intermediate links. At the same time, by precisely controlling the temperature, time, pH value and other parameters of each step, the stability and controllability of the process can be ensured. This reduces the difficulty of operation and improves production efficiency.

[0098] Fourth, the use of impurity-free solid vanadium slag in the Bayer process of alumina to prepare ammonium metavanadate as raw material not only reduces the cost of raw materials, but also maximizes the use of resources. At the same time, by optimizing the process flow and parameter settings, this method can reduce energy consumption and production costs while ensuring product quality.

[0099] 5. High-purity vanadium pentoxide is widely used in aerospace, electronics, magnetic materials and other fields. This method can produce high-purity vanadium pentoxide products that meet the needs of different fields, enhancing market adaptability. At the same time, by improving product purity and reducing production costs, this method can significantly enhance the market competitiveness and profitability of enterprises, helping enterprises achieve high-quality development.

[0100] In summary, the method of preparing high-purity vanadium pentoxide by the acid-base combined method has shown significant advantages in purity improvement, resource recycling, process optimization, cost control and market adaptability. The successful application of this method will bring significant economic and social benefits to enterprises and promote the sustainable development of the vanadium industry.

[0101] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0102] Example 1

[0103] The start-up process, acid and alkali methods of vanadium precipitation are both prepared using water as the solvent.

[0104] Acid precipitation of vanadium: add 60g of ammonium metavanadate to 600ml water at 60℃, adjust the pH to 2.6 with 98% sulfuric acid at 70℃, raise the temperature to 99℃, keep warm for 30min, and stir all the time. Then separate the solid and liquid and wash with water to obtain ammonium polyvanadate solid. Alkaline precipitation of vanadium: add 40g of ammonium polyvanadate to 600ml water, add at 85℃, add ammonia water to adjust the pH to 8.5, keep warm for 20min, cool down to 35℃, keep warm for 90min, separate the solid and liquid and wash with water to obtain high-purity ammonium metavanadate. High-purity ammonium metavanadate is calcined at 500℃ for 2 hours to obtain 99.97% high-purity vanadium pentoxide.

[0105] Example 2

[0106] In the first circulation process, the mother liquor of the acid-alkali vanadium precipitation in Example 1 is used as the solvent in the first circulation process, and is named acid-process circulating liquid and alkaline-process circulating liquid.

[0107] Acid precipitation of vanadium: Add 50g of ammonium metavanadate to 500ml of acid circulating liquid at 65℃, add sulfuric acid at 75℃ to adjust the pH to 2.8, raise the temperature to 98℃, and keep it warm for 30min. Stirring is always in the process. Then solid-liquid separation and water washing are performed to obtain ammonium polyvanadate solid. Alkaline precipitation of vanadium: Add 35g of ammonium polyvanadate to 500ml of alkaline circulating liquid at 85℃, add ammonia water to adjust the pH to 8.6, keep warm for 20min, cool down to 30℃, keep warm for 80min, separate the solid and liquid and wash with water to obtain high-purity ammonium metavanadate. High-purity ammonium metavanadate is calcined at 520℃ for 2 hours to obtain 99.95% high-purity vanadium pentoxide.

[0108] Example 3

[0109] In the second circulation process, the mother liquor of acid and alkaline vanadium precipitation in Example 2 is used as the solvent in the second circulation process, which is named acid circulating liquid and alkaline circulating liquid.

[0110] Acid precipitation of vanadium: 40g of ammonium metavanadate is added to 400ml of acid circulating liquid at 70℃, sulfuric acid is added at 80℃ to adjust the pH to 2.9, the temperature is raised to 96℃, and the temperature is kept for 35min, and the stirring state is always in the process. Then the solid-liquid separation and water washing are obtained to obtain the ammonium polyvanadate solid. Alkaline precipitation of vanadium: 28g of ammonium polyvanadate is added to 400ml of alkaline circulating liquid at 88℃, ammonia water is added to adjust the pH value to 8.8, the temperature is kept for 25min and the temperature is lowered to 28℃, the temperature is kept for 70min, and the solid-liquid separation and water washing are obtained to obtain high-purity ammonium metavanadate. High-purity ammonium metavanadate is calcined at 530℃ for 2 hours to obtain 99.94% high-purity vanadium pentoxide.

[0111] Example 4

[0112] In the third circulation process, the mother liquor of the acid-alkali vanadium precipitation in Example 3 is used as the solvent in the third circulation process, which is named acid-process circulating liquid and alkaline-process circulating liquid.

[0113] Acid precipitation of vanadium: 30g of ammonium metavanadate is added to 300ml of acid circulating liquid at 70℃, sulfuric acid is added at 80℃ to adjust the pH to 3, the temperature is raised to 95℃, and the temperature is kept for 40min, and the stirring state is always in the process. Then the solid-liquid separation and water washing are obtained to obtain the ammonium polyvanadate solid. Alkaline precipitation of vanadium: 20g of ammonium polyvanadate is added to 300ml of alkaline circulating liquid at 90℃, ammonia water is added to adjust the pH value to 9, the temperature is kept for 20min and the temperature is lowered to 28℃, and the temperature is kept for 60min, and the solid-liquid separation and water washing are obtained to obtain high-purity ammonium metavanadate. High-purity ammonium metavanadate is calcined at 540℃ for 2 hours to obtain 99.93% high-purity vanadium pentoxide.

[0114] Example 5

[0115] In the fourth circulation process, the mother liquor of acid-alkali vanadium precipitation in Example 4 is used as the solvent in the fourth circulation process, and is named acid-process circulating liquid and alkaline-process circulating liquid.

[0116] Acid precipitation of vanadium: Add 25g of ammonium metavanadate to 250ml of acid circulating liquid at 75℃, add sulfuric acid at 85℃ to adjust the pH to 3.1, raise the temperature to 99℃, keep warm for 30min, and stir all the time. Then separate the solid and liquid and wash with water to obtain ammonium polyvanadate solid. Alkaline precipitation of vanadium: Add 18g of ammonium polyvanadate to 250ml of alkaline circulating liquid at 95℃, add ammonia water to adjust the pH to 9, keep warm for 15min and cool down to 25℃, keep warm for 60min, separate the solid and liquid and wash with water to obtain high-purity ammonium metavanadate. High-purity ammonium metavanadate is calcined at 550℃ for 2 hours to obtain 99.92% high-purity vanadium pentoxide.

[0117] Example 6

[0118] After the acid method circulating mother liquor and the alkaline method circulating mother liquor have been circulated for 5 times, the mother liquor is purified. Based on the principle of reducing the introduction of impurities, calcium hydroxide is used for purification. The purification temperature of the acid method circulating mother liquor is between 60℃ and 99℃, and the purification temperature of the alkaline method circulating mother liquor is between 20℃ and 80℃. The amount of calcium hydroxide is added according to the sulfate content of the circulating liquid. The results of the circulating liquid after purification are shown in Table 1.

[0119] Table 1 Circulating fluid purification results of Example 6

[0120]

[0121] As shown in Table 1, calcium hydroxide has a good purification effect, which not only reduces the sulfate content, but also reduces the content of impurity phosphorus and silicon. The product of calcium hydroxide purification is CaSO4.2H2O, and the purity of CaSO4.2H2O is greater than 95%, which can be sold as a product. The process is pollution-free and emission-free.

[0122] Purification reasons: excessive sulfate content in the acid process circulating liquid will increase the viscosity of the solution and affect precipitation separation; sulfate content in the alkaline process circulating mother liquor higher than 20g / L will cause incomplete dissolution of polyvanadic acid, reducing the vanadium recovery rate and purity; accumulation of impurity phosphorus and silicon to a certain extent will also reduce the purity of the vanadium product. Purification effectively reduces the sulfate and impurity content, and the purified circulating liquid meets the needs of circulating production of high-purity vanadium pentoxide.

[0123] Example 7

[0124] The mother liquors from the acid and alkali processes were purified and used as solvents in the experiment.

[0125] Acid precipitation of vanadium: Add 25g of ammonium metavanadate to 250ml of acid circulating liquid at 75℃, add sulfuric acid at 85℃ to adjust the pH to 3.1, raise the temperature to 99℃, keep warm for 30min, and stir all the time. Then separate the solid and liquid and wash with water to obtain ammonium polyvanadate solid. Alkaline precipitation of vanadium: Add 18g of ammonium polyvanadate to 250ml of alkaline circulating liquid at 95℃, add ammonia water to adjust the pH to 9, keep warm for 15min and cool down to 23℃, keep warm for 60min, separate the solid and liquid and wash with water to obtain high-purity ammonium metavanadate. High-purity ammonium metavanadate is calcined at 550℃ for 2 hours to obtain 99.96% high-purity vanadium pentoxide.

[0126] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0127] In the embodiment of the present application, the technical idea of ​​producing high-purity vanadium pentoxide from ammonium metavanadate is an acid-base combined secondary crystallization method, and the purpose of producing high-purity vanadium pentoxide from ammonium metavanadate is achieved by two crystallization precipitations of vanadium by acid method and alkali method. The method and parameters of the invention process are provided. The process is simple, controllable, low-cost, closed-loop, pollution-free, and can produce 99.9% high-purity vanadium pentoxide, which can improve corporate benefits, market competitiveness, and added value of vanadium products, and meet the high-end market demand for vanadium products.

[0128] In the embodiment of the present application, the preparation method is a closed-loop process, and the acidic circulating fluid and the alkaline circulating fluid are recycled after being purified by adding impurity removers under certain conditions, and the purified solid calcium sulfate dihydrate can be sold as a by-product. The present application adopts an acid-base combined secondary crystallization method to obtain high-purity vanadium pentoxide. The process is low-cost, closed-loop production, pollution-free, and can produce 99.9% high-purity vanadium pentoxide, increase the added value of vanadium products, and meet the high-end market demand for vanadium products.

[0129] In the embodiment of the present application, ammonium metavanadate is dissolved in an acidic circulating mother liquor at a certain solid content, temperature, and pH, the temperature is raised to a certain temperature, and the temperature is kept for a certain time to precipitate vanadium to obtain the product ammonium polyvanadate, and then the ammonium polyvanadate is dissolved in an alkaline circulating mother liquor at a certain solid content, temperature, pH, and time, the temperature is lowered to a certain temperature, and the temperature is kept for a certain time to precipitate vanadium to obtain high-purity ammonium metavanadate. The high-purity ammonium metavanadate is calcined to obtain high-purity vanadium pentoxide, thereby providing a method for purifying acidic and alkaline circulating mother liquors.

[0130] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing high-purity vanadium pentoxide from ammonium metavanadate in a closed circuit, the method comprising: The ammonium metavanadate raw material is subjected to acid vanadium precipitation to obtain ammonium polyvanadate; wherein the ammonium metavanadate is prepared from vanadium slag extracted from Bayer process alumina production; subjecting the ammonium polyvanadate to alkaline precipitation of vanadium to obtain high-purity ammonium metavanadate; and The high-purity ammonium metavanadate is roasted to obtain vanadium pentoxide.

2. The method according to claim 1, characterized in that The method of subjecting the ammonium metavanadate raw material to acid precipitation of vanadium to obtain ammonium polyvanadate comprises: Adding the ammonium metavanadate raw material into a solvent having a first set temperature to obtain a first mixed solution; At a second set temperature, adjusting the pH of the first mixed solution to a first set pH to obtain a second mixed solution; At a third set temperature, subjecting the second mixed solution to a heat preservation treatment for a first set time to precipitate vanadium, thereby obtaining a third mixed solution; The third mixed liquid is subjected to solid-liquid separation to obtain ammonium polyvanadate and acidic circulating mother liquor.

3. The method according to claim 2, characterized in that The first set temperature is 60°C to 85°C; and / or, The second set temperature is 70°C to 90°C; and / or, The third set temperature is 95° C. to 99° C., and the first set time is 30 min to 60 min.

4. The method according to claim 2, characterized in that: The pH of the first mixed solution is adjusted using sulfuric acid, and the first set pH is 2.5-3.

5.

5. The method according to claim 2, characterized in that: The acidic circulating mother liquor is circulated for acid dissolving the ammonium metavanadate raw material to form a closed cycle; the method further comprises: The acidic circulating mother liquor is subjected to a first purification treatment using calcium hydroxide; the temperature of the first purification treatment is 60° C. to 99° C., and the time of the first purification treatment is 60 min to 120 min.

6. The method according to claim 1, characterized in that The step of subjecting the ammonium polyvanadate to alkaline precipitation of vanadium to obtain high-purity ammonium metavanadate comprises: adding ammonium polyvanadate to a solvent having a fourth set temperature, and adjusting the pH to the second set pH to obtain a fourth mixed solution; At the fourth set temperature, the fourth mixed solution is subjected to a heat preservation treatment for a second set time to dissolve the ammonium polyvanadate with alkali to obtain a fifth mixed solution; The fifth mixed solution is cooled to a fifth set temperature and subjected to a heat preservation treatment for a third set time to precipitate ammonium metavanadate, thereby obtaining a sixth mixed solution; The sixth mixed liquid is subjected to solid-liquid separation to obtain the ammonium metavanadate and alkaline circulating mother liquor.

7. The method according to claim 6, characterized in that The fourth set temperature is 85° C. to 95° C., and the second set time is 15 min to 30 min; and / or, The fifth set temperature is 20° C. to 40° C., and the third set time is 60 min to 120 min.

8. The method according to claim 6, characterized in that The pH is adjusted to the second set pH using ammonia water, and the second set pH is 8.5-9.

5.

9. The method according to claim 6, characterized in that The alkaline circulating mother liquor is circulated for alkali dissolution of ammonium polyvanadate to form a closed cycle; the method further comprises: The alkaline circulating mother liquor is subjected to a second purification treatment using calcium hydroxide; the temperature of the second purification treatment is 20° C. to 80° C., and the time of the second purification treatment is 60 min to 120 min.

10. The method according to claim 1, characterized in that The calcination temperature is 500° C. to 550° C., and the calcination time is 90 min to 150 min.

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