Method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution

Abstract

The invention discloses a method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution, which comprises the following steps: adjusting the pH value of the high-concentration sodium vanadium solution with acid, sequentially adding an inorganic ammonium salt and an organic ammonium salt, respectively reacting, carrying out solid-liquid separation to obtain vanadium-containing precipitate, dissolving the vanadium-containing precipitate, adding ammonium sulfate to prepare ammonium metavanadate, and filtering to obtain the high-purity vanadium pentoxide. And reducing ammonium metavanadate to prepare vanadium pentoxide. According to the method, introduction of more impurities due to hydrolysis in the vanadium precipitation process of the high-concentration sodium vanadium solution is effectively prevented. The method is simple in technological process, and does not need the procedures of impurity removal, high temperature and the like.

Description

Technical Field

[0001] The invention relates to the technical field of vanadium oxide preparation, in particular to a method for preparing high-purity vanadium pentoxide from a high-concentration sodium vanadium solution. Background Art

[0002] Vanadium is mainly used in the steel industry to significantly improve the performance of steel. At present, the industrial precipitation of vanadium uses sodium vanadium liquid obtained by sodium roasting-water leaching and calcium acidic vanadium liquid obtained by calcium roasting-acid leaching as raw materials, adds ammonium salt, and precipitates vanadium-containing precipitates under high temperature conditions to prepare vanadium pentoxide. At present, due to the high concentration of sodium vanadium liquid, it is easy to hydrolyze during the precipitation process, resulting in a high impurity content, and it is impossible to prepare high-purity vanadium pentoxide. In industry, most of the methods used are to re-dissolve and purify the ammonium polyvanadate precipitated by the sodium vanadium liquid, and add reducing agents to prepare high-purity vanadium pentoxide. The process is long, the vanadium loss is high, and the vanadium yield is low.

[0003] CN 117383613 B discloses a method for preparing vanadium pentoxide, which comprises the following steps: (1) alkali dissolution: mixing sodium hydroxide, sodium carbonate, raw materials containing vanadium ammonium salt and water, heating for reaction, and filtering; (2) primary impurity removal: adding ferric sulfate to the filtrate, stirring, adding sodium sulfate, stirring for reaction, cooling and standing, and filtering; (3) secondary impurity removal: adjusting the pH of the filtrate to 8-9, adding sodium dimethyldithiocarbamate, heating for reaction, adding copper sulfate, stirring for reaction, cooling and standing, and filtering; (4) vanadium precipitation: adding hydrogen peroxide solution to the filtrate, stirring until the solution changes color, then adding ammonia water to adjust the pH to 9-9.8, then adding ammonium salt, heating and stirring for reaction, and filtering; (5) eluting potassium and sodium; (6) drying and roasting. The prior art adopts a chemical precipitation method to prepare high-purity vanadium pentoxide, and has the advantage of strong adaptability to raw materials containing vanadium ammonium salt obtained by extracting vanadium from waste catalysts. However, the prior art includes impurity removal and has a long process flow.

[0004] CN 118458822 A discloses a method for preparing ammonium polyvanadate from high-concentration vanadium solution, comprising the following steps: a. first adding 5 to 15 m 3High-concentration vanadium liquid, add the ammonium salt solution required to meet the total vanadium liquid volume of the entire reactor at one time, and start stirring; add sulfuric acid to adjust the pH value of the solution to 1.9-2.2, pass steam to heat to 80-100°C, and keep it for 20-30 minutes; continue to add a certain volume of high-concentration vanadium liquid, add sulfuric acid to adjust the pH value of the solution to 1.9-2.2, continue to pass steam to heat to 80-100°C, and keep it for 20-60 minutes; after the reaction is completed, the slurry is pumped into a filter press for pressure filtration, water washing, and drying, and finally a qualified ammonium polyvanadate product is obtained. This existing technology can greatly increase the concentration of vanadium precipitation vanadium liquid to 30-90g / L, reduce the generation of vanadium precipitation wastewater, speed up the precipitation rate, and increase the specific gravity of ammonium polyvanadate material pile. However, this existing technology heats the reaction under stirring conditions, and the K2O+Na2O content in the ammonium polyvanadate product is relatively high.

[0005] CN 115010176 B discloses a method for preparing high-purity vanadium pentoxide, which comprises the following steps: a. alkali dissolution of crude vanadium: ammonium metavanadate, ferric citrate and water are mixed and dissolved, alkali is added to the system, stirred and precipitated to obtain a vanadium precipitation mother liquor; b. ammonium salt vanadium precipitation: H2O2 and ammonium citrate are added to the vanadium precipitation mother liquor, vanadium precipitation is obtained, and an ammonium metavanadate product is obtained; c. calcination: the ammonium metavanadate product is calcined to obtain high-purity vanadium pentoxide; the purity of the high-purity vanadium pentoxide is not less than 99.0%. The prior art obtains high-purity ammonium metavanadate through triple impurity removal, and after high-temperature calcination, vanadium pentoxide with a purity greater than 99.5% is obtained. The method has the advantages of simple process, low cost, good impurity removal effect, etc. However, the prior art uses ammonium metavanadate as a raw material, and uses citric acid and its corresponding salt as an impurity remover and vanadium precipitation ammonium salt to obtain high-purity ammonium metavanadate and vanadium pentoxide.

[0006] CN 115636441 A discloses a method for preparing high-density low-sodium ammonium polyvanadate by sodiumizing vanadium liquid, comprising the following steps in sequence: S1, adjusting the pH value of the vanadium liquid to 5.5-6.5; S2, controlling the temperature of the vanadium liquid to 40-50°C; S3, adding a composite ammonium salt to the vanadium liquid, the composite ammonium salt comprising ammonium bicarbonate and ammonium acetate; S4, activating the vanadium liquid for a predetermined time at a temperature of 40-50°C and a pH value of 4-4.5; S5, adding ammonium sulfate to the vanadium liquid; S6, adjusting the pH value of the vanadium liquid to 1.5-1.8; S7, heating the vanadium liquid to boiling, then filtering and washing to obtain ammonium polyvanadate; in step S1, adjusting the pH value of the vanadium liquid by sulfuric acid; in step S3, the mass ratio of ammonium bicarbonate to ammonium acetate in the composite ammonium salt is 1:0.2; in step S3, the ratio of the mass of the added composite ammonium salt to the total mass of vanadium in the vanadium liquid is 0.05-0.2. The prior art discloses that the use of a composite ammonium salt containing an inorganic ammonium salt, ammonium bicarbonate, and an organic ammonium salt, ammonium acetate, can achieve the reaction effect of removing sodium and increasing the density ratio, and vanadium is precipitated after using ammonium sulfate and adjusting the pH value with sulfuric acid. However, the prior art precipitates vanadium at high temperature, and the process flow is relatively complicated.

[0007] CN 104973626 B discloses a method for preparing high-purity ammonium metavanadate from sodium vanadium solution. The method comprises the following steps: (1) mixing polyvinyl alcohol, a soluble ammonium salt and the sodium vanadium solution, adjusting the pH value of the obtained mixture to neutral or weakly alkaline after the soluble ammonium salt is dissolved, and reacting at the pH value; (2) performing solid-liquid separation on the mixture obtained by the reaction, and drying the separated solid; in step (1), the reaction conditions include: temperature of 0-60°C; time of 30-180min; reaction is carried out under stirring; ammonium metavanadate is precipitated by adding surfactant polyvinyl alcohol and soluble ammonium salt to the sodium vanadium solution, so that the vanadium precipitation rate is as high as more than 99%, and the density of the prepared ammonium metavanadate reaches 1.5g / cm 3 The purity is as high as 99.5%. The prior art discloses that the reaction can occur at a lower temperature of 0-60°C due to the introduction of polyvinyl alcohol. However, the polyvinyl alcohol introduced in the prior art needs to be recycled, and the vanadium is usually present in the form of pentavalent vanadium. If it is in a low-valent state, an oxidant needs to be added. In addition, the purity of the vanadium pentoxide prepared by the prepared ammonium metavanadate is not disclosed.

[0008] Based on this, there is room for improvement in the preparation of high-purity vanadium pentoxide from high-concentration sodium vanadium solution. Summary of the invention

[0009] In view of this, the present invention provides a method for preparing high-purity vanadium pentoxide from a high-concentration sodium vanadium liquid, which solves the problems of long process flow, high vanadium loss and low vanadium yield in the industrial preparation of high-purity vanadium pentoxide by means of re-dissolving and purifying ammonium polyvanadate precipitated from the sodium vanadium liquid and adding a reducing agent.

[0010] The invention provides a method for preparing high-purity vanadium pentoxide from a high-concentration sodium vanadium solution, comprising: adjusting the pH value of the high-concentration sodium vanadium solution by acid, sequentially adding an inorganic ammonium salt and an organic ammonium salt to react with each other and separate the solid from the liquid to obtain a vanadium-containing precipitate, adding ammonium sulfate to the vanadium-containing precipitate after the vanadium-containing precipitate is dissolved to obtain ammonium metavanadate, and reducing the ammonium metavanadate to prepare vanadium pentoxide.

[0011] In some embodiments, the acid is sulfuric acid.

[0012] In some embodiments, the method for preparing high-purity vanadium pentoxide from a high-concentration sodium vanadium solution comprises the following steps: Step a, adding sulfuric acid to a high concentration sodium vanadium solution at a first temperature, adjusting the pH value to a first pH value, and obtaining a vanadium precipitation pre-solution; Step b, adding an inorganic ammonium salt to the pre-vanadium precipitation solution according to a first ammonium addition coefficient, reacting for a first time, adding an organic ammonium salt according to a second ammonium addition coefficient, reacting for a second time, and separating the solid and the liquid to obtain a vanadium-containing precipitate; Step c, adding deionized water at a first liquid-to-solid ratio to dissolve the vanadium-containing precipitate at a second temperature to obtain a high-purity vanadium liquid; Step d, cooling the high-purity vanadium liquid to a third temperature, adding alkali solution to adjust the pH value to a second pH value, adding ammonium sulfate according to a third ammonium addition coefficient, and reacting for a third time to obtain ammonium metavanadate; Step e, preparing vanadium pentoxide by high-temperature decomposition of ammonium metavanadate.

[0013] In some embodiments, in step a, the vanadium concentration in the high concentration sodium vanadium solution is 40-60 g / L.

[0014] In some embodiments, in step a, the first temperature is 40-60° C., and the first pH value is 4-7.

[0015] In some embodiments, in step b, the first ammonium addition coefficient is 1.4-2.0 in terms of mass ratio, the inorganic ammonium salt is ammonium sulfate, and the first time is 40-60 minutes.

[0016] In some embodiments, in step b, the second ammonium addition coefficient is 0.2-0.5 in terms of mass ratio, the organic ammonium salt is tetrabutylammonium bromide or tetraethylammonium bromide, and the second time is 15-30 min.

[0017] In some embodiments, in step c, the first liquid-to-solid ratio is 6-8:1, and the second temperature is 90-95°C.

[0018] In some embodiments, in step d, the third temperature is 20-40° C., the alkali solution is aqueous ammonia, and the second pH value is 6-8.

[0019] In some embodiments, in step d, the third ammonium addition coefficient is 1.2-2.0 in terms of molar ratio, and the third time is 60-120 min.

[0020] Beneficial effects of the present invention: The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium liquid of the present invention comprises the following steps: firstly, adjusting the pH value of the high-concentration sodium vanadium liquid by sulfuric acid to inhibit the hydrolysis of the high-concentration sodium vanadium liquid; secondly, using an organic ammonium salt to recover the incompletely precipitated portion of the inorganic ammonium salt; the vanadium recovery rate is high, the product quality is high, and the hydrolysis of the high-concentration sodium vanadium liquid during the vanadium precipitation process is effectively prevented to introduce more impurities. The method of the present invention has a simple process flow and does not require impurity removal, high temperature and other processes. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments.

[0022] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. The subsequent embodiments will not explain this one by one.

[0023] The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution of the present invention comprises: adjusting the pH value of the high-concentration sodium vanadium solution by acid, adding inorganic ammonium salt and organic ammonium salt in sequence to react with each other and separate the solid and liquid to obtain vanadium-containing precipitate, adding ammonium sulfate to prepare ammonium metavanadate after the vanadium-containing precipitate is dissolved, and reducing the ammonium metavanadate to prepare vanadium pentoxide.

[0024] In some embodiments, the acid is sulfuric acid.

[0025] Sulfuric acid is a strong acid. Adding it to high-concentration sodium vanadium solution can reduce the pH value of the solution. When the solution is acidic, the concentration of hydrogen ions around the vanadium ions will increase. According to the principle of chemical equilibrium, this will inhibit the hydrolysis reaction between vanadium ions and water, thereby reducing the generation of hydrolysis products; sulfate ions can complex with vanadium ions in the sodium vanadium solution to form relatively stable complex ions. The presence of these complex ions reduces the concentration of free vanadium ions in the solution, reduces the concentration of reactants in the hydrolysis reaction, and thus inhibits the hydrolysis reaction; there may be some impurity ions in the high-concentration sodium vanadium solution, and these impurity ions may promote the hydrolysis of the vanadium solution. Sulfuric acid can react with some impurity ions, convert them into precipitates or more stable compounds and remove them, thereby indirectly inhibiting the hydrolysis of the sodium vanadium solution. Sulfuric acid can inhibit the hydrolysis of high-concentration sodium vanadium solution.

[0026] Compared with the prior art, the method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium liquid of the present invention firstly adjusts the pH value of the high-concentration sodium vanadium liquid by sulfuric acid to inhibit the hydrolysis of the high-concentration sodium vanadium liquid, and then uses organic ammonium salt to recover the part of the inorganic ammonium salt that is not completely precipitated, so that the vanadium recovery rate is high and the product quality is high, and the hydrolysis of the high-concentration sodium vanadium liquid during the vanadium precipitation process is effectively prevented to introduce more impurities. The problem of long process flow, high vanadium loss and low vanadium yield in the industrial preparation of high-purity vanadium pentoxide by means of re-dissolving and purifying the ammonium polyvanadate precipitated from the sodium vanadium liquid and adding a reducing agent is solved.

[0027] The method for preparing high-purity vanadium pentoxide from a high-concentration sodium vanadium solution of the present invention comprises the following steps: Step a, adding sulfuric acid to a high concentration sodium vanadium solution at a first temperature, adjusting the pH value to a first pH value, and obtaining a vanadium precipitation pre-solution; Step b, adding an inorganic ammonium salt to the pre-vanadium precipitation solution according to a first ammonium addition coefficient, reacting for a first time, adding an organic ammonium salt according to a second ammonium addition coefficient, reacting for a second time, and separating the solid and the liquid to obtain a vanadium-containing precipitate; Step c, adding deionized water at a first liquid-to-solid ratio to dissolve the vanadium-containing precipitate at a second temperature to obtain a high-purity vanadium liquid; Step d, cooling the high-purity vanadium liquid to a third temperature, adding alkali solution to adjust the pH value to a second pH value, adding ammonium sulfate according to a third ammonium addition coefficient, and reacting for a third time to obtain ammonium metavanadate; Step e, preparing vanadium pentoxide by high-temperature decomposition of ammonium metavanadate.

[0028] In some embodiments, in step a, the vanadium concentration in the high concentration sodium vanadium solution is 40-60 g / L.

[0029] In some embodiments, in step a, the first temperature is 40-60° C., and the first pH value is 4-7.

[0030] In some embodiments, in step b, the first ammonium addition coefficient is 1.4-2.0 in terms of mass ratio, the inorganic ammonium salt is ammonium sulfate, and the first time is 40-60 minutes.

[0031] When ammonium sulfate is added to the sodium vanadium solution, a double decomposition reaction occurs to generate ammonium metavanadate precipitate. For example, in some processes for preparing vanadium pentoxide, ammonium sulfate reacts with sodium vanadate in the sodium vanadium solution. By controlling reaction conditions such as pH and temperature, the precipitation reaction can be made more complete, thereby achieving the separation and purification of vanadium. The ammonium ions in the ammonium sulfate may undergo ion exchange with the sodium ions in the sodium vanadium solution. However, the extent of this reaction is relatively small, and the impact on the entire system is usually not as significant as the precipitation reaction.

[0032] In the presence of sulfuric acid, after ammonium sulfate is dissolved, sulfate ions combine with sodium ions in the sodium vanadium solution. At the same time, in the acidic environment provided by sulfuric acid, hydrogen ions combine with vanadate ions, prompting substances such as sodium metavanadate in the sodium vanadium solution to be converted into sodium vanadate. As the reaction proceeds, when the concentration of ammonium ions, vanadate ions, and pH value in the solution reach a certain level, a vanadium precipitation reaction will occur to generate ammonium metavanadate precipitate. Acidic conditions will inhibit the hydrolysis of ammonium ions, allowing ammonium sulfate to exist relatively stably in the solution, which is conducive to its full reaction with the components in the sodium vanadium solution. In addition, if the sodium vanadium solution contains certain impurity ions, sulfate ions may react with these impurity ions to generate insoluble sulfate precipitates, thereby achieving an impurity removal effect.

[0033] In some embodiments, in step b, the second ammonium addition coefficient is 0.2-0.5 in terms of mass ratio, the organic ammonium salt is tetrabutylammonium bromide or tetraethylammonium bromide, and the second time is 15-30 min.

[0034] Tetrabutylammonium bromide will ionize into tetrabutylammonium ions and bromide ions in the solution. Tetrabutylammonium ions may undergo ion exchange with sodium ions to generate tetrabutylammonium vanadium and sodium bromide. However, because the properties of sodium ions and tetrabutylammonium ions are different and the reaction is also affected by solution concentration, temperature and other conditions, the degree of this reaction may be small. Under normal circumstances, tetrabutylammonium bromide itself does not have strong oxidizing or reducing properties, but the vanadium element in the sodium vanadium solution has multiple valence states, and vanadium with different valence states has different redox properties. If there are suitable conditions in the solution, such as a specific pH value, other reactants, etc., tetrabutylammonium bromide may affect the redox reaction of vanadium ions, changing its reaction rate or reaction direction. For example, it may act as a phase transfer catalyst to make the transfer of vanadium ions between different phases easier, thereby promoting the redox reaction. Tetrabutylammonium ions have a certain spatial structure and charge distribution, and may undergo coordination reactions with vanadium ions in the sodium vanadium solution to form coordination compounds. However, whether this coordination reaction occurs and the stability of the coordination compound depend on factors such as the properties of the vanadium ion, other components in the solution, and reaction conditions.

[0035] Tetraethylammonium bromide will ionize into tetraethylammonium ions and bromide ions in the solution. Tetraethylammonium ions may undergo ion exchange with sodium ions in the sodium vanadium solution, but the degree of reaction is small and is affected by the solution concentration, temperature and other conditions. Tetraethylammonium bromide itself is usually not strongly oxidizing or reducing, but it may affect the redox reaction of vanadium ions in the sodium vanadium solution. As a phase transfer catalyst, it makes it easier for vanadium ions to transfer between different phases, thereby promoting the redox reaction. Tetraethylammonium ions may undergo coordination reaction with vanadium ions in the sodium vanadium solution to form coordination compounds. Whether this reaction occurs and the stability of the coordination compounds depend on the properties of the vanadium ions, the composition of the solution and the reaction conditions.

[0036] In some embodiments, in step c, the first liquid-to-solid ratio is 6-8:1, and the second temperature is 90-95°C.

[0037] In some embodiments, in step d, the third temperature is 20-40°C, and the second pH value is 6-8.

[0038] In some embodiments, in step d, the alkali solution is aqueous ammonia.

[0039] In some embodiments, in step d, the third ammonium addition coefficient is 1.2-2.0 in terms of molar ratio, and the third time is 60-120 min.

[0040] In the present application, the ammonium addition coefficient refers to the ratio of the amount of ammonium salt added to the vanadium content in the solution. The first ammonium addition coefficient refers to the ratio of the mass of the inorganic ammonium salt to the mass of the vanadium in the pre-vanadium precipitation solution. The second ammonium addition coefficient refers to the ratio of the mass of the organic ammonium salt to the mass of the vanadium in the pre-vanadium precipitation solution. The third ammonium addition coefficient refers to the ratio of the amount of ammonium sulfate to the amount of vanadium in the high-purity vanadium solution.

[0041] Example 1 At 40°C, sulfuric acid was added to 100 mL of high-concentration sodium vanadium solution, the vanadium concentration in the high-concentration sodium vanadium solution was 40 g / L, the pH value was adjusted to 4, and a vanadium precipitation pre-liquid was obtained. Inorganic ammonium sulfate was added to the vanadium precipitation pre-liquid at an ammonium addition coefficient of 1.4, and the reaction lasted for 40 minutes. Tetrabutylammonium bromide was added at an ammonium addition coefficient of 0.2, and the reaction lasted for 15 minutes. Solid-liquid separation was performed to obtain a vanadium-containing precipitate. Deionized water was added at a liquid-solid ratio of 6:1, and the vanadium-containing precipitate was dissolved at 90°C to obtain a high-concentration vanadium solution. The high-purity vanadium solution was cooled to 20°C, ammonia water was added to adjust the pH value to 6, and ammonium sulfate was added at an ammonium addition coefficient of 1.2. The reaction lasted for 60 minutes to obtain ammonium metavanadate, and ammonium metavanadate was decomposed at high temperature to obtain vanadium pentoxide, and the purity of vanadium pentoxide was 99.95%.

[0042] Example 2 At 50°C, sulfuric acid was added to 100 mL of high-concentration sodium vanadium solution, the vanadium concentration in the high-concentration sodium vanadium solution was 50 g / L, and the pH value was adjusted to 6 to obtain a vanadium precipitation pre-liquid. Inorganic ammonium sulfate was added to the vanadium precipitation pre-liquid at an ammonium addition coefficient of 1.6, and after reacting for 50 minutes, tetrabutylammonium bromide was added at an ammonium addition coefficient of 0.3. After reacting for 20 minutes, solid-liquid separation was performed to obtain a vanadium-containing precipitate. Deionized water was added at a liquid-solid ratio of 7:1, and the vanadium-containing precipitate was dissolved at 92°C to obtain a high-concentration vanadium solution. The high-purity vanadium solution was cooled to 25°C, ammonia water was added to adjust the pH value to 7, and ammonium sulfate was added at an ammonium addition coefficient of 1.8. The reaction was carried out for 90 minutes to obtain ammonium metavanadate, and ammonium metavanadate was decomposed at high temperature to obtain vanadium pentoxide, and the purity of vanadium pentoxide was 99.91%.

[0043] Example 3 At 60°C, sulfuric acid was added to 100 mL of high-concentration sodium vanadium solution, the vanadium concentration in the high-concentration sodium vanadium solution was 60 g / L, and the pH value was adjusted to 7 to obtain a vanadium precipitation pre-liquid. Inorganic ammonium sulfate was added to the vanadium precipitation pre-liquid at an ammonium addition coefficient of 2.0, and after reacting for 60 minutes, tetraethylammonium bromide was added at an ammonium addition coefficient of 0.3. After reacting for 30 minutes, solid-liquid separation was performed to obtain a vanadium-containing precipitate. Deionized water was added at a liquid-solid ratio of 8:1, and the vanadium-containing precipitate was dissolved at 95°C to obtain a high-concentration vanadium solution. The high-purity vanadium solution was cooled to 30°C, ammonia water was added to adjust the pH value to 8, and ammonium sulfate was added at an ammonium addition coefficient of 2, and the reaction was carried out for 120 minutes to obtain ammonium metavanadate. Ammonium metavanadate was decomposed at high temperature to obtain vanadium pentoxide, and the purity of vanadium pentoxide was 99.92%.

[0044] Comparative Example At 50°C, sulfuric acid was added to 100 mL of high-concentration sodium vanadium solution, the vanadium concentration in the high-concentration sodium vanadium solution was 50 g / L, and the pH value was adjusted to 6 to obtain a vanadium precipitation pre-liquid. Inorganic ammonium salt ammonium sulfate was added to the vanadium precipitation pre-liquid at an ammonium addition coefficient of 1.6, and the reaction was carried out at a temperature of 95°C for 50 minutes, followed by solid-liquid separation to obtain ammonium polyvanadate. Deionized water was added at a liquid-solid ratio of 7:1, and sodium hydroxide was added at 92°C to dissolve the ammonium polyvanadate to obtain a high-concentration vanadium solution. Ammonium sulfate was added at an ammonium addition coefficient of 1.8, and the reaction was carried out for 90 minutes to obtain ammonium metavanadate. Ammonium metavanadate was decomposed at high temperature to obtain vanadium pentoxide, and the purity of vanadium pentoxide was 98%.

[0045] It can be seen from Examples 1-3 and the comparative example that the purity of the vanadium pentoxide product of Examples 1-3 is higher than that of the vanadium pentoxide product of the comparative example, and Examples 1-3 do not need to react at 95° C., which simplifies the process flow.

[0046] The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium liquid can effectively prevent hydrolysis of the high-concentration sodium vanadium liquid during vanadium precipitation and the introduction of more impurities; organic ammonium salt is used to recover the incompletely precipitated part of the inorganic ammonium salt, so the vanadium recovery rate is high and the product quality is high; the process flow is simple and does not require impurity removal, high temperature and other processes.

[0047] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0048] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A method for preparing high-purity vanadium pentoxide from a high-concentration sodium vanadium solution, characterized in that: include: After adjusting the pH value of the high-concentration sodium vanadium solution by acid, inorganic ammonium salt and organic ammonium salt are added in sequence to react with each other and separate the solid and liquid to obtain a vanadium-containing precipitate. After the vanadium-containing precipitate is dissolved, ammonium sulfate is added to prepare ammonium metavanadate, and the ammonium metavanadate is reduced to prepare vanadium pentoxide.

2. The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution according to claim 1, characterized in that: The acid is sulfuric acid.

3. The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution according to claim 2, characterized in that: The following steps are involved: Step a, adding the sulfuric acid to the high concentration sodium vanadium solution at a first temperature, adjusting the pH value to a first pH value, and obtaining a vanadium precipitation pre-solution; Step b, adding an inorganic ammonium salt to the vanadium precipitation pre-liquid according to a first ammonium addition coefficient, reacting for a first time, adding an organic ammonium salt according to a second ammonium addition coefficient, reacting for a second time, and performing solid-liquid separation to obtain the vanadium-containing precipitate; Step c, adding deionized water at a first liquid-to-solid ratio to dissolve the vanadium-containing precipitate at a second temperature to obtain a high-purity vanadium liquid; Step d, cooling the high-purity vanadium liquid to a third temperature, adding alkali solution to adjust the pH value to a second pH value, adding ammonium sulfate according to a third ammonium addition coefficient, and reacting for a third time to obtain ammonium metavanadate; Step e, the ammonium metavanadate is decomposed at high temperature to prepare vanadium pentoxide.

4. The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution according to claim 3, characterized in that: In the step a, the vanadium concentration in the high-concentration sodium vanadium solution is 40-60 g / L.

5. The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution according to claim 3, characterized in that: In the step a, the first temperature is 40-60° C., and the first pH value is 4-7.

6. The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution according to claim 3, characterized in that: In the step b, the first ammonium addition coefficient is 1.4-2.0 in terms of mass ratio, the inorganic ammonium salt is ammonium sulfate, and the first time is 40-60 minutes.

7. The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution according to claim 3, characterized in that: In the step b, the second ammonium addition coefficient is 0.2-0.5 in terms of mass ratio, the organic ammonium salt is tetrabutylammonium bromide or tetraethylammonium bromide, and the second time is 15-30 minutes.

8. The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution according to claim 3, characterized in that: In the step c, the first liquid-to-solid ratio is 6-8:1, and the second temperature is 90-95°C.

9. The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution according to claim 3, characterized in that: In the step d, the third temperature is 20-40° C., the alkali solution is aqueous ammonia, and the second pH value is 6-8.

10. The method for preparing high-purity vanadium pentoxide from high-concentration sodium vanadium solution according to claim 3, characterized in that: In the step d, the third ammonium addition coefficient is 1.2-2.0 in terms of molar ratio, and the third time is 60-120 min.