A method for separating vanadium and chromium in a vanadium-chromium solution

Abstract

This invention discloses a method for separating vanadium and chromium in a vanadium-chromium solution, belonging to the field of wet separation of vanadium-chromium solutions. This method addresses the problem that existing technologies cannot achieve deep separation of vanadium and chromium. The method first adds a reducing agent to the vanadium-chromium solution, converting the highly soluble hexavalent chromate anion into a lower valence state, easily precipitated Cr. 3+ Cations, then add Mn 2+ The chromium removal agent efficiently precipitates trivalent chromium ions from vanadium-containing solutions, achieving deep separation of vanadium and chromium in the liquid phase. Compared with traditional chemical precipitation methods, the vanadium-chromium separation method of this invention has advantages such as high separation coefficient, simple and easy-to-use process, low equipment requirements, convenient operation, and suitability for industrial production.

Description

Technical Field

[0001] This invention relates to the technical field of wet deep separation of vanadium-chromium solutions, and more specifically to a method for separating vanadium and chromium in vanadium-chromium solutions. Background Technology

[0002] Chromium and vanadium are adjacent in atomic number and have similar chemical properties. Vanadium-bearing minerals are often accompanied by chromium-bearing minerals, such as chromite in vanadium-titanium magnetite. According to statistics, 98% of the proven vanadium-bearing minerals come from vanadium-titanium magnetite. The vanadium slag produced during the iron smelting process of vanadium-titanium magnetite, after being processed through "sodium roasting-water leaching," yields sodium vanadium solution, an important vanadium-bearing raw material. Because this solution is alkaline, most cations are removed through hydrolysis and precipitation, while anions such as Cr and Si enter the vanadium solution, making the purification of the vanadium solution extremely difficult.

[0003] Chemical precipitation is the most widely used and common method for separating vanadium and chromium. Its principle involves adding a precipitant to the vanadium-chromium solution that precipitates vanadium ions while avoiding reaction with chromium ions, thus separating vanadium and chromium into solid and liquid phases respectively. Depending on the precipitant, chemical precipitation is mainly divided into aluminum salt precipitation, magnesium salt precipitation, calcium salt precipitation, and iron salt precipitation. Chemical precipitation has advantages such as a relatively simple process flow, low cost, low operational control requirements, and ease of industrial production. However, it can only yield low-chromium vanadium products and is difficult to achieve deep separation. To prepare high-purity vanadium products, a secondary chromium removal process is required, which leads to a long process flow, high vanadium loss rate, and high cost.

[0004] Patent CN112430740A discloses a method for enhancing vanadium-chromium separation by synergistic roasting of vanadium slag using calcium and manganese salts. This method involves mixing vanadium slag, calcium salts, and manganese salts, followed by high-temperature roasting to obtain roasted clinker. The clinker is then acid-leached to obtain a vanadium-containing leachate. During this process, the vanadium leaching rate is greater than 90%, while the chromium leaching rate is less than 0.5%. The main innovation of this method is the addition of calcium and manganese salts during roasting, which solidifies the chromium in the clinker within the slag, thereby achieving the extraction of vanadium and the separation of vanadium and chromium from the vanadium slag. However, this method also suffers from the problem of insufficient vanadium-chromium separation and does not address vanadium-chromium separation technology in solution systems.

[0005] In recent years, other methods for vanadium-chromium separation have been developed, such as ion exchange and stepwise crystallization. Patent CN101538652 discloses a method for separating and recovering vanadium-chromium from vanadium-chromium waste. First, the vanadium-chromium waste is leached with an alkali to obtain a vanadium-chromium solution, and then vanadium-chromium separation is achieved through ion exchange. While ion exchange has excellent adsorption selectivity and high adsorption capacity, effectively removing cationic impurities, it often results in poor impurity removal when dealing with anionic impurities, as a small amount of anionic impurities may simultaneously replace vanadium ions. Furthermore, ion exchange has drawbacks such as cumbersome operation, the generation of large amounts of wastewater during desorption, long production cycles, and limited processing capacity. The Institute of Process Engineering, Chinese Academy of Sciences, proposed a sub-molten salt high-efficiency clean vanadium extraction technology. This technology prepares a vanadium-chromium solution from vanadium-chromium materials through pressurized alkali leaching. By studying the solubility and phase equilibrium characteristics of vanadium and chromium in alkaline media, sodium vanadate and sodium chromate crystals are prepared through stepwise crystallization, achieving efficient separation of vanadium and chromium. However, this method is energy-intensive and difficult to implement for continuous industrial production.

[0006] Therefore, most existing vanadium-chromium separation methods can only achieve preliminary separation of vanadium and chromium, and cannot achieve deep separation of vanadium and chromium, especially in liquid phase systems. Although a few technologies can achieve efficient separation of vanadium and chromium, these technologies are difficult to apply in industry, and further improvements are necessary. Summary of the Invention

[0007] The purpose of this invention is to provide a method for separating vanadium and chromium from a vanadium-chromium solution to solve the aforementioned problems existing in the prior art.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0009] According to one aspect of the present invention, a method for separating vanadium and chromium from a vanadium-chromium solution is provided, the method comprising the following steps:

[0010] Step S1: Adjust the pH of the vanadium-chromium solution to 5-10, add a reducing agent to reduce the hexavalent chromium ions in the solution to trivalent chromium ions, and obtain solution L1;

[0011] Step S2: Adjust the pH of solution L1 to 8.5-12.5, add a chromium removal agent containing divalent manganese ions, so that trivalent chromium ions and divalent manganese ions in the solution co-precipitate to obtain mixed solution L2;

[0012] Step S3: Filter the mixture L2 to separate the precipitate and solution, obtaining a chromium-containing precipitate and a vanadium-containing filtrate L3.

[0013] According to one embodiment of the present invention, the chromium removal agent containing divalent manganese ions is a soluble divalent manganese salt.

[0014] According to one embodiment of the present invention, the soluble divalent manganese salt is selected from one or more of manganese sulfate, manganese chloride, and manganese nitrate.

[0015] According to one embodiment of the present invention, the amount of chromium removal agent added meets the following requirements: n Mn / n Cr =1.5 to 8.0, where n Mn The amount of Mn in the chromium removal agent 2+ The amount of substance, n Cr Represents the Cr content in the vanadium-chromium solution 6+ The amount of substance.

[0016] According to one embodiment of the present invention, the amount of chromium removal agent added and the pH value of the solution after pH adjustment in step S2 must satisfy the following relationship:

[0017] When pH = 11–12.5, n Cr :n Mn =1:(1.5~3);

[0018] When pH = 9.5–11, n Cr :n Mn =1:(3~6);

[0019] When pH = 8.5–9.5, n Cr :n Mn =1:(6~8).

[0020] According to one embodiment of the present invention, the coprecipitation temperature is 80–100°C and the reaction time is 0.5–3 h.

[0021] According to one embodiment of the present invention, the reducing agent is selected from one or more of sodium metabisulfite, sodium sulfite, and vanadium oxysulfate.

[0022] According to one embodiment of the present invention, the stoichiometric ratio of the reducing agent to hexavalent chromium ions is 1.1 to 6.5, wherein the relationship between the reducing agent and the pH value must meet the following requirements:

[0023] When pH = 5 to 7, the stoichiometric ratio of the reducing agent to hexavalent chromium ions is 1.1 to 1.5, and the reducing agent is selected from one or more of sodium metabisulfite, sodium sulfite, and vanadium oxysulfate.

[0024] When pH = 7-8, the stoichiometric ratio of the reducing agent to hexavalent chromium ions is 1.5-3.5, and the reducing agent is selected from one or more of sodium metabisulfite and sodium sulfite;

[0025] When pH = 8 to 10, the stoichiometric ratio of the reducing agent to hexavalent chromium ions is 3.5 to 6.5, and the reducing agent is selected from one or more of sodium metabisulfite and sodium sulfite.

[0026] According to one embodiment of the present invention, the reduction reaction is carried out at a temperature of 30–100°C for a time of 0.5–6 h.

[0027] According to one embodiment of the present invention, sulfuric acid is used to adjust the pH value in step S1, and sodium hydroxide is used to adjust the pH value in step S2.

[0028] Due to the adoption of the above technical solutions, the method for separating vanadium and chromium in a vanadium-chromium solution provided by the present invention has at least one of the following beneficial effects compared with the prior art:

[0029] (1) The method of the present invention converts highly soluble hexavalent chromate anions into easily precipitated low-valence Cr by adding a reducing agent to a chromium-vanadium solution. 3+ Cations, then add Mn 2+ The chromium removal agent enables the efficient precipitation of trivalent chromium ions in vanadium-containing solutions, achieving deep separation of vanadium and chromium in the liquid phase without introducing excessive manganese ions, thus having no impact on the downstream vanadium precipitation process. The chromium ion content in the separated vanadium solution is reduced to below 0.5 ppm, and the manganese ion content is controlled below 1 ppm. The chromium removal effect is excellent, and the prepared ultrapure vanadium solution meets the purity requirements of various industries for vanadium sources.

[0030] (2) Compared with the traditional chemical precipitation method, the vanadium-chromium separation method of the present invention has the advantages of high separation coefficient, simple and easy-to-use process, low equipment requirements, convenient operation and suitability for industrial production. Attached Figure Description

[0031] Figure 1 The XRD pattern of the precipitate after vacuum calcination obtained in Example 1;

[0032] Figure 2 This is a SEM image of the precipitate obtained in Example 1. Detailed Implementation

[0033] The following provides a detailed description of specific embodiments of this disclosure. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit this disclosure.

[0034] Furthermore, the reference to "embodiment" herein means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand that some embodiments described herein can be combined with other embodiments.

[0035] This invention provides a method for separating vanadium and chromium from a vanadium-chromium solution, which generally includes the following steps:

[0036] Step S1: Adjust the pH of the vanadium-chromium solution to 5-10, add a reducing agent to reduce the hexavalent chromium ions in the solution to trivalent chromium ions, and obtain solution L1;

[0037] Step S2: Adjust the pH of solution L1 to 8.5-12.5, add a chromium removal agent containing divalent manganese ions, so that trivalent chromium ions and divalent manganese ions in the solution co-precipitate to obtain mixed solution L2;

[0038] Step S3: Filter the mixture L2 to separate the precipitate and solution, obtaining a chromium-containing precipitate and a vanadium-containing filtrate L3.

[0039] In the above-described method of the present invention, a chromium removal agent containing divalent manganese ions is used. The term "chromium removal agent" refers to a substance that, in an alkaline solution environment, can interact with chromium ions, promoting the hydrolysis and precipitation of chromium ions and physical adsorption of chromium ions through flocculation. Here, the "chromium removal agent" has a dual function, encompassing both chemical co-precipitation (co-precipitation is a chemical adsorption process) and physical adsorption (flocculation). In an alkaline solution environment, when divalent manganese ions begin to hydrolyze and form manganese hydroxide flocculent precipitate, the surface ionic charge is not yet balanced. At this time, Mn(OH)3 is formed. - and Mn(OH)4 2- Ions will adsorb Cr, which has lower solubility. 3+ Furthermore, the lower the solubility, the easier it is to be adsorbed. Since the solubility product constant of Cr(OH)3 (25℃, pH=7) is 6.3×10⁻⁶. -31 The solubility product constant of Mn(OH)₂ is 1.9 × 10⁻⁶. -13 Therefore, the large amount of manganese hydroxide precipitate formed by the addition of manganese ions will rapidly adsorb trivalent chromium ions in the solution, ultimately forming a co-precipitate of manganese hydroxide and chromium hydroxide through surface adsorption. This process mainly includes the following reactions:

[0040] Mn 2+ +OH-→Mn(OH)2↓

[0041] Mn(OH)₂↓+OH⁻→Mn(OH)₃ - Mn(OH)2↓+2OH-→Mn(OH)4 2-

[0042] 3Mn(OH)3 - +Cr 3+ →3Mn(OH)2·Cr(OH)3↓.

[0043] In addition, some Cr in the vanadium solution 3+Ions also hydrolyze to form Cr(OH)3, and the flocculent precipitate of Mn(OH)2 further flocculates and traps the Cr(OH)3 precipitate. The dual effects of chemical adsorption and physical flocculation achieve deep separation of vanadium and chromium in the liquid phase environment, resulting in an ultrapure vanadium solution.

[0044] In the method of the present invention, the selection of the chromium removal agent is crucial, and it needs to meet the following requirements: (1) The chromium removal agent must be able to remove chromium. 3+ (1) Highly efficient removal; (2) Chromium removal agents cannot react with vanadate to produce precipitates, such as Ba. 2+ Ca 2+ Fe 3+ (3) The chromium removal agent must not introduce excessive impurity ions into the vanadium solution. In the method of the present invention, the chromium removal agent is a soluble divalent manganese salt, which can meet the above requirements.

[0045] This method can reduce the chromium content in vanadium solutions to below 0.5 ppm, while also controlling the manganese ion content introduced into the vanadium solution to below 1 ppm. This achieves deep separation of vanadium and chromium in the solution without introducing excessive manganese ions. Furthermore, this process is simple, has a short flow, achieves deep vanadium-chromium separation, is suitable for large-scale production, and reduces the purification cost of high-chromium vanadium solutions.

[0046] In one embodiment of the present invention, in step S1, the pH value of the vanadium-chromium solution is adjusted by adding an acid. The acid can be selected from one or more of hydrochloric acid, nitric acid, and sulfuric acid. The pH value of the solution is adjusted to a suitable range to facilitate the subsequent reduction reaction. In the method of the present invention, the pH value range is limited to 5-10. When the pH value is below 5, vanadium ions will hydrolyze to form polyvanadate precipitates, affecting the reduction of hexavalent chromium. When the pH value is above 10, the reduction efficiency is extremely low, and the reduction is incomplete.

[0047] In one embodiment of the present invention, in step S1, the reducing agent is selected from reducing agents capable of reducing hexavalent chromium ions to trivalent chromium ions in an environment with pH < 10, such as, but not limited to, one or more of sodium metabisulfite, sodium sulfite, and vanadium oxysulfate, or vanadium-based reducing agents (e.g., one or more of vanadium sulfate, vanadium oxychloride, vanadium oxalate, and vanadium dioxide), or sulfur-containing reducing agents (e.g., one or more of sodium thiosulfate, hydrogen sulfide, sodium sulfide, and sodium hydrosulfide) and organic reducing agents (e.g., one or more of vitamin C, oxalic acid, formic acid, tartaric acid, and citric acid).

[0048] In one embodiment of the present invention, in step S1, the stoichiometric ratio (amount of substance) of the reducing agent and hexavalent chromium ions is 1.1 to 6.5, the reaction temperature is 30 to 100°C, and the stirring reaction time is 0.5 to 6 hours.

[0049] In one embodiment of the present invention, in step S1, the relationship between the amount of reducing agent and the pH value must meet the following requirements:

[0050] When pH = 5-7, the stoichiometric ratio of the reducing agent to hexavalent chromium ions is 1.1-1.5, and the reducing agent is preferably one or more of sodium metabisulfite, sodium sulfite, and vanadium oxysulfate;

[0051] When pH = 7-8, the stoichiometric ratio of the reducing agent to hexavalent chromium ions is 1.5-3.5. The reducing agent is preferably sodium metabisulfite and / or sodium sulfite. Within this pH range, vanadium oxysulfate will lose its reducing effect due to the formation of vanadium oxyhydroxide precipitate.

[0052] When pH = 8 to 10, the stoichiometric ratio of the reducing agent to hexavalent chromium ions is 3.5 to 6.5. The reducing agent is preferably sodium metabisulfite and / or sodium sulfite. Within this pH range, vanadium oxysulfate will lose its reducing effect due to the formation of vanadium oxyhydroxide precipitate.

[0053] In one embodiment of the present invention, in step S2, the pH value of solution L1 is adjusted by adding an alkali to the solution. The alkali can be selected from NaOH or KOH. The pH value of the solution is adjusted to a suitable range so that trivalent chromium ions are fully hydrolyzed and co-precipitated. In the method of the present invention, the pH value range is limited to 8.5–12.5; when the pH value is below 8.5, Cr… 3+ Incomplete hydrolysis and incomplete separation of vanadium and chromium, coupled with a pH value higher than 12.5, can lead to chromium return, where some of the precipitated chromium hydroxide dissolves in the alkaline solution to form sodium chromate.

[0054] In one embodiment of the present invention, in step S2, the chromium removal agent containing divalent manganese ions is selected from one or more of manganese sulfate, manganese chloride, manganese nitrate, or hydrates of these substances. The amount of chromium removal agent added satisfies n Mn / n Cr =1.5 to 8.0, where n Mn The amount of Mn in the chromium removal agent 2+ The amount of substance, n Cr Represents the Cr content in the vanadium-chromium solution 6+ The amount of substance. The temperature range for coprecipitation is 80–100℃, and the stirring time is 0.5–3 h.

[0055] In one embodiment of the present invention, in step S2, the amount of chromium removal agent containing divalent manganese ions added must satisfy the following relationship with the pH value of the solution:

[0056] When pH = 11–12.5, n Cr :n Mn =1:(1.5~3);

[0057] When pH = 9.5–11, n Cr :n Mn =1:(3~6);

[0058] When pH = 8.5–9.5, n Cr :n Mn =1:(6~8);

[0059] Among them, within each pH range, the amount of chromium removal agent consumed increases as the pH value decreases.

[0060] The technical solution of the present invention will be further illustrated by specific embodiments below. Unless otherwise stated, the raw materials, equipment, consumables, etc. used in the following embodiments can all be obtained through conventional commercial means.

[0061] In the following embodiments, V ions in the vanadium filtrate were detected by potassium permanganate oxidation-ferrous ammonium sulfate titration; Cr and Mn ions were detected by ICP-MS, inductively coupled plasma mass spectrometry.

[0062] Example 1

[0063] One L of sodium vanadium solution was taken from the Panzhihua Iron and Steel Group Vanadium Products Branch. This vanadium solution was obtained from vanadium slag produced during the ironmaking process through "sodium roasting-water leaching". The concentration of Cr ions was 2.05 g / L, and the concentration of V ions was 44.12 g / L. Sulfuric acid solution was added dropwise to adjust the pH to 5.0, followed by the addition of 31.42 g of VOSO4 (32.5% water content). The mixture was stirred at 30°C for 0.5 h. The pH was then adjusted to 12.5 with sodium hydroxide, and the solution was heated to 80°C. 10 g of manganese sulfate monohydrate (MnSO4·H2O) was added, and the mixture was stirred for 0.5 h. After the reaction was complete, the mixture was filtered to obtain a blue-green filter cake and a colorless vanadium filtrate. The contents of Cr, Mn, and V ions in the vanadium filtrate were measured, and the results are shown in Table 1 below.

[0064] Table 1. Analytical results of vanadium filtrate composition

[0065] Cr Mn V 0.12ppm 0.83ppm 43.07g / L

[0066] On the other hand, to verify the phase, composition, and characteristics of the precipitate, the precipitate (excluding chromium slag) obtained in this example was calcined at 800°C for 2 hours under vacuum and subjected to XRD analysis. The results are as follows: Figure 1 As shown, analysis revealed that the main phases are Cr2O3, MnO2, and NaVO3. MnO2 is formed because Mn(OH)2 is easily oxidized in air, transforming into a tetravalent state. Figure 2The SEM image of the chromium removal slag shows that it consists of fine particles and lumpy aggregates.

[0067] Example 2

[0068] One L of vanadium-chromium slag alkaline leaching solution was measured. The Cr ion concentration in this solution was 15.99 g / L, and the V ion concentration was 35.60 g / L. Sulfuric acid solution was added dropwise to adjust the pH to 7.5. Then, 174 g of anhydrous sodium sulfite was added, and the solution was stirred at 70 °C for 2 h. The pH was then adjusted to 11.0 with sodium hydroxide, and the solution was heated to 90 °C. 245 g of manganese chloride tetrahydrate (MnCl₂·4H₂O) was added, and the solution was stirred for 1.5 h. After the reaction was complete, the solution was filtered to obtain a dark green filter cake and a colorless vanadium filtrate. The Cr, Mn, and V ion contents in the vanadium filtrate were determined, and the results are shown in Table 2 below.

[0069] Table 2. Analytical results of vanadium filtrate composition

[0070] Cr Mn V 0.29ppm 0.91ppm 34.88g / L

[0071] Example 3

[0072] A 1L chromium-vanadium mixed solution was prepared using sodium vanadate and sodium chromate reagents, respectively. The Cr ion concentration in this mixed solution was 5.00 g / L, and the V ion concentration was 40.00 g / L. Sulfuric acid solution was added dropwise to adjust the pH to 10, then 89 g of sodium metabisulfite was added, and the mixture was stirred at 100℃ for 6 h. The pH was then adjusted to 8.5 with sodium hydroxide, and the solution was heated to 100℃. 193 g of manganese nitrate tetrahydrate (Mn(NO3)2·4H2O) was added, and the mixture was stirred for 3 h. After the reaction was complete, the mixture was filtered to obtain a dark green filter cake and a colorless vanadium filtrate. The Cr, Mn, and V ion contents in the vanadium filtrate were determined, and the results are shown in Table 3 below.

[0073] Table 3. Detection results of vanadium filtrate composition

[0074] Cr Mn V 0.44ppm 0.63ppm 38.37g / L

[0075] Comparative Example 1

[0076] One L of vanadium sodium solution was taken from the Panzhihua Iron and Steel Group Vanadium Products Branch. The Cr ion concentration was 2.05 g / L, and the V ion concentration was 44.12 g / L. Sulfuric acid solution was added dropwise to adjust the pH to 5.0, followed by the addition of 31.42 g of VOSO4 (32.5% water content). The mixture was stirred at 30°C for 0.5 h. The pH was then adjusted to 12.5 with sodium hydroxide, and the reaction was carried out at 80°C with stirring for another 0.5 h. After the reaction, the mixture was filtered to obtain a blue-green filter cake and a colorless vanadium filtrate. The composition of the vanadium filtrate was analyzed, and the results are shown in Table 4 below.

[0077] Table 4. Analytical results of vanadium filtrate composition

[0078] Cr Mn V 6.70ppm - 43.33g / L

[0079] A comparison with Example 1 shows that without the addition of Mn-containing... 2+ When using chromium removal agents, the high chromium content in the solution results in poor chromium removal and incomplete separation of vanadium and chromium.

[0080] Comparative Example 2

[0081] One L of vanadium-chromium slag alkaline leaching solution was measured. The Cr ion concentration in this solution was 15.99 g / L, and the V ion concentration was 35.60 g / L. Sulfuric acid solution was added dropwise to adjust the pH to 7.5. Then, 174 g of anhydrous sodium sulfite was added, and the solution was stirred at 70°C for 2 hours. The pH was then adjusted to 11.0 with sodium hydroxide. The solution was heated to 90°C and stirred for 1.5 hours. After the reaction was complete, the solution was filtered to obtain a light green filter cake and a pale green vanadium filtrate. The vanadium filtrate was analyzed, and the results are shown in Table 5 below.

[0082] Table 5. Analytical results of vanadium filtrate composition.

[0083] Cr Mn V 11.35ppm - 33.76g / L

[0084] A comparison with Example 2 shows that when pH = 11 and no Mn-containing substance is added... 2+ When using chromium removal agents, the hydrolysis effect of trivalent chromium ions in the solution is poor, the residual chromium content is high, and the separation of vanadium and chromium is incomplete.

[0085] Comparative Example 3

[0086] A 1L chromium-vanadium mixed solution was prepared using sodium vanadate and sodium chromate reagents, respectively. The Cr ion concentration in this mixed solution was 5.00 g / L, and the V ion concentration was 40.00 g / L. Sulfuric acid solution was added dropwise to adjust the pH to 10, then 89 g of sodium metabisulfite was added, and the mixture was stirred at 100℃ for 6 hours. The pH was then adjusted to 8.5 using sodium hydroxide, and the solution was heated to 100℃ and stirred for 3 hours. After the reaction was complete, the mixture was filtered to obtain a light green filter cake and a green vanadium filtrate. The results of the vanadium filtrate analysis are shown in Table 6 below.

[0087] Table 6. Analytical results of vanadium filtrate composition

[0088] Cr Mn V 34.55ppm - 39.22g / L

[0089] A comparison with Example 3 shows that when pH = 8.5 and no Mn-containing substances are added... 2+ When using chromium removal agents, the hydrolysis effect of trivalent chromium ions in the solution becomes even worse, the residual chromium content increases, and the vanadium-chromium separation effect is poor.

[0090] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0091] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0092] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for separating vanadium and chromium in a vanadium-chromium solution, characterized by, Includes the following steps: Step S1: Adjust the pH of the vanadium-chromium solution to 5-10, add a reducing agent to reduce the hexavalent chromium ions in the solution to trivalent chromium ions, and obtain solution L1; Step S2: Adjust the pH of solution L1 to 8.5~12.5, add a chromium removal agent containing divalent manganese ions, so that the trivalent chromium ions and the divalent manganese ions in the solution co-precipitate to obtain mixed solution L2. The amount of chromium removal agent added meets the following requirements: n Mn / n Cr =1.5~8.0, where n Mn The amount of Mn in the chromium removal agent 2+ The amount of substance, n Cr Represents the Cr content in the vanadium-chromium solution 6+ The amount of substance; Step S3: Filter the mixture L2 to separate the precipitate and solution, obtaining a chromium-containing precipitate and a vanadium-containing filtrate L3.

2. The method of claim 1, wherein, The chromium removal agent containing divalent manganese ions is a soluble divalent manganese salt.

3. The method of claim 2, wherein, The soluble divalent manganese salt is selected from one or more of manganese sulfate, manganese chloride, and manganese nitrate.

4. The method of claim 1, wherein, The amount of chromium removal agent added must satisfy the following relationship with the pH value of the solution after pH adjustment in step S2: When pH = 11~12.5, n Cr :n Mn =1: (1.5~3); n = 1 : (3-6) when pH = 9.5-11 Cr n = 1 : (3-6) when pH = 9.5-11 Mn n = 1 : (3-6) when pH = 9.5-11 When pH = 8.5~9.5, n Cr :n Mn =1: (6~8).

5. The method of claim 1, wherein, The coprecipitation temperature is 80~100℃, and the reaction time is 0.5~3h.

6. The method of claim 1, wherein, The reducing agent is selected from one or more of sodium metabisulfite, sodium sulfite, and vanadium oxysulfate.

7. The method of claim 6, wherein, The stoichiometric ratio of the reducing agent to hexavalent chromium ions is 1.1 to 6.5, and the relationship between the reducing agent and pH value must meet the following requirements: When pH=5~7, the stoichiometric ratio of the reducing agent to hexavalent chromium ions is 1.1~1.5, and the reducing agent is selected from one or more of sodium metabisulfite, sodium sulfite, and vanadium oxysulfate; When pH=7~8, the stoichiometric ratio of the reducing agent to hexavalent chromium ions is 1.5~3.5, and the reducing agent is selected from one or more of sodium metabisulfite and sodium sulfite; When pH=8~10, the stoichiometric ratio of the reducing agent to hexavalent chromium ions is 3.5~6.5, and the reducing agent is selected from one or more of sodium metabisulfite and sodium sulfite.

8. The method of claim 1, wherein, The reduction reaction is carried out at a temperature of 30~100℃ for 0.5~6h.

9. The method of claim 1, wherein, In step S1, sulfuric acid is used to adjust the pH value, and in step S2, sodium hydroxide is used to adjust the pH value.

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