Method for separating aluminum and vanadium in sodium metaaluminate solution

Abstract

The invention relates to a method for separating aluminum and vanadium in a sodium metaaluminate solution. According to the technical scheme, the method comprises the following steps: preheating a sodium metaaluminate solution to a certain temperature, and adding a pH regulator into the sodium metaaluminate solution; adjusting the pH value, carrying out solid-liquid separation, adding clear water into the filter cake, uniformly stirring, adding a certain amount of vanadium removal agent, carrying out hydrothermal aging under certain conditions, and carrying out solid-liquid separation on the slurry after hydrothermal aging to obtain a hydrated alumina filter cake; washing and drying the hydrated alumina filter cake to obtain an aluminum product; the filtrate is a sodium metavanadate solution. The method has the characteristics of simple process and good aluminum-vanadium separation effect, the content of V2O5 in the aluminum product is less than or equal to 0.02%, and the vanadium separation rate is more than 99.75%.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, and in particular to a method for separating aluminum and vanadium from sodium aluminate solution. Background Technology

[0002] Bauxite is the most important mineral resource for alumina production, and it typically contains about 0.1% vanadium. During the Bayer process for bauxite, with the use of caustic soda, approximately 30%–40% of the vanadium enters the sodium aluminate solution along with the aluminum, and is further enriched through the recycling of the mother liquor. Once vanadium accumulates to a certain level in the sodium aluminate solution, it causes the aluminum hydroxide particles generated from the seed crystal decomposition to become finer, negatively impacting alumina production. Furthermore, vanadium entering the electrolytic cell with the alumina significantly reduces the current efficiency during aluminum electrolysis.

[0003] When recovering aluminum from industrial waste containing aluminum and vanadium, the precipitation pH values ​​of aluminum and vanadium are quite similar, and both are amphoteric and soluble in acids and bases. Therefore, when recovering aluminum resources through alkaline dissolution, a certain amount of vanadium inevitably remains in the sodium aluminate solution, ultimately affecting the purity of the aluminum product. Thus, a simple and effective method for separating aluminum and vanadium from sodium aluminate solution is of positive significance for impurity removal and aluminum and vanadium resource recycling in my country's alumina process.

[0004] Currently, the main methods for separating aluminum and vanadium include: mother liquor evaporation and crystallization, extraction separation, and resin adsorption.

[0005] Patent CN103159259A provides a method for extracting vanadium pentoxide from the mother liquor of the Bayer process for alumina production. The method involves cooling the mother liquor and inoculating it with vanadium salts; filtering the crystallized mother liquor to obtain vanadium salt crystals; dissolving the vanadium salt crystals in sulfuric acid solution by heating; removing impurities and filtering; adding NH4Cl or (NH4)2SO4 to precipitate ammonium metavanadate, which is then calcined to obtain high-purity V2O5. Mother liquor crystallization is a relatively mature industrial method. It is based on the fact that the solubility of sodium aluminate and sodium metavanadate is much lower when they coexist than when they exist alone. After the mother liquor is evaporated and concentrated to a certain extent, lowering the solution temperature causes sodium metavanadate to crystallize. However, this method has a low vanadium recovery rate, high energy consumption, poor aluminum-vanadium separation effect, and is only suitable for mother liquors with high vanadium content. Literature review results show that when the vanadium content in the sodium aluminate solution is 0.4 g / L, the vanadium recovery rate of the mother liquor crystallization method is only 45.34%.

[0006] Patent CN11553783A provides an extraction system for vanadium extraction and a method for extracting and removing vanadium from aluminum-containing hydrochloric acid solutions. The vanadium extraction system consists of a neutral alcohol and a diluent, with a volume ratio of neutral alcohol to diluent of 10%–90%; wherein the neutral alcohol is a C5–C10 alcohol. This method can extract vanadium from aluminum-containing hydrochloric acid solutions. While the extraction method achieves higher vanadium recovery and better aluminum-vanadium separation efficiency, its process is complex. Furthermore, using organic solvents as extractants increases the COD content in the wastewater, necessitating wastewater treatment before discharge, further complicating the process.

[0007] Patent CN114990359A discloses a method for enriching vanadium using anion exchange resin. The method involves soaking roasted vanadium-containing ore powder in an acidic solution, filtering to obtain a filtrate, adsorbing vanadium compounds from the filtrate using anion exchange resin, and then desorbing the adsorbed vanadium compounds from the anion exchange resin using a solution containing oxalic acid and sulfuric acid to obtain an eluent. Compared to crystallization, resin adsorption is simpler to operate and has higher separation efficiency. However, operation in a strongly alkaline environment causes significant damage to the resin, shortening its lifespan, and the cost of replacing the adsorption resin is high, limiting the application of this method in this field.

[0008] In summary, existing methods for separating aluminum and vanadium from alkaline sodium aluminate solutions suffer from problems such as low aluminum-vanadium separation rates, complex processes, and high processing costs. A simple and efficient method for separating aluminum and vanadium from vanadium-containing sodium aluminate solutions is lacking. Summary of the Invention

[0009] The technical problem solved by this invention is to provide a method for separating aluminum and vanadium in sodium aluminate solution. The method provided in this application can effectively separate aluminum and vanadium in sodium aluminate solution, and is simple to operate and has a high separation rate.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A method for separating aluminum and vanadium in sodium aluminate solution, characterized in that the separation method includes the following steps:

[0012] A) Preheat the sodium aluminate solution to a certain temperature, and add a pH adjuster to adjust the pH value of the sodium aluminate solution to 10-12.

[0013] B) After adjusting the pH value, solid-liquid separation is carried out. The filter cake is added to clean water and stirred evenly. A certain amount of vanadium removal agent is added and hydrothermally aged under certain conditions. After hydrothermal aging, the slurry is separated into solid and liquid again to obtain hydrated alumina filter cake and vanadium-containing filtrate.

[0014] C) The hydrated alumina filter cake is washed and dried to obtain aluminum product; the filtrate produced in the process is sodium metavanadate solution.

[0015] In step A), the sodium aluminate solution has an Al2O3 concentration ≤30g / L, a V2O5 concentration ≤3g / L, and a caustic ratio of 1.3 to 1.8; the preheating temperature is 70 to 90℃; the pH adjuster added to the sodium aluminate solution can be an acidic gas such as CO2, or one or more of sulfuric acid, hydrochloric acid, nitric acid, etc.

[0016] In step B), the hydrothermal aging under certain conditions is as follows: the reaction temperature is 90-220℃, the reaction time is 3-20h, and the solid content of the aged slurry is 3%-8%.

[0017] In step B), the vanadium removal agent is a soluble sulfate such as sodium sulfate or potassium sulfate, or one or more of them, and the amount of vanadium removal agent added is such that the molar ratio of sulfate to vanadium is 3 to 15:1.

[0018] In step C), the filter cake washing method is multi-stage countercurrent pulping and washing, with a washing water temperature of 60-90℃ and a pulping and washing time of 0.5-2h; the drying temperature is 100-120℃.

[0019] This invention discloses a method for separating aluminum and vanadium from a sodium aluminate solution, characterized by: adjusting the pH of the vanadium-containing sodium aluminate solution at 70–90°C to allow aluminum to form a hydrated alumina precursor with a certain crystal structure under these conditions; followed by hydrothermal aging at 90–220°C to reduce crystal surface defects; adding soluble sulfate during the aging process to replace the metavanadate adsorbed on the surface of the hydrated alumina crystals with sulfate ions, further reducing the metavanadate content in the aluminum product; thus improving the separation effect of aluminum and vanadium, with the V2O5 content in the aluminum product ≤0.02% and the vanadium separation rate above 99.75%.

[0020] This invention separates aluminum and vanadium in a sodium metavanadate solution containing vanadium to obtain hydrated alumina and sodium metavanadate solution. This invention has the advantages of simple operation and high separation rate of aluminum and vanadium. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a simplified process flow diagram of the method for separating aluminum and vanadium in sodium vanadate solution according to the present invention.

[0023] Figure 2 XRD pattern of hydrated alumina prepared in this invention Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Example 1

[0027] A sodium aluminate solution containing 30 g / L Al2O3 and 3 g / L V2O5 was heated to 90°C, and CO2 gas was introduced into it. The final pH value was 10.5. After the reaction, the slurry was heated to 200°C, and sodium sulfate was added. The molar ratio of sulfate to vanadium was 10:1. The hydrothermal reaction was carried out under heat and pressure for 6 hours.

[0028] After hydrothermal reaction, the slurry is separated into solid and liquid phases. The precipitate is washed with distilled water until neutral and dried to obtain hydrated alumina crystals.

[0029] Its hydrated alumina has the following chemical composition: Na2O content 0.05%, Al2O3 content 82.73%, V2O5 content 0.01%, and H2O content 16%.

[0030] The filtrate was a sodium metavanadate solution.

[0031] Its sodium metavanadate has the following chemical composition: Na2O content 32.15%, Al2O3 content 0.46%, and V2O5 content 63.55%.

[0032] The calculations show that the Al2O3 separation rate in Example 1 is 99.93% and the V2O5 separation rate is 99.88%.

[0033] Example 2

[0034] A sodium aluminate solution containing 30 g / L Al2O3 and 3 g / L V2O5 was heated to 70°C, and CO2 gas was introduced into it. The final pH value was 10.5. After the reaction, the slurry was heated to 200°C, and sodium sulfate was added. The molar ratio of sulfate to vanadium was 10:1. The hydrothermal reaction was carried out under heat and pressure for 6 hours.

[0035] After hydrothermal reaction, the slurry is separated into solid and liquid phases. The precipitate is washed with distilled water until neutral and dried to obtain hydrated alumina crystals.

[0036] Its hydrated alumina has the following chemical composition: Na2O content 0.06%, Al2O3 content 82.07%, V2O5 content 0.01%, and H2O content 17%.

[0037] The filtrate was a sodium metavanadate solution.

[0038] Its sodium metavanadate has the following chemical composition: Na2O content 32.19%, Al2O3 content 0.47%, and V2O5 content 63.11%.

[0039] The calculations showed that the Al2O3 separation rate was 99.92% and the V2O5 separation rate was 99.88% in Example 2.

[0040] Example 3

[0041] A sodium aluminate solution containing 30 g / L Al2O3 and 3 g / L V2O5 was heated to 90°C, and CO2 gas was introduced into it. The final pH value was 10.5. After the reaction, the slurry was heated to 170°C, and sodium sulfate was added. The molar ratio of sulfate to vanadium was 10:1. The hydrothermal reaction was carried out under heat and pressure for 6 hours.

[0042] Its hydrated alumina has the following chemical composition: Na2O content 0.05%, Al2O3 content 79.83%, V2O5 content 0.02%, and H2O content 16%.

[0043] The filtrate was a sodium metavanadate solution.

[0044] Its sodium metavanadate has the following chemical composition: Na2O content 32.26%, Al2O3 content 0.49%, and V2O5 content 63.04%.

[0045] Calculations showed that the Al2O3 yield was 99.92% and the V2O5 separation rate was 99.75% in Example 3.

[0046] Comparative Example 1 (Reaction temperature was lowered when adjusting the pH of sodium aluminate)

[0047] A sodium aluminate solution containing 30 g / L Al2O3 and 3 g / L V2O5 was introduced into the solution at room temperature with CO2 gas introduced into it, and the final pH value was 10.5. After the reaction, the slurry was heated to 200℃, sodium sulfate was added, and the molar ratio of sulfate to vanadium was 10:1. The hydrothermal reaction was carried out under heat and pressure for 6 hours.

[0048] After hydrothermal reaction, the slurry is separated into solid and liquid phases. The precipitate is washed with distilled water until neutral and dried to obtain hydrated alumina crystals.

[0049] Its hydrated alumina has the following chemical composition: Na2O content 0.15%, Al2O3 content 79.72%, V2O5 content 1.4%, and H2O content 18%.

[0050] The filtrate was a sodium metavanadate solution.

[0051] Its sodium metavanadate has the following chemical composition: Na2O content 33.25%, Al2O3 content 2.55%, and V2O5 content 58.02%.

[0052] The calculations showed that the Al2O3 yield in Comparative Example 1 was 99.56%, and the V2O5 separation rate was 82.44%.

[0053] Comparative Example 2 (lower hydrothermal reaction temperature, no sodium sulfate added)

[0054] A sodium aluminate solution containing 30 g / L Al2O3 and 3 g / L V2O5 was preheated to 90°C, and CO2 gas was introduced into it. The final pH value was 10.5. After the reaction, the slurry was kept at 90°C and pressure for 6 hours.

[0055] After hydrothermal reaction, the slurry is separated into solid and liquid phases. The precipitate is washed with distilled water until neutral and dried to obtain hydrated alumina.

[0056] Its hydrated alumina has the following chemical composition: Na2O content 0.15%, Al2O3 content 69.72%, V2O5 content 1.6%, and H2O content 28%.

[0057] The filtrate was a sodium metavanadate solution.

[0058] Its sodium metavanadate has the following chemical composition: Na2O content 33.64%, Al2O3 content 4.22%, and V2O5 content 57.12%.

[0059] The calculations showed that the Al2O3 yield in Comparative Example 2 was 99.26%, and the V2O5 separation rate was 77.05%.

[0060] Comparative Example 3 (Separation effect under carbon fractionation reaction conditions)

[0061] A sodium aluminate solution containing 30 g / L Al2O3 and 3 g / L V2O5 was purged with CO2 gas at 20–30 °C, with the final pH value being 10.5. The slurry after the reaction was kept at 90 °C and pressure for 6 hours.

[0062] After hydrothermal reaction, the slurry is separated into solid and liquid phases. The precipitate is washed with distilled water until neutral and dried to obtain hydrated alumina crystals.

[0063] Its hydrated alumina has the following chemical composition: Na2O content 0.35%, Al2O3 content 65.23%, V2O5 content 2.9%, and H2O content 35.28%.

[0064] The filtrate was a sodium metavanadate solution.

[0065] Its sodium metavanadate has the following chemical composition: Na2O content 32.25%, Al2O3 content 11.48%, and V2O5 content 55.82%.

[0066] The calculations showed that the Al2O3 separation rate in Comparative Example 3 was 97.94%, and the V2O5 separation rate was 55.54%.

[0067] In summary, the embodiments of the present invention can not only achieve the separation of aluminum and vanadium in sodium aluminate solution, but also have a simple process flow and a high aluminum and vanadium recovery rate, effectively solving the problems of low aluminum and vanadium separation rate and complex process flow when separating aluminum and vanadium in sodium aluminate solution containing vanadium.

[0068] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0069] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for separating aluminum and vanadium in sodium aluminate solution, characterized in that, The separation method includes the following steps: A) Preheat the sodium aluminate solution to a certain temperature, and add a pH adjuster to adjust the pH value of the sodium aluminate solution to 10-12. B) After adjusting the pH value, solid-liquid separation is carried out. The filter cake is added to clean water and stirred evenly. A certain amount of vanadium removal agent is added and hydrothermally aged under certain conditions. After hydrothermal aging, the slurry is separated into solid and liquid again to obtain hydrated alumina filter cake and vanadium-containing filtrate. C) The hydrated alumina filter cake is washed and dried to obtain an aluminum product; the filtrate is a sodium metavanadate solution.

2. The method according to claim 1, characterized in that, In step A), the sodium aluminate solution has an Al2O3 concentration ≤30g / L, a V2O5 concentration ≤3g / L, and a caustic ratio of 1.3 to 1.

8.

3. The method according to claim 1, characterized in that, In step A), the preheating temperature of the sodium aluminate is 70-90°C; the pH adjuster added to the sodium aluminate solution can be an acidic gas such as CO2, or one or more of sulfuric acid, hydrochloric acid, nitric acid, etc.

4. The method according to claim 1, characterized in that, In step B), the hydrothermal aging conditions are: reaction temperature 90–220°C, reaction time 3–20 h, and solid content of the aged slurry 3%–8%.

5. The method according to claim 1, characterized in that, In step B), the vanadium removal agent is a soluble sulfate such as sodium sulfate or potassium sulfate, and the amount added is such that the molar ratio of sulfate to vanadium is 3 to 15:1.

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