Method for closed-loop preparation of ammonium metavanadate from vanadium slag

Abstract

The embodiment of the invention provides a method for closed-loop preparation of ammonium metavanadate from vanadium slag, impurities of the vanadium slag comprise at least one of phosphorus, silicon, aluminum, fluorine, iron, titanium, calcium, magnesium, manganese, copper, zinc, oxalate and organic salt, and the method comprises the steps that the impurity-containing vanadium slag and a first liquid medium are mixed for leaching treatment, and vanadium-containing leachate is obtained; calcium salt is added into the leachate for impurity removal treatment, and a purified vanadium-containing solution is obtained; adding a precipitator into the purified vanadium-containing solution for precipitation to obtain ammonium metavanadate and a mother solution; cooling the mother liquor, and separating out solid salt to obtain a recyclable second liquid medium; the calcium salt comprises at least one of calcium sulfate, calcium chloride, calcium nitrate, calcium carbonate, calcium hydroxide and calcium oxide. And the recovery rate and the vanadium purity of vanadium extraction from the vanadium slag can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgy, and particularly relates to a method for preparing ammonium metavanadate by closed circuit of vanadium slag. BACKGROUND

[0002] At present, the raw materials for extracting vanadium are various, including vanadium-titanium magnetite, vanadium slag, stone coal, waste vanadium catalyst and ammonium metavanadate, etc. Each kind of raw material corresponds to different vanadium extraction methods. In the low-temperature Bayer process of producing aluminum oxide, vanadium slag containing aluminum, phosphorus, silicon, fluorine, oxalate, organic salt and other impurities will be produced. These impurities increase the difficulty of extracting vanadium from vanadium slag, resulting in low vanadium recovery rate.

[0003] The existing vanadium extraction method for such vanadium slag is complicated, including placing the vanadium slag in water at a specific temperature for leaching, adjusting the pH value to a specific range, filtering to obtain a first filtrate, then performing two impurity removal operations to obtain a second filtrate, and finally adding a soluble ammonium salt to obtain ammonium metavanadate solid.

[0004] Therefore, developing a new method capable of simplifying the process, improving the vanadium recovery rate and realizing closed circuit production has become a technical problem to be solved. SUMMARY

[0005] The present application provides a method for preparing ammonium metavanadate by closed circuit of vanadium slag, to solve the technical problem of how to improve the recovery rate of vanadium extraction from vanadium slag.

[0006] The present application provides a method for preparing ammonium metavanadate by closed circuit of vanadium slag, wherein the impurities of the vanadium slag include at least one of phosphorus, silicon, aluminum, fluorine, iron, titanium, calcium, magnesium, manganese, copper, zinc, oxalate, organic salt, and the method comprises:

[0007] Mixing the vanadium slag containing impurities with a first liquid medium to perform leaching treatment, to obtain a vanadium-containing leaching solution;

[0008] Adding a calcium salt to the leaching solution to perform impurity removal treatment, to obtain a purified vanadium-containing solution;

[0009] Adding a precipitant to the purified vanadium-containing solution to perform precipitation, to obtain ammonium metavanadate and a mother liquor;

[0010] Performing cooling treatment on the mother liquor to precipitate solid salt, to obtain a second liquid medium that can be recycled;

[0011] The calcium salt includes at least one of calcium sulfate, calcium chloride, calcium nitrate, calcium carbonate, calcium hydroxide and calcium oxide.

[0012] Optionally, the first liquid medium is water or a solution containing a soluble salt.

[0013] Optionally, the solution containing soluble salt includes at least one of the following: ammonium sulfate solution, ammonium chloride solution, ammonium nitrate solution, sodium sulfate solution, sodium chloride solution, sodium nitrate solution, potassium sulfate solution, potassium chloride solution, potassium nitrate solution, magnesium sulfate solution, magnesium chloride solution, magnesium nitrate solution.

[0014] Optionally, the mass of the calcium salt is 1.2 to 1.5 times the mass of the calcium salt required to convert all the phosphorus in the vanadium slag into calcium phosphate.

[0015] Optionally, the precipitant contains NH4 + The molar ratio of NH4 + to V in the vanadium slag is 3.5 to 4.5.

[0016] Optionally, the precipitant includes at least one of the following: ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium hydroxide, ammonium phosphate, ammonium oxalate, ammonium citrate, ammonium acetate.

[0017] Optionally, the ammonium metavanadate is calcined to obtain vanadium pentoxide; the purity of the vanadium pentoxide is ≥ 99%.

[0018] Optionally, the temperature range of the cooling treatment is 0 to 15°C.

[0019] Optionally, the solid salt includes at least one of the following: sodium sulfate decahydrate, anhydrous sodium sulfate, calcium sulfate, sodium chloride, magnesium sulfate, magnesium chloride, potassium sulfate, potassium chloride, sodium nitrate, potassium nitrate, magnesium nitrate.

[0020] Optionally, the parameters of the leaching treatment include at least one of the following: temperature range of 30 to 90°C, holding time of 10 to 120 minutes, pH value of 8 to 10, liquid-solid ratio of 2:1 to 8:1; and / or,

[0021] The parameters of the impurity removal treatment include at least one of the following: pH value range of 8 to 10, temperature range of 80 to 99°C, holding time of 60 to 120 minutes; and / or,

[0022] The parameters of the precipitation treatment include at least one of the following: temperature range of 10 to 50°C, holding time of 20 to 90 minutes.

[0023] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0024] The embodiments of the present application provide a method for preparing ammonium metavanadate from vanadium slag in a closed circuit. The core of the method is to remove impurities precisely while retaining vanadium elements to the maximum extent by adopting a step-by-step treatment method for the complex impurity components (such as phosphorus, silicon, aluminum, fluorine, etc.) in the vanadium slag. First, the impurity-containing vanadium slag is mixed with a first liquid medium for leaching treatment, so that vanadium is dissolved from the solid slag into the liquid phase to form a vanadium-containing leaching solution. This process is the basic step for extracting vanadium, which ensures that vanadium can enter the subsequent processing link. Then, calcium salt is added to the leaching solution for impurity removal treatment. The calcium salt reacts with the impurities in the leaching solution to form insoluble compounds and precipitates, thereby separating the impurities from the liquid phase. For example, the calcium salt can form stable precipitates with phosphorus, silicon, aluminum and other impurities, while vanadium remains in the solution in a soluble form. This process is a key link for improving the recovery rate, because it not only removes a large amount of impurities that interfere with the subsequent vanadium extraction process, but also avoids the wrapping or adsorption of impurities on vanadium, so that vanadium can enter the next step of processing more purely. Subsequently, a precipitating agent is added to the purified vanadium-containing solution to precipitate and separate ammonium metavanadate. After the impurity removal treatment, the impurities are effectively removed, so that the purity of the precipitated ammonium metavanadate is significantly improved. Since the wrapping effect of impurities on vanadium is eliminated, the recovery rate of vanadium is significantly improved. Finally, the mother liquor after precipitation is subjected to cooling treatment to precipitate solid salt, and a second liquid medium that can be recycled is obtained. This process not only realizes the recycling of resources and reduces production costs, but also further reduces the interference of impurities on the system, providing a purer environment for the subsequent vanadium extraction operation. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate preferred embodiments of the present application and, together with the description, serve to explain the principles of the application.

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, those skilled in the art can derive other related drawings without creative labor.

[0027] Figure 1 A flowchart of a method for preparing ammonium metavanadate from vanadium slag in a closed circuit provided by the embodiments of the present application. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and superiorities of the embodiments of the present application clearer, the technical solutions will be described below in detail with reference to the drawings. Please note that the embodiments mentioned are only examples and not all possible implementations. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0029] The range descriptions described herein, such as numerical range, ratio range, etc., include all possible subranges and single values within the range, for example, the range description of "1 to 6" or "1-6" covers all subranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "include", "contain" and the like used herein mean "including but not limited to"; the relationship terms "first", "second" and the like are only used to distinguish different entities or operations, and do not imply actual sequence or relationship; "and / or" means that multiple cases can exist independently or simultaneously; "at least one", "multiple", "at least one" and the like refer to any combination of the corresponding objects, including single or multiple combinations. The proportional relationship involved herein, such as mass ratio, molar ratio, etc., should be understood as the corresponding relationship between the front and the rear in the proportional form according to the description order. The raw materials, reagents, instruments and equipment used herein can be purchased or prepared by existing methods.

[0030] Figure 1 A flow chart of a method for preparing ammonium metavanadate from vanadium slag in a closed circuit is provided in the embodiments of the present application.

[0031] Please refer to Figure 1 The embodiments of the present application provide a method for preparing ammonium metavanadate from vanadium slag in a closed circuit, the impurities of the vanadium slag include at least one of phosphorus, silicon, aluminum, fluorine, iron, titanium, calcium, magnesium, manganese, copper, zinc, oxalate, organic salt, and the method comprises:

[0032] S1, mixing the vanadium slag containing impurities with a first liquid medium to perform leaching treatment, to obtain a vanadium-containing leaching solution;

[0033] S2, adding a calcium salt to the leaching solution to perform impurity removal treatment, to obtain a purified vanadium-containing solution;

[0034] S3, adding a precipitant to the purified vanadium-containing solution to perform precipitation, to obtain ammonium metavanadate and a mother liquor;

[0035] S4, performing cooling treatment on the mother liquor to precipitate solid salt, to obtain a second liquid medium that can be recycled;

[0036] The calcium salt includes at least one of calcium sulfate, calcium chloride, calcium nitrate, calcium carbonate, calcium hydroxide, and calcium oxide.

[0037] Impurity-containing vanadium slag: refers to a raw material containing vanadium elements but mixed with various impurities (such as phosphorus, silicon, aluminum, etc.), usually derived from the low-temperature Bayer process of aluminum oxide production. First liquid medium: a solvent for leaching vanadium elements from vanadium slag, usually water or other solutions containing soluble salts. Calcium salt: a chemical reagent for impurity removal, which can react with impurities to form precipitates, thereby removing impurities. Precipitating agent: a chemical reagent for precipitating vanadium from the solution as ammonium metavanadate. Mother liquor: the remaining liquid after the precipitation reaction, which may contain unreacted reagents or impurities.

[0038] Mixing the impurity-containing vanadium slag with the first liquid medium, through chemical dissolution, vanadium enters the liquid phase from the solid slag, forming a vanadium-containing leaching solution. The key to the leaching step is to utilize the chemical properties (such as acidity or alkalinity) and physical conditions (such as temperature regulation and sufficient stirring) of the liquid medium to achieve effective separation of vanadium and impurities. Add calcium salt to the leaching solution, which reacts with acidic root ions (such as phosphate, sulfate, etc.) or metal ions (such as aluminum ions, iron ions, etc.) in the impurities to form insoluble precipitates. Specifically, calcium ions combine with phosphate ions to form calcium phosphate precipitates, effectively removing impurities in the liquid phase and obtaining a more pure vanadium-containing solution. Add a precipitating agent to the purified vanadium-containing solution, which reacts with vanadium ions to form ammonium metavanadate precipitates. The chemical formula of ammonium metavanadate is NH4VO3, and the precipitation process is to adjust the pH value, temperature, etc. of the solution to make vanadium ions combine with NH4 + ions to form insoluble ammonium metavanadate crystals. Subsequently, the mother liquor after precipitation treatment is subjected to cooling measures to promote the precipitation of soluble salts due to the decrease in solubility, converting into solid salts. This process utilizes the property that the solubility of salts changes with temperature, and by lowering the temperature, the solubility of the salt decreases, thus precipitating solid salt, achieving purification and resource recovery of the mother liquor. This method can be used to treat various impurity-containing vanadium slag, especially suitable for resource utilization of industrial waste slag, which can effectively extract high-purity vanadium products, widely used in chemical, metallurgical, electronic and other fields. +

[0039] In some embodiments, the first liquid medium is water or a solution containing soluble salts.

[0040] ​The first liquid medium is water or a solution containing soluble salts. Water is one of the most commonly used leaching media due to its low cost and easy operation. The solution containing soluble salts can adjust the ionic strength and pH of the solution, thereby improving the leaching efficiency of vanadium. For example, ammonium sulfate solution can provide an acidic environment to promote the dissolution of vanadium; and sodium chloride solution can improve the leaching rate of vanadium through ion exchange. This method is suitable for vanadium residues containing impurities from different sources, especially when dealing with vanadium residues with high impurity content. By selecting the appropriate soluble salt solution, the leaching efficiency and vanadium recovery rate can be significantly improved.

[0041] In some embodiments, the solution containing soluble salts includes at least one of: ammonium sulfate solution, ammonium chloride solution, ammonium nitrate solution, sodium sulfate solution, sodium chloride solution, sodium nitrate solution, potassium sulfate solution, potassium chloride solution, potassium nitrate solution, magnesium sulfate solution, magnesium chloride solution, magnesium nitrate solution.

[0042] Certain soluble salts, such as ammonium sulfate, can provide an acidic environment to promote the dissolution of vanadium. Vanadium is more easily leached from solid residues under low alkaline conditions. Soluble salts can increase the ionic strength of the solution, affecting the solubility and migration ability of vanadium ions. For example, sodium chloride solution effectively improves the leaching rate of vanadium by utilizing ion exchange. Certain soluble salts can form stable complexes with impurities, reducing the interference of impurities on vanadium leaching. For example, ammonium nitrate can form complexes with some impurities, thereby improving the purity of vanadium.

[0043] In some embodiments, the mass of the calcium salt is 1.2 to 1.5 times the mass of calcium salt required to generate calcium phosphate from all phosphorus in the vanadium residue.

[0044] The mass of the calcium salt is 1.2 to 1.5 times the mass of calcium salt required to generate calcium phosphate from all phosphorus in the vanadium residue, which is optimized based on the molar ratio of the chemical reaction and actual operation experience. The calcium salt reacts with acidic anions or metal ions in the impurities to form insoluble compounds. For example: removal of phosphate ions: calcium ions react with phosphate ions to form calcium phosphate precipitate:

[0045] 3Ca 2+ + 2H3PO4→ Ca3(PO4)2↓ + 6H +

[0046] Calcium ions can also undergo coprecipitation reactions with aluminum ions, iron ions, and other metal ions to further remove impurities. By precisely controlling the amount of calcium salt added, impurities can be effectively removed, and the problem of waste and secondary pollution caused by excessive calcium salt can be prevented.

[0047] For example, the mass of the calcium salt is 1.2 times, 1.3 times, 1.4 times, or 1.5 times the mass of calcium salt required to generate calcium phosphate from all phosphorus in the vanadium residue.

[0048] In some embodiments, the precipitant contains NH4 + , the molar ratio of NH4 + in the precipitant to V in the vanadium slag is 3.5 to 4.5.

[0049] The precipitant contains NH4 + , NH4 + in the precipitant chemically reacts with vanadium ions to form ammonium metavanadate precipitate. The molar ratio of NH4 + in the precipitant to vanadium ions is 3.5 to 4.5, which is the result of optimization based on chemical reaction equilibrium and actual operation. The reaction process is as follows: precipitation reaction of vanadium ions: vanadium ions (usually in the form of V 5+ react with NH4 + to form ammonium metavanadate precipitate.

[0050] By controlling the molar ratio of NH4 + to vanadium, the conditions of the precipitation reaction can be optimized, and the precipitation efficiency and purity can be improved. For example, a higher concentration of NH4 + can promote the precipitation of vanadium ions, but too high a concentration can lead to the co-precipitation of impurities, affecting product purity.

[0051] As an example: the molar ratio of NH4 + in the precipitant to V in the vanadium slag is 3.5, 4, 4.5.

[0052] In some embodiments, the precipitant includes at least one of the following: ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium hydroxide, ammonium phosphate, ammonium oxalate, ammonium citrate, ammonium acetate.

[0053] The precipitant includes ammonium sulfate, ammonium chloride, ammonium nitrate, etc., and NH4 + ions in these precipitants are the key active ingredients. The choice of different precipitants has a significant impact on the conditions and effects of the precipitation reaction: ammonium sulfate completely dissociates in water, providing a large amount of NH4 4+ ions, promoting the precipitation of vanadium. Ammonium chloride dissociates in water to form NH4 + and Cl-ions, NH4 + is used to precipitate vanadium, while Cl-ions have little effect on the precipitation reaction. Ammonium nitrate dissociates in water to form NH4 + and NO3 - ions, NH4 + is used to precipitate vanadium, while NO3 - ions have little effect on the precipitation reaction. By choosing these precipitants, the conditions of the precipitation reaction can be optimized, and the precipitation efficiency and purity can be improved. In some embodiments, the ammonium metavanadate is calcined to obtain vanadium pentoxide; the purity of the vanadium pentoxide is ≥ 99%.

[0054] Vanadium pentoxide (V2O5): An important vanadium compound with high purity and good chemical stability, widely used in chemical industry, metallurgy and electronics. Ammonium metavanadate is calcined to convert into vanadium pentoxide (V2O5). The calcination process is a high-temperature oxidation reaction, by controlling the calcination temperature and time, can ensure that ammonium metavanadate is completely converted into high-purity vanadium pentoxide.

[0055] By optimizing the calcination conditions, the organic impurities and water in ammonium metavanadate can be removed, and vanadium pentoxide with purity ≥99% can be obtained. High-purity vanadium pentoxide has important application value in chemical industry, metallurgy and other fields.

[0056] In some embodiments, the temperature range of the cooling treatment is 0°C to 15°C.

[0057] Cooling treatment: The process of precipitating soluble salts in the mother liquor into solid salts by reducing the temperature. The mother liquor is subjected to cooling treatment to precipitate soluble salts in it into solid salts. The temperature range of the cooling treatment is 0°C to 15°C, which is selected based on the characteristics of the solubility of salts changing with temperature. For example: sodium sulfate has low solubility at low temperature, and can be precipitated into solid salt (such as sodium sulfate decahydrate) by cooling. Sodium chloride has low solubility at low temperature, and can be precipitated into solid salt by cooling. Through cooling treatment, the recovery and reuse of salts in the mother liquor can be achieved, reducing production costs and reducing wastewater discharge.

[0058] As an example: the temperature of the cooling treatment can be 0°C, 2°C, 4°C, 6°C, 8°C, 10°C, 12°C, 15°C.

[0059] In some embodiments, the solid salt includes at least one of the following: sodium sulfate decahydrate, anhydrous sodium sulfate, calcium sulfate, sodium chloride, magnesium sulfate, magnesium chloride, potassium sulfate, potassium chloride, sodium nitrate, potassium nitrate, magnesium nitrate.

[0060] Solid salt: Insoluble salt precipitated from the mother liquor during cooling treatment. During the cooling treatment of the mother liquor, the precipitation of solid salt is based on the characteristics of the solubility of salts changing with temperature. The solubility of different salts decreases significantly at low temperature, thus precipitating into solid. For example: sodium sulfate decahydrate, anhydrous sodium sulfate, calcium sulfate, sodium chloride, magnesium sulfate, magnesium chloride and other salts have low solubility at low temperature, and are easy to precipitate. By precipitating solid salt, the purification and resource recovery of the mother liquor can be achieved, reducing production and reducing wastewater discharge.

[0061] In some embodiments, the parameters of the leaching treatment include at least one of the following: the temperature range is 30°C to 90°C, the holding time is 10 to 120 minutes, the pH value is 8 to 10, the liquid-solid ratio is 2:1 to 8:1; and / or,

[0062] The parameters of the impurity removal treatment include at least one of the following: pH value range of 8 to 10, temperature range of 80°C to 99°C, and holding time of 60 to 120 minutes; and / or,

[0063] The parameters of the precipitation treatment include at least one of the following: temperature range of 10°C to 50°C, and holding time of 20 to 90 minutes.

[0064] The liquid-solid ratio (L / S ratio) refers to the ratio of the volume of the liquid medium to the mass of the solid material in the leaching or dissolution process. The leaching treatment parameters are as follows: temperature range of 30°C to 90°C. Temperature has a significant impact on the leaching efficiency of vanadium. Higher temperature can accelerate the chemical reaction rate and improve the solubility of vanadium. Holding time of 10 to 120 minutes. The holding time determines the reaction time of vanadium with the liquid medium, and longer holding time can improve the leaching rate of vanadium. The pH value is 8 to 10. Low alkalinity conditions are beneficial to the dissolution of vanadium, and by adjusting the pH value, the leaching efficiency of vanadium can be optimized. Liquid-solid ratio of 2:1 to 8:1. The liquid-solid ratio determines the contact area and reaction degree of the liquid medium and the vanadium slag, and higher liquid-solid ratio can improve the leaching rate of vanadium.

[0065] The impurity removal treatment parameters are as follows: pH value range of 8 to 10. Alkaline conditions are beneficial to the precipitation reaction of calcium salt and impurities, and by adjusting the pH value, the impurity removal effect can be optimized. Temperature range of 80°C to 99°C. Higher temperature can accelerate the chemical reaction rate and improve the impurity removal efficiency. Holding time of 60 to 120 minutes. The holding time determines the reaction time of calcium salt and impurities, and longer holding time can improve the impurity removal effect.

[0066] The precipitation treatment parameters are as follows: temperature range of 10°C to 50°C. Temperature has a significant impact on the rate of precipitation reaction and the crystallization quality of the precipitate. Moderate temperature can improve the precipitation efficiency and purity. Holding time of 20 to 90 minutes. The holding time determines the degree of precipitation reaction, and longer holding time can improve the precipitation efficiency.

[0067] As an example:

[0068] The leaching treatment parameters can be as follows:

[0069] Temperature: 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C.

[0070] Holding time: 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, 120 minutes.

[0071] pH value: 8.0, 8.5, 9.0, 9.5, 10.0.

[0072] Liquid-solid ratio: 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1.

[0073] The impurity removal treatment parameters can be:

[0074] pH value: 8.0, 8.5, 9.0, 9.5, 10.0.

[0075] Temperature: 80℃, 85℃, 90℃, 95℃, 99℃.

[0076] Soaking time: 60 minutes, 70 minutes, 80 minutes, 90 minutes, 100 minutes, 110 minutes, 120 minutes.

[0077] The treatment parameters can be:

[0078] Temperature: 10℃, 20℃, 30℃, 40℃, 50℃,

[0079] Soaking time: 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, 70 minutes, 80 minutes, 90 minutes,

[0080] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and not used to limit the scope of the present application. The experimental methods in the following examples without specific conditions are generally determined according to the industry standards. If there is no corresponding industry standard, it is determined according to the general international standards, conventional conditions or according to the conditions suggested by the manufacturer.

[0081] In the following examples and comparative examples, the composition of the vanadium slag is as follows:

[0082]

[0083] Example 1

[0084] 1. Vanadium slag leaching:

[0085] 260g of wet vanadium slag (containing 41.7% moisture) was added to 500mL of circulating liquid.

[0086] The mixture was heated to 40℃.

[0087] An appropriate amount of sulfuric acid was added to adjust the pH value to 8.

[0088] The vanadium slag was fully leached at 40℃ for 20 minutes to obtain a leaching slurry.

[0089] 2. Impurity removal of leaching slurry:

[0090] The leaching slurry was heated to 80℃.

[0091] The amount of calcium sulfate is calculated according to the content of phosphorus in the vanadium slag, and the mass of calcium sulfate is 1.2 times the mass of calcium sulfate required for the phosphorus in the vanadium slag to form calcium phosphate.

[0092] The calculated amount of calcium sulfate is added.

[0093] The impurities and calcium sulfate are allowed to fully react at 80°C for 120 minutes to form insoluble precipitates.

[0094] Solid-liquid separation is performed to obtain the vanadium precipitation original solution.

[0095] 3. Ammonium metavanadate is crystallized and precipitated from the vanadium precipitation original solution:

[0096] The vanadium precipitation original solution is cooled to 40°C.

[0097] According to the NH4 + :V molar ratio of 4, ammonium sulfate is added.

[0098] After the addition of ammonium sulfate, the solution is cooled to 20°C.

[0099] The ammonium metavanadate is allowed to fully crystallize and precipitate at 20°C for 20 minutes.

[0100] Solid-liquid separation is performed to obtain ammonium metavanadate solids and a vanadium precipitation mother liquor.

[0101] 4. Vanadium precipitation mother liquor treatment:

[0102] The vanadium precipitation mother liquor is cooled to 0°C.

[0103] The sodium sulfate decahydrate is allowed to precipitate at 0°C for 30 minutes.

[0104] Solid-liquid separation is performed to obtain sodium sulfate decahydrate solids and a circulating liquid.

[0105] The circulating liquid is returned to the leaching step for the leaching of the next batch of vanadium slag.

[0106] Example 2

[0107] 1. Vanadium slag leaching:

[0108] 260g of wet vanadium slag (containing 41.7% moisture) is added to 500mL of circulating liquid.

[0109] The mixture is heated to 50°C.

[0110] An appropriate amount of sulfuric acid is added to adjust the pH value to 8.5.

[0111] The vanadium slag is allowed to fully leach at 50°C for 30 minutes to obtain a leaching slurry.

[0112] 2. Impurity removal from the leaching slurry:

[0113] The leaching slurry is warmed to 85°C.

[0114] The amount of calcium sulfate is calculated according to the phosphorus content in the vanadium slag, and the mass of calcium sulfate is 1.25 times the mass of calcium sulfate required for the phosphorus in the vanadium slag to form calcium phosphate.

[0115] The calculated amount of calcium sulfate is added.

[0116] The impurities and calcium sulfate are allowed to fully react at 85°C for 100 minutes to form insoluble precipitates.

[0117] Solid-liquid separation is performed to obtain the vanadium precipitation original solution.

[0118] 3. Ammonium metavanadate is crystallized and precipitated from the vanadium precipitation original solution:

[0119] The vanadium precipitation original solution is cooled to 45°C.

[0120] Ammonium sulfate is added according to the NH4 + :V molar ratio of 3.5.

[0121] After the addition of ammonium sulfate, the solution is cooled to 27°C.

[0122] The solution is allowed to stand at 27°C for 30 minutes to fully crystallize and precipitate the ammonium metavanadate.

[0123] Solid-liquid separation is performed to obtain ammonium metavanadate solids and a vanadium precipitation mother liquor.

[0124] 4. Vanadium precipitation mother liquor treatment:

[0125] The vanadium precipitation mother liquor is cooled to 3°C.

[0126] The solution is allowed to stand at 3°C for 50 minutes to precipitate sodium sulfate decahydrate.

[0127] Solid-liquid separation is performed to obtain sodium sulfate decahydrate solids and a circulating liquid.

[0128] The circulating liquid is returned to the leaching step for the leaching of the next batch of vanadium slag.

[0129] Example 3

[0130] 1. Vanadium slag leaching:

[0131] 260 g of wet vanadium slag (containing 41.7% moisture) is added to 500 mL of circulating liquid.

[0132] The mixture is heated to 60°C.

[0133] An appropriate amount of sulfuric acid is added to adjust the pH to 9.

[0134] The solution is allowed to stand at 60°C for 40 minutes to fully leach the vanadium slag, obtaining a leaching slurry.

[0135] 2. Impurity removal from leaching slurry:

[0136] The leaching slurry is heated to 90°C.

[0137] The amount of calcium sulfate is calculated according to the phosphorus content in the vanadium slag, and the mass of calcium sulfate is 1.3 times the mass of calcium sulfate required for the phosphorus in the vanadium slag to form calcium phosphate.

[0138] The calculated amount of calcium sulfate is added.

[0139] The impurities and calcium sulfate are fully reacted to form insoluble precipitates at 90°C for 90 minutes.

[0140] Solid-liquid separation is performed to obtain the vanadium precipitation stock solution.

[0141] 3. Crystallization and precipitation of ammonium metavanadate from the vanadium precipitation stock solution:

[0142] The vanadium precipitation stock solution is cooled to 50°C.

[0143] Ammonium sulfate is added according to the NH4 + :V molar ratio of 3.8.

[0144] After adding ammonium sulfate, the solution is cooled to 30°C.

[0145] The ammonium metavanadate is fully crystallized and precipitated at 30°C for 40 minutes.

[0146] Solid-liquid separation is performed to obtain ammonium metavanadate solids and a vanadium precipitation mother liquor.

[0147] 4. Treatment of the vanadium precipitation mother liquor:

[0148] The vanadium precipitation mother liquor is cooled to 5°C.

[0149] The sodium sulfate decahydrate is precipitated at 5°C for 40 minutes.

[0150] Solid-liquid separation is performed to obtain sodium sulfate decahydrate solids and a circulating liquid.

[0151] The circulating liquid is returned to the leaching step for the leaching of the next batch of vanadium slag.

[0152] Example 4

[0153] 1. Leaching of vanadium slag:

[0154] 260 g of wet vanadium slag (containing 41.7% moisture) is added to 500 mL of circulating liquid.

[0155] The mixture is heated to 70°C.

[0156] An appropriate amount of sulfuric acid is added to adjust the pH value to 9.5.

[0157] The vanadium residue is kept at 70°C for 50 minutes to allow sufficient leaching, and a leaching slurry is obtained.

[0158] 2. Impurity removal from the leaching slurry:

[0159] The leaching slurry is heated to 95°C.

[0160] The amount of calcium sulfate is calculated according to the phosphorus content in the vanadium residue, and the mass of calcium sulfate is 1.35 times the mass of calcium sulfate required to convert all the phosphorus in the vanadium residue into calcium phosphate.

[0161] The calculated amount of calcium sulfate is added.

[0162] The mixture is kept at 95°C for 80 minutes to allow the impurities to fully react with the calcium sulfate and form insoluble precipitates.

[0163] Solid-liquid separation is performed to obtain a vanadium precipitation stock solution.

[0164] 3. Crystallization of ammonium metavanadate from the vanadium precipitation stock solution:

[0165] The vanadium precipitation stock solution is cooled to 55°C.

[0166] Ammonium sulfate is added according to the molar ratio of NH4 + :V of 4.2.

[0167] After adding the ammonium sulfate, the solution is cooled to 35°C.

[0168] The mixture is kept at 35°C for 50 minutes to allow the ammonium metavanadate to fully crystallize.

[0169] Solid-liquid separation is performed to obtain ammonium metavanadate solids and a vanadium precipitation mother liquor.

[0170] 4. Treatment of the vanadium precipitation mother liquor:

[0171] The vanadium precipitation mother liquor is cooled to 8°C.

[0172] The mixture is kept at 8°C for 50 minutes to allow the sodium sulfate decahydrate to precipitate.

[0173] Solid-liquid separation is performed to obtain sodium sulfate decahydrate solids and a circulating liquid.

[0174] The circulating liquid is returned to the leaching step for the leaching of the next batch of vanadium residue.

[0175] Example 5

[0176] 1. Leaching of vanadium residue:

[0177] 260 g of wet vanadium residue (containing 41.7% moisture) is added to 500 mL of circulating liquid.

[0178] The mixture is heated to 80°C.

[0179] Add appropriate amount of sulfuric acid to adjust the pH value to 10.

[0180] Keep the vanadium slag at 80°C for 60 minutes to fully leach, and obtain the leaching slurry.

[0181] 2. Impurity removal from the leaching slurry:

[0182] Warm the leaching slurry to 99°C.

[0183] Calculate the amount of calcium sulfate according to the phosphorus content in the vanadium slag, and the mass of calcium sulfate is 1.4 times the mass of calcium sulfate required to make all the phosphorus in the vanadium slag into calcium phosphate.

[0184] Add the calculated amount of calcium sulfate.

[0185] Keep the temperature at 99°C for 60 minutes to fully react the impurities with calcium sulfate and generate insoluble precipitates.

[0186] Perform solid-liquid separation to obtain the vanadium precipitation stock solution.

[0187] 3. Crystallization of ammonium metavanadate from the vanadium precipitation stock solution:

[0188] Cool the vanadium precipitation stock solution to 60°C.

[0189] Add ammonium sulfate according to the NH4 + :V molar ratio of 3.5.

[0190] After adding ammonium sulfate, cool the solution to 40°C.

[0191] Keep the temperature at 40°C for 60 minutes to fully crystallize ammonium metavanadate.

[0192] Perform solid-liquid separation to obtain ammonium metavanadate solid and vanadium precipitation mother liquor.

[0193] 4. Treatment of vanadium precipitation mother liquor:

[0194] Cool the vanadium precipitation mother liquor to 10°C.

[0195] Keep the temperature at 10°C for 60 minutes to precipitate sodium sulfate decahydrate.

[0196] Perform solid-liquid separation to obtain sodium sulfate decahydrate solid and circulating liquid.

[0197] The circulating liquid is returned to the leaching step for the leaching of the next batch of vanadium slag.

[0198] Example 6

[0199] 1. Vanadium slag leaching:

[0200] Add 260g of wet vanadium slag (containing 41.7% moisture) to 625mL of circulating liquid.

[0201] The mixture is heated to 75°C.

[0202] Add appropriate amount of sulfuric acid to adjust the pH value to 9.2.

[0203] The vanadium slag is kept at 75°C for 45 minutes to fully leach, and a leaching slurry is obtained.

[0204] 2. Impurity removal from the leaching slurry:

[0205] The leaching slurry is warmed to 92°C.

[0206] The amount of calcium sulfate is calculated according to the phosphorus content in the vanadium slag, and the mass of calcium sulfate is 1.45 times the mass of calcium sulfate required to make all the phosphorus in the vanadium slag into calcium phosphate.

[0207] The calculated amount of calcium sulfate is added.

[0208] The impurities and calcium sulfate are fully reacted at 92°C for 110 minutes to generate insoluble precipitates.

[0209] Solid-liquid separation is performed to obtain a vanadium precipitation primary solution.

[0210] 3. Crystallization and precipitation of ammonium metavanadate from the vanadium precipitation primary solution:

[0211] The vanadium precipitation primary solution is cooled to 52°C.

[0212] Ammonium sulfate is added according to the NH4 + :V molar ratio of 4.5.

[0213] After adding ammonium sulfate, the solution is cooled to 32°C.

[0214] The ammonium metavanadate is fully crystallized and precipitated at 32°C for 45 minutes.

[0215] Solid-liquid separation is performed to obtain ammonium metavanadate solids and a vanadium precipitation mother liquor.

[0216] 4. Treatment of the vanadium precipitation mother liquor:

[0217] The vanadium precipitation mother liquor is cooled to 7°C.

[0218] The sodium sulfate decahydrate is precipitated at 7°C for 45 minutes.

[0219] Solid-liquid separation is performed to obtain sodium sulfate decahydrate solids and a circulating liquid.

[0220] The circulating liquid is returned to the leaching step for the leaching of the next batch of vanadium slag.

[0221] Comparative Example 1 (without treatment of the vanadium precipitation mother liquor)

[0222] Impurity removal step: one impurity removal is performed using calcium sulfate.

[0223] Vanadium precipitation step: Ammonium sulfate was added according to NH4:V molar ratio of 4. + :V molar ratio of 4.

[0224] Vanadium precipitation mother liquor treatment: The vanadium precipitation mother liquor was not treated.

[0225] Operation steps:

[0226] 260 g of wet vanadium slag (containing 41.7% moisture) was added to 500 mL of circulating liquid.

[0227] The mixture was heated to 40°C.

[0228] Subsequently, an appropriate amount of sulfuric acid was added to adjust the pH value to 8.

[0229] The vanadium slag was fully leached at 40°C for 20 minutes to obtain a leaching slurry.

[0230] The leaching slurry was heated to 80°C, an appropriate amount of calcium sulfate was added, and the temperature was maintained for 60 minutes for solid-liquid separation.

[0231] The filtrate after impurity removal was cooled to 40°C, and ammonium sulfate was added according to NH4:V molar ratio of 4.

[0232] After that, the solution was cooled to 20°C and maintained at this temperature for 20 minutes, and then solid-liquid separation was performed to finally obtain ammonium metavanadate solid and vanadium precipitation mother liquor.

[0233] Effect data: The effect data of Examples 1 to 6 and Comparative Example 1 are shown in Table 1.

[0234] Experimental method of effect data:

[0235] 1. Determination of ammonium metavanadate purity: X-ray diffraction (XRD) and chemical analysis method were used.

[0236] 2. Calculation of vanadium recovery rate: The vanadium content of the leaching solution and the final product was determined by chemical analysis method.

[0237] 3. Evaluation of vanadium precipitation mother liquor treatment effect: The content of main components in the mother liquor was determined by chemical analysis method.

[0238] Table 1

[0239] Experiment No. Ammonium metavanadate purity (%) Vanadium recovery (%) Vanadium precipitation mother liquor treatment Remarks Example 1 99.26 95.2％ Recycle use - Example 2 99.12 95.5％ Recycle use - Example 3 99.19 95.8％ Recycle use - Example 4 99.21 96％ Recycle use - Example 5 99.28 96.5％ Recycle use - Example 6 99.30 96.8％ Recycle use - Comparative Example 1 88 85％ Untreated Untreated vanadium precipitation mother liquor

[0240] From the above effect data table, the differences between different examples and comparative examples can be directly compared. The following conclusions can be drawn:

[0241] The method of the present application has significant advantages in improving the purity of ammonium metavanadate, the recovery rate of vanadium, and realizing the recycling of vanadium precipitation mother liquor.

[0242] In terms of purity of ammonium metavanadate, the purity of examples 1 to 6 all reached 99.0% or more, among which the purity of example 6 was the highest, being 99.30%. In contrast, the purity of comparative example 1 (untreated vanadium precipitation mother liquor) was 88%, all lower than the examples. This shows that the present application can realize closed-circuit production and improve product purity by treating the mother liquor.

[0243] In terms of vanadium recovery rate, the recovery rate of examples 1 to 6 all reached 95% or more, while the recovery rate of comparative example 1 (untreated vanadium precipitation mother liquor) was 85%, significantly lower than the examples. This shows that the present application can realize closed-circuit production, improve vanadium recovery rate and reduce vanadium loss by treating the mother liquor.

[0244] The above description is merely one specific implementation of the present application, which enables those skilled in the art to 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 these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing ammonium metavanadate from vanadium slag in a closed circuit, wherein the impurities in the vanadium slag include at least one of the following: phosphorus, silicon, aluminum, fluorine, iron, titanium, calcium, magnesium, manganese, copper, zinc, oxalate, or organic salt, wherein the method comprises: The vanadium slag containing impurities is mixed with a first liquid medium for leaching treatment to obtain a vanadium-containing leachate. Calcium salts were added to the leachate for impurity removal to obtain a purified vanadium-containing solution. A precipitant was added to the purified vanadium-containing solution to precipitate the vanadium, yielding ammonium metavanadate and mother liquor. The mother liquor is cooled to precipitate solid salt, resulting in a recyclable second liquid medium. The calcium salt includes at least one of the following: calcium sulfate, calcium chloride, calcium nitrate, calcium carbonate, calcium hydroxide, and calcium oxide.

2. The method according to claim 1, characterized in that, The first liquid medium is water or a solution containing soluble salts.

3. The method according to claim 2, characterized in that, The solution containing soluble salts includes at least one of the following: ammonium sulfate solution, ammonium chloride solution, ammonium nitrate solution, sodium sulfate solution, sodium chloride solution, sodium nitrate solution, potassium sulfate solution, potassium chloride solution, potassium nitrate solution, magnesium sulfate solution, magnesium chloride solution, and magnesium nitrate solution.

4. The method according to claim 1, characterized in that, The mass of the calcium salt is 1.2 to 1.5 times the mass of the calcium salt that causes all the phosphorus in the vanadium slag to be converted into calcium phosphate.

5. The method according to claim 1, characterized in that, The precipitant contains NH4 + Its NH4 + The molar ratio of V in the vanadium slag is 3.5 to 4.

5.

6. The method according to claim 4, characterized in that, The precipitant includes at least one of the following: ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium carbonate, ammonium hydroxide, ammonium phosphate, ammonium oxalate, ammonium citrate, and ammonium acetate.

7. The method according to claim 1, characterized in that, The ammonium metavanadate is calcined to obtain vanadium pentoxide; the purity of the vanadium pentoxide is ≥99%.

8. The method according to claim 1, characterized in that, The temperature range for the cooling process is 0°C to 15°C.

9. The method according to claim 1, characterized in that, The solid salt includes at least one of the following: sodium sulfate decahydrate, anhydrous sodium sulfate, calcium sulfate, sodium chloride, magnesium sulfate, magnesium chloride, potassium sulfate, potassium chloride, sodium nitrate, potassium nitrate, and magnesium nitrate.

10. The method according to claim 1, characterized in that, The parameters of the leaching treatment include at least one of the following: a temperature range of 30°C to 90°C, a holding time of 10 to 120 minutes, a pH value of 8 to 10, and a liquid-to-solid ratio of 2:1 to 8:1; and / or, The parameters of the impurity removal treatment include at least one of the following: pH value range of 8 to 10, temperature range of 80°C to 99°C, and holding time of 60 to 120 minutes; and / or, The parameters of the precipitation treatment include at least one of the following: a temperature range of 10°C to 50°C and a holding time of 20 to 90 minutes.

Images