Washing method of high-purity ammonium metavanadate

Abstract

The invention relates to the field of hydrometallurgy, and provides a high-purity ammonium metavanadate washing method which comprises the following steps: preparing oxalic acid into an acidic solution, and preparing ammonium bicarbonate into a weakly alkaline solution; adding the acid solution into the crude ammonium metavanadate, stirring or soaking and washing under a preset first temperature condition, and carrying out solid-liquid separation after washing to obtain primarily washed ammonium metavanadate; and adding the weakly alkaline solution into the primarily washed ammonium metavanadate, stirring or soaking and washing, and carrying out solid-liquid separation after washing to obtain the high-purity ammonium metavanadate. The ammonium metavanadate is washed, and impurities adsorbed on the surface of the ammonium metavanadate can be remarkably removed. The solvent is in full contact with the surface of the ammonium metavanadate, adsorbed impurities are dissolved or dispersed into the solvent, and a washing solution is separated from an ammonium metavanadate solid, so that the impurities on the surface are effectively removed, the content of the impurities in the ammonium metavanadate is further reduced, and the purity of a product is effectively improved. The method has high operability and is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgy, and more specifically to a washing method for high-purity ammonium metavanadate. Background Technology

[0002] High-quality ammonium metavanadate (AM) is characterized by high purity and multiple functionalities. High-purity vanadium pentoxide is often used in the production of electrolytes, and it is prepared by calcining AM. AM plays a crucial role in the preparation of high-purity vanadium pentoxide, but currently, AM in actual production generally suffers from high levels of impurities such as metallic elements and sulfur. These impurities have a wide range of sources, possibly introduced during the mining and processing of raw materials, or contaminated during equipment wear and environmental pollution. The impurity content in AM is one of the main factors affecting the purity of vanadium pentoxide. When the impurity content in AM is high, these impurities may undergo a series of complex chemical reactions during the calcination process to prepare vanadium pentoxide, generating new compounds or remaining in the final product. Metallic impurities may form solid solutions with vanadium at high temperatures, altering the crystal structure of vanadium pentoxide and thus affecting its physicochemical properties. Sulfur impurities may generate sulfide gases during calcination, not only polluting the environment but also leaving sulfur residues in the product, reducing the purity of vanadium pentoxide. The presence of these impurities will seriously affect the performance of the electrolyte prepared using vanadium pentoxide as a raw material, thereby reducing the overall performance and reliability of vanadium-based batteries. Summary of the Invention

[0003] In view of this, the present invention proposes a washing method for high-purity ammonium metavanadate, which has the advantages of removing residues by calcination, good washing effect, strong operability, and low environmental pollution, and has broad application prospects and economic value.

[0004] To achieve the above objectives, this invention proposes a washing method for high-purity ammonium metavanadate, comprising the following steps: Oxalic acid was prepared as an acidic solution, and ammonium bicarbonate was prepared as a weakly alkaline solution. The acidic solution is added to the crude ammonium metavanadate, and the mixture is stirred or soaked and washed under a preset first temperature condition. After washing, the solid and liquid are separated to obtain the pre-washed ammonium metavanadate. The weakly alkaline solution is added to the initial washing ammonium metavanadate, and the mixture is stirred or soaked for washing. After washing, the solid and liquid are separated to obtain high-purity ammonium metavanadate.

[0005] In some embodiments, the oxalic acid is mixed with pure water to prepare an acidic solution with a mass fraction of 1%-5%.

[0006] In some embodiments, the ammonium bicarbonate is mixed with pure water to form an ammonium bicarbonate solution with a mass fraction of 1%-5%.

[0007] In some embodiments, the liquid-to-solid ratio of the acidic solution added to the crude ammonium metavanadate is in the range of 2-5:1 mL / g.

[0008] In some embodiments, the liquid-to-solid ratio of the ammonium metavanadate added to the weakly alkaline solution during the initial washing is in the range of 2-5:1 mL / g.

[0009] In some embodiments, the preset first temperature condition is 30-60°C.

[0010] In some embodiments, the acidic solution forms a complex with the metal ions in the crude ammonium metavanadate; Monitor the concentration of the complex in the acidic solution, and replace the acidic solution when the concentration exceeds a threshold.

[0011] In some embodiments, when the high-purity ammonium metavanadate is used for calcination, vanadium pentoxide is directly prepared. When the high-purity ammonium metavanadate is not used for calcination, it is washed with pure water.

[0012] In some embodiments, an ethanol solution is added to a weakly alkaline solution to adsorb Na ions and K ions.

[0013] In some embodiments, washing is performed using a combination of ultrasonic waves and an agitator.

[0014] The present invention has at least the following beneficial technical effects: This invention provides a washing treatment for ammonium metavanadate, which significantly removes impurities adsorbed on its surface. The solvent comes into full contact with the surface of the ammonium metavanadate, dissolving or dispersing the adsorbed impurities into the solvent. The washing solution is then separated from the solid ammonium metavanadate, effectively removing surface impurities and further reducing the impurity content in the ammonium metavanadate, thus significantly improving the purity of the product. It has high operability and is suitable for large-scale industrial production. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings: Figure 1 A flowchart of a washing method for high-purity ammonium metavanadate according to an embodiment of the present invention is shown. Detailed Implementation

[0016] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0017] Furthermore, the reference to "embodiment" herein means that a particular 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. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0018] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as in the embodiments of this application.

[0019] Please see Figure 1 This invention proposes a washing method for high-purity ammonium metavanadate, comprising the following steps: Oxalic acid was prepared as an acidic solution, and ammonium bicarbonate was prepared as a weakly alkaline solution. The acidic solution is added to the crude ammonium metavanadate, and the mixture is stirred or soaked and washed under a preset first temperature condition. After washing, the solid and liquid are separated to obtain the pre-washed ammonium metavanadate. The weakly alkaline solution is added to the initial washing ammonium metavanadate, and the mixture is stirred or soaked for washing. After washing, the solid and liquid are separated to obtain high-purity ammonium metavanadate.

[0020] The purpose of this invention is to overcome the shortcomings of existing methods for washing ammonium metavanadate with pure water and ammonium chloride solution, which result in high levels of impurities such as metal elements and sulfur in ammonium metavanadate. This invention provides a washing method for high-purity ammonium metavanadate, which features the advantages of removing residues by calcination, good washing effect, strong operability, and low environmental pollution. It has broad application prospects and economic value.

[0021] This invention provides ammonium metavanadate. Oxalic acid is prepared into a 1%-5% acidic solution using pure water, and ammonium bicarbonate is prepared into a 1%-5% weakly alkaline solution. The solution is then stirred or soaked in 1%-5% oxalic acid at a liquid-to-solid ratio of 2-5:1 at 30℃-60℃ for 10-60 minutes. After washing, the solid and liquid are separated. The resulting ammonium metavanadate is then stirred or soaked in a 1%-5% ammonium bicarbonate solution at room temperature for 10-30 minutes at a liquid-to-solid ratio of 2-5:1. This ammonium metavanadate is used for calcining vanadium pentoxide. If the finished product is ammonium metavanadate, it needs to be washed with pure water at a liquid-to-solid ratio of 2-5:1.

[0022] The main principle is to use ammonium metavanadate as raw material. Based on traditional pure water or ammonium chloride washing processes, the ammonium metavanadate is first washed with a diluted oxalic acid solution. Theoretically, oxalic acid will form complexes with metal ions such as Fe, Al, Mn, Na, K, Mg, Zn, Cu, Ni, and Co in the ammonium metavanadate, thus retaining impurities in the washing solution. After solid-liquid separation, washing is performed with ammonium bicarbonate solution. Ammonium bicarbonate solution is weakly alkaline, neutralizing residual oxalic acid during washing without introducing elements such as S and Cl. When ammonium metavanadate is calcined to produce vanadium pentoxide, the residual ammonium bicarbonate decomposes into NH3, CO2, and H2O, without introducing impurities, thus producing high-quality vanadium pentoxide. If the ammonium metavanadate is not calcined, pure water washing is used to remove residual ammonium bicarbonate impurities. The oxalic acid washing solution is mixed with a vanadium-containing solution for ammonium polyvanadate precipitation, and the ammonium bicarbonate washing solution is mixed with a vanadium solution for ammonium metavanadate precipitation, recovering residual vanadium from the washing solution.

[0023] First, crude ammonium metavanadate is used, followed by washing with 1%-5% oxalic acid. Through a dual mechanism of complexation and acid dissolution, metal ions are selectively transferred into the solution. Impurities are removed during solid-liquid separation. This method has high impurity removal efficiency, low process requirements, simple equipment, and does not introduce impurities such as Cl and S, making it highly compatible with industrial production.

[0024] Washing with ammonium bicarbonate solution first neutralizes the residual oxalic acid solution, and the presence of ammonium ions in the solution reduces vanadium loss. It further replaces Na and K ions in ammonium metavanadate, improving the impurity removal effect.

[0025] The washing solution (oxalic acid washing solution) is mixed with vanadium-containing solution for ammonium polyvanadate precipitation. Due to the complexing effect of oxalic acid, the introduction of impurities into the ammonium polyvanadate is reduced, and the vanadium dissolved during the washing process is recovered.

[0026] The secondary washing (ammonium bicarbonate washing solution) is mixed with vanadium-containing solution for ammonium metavanadate precipitation. This can effectively utilize ammonium ions in the washing solution and recover vanadium in the solution, which is a high-efficiency and low-cost production technology.

[0027] In some embodiments, the oxalic acid is mixed with pure water to prepare an acidic solution with a mass fraction of 1%-5%.

[0028] A 1%-5% oxalic acid solution increases the solubility of substances. Oxalate ions can form soluble complexes with metal ions, allowing these substances to dissolve more readily in solution. This is highly beneficial for subsequent separation and purification operations, enabling more complete dissolution, improving raw material utilization, and reducing production costs.

[0029] In some embodiments, the ammonium bicarbonate is mixed with pure water to form an ammonium bicarbonate solution with a mass fraction of 1%-5%.

[0030] Ammonium bicarbonate ionizes in water, producing ammonium and bicarbonate ions. Within a concentration range of 1%-5%, the ion concentration in the solution is moderate. When an ammonium bicarbonate solution is added to an acid-washed system, the bicarbonate and ammonium ions in the solution react with the hydrogen ions in the acidic substance, achieving acid-base neutralization. This allows for precise adjustment of the solution's pH to a suitable range. It can also interact with sodium and potassium ions, achieving adsorption. From a chemical perspective, ammonium bicarbonate creates a specific ionic environment in aqueous solution, where bicarbonate and ammonium ions interact with sodium and potassium ions through electrostatic attraction. Simultaneously, certain tiny particles or colloidal substances in the ammonium bicarbonate solution may also adsorb sodium and potassium ions onto their surfaces through physical adsorption.

[0031] In some embodiments, the liquid-to-solid ratio of the acidic solution added to the crude ammonium metavanadate is in the range of 2-5:1 mL / g.

[0032] This provides sufficient contact space and a suitable reaction environment for crude ammonium metavanadate and the acidic solution. Besides its main component, ammonium metavanadate, crude ammonium metavanadate also contains impurities and unreacted raw materials. When the acidic solution comes into contact with crude ammonium metavanadate, a sufficient volume of liquid is needed to dissolve the soluble components and promote a complete chemical reaction. The acidic solution can uniformly coat the crude ammonium metavanadate particles, allowing active components such as hydrogen ions in the solution to fully contact the ammonium metavanadate and impurities. Under acidic conditions, ammonium metavanadate undergoes a series of hydrolysis and transformation reactions. A sufficient volume of liquid ensures these reactions proceed in the intended direction, converting the ammonium metavanadate into a form easier for subsequent processing, while simultaneously dissolving or reacting impurities, thereby improving raw material utilization and product purity. If the liquid-to-solid ratio is too low, insufficient liquid volume will prevent some crude ammonium metavanadate from fully contacting the acidic solution, resulting in incomplete reaction, wasted raw materials, and decreased product quality. Conversely, while a high liquid-to-solid ratio ensures a complete reaction, it increases the workload and cost of subsequent processing.

[0033] In some embodiments, the liquid-to-solid ratio of the ammonium metavanadate added to the weakly alkaline solution during the initial washing is in the range of 2-5:1 mL / g.

[0034] A weakly alkaline solution can effectively encapsulate the initially washed ammonium metavanadate particles. The alkaline components in the solution, such as hydroxide ions, can neutralize acidic impurities, converting them into water-soluble salts, which are then eluted from the surface and interior of the ammonium metavanadate. For metal ion impurities, the weakly alkaline environment may cause them to form hydroxide precipitates or detach from the ammonium metavanadate structure through ion exchange and other mechanisms, entering the solution.

[0035] In some embodiments, the preset first temperature condition is 30-60°C.

[0036] A temperature range of 30-60℃ provides a relatively mild and stable environment for ammonium metavanadate-related reactions, allowing the reaction to proceed in the intended direction and reducing the occurrence of side reactions. In the conversion reaction of ammonium metavanadate, excessively high temperatures may lead to excessive decomposition of ammonium metavanadate or unnecessary reactions with other impurities, generating byproducts and reducing the purity and yield of the target product. Within the 30-60℃ temperature range, the molecular energy in the reaction system is moderate, which can suppress side reactions, thereby improving product quality and consistency.

[0037] In some embodiments, the acidic solution forms a complex with the metal ions in the crude ammonium metavanadate; Monitor the concentration of the complex in the acidic solution, and replace the acidic solution when the concentration exceeds a threshold.

[0038] As the reaction proceeds, metal ions in the acidic solution continuously combine with the ligand to form complexes, and the concentration of these complexes gradually increases. When the complex concentration exceeds a set threshold, it means that the ligand in the acidic solution is nearing saturation. Continuing to use this solution will not effectively remove metal ion impurities from the crude ammonium metavanadate, and may even cause the already formed complexes to re-dissociate, leading to re-contamination of the product by the metal ions. Therefore, it is necessary to replace the acidic solution promptly to ensure effective impurity removal.

[0039] The concentration of the complex is determined to be within the threshold of 0.5 mol / L. If it exceeds this threshold, the acidic solution is replaced. Effective removal of metal ion impurities from crude ammonium metavanadate significantly improves the purity of the product. Monitoring the complex concentration and replacing the acidic solution as needed ensures the impurity removal process remains optimal, preventing process fluctuations caused by acidic solution failure. This contributes to improved stability and controllability of the entire production process, reducing defect rates and production accidents. Real-time adjustment of the acidic solution usage based on the complex concentration avoids overuse and waste. Furthermore, the replaced acidic solution can be recycled to recover useful components, achieving resource recycling and reducing production costs.

[0040] In some embodiments, when the high-purity ammonium metavanadate is used for calcination, vanadium pentoxide is directly prepared. When the high-purity ammonium metavanadate is not used for calcination, it is washed with pure water.

[0041] In some embodiments, an ethanol solution is added to a weakly alkaline solution to adsorb Na ions and K ions.

[0042] Ethanol is a polar solvent, and its hydroxyl groups can bind to Na and K ions through dipole-ion interactions, forming a weak coordination structure. The addition of ethanol lowers the dielectric constant of the solution, weakens the solvation effect of water molecules on Na and K ions, promotes ion aggregation, and enhances the adsorption of Na and K ions in the weakly alkaline environment.

[0043] Under weakly alkaline conditions, the adsorption efficiency of Na and K ions is significantly higher than that of multivalent metal ions, enabling the targeted removal of specific ions. The addition of ethanol can further suppress interference from coexisting impurities and improve separation purity.

[0044] In some embodiments, washing is performed using a combination of ultrasonic waves and an agitator.

[0045] Ultrasonic waves generate high-frequency vibrations in the liquid, inducing the formation, growth, and violent collapse of microbubbles. The shock waves and microjets released during bubble collapse can penetrate the surface of ammonium metavanadate particles, stripping impurities adhering to the particle surface and simultaneously promoting full contact between the solution and particles. The rotating impeller generates forced convection, creating a uniform flow field in the washing liquid within the reactor and avoiding localized concentration gradients. Its shear force disperses ammonium metavanadate agglomerates, increasing the contact area between particles and solution, further accelerating the dissolution and diffusion of impurities.

[0046] The washing method for high-purity ammonium metavanadate according to the present invention specifically includes the following steps: (1) Oxalic acid is mixed with pure water (deionized water) to prepare an oxalic acid solution with a mass fraction of 1%-5% for later use. Ammonium bicarbonate is mixed with pure water (deionized water) to prepare an ammonium bicarbonate solution with a mass fraction of 1%-5%.

[0047] (2) Add crude ammonium metavanadate to oxalic acid solution for washing, with a liquid-to-solid ratio of 2-5:1. Heat to 30-60℃ and wash for 10-60 minutes under stirring. After washing, separate the solid and liquid.

[0048] (3) The solid is washed twice with ammonium bicarbonate solution.

[0049] (4) Oxalic acid washing solution mixed with vanadium-containing solution precipitates ammonium polyvanadate.

[0050] (5) Ammonium bicarbonate washing solution mixed with vanadium-containing solution precipitates ammonium metavanadate.

[0051] According to a preferred embodiment of the present invention, in the method for washing high-purity ammonium metavanadate, impurity ions and residual precipitants are removed based on the acidic dissolution and complexation of oxalic acid. During washing with ammonium bicarbonate, the residual oxalic acid solution is neutralized, and the impurity elements in the ammonium metavanadate are washed a second time. Using this method, the Na, S, Fe, Al, Mn in ammonium metavanadate can be reduced to below 0.01%.

[0052] The present invention will be further illustrated by the following examples, but the scope of protection of the present invention is not limited thereto.

[0053] Example 1 This embodiment illustrates a washing method for high-purity ammonium metavanadate provided by the present invention.

[0054] Take 500g of ammonium metavanadate, with K, Na, S, Cr, Al, and Fe contents of 0.006%, 0.015%, 0.013%, 0.004%, 0.006%, and 0.012%, respectively. Prepare a 2% oxalic acid solution with pure water and a 2% ammonium bicarbonate solution with pure water. First, wash the ammonium metavanadate with the oxalic acid solution at a liquid-to-solid ratio of 2:1, heat to 40℃, and stir for 30 min. After washing, separate the solid and liquid. Wash the obtained ammonium metavanadate with the ammonium bicarbonate solution at a liquid-to-solid ratio of 2:1, stir for 20 min, and then separate the solid and liquid. After drying the solid, test the impurity content. The contents of K, Na, S, Cr, Al, and Fe are 0.002%, 0.003%, 0.005%, 0.002%, 0.002%, and 0.005%, respectively.

[0055] Example 2 This embodiment illustrates a washing method for high-purity ammonium metavanadate provided by the present invention.

[0056] Take 500g of ammonium metavanadate, with K, Na, S, Cr, Al, and Fe contents of 0.006%, 0.015%, 0.013%, 0.004%, 0.006%, and 0.012%, respectively. Prepare a 2.5% oxalic acid solution with pure water and a 2.5% ammonium bicarbonate solution with pure water. First, wash the ammonium metavanadate with the oxalic acid solution at a liquid-to-solid ratio of 2:1, heat to 40℃, and stir for 30 min. After washing, separate the solid and liquid. Wash the obtained ammonium metavanadate with the ammonium bicarbonate solution at a liquid-to-solid ratio of 2:1, stir for 20 min, and then separate the solid and liquid. After drying the solid, test the impurity content. The contents of K, Na, S, Cr, Al, and Fe are 0.002%, 0.003%, 0.005%, 0.002%, 0.002%, and 0.004%, respectively.

[0057] Example 3 This embodiment illustrates a washing method for high-purity ammonium metavanadate provided by the present invention.

[0058] Take 500g of ammonium metavanadate, with K, Na, S, Cr, Al, and Fe contents of 0.006%, 0.015%, 0.013%, 0.004%, 0.006%, and 0.012%, respectively. Prepare a 3% oxalic acid solution with pure water and a 3% ammonium bicarbonate solution with pure water. First, wash the ammonium metavanadate with the oxalic acid solution at a liquid-to-solid ratio of 2:1, heat to 40℃, and stir for 30 min. After washing, separate the solid and liquid. Wash the obtained ammonium metavanadate with the ammonium bicarbonate solution at a liquid-to-solid ratio of 2:1, stir for 20 min, and then separate the solid and liquid. After drying the solid, test the impurity content. The contents of K, Na, S, Cr, Al, and Fe are 0.002%, 0.002%, 0.004%, 0.002%, 0.001%, and 0.004%, respectively.

[0059] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of 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.

[0060] 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.

[0061] 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 washing method for high-purity ammonium metavanadate, characterized in that, Includes the following steps: Oxalic acid was prepared as an acidic solution, and ammonium bicarbonate was prepared as a weakly alkaline solution. The acidic solution is added to the crude ammonium metavanadate, and the mixture is stirred or soaked and washed under a preset first temperature condition. After washing, the solid and liquid are separated to obtain the pre-washed ammonium metavanadate. The weakly alkaline solution is added to the initial washing ammonium metavanadate, and the mixture is stirred or soaked for washing. After washing, the solid and liquid are separated to obtain high-purity ammonium metavanadate.

2. The washing method for high-purity ammonium metavanadate according to claim 1, characterized in that, The oxalic acid is mixed with pure water to prepare an acidic solution with a mass fraction of 1%-5%.

3. The washing method for high-purity ammonium metavanadate according to claim 1, characterized in that, The ammonium bicarbonate is mixed with pure water to form an ammonium bicarbonate solution with a mass fraction of 1%-5%.

4. The washing method for high-purity ammonium metavanadate according to claim 1, characterized in that, The liquid-to-solid ratio of the acidic solution added to the crude ammonium metavanadate is in the range of 2-5:1 mL / g.

5. The washing method for high-purity ammonium metavanadate according to claim 1, characterized in that, The liquid-to-solid ratio of the ammonium metavanadate added to the weakly alkaline solution during the initial washing is in the range of 2-5:1 mL / g.

6. The washing method for high-purity ammonium metavanadate according to claim 1, characterized in that, The preset first temperature condition is 30-60℃.

7. The washing method for high-purity ammonium metavanadate according to claim 1, characterized in that, The acidic solution forms a complex with the metal ions in the crude ammonium metavanadate. Monitor the concentration of the complex in the acidic solution, and replace the acidic solution when the concentration exceeds a threshold.

8. The washing method for high-purity ammonium metavanadate according to claim 1, characterized in that, When the high-purity ammonium metavanadate is used for calcination, vanadium pentoxide is directly prepared. When the high-purity ammonium metavanadate is not used for calcination, it is washed with pure water.

9. The washing method for high-purity ammonium metavanadate according to claim 1, characterized in that, Adding ethanol solution to a weakly alkaline solution is used to adsorb Na and K ions.

10. The washing method for high-purity ammonium metavanadate according to claim 1, characterized in that, Washing is performed using both ultrasonic waves and an agitator.

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