Ammonium metavanadate purification method with zero wastewater discharge

Abstract

The invention discloses an ammonium metavanadate purification method with zero wastewater discharge, and relates to the technical field of ammonium metavanadate purification, and the method is characterized by comprising the following steps: pretreatment dissolution: grinding a crude product ammonium metavanadate, and preparing an ammonium metavanadate solution by matching with hot water and a cosolvent under the assistance of ultrasonic wave; under the condition of 60-80 DEG C, adjusting the pH value to 5-6.5 by using a weakly acidic reagent, carrying out rapid stirring reaction, adjusting the pH value to 7-8.5 by using a weakly alkaline reagent, carrying out slow stirring reaction, standing and filtering to obtain a deeply purified ammonium metavanadate solution; cooling the purified solution to 53-58 DEG C, adding a crystallization accelerant to induce crystal nucleus generation, cooling to 35-40 DEG C to promote crystal growth, and performing centrifugal separation to obtain high-purity ammonium metavanadate crystals and low-concentration mother liquor; washing and drying the high-purity crystal to obtain a high-purity ammonium metavanadate product; and heating the low-concentration mother liquor, supplementing the ground crude product ammonium metavanadate, and repeating the dissolving process. According to the method, 100% cyclic utilization of water resources and residual vanadium resources is achieved, and'zero wastewater discharge 'is achieved.

Description

Technical Field

[0001] This invention relates to the field of ammonium metavanadate purification technology, and more specifically, to a method for purifying ammonium metavanadate with zero wastewater discharge. Background Technology

[0002] Vanadium, as an important transition metal element, occupies an irreplaceable strategic position in modern industrial systems due to its abundant valence states (+2, +3, +4, +5), excellent electrochemical activity, and catalytic performance. Its compounds are widely used in iron and steel metallurgy (as alloying additives to improve strength and toughness), the chemical industry (as catalysts in sulfuric acid production, flue gas denitrification, etc.), the new energy field (as active material in the electrolyte of all-vanadium redox flow batteries), and emerging functional materials (such as optical materials and precursors for superconducting materials). Ammonium metavanadate is the most crucial and universal intermediate compound connecting primary vanadium resources (such as crude products extracted from vanadium-titanium magnetite, coal shale, or spent catalysts) with the aforementioned high-end application end products. High-purity vanadium pentoxide ( The preparation of vanadium battery electrolytes (≥99.9%) is usually based on the thermal decomposition of high-purity ammonium metavanadate; the synthesis of vanadium battery electrolytes (such as vanadium oxysulfate solution) also depends on high-purity vanadium sources to ensure long-term stability and efficiency.

[0003] However, vanadium in nature or in primary industrial products is always accompanied by various impurities. Industrial-grade ammonium metavanadate obtained through the traditional "roasting-leaching-precipitation" process typically has a purity of only 95% to 98%, and its impurity profile is complex, mainly including alkali metal and alkaline earth metal ions such as potassium (…). ),sodium( ),calcium( ),magnesium( Transition metal ions: such as iron ( ),chromium( ),manganese( Non-metallic oxygen-containing anions: such as phosphate (…). ), arsenate ( ), silicate ( Or in its polymeric colloidal form (existing), sulfate ( Others include molybdenum (Mo) and aluminum (Al).

[0004] The presence of these impurities, even in minute quantities, can have a catastrophic impact on the performance of the final material. For example, in all-vanadium redox flow batteries, impurity ions (especially...) , , , Impurities can significantly alter the ionic strength and conductivity of the electrolyte, competitively cross ion exchange membranes, leading to decreased coulombic efficiency, accelerated capacity decay, and even precipitation that clogs flow channels. In catalysis, certain poisons (such as As and P) can irreversibly occupy the active sites of catalysts, causing catalyst deactivation. Therefore, developing high-purification technologies that can deeply, economically, and environmentally remove these impurities, especially those with chemical behaviors similar to vanadium, is crucial for transforming vanadium resources from commodities to high-tech materials, possessing significant scientific and industrial value.

[0005] For a long time, the industrial purification of ammonium metavanadate has mainly relied on traditional methods based on the principle of chemical precipitation, such as the alkali dissolution-ammonium salt precipitation method. Although these processes are mature and have a large processing capacity, their inherent defects are fully exposed when pursuing ultra-high purity of 99.5% or even electronic grade (99.99%), which are mainly reflected in: (1) The paradox of "introduction-removal": The strong alkali (NaOH / KOH) introduced to dissolve the raw materials becomes difficult to completely remove from the product. The source of impurities has fallen into a dilemma of "introducing new impurities in order to purify".

[0006] (2) High environmental cost: The precipitation process generates a large amount of high salt ( , High ammonia nitrogen ( Wastewater is difficult and costly to treat, leaving a heavy environmental footprint and running counter to increasingly stringent environmental regulations worldwide.

[0007] (3) Low resource utilization: Due to the “common ion effect”, the mother liquor after precipitation cannot be directly reused to dissolve raw materials, resulting in a limited recovery rate of vanadium (usually <95%) and the consumption of a large amount of fresh water, which does not conform to the principle of circular economy.

[0008] These bottlenecks not only restrict the upward mobility of my country's vanadium products in the high-end value chain, but also place enormous environmental and cost pressures on related industries. Therefore, this invention provides a zero-wastewater discharge method for purifying ammonium metavanadate. Summary of the Invention

[0009] The purpose of this invention is to provide a zero-wastewater purification method for ammonium metavanadate, thereby solving the above-mentioned problems.

[0010] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a method for purifying ammonium metavanadate with zero wastewater discharge, comprising the following steps: S1. Grind the crude ammonium metavanadate, dissolve it in hot water, add a co-solvent, and simultaneously emit ultrasound into the solid-liquid mixture to obtain an ammonium metavanadate solution after dissolution. S2. Keep the temperature of the ammonium metavanadate solution at 60-80℃. Under rapid stirring, first add a weak acidic impurity remover, control the pH to 5-6.5, and react for 1-5 minutes. Then adjust to slow stirring, add a weak alkaline impurity remover, control the pH to 7-8.5, and react for 8-20 minutes. Finally, stop stirring, let stand, filter, and obtain a deeply purified ammonium metavanadate solution. S3. Under rapid stirring conditions, the deeply purified and impurity-removed ammonium metavanadate solution is cooled to 53-58℃. At this time, the stirring speed is adjusted to medium speed, a crystallization promoter is added, and the reaction is kept at this temperature for 40-90 minutes to promote the crystallization and precipitation of ammonium metavanadate. Then, the temperature is cooled to 35-40℃ and the reaction is kept at this temperature for 20-40 minutes to promote the crystal growth of ammonium metavanadate. Finally, high-purity ammonium metavanadate crystals and low-concentration ammonium metavanadate mother liquor are obtained by centrifugation and filtration. S4. Wash and dry the high-purity ammonium metavanadate crystals to obtain the high-purity ammonium metavanadate product; S5. Heat the low-concentration ammonium metavanadate mother liquor, add the powder of crude ammonium metavanadate after grinding, add a co-solvent, and simultaneously emit ultrasound into the solid-liquid mixture. After dissolution, a high-concentration ammonium metavanadate solution is obtained for the second time. S6. Repeat steps S2-S5 to achieve purification of ammonium metavanadate with zero wastewater discharge.

[0011] The present invention is further configured such that, in step S1, the co-solvent is glycerol or polyethylene glycol.

[0012] The present invention is further configured such that: in step S1, the hot water temperature is 70-90℃; and in step S5, the heating temperature is 70-90℃.

[0013] The present invention is further configured such that, in step S1, the mass ratio of ammonium metavanadate to hot water is 1:(10-15).

[0014] The present invention is further configured such that, in steps S2 and S3, the stirring speed of the rapid stirring is 100-300 rpm; the stirring speed of the medium-speed stirring is 60-100 rpm; and the stirring speed of the low-speed stirring is 20-60 rpm.

[0015] The present invention is further configured such that, in steps S1 and S5, the frequency of the ultrasonic wave is 25-40 kHz.

[0016] The present invention is further configured such that, in steps S1 and S5, the crude ammonium metavanadate is ground to 150-200 mesh.

[0017] The present invention is further configured such that, in step S2, the weakly alkaline impurity remover is one or more of magnesium oxide, calcium oxide, sodium aluminate, and calcium hydroxide.

[0018] The present invention is further configured such that, in step S2, the weakly acidic impurity remover is one or more of polyaluminum chloride, aluminum sulfate, magnesium chloride, and magnesium sulfate.

[0019] The present invention is further configured such that, in step S3, the crystallization promoter is ammonium citrate.

[0020] The present invention is further configured such that, in step S2, the settling time is 30-90 minutes.

[0021] In summary, the present invention has the following beneficial effects: 1. Innovation in process concept and system design (1) With “zero wastewater discharge” as the primary goal, this invention constructs a complete mother liquor recycling-feeding regeneration system. The low-concentration mother liquor after centrifugation is not discharged but directly used as the dissolving medium for the next batch. The concentration is restored by adding crude raw materials, thus achieving 100% recycling of water resources and residual vanadium resources.

[0022] (2) This invention differs from the “dead knot” of traditional precipitation method mother liquor that cannot be reused due to salt accumulation, and also from the problem of impurity accumulation in simple recrystallization mother liquor. This patent defines “wastewater” as a process medium in essence through the concept of “forced circulation + synchronous purification and regeneration”, and realizes the complete internal circulation of the production system.

[0023] 2. Innovation in process enhancement and coupling techniques (1) This invention enhances the dissolution technology through the synergistic effect of "ultrasonic cavitation-co-solvent". The ultrasonic cavitation effect is introduced into the dissolution stage to form a physical-chemical synergy with the chemical co-solvent. The micro-jets and local high temperature and pressure generated by ultrasound can effectively break particles and enhance mass transfer. Especially for fine particles after grinding, it can significantly improve the dissolution rate and final concentration, which solves the bottleneck of low solubility and slow dissolution inherent in hot water method, and provides a high concentration starting point for high-efficiency circulation.

[0024] (2) This invention employs a smart segmented pH gradient removal technology of "acid first, then alkali," designing a refined two-stage pH control process of "weak acid removal → weak alkali removal," and matching it with a stirring sequence of "fast stirring → slow stirring → settling." The acidic stage (pH 5-6.5) is completed quickly with rapid stirring, aiming to selectively precipitate or complex specific metallic impurities (such as iron and aluminum) that are more easily removed under weak acidity. The alkaline stage (pH 7-8.5) switches to slow stirring and extends the reaction time, aiming to remove anionic impurities such as silicon, phosphorus, and arsenic, and to make the previously formed flocs denser. The settling stage promotes the full growth and sedimentation of the flocs. This segmented strategy avoids the limitations of degrading all impurities under a single pH condition, achieving sequential, selective, and deep removal of complex impurity profiles. Simultaneously, by matching the stirring program, it optimizes reaction kinetics and solid-liquid separation performance.

[0025] 3. Innovation in crystallization process control (1) The present invention uses a temperature-controlled graded crystallization technology induced by a "crystallization promoter". In the crystallization stage, instead of using the traditional external ammonium salt or seed crystal, a crystallization promoter is introduced. The crystallization promoter changes the crystal interface energy at the microscopic level, reduces the nucleation barrier, and induces the formation of more regular and easier-to-filter crystals. The precipitation rate of ammonium metavanadate is >85% (the cooling temperature can be controlled at 35-40℃). In contrast, the precipitation rate of ammonium metavanadate that is directly cooled without adding a crystallization promoter is generally <45%, and the temperature needs to be lowered to below 25℃, which is not conducive to industrial production.

[0026] (2) The present invention uses a two-stage precise cooling process (53-58℃ heat preservation for crystallization → 35-40℃ heat preservation for growth). The staged cooling first creates a supersaturation suitable for large-scale crystallization, and then provides conditions for slow crystal growth, thereby ensuring both high precipitation rate and high crystal quality (reducing impurity encapsulation and improving particle size uniformity).

[0027] (3) The modular and continuous design of “dissolution-removal-crystallization-circulation” makes the process easy to achieve automated control and transition to continuous production mode. Each cycle is fixed, which facilitates production management and quality monitoring. Attached Figure Description

[0028] Figure 1 This is a flowchart of a zero-wastewater ammonium metavanadate purification method according to the present invention. Detailed Implementation

[0029] 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.

[0030] Example 1: (1) First cycle dissolution process 350 kg of crude ammonium metavanadate was ball-milled to an average particle size of approximately 80 μm (equivalent to 180 mesh). In a 6000 L jacketed heated reactor, 5000 L of deionized water was added, heated to 80 °C, and rapid stirring (200 rpm) was initiated. The ground crude ammonium metavanadate was added to the reactor at a uniform rate, along with a co-solvent (0.01 L glycerol). Alternatively, polyethylene glycol can be used as the co-solvent. The mixture was stirred and dissolved for 15 minutes. An ultrasonic generator (28 kHz) was then activated, and stirring continued for 20 minutes under ultrasonic cavitation until the solid phase was completely dissolved, yielding a pale yellow, transparent ammonium metavanadate solution.

[0031] (2) First cycle deep purification and impurity removal process Maintain the solution temperature at 70±2℃ and keep stirring rapidly (200 rpm). Slowly add a weakly acidic impurity remover (2 kg polyaluminum chloride) to the solution. Alternatively, aluminum sulfate, magnesium chloride, or magnesium sulfate can be used. Control the pH to 5-6.5 and stir for 1 minute. Then reduce the stirring speed to 40 rpm (slow stirring) and add a weakly alkaline impurity remover (1 kg magnesium oxide). Alternatively, calcium oxide, sodium aluminate, or calcium hydroxide can be used. Continue stirring for 8 minutes. Then stop stirring and let stand for 30 minutes to form distinct layers: a clear, transparent liquid on top and a white flocculent precipitate on the bottom. Filter using a filter press to obtain a purified, clear, and transparent ammonium metavanadate solution.

[0032] (3) First cycle crystallization separation process The purified ammonium metavanadate solution was transferred to a crystallization reactor, and rapid stirring (200 rpm) was started. The solution was then cooled to 53°C using cooling water at a rate of 1.5°C / min. The stirring speed was then adjusted to 80 rpm (medium speed), and 1.5 kg of ammonium citrate was added. The reaction was maintained at 53±1°C for 40 minutes, during which numerous fine crystal nuclei appeared and gradually grew. The solution was then cooled to 35°C at a rate of 0.5°C / min and maintained for 20 minutes to promote further crystal growth and maturation.

[0033] The crystallized slurry was transferred to a fully automatic scraper centrifuge for solid-liquid separation to obtain wet ammonium metavanadate and mother liquor. The wet ammonium metavanadate was washed twice with deionized water at room temperature, and centrifuged to dehydrate after each wash, finally obtaining high-purity wet ammonium metavanadate crystals.

[0034] (4) Drying of the first cycle of products The wet crystals were placed in a high-efficiency fluidized bed dryer and dried at 75°C for 10 minutes to obtain a dry, high-purity ammonium metavanadate product. =300.6kg.

[0035] (5) Second cycle restart 5000L of mother liquor obtained from the first cycle was pumped into the reactor and heated to 80℃. Rapid stirring (200rpm) was started. According to the material balance calculation, the mass of crude ammonium metavanadate to be added was: m2=300.6kg. 300.6kg of crude ammonium metavanadate, also ground to 180 mesh, was added to the reactor, and 0.01L of glycerol was added at the same time. The mixture was stirred and dissolved for 15 minutes. Ultrasonic dissolution (28kHz) was started for 20 minutes to obtain a high-concentration ammonium metavanadate solution for the second cycle. Then, steps (2)-(5) were repeated to achieve purification of ammonium metavanadate with zero wastewater discharge.

[0036] Example 2: (1) First cycle dissolution process 400 kg of crude ammonium metavanadate was ball-milled to an average particle size of approximately 74 μm (equivalent to 200 mesh). In a 6000 L jacketed heated reactor, 5000 L of deionized water was added, heated to 85 °C, and rapid stirring was initiated (150 rpm). The ground crude ammonium metavanadate was added to the reactor at a uniform rate, along with a co-solvent (0.02 L glycerol). Alternatively, polyethylene glycol can be used as the co-solvent. The mixture was stirred and dissolved for another 20 minutes. An ultrasonic generator (31 kHz) was then activated, and stirring continued for 25 minutes under ultrasonic cavitation until the solid phase was completely dissolved, yielding a pale yellow, transparent ammonium metavanadate solution.

[0037] (2) First cycle deep purification and impurity removal process Maintain the solution temperature at 74±2℃ and keep stirring rapidly (150 rpm). Slowly add a weakly acidic impurity remover (4 kg polyaluminum chloride) to the solution. Alternatively, aluminum sulfate, magnesium chloride, or magnesium sulfate can be used. Control the pH to 5-6.5 and stir for 2 minutes. Then reduce the stirring speed to 30 rpm (slow stirring) and add a weakly alkaline impurity remover (2 kg magnesium oxide). Alternatively, calcium oxide, sodium aluminate, or calcium hydroxide can be used. Continue stirring for 13 minutes. Then stop stirring and let stand for 40 minutes to form distinct layers: a clear, transparent liquid on top and a white flocculent precipitate on the bottom. Filter using a filter press to obtain a purified, clear, and transparent ammonium metavanadate solution.

[0038] (3) First cycle crystallization separation process The purified ammonium metavanadate solution was transferred to a crystallization reactor, and rapid stirring (150 rpm) was started. The solution was then cooled to 55°C using cooling water at a rate of 2°C / min. The stirring speed was then adjusted to 70 rpm (medium speed), and 2.5 kg of ammonium citrate was added. The reaction was maintained at 55±1°C for 60 minutes, during which numerous fine crystal nuclei appeared and gradually grew. The solution was then cooled to 37°C at a rate of 0.7°C / min and maintained for 30 minutes to promote further crystal growth and maturation.

[0039] The crystallized slurry was transferred to a fully automatic scraper centrifuge for solid-liquid separation to obtain wet ammonium metavanadate and mother liquor. The wet ammonium metavanadate was washed twice with deionized water at room temperature, and centrifuged to dehydrate after each wash, finally obtaining high-purity wet ammonium metavanadate crystals.

[0040] (4) Drying of the first cycle of products The wet crystals were placed in a high-efficiency fluidized bed dryer and dried at 70°C for 15 minutes to obtain a dry, high-purity ammonium metavanadate product. =345.1kg.

[0041] (5) Second cycle restart 5000L of mother liquor obtained from the first cycle was pumped into the reactor and heated to 85℃. Rapid stirring (150rpm) was started. According to the material balance calculation, the mass of crude ammonium metavanadate to be added was: m2=345.1. 345.1kg of crude ammonium metavanadate, also ground to 200 mesh, was added to the reactor, and 0.02L of glycerol was added at the same time. The mixture was stirred and dissolved for 20 minutes. Ultrasonic dissolution (31kHz) was started for 25 minutes to obtain a high-concentration ammonium metavanadate solution for the second cycle. Then, steps (2)-(5) were repeated to achieve purification of ammonium metavanadate with zero wastewater discharge.

[0042] Example 3: (1) First cycle dissolution process 450 kg of crude ammonium metavanadate was ball-milled to an average particle size of approximately 58 μm (corresponding to 250 mesh). In a 6000 L jacketed heated reactor, 5000 L of deionized water was added, heated to 88 °C, and rapid stirring (220 rpm) was initiated. The ground crude ammonium metavanadate was added to the reactor at a uniform rate, along with a co-solvent (0.04 L glycerol). Alternatively, polyethylene glycol can be used as the co-solvent. The mixture was stirred and dissolved for 25 minutes. An ultrasonic generator (35 kHz) was then activated, and stirring continued for 30 minutes under ultrasonic cavitation until the solid phase was completely dissolved, yielding a pale yellow, transparent ammonium metavanadate solution.

[0043] (2) First cycle deep purification and impurity removal process Maintain the solution temperature at 78±2℃ and keep stirring rapidly (220 rpm). Slowly add a weakly acidic impurity remover (5 kg polyaluminum chloride) to the solution. Alternatively, aluminum sulfate, magnesium chloride, or magnesium sulfate can be used. Control the pH to 5-6.5 and stir for 4 minutes. Then reduce the stirring speed to 50 rpm (slow stirring) and add a weakly alkaline impurity remover (2.5 kg magnesium oxide). Alternatively, calcium oxide, sodium aluminate, or calcium hydroxide can be used. Continue stirring for 16 minutes. Then stop stirring and let stand for 60 minutes to form distinct layers: a clear, transparent liquid on top and a white flocculent precipitate on the bottom. Filter using a filter press to obtain a purified, clear, and transparent ammonium metavanadate solution.

[0044] (3) First cycle crystallization separation process The purified ammonium metavanadate solution was transferred to a crystallization reactor, and rapid stirring (220 rpm) was started. The solution was then cooled to 55°C using cooling water at a rate of 2.5°C / min. The stirring speed was then adjusted to 85 rpm (medium speed), and 4 kg of ammonium citrate was added. The reaction was maintained at 58±1°C for 80 minutes, during which numerous fine crystal nuclei appeared and gradually grew. The solution was then cooled to 39°C at a rate of 0.9°C / min and maintained for 40 minutes to promote further crystal growth and maturation.

[0045] The crystallized slurry was transferred to a fully automatic scraper centrifuge for solid-liquid separation to obtain wet ammonium metavanadate and mother liquor. The wet ammonium metavanadate was washed twice with deionized water at room temperature, and centrifuged to dehydrate after each wash, finally obtaining high-purity wet ammonium metavanadate crystals.

[0046] (4) Drying of the first cycle of products The wet crystals were placed in a high-efficiency fluidized bed dryer and dried at 65°C for 20 minutes to obtain a dry, high-purity ammonium metavanadate product. =395.2kg.

[0047] (5) Second cycle restart 5000L of mother liquor obtained from the first cycle was pumped into the reactor and heated to 88℃. Rapid stirring (220rpm) was started. According to the material balance calculation, the mass of crude ammonium metavanadate to be added was m2=395.2kg. 395.2kg of crude ammonium metavanadate, also ground to 250 mesh, was added to the reactor, and 0.04L of glycerol was added at the same time. The mixture was stirred and dissolved for 25 minutes. Ultrasonic dissolution (35kHz) was started for 30 minutes to obtain a high-concentration ammonium metavanadate solution for the second cycle. Then, steps (2)-(5) were repeated to achieve purification of ammonium metavanadate with zero wastewater discharge.

[0048] Comparative Example 1: This comparative example uses an alkali dissolution-ammonium salt precipitation method to purify crude ammonium metavanadate, as follows: (1) Take 5 tons of distilled water into a reaction vessel, heat it to 50°C, add 550 kg of industrial grade 98% crude ammonium metavanadate and 11 kg of sodium hydroxide, stir quickly and heat to 70°C to obtain a vanadium-containing solution. At this time, the pH value is about 9.5. Then filter it through a filter press to obtain a vanadium-containing solution. (2) The temperature of the vanadium-containing solution was lowered to about 50°C, 1100 kg of ammonium chloride was added, and the mixture was stirred for 60 min. The temperature was then lowered to 32°C and maintained for 30 min. After recrystallization was completed, the solution was added to a centrifuge for centrifugation to obtain high-purity ammonium metavanadate and 5 tons of high-salt wastewater. (3) The ammonium metavanadate crystals obtained after centrifugation are washed three times with distilled water, and after solid-liquid separation, they are dried in a drying oven at 70°C to obtain high-purity ammonium metavanadate product.

[0049] (4) High-salt wastewater cannot be recycled, and direct discharge will cause serious environmental pollution. The cost of harmless treatment is high.

[0050] Comparative Example 2: This comparative example uses a water-soluble ammonium salt precipitation method to purify crude ammonium metavanadate, as follows: (1) Take 5 tons of distilled water into a reaction vessel, heat it to 80°C, add 183 kg of industrial grade 98% crude ammonium metavanadate, stir quickly and heat to 80°C to obtain a vanadium-containing solution; add 30 kg of ammonia water to the vanadium-containing solution until its pH value is 8, stir to dissolve and obtain a vanadium-containing solution. (2) The temperature of the vanadium-containing solution was lowered to about 50°C, 275 kg of ammonium chloride was added, and the mixture was stirred for 60 min. The temperature was then lowered to 30°C and maintained for 60 min. After recrystallization was completed, the solution was added to a centrifuge for centrifugation to obtain high-purity ammonium metavanadate and 5 tons of high-salt wastewater. (3) The ammonium metavanadate crystals obtained after centrifugation are washed three times with distilled water, and after solid-liquid separation, they are dried in a drying oven at 70°C to obtain high-purity ammonium metavanadate product.

[0051] (4) High-salt wastewater cannot be recycled, and direct discharge will cause serious environmental pollution. The cost of harmless treatment is extremely high.

[0052] The comparison results of energy consumption and economic efficiency are shown in Table 1, and the quality indicators and measured results of the products are shown in Table 2.

[0053] Table 1. Comparison of Energy Consumption and Economic Efficiency

[0054] Table 2 Product quality indicators and measured results

[0055] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for purifying ammonium metavanadate with zero wastewater discharge, characterized in that: Includes the following steps: S1. Grind the crude ammonium metavanadate, dissolve it in hot water, add a co-solvent, and simultaneously emit ultrasound into the solid-liquid mixture to obtain an ammonium metavanadate solution after dissolution. S2. Keep the temperature of the ammonium metavanadate solution at 60-80℃. Under rapid stirring, first add a weak acidic impurity remover, control the pH to 5-6.5, and react for 1-5 minutes. Then adjust to slow stirring, add a weak alkaline impurity remover, control the pH to 7-8.5, and react for 8-20 minutes. Finally, stop stirring, let stand, filter, and obtain a deeply purified ammonium metavanadate solution. S3. Under rapid stirring conditions, the deeply purified and impurity-removed ammonium metavanadate solution is cooled to 53-58℃. At this time, the stirring speed is adjusted to medium speed, a crystallization promoter is added, and the reaction is kept at this temperature for 40-90 minutes to promote the crystallization and precipitation of ammonium metavanadate. Then, the temperature is cooled to 35-40℃ and the reaction is kept at this temperature for 20-40 minutes to promote the crystal growth of ammonium metavanadate. Finally, high-purity ammonium metavanadate crystals and low-concentration ammonium metavanadate mother liquor are obtained by centrifugation and filtration. S4. Wash and dry the high-purity ammonium metavanadate crystals to obtain the high-purity ammonium metavanadate product; S5. Heat the low-concentration ammonium metavanadate mother liquor, add the powder of crude ammonium metavanadate after grinding, add a co-solvent, and simultaneously emit ultrasound into the solid-liquid mixture. After dissolution, a high-concentration ammonium metavanadate solution is obtained for the second time. S6. Repeat steps S2-S5 to achieve purification of ammonium metavanadate with zero wastewater discharge.

2. The method for purifying ammonium metavanadate with zero wastewater discharge according to claim 1, characterized in that: In step S1, the co-solvent is glycerol or polyethylene glycol.

3. The method for purifying ammonium metavanadate with zero wastewater discharge according to claim 1, characterized in that: In step S1, the mass ratio of ammonium metavanadate to hot water is 1:(10-15).

4. The method for purifying ammonium metavanadate with zero wastewater discharge according to claim 1, characterized in that: In step S1, the hot water temperature is 70-90℃; in step S5, the heating temperature is 70-90℃.

5. The method for purifying ammonium metavanadate with zero wastewater discharge according to claim 1, characterized in that: in In steps S2 and S3, the stirring speed of the rapid stirring is 100-300 rpm; the stirring speed of the medium-speed stirring is 60-100 rpm; and the stirring speed of the low-speed stirring is 20-60 rpm.

6. The method for purifying ammonium metavanadate with zero wastewater discharge according to claim 1, characterized in that: In steps S1 and S5, the frequency of the ultrasonic wave is 25-40 kHz.

7. The method for purifying ammonium metavanadate with zero wastewater discharge according to claim 1, characterized in that: in In step S2, the weakly alkaline impurity remover is one or more of magnesium oxide, calcium oxide, sodium aluminate, and calcium hydroxide.

8. The method for purifying ammonium metavanadate with zero wastewater discharge according to claim 1, characterized in that: in In step S2, the weakly acidic impurity remover is one or more of polyaluminum chloride, aluminum sulfate, magnesium chloride, and magnesium sulfate.

9. The method for purifying ammonium metavanadate with zero wastewater discharge according to claim 1, characterized in that: In step S3, the crystallization promoter is ammonium citrate.

10. The method for purifying ammonium metavanadate with zero wastewater discharge according to claim 1, characterized in that: In step S2, the settling time is 30-90 minutes.

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