Process for extracting high-purity vanadium pentoxide from ammonium polyvanadate

Abstract

The invention discloses a process for extracting high-purity vanadium pentoxide from ammonium polyvanadate, and belongs to the technical field of nonferrous metallurgy. According to the process, efficient purification of vanadium pentoxide is achieved through the steps of sodium hydroxide dissolution, pH adjustment, gradient impurity removal, precise filtration, freezing-unfreezing circulation, high-purity water washing, centrifugal dewatering, two-stage firing and the like. In the process, the gradient impurity removal technology effectively reduces the content of impurities such as iron, sodium and the like, the precision filtration system ensures low residue of the impurities, the freezing-unfreezing circulation step further improves the crystal purity, and the two-stage firing process realizes directional conversion of the alpha-V2O5 crystal form. The purity of the obtained vanadium pentoxide product reaches up to 99.99% or above, the Na < + > content is smaller than or equal to 2 ppm, the Fe residue is smaller than or equal to 5 ppm, the alpha-V2O5 crystal form proportion is larger than or equal to 98%, the problems that in a traditional process, deep impurity removal is difficult, the product purity is insufficient, and crystal form conversion is incomplete are remarkably solved, and an effective technical approach is provided for preparing high-purity vanadium pentoxide.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal metallurgy, and in particular relates to a process for extracting high-purity vanadium pentoxide from ammonium polyvanadate. Background Art

[0002] The current industrial production of vanadium pentoxide (V2O5) mainly adopts the sodium roasting-water leaching purification process. This process has inherent defects in the acid leaching stage. The iron (Fe 2+ / Fe 3+ ), manganese (Mn 2+ ) and other multivalent metal ions easily form stable complexes with vanadate, resulting in low efficiency of conventional chemical precipitation. Studies have shown (Metall.Trans.B, 2019) that when the system pH is greater than 2.5, Fe 3+ With VO 3- The formation of [Fe(VO3)3] colloids, with residual iron content >50ppm for a long time, seriously restricts the production of high-purity V2O5 (≥99.95%). In addition, the secondary impurities introduced by calcium and magnesium precipitants further increase the difficulty of purification. In the ammonium salt precipitation process, the crystallization process of ammonium metavanadate (NH4VO3) faces the problem of ion encapsulation (J.Cryst.Growth, 2021). Due to Na + , K + With NH4 + Due to their similar ionic radii, they embed into NH₄VO₃ lattice defects during rapid crystallization, resulting in a product purity cap of 99.5%. Furthermore, the traditional muffle furnace calcination process suffers from incomplete V₂O₅ conversion due to insufficient temperature control accuracy (±25°C). While improved technologies such as ion exchange (CN112430719A) and solvent extraction (US20200340006) have been developed, application bottlenecks persist. Exchange resins are susceptible to silica gel contamination, leading to flux degradation, and organic phase entrainment in the extractant requires secondary calcination for removal. While membrane separation technology (CN113292063B) can remove impurities, it cannot address the issues of crystal encapsulation and crystal form control. Therefore, developing an integrated process that combines deep impurity removal, high-purity crystallization, and crystal form control is a key path to breaking through the technical barriers to high-purity V₂O₅. Summary of the Invention

[0003] To solve the problems of difficulty in deep impurity removal, insufficient product purity and incomplete crystal conversion in the current vanadium pentoxide production process.

[0004] In order to solve the above problems, the present invention provides the following technical solutions: A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate, characterized by comprising the following steps: S1: Add ammonium polyvanadate to 8-12wt% sodium hydroxide solution, stir and dissolve at 100±2℃ for 30min, solid-liquid ratio 1:5; S2: adding sulfuric acid dropwise to adjust the pH to 7-9 to form a sodium vanadate solution; S3: First add magnesium chloride and stir for 5 minutes, then add calcium chloride to remove impurities in a gradient manner; S4: precision filtration through a 5μm ceramic membrane and a 0.22μm high-density polyethylene filter tube in sequence; S5: adding ammonium chloride to react and form ammonium metavanadate crystals; S6: Wash the product with 18.2 MΩ·cm ultrapure water; S7: Centrifugal dehydration to a water content of ≤5%; S8: Two-stage calcination: keep at 300℃ for 1 hour to remove ammonium, then calcine at 500±5℃ for 2 hours to obtain high-purity vanadium pentoxide.

[0005] Preferably, the amount of magnesium chloride added to the S3 is 0.3-0.8 g / L, which precipitates silicon and phosphorus impurities to form MgSiO3 / Mg3(PO4)2; the amount of calcium chloride added is 0.8-1.5 g / L, which co-precipitates iron and manganese ions to form CaFe(SO4)2 / CaMnO4.

[0006] Preferably, a high-density polyethylene filter tube with a porosity of 0.22±0.02 μm is used in S4; a 0.1 μm polytetrafluoroethylene filter element is provided at the terminal.

[0007] Preferably, the reaction conditions of ammonium chloride in S5 are: a molar ratio of ammonium chloride to vanadium of 2.0-3.0:1; a reaction temperature of 55-65° C., and a reaction time of 1.5-2.5 h.

[0008] Preferably, a freeze-thaw cycle is added after the crystallization step in S5: freezing at -20°C for 2 hours and then thawing at 25°C; repeating the cycle 1-3 times.

[0009] Preferably, the high-purity water washing conditions in S6 are: washing times ≥ 3 times; water temperature is maintained at 25±2°C.

[0010] Preferably, the centrifugal dehydration parameters in S7 are: rotation speed 2800-3200 rpm; time 8-12 min.

[0011] Preferably, the two-stage burning process in S8 is: the first stage is kept at 300±10°C for 60±5 minutes; the second stage is burned at 500±10°C for 120±10 minutes.

[0012] Preferably, the two-stage calcination process needs to control the heating rate from 300°C to 500°C to be controlled at 3°C / min.

[0013] Preferably, the product obtained by the process of extracting high-purity vanadium pentoxide from ammonium polyvanadate has a V2O5 purity of ≥99.99%; Na+ ≤2ppm, Fe ≤5ppm; and an α-V2O5 crystal proportion of ≥98%.

[0014] The effects and advantages of the process of extracting high-purity vanadium pentoxide from ammonium polyvanadate of the present invention are as follows: 1. This patent uses a gradient impurity removal process to make the Fe residue ≤5ppm, Na + ≤2ppm.

[0015] 2. This patent allows precise control of the crystal form. Through two-stage calcination (300°C and 500°C), the α-V2O5 crystal form accounts for ≥98%, and the lattice density is improved.

[0016] 3. This patent adds a -20℃ freezing for 2h followed by a 25℃ thawing cycle after step 5 to improve the purity of the crystals.

[0017] 4. This patented gradient filtration system: 0.22μm filter tube combined with 0.1μm terminal filter element, precisely filters impurities and improves the purity of V2O5. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention discloses a flow chart of a process for extracting high-purity vanadium pentoxide from ammonium polyvanadate. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention. It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus. In the absence of further restrictions, the elements defined by the sentence "include..." do not exclude the presence of other identical elements in the process, method, article or apparatus that includes the elements.

[0020] Example 1 This embodiment provides a process for extracting high-purity vanadium pentoxide from ammonium polyvanadate, which is applicable to the field of non-ferrous metallurgy technology and includes the following implementation contents: Purpose of the experiment: The invention discloses a process for extracting high-purity vanadium pentoxide from ammonium polyvanadate.

[0021] Experimental materials: Ammonium polyvanadate (NH4VO3), 10wt% sodium hydroxide (NaOH) aqueous solution, sulfuric acid (H2SO4, diluted to 20% for pH adjustment), magnesium chloride (MgCl2, added at 0.5g / L), calcium chloride (CaCl2, added at 1.2g / L), ammonium chloride (NH4Cl), and ultrapure water (resistivity 18.2MΩ·cm, GB / T 6682-2008 standard). Experimental equipment: Alkali corrosion-resistant reactor (made of 316L stainless steel), constant temperature water bath, gradient filtration unit (integrated with 5μm ceramic membrane pre-filtration unit and 0.22μm polyethylene terminal filter tube), high-speed centrifuge, inductively coupled plasma optical emission spectrometer (ICP-OES, PerkinElmer Avio 500), atomic absorption spectrometer (AAS, Thermo Fisher iCE 3500), ion chromatograph (Dionex ICS-5000+), and X-ray diffractometer (XRD, Bruker D8 Advance).

[0022] Experimental steps: S1: Add 100g of ammonium polyvanadate to 8-12wt% sodium hydroxide solution, stir and dissolve at 100±2℃ for 30min, solid-liquid ratio 1:5; S2: adding 20% ​​sulfuric acid dropwise to adjust the pH to 8.0 to form a sodium vanadate solution; S3: First add 0.5g / L magnesium chloride and stir for 5min, then add 1.2g / L calcium chloride to remove impurities in a gradient manner; S4: precision filtration through a 5μm ceramic membrane and a 0.22μm high-density polyethylene filter tube in sequence; S5: Add ammonium chloride (ammonium chloride to vanadium molar ratio 2.5:1) and react at 60°C for 2 hours to generate ammonium metavanadate crystals; S6: Wash the product three times with 18.2 MΩ·cm ultrapure water (50 mL each time, water temperature 25°C): S7: After washing, the mixture was centrifuged at 3000 rpm for 10 min, and the water content of the product was measured to be 4.7%.

[0023] S8: Two-stage calcination, the dehydrated product is placed in a programmable temperature-controlled furnace, the first stage: keeping warm at 300℃ for 60 minutes to remove ammonium ions; the second stage: calcining at 500±5℃ for 120 minutes to complete the crystal transformation; cooling to room temperature to obtain V2O5 powder.

[0024] Experimental results: See Table 1 for details.

[0025] Table 1: Test results of Example 1 <![CDATA[V2O5 purity]]> Fe residue Na⁺ content <![CDATA[Ratio of α-V2O5]]> Example 1 99.992% 3.2ppm 1.8ppm 99.3% Example 1 A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate. The purity of V2O5 is as high as 99.992% (far exceeding the ≤99.5% of traditional processes). This is mainly due to the dual synergistic effect of gradient impurity removal and precision filtration. The residual Fe content is as low as 3.2ppm. This is due to the optimization of CaCl2 directional co-precipitation and filtration. After adding CaCl2, Ca 2+ with Fe 2+ / Fe 3+ Form a stable CaFe(SO4)2 precipitate to achieve targeted removal of Fe ions. + The content is controlled at 1.8ppm, thanks to ultrapure water washing and crystallization optimization, the ammonium chloride precipitation reaction controls the slow growth of crystals to avoid Na + Embedded. α-V2O5 crystal accounts for 99.3% mainly due to the directional transformation of the crystal form during the two-stage calcination. The first stage is kept at 300℃ for 1h to remove NH4 + , to avoid lattice distortion caused by sudden exotherm, the second stage is calcined at 500±5℃ for 2h to provide activation energy, which promotes the transformation of V2O5 from metastable γ phase to dense α phase.

[0026] Example 2 refer to Figure 1 This embodiment provides a process for extracting high-purity vanadium pentoxide from ammonium polyvanadate. A freeze-thaw cycle step is added to the basic process of Example 1 to verify the effect of this step on performance. The process includes the following implementation contents: Purpose of the experiment: A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate includes a new freeze-thaw cycle step to achieve crystal structure optimization and deep impurity removal.

[0027] Experimental materials: Ammonium polyvanadate (NH4VO3), 10wt% sodium hydroxide (NaOH) aqueous solution, sulfuric acid (H2SO4, diluted to 20% for pH adjustment), magnesium chloride (MgCl2, addition amount 0.5g / L), calcium chloride (CaCl2, addition amount 1.2g / L), ammonium chloride (NH4Cl), ultrapure water (resistivity 18.2MΩ·cm, GB / T 6682-2008 standard).

[0028] Experimental steps: S1: Add 100g of ammonium polyvanadate to 8-12wt% sodium hydroxide solution, stir and dissolve at 100±2℃ for 30min, solid-liquid ratio 1:5; S2: adding 20% ​​sulfuric acid dropwise to adjust the pH to 8.0 to form a sodium vanadate solution; S3: First add 0.5g / L magnesium chloride and stir for 5min, then add 1.2g / L calcium chloride to remove impurities in a gradient manner; S4: precision filtration through a 5μm ceramic membrane and a 0.22μm high-density polyethylene filter tube in sequence; S5: Add ammonium chloride (ammonium chloride to vanadium molar ratio 2.5:1) and allow to react at 60°C for 2 hours to form ammonium metavanadate crystals. Transfer the crystals to a polytetrafluoroethylene container and place in a -20°C freezer for 2 hours. Remove the container and place in a 25°C constant temperature thawing tank to thaw until completely liquid. Repeat the -20°C freezer for 2 hours and then the 25°C thawing cycle three times. S6: Wash the product three times with 18.2 MΩ·cm ultrapure water (50 mL each time, water temperature 25°C): S7: After washing, the mixture was centrifuged at 3000 rpm for 10 min, and the water content of the product was measured to be 4.7%.

[0029] S8: Two-stage calcination, the dehydrated product is placed in a programmable temperature-controlled furnace, the first stage: keeping warm at 300℃ for 60 minutes to remove ammonium ions; the second stage: calcining at 500±5℃ for 120 minutes to complete the crystal transformation; cooling to room temperature to obtain V2O5 powder.

[0030] Experimental results: See Table 2 for details.

[0031] Table 2: Test results of Example 2 <![CDATA[V2O5 purity]]> Fe residue Na⁺ content <![CDATA[Proportion of α-V2O5]]> Example 2 99.997% 1.8ppm 0.5ppm 99.5% Example 2 A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate, with the purity of V2O5 increased to 99.997%. The precipitate is sheared and broken during the freezing process, which is beneficial for subsequent washing. The freeze-thaw cycle causes the crystals to undergo directional rearrangement, reducing impurity inclusion. The Fe residue is reduced to 1.8ppm because the precipitate is broken and more active sites are exposed, making it easier for iron ions to desorb and detach during ultrapure water washing. Na + The content is 0.5ppm. At -20℃ freezing stage, the water in the crystal gap freezes and expands, strongly squeezing the lattice defect area, forcing Na + Small ions such as Na are discharged from the ammonium metavanadate lattice. When thawed at 25℃, the discharged Na + It enters the liquid phase with the meltwater and is completely removed after washing with ultrapure water. This increases the proportion of the α-V2O5 crystal form, and the crystal size distribution is concentrated after freeze-thaw. During calcination, the heat is evenly distributed, avoiding local overheating that can lead to the formation of the γ phase.

[0032] Example 3 This example provides a process for extracting high-purity vanadium pentoxide from ammonium polyvanadate, and verifies the effect of the burning method on the performance, including the following implementation contents: Purpose of the experiment: A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate was developed to verify the negative effects of direct 500°C calcination.

[0033] Experimental materials: Ammonium polyvanadate (NH4VO3), 10wt% sodium hydroxide (NaOH) aqueous solution, sulfuric acid (H2SO4, diluted to 20% for pH adjustment), magnesium chloride (MgCl2, addition amount 0.5g / L), calcium chloride (CaCl2, addition amount 1.2g / L), ammonium chloride (NH4Cl), ultrapure water (resistivity 18.2MΩ·cm, GB / T 6682-2008 standard).

[0034] Experimental steps: S1: Add 100g of ammonium polyvanadate to 8-12wt% sodium hydroxide solution, stir and dissolve at 100±2℃ for 30min, solid-liquid ratio 1:5; S2: adding 20% ​​sulfuric acid dropwise to adjust the pH to 8.0 to form a sodium vanadate solution; S3: First add 0.5g / L magnesium chloride and stir for 5min, then add 1.2g / L calcium chloride to remove impurities in a gradient manner; S4: precision filtration through a 5μm ceramic membrane and a 0.22μm high-density polyethylene filter tube in sequence; S5: Add ammonium chloride (ammonium chloride to vanadium molar ratio 2.5:1) and react at 60°C for 2 hours to generate ammonium metavanadate crystals; S6: Wash the product three times with 18.2 MΩ·cm ultrapure water (50 mL each time, water temperature 25°C): S7: After washing, the mixture was centrifuged at 3000 rpm for 10 min, and the water content of the product was measured to be 4.7%.

[0035] S8: The dehydrated product was placed in a programmed muffle furnace under N2 atmosphere and directly calcined at 500°C for 1 h, then cooled to room temperature to obtain V2O5 powder.

[0036] Experimental results: See Table 3 for details.

[0037] Table 3: Test results of Example 3 <![CDATA[V2O5 purity]]> Fe residue Na⁺ content <![CDATA[Proportion of α-V2O5]]> Example 3 99.62% 28ppm 42ppm 73.5% Example 3 A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate. The purity of V2O5 is reduced to 99.62%. The direct high temperature of 500°C causes the ammonium salt to decompose instantly, generating a violent steam shock. The steam pressure breaks through the crystal surface to form microcracks, which makes the Fe and Na wrapped inside+ Impurities are exposed again. The Fe residue is 28ppm. The steam explosion effect causes microcracks, which provide diffusion channels for Fe impurities, causing the Fe impurities buried inside to be exposed to the surface again. + When the content rises to 42ppm, direct calcination at 500°C accelerates the dehydration rate, which leads to entrapment in the amorphous region. The proportion of α-V2O5 crystals decreases significantly. Direct calcination at 500°C disrupts the thermodynamic / kinetic equilibrium of the directional transformation of the crystals, leading to the formation of a large amount of metastable phases.

[0038] Comparative Example 1 A process for extracting high-purity vanadium pentoxide from traditional ammonium polyvanadate is provided, which is applicable to the field of non-ferrous metal metallurgy technology and includes the following implementation contents: Purpose of the experiment: A process for extracting high-purity vanadium pentoxide from traditional ammonium polyvanadate omits the precision filtration step and verifies the effect of ordinary filter paper filtration.

[0039] Experimental materials: Ammonium polyvanadate (NH4VO3), 10wt% sodium hydroxide (NaOH) aqueous solution, sulfuric acid (H2SO4, diluted to 20% for pH adjustment), magnesium chloride (MgCl2, addition amount 0.5g / L), calcium chloride (CaCl2, addition amount 1.2g / L), ammonium chloride (NH4Cl), ultrapure water (resistivity 18.2MΩ·cm, GB / T 6682-2008 standard).

[0040] Experimental steps: S1: Add 100g of ammonium polyvanadate to 8-12wt% sodium hydroxide solution, stir and dissolve at 100±2℃ for 30min, solid-liquid ratio 1:5; S2: adding 20% ​​sulfuric acid dropwise to adjust the pH to 8.0 to form a sodium vanadate solution; S3: First add 0.5g / L magnesium chloride and stir for 5min, then add 1.2g / L calcium chloride to remove impurities in a gradient manner; S4: Filter using ordinary qualitative filter paper (pore size 20 μm); S5: Add ammonium chloride (ammonium chloride to vanadium molar ratio 2.5:1) and allow to react at 60°C for 2 hours to form ammonium metavanadate crystals. Transfer the crystals to a polytetrafluoroethylene container and place in a -20°C freezer for 2 hours. Remove the container and place in a 25°C constant temperature thawing tank to thaw until completely liquid. Repeat the -20°C freezer for 2 hours and then the 25°C thawing cycle three times. S6: Wash the product three times with 18.2 MΩ·cm ultrapure water (50 mL each time, water temperature 25°C): S7: After washing, the mixture was centrifuged at 3000 rpm for 10 min, and the water content of the product was measured to be 4.7%.

[0041] S8: Two-stage calcination, the dehydrated product is placed in a programmable temperature-controlled furnace, the first stage: keeping warm at 300℃ for 60 minutes to remove ammonium ions; the second stage: calcining at 500±5℃ for 120 minutes to complete the crystal transformation; cooling to room temperature to obtain V2O5 powder.

[0042] Experimental results: See Table 4 for details.

[0043] Table 4: Comparative Example 1 test results <![CDATA[V2O5 purity]]> Fe residue Na⁺ content <![CDATA[Proportion of α-V2O5]]> Comparative Example 1 99.21% 15ppm 8.7ppm 95.1% Comparative Example 1 provides a traditional process for extracting high-purity vanadium pentoxide using ammonium polyvanadate. The pore size of ordinary filter paper (20μm) is much larger than the size of colloidal impurities (0.1-0.5μm), resulting in filtration failure and the penetration of impurities such as silicon and iron. The Fe residue is 15ppm. The pore size of ordinary filter paper (20μm) is much larger than the particle size of Fe(OH)3 colloid (50-200nm). Omitting precision filtration destroys the gradient impurity removal effect. The unretained iron colloid is fixed in the product through a crystallization-burning chain reaction, resulting in an Fe residue of 15ppm. + The content is 8.7ppm. The pore size of ordinary filter paper (20μm) is much larger than the ionic size of dissolved sodium salts (such as Na2SiO3 and NaCl) (<1nm), allowing the sodium salts to freely pass through the filter paper and enter the crystallization system. The α-V2O5 content is 95.1%. Filter failure allows impurities to penetrate, causing lattice distortion and heterogeneous nucleation, hindering phase transition diffusion and leading to the growth of metastable phases.

[0044] Example 1 provides a process for extracting high-purity vanadium pentoxide from ammonium polyvanadate. The process achieves a V2O5 purity of up to 99.992% through the dual synergistic effect of gradient impurity removal and precision filtration. The experiment uses ammonium polyvanadate as the main raw material. After a series of steps such as sodium hydroxide dissolution, sulfuric acid pH adjustment, magnesium chloride and calcium chloride impurity removal, precision filtration, ammonium chloride precipitation, ultrapure water washing, centrifugal dehydration, and temperature-controlled calcination, a high-purity vanadium pentoxide powder is finally obtained. The key to this process is that gradient impurity removal effectively removes impurities such as iron, while precision filtration further ensures low impurity residues. In addition, by optimizing washing and calcination conditions, the Na + content, and promoted the directional transformation of α-V2O5 crystal form, making the purity of the final product far exceed that of traditional processes.

[0045] Example 2 adds a freeze-thaw cycle step based on Example 1 to verify the effect of this step on performance. The experimental results show that the freeze-thaw cycle further improves the purity of V2O5 to 99.997% and significantly reduces the residual Fe and Na +During the freezing process, the precipitate is sheared and broken, which facilitates subsequent washing and impurity removal. The freeze-thaw cycle also causes directional rearrangement of the crystals, reducing impurity inclusions and thus improving product purity. In addition, this step helps optimize the crystal size distribution, ensuring more uniform heating during calcination, further increasing the proportion of the α-V2O5 crystal form. This improvement provides a more efficient process path for extracting high-purity vanadium pentoxide.

[0046] Example 3 verifies the effect of the burning method on the extraction performance of high-purity vanadium pentoxide. Unlike Examples 1 and 2, this example adopts a direct high-temperature burning method. However, the experimental results show that this burning method leads to a significant decrease in the purity of V2O5, and the residual Fe and Na + The content increased significantly. Direct high-temperature calcination disrupted the slow decomposition process of the ammonium salt, generating intense steam shock, which caused microcracks to form on the crystal surface, exposing impurities trapped within. Furthermore, the rapid dehydration process exacerbated the impurity entrapment, further reducing the purity of the product. This result demonstrates that the calcination method is crucial for extracting high-purity vanadium pentoxide, and strict control of calcination conditions is required to ensure product quality.

[0047] Comparative Example 1 provides a process for extracting high-purity vanadium pentoxide from traditional ammonium polyvanadate, but the experimental results show that its effect is not ideal. The key is that the process uses ordinary filter paper for filtration, and the pore size of ordinary filter paper is much larger than the size of colloidal impurities, resulting in filtration failure. This allows impurities such as iron to pass through the filter and enter the subsequent steps, seriously affecting the purity of the product. In addition, filtration failure also destroys the gradient impurity removal effect, resulting in an increase in Fe residual content. At the same time, since impurities such as sodium salts can also freely pass through the filter paper and enter the crystallization system, Na + The content is also relatively high. Ultimately, the proportion of the α-V2O5 crystal form in the product is also affected to a certain extent. This comparative experiment emphasizes the importance of precision filtration in the extraction of high-purity vanadium pentoxide.

[0048] Those skilled in the art will appreciate that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented with electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0049] In addition, each functional module in each embodiment of the present application may be integrated into one processing module, or each module may exist physically separately, or two or more modules may be integrated into one module.

[0050] The above is only a specific implementation method of the present application, but the scope of protection of the present application is not limited to this. Any technician familiar with this technical field can easily think of changes or replacements within the technical scope disclosed in this application, which should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

[0051] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection of the present invention.

Claims

1. A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate, characterized in that: The following steps are involved: S1: Add ammonium polyvanadate to 8-12wt% sodium hydroxide solution, stir and dissolve at 100±2℃ for 30min, solid-liquid ratio 1:5; S2: adding sulfuric acid dropwise to adjust the pH to 7-9 to form a sodium vanadate solution; S3: First add magnesium chloride and stir for 5 minutes, then add calcium chloride to remove impurities in a gradient manner; S4: precision filtration through a 5μm ceramic membrane and a 0.22μm high-density polyethylene filter tube in sequence; S5: adding ammonium chloride to react and form ammonium metavanadate crystals; S6: Wash the product with 18.2 MΩ·cm ultrapure water; S7: Centrifugal dehydration to a water content of ≤5%; S8: Two-stage calcination: keep at 300℃ for 1 hour to remove ammonium, then calcine at 500±5℃ for 2 hours to obtain high-purity vanadium pentoxide.

2. A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate as claimed in claim 1, characterized in that: The amount of magnesium chloride added to the S3 is 0.3-0.8 g / L, which precipitates silicon and phosphorus impurities to form MgSiO3 / Mg3(PO4)2; the amount of calcium chloride added is 0.8-1.5 g / L, which co-precipitates iron and manganese ions to form CaFe(SO4)2 / CaMnO4.

3. A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate as claimed in claim 1, characterized in that: The S4 uses a high-density polyethylene filter tube with a porosity of 0.22±0.02 μm; a 0.1 μm polytetrafluoroethylene filter element is set at the terminal.

4. A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate as claimed in claim 1, characterized in that: The reaction conditions of ammonium chloride in S5 are: a molar ratio of ammonium chloride to vanadium of 2.0-3.0:1; a reaction temperature of 55-65° C., and a reaction time of 1.5-2.5 h.

5. A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate as claimed in claim 1, characterized in that: After the crystallization step in S5, a freeze-thaw cycle is added: freezing at -20°C for 2 hours and then thawing at 25°C; the cycle is repeated 1-3 times.

6. A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate as claimed in claim 1, characterized in that: The high-purity water washing conditions in S6 are: washing times ≥ 3 times; water temperature maintained at 25±2°C.

7. A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate as claimed in claim 1, characterized in that: The centrifugal dehydration parameters in S7 are: rotation speed 2800-3200 rpm; time 8-12 min.

8. A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate as claimed in claim 1, characterized in that: The two-stage burning process in S8 is as follows: the first stage is kept at 300±10°C for 60±5 minutes; the second stage is burned at 500±10°C for 120±10 minutes.

9. A process for extracting high-purity vanadium pentoxide from ammonium polyvanadate as claimed in claim 8, characterized in that: The two-stage calcination process needs to control the heating rate from 300°C to 500°C to be controlled at 3°C / min.

10. The product obtained by the process of extracting high-purity vanadium pentoxide from ammonium polyvanadate according to any one of claims 1 to 9, characterized in that: V2O5 purity ≥99.99%; Na + ≤2ppm, Fe≤5ppm; α-V2O5 crystal proportion ≥98%.

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