Efficient impurity removal method of sodium metavanadate solution, battery-grade vanadium powder and preparation method thereof

Abstract

The application relates to a high-efficiency impurity removal method of a sodium metavanadate solution, a battery-grade vanadium powder and a preparation method, and belongs to the technical field of vanadium pentoxide preparation. A complexing agent is added into a sodium metavanadate solution to be treated, the pH value of the sodium metavanadate solution to be treated is 8.5-9.0, and the temperature is 35 DEG C-45 DEG C; the complexing agent comprises ethylenediamine disodium o-phenylacetate and diethylenetriamine pentaacetic acid; and the molecular weight cut-off value of a nanofiltration membrane used for nanofiltration is 150 Da-180 Da. The method adopts nanofiltration membrane filtration technology and combined complexing agents, significantly improves the selective retention effect of nanofiltration membranes on arsenic and silicon impurities, realizes the preparation of high-purity sodium metavanadate, the obtained battery-grade vanadium powder has high vanadium pentoxide purity, meets the standard of a full vanadium redox flow battery electrolyte, and provides a new approach for the production of the battery-grade vanadium powder.

Description

Technical Field

[0001] This invention relates to the field of vanadium pentoxide preparation technology, and more specifically, to an efficient method for removing impurities from sodium metavanadate solution, battery-grade vanadium powder and its preparation method. Background Technology

[0002] A vanadium redox flow battery is a type of battery that uses vanadium as the active material in a circulating liquid state. This unique circulating operating mode gives vanadium batteries flexibility in energy storage capacity, allowing for adjustments to the electrolyte volume to meet different needs. Vanadium redox flow batteries exhibit excellent characteristics in terms of safety and cycle life.

[0003] 1) Vanadium batteries use an inorganic water-based electrolyte, eliminating the risk of combustion and explosion, and ensuring stable operation under normal temperature and pressure, completely preventing thermal runaway. The battery system exhibits excellent consistency, coupled with an efficient battery management mechanism, ensuring high operational reliability.

[0004] 2) Vanadium redox flow batteries have a calendar life of up to 25 years and a cycle life of up to 16,000 charge-discharge cycles. The electrodes do not participate in the reaction process, and deep charge-discharge cycles do not affect battery life. Capacity can be maintained at zero degradation. Vanadium batteries can achieve 100% capacity retention throughout their entire lifespan, with no efficiency degradation, providing a solid guarantee for long-term stable energy storage and supply.

[0005] The main raw material for the electrolyte of vanadium redox flow batteries is powdered vanadium pentoxide, which has high quality requirements. In addition to a purity requirement of greater than 99.5%, there are strict requirements for 18 trace elements, including arsenic (As) ≤2mg / kg and silicon (Si) ≤40mg / kg.

[0006] Current common processing technology involves preparing sodium metavanadate solution by redissolving ammonium metavanadate with alkali, performing deep impurity removal, and then adding ammonium salt for secondary crystallization to obtain high-purity ammonium metavanadate. After calcination, it yields vanadium powder. However, this common technology suffers from a complex processing flow, low yield of high-purity ammonium metavanadate from secondary crystallization (vanadium loss not less than 15%), high production costs, and unsatisfactory removal of arsenic, phosphorus, and silicon, making it difficult to meet the quality requirements of battery-grade high-purity vanadium powder. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an efficient method for removing impurities from sodium metavanadate solution, battery-grade vanadium powder and its preparation method.

[0008] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: This invention provides an efficient method for removing impurities from sodium metavanadate solution, which involves adding a complexing agent to the sodium metavanadate solution to be treated and reacting it, then performing nanofiltration on the solution after the reaction to obtain a high-purity sodium metavanadate solution and a concentrated solution containing the impurities. The impurities in the sodium metavanadate solution to be treated include arsenic, phosphorus, and silicon; the pH value of the sodium metavanadate solution to be treated is 8.5-9.0, and the temperature is 35℃-45℃. The complexing agent includes sodium ethylenediamine di-o-phenylacetate and diethylenetriaminepentaacetic acid, and the nanofiltration membrane used in the nanofiltration has a molecular weight cutoff of 150 Da-180 Da.

[0009] Based on the above technical solution, the present invention can be further improved as follows.

[0010] Furthermore, in the complexing agent, based on the total mass of arsenic, phosphorus, and silicon in the sodium metavanadate solution to be treated being 100%, the mass percentage of sodium ethylenediamine di-o-phenylacetate is 0.2%-0.3%, and the mass percentage of diethylenetriaminepentaacetic acid is 0.2%-0.3%.

[0011] Furthermore, in the complexing agent, the mass percentage of sodium ethylenediamine di-o-phenylacetate is 0.3%, and the mass percentage of diethylenetriaminepentaacetic acid is 0.3%.

[0012] Furthermore, the molecular weight cutoff of the nanofiltration membrane is 150 Da.

[0013] Furthermore, the sodium metavanadate solution to be treated was prepared from vanadium-containing alkaline slag extracted from alumina using the Bayer process.

[0014] Furthermore, the concentration of vanadium pentoxide in the sodium metavanadate solution to be treated is 80-100 g / L.

[0015] The present invention also provides a high-purity sodium metavanadate solution, which is obtained by removing impurities from the sodium metavanadate solution using the method described above.

[0016] The present invention also provides a method for preparing battery-grade vanadium powder, wherein a high-purity sodium metavanadate solution as described above is heated to 50°C-55°C, ammonium sulfate is added and ammonium metavanadate crystals are crystallized out, after solid-liquid separation, the ammonium metavanadate crystals are calcined to obtain battery-grade vanadium powder.

[0017] Furthermore, the calcination temperature is 450℃-550℃, and the time is 1.5-2.5 hours.

[0018] The present invention also provides a battery-grade vanadium powder, which is prepared by the method described above.

[0019] The beneficial effects of this invention are as follows: (1) The efficient impurity removal method for sodium metavanadate solution of the present invention uses nanofiltration membrane filtration technology to effectively separate VO3. - With HAsO4 2- HPO4 2- SiO3 2- Impurity ions, etc., utilize the charge difference of ions with different valence states under specific pH conditions to achieve selective permeation, thereby increasing the permeability of metavanadate while the retention rate of hydrogen arsenate is as high as 99.5% or more. (2) The efficient method for removing impurities from sodium metavanadate solution of the present invention uses sodium ethylenediamine di-o-phenylacetate and diethylenetriaminepentaacetic acid as a combined complexing agent. The synergistic effect of the two significantly improves the selective retention effect of nanofiltration membrane on arsenic and silicon impurities. (3) The efficient method for removing impurities from sodium metavanadate solution of the present invention has a short process flow, simple operation, stable operation of nanofiltration membrane system and long membrane service life. Compared with ion exchange resin process, it has the advantages of low equipment investment, large processing capacity and low operating cost, and is more suitable for large-scale industrial continuous production. (4) The method for preparing battery-grade vanadium powder of the present invention realizes the one-step preparation of battery-grade high-purity vanadium powder from sodium metavanadate solution prepared by Bayer process alumina vanadium-containing alkaline slag, which eliminates the complicated process of traditional ammonium metavanadate recrystallization, avoids the problem of high vanadium loss caused by secondary crystallization, significantly improves the utilization rate of vanadium resources and reduces production costs. (5) The battery-grade vanadium powder of the present invention has stable and reliable product quality, with a vanadium pentoxide purity of 99.95%, and all trace elements meet the standards of vanadium redox flow battery electrolyte. Attached Figure Description

[0020] Figure 1 The flowchart below illustrates a highly efficient method for removing impurities from sodium metavanadate solution, as described in one embodiment of the present invention. Detailed Implementation

[0021] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0022] The present invention discloses a highly efficient method for removing impurities from sodium metavanadate solution. A complexing agent is added to the sodium metavanadate solution to be treated and reacted. The resulting solution is then subjected to nanofiltration to obtain a high-purity sodium metavanadate solution and a concentrated solution containing impurities. The impurities in the sodium metavanadate solution to be treated include arsenic, phosphorus, and silicon. The pH value of the sodium metavanadate solution to be treated is 8.5-9.0, and the temperature is 35℃-45℃. The complexing agent includes sodium ethylenediamine di-o-phenylacetate and diethylenetriaminepentaacetic acid. The nanofiltration membrane used in the nanofiltration process has a molecular weight cutoff of 150 Da-180 Da.

[0023] The present invention provides a highly efficient method for removing impurities from sodium metavanadate solution. By using nanofiltration technology, vanadium in the sodium metavanadate solution is effectively separated from phosphorus, arsenic, and silicon impurities, thereby improving the impurity removal efficiency and producing ammonium metavanadate products that meet the requirements for battery-grade high-purity vanadium powder.

[0024] The principle of the above-mentioned efficient impurity removal method of the present invention is as follows: when the solution pH>11, vanadium, arsenic, phosphorus, and silicon are respectively removed by VO4. 3- AsO4 3- PO4 3- SiO3 2- Vanadium, arsenic, phosphorus, and silicon exist in various forms, including VO3, when the solution pH is 8-9. - ,HAsO4 2- HPO4 2- SiO3 2- Vanadium, arsenic, phosphorus, and silicon exist in the forms of V, etc.; when the solution pH < 4, vanadium, arsenic, phosphorus, and silicon exist in the forms of V, etc. 10 O 28 6- H2AsO4 - H2PO4 - It exists in forms such as SiO2˙nH2O. This invention employs nanofiltration membrane filtration to separate vanadium from elements such as arsenic, phosphorus, and silicon based on their low valence states (negative one) and high valence states (negative two and above). By controlling the solution pH to 8-9 according to the differences in valence states under different pH conditions, vanadium exists in its monovalent state (VO3). - HAsO4 in divalent states with phosphorus, arsenic, and silicon 2- HPO4 2- SiO3 2- The mixture is effectively separated to achieve efficient impurity removal, resulting in a high-purity sodium metavanadate solution. This solution is then used to prepare high-purity ammonium metavanadate that meets the requirements for battery-grade high-purity vanadium powder in a one-step process.

[0025] This invention uses a nanofiltration membrane with a molecular weight cutoff of 150 Da-180 Da to allow AsO4 to pass through. 2- HPO4 2- SiO3 2- The retention rate can reach 99.5%, VO3 - With a transmittance of 80%, it can separate vanadium from impurities such as arsenic, phosphorus, and silicon. The concentration of As in the separated sodium metavanadate solution is less than 0.1 g / L, the concentration of Si is less than 0.01 g / L, and the concentration of phosphorus also meets the requirements.

[0026] This invention uses sodium ethylenediamine di-o-phenylacetate and diethylenetriaminepentaacetic acid as complexing agents, which can effectively complex hydrogen arsenate, phosphate and silicate ions, thereby ensuring the impurity removal effect.

[0027] Preferably, in the complexing agent, based on the total mass of arsenic, phosphorus, and silicon in the sodium metavanadate solution to be treated (100%), the mass percentage of sodium ethylenediamine di-o-phenylacetate is 0.2%-0.3%, and the mass percentage of diethylenetriaminepentaacetic acid is 0.2%-0.3%. Sodium ethylenediamine di-o-phenylacetate has a specific and strong complexing effect on silicate ions, which can significantly reduce the silicate permeability, while diethylenetriaminepentaacetic acid exhibits excellent complexing ability on hydrogen arsenate ions, significantly reducing the hydrogen arsenate permeability. When the two work synergistically, the retention rates of arsenic and silicon impurities both reach extremely high levels. Based on the good complexing of arsenic and silicon, phosphorus can also be effectively removed.

[0028] Further preferably, the mass percentage of sodium ethylenediamine di-o-phenylacetate is 0.3%, and the mass percentage of diethylenetriaminepentaacetic acid is 0.3%. When the amount of each complexing agent is 0.3%, the purity of vanadium pentoxide in the nanofiltration membrane clear liquid can reach 99.95%, and the arsenic, silicon and phosphorus contents are significantly reduced, which fully meets the stringent requirements of vanadium redox flow battery electrolyte for arsenic content of less than 2 mg / kg and silicon content of less than 40 mg / kg.

[0029] Preferably, based on the above-mentioned complexing agent dosage, the molecular weight cutoff of the nanofiltration membrane is 150 Da. When the 150 Da nanofiltration membrane is used in conjunction with 0.3% sodium ethylenediamine di-o-phenylacetate and 0.3% diethylenetriaminepentaacetic acid, the synergistic effect of the complexing agent increasing the effective size of impurity ions and the membrane's sieving effect further enhances the arsenic and silicon rejection rates to over 99%. The final vanadium pentoxide product has an arsenic content of less than 2 mg / kg and a silicon content of less than 40 mg / kg, fully meeting the stringent quality standards for vanadium redox flow battery electrolytes. Furthermore, this membrane specification demonstrates good industrial applicability in terms of operating pressure, flux stability, and antifouling performance, providing reliable technical support for the one-step, short-process production of battery-grade high-purity vanadium powder.

[0030] The sodium metavanadate solution used in this invention is prepared from vanadium-containing alkaline slag extracted from alumina using the Bayer process; it can achieve efficient recovery of vanadium resources associated with alumina production, transforming vanadium-containing materials that might otherwise be treated as waste into high-value-added battery-grade vanadium products, which is in line with the concepts of circular economy and clean production.

[0031] Preferably, the concentration of vanadium pentoxide in the sodium metavanadate solution to be treated is 80-100 g / L.

[0032] like Figure 1 As shown, in one embodiment of the present invention, the efficient impurity removal method specifically includes the following steps: S1. Obtain vanadium-containing alkaline slag extracted from alumina by the Bayer process, and prepare a vanadium-containing alkaline slag leachate. Measure the pH value of the leachate and adjust it using conventional methods to bring it within the range of 8.5-9.0. The solution with the adjusted pH is the sodium metavanadate solution to be treated.

[0033] If the pH of the solution is within the above range, no adjustment is required.

[0034] Preferably, the reagent used to adjust the pH value can be a commonly used acid or base, such as sodium hydroxide, potassium hydroxide, dilute hydrochloric acid, dilute sulfuric acid, etc.

[0035] S2. The initial temperature of the dissolution solution in step S1 is generally greater than 60℃. After pH adjustment, the temperature of the sodium metavanadate solution to be treated is reduced to 35℃-45℃. Then, a complexing agent containing sodium ethylenediamine di-o-phenylacetate and diethylenetriaminepentaacetic acid is added, and the mixture is stirred and reacted.

[0036] Preferably, heat treatment is required when the initial temperature of the leachate is below 35°C.

[0037] Preferably, the reaction time is 0.5-1.5 hours.

[0038] S3. After the reaction is completed, the reaction solution is filtered using a nanofiltration membrane to obtain a clear solution and a concentrated solution. The clear solution is a high-purity sodium metavanadate solution, and the concentrated solution is a concentrated solution containing impurities such as phosphorus, arsenic and silicon.

[0039] The high-purity sodium metavanadate solution of the present invention is obtained by removing impurities from the sodium metavanadate solution using the method described above. This high-purity sodium metavanadate solution can be used to prepare battery-grade vanadium powder.

[0040] The method for preparing battery-grade vanadium powder of the present invention involves heating a high-purity sodium metavanadate solution as described above to 50°C-55°C, adding ammonium sulfate, and then crystallizing ammonium metavanadate crystals. After solid-liquid separation, the ammonium metavanadate crystals are calcined to obtain battery-grade vanadium powder. The high-purity sodium metavanadate solution obtained after impurity removal from the sodium metavanadate solution is used to prepare battery-grade high-purity vanadium powder ammonium metavanadate in one step, which can achieve the effects of short process and low cost.

[0041] Specifically, this preparation method eliminates the complex recrystallization process of traditional ammonium metavanadate, avoiding the problem of vanadium loss of no less than 15% caused by secondary crystallization. Vanadium recovery is significantly improved, greatly reducing the consumption of chemical reagents such as sodium hydroxide and ammonium salts, as well as the corresponding wastewater treatment burden, resulting in low production costs. The selective and efficient impurity removal characteristics of nanofiltration membrane separation technology ensure batch-to-batch stability of product quality, and the nanofiltration membrane has a long service life and is easy to operate and maintain, making it suitable for large-scale continuous production.

[0042] Preferably, the calcination temperature is 450℃-550℃ and the time is 1.5-2.5 hours.

[0043] The battery-grade vanadium powder of this invention is prepared using the method described above. This battery-grade vanadium powder possesses significant advantages such as extremely high purity, precise impurity control, short production process, substantial cost advantages, and good quality stability. The vanadium pentoxide purity of the product reaches over 99.95%, with arsenic content as low as 1.85 mg / kg and silicon content as low as 29 mg / kg, far exceeding the stringent standards of arsenic ≤2 mg / kg and silicon ≤40 mg / kg for vanadium redox flow battery electrolytes.

[0044] The present invention will be illustrated below through specific embodiments and comparative examples.

[0045] It should be noted that the content of each metal element in each embodiment is expressed by its corresponding oxide, and does not mean that the solution actually contains these oxides.

[0046] Example 1 Nanofiltration Membrane Selection Experiment In this embodiment, nanofiltration membranes with different molecular weight cutoff values ​​were used for treatment to determine the optimal molecular weight cutoff value for the nanofiltration membrane.

[0047] The sodium metavanadate solution to be treated in this embodiment is a leaching solution of vanadium-containing alkaline slag extracted from alumina using the Bayer process. It has a volume of 2 L, a density of 1.32 g / mL, and a mass of 2640 g. Its main components and concentrations are: V₂O₅: 98 g / L; P₂O₅: 32 g / L; As₂O₃: 38 g / L; SiO₂: 1.89 g / L; Na₂SO₄: 135 g / L. The main substances and concentrations in the solution are: NaVO₃: 131 g / L; Na₂HPO₄: 64 g / L; Na₂HAsO₄: 71 g / L; Na₂SiO₃: 3.84 g / L; Na₂SO₄: 135 g / L. The total salt content of the solution is 30.74% by mass.

[0048] Since this embodiment examines the molecular weight cutoff value of the nanofiltration membrane, no chelating or complexing agent is added; instead, 14L of water is directly added to 2L of the sodium metavanadate solution to be treated for dilution.

[0049] This embodiment specifically uses negatively charged polyamide composite nanofiltration membranes ranging from 100-400 Da for experimental purposes. The filtration effects of nanofiltration membranes with different molecular weight cutoffs are as follows: (1) 100 Da nanofiltration membrane filtration. The diluted sodium metavanadate solution to be treated was filtered using a 100 Da membrane. After filtration, a clear liquid and a concentrated liquid were obtained. The detection results of the two were as follows: The mass of the clear liquid was 7914.18 g, the volume was 7.91 L, and the components and concentrations were: V2O5: 0 g / L; P2O5: 0 g / L; As2O3: 0 g / L; SiO2: 0 g / L.

[0050] The concentrated solution had a mass of 8725.82 g and a volume of 8.09 L. The solution composition was as follows: V2O5: 24.24 g / L; P2O5: 7.92 g / L; As2O3: 9.40 g / L; SiO2: 0.47 g / L; Na2SO4: 39.52 g / L.

[0051] Using a nanofiltration membrane with a molecular weight of 100 Da, since the molecular weights of all components in the solution are greater than 100, all components are 100% retained, and only 50% of the water permeates through the nanofiltration membrane.

[0052] (2) 120 Da nanofiltration membrane filtration. The diluted sodium metavanadate solution to be treated was filtered using a 120 Da membrane. The filtered solution yielded a clear liquid and a concentrated liquid. The detection results for both were as follows: The mass of the clear liquid was 9497.01 g, the volume was 9.31 L, and the components and concentrations were V2O5: 3.16 g / L; P2O5: 0 g / L; As2O3: 0 g / L; SiO2: 0 g / L.

[0053] The concentrated solution had a mass of 7925.23 g and a volume of 6.69 L. The solution composition was as follows: V2O5: 24.91 g / L; P2O5: 9.57 g / L; As2O3: 11.36 g / L; SiO2: 0.57 g / L; Na2SO4: 40.42 g / L.

[0054] Using a nanofiltration membrane with a molecular weight of 120 Da, the permeability of metavanadate in the solution is 15%, while other salts are retained. Although monovalent vanadate ions can be effectively separated from other divalent ions, the low permeability of vanadate ions and the low solution concentration make industrial production uneconomical.

[0055] (3) 150 Da nanofiltration membrane filtration. The diluted sodium metavanadate solution to be treated was filtered using a 150 Da membrane. The filtered solution yielded a clear liquid and a concentrated liquid. The detection results for both were as follows: The weight of the clear liquid was 9654.98 g, the volume was 9.52 L, and the composition was V2O5: 16.47 g / L; P2O5: 0.67 g / L; As2O3: 0.40 g / L; SiO2: 0.04 g / L; Na2SO4: 2.84 g / L.

[0056] The concentrated solution had a mass of 6885.02 g and a volume of 6.48 L. The solution composition was as follows: V2O5: 6.05 g / L; P2O5: 8.89 g / L; As2O3: 11.15 g / L; SiO2: 0.53 g / L; Na2SO4: 34.57 g / L.

[0057] Using a nanofiltration membrane with a molecular weight of 150 Da, the permeability of metavanadate in the solution reached 80%, the permeability of hydrogen phosphate, silicate and sulfate was 10%, and the permeability of hydrogen arsenate was 5%.

[0058] (4) 180Da nanofiltration membrane filtration. The diluted sodium metavanadate solution to be treated was filtered using a 180Da membrane. The filtered solution yielded a clear liquid and a concentrated liquid. The detection results for both were as follows: The mass of the clear liquid was 11439.28 g, the volume was 11.08 L, and the composition was V2O5: 15.92 g / L; P2O5: 1.44 g / L; As2O3: 1.03 g / L; SiO2: 0.09 g / L; Na2SO4: 6.10 g / L.

[0059] The concentrated solution had a mass of 5200.72 g and a volume of 4.92 L. The solution composition was as follows: V2O5: 3.98 g / L; P2O5: 7.76 g / L; As2O3: 13.13 g / L; SiO2: 0.58 g / L; Na2SO4: 41.22 g / L.

[0060] Using a nanofiltration membrane with a molecular weight of 180 Da, the permeability of metavanadate in the solution reached 90%, the permeability of hydrogen phosphate, silicate and sulfate was 25%, and the permeability of hydrogen arsenate was 15%.

[0061] (5) 200 Da nanofiltration membrane filtration. The diluted sodium metavanadate solution to be treated was filtered using a 200 Da membrane. The filtered solution yielded a clear liquid and a concentrated liquid. The detection results for both were as follows: The mass of the clear liquid was 12373.92 g, the volume was 11.87 L, and the composition was V2O5: 15.68 g / L; P2O5: 2.70 g / L; As2O3: 2.24 g / L; SiO2: 0.16 g / L; Na2SO4: 11.39 g / L.

[0062] The concentrated solution had a mass of 4266.08 g and a volume of 4.13 L. The solution composition was as follows: V2O5: 2.37 g / L; P2O5: 7.75 g / L; As2O3: 11.96 g / L; SiO2: 0.46 g / L; Na2SO4: 32.75 g / L.

[0063] Using a nanofiltration membrane with a molecular weight of 200 Da, the permeability of metavanadate in the solution reached 95%, the permeability of hydrogen phosphate, silicate and sulfate was 50%, and the permeability of hydrogen arsenate was 35%.

[0064] (6) 250 Da nanofiltration membrane filtration. The diluted sodium metavanadate solution to be treated was filtered using a 250 Da membrane. The filtered solution yielded a clear liquid and a concentrated liquid. The detection results for both were as follows: The mass of the clear liquid was 12468.07 g, the volume was 11.87 L, and the composition was as follows: V2O5: 16.43 g / L; P2O5: 3.50 g / L; As2O3: 3.20 g / L; SiO2: 0.21 g / L; Na2SO4: 14.81 g / L.

[0065] The concentrated solution had a mass of 4171.93 g and a volume of 4.13 L. The solution composition was: V2O5: 0.24 g / L; P2O5: 5.43 g / L; As2O3: 9.20 g / L; SiO2: 0.32 g / L; Na2SO4: 22.92 g / L.

[0066] Using a nanofiltration membrane with a molecular weight of 250 Da, the permeability of metavanadate in the solution reached over 99%, the permeability of hydrogen phosphate, silicate, and sulfate was 65%, and the permeability of hydrogen arsenate was 50%.

[0067] Based on the experimental results of the above nanofiltration membranes, nanofiltration membranes with molecular weights of 150 Da and 180 Da were selected.

[0068] Example 2: Chelating or Complexing Agent Selection Experiment This embodiment employs various chelating or complexing agents to screen for the optimal type. Since the vanadium redox flow battery electrolyte has relatively low requirements for phosphorus, sodium, and sulfur, this embodiment focuses on testing the membrane separation of macromolecular complexes formed by hydrogen arsenate and silicate ions.

[0069] Based on the experimental results of Example 1, this example uses a 150 Da nanofiltration membrane for the experiment, and the leaching solution of the vanadium-containing alkaline slag used in this example is the same as that in Example 1.

[0070] The chelating agents or complexing agents in this embodiment are: polyacrylamide, polyvinyl alcohol, EDTA polymer, sodium ethylenediamine di-o-phenylacetate, ethylenediaminetetraacetamide, and diethylenetriaminepentaacetic acid. Each of the above chelating agents or complexing agents is added in solid form, at a rate of 1% of the total sodium vanadate solution, i.e., 26.4g is added to each 2L solution, followed by dilution with 14L of water.

[0071] After dilution, the mass of the membrane filtration stock solution corresponding to each chelating or complexing agent was 16666.40 g, and the volume was 16.01 L. The clarified and concentrated solutions after treatment with each chelating or complexing agent were analyzed, and the results are as follows: (1) 1% polyacrylamide: The mass of the clear liquid is 9754.14g, the volume is 9.50L, and the composition is V2O5: 16.51g / L; P2O5: 0.67g / L; As2O3: 0.36g / L; SiO2: 0.04g / L; Na2SO4: 2.85g / L. The mass of the concentrated liquid is 6912.26g, the volume is 6.51L, and the composition is V2O5: 6.02g / L; P2O5: 8.85g / L; As2O3: 11.14g / L; SiO2: 0.52g / L; Na2SO4: 37.37g / L.

[0072] Using polyacrylamide as a complexing agent, the permeability of metavanadate in the solution reached 80%, while the permeability of hydrogen phosphate, silicate, and sulfate was 10%, and the permeability of hydrogen arsenate was 5%. Compared to the solution without a complexing agent, the change was minimal, indicating that adding 1% polyacrylamide did not achieve a complexing effect.

[0073] (2) 1% polyvinyl alcohol: The mass of the clear liquid is 9754.41g, the volume is 9.50L, and the composition is V2O5: 16.51g / L; P2O5: 0.67g / L; As2O3: 0.37g / L; SiO2: 0.04g / L; Na2SO4: 2.85g / L. The mass of the concentrated liquid is 6911.99g, the volume is 6.51L, and the composition is V2O5: 6.02g / L; P2O5: 8.84g / L; As2O3: 11.13g / L; SiO2: 0.52g / L; Na2SO4: 37.37g / L.

[0074] Using polyvinyl alcohol as a complexing agent, the permeability of metavanadate in the solution reached 80%, while the permeability of hydrogen phosphate, silicate, and sulfate was 10%, and the permeability of hydrogen arsenate was 5%. Compared to the solution without a complexing agent, the change was minimal, indicating that adding 1% polyvinyl alcohol did not achieve a complexing effect.

[0075] (3) 1% EDTA polymer: The mass of the clear liquid is 9754.59 g, the volume is 9.50 L, and the composition is V2O5: 16.51 g / L; P2O5: 0.67 g / L; As2O3: 0.40 g / L; SiO2: 0.02 g / L; Na2SO4: 2.85. The mass of the concentrated liquid is 6911.81 g, the volume is 6.51 L, and the composition is V2O5: 6.02 g / L; P2O5: 8.84 g / L; As2O3: 11.13 g / L; SiO2: 0.55 g / L; Na2SO4: 37.37 g / L.

[0076] Using EDTA polymer as a complexing agent, the permeability of metavanadate in the solution reached 80%, while the permeability of hydrogen phosphate and sulfate was 10%, and that of hydrogen arsenate was 5%. Compared to the solution without a complexing agent, the change was minimal, indicating that the addition of 1% EDTA did not have a complexing effect on hydrogen arsenate, hydrogen phosphate, and sulfate. The permeability of silicate decreased from 10% to 5%, indicating that it had a certain complexing effect on silicate.

[0077] (4) 1% ethylenediamine di-o-phenylacetic acid sodium salt: The mass of the clear solution is 9754.25 g, the volume is 9.50 L, and the composition is V2O5: 16.51 g / L; P2O5: 0.67 g / L; As2O3: 0.40 g / L; SiO2: 0.002 g / L; Na2SO4: 2.85. The mass of the concentrated solution is 6912.15 g, the volume is 6.51 L, and the composition is V2O5: 6.02 g / L; P2O5: 8.84 g / L; As2O3: 11.09 g / L; SiO2: 0.58 g / L; Na2SO4: 37.37 g / L.

[0078] Using sodium ethylenediamine di-o-phenylacetate as a complexing agent, the permeability of metavanadate in the solution reached 80%, while the permeability of hydrogen phosphate and sulfate was 10%, and that of hydrogen arsenate was 5%. Compared to the solution without a complexing agent, the change was minimal, indicating that adding 1% sodium ethylenediamine di-o-phenylacetate did not achieve a complexing effect on hydrogen arsenate, hydrogen phosphate, or sulfate. The permeability of silicate decreased from 10% to 0.5%, indicating a strong complexing effect on silicate.

[0079] (5) 1% ethylenediaminetetraacetamide: The mass of the clear solution is 9742.48 g, the volume is 9.50 L, and the composition is V2O5: 16.51 g / L; P2O5: 0.34 g / L; As2O3: 0.08 g / L; SiO2: 0.02 g / L; Na2SO4: 2.85. The mass of the concentrated solution is 6923.92 g, the volume is 6.51 L, and the composition is V2O5: 6.02 g / L; P2O5: 9.34 g / L; As2O3: 11.55 g / L; SiO2: 0.55 g / L; Na2SO4: 37.37 g / L.

[0080] Using ethylenediaminetetraacetamide as a complexing agent, the permeability of hydrogen phosphate and silicate decreased from 10% to 5%, and the permeability of hydrogen arsenate decreased to 1%. This indicates that 1% ethylenediaminetetraacetamide has a certain complexing effect on hydrogen arsenate, hydrogen phosphate, and sulfate.

[0081] (6) 1% diethylenetriaminepentaacetic acid: The mass of the clear liquid is 9737.77 g, the volume is 9.50 L, and the composition is V2O5: 16.51 g / L; P2O5: 0.13 g / L; As2O3: 0.04 g / L; SiO2: 0.01 g / L; Na2SO4: 2.85. The mass of the concentrated liquid is 6928.63 g, the volume is 6.51 L, and the composition is V2O5: 6.02 g / L; P2O5: 9.63 g / L; As2O3: 11.61 g / L; SiO2: 0.56 g / L; Na2SO4: 37.37 g / L.

[0082] Using 1% diethylenetriaminepentaacetic acid as a complexing agent, it has a strong complexing effect on hydrogen arsenate, and also has a relatively strong complexing effect on hydrogen phosphate and sulfate.

[0083] Based on the above experimental results, sodium ethylenediamine di-o-phenylacetate has a strong complexing effect on silicate ions, and diethylenetriaminepentaacetic acid has a strong complexing effect on hydrogen arsenate ions. Therefore, both were selected as complexing agents.

[0084] Example 3: Experiment on the dosage of chelating agents or complexing agents in combination Based on Example 2, this example uses a combination of sodium ethylenediamine di-o-phenylacetate and diethylenetriaminepentaacetic acid for experiments. Experiments were conducted using varying dosage ratios to determine the optimal complexing effect and the optimal amount of complexing agent. A nanofiltration membrane with a molecular weight of 150 Da was selected.

[0085] (1) Combination of 1% sodium di-o-phenylacetate and 1% diethylenetriaminepentaacetic acid: The mass of the clear liquid was 9734.95 g, the volume was 9.50 L, and the composition was V2O5: 16.51 g / L; P2O5: 0.03 g / L; As2O3: 0.002 g / L; SiO2: 0.001 g / L; Na2SO4: 2.85. The mass of the concentrated liquid was 6957.85 g, the volume was 6.51 L, and the composition was V2O5: 6.01 g / L; P2O5: 9.76 g / L; As2O3: 11.65 g / L; SiO2: 0.58 g / L; Na2SO4: 37.31 g / L.

[0086] Through combined complexation, both hydrogen arsenate and silicate ions achieved excellent complexation effects, resulting in a significant degree of separation from vanadate ions.

[0087] (2) A compound of 0.5% sodium di-o-phenylacetate and 0.5% diethylenetriaminepentaacetic acid: The mass of the clear liquid was 9734.96 g, the volume was 9.50 L, and the composition was V2O5: 16.51 g / L; P2O5: 0.03 g / L; As2O3: 0.002 g / L; SiO2: 0.001 g / L; Na2SO4: 2.85. The mass of the concentrated liquid was 6957.84 g, the volume was 6.51 L, and the composition was V2O5: 6.01 g / L; P2O5: 9.76 g / L; As2O3: 11.65 g / L; SiO2: 0.58 g / L; Na2SO4: 37.31 g / L.

[0088] Through combined complexation, both hydrogen arsenate and silicate ions achieved excellent complexation effects, resulting in a significant degree of separation from vanadate ions.

[0089] (3) A compound of 0.3% sodium di-o-phenylacetate and 0.3% diethylenetriaminepentaacetic acid: The mass of the clear liquid was 9734.97 g, the volume was 9.50 L, and the composition was V2O5: 16.51 g / L; P2O5: 0.03 g / L; As2O3: 0.002 g / L; SiO2: 0.001 g / L; Na2SO4: 2.85. The mass of the concentrated liquid was 6957.83 g, the volume was 6.51 L, and the composition was V2O5: 6.01 g / L; P2O5: 9.76 g / L; As2O3: 11.65 g / L; SiO2: 0.58 g / L; Na2SO4: 37.31 g / L.

[0090] Through combined complexation, both hydrogen arsenate and silicate ions achieved excellent complexation effects, resulting in a significant degree of separation from vanadate ions.

[0091] The results of the three sets of experiments were basically the same, indicating that adding 0.3% of the complexing agent to each group was sufficient to meet the requirements.

[0092] (4) A compound of 0.2% sodium di-o-phenylacetate and 0.2% diethylenetriaminepentaacetic acid: The mass of the clear liquid was 9735.40 g, the volume was 9.50 L, and the composition was V2O5: 16.51 g / L; P2O5: 0.05 g / L; As2O3: 0.004 g / L; SiO2: 0.002 g / L; Na2SO4: 2.85. The mass of the concentrated liquid was 6957.83 g, the volume was 6.51 L, and the composition was V2O5: 6.01 g / L; P2O5: 9.73 g / L; As2O3: 11.65 g / L; SiO2: 0.58 g / L; Na2SO4: 37.31 g / L.

[0093] The effect of adding 0.2% of each complexing agent is slightly worse than that of adding 0.3% of each.

[0094] Therefore, based on the experimental results of this embodiment, the optimal complexing agent is selected as either a combination of 0.3% sodium ethylenediamine di-o-phenylacetate and 0.3% diethylenetriaminepentaacetic acid, or a combination of 0.2% sodium ethylenediamine di-o-phenylacetate and 0.2% diethylenetriaminepentaacetic acid.

[0095] Example 4: Experiment on the preparation of battery-grade vanadium powder Based on the experimental results of Example 3, this example uses 0.3% sodium ethylenediamine di-o-phenylacetate and 0.3% diethylenetriaminepentaacetic acid as composite complexing agents (Experimental Group 1), and 0.2% sodium ethylenediamine di-o-phenylacetate and 0.2% diethylenetriaminepentaacetic acid as composite complexing agents (Experimental Group 2). These are used to treat different samples to obtain a high-purity sodium metavanadate solution (i.e., the clear liquid after nanofiltration), which is then used to prepare battery-grade high-purity vanadium powder. This example uses a 150 Da nanofiltration membrane, and the specific preparation process is as follows: Take 5 L of the filtered liquid from experimental group 1 and experimental group 2 respectively, heat it to 50℃, add orange peel, add ammonium sulfate with a purity ≥99.5%, stir to crystallize and precipitate ammonium metavanadate crystals, calcine in a muffle furnace at 500℃ for 2 hours to obtain powdered product.

[0096] The purity of vanadium pentoxide and the content of arsenic and silicon in the powdered products of each experimental group were determined. The test data are as follows: (1) Experimental group 1: The mass percentage of vanadium pentoxide is 99.95%, indicating that its vanadium pentoxide has high purity; the As content is 1.85 mg / kg; the Si content is 29 mg / kg, which meets the requirements of the electrolyte of vanadium redox flow battery.

[0097] (2) Experimental group 2: The mass percentage of vanadium pentoxide is 99.85%, indicating that its vanadium pentoxide purity is high; the As content is 3.68 mg / kg; the Si content is 39 mg / kg, and the As content does not meet the requirements of the electrolyte for vanadium redox flow batteries.

[0098] The experimental results above show that adding 0.3% sodium ethylenediamine di-o-phenylacetate and 0.3% sodium ethylenediamine di-o-phenylacetate as complexing agents to a sodium vanadate solution, diluting it with water, filtering it through a nanofiltration membrane with a molecular weight of 150 Da, adding ammonium sulfate to the membrane filtrate to prepare ammonium metavanadate, and calcining it can yield powdered vanadium that meets the requirements of an all-vanadium redox flow battery electrolyte.

[0099] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A highly efficient method for removing impurities from sodium metavanadate solution, characterized in that, A complexing agent is added to the sodium metavanadate solution to be treated and the reaction is carried out. The solution after the reaction is subjected to nanofiltration to obtain a high-purity sodium metavanadate solution and a concentrated solution containing the impurities. The impurities in the sodium metavanadate solution to be treated include arsenic, phosphorus, and silicon; the pH value of the sodium metavanadate solution to be treated is 8.5-9.0, and the temperature is 35℃-45℃. The complexing agent includes sodium ethylenediamine di-o-phenylacetate and diethylenetriaminepentaacetic acid, and the nanofiltration membrane used in the nanofiltration has a molecular weight cutoff of 150 Da-180 Da.

2. The method for efficiently removing impurities from sodium metavanadate solution according to claim 1, characterized in that, In the complexing agent, based on the total mass of arsenic, phosphorus, and silicon in the sodium metavanadate solution to be treated being 100%, the mass percentage of sodium ethylenediamine di-o-phenylacetate is 0.2%-0.3%, and the mass percentage of diethylenetriaminepentaacetic acid is 0.2%-0.3%.

3. The method for efficiently removing impurities from sodium metavanadate solution according to claim 2, characterized in that, In the complexing agent, the mass percentage of sodium ethylenediamine di-o-phenylacetate is 0.3%, and the mass percentage of diethylenetriaminepentaacetic acid is 0.3%.

4. The method for efficiently removing impurities from sodium metavanadate solution according to claim 3, characterized in that, The molecular weight cutoff of the nanofiltration membrane is 150 Da.

5. A highly efficient method for removing impurities from sodium metavanadate solution according to any one of claims 1-4, characterized in that, The sodium metavanadate solution to be treated was prepared from vanadium-containing alkaline slag extracted from alumina using the Bayer process.

6. The method for efficiently removing impurities from sodium metavanadate solution according to claim 5, characterized in that, The concentration of vanadium pentoxide in the sodium metavanadate solution to be treated is 80-100 g / L.

7. A high-purity sodium metavanadate solution, characterized in that, The sodium metavanadate solution was purified using any one of the methods described in claims 1-6.

8. A method for preparing battery-grade vanadium powder, characterized in that, The high-purity sodium metavanadate solution as described in claim 7 is heated to 50℃-55℃, and ammonium sulfate is added to crystallize out ammonium metavanadate crystals. After solid-liquid separation, the ammonium metavanadate crystals are calcined to obtain battery-grade vanadium powder.

9. The method for preparing battery-grade vanadium powder according to claim 8, characterized in that, The calcination temperature is 450℃-550℃, and the time is 1.5-2.5 hours.

10. A battery-grade vanadium powder, characterized in that, It is prepared by the method described in claim 8 or 9.

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