A method for preparing high-purity vanadium pentoxide by using a double ligand homogeneous vanadium precipitation

Abstract

The application discloses a method for preparing high-purity vanadium pentoxide by double-ligand homogeneous vanadium precipitation, which comprises the following steps: pretreating a vanadium-containing liquid to obtain a vanadium-rich liquid with a vanadium concentration of 15-35 g / L and a pH of 7.5-8.5; stirring the vanadium-rich liquid at a constant temperature of 85-95 DEG C, and adding a double-ligand mixed liquid prepared by mixing melamine and glycine at a molar ratio of 1:1-2.5 into the vanadium-rich liquid drop by drop, and reacting at the constant temperature for 2-4 h; filtering, washing and drying the reaction product to obtain a precursor; and finally preparing vanadium pentoxide products through two-stage temperature control calcination. The method utilizes the synergistic effect of melamine for regulating aggregation nucleation and glycine for improving crystal surface adsorption, effectively delays disordered precipitation and inhibits the enrichment of alkali metal impurities, and high-purity vanadium pentoxide with a purity of more than 99.5% is prepared, so that the secondary purification process is simplified, and the comprehensive energy consumption and environmental protection pressure are reduced.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, specifically to a method for preparing high-purity vanadium pentoxide by homogeneous precipitation of vanadium with two ligands. Background Technology

[0002] High-purity vanadium pentoxide (purity ≥ 99.5%) is the core raw material for preparing electrolytes for all-vanadium redox flow batteries and aerospace-grade vanadium alloys. In the existing technology, the wet extraction of vanadium from vanadium-containing smelting slag mostly adopts the ammonium salt (such as ammonium chloride and ammonium sulfate) precipitation method, and the reaction formula is shown in formula (1).

[0003]

[0004] Equation (1)

[0005] However, the existing vanadium precipitation process still has the following defects: (1) the precipitation rate is too fast, and the local supersaturation is high, resulting in disordered crystal growth; (2) alkali metal entrainment is severe, Na + K + (3) It is easy to enter the precipitate through surface adsorption or lattice embedding; (4) The purity is limited, and the purity of a single precipitation product is usually difficult to exceed 99%; (5) The process is complicated and requires multiple purification steps of "precipitation-dissolution-reprecipitation"; (6) The environmental pressure is high and a large amount of ammonia nitrogen-containing wastewater is generated.

[0006] Although existing technologies use organic ligands such as melamine to replace ammonium salts for vanadium precipitation—for example, patent CN113025833A discloses a method for precipitating vanadium from a high-concentration vanadium solution—which involves adjusting the high-concentration vanadium solution to a weakly acidic state, heating it, and adding melamine alone for precipitation—the control of the crystal growth process by a single ligand is insufficient, and its inhibitory effect on alkali metal ions is limited. Therefore, there is an urgent need for a process that can effectively suppress alkali metal entrainment in a single precipitation process. Summary of the Invention

[0007] To address the technical problems of disordered crystal growth, severe alkali metal entrainment, low purity from single precipitation, and complex process flow in existing technologies, this invention provides a method for preparing high-purity vanadium pentoxide by homogeneous precipitation with dual ligands.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A method for preparing high-purity vanadium pentoxide by homogeneous precipitation of vanadium with two ligands, characterized by comprising the following steps:

[0010] S1. Pre-treat the vanadium-containing solution to obtain a vanadium-rich solution with a vanadium concentration of 15-35 g / L and a pH of 7.5-8.5;

[0011] S2. Heat the vanadium-rich solution obtained in step S1 to 85-95℃ and stir at a constant temperature of 200-400 rpm. Add the dual-ligand mixture dropwise to the vanadium-rich solution at a flow rate of 2-5 mL / min. After the addition is complete, react at a constant temperature for 2-4 hours. The dual-ligand mixture is prepared by dissolving melamine and glycine in water at a molar ratio of 1:1-2.5 to prepare the dual-ligand mixture, and controlling the total molar amount of the dual ligands to the molar ratio of vanadium in the vanadium-rich solution to be 0.05-0.2:1.

[0012] S3. After the reaction is complete, the resulting suspension is filtered, and the filter cake is washed and dried to obtain the precursor.

[0013] S4. Heat the precursor to 300-350℃ and hold for 1-2 hours; then heat to 520-560℃ and hold for calcination for 2-3 hours, then cool to obtain vanadium pentoxide.

[0014] In the technical solution provided by this invention, melamine is mainly used to regulate the aggregation and nucleation behavior during the vanadium precipitation process, while glycine is mainly used to improve the adsorption balance on the crystal surface and inhibit the continuous enrichment of impurity ions on the crystal surface. When combined, the two can, to a certain extent, delay the rapid precipitation of disordered substances and promote the formation of more regular precursors, thereby improving the purity of the final product.

[0015] Further, in step S1, the pretreatment includes iron removal, silicon removal and phosphorus removal, so that the purified vanadium-rich solution contains Fe ≤ 10 mg / L, Si ≤ 15 mg / L and P ≤ 5 mg / L.

[0016] Furthermore, in step S1, when the total Na concentration in the vanadium-rich solution is greater than 5 mg / L, pre-desalination is performed using capacitive deionization in the pretreatment.

[0017] Furthermore, in step S2, the water temperature used to dissolve the dual ligands is 85℃-95℃.

[0018] Further, in step S2, the method for preparing the dual-ligand mixture is to dissolve melamine and glycine in water at a molar ratio of 1:1-2 to prepare the dual-ligand mixture, and control the total molar amount of the dual ligands to the molar ratio of vanadium in the vanadium-rich solution to be 0.1-0.15:1.

[0019] Further, in step S3, the obtained suspension is filtered while hot, the filter cake is washed 2-3 times with deionized water, and dried at 80-120℃.

[0020] Further, the specific method of step S4 is as follows: under air or oxygen-rich atmosphere, the precursor is first heated to 300-350℃ at a rate of 2-3℃ / min and held at that temperature for 1-2h; then heated to 520-560℃ at a rate of 4-6℃ / min and held at that temperature for calcination for 2-3h, and then cooled to obtain vanadium pentoxide.

[0021] The present invention also provides the following technical solutions:

[0022] A high-purity vanadium pentoxide was prepared using the method described above.

[0023] Furthermore, the product properties of the high-purity vanadium pentoxide are: purity ≥ 99.5%, Na content ≤ 0.015%, and K content ≤ 0.01%.

[0024] Furthermore, the product properties of the high-purity vanadium pentoxide are: purity ≥ 99.7%, Na content ≤ 0.01%, and K content ≤ 0.01%.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] Significantly improved purity: The vanadium precipitation process is synergistically regulated by melamine and glycine dual ligands. Melamine regulates aggregation and nucleation behavior, while glycine improves the adsorption balance on the crystal surface. The combination of the two effectively delays the disordered rapid precipitation and promotes the formation of more regular precursors, thereby greatly reducing the entrainment and encapsulation of alkali metal impurities such as Na and K. After calcination, the precursor can be used to obtain vanadium pentoxide products with high purity.

[0027] The process is simplified and efficient: Alkali metal ions can be effectively suppressed in a single precipitation process, and high-purity vanadium pentoxide can be directly obtained after two stages of temperature-controlled calcination. This eliminates the repeated steps of secondary dissolution and reprecipitation that are required in traditional processes, thus shortening the process chain.

[0028] Significantly improved environmental friendliness: Replacing traditional ammonium salts with dual ligands for vanadium precipitation fundamentally eliminates the generation of ammonium-containing wastewater, reduces the difficulty of wastewater treatment and environmental pressure, and reduces the load of high-salt waste liquid. Attached Figure Description

[0029] Figure 1 This is a flowchart of the method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with dual ligands in an embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram illustrating the control of vanadium precipitation and calcination conversion in the method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with dual ligands in an embodiment of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] Example 1

[0033] This embodiment provides a method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with two ligands, the flowchart of which is shown below. Figure 1 As shown; the specific steps are as follows. Figure 2 This is a schematic diagram illustrating the control of vanadium precipitation and calcination conversion in the method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with dual ligands in an embodiment of the present invention.

[0034] S1. Vanadium is extracted from the vanadium-containing smelting slag, and conventional iron, silicon, and phosphorus removal are carried out. Pre-salting is performed using capacitive deionization to ensure that the purified vanadium-rich liquid contains Fe≤10mg / L, Si≤15mg / L, P≤5mg / L, and Na≤5mg / L. Then, the pH is adjusted to 8.0.

[0035] S2. Take 1L of the vanadium-rich solution obtained in step S1, heat it to 90℃, and stir it at a constant temperature of 300rpm. Add the dual-ligand mixture dropwise to the vanadium-rich solution at a flow rate of 2-5mL / min. After the addition is complete, stir and react at a constant temperature for 3h. The dual-ligand mixture is prepared by dissolving 2g of the structure-directing agent melamine and 1.8g of the crystal face masking agent glycine (the molar ratio of the two is 1:1.5, and the molar ratio of the total molar amount of the dual ligands to the molar amount of vanadium in the vanadium-rich solution is 0.1:1) in 100mL of hot deionized water at 90℃ and stirring thoroughly until completely dissolved to prepare the dual-ligand mixture.

[0036] like Figure 2 As shown, melamine acts as a structure guide, mainly used to regulate the aggregation and nucleation behavior during vanadium precipitation, while glycine acts as a crystal facet mask, mainly used to improve the adsorption balance on the crystal surface and inhibit the continuous enrichment of impurity ions on the crystal surface. The combination of these two substances can, to a certain extent, delay the rapid precipitation of disordered materials, promote the formation of more regular precursors, and inhibit the entrainment of alkali metal impurities such as Na and K, thereby improving the purity of the final product.

[0037] S3. After the reaction is complete, the resulting suspension is filtered while hot, the filter cake is washed three times with deionized water, and dried at 100°C to obtain the precursor.

[0038] S4. Under air atmosphere, the precursor is placed in a muffle furnace, heated to 320°C at a rate of 2.5°C / min and held for 1.5 h; then heated to 550°C at a rate of 5°C / min and held for calcination for 2.5 h, and cooled to obtain vanadium pentoxide.

[0039] like Figure 2 As shown, the precursor is calcined to obtain high-purity vanadium pentoxide.

[0040] Results: The obtained vanadium pentoxide product had a purity of 99.82%, a Na content of 0.005%, a K content of 0.003%, and a vanadium precipitation rate of 98.5%. The test results indicate that the trace amounts of Fe, Si, and P impurity ions remaining after S1 pretreatment, under the masking effect of the dual-ligand system, mainly remained in the vanadium precipitation mother liquor and did not undergo significant co-precipitation enrichment in the final product, effectively ensuring the purity of the vanadium pentoxide product.

[0041] Example 2

[0042] This embodiment provides a method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with dual ligands.

[0043] The difference between this embodiment and Example 1 is that in step S2, the preparation method of the dual-ligand mixture is to dissolve melamine and glycine in 100 mL of 90°C hot deionized water at a molar ratio of 1:1, stir thoroughly to make it completely dissolved, prepare the dual-ligand mixture, and control the total molar amount of dual ligands to the molar ratio of vanadium in the vanadium-rich solution to be 0.1:1.

[0044] All other process parameters in this embodiment are the same as those in Embodiment 1.

[0045] The performance results of the vanadium pentoxide product obtained in this embodiment are shown in Table 1.

[0046] Example 3

[0047] This embodiment provides a method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with dual ligands.

[0048] The difference between this embodiment and embodiment 1 is that in step S2, the method for preparing the dual-ligand mixture is to dissolve melamine and glycine in 100 mL of 90°C hot deionized water at a molar ratio of 1:2, stir thoroughly to ensure complete dissolution, prepare the dual-ligand mixture, and control the total molar amount of dual ligands to the molar ratio of vanadium in the vanadium-rich solution to be 0.1:1.

[0049] All other process parameters in this embodiment are the same as those in Embodiment 1.

[0050] The performance results of the vanadium pentoxide product obtained in this embodiment are shown in Table 1.

[0051] Example 4

[0052] This embodiment provides a method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with dual ligands.

[0053] The difference between this embodiment and Embodiment 1 is that in step S2, the preparation method of the dual-ligand mixture is to dissolve melamine and glycine in 100 mL of 90°C hot deionized water at a molar ratio of 1:2.5, stir thoroughly to make them completely dissolved, prepare the dual-ligand mixture, and control the total molar amount of dual ligands to the molar ratio of vanadium in the vanadium-rich solution to be 0.1:1.

[0054] All other process parameters in this embodiment are the same as those in Embodiment 1.

[0055] The performance results of the vanadium pentoxide product obtained in this embodiment are shown in Table 1.

[0056] Example 5

[0057] This embodiment provides a method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with dual ligands.

[0058] The difference between this embodiment and embodiment 1 is that in step S2, the reaction temperature is 85°C and the reaction time is 4 hours.

[0059] All other process parameters in this embodiment are the same as those in Embodiment 1.

[0060] The performance results of the vanadium pentoxide product obtained in this embodiment are shown in Table 1.

[0061] Example 6

[0062] This embodiment provides a method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with dual ligands.

[0063] The difference between this embodiment and embodiment 1 is that in step S2, the reaction temperature is 95°C and the reaction time is 2 hours.

[0064] All other process parameters in this embodiment are the same as those in Embodiment 1.

[0065] The performance results of the vanadium pentoxide product obtained in this embodiment are shown in Table 1.

[0066] Example 7

[0067] This embodiment provides a method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with dual ligands.

[0068] The difference between this embodiment and Embodiment 1 is that in step S1, the pH of the vanadium-rich solution is adjusted to 7.5.

[0069] All other process parameters in this embodiment are the same as those in Embodiment 1.

[0070] The performance results of the vanadium pentoxide product obtained in this embodiment are shown in Table 1.

[0071] Example 8

[0072] This embodiment provides a method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with dual ligands.

[0073] The difference between this embodiment and Embodiment 1 is that in step S1, the pH of the vanadium-rich solution is adjusted to 8.5.

[0074] All other process parameters in this embodiment are the same as those in Embodiment 1.

[0075] The performance results of the vanadium pentoxide product obtained in this embodiment are shown in Table 1.

[0076] Comparative Example 1

[0077] Comparative Example 1 provides a method for preparing vanadium pentoxide.

[0078] The difference between this comparative example and Example 1 is that in step S2, only melamine (i.e., a monoligand, instead of a diligand) is added as a vanadium precipitant. The amount of melamine added is controlled to be the same as the total molar amount of the diligand in Example 1 (i.e., the molar ratio of melamine to vanadium in the vanadium-rich solution is 0.1:1). It is dissolved in 100 mL of 90°C hot deionized water and stirred thoroughly to ensure complete dissolution, thus preparing a ligand solution. This solution is then added dropwise to the vanadium-rich solution at a flow rate of 2-5 mL / min using a peristaltic pump.

[0079] All other process parameters in this comparative example are the same as those in Example 1.

[0080] The performance results of the vanadium pentoxide product obtained in this comparative example are shown in Table 1.

[0081] Comparative Example 2

[0082] Comparative Example 2 provides a method for preparing vanadium pentoxide.

[0083] The difference between this comparative example and Example 1 is that only glycine (i.e., a single ligand, replacing the dual ligand) is added as a vanadium precipitant. The amount of glycine added is controlled to be the same as the total molar amount of the dual ligand in Example 1 (i.e., the molar ratio of glycine to vanadium in the vanadium-rich solution is 0.1:1). It is dissolved in 100 mL of 90°C hot deionized water and stirred thoroughly to ensure complete dissolution, thus preparing a ligand solution. This solution is then added dropwise to the vanadium-rich solution at a flow rate of 2-5 mL / min using a peristaltic pump.

[0084] All other process parameters in this comparative example are the same as those in Example 1.

[0085] The performance results of the vanadium pentoxide product obtained in this comparative example are shown in Table 1.

[0086] Comparative Example 3

[0087] Comparative Example 3 provides a method for preparing vanadium pentoxide.

[0088] The difference between this comparative example and Example 1 is that a conventional ammonium salt vanadium precipitation process was used, with ammonium chloride selected as the vanadium precipitant. 42g of solid powdered ammonium chloride was slowly added to the system at a molar ratio of ammonium to vanadium (ammonium addition coefficient) of 2:1 to initiate the precipitation reaction. (The ammonia nitrogen wastewater load was significantly increased in this comparative example).

[0089] All other process parameters in this comparative example are the same as those in Example 1.

[0090] The performance results of the vanadium pentoxide product obtained in this comparative example are shown in Table 1.

[0091] Performance testing

[0092] The performance test results of the examples and comparative examples are shown in Table 1.

[0093] Table 1 Performance test results in the examples and comparative examples

[0094]

[0095] As can be seen from the vanadium precipitation effect data of the above embodiments and comparative examples, when melamine or glycine was used alone as the vanadium precipitation agent in Comparative Examples 1-2, the purity of the prepared vanadium pentoxide was low, and the content of Na and K impurities was high. However, when the embodiments of the present invention use a combination of melamine and glycine, the Na and K impurity content of the vanadium pentoxide product can be further reduced while maintaining a high vanadium precipitation rate, thereby effectively ensuring the high purity of vanadium pentoxide. By comparing the test results of Examples 1-4, it can be seen that when the proportion of glycine is too high (such as in Example 4), although the impurity inhibition effect can still be maintained, the vanadium precipitation rate will be affected to a certain extent. Therefore, the optimal molar ratio range of melamine and glycine in this application is 1:1-2. At the same time, within a reasonable temperature and pH range (Examples 5-8), the dual ligands can exert excellent vanadium precipitation and impurity inhibition effects, demonstrating the good adaptability of the process.

[0096] The foregoing descriptions have outlined some exemplary embodiments of the present invention. It is understood that these embodiments are merely illustrative and do not constitute a limitation on the scope of protection of the present invention. Features in these embodiments can be rearranged in suitable ways, and the resulting solutions remain within the scope of protection claimed by the present invention. All other embodiments obtained by those skilled in the art based on the foregoing embodiments without inventive effort, i.e., all modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing high-purity vanadium pentoxide by homogeneous precipitation of vanadium with two ligands, characterized in that, Includes the following steps: S1. Pre-treat the vanadium-containing solution to obtain a vanadium-rich solution with a vanadium concentration of 15-35 g / L and a pH of 7.5-8.5; S2. Heat the vanadium-rich solution obtained in step S1 to 85-95℃ and stir at a constant temperature of 200-400 rpm. Add the dual-ligand mixture dropwise to the vanadium-rich solution at a flow rate of 2-5 mL / min. After the addition is complete, react at a constant temperature for 2-4 hours. The dual-ligand mixture is prepared by dissolving melamine and glycine in water at a molar ratio of 1:1-2.5 to prepare the dual-ligand mixture, and controlling the total molar amount of the dual ligands to the molar ratio of vanadium in the vanadium-rich solution to be 0.05-0.2:

1. S3. After the reaction is complete, the resulting suspension is filtered, and the filter cake is washed and dried to obtain the precursor. S4. Heat the precursor to 300-350℃ and keep it at that temperature for 1-2 hours; The temperature is then raised to 520-560℃ and calcined for 2-3 hours, followed by cooling to obtain vanadium pentoxide.

2. The method for preparing high-purity vanadium pentoxide by homogeneous vanadium precipitation with dual ligands according to claim 1, characterized in that, In step S1, the pretreatment includes iron removal, silicon removal and phosphorus removal, so that the purified vanadium-rich solution contains Fe ≤ 10 mg / L, Si ≤ 15 mg / L and P ≤ 5 mg / L.

3. The method for preparing high-purity vanadium pentoxide by homogeneous precipitation of vanadium with two ligands according to claim 2, characterized in that, When the total Na concentration in the vanadium-rich solution is greater than 5 mg / L, pre-desalination is performed using capacitive deionization in the pretreatment.

4. The method for preparing high-purity vanadium pentoxide by homogeneous precipitation of vanadium with two ligands according to claim 1, characterized in that, In step S2, the water temperature used to dissolve the dual ligands is 85℃-95℃.

5. The method for preparing high-purity vanadium pentoxide by homogeneous precipitation of vanadium with two ligands according to claim 1, characterized in that, In step S2, the preparation method of the dual-ligand mixture is to dissolve melamine and glycine in water at a molar ratio of 1:1-2 to prepare the dual-ligand mixture, and control the total molar amount of the dual ligands to the molar ratio of vanadium in the vanadium-rich solution to be 0.1-0.15:

1.

6. The method for preparing high-purity vanadium pentoxide by homogeneous precipitation of vanadium with two ligands according to claim 1, characterized in that, In step S3, the obtained suspension is filtered while hot, the filter cake is washed 2-3 times with deionized water, and dried at 80-120℃.

7. The method for preparing high-purity vanadium pentoxide by homogeneous precipitation of vanadium with two ligands according to claim 1, characterized in that, The specific method for step S4 is as follows: Under air or an oxygen-rich atmosphere, the precursor is first heated to 300-350℃ at a rate of 2-3℃ / min and held at that temperature for 1-2 hours; then heated to 520-560℃ at a rate of 4-6℃ / min and held at that temperature for calcination for 2-3 hours, and then cooled to obtain vanadium pentoxide.

8. A high-purity vanadium pentoxide, characterized in that, It is prepared using the method described in any one of claims 1-7.

9. The high-purity vanadium pentoxide according to claim 8, characterized in that, The product properties of the high-purity vanadium pentoxide are: purity ≥ 99.5%, Na content ≤ 0.015%, and K content ≤ 0.01%.

10. The high-purity vanadium pentoxide according to claim 9, characterized in that, The product properties of the high-purity vanadium pentoxide are: purity ≥ 99.7%, Na content ≤ 0.01%, and K content ≤ 0.01%.

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