Method for preparing low-lead ammonium polyvanadate by using calcified acid vanadium leaching liquid

Abstract

The invention belongs to the field of purification and extraction of vanadium. The invention discloses a method for preparing low-lead ammonium polyvanadate by using a calcified acid vanadium leaching solution. The method comprises the following steps: taking a qualified liquid supernatant of the calcified acid leaching vanadium liquid, and controlling the pH value of the supernatant to be 2.4-3.0; adding ethylenediaminetetraacetic acid into the supernate, and stirring for a preset time to enable lead ions in the solution to be fully complexed with the ethylenediaminetetraacetic acid; adjusting the pH value of the solution to the pH value required by vanadium precipitation under an acidic condition; adding a vanadium precipitation agent into the solution; and heating the solution added with the vanadium precipitation agent to precipitate vanadium, filtering, and drying the solid to obtain the low-lead ammonium polyvanadate. According to the method, EDTA serves as a lead ion complexing agent, lead ions in the solution are combined with EDTA before vanadium precipitation, the stability of the lead ions in the solution is improved, the probability that lead precipitates along with vanadium in the follow-up vanadium precipitation process is reduced, the content of lead in ammonium polyvanadate is reduced, and a low-lead APV product meeting the battery application requirement can be obtained.

Description

Technical Field

[0001] This invention relates to the field of vanadium purification and extraction, and specifically to a method for preparing low-lead ammonium polyvanadate using calcified acid leaching vanadium solution. Background Technology

[0002] Vanadium is an important alloying element widely used in steel, chemical, and aerospace industries, and is often referred to as the "MSG of modern industry." my country is rich in vanadium-titanium magnetite resources. For vanadium extraction from vanadium-titanium magnetite, a common process involves blast furnace ironmaking followed by converter vanadium extraction to obtain vanadium slag, from which vanadium is then extracted. Vanadium extraction from vanadium slag mainly includes sodium vanadium extraction and calcification vanadium extraction processes.

[0003] The sodium vanadium extraction process for vanadium slag first involves mixing vanadium slag with sodium salts (such as sodium carbonate or sodium sulfate) in a specific ratio and then oxidizing and roasting it to convert vanadium into soluble sodium metavanadate. The roasted clinker is then leached in water to allow vanadium to enter the solution. The leachate is then subjected to precipitation treatment by adding ammonium salts and adjusting the pH to alkaline to form ammonium polyvanadate precipitate. The leachate from sodium vanadium extraction is typically alkaline, and the impurity ions in the leachate are generally ions that can coexist under alkaline conditions, such as chromium, aluminum, sodium, and potassium, but lead is not present. Therefore, the preparation of ammonium polyvanadate using sodium vanadium extraction leachate avoids the problem of lead impurities contaminating the ammonium polyvanadate.

[0004] Compared to sodium vanadium extraction, the vanadium slag calcification process has significant advantages in terms of environmental protection, resource utilization, cost-effectiveness, and equipment adaptability. The calcification process mainly includes calcium salt roasting, acid leaching, impurity removal, vanadium precipitation, and melting / reduction. Roasting-acid leaching is the key step affecting the overall vanadium oxide yield. To maximize the vanadium leaching effect from the roasted clinker, a primary acid leaching of the clinker followed by a secondary deep acid leaching of the tailings is currently used. The pH value of the deep leaching is relatively low (approximately 1.0). Under these strongly acidic conditions, some lead in the material is leached into the solution. Subsequent solution circulation causes the lead concentration in the vanadium leaching solution to gradually increase. Currently, the lead concentration in a qualified leaching solution is approximately 0.012 g / L. The lead content in the APV (ammonium polyvanadate) prepared from this solution reaches 0.02%, which cannot meet the quality requirements (lead content <0.01%) for high-end applications such as vanadium batteries.

[0005] Patent CN119410915A discloses a method for acid leaching vanadium extraction and solution purification of vanadium slag calcified clinker, comprising: S1, performing a first acid leaching on the calcified vanadium extraction clinker, and adding a decontaminant in the later stage of the first leaching to remove impurities P and Pb; S2, after the first leaching, filtering and washing to obtain a primary leaching solution, a primary washing solution, and a primary vanadium extraction tailings; S3, performing a second acid leaching on the primary vanadium extraction tailings, and filtering and washing after the second leaching to obtain a secondary leaching solution, a secondary washing solution, and a secondary vanadium extraction tailings; S4, using the primary leaching solution for subsequent vanadium precipitation, using the primary washing solution as the mother liquor for the first acid leaching in S1, using the secondary leaching solution for washing after the first leaching in S2, and using the secondary washing solution as the mother liquor for the second acid leaching in S3.

[0006] Patent CN119640055A discloses a method for removing lead during the vanadium extraction process of vanadium slag calcification, comprising: collecting data from a blank control group; determining the amount of lead removal agent based on the lead concentration data in the qualified acid leaching solution; determining the batch and amount of lead removal agent to be added based on the ratio of lead concentration in the leaching mother liquor to that in the qualified acid leaching solution in the blank control group; adding the lead removal agent in batches; separating the solid and liquid after leaching to obtain lead precipitate and primary purification solution; allowing the primary purification solution to settle and stand, and taking the upper layer of qualified purification solution as lead-free vanadium solution; and precipitating and drying the lead-free vanadium solution to prepare low-lead APV products.

[0007] Existing technologies for reducing lead content in APVs often employ impurity removal agents to remove lead from the solution, which requires more steps, and some impurity removal agents may introduce other impurities into the solution.

[0008] Therefore, how to prepare low-lead ammonium polyvanadate using calcified acid leaching vanadium solution with a simpler process has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0009] To address the aforementioned problems in the prior art, this invention provides a method for preparing low-lead ammonium polyvanadate using calcified acid leaching vanadium solution.

[0010] According to one aspect of the present invention, a method for preparing low-lead ammonium polyvanadate using calcified vanadium leaching solution is provided, the method comprising the following steps: Take the supernatant of the qualified calcified vanadium leaching solution, and control the pH value of the supernatant at 2.4~3.0; Add ethylenediaminetetraacetic acid to the supernatant and stir for a predetermined time to allow the lead ions in the solution to fully complex with the ethylenediaminetetraacetic acid; The pH of the solution is adjusted to the pH value required for vanadium precipitation under acidic conditions; Add a vanadium precipitant to the solution; The solution with the added vanadium precipitant was heated to precipitate vanadium, and the solid was dried after filtration to obtain the low-lead ammonium polyvanadate.

[0011] According to one embodiment of the present invention, the molar amount of ethylenediaminetetraacetic acid added is 1 to 10 times the molar amount of lead ions contained in the supernatant.

[0012] According to one embodiment of the present invention, the stirring time is 30~180 min and the stirring speed is 300~400 r / min.

[0013] According to one embodiment of the present invention, the lead ions are complexed with the ethylenediaminetetraacetic acid at room temperature.

[0014] According to one embodiment of the present invention, the pH value of the solution is adjusted to 1.5-2.2 before adding the vanadium precipitating agent.

[0015] According to one embodiment of the present invention, the vanadium precipitation agent includes at least one of ammonium sulfate, ammonium chloride, ammonium bicarbonate, or ammonium carbonate.

[0016] According to one embodiment of the present invention, the vanadium precipitant is ammonium sulfate.

[0017] According to one embodiment of the present invention, the amount of vanadium precipitation agent added is 0.3 to 1 times the molar amount of vanadium ions, calculated based on ammonium ions.

[0018] According to one embodiment of the present invention, the temperature for vanadium precipitation is 80~100°C.

[0019] According to one embodiment of the present invention, the qualified liquid is allowed to stand for more than 24 hours before the supernatant is taken.

[0020] The method of the present invention for preparing low-lead ammonium polyvanadate using calcified acid leaching vanadium solution has at least one of the following advantages compared with the prior art: (1) The method of preparing low-lead ammonium polyvanadate using calcified acid leaching vanadium solution of the present invention first uses ethylenediaminetetraacetic acid (EDTA) as a lead ion complexing agent before vanadium precipitation. Before vanadium precipitation, the lead ions in the solution are combined with EDTA to improve the stability of lead ions in the solution, reduce the probability of lead precipitation with vanadium in the subsequent vanadium precipitation process, reduce the lead content in ammonium polyvanadate, and obtain a low-lead APV product that meets the requirements of battery application. (2) This invention improves the vanadium-lead separation efficiency and further reduces the lead content in APV products by optimizing the raw material acquisition method, solution pH value, complexation reaction conditions, vanadium precipitation conditions and other aspects. (3) This invention does not introduce other ions. After vanadium precipitation, water treatment is carried out. After the wastewater treatment is completed, the water can be returned to the leaching system for recycling. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a flowchart of a method for preparing low-lead ammonium polyvanadate using calcified acid leaching vanadium solution according to an embodiment of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and specific examples.

[0024] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0025] It should be understood that the embodiments of the invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in this invention, those skilled in the art will readily recognize that various modifications are possible without substantially departing from the teachings of the invention. Accordingly, all such modifications should be included within the scope of the invention. Other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, and parameters of the following exemplary embodiments without departing from the spirit of the invention.

[0026] According to one aspect of the present invention, a method for preparing low-lead ammonium polyvanadate using a calcified acid leaching solution is provided. For example... Figure 1 As shown, the method generally includes the following steps: Step S1: Take the supernatant of the qualified calcified vanadium leaching solution, and control the pH value of the supernatant at 2.4~3.0; Step S2: Add ethylenediaminetetraacetic acid to the supernatant and stir for a predetermined time to allow the lead ions in the solution to fully complex with ethylenediaminetetraacetic acid; Step S3: Adjust the pH of the solution to the pH value required for vanadium precipitation under acidic conditions; Step S4: Add vanadium precipitating agent to the solution; Step S5: Heat the solution with added vanadium precipitant to precipitate vanadium, filter and dry the solid to obtain low-lead ammonium polyvanadate.

[0027] The method of preparing low-lead ammonium polyvanadate using calcified acid leaching vanadium solution of the present invention first uses ethylenediaminetetraacetic acid (EDTA) as a lead ion complexing agent before vanadium precipitation. EDTA reacts with lead ions as follows:

[0028] Before vanadium precipitation, lead ions in the solution are combined with EDTA to improve the stability of lead ions in the solution, reduce the probability of lead precipitating with vanadium during the subsequent vanadium precipitation process, and reduce the lead content in ammonium polyvanadate, thereby obtaining a low-lead APV product that meets the requirements of battery applications.

[0029] Taking the supernatant of the qualified solution can remove solid suspended matter, providing a pure and uniform reaction environment for the subsequent vanadium precipitation reaction, thereby ensuring the high purity and high recovery rate of the final product.

[0030] The pH of the supernatant should be controlled between 2.4 and 3.0, preferably between 2.6 and 2.8. Too high a pH is unfavorable for the binding of lead ions with EDTA, while too low a pH will cause some vanadium ions to precipitate prematurely under acidic conditions. The prematurely formed vanadium precipitate may contain lead ions, leading to an increase in the lead content of the APV product.

[0031] In some embodiments, the molar amount of EDTA added is 1 to 10 times, preferably 2 to 8 times, and more preferably 3 to 5 times, the molar amount of lead ions in the supernatant. Since the solution may contain other ions that consume some of the EDTA, setting the EDTA dosage within this range is intended to promote sufficient complexation of lead ions and achieve the lead reduction target.

[0032] In some embodiments, to ensure sufficient complexation of lead ions with ethylenediaminetetraacetic acid, stirring is required for a stirring time of 30–180 min, preferably 60–120 min. The stirring speed is 300–400 r / min, preferably 300–350 r / min.

[0033] In some embodiments, lead ions complex with ethylenediaminetetraacetic acid (EDTA) at room temperature. If the temperature increases, it promotes the hydrolysis and precipitation of vanadium ions in the solution under these acidic conditions. The prematurely formed vanadium precipitate may contain lead ions, leading to an increase in the lead content of the APV product.

[0034] In some embodiments, after lead ions have fully complexed with ethylenediaminetetraacetic acid (EDTA), the pH of the solution is adjusted to 1.5–2.2, preferably 1.6–2.0. pH adjustment can be achieved by adding sulfuric acid to the solution. Adjusting the pH to this range is suitable for the polymerization and hydrolysis of vanadate ions, which then combine with ammonium ions to form ammonium polyvanadate precipitate, thus improving vanadium yield and resulting in high-purity ammonium polyvanadate. Furthermore, within this pH range, the stability constant of the lead-EDTA complex is very high, effectively "locking in" the lead ions, ensuring they exist in a soluble form in the solution without contaminating the ammonium polyvanadate precipitate. Conversely, if the pH is too low, some lead ions and the EDTA complex may experience decreased stability due to protonation, increasing the risk of lead ions co-precipitating with vanadium.

[0035] The pH of the solution is adjusted to 1.5-2.2 before adding the vanadium precipitant for vanadium precipitation. In some embodiments, the vanadium precipitant includes at least one of ammonium sulfate, ammonium chloride, ammonium bicarbonate, or ammonium carbonate; more specifically, ammonium sulfate is used. Ammonium sulfate does not introduce chloride ions into the system, making it particularly suitable for applications with strict requirements on chloride content, such as vanadium batteries. Using ammonium sulfate as the vanadium precipitant also facilitates subsequent solution recycling.

[0036] In some embodiments, the amount of vanadium precipitant added is 0.3 to 1 times the molar amount of ammonium ions, preferably 0.4 to 0.6 times the molar amount of vanadium ions.

[0037] In some embodiments, the temperature of the vanadium precipitation operation is 50~100℃, preferably 80~100℃.

[0038] In some embodiments, the qualified solution is allowed to stand for more than 24 hours before taking the supernatant, specifically 24 to 48 hours.

[0039] The technical solution of the present invention will be further illustrated by specific embodiments below. Unless otherwise stated, the raw materials, equipment, consumables, etc. used in the following embodiments can all be obtained through conventional commercial means.

[0040] The vanadium leaching solution used in the following examples and comparative examples is a qualified solution after vanadium leaching and roasting, wherein the V content is about 23 g / L and the Pb content is about 0.012 g / L.

[0041] Example 1 The qualified vanadium leaching solution was placed in a beaker and allowed to stand for 24 hours. 1 L of the supernatant (containing 0.012 g of Pb, approximately 5.79 × 10⁻⁶) was then collected. -5 Add sulfuric acid to control the pH value at 2.4~2.6. Add EDTA (6×10⁻⁶ mol) under room temperature and stirring (300 r / min) conditions. -5The solution was prepared by stirring for 40 minutes with EDTA:Pb = 6 mol: 5.79 mol. Sulfuric acid was added to the solution to adjust the pH to 1.5-1.7. Ammonium sulfate was then added, with the amount of ammonium sulfate added being 0.4 times the molar amount of vanadium ions (based on ammonium ion content). The temperature was raised to 90℃, and the mixture was stirred for 60 minutes. The solution was filtered and the solid was dried to obtain APV. The Pb content in the APV was 0.007%, lower than the lead content requirement of less than 0.01% for vanadium battery materials.

[0042] Example 2 The qualified vanadium leaching solution was placed in a beaker and allowed to stand for 36 hours. 1 L of the supernatant (containing 0.012 g of Pb, approximately 5.79 × 10⁻⁶ g) was then collected. -5 Add sulfuric acid to control the pH value at 2.6~2.8, and add EDTA (8×10⁻⁶ mol) under the conditions of room temperature and stirring (330 r / min). -5 The solution was prepared by stirring for 8 mol of EDTA and 5.79 mol of Pb, with the reaction mixture stirred for 80 min. Sulfuric acid was added to the solution to adjust the pH to 1.6–1.8. Ammonium sulfate was then added, with the amount of ammonium sulfate added being 0.45 times the molar amount of vanadium ions (based on ammonium ion content). The mixture was heated to 90 °C and stirred for 70 min. The solution was filtered and the solid was dried to obtain APV. The Pb content in the APV was 0.006%, lower than the lead content requirement of less than 0.01% for vanadium battery materials.

[0043] Example 3 The qualified vanadium leaching solution was placed in a beaker and allowed to stand for 48 hours. 1 L of the supernatant (containing 0.012 g of Pb, approximately 5.79 × 10⁻⁶) was then collected. -5 Add sulfuric acid to control the pH value at 2.6~2.8, and add EDTA (1.5×10 mol) under the conditions of room temperature and stirring (350 r / min). -4 The solution was prepared by stirring for 120 min with EDTA:Pb = 15 mol: 5.79 mol. Sulfuric acid was added to the solution to adjust the pH to 1.8-2.0. Ammonium sulfate was then added, with the amount of ammonium sulfate added being 0.5 times the molar amount of vanadium ions (based on ammonium ion concentration). The mixture was heated to 95℃ and stirred for 80 min. The solution was filtered and the solid was dried to obtain APV. The Pb content in the APV was 0.005%, lower than the lead content requirement of less than 0.01% for vanadium battery materials.

[0044] Example 4 The qualified vanadium leaching solution was placed in a beaker and allowed to stand for 48 hours. 1 L of the supernatant (containing 0.012 g of Pb, approximately 5.79 × 10⁻⁶) was then collected. -5Add sulfuric acid to control the pH value at 2.8~3.0, and add EDTA (2×10⁻⁶ mol) under the conditions of room temperature and stirring (380 r / min). -4 The solution was prepared by stirring for 150 min with EDTA:Pb = 20 mol: 5.79 mol. Sulfuric acid was added to the solution to adjust the pH to 1.9–2.1. Ammonium sulfate was then added, with the amount of ammonium sulfate added being 0.55 times the molar amount of vanadium ions (based on ammonium ion content). The mixture was heated to 95 °C and stirred for 90 min. The solid was then filtered and dried to obtain APV. The Pb content in the APV was 0.005%, lower than the lead content requirement of less than 0.01% for vanadium battery materials.

[0045] Example 5 The qualified vanadium leaching solution was placed in a beaker and allowed to stand for 48 hours. 1 L of the supernatant (containing 0.012 g of Pb, approximately 5.79 × 10⁻⁶) was then collected. -5 Add sulfuric acid to control the pH value at 2.8~3.0, and add EDTA (5×10⁻⁶ mol) under the conditions of room temperature and stirring (400 r / min). -4 The solution was prepared by stirring for 180 min with EDTA:Pb = 50 mol: 5.79 mol. Sulfuric acid was added to the solution to adjust the pH to 2.0-2.2. Ammonium sulfate was then added, with the amount of ammonium sulfate added being 0.6 times the molar amount of vanadium ions (based on ammonium ion content). The temperature was raised to 95℃, and the mixture was stirred for 90 min. The solution was filtered and the solid was dried to obtain APV. The Pb content in the APV was 0.006%, lower than the lead content requirement of less than 0.01% for vanadium battery materials.

[0046] Comparative Example 1 The qualified vanadium leaching solution was placed in a beaker and allowed to stand for 48 hours. 1 L of the supernatant (containing 0.012 g of Pb, approximately 5.79 × 10⁻⁶) was then collected. -5 Add sulfuric acid to the solution to adjust the pH to 1.8-2.0. Add ammonium sulfate to the solution, with the amount of ammonium sulfate added being 0.45 times the molar amount of vanadium ions (calculated as ammonium ions). Heat to 95℃, stir for 80 min, filter, and dry the solid to obtain APV. The Pb content in the APV is 0.026%, which does not meet the requirement of less than 0.01% lead content for vanadium batteries.

[0047] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of the present invention is limited to these examples. Within the framework of the present invention, technical features of the above embodiments or different embodiments can also be combined, and many other variations of different aspects of the present invention as described above exist, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing low-lead ammonium polyvanadate by using calcified acid leaching vanadium solution, characterized in that, The method comprises the following steps: taking supernatant of qualified calciumized acid leaching vanadium solution, wherein the pH value of the supernatant is controlled at 2.4-3.0; adding ethylenediaminetetraacetic acid to the supernatant and stirring for a predetermined time to fully complex lead ions in the solution with the ethylenediaminetetraacetic acid; adjusting the pH value of the solution to a pH value required for vanadium precipitation in an acidic condition; adding a vanadium precipitating agent to the solution; heating the solution to which the vanadium precipitating agent is added to precipitate vanadium, drying the solid after filtration, and obtaining the low-lead ammonium polyvanadate.

2. The method for preparing low-lead polyvanadic acid ammonium by using calcified acid leaching vanadium solution according to claim 1, characterized in that, The added amount of the ethylenediaminetetraacetic acid is 1-10 times the molar amount of lead ions contained in the supernatant.

3. The method for preparing low-lead polyvanadic acid ammonium by using calcified acid leaching vanadium solution according to claim 1, characterized in that, The stirring time is 30-180 min, and the stirring speed is 300-400 r / min.

4. The method for preparing low-lead polyvanadic acid ammonium by using calcified acid leaching vanadium solution according to claim 1, characterized in that, The lead ions are complexed with the ethylenediaminetetraacetic acid at room temperature.

5. The method for preparing low-lead polyvanadic acid ammonium by using calcified acid leaching vanadium solution according to claim 1, characterized in that, The pH value of the solution is adjusted to 1.5-2.2 before adding the vanadium precipitating agent.

6. The method for preparing low-lead polyvanadic acid ammonium by using calcified acid leaching vanadium solution according to claim 1, characterized in that, The vanadium precipitating agent comprises at least one of ammonium sulfate, ammonium chloride, ammonium bicarbonate or ammonium carbonate.

7. The method for preparing low-lead polyvanadic acid ammonium by using calcified acid leaching vanadium solution according to claim 6, characterized in that, The vanadium precipitating agent is ammonium sulfate.

8. The method for preparing low-lead polyvanadic acid ammonium by using calcified acid leaching vanadium solution according to claim 6, characterized in that, The added amount of the vanadium precipitating agent is 0.3-1 times the molar amount of vanadium ions in terms of ammonium ions. 9.The method for preparing low-lead polyvanadic acid ammonium by using calcified acid leaching vanadium solution according to claim 1, characterized in that, The temperature of the vanadium precipitation operation is 80-100℃.

10. The method for preparing low-lead polyvanadic acid ammonium by using calcified acid leaching vanadium solution according to claim 1, characterized in that, The qualified solution is allowed to stand for more than 24 h before the supernatant is taken.

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