A method for purifying and extracting vanadium from secondary resources

Abstract

This invention belongs to the field of waste material and waste liquid treatment technology, and relates to a method for purifying and extracting vanadium from secondary resources. The method includes: reducing the leachate obtained by leaching vanadium-containing waste residue from titanium dioxide waste acid to convert all vanadium into tetravalent vanadium; adjusting the pH to obtain a pre-extraction liquid; extracting the pre-extraction liquid with an acidic phosphorus extractant to obtain an organic phase loaded with vanadium, iron, and titanium; washing the organic phase with dilute sulfuric acid to remove impurities; further processing sequentially to obtain a pentavalent vanadium back-extraction liquid, an oxalate iron complex liquid, and a titanium peroxide complex liquid, and regenerating the extractant; the vanadium recovery rate and product purity are significantly improved, solving the problems of complex processing flow, multiple precipitation and back-extraction, high cost, and insufficient vanadium product purity in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of waste material and waste liquid treatment technology, and in particular to a method for purifying and extracting vanadium from secondary resources. Background Technology

[0002] The sulfuric acid process is one of the mainstream industrial processes for producing titanium dioxide. During large-scale production, this process generates a large amount of titanium dioxide waste acid byproducts, resulting in a massive amount of solid waste. Industry statistics show that for every ton of finished titanium dioxide produced, 6-12 tons of titanium dioxide waste acid are generated simultaneously. This waste acid has a complex composition and significant polluting properties. The concentration of free sulfuric acid in titanium dioxide waste acid can reach 20%-25%, and it is also enriched with various heavy metal ions such as iron, titanium, vanadium, and manganese. It exhibits strong corrosiveness and toxicity, classifying it as a typical hazardous waste. Direct discharge would severely pollute soil, water bodies, and the atmosphere, causing irreversible harm to ecosystems and human health. Therefore, it must undergo professional and harmless treatment.

[0003] Currently, the mainstream treatment methods for titanium dioxide waste acid in the industrial sector are concentration and recovery processes and lime neutralization processes. However, both of these traditional processes have significant technical defects and application drawbacks, making it difficult to achieve efficient, low-cost, and resource-based treatment. The concentration and recovery process requires high-temperature evaporation to concentrate the waste acid and recover sulfuric acid. This process is not only extremely energy-intensive and has high equipment investment costs, but the large amount of metallic impurities in the waste acid easily causes scaling and clogging of the equipment during concentration, significantly reducing equipment lifespan and operating efficiency. Furthermore, it only achieves the recovery of sulfuric acid as a single resource, with all valuable metal components in the waste acid being lost, resulting in extremely low resource utilization. The lime neutralization process achieves harmless treatment by neutralizing sulfuric acid in waste acid with lime. Although the process is simple to operate, its core drawback is that the disposal process generates a large amount of mixed sulfate waste residue. The waste residue is produced in large quantities, has a complex composition, and is difficult to reuse. It can only be disposed of by landfill, which not only occupies a large amount of land resources, but also poses environmental risks such as heavy metal leakage and secondary soil pollution. At the same time, this process only achieves the harmless treatment of waste acid, and cannot recover valuable resources at all, resulting in a serious waste of sulfur and metal resources and extremely high comprehensive treatment costs.

[0004] Vanadium-containing waste slag is a large-scale industrial solid waste generated by various industries such as vanadium metallurgy, steel smelting, petrochemicals, and vanadium extraction from coal. It mainly includes tailings from primary vanadium slag extraction, steel slag from vanadium alloy smelting, spent vanadium catalysts, vanadium extraction waste slag from coal, and various vanadium product production residues. This type of waste slag is abundant and presents significant treatment challenges: First, the overall vanadium grade in the waste slag is low, and it exists in multiple valence states, making extraction and separation difficult. Second, the waste slag is accompanied by toxic heavy metals such as chromium and lead, as well as a large number of impurities such as silicon, aluminum, phosphorus, and iron. These impurities are tightly bound to vanadium, representing a core technical bottleneck in the vanadium separation, purification, and refining process, and easily leading to substandard vanadium product purity. Third, the composition of vanadium-containing waste slag varies greatly depending on the production industry and process, lacking a universal and applicable treatment process, making targeted treatment highly challenging.

[0005] Currently, the industry's treatment processes for vanadium-containing waste slag are mainly divided into pyrometallurgical processes, hydrometallurgical processes, and combined processes of the two. However, all existing processes have significant technical shortcomings, severely limiting their industrial application. Pyrometallurgical processes involve high energy consumption due to high-temperature roasting, severe flue gas pollution, and extremely low extraction efficiency for low-grade vanadium-containing waste slag, resulting in poor recovery rates of valuable vanadium resources. Traditional hydrometallurgical processes consume large amounts of acids and alkalis, have cumbersome processes, and are difficult to effectively remove impurities such as silicon, aluminum, and phosphorus, leading to high subsequent purification costs. While the combined pyrometallurgical-hydrometallurgical process improves the vanadium extraction rate to some extent, the overall process is complex, requires large equipment investment, and has high operating costs. Especially for low-grade vanadium-containing waste slag, the processing cost of existing treatment processes is generally higher than the economic value of vanadium products, resulting in no industrial economic benefits. This leads to a large amount of low-grade vanadium-containing waste slag being stored in the open, causing long-term idle waste of valuable resources such as vanadium, iron, and silicon. Furthermore, the leaching of heavy metals during the storage process causes continuous environmental pollution problems.

[0006] In summary, existing technologies for treating titanium dioxide waste acid suffer from drawbacks such as high energy consumption, high cost, large increase in waste residue, low resource utilization, and severe secondary pollution. Vanadium-containing waste residue treatment faces challenges including difficulty in impurity separation, poor process universality, lack of treatment value for low-grade waste residue, and low resource recovery rate. Furthermore, the industry currently lacks mature processes for the co-treatment of titanium dioxide waste acid and vanadium-containing waste residue, making it impossible to achieve efficient, harmless, and high-value resource utilization of both types of industrial hazardous and solid waste. Therefore, developing a new process route that combines waste treatment with waste disposal, is simple, low-cost, and has high resource utilization, simultaneously achieving the harmless disposal of titanium dioxide waste acid and the high-value resource recovery of vanadium-containing waste residue, is a core technical challenge that urgently needs to be addressed in this field. Summary of the Invention

[0007] Based on the above analysis, the present invention aims to provide a method for purifying and extracting vanadium from secondary resources, in order to solve at least one of the problems existing in the prior art in the disposal of titanium dioxide waste acid and vanadium-containing waste residue, such as complex process flow, high cost, low resource utilization rate, insufficient product purity, and difficulty in co-disposing of the two types of hazardous waste.

[0008] The objective of this invention is mainly achieved through the following technical solutions: A method for purifying and extracting vanadium from secondary resources includes: S1. Reduce the leachate obtained by leaching vanadium-containing waste residue from titanium dioxide waste acid to convert all vanadium into tetravalent vanadium. After adjusting the pH, obtain the pre-extraction solution. S2. The pre-extraction solution was extracted using an acidic phosphorus extractant to obtain an organic phase loaded with vanadium, iron, and titanium. S3. Wash the organic phase with dilute sulfuric acid to remove impurities; S4. Selective back-extraction of the washed organic phase was performed using hydrogen peroxide solution to obtain pentavalent vanadium back-extraction solution; S5. The organic phase after selective back-extraction in step S4 is back-extracted with oxalic acid solution to obtain oxalic acid iron complex solution. S6. The organic phase after back-extraction in step S5 is back-extracted using a mixed solution of sulfuric acid and hydrogen peroxide to obtain a titanium peroxide complex solution and regenerate the acidic phosphorus extractant.

[0009] Preferably, step S1 includes: S101: Adjust the pH value of the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching to 1.0-2.0 before reduction to ensure the acidic environment required for the reduction reaction; add a reducing agent to the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching and reduce it at 60-80℃; S102: Adjust the pH value of the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching process to 1.5-2.5.

[0010] Preferably, the reducing agent in step S101 is selected from one or more of sodium sulfite, sodium thiosulfate, sodium metabisulfite, sodium sulfide, ascorbic acid, oxalic acid, sulfur dioxide, and reduced iron powder.

[0011] Preferably, the pH of the dilute sulfuric acid solution used for washing in step S3 is 1 to 2.

[0012] Preferably, step S4 includes: using hydrogen peroxide solution to perform multi-stage cross-flow back-extraction on the washed organic phase to obtain a vanadium-poor organic phase and a pentavalent vanadium back-extraction solution.

[0013] Preferably, the multi-stage cross-flow cyclic back-extraction includes: Multiple cross-flow interconnected circulation units, each circulation unit is equipped with an inlet, an organic phase inlet, an outlet, and an organic phase outlet; In two adjacent recycling units, the organic phase outlet of the preceding recycling unit is connected in series with the organic phase inlet of the following recycling unit; the recycling unit where the vanadium-poor organic phase discharge end after vanadium back-extraction is located is defined as the first-level recycling unit, and the recycling unit where the vanadium-rich organic phase inlet end is located in multiple connected recycling units is defined as the nth-level recycling unit; the vanadium-rich organic phase enters from the organic phase inlet of the nth-level recycling unit, and after being back-extracted through multiple recycling units in sequence, it is transformed into a vanadium-poor organic phase and discharged from the organic phase outlet of the first-level recycling unit; where n is the recycling unit level sequence. The back-extraction reagent enters through the inlet and exits through the outlet of the first-stage circulation unit. After passing through the external circulation pipeline, it re-enters the inlet and completes multiple cycles within the first-stage circulation unit. Then, it enters the inlet of the next-stage circulation unit and circulates multiple times within the next-stage circulation unit, and so on, until it completes multiple cycles within the nth-stage circulation unit and is discharged through the outlet of the nth-stage circulation unit to obtain pentavalent vanadium back-extraction solution. Each stage of the circulation unit can independently circulate the aqueous phase through the inlet, outlet, and external circulation pipeline; after the circulation ends, the intermediate back-extraction product is discharged from the outlet of the previous stage of the circulation unit, and the intermediate back-extraction product is used as the inlet of the next stage of the circulation unit for continued circulation. In the circulation unit, the back-extraction reagent moves in the opposite direction to the organic phase, resulting in countercurrent extraction. After each cycle of back-extraction in each circulation unit, hydrogen peroxide is added before the next cycle begins.

[0014] Preferably, the concentration of hydrogen peroxide solution required for different circulation units gradually increases from the first-level circulation unit to the nth-level circulation unit, with each level increasing by 0.2% to 1.0%.

[0015] Preferably, when the vanadium concentration in the hydrogen peroxide solution of the nth stage circulation unit reaches 8~10 g / L, the pentavalent vanadium back-extraction solution is discharged from the outlet of the nth stage circulation unit.

[0016] Preferably, in step S6, the sulfuric acid concentration in the mixed solution is 2-4 mol / L, and the hydrogen peroxide mass concentration in the mixed solution is 1%-5%.

[0017] A combined application of titanium dioxide waste acid and vanadium-containing waste residue for obtaining precursors for the preparation of vanadium, and / or titanium, and / or iron, using the above-described method for purifying and extracting vanadium from secondary resources.

[0018] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: (1) This invention utilizes an integrated continuous process of vanadium pre-reduction and valence control, synergistic co-extraction of vanadium, iron, and titanium, and selective back-extraction in the order of vanadium → iron → titanium. Using vanadium-containing waste residue from titanium dioxide waste acid leaching as raw material, it achieves efficient separation and purification of vanadium, iron, and titanium sequentially. It realizes waste-to-waste treatment and high-value utilization of resources, simultaneously obtaining high-purity pentavalent vanadium back-extraction solution, ferric oxalate complex solution, and titanium peroxide complex solution within a single process flow. The extractant is recyclable, the process is short, energy consumption is low, and reagent consumption is minimal. The vanadium recovery rate and product purity are significantly improved. The vanadium concentration in the extraction solution is 8–10 g / L, with a purity ≥99.99% and a yield ≥98%; the iron concentration in the ferric oxalate complex solution is 5–10 g / L, with a purity ≥99.9%; and the titanium peroxide complex solution has a titanium concentration of 1–5 g / L, with a purity ≥99.9%. This solution addresses one of the problems of existing technologies, such as complex processing procedures, multiple precipitation and back-extraction, high costs, and insufficient purity of vanadium products. It also overcomes one of the industry pain points, such as the difficulty in co-utilizing titanium dioxide waste acid and vanadium-containing waste residue, low recovery rate of valuable metals, and the generation of secondary pollution and large amounts of waste residue.

[0019] (2) The present invention adopts a co-processing method of directly leaching vanadium-containing waste residue with titanium dioxide waste acid, which realizes the treatment of hazardous waste with waste, greatly reduces acid consumption and treatment costs, and solves the technical problems of difficult co-utilization of titanium dioxide waste acid and vanadium-containing waste residue, complex treatment process, low resource utilization rate and easy generation of secondary pollution.

[0020] (3) The present invention directionally reduces vanadium in the leachate to tetravalent and precisely controls the pH, thereby improving the extraction selectivity and separation efficiency, enhancing the separation effect of vanadium and impurity elements, avoiding multiple neutralization and precipitation, and solving the technical problems of difficult extraction and separation of vanadium from low-grade vanadium-containing waste residue and serious interference from impurities.

[0021] (4) The present invention uses acidic phosphorus extractant to simultaneously co-extract vanadium, iron and titanium, realizing the integrated loading of the three valuable metals, simplifying the process flow, and solving the technical problems of the traditional step-by-step extraction process being cumbersome, requiring large equipment investment and high operating costs.

[0022] (5) The present invention uses low-concentration hydrogen peroxide to selectively back-extract vanadium in a graded cross-flow manner, oxidizing vanadium to pentavalent and forming a stable water-soluble peroxide vanadium complex, thereby achieving efficient separation of vanadium from iron and titanium and obtaining high-purity pentavalent vanadium back-extraction solution, thus solving the technical problems of incomplete separation of vanadium, iron and titanium and insufficient purity of vanadium products.

[0023] (6) The present invention uses oxalic acid solution to back-extract iron in steps. It utilizes the strong complexation effect of oxalic acid with iron to selectively remove iron without back-extracting titanium, thus obtaining a high-purity oxalic acid iron complex solution, which solves the technical problems of difficult separation of iron from vanadium and titanium and mutual contamination of products.

[0024] (7) The present invention uses a sulfuric acid-hydrogen peroxide mixed solution to back-extract titanium and regenerate the extractant, which realizes efficient recovery of titanium and reusability of the extractant, reduces reagent consumption, and solves the technical problems of large extractant loss, incomplete recovery of valuable metals and poor process economy.

[0025] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0026] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0027] Figure 1 This is a process flow diagram of the method for purifying and extracting vanadium from secondary resources according to the present invention; Figure 2 This is a process flow diagram of the multi-stage cross-flow cyclic back-extraction of the present invention. Detailed Implementation

[0028] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0029] On one hand, this invention discloses a method for purifying and extracting vanadium from secondary resources, comprising: S1. Reduce the leachate obtained by leaching vanadium-containing waste residue from titanium dioxide waste acid to convert all vanadium into tetravalent vanadium. After adjusting the pH, obtain the pre-extraction solution. S2. The pre-extraction solution was extracted using an acidic phosphorus extractant to obtain an organic phase loaded with vanadium, iron, and titanium. S3. Wash the organic phase with dilute sulfuric acid to remove impurities such as sodium and potassium; S4. Selective back-extraction of the washed organic phase was performed using hydrogen peroxide solution to obtain pentavalent vanadium back-extraction solution; S5. The organic phase after selective back-extraction in step S4 is back-extracted with oxalic acid solution to obtain oxalic acid iron complex solution. S6. The organic phase after back-extraction in step S5 is back-extracted using a mixed solution of sulfuric acid and hydrogen peroxide to obtain a titanium peroxide complex solution and regenerate the acidic phosphorus extractant.

[0030] In implementation, step S1 directly uses titanium dioxide waste acid to leach vanadium-containing waste residue, achieving co-processing of hazardous waste, significantly reducing acid consumption and treatment costs, directionally reducing vanadium to tetravalent, improving extraction selectivity and separation efficiency, enhancing the separation effect of V from other impurity elements in the pre-extraction liquid, and avoiding multiple neutralization and precipitation; vanadium, iron, and titanium are extracted simultaneously, and then selectively back-extracted in the order of vanadium → iron → titanium to achieve efficient separation of the three, obtaining high-purity vanadium, iron, and titanium products without complex purification.

[0031] Compared with existing technologies, this invention utilizes an integrated continuous process of vanadium pre-reduction and valence control, synergistic co-extraction of vanadium, iron, and titanium, and stepwise selective back-extraction in the order of vanadium → iron → titanium. Using vanadium-containing waste residue from titanium dioxide waste acid leaching as raw material, it achieves efficient separation and purification of vanadium, iron, and titanium sequentially. This process realizes waste-to-waste treatment and high-value utilization of resources, simultaneously obtaining high-purity pentavalent vanadium back-extraction solution, ferric oxalate complex solution, and titanium peroxide complex solution within a single process flow. The extractant is recyclable, the process is short, energy consumption is low, reagent consumption is minimal, and vanadium recovery rate and product purity are significantly improved. The pentavalent vanadium back-extraction solution has a vanadium concentration of 8–10 g / L, a purity of ≥99.99%, and a yield of ≥98%; the ferric oxalate complex solution has an iron concentration of 5–10 g / L and a purity of ≥99.9%; and the titanium peroxide complex solution has a titanium concentration of 1–5 g / L and a purity of ≥99.9%. This solves the problems of complex processing procedures, multiple precipitation and back-extraction, high costs, and insufficient purity of vanadium products in existing technologies. At the same time, it overcomes the industry pain points of difficulty in co-utilizing titanium dioxide waste acid and vanadium-containing waste residue, low recovery rate of valuable metals, and easy generation of secondary pollution and large amounts of waste residue.

[0032] Compared with existing technologies, this invention adopts a synergistic treatment method of directly leaching vanadium-containing waste residue with titanium dioxide waste acid, which realizes the treatment of hazardous waste with waste, significantly reduces acid consumption and treatment costs, and solves the technical problems of difficult co-utilization of titanium dioxide waste acid and vanadium-containing waste residue, complex treatment process, low resource utilization rate, and easy generation of secondary pollution.

[0033] Specifically, the main elemental composition of the leachate obtained from the acid leaching of titanium dioxide waste and vanadium-containing waste residue in S1 is shown in the table below: Table 1. Elemental composition of vanadium-containing waste leachate from titanium dioxide waste acid leaching.

[0034] Specifically, step S1 includes: S101: Adjust the pH value of the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching to 1.0-2.0 before reduction to ensure the acidic environment required for the reduction reaction; add a reducing agent to the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching and reduce it at 60-80℃; S102: Adjust the pH of the vanadium-containing waste slag leachate from the titanium dioxide waste acid leaching after reduction to 1.5-2.5 to meet the optimal pH range of the acidic phosphorus extractant in step S2, and obtain the pre-extraction liquid after filtration.

[0035] Specifically, in step S101, the reducing agent is selected from one or more of sodium sulfite, sodium thiosulfate, sodium metabisulfite, sodium sulfide, ascorbic acid, oxalic acid, sulfur dioxide, and reduced iron powder.

[0036] Specifically, in step S101, the amount of reducing agent used is 1 to 1.3 times the theoretical equivalent required for reduction.

[0037] Specifically, the reduction temperature in step S101 can be 60°C, 65°C, 70°C, 75°C or 80°C.

[0038] It should be noted that sodium sulfite, sodium thiosulfate, sodium metabisulfite, sodium sulfide, ascorbic acid, oxalic acid, sulfur dioxide, and reduced iron powder can increase the reduction reaction rate at 60~80℃, while preventing incomplete reduction due to excessively low temperature.

[0039] Specifically, in step S2, the extraction ratio is O / A = 1~2:1, the number of extraction stages is 2~4, and the temperature is 40~50℃, which can be 40℃, 42℃, 44℃, 46℃, 48℃ or 50℃.

[0040] It should be noted that an extraction temperature of 40-50℃ can improve the extraction efficiency of vanadium; this temperature can also reduce the viscosity of the organic phase, allowing the organic phase and aqueous phase to separate quickly and clearly, avoiding emulsification, entrainment or the appearance of a third phase, and improving the stability of continuous operation.

[0041] Specifically, in step S2, the acidic phosphorus extractant, by volume fraction, includes 10-30% of the main extractant, 5-15% of the co-extractant, and the remainder is a diluent.

[0042] Specifically, the volume fraction of the main extractant can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, or 30%; the volume fraction of the co-extractant can be 5%, 7%, 9%, 11%, 13%, or 15%.

[0043] Specifically, the main extractant is one or more of P204 and P507; the co-extractant is one or more of TBP (tributyl phosphate), TRPO (trialkylphosphine oxide), 2-octanol, isooctanol, and n-octanol; and the diluent can be kerosene.

[0044] Compared with existing technologies, this invention uses acidic phosphorus extractants to simultaneously co-extract vanadium, iron, and titanium, achieving integrated loading of the three valuable metals, simplifying the process flow, and solving the technical problems of cumbersome step-by-step extraction processes, large equipment investment, and high operating costs in traditional processes.

[0045] Specifically, the pH of the dilute sulfuric acid solution used for washing in step S3 is 1~2.

[0046] Preferably, step S3, washing the organic phase with dilute sulfuric acid, includes: performing 1-2 stages of countercurrent washing at 40-50°C using a centrifugal extractor to obtain a post-wash organic load and a wash water ratio of O / A = 10-15:1.

[0047] Specifically, the washing temperature can be 40℃, 42℃, 44℃, 46℃, 48℃ or 50℃.

[0048] Step S4 includes: using hydrogen peroxide solution to perform multi-stage cross-flow back-extraction on the washed organic phase to obtain a vanadium-poor organic phase and a pentavalent vanadium back-extraction solution.

[0049] Specifically, the mass concentration range of the hydrogen peroxide solution in step S4 is 0.5% to 3%, and can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3.0%.

[0050] Specifically, in step S4, the multi-stage cross-flow cyclic back-extraction ratio O / A = 1~3:1, the temperature is 20~30℃, and it can be 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3.0:1, with 2 to 3 stages.

[0051] It should be noted that H2O2 can react with VO extracted into the organic phase. 2+ The ions react. Not only are they oxidized from V(IV) to V(V), but more importantly, V(V) reacts with H₂O₂ to form a very stable and water-soluble orange-red "vanadium peroxide complex" (such as VO(O₂)). + The iron is displaced into the aqueous phase, thus achieving the purpose of back-extraction. Iron cannot form stable, soluble complexes with hydrogen peroxide, and therefore does not undergo effective coordination reactions; thus, iron is not back-extracted. Although titanium can react with hydrogen peroxide to form corresponding titanium peroxide complexes, this is limited by reaction conditions. Sufficient acidity is required to back-extract it from the organic phase to the aqueous phase, and the acidity of a simple hydrogen peroxide solution is insufficient. Therefore, in this back-extraction step, virtually no titanium is back-extracted.

[0052] Using 2-3 stages of cross-flow back-extraction to gradually increase the back-extraction depth can completely remove vanadium from the organic phase. The back-extraction solution has uniform composition and stable purity, making it suitable for continuous production.

[0053] Specifically, multi-level cross-flow cyclic back-extraction, such as Figure 2 As shown, it includes: Multiple cross-flow interconnected circulation units, each circulation unit is equipped with an inlet, an organic phase inlet, an outlet, and an organic phase outlet; In two adjacent recycling units, the organic phase outlet of the preceding recycling unit is connected in series with the organic phase inlet of the following recycling unit; the recycling unit where the vanadium-poor organic phase discharge end after vanadium back-extraction is located is defined as the first-level recycling unit, and the recycling unit where the vanadium-rich organic phase inlet end is located in multiple connected recycling units is defined as the nth-level recycling unit; the vanadium-rich organic phase enters from the organic phase inlet of the nth-level recycling unit, and after being back-extracted through multiple recycling units in sequence, it is transformed into a vanadium-poor organic phase and discharged from the organic phase outlet of the first-level recycling unit; where n is the recycling unit level sequence. The back-extraction reagent enters through the inlet and exits through the outlet of the first-stage circulation unit. After passing through the external circulation pipeline, it re-enters the inlet and completes multiple cycles within the first-stage circulation unit. Then, it enters the inlet of the next-stage circulation unit and circulates multiple times within the next-stage circulation unit, and so on, until it completes multiple cycles within the nth-stage circulation unit and is discharged through the outlet of the nth-stage circulation unit to obtain pentavalent vanadium back-extraction solution. Each stage of the circulation unit can independently circulate the aqueous phase through the inlet, outlet, and external circulation pipeline; after the circulation ends, the intermediate back-extraction product is discharged from the outlet of the previous stage of the circulation unit, and the intermediate back-extraction product is used as the inlet of the next stage of the circulation unit for continued circulation. In the circulation unit, the back-extraction reagent moves in the opposite direction to the organic phase, resulting in countercurrent extraction. After each cycle of back-extraction in each circulation unit, hydrogen peroxide is added before the next cycle begins.

[0054] Specifically, when the vanadium concentration in the hydrogen peroxide solution of the nth-stage circulation unit reaches 8~10 g / L, the pentavalent vanadium back-extraction solution is discharged from the outlet of the nth-stage circulation unit.

[0055] In implementation, taking a 3-stage cross-flow cyclic back-extraction as an example, there are 3 stages of cyclic units: The vanadium-rich organic phase enters from the organic phase inlet of the third-stage circulation unit and is finally discharged from the organic phase outlet of the first-stage circulation unit. Hydrogen peroxide solutions of different concentrations enter from the inlets of the first, second, and third-stage circulation units respectively. The vanadium-rich organic phase is sequentially back-extracted with hydrogen peroxide solutions of different concentrations through the third, second, and first-stage circulation units. Meanwhile, the hydrogen peroxide solution in the three circulation units continuously enriches vanadium as the back-extraction solution. When the vanadium concentration in the hydrogen peroxide solution in the third-stage circulation unit reaches 8~10 g / L, the hydrogen peroxide solution in the third-stage circulation unit is discharged as a qualified pentavalent vanadium back-extraction solution. The hydrogen peroxide solution that has completed back-extraction in the second-stage circulation unit is used as a new back-extraction reagent in the third-stage circulation unit. Similarly, the hydrogen peroxide solution that has completed back-extraction in the first-stage circulation unit is used as a new back-extraction reagent in the second-stage circulation unit, and new hydrogen peroxide solution is added to the first-stage circulation unit as a new back-extraction reagent.

[0056] In each cycle of the first-stage circulation unit to the third-stage circulation unit, hydrogen peroxide solution is replenished from the hydrogen peroxide solution inlet, so that the mass of hydrogen peroxide replenished is greater than or equal to the amount of hydrogen peroxide consumed. When the vanadium concentration in the hydrogen peroxide solution reaches 8-10 g / L again in the third-stage circulation unit, the hydrogen peroxide solution in the third-stage circulation unit is discharged as a qualified pentavalent vanadium back-extraction solution. The hydrogen peroxide solutions that have completed back-extraction in the first-stage and second-stage circulation units are used as back-extraction reagents for the next stage.

[0057] Preferably, the concentration of hydrogen peroxide solution replenished in different circulation units gradually increases from the first circulation unit to the nth circulation unit, with each level increasing by 0.2% to 1.0%.

[0058] Furthermore, using a three-stage cross-flow back-extraction process as an example, the concentration of hydrogen peroxide solution replenished in different stages of the circulation unit is illustrated: First-stage circulation unit: Prepare a low-concentration hydrogen peroxide solution (e.g., 0.5% ~ 1.0%). Second cycle unit: Prepare a medium concentration hydrogen peroxide solution (e.g., 1.2% ~ 2.0%). Level 3 circulation unit: Prepare high-concentration hydrogen peroxide solution (e.g., 2.2% ~ 3.0%).

[0059] Compared with existing technologies, this invention uses low-concentration hydrogen peroxide for staged cross-flow selective back-extraction of vanadium, oxidizing vanadium to pentavalent and forming a stable water-soluble vanadium peroxide complex, thereby achieving efficient separation of vanadium from iron and titanium and obtaining a high-purity pentavalent vanadium back-extraction solution. This solves the technical problems of incomplete separation of vanadium, iron and titanium and insufficient purity of vanadium products.

[0060] Regarding step S5, it should be noted that ferric iron readily forms a stable complex [Fe(C2O4)3]³ with oxalate. - (Stability constant K≈1.6×10) 20The complexation reaction is extremely fast, and the iron oxalate complex exists stably in the solution. After the hydrogen peroxide treatment in step S3, the titanium has been transformed into a complex of titanium peroxide and the organic phase in the organic phase. Due to the high kinetic energy barrier of coordination exchange, the oxalate group cannot effectively replace the peroxy group, so the titanium cannot be back-extracted from the organic phase, thus achieving the separation of titanium and iron.

[0061] Specifically, the concentration of the oxalic acid solution in step S5 is 0.1~0.5 mol / L, which can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L.

[0062] It should be noted that insufficient oxalate content prevents sufficient complexation with iron in the organic phase, resulting in incomplete iron back-extraction and high residual iron in the organic phase. Furthermore, excessively low complexation solution concentration increases subsequent processing costs; excessively high oxalate concentration easily triggers salting out and solid precipitation, leading to poor emulsification and phase separation, and also increases raw material costs. Controlling the oxalate solution concentration to 0.1~0.5 mol / L ensures a suitable oxalate concentration, allowing for stable formation of an iron oxalate complex with iron, ensuring thorough iron back-extraction; simultaneously, it stabilizes the complex system, preventing precipitation and ensuring good phase separation between the two phases.

[0063] Specifically, step S5 includes: controlling the ratio O / A = 5~10:1, and obtaining a lean iron organic phase and an iron oxalate complex solution by countercurrent back-extraction in a centrifugal extractor at 40~50℃ for 2~5 stages.

[0064] Specifically, in step S5, the back-extraction ratio O / A is 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1.

[0065] A back-extraction temperature of 40-50℃ can effectively reduce the viscosity of the organic phase, accelerate the decomposition and mass transfer rate of iron, and make the two phases clearly separated and without emulsification, ensuring continuous and stable operation; at the same time, the ferric oxalate complex is stable at this temperature and will not decompose.

[0066] With 2 to 5 stages of back-extraction, the two phases flow in opposite directions and come into full contact multiple times, gradually increasing the iron back-extraction rate and removing iron from the organic phase to the maximum extent. At the same time, it ensures that the ferric oxalate complex solution has uniform composition and stable quality, making it suitable for continuous operation of centrifugal extractors.

[0067] Compared with existing technologies, this invention uses oxalic acid solution for stepwise back-extraction of iron, and utilizes the strong complexation of oxalic acid with iron to selectively remove iron without back-extracting titanium, thus obtaining a high-purity oxalate iron complex solution, which solves the technical problems of difficult separation of iron from vanadium and titanium and cross-contamination of products.

[0068] Specifically, in step S6, the sulfuric acid concentration in the mixed solution is 2~4 mol / L, which can be 2 mol / L, 3 mol / L, or 4 mol / L; the hydrogen peroxide mass concentration in the mixed solution is 1%~5%, which can be 1%, 2%, 3%, 4%, or 5%.

[0069] It should be noted that the sulfuric acid concentration in the mixed solution is 2-4 mol / L and the hydrogen peroxide concentration is 1%-5%, which forces the titanium peroxide complex to undergo protonation and rearrangement, forming a new, more water-soluble material structure (such as [Ti(O2)(H2O)4]²). + Or [Ti(O2)(SO4)2] 2- This improves the back-extraction efficiency, while the high acidity inhibits the hydrolysis and polymerization of titanium, preventing the formation of insoluble titanium oxides and achieving effective back-extraction of titanium.

[0070] Specifically, step S6 includes: using a mixed solution of sulfuric acid and hydrogen peroxide as the back-extraction reagent, controlling the ratio to be O / A = 5~10:1, and obtaining a blank extractant and a titanium peroxide complex solution by countercurrent back-extraction in a centrifugal extractor at 25~30℃ for 2~5 stages.

[0071] The reaction is mild at a back-extraction temperature of 25~30℃, the hydrogen peroxide decomposition rate is low, and the oxidative complexation system is stable. At this temperature, the two phases have good fluidity and clear phase separation, making it suitable for continuous operation of centrifugal extractors.

[0072] The number of back-extraction stages 2 to 5 allows for multi-stage counter-current contact between the two phases, enabling progressively deeper back-extraction of titanium ions, thoroughly purifying the organic phase, and obtaining a recyclable blank extractant; at the same time, it ensures uniform enrichment of titanium and stable quality of the complexing solution.

[0073] Compared with existing technologies, this invention uses a sulfuric acid-hydrogen peroxide mixed solution to back-extract titanium and regenerate the extractant, achieving efficient recovery of titanium and reusability of the extractant, reducing reagent consumption, and solving the technical problems of high extractant loss, incomplete recovery of valuable metals, and poor process economy.

[0074] Secondly, this invention discloses a combined application of titanium dioxide waste acid and vanadium-containing waste residue for obtaining precursors for the preparation of vanadium, and / or titanium, and / or iron, using the above-described method for purifying and extracting vanadium from secondary resources.

[0075] To better illustrate the present invention, the following embodiments and comparative examples are provided: Example 1 This embodiment discloses a method for purifying and extracting vanadium from secondary resources, as shown in Figure 1, including: S1. The leachate obtained by leaching vanadium-containing waste residue from titanium dioxide waste acid is reduced to convert all vanadium into tetravalent vanadium. After adjusting the pH, the pre-extraction solution is obtained, which includes: S101: Adjust the pH value of the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching to 1.3 before reduction to ensure the acidic environment required for the reduction reaction; add a reducing agent to the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching to the reducing agent, sulfur dioxide is selected as the reducing agent, and the amount of reducing agent is 1.1 times the theoretical equivalent required for reduction, and reduce at 60℃. S102: Adjust the pH value of the vanadium-containing waste slag leachate from the titanium dioxide waste acid leaching after reduction to 2.0 to meet the optimal pH value range of the acidic phosphorus extractant in step S2, and obtain the pre-extraction liquid after filtration.

[0076] The elemental composition of the vanadium-containing waste residue leachate from titanium dioxide waste acid leaching is as follows: V 5.6 g / L, Fe 38 g / L, Ti 0.6 g / L, and the contents of Na, Ca, Mg, Mn, Al, Cr, P, Si, Sc, etc. are in trace to gram concentrations.

[0077] S2. The pre-extraction solution is extracted using an acidic phosphorus extractant to obtain an organic phase loaded with vanadium, iron, and titanium. The acidic phosphorus extractant, by volume fraction, includes 20% P2O4 (main extractant), 10% TBP (co-extractant), and the remainder is kerosene diluent. The extraction ratio is O / A = 1.5:1, the extraction stage is 3 stages, and the temperature is 45℃.

[0078] S3. Wash the organic phase with dilute sulfuric acid at pH 1.5 to remove impurities such as sodium and potassium, including: after two-stage countercurrent washing in a centrifugal extractor at 45°C, the washed organic load and wash water are obtained, with the ratio controlled at O / A = 12:1.

[0079] S4. Using hydrogen peroxide solution, the washed organic phase is subjected to multi-stage cross-flow circulation back-extraction to obtain a vanadium-poor organic phase and a pentavalent vanadium back-extraction solution. The back-extraction ratio O / A = 1.0:1, and a 3-stage cross-flow back-extraction is used to selectively back-extract the washed organic phase to obtain a pentavalent vanadium back-extraction solution. The temperature is 25℃. The vanadium-rich organic phase enters from the organic phase inlet of the third-stage circulation unit and is finally discharged from the organic phase outlet of the first-stage circulation unit. Hydrogen peroxide solutions of different concentrations enter from the inlets of the first, second, and third-stage circulation units respectively. The vanadium-rich organic phase is sequentially back-extracted with hydrogen peroxide solutions of different concentrations through the third, second, and first-stage circulation units. Meanwhile, the hydrogen peroxide solution in the three circulation units continuously enriches vanadium as the back-extraction solution. When the vanadium concentration in the hydrogen peroxide solution in the third-stage circulation unit reaches approximately 9 g / L, the hydrogen peroxide solution in the third-stage circulation unit is discharged as a qualified pentavalent vanadium back-extraction solution. The hydrogen peroxide solution that has completed back-extraction in the second-stage circulation unit is used as a new back-extraction reagent in the third-stage circulation unit. Similarly, the hydrogen peroxide solution that has completed back-extraction in the first-stage circulation unit is used as a new back-extraction reagent in the second-stage circulation unit, and new hydrogen peroxide solution is added to the first-stage circulation unit as a new back-extraction reagent.

[0080] In each cycle of the first-stage circulation unit to the third-stage circulation unit, hydrogen peroxide solution is replenished from the hydrogen peroxide solution inlet, so that the mass of hydrogen peroxide replenished is greater than or equal to the amount of hydrogen peroxide consumed. The vanadium concentration in the hydrogen peroxide solution in the third-stage circulation unit reaches nearly 9 g / L again. The hydrogen peroxide solution in the third-stage circulation unit is discharged as a qualified pentavalent vanadium back-extraction solution. The hydrogen peroxide solutions that have completed back-extraction in the first and second-stage circulation units are used as back-extraction reagents for the next stage. The pentavalent vanadium back-extraction solution is collected from the outlet of the third-stage circulation unit.

[0081] The hydrogen peroxide solution inlet of the primary circulation unit (stage 1) is supplemented with a hydrogen peroxide solution concentration of 0.8%; the hydrogen peroxide solution inlet of the intermediate circulation unit (stage 2) is supplemented with a hydrogen peroxide solution concentration of 1.6%; and the hydrogen peroxide solution inlet of the final circulation unit (stage 3) is supplemented with a hydrogen peroxide solution concentration of 2.6%.

[0082] S5. The organic phase after selective back-extraction in step S4 is back-extracted using 0.3 mol / L oxalic acid solution, with the ratio O / A controlled at 7:1. After three-stage countercurrent back-extraction in a centrifugal extractor at 45°C, an iron-poor organic phase and an oxalate complex solution are obtained.

[0083] S6. A mixed solution containing 3 mol / L sulfuric acid and 3% hydrogen peroxide was used as the back-extraction reagent. The ratio was controlled at O / A = 7:1. After three-stage countercurrent back-extraction in a centrifugal extractor at 28℃, a blank extractant and a titanium peroxide complex solution were obtained, thus regenerating the extractant.

[0084] ICP-OES analysis of pentavalent vanadium back-extraction solution, ferric oxalate complex solution, and titanium peroxide complex solution showed the following results: The vanadium concentration in the pentavalent vanadium back-extraction solution was 8.6 g / L, the purity was 99.993%, and the yield reached 98.57%. The Fe concentration in the ferric oxalate complex solution was 7.8 g / L, and the purity was 99.96%. The concentration of Ti in the titanium peroxide complex solution was 1.8 g / L, and the purity was 99.94%.

[0085] Example 2 This embodiment discloses a method for purifying and extracting vanadium from secondary resources, as shown in Figure 1, including: S1. The leachate obtained by leaching vanadium-containing waste residue from titanium dioxide waste acid is reduced to convert all vanadium into tetravalent vanadium. After adjusting the pH, the pre-extraction solution is obtained, which includes: S101: Adjust the pH value of the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching to 1.5 before reduction to ensure the acidic environment required for the reduction reaction; add a reducing agent to the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching to the reducing agent, oxalic acid is selected as the reducing agent, and the amount of reducing agent is 1.2 times the theoretical equivalent required for reduction, and reduce at 70℃. S102: Adjust the pH value of the vanadium-containing waste slag leachate from the titanium dioxide waste acid leaching after reduction to 2.2 to meet the optimal pH value range of the acidic phosphorus extractant in step S2, and obtain the pre-extraction liquid after filtration.

[0086] The elemental composition of the vanadium-containing waste residue leachate from titanium dioxide waste acid leaching is as follows: V 4.2 g / L, Fe 29 g / L, Ti 0.8 g / L, and the contents of Na, Ca, Mg, Mn, Al, Cr, P, Si, Sc, etc. are in trace to gram concentrations.

[0087] S2. The pre-extraction solution was extracted using an acidic phosphorus extractant to obtain an organic phase loaded with vanadium, iron, and titanium. The acidic phosphorus extractant, by volume fraction, includes 15% P204 (main extractant), 5% TBP (co-extractant), and the remainder is kerosene diluent; The extraction ratio was O / A = 2:1, the extraction stage was 3, and the temperature was 45℃.

[0088] S3. Wash the organic phase with dilute sulfuric acid at pH 2.0 to remove impurities such as sodium and potassium, including: After two-stage countercurrent washing in a centrifugal extractor at 45°C, the washed organic load and wash water were obtained, with the ratio controlled at O / A = 10:1.

[0089] S4. Using hydrogen peroxide solution, the washed organic phase is back-extracted in a multi-stage cross-flow cycle to obtain a vanadium-poor organic phase and a pentavalent vanadium back-extraction solution. The back-extraction ratio O / A = 2:1, and a 3-stage cross-flow back-extraction is used to selectively back-extract the washed organic phase to obtain a pentavalent vanadium back-extraction solution. The temperature is 30℃. Multi-stage cross-flow circulation back-extraction uses the same 3-stage cross-flow circulation back-extraction as in Example 1. In each cycle, hydrogen peroxide solution is replenished from the hydrogen peroxide solution inlet, so that the mass of hydrogen peroxide replenished is greater than or equal to the amount of hydrogen peroxide consumed. The vanadium concentration in the final circulation unit reaches nearly 9 g / L, and the pentavalent vanadium back-extraction solution is collected from the outlet of the third circulation unit.

[0090] The hydrogen peroxide solution inlet of the primary circulation unit (stage 1) is replenished with a hydrogen peroxide solution concentration of 1% by mass. The hydrogen peroxide solution inlet of the intermediate circulation unit (stage 2) is replenished with a hydrogen peroxide solution concentration of 2%; The hydrogen peroxide solution inlet of the final circulation unit (stage 3) is replenished with a hydrogen peroxide solution concentration of 3%.

[0091] S5. The organic phase after selective back-extraction in step S4 is back-extracted using 0.5 mol / L oxalic acid solution, with the ratio O / A controlled at 7:1. After four stages of countercurrent back-extraction in a centrifugal extractor at 45°C, an iron-poor organic phase and an oxalate complex solution are obtained.

[0092] S6. A mixed solution containing 2.5 mol / L sulfuric acid and 4% hydrogen peroxide was used as the back-extraction reagent. The ratio was controlled at O / A = 6:1. After four stages of countercurrent back-extraction in a centrifugal extractor at 28°C, a blank extractant and a titanium peroxide complex solution were obtained, thus regenerating the extractant.

[0093] ICP-OES analysis of pentavalent vanadium back-extraction solution, ferric oxalate complex solution, and titanium peroxide complex solution showed the following results: The vanadium concentration in the pentavalent vanadium back-extraction solution was 8.7 g / L, the purity was 99.994%, and the yield reached 98.36%. The Fe concentration in the ferric oxalate complex solution was 8.5 g / L, and the purity was 99.95%. The concentration of Ti in the titanium peroxide complex solution was 1.5 g / L, and the purity was 99.97%.

[0094] Example 3 This embodiment discloses a method for purifying and extracting vanadium from secondary resources, as shown in Figure 1, including: S1. The leachate obtained by leaching vanadium-containing waste residue from titanium dioxide waste acid is reduced to convert all vanadium into tetravalent vanadium. After adjusting the pH, the pre-extraction solution is obtained, which includes: S101: Adjust the pH value of the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching to 1.4 before reduction to ensure the acidic environment required for the reduction reaction; add a reducing agent to the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching to the reducing agent, sodium thiosulfate, and the amount of reducing agent is 1.1 times the theoretical equivalent required for reduction, and reduce at 65℃. S102: Adjust the pH value of the vanadium-containing waste slag leachate from the titanium dioxide waste acid leaching after reduction to 1.8 to meet the optimal pH value range of the acidic phosphorus extractant in step S2, and obtain the pre-extraction liquid after filtration.

[0095] The elemental composition of the vanadium-containing waste residue leachate from titanium dioxide waste acid leaching is as follows: V 5.1 g / L, Fe 34 g / L, Ti 1.2 g / L, and the contents of Na, Ca, Mg, Mn, Al, Cr, P, Si, Sc, etc. are in trace to gram concentrations.

[0096] S2. The pre-extraction solution was extracted using an acidic phosphorus extractant to obtain an organic phase loaded with vanadium, iron, and titanium. The acidic phosphorus extractant, by volume fraction, includes 25% P2O4 (main extractant), 8% TBP (co-extractant), and the remainder is kerosene diluent; The extraction ratio was O / A = 1.3:1, the extraction stage was 4 stages, and the temperature was 45℃.

[0097] S3. Wash the organic phase with dilute sulfuric acid at pH 2.0 to remove impurities such as sodium and potassium, including: After two-stage countercurrent washing in a centrifugal extractor at 45°C, the washed organic load and wash water were obtained, with the ratio controlled at O / A = 13:1.

[0098] S4. Using hydrogen peroxide solution, the washed organic phase is back-extracted in a multi-stage cross-flow cycle to obtain a vanadium-poor organic phase and a pentavalent vanadium back-extraction solution. The back-extraction ratio O / A = 3:1, and a 3-stage cross-flow back-extraction is used to selectively back-extract the washed organic phase to obtain a pentavalent vanadium back-extraction solution. The temperature is 23℃. Multi-stage cross-flow circulation back-extraction uses the same 3-stage cross-flow circulation back-extraction as in Example 1. In each cycle, hydrogen peroxide solution is replenished from the hydrogen peroxide solution inlet, so that the mass of hydrogen peroxide replenished is greater than or equal to the amount of hydrogen peroxide consumed. The vanadium concentration in the final circulation unit reaches nearly 10 g / L, and the pentavalent vanadium back-extraction solution is collected from the outlet of the third circulation unit.

[0099] The hydrogen peroxide solution inlet of the primary circulation unit (stage 1) is replenished with a hydrogen peroxide solution concentration of 0.9%. The hydrogen peroxide solution inlet of the intermediate circulation unit (stage 2) is replenished with a hydrogen peroxide solution concentration of 1.8%. The hydrogen peroxide solution inlet of the final circulation unit (stage 3) is replenished with a hydrogen peroxide solution concentration of 2.8%.

[0100] S5. The organic phase after selective back-extraction in step S4 is back-extracted using 0.4 mol / L oxalic acid solution, with the ratio O / A controlled at 8:1. After five stages of countercurrent back-extraction in a centrifugal extractor at 45°C, an iron-poor organic phase and an oxalate complex solution are obtained.

[0101] S6. A mixed solution containing 4 mol / L sulfuric acid and 5% hydrogen peroxide was used as the back-extraction reagent. The ratio was controlled at O / A = 8:1. After five stages of countercurrent back-extraction in a centrifugal extractor at 30°C, a blank extractant and a titanium peroxide complex solution were obtained, thus regenerating the extractant.

[0102] ICP-OES analysis of pentavalent vanadium back-extraction solution, ferric oxalate complex solution, and titanium peroxide complex solution showed the following results: The vanadium pentavalent stripping solution had a V concentration of 9.6 g / L and a purity of 99.995%, with a yield of 98.45%; the ferric oxalate complex solution had an Fe concentration of 8.9 g / L and a purity of 99.96%; and the titanium peroxide complex solution had a Ti concentration of 1.3 g / L and a purity of 99.93%.

[0103] Example 4 This embodiment discloses a method for purifying and extracting vanadium from secondary resources. The difference between this method and Embodiment 1 is that the elemental composition of the vanadium-containing waste leaching solution from titanium dioxide waste acid leaching is different: V 3.9 g / L, Fe 42 g / L, Ti 1.1 g / L, and the contents of Na, Ca, Mg, Mn, Al, Cr, P, Si, Sc, etc. are in trace to gram concentrations, and pH=1.1.

[0104] ICP-OES analysis of pentavalent vanadium back-extraction solution, ferric oxalate complex solution, and titanium peroxide complex solution showed the following results: The vanadium concentration in the pentavalent vanadium back-extraction solution was 9.1 g / L, the purity was 99.992%, and the yield reached 98.69%. The Fe concentration in the ferric oxalate complex solution was 8.2 g / L, and the purity was 99.97%. The concentration of Ti in the titanium peroxide complex solution was 1.4 g / L, and the purity was 99.96%.

[0105] Analysis of the above results shows that: In Examples 1-4, the vanadium concentration in the pentavalent vanadium back-extraction solution was 8.6–9.6 g / L, with a purity ≥99.992% and a yield ≥98.36%; the iron concentration in the ferric oxalate complex solution was 7.8–8.9 g / L, with a purity ≥99.95%; and the titanium concentration in the titanium peroxide complex solution was 1.3–1.8 g / L, with a purity ≥99.93%. All indicators were stable and reached high purity levels. Relying on the integrated process of co-leaching of titanium dioxide waste acid and vanadium-containing waste residue, vanadium pre-reduction and valence control, co-extraction of vanadium, iron and titanium with acidic phosphorus extractant and selective back-extraction with hydrogen peroxide, stepwise back-extraction of iron with oxalic acid, and back-extraction of titanium with sulfuric acid-hydrogen peroxide mixture, efficient separation and purification of vanadium, iron and titanium are achieved. The extractant can be recycled and regenerated. The process is short, with low energy and reagent consumption, significantly improving the vanadium recovery rate and product purity. At the same time, it solves the industry pain points of difficult co-utilization of hazardous waste, low recovery rate of valuable metals, and easy generation of secondary pollution.

[0106] Comparative Example 1 In Comparative Example 1, the hydrogen peroxide solution inlet of the primary circulation unit (stage 1), intermediate circulation unit (stage 2), and final circulation unit (stage 3) all had a hydrogen peroxide solution mass concentration of 1.6%, and the rest was the same as in Example 1.

[0107] The results showed that the concentration of hydrogen peroxide solution in each circulation unit was consistent and low, which led to a decrease in the efficiency of single-stage back-extraction. Incomplete vanadium back-extraction occurred within a limited number of stages, resulting in low circulation enrichment efficiency. A large amount of vanadium was not back-extracted and entered the downstream back-extraction process. Although the product indicators of pentavalent vanadium back-extraction solution obtained by long-term circulation were still qualified, the yield dropped significantly. Moreover, due to the incomplete vanadium back-extraction and low circulation enrichment efficiency, the impurities in the outlet solution obtained from subsequent anti-iron and anti-titanium processes were seriously excessive, resulting in insufficient product purity.

[0108] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for purifying and extracting vanadium from secondary resources, characterized in that, include: S1. Reduce the leachate obtained by leaching vanadium-containing waste residue from titanium dioxide waste acid to convert all vanadium into tetravalent vanadium. After adjusting the pH, obtain the pre-extraction solution. S2. The pre-extraction solution was extracted using an acidic phosphorus extractant to obtain an organic phase loaded with vanadium, iron, and titanium. S3. Wash the organic phase with dilute sulfuric acid to remove impurities; S4. Selective back-extraction of the washed organic phase was performed using hydrogen peroxide solution to obtain pentavalent vanadium back-extraction solution; S5. The organic phase after selective back-extraction in step S4 is back-extracted with oxalic acid solution to obtain oxalic acid iron complex solution. S6. The organic phase after back-extraction in step S5 is back-extracted using a mixed solution of sulfuric acid and hydrogen peroxide to obtain a titanium peroxide complex solution and regenerate the acidic phosphorus extractant.

2. The method for purifying and extracting vanadium from secondary resources according to claim 1, characterized in that, Step S1 includes: S101: Adjust the pH value of the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching to 1.0-2.0 before reduction to ensure the acidic environment required for the reduction reaction; add a reducing agent to the vanadium-containing waste leaching solution from the titanium dioxide waste acid leaching and reduce it at 60-80℃; S102: Adjust the pH value of the vanadium-containing waste slag leachate from the titanium dioxide waste acid leaching process to 1.5-2.

5.

3. The method for purifying and extracting vanadium from secondary resources according to claim 2, characterized in that, In step S101, the reducing agent is selected from one or more of sodium sulfite, sodium thiosulfate, sodium metabisulfite, sodium sulfide, ascorbic acid, oxalic acid, sulfur dioxide, and reduced iron powder.

4. The method for purifying and extracting vanadium from secondary resources according to claim 1, characterized in that, The pH of the dilute sulfuric acid solution used for washing in step S3 is 1~2.

5. The method for purifying and extracting vanadium from secondary resources according to claim 4, characterized in that, Step S4 includes: using hydrogen peroxide solution to perform multi-stage cross-flow back-extraction on the washed organic phase to obtain a vanadium-poor organic phase and a pentavalent vanadium back-extraction solution.

6. The method for purifying and extracting vanadium from secondary resources according to claim 5, characterized in that, The multi-stage cross-flow cyclic back-extraction includes: Multiple cross-flow interconnected circulation units, each circulation unit is equipped with an inlet, an organic phase inlet, an outlet, and an organic phase outlet; In two adjacent recycling units, the organic phase outlet of the preceding recycling unit is connected in series with the organic phase inlet of the following recycling unit; the recycling unit where the vanadium-poor organic phase discharge end after vanadium back-extraction is located is defined as the first-level recycling unit, and the recycling unit where the vanadium-rich organic phase inlet end is located in multiple connected recycling units is defined as the nth-level recycling unit; the vanadium-rich organic phase enters from the organic phase inlet of the nth-level recycling unit, and after being back-extracted through multiple recycling units in sequence, it is transformed into a vanadium-poor organic phase and discharged from the organic phase outlet of the first-level recycling unit; where n is the recycling unit level sequence. The back-extraction reagent enters through the inlet and exits through the outlet of the first-stage circulation unit. After passing through the external circulation pipeline, it re-enters the inlet and completes multiple cycles within the first-stage circulation unit. Then, it enters the inlet of the next-stage circulation unit and circulates multiple times within the next-stage circulation unit, and so on, until it completes multiple cycles within the nth-stage circulation unit and is discharged through the outlet of the nth-stage circulation unit to obtain pentavalent vanadium back-extraction solution. Each stage of the circulation unit can independently circulate the aqueous phase through the inlet, outlet, and external circulation pipeline; after the circulation ends, the intermediate back-extraction product is discharged from the outlet of the previous stage of the circulation unit, and the intermediate back-extraction product is used as the inlet of the next stage of the circulation unit for continued circulation. In the circulation unit, the back-extraction reagent moves in the opposite direction to the organic phase, resulting in countercurrent extraction. After each cycle of back-extraction in each circulation unit, hydrogen peroxide is added before the next cycle begins.

7. The method for purifying and extracting vanadium from secondary resources according to claim 6, characterized in that, The required concentration of hydrogen peroxide solution in different circulation units gradually increases from the first-level circulation unit to the nth-level circulation unit, with an increase of 0.2% to 1.0% in each level.

8. The method for purifying and extracting vanadium from secondary resources according to claim 6, characterized in that, When the vanadium concentration in the hydrogen peroxide solution of the nth stage circulation unit reaches 8~10g / L, the pentavalent vanadium back-extraction solution is discharged from the outlet of the nth stage circulation unit.

9. A method for purifying and extracting vanadium from secondary resources according to any one of claims 1-8, characterized in that, In step S6, the sulfuric acid concentration in the mixed solution is 2-4 mol / L, and the hydrogen peroxide mass concentration in the mixed solution is 1%-5%.

10. A combined application of titanium dioxide waste acid and vanadium-containing waste residue, characterized in that, For obtaining precursors for the preparation of vanadium, and / or titanium, and / or iron, the method for purifying and extracting vanadium from secondary resources as described in any one of claims 1-9 is used.

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