A method for purifying and concentrating vanadium-containing leach liquor in a vanadium metallurgical process

Abstract

A method for purifying and concentrating vanadium-containing leaching solution in a vanadium metallurgy process belongs to the field of comprehensive utilization of vanadium metallurgy resources and membrane separation technology. The method realizes reconfiguration of vanadium anions through pH regulation, and realizes that the total removal rate of impurity components in the vanadium-containing leaching solution reaches more than 90% and the total recovery rate of vanadium is not less than 92% by combining multi-stage filtration, safety filtration and nanofiltration-reverse osmosis combined separation technology. After the system continuously operates for 72 hours, the removal rates of impurity components, the removal rate of colloidal substances and the recovery rate of membrane flux can still be maintained at a high level, and the stability is significantly improved compared with single-stage membrane separation technology. By using the method, directional impurity removal, efficient concentration and closed-loop reuse of reverse osmosis permeate of the vanadium-containing leaching solution are realized, the production cost and pollution discharge are reduced, and the process stability and industrial applicability are improved.

Description

Technical Field

[0001] This invention belongs to the field of vanadium metallurgical resource comprehensive utilization and membrane separation technology, specifically relating to a method for purifying and concentrating vanadium-containing leachate in vanadium metallurgical processes. In particular, it relates to a method for directional impurity removal, high-efficiency concentration, and closed-loop recycling of vanadium-containing leachate based on pH control, vanadium anion reconstruction, multi-stage filtration, nanofiltration-reverse osmosis combined separation, and permeate recycling. It is applicable to the treatment of vanadium-containing leachate obtained after sodium roasting or calcination roasting of vanadium-titanium magnetite, vanadium slag, and other vanadium-containing materials. Background Technology

[0002] In the vanadium metallurgy industry, vanadium-containing materials such as vanadium-titanium magnetite and vanadium slag, after sodium roasting or calcination roasting, typically require leaching to obtain vanadium-containing leachate. The resulting vanadium-containing leachate, in addition to the target vanadium component, usually contains impurities such as Fe, Al, Mg, Si, and P, as well as suspended particles and colloidal substances. These vanadium-containing leachates generally suffer from low vanadium concentrations and complex impurity profiles, making it difficult to directly meet the requirements for vanadium concentration and impurity content in subsequent vanadium precipitation processes. Therefore, the purification, impurity removal, and concentration of vanadium-containing leachate are crucial steps in the vanadium metallurgy process.

[0003] In existing technologies, the concentration and impurity removal of vanadium-containing leachates mainly employ the following methods:

[0004] 1. Repeated leaching method: The vanadium concentration is increased by leaching multiple times, but this method is prone to the simultaneous enrichment of impurity components such as Fe, Al, Mg, Si, and P, which aggravates the co-precipitation of vanadium and impurities during the subsequent vanadium precipitation process, resulting in vanadium loss. At the same time, it increases the consumption of leaching agent and the burden of subsequent impurity removal.

[0005] 2. Ion adsorption method: This method utilizes the selective adsorption of vanadium by adsorbents to achieve enrichment. However, it has limited adsorption capacity, a complex desorption process, a slow processing speed, and high costs for adsorbent regeneration and equipment operation, making it difficult to meet the requirements of large-scale continuous production.

[0006] 3. Solvent extraction method: Vanadium is separated from impurities and concentrated by organic extractants. However, this method usually requires the use of organic solvents, which poses risks of extractant loss, organic phase entrainment and secondary pollution. In addition, the extraction-back-extraction stages are numerous, the process is complex, and the operating cost is high.

[0007] 4. Single-stage membrane separation: Some technologies use a single nanofiltration membrane or reverse osmosis membrane for treatment. While single-stage nanofiltration membranes can remove some impurities, they are difficult to achieve efficient vanadium concentration simultaneously. While single-stage reverse osmosis membranes can increase the concentration of vanadium-containing solution, they are sensitive to colloids, suspended particles, and multivalent metal impurities, easily leading to membrane fouling, flux reduction, and frequent cleaning, affecting system stability. Furthermore, existing membrane separation methods often focus on membrane pore size, operating pressure, and retention capacity, failing to fully utilize the species characteristic of vanadium forming vanadate anions under alkaline conditions. This results in unsatisfactory selective separation of vanadium from impurities such as Fe, Al, Mg, Si, and P.

[0008] 5. Chemical precipitation-concentration combined method: First, chemical reagents are added to remove impurities, and then evaporation and concentration are carried out. However, this method requires the introduction of more chemical reagents, which may cause vanadium to co-precipitate with impurities and result in vanadium loss. At the same time, evaporation and concentration consumes a lot of energy, and the wastewater containing salt or impurities generated during the process is difficult to reuse directly, increasing the burden of wastewater treatment.

[0009] In addition, in existing technologies, the permeate or wastewater after vanadium leaching is often discharged directly, which not only wastes water resources but may also increase environmental treatment pressure due to alkalinity or impurity ions. Some recycling technologies are also affected by insufficient purity of the recycled solution, which can affect the leaching effect, leading to a decrease in vanadium leaching rate or the accumulation of impurities in the system.

[0010] Therefore, there is an urgent need to develop a method for treating vanadium-containing leachate that can improve the vanadium species morphology through pH control and combine filtration pretreatment, membrane separation concentration and permeate recycling, so as to simultaneously achieve the purification, concentration and water resource recycling of vanadium-containing leachate, reduce vanadium loss and membrane fouling, and improve process stability and industrial applicability. Summary of the Invention

[0011] The purpose of this invention is to overcome the problems in existing vanadium-containing leachate treatment technologies, such as difficulty in simultaneously achieving concentration and impurity removal, significant vanadium loss, severe membrane fouling, and water waste. This invention provides a method for purifying and concentrating vanadium-containing leachates during vanadium metallurgy. This method achieves vanadium anion reconstruction through pH adjustment and combines multi-stage filtration, security filtration, and nanofiltration-reverse osmosis combined separation technologies to achieve targeted impurity removal, efficient concentration, and closed-loop reuse of reverse osmosis permeate from the vanadium-containing leachate. This reduces production costs and wastewater discharge, and improves process stability and industrial applicability.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] A method for purifying and concentrating vanadium-containing leaching solution during vanadium metallurgy, comprising the following steps:

[0014] 1. Leaching of vanadium-containing materials: Vanadium-containing clinker after sodium roasting or calcination is fed into a leaching tank, and a leaching agent is added at a solid-liquid ratio of 1:(2.5~3.0). The mixture is stirred and leached at 90℃~100℃ for 1.5h~3.0h. After leaching, a vanadium-containing leachate is obtained. The leaching agent is one of water, alkaline aqueous solution, or acidic aqueous solution. The vanadium concentration in the vanadium-containing leachate is 8g / L~20g / L, and the impurity element content is: Fe 2g / L~8g / L, Al 3g / L~12g / L, Mg 1g / L~5g / L, Si 0.5g / L~3g / L, P 0.01g / L~0.1g / L.

[0015] 2. pH adjustment and vanadium anion reconstruction: An alkaline regulator is added to the vanadium-containing leachate to adjust the pH of the solution to 9.0-12.5, preferably 10.0-11.5. The mixture is stirred for 10-30 minutes to allow vanadium to be converted to vanadium as VO4+. 3- HVO4 2- The vanadate anion is present to obtain a vanadium anion reconstructed solution; the alkaline regulator is one or more of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0016] 3. Multi-stage filtration: The vanadium anion reconstituted solution is sequentially fed into a 300-mesh coarse filter, a 2000-mesh medium filter, and a 4000-mesh fine filter, and filtered under conditions of 0.1MPa~0.3MPa and 40℃~60℃. The single-stage filtration flux is 50L / (m³). 2 ·h)~100L / (m 2 •h) to remove solid particulate impurities (such as unreacted clinker particles, oxide precipitates, etc.) from the leachate to obtain a primary vanadium-containing solution.

[0017] 4. Security Filtration: The vanadium-containing solution is fed into a security filter and filtered under conditions of 0.1MPa~0.2MPa and 25℃~40℃. The filtration accuracy is 5μm~10μm, and the filtration flux is 80L / (m³). 2 ·h)~150L / (m 2 •h) Removes fine particulate matter and colloidal precursors to prevent subsequent membrane module blockage.

[0018] 5. Membrane module separation: The vanadium-containing solution after security filtration is fed into a membrane module separation system for separation. The membrane module separation system consists of a first membrane module and a second membrane module connected in series. The operating temperature is 25℃~40℃, and the overall permeate recovery rate of the membrane module separation system is 45%~55%. The overall permeate recovery rate is the ratio of the total amount of permeate obtained from the membrane module separation system to the total amount of pretreated vanadium-containing solution entering the membrane module separation system.

[0019] The first membrane module is a nanofiltration membrane module with a molecular weight cutoff of 100 Da to 300 Da and an operating pressure of 0.8 MPa to 1.5 MPa. The nanofiltration membrane module utilizes the surface charge effect and size sieving effect of the membrane to achieve selective separation of vanadate anions from impurity components such as Fe, Al, Mg, Si, and P, as well as colloidal substances, to obtain vanadium-enriched solution and impurity permeate.

[0020] The second membrane module is a reverse osmosis membrane module, operating at a pressure of 1.5 MPa to 3.0 MPa, used to further concentrate the vanadium-enriched solution to obtain vanadium-enriched solution and reverse osmosis permeate. The vanadium concentration in the vanadium-enriched solution is 30 g / L to 40 g / L, which meets the requirements of subsequent vanadium precipitation processes for vanadium concentration and impurity content. The Na2O concentration in the reverse osmosis permeate is 1.5 g / L to 3.0 g / L, the total impurity content is ≤50 ppm, and the pH value is 8.5 to 10.0.

[0021] As a further preferred method, during the continuous operation of the membrane module separation system, the first membrane module and / or the second membrane module are cleaned online with a 0.5 mol / L to 1.0 mol / L sodium hydroxide solution every 8 to 12 hours for a cleaning time of 30 to 60 minutes, and the membrane flux recovery rate after cleaning is not less than 95%.

[0022] 6. Closed-loop circulation: The vanadium-enriched solution obtained from the second membrane module is sent to the vanadium precipitation process to prepare ammonium polyvanadate, ammonium metavanadate, or vanadium pentoxide products; the reverse osmosis permeate generated by the second membrane module is returned as recycled water to the vanadium-containing material leaching step for recycling, forming a closed-loop circulation system of "leaching - pH adjustment - filtration - membrane separation - vanadium precipitation - permeate recycling".

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. Simultaneous purification and concentration: This invention achieves simultaneous purification and concentration by adjusting pH and reconstructing vanadium anions, so that vanadium exists mainly in the form of vanadate anions. Combined with selective separation by nanofiltration membrane and efficient concentration by reverse osmosis membrane, it can remove various impurities and colloidal substances such as Fe, Al, Mg, Si, and P, achieving a total impurity removal rate of over 90%. At the same time, it increases the vanadium concentration to 30g / L~40g / L, meeting the requirements of subsequent vanadium precipitation processes for vanadium concentration and impurity content. This solves the problem of difficulty in simultaneously purifying and concentrating vanadium-containing leachate in existing technologies.

[0025] 2. High vanadium recovery rate: This invention does not use a large amount of chemical precipitant for impurity removal, thus reducing vanadium loss caused by co-precipitation of impurities and vanadium; through a combination of pH control, nanofiltration selective separation and reverse osmosis concentration, the total vanadium recovery rate is not less than 92%, which is 4 to 7 percentage points higher than the vanadium recovery rate of 85% to 88% in the prior art.

[0026] 3. Low membrane fouling and high stability: This invention incorporates pH adjustment, multi-stage filtration, and security filtration steps before membrane separation, which effectively removes unreacted clinker particles, oxide precipitates, suspended particles, and colloidal precursors, significantly reducing the fouling risk of nanofiltration and reverse osmosis membranes. Combined with online cleaning, the system maintains a high removal rate of impurities, colloidal substances, and membrane flux recovery rate even after 72 hours of continuous operation, demonstrating significantly improved stability compared to single-stage membrane separation technology.

[0027] 4. Closed-loop water reuse: The reverse osmosis permeate obtained by this invention has low impurity content and a certain alkalinity, which can be recycled as alkaline freshwater in the leaching process. The reuse rate can reach 40%~60%, and the amount of fresh alkaline solution used can be reduced by 30%~40%, which significantly reduces water consumption and wastewater discharge.

[0028] 5. Simple process and low cost: This invention does not require complex chemical impurity removal reagents, organic extraction systems, or high-energy-consuming evaporation and concentration equipment. It mainly consists of units such as pH adjustment, multi-stage filtration, security filtration, nanofiltration, reverse osmosis, and permeate recycling. The process is simple and easy to connect with existing sodium roasting or calcination roasting vanadium-containing leachate treatment processes. When calculated based on the same treatment scale, the equipment investment is reduced by 20% to 30% compared to the solvent extraction method, and the operating cost is reduced by 15% to 25%. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the process flow for purifying and concentrating vanadium-containing leaching solution in the vanadium metallurgical process of the present invention.

[0030] Figure 2 This is a schematic diagram showing the distribution of vanadium species under different pH conditions.

[0031] Figure 3 This is a schematic diagram of the selective migration and nanofiltration separation mechanism of vanadium anions.

[0032] Figure 4 A comparison chart showing the changes in membrane flux and cleaning recovery rate of the membrane combination separation system under different operating times. Detailed Implementation

[0033] like Figure 1As shown, this invention provides a method for purifying and concentrating vanadium-containing leaching solution in vanadium metallurgy, mainly including steps such as leaching of vanadium-containing materials, pH adjustment and vanadium anion reconstruction, multi-stage filtration, security filtration, nanofiltration selective separation, reverse osmosis concentration, vanadium precipitation of enriched vanadium solution, and reuse of reverse osmosis permeate. Through the above steps, a closed-loop process system of "leaching—pH adjustment—filtration—membrane separation—vanadium precipitation—permeate reuse" can be formed.

[0034] In the method provided by this invention, the pH of the vanadium-containing leachate is adjusted to reconstruct vanadium anions before subsequent filtration and concentration steps. For example... Figure 2 As shown, the speciation of vanadium in solution changes under different pH conditions. When the solution pH is adjusted to the range of 9.0–12.5, vanadium mainly exists as HVO4. 2- VO4 3- The presence of vanadate anions facilitates the selective separation of vanadium components from impurities such as Fe, Al, Mg, Si, and P via nanofiltration membranes.

[0035] The method provided by this invention includes the following mechanism for the selective migration and nanofiltration separation of vanadium anions: Figure 3 As shown, after pH adjustment and vanadium anion reconstruction, the vanadium-containing solution enters the nanofiltration membrane module. The nanofiltration membrane utilizes the surface charge effect and size sieving effect to selectively separate vanadate anions from impurity components, obtaining a vanadium-enriched solution and an impurity permeate. Subsequently, the vanadium-enriched solution enters the reverse osmosis membrane module for further concentration, obtaining a vanadium-enriched solution that meets the requirements of the subsequent vanadium precipitation process.

[0036] Compared to membrane separation processes without pH adjustment or adequate pretreatment, this invention removes some suspended particles, colloidal substances, and membrane fouling precursors through pH adjustment, multi-stage filtration, and security filtration, thus slowing down membrane flux decline. Simultaneously, combined with regular online cleaning, it maintains a high membrane flux recovery rate (results are shown in the figure). Figure 4 As shown in the figure, this improves the continuous operation stability of the membrane module separation system.

[0037] The present invention provides a method for purifying and concentrating vanadium-containing leaching solution in vanadium metallurgy, the specific steps of which are as follows:

[0038] 1. Leaching of vanadium-containing materials: Vanadium-containing clinker, after sodium roasting or calcination roasting, is fed into a leaching tank. A leaching agent is added at a solid-liquid ratio of 1:(2.5~3.0), and leaching is carried out at 90℃~100℃ with stirring for 1.5h~3.0h. After leaching, a vanadium-containing leachate is obtained. The leaching agent is a sodium hydroxide solution or a dilute sulfuric acid solution, selected according to the roasting process of the vanadium-containing material. The initial vanadium mass concentration in the vanadium-containing leachate is 8g / L~20g / L. The leaching agent is one or more of water, alkaline aqueous solution, or acidic aqueous solution.

[0039] 2. pH Adjustment and Vanadium Anion Reconstruction: An alkaline adjuster is added to the vanadium-containing leachate to adjust the pH of the solution to 9.0-12.5, preferably 10.0-11.5. The mixture is stirred for 10-30 minutes to allow V to exist in the form of vanadate anions, thus obtaining a vanadate anion reconstructed solution. The vanadate anions include VO42-. 3- HVO4 2- One or more of the following; the alkalinity regulator is one or more of sodium hydroxide, potassium hydroxide, and sodium carbonate.

[0040] 3. Multi-stage filtration: The vanadium anion reconstituted solution is sequentially fed into a 300-mesh coarse filter, a 2000-mesh medium filter, and a 4000-mesh fine filter, and filtered under conditions of 0.1MPa~0.3MPa and 40℃~60℃. The single-stage filtration flux is 50L / (m³). 2 ·h)~100L / (m 2 •h) Remove unreacted clinker particles, oxide precipitates, suspended particles and some colloidal substances to obtain a primary vanadium-containing liquid.

[0041] 4. Security Filtration: The vanadium-containing solution is fed into a security filter and filtered under conditions of 0.1MPa~0.2MPa and 25℃~40℃. The filtration accuracy is 5μm~10μm, and the filtration flux is 80L / (m³). 2 ·h)~150L / (m 2 •h) to further remove fine particulate matter and colloidal precursors, avoiding clogging of subsequent nanofiltration and reverse osmosis membrane modules.

[0042] 5. Membrane Module Separation: The vanadium-containing solution after security filtration is fed into a membrane module separation system for separation at 25℃~40℃. The overall permeate recovery rate of the membrane module separation system is 45%~55%; the overall permeate recovery rate is the ratio of the total amount of permeate obtained by the membrane module separation system to the total amount of pretreated vanadium-containing solution entering the membrane module separation system. The membrane module separation system includes a nanofiltration membrane module and a reverse osmosis membrane module arranged sequentially. The nanofiltration membrane module uses a nanofiltration membrane with a molecular weight cutoff of 100Da~300Da, and operates at a pressure of 0.8MPa~1.5MPa. It is used to selectively separate vanadate anions from impurities such as Fe, Al, Mg, Si, and P to obtain vanadium-enriched solution and impurity permeate. The reverse osmosis membrane module operates at a pressure of 1.5MPa~3.0MPa and is used to further concentrate the vanadium-enriched solution to obtain vanadium-enriched solution and reverse osmosis permeate.

[0043] As a further preferred method, during the continuous operation of the membrane module separation system, the nanofiltration membrane module and / or reverse osmosis membrane module are cleaned online with a sodium hydroxide solution of 0.5 mol / L to 1.0 mol / L every 8 to 12 hours to restore membrane flux and maintain stable system operation. The cleaning time is 30 to 60 minutes, and the membrane flux recovery rate after cleaning is not less than 95%.

[0044] 6. Closed-loop circulation: The vanadium-enriched solution obtained from the reverse osmosis membrane module is sent to the vanadium precipitation process to prepare ammonium polyvanadate, ammonium metavanadate or vanadium pentoxide products; the reverse osmosis permeate is returned as recycled water to the vanadium-containing material leaching step for reuse.

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be understood that the following embodiments are only for illustrating the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Conventional substitutions, parameter adjustments, or equivalent transformations made by those skilled in the art based on the disclosure of the present invention without departing from the concept of the present invention should all fall within the scope of protection of the present invention.

[0046] Example 1:

[0047] This embodiment provides a method for purifying and concentrating vanadium-containing leachate during vanadium metallurgy, illustrating the purification and concentration effect of the present invention on the leachate from sodium-roasted vanadium-containing clinker, comprising the following steps:

[0048] 1. Leaching of vanadium-containing materials: Vanadium-containing clinker after sodium roasting was taken and sodium hydroxide solution was added at a solid-liquid ratio of 1:2.8. The mixture was stirred and leached at 95°C for 2.0 h to obtain a vanadium-containing leachate. Analysis showed that the vanadium concentration in the leachate was 12.5 g / L, and the impurity contents were: Fe 3.2 g / L, Al 4.5 g / L, Mg 1.8 g / L, Si 0.9 g / L, and P 0.03 g / L.

[0049] 2. pH adjustment and vanadium anion reconstruction: Sodium hydroxide solution was added to the vanadium-containing leachate to adjust the pH to 10.5. The mixture was stirred for 20 minutes to allow vanadium to be mainly converted into HVO4. 2- VO4 3- Vanadate anions are present in the form of vanadate anions to obtain a vanadium anion reconstructed solution.

[0050] 3. Multi-stage filtration: The vanadium anion reconstituted solution is sequentially filtered through a 300-mesh coarse filter, a 2000-mesh medium filter, and a 4000-mesh fine filter. The operating pressure is 0.2 MPa, the operating temperature is 50℃, and the single-stage filtration throughput is 80 L / (m³). 2 •h) Remove unreacted clinker particles, oxide precipitates and suspended particles to obtain a primary vanadium-containing liquid.

[0051] 4. Security Filtration: The vanadium-containing solution is filtered through an 8μm security filter at an operating pressure of 0.15MPa, an operating temperature of 30℃, and a filtration flux of 120L / (m³). 2 ·h), further remove fine particulate matter and colloidal precursors to obtain pretreated vanadium-containing solution.

[0052] 5. Membrane Module Separation: The pretreated vanadium-containing solution was fed into a membrane module separation system for separation at 35℃. The first membrane module was a nanofiltration membrane with a molecular weight cutoff of 200 Da, operating at a pressure of 1.2 MPa; the second membrane module was a reverse osmosis membrane, operating at a pressure of 2.2 MPa. The overall permeate recovery rate was 50%. The nanofiltration membrane module was used to selectively separate vanadate anions from impurities such as Fe, Al, Mg, Si, and P, while the reverse osmosis membrane module was used to further concentrate the vanadium-enriched solution. After treatment, the vanadium concentration in the resulting vanadium-enriched solution was 36.8 g / L. The removal rates of Fe, Al, Mg, Si, and P were 96.5%, 97.2%, 95.8%, 99.1%, and 98.3%, respectively. The total removal rate of impurities was greater than 90%, and the removal rate of colloidal substances was 92.6%. After 10 hours of continuous operation, the membrane module separation system was cleaned online with 0.8 mol / L sodium hydroxide solution for 45 minutes, resulting in a membrane flux recovery rate of 96.2%.

[0053] 6. Closed-loop circulation and vanadium precipitation: The resulting vanadium-enriched solution is sent to the vanadium precipitation process to prepare ammonium metavanadate; the reverse osmosis permeate is returned to the leaching process for reuse. Testing showed that the Na₂O concentration in the reverse osmosis permeate was 2.2 g / L, the total impurity content was 32 ppm, and the pH was 9.2. In this embodiment, the total vanadium recovery rate was 94.7%, and the purity of the vanadium-precipitated product, ammonium metavanadate, was not less than 99.0%.

[0054] This embodiment illustrates that the present invention can simultaneously purify and concentrate vanadium-containing leachate, increasing the vanadium mass concentration from 12.5 g / L to 36.8 g / L, while maintaining a high vanadium recovery rate and membrane flux recovery rate.

[0055] Example 2:

[0056] This embodiment provides a method for purifying and concentrating vanadium-containing leachate during vanadium metallurgy, illustrating the purification and concentration effect of the present invention on vanadium-containing clinker leachate obtained from calcination roasting, and includes the following steps:

[0057] 1. Leaching of vanadium-containing materials: Vanadium-containing clinker after calcination and roasting was taken and diluted with dilute sulfuric acid solution at a solid-liquid ratio of 1:3.0. The mixture was stirred and leached at 98℃ for 2.5 hours to obtain a vanadium-containing leachate. Analysis showed that the vanadium concentration in the leachate was 16.8 g / L, and the impurity contents were: Fe 5.7 g / L, Al 7.8 g / L, Mg 3.2 g / L, Si 1.8 g / L, and P 0.07 g / L.

[0058] 2. pH adjustment and vanadium anion reconstruction: Sodium hydroxide solution was added to the above vanadium-containing leachate to adjust the pH of the solution to 11.0. The mixture was stirred for 25 min to allow vanadium to exist mainly in the form of vanadate anions, thus obtaining a vanadium anion reconstructed solution.

[0059] 3. Multi-stage filtration: The vanadium anion reconstituted solution is sequentially filtered through a 300-mesh coarse filter, a 2000-mesh medium filter, and a 4000-mesh fine filter. The operating pressure is 0.25 MPa, the operating temperature is 55℃, and the single-stage filtration throughput is 70 L / (m³). 2 •h) is used to remove solid particles, oxide precipitates, and some colloidal substances to obtain a primary vanadium-containing solution.

[0060] 4. Security Filtration: The vanadium-containing solution is filtered through a 10μm security filter at an operating pressure of 0.18MPa, an operating temperature of 35℃, and a filtration flux of 100L / (m³). 2 ·h), to obtain a pretreated vanadium-containing solution.

[0061] 5. Membrane Module Separation: The pretreated vanadium-containing solution was fed into a membrane module separation system for separation at 38℃. The first membrane module was a nanofiltration membrane with a molecular weight cutoff of 250 Da, operating at a pressure of 1.4 MPa; the second membrane module was a reverse osmosis membrane, operating at a pressure of 2.8 MPa. The overall permeate recovery rate was 52%. After treatment, the vanadium concentration in the enriched vanadium-containing solution was 38.5 g / L. The removal rates of Fe, Al, Mg, Si, and P were 95.8%, 96.5%, 94.3%, 98.7%, and 97.8%, respectively. The total removal rate of impurities was greater than 90%, and the removal rate of colloidal substances was 91.8%. After 12 hours of operation, the membrane module separation system was cleaned online with 1.0 mol / L sodium hydroxide solution for 60 minutes, and the membrane flux recovery rate was 95.5%.

[0062] 6. Closed-loop circulation and vanadium precipitation: The resulting vanadium-enriched solution is sent to the vanadium precipitation process for the preparation of ammonium polyvanadate; the reverse osmosis permeate is returned to the leaching process for reuse. Testing showed that the Na₂O concentration in the reverse osmosis permeate was 2.8 g / L, the total impurity content was 45 ppm, and the pH was 8.8. In this embodiment, the total vanadium recovery rate was 93.2%, and the purity of the vanadium-precipitated product, ammonium polyvanadate, was not less than 98.8%.

[0063] This embodiment demonstrates that, even under conditions of high initial impurity content in the leaching solution of calcined roasted clinker, the present invention can still effectively remove impurity components such as Fe, Al, Mg, Si, and P, and efficiently concentrate vanadium.

[0064] Example 3:

[0065] This embodiment provides a method for purifying and concentrating vanadium-containing leaching solution during vanadium metallurgy, illustrating the effectiveness of the invention under low initial vanadium concentration and low pH boundary conditions, and includes the following steps:

[0066] 1. Leaching of vanadium-containing materials: Vanadium-containing clinker after sodium roasting was added to a sodium hydroxide solution at a solid-liquid ratio of 1:2.5. The mixture was stirred and leached at 90°C for 1.5 hours to obtain a vanadium-containing leachate. Analysis showed that the vanadium concentration in the leachate was 8.6 g / L, and the impurity contents were: Fe 2.4 g / L, Al 3.5 g / L, Mg 1.2 g / L, Si 0.6 g / L, and P 0.02 g / L.

[0067] 2. pH Adjustment and Vanadium Anion Reconstruction: Sodium hydroxide solution was added to the vanadium-containing leachate to adjust the pH to 9.0. The mixture was stirred for 15 minutes to obtain a vanadium anion reconstructed solution. Under this pH condition, vanadium can be converted into vanadium anions as HVO4. 2- VO4 3- The presence of vanadate anions is beneficial for subsequent nanofiltration selective separation.

[0068] 3. Multi-stage filtration: The vanadium anion reconstituted solution is sequentially filtered through a 300-mesh coarse filter, a 2000-mesh medium filter, and a 4000-mesh fine filter. The operating pressure is 0.1 MPa, the operating temperature is 40℃, and the single-stage filtration throughput is 90 L / (m³). 2 ·h), to obtain a vanadium-containing solution.

[0069] 4. Security Filtration: The vanadium-containing solution is filtered through a 5μm security filter at an operating pressure of 0.1MPa, an operating temperature of 25℃, and a filtration flux of 130L / (m³). 2 ·h), to obtain a pretreated vanadium-containing solution.

[0070] 5. Membrane Module Separation: The pretreated vanadium-containing solution was fed into a membrane module separation system for separation at 25°C. The first membrane module used a nanofiltration membrane with a molecular weight cutoff of 100 Da, operating at a pressure of 0.8 MPa; the second membrane module used a reverse osmosis membrane, operating at a pressure of 1.8 MPa. The overall permeate recovery rate was 45%. Analysis showed that the vanadium concentration in the enriched vanadium-containing solution was 30.8 g / L. The removal rates of Fe, Al, Mg, Si, and P were 95.1%, 95.8%, 91.2%, 98.2%, and 95.5%, respectively. The total removal rate of impurities was greater than 90%, the removal rate of colloidal substances was 91.0%, and the total vanadium recovery rate was 92.8%. After 8 hours of operation, the membrane module separation system was cleaned online with 0.5 mol / L sodium hydroxide solution for 30 minutes, resulting in a membrane flux recovery rate of 95.3%.

[0071] 6. Closed-loop circulation and vanadium precipitation: The resulting vanadium-enriched solution is sent to the vanadium precipitation process, while the reverse osmosis permeate is returned to the leaching process for recycling. The resulting vanadium-enriched solution meets the requirements for vanadium concentration and impurity content in the subsequent vanadium precipitation process.

[0072] This embodiment demonstrates that, under conditions of low initial vanadium concentration, pH adjusted to near the lower limit of the range defined in this invention, and low membrane operating pressure, this invention can still increase the vanadium concentration to over 30 g / L and achieve good impurity removal and vanadium recovery effects.

[0073] As shown in the results of Examples 1-3, under conditions where the initial vanadium mass concentration is 8.6 g / L to 16.8 g / L and the contents of impurities such as Fe, Al, Mg, Si, and P fluctuate significantly, the present invention can achieve a vanadium mass concentration of over 30 g / L in the enriched vanadium-containing solution, a total impurity removal rate of over 90%, and a total vanadium recovery rate of over 92%. This indicates that the present invention has a good treatment effect on vanadium-containing leachate with initial vanadium concentration and impurity content fluctuating within a certain range.

[0074] Example 4:

[0075] This embodiment provides a method for purifying and concentrating vanadium-containing leaching solution during vanadium metallurgy, illustrating the effectiveness of the invention under conditions of high initial vanadium concentration and high pH boundary, and includes the following steps:

[0076] 1. Leaching of vanadium-containing materials: Vanadium-containing clinker after sodium roasting was added to a sodium hydroxide solution at a solid-liquid ratio of 1:3.0. The mixture was stirred and leached at 100°C for 3.0 hours to obtain a vanadium-containing leachate. Analysis showed that the vanadium concentration in the leachate was 18.0 g / L, and the impurity contents were: Fe 4.8 g / L, Al 6.9 g / L, Mg 2.9 g / L, Si 1.5 g / L, and P 0.06 g / L.

[0077] 2. pH adjustment and vanadium anion reconstruction: Sodium hydroxide solution was added to the vanadium-containing leachate to adjust the pH to 12.5. The mixture was stirred for 20 minutes to allow vanadium to be mainly converted into VO4+. 3- Vanadate anions are present in the form of vanadate anions to obtain a vanadium anion reconstructed solution.

[0078] 3. Multi-stage filtration: The vanadium anion reconstituted solution is sequentially filtered through a 300-mesh coarse filter, a 2000-mesh medium filter, and a 4000-mesh fine filter. The operating pressure is 0.3 MPa, the operating temperature is 60℃, and the single-stage filtration throughput is 60 L / (m³). 2 ·h), to obtain a vanadium-containing solution.

[0079] 4. Security Filtration: The vanadium-containing solution is filtered through a 10μm security filter at an operating pressure of 0.2MPa, an operating temperature of 40℃, and a filtration flux of 90L / (m³). 2 ·h), to obtain a pretreated vanadium-containing solution.

[0080] 5. Membrane Module Separation: The pretreated vanadium-containing solution was fed into a membrane module separation system for separation at 35℃. The first membrane module was a nanofiltration membrane with a molecular weight cutoff of 300 Da, operating at a pressure of 1.5 MPa; the second membrane module was a reverse osmosis membrane, operating at a pressure of 3.0 MPa. The overall permeate recovery rate was 55%. Analysis showed that the vanadium concentration in the enriched vanadium-containing solution was 39.6 g / L, and the removal rates of Fe, Al, Mg, Si, and P were 94.9%, 95.6%, 93.8%, 98.4%, and 96.9%, respectively. The total removal rate of impurities was greater than 90%, the removal rate of colloidal substances was 91.6%, and the total vanadium recovery rate was 95.7%. After 12 hours of operation, the membrane module separation system was cleaned online with a 1.0 mol / L sodium hydroxide solution for 60 minutes, resulting in a membrane flux recovery rate of 95.4%.

[0081] 6. Closed-loop circulation and vanadium precipitation: The obtained vanadium-enriched solution is sent to the vanadium precipitation process, and the reverse osmosis permeate is returned to the leaching process for recycling. The purity of the obtained vanadium precipitation product is not less than 99.0%.

[0082] This embodiment illustrates that, even when the pH is adjusted to near the upper limit of the range defined in this invention and the initial vanadium concentration is relatively high, this invention can still achieve effective purification and concentration of vanadium-containing leachate.

[0083] Example 5:

[0084] This embodiment provides a method for purifying and concentrating vanadium-containing leaching solution during vanadium metallurgy, illustrating the purification and concentration effect of this invention on vanadium-containing clinker leaching solution when water is used as the leaching agent, including the following steps:

[0085] 1. Leaching of vanadium-containing materials: Vanadium-containing clinker after sodium roasting was taken, and water was added as a leaching agent at a solid-liquid ratio of 1:2.8. The mixture was stirred and leached at 95℃ for 2.0 h to obtain a vanadium-containing leachate. The vanadium concentration in the leachate was found to be 10.8 g / L, and the impurity contents were: Fe 2.8 g / L, Al 4.1 g / L, Mg 1.5 g / L, Si 0.8 g / L, and P 0.025 g / L.

[0086] 2. pH adjustment and vanadium anion reconstruction: Sodium hydroxide solution was added to the vanadium-containing leachate to adjust the pH to 10.5. The mixture was stirred for 20 minutes to allow vanadium to be mainly converted into HVO4. 2- VO4 3- Vanadate anions are present in the form of vanadate anions to obtain a vanadium anion reconstructed solution.

[0087] 3. Multi-stage filtration: The vanadium anion reconstituted solution is sequentially filtered through a 300-mesh coarse filter, a 2000-mesh medium filter, and a 4000-mesh fine filter. The operating pressure is 0.2 MPa, the operating temperature is 50℃, and the single-stage filtration throughput is 80 L / (m³). 2 •h) Remove unreacted clinker particles, oxide precipitates and suspended particles to obtain a primary vanadium-containing liquid.

[0088] 4. Security Filtration: The vanadium-containing solution is filtered through an 8μm security filter at an operating pressure of 0.15MPa, an operating temperature of 30℃, and a filtration flux of 120L / (m³). 2 ·h), further remove fine particulate matter and colloidal precursors to obtain pretreated vanadium-containing solution.

[0089] 5. Membrane Module Separation: The pretreated vanadium-containing solution was fed into a membrane module separation system for separation at 35°C. The first membrane module was a nanofiltration membrane with a molecular weight cutoff of 200 Da, operating at a pressure of 1.2 MPa; the second membrane module was a reverse osmosis membrane, operating at a pressure of 2.2 MPa. The overall permeate recovery rate was 50%. The nanofiltration membrane module was used to selectively separate vanadate anions from impurities such as Fe, Al, Mg, Si, and P, while the reverse osmosis membrane module was used to further concentrate the vanadium-enriched solution. After treatment, the vanadium concentration in the resulting vanadium-enriched solution was 34.5 g / L. The removal rates of Fe, Al, Mg, Si, and P were 95.8%, 96.4%, 94.9%, 98.6%, and 97.2%, respectively. The total removal rate of impurities was greater than 90%, and the removal rate of colloidal substances was 91.9%. After 10 hours of continuous operation, the membrane module separation system was cleaned online with 0.8 mol / L sodium hydroxide solution for 45 minutes, resulting in a membrane flux recovery rate of 95.9%.

[0090] 6. Closed-loop circulation and vanadium precipitation: The resulting vanadium-enriched solution is sent to the vanadium precipitation process to prepare ammonium metavanadate; the reverse osmosis permeate is returned to the leaching process for reuse. Testing showed that the Na₂O concentration in the reverse osmosis permeate was 1.8 g / L, the total impurity content was 35 ppm, and the pH was 9.0. In this example, the total vanadium recovery rate was 93.8%, and the purity of the vanadium-precipitated product, ammonium metavanadate, was not less than 98.8%.

[0091] This embodiment demonstrates that when water is used as a leaching agent to treat sodium-roasted vanadium-containing clinker, the present invention can still achieve effective purification and concentration of the vanadium-containing leachate, increasing the vanadium mass concentration from 10.8 g / L to 34.5 g / L, while maintaining a high impurity removal rate, vanadium recovery rate, and membrane flux recovery rate.

[0092] Example 6:

[0093] This embodiment provides a method for purifying and concentrating vanadium-containing leaching solution in vanadium metallurgy, which is used to illustrate the treatment effect of the present invention under different pH conditions, and further to illustrate the rationality of the preferred pH range.

[0094] The raw materials and process flow used in this embodiment are the same as those in Embodiment 1. The difference is that when adjusting the pH and reconstructing vanadium anions, the pH of the solution is adjusted to 9.0, 10.0, 10.5, 11.0, 11.5 and 12.5, and the reaction is stirred for 20 minutes to convert vanadium into vanadate anion form, thus obtaining vanadium anion reconstruction solutions under different pH conditions.

[0095] The vanadium concentration, total removal rate of impurities, removal rate of colloidal substances, total vanadium recovery rate, and membrane flux recovery rate after cleaning of the vanadium-enriched solutions obtained under different pH conditions in this embodiment after multi-stage filtration, security filtration, membrane module separation, closed-loop circulation, and vanadium precipitation were measured. The results are shown in the table below:

[0096] Table 1. Treatment effect of vanadium-containing leachate under different pH conditions;

[0097] ;

[0098] As shown in Table 1, when the pH is controlled within the range of 9.0 to 12.5, the vanadium concentration in the enriched vanadium-containing solution can reach more than 30 g / L, the total removal rate of impurity components is greater than 90%, the total vanadium recovery rate is higher than 92%, and the membrane flux recovery rate after cleaning is not less than 95%. This indicates that the pH range specified in this invention can meet the requirements for purification, concentration, and stable operation of vanadium-containing leachate.

[0099] Further comparisons show that when the pH is controlled within the range of 10.0 to 11.5, the overall vanadium concentration, total impurity removal rate, colloidal substance removal rate, total vanadium recovery rate, and membrane flux recovery rate after cleaning are all relatively high in the vanadium enrichment solution; among them, the overall effect is better when the pH is between 10.5 and 11.0. This indicates that it is reasonable to optimize the pH control to 10.0 to 11.5.

[0100] To further illustrate the continuous operation stability of the membrane module combined separation system of the present invention, the pretreated vanadium-containing solution after pH adjustment, multi-stage filtration, and security filtration in Example 1 was used as the feed liquid and continuously fed into the nanofiltration-reverse osmosis membrane module combined separation system for continuous operation, specifically according to the following process parameters:

[0101] The nanofiltration membrane has a molecular weight cutoff of 200 Da and an operating pressure of 1.2 MPa; the reverse osmosis membrane operates at 2.2 MPa; the overall system recovery rate is controlled at 50%, and the operating temperature is 35℃. The system runs continuously for 72 hours, and is cleaned online for 45 minutes every 10 hours with 0.8 mol / L sodium hydroxide solution.

[0102] The vanadium concentration, impurity removal rate, and membrane flux recovery rate of the vanadium-enriched solution were measured after 24h, 48h, and 72h of operation, respectively. The results are shown in the table below:

[0103] Table 2. Continuous operation results of the membrane module combined separation system;

[0104] ;

[0105] As shown in Table 2, after 72 hours of continuous operation, the vanadium concentration in the vanadium-enriched solution remained above 35 g / L, the total removal rate of impurities was still greater than 90%, and the membrane flux recovery rate after cleaning was still higher than 95%. This indicates that the combination of pH adjustment, multi-stage filtration, security filtration, and online cleaning effectively mitigates membrane fouling and ensures the continuous and stable operation of the membrane module separation system.

[0106] To further illustrate the closed-loop reuse effect of the reverse osmosis permeate of the present invention, the permeate generated by the reverse osmosis membrane module in Example 1 was used as the reuse liquid. Testing revealed that the Na₂O concentration in this reverse osmosis permeate was 2.2 g / L, the total impurity content was 32 ppm, and the pH value was 9.2, classifying it as low-impurity alkaline fresh water. The reverse osmosis permeate was used to replace fresh water at ratios of 40%, 50%, and 60% and returned to the leaching process for vanadium-containing clinker leaching tests. The vanadium-containing leachates obtained from each group were then subjected to pH adjustment, multi-stage filtration, security filtration, nanofiltration separation, and reverse osmosis concentration treatment according to the steps of the present invention. The leaching and subsequent membrane treatment results under different reuse ratios are shown in the table below:

[0107] Table 3. Reuse efficiency of reverse osmosis permeate;

[0108] ;

[0109] As shown in Table 3, when the reverse osmosis permeate is returned to the leaching process at a ratio of 40% to 60%, the vanadium concentration in the leaching solution does not decrease significantly. The vanadium concentration in the vanadium-enriched solution obtained from subsequent membrane separation and concentration remains above 35 g / L, the total removal rate of impurities is still greater than 90%, and the total vanadium recovery rate is still higher than 92%. Simultaneously, because the reverse osmosis permeate contains a certain degree of alkalinity, the amount of fresh alkali solution replenished can be reduced by 30% to 40%. This indicates that the reverse osmosis permeate obtained by this invention can be directly reused as high-purity alkaline fresh water in the leaching process, achieving closed-loop water resource recycling and reducing the consumption of fresh water and fresh alkali solution.

[0110] The process of this invention mainly includes pH adjustment, multi-stage filtration, security filtration, nanofiltration membrane module, reverse osmosis membrane module, online cleaning, and permeate recycling unit; the solvent extraction method mainly includes multi-stage extraction, back-extraction, phase separation, organic phase circulation, and subsequent concentration unit; the combined chemical precipitation-evaporation concentration method mainly includes chemical impurity removal, solid-liquid separation, evaporation concentration, and wastewater treatment unit. To further illustrate the reduction in equipment investment and operating costs compared to existing processes, calculations are performed based on the same treatment scale, similar influent vanadium concentration, and the same target concentration requirements. The treatment scale is based on 100m³. 3 The vanadium concentration in the influent is 8 g / L to 20 g / L, and the target vanadium concentration in the enriched vanadium-containing solution is 30 g / L to 40 g / L. Comparative processes include the process of this invention, solvent extraction, and a combined chemical precipitation-evaporation concentration method (calculated with the equipment investment and operating cost index of the process of this invention both set at 100). The comparison results are shown in the table below:

[0111] Table 4. Comparison of investment and operating costs of equipment for different processing technologies;

[0112] ;

[0113] As shown in Table 4, under the same processing scale and the same target concentration requirements, the process of this invention eliminates the need for multi-stage extraction-back-extraction equipment, organic phase circulation systems, and high-energy-consuming evaporation and concentration equipment, resulting in simpler equipment configuration. Based on the equipment investment index, the equipment investment of this invention is reduced by approximately 20% to 30% compared to solvent extraction. Furthermore, the main energy consumption of this invention comes from the pumping and membrane separation processes, eliminating the need for evaporation and concentration, and the reverse osmosis permeate can be returned to the leaching process, reducing the consumption of fresh water and fresh alkali solution. Considering both energy and reagent consumption, the operating cost of this invention is reduced by approximately 15% to 25% compared to existing solvent extraction or chemical precipitation-evaporation concentration combined methods.

[0114] In summary, this invention not only enables the purification, concentration, and reuse of vanadium-containing leachate, but also reduces equipment investment and operating costs, thus possessing significant industrial application value.

[0115] Comparative Example 1:

[0116] This comparative example provides a method for purifying and concentrating vanadium-containing leachate to illustrate the treatment effect without pH adjustment and vanadium anion reconstruction.

[0117] This comparative example uses the same vanadium-containing leachate as Example 1 as the raw material, the difference being that: pH adjustment and vanadium anion reconstruction are not performed; instead, the vanadium-containing leachate is directly subjected to multi-stage filtration, security filtration, nanofiltration, and reverse osmosis treatment in sequence. All other filtration conditions, nanofiltration membrane molecular weight cutoff, operating pressure, reverse osmosis operating pressure, operating temperature, and system recovery rate are the same as in Example 1.

[0118] Testing revealed that the vanadium concentration in the enriched vanadium-containing solution was 29.4 g / L. The total removal rate of impurities (Fe, Al, Mg, Si, P) was 81.6%, the removal rate of colloidal substances was 84.2%, and the total vanadium recovery rate was 82.4%. After 10 hours of operation, the membrane flux of the membrane module separation system decreased significantly. After online cleaning with 0.8 mol / L sodium hydroxide solution for 45 minutes, the membrane flux recovery rate was 89.6%.

[0119] Compared with Example 1, this comparative example did not convert vanadium to vanadate anion by pH adjustment, resulting in a decrease in the selective separation effect of nanofiltration membrane on vanadium components and impurity components. The vanadium recovery rate and impurity removal rate were significantly reduced, indicating that pH adjustment and vanadium anion reconstruction are key steps to achieve the technical effect of this invention.

[0120] Comparative Example 2:

[0121] This comparative example provides a method for purifying and concentrating vanadium-containing leachate to illustrate the treatment effect when the pH is below the range defined in this invention.

[0122] This comparative example uses the same vanadium-containing leachate as Example 1 as the raw material, the difference being that the pH of the vanadium-containing leachate is adjusted to 8.0, which is lower than the pH range of 9.0~12.5 specified in this invention. The remaining multi-stage filtration, security filtration, nanofiltration, reverse osmosis, and online cleaning conditions are the same as in Example 1.

[0123] Testing revealed that the vanadium concentration in the enriched vanadium-containing solution was 28.6 g / L. The total removal rate of impurities (Fe, Al, Mg, Si, P) was 82.4%, the removal rate of colloidal substances was 84.7%, and the total vanadium recovery rate was 84.9%. After 10 hours of operation, the membrane flux decreased by 29.5%, and the membrane flux recovery rate after online cleaning was 90.8%.

[0124] Compared to Example 1, when the pH is below 9.0, the formation of vanadate anions is insufficient, which is detrimental to the selective separation achieved by the nanofiltration membrane using charge effect and size sieving effect. This results in a decrease in vanadium enrichment effect, impurity removal effect, and membrane flux recovery effect. This demonstrates the necessity of controlling the pH within the range of 9.0 to 12.5 in this invention.

[0125] Comparative Example 3:

[0126] This comparative example provides a method for purifying and concentrating vanadium-containing leachate to illustrate the treatment effect when the pH is higher than the range defined in this invention.

[0127] This comparative example uses the same vanadium-containing leachate as Example 1 as the raw material, the difference being that the pH of the vanadium-containing leachate is adjusted to 13.0, which is higher than the pH range of 9.0~12.5 specified in this invention. The remaining multi-stage filtration, security filtration, nanofiltration, reverse osmosis, and online cleaning conditions are the same as in Example 1.

[0128] Testing revealed that the vanadium concentration in the enriched vanadium-containing solution was 34.1 g / L. The total removal rate of impurities (Fe, Al, Mg, Si, P) was 87.6%, the removal rate of colloidal substances was 86.3%, and the total vanadium recovery rate was 88.5%. After 10 hours of operation, the membrane flux decreased by 33.2%, and the membrane flux recovery rate after online cleaning was 91.5%.

[0129] Compared to Example 1, when the pH is higher than 12.5, the solution alkalinity is too high, which increases the stability of some impurity components and colloidal substances, easily aggravating membrane fouling and affecting the selective separation effect of nanofiltration. As a result, the impurity removal rate, total vanadium recovery rate, and membrane flux recovery rate are all lower than those of the present invention. This indicates that controlling the upper limit of pH to within 12.5 is beneficial to maintaining stable system operation.

[0130] Comparative Example 4:

[0131] This comparative example provides a method for purifying and concentrating vanadium-containing leachate to illustrate the treatment effect without multi-stage filtration and security filtration pretreatment.

[0132] This comparative example uses the same vanadium-containing leachate as in Example 1 as the raw material, and adjusts the pH of the solution to 10.5 according to the method in Example 1. The difference is that after pH adjustment, the solution is not subjected to 300-mesh coarse filtration, 2000-mesh medium filtration, 4000-mesh fine filtration, or security filtration, but is directly introduced into the nanofiltration-reverse osmosis membrane module combined separation system. The remaining nanofiltration, reverse osmosis, and online cleaning conditions are the same as in Example 1.

[0133] Testing revealed that the vanadium concentration in the enriched vanadium-containing solution was 35.2 g / L. The total removal rate of Fe, Al, Mg, Si, and P impurities was 88.1%, the removal rate of colloidal substances was 76.5%, and the total vanadium recovery rate was 90.3%. After 8 hours of operation, the membrane flux decreased by 41.8%, and the membrane flux recovery rate after online cleaning was 88.9%.

[0134] Compared to Example 1, this comparative example did not include multi-stage filtration and security filtration. Unreacted clinker particles, oxide precipitates, suspended particles, and colloidal precursors directly entered the membrane module, resulting in increased membrane fouling, a significant decrease in membrane flux, and poorer cleaning and recovery performance. This demonstrates that multi-stage filtration and security filtration can effectively reduce the risk of membrane fouling and are crucial steps in ensuring the continuous and stable operation of the membrane module separation system.

[0135] Comparative Example 5:

[0136] This comparative example provides a method for purifying and concentrating vanadium-containing leachate to illustrate the treatment effect when only reverse osmosis membrane is used for concentration without setting a nanofiltration membrane module.

[0137] This comparative example uses the same vanadium-containing leachate as in Example 1 as the raw material, and performs pH adjustment, multi-stage filtration, and security filtration according to the method in Example 1. The difference is that a nanofiltration membrane module is not used; the pretreated vanadium-containing solution is directly fed into a reverse osmosis membrane module for concentration. The reverse osmosis operating pressure is 2.2 MPa, the operating temperature is 35°C, and the concentration endpoint is controlled to ensure that the vanadium mass concentration in the concentrated vanadium-containing solution reaches above 30 g / L.

[0138] Testing revealed that the vanadium concentration in the concentrated vanadium-containing solution was 35.2 g / L, the total removal rate of Fe, Al, Mg, Si, and P impurities was 72.8%, the removal rate of colloidal substances was 70.4%, and the total vanadium recovery rate was 86.5%. After 8 hours of continuous operation, the membrane flux decreased by 38.7%, and the membrane flux recovery rate after online cleaning was 90.2%. The purity of the vanadium precipitate was 92.3%.

[0139] Compared to Example 1, although this comparative example can increase the vanadium concentration through reverse osmosis, the lack of selective impurity removal by nanofiltration membranes leads to the co-enrichment of impurities such as Fe, Al, Mg, Si, and P, as well as some colloidal substances, along with vanadium. This results in a higher impurity content in the concentrate, a decrease in the purity of the vanadium-precipitated product, and increased membrane fouling. This demonstrates the crucial role of nanofiltration membrane modules in achieving the selective separation of vanadium from impurities.

[0140] Comparative Example 6:

[0141] This comparative example provides a method for purifying and concentrating vanadium-containing leachate to illustrate the treatment effect when using a traditional chemical precipitation-evaporation concentration process.

[0142] This comparative example uses the same vanadium-containing leachate as in Example 1 as the raw material, and employs a traditional method of chemical precipitation for impurity removal followed by evaporation and concentration. Specifically, a chemical impurity remover is added to the vanadium-containing leachate for precipitation and impurity removal. After solid-liquid separation, the filtrate is evaporated and concentrated to achieve a vanadium concentration of 30 g / L or higher in the concentrated solution.

[0143] Testing revealed that the vanadium concentration in the concentrated vanadium-containing solution was 34.6 g / L, the total removal rate of Fe, Al, Mg, Si, and P impurities was 88.2%, the vanadium loss rate was 7.8%, and the total vanadium recovery rate was 87.2%. The process requires a significant amount of chemical impurity removal agents and generates wastewater containing salt and impurities, which is difficult to directly return to the leaching process for recycling. Furthermore, the evaporation and concentration process consumes a large amount of energy, resulting in a higher overall operating cost than the process described in this invention.

[0144] Compared to Example 1, while the traditional chemical precipitation-evaporation concentration process can increase vanadium concentration, it suffers from problems such as vanadium loss due to co-precipitation with impurities, high reagent consumption, difficulty in wastewater reuse, and high energy consumption. This invention employs a process route involving pH adjustment, multi-stage filtration, nanofiltration-reverse osmosis combined separation, and permeate reuse, which can achieve purification, concentration, and water resource recycling while reducing vanadium loss.

[0145] Comparative Example 7:

[0146] This comparative example provides a method for purifying and concentrating vanadium-containing leachate to illustrate the treatment effect when using traditional solvent extraction methods.

[0147] This comparative example uses the same vanadium-containing leachate as in Example 1 as the raw material, and employs solvent extraction for vanadium enrichment and impurity removal. The method includes steps such as extraction, back-extraction, organic phase recycling, and subsequent concentration.

[0148] After calculation, under the same processing scale, similar influent vanadium concentration, and the same target concentration requirements, solvent extraction requires multi-stage extraction tanks, back-extraction tanks, mixing and clarifiers, organic phase storage tanks, and organic phase circulation systems, resulting in complex equipment configuration. It also consumes organic extractants, diluents, and back-extraction agents, posing risks of organic phase entrainment, extractant loss, and secondary pollution. Based on the same processing scale, the equipment investment index for solvent extraction is 125-143, and the comprehensive operating cost index is 118-133; while the equipment investment index and comprehensive operating cost index for the process of this invention are both calculated as 100.

[0149] Compared to Example 1, solvent extraction involves more equipment, a more complex process, and higher reagent consumption and operating and maintenance costs. This invention eliminates the need for multi-stage extraction-back-extraction equipment and an organic phase circulation system, primarily achieving impurity removal and concentration through membrane array separation. Therefore, equipment investment is reduced by approximately 20%–30% compared to solvent extraction, and operating costs are reduced by approximately 15%–25%.

[0150] In summary, without pH adjustment and vanadium anion reconstruction, the selective separation effect between vanadium components and impurity components significantly decreases, leading to a reduction in vanadium enrichment, impurity removal rate, and total vanadium recovery rate. Comparative Examples 2 and 3 show that when the pH is below 9.0 or above 12.5, it is difficult to achieve the purification, concentration, and stable membrane operation effects described in the embodiments of this invention, indicating the necessity of controlling the pH within the range of 9.0 to 12.5. Comparative Example 4 shows that without multi-stage filtration and security filtration pretreatment, membrane fouling is significantly aggravated, and the membrane flux recovery rate decreases. Comparative Example 5 shows that although reverse osmosis membrane concentration can increase vanadium concentration, it is difficult to effectively remove impurity components such as Fe, Al, Mg, Si, and P, resulting in a decrease in the purity of the vanadium precipitate. Comparative Examples 6 and 7 show that traditional chemical precipitation-evaporation concentration processes and solvent extraction methods have problems such as significant vanadium loss, high energy consumption, difficulty in wastewater reuse, complex equipment configuration, and high operating costs.

[0151] Therefore, this invention, through the synergistic effects of pH adjustment and vanadium anion reconstruction, multi-stage filtration, security filtration, nanofiltration-reverse osmosis combined separation, and permeate recycling, can achieve efficient enrichment of vanadium in vanadium-containing leachate, effective removal of impurity components, reduction of membrane fouling, and recycling of permeate. It has a high vanadium recovery rate, good membrane operation stability, and low operating cost.

Claims

1. A method for purifying and concentrating vanadium-containing leaching solution during vanadium metallurgy, characterized in that, Includes the following steps: S1. Leaching of vanadium-containing materials: The vanadium-containing clinker after roasting is leached under the action of a leaching agent to obtain a vanadium-containing leachate; S2. pH Adjustment and Vanadium Anion Reconstruction: An alkaline adjuster is added to the vanadium-containing leachate to adjust the pH to 9.0-12.

5. The mixture is stirred to allow vanadium to exist as vanadate anions, resulting in a vanadate anion reconstructed solution. The vanadate anions include VO42-. 3- HVO4 2- One or more of the following; S3. Multi-stage filtration: The vanadium anion reconstruction solution is sequentially fed into a 300-mesh coarse filter, a 2000-mesh medium filter, and a 4000-mesh fine filter for filtration to remove solid particulate impurities from the leachate and obtain a primary vanadium-containing solution. S4. Security filtration: The primary vanadium-containing liquid is sent to a security filter for filtration to remove fine particles and colloidal precursors, resulting in a secondary vanadium-containing liquid. S5. Membrane assembly separation: The secondary vanadium-containing solution is fed into a membrane assembly separation system for separation; the membrane assembly separation system consists of a first membrane module and a second membrane module connected in series, wherein the first membrane module is a nanofiltration membrane module and the second membrane module is a reverse osmosis membrane module; the secondary vanadium-containing solution is filtered by the nanofiltration membrane module to obtain a vanadium-enriched solution and an impurity permeate; the vanadium-enriched solution is filtered by the reverse osmosis membrane module to obtain a vanadium-enriched solution and a reverse osmosis permeate; S6. Closed-loop circulation: The vanadium-enriched solution is sent to the vanadium precipitation process, and the reverse osmosis permeate is returned to the vanadium-containing material leaching step for recycling, forming a closed-loop circulation system of "leaching - pH adjustment - filtration - membrane separation - vanadium precipitation - permeate recycling".

2. The method for purifying and concentrating vanadium-containing leaching solution in vanadium metallurgy according to claim 1, characterized in that, The operating temperature for the membrane module separation process is 25℃~40℃; The nanofiltration membrane module has a molecular weight cutoff of 100 Da to 300 Da and an operating pressure of 0.8 MPa to 1.5 MPa. The reverse osmosis membrane module operates at a pressure of 1.5 MPa to 3.0 MPa.

3. The method for purifying and concentrating vanadium-containing leaching solution in vanadium metallurgy according to claim 2, characterized in that, The vanadium concentration in the enriched vanadium solution is 30 g / L to 40 g / L; the Na2O concentration in the reverse osmosis permeate is 1.5 g / L to 3.0 g / L, the total impurity content is ≤50 ppm, and the pH value is 8.5 to 10.0; the overall permeate recovery rate of the membrane module combination separation system is 45% to 55%.

4. The method for purifying and concentrating vanadium-containing leaching solution in vanadium metallurgy according to claim 2, characterized in that, During continuous operation of the membrane module separation system, every 8 to 12 hours, the first membrane module and / or the second membrane module are cleaned online with a 0.5 mol / L to 1.0 mol / L sodium hydroxide solution for 30 to 60 minutes. After cleaning, the membrane flux recovery rate is not less than 95%.

5. The method for purifying and concentrating vanadium-containing leaching solution in vanadium metallurgy according to claim 1, characterized in that, In S1, the calcination treatment is sodium calcination or calcination; The leaching process involves mixing vanadium-containing clinker with a leaching agent at a solid-liquid ratio of 1:(2.5~3.0) and leaching at 90℃~100℃ for 1.5h~3.0h with stirring; wherein the leaching agent is one of water, alkaline aqueous solution or acidic aqueous solution; The vanadium-containing leachate has a vanadium concentration of 8 g / L to 20 g / L and impurity element contents of 2 g / L to 8 g / L, 3 g / L to 12 g / L, 1 g / L to 5 g / L, 0.5 g / L to 3 g / L, and 0.01 g / L to 0.1 g / L.

6. A method for purifying and concentrating vanadium-containing leaching solution in a vanadium metallurgical process according to claim 1, characterized in that, Adjust the pH of the vanadium-containing leachate to 10.0~11.

5.

7. The method for purifying and concentrating vanadium-containing leaching solution in vanadium metallurgy according to claim 1, characterized in that, In S2, the stirring reaction time is 10 min to 30 min; The alkalinity regulator is one or more of sodium hydroxide, potassium hydroxide, and sodium carbonate.

8. The method for purifying and concentrating vanadium-containing leaching solution in vanadium metallurgy according to claim 1, characterized in that, In S3, multi-stage filtration is performed under conditions of 0.1MPa~0.3MPa and 40℃~60℃; the single-stage filtration flux is 50L / (m³). 2 ·h)~100L / (m 2 ·h).

9. The method for purifying and concentrating vanadium-containing leaching solution in vanadium metallurgy according to claim 1, characterized in that, In S4, security filtration is carried out under conditions of 0.1MPa~0.2MPa and 25℃~40℃, with a filtration accuracy of 5μm~10μm and a filtration flux of 80L / (m²). 2 ·h)~150L / (m 2 ·h).

10. A method for purifying and concentrating vanadium-containing leaching solution in a vanadium metallurgical process according to any one of claims 1 to 9, characterized in that, The total removal rate of impurity components in vanadium-containing leachate is over 90%.

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