Method and system for deep vanadium removal from high-concentration vanadium-containing sodium nitrate wastewater

Abstract

The present application relates to the field of industrial wastewater treatment and vanadium resource recovery, and discloses a method and system for deep vanadium removal from high-concentration vanadium-containing sodium nitrate wastewater. The method comprises: passing the high-concentration vanadium-containing sodium nitrate wastewater into the middle chamber of a fluidized bed electrodialysis device, and filling the middle chamber with weak base anion exchange resin; adjusting the pH of the wastewater to be acidic, applying a direct current voltage to strengthen ion migration, and allowing vanadium to be selectively adsorbed by the resin in the form of vanadate anions; when the adsorption capacity of the resin reaches 70%-90% of the saturation capacity, an oxidizing agent and a calcium-containing precipitant are sequentially added to convert the residual vanadium on the resin and in the wastewater into vanadium-containing precipitates, and the vanadium-removed sodium nitrate wastewater and vanadium-rich solid products are obtained by filtration and separation. The present application can stably remove vanadium from 0.1-0.5g / L to below 5mg / L in sodium nitrate wastewater, meet the subsequent sodium nitrate wastewater treatment requirements, and realize the resource utilization of vanadium resources.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment and vanadium resource recovery, and particularly to a method and system for removing vanadium from high-concentration vanadium-containing sodium nitrate wastewater. Background Technology

[0002] In chemical production, hydrometallurgy, and vanadium battery electrolyte regeneration processes, high-sodium nitrate and vanadium-containing industrial wastewater is easily generated. Typical components of this wastewater include sodium nitrate concentrations of 50-220 g / L and vanadium concentrations of 0.1-0.5 g / L. Vanadium is a toxic and hazardous pollutant; if not removed beforehand, it will significantly affect subsequent biological treatment, membrane treatment, or evaporation crystallization processes for sodium nitrate wastewater, leading to equipment contamination, reduced treatment efficiency, and substandard effluent. Furthermore, the direct discharge of vanadium, a strategic resource, would result in resource waste. Therefore, vanadium in the wastewater must be removed to below 5 mg / L to ensure stable operation of subsequent sodium nitrate wastewater treatment. Traditional purification technologies all face significant bottlenecks under these specific conditions, making it difficult to achieve deep vanadium removal economically and efficiently. Chemical precipitation method: If calcium, magnesium, or iron salts are directly added to the above-mentioned high-concentration sodium nitrate solution as precipitants, a significant amount of sodium nitrate will be lost (usually greater than 5%) due to a severe co-precipitation effect. Furthermore, this method has limited vanadium removal depth, and the residual vanadium content in the treated solution is typically higher than 10 mg / L, which cannot meet the requirements for ultra-high purity.

[0003] Solvent extraction: When using phosphoric acid extractants such as tributyl phosphate (TBP) and di(2-ethylhexyl)phosphoric acid (P204) to treat high-salt solutions, salting-out can easily lead to emulsification or the formation of a difficult-to-separate third phase, causing operational difficulties. Furthermore, the back-extraction process typically requires high-concentration acids, introducing new impurity ions such as chloride and sulfate, which may cause secondary contamination of product purity.

[0004] Ion exchange method: Commercially available strong-base anion exchange resins (such as type 201×7) are used in high-concentration competitive anions nitrate (NO3) 3- Under the condition of presence, for the target impurity vanadate ion (such as VO4), 3- H2VO4 - The selectivity of vanadium-containing resins (such as vanadium-containing polymers) is extremely low, with a selectivity coefficient typically less than 2. This results in a very small effective adsorption capacity for vanadium, rapid vanadium penetration during dynamic adsorption, and low throughput. Furthermore, the high osmotic pressure environment easily leads to swelling, cracking, or physical breakage of resin particles, affecting the long-term stable operation of the device.

[0005] Membrane separation and electrochemical methods: Methods such as electrodialysis and membrane electrolysis are theoretically feasible, but they have problems such as extremely high energy consumption, easy fouling or clogging of ion exchange membranes, and high investment and operating costs.

[0006] Among existing patent technologies, application number CN201910014654.2 discloses a method for determining the vanadium content in the supported liquid used for SCR catalyst regeneration. Its core lies in analysis and detection, and is unrelated to the process objective of separation and purification. Application number CN201910482594.7 discloses a method for quantitative detection of vanadium valence state based on high-performance liquid chromatography (HPLC). While this method is accurate, the equipment is expensive, the operation is complex, and the analysis cycle is long, making it unsuitable for online or rapid detection and control in industrial production processes.

[0007] Therefore, it is still necessary to develop a continuous, low-cost purification technology that can directly treat high-salt raw solutions, avoid sodium nitrate loss, not introduce new impurities, and stably reduce the vanadium content to below 5 mg / L. Summary of the Invention

[0008] To address the shortcomings of the existing technology, a method and system for removing vanadium from high-concentration sodium nitrate wastewater containing vanadium is provided, achieving selective separation and resource recovery of trace vanadium impurities in high-concentration sodium nitrate brine.

[0009] To achieve the above objectives, the following technical solution is adopted: This invention provides a method for removing vanadium from high-concentration sodium nitrate wastewater containing vanadium, comprising the following steps: High-concentration vanadium-containing sodium nitrate wastewater is fed into the intermediate chamber of a fluidized bed electrodialysis device, which is filled with a weak base anion exchange resin. A DC voltage is applied between the anode and cathode chambers of the fluidized bed electrodialysis device, and the pH value of the high-concentration vanadium-containing sodium nitrate wastewater in the intermediate chamber is adjusted to the acidic range under the action of the electric field, so that the vanadium in the high-concentration vanadium-containing sodium nitrate wastewater exists in the form of vanadate anions and is adsorbed by the weak base anion exchange resin, thereby obtaining vanadium-loaded weak base anion exchange resin and purified liquid. When the adsorption capacity of the weak base anion exchange resin for vanadium reaches 70-90% of its saturation capacity, the feeding is stopped and the system is switched to regeneration mode. The regeneration mode includes: sequentially adding an oxidant and a calcium-containing precipitant into the intermediate chamber to react and convert the vanadium on the vanadium-loaded weak base anion exchange resin and the vanadium in the purification liquid into vanadium-containing precipitate. After filtration and separation, sodium nitrate wastewater and vanadium-containing precipitate after vanadium removal are obtained. The vanadium-containing precipitate is then post-treated to obtain a vanadium-rich solid product.

[0010] In some embodiments, at least a portion of the side-flow liquid is drawn from the cathode chamber and subjected to membrane separation to obtain a concentrate and a permeate. The concentrate is returned to the anode chamber, and the permeate is used as a backwash solution for the weak base anion exchange resin.

[0011] In some embodiments, the concentration of sodium nitrate in the high-concentration sodium nitrate wastewater containing vanadium is 150-220 g / L, and the concentration of vanadium is 0.1-0.5 g / L.

[0012] In some embodiments, a DC voltage of 0.6-1.0V is applied between the anode and cathode chambers of the fluidized bed electrodialysis apparatus, such that the pH value of the high-concentration sodium nitrate wastewater containing vanadium in the intermediate chamber is controlled within the range of 2.5-4.0.

[0013] In some embodiments, the oxidant is chlorate; after the oxidant is added, the pH value of the reaction is 1.0-3.0, the temperature is 15-40°C, and the reaction time is 10-60 minutes.

[0014] In some embodiments, the calcium-containing precipitant is a calcium nitrate solution; the molar ratio of calcium ions to vanadium in the calcium-containing precipitant is 0.7:1 to 1.2:1; and the reaction time after adding the precipitant is 10-40 minutes.

[0015] In some embodiments, the membrane separation is performed using a nanofiltration membrane; at least a portion of the sideflow liquid drawn from the cathode chamber accounts for 5%-10% of the total sideflow liquid volume.

[0016] The present invention also provides a system for removing vanadium from high-concentration vanadium-containing sodium nitrate wastewater, for implementing the method described above, comprising: A fluidized bed electrodialysis device is provided, comprising an anode chamber, an intermediate chamber, and a cathode chamber in sequence. The intermediate chamber is filled with a weak base anion exchange resin and is equipped with an inlet for introducing high-concentration vanadium-containing sodium nitrate wastewater. A liquid distributor for fluidizing the resin bed is provided at the bottom of the intermediate chamber. A DC power supply, electrically connected to the anode chamber and the cathode chamber, is used to apply a DC voltage; An oxidant dosing unit is connected to the dosing port of the intermediate chamber via a pipeline; A precipitant dosing unit is connected to the dosing port of the intermediate chamber via a pipeline; A filtration unit, which is connected to the outlet of the intermediate chamber via a pipeline, is used to separate the solid-liquid mixture in the intermediate chamber.

[0017] In some embodiments, the system further includes: A salinity maintenance unit includes a membrane separation device. The inlet of the membrane separation device is connected to the outlet of the cathode chamber via a pipeline. The concentrate outlet of the membrane separation device is connected to the inlet of the anode chamber via a pipeline. The permeate outlet of the membrane separation device is connected to the flushing liquid inlet of the intermediate chamber via a pipeline.

[0018] In some embodiments, the system further includes a programmable logic controller (PLC) that controls the switching of feeding, regeneration, dosing, and filtration operations of the fluidized bed electrodialysis unit.

[0019] The present invention has the following beneficial technical effects: The method and system for removing vanadium from high-concentration sodium nitrate wastewater of the present invention aim to deeply purify the vanadium concentration in the solution from 0.1-0.5 g / L to below 5 mg / L without diluting the high-concentration sodium nitrate wastewater, without introducing organic solvents, and under the condition of achieving closed-loop circulation of water and salt within the system, without introducing new impurities, while ensuring a sodium nitrate recovery rate of >98%, and producing a vanadium-rich solid product with economic value as a byproduct, namely vanadium slag, which meets the requirements of subsequent sodium nitrate wastewater treatment and realizes the resource utilization of vanadium resources. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of a method for removing vanadium from high-concentration sodium nitrate wastewater according to an embodiment of the present invention; Figure 2 This is a schematic diagram of a system for removing vanadium from high-concentration sodium nitrate wastewater according to an embodiment of the present invention.

[0022] List of reference numerals 1-Anode chamber; 2-Intermediate chamber; 3-Cathode chamber; 4-DC power pulse controller; 5-Oxidant storage tank and dosing system; 6-Flocculant storage tank and dosing system; 7-Nanofiltration membrane unit; 8-Surfactant inlet; 9-Electrode liquid inlet; 10-Filtered electrode liquid outlet; 11-Cathode chamber purified liquid outlet; 12-Anode chamber purified liquid outlet. Detailed Implementation

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

[0024] It should be understood that the embodiments of the invention shown in the exemplary embodiments are merely illustrative. Although only a few embodiments have been described in detail in this invention, those skilled in the art will readily recognize that various modifications are possible without substantially departing from the teachings of the invention. Accordingly, all such modifications should be included within the scope of the invention. Other substitutions, modifications, variations, and deletions can be made to the design, operating conditions, and parameters of the following exemplary embodiments without departing from the spirit of the invention.

[0025] In view of the above objectives, one aspect of the embodiments of the present invention is as follows: Figure 1-2 As shown, a method for removing vanadium from high-concentration sodium nitrate wastewater containing vanadium is proposed. Figure 1 The diagram shown is a schematic flowchart of the method.

[0026] like Figure 1 As shown, the method may include the following steps: S101. High-concentration vanadium-containing sodium nitrate wastewater is introduced into the intermediate chamber of a fluidized bed electrodialysis device, which is filled with a weak base anion exchange resin. A DC voltage is applied between the anode and cathode chambers of the fluidized bed electrodialysis device, and the pH value of the high-concentration vanadium-containing sodium nitrate wastewater in the intermediate chamber is adjusted to the acidic range under the action of the electric field, so that the vanadium in the high-concentration vanadium-containing sodium nitrate wastewater exists in the form of vanadate anions and is adsorbed by the weak base anion exchange resin, thereby obtaining vanadium-loaded weak base anion exchange resin and purified liquid. S102. When the adsorption capacity of the weak base anion exchange resin for vanadium reaches 70-90% of its saturation capacity, the feeding is stopped and the regeneration mode is switched. The regeneration mode includes: adding an oxidant and a calcium-containing precipitant sequentially into the intermediate chamber to react and convert the vanadium on the vanadium-loaded weak base anion exchange resin and the vanadium in the purification liquid into vanadium-containing precipitate. After filtration and separation, sodium nitrate wastewater and vanadium-containing precipitate after vanadium removal are obtained. The vanadium-containing precipitate is then post-treated to obtain a vanadium-rich solid product.

[0027] Specifically, the method includes: passing high-concentration vanadium-containing sodium nitrate wastewater into the intermediate chamber of a fluidized bed electrodialysis device, the intermediate chamber being filled with a weak-base anion exchange resin; adjusting the pH of the wastewater to acidic, applying a DC voltage to enhance ion migration, so that vanadium is selectively adsorbed by the resin in the form of vanadate anions; when the resin adsorption capacity reaches 70%–90% of its saturation capacity, sequentially adding an oxidant and a calcium-containing precipitant to convert residual vanadium on the resin and in the wastewater into vanadium-containing precipitates, and filtering to separate the vanadium-removed sodium nitrate wastewater and vanadium-rich solid products. In some embodiments, at least a portion of the side-flow liquid is drawn from the cathode chamber, treated by membrane separation to obtain a concentrate and a permeate, the concentrate being returned to the anode chamber, and the permeate being used as backwashing liquid for the weak-base anion exchange resin.

[0028] In some embodiments, in high-concentration vanadium-containing sodium nitrate wastewater, the concentration of sodium nitrate is 150-220 g / L, and the concentration of vanadium is 0.1-0.5 g / L.

[0029] In some embodiments, a DC voltage of 0.6-1.0V is applied between the anode and cathode chambers of the fluidized bed electrodialysis device, thereby controlling the pH value of the high-concentration vanadium-containing sodium nitrate wastewater in the intermediate chamber within the range of 2.5-4.0. Specifically, by optimizing the electric field strength, the local pH of the reaction system is precisely controlled to the optimal range, allowing vanadium to exist in the most easily adsorbed polyanionic form, while avoiding increased energy consumption or water decomposition side reactions caused by excessive voltage, achieving an optimal balance between separation efficiency and energy consumption.

[0030] In some embodiments, the oxidant is chlorate; after the addition of the oxidant, the reaction pH is 1.0-3.0, the temperature is 15-40°C, and the reaction time is 10-60 minutes. Specifically, the chlorate is preferably NaClO3. This ensures that all vanadium in its valence state adsorbed on the resin is completely and rapidly oxidized to pentavalent, providing a uniform precursor for subsequent precipitation reactions, while the mild conditions avoid oxidative damage to the resin and corrosion of the equipment.

[0031] In some embodiments, the calcium-containing precipitant is a calcium nitrate solution; the molar ratio of calcium ions to vanadium in the calcium-containing precipitant is 0.7:1 to 1.2:1; and the reaction time after adding the precipitant is 10-40 minutes. Specifically, using calcium nitrate as the precipitant, under optimized proportions, it can efficiently combine with vanadium produced by oxidation to form calcium metavanadate precipitate with extremely low solubility, achieving vanadium solidification and enrichment. The resulting vanadium slag has high purity and less excess calcium ions, reducing the risk of scaling in subsequent systems.

[0032] In some embodiments, membrane separation is performed using a nanofiltration membrane; at least a portion of the sidestream liquid drawn from the cathode chamber accounts for 5%-10% of the total sidestream liquid volume. Specifically, nanofiltration can effectively retain divalent ions (such as Ca2+). 2+ ), while allowing monovalent ions (Na) + This process precisely removes accumulated divalent ions from the system, maintaining the stability of the electrolyte composition in the main system. Simultaneously, the generated permeate can be used as flushing water, achieving both internal water balance and controlled removal of impurity ions.

[0033] Specifically, the high-concentration sodium nitrate wastewater (containing 0.1-0.5 g / L vanadium) to be treated is pumped into the intermediate chamber from the bottom. The flow rate is controlled to maintain the resin bed in a fluidized state with a 20-30% expansion rate, which greatly enhances mass transfer efficiency and prevents channeling. A low DC voltage of 0.6-1.0 V is applied between the anode and cathode chambers. Under the influence of the electric field, the local pH of the intermediate chamber solution is adjusted to a weakly acidic range of 2.5-4.0. Under these conditions, vanadium mainly exists as polyvanadate anions (such as V...10 O 28 6- Vanadium exists in the form of sodium nitrate ions, and its size and charge characteristics enable it to be selectively adsorbed by weak base resins, while a large number of monovalent nitrate ions are not adsorbed, thus achieving efficient separation of vanadium from the sodium nitrate matrix.

[0034] When the resin's adsorption capacity for vanadium reaches 70-90% of its saturation capacity, feeding is stopped and the system switches to regeneration mode. First, an acidic solution containing an oxidant (such as NaClO3) is injected into the intermediate chamber. The reaction is carried out for 10-60 minutes at pH 1.0-3.0 and a temperature of 15-40℃ to ensure that all vanadium on the resin and in the residual solution (including any low-valent vanadium, such as tetravalent vanadium) is oxidized to pentavalent vanadium. Then, a calcium nitrate solution is added directly to the system as a precipitant, controlling the Ca / V molar ratio at 0.7:1 to 1.2:1. The mixture is stirred for 10-40 minutes to generate calcium metavanadate (Ca(VO3)2), a precipitate with extremely low solubility. After solid-liquid separation by filtration, the solid product is mainly Ca(VO3)2. The calcium metavanadate, after washing, calcination, or acid treatment, can be converted into a vanadium-rich solid product containing V2O5. This process yields a purified sodium nitrate solution with a vanadium content of less than 5 mg / L and vanadium slag with a V₂O₅ content of ≥30 wt%. The filtrate can be returned to the system for recycling, achieving zero loss of sodium salts.

[0035] To maintain the long-term stability of the device and avoid impurity ions (such as OH-) - Ca 2+ To prevent water accumulation, the system incorporates a salinity maintenance unit. 5-10% of the side-flow liquid is drawn from the cathode chamber outlet and separated through a nanofiltration membrane (such as the NF90 type). The nanofiltration concentrate (enriched with divalent ions) is returned to the anode chamber, while the permeate (mainly clean water containing trace amounts of alkali) is used as the periodic backwash liquid for the resin, thus achieving water balance and zero wastewater discharge for the entire system.

[0036] like Figure 2 As shown, the present invention also provides a system for removing vanadium from high-concentration vanadium-containing sodium nitrate wastewater, for implementing the method described above, comprising: The fluidized bed electrodialysis device comprises an anode chamber 1, an intermediate chamber 2, and a cathode chamber 3. The intermediate chamber 2 is filled with a weak base anion exchange resin and has an inlet (raw solution inlet 8) for introducing high-concentration vanadium-containing sodium nitrate wastewater. A distributor is located at the bottom of the intermediate chamber 2 to fluidize the resin bed. The device also includes a cathode chamber purified solution outlet 11 and an anode chamber purified solution outlet 12, through which the purified solution is discharged.

[0037] A DC power supply, electrically connected to the anode and cathode chambers, is used to apply a DC voltage. A DC power supply pulse controller 4 is preferably used as the DC power supply.

[0038] The oxidizer dosing unit is connected to the dosing port of the intermediate chamber via a pipeline. The oxidizer dosing unit preferably uses an oxidizer storage tank and dosing system 5.

[0039] The precipitant dosing unit is connected to the dosing port of the intermediate chamber via pipeline. Preferably, the precipitant dosing unit uses a precipitant storage tank and dosing system 6.

[0040] The filtration unit is connected to the outlet of the intermediate chamber via a pipeline and is used to separate the solid-liquid mixture in the intermediate chamber.

[0041] In some embodiments, the system further includes a salinity maintenance unit, which includes a membrane separation device. The inlet of the membrane separation device is connected to the outlet of the cathode chamber via a pipeline, the concentrate outlet of the membrane separation device is connected to the inlet of the anode chamber via a pipeline, and the permeate outlet of the membrane separation device is connected to the flushing liquid inlet of the intermediate chamber via a pipeline. Specifically, the membrane separation device preferably uses a nanofiltration membrane unit 7. The inlet of the membrane separation device is also the polar liquid inlet 9 of the nanofiltration membrane unit. 5-10% of the side-flow liquid from the cathode chamber outlet enters the nanofiltration membrane unit through the polar liquid inlet 9. The filtered polar liquid (i.e., the concentrate, which is enriched with divalent ions) is discharged to the anode chamber 1 through the filtered polar liquid outlet 10. The permeate (mainly clean water containing trace amounts of alkali) is used as the periodic backwash liquid for the resin, thereby achieving water balance and zero wastewater discharge for the entire system.

[0042] In some embodiments, the system further includes a programmable logic controller (PLC) that controls the switching of feeding, regeneration, dosing, and filtration operations of the fluidized bed electrodialysis unit.

[0043] In some embodiments, the intermediate chamber is filled with a specific type of weak base anion exchange resin (preferably tertiary amine type).

[0044] The method and system for removing vanadium from high-concentration sodium nitrate wastewater of the present invention aim to deeply purify the vanadium concentration in the solution from 0.1-0.5 g / L to below 5 mg / L without diluting the high-concentration sodium nitrate stock solution, without introducing organic solvents, and under the condition of achieving closed-loop circulation of water and salt in the system, without introducing new impurities, while ensuring a sodium nitrate recovery rate of >98%, and producing a vanadium-rich solid product with economic value, namely vanadium slag.

[0045] The present invention will be further illustrated by the following examples.

[0046] Example 1 Stock solution: NaNO3 concentration 180g / L, vanadium concentration 0.20g / L, pH 7.2.

[0047] Procedure: The intermediate chamber is filled with 30 mL of tertiary amine-type weak base resin, and the fluidization expansion rate is controlled at 25%. A DC voltage of 0.8 V (current density approximately 100 A·m) is applied. -2 A 1.2V reverse pulse was applied for 30 seconds every 30 minutes. After 4 hours of operation, the resin was saturated with adsorption. The tubing was switched, and a solution containing 2 g / L NaClO3 (pH adjusted to 1.5) was injected for oxidation for 30 minutes. Then, a calcium nitrate solution (Ca / V molar ratio = 0.9:1) was added, stirred for 20 minutes, and then filtered.

[0048] Results: The vanadium content in the purified sodium nitrate solution decreased to 3 mg / L, the sodium nitrate recovery rate was 98.7%, and the V2O5 content in the obtained vanadium slag was 31.2 wt%.

[0049] Example 2 Three sets of the aforementioned electrodialysis devices were connected in parallel, and adsorption and regeneration operations were alternately controlled by a PLC to achieve continuous feeding and discharging. The system operated continuously for 720 hours (30 days) under the conditions of the original solution in Example 1. The system operated stably, with no resin breakage, and the average current efficiency remained at approximately 87%. The purification effect was more than 95% consistent with the data from Example 1.

[0050] Example 3 The stock solution is the same as in Example 1. The resin bed expansion rate is controlled to be approximately 20%. A DC voltage of 0.6V is applied. Other steps and conditions are the same as in Example 1.

[0051] Results: The vanadium content in the purified solution was 2 mg / L, and the sodium nitrate recovery rate was 98.5%.

[0052] Example 4 The stock solution is the same as in Example 1. The resin bed expansion rate is controlled to be approximately 30%. A DC voltage of 1.0V is applied. Other steps and conditions are the same as in Example 1.

[0053] Results: The vanadium content in the purified solution was 2 mg / L, and the sodium nitrate recovery rate was 98.2%.

[0054] Example 5 The original solution was the same as in Example 1. The adsorption conditions were the same as in Example 1. During the precipitation step, the Ca / V molar ratio was controlled at 0.7:1.

[0055] Results: The vanadium content in the purified solution was 3 mg / L, and the sodium nitrate recovery rate was 99.0%.

[0056] Example 6 The stock solution was the same as in Example 1. The adsorption conditions were the same as in Example 1. During the precipitation step, the Ca / V molar ratio was controlled at 1.2:1.

[0057] Results: The vanadium content in the purified solution was 2 mg / L, and the sodium nitrate recovery rate was 98.0%.

[0058] The calculation is based on an industrial plant that processes 100,000 tons of vanadium-containing sodium nitrate brine annually. This system can deeply purify sodium nitrate and produce approximately 20 tons or more of vanadium slag with a V₂O₅ content of ≥30wt% as a byproduct.

[0059] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. Although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0060] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for deep vanadium removal from high-concentration sodium nitrate wastewater containing vanadium, characterized in that, Includes the following steps: High-concentration vanadium-containing sodium nitrate wastewater is fed into the intermediate chamber of a fluidized bed electrodialysis device, which is filled with a weak base anion exchange resin. A DC voltage is applied between the anode and cathode chambers of the fluidized bed electrodialysis device, and the pH value of the high-concentration vanadium-containing sodium nitrate wastewater in the intermediate chamber is adjusted to the acidic range under the action of the electric field, so that the vanadium in the high-concentration vanadium-containing sodium nitrate wastewater exists in the form of vanadate anions and is adsorbed by the weak base anion exchange resin, thereby obtaining vanadium-loaded weak base anion exchange resin and purified liquid. When the adsorption capacity of the weak base anion exchange resin for vanadium reaches 70-90% of its saturation capacity, the feeding is stopped and the system is switched to regeneration mode. The regeneration mode includes: sequentially adding an oxidant and a calcium-containing precipitant into the intermediate chamber to react and convert the vanadium on the vanadium-loaded weak base anion exchange resin and the vanadium in the purification liquid into vanadium-containing precipitate. After filtration and separation, sodium nitrate wastewater and vanadium-containing precipitate after vanadium removal are obtained. The vanadium-containing precipitate is then post-treated to obtain a vanadium-rich solid product.

2. The method for removing vanadium from high-concentration sodium nitrate wastewater according to claim 1, characterized in that, At least a portion of the side-flow liquid is drawn from the cathode chamber and subjected to membrane separation to obtain a concentrate and a permeate. The concentrate is returned to the anode chamber, and the permeate is used as a backwash solution for the weak base anion exchange resin.

3. The method for removing vanadium from high-concentration sodium nitrate wastewater according to claim 1, characterized in that, The high-concentration sodium nitrate wastewater containing vanadium has a sodium nitrate concentration of 150-220 g / L and a vanadium concentration of 0.1-0.5 g / L.

4. The method for removing vanadium from high-concentration sodium nitrate wastewater according to claim 1, characterized in that, The DC voltage applied between the anode and cathode chambers of the fluidized bed electrodialysis device is 0.6-1.0V, so that the pH value of the high-concentration sodium nitrate wastewater containing vanadium in the intermediate chamber is controlled within the range of 2.5-4.

0.

5. The method for removing vanadium from high-concentration sodium nitrate wastewater according to claim 1, characterized in that, The oxidant is chlorate; after adding the oxidant, the pH value of the reaction is 1.0-3.0, the temperature is 15-40℃, and the reaction time is 10-60 minutes.

6. The method for removing vanadium from high-concentration sodium nitrate wastewater according to claim 1, characterized in that, The calcium-containing precipitant is a calcium nitrate solution; the molar ratio of calcium ions to vanadium in the calcium-containing precipitant is 0.7:1 to 1.2:1; the reaction time after adding the precipitant is 10-40 minutes.

7. The method for removing vanadium from high-concentration sodium nitrate wastewater according to claim 2, characterized in that, The membrane separation is performed using a nanofiltration membrane; at least a portion of the side-flow liquid drawn from the cathode chamber accounts for 5%-10% of the total side-flow liquid volume.

8. A system for removing vanadium from high-concentration vanadium-containing sodium nitrate wastewater, for implementing the method according to any one of claims 1-7, characterized in that, include: A fluidized bed electrodialysis device is provided, comprising an anode chamber, an intermediate chamber, and a cathode chamber in sequence. The intermediate chamber is filled with a weak base anion exchange resin and is equipped with an inlet for introducing high-concentration vanadium-containing sodium nitrate wastewater. A liquid distributor for fluidizing the resin bed is provided at the bottom of the intermediate chamber. A DC power supply, electrically connected to the anode chamber and the cathode chamber, is used to apply a DC voltage; An oxidant dosing unit is connected to the dosing port of the intermediate chamber via a pipeline; A precipitant dosing unit is connected to the dosing port of the intermediate chamber via a pipeline; A filtration unit, which is connected to the outlet of the intermediate chamber via a pipeline, is used to separate the solid-liquid mixture in the intermediate chamber.

9. The system according to claim 8, characterized in that, The system also includes: A salinity maintenance unit includes a membrane separation device. The inlet of the membrane separation device is connected to the outlet of the cathode chamber via a pipeline. The concentrate outlet of the membrane separation device is connected to the inlet of the anode chamber via a pipeline. The permeate outlet of the membrane separation device is connected to the flushing liquid inlet of the intermediate chamber via a pipeline.

10. The system according to claim 9, characterized in that, The system also includes a programmable logic controller (PLC) that controls the switching of feeding, regeneration, dosing, and filtration operations of the fluidized bed electrodialysis unit.

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