Vanadium electrolyte wastewater multi-metal grading recovery method

Abstract

The invention belongs to the technical field of industrial wastewater treatment and resource recovery, and particularly discloses a multi-metal graded recovery method for vanadium electrolyte wastewater. The method comprises the following steps: adjusting the pH value of the vanadium electrolyte wastewater to 2.0-3.0, adding an oxidizing agent to oxidize ferrous iron into ferric iron, then adjusting the pH value to 4.0-5.0, carrying out iron-aluminum co-precipitation reaction, and carrying out solid-liquid separation to obtain primary filtrate and iron-aluminum slag; adding soluble ammonium salt into the primary filtrate, adjusting the pH value to 8.0-9.0, carrying out vanadium precipitation reaction, and carrying out solid-liquid separation to obtain secondary filtrate and ammonium polyvanadate precipitate; adding a reducing agent into the secondary filtrate to reduce hexavalent chromium into trivalent chromium, then adjusting the pH value to 8.5-9.5, carrying out a chromium precipitation reaction, and carrying out solid-liquid separation to obtain a tertiary filtrate and a chromium hydroxide precipitate; and carrying out deep purification and extraction on the third-stage filtrate to obtain wastewater meeting the discharge standard. According to the method, multiple metals such as vanadium, iron, aluminum and chromium can be recovered from the vanadium electrolyte wastewater in a grading manner, and meanwhile, the wastewater can be discharged up to the standard.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of industrial wastewater treatment and resource recovery, and particularly relates to a method for multi-metal grading recovery of vanadium electrolyte wastewater. BACKGROUND

[0002] Vanadium electrolyte wastewater mainly comes from vanadium battery production, metallurgy and chemical industry, and contains high-concentration vanadium and other heavy metals (such as Fe, Al and Cr). The existing technologies mainly focus on single metal recovery (such as vanadium), and have the following problems: (1) Resource waste: other high-value metals are not effectively recovered; (2) High treatment cost: single precipitation or ion exchange is mainly used, and a large amount of reagent is consumed; (3) Secondary pollution: residual heavy metals are not deeply treated, and the discharge does not meet the standard.

[0003] Therefore, there is an urgent need for a comprehensive solution of multi-metal grading recovery, closed-loop process and economic environmental protection. SUMMARY

[0004] In view of the above problems of the prior art, the application provides a method for multi-metal grading recovery of vanadium electrolyte wastewater, which aims to realize efficient grading recovery of multi-metals in vanadium electrolyte wastewater through step-by-step control of pH, oxidation-reduction potential and selective extraction, and ensure that the wastewater meets the discharge standard.

[0005] In order to achieve the above purpose, the application adopts the following technical scheme: According to the application, a method for multi-metal grading recovery of vanadium electrolyte wastewater is provided, which comprises the following steps: S1: adjusting the pH of vanadium electrolyte wastewater to 2.0-3.0, adding an oxidizing agent to oxidize divalent iron to trivalent iron, then adjusting the pH to 4.0-5.0 to perform iron-aluminum co-precipitation reaction, and after solid-liquid separation, obtaining a first filtrate and iron-aluminum slag; S2: adding soluble ammonium salt to the first filtrate obtained in step S1, adjusting the pH to 8.0-9.0 to perform vanadium precipitation reaction, and after solid-liquid separation, obtaining a second filtrate and ammonium polyvanadate precipitate; S3: adding a reducing agent to the second filtrate obtained in step S2 to reduce hexavalent chromium to trivalent chromium, then adjusting the pH to 8.5-9.5 to perform chromium precipitation reaction, and after solid-liquid separation, obtaining a third filtrate and chromium hydroxide precipitate; S4: deeply purifying and extracting the third filtrate to obtain wastewater meeting the discharge standard.

[0006] According to some embodiments of the application, in step S1, the oxidizing agent is hydrogen peroxide, and the addition amount of the hydrogen peroxide is 5%-20% of the volume of the vanadium electrolyte wastewater.

[0007] According to some embodiments of the present application, in step S1, sodium hydroxide is used to adjust the pH to 4.0-5.0.

[0008] According to some embodiments of the present application, in step S1, after the addition of the oxidizing agent, the reaction is stirred for 10-60 minutes.

[0009] According to some embodiments of the present application, in step S1, after the pH is adjusted to 4.0-5.0, the reaction is allowed to stand for 10-60 minutes.

[0010] According to some embodiments of the present application, in step S2, the soluble ammonium salt is at least one of ammonium sulfate, ammonium chloride, ammonium nitrate and ammonium carbonate, and the amount of the soluble ammonium salt added is 2-4 times the molar amount of vanadium in the vanadium electrolyte wastewater.

[0011] According to some embodiments of the present application, in step S3, the reducing agent is at least one of sodium sulfide, sodium hydrosulfide, sodium thiosulfate or sodium metabisulfite, and the amount of the reducing agent added is 1-2 times the molar amount of hexavalent chromium in the vanadium electrolyte wastewater.

[0012] According to some embodiments of the present application, in step S3, after the addition of the reducing agent, the reaction is stirred for 10-60 minutes.

[0013] According to some embodiments of the present application, in step S3, after the pH is adjusted to 8.5-9.5, the reaction is allowed to stand for 10-60 minutes.

[0014] According to some embodiments of the present application, in step S4, the deep purification and extraction of the tertiary filtrate includes: adsorbing the tertiary filtrate with activated carbon to remove organic matter; and extracting the tertiary filtrate with active resin to remove residual trace metals.

[0015] With the above technical solutions, the present application has the following beneficial effects: The vanadium electrolyte wastewater multi-metal fractional recovery method provided by the present application can fractionally recover vanadium (V), iron (Fe), aluminum (Al), chromium (Cr) and other multi-metals from vanadium electrolyte wastewater, and can ensure that the wastewater meets the discharge standard at the same time. Specifically, first, iron and aluminum in the vanadium electrolyte wastewater are recovered in the form of iron-aluminum slag through iron-aluminum co-precipitation, then vanadium in the vanadium electrolyte wastewater is recovered in the form of ammonium polyvanadate precipitate through vanadium precipitation, then chromium in the vanadium electrolyte wastewater is recovered in the form of chromium hydroxide precipitate through chromium precipitation, and finally, after deep purification and extraction of residual liquid (i.e. tertiary filtrate) to remove organic matter and residual trace metals, wastewater meeting the discharge standard can be obtained. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments 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.

[0017] Figure 1 The flowchart shows the multi-metal graded recovery method for vanadium electrolyte wastewater provided by the present invention. Detailed Implementation

[0018] 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 accompanying drawings.

[0019] In view of the problems of high cost of vanadium electrolyte wastewater treatment, ineffective recovery of high-value metals, lack of deep treatment of residual heavy metals, and failure to meet emission standards in existing technologies, this invention provides an efficient and environmentally friendly method for graded recovery of multiple metals such as vanadium (V), iron (Fe), aluminum (Al), and chromium (Cr) from vanadium electrolyte wastewater.

[0020] According to the present invention, a method for graded recovery of multiple metals from vanadium electrolyte wastewater is provided, such as... Figure 1 As shown, it includes the following steps: S1: Adjust the pH of the vanadium electrolyte wastewater to 2.0-3.0, add an oxidant to oxidize ferrous iron to ferric iron, then adjust the pH to 4.0-5.0 to carry out an iron-aluminum co-precipitation reaction, and after solid-liquid separation, obtain a primary filtrate and iron-aluminum slag; S2: Add a soluble ammonium salt to the primary filtrate obtained in step S1, adjust the pH to 8.0-9.0 to carry out a vanadium precipitation reaction, and after solid-liquid separation, obtain a secondary filtrate and ammonium polyvanadate precipitate; S3: Add a reducing agent to the secondary filtrate obtained in step S2 to reduce hexavalent chromium to trivalent chromium, then adjust the pH to 8.5-9.5 to carry out a chromium precipitation reaction, and after solid-liquid separation, obtain a tertiary filtrate and chromium hydroxide precipitate; S4: Perform deep purification and extraction on the tertiary filtrate to obtain wastewater that meets the discharge standards.

[0021] The present invention provides a method for graded recovery of multiple metals from vanadium electrolyte wastewater, which can gradedly recover vanadium (V), iron (Fe), aluminum (Al), chromium (Cr), and other metals from vanadium electrolyte wastewater while ensuring that the wastewater meets discharge standards. Specifically, iron and aluminum in the vanadium electrolyte wastewater are first recovered in the form of iron-aluminum slag through iron-aluminum co-precipitation. Then, vanadium in the vanadium electrolyte wastewater is recovered in the form of ammonium polyvanadate precipitation through vanadium precipitation reaction. Next, chromium in the vanadium electrolyte wastewater is recovered in the form of chromium hydroxide precipitation through chromium precipitation reaction. Finally, after deep purification and extraction of the residual liquid (i.e., the tertiary filtrate) to remove organic matter and residual trace metals, wastewater that meets discharge standards can be obtained.

[0022] This invention employs stepwise pH, redox potential, and selective extraction techniques to achieve efficient, graded recovery of multiple metals from vanadium electrolyte wastewater, while ensuring that the wastewater meets discharge standards. Based on the significant differences in the pH value for hydrolysis precipitation, solubility product (Ksp) for hydroxide formation, complexing ability, and extraction characteristics under specific valence states of various metal ions in aqueous solutions, the selective separation of metal ions is achieved by precisely controlling the chemical environment of the solution. Different metal ions require different pH values ​​to form hydroxide precipitates, based on the solubility product rule. By controlling the pH, the concentration product of a certain metal ion can exceed its solubility product, leading to preferential precipitation, while other metals remain in the solution. The solubility product formula is as follows: Ksp = [M n+ ][OH - ] n , Where Ksp is the solubility product, [M n+ [OH] represents the concentration of metal ions coexisting with the precipitate in a saturated solution of a metal hydroxide precipitate. - [ ] represents the hydroxide ion concentration in a saturated solution of a metal hydroxide precipitate. For a metal hydroxide precipitate M(OH) n For every slight increase in pH, [OH-] - As the ion product increases, it approaches or exceeds Ksp, leading to precipitation.

[0023] The core principle of the metal ion recovery sequence setting in this invention is to prioritize the removal of interfering factors, thereby creating optimal conditions for the efficient and high-purity recovery of high-value metals.

[0024] Step 1: Prioritize the removal of iron (Fe) and aluminum (Al). (a) Preferred precipitation characteristics: Fe 3+ And Al 3+ They are amphoteric metals, but they have a very low and narrow pH window for forming hydroxide precipitates (Fe). 3+ Precipitation begins at pH 2-3 and is almost complete at pH 3.5; Al3+ The Fe and Al hydroxides are very strong adsorbents and coprecipitation carriers, so if they are not removed in advance, the recovery rate and product purity of all subsequent steps will be greatly reduced.

[0025] (II) Eliminate coprecipitation interference: Fe and Al hydroxides are very strong adsorbents and coprecipitation carriers, if not removed in advance, the recovery rate and product purity of all subsequent steps will be greatly reduced.

[0026] Second step: reduction and separation of vanadium / cromium (I) Valence state regulation is the key: after the first step, the main metals in the solution are V (V 5+ ) and Cr (Cr 6+ ), which exist in the form of high-valence oxygen-containing anions and are similar in chemical behavior, making them difficult to separate directly.

[0027] (II) Selective reduction: the goal is to reduce V 5+ to V 4+ (VO 2+ ), while keeping Cr as Cr 6+ as much as possible. Because V 4+ will hydrolyze and precipitate under weakly acidic conditions, while Cr 6+ (CrO4² - ) has high solubility under acidic to neutral conditions and will not precipitate. Therefore, vanadium is precipitated first, followed by chromium.

[0028] Third step: recovery of chromium (Cr) After separation in the previous step, the main remaining metals in the solution are Cr 6+ and some other trace heavy metals (such as Ni, Cu, etc.), so chromium can be recovered first, and other trace heavy metals can be extracted later.

[0029] The invention will be described in detail for each step.

[0030] Step S1 aims to recover iron and aluminum in vanadium electrolyte wastewater in the form of iron-aluminum slag through iron-aluminum coprecipitation, wherein the pH of the vanadium electrolyte wastewater is adjusted to 2.0-3.0 because Fe 3+ starts to precipitate at pH 2-3 and precipitates completely at pH ~3.5; the pH is adjusted to 4.0-5.0 because Al 3+ starts to precipitate at pH 4-5.

[0031] In some embodiments, in step S1, the oxidizing agent used is hydrogen peroxide (H2O2). It should be understood that the present invention is not limited to this, and other oxidizing agents that can oxidize divalent iron to trivalent iron can also be used.

[0032] In the case of using hydrogen peroxide as the oxidant, the amount of hydrogen peroxide added is 5%-20% of the volume of the vanadium electrolyte wastewater, so as to ensure that complete oxidation of the divalent iron is achieved. Preferably, the amount of hydrogen peroxide added is 10% of the volume of the vanadium electrolyte wastewater.

[0033] In some embodiments, in step S1, before the addition of the oxidant, the pH of the vanadium electrolyte wastewater is adjusted to 2.0-3.0 using an acid (for example, concentrated sulfuric acid). The initial pH of the vanadium electrolyte wastewater is generally 4.5-5.5. The pH before the addition of the oxidant can typically but non-limitingly be adjusted to 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0.

[0034] In some embodiments, in step S1, after the addition of the oxidant, the reaction is stirred for 10-60 minutes, so as to ensure that the divalent iron is fully oxidized to trivalent iron. The reaction stirring time can typically but non-limitingly be set to 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes.

[0035] In some embodiments, in step S1, after the oxidation of the divalent iron to trivalent iron, the pH is adjusted to 4.0-5.0 using sodium hydroxide (NaOH). The pH can typically but non-limitingly be adjusted to 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0.

[0036] In some embodiments, in step S1, after the adjustment of the pH to 4.0-5.0, the reaction is allowed to stand for 10-60 minutes, so as to ensure that the iron and aluminum are fully settled. The reaction standing time can typically but non-limitingly be set to 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes.

[0037] In one specific example, step S1 comprises: ① adjusting the pH of the vanadium electrolyte wastewater to 2.0-3.0, adding H2O2 to oxidize Fe2+ to Fe3+; ② slowly adding NaOH to a pH of 4.0-5.0, generating Fe(OH)3 and Al(OH)3 precipitates, centrifuging and separating, and recovering the iron and aluminum sludge. 2+ To Fe3+ 3+ ; ② slowly adding NaOH to a pH of 4.0-5.0, generating Fe(OH)3 and Al(OH)3 precipitates, centrifuging and separating, and recovering the iron and aluminum sludge.

[0038] Step S2 aims to recover the vanadium in the vanadium electrolyte wastewater in the form of ammonium polyvanadate precipitate through a vanadium precipitation reaction, wherein a soluble ammonium salt is used as a precipitant for the vanadium precipitation.

[0039] In some embodiments, in step S2, the soluble ammonium salt is at least one of ammonium sulfate, ammonium chloride, ammonium nitrate, and ammonium carbonate. Preferably, the soluble ammonium salt is ammonium sulfate ((NH4)2SO4).

[0040] In some embodiments, in step S2, the amount of the soluble ammonium salt added is 2-4 times the molar amount of vanadium in the vanadium electrolyte wastewater in terms of the molar amount of ammonium ions, so as to facilitate ensuring complete recovery of vanadium. In a specific example, the amount of the ammonium salt added is 2-4 times the molar amount of vanadium in the vanadium electrolyte wastewater in terms of the molar amount of ammonium ions, and the specific amount is between 10 g and 30 g.

[0041] In some embodiments, in step S2, after the soluble ammonium salt is added, an alkali solution (for example, sodium hydroxide) is used to adjust the pH to 8.0-9.0, and the pH can be typically but not limitingly adjusted to 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9, 9.0.

[0042] In some embodiments, the ammonium polyvanadate precipitate can be calcined to obtain vanadium pentoxide.

[0043] In a specific example, step S2 includes: adding ammonium sulfate ((NH4)2SO4) as a precipitant to the first-stage filtrate, adjusting the pH to 8.0-9.0, generating an ammonium polyvanadate (NH4V3O8) precipitate, and calcining to obtain V2O5 after centrifugation.

[0044] Step S3 aims to recover chromium in the vanadium electrolyte wastewater in the form of chromium hydroxide precipitate through a chromium precipitation reaction.

[0045] In some embodiments, in step S3, the reducing agent is at least one of sodium sulfide, sodium hydrosulfide, sodium thiosulfate, or sodium pyrosulfite. Preferably, the reducing agent is sodium pyrosulfite (Na2S2O5).

[0046] In the case of using sodium pyrosulfite as the reducing agent, the amount of sodium pyrosulfite added is 1-2 times the molar amount of hexavalent chromium in the vanadium electrolyte wastewater in terms of the molar amount, so as to facilitate ensuring complete reduction of hexavalent chromium. In a specific example, the amount of sodium pyrosulfite added is 1-2 times the molar amount of hexavalent chromium in the vanadium electrolyte wastewater in terms of the molar amount, and the specific amount is between 6 g and 15 g.

[0047] In some embodiments, in step S3, after the reducing agent is added, the reaction is stirred for 10-60 minutes to ensure that the hexavalent chromium is fully reduced to trivalent chromium. The stirring reaction time can be typically but not limitingly set to 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 60 minutes.

[0048] In some embodiments, in step S3, after the hexavalent chromium is reduced to trivalent chromium, the pH is adjusted to 8.5-9.5 using a lye (e.g. sodium hydroxide). The pH can typically but not limitatively be adjusted to 8.5, 8.6, 8.7, 8.8, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5.

[0049] In some embodiments, in step S3, after the pH is adjusted to 8.5-9.5, the reaction is left to stand for 10-60 minutes to ensure full settling of the chromium. The standing time can typically but not limitatively be set to 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes.

[0050] In one specific example, step S3 comprises: adding sodium pyrosulfite (Na2S2O5) to reduce Cr 6+ to Cr 3+ , adjusting the pH to 8.5-9.5 to generate Cr(OH)3precipitate.

[0051] Step S4 aims to remove organic matter and residual trace metals from the residual liquid (i.e. the tertiary filtrate) to bring it to discharge standards.

[0052] In some embodiments, in step S4, the deep purification and extraction of the tertiary filtrate comprises: adsorbing the tertiary filtrate using activated carbon to remove organic matter; and extracting the tertiary filtrate using active resin to remove residual trace metals. The organic phase is recycled after regeneration.

[0053] After deep purification and extraction, the final effluent is detected to have a heavy metal content lower than the “Integrated Wastewater Discharge Standard” (GB8978-1996).

[0054] The application is further described below in connection with specific embodiments: The vanadium electrolyte wastewater used in the following examples is: wastewater generated in the process of preparing vanadium electrolyte by vanadium fusion technology short process, with a water volume of 20-30 m 3 / d, acidic, ink green in color, and containing a small amount of oil droplets, with Cr, V, Fe mainly in low valence state. The Cr content is 1.5-2.5 g / L, the V content is 0.2-1.0 g / L, and the Fe content is 0.56-0.8 g / L.

[0055] Example 1 1. Measure 500 ml of vanadium electrolyte wastewater, add 50 ml of H2O2, stir for 30 minutes, adjust the pH to 4.5 with sodium hydroxide, stand for 30 min, filter, and obtain aluminum and iron precipitate on the filter paper, the obtained filtrate is the primary filtrate; 2. Add (NH4)2SO4 to the primary filtrate to adjust the pH to 8.5 to obtain ammonium polyvanadate and secondary filtrate, and the V2O5 purity of the ammonium polyvanadate after calcination reaches 96%; 3. Add Na2S2O5 to the secondary filtrate to adjust the pH to 9.0, and stand for 30 min, filter, and obtain precipitate on filter paper, and the obtained filtrate is tertiary filtrate; 4. After removing organic matter by activated carbon adsorption and extracting residual trace metals by active resin, the obtained is final effluent.

[0056] The final effluent is detected. The V in the final effluent is 0.033 g / l, and the chromium is 0.021 g / L, which meets the discharge standard.

[0057] Example 2 1. Measure 800 ml of vanadium electrolyte wastewater, add 80 ml of H2O2, stir for 30 min, adjust the pH to 4.8 with sodium hydroxide, stand for 30 min, filter, and obtain aluminum and iron precipitate on filter paper, and the obtained filtrate is primary filtrate; 2. Add (NH4)2SO4 to the primary filtrate to adjust the pH to 8.7 to obtain ammonium polyvanadate and secondary filtrate, and the V2O5 purity of the ammonium polyvanadate after calcination reaches 95.8%; 3. Add Na2S2O5 to the secondary filtrate to adjust the pH to 9.2, and stand for 30 min, filter, and obtain precipitate on filter paper, and the obtained filtrate is tertiary filtrate; 4. After removing organic matter by activated carbon adsorption and extracting residual trace metals by active resin, the obtained is final effluent.

[0058] The final effluent is detected. The V in the final effluent is 0.030 g / l, and the chromium is 0.022 g / L, which meets the discharge standard.

[0059] In summary, the multi-metal staged recovery method for vanadium electrolyte wastewater provided by the application can realize efficient staged recovery of multi-metals in vanadium electrolyte wastewater, and ensure that the wastewater meets the discharge standard.

[0060] The above is an exemplary embodiment disclosed by the application, and the sequence of the above application embodiment disclosure is only for description, not representing the advantages and disadvantages of the embodiments. However, it should be noted that the discussion of any of the above embodiments is only exemplary, and is not intended to limit the scope of the application (including claims) to these examples. Various changes and modifications can be made without departing from the scope defined by the claims. In addition, although the elements disclosed in the embodiments of the application can be described or claimed in singular form, they can also be understood as plural unless explicitly limited to singular.

[0061] Those skilled in the art should understand that the above discussion of any embodiment is only exemplary, and is not intended to mean that the scope of the embodiments disclosed by the present application (including claims) is limited to these examples; under the idea of the embodiments of the present application, the above embodiments or technical features among different embodiments can also be combined, and there are many other changes of different aspects of the embodiments of the present application as described above, which are not provided in details for the sake of brevity. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the present application shall be included in the protection scope of the embodiments of the present application.

Claims

1. A method for multi-metal fractional recovery of vanadium electrolyte wastewater, characterized in that, The method comprises the following steps: S1: adjusting the pH of the vanadium electrolyte wastewater to 2.0-3.0, adding an oxidizing agent to oxidize the divalent iron to trivalent iron, then adjusting the pH to 4.0-5.0, and performing an iron-aluminum co-precipitation reaction, after solid-liquid separation, obtaining a primary filtrate and an iron-aluminum residue; S2: adding a soluble ammonium salt to the primary filtrate obtained in step S1, adjusting the pH to 8.0-9.0, and performing a vanadium precipitation reaction, after solid-liquid separation, obtaining a secondary filtrate and an ammonium polyvanadate precipitate; S3: adding a reducing agent to the secondary filtrate obtained in step S2 to reduce hexavalent chromium to trivalent chromium, then adjusting the pH to 8.5-9.5, and performing a chromium precipitation reaction, after solid-liquid separation, obtaining a tertiary filtrate and a chromium hydroxide precipitate; S4: performing deep purification and extraction on the tertiary filtrate to obtain wastewater meeting the discharge standard.

2. The vanadium electrolyte wastewater multi-metal fractional recovery method according to claim 1, characterized in that, In step S1, the oxidizing agent is hydrogen peroxide, and the addition amount of the hydrogen peroxide is 5%-20% of the volume of the vanadium electrolyte wastewater.

3. The vanadium electrolyte wastewater multi-metal fractional recovery method according to claim 1, characterized in that, In step S1, sodium hydroxide is used to adjust the pH to 4.0-5.

0.

4. The vanadium electrolyte wastewater multi-metal fractional recovery method according to claim 1, characterized in that, In step S1, after adding the oxidizing agent, stirring is performed for 10-60 minutes.

5. The vanadium electrolyte wastewater multi-metal fractional recovery method according to claim 1, characterized in that, In step S1, after adjusting the pH to 4.0-5.0, standing is performed for 10-60 minutes.

6. The vanadium electrolyte wastewater multi-metal fractional recovery method according to claim 1, characterized in that, In step S2, the soluble ammonium salt is at least one of ammonium sulfate, ammonium chloride, ammonium nitrate, and ammonium carbonate, and the addition amount of the soluble ammonium salt is 2-4 times the molar amount of vanadium in the vanadium electrolyte wastewater.

7. The vanadium electrolyte wastewater multi-metal fractional recovery method according to claim 1, characterized in that, In step S3, the reducing agent is at least one of sodium sulfide, sodium hydrosulfide, sodium thiosulfate, or sodium metabisulfite, and the addition amount of the reducing agent is 1-2 times the molar amount of hexavalent chromium in the vanadium electrolyte wastewater.

8. The vanadium electrolyte wastewater multi-metal fractional recovery method according to claim 1, characterized in that, In step S3, after adding the reducing agent, stirring is performed for 10-60 minutes.

9. The vanadium electrolyte wastewater multi-metal fractional recovery method according to claim 1, characterized in that, In step S3, after adjusting the pH to 8.5-9.5, standing is performed for 10-60 minutes.

10. The vanadium electrolyte wastewater multi-metal fractional recovery method according to claim 1, characterized in that, In step S4, the deep purification and extraction of the tertiary filtrate comprises: using activated carbon to adsorb the tertiary filtrate to remove organic matter; and using active resin to extract the tertiary filtrate to remove residual trace metals.

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