Process for extracting vanadium from crystallized vanadium slag using Bayer process mother liquor

Abstract

The present invention discloses a process for extracting vanadium by crystallizing vanadium slag from the seed liquor of the Bayer process. The process comprises the following steps: dissolving the vanadium slag in a sodium hydroxide solution of a certain concentration, adding a vanadium precipitating agent to selectively precipitate vanadium, and filtering to obtain a vanadium-precipitated liquid and a vanadium-enriched slag; the vanadium precipitating agent is lead sulfate; sodium hydroxide is added to the vanadium-precipitated liquid, followed by cooling and crystallization to remove impurities, filtering, and returning the filtrate to the vanadium slag dissolution process; leaching the vanadium-enriched slag with a leaching agent, filtering, and obtaining a leached slag and a vanadium-enriched liquid; the leached slag is returned to the vanadium precipitation step for recycling; and the vanadium-enriched liquid is subjected to vanadium precipitation and roasting steps to obtain a vanadium product. The present invention achieves selective vanadium extraction from vanadium slag without the need for large amounts of acid for neutralization. The process is simple to operate, has a high vanadium recovery rate, recyclable vanadium precipitating agent and process water, and has a low waste emission rate, which is beneficial to environmental protection and low cost.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to the extraction of vanadium, and more particularly to a process for extracting vanadium by crystallizing vanadium slag from seed liquor of the Bayer process. Background Art

[0002] Vanadium is a widely used, important metal known as the "vitamin of modern industry." Currently, raw materials for vanadium extraction primarily include secondary vanadium slag resources, including vanadium-titanium magnetite smelting tailings, stone coal, vanadium-containing uranium ore, petroleum ash, and spent catalysts. Secondary vanadium slag, due to its high vanadium content, holds great recycling value.

[0003] Bauxite is rich in vanadium. During the Bayer process, over 30% of the vanadium dissolves into the solution and accumulates continuously as the mother liquor circulates, posing a threat to the aluminum hydroxide seeding process. Numerous methods exist for extracting vanadium from solutions. However, due to the strong alkalinity of sodium aluminate solutions and their rich content of various anions, traditional extraction, adsorption, and ion exchange methods are difficult to apply directly to sodium aluminate solutions. While chemical precipitation offers advantages, it suffers from poor selectivity for vanadium and often co-precipitates impurity ions, making the vanadium slag difficult to reuse. Patent CN200610109366.8 proposes a method for preparing vanadium pentoxide by adding calcium oxide to the denominator, leaching the precipitate with sodium bicarbonate, secondary precipitation with the leachate, secondary reverse leaching of the precipitate, and neutralization and hydrolysis of the leachate. While using lime for vanadium precipitation is cost-effective, it results in significant aluminum loss in the mother liquor, poor vanadium precipitation efficiency, low vanadium content in the slag, and cumbersome subsequent solution purification and separation processes, hindering industrial application. Patent document CN200910243362.2 proposes adding BaO to the Bayer process seed liquor to precipitate vanadium, and leaching the vanadium-precipitated slag with sodium carbonate. However, in practice, the impurity ions in the seed liquor are complex, the composition of the vanadium-precipitated slag is complex, and BaO is difficult to reuse. In addition, the sodium carbonate leaching effect is not ideal.

[0004] The mother liquor evaporation cooling crystallization method is commonly used in industry to remove vanadium, phosphorus, arsenic, fluorine and other impurity ions from the Bayer process simultaneously. Due to the special ion composition of sodium aluminate solution, impurities vanadium, phosphorus, arsenic and fluorine will be converted into Na7M2F·19H2O (M=VO4 3- , PO4 3- , AsO4 3- ) sodium salt crystallizes and precipitates, mixed with a small amount of Na2C2O4, Na2CO3, and Na2SO4. This method is mature in technology and simple in equipment. It can obtain vanadium slag with a high vanadium content for further vanadium extraction. This vanadium slag is called Bayer process seed liquor crystallization vanadium slag.

[0005] The traditional vanadium slag treatment process involves dissolving the vanadium slag in water and then precipitating vanadium with ammonium salts. Because the vanadium slag contains a large amount of sodium and alkali components, direct vanadium precipitation requires a large amount of sulfuric acid for neutralization. This impurity removal process also results in significant vanadium loss, resulting in low purity of the precipitated vanadium product. The wastewater produced after vanadium precipitation, which contains large amounts of sodium and ammonium sulfate, is difficult to recycle. The ammonium sulfate-sodium sulfate crystalline mixture produced by evaporation and crystallization is classified as a hazardous solid waste in my country and requires further treatment before it can be digested. To further extract vanadium from Bayer process vanadium slag crystallized from the denominator liquor, further optimization of the vanadium extraction process is needed, and a simpler, more environmentally friendly, and greener process flow is needed. Summary of the Invention

[0006] The purpose of the present invention is to provide a process for extracting vanadium by using Bayer process seed liquor crystallized vanadium slag.

[0007] To achieve the above objectives, the present invention provides the following specific technical solutions.

[0008] A process for extracting vanadium by crystallizing vanadium slag from Bayer process seed liquor comprises the following steps:

[0009] Step S1, dissolving vanadium slag in a sodium hydroxide solution, adding a vanadium precipitating agent to selectively precipitate vanadium, and filtering to obtain a vanadium precipitated liquid and vanadium-enriched slag; the vanadium precipitating agent is lead sulfate;

[0010] Step S2, cooling and crystallizing the solution after vanadium precipitation, filtering, and returning the filtrate to step S1;

[0011] Step S3, leaching the vanadium-enriched slag with a leaching agent, filtering to obtain leached slag and vanadium-enriched liquid; the leaching agent is a mixed solution of sulfuric acid and a reducing agent.

[0012] Furthermore, as a preferred embodiment, in step S1, the concentration of the sodium hydroxide solution is 1-10 wt %; and the solid-liquid ratio of the vanadium slag to the sodium hydroxide solution is 1:1-10 g / mL.

[0013] Furthermore, as a preferred embodiment, in step S1, when the vanadium precipitating agent is added to selectively precipitate vanadium, the amount of lead sulfate added is such that the molar ratio of Pb / V is 1 to 2:1, and the system temperature is 60 to 100°C.

[0014] Furthermore, as a preferred embodiment, in step S2, the cooling crystallization process comprises adjusting the concentration of sodium hydroxide in the vanadium precipitation solution to 5-20 wt%, and crystallizing the impurity sodium salt at 5-25°C. Filtering the crystallized solution and crystallization slag obtains the crystallized solution, which is returned to step S1 to dissolve the vanadium slag.

[0015] Furthermore, as a preferred embodiment, the process for leaching vanadium-enriched slag in step S3 is as follows: adding a leaching agent solution to the vanadium-enriched slag at a solid-liquid ratio of (1:1-10) g / mL, stirring, and filtering to obtain a vanadium-enriched solution and lead sulfate; the leaching agent is H + Sulfuric acid is added at a molar ratio of 2 to 3:1 to Pb, and a reducing agent is added at 0.9 to 1.1 times the theoretical amount required to reduce V(V) to V(IV).

[0016] Furthermore, as a preferred embodiment, the reducing agent in step S3 is at least one of sulfur dioxide, sodium sulfite, ammonium sulfite, sodium metabisulfite, and sodium thiosulfate;

[0017] Furthermore, as a preferred solution, the leaching residue obtained in step S3 is returned to step S1 as a vanadium precipitation agent.

[0018] Furthermore, the process for extracting vanadium by crystallizing vanadium slag from the Bayer process seed liquor further comprises the following steps:

[0019] Step S4: the vanadium-enriched liquid in step S3 is filtered after the vanadium precipitation process to obtain vanadium precipitation slag and vanadium precipitation filtrate; the vanadium precipitation slag is roasted to obtain vanadium pentoxide product.

[0020] Furthermore, the method further comprises the following steps: the vanadium precipitation filtrate in step S4 is returned to step S3.

[0021] Furthermore, as a preferred embodiment, in step S4, the vanadium precipitation process refers to one of hydrolysis vanadium precipitation and ammonium salt vanadium precipitation.

[0022] The specific process of hydrolyzing vanadium precipitation is as follows: using a pH regulator to adjust the pH of the vanadium-enriched liquid to 5-6, stirring, and filtering to obtain hydrated vanadium dioxide and a vanadium precipitation liquid.

[0023] The hydrated vanadium dioxide is oxidized and calcined at 550-750℃ to obtain the vanadium pentoxide product;

[0024] The specific process of ammonium salt precipitation of vanadium is as follows: adding an oxidant to the vanadium-enriched solution, adding a pH regulator to adjust the pH of the vanadium-enriched solution to 2-3, stirring, and filtering to obtain ammonium polyvanadate and vanadium-precipitated solution.

[0025] Ammonium polyvanadate is calcined at 450-650°C to obtain vanadium pentoxide product.

[0026] Furthermore, as a preferred embodiment, the oxidant is one of hydrogen peroxide or ammonium persulfate; the oxidant is added at 0.9 to 1.1 times the theoretical amount required to oxidize V(IV) to V(V).

[0027] Furthermore, as a preferred embodiment, the pH regulator is at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, and ammonia water.

[0028] The technical solution provided by the present invention has the following obvious beneficial effects:

[0029] (1) For the strongly alkaline solution obtained after the dissolution of vanadium slag, the present invention adopts lead sulfate to precipitate vanadium, taking advantage of the alkaline characteristics of the vanadium-containing solution. It does not require the consumption of a large amount of acid for neutralization operation, and can selectively extract vanadium from the solution containing impurities such as phosphorus, arsenic, and fluorine.

[0030] (2) The liquid after vanadium precipitation contains impurities such as phosphorus, arsenic, and fluorine. Since the present invention uses lead sulfate to precipitate vanadium, the liquid after vanadium precipitation contains sufficient SO4 2- When crystallizing at low temperature, it is difficult for the single salt of sodium to precipitate, but the sodium salt can produce the common ion effect and SO4 at low temperature. 2- With the presence of AsO4, phosphorus, arsenic, fluorine, etc. in the solution are easily precipitated in the form of 2Na3AsO4·NaF, 2Na3PO4·NaF, and Na2SO4·NaF complex salts during low-temperature crystallization, thus avoiding the enrichment of impurity ions during the liquid circulation after vanadium precipitation and realizing the recycling of vanadium precipitation mother liquor. 3- PO4 3- 、F - 、SO4 2- When the four ions exist at the same time, 2Na3AsO4·NaF, 2Na3PO4·NaF and Na2SO4·NaF complex salts will be generated, which have lower solubility than single sodium salts. This synergistic effect promotes the removal of impurity ions.

[0031] (3) The vanadium enrichment slag can be effectively leached after reduction acid leaching, and the vanadium precipitation agent lead sulfate is regenerated at the same time, which greatly reduces the raw material cost.

[0032] (4) After the vanadium-enriched liquid has gone through the vanadium precipitation process, the liquid after vanadium precipitation can be returned to continue to be used for leaching of vanadium-enriched slag, thus realizing the closed-loop circulation of process water.

[0033] (5) The entire process of extracting vanadium by crystallizing vanadium slag from the seed liquor of the Bayer process realizes the recycling of vanadium precipitation reagents and process water, avoids the generation of ammonia nitrogen wastewater and waste slag, and realizes low-carbon green metallurgy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a process flow chart for preparing vanadium pentoxide by crystallizing vanadium slag from Bayer process seed liquor, as adopted in an embodiment of the present invention.

[0035] Figure 2 This is the XRD pattern of the crystalline slag obtained in Example 1.

[0036] Figure 3 This is the XRD pattern of the crystallized slag obtained in Comparative Example 1. DETAILED DESCRIPTION

[0037] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0038] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0039] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0040] Figure 1 This is a process flow chart used in the following examples.

[0041] Example 1

[0042] The process of this embodiment is as follows:

[0043] Step (1): Take 1000g vanadium slag (Na2O 23.43%, V 9.56%, P 1.65%, As 1.28%, F 3.97%, Al2O31.34%, CO3 2- 0.56%, SO4 2- 0.16%, C2O4 2- 0.23%) was added with 10L of sodium hydroxide (4wt%) solution, heated to dissolve, and then lead sulfate was added at a Pb / V molar ratio of 1.7:1. The mixture was stirred at 70°C for 60 minutes and filtered to obtain the vanadium precipitation liquid and vanadium-enriched slag. The vanadium precipitation rate reached 99.41%.

[0044] Step (2): Sodium hydroxide is added to the obtained vanadium precipitation solution to a sodium hydroxide concentration of 20 wt %, and the mixture is stirred at 25°C for 5 h. A large amount of precipitate is precipitated, and the crystallized solution and crystallized slag are obtained by filtration. The removal rates of phosphorus, arsenic and fluorine in the solution are 92.41%, 95.93% and 91.56% respectively. The crystallized solution is returned to step (1) for dissolving the vanadium slag.

[0045] Figure 2 This is the phase analysis diagram of the crystallization slag. It can be seen from the figure that the crystallization slag is 2Na3AsO4·NaF, 2Na3PO4·NaF, and Na2SO4·NaF complex salt.

[0046] Step (3): Add the vanadium-enriched slag to the leaching agent at a solid-liquid ratio of 1:10 g / mL. +Sulfuric acid is added at a molar ratio of V / Pb of 2.5:1, and ammonium sulfite is added at 1.1 times the theoretical amount required to reduce V(V) to V(IV). The mixture is stirred and leached at 80°C for 5 hours. The vanadium-enriched solution with a V concentration of 10.21 g / L and the leaching residue are obtained by filtration. The obtained leaching residue is returned to step (1) for vanadium precipitation.

[0047] Step (4): Add ammonia water to the obtained vanadium-enriched liquid to adjust the pH to 5.5, stir at 25°C for 30 minutes, and then filter and separate the hydrated vanadium dioxide solid and the vanadium precipitation liquid. The vanadium precipitation rate is 98.56%.

[0048] The hydrated vanadium dioxide solid is oxidatively calcined at 650°C for 5 hours to obtain a vanadium pentoxide product containing 99.65% vanadium. The vanadium precipitated solution is acidified and returned to step (3).

[0049] Comparative Example 1

[0050] The difference between the process of this comparative example and that of Example 1 is that the vanadium precipitating agent is lead carbonate instead of lead sulfate. The specific process is as follows:

[0051] Step (1): Take 1000g vanadium slag (Na2O 23.43%, V 9.56%, P 1.65%, As 1.28%, F 3.97%, Al2O31.34%, CO3 2- 0.56%, SO4 2- 0.16%, C2O4 2- 0.23%) was added with 10L of sodium hydroxide (4wt%) solution, heated to dissolve, and then lead carbonate was added at a Pb / V molar ratio of 1.7:1. The mixture was stirred at 70°C for 60 minutes and filtered to obtain the vanadium precipitation liquid and vanadium-enriched slag. The vanadium precipitation rate reached 99.41%.

[0052] Step (2): Sodium hydroxide is added to the obtained vanadium precipitation solution to a sodium hydroxide concentration of 20 wt %, and the mixture is stirred at 25°C for 5 h. A precipitate is precipitated, and the crystallized solution and crystallized residue are obtained by filtration. The removal rates of phosphorus, arsenic and fluorine in the solution are 91.95%, 95.64% and 52.56%, respectively.

[0053] Figure 3 This is the phase analysis diagram of the crystallization slag. It can be seen from the figure that the crystallization slag is 2Na3AsO4·NaF, 2Na3PO4·NaF double salt, Na2CO3·H2O and NaF.

[0054] It can be seen that when lead carbonate is used as a vanadium precipitation agent, it is difficult for carbonate ions to produce a double salt effect on fluoride ions.

[0055] Step (3): Add the vanadium-enriched slag to the leaching agent at a solid-liquid ratio of 1:10 g / mL. +Sulfuric acid was added at a molar ratio of V / Pb of 2.5:1, and ammonium sulfite was added at 1.1 times the theoretical amount required to reduce V(V) to V(IV). The mixture was stirred and leached at 80°C for 5 h. The vanadium-enriched solution with a V concentration of 10.19 g / L and the leaching residue were filtered to obtain the vanadium-enriched solution. The leaching residue was returned to step (1) for vanadium precipitation.

[0056] Step (4): Add ammonia water to the obtained vanadium-enriched liquid to adjust the pH to 5.5, stir at 25°C for 30 min, and then filter and separate the hydrated vanadium dioxide solid and the vanadium precipitation liquid. The vanadium precipitation rate is 99.16%.

[0057] The hydrated vanadium dioxide solid is oxidatively calcined at 650°C for 5 hours to obtain a vanadium pentoxide product containing 99.52% vanadium. The vanadium precipitated solution is acidified and returned to step (3).

[0058] Comparative Example 2

[0059] The difference between the process of this comparative example and that of Example 1 is that the vanadium precipitating agent is lead hydroxide instead of lead sulfate. The specific process is as follows:

[0060] Step (1): Take 1000g vanadium slag (Na2O 23.43%, V 9.56%, P 1.65%, As 1.28%, F 3.97%, Al2O31.34%, CO3 2- 0.56%, SO4 2- 0.16%, C2O4 2- 0.23%) was added with 10L of sodium hydroxide (4wt%) solution, heated to dissolve, and then lead hydroxide was added at a Pb / V molar ratio of 1.7:1. The mixture was stirred at 70°C for 60 minutes and filtered to obtain the vanadium precipitation liquid and vanadium-enriched slag. The vanadium precipitation rate reached 99.89%.

[0061] Step (2): Sodium hydroxide is added to the obtained vanadium precipitation solution to a sodium hydroxide concentration of 20 wt %, and the mixture is stirred at 25°C for 5 h. A precipitate is precipitated, and the crystallized solution and crystallized residue are obtained by filtration. The removal rates of phosphorus, arsenic and fluorine in the solution are 92.15%, 95.58% and 51.32%, respectively.

[0062] It can be seen that it is difficult to achieve a good fluoride ion removal effect by using lead hydroxide as a vanadium precipitation agent.

[0063] Step (3): Add the vanadium-enriched slag to the leaching agent at a solid-liquid ratio of 1:10 g / mL. + Sulfuric acid was added at a molar ratio of V / Pb of 2.5:1, and ammonium sulfite was added at 1.1 times the theoretical amount required to reduce V(V) to V(IV). The mixture was stirred and leached at 80°C for 5 h. The vanadium-enriched solution with a V concentration of 10.19 g / L and the leaching residue were filtered to obtain the vanadium-enriched solution. The leaching residue was returned to step (1) for vanadium precipitation.

[0064] Step (4): Add ammonia water to the obtained vanadium-enriched liquid to adjust the pH to 5.5, stir at 25°C for 30 min, and then filter and separate the hydrated vanadium dioxide solid and the vanadium precipitation liquid. The vanadium precipitation rate is 99.16%.

[0065] The hydrated vanadium dioxide solid is oxidatively calcined at 650°C for 5 hours to obtain a vanadium pentoxide product containing 99.63% vanadium. The vanadium precipitation solution is acidified and returned to step (3).

[0066] Example 2

[0067] Step (1): Take 200g vanadium slag (Na2O 30.16%, V 10.15%, P 2.16%, As 1.87%, F 2.96%, CO3 2- 5.22%) was placed in 1L of 1wt% sodium hydroxide solution and dissolved with stirring at 100°C. Then, lead sulfate was added at a Pb / V molar ratio of 2:1. The mixture was stirred for 1 hour and filtered to obtain the vanadium precipitation liquid and vanadium-enriched slag. The vanadium precipitation rate reached 99.89%.

[0068] Step (2): add sodium hydroxide to the obtained vanadium precipitation solution until the concentration of sodium hydroxide is 5 wt.%, cool at 5°C to crystallize the impurity sodium salt, filter to obtain the crystallized solution and crystallized slag, and return the crystallized solution to step (1) for dissolving the vanadium slag.

[0069] Step (3): Add the obtained vanadium-enriched slag to the leaching agent at a solid-liquid ratio of 1:5 g / mL, and the leaching agent is + Sulfuric acid is added at a molar ratio of vanadium to lead (Pb) of 3:1, and sodium thiosulfate is added at 1 times the theoretical amount required to reduce V(V) to V(IV). The mixture is stirred and leached at 90°C for 4 hours. The vanadium-enriched solution with a V concentration of 25.19 g / L and the leaching residue are obtained by filtration. The obtained leaching residue is returned to step (1) for vanadium precipitation.

[0070] Step (4): Add ammonium persulfate in an amount equal to 1 times the theoretical amount required for oxidation of V(IV) to V(V) in the obtained vanadium-enriched solution, and add aqueous ammonia to adjust the pH to 3. Stir at 90°C for 60 minutes, and then filter and separate the ammonium polyvanadate solid and the vanadium-precipitated solution. The vanadium precipitation rate is 99.56%.

[0071] The ammonium polyvanadate solid is calcined at 650°C for 1 hour to obtain a vanadium pentoxide product containing 99.69% vanadium. The solution after vanadium precipitation is returned to step (3).

[0072] Example 3

[0073] Step (1): Take 200g vanadium slag (Na2O 30.16%, V 10.15%, P 2.16%, As 1.87%, F 2.96%, CO32- 5.22%) was placed in 1L of 10wt% sodium hydroxide solution and dissolved with stirring at 60°C. Lead sulfate was then added at a Pb / V molar ratio of 1:1. The mixture was stirred for 2h and filtered to obtain the vanadium precipitation liquid and vanadium-enriched slag. The vanadium precipitation rate reached 98.92%.

[0074] Step (2): add sodium hydroxide to the obtained vanadium precipitation solution to a concentration of 15 wt.%, stir at 10°C for 3 h to precipitate the impurity sodium salt, filter to obtain the crystallized solution and crystallized slag, and return the crystallized solution to step (1) for dissolving the vanadium slag.

[0075] Step (3): Add the obtained vanadium-enriched slag to the leaching agent at a solid-liquid ratio of 1:1 g / mL, and the leaching agent is + Sulfuric acid is added at a molar ratio of V / Pb of 2:1, and sodium metabisulfite is added at 0.9 times the theoretical amount required to reduce V(V) to V(IV). The mixture is stirred and leached at 90°C for 4 hours. The vanadium-enriched solution with a V concentration of 20.26 g / L and the leaching residue are obtained by filtration. The obtained leaching residue is returned to step (1) for vanadium precipitation.

[0076] Step (4): Add ammonium persulfate in an amount equal to 1 times the theoretical amount required for oxidation of V(IV) to V(V) in the obtained vanadium-enriched solution, and add aqueous ammonia to adjust the pH to 2. Stir at 90°C for 60 minutes, and then filter and separate the ammonium polyvanadate solid and the vanadium-precipitated solution. The vanadium precipitation rate is 99.06%.

[0077] The ammonium polyvanadate solid is calcined at 550°C for 3 hours to obtain a vanadium pentoxide product containing 99.35% vanadium. The solution after vanadium precipitation is returned to step (3).

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A process for extracting vanadium by crystallizing vanadium slag from Bayer process seed liquor, characterized in that: The following steps are involved: Step S1, dissolving vanadium slag in a sodium hydroxide solution, adding a vanadium precipitating agent to selectively precipitate vanadium, and filtering to obtain a vanadium precipitated liquid and vanadium-enriched slag; the vanadium precipitating agent is lead sulfate; Step S2, cooling and crystallizing the solution after vanadium precipitation, filtering, and returning the filtrate to step S1; Step S3, leaching the vanadium-enriched slag with a leaching agent, filtering to obtain leached slag and vanadium-enriched liquid; the leaching agent is a mixed solution of sulfuric acid and a reducing agent.

2. The process for extracting vanadium by crystallizing vanadium slag from Bayer process seed liquor as claimed in claim 1, characterized in that: In step S1, the concentration of the sodium hydroxide solution is 1-10 wt %; and the solid-liquid ratio of the vanadium slag to the sodium hydroxide solution is 1:1-10 g / mL.

3. The process for extracting vanadium by crystallizing vanadium slag from Bayer process seed liquor as claimed in claim 1, characterized in that: In step S1, when a vanadium precipitating agent is added to selectively precipitate vanadium, lead sulfate is added in an amount according to a Pb / V molar ratio of 1 to 2:1, and the system temperature is 60 to 100°C.

4. The process for extracting vanadium by crystallizing vanadium slag from Bayer process seed liquor according to any one of claims 1 to 3, characterized in that: In step S2, the cooling crystallization process is as follows: adjusting the concentration of sodium hydroxide in the solution after vanadium precipitation to 5-20 wt %, and crystallizing the impurity sodium salt at 5-25°C.

5. The process for extracting vanadium by crystallizing vanadium slag from Bayer process seed liquor as claimed in claim 1, characterized in that: The process of leaching vanadium-enriched slag in step S3 is as follows: adding a leaching agent solution to the vanadium-enriched slag at a solid-liquid ratio of (1:1-10) g / mL; the leaching agent is H + Sulfuric acid is added at a molar ratio of 2 to 3:1 to Pb, and a reducing agent is added at 0.9 to 1.1 times the theoretical amount required to reduce V(V) to V(IV).

6. The process for extracting vanadium by crystallizing vanadium slag from Bayer process seed liquor according to claim 1 or 5, characterized in that: The reducing agent in step S3 is at least one of sulfur dioxide, sodium sulfite, ammonium sulfite, sodium metabisulfite, and sodium thiosulfate.

7. The process for extracting vanadium by crystallizing vanadium slag from Bayer process seed liquor as claimed in claim 1, characterized in that: The leaching residue obtained in step S3 is returned to step S1 as a vanadium precipitation agent.

8. The process for extracting vanadium by crystallizing vanadium slag from Bayer process seed liquor as claimed in claim 1, characterized in that: The following steps are also included: Step S4: the vanadium-enriched liquid in step S3 is filtered after the vanadium precipitation process to obtain vanadium precipitation slag and vanadium precipitation filtrate; the vanadium precipitation slag is roasted to obtain vanadium pentoxide product.

9. The process for extracting vanadium by crystallizing vanadium slag from Bayer process seed liquor as claimed in claim 8, characterized in that: The following steps are also included: The vanadium precipitation filtrate in step S4 is returned to step S3.

10. The process for extracting vanadium by crystallizing vanadium slag from Bayer process seed liquor as claimed in claim 8, characterized in that: In step S4, the vanadium precipitation process refers to one of hydrolysis vanadium precipitation and ammonium salt vanadium precipitation.

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