Method for neutralizing waste acid and enriching iron and vanadium from vanadium-containing steel slag

Abstract

The invention relates to the technical field of resource utilization of metallurgical and chemical wastes, in particular to a method for neutralizing waste acid and enriching ferrovanadium from vanadium-containing steel slag. The method comprises the following steps: S1, grinding the vanadium-containing steel slag into fine powder, and adding water according to a liquid-solid ratio of 1g: (1-1.5) ml to prepare slurry; s2, preparing the sulfuric acid process titanium dioxide byproduct waste acid and the acid wastewater into dilute acid with the concentration of 5-15%; s3, dilute acid is added into the slurry, the pH is controlled to be 6-8, the reaction temperature is larger than or equal to 50 DEG C, and continuous stirring reaction is conducted; s4, after the reaction is completed, heating to 90 DEG C or above, and keeping boiling for 30-60 minutes; and S5, flotation separation is conducted, and gypsum slag and an iron-rich vanadium material are obtained.

Description

Technical Field

[0001] This invention relates to the field of metallurgical and chemical waste resource utilization technology, specifically to a method for neutralizing waste acid and enriching iron and vanadium in vanadium-containing steel slag. Background Technology

[0002] Titanium dioxide waste acid is produced during the sulfuric acid process for titanium dioxide production. For every ton of titanium dioxide produced, approximately 7 tons of waste acid are generated. High-concentration titanium dioxide waste acid has a sulfuric acid content of about 15-25% (wt). Direct discharge without treatment will cause significant environmental pollution. Vanadium-containing steel slag refers to water-quenched slag (i.e., cooled with water) generated during the smelting of vanadium-titanium magnetite. It is classified as general solid waste and is usually discarded as waste. Both of these are industrial wastes in large quantities and difficult to dispose of, not only affecting normal production but also causing incalculable harm to the environment. Most steel companies have to pay out of pocket to dispose of steel slag or can only store it in slag yards, which has become a bottleneck problem for the comprehensive utilization of resources in the steel industry.

[0003] Panzhihua Iron and Steel Group's converter slag is a vanadium-containing steel slag, containing 0.6-1.0% V and 20-25% TFe, and has high recycling value.

[0004] In existing technologies, there are methods that attempt to combine steel slag with titanium dioxide waste acid to achieve resource utilization. For example, Chinese patent application CN120311027A discloses a method for extracting vanadium using high-calcium steel slag and titanium dioxide waste acid. This method mainly involves reacting high-calcium steel slag powder with titanium dioxide waste acid under strongly acidic conditions (pH 1.5~1.8), followed by solid-liquid separation, and then subjecting the vanadium-containing filtrate to a series of purification and refinement processes (such as extraction and crystallization) to finally obtain a high-purity vanadium product (such as ammonium metavanadate). However, this existing technical solution has the following significant defects and unresolved technical problems: Incomplete resource recovery: This method only focuses on extracting vanadium from steel slag, and does not effectively recover iron, which is present in higher quantities and has greater value. Iron ultimately ends up in waste slag and is discarded, resulting in a serious waste of resources.

[0005] The problem of waste acid treatment has not been completely solved: This process is carried out under strongly acidic conditions, and its purpose is only to use the acidity of the waste acid to leach vanadium, without achieving complete neutralization of the waste acid. The system after the reaction still requires further treatment, and the sulfate ions in the waste acid eventually become new solid waste or wastewater that needs to be treated, failing to fundamentally reduce the waste acid treatment costs and environmental burden of titanium dioxide production enterprises.

[0006] Complex process and high cost: To obtain high-purity vanadium products, complex chemical purification unit operations such as extraction, crystallization, and resin adsorption must be introduced. This results in a long process flow, large equipment investment, and high operating costs, making it unsuitable for large-scale, low-value bulk solid waste treatment scenarios.

[0007] Therefore, existing steel slag treatment technologies, including the method disclosed in CN120311027A, still have many shortcomings. They are unable to achieve efficient and coordinated recovery of multiple valuable resources such as iron and vanadium from vanadium-containing steel slag, and also lack an effective way to treat waste acid and acidic wastewater from the sulfuric acid process of titanium dioxide production at low cost and thoroughly. Developing a new technological solution that can simultaneously solve the above problems is urgently needed. Summary of the Invention

[0008] In view of this, the present invention proposes a method for neutralizing waste acid and enriching iron and vanadium in vanadium-containing steel slag, which can at least solve the above-mentioned problems.

[0009] The method for neutralizing waste acid and enriching iron and vanadium in vanadium-containing steel slag proposed in this application includes the following steps: S1, vanadium-containing steel slag is ground into fine powder and mixed with water at a liquid-solid ratio of 1g:1~1.5ml to make a slurry; S2, prepare a dilute acid with a concentration of 5-15% byproducts of the sulfuric acid process for titanium dioxide production, using waste acid and acidic wastewater. S3, add the dilute acid to the slurry, control the pH between 6 and 8, keep the reaction temperature ≥50℃, and continue stirring the reaction; S4, after the reaction is complete, heat to above 90°C and keep boiling for 30-60 minutes; S5 is used for flotation separation to obtain gypsum slag and iron-vanadium rich material.

[0010] In some embodiments, the particle size of the finely ground vanadium-containing steel slag is less than 300 mesh, which significantly improves the speed and efficiency of subsequent chemical reactions by increasing the specific surface area of ​​the material.

[0011] In some embodiments, the ratio of the mass of fine powder in step S1 to the volume of dilute acid in step S3 is 1 g:(1.5~2.5) ml. This ratio can ultimately promote the simultaneous improvement of gypsum purity and iron-vanadium rich material grade, and enhance the overall economic efficiency of the process.

[0012] In some embodiments, during the preparation of dilute acid, the acid concentration of waste acid is 15-25%, and the acid concentration of acidic wastewater is 3-5%.

[0013] In some embodiments, step S3 further includes controlling the stirring reaction time to be 2-3 hours.

[0014] In some embodiments, in step S5, the flotation reagents used for flotation separation include sodium dodecylbenzenesulfonate and a soluble starch solution.

[0015] In some embodiments, the concentration of the soluble starch solution is 5-15%.

[0016] In some embodiments, the vanadium content in the iron-vanadium rich material is ≥1.5wt%, the iron grade is ≥40wt%, and the silicon dioxide content is ≤22wt%.

[0017] In some embodiments, the calcium sulfate dihydrate content in the gypsum residue is ≥82wt%.

[0018] In some embodiments, in step S3, the stirring speed is controlled to be 200~250 r / min.

[0019] The beneficial effects of this invention are as follows: The method for neutralizing waste acid and enriching iron and vanadium in vanadium-containing steel slag proposed in this invention can not only efficiently recover usable resources in vanadium-containing steel slag, but also use steel slag to treat waste acid and acidic wastewater from the by-product of the sulfuric acid process for titanium dioxide, reducing wastewater treatment costs and achieving the effect of treating waste with waste. At the same time, it has a low treatment cost and is suitable for large-scale production. Specifically, this invention can have the following effects: (1) Efficient resource recovery: After treatment by this method, the vanadium-rich material obtained has a vanadium content of more than 1.5%, an iron grade of more than 40%, and a silicon dioxide content of 22%. It can be used to replace medium powder in vanadium-titanium ore sintering, realizing the efficient recovery of effective resources in vanadium-containing steel slag. (2) Treating waste with waste: This application inputs two types of waste (vanadium-containing steel slag + titanium dioxide waste acid / wastewater), uses the acid of the waste acid to dissolve the steel slag, and uses the alkali of the steel slag to neutralize the waste acid. It outputs two valuable products (iron-vanadium-rich material + gypsum). This invention cleverly utilizes the properties of one type of waste to treat another, while simultaneously recovering valuable components from both, thus solving a systemic technical challenge in the synergistic treatment and conversion of various solid / liquid wastes. (3) Cost advantage: This application controls the reaction to proceed under neutral (pH 6-8) conditions, utilizing alkaline oxides (such as CaO) in steel slag to completely neutralize the acidity in the waste acid, while simultaneously generating valuable byproduct gypsum. This replaces the traditional neutralization process using expensive limestone or quicklime, significantly reducing the wastewater treatment cost for sulfuric acid process titanium dioxide enterprises. It is suitable for large-scale production promotion, bringing considerable economic and environmental benefits to steel enterprises and sulfuric acid process titanium dioxide enterprises. 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 embodiments can be obtained based on these drawings without creative effort.

[0021] Figure 1The flowchart illustrates a method for neutralizing waste acid and enriching iron and vanadium in vanadium-containing steel slag according to an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0024] like Figure 1 As shown, the method for neutralizing waste acid and enriching iron and vanadium in vanadium-containing steel slag proposed in this invention includes the following steps: S1, vanadium-containing steel slag is ground into fine powder and mixed with water at a liquid-solid ratio of 1g:1~1.5ml to make a slurry; S2, prepare a dilute acid with a concentration (mass percentage concentration) of 5-15% by-product waste acid and acidic wastewater from the sulfuric acid process for titanium dioxide production; S3, add dilute acid to the slurry, control the pH between 6 and 8, keep the reaction temperature ≥50℃, and continue stirring the reaction; S4, after the reaction is complete, heat to above 90°C and keep boiling for 30-60 minutes; S5 is subjected to flotation separation to obtain gypsum slag (a solid byproduct with calcium sulfate dihydrate (CaSO4·2H2O) as the main component) and iron-vanadium rich material.

[0025] The steel slag in this application contains 0.6-1.0% V and 20-25% TFe, which has high recycling value. The method for neutralizing waste acid and enriching iron and vanadium in vanadium-containing steel slag proposed in this invention can not only efficiently recover usable resources in vanadium-containing steel slag, but also use steel slag to treat waste acid and acidic wastewater from the by-product of the sulfuric acid process for titanium dioxide, reduce wastewater treatment costs, achieve the effect of treating waste with waste, and have low treatment costs, making it suitable for large-scale production. Specifically, this invention can have the following effects: (1) Efficient resource recovery: After being treated by this method, the vanadium-rich material obtained has a vanadium content of more than 1.5%, an iron grade of more than 40%, and a silicon dioxide content of less than 22%. It can replace medium powder (a specific particle size iron ore powder raw material used in the sintering process) in the vanadium-titanium ore sintering, realizing the efficient recovery of effective resources in vanadium-containing steel slag. (2) Waste-to-waste treatment: This application inputs two types of waste (vanadium-containing steel slag + titanium dioxide waste acid / wastewater), utilizes the acid in the waste acid to dissolve the steel slag, and utilizes the alkali in the steel slag to neutralize the waste acid. It outputs two valuable products (iron-vanadium-rich material + gypsum). It cleverly utilizes the properties of one type of waste to treat another type of waste, and simultaneously recovers the valuable components from both, solving the systemic technical problem of the synergistic treatment and conversion of multiple solid / liquid wastes. (3) Cost advantage: This application controls the reaction to be carried out under neutral conditions (pH 6~8), utilizing the alkaline oxides (such as CaO) in the steel slag to completely neutralize the acidity in the waste acid, while generating the valuable by-product gypsum. It replaces the traditional neutralization process using expensive limestone or quicklime, significantly reducing the wastewater treatment cost of sulfuric acid process titanium dioxide enterprises, making it suitable for large-scale promotion and production, and bringing considerable economic and environmental benefits to steel enterprises and sulfuric acid process titanium dioxide enterprises.

[0026] In some embodiments, the particle size of the finely ground vanadium-containing steel slag is less than 300 mesh, which significantly improves the speed and efficiency of subsequent chemical reactions by increasing the specific surface area of ​​the material.

[0027] In some embodiments, the ratio of the mass of fine powder in step S1 to the volume of dilute acid in step S3 is 1g:(1.5~2.5)ml. This ratio can ultimately promote the simultaneous improvement of gypsum purity and iron-vanadium rich material grade, and enhance the overall economic efficiency of the process.

[0028] In some embodiments, during the preparation of dilute acid, the acid concentration (mass percentage concentration) of the waste acid is 15-25%, and the acid concentration (mass percentage concentration) of the acidic wastewater is 3-5%, so as to achieve "waste treatment with waste" while precisely controlling the acid concentration to optimize the reaction process. This ratio can utilize the high concentration of waste acid to provide sufficient H₂. +Ions are used to efficiently neutralize the alkalinity of steel slag and leach iron and vanadium elements. The low-concentration acidic wastewater can also be used for dilution, preventing excessively vigorous reactions due to high acidity that could produce harmful gases (such as CO2) or generate fine gypsum crystals that are detrimental to subsequent flotation separation. This formulation ultimately ensures that the reaction system can stably and controllably reach the target pH value (6-8), creating ideal conditions for subsequent iron and vanadium hydrolysis enrichment and gypsum crystal growth.

[0029] In some embodiments, to provide sufficient time for key chemical reactions such as neutralization, leaching, and gypsum crystal nucleus formation, step S3 further includes controlling the stirring reaction time to 2-3 hours. This duration ensures that the alkaline components in the steel slag are completely neutralized by the waste acid, stabilizing the system pH within the target range (6-8), while simultaneously promoting the maximum dissolution and leaching of valuable elements such as iron and vanadium from the slag phase. Furthermore, sufficient reaction time facilitates the generation of a large number of uniformly sized and morphologically complete dihydrate calcium sulfate (gypsum) microcrystals, laying a solid foundation for the regular growth of gypsum crystals in the subsequent boiling and maturation stage and the final efficient flotation separation.

[0030] In some embodiments, in step S5, the flotation reagents used for flotation separation include sodium dodecylbenzenesulfonate and a soluble starch solution. The concentration (mass percentage concentration) of the soluble starch solution is 10% to achieve efficient and highly selective separation of gypsum slag and iron-vanadium-rich materials. Specifically, sodium dodecylbenzenesulfonate, as an anionic collector, has hydrophobic groups that can selectively adsorb onto the surface of iron-vanadium-rich hydrolysis products (such as ferric hydroxide), making them hydrophobic and easy to adhere to bubbles and float. Soluble starch, as an effective inhibitor of gypsum, selectively coats the hydrophilic gypsum crystal surface through hydrogen bonds and other forces, enhancing its hydrophilicity and making it difficult for it to float, thus remaining at the bottom of the tank. The synergistic effect of these two reagents, along with the suitable viscosity and covering power provided by the 10% starch concentration, significantly improves the selectivity of the flotation process, ultimately successfully obtaining pure gypsum slag and high-grade iron-vanadium-rich materials.

[0031] In some embodiments, the vanadium-rich vanadium material has a vanadium content of ≥1.5wt%, an iron grade of ≥40wt%, and a silicon dioxide content of ≤22wt%. It can replace medium powder in the sintering of vanadium-titanium ore, achieving efficient recovery of effective resources from vanadium-containing steel slag.

[0032] In some embodiments, the calcium sulfate dihydrate content in the gypsum residue is ≥82wt%, which is of high purity and has the qualifications and value for resource utilization as commercial gypsum. This allows the gypsum residue to be used directly as a cement retarder or a raw material for gypsum building materials without complex purification.

[0033] In some embodiments, in step S3, the stirring speed is controlled to be 200~250 r / min to ensure that the solid and liquid phases in the reaction system are in full and uniform contact, effectively avoiding the sedimentation and agglomeration of steel slag fine powder, thereby accelerating mass transfer and reaction rate, making acid slag neutralization more thorough and iron and vanadium leaching more complete.

[0034] The present invention will be further described below with reference to specific embodiments.

[0035] Example 1 Steel slag grinding and pulping: Take a certain amount of vanadium-containing steel slag and grind it into fine powder below 300 mesh using equipment such as a ball mill. Weigh 1000g of the ground steel slag powder and add 1000ml of water at a liquid-solid ratio of 1g:1ml. Stir thoroughly in a mixing tank to make a uniform slurry.

[0036] Acid preparation: Measure 500ml of waste acid from the by-product of the sulfuric acid process for titanium dioxide (acid concentration of 20%) and 1500ml of acidic wastewater (acid concentration of 5%), mix them evenly, and prepare 2000ml of dilute acid with a concentration of 10%.

[0037] Acid leaching reaction: The prepared dilute acid is slowly added to the mixing tank containing steel slag slurry at a controlled flow rate. The stirring device is turned on, and the stirring speed is controlled at 200 r / min. At the same time, the reaction temperature is monitored with a thermometer. When the temperature reaches above 50℃, the reaction is continued to be stirred for 2 hours. During this period, alkaline substances (such as sodium hydroxide) or acidic substances (such as dilute sulfuric acid) are added to control the pH value of the system between 6 and 8.

[0038] Post-processing and testing: After the reaction, the slurry was heated to 90°C and kept boiling for 30 minutes. Then, the slurry was cooled to 50°C and transferred to a flotation device. Appropriate amounts of sodium dodecylbenzenesulfonate and a 10% concentration of soluble starch solution were added as flotation reagents for separation. The final product was gypsum slag and iron-vanadium rich material.

[0039] Tests showed that the calcium sulfate dihydrate content in the gypsum residue was 82 wt%, the vanadium content in the iron-vanadium rich material was 1.6 wt%, the iron content was 42 wt%, and the silicon dioxide content was 22 wt%.

[0040] Example 2 Steel slag grinding and pulping: Another batch of vanadium-containing steel slag was selected and ground into fine powder of less than 300 mesh using equipment such as a vibratory mill. 1500g of the ground steel slag powder was weighed, added to 1500ml of water, and stirred thoroughly in a mixing tank to make a uniform slurry.

[0041] Acid preparation: Measure 750ml of waste acid from the by-product of the sulfuric acid process for titanium dioxide (acid concentration of 20%) and 2250ml of acidic wastewater (acid concentration of 5%), mix them evenly, and prepare 3000ml of dilute acid with a concentration of 10%.

[0042] Acid leaching reaction: The prepared dilute acid solution is slowly added to the mixing tank containing steel slag slurry at a controlled flow rate. The stirring device is turned on, and the stirring speed is controlled at 250 r / min. At the same time, the reaction temperature is monitored with a thermometer. When the reaction temperature reaches above 55℃, the reaction is continued to be stirred for 2.5 hours. During this period, alkaline substances (such as sodium hydroxide) or acidic substances (such as dilute sulfuric acid) are added to control the pH value of the system between 6.5 and 7.5.

[0043] Post-processing and testing: After the reaction, the slurry was heated to 90°C and kept boiling for 30 minutes. Then, the slurry was cooled to 50°C and transferred to a flotation device. Appropriate amounts of sodium dodecylbenzenesulfonate and a 10% concentration of soluble starch solution were added as flotation reagents for separation. The final product was gypsum slag and iron-vanadium rich material.

[0044] Tests showed that the calcium sulfate dihydrate content in the gypsum slag was 83 wt%, the vanadium content in the iron-vanadium rich material was 1.7 wt%, the iron content was 43 wt%, and the silicon dioxide content was 22 wt%.

[0045] Example 3 Steel slag grinding and pulping: Another batch of vanadium-containing steel slag was selected and ground into fine powder below 300 mesh using a vertical mill. 2000g of the ground steel slag powder was weighed and added to 2400ml of water at a liquid-to-solid ratio of 1g:1.2ml. The mixture was stirred thoroughly in a mixing tank at 200r / min for 20 minutes to form a uniform slurry.

[0046] Acid preparation: Measure 800ml of waste acid from the by-product of the sulfuric acid process for titanium dioxide (acid concentration of 20%) and 3200ml of acidic wastewater (acid concentration of 4%), mix them evenly, and prepare 4000ml of dilute acid with a concentration of 7.2%.

[0047] Acid leaching reaction: The prepared dilute acid was slowly added to the mixing tank containing steel slag slurry at a controlled flow rate. The agitator was turned on, and the stirring speed was controlled at 220 r / min. The reaction temperature was monitored with a thermometer. Timing was started when the temperature reached 60℃, and the reaction was continued with stirring for 2.5 hours. During the reaction, a small amount of sodium hydroxide solution was added to stabilize the pH value of the system between 6.5 and 7.0.

[0048] Post-processing and testing: After the reaction, the slurry was heated to 92°C and kept boiling for 40 minutes. Then, the slurry was cooled to 50°C and transferred to a flotation device. Sodium dodecylbenzenesulfonate (0.1% by weight of the total slurry) and a 10% soluble starch solution (0.2% by weight of the total slurry) were added as flotation reagents for separation. The final product was gypsum slag and iron-vanadium rich material.

[0049] Tests showed that the gypsum residue contained 83.5 wt% calcium sulfate dihydrate, the iron-vanadium rich material contained 1.62 wt% vanadium, 42.8 wt% iron, and 20.5 wt% silicon dioxide.

[0050] Example 4 Steel slag grinding and pulping: Another batch of vanadium-containing steel slag was selected and ground into fine powder below 300 mesh using a vertical mill. 2000g of the ground steel slag powder was weighed and added to 3000ml of water at a liquid-solid ratio of 1g:1.5ml. The mixture was stirred thoroughly in a mixing tank at 180r / min for 20 minutes to prepare a uniform slurry.

[0051] Acid preparation: Measure 1000ml of waste acid from the by-product of the sulfuric acid process for titanium dioxide (acid concentration of 22%) and 3000ml of acidic wastewater (acid concentration of 4.5%), mix them evenly, and prepare 4000ml of dilute acid with a concentration of 8.1%.

[0052] Acid leaching reaction: The prepared dilute acid was slowly added to the mixing tank containing steel slag slurry at a controlled flow rate. The agitator was turned on, and the stirring speed was controlled at 200 r / min. The reaction temperature was monitored with a thermometer. When the temperature reached 58℃, the timing was started, and the reaction was continued with stirring for 3 hours. During the reaction, a small amount of sodium hydroxide solution was added to stabilize the pH value of the system between 6.8 and 7.2.

[0053] Post-processing and testing: After the reaction, the slurry was heated to 90°C and kept boiling for 50 minutes. Then, the slurry was cooled to 50°C and transferred to a flotation device. Sodium dodecylbenzenesulfonate (0.12% by weight of the total slurry) and a 10% soluble starch solution (0.25% by weight) were added as flotation reagents for separation. The final product was gypsum slag and iron-vanadium rich material.

[0054] Tests showed that the gypsum residue contained 84.2 wt% calcium sulfate dihydrate, the iron-vanadium rich material contained 1.65 wt% vanadium, the iron content was 43.5 wt%, and the silicon dioxide content was 19.8 wt%.

[0055] The above embodiments demonstrate that the method for enriching iron and vanadium in vanadium-containing steel slag of the present invention can stably and efficiently recover resources from steel slag and treat titanium dioxide waste acid and acidic wastewater, showing good application prospects. It also has low processing costs, making it suitable for large-scale production.

[0056] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0057] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for neutralizing waste acid and enriching iron and vanadium from vanadium-containing steel slag, characterized in that, The method comprises the following steps: S1, grinding vanadium-containing steel slag into fine powder, adding water to prepare a slurry according to a liquid-solid ratio of 1g:1-1.5ml; S2, preparing waste acid and acidic wastewater by-product of sulfuric acid method titanium dioxide into dilute acid with a concentration of 5-15%; S3, adding the dilute acid into the slurry, controlling the pH to be between 6-8, the reaction temperature to be greater than or equal to 50 DEG C, and continuously stirring the reaction; S4, after the reaction is completed, heating to above 90 DEG C and keeping boiling for 30-60 minutes; S5, performing flotation separation to obtain gypsum slag and iron-vanadium-rich material.

2. The method of claim 1, wherein, The particle size of the fine vanadium-containing steel slag is less than 300 mesh.

3. The method of claim 1, wherein, The ratio of the mass of the fine powder in step S1 to the volume of the dilute acid in step S3 is 1g:(1.5-2.5)ml.

4. The method of claim 1, wherein, In the preparation of the dilute acid, the acid concentration of the waste acid is 15-25%, and the acid concentration of the acidic wastewater is 3-5%.

5. The method of claim 1, wherein, In step S3, the stirring reaction time is controlled to be 2-3 hours.

6. The method of claim 1, wherein, In step S5, the flotation reagent used in the flotation separation includes sodium dodecyl benzene sulfonate and soluble starch solution.

7. The method of claim 6, wherein, The concentration of the soluble starch solution is 5-15%.

8. The method of claim 1, wherein, The vanadium content in the iron-vanadium-rich material is greater than or equal to 1.5wt%, the iron grade is greater than or equal to 40wt%, and the silicon dioxide content is less than or equal to 22wt%.

9. The method of claim 1, wherein, The calcium sulfate dihydrate content in the gypsum slag is greater than or equal to 82wt%.

10. The method of claim 1, wherein, In step S3, the stirring speed is controlled to be 200-250r / min.

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