Method for high-efficiency vanadium extraction and impurity removal from spent SCR catalyst

Abstract

The application discloses a kind of SCR waste catalyst high-efficiency vanadium extraction impurity removal method, belong to catalyst processing technical field, the method includes the following steps: step S1, after reduction acid immersion, the pickling mother liquor obtained from waste SCR catalyst is slowly added under stirring condition Basic regulator, adjust pH to 4.5~5.5, stirring reaction, filter cake containing vanadium is obtained by pressure filtration;Step S2, filter cake containing vanadium is stirred into pulp by adding water, then add oxidizing agent, obtain the slurry after oxidation;Step S3, to the slurry after oxidation, adjust the alkaline regulator alkaline regulator, stirring reaction, pressure filtration is obtained by vanadium-containing alkaline leaching solution;Step S4, vanadium-containing alkaline leaching solution is added to sodium silicate solution, stirring reaction is carried out at 60~80 DEG C temperature, and pressure filtration is obtained after impurity removal by crude vanadium solution;Step S5, evaporation crystallization: evaporation concentration, crystallization, and recovery vanadium is obtained.By multistage collaborative impurity removal, the efficient enrichment and purification of vanadium are realized, resource recovery rate is high, and byproduct can be reused.

Description

Technical Field

[0001] This invention belongs to the field of catalyst treatment technology, specifically relating to a method for efficient vanadium extraction and impurity removal from spent SCR catalysts. Background Technology

[0002] Vanadium-titanium selective catalytic reduction (SCR) catalysts for denitrification are widely used in flue gas denitrification treatment in industries such as power and steel due to their excellent catalytic performance. However, these catalysts gradually deactivate during use due to mechanical wear, chemical poisoning, or thermal sintering, typically requiring replacement every 3 to 5 years. This generates a large amount of spent catalyst, making their harmless treatment and resource utilization crucial for environmental protection and the recycling of strategic metal resources.

[0003] Currently, the main processes for recovering vanadium from spent SCR catalysts are alkaline leaching and acid leaching. Vanadium in spent catalysts mainly exists as vanadium pentoxide (V₂O₅), which is soluble in both acidic and alkaline media; while tungsten and titanium exist as WO₃ and TiO₂, respectively, with extremely low solubility in acidic solutions. Although alkaline leaching can simultaneously leach vanadium and tungsten, it co-leaches a large number of impurities, leading to a lengthy subsequent separation process and limited product purity. In contrast, acid leaching can selectively dissolve vanadium, achieving preliminary separation from the main components such as tungsten and titanium. However, pentavalent vanadium (V₂O₅)... 5+ In acidic environments, it is usually in the form of VO2. + The presence of VO2 in its soluble form and its low solubility limit the extraction efficiency of direct acid leaching. Therefore, in industrial practice, reducing agents are often introduced to convert the poorly soluble VO2 into a solvent. + Reduced to VO, which has higher solubility in acid. 2+ This significantly improves the leaching rate of vanadium, and the process is known as "reduction acid leaching".

[0004] While reducing acid leaching can effectively extract vanadium, the resulting mother liquor has a complex composition. Besides the target element vanadium, it also contains aluminum dissolved from the catalyst support, iron carried over from the raw materials, and other metal ions introduced from the equipment, forming a multi-component coexisting system with high ionic strength. For the purification of such complex solutions, industrially, neutralization precipitation is mainly used, which involves adjusting the pH of the system to cause specific metal ions to precipitate as hydroxides, thus achieving separation. However, in multi-component systems, the precipitation pH ranges of various metal ions significantly overlap, resulting in extremely poor selectivity for the precipitation reaction. Specifically, aluminum ions (Al... 3+ The initial pH for the precipitation of hydroxide of ferric ions is approximately 5.0, and the complete precipitation pH is approximately 7.0; ferric ions (Fe3+) 3+ The initial pH for the precipitation of vanadium hydroxide is approximately 2.0, and the complete precipitation pH is approximately 4.0; while tetravalent vanadium (V) 4+Hydrolysis and precipitation begin within the pH range of 4.0–6.0. ​​The overlap of these precipitation ranges makes it difficult to achieve effective separation of vanadium from iron and aluminum under a single pH condition, often resulting in the loss of vanadium through co-precipitation with impurities, or the residual impurity ions in the solution contaminating subsequent products.

[0005] To improve separation efficiency, existing technologies attempt to employ a segmented neutralization precipitation strategy, which involves precisely controlling different pH stages to precipitate iron, aluminum, and enrich vanadium separately. However, in actual industrial wastewater, the concentrations of various metal ions differ significantly, and complex chemical behaviors such as complexation, co-precipitation, and adsorption exist, making it difficult to achieve ideal separation boundaries through theoretical segmented precipitation. Of particular concern is aluminum, the main leaching component of the spent catalyst carrier (TiO2-Al2O3 composite oxide), which typically has a high concentration in the pickling mother liquor. Its chemical properties are very similar to vanadium, and it readily co-precipitates with vanadium during pH adjustment, becoming a major limiting factor affecting vanadium recovery and product purity. The core technical challenge of existing technologies in treating such multi-component vanadium-containing wastewater lies in the difficulty of selectively separating vanadium from impurities such as iron and aluminum. This is especially pronounced in systems with high aluminum content, where overlapping precipitation zones are more significant, leading to low vanadium recovery and poor product purity. Furthermore, the large amount of vanadium slag containing iron and aluminum generated during the neutralization precipitation process is hazardous waste, incurring high disposal costs, and the vanadium entrained in the slag is difficult to recover economically, resulting in resource waste.

[0006] In summary, existing technologies struggle to selectively separate vanadium from impurities such as iron and aluminum when treating vanadium-containing wastewater generated from the reduction and acid leaching of spent SCR catalysts. This is particularly problematic in multi-component systems with high aluminum content, where overlapping precipitation zones are a significant issue. This results in low vanadium recovery rates, poor product purity, and high solid waste production, becoming a key bottleneck restricting the technological economics and environmental friendliness of SCR spent catalyst resource utilization. Therefore, developing a new method for efficient vanadium recovery and deep removal of impurities such as aluminum from spent SCR catalysts is crucial for improving overall resource utilization efficiency and ensuring product quality. Summary of the Invention

[0007] The purpose of this invention is to provide a method for efficient vanadium extraction and impurity removal from spent SCR catalysts, in order to solve the problem of low vanadium recovery efficiency.

[0008] The objective of this invention can be achieved through the following technical solutions: This invention provides a method for efficient vanadium extraction and impurity removal from spent SCR catalysts, comprising the following steps: Step S1: Precipitation and enrichment of vanadium: The acid washing mother liquor obtained after reducing and acid leaching the waste SCR catalyst was slowly added with an alkaline regulator under stirring to adjust the pH to 4.5-5.5. The reaction was stirred for 1.5-2.5 hours to precipitate low-valence vanadium (trivalent and tetravalent) in the acid washing mother liquor as hydroxides, while some impurities such as iron and aluminum were co-precipitated. After the reaction was completed, the mixture was filtered to obtain a vanadium-containing filter cake. Step S2, Oxidation Treatment Add water to the vanadium-containing filter cake obtained in step S1 and stir to make slurry. Then add an oxidant and oxidize at room temperature for 0.5~1.5h to oxidize the residual low-valent vanadium (trivalent and tetravalent) in the filter cake to pentavalent vanadium to obtain oxidized slurry. Step S3, Alkali Leaching Add an alkaline regulator to the oxidized slurry obtained in step S2 to adjust the pH to 9-11, and stir the reaction at 85-98℃ for 1.5-2.5 hours to allow vanadium to transfer from the solid phase to the liquid phase in the form of sodium vanadate; after the reaction is completed, filter the solution to obtain vanadium-containing alkaline leaching solution and leaching residue. Step S4: Aluminum Removal Add Na2SiO3 solution to the vanadium-containing alkaline leaching solution obtained in step S3, and stir the reaction at 60~80℃ for 1.5~2.5h to cause aluminum impurities in the solution to form aluminosilicate precipitates; after the reaction is completed, filter the solution to obtain crude vanadium solution after impurity removal. Step S5: Evaporation and Crystallization The crude vanadium solution obtained in step S4 is evaporated, concentrated, and crystallized to obtain recovered vanadium.

[0009] In some possible implementations, the alkaline regulator in steps S1 and S3 is a sodium hydroxide solution; In step S2, the oxidant is a hydrogen peroxide solution with a concentration of 10-30%. The amount of oxidant used can be adjusted according to the actual situation and may be in excess. The amount of Na2SiO3 solution used in step S4 should be adjusted according to the actual situation, with a slight excess.

[0010] In some possible implementations, the acid washing mother liquor obtained after reducing and acid leaching the spent SCR catalyst includes the following steps: The spent SCR catalyst is crushed to a particle size of less than 0.05 mm, added to an acid leaching solution at a solid-liquid ratio of 1:2-5, and then filtered to obtain leaching residue and acid washing mother liquor.

[0011] In some possible implementations, the acid leaching solution is either hydrochloric acid or sulfuric acid, with a mass fraction of 5%; The reducing agent is sodium sulfite, and the amount of reducing agent added is 3% of the mass of the spent SCR catalyst.

[0012] In some possible implementations, step S4 also includes deep aluminum removal: Aluminum ions in the crude vanadium solution after impurity removal are adsorbed using an adsorbent with specific adsorption properties for aluminum ions.

[0013] Deep aluminum removal includes the following steps: The pH of the crude vanadium solution was adjusted to 1-4 (preferably 4), and adsorbent was added at a ratio of 1 g / L. Adsorption was carried out for 100-150 min, followed by separation to obtain a vanadium solution with deep aluminum removal. The adsorbent was prepared using 3 mol·L⁻¹ hydrochloric acid. -1 Acid pickling followed by water washing achieves regeneration. The pickling solution serves as a reducing acid leaching solution, minimizing vanadium loss.

[0014] Preferably, after adjusting the pH of the crude vanadium solution to 1-4, an appropriate amount of H2O2 is added before adsorption to completely oxidize vanadium to V(V) and peroxyvanadate anion [VO(O2)2]. - Reduce vanadium loss caused by adsorption by adsorbents at the source.

[0015] In some possible implementations, the adsorbent is prepared through the following steps: The terminal amino hyperbranched magnetic support was added to an ethanol aqueous solution, followed by ammonium persulfate. Under nitrogen protection, acrylic acid and aluminum sulfate octadecylhydrate were added, and the mixture was stirred at 30-35℃ for 40-60 min. A crosslinking agent was then added, and the temperature was raised to 55-60℃. The mixture was stirred and reacted for 24 h. After the reaction was completed, the adsorbent was obtained by magnetic separation, elution with hydrochloric acid, washing with water, and drying.

[0016] The ratio of amino-terminated hyperbranched magnetic carrier, acrylic acid, and ammonium persulfate is 1g:1.5g:0.3g; the molar ratio of acrylic acid to aluminum sulfate octadecylhydrate is 6:1; and the molar ratio of acrylic acid to crosslinking agent is 1:6.

[0017] In some possible implementations, the crosslinking agent comprises ethylene glycol dimethacrylate and N,N'-methylenebisacrylamide. The molar ratio of ethylene glycol dimethacrylate to N,N'-methylenebisacrylamide is 2:1.

[0018] In some possible implementations, the terminal amino hyperbranched magnetic carrier is prepared by alternating Michael addition and amidation reactions using aminated magnetic carriers, methyl acrylate, and ethylenediamine as raw materials.

[0019] The amino-terminated hyperbranched magnetic support is prepared by the following steps: Aminated magnetic support was added to methanol, followed by methyl acrylate. The mixture was stirred and reacted at 25°C for 10-12 hours. After the reaction was completed, the mixture was filtered, washed with ethanol, and dried. The dried product was then added to ethylenediamine and stirred and reacted at 25°C under nitrogen protection for another 15-20 hours. The mixture was then filtered, washed with ethanol, and dried. The ratio of aminated magnetic support, methanol, methyl acrylate, and ethylenediamine was 8 g: 80 mL: 5 mL: 8 mL. The dried product was added to methanol, followed by methyl acrylate. The mixture was stirred and reacted at 40°C for 10-12 hours. After the reaction was completed, the product was filtered, washed with ethanol, and dried. The dried product was then added to ethylenediamine and stirred and reacted at 40°C under nitrogen protection for another 15-20 hours. The product was then filtered, washed with ethanol, and dried to obtain the terminal amino hyperbranched magnetic support. The ratio of the dried product, methanol, methyl acrylate, and ethylenediamine was 6 g: 60 mL: 20 mL: 16 mL.

[0020] In some possible implementations, the aminated magnetic support is prepared by a sol-gel method using ethanol as a solvent and Fe3O4 powder, tetraethyl orthosilicate, and an aminosilane coupling agent as raw materials. This magnetic support is prepared through the following steps: Fe3O4 powder and water were mixed and ultrasonically dispersed. Ethanol was added, followed by ammonia to adjust the pH to around 10. Then, tetraethyl orthosilicate was added and reacted at room temperature for 30-40 minutes. An aminosilane coupling agent was added and reacted at room temperature for 10-12 hours. After the reaction was completed, the mixture was separated into solid and liquid components, washed, and dried to obtain the aminated magnetic carrier.

[0021] In some possible implementations, the ratio of Fe3O4 powder, tetraethyl orthosilicate, and aminosilane coupling agent is 5g:2-3mL:2-3g; The Fe3O4 powder has a particle size of 20-50 μm, the ammonia concentration is 20%, the volume ratio of water to ethanol in the above system is about 1:4, and the total solid to liquid ratio in the system is about 1 g: 20 mL. The aminosilane coupling agent is one of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0022] The beneficial effects of this invention are: This invention provides a method for efficient vanadium extraction and impurity removal from spent SCR catalysts. The method employs multi-stage synergistic impurity removal to achieve efficient enrichment and purification of vanadium. Under acidic conditions, it preferentially enriches low-valent vanadium and initially removes some impurities. Oxidation converts insoluble low-valent vanadium into readily soluble pentavalent vanadium, creating conditions for subsequent alkaline leaching. The alkaline leaching process achieves efficient separation of vanadium from insoluble substances such as titanium and tungsten. Finally, deep aluminum removal using sodium silicate solves the problem of difficult separation of aluminum and vanadium under alkaline conditions. This step-by-step treatment avoids co-precipitation of impurities and significantly improves the purity of the crude vanadium product.

[0023] The method provided in this invention is highly targeted and effectively solves the problem of removing trace amounts of highly toxic impurities (thallium). The multi-step precipitation and separation process in the early stages simultaneously removes thallium during the vanadium enrichment process. Data shows that in step S1, thallium co-precipitates with vanadium, iron, aluminum, etc., or is adsorbed and removed, thus preventing highly toxic thallium from entering subsequent processes, contaminating the final product, or posing environmental risks.

[0024] Compared to the lengthy traditional processes that rely on repeated purification with multiple reagents or solvent extraction, the method provided in this invention achieves enrichment, transformation, leaching, and impurity removal within the same system through precise control of pH and reaction conditions. This results in a shorter process with fewer operating units. The final step introduces a small amount of sodium silicate for aluminum removal, avoiding the use of strong oxidants or organic solvents and reducing the risk of equipment corrosion and secondary pollution. Furthermore, due to the high impurity removal efficiency, the resulting solid waste (such as leaching residue and aluminum removal slag) has a relatively simple composition, facilitating subsequent disposal or resource utilization. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Obviously, the following description is merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0027] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structure may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter of the claims.

[0028] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and all technical features and optional technical features of this application can be combined to form new technical solutions.

[0029] The following is a detailed description of a method for efficient vanadium extraction and impurity removal from spent SCR catalysts, as described in this application.

[0030] The following is a detailed description with reference to specific examples.

[0031] Example 1

[0032] This embodiment provides a method for efficient vanadium extraction and impurity removal from spent SCR catalysts, including the following steps: Step S1, vanadium precipitation and enrichment: The acid washing mother liquor obtained after reducing and acid leaching the waste SCR catalyst is slowly added to sodium hydroxide solution under stirring conditions to adjust the pH to 5. The reaction is stirred for 5 hours. After the reaction is completed, the mixture is filtered to obtain a vanadium-containing filter cake. The acid washing mother liquor obtained after reducing and acid leaching of waste SCR catalyst includes the following steps: The spent SCR catalyst is crushed to a particle size of less than 0.05 mm, added to an acid leaching solution at a solid-liquid ratio of 1:3, and leached. The leaching residue and acid washing mother liquor are obtained by filtration and separation. The acid leaching solution is hydrochloric acid with a mass fraction of 5%. The reducing agent is sodium sulfite, and the amount of reducing agent added is 3% of the mass of the spent SCR catalyst.

[0033] Step S2, Oxidation treatment: Add water to the vanadium-containing filter cake obtained in step S1 and stir to make slurry. Then add an oxidant and oxidize at room temperature for 5 hours to obtain oxidized slurry. The oxidant is hydrogen peroxide solution with a concentration of 30%.

[0034] Step S3, Alkali Leaching: Add sodium hydroxide solution to the oxidized slurry obtained in step S2, adjust the pH to 10, stir the reaction at 90℃ for 2 hours, filter the solution after the reaction is completed to obtain vanadium-containing alkaline leaching solution and leaching residue. Step S4, aluminum removal: Add Na2SiO3 solution to the vanadium-containing alkaline leaching solution obtained in step 3, stir and react at 70℃ for 2 hours, filter after the reaction is completed to obtain crude vanadium solution after impurity removal. Step S5, Evaporation and Crystallization: The crude vanadium solution obtained in step S4 is evaporated, concentrated, and crystallized to obtain recovered vanadium.

[0035] The recovery results are shown in Table 1 below: Table 1

[0036] Note: " / " indicates that it does not include.

[0037] Example 2

[0038] The difference between this embodiment and Example 1 is that the content of the components in the pickling mother liquor is different, while the other raw materials and preparation process remain the same as in Example 1.

[0039] The recovery results are shown in Table 2 below: Table 2

[0040] Note: " / " indicates that it does not include.

[0041] Example 3

[0042] This embodiment provides a method for efficient vanadium extraction and impurity removal from spent SCR catalysts, including the following steps: Step S1, Vanadium precipitation and enrichment: The acid washing mother liquor obtained after reducing and acid leaching the waste SCR catalyst is slowly added to sodium hydroxide solution under stirring to adjust the pH to 4.5. The reaction is stirred for 1.5 hours. After the reaction is completed, the mixture is filtered to obtain a vanadium-containing filter cake. The acid washing mother liquor obtained after reducing and acid leaching of waste SCR catalyst includes the following steps: The spent SCR catalyst is crushed to a particle size of less than 0.05 mm, added to an acid leaching solution at a solid-liquid ratio of 1:3, and leached. The leaching residue and acid washing mother liquor are obtained by filtration and separation. The acid leaching solution is hydrochloric acid with a mass fraction of 5%. The reducing agent is sodium sulfite, and the amount of reducing agent added is 3% of the mass of the spent SCR catalyst.

[0043] Step S2, Oxidation treatment: Add the vanadium-containing filter cake obtained in step S1 to water and stir to make a slurry. Then add an oxidant and oxidize at room temperature for 0.5 hours to obtain an oxidized slurry. The oxidant is a hydrogen peroxide solution with a concentration of 30%.

[0044] Step S3, Alkali Leaching: Add sodium hydroxide solution to the oxidized slurry obtained in step S2, adjust the pH to 11, stir and react at 98℃ for 1.5h, filter after the reaction to obtain vanadium-containing alkaline leaching solution and leaching residue; Step S4, aluminum removal: Add Na2SiO3 solution to the vanadium-containing alkaline leaching solution obtained in step 3, stir and react at 60℃ for 2.5h, filter after the reaction is completed to obtain crude vanadium solution after impurity removal; Step S5, Evaporation and Crystallization: The crude vanadium solution obtained in step S4 is evaporated, concentrated, and crystallized to obtain recovered vanadium.

[0045] The recovery results are shown in Table 3 below: Table 3

[0046] Note: " / " indicates that it does not include.

[0047] Example 4

[0048] This embodiment provides a method for efficient vanadium extraction and impurity removal from spent SCR catalysts, including the following steps: Step S1, Vanadium precipitation and enrichment: The acid washing mother liquor obtained after reducing and acid leaching the waste SCR catalyst is slowly added to sodium hydroxide solution under stirring to adjust the pH to 5.5. The reaction is stirred for 2.5 hours. After the reaction is completed, the mixture is filtered to obtain a vanadium-containing filter cake. The acid washing mother liquor obtained after reducing and acid leaching of waste SCR catalyst includes the following steps: The spent SCR catalyst is crushed to a particle size of less than 0.05 mm, added to an acid leaching solution at a solid-liquid ratio of 1:3, and leached. The leaching residue and acid washing mother liquor are obtained by filtration and separation. The acid leaching solution is hydrochloric acid with a mass fraction of 5%. The reducing agent is sodium sulfite, and the amount of reducing agent added is 3% of the mass of the spent SCR catalyst.

[0049] Step S2, Oxidation treatment: Add water to the vanadium-containing filter cake obtained in step S1 and stir to make slurry. Then add an oxidant and oxidize at room temperature for 1.5 hours to obtain oxidized slurry. The oxidant is hydrogen peroxide solution with a concentration of 30%.

[0050] Step S3, Alkali Leaching: Add sodium hydroxide solution to the oxidized slurry obtained in step S2, adjust the pH to 11, stir and react at 98℃ for 1.5h, filter after the reaction to obtain vanadium-containing alkaline leaching solution and leaching residue; Step S4, aluminum removal: Add Na2SiO3 solution to the vanadium-containing alkaline leaching solution obtained in step 3, stir and react at 80℃ for 1.5h, filter after the reaction is completed to obtain crude vanadium solution after impurity removal; Step S5, Evaporation and Crystallization: The crude vanadium solution obtained in step S4 is evaporated, concentrated, and crystallized to obtain recovered vanadium.

[0051] The recovery results are shown in Table 4 below: Table 4

[0052] Note: " / " indicates that it does not include.

[0053] Examples 5-8 and Comparative Examples 1-2 all used the same alkaline leachate as in Example 1.

[0054] Example 5

[0055] This embodiment provides a method for efficient vanadium extraction and impurity removal from spent SCR catalysts, including the following steps: The difference between this embodiment and Embodiment 1 is that an adsorbent with specific adsorption properties for aluminum ions is used to adsorb aluminum ions from the crude vanadium solution after impurity removal.

[0056] Deep aluminum removal includes the following steps: The pH of the crude vanadium solution was adjusted to 4, and adsorbent was added at a ratio of 1 g / L. Adsorption was carried out for 120 min, followed by separation to obtain a vanadium solution with deep aluminum removal. The adsorbent was prepared using 3 mol·L⁻¹ hydrochloric acid. -1 The process involves acid washing followed by water washing to achieve regeneration, while the remaining raw materials and preparation process remain the same as in Example 1.

[0057] The adsorbent is prepared through the following steps: Fe3O4 powder and water were mixed and ultrasonically dispersed. Ethanol was added, followed by ammonia to adjust the pH to 10. Tetraethyl orthosilicate was then added, and the mixture was reacted at room temperature for 30 minutes. An aminosilane coupling agent was then added, and the mixture was reacted at room temperature for 10 hours. After the reaction was completed, the mixture was separated into solid and liquid components, washed, and dried to obtain an aminated magnetic carrier. The ratio of Fe3O4 powder, tetraethyl orthosilicate, and aminosilane coupling agent was 5 g: 2 mL: 2 g. The particle size of Fe3O4 powder was 20-50 μm, the concentration of ammonia was 20%, the volume ratio of water to ethanol in the above system was approximately 1:4, and the ratio of total solid to liquid in the system was approximately 1 g: 20 mL. The aminosilane coupling agent was N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0058] Aminated magnetic support was added to methanol, followed by methyl acrylate. The mixture was stirred and reacted at 25°C for 10 hours. After the reaction was completed, the mixture was filtered, washed with ethanol, and dried. The dried product was then added to ethylenediamine and stirred and reacted at 25°C under nitrogen protection for another 15 hours. The mixture was then filtered, washed with ethanol, and dried. The ratio of aminated magnetic support, methanol, methyl acrylate, and ethylenediamine was 8 g: 80 mL: 5 mL: 8 mL. The dried product was added to methanol, followed by methyl acrylate. The mixture was stirred and reacted at 40°C for 10 hours. After the reaction was completed, the product was filtered, washed with ethanol, and dried. The dried product was then added to ethylenediamine and stirred and reacted at 40°C under nitrogen protection for another 15 hours. The product was then filtered, washed with ethanol, and dried to obtain the terminal amino hyperbranched magnetic support. The ratio of the dried product, methanol, methyl acrylate, and ethylenediamine was 6 g: 60 mL: 20 mL: 16 mL.

[0059] The terminal amino hyperbranched magnetic support was added to an ethanol aqueous solution, followed by ammonium persulfate. Under nitrogen protection, acrylic acid and aluminum sulfate octadecylhydrate were added, and the mixture was stirred at 30°C for 40 min. A crosslinking agent was then added, and the temperature was raised to 55°C. The mixture was stirred and reacted for 24 h. After the reaction was completed, the adsorbent was obtained by magnetic separation, elution with hydrochloric acid, washing with water, and drying.

[0060] The ratio of the terminal amino-terminated hyperbranched magnetic carrier, acrylic acid, and ammonium persulfate is 1 g:1.5 g:0.3 g; the molar ratio of acrylic acid to aluminum sulfate octadecylhydrate is 6:1; and the molar ratio of acrylic acid to crosslinking agent is 1:6. The crosslinking agent comprises ethylene glycol dimethacrylate and N,N'-methylenebisacrylamide. The molar ratio of ethylene glycol dimethacrylate to N,N'-methylenebisacrylamide is 2:1.

[0061] The recovery results are shown in Table 5 below: Table 5

[0062] Note: " / " indicates that it does not include.

[0063] After five cycles of adsorbent circulation, the adsorption capacity decreased to 95% of the original adsorption capacity.

[0064] Example 6

[0065] This embodiment provides a method for efficient vanadium extraction and impurity removal from spent SCR catalysts, including the following steps: The difference between this embodiment and Embodiment 1 is that an adsorbent with specific adsorption properties for aluminum ions is used to adsorb aluminum ions from the crude vanadium solution after impurity removal.

[0066] Deep aluminum removal includes the following steps: The pH of the crude vanadium solution was adjusted to 4, and adsorbent was added at a ratio of 1 g / L. Adsorption was carried out for 120 min, followed by separation to obtain a vanadium solution with deep aluminum removal. The adsorbent was prepared using 3 mol·L⁻¹ hydrochloric acid. -1 The process involves acid washing followed by water washing to achieve regeneration, while the remaining raw materials and preparation process remain the same as in Example 1.

[0067] The adsorbent is prepared through the following steps: Fe3O4 powder and water were mixed and ultrasonically dispersed. Ethanol was added, followed by ammonia to adjust the pH to 10. Tetraethyl orthosilicate was then added, and the mixture was reacted at room temperature for 40 minutes. An aminosilane coupling agent was then added, and the mixture was reacted at room temperature for 12 hours. After the reaction was completed, the mixture was separated into solid and liquid components, washed, and dried to obtain an aminated magnetic carrier. The ratio of Fe3O4 powder, tetraethyl orthosilicate, and aminosilane coupling agent was 5 g: 3 mL: 3 g. The particle size of Fe3O4 powder was 20-50 μm, the concentration of ammonia was 20%, the volume ratio of water to ethanol in the above system was approximately 1:4, and the ratio of total solid to liquid in the system was approximately 1 g: 20 mL. The aminosilane coupling agent was N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane.

[0068] Aminated magnetic support was added to methanol, followed by methyl acrylate. The mixture was stirred and reacted at 25°C for 12 hours. After the reaction was completed, the mixture was filtered, washed with ethanol, and dried. The dried product was then added to ethylenediamine and stirred and reacted at 25°C under nitrogen protection for another 20 hours. The mixture was then filtered, washed with ethanol, and dried. The ratio of aminated magnetic support, methanol, methyl acrylate, and ethylenediamine was 8 g: 80 mL: 5 mL: 8 mL. The dried product was added to methanol, followed by methyl acrylate. The mixture was stirred and reacted at 40°C for 12 hours. After the reaction was completed, the product was filtered, washed with ethanol, and dried. The dried product was then added to ethylenediamine and stirred and reacted at 40°C under nitrogen protection for another 20 hours. The product was then filtered, washed with ethanol, and dried to obtain the terminal amino hyperbranched magnetic support. The ratio of the dried product, methanol, methyl acrylate, and ethylenediamine was 6 g: 60 mL: 20 mL: 16 mL.

[0069] The terminal amino hyperbranched magnetic support was added to an ethanol aqueous solution, followed by ammonium persulfate. Under nitrogen protection, acrylic acid and aluminum sulfate octadecylhydrate were added, and the mixture was stirred at 35°C for 60 min. A crosslinking agent was then added, and the temperature was raised to 60°C. The mixture was stirred for 24 h after the reaction was completed. After magnetic separation, the adsorbent was obtained by elution with hydrochloric acid, washing with water, and drying.

[0070] The ratio of terminal amino-terminated hyperbranched magnetic carrier, acrylic acid, and ammonium persulfate was 1 g:1.5 g:0.3 g; the molar ratio of acrylic acid to aluminum sulfate octadecylhydrate was 6:1; and the molar ratio of acrylic acid to crosslinking agent was 1:6. The crosslinking agent comprised ethylene glycol dimethacrylate and N,N'-methylenebisacrylamide. The molar ratio of ethylene glycol dimethacrylate to N,N'-methylenebisacrylamide was 2:1. The recovery results are shown in Table 6 below. Table 6

[0071] Note: " / " indicates that it does not include.

[0072] After five cycles of adsorbent circulation, the adsorption capacity decreased to 94% of the original adsorption capacity.

[0073] Example 7

[0074] This embodiment provides a method for efficient vanadium extraction and impurity removal from spent SCR catalysts. The difference between this embodiment and Embodiment 5 lies in the depth of aluminum removal, which includes the following steps: The pH of the crude vanadium solution was adjusted to 4. Before adsorption, an appropriate amount of H₂O₂ was added to completely oxidize the vanadium to V(V). Adsorbent was then added at a ratio of 1 g / L, and adsorption was carried out for 120 min. After separation, a vanadium solution with deep aluminum removal was obtained. The adsorbent was prepared using 3 mol·L⁻¹ hydrochloric acid. -1 The process involves acid washing followed by water washing to achieve regeneration, while the remaining raw materials and preparation process remain the same as in Example 5.

[0075] The recovery results are shown in Table 7 below: Table 7

[0076] Note: " / " indicates that it does not include.

[0077] Example 8

[0078] This embodiment provides a method for efficient vanadium extraction and impurity removal from spent SCR catalysts. The difference between this embodiment and Embodiment 6 lies in the depth of aluminum removal, which includes the following steps: The pH of the crude vanadium solution was adjusted to 4. Before adsorption, an appropriate amount of H₂O₂ was added to completely oxidize the vanadium to V(V). Adsorbent was then added at a ratio of 1 g / L, and adsorption was carried out for 120 min. After separation, a vanadium solution with deep aluminum removal was obtained. The adsorbent was prepared using 3 mol·L⁻¹ hydrochloric acid. -1 The process involves acid washing followed by water washing to achieve regeneration, while the remaining raw materials and preparation process remain the same as in Example 6.

[0079] The recovery results are shown in Table 8 below: Table 8

[0080] Note: " / " indicates that it does not include.

[0081] Comparative Example 1

[0082] The difference between this comparative example and Example 1 is that sodium silicate was not used for alkaline leaching; that is, the leaching solution used in this comparative example is alkaline. See Table 9 below: Table 9

[0083] Note: " / " indicates that it does not include.

[0084] This means that the aluminum residue in Comparative Example 1 is relatively high.

[0085] Comparative Example 2

[0086] The difference between this comparative example and Example 5 is that the adsorbent is different. The adsorbent in this comparative example is prepared by the following steps: Aminated magnetic carriers were added to an aqueous ethanol solution, followed by ammonium persulfate. Under nitrogen protection, acrylic acid and aluminum sulfate octadecylhydrate were added, and the mixture was stirred at 30-35℃ for 40-60 min. A crosslinking agent was then added, and the temperature was raised to 55-60℃. The mixture was stirred and reacted for 24 h. After the reaction was completed, the adsorbent was obtained by magnetic separation, elution with hydrochloric acid, washing with water, and drying.

[0087] The ratio of aminated magnetic carrier, acrylic acid, and ammonium persulfate is 1g:1.5g:0.3g; the molar ratio of acrylic acid to aluminum sulfate octadecylhydrate is 6:1; the molar ratio of acrylic acid to crosslinking agent is 1:6; the crosslinking agent includes ethylene glycol dimethacrylate and N,N'-methylenebisacrylamide in a molar ratio of 2:1.

[0088] The recovery results are shown in Table 10 below: Table 10

[0089] Note: " / " indicates that it does not include.

[0090] In this comparative example, the adsorption capacity of the adsorbent decreased to 82% of its original adsorption capacity after 5 cycles.

[0091] Comparative Example 3

[0092] The difference between this comparative example and comparative example 2 is that the crosslinking agent is ethylene glycol dimethacrylate, while the other raw materials and preparation process remain the same as those in comparative example 2.

[0093] The recovery results are shown in Table 11 below: Table 11

[0094] Note: " / " indicates that it does not include.

[0095] In this comparative example, the adsorption capacity of the adsorbent decreased to 79% of the original adsorption capacity after 5 cycles.

[0096] According to the comparison between Examples 1-8 and Comparative Examples 1-2, the preparation method of the present invention can reduce the aluminum content (crude vanadium solution) to below 0.1 g / L (0.082 g / L, 260 mL in Example 1). In Examples 5-8 and Comparative Examples 2-3, the use of self-made adsorbents can further reduce the aluminum content to the point of being free of aluminum ions, which can be applied to methods with high requirements for aluminum residue. Comparative Example 2 did not introduce a hyperbranched structure; Comparative Example 3 did not introduce a hyperbranched structure and used a single crosslinking agent, ethylene glycol dimethacrylate (compared to ethylene glycol dimethacrylate, N,N'-methylenebisacrylamide is more rigid due to its extremely short methylene bridge chains and the hydrogen bonding of amide groups, forming a more rigid crosslinked network); Examples 5-8 introduced a hyperbranched structure and a rigid crosslinking agent, which improved the capacity of the adsorbent after cyclic regeneration. The hyperbranched structure provides a high-density, multi-terminal functional group array, and even if some sites are deactivated during regeneration, sufficient redundant active centers are still retained; at the same time, its three-dimensional network prevents functional groups from collapsing or becoming embedded during elution, ensuring the continued accessibility of sites. The rigid crosslinking agent constructs a rigid framework in the polymer network, which is maintained after multiple cycles; the adsorbent in this invention can resist chemical hydrolysis caused by acid washing, and the density of the hyperbranched framework restricts the inward diffusion of corrosive media, significantly improving the chemical and mechanical durability of the adsorbent material in a strong acid regeneration environment.

[0097] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0098] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for efficient vanadium extraction and impurity removal from spent SCR catalysts, characterized in that, Includes the following steps: Step S1, vanadium precipitation and enrichment: The acid washing mother liquor obtained after reducing and acid leaching the waste SCR catalyst is slowly added with an alkaline regulator under stirring to adjust the pH to 4.5~5.

5. The reaction is stirred for 1.5~2.5h. After the reaction is completed, the filter is pressure filtered to obtain a vanadium-containing filter cake. Step S2, Oxidation treatment: Add the vanadium-containing filter cake to water and stir to make a slurry. Then add an oxidant and oxidize at room temperature for 0.5~1.5 hours to obtain the oxidized slurry. Step S3, Alkali Leaching: Add an alkaline regulator to the oxidized slurry to adjust the pH to 9-11, stir and react at 85-98℃ for 1.5-2.5 hours, filter after the reaction to obtain vanadium-containing alkaline leaching solution; Step S4, aluminum removal: Add Na2SiO3 solution to the vanadium-containing alkaline leaching solution, stir and react at 60~80℃ for 1.5~2.5h, filter under pressure after the reaction is completed to obtain crude vanadium solution after impurity removal; Step S5, Evaporation and Crystallization: Evaporate and concentrate, then crystallize to obtain recovered vanadium.

2. The method for efficient vanadium extraction and impurity removal from spent SCR catalysts according to claim 1, characterized in that, In steps S1 and S3, the alkaline regulator is sodium hydroxide solution; In step S2, the oxidant is a hydrogen peroxide solution.

3. The method for efficient vanadium extraction and impurity removal from spent SCR catalysts according to claim 1, characterized in that, The acid washing mother liquor obtained after reducing and acid leaching of waste SCR catalyst includes the following steps: The spent SCR catalyst was crushed to a particle size of less than 0.05 mm and added to an acid leaching solution at a solid-liquid ratio of 1:2-5. The leaching residue and acid washing mother liquor were obtained by filtration and separation.

4. The method for efficient vanadium extraction and impurity removal from spent SCR catalysts according to claim 1, characterized in that, The acid leaching solution is either hydrochloric acid or sulfuric acid; the reducing agent is sodium sulfite.

5. The method for efficient vanadium extraction and impurity removal from spent SCR catalysts according to claim 1, characterized in that, Step S4 also includes deep aluminum removal: using an adsorbent with specific adsorption properties for aluminum ions to adsorb aluminum ions from the crude vanadium solution after impurity removal.

6. The method for efficient vanadium extraction and impurity removal from spent SCR catalysts according to claim 5, characterized in that, The adsorbent is prepared through the following steps: The terminal amino hyperbranched magnetic support was added to an ethanol aqueous solution, ammonium persulfate was added, and acrylic acid and aluminum sulfate octadecylhydrate were added under nitrogen protection. The mixture was stirred at 30-35℃ for 40-60 min, a crosslinking agent was added, the temperature was raised to 55-60℃, and the mixture was stirred for 24 h. After the reaction was completed, the adsorbent was obtained by magnetic separation, elution with hydrochloric acid, washing with water, and drying. The ratio of amino-terminated hyperbranched magnetic carrier, acrylic acid, and ammonium persulfate is 1g:1.5g:0.3g; the molar ratio of acrylic acid to aluminum sulfate octadecylhydrate is 6:1; and the molar ratio of acrylic acid to crosslinking agent is 1:

6.

7. The method for efficient vanadium extraction and impurity removal from SCR waste catalyst according to claim 6, characterized in that, The crosslinking agent includes ethylene glycol dimethacrylate and N,N'-methylenebisacrylamide.

8. The method for efficient vanadium extraction and impurity removal from spent SCR catalysts according to claim 6, characterized in that, The terminal amino hyperbranched magnetic carrier is prepared by alternating Michael addition and amidation reactions using aminated magnetic carrier, methyl acrylate and ethylenediamine as raw materials.

9. A method for efficient vanadium extraction and impurity removal from spent SCR catalysts according to claim 8, characterized in that, Aminated magnetic carriers are prepared by sol-gel method using ethanol as solvent and Fe3O4 powder, tetraethyl orthosilicate and aminosilane coupling agent as raw materials.

10. A method for efficient vanadium extraction and impurity removal from spent SCR catalysts according to claim 9, characterized in that, The aminosilane coupling agent is one of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane.

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