A pretreatment method of 3-cyanopyridine wastewater

Abstract

This invention discloses a pretreatment method for 3-cyanopyridine wastewater, belonging to the field of wastewater pretreatment technology. This method uses a modified magnetic porous adsorbent as its core and achieves continuous pretreatment of 3-cyanopyridine wastewater through a magnetically controlled adsorption separation device. The adsorbent uses a carboxyl-block polyarylene ether nitrile as a stable porous adsorption framework, introducing nitrile-carboxyl dual-target adsorption sites into the molecular chain. Simultaneously, graphene composite magnetic particles are introduced into the carboxyl-block polyarylene ether nitrile, providing rapid magnetic response separation performance. Through the deep synergy of highly selective adsorption and magnetically controlled separation, effective removal and resource recovery of 3-cyanopyridine are achieved. It can maintain stable treatment performance during long-term continuous operation and is suitable for the industrial pretreatment of 3-cyanopyridine production wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater pretreatment technology, specifically a pretreatment method for 3-cyanopyridine wastewater. Background Technology

[0002] 3-Cyanopyridine, a key fine chemical intermediate, is widely used in the synthesis of pharmaceuticals, pesticides, and other chemicals. Its production inevitably generates large quantities of high-concentration organic wastewater. This wastewater contains not only extremely high concentrations of 3-cyanopyridine but also a large number of complex synthetic byproducts. Given the high economic value of 3-cyanopyridine itself, shifting from "end-stage destructive degradation" to "front-end high-purity resource recovery" in the wastewater pretreatment stage to achieve efficient enrichment and recovery of 3-cyanopyridine is an urgent need for relevant enterprises to reduce costs, increase efficiency, and pursue green recycling.

[0003] To achieve the enrichment and recovery of specific organic materials in industrial wastewater, commonly used pretreatment methods mainly include solvent extraction, membrane separation, and adsorption. Among these, adsorption separation technology has become a research hotspot and mainstream development direction in this field due to its simple operation, low operating cost, and regenerable adsorbent. Chinese patent application CN116832793A discloses an industrial wastewater adsorbent and its preparation method. By mixing heavy metals such as nickel salts, iron salts, and chromium salts with organic reagents such as sodium propylene sulfonate and citric acid under strong acid conditions, and then neutralizing and precipitating with calcium salts, a composite adsorbent is prepared. After adsorption saturation, desorption regeneration is achieved using desorption agents such as sodium chloride and sodium hydroxide to realize the recycling of the adsorbent and the purification of wastewater.

[0004] In the above-mentioned technical solutions, the composite adsorbent mainly relies on non-specific metal coordination or physical interception. When faced with complex fine chemical wastewater, the adsorbent will indiscriminately co-adsorb a large number of competing impurities. This not only makes the downstream desorption and separation extremely difficult, but also forces the desorption process to rely on harsh reagents such as strong alkali and high salt. However, under such harsh desorption conditions, high-value target organic matter is prone to irreversible structural degradation, which ultimately seriously reduces the recovery rate of target products and the overall wastewater treatment efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a pretreatment method for 3-cyanopyridine wastewater. By preparing a modified magnetic porous adsorbent with high selective capture capacity and rapid magnetic response solid-liquid separation characteristics for 3-cyanopyridine, and then combining it with a magnetron adsorption-in-situ elution-recycling process system, the highly toxic and high-value 3-cyanopyridine can be efficiently enriched, accurately separated and recovered with high purity in complex industrial wastewater. This method has excellent process stability and extremely high economic and environmental benefits.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A pretreatment method for 3-cyanopyridine wastewater includes the following steps:

[0008] Step 1: Collect 3-cyanopyridine wastewater into a wastewater collection tank, filter it through a multi-media filter, and then send the filtered wastewater into a pH adjustment tank to adjust the pH value to 4-6. Subsequently, add the adjusted wastewater into a magnetic adsorption separation vessel, add a modified magnetic porous adsorbent, and adsorb at 25-35℃ for 2-4 hours. Under the action of a magnetic field, rapid magnetic flocculation and sedimentation are achieved to realize solid-liquid separation. After the concentration of 3-cyanopyridine in the supernatant drops to below 50 mg / L, it is discharged to the subsequent biochemical treatment unit.

[0009] Step 2: Add anhydrous ethanol as eluent to the magnetron adsorption separation vessel, stir at 25-35℃ for 20-40 minutes, turn on the electromagnetic field control device and extract the eluent. The adsorbent in the vessel is rinsed with deionized water and then directly circulated in the vessel for the adsorption process in Step 1. At the same time, the eluent is distilled under reduced pressure to recover 3-cyanopyridine, thus completing the pretreatment of 3-cyanopyridine wastewater.

[0010] Furthermore, the solid-liquid ratio of the adjusted wastewater to the modified magnetic porous adsorbent is 1-5 g / L.

[0011] Furthermore, the solid-liquid ratio of the modified magnetic porous adsorbent to anhydrous ethanol is 1g:10-30mL.

[0012] Furthermore, the preparation process of the modified magnetic porous adsorbent is as follows:

[0013] Carboxyl-containing block polyarylene ether nitrile and N,N-dimethylacetamide were placed in a reaction vessel and stirred at 60-70℃ for 2-4 hours. Graphene composite magnetic particles were added and ultrasonically dispersed at the same temperature for 1-2 hours. The reaction solution was poured into a mold and immersed in deionized water for 46-50 hours. After removal, it was freeze-dried to constant weight to obtain the modified magnetic porous adsorbent.

[0014] Furthermore, the ratio of carboxyl-block polyarylene ether nitrile, N,N-dimethylacetamide and graphene composite magnetic particles is 100-200g: 1-2L: 10-30g.

[0015] Furthermore, the preparation process of graphene composite magnetic particles is as follows:

[0016] Graphene oxide and deionized water were placed in a reaction vessel under a nitrogen atmosphere and ultrasonically dispersed at 25-35℃ for 1-2 hours. Ferric chloride hexahydrate and ferrous sulfate heptahydrate were added, and a 25wt% ammonia solution was added dropwise to adjust the pH of the reaction solution to 10-12. The mixture was stirred at the same temperature for 1-2 hours, magnetically separated, washed, and freeze-dried to constant weight to obtain graphene composite magnetic particles.

[0017] Furthermore, the ratio of graphene oxide, deionized water, ferric chloride hexahydrate, and ferrous sulfate heptahydrate is 6-12g: 1.2-1.5L: 60-100g: 30-50g.

[0018] Furthermore, the preparation process of carboxyl-containing block polyarylene ether nitrile is as follows:

[0019] Fluorine-terminated hydrophilic oligomer solutions and hydroxyl-terminated hydrophobic oligomer solutions were placed in a reaction vessel and stirred at 180-190℃ for 3-5 hours. After cooling to 25-35℃, the reaction solution was added to a mixed solution of deionized water and anhydrous ethanol in a volume ratio of 1:1 to precipitate the product. The product was filtered, and the filter cake was added to a 1 mol / L hydrochloric acid solution. The mixture was stirred at 40-50℃ for 1-2 hours, filtered, washed, and vacuum dried to constant weight to obtain carboxyl-block polyarylene ether nitrile.

[0020] Furthermore, the volume ratio of the fluorine-capped hydrophilic oligomer solution to the hydroxyl-capped hydrophobic oligomer solution is 1:1.

[0021] Furthermore, the preparation process of the hydroxyl-terminated hydrophobic oligomer solution is as follows:

[0022] Bisphenol A, 2,6-difluorobenzonitrile, potassium carbonate, toluene, and N-methylpyrrolidone were placed in a reaction vessel and refluxed at 140-150℃ for 2-4 hours to remove toluene from the system. The mixture was then cooled to room temperature to obtain a hydroxyl-terminated hydrophobic oligomer solution.

[0023] Furthermore, the ratio of bisphenol A, 2,6-difluorobenzonitrile, potassium carbonate, toluene, and N-methylpyrrolidone is 60-70g: 30-40g: 50-60g: 60-80mL: 180-220mL.

[0024] Furthermore, the preparation process of the fluorine-terminated hydrophilic oligomer solution is as follows:

[0025] Bisphenolic acid, 2,6-difluorobenzonitrile, potassium carbonate, toluene, and N-methylpyrrolidone were placed in a reaction vessel and refluxed at 140-150℃ for 2-4 hours to remove toluene from the system. The mixture was then cooled to room temperature to obtain a fluorinated hydrophilic oligomer solution.

[0026] Furthermore, the ratio of bisphenol A, 2,6-difluorobenzonitrile, potassium carbonate, toluene, and N-methylpyrrolidone is 70-80g: 35-45g: 50-60g: 60-80mL: 180-220mL.

[0027] The beneficial effects of this invention are:

[0028] 1. In the pretreatment of 3-cyanopyridine wastewater, this invention uses amphiphilic carboxyl-containing block polyarylene ether nitrile as the adsorbent matrix. The aromatic ring-nitrile structure of the polyarylene ether nitrile constructs a rigid porous framework that is resistant to acids and alkalis and swelling. At the same time, the inherent polar nitrile groups in the polyarylene ether nitrile framework and the carboxyl groups introduced by block copolymerization form a dual synergistic adsorption mechanism. The nitrile groups enrich 3-cyanopyridine molecules through dipole-dipole interactions. The carboxyl groups form strong hydrogen bonds and acid-base pairs with the pre-enriched 3-cyanopyridine molecules, achieving precise anchoring. Under complex water system conditions, this invention enables targeted recognition of 3-cyanopyridine, significantly reduces co-adsorption of impurities, and greatly improves the adsorption selectivity and saturation adsorption capacity of 3-cyanopyridine, laying a core foundation for subsequent high-purity resource recovery.

[0029] 2. In the pretreatment of 3-cyanopyridine wastewater, this invention uses graphene composite magnetic particles as a functional modifying component, achieving synergistic optimization of adsorption and magnetic separation performance. Through the large specific surface area of ​​graphene oxide sheets and the coordination and anchoring effect of oxygen-containing groups on the surface, highly dispersed loading of magnetic nanoparticles is achieved, providing stable magnetic response performance for the adsorbent. Simultaneously, the polar nitrile groups of polyarylene ether nitrile can form dipole-hydrogen bond interactions with the oxygen-containing groups on the graphene oxide surface, significantly improving the interfacial compatibility between the composite magnetic particles and the polymer matrix, preventing magnetic particle aggregation and detachment, and ensuring the stability of the magnetic response performance and adsorption capacity of the adsorbent during recycling. This provides reliable support for long-term continuous wastewater pretreatment.

[0030] 3. In the pretreatment of 3-cyanopyridine wastewater, this invention utilizes a porous framework constructed from carboxyl-block polyarylene ether nitrile to provide a low-resistance, rapid mass transfer channel for the 3-cyanopyridine target molecule. This allows the dual-targeting active sites enriched on the pore surface, consisting of nitrile and carboxyl groups, to fully contact the target molecule, significantly improving adsorption efficiency. This provides the core kinetic basis for the efficient adsorption treatment of the entire process under ambient temperature and pressure. Simultaneously, the graphene composite magnetic particles in the matrix endow the adsorbent with strong and stable magnetic response properties, enabling precise and rapid solid-liquid separation through an external electromagnetic field control device. This reduces material loss and loss of active sites, allowing the adsorbent to maintain stable adsorption performance and resource recovery rate during long-term continuous operation. This simultaneously achieves wastewater detoxification and compliant pretreatment, as well as the economical recovery of high-value 3-cyanopyridine. Detailed Implementation

[0031] 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.

[0032] Example 1: This example provides a modified magnetic porous adsorbent for the pretreatment of 3-cyanopyridine wastewater, prepared through the following steps:

[0033] S1: Place 70g of bisphenol acid, 35g of 2,6-difluorobenzonitrile, 50g of potassium carbonate, 60mL of toluene and 180mL of N-methylpyrrolidone in a reaction vessel, stir at 200r / min at 140℃ and dehydrate and reflux for 2h. After the reaction is completed, heat up to remove the toluene in the system and cool to room temperature to obtain a fluorinated hydrophilic oligomer solution.

[0034] S2: 60g bisphenol A, 30g 2,6-difluorobenzonitrile, 50g potassium carbonate, 60mL toluene and 180mL N-methylpyrrolidone were placed in a reaction vessel and stirred at 200r / min at 140℃ for 2h under dehydration and reflux. After the reaction was completed, the toluene in the system was removed by heating and then cooled to room temperature to obtain a hydroxyl-terminated hydrophobic oligomer solution.

[0035] S3: Fluorine-terminated hydrophilic oligomer solution and hydroxyl-terminated hydrophobic oligomer solution were placed in a reaction vessel at a volume ratio of 1:1 and stirred at 200 r / min for 3 h at 180 °C. After the reaction was completed, the mixture was cooled to 25 °C. The reaction solution was added to a mixed solution of deionized water and anhydrous ethanol at a volume ratio of 1:1 to precipitate the product. The product was filtered, and the filter cake was added to a 1 mol / L hydrochloric acid solution. The mixture was stirred at 40 °C for 1 h and then filtered. The filter cake was washed with deionized water until the last washing solution was neutral. The product was then vacuum dried at 60 °C to constant weight to obtain carboxyl-block polyarylene ether nitrile.

[0036] S4: 6g of graphene oxide and deionized water were placed in a reaction vessel under a nitrogen atmosphere and ultrasonically dispersed at 25°C for 1h. 60g of ferric chloride hexahydrate and 30g of ferrous sulfate heptahydrate were added, and a 25wt% ammonia solution was added dropwise to adjust the pH of the reaction solution to 10. The mixture was stirred at 200r / min for 1h at the same temperature. After the reaction was completed, the mixture was magnetically separated, and the product was washed twice with deionized water and freeze-dried to constant weight to obtain graphene composite magnetic particles.

[0037] S5: Place 100g of carboxyl-containing block polyarylene ether nitrile and 1L of N,N-dimethylacetamide in a reaction vessel and stir at 400-600r / min for 2h at 60℃. Add 10g of graphene composite magnetic particles and ultrasonically disperse at the same temperature for 1h. After the reaction is completed, pour the reaction solution into a mold and immerse it in deionized water for 46h. Remove it and freeze-dry it to constant weight to obtain the modified magnetic porous adsorbent.

[0038] Example 2: This example provides a modified magnetic porous adsorbent for the pretreatment of 3-cyanopyridine wastewater, prepared through the following steps:

[0039] S1: 75g of bisphenol acid, 40g of 2,6-difluorobenzonitrile, 55g of potassium carbonate, 70mL of toluene and 200mL of N-methylpyrrolidone were placed in a reaction vessel and stirred at 250r / min at 145℃ for 3h under dehydration and reflux. After the reaction was completed, the toluene in the system was removed by heating and then cooled to room temperature to obtain a fluorinated hydrophilic oligomer solution.

[0040] S2: Place 65g bisphenol A, 35g 2,6-difluorobenzonitrile, 50-60g potassium carbonate, 60-80mL toluene and 180-220mL N-methylpyrrolidone in a reaction vessel, stir and dehydrate under reflux at 200-300r / min at 140-150℃ for 2-4h. After the reaction is completed, heat up to remove the toluene from the system, cool to room temperature, and obtain a hydroxyl-terminated hydrophobic oligomer solution.

[0041] S3: Fluorine-terminated hydrophilic oligomer solution and hydroxyl-terminated hydrophobic oligomer solution were placed in a reaction vessel at a volume ratio of 1:1 and stirred at 250 r / min for 4 h at 185 °C. After the reaction was completed, the mixture was cooled to 30 °C. The reaction solution was added to a mixed solution of deionized water and anhydrous ethanol at a volume ratio of 1:1 to precipitate the product. The product was filtered, and the filter cake was added to a 1 mol / L hydrochloric acid solution. The mixture was stirred at 45 °C for 1.5 h and then filtered. The filter cake was washed with deionized water until the final washing solution was neutral. The product was then vacuum dried at 70 °C to constant weight to obtain carboxyl-block polyarylene ether nitrile.

[0042] S4: 9g of graphene oxide and deionized water were placed in a reaction vessel under a nitrogen atmosphere and ultrasonically dispersed at 30℃ for 1.5h. 80g of ferric chloride hexahydrate and 40g of ferrous sulfate heptahydrate were added, and a 25wt% ammonia solution was added dropwise to adjust the pH of the reaction solution to 11. The mixture was stirred at 250r / min for 1.5h at the same temperature. After the reaction was completed, the mixture was magnetically separated, and the product was washed three times with deionized water and freeze-dried to constant weight to obtain graphene composite magnetic particles.

[0043] S5: 150g of carboxyl-containing block polyarylene ether nitrile and 1.5L of N,N-dimethylacetamide were placed in a reaction vessel and stirred at 500r / min for 3h at 65℃. 20g of graphene composite magnetic particles were added and ultrasonically dispersed at the same temperature for 1.5h. After the reaction was completed, the reaction solution was poured into a mold and immersed in deionized water for 48h. After removal, it was freeze-dried to constant weight to obtain the modified magnetic porous adsorbent.

[0044] Example 3: This example provides a modified magnetic porous adsorbent for the pretreatment of 3-cyanopyridine wastewater, prepared through the following steps:

[0045] S1: Place 80g of bisphenol acid, 45g of 2,6-difluorobenzonitrile, 60g of potassium carbonate, 80mL of toluene and 220mL of N-methylpyrrolidone in a reaction vessel, stir at 300r / min at 150℃ and dehydrate and reflux for 4h. After the reaction is completed, heat up to remove the toluene in the system and cool to room temperature to obtain a fluorinated hydrophilic oligomer solution.

[0046] S2: 70g bisphenol A, 40g 2,6-difluorobenzonitrile, 60g potassium carbonate, 80mL toluene and 220mL N-methylpyrrolidone were placed in a reaction vessel and stirred at 300r / min at 150℃ for 4h under dehydration and reflux. After the reaction was completed, the toluene in the system was removed by heating and then cooled to room temperature to obtain a hydroxyl-terminated hydrophobic oligomer solution.

[0047] S3: Fluorine-terminated hydrophilic oligomer solution and hydroxyl-terminated hydrophobic oligomer solution were placed in a reaction vessel at a volume ratio of 1:1 and stirred at 300 r / min for 5 h at 190 °C. After the reaction was completed, the mixture was cooled to 35 °C. The reaction solution was added to a mixed solution of deionized water and anhydrous ethanol at a volume ratio of 1:1 to precipitate the product. The product was filtered, and the filter cake was added to a 1 mol / L hydrochloric acid solution. The mixture was stirred at 50 °C for 2 h and then filtered. The filter cake was washed with deionized water until the last washing solution was neutral. The product was then vacuum dried at 60-80 °C to constant weight to obtain carboxyl-block polyarylene ether nitrile.

[0048] S4: 12g of graphene oxide and deionized water were placed in a reaction vessel under a nitrogen atmosphere and ultrasonically dispersed at 35°C for 2h. 100g of ferric chloride hexahydrate and 50g of ferrous sulfate heptahydrate were added, and a 25wt% ammonia solution was added dropwise to adjust the pH of the reaction solution to 12. The mixture was stirred at 300r / min for 2h at the same temperature. After the reaction was completed, the mixture was magnetically separated, and the product was washed four times with deionized water and freeze-dried to constant weight to obtain graphene composite magnetic particles.

[0049] S5: 200g of carboxyl-containing block polyarylene ether nitrile and 2L of N,N-dimethylacetamide were placed in a reaction vessel and stirred at 600r / min at 70℃ for 4h. 30g of graphene composite magnetic particles were added and ultrasonically dispersed at the same temperature for 2h. After the reaction was completed, the reaction solution was poured into a mold and soaked in deionized water for 50h. After removal, it was freeze-dried to constant weight to obtain the modified magnetic porous adsorbent.

[0050] The modified magnetic porous adsorbents prepared in Examples 1-3 above were first used to prepare two functional oligomers via aromatic nucleophilic substitution polycondensation: Bisphenolic acid and 2,6-difluorobenzonitrile were used as monomers, and potassium carbonate was used as a salt-forming catalyst. The phenolic hydroxyl groups of bisphenolic acid were activated to generate phenoxy anions, which underwent nucleophilic substitution polycondensation with the ortho-activated fluorine atoms of the cyano group on 2,6-difluorobenzonitrile. Fluorine-terminated hydrophilic oligomer solutions were obtained by controlling the monomer ratio. Bisphenol A and 2,6-difluorobenzonitrile were used as monomers, and the same process was carried out... Nucleophilic substitution condensation polymerization yields a hydroxyl-terminated hydrophobic oligomer solution through monomer ratio control. The two oligomers are then mixed, and a block copolymerization nucleophilic substitution reaction is performed to covalently bond the active fluorine atoms at the end groups of the hydrophilic oligomers with the phenolic anions at the end groups of the hydrophobic oligomers, constructing an amphiphilic block polyarylene ether nitrile framework. Acidification treatment reduces the carboxyl groups of the salt to free carboxyl groups, yielding a carboxyl-containing block polyarylene ether nitrile. Simultaneously, an alkaline in-situ coprecipitation reaction is used to anchor Fe through the coordination of oxygen-containing groups on the graphene oxide surface. 2+ with Fe 3+ In a strongly alkaline system, Fe3O4 magnetic nanoparticles with strong magnetic responsiveness are grown in situ on graphene oxide through hydrolysis and co-precipitation, resulting in graphene composite magnetic particles. Finally, using a solvent-inducible phase inversion method with N,N-dimethylacetamide as a good solvent, a homogeneous casting solution of carboxyl-block polyarylene ether nitrile and graphene composite magnetic particles is immersed in deionized water (a non-solvent), undergoing a solvent / non-solvent exchange process. The good solvent rapidly diffuses from the polymer phase to the aqueous phase, while water molecules permeate into the polymer solution, causing a sharp decrease in the solubility of polymer segments and resulting in solidification and precipitation. This ultimately forms a material with a large number of interconnected microporous structures, yielding a modified magnetic porous adsorbent.

[0051] Example 4: This example provides a pretreatment method for 3-cyanopyridine wastewater, including the following steps:

[0052] Step 1: Collect 3-cyanopyridine wastewater into a wastewater collection tank and pass it through a multi-media filter to intercept and remove large particulate suspended solids and colloidal impurities. Then, send the filtered wastewater into a pH adjustment tank to adjust the pH value of the wastewater to 4. Subsequently, add the adjusted wastewater into a magnetically controlled adsorption separation vessel and add the modified magnetic porous adsorbent prepared in Example 1 at a solid-liquid ratio of 1 g / L. Stir and adsorb at 100 r / min for 2 h at 25 °C. After adsorption saturation, stop stirring and turn on the external electromagnetic field control device. Under the action of the magnetic field, rapid magnetic flocculation and sedimentation for 1 min is achieved to realize solid-liquid separation. After the concentration of 3-cyanopyridine in the supernatant drops to below 50 mg / L, it is discharged to the subsequent biochemical treatment unit.

[0053] Step 2: Add anhydrous ethanol (desorbent) to the magnetically controlled adsorption separation vessel. The solid-liquid ratio of the modified magnetic porous adsorbent to anhydrous ethanol is 1:10. Elute at 150 r / min for 20 min at 25℃. After elution, turn on the electromagnetic field control device again and extract the eluent. The adsorbent remaining in the vessel is rinsed in situ with deionized water and then directly circulated in the vessel for the adsorption process in Step 1. At the same time, the extracted eluent is sent to a vacuum distillation device to remove and recover alcohol solvents and recover 3-cyanopyridine, thus completing the pretreatment of 3-cyanopyridine wastewater.

[0054] Example 5: This example provides a pretreatment method for 3-cyanopyridine wastewater, comprising the following steps:

[0055] Step 1: Collect 3-cyanopyridine wastewater into a wastewater collection tank and pass it through a multi-media filter to intercept and remove large particulate suspended solids and colloidal impurities. Then, send the filtered wastewater into a pH adjustment tank to adjust the pH value of the wastewater to 5. Subsequently, add the adjusted wastewater into a magnetic control adsorption separation vessel and add the modified magnetic porous adsorbent prepared in Example 2 at a solid-liquid ratio of 3 g / L. Stir and adsorb at 125 r / min for 3 h at 30 °C. Under the action of a magnetic field, achieve solid-liquid separation by rapid magnetic flocculation sedimentation for 2 min. After the concentration of 3-cyanopyridine in the supernatant drops to below 50 mg / L, it is discharged to the subsequent biochemical treatment unit.

[0056] Step 2: Add anhydrous ethanol (desorbent) to the magnetically controlled adsorption separation vessel. The solid-liquid ratio of the modified magnetic porous adsorbent to anhydrous ethanol is 1:20. Stir and elute at 175 r / min for 30 min at 30℃. After elution, turn on the electromagnetic field control device again and extract the eluent. The adsorbent remaining in the vessel is rinsed in situ with deionized water and then directly circulated in the vessel for the adsorption process in Step 1. At the same time, the extracted eluent is sent to a vacuum distillation device to remove and recover alcohol solvents and recover 3-cyanopyridine, thus completing the pretreatment of 3-cyanopyridine wastewater.

[0057] Example 6: This example provides a pretreatment method for 3-cyanopyridine wastewater, including the following steps:

[0058] Step 1: Collect 3-cyanopyridine wastewater into a wastewater collection tank and pass it through a multi-media filter to intercept and remove large particulate suspended solids and colloidal impurities. Then, send the filtered wastewater into a pH adjustment tank to adjust the pH value to 6. Subsequently, add the adjusted wastewater into a magnetically controlled adsorption separation vessel and add the modified magnetic porous adsorbent prepared in Example 3 at a solid-liquid ratio of 5 g / L. Stir and adsorb at 150 r / min for 4 h at 35 °C. After adsorption saturation, stop stirring and turn on the external electromagnetic field control device. Under the action of the magnetic field, rapid magnetic flocculation and sedimentation for 3 min is achieved to realize solid-liquid separation. After the concentration of 3-cyanopyridine in the supernatant drops to below 50 mg / L, it is discharged to the subsequent biochemical treatment unit.

[0059] Step 2: Add anhydrous ethanol (desorbent) to the magnetically controlled adsorption separation vessel. The solid-liquid ratio of the modified magnetic porous adsorbent to anhydrous ethanol is 1:30. Stir and elute at 200 r / min for 40 min at 35℃. After elution, turn on the electromagnetic field control device again and extract the eluent. The adsorbent remaining in the vessel is rinsed in situ with deionized water and then directly circulated in the vessel for the adsorption process in Step 1. At the same time, the extracted eluent is sent to a vacuum distillation device to remove and recover alcohol solvents and recover 3-cyanopyridine, thus completing the pretreatment of 3-cyanopyridine wastewater.

[0060] Comparative Example 1: The difference from Example 2 is that in step S5, commercially available polyarylene ether nitrile is used instead of the carboxyl-containing block polyarylene ether nitrile prepared in step S3, while the other steps remain unchanged, to prepare a modified magnetic porous adsorbent.

[0061] Comparative Example 2: The difference from Example 2 is that the graphene oxide in step S4 is removed, while the other steps remain unchanged, and a modified magnetic porous adsorbent is prepared.

[0062] Comparative Example 3: The difference from Example 2 is that the graphene composite magnetic particles prepared in step S4 are removed in step S5, while the other steps remain unchanged, and a modified magnetic porous adsorbent is prepared.

[0063] The graphene oxide purchased in the above examples and comparative examples was produced by Shanghai Aladdin Biochemical Technology Co., Ltd., with a sheet diameter of 1-5 μm; the commercially available polyaryletheronitrile was produced by Shandong Taihe Technology Co., Ltd., with an average molecular weight of 80,000 Da.

[0064] The modified magnetic porous adsorbents prepared in Examples 1-3 and Comparative Examples 1-3 were used for the pretreatment of simulated 3-cyanopyridine wastewater, and their treatment performance was evaluated. The test results are shown in Table 1.

[0065] Experimental preparation: A commonly used laboratory magnetic adsorption separation simulation device was used to simulate the pretreatment of 3-cyanopyridine wastewater. Simulated 3-cyanopyridine industrial wastewater was prepared with the following components and concentrations: 1000 mg / L 3-cyanopyridine, 500 mg / L 3-methylpyridine, and 500 mg / L nicotinamide. The pH value was adjusted to 5.0 for later use.

[0066] Adsorption treatment and recovery performance test: Referring to the wastewater pretreatment process in Example 2, 1L of prepared simulated 3-cyanopyridine industrial wastewater was taken, and 3g of modified magnetic porous adsorbent was added at a solid-liquid ratio of 3g / L. After adsorption, the supernatant sample was taken, and the concentration of 3-cyanopyridine in the supernatant was determined by liquid chromatography. The removal rate of 3-cyanopyridine was calculated as follows: Removal rate (%) = [(C0-C1) / C0]×100%, where C0 is the initial concentration of 3-cyanopyridine in the simulated wastewater (mg / L), and C1 is the concentration of 3-cyanopyridine in the supernatant (mg / L). The lower the concentration, the better the adsorption effect of the adsorbent.

[0067] To verify the recovery effect of the adsorbent on 3-cyanopyridine, after separating the supernatant, 60 mL of anhydrous ethanol was added to the container as a desorbent according to a solid-liquid ratio of 1:20 for the modified magnetic porous adsorbent and anhydrous ethanol. The eluent sample was collected, and the concentration of 3-cyanopyridine was measured again. The recovery rate of 3-cyanopyridine was calculated as follows: recovery rate (%) = (C2×V2) / (C0×V0)×100%, where C2 is the concentration of 3-cyanopyridine in the recovered solution (mg / L), V2 is the volume of the recovered solution (L), C0 is the initial concentration of 3-cyanopyridine in the simulated wastewater (mg / L), and V0 is the volume of the simulated wastewater treated (1L). A higher recovery rate indicates a better recovery effect of the adsorbent on 3-cyanopyridine.

[0068] Table 1 Adsorption and Recovery Performance Test Table

[0069] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Concentration of 3-cyanopyridine in the supernatant (mg / L) 38 12 25 320 105 22 3-Cyanopyridine removal rate (%) 96.2 98.8 97.5 68.0 89.5 97.8 Concentration of 3-cyanopyridine in the eluent (mg / L) 15030 15640 15130 6230 13610 12715 3-Cyanopyridine recovery rate (%) 90.2 93.8 90.8 37.4 81.7 78.0

[0070] As shown in Table 1, the modified magnetic porous adsorbents prepared in Examples 1-3 above exhibit better adsorption and recovery rates for 3-cyanopyridine than the comparative examples. This indicates that the modified magnetic porous adsorbents prepared in this invention achieve highly selective and precise adsorption of 3-cyanopyridine through a dual-target adsorption site of nitrile-carboxyl groups constructed from carboxyl-block polyarylene ether nitrile. Simultaneously, with the synergistic effect of graphene composite magnetic particles, excellent magnetic response separation performance is also achieved, stably fulfilling the dual requirements of wastewater detoxification pretreatment and high-value recovery of target substances.

[0071] The adsorbent prepared in Comparative Example 1 showed a significant decrease in both adsorption rate and recovery rate for 3-cyanopyridine. This may be because the polymer backbone of commercially available polyarylether nitrile does not contain free carboxyl sites that can form a strong specific interaction with 3-cyanopyridine, thus failing to form a dual synergistic adsorption mechanism of nitrile and carboxyl groups. In complex wastewater systems containing multiple coexisting impurities, severe competitive adsorption may easily occur, leading to a significant decrease in adsorption capacity and selectivity for the target analyte, resulting in poor wastewater treatment effect and resource recovery capacity.

[0072] The recovery rate of 3-cyanopyridine by the adsorbent prepared in Comparative Example 2 decreased significantly. This may be because the adsorbent prepared in Comparative Example 2 removed the graphene oxide component, which could not achieve a high dispersion loading of magnetic nanoparticles, leading to the aggregation of magnetic particles. This not only reduced the specific surface area and the number of effective adsorption sites of the material, but also weakened the magnetic response performance of the material, resulting in a decrease in the adsorbent's ability to recover 3-cyanopyridine.

[0073] The adsorbent prepared in Comparative Example 3 showed a high adsorption and removal rate of 3-cyanopyridine, but the recovery rate decreased significantly. This may be because the adsorbent prepared in Comparative Example 32 removed the graphene composite magnetic particles, resulting in an adsorbent without magnetic response performance. It could not achieve rapid in-situ solid-liquid separation through a magnetic field, and the adsorbent was prone to loss during the separation process. The 3-cyanopyridine on the adsorbent was also lost, leading to a significant decrease in the resource recovery rate.

[0074] 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.

Claims

1. A pretreatment method for 3-cyanopyridine wastewater, characterized in that, Includes the following steps: Step 1: Collect 3-cyanopyridine wastewater into a wastewater collection tank, filter it through a multi-media filter, and send the filtered wastewater into a pH adjustment tank to adjust the pH value of the wastewater to 4-6. Then, add the pH-adjusted wastewater into a magnetic adsorption separation vessel, add a modified magnetic porous adsorbent, and adsorb at 25-35℃ for 2-4 hours. Under the action of a magnetic field, rapid magnetic flocculation and sedimentation are achieved to realize solid-liquid separation. After the concentration of 3-cyanopyridine in the supernatant drops to below 50 mg / L, it is discharged to the subsequent biochemical treatment unit. Step 2: Add anhydrous ethanol as eluent to the magnetron adsorption separation vessel, stir at 25-35℃ for 20-40 minutes, turn on the electromagnetic field control device and extract the eluent. The adsorbent in the vessel is rinsed with deionized water and then directly circulated in the vessel for the adsorption process in Step 1. At the same time, the eluent is distilled under reduced pressure to recover 3-cyanopyridine, thus completing the pretreatment of 3-cyanopyridine wastewater.

2. The pretreatment method for 3-cyanopyridine wastewater according to claim 1, characterized in that, The modified magnetic porous adsorbent described in step one is prepared through the following steps: Carboxyl-containing block polyarylene ether nitrile and N,N-dimethylacetamide were placed in a reaction vessel and stirred at 60-70℃ for 2-4 hours. Graphene composite magnetic particles were added and ultrasonically dispersed at the same temperature for 1-2 hours. The reaction solution was poured into a mold and immersed in deionized water for 46-50 hours. After removal, it was freeze-dried to constant weight to obtain the modified magnetic porous adsorbent.

3. The pretreatment method for 3-cyanopyridine wastewater according to claim 2, characterized in that, The ratio of the carboxyl-containing block polyarylene ether nitrile, N,N-dimethylacetamide and graphene composite magnetic particles is 100-200g: 1-2L: 10-30g.

4. The pretreatment method for 3-cyanopyridine wastewater according to claim 3, characterized in that, The graphene composite magnetic particles are prepared through the following steps: Graphene oxide and deionized water were placed in a reaction vessel under a nitrogen atmosphere and ultrasonically dispersed at 25-35℃ for 1-2 hours. Ferric chloride hexahydrate and ferrous sulfate heptahydrate were added, and a 25wt% ammonia solution was added dropwise to adjust the pH of the reaction solution to 10-12. The mixture was stirred at the same temperature for 1-2 hours, magnetically separated, washed, and freeze-dried to constant weight to obtain graphene composite magnetic particles.

5. The pretreatment method for 3-cyanopyridine wastewater according to claim 4, characterized in that, The ratio of the amount of graphene oxide, deionized water, ferric chloride hexahydrate and ferrous sulfate heptahydrate is 6-12g: 1.2-1.5L: 60-100g: 30-50g.

6. The pretreatment method for 3-cyanopyridine wastewater according to claim 2, characterized in that, The carboxyl-containing block polyarylene ether nitrile is prepared by the following steps: Fluorine-terminated hydrophilic oligomer solutions and hydroxyl-terminated hydrophobic oligomer solutions were placed in a reaction vessel and stirred at 180-190℃ for 3-5 hours. After cooling to 25-35℃, the reaction solution was added to a mixed solution of deionized water and anhydrous ethanol at a volume ratio of 1:1 to precipitate the product. The product was filtered, and the filter cake was added to a 1 mol / L hydrochloric acid solution. The mixture was stirred at 40-50℃ for 1-2 hours, filtered, washed, and vacuum dried to constant weight to obtain carboxyl-block polyarylene ether nitrile. The volume ratio of the fluorine-capped hydrophilic oligomer solution to the hydroxyl-capped hydrophobic oligomer solution is 1:

1.

7. The pretreatment method for 3-cyanopyridine wastewater according to claim 6, characterized in that, The preparation process of the hydroxyl-terminated hydrophobic oligomer solution is as follows: Bisphenol A, 2,6-difluorobenzonitrile, potassium carbonate, toluene and N-methylpyrrolidone were placed in a reaction vessel and dehydrated and refluxed at 140-150℃ for 2-4 hours. The toluene in the system was removed by heating and then cooled to room temperature to obtain a hydroxyl-terminated hydrophobic oligomer solution. The ratio of bisphenol A, 2,6-difluorobenzonitrile, potassium carbonate, toluene and N-methylpyrrolidone is 60-70g: 30-40g: 50-60g: 60-80mL: 180-220mL.

8. The pretreatment method for 3-cyanopyridine wastewater according to claim 6, characterized in that, The preparation process of the fluorine-terminated hydrophilic oligomer solution is as follows: Bisphenolic acid, 2,6-difluorobenzonitrile, potassium carbonate, toluene and N-methylpyrrolidone were placed in a reaction vessel and dehydrated and refluxed at 140-150℃ for 2-4 hours. The toluene in the system was removed by heating and then cooled to room temperature to obtain a fluorinated hydrophilic oligomer solution. The ratio of bisphenol acid, 2,6-difluorobenzonitrile, potassium carbonate, toluene and N-methylpyrrolidone is 70-80g: 35-45g: 50-60g: 60-80mL: 180-220mL.

9. The pretreatment method for 3-cyanopyridine wastewater according to claim 1, characterized in that, The solid-liquid ratio of the pH-adjusted wastewater to the modified magnetic porous adsorbent in step one is 1L:1-5g.

10. The pretreatment method for 3-cyanopyridine wastewater according to claim 1, characterized in that, In step two, the solid-liquid ratio of the modified magnetic porous adsorbent and anhydrous ethanol is 1g:10-30mL.