Membrane extraction method and membrane extraction contactor device for efficiently treating acrylonitrile wastewater

Abstract

The invention provides a membrane extraction method for efficiently treating acrylonitrile wastewater and a membrane extraction contactor device, which are particularly suitable for removing acrylonitrile in the acrylonitrile wastewater and recycling the acrylonitrile, and belongs to the technical field of membrane extraction. According to the method disclosed by the invention, a two-phase non-contact mass transfer interface is constructed through a microporous hydrophobic membrane, so that a material liquid phase and an extracting agent flow independently; and the extracted organic phase enters a back extraction contact unit, so that extraction and back extraction are synchronously carried out to maintain a transmembrane concentration gradient and avoid saturation of the extraction agent. According to the device, the extraction contact unit and the back-extraction contact unit which are symmetrically arranged are adopted to form a circulating system, and continuous extraction and recovery of acrylonitrile can be achieved. The extraction-back extraction system adopted by the method can keep high mass transfer flux, extraction balance can be rapidly achieved, the extraction rate is higher than 92.5%, the bottleneck that the extraction performance is reduced due to extraction agent saturation in the solvent extraction process is broken through, and the method is suitable for efficient treatment of high-concentration acrylonitrile wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of membrane extraction technology, in particular to a membrane extraction method and a membrane extraction contactor device for efficiently treating acrylonitrile wastewater, which are particularly suitable for removing acrylonitrile from acrylonitrile wastewater and realizing acrylonitrile recovery. BACKGROUND

[0002] Acrylonitrile (AN) is a colorless transparent liquid with a bitter almond odor, which is a highly toxic organic compound with acute toxicity, chronic toxicity, carcinogenicity, reproductive toxicity, and teratogenicity. Acrylonitrile belongs to volatile organic compounds (VOCs), which has a low boiling point (77.3℃) and is easy to volatilize into the atmosphere, causing long-term harm to human health and the ecosystem through food chain enrichment. In China, about 1.5 tons of acrylonitrile-containing wastewater are generated per ton of acrylonitrile produced in the production and downstream processing of acrylonitrile. The sources of acrylonitrile wastewater include ammonia oxidation reaction device discharge water, separation and purification water washing waste liquid, equipment cleaning water, and residual wastewater of unreacted monomers in processes such as acrylic fiber polymerization and ABS resin synthesis. Such wastewater is classified as a typical refractory organic wastewater due to its high toxicity, poor biodegradability, poor biodegradability, and complex composition. The “Integrated Wastewater Discharge Standard (GB 8987-1996)” of China sets strict limits on acrylonitrile discharge, with a first-level discharge limit of 2 mg·L -1 and a drinking water limit of 0.1 mg·L -1 .

[0003] For the treatment of acrylonitrile wastewater, a diversified technology system has been formed at home and abroad, mainly covering physical, chemical, and biological methods. The incineration method for treating acrylonitrile wastewater has the advantages of complete treatment, strong adaptability, etc., but also has the limitations of poor energy economy, risk of secondary pollution, large equipment investment, etc. The four-effect evaporation method has the advantages of high efficiency, energy saving, and resource recovery in acrylonitrile wastewater treatment, but still has some significant disadvantages in practical application. The corrosion resistance of equipment materials is extremely high under high temperature environment, and the cost of commonly used materials such as titanium alloy or hastelloy is high, increasing the difficulty and cost of maintenance. Fenton oxidation method as a kind of efficient and mature wastewater treatment technology has the advantages of mild reaction conditions, simple operation, significant degradation effect on refractory organic matter, etc. However, this technology still has limitations in practical application: a large amount of H2O2 and Fe 2+ reagents need to be added and the addition ratio needs to be precisely controlled, which increases the treatment cost; on the other hand, the generated iron sludge (containing Fe 3+ precipitate and undegraded organic matter) not only increases the cost of solid waste disposal, but also may cause secondary pollution, which needs to be treated by subsequent processes.

[0004] Membrane extraction (also known as supported liquid membrane extraction) is a new separation technology combining membrane separation and liquid-liquid extraction. One phase of liquid wets the membrane pores by capillary action, and the other phase of liquid cannot wet the membrane pores, forming a stable liquid-membrane interface in the non-wetting side of the membrane pores. Under the control of transmembrane pressure, solutes diffuse across the interface driven by chemical potential difference, realizing non-dispersive mass transfer between the two phases. Membrane extraction has the characteristics of high mass transfer efficiency, controllable interface, independent flow of two-phase fluids, and suitability for high-viscosity or easily emulsified systems. In recent years, membrane extraction contactors have been gradually used for the separation of high-value components and the pretreatment of highly toxic wastewater. However, the existing membrane extraction technology still has the following common problems: the membrane pores are easily wetted by the water phase or impurities, leading to interface instability; the risk of membrane fouling increases under high concentration or complex systems; the extractant is easily saturated during mass transfer, leading to a decrease in mass transfer flux; extraction and back-extraction are usually carried out in steps, the process is long and energy-consuming, and it is difficult to realize continuous operation and industrial scaling. Therefore, the existing membrane extraction process still has engineering limitations such as insufficient stability, decreased mass transfer driving force, and high operating cost in treating high-concentration and difficult-to-degrade acrylonitrile wastewater.

[0005] Therefore, how to realize efficient mass transfer under the premise of ensuring interface stability, avoid efficiency decline caused by extractant saturation, and make the extraction process have the ability of continuous operation and industrial scaling, has become a technical problem to be solved in the field of deep treatment and resource utilization of acrylonitrile wastewater. SUMMARY

[0006] According to the above technical problems, a membrane extraction method and a membrane extraction contactor device for efficiently treating acrylonitrile wastewater are provided, which uses a polytetrafluoroethylene (PTFE) microporous hydrophobic membrane to construct an efficient mass transfer interface between the two phases of the membrane extraction contactor, realizes simultaneous membrane extraction and back-extraction, and is used for efficient treatment and resource recovery of acrylonitrile wastewater.

[0007] The present application mainly uses a microporous hydrophobic membrane as a non-contact mass transfer interface of a membrane extraction contactor, realizes non-dispersive contact of a feed liquid phase and an extractant through physical isolation, and components are transferred across the membrane only by molecular diffusion. The membrane extraction contactor takes advantage of the porous membrane to provide a large specific surface area, significantly improving the mass transfer efficiency, and the two-phase fluids are separated and can be operated independently, suitable for high-viscosity or easily emulsified systems. By coupling the design of the membrane extraction contactor, simultaneous extraction and back-extraction operation is realized, the extractant is connected to the extraction unit and the back-extraction unit in the circulating flow, the solute in the extractant is removed in time, the concentration gradient between the feed liquid phase and the extractant is maintained, and the mass transfer efficiency is significantly improved. The membrane extraction contactor avoids the problems of phase dispersion and entrainment in traditional extraction processes, has the characteristics of low energy consumption and resistance to complex system interference, supports extractant regeneration and continuous operation, and is suitable for deep removal of acrylonitrile and other difficult-to-degrade pollutants in industrial wastewater. The present application provides a solution for efficient and green separation.

[0008] The technical means employed in this invention are as follows: A membrane extraction method for efficiently treating acrylonitrile wastewater includes: By using a microporous hydrophobic membrane as a two-phase non-contact mass transfer interface, the feed liquid phase and the extractant flow independently on both sides of the membrane; solvent entrainment caused by phase dispersion is eliminated, and organic solvent loss is greatly reduced.

[0009] Adjusting the transmembrane pressure difference to make the pressure of the feed liquid phase higher than that of the extractant creates a stable membrane interface at the microporous hydrophobic membrane pores, allowing acrylonitrile to diffuse from the feed liquid phase to the extractant. The acrylonitrile-containing organic phase obtained from the extractant is transported to the back-extraction contact unit in another membrane extraction contactor, so that it comes into contact with the back-extraction agent, thereby achieving simultaneous extraction and back-extraction. The extractant circulates between the extraction and back-extraction contact units, thus overcoming the limitations of the extractant's physical properties and eliminating the need for gravity sedimentation to achieve phase separation. The integrated design of the membrane modules enables simultaneous extraction and back-extraction operations to maintain the transmembrane concentration gradient, thereby improving the treatment efficiency of acrylonitrile wastewater.

[0010] Furthermore, both the extraction contact unit and the back-extraction contact unit include a feed liquid phase chamber, a microporous hydrophobic membrane, and an extraction chamber or a back-extraction chamber arranged sequentially, and the extractant circulates between the extraction chamber of the extraction contact unit and the feed liquid phase chamber of the back-extraction contact unit.

[0011] Furthermore, the microporous hydrophobic membrane is a PTFE membrane, which serves as a two-phase contact barrier for the membrane extraction contactor. It has a pore size of 0.1-0.9 μm, a porosity of 50-85%, a water contact angle greater than 120°, and a contact angle with the extractant less than 50°. The extractant spontaneously wets and fills the membrane pore structure.

[0012] Further, the extractant is at least one selected from diisobutylmethanol, tributyl phosphate, tetrabutylurea, trioctyl phosphate, mesitylene, n-octanol, n-heptane, or diisooctyl phosphate.

[0013] Further, the back-extraction agent is at least one of diethylenetriaminepentaacetic acid, sodium thiocyanate, sodium citrate, sodium oxalate, or sodium acetate.

[0014] Furthermore, the operating conditions for the extraction and back-extraction processes are: the acrylonitrile concentration in the feed liquid phase is 500-6000 mg·L⁻¹. -1 The volume of acrylonitrile wastewater and extractant is 0.05-0.5 L; the flow rate of acrylonitrile wastewater and extractant is 0.02-1 L / min. -1 The extraction temperature was 15-30 ℃; the transmembrane pressure difference was 0.01-0.2 MPa; the amount of back-extraction agent was 0.1-1 L, and the back-extraction agent flow rate was 0.02-1 L·min.-1 .

[0015] The present invention also provides a membrane extraction contactor device for efficiently treating acrylonitrile wastewater, comprising: An extraction contact unit includes a feed liquid phase chamber, a microporous hydrophobic membrane, and an extraction chamber arranged sequentially. The back-extraction contact unit includes a feed liquid phase chamber, a microporous hydrophobic membrane, and a back-extraction chamber arranged sequentially. The circulating connection structure is used to connect the extraction chamber of the extraction contact unit with the feed liquid phase chamber of the back-extraction contact unit, so that the extractant circulates between the two contact units, thereby realizing the simultaneous extraction and back-extraction.

[0016] Furthermore, the membrane extraction contactor device includes both an extraction contact unit and a reverse extraction contact unit. Both the extraction contact unit and the reverse extraction contact unit adopt a modular symmetrical design, consisting of two symmetrical contact units on the left and right and a microporous hydrophobic membrane in the middle, and are fixed by bolts.

[0017] Furthermore, a chamber structure is formed in the middle of the two symmetrical contact units on the left and right sides to accommodate the liquid phase or extractant. The inner diameter of the middle chamber is 30 mm, the height is 15 mm, and the effective mass transfer area is 7.07 cm². 2 The chamber connections are sealed with nitrile rubber O-rings.

[0018] Furthermore, the microporous hydrophobic membrane is a PTFE membrane with a pore size of 0.1-0.9 μm, a porosity of 50-85%, a water contact angle greater than 120°, and a contact angle to the extractant less than 50°.

[0019] This invention addresses the problems of high acrylonitrile content, strong toxicity, low efficiency, and high energy consumption in traditional treatment methods for acrylonitrile wastewater. By constructing a non-contact membrane interface mass transfer system, it achieves efficient separation and recovery of acrylonitrile, offering the following advantages: 1. This invention couples the extraction contact unit with the back-extraction contact unit, allowing the extractant to circulate between the two units and form a continuous transmembrane concentration gradient, effectively avoiding the problem of decreased extraction efficiency caused by extractant saturation. This system maintains a high mass transfer flux, can quickly reach extraction equilibrium, and maintains a stable extraction rate greater than 92.5%, thereby significantly improving the purification efficiency and resource recovery capacity of acrylonitrile wastewater.

[0020] 2. This invention uses a microporous hydrophobic membrane as a two-phase contact barrier, allowing the feed liquid phase and extractant to flow independently on both sides of the membrane, completely eliminating phase dispersion, emulsification, and solvent entrainment phenomena commonly found in traditional liquid-liquid extraction. Since mass transfer occurs only at the membrane interface, the system can operate stably with significantly reduced solvent loss, resulting in higher overall economic efficiency and safety.

[0021] 3. The membrane extraction-reverse extraction contactors of this invention all adopt a modular symmetrical structure. Different specifications of treatment units can be constructed by changing the partitions, the area of ​​the microporous hydrophobic membrane, etc., to adapt to the treatment needs of acrylonitrile wastewater with different concentrations and flow rates. The overall structure of the device is simple and easy to assemble, making it suitable for continuous and large-scale industrial operation.

[0022] 4. Because the system requires only a low transmembrane pressure differential during operation, this invention will not cause mechanical damage to the membrane structure; at the same time, the liquid flows independently on both sides of the membrane without turbulence or impact, which can significantly reduce the risk of membrane fouling. Compared with other membrane separation technologies, this process is more friendly to membrane materials, which is beneficial to extending the service life of hydrophobic membranes and reducing maintenance costs.

[0023] In summary, this invention, by constructing an integrated membrane extraction-back extraction device composed of an extraction contact unit and a back extraction contact unit, achieves a high mass transfer flux, low energy consumption, low solvent loss, and high recovery efficiency for acrylonitrile wastewater treatment. This system not only efficiently removes and recovers acrylonitrile, but also exhibits strong stability, high adaptability, and ease of industrialization, providing an economical and sustainable high-efficiency treatment solution for high-concentration, recalcitrant acrylonitrile wastewater. Attached Figure Description

[0024] 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 some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the membrane (reverse) extraction mechanism in the membrane extraction method for efficiently treating acrylonitrile wastewater provided by the present invention.

[0026] Figure 2 This is a schematic diagram of the extraction unit or back-extraction unit in the membrane extraction contactor device for efficiently treating acrylonitrile wastewater provided by the present invention.

[0027] Figure 3 A detailed process flow diagram of an embodiment of the apparatus provided by the present invention.

[0028] In the diagram: 1. Transmembrane pressure difference direction of the extraction unit; 2. PTFE microporous hydrophobic membrane of the extraction unit; 3. Liquid contact area on both sides of the extraction unit; 4. Feed phase of the extraction unit; 5. Acrylonitrile molecules to be extracted; 6. Extraction solution of the extraction unit; 7. Transmembrane pressure difference direction of the back-extraction unit; 8. PTFE microporous hydrophobic membrane of the back-extraction unit; 9. Liquid contact area on both sides of the back-extraction unit; 10. Feed phase of the back-extraction unit; 11. Acrylonitrile molecules undergoing back-extraction; 12. Back-extraction liquid; 13. Fixed orifice; 14. Pipeline passage; 15. Raw material tank; 16. Raw material liquid; 17. Input pipe I; 18. Output pipe I; 19. Pressure gauge I 20. Valve I; 21. Peristaltic pump I; 22. Online flow meter I; 23. Extraction unit; 24. Output pipe II; 25. Input pipe II; 26. Pressure gauge II; 27. Valve II; 28. Peristaltic pump II; 29. ​​Flow meter II; 30. Extraction tank; 31. Extraction solution; 32. Output pipe III; 33. Input pipe III; 34. Pressure gauge III; 35. Valve III; 36. Peristaltic pump III; 37. Flow meter III; 38. Back-extraction unit; 39. Output pipe IV; 40. Input pipe IV; 41. Pressure gauge IV; 42. Valve IV; 43. Peristaltic pump IV; 44. Flow meter IV; 45. Back-extraction tank; 46. Back-extraction solution. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] This invention provides a highly efficient membrane extraction method and membrane extraction contactor device for treating acrylonitrile wastewater, wherein the membrane extraction contactor device includes both an extraction contact unit and a back-extraction contact unit. Figure 1 As shown, in the extraction system, the extraction contact unit consists of the extraction unit feed liquid phase 4, the extraction unit PTFE microporous hydrophobic membrane 2, and the extraction unit extract liquid 6. The transmembrane pressure difference direction 1 of the extraction unit is the pressure difference direction. Acrylonitrile wastewater, as the extraction unit feed liquid phase 4, passes through the extraction unit PTFE microporous hydrophobic membrane 2 (liquid contact area 3 on both sides of the extraction unit) under the action of pressure difference. The acrylonitrile molecules to be extracted 5 enter the extraction unit extract liquid 6. That is, by adjusting the transmembrane pressure difference (the pressure of the feed liquid phase is slightly greater than the pressure of the extract liquid), a fixed contact interface is formed at the membrane pores on the feed liquid phase side. At this interface, acrylonitrile molecules diffuse from the feed liquid phase to the extract liquid.

[0031] In the back-extraction system, the back-extraction unit consists of a back-extraction unit feed liquid phase 10, a back-extraction unit PTFE microporous hydrophobic membrane 8, and a back-extraction liquid 12. The transmembrane pressure difference direction 7 of the back-extraction unit is the pressure difference direction. Under the action of the pressure difference, the extraction liquid containing acrylonitrile, as the back-extraction unit feed liquid phase 10, passes through the back-extraction unit PTFE microporous hydrophobic membrane 8 (liquid contact area 9 on both sides of the back-extraction unit). Acrylonitrile molecules 11 carrying the back-extraction enter the back-extraction liquid 12 to achieve back-extraction. Membrane extraction and back-extraction occur simultaneously, reducing the concentration of extractable substances in the organic phase. The extraction-back-extraction system can maintain a high mass transfer flux, enabling the continuous extraction and recovery of acrylonitrile from acrylonitrile wastewater.

[0032] like Figure 2 As shown, taking the extraction unit as an example, it adopts a modular symmetrical design, mainly composed of two symmetrical units on the left and right, with the extraction unit's PTFE microporous hydrophobic membrane 2 in the middle. The two symmetrical units sandwich this membrane in the middle and are fixed to it using bolts at fixing holes 13. The core component of this left and right unit is the intermediate chamber, with structural parameters of an inner diameter of 30 mm, a height of 15 mm, and an effective mass transfer area of ​​7.07 cm². 2 The chamber connections are sealed with solvent-resistant nitrile rubber O-rings. Pipeline passage 14 is used to introduce the feed liquid phase or extractant.

[0033] like Figure 3 The diagram shown is a process flow chart of the present invention. In the extraction system: acrylonitrile wastewater of a certain concentration is used as raw material liquid 16 and enters the raw material tank 15. The raw material liquid 16 is transported into the extraction unit 23 by peristaltic pump I21 along the input pipe I17. The flow rate is monitored by online flow meter I22. After the raw material liquid 16 enters the feed chamber of the extraction unit 23, the acrylonitrile enters the extraction unit 23 through the PTFE microporous hydrophobic membrane 2 (which has good hydrophobicity, the feed liquid phase cannot wet the membrane pores, and the organic phase spontaneously permeates and completely fills the membrane pores through capillary effect). In the extraction chamber, the extracted liquid is circulated back to the feed tank 15 via the output pipe I18. The output liquid pressure is monitored by pressure gauge I19 and regulated by valve I20. The extraction liquid 31 in the extraction tank 30 enters the extraction chamber through the input pipe II25 and peristaltic pump II28 to extract acrylonitrile. The flow rate is monitored by online flow meter II29. The liquid after the extractant has extracted acrylonitrile is circulated back into the extraction tank 30 via the output pipe II24. The pressure of this section of liquid is monitored by pressure gauge II26 and regulated by valve II27, thus completing the extraction process.

[0034] In the back-extraction system: the extractant liquid 31 containing acrylonitrile is pumped into the feed chamber of the back-extraction unit 38 via pump III36 and input pipe III32. The flow rate is monitored by flow meter III37. Acrylonitrile passes through the PTFE microporous hydrophobic membrane 8 into the back-extraction chamber of the back-extraction unit 38. The back-extracted liquid returns to the extraction tank 30 via output pipe III33. The pressure in this section is monitored by pressure gauge III34 and regulated by valve III35. The back-extraction liquid 46 in the back-extraction tank 45 is transported into the back-extraction unit 38 via peristaltic pump IV43 and input pipe IV40. The flow rate in this section is monitored by flow meter IV44. The back-extraction liquid 46, carrying acrylonitrile, circulates back to the back-extraction tank 45 via output pipe IV39. The pressure in this section is monitored by pressure gauge IV41 and regulated by valve IV42, completing the back-extraction process. Membrane extraction and back-extraction occur simultaneously. The extraction-back-extraction system maintains a high mass transfer flux, enabling the continuous extraction and recovery of acrylonitrile from acrylonitrile wastewater.

[0035] Example 1 A membrane extraction contactor device was constructed, in which a PTFE microporous hydrophobic membrane with an average pore size of 0.4 μm and a porosity of 76.5% was selected as the two-phase contact barrier in the membrane extraction device, and the acrylonitrile concentration in the feed phase was 3000 mg·L⁻¹. -1 The transmembrane pressure difference was 0.03 MPa, and the flow rates of the feed liquid and the extractant tetrabutylurea were 0.2 L·min. -1 and 0.05 L·min -1 In the back-extraction system, a PTFE microporous hydrophobic membrane with an average pore size of 0.6 μm and a porosity of 85.3% was selected as the two-phase contact barrier in the back-extraction device, and the concentration of sodium thiocyanate as the back-extraction agent was 2.5 mol·L⁻¹. -1 The transmembrane pressure difference was 0.03 MPa, the dosage was 0.3 L, and the back-extraction flow rate was 0.2 L·min. -1 After 30 minutes of extraction, the system reached equilibrium with an extraction rate of 94.44%. The concentration of substances in each compartment was measured using a Shimadzu TOC-L total organic carbon analyzer. The extraction rate was calculated by converting the total organic carbon / total nitrogen (TOC / TN) ratio into the concentration of each substance.

[0036] Example 2 A membrane extraction contactor device was constructed, in which a PTFE microporous hydrophobic membrane with an average pore size of 0.5 μm and a porosity of 78.5% was selected as the two-phase contact barrier in the membrane extraction device, and the acrylonitrile concentration in the feed phase was 4000 mg·L⁻¹. -1 The transmembrane pressure difference was 0.04 MPa, and the flow rates of the feed liquid phase and the extractant tetrabutylurea were 0.09 L·min. -1 and 0.15 L·min -1In the back-extraction system, a PTFE microporous hydrophobic membrane with an average pore size of 0.8 μm and a porosity of 82% was selected as the two-phase contact barrier in the back-extraction device, and the concentration of sodium acetate as the back-extraction agent was 2.4 mol·L⁻¹. -1 The transmembrane pressure difference was 0.05 MPa, the dosage was 0.45 L, and the back-extraction flow rate was 0.08 L·min. -1 After 35 minutes of extraction, the system reached equilibrium with an extraction rate of 92.3%. The concentration of substances in each compartment was measured using a Shimadzu TOC-L total organic carbon analyzer. The extraction rate was calculated by converting the total organic carbon / total nitrogen (TOC / TN) ratio into the concentration of each substance.

[0037] Example 3 A membrane extraction contactor device was constructed, in which a PTFE microporous hydrophobic membrane with an average pore size of 0.6 μm and a porosity of 79% was selected as the two-phase contact barrier in the membrane extraction device, and the acrylonitrile concentration in the feed phase was 4500 mg·L⁻¹. -1 The transmembrane pressure difference was 0.06 MPa, and the flow rates of the feed liquid and the extractant tetrabutylurea were 0.08 L·min. -1 and 0.1 L·min -1 In the back-extraction system, a PTFE microporous hydrophobic membrane with an average pore size of 0.7 μm and a porosity of 80.5% was selected as the two-phase contact barrier in the back-extraction device, and the concentration of citric acid as the back-extraction agent was 2.45 mol·L⁻¹. -1 The transmembrane pressure difference was 0.1 MPa, the dosage was 0.6 L, and the back-extraction flow rate was 0.3 L·min. -1 After 35 minutes of extraction, the system reached equilibrium with an extraction rate of 91.5%. The concentration of substances in each compartment was measured using a Shimadzu TOC-L total organic carbon analyzer. The extraction rate was calculated by converting the total organic carbon / total nitrogen (TOC / TN) ratio into the concentration of each substance.

[0038] Example 4 A membrane extraction contactor device was constructed, in which a PTFE microporous hydrophobic membrane with an average pore size of 0.7 μm and a porosity of 80% was selected as the two-phase contact barrier in the membrane extraction device, and the acrylonitrile concentration in the feed phase was 4700 mg·L⁻¹. -1 The transmembrane pressure difference was 0.09 MPa, and the flow rates of the feed liquid and the extractant tetrabutylurea were 0.15 L·min. -1 and 0.2 L·min -1 In the back-extraction system, a PTFE microporous hydrophobic membrane with an average pore size of 0.65 μm and a porosity of 83.5% was selected as the two-phase contact barrier in the back-extraction device, and the concentration of the back-extraction agent diethylenetriaminepentaacetic acid was 2.4 mol·L⁻¹. -1 The transmembrane pressure difference was 0.13 MPa, the dosage was 0.7 L, and the back-extraction flow rate was 0.2 L·min.-1 After 34 minutes of extraction, the system reached equilibrium with an extraction rate of 91.1%. The concentration of substances in each compartment was measured using a Shimadzu TOC-L total organic carbon analyzer. The extraction rate was calculated by converting the total organic carbon / total nitrogen (TOC / TN) ratio into the concentration of each substance.

[0039] Example 5 A membrane extraction contactor device was constructed, in which a PTFE microporous hydrophobic membrane with an average pore size of 0.75 μm and a porosity of 82.5% was selected as the two-phase contact barrier in the membrane extraction device, and the acrylonitrile concentration in the feed phase was 4600 mg·L⁻¹. -1 The transmembrane pressure difference was 0.16 MPa, and the flow rates of the feed liquid phase and the extractant tetrabutylurea were 0.07 L·min. -1 and 0.15 L·min -1 In the back-extraction system, a PTFE microporous hydrophobic membrane with an average pore size of 0.65 μm and a porosity of 81.5% was selected as the two-phase contact barrier in the back-extraction device, and the concentration of sodium oxalate as the back-extraction agent was 2.5 mol·L⁻¹. -1 The transmembrane pressure difference was 0.16 MPa, the dosage was 0.8 L, and the back-extraction flow rate was 0.25 L·min. -1 After 35 minutes of extraction, the system reached equilibrium with an extraction rate of 90.6%. The concentration of substances in each compartment was measured using a Shimadzu TOC-L total organic carbon analyzer. The extraction rate was calculated by converting the total organic carbon / total nitrogen (TOC / TN) ratio into the concentration of each substance.

[0040] Example 6 A membrane extraction contactor device was constructed, in which a PTFE microporous hydrophobic membrane with an average pore size of 0.5 μm and a porosity of 83% was selected as the two-phase contact barrier in the membrane extraction device, and the acrylonitrile concentration in the feed phase was 5000 mg·L⁻¹. -1 The transmembrane pressure difference was 0.17 MPa, and the flow rates of the feed liquid and the extractant tetrabutylurea were 0.12 L·min. -1 and 0.16 L·min -1 In the back-extraction system, a PTFE microporous hydrophobic membrane with an average pore size of 0.7 μm and a porosity of 80.5% was selected as the two-phase contact barrier in the back-extraction device, and the concentration of the back-extraction agent diethylenetriaminepentaacetic acid was 2.4 mol·L⁻¹. -1 The transmembrane pressure difference was 0.18 MPa, the dosage was 0.75 L, and the back-extraction flow rate was 0.3 L·min. -1 After 40 minutes of extraction, the system reached equilibrium with an extraction rate of 91.8%. The concentration of substances in each compartment was measured using a Shimadzu TOC-L total organic carbon analyzer. The extraction rate was calculated by converting the total organic carbon / total nitrogen (TOC / TN) ratio into the concentration of each substance.

[0041] Example 7 A membrane extraction contactor device was constructed, in which a PTFE microporous hydrophobic membrane with an average pore size of 0.4 μm and a porosity of 78.5% was selected as the two-phase contact barrier in the membrane extraction device, and the acrylonitrile concentration in the feed phase was 3500 mg·L⁻¹. -1 The transmembrane pressure difference was 0.03 MPa, and the flow rates of the feed liquid phase and the extractant tetrabutylurea were 0.08 L·min. -1 and 0.1 L·min -1 In the back-extraction system, a PTFE microporous hydrophobic membrane with an average pore size of 0.6 μm and a porosity of 85.3% was selected as the two-phase contact barrier in the back-extraction device, and the concentration of sodium thiocyanate as the back-extraction agent was 2.5 mol·L⁻¹. -1 The transmembrane pressure difference was 0.13 MPa, the dosage was 0.45 L, and the back-extraction flow rate was 0.2 L·min. -1 After 35 minutes of extraction, the system reached equilibrium with an extraction rate of 92.5%. The concentration of substances in each compartment was measured using a Shimadzu TOC-L total organic carbon analyzer. The extraction rate was calculated by converting the total organic carbon / total nitrogen (TOC / TN) ratio into the concentration of each substance.

[0042] Examples 1-7 demonstrate that the membrane extraction method and membrane extraction contactor device for treating acrylonitrile wastewater provided by this invention can achieve simultaneous extraction and back-extraction, effectively maintaining the extraction capacity of the extractant. The membrane extraction contactor can quickly reach extraction equilibrium, with extraction rates all exceeding 92.5%, increasing the initial concentration and volume of the material phase. This system still has high treatment efficiency for acrylonitrile wastewater, breaking through the bottleneck of extractant saturation in traditional solvent extraction, and providing an efficient treatment solution for high-concentration, recalcitrant acrylonitrile wastewater. The overall device has significant economic and sustainable advantages.

[0043] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A membrane extraction method for efficiently treating acrylonitrile wastewater, characterized in that, By using a microporous hydrophobic membrane as a two-phase non-contact mass transfer interface, the feed liquid phase and the extractant can flow independently on both sides of the membrane. Adjusting the transmembrane pressure difference to make the pressure of the feed liquid phase higher than that of the extractant creates a stable membrane interface at the microporous hydrophobic membrane pores, allowing acrylonitrile to diffuse from the feed liquid phase to the extractant. The acrylonitrile-containing organic phase obtained from the extractant is transported to the back-extraction contact unit in another membrane extraction contactor, so that it comes into contact with the back-extraction agent, thereby achieving simultaneous extraction and back-extraction. The extractant is circulated between the extraction contact unit and the back-extraction contact unit to maintain the transmembrane concentration gradient, thereby improving the treatment efficiency of acrylonitrile wastewater.

2. The membrane extraction method according to claim 1, characterized in that, Both the extraction contact unit and the back-extraction contact unit include a feed liquid phase chamber, a microporous hydrophobic membrane, and an extraction chamber or a back-extraction chamber arranged sequentially. The extractant circulates between the extraction chamber of the extraction contact unit and the feed liquid phase chamber of the back-extraction contact unit.

3. The membrane extraction method according to claim 1, characterized in that, The microporous hydrophobic membrane is a PTFE membrane with a pore size of 0.1-0.9 μm, a porosity of 50-85%, a water contact angle greater than 120°, and a contact angle with the extractant less than 50°. The extractant spontaneously wets and fills the membrane pore structure.

4. The membrane extraction method according to claim 1, characterized in that, The extractant is at least one of diisobutylmethanol, tributyl phosphate, tetrabutylurea, trioctyl phosphate, mesitylene, n-octanol, n-heptane, or diisooctyl phosphate.

5. The membrane extraction method according to claim 1, characterized in that, The back-extraction agent is at least one of diethylenetriaminepentaacetic acid, sodium thiocyanate, sodium citrate, sodium oxalate, or sodium acetate.

6. The membrane extraction method according to claim 1, characterized in that, The extraction and back-extraction processes are performed under the following operating conditions: the acrylonitrile concentration in the feed phase is 500-6000 mg·L⁻¹. -1 The volume of acrylonitrile wastewater and extractant is 0.05-0.5 L; the flow rate of acrylonitrile wastewater and extractant is 0.02-1 L / min. -1 The extraction temperature was 15-30 ℃; the transmembrane pressure difference was 0.01-0.2 MPa; the amount of back-extraction agent was 0.1-1 L, and the flow rate was 0.02-1 L·min. -1 .

7. A membrane extraction contactor device for efficiently treating acrylonitrile wastewater, characterized in that, include: An extraction contact unit includes a feed liquid phase chamber, a microporous hydrophobic membrane, and an extraction chamber arranged sequentially. The back-extraction contact unit includes a feed liquid phase chamber, a microporous hydrophobic membrane, and a back-extraction chamber arranged sequentially. The circulating connection structure is used to connect the extraction chamber of the extraction contact unit with the feed liquid phase chamber of the back-extraction contact unit, so that the extractant circulates between the two contact units, thereby realizing the simultaneous extraction and back-extraction.

8. The membrane extraction contactor device according to claim 7, characterized in that, Both the extraction contact unit and the reverse extraction contact unit adopt a modular symmetrical design, consisting of two symmetrical contact units on the left and right and a microporous hydrophobic membrane in the middle, and are fixed by bolts.

9. The membrane extraction contactor device according to claim 8, characterized in that, The two symmetrical contact units on the left and right sides form a chamber structure in the middle to accommodate the liquid phase or extractant. The inner diameter of the middle chamber is 30 mm, the height is 15 mm, and the effective mass transfer area is 7.07 cm². 2 The chamber connections are sealed with nitrile rubber O-rings.

10. The membrane extraction contactor device according to claim 9, characterized in that, The microporous hydrophobic membrane is a PTFE membrane with a pore size of 0.1-0.9 μm, a porosity of 50-85%, a water contact angle greater than 120°, and a contact angle to the extractant less than 50°.

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