Janus distillation membrane for treating industrial high-salinity oil-containing wastewater and preparation method of Janus distillation membrane

Abstract

The invention discloses a Janus distillation membrane capable of being used for industrial high-salt oil-containing wastewater treatment and a preparation method of the Janus distillation membrane, halloysite nanotubes are coated on a polytetrafluoroethylene membrane by using a bonding layer constructed by cysteine and lysozyme to prepare an HNTs / PTFE composite membrane, and then polymer-polyacrylic acid and polyvinyl alcohol are introduced to carry out surface modification on the HNTs / PTFE composite membrane to prepare the Janus distillation membrane. And the HNTs-PTFE-PAA / PVA composite membrane is prepared. The HNTs are added, so that the roughness of the surface of the membrane can be reduced, the overall structure of the membrane can be kept, and the water molecule permeation rate can be increased. And PAA and PVA molecular chains contain a large number of charged hydrophilic groups, so that the underwater oleophobic performance of the HNTs-PTFE-PAA / PVA composite membrane can be further enhanced. The Janus distillation membrane shows excellent flux and salt rejection rate, has a wide application prospect in the field of industrial high-salt oil-containing wastewater treatment, and is beneficial to popularization and application.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment membrane materials technology, and in particular to a Janus distillation membrane for treating industrial high-salt and oily wastewater and its preparation method. Background Technology

[0002] High-salinity, oily wastewater from industrial discharges is a thorny problem in current industrial pollution control. Its high salinity significantly inhibits microbial activity, while the oily components easily form stubborn emulsions. The synergistic effect of these two factors makes traditional wastewater treatment technologies ineffective. This type of wastewater not only clogs pipes and equipment but also disrupts the ecological balance of aquatic bodies. Harmful substances within it accumulate through the food chain, posing a potential threat to human health. This sharply conflicts with the principles of ecological priority and low-carbon development, clearly violating the requirements of modern industrial clean production and a circular economy. Therefore, there is an urgent need for efficient and economical high-salinity, oily wastewater treatment technologies. Currently, common methods for treating high-salinity, oily industrial wastewater include physical, chemical, physicochemical, and biological methods. Among these, membrane separation technology belongs to the physicochemical method, offering advantages such as simple operation, ease of control, no need for external chemical reagents, environmental friendliness, and continuous operation. Polytetrafluoroethylene (PTFE) membranes are widely used in oily wastewater treatment due to their excellent chemical and mechanical stability. However, PTFE membranes are easily fouled during membrane distillation due to their hydrophobic properties, leading to membrane pore blockage. Furthermore, PTFE membranes are ineffective at preventing salt scaling when separating oily wastewater containing salt ions. Therefore, it is necessary to develop a distillation membrane for treating high-salt, oily industrial wastewater. Summary of the Invention

[0003] The purpose of this invention is to provide a hydrophilic-hydrophobic bifunctional (Janus) distillation membrane for treating high-salt, oily industrial wastewater and its preparation method, thereby solving the aforementioned technical problems. This invention utilizes halloysite nanotubes (HNTs), polyacrylic acid (PAA), and polyvinyl alcohol (PVA) to modify polytetrafluoroethylene (PTFE) membranes, preparing HNTs-PTFE-PAA / PVA composite membranes. Halloysite nanotubes (HNTs), due to their high hydroxyl content and excellent mechanical properties, can be added to the membrane to improve its hydrophilicity, antifouling properties, and salt ion retention capacity. Polyacrylic acid (PAA) and polyvinyl alcohol (PVA), rich in hydrophilic groups, enhance the membrane's hydrophilicity and underwater oleophobicity, and PVA's anti-swelling properties ensure structural integrity. Therefore, the hydrophilic groups of PAA and PVA can combine with water molecules through electrostatic interactions to form a strong hydration layer on the membrane surface to resist fouling. Durable and robust Janus membranes can be prepared by adding HNTs to PTFE as a substrate and combining PAA and PVA, which has good application prospects in membrane distillation.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing a Janus distillation membrane for treating industrial high-salt and oily wastewater, the method comprising the following steps:

[0006] 1) Load one side of a double-sided hydrophobic polytetrafluoroethylene (PTFE) membrane onto a sodium hydroxide solution (one side of the membrane is left to float on the sodium hydroxide solution), and dry to obtain a PTFE substrate treated with sodium hydroxide.

[0007] 2) Mix halloysite nanotubes (HNTs) aqueous dispersion, lysozyme aqueous solution and L-cysteine ​​aqueous solution to obtain a mixed solution; load one side of the PTFE substrate treated with sodium hydroxide onto the mixed solution (the side of the PTFE substrate treated with sodium hydroxide is left to float on the mixed solution), and incubate for a certain time, then dry to prepare an HNTs / PTFE composite membrane, thus obtaining the modified membrane;

[0008] 3) Mix polyacrylic acid (PAA) solution and polyvinyl alcohol (PVA) solution to obtain a mixed solution. Coat (e.g., drop-coat) the modified surface of the above-mentioned modified film (HNTs / PTFE composite film) for loading to obtain a composite Janus film, namely HNTs-PTFE-PAA / PVA composite film (denoted as MHP).

[0009] Furthermore, in step 1), the diameter of the double-sided hydrophobic polytetrafluoroethylene (PTFE) membrane is 30-60 mm, and the pore size is 0.2-0.5 μm.

[0010] Furthermore, in step 1), the mass fraction of the sodium hydroxide solution used to treat the double-sided hydrophobic PTFE membrane is 5-10%, and the volume is 15-25 mL; the loading is carried out at 40-90°C for 30-60 min; the drying time is 10-40 min, and the drying temperature is 20-30°C.

[0011] Furthermore, in step 2), the halloysite nanotubes have an inner diameter of 10-30 nm, an outer diameter of 50-70 nm, a wall thickness of 20-60 nm, and a length of 200-1500 nm.

[0012] Furthermore, in step 2), an aqueous dispersion of halloysite nanotubes (HNTs) is prepared by ultrasonication and cell disruption.

[0013] Furthermore, the ultrasound and cell wall disruption times are both 20–40 min.

[0014] Furthermore, in step 2), the concentration of the halloysite nanotube aqueous dispersion is 2–8 mg / mL.

[0015] Furthermore, in step 2), the concentration of the L-cysteine ​​aqueous solution is 10-18 mg / mL, the concentration of the lysozyme aqueous solution is 2-8 mg / mL, and the pH of the L-cysteine ​​aqueous solution is 8.5-10.5.

[0016] Furthermore, in step 2), a certain concentration of L-cysteine ​​and lysozyme aqueous solution is prepared, and the pH of the L-cysteine ​​solution is adjusted using sodium hydroxide solution.

[0017] Furthermore, in step 2), the concentration of the sodium hydroxide solution is 0.8–1.2 mol / mL.

[0018] Furthermore, in step 2), the volume ratio of halloysite nanotube aqueous dispersion, lysozyme aqueous solution and L-cysteine ​​aqueous solution in the mixed solution is 1:0.5:0.5 to 1:2:2.

[0019] Furthermore, in step 2), the mixed solution of halloysite nanotube aqueous dispersion, lysozyme aqueous solution and L-cysteine ​​aqueous solution is sonicated before culturing the PTFE substrate. The sonication time is 10-30 min and the volume of the mixed solution is 20-40 mL.

[0020] Furthermore, in step 2), the PTFE substrate loading is carried out at 20-30°C for 3-7 hours; the drying temperature is 20-60°C and the drying time is 2-6 hours.

[0021] Furthermore, in step 3), the mass fraction of both PAA solution and PVA solution is 1-5 wt%, and the mixing volume ratio of PAA solution and PVA solution is 1:0.5 to 1:2; the culture temperature is 20-80℃, and the culture time is 0.5-3h.

[0022] Furthermore, in step 3), the ratio of the mixed solution to the double-sided hydrophobic polytetrafluoroethylene (PTFE) membrane is 1-3 mL (volume): 30-60 mm (diameter).

[0023] Furthermore, in step 3), the molecular weight of PAA is 8.0 × 10⁻⁶. 6 -1.5×10 7 g mol -1 The molecular weight of PVA is 1.0 × 10⁻⁶. 5 -1.5×10 5 g mol -1 .

[0024] The present invention also provides a Janus distillation membrane for treating industrial high-salt and oily wastewater prepared by the above preparation method.

[0025] The present invention also provides an application of the above-mentioned Janus distillation membrane in the treatment of industrial high-salt and oily wastewater.

[0026] Furthermore, the high salt content in the high-salt oily wastewater is defined as a total salt content of at least 1% (based on the mass fraction of NaCl), for example, containing 3.5 wt% sodium chloride.

[0027] Furthermore, the high-salt, oily wastewater also contains calcium chloride and sodium sulfate.

[0028] Furthermore, the oil in the high-salt, oily wastewater is kerosene, diesel oil, soybean oil, etc., such as n-hexadecane.

[0029] The oil-water separation membrane with a hydrophilic-hydrophobic bifunctional (Janus) structure and asymmetric wetting properties prepared by this invention can effectively treat complex high-salt and oily wastewater. This membrane combines a hydrophilic-oleophobic surface layer with a hydrophobic bottom layer having low surface energy and high roughness, exhibiting effective repulsion against surfactants and oily substances, thereby achieving excellent antifouling and antiwetting properties.

[0030] This invention utilizes a cysteine ​​and lysozyme-based adhesive layer to coat halloysite nanotubes (HNTs) onto a polytetrafluoroethylene (PTFE) membrane, preparing an HNTs / PTFE composite membrane. Further surface modification of the HNTs / PTFE composite membrane with polymers—polyacrylic acid (PAA) and polyvinyl alcohol (PVA)—results in an HNTs-PTFE-PAA / PVA composite membrane (MHP). The addition of HNTs reduces membrane surface roughness while maintaining the overall membrane structure and accelerates water molecule permeation. The PAA and PVA molecular chains contain numerous charged hydrophilic groups, further enhancing the underwater oleophobic properties of the HNTs-PTFE-PAA / PVA composite membrane. The M2-H4-P (4 mg / mL HNTs) Janus distillation membrane exhibited excellent flux and salt rejection rate in both membrane distillation scaling experiments (feed containing 40 mM calcium chloride, 40 mM sodium sulfate, and 3.5 wt% sodium chloride solution) and membrane distillation fouling experiments (feed containing 2000 ppm n-hexadecane and 3.5 wt% sodium chloride solution). It shows broad application prospects in the treatment of high-salt, oily industrial wastewater and is conducive to its widespread application.

[0031] The beneficial effects of this invention are:

[0032] (1) The Janus distillation membrane prepared in this invention for treating industrial high-salt and oily wastewater has low synthetic material cost, is non-toxic and environmentally friendly, and has a simple preparation method.

[0033] (2) The Janus distillation membrane prepared in this invention has good flux and salt rejection rate in the salt rejection experiment.

[0034] (3) The Janus distillation membrane prepared in this invention exhibits excellent antifouling and anti-scaling properties, and has a promising future in the treatment of industrial high-salt and oily wastewater, which is conducive to its widespread application. Attached Figure Description

[0035] Figure 1 A photograph of the M2-H4-P membrane prepared in Example 1 for treating industrial high-salt and oily wastewater.

[0036] Figure 2 This is a diagram showing the water contact angles of different distillation membranes in Example 5.

[0037] Figure 3 The diagram shows the permeation flux and salt rejection rate of different distillation membranes in Example 6.

[0038] Figure 4 The diagram shows the permeate flux and salt cutoff of different distillation membranes used in the scaling experiment in Example 7.

[0039] Figure 5 The permeation flux and salt cutoff diagrams are for the fouling experiments conducted on different distillation membranes in Example 8.

[0040] Figure 6 A schematic diagram of the apparatus used for membrane distillation experiments with a Janus distillation membrane. Detailed Implementation

[0041] This invention provides a method for preparing a Janus distillation membrane for treating industrial high-salt and oily wastewater, the method comprising the following steps:

[0042] 1) An aqueous dispersion of halloysite nanotubes was prepared by ultrasonication and cell wall disruption;

[0043] 2) Prepare aqueous solutions of L-cysteine ​​and lysozyme of a certain concentration respectively, and adjust the pH of the L-cysteine ​​solution with sodium hydroxide solution.

[0044] 3) Load one side of the double-sided hydrophobic polytetrafluoroethylene (PTFE) membrane onto a sodium hydroxide solution and dry it to obtain a PTFE substrate treated with sodium hydroxide.

[0045] 4) Mix halloysite nanotube aqueous dispersion, lysozyme aqueous solution and L-cysteine ​​aqueous solution to obtain a mixed solution; load one side of the PTFE substrate treated with sodium hydroxide onto the mixed solution, incubate for a certain time, dry, and prepare HNTs / PTFE composite membrane to obtain the modified membrane;

[0046] 5) Prepare a polyacrylic acid (PAA) solution and a polyvinyl alcohol (PVA) solution, and mix them to obtain a mixed solution. Coat (e.g., drop-coat) the modified surface of the modified film (HNTs / PTFE composite film) with the mixed solution to obtain a composite Janus film.

[0047] In this invention, in step 1), the halloysite nanotube has an inner diameter of 10-30 nm, an outer diameter of 50-70 nm, a wall thickness of 20-60 nm, and a length of 200-1500 nm, preferably an inner diameter of 20 nm, an outer diameter of 60 nm, a wall thickness of 40 nm, and a length of 500 nm.

[0048] In this invention, in step 1), the ultrasonic and cell wall breaking times are 20-40 min, preferably 25-35 min, and more preferably 30 min.

[0049] In this invention, in step 1), the concentration of the halloysite nanotube aqueous dispersion is 2-8 mg / mL, preferably 3-6 mg / mL, and more preferably 4 mg / mL.

[0050] In this invention, in step 2), the concentration of the L-cysteine ​​aqueous solution is 10-18 mg / mL, preferably 12-16 mg / mL, and more preferably 14 mg / mL; the concentration of the lysozyme aqueous solution is 2-8 mg / mL, preferably 6-8 mg / mL, and more preferably 8 mg / mL; the concentration of the sodium hydroxide solution is 0.8-1.2 mol / mL, preferably 1 mol / mL; and the pH of the L-cysteine ​​aqueous solution is adjusted to 8.5-10.5, preferably 9.

[0051] In this invention, in step 3), the mass fraction of the sodium hydroxide solution used to treat the double-sided hydrophobic PTFE membrane is 5-10%, preferably 7%; the volume of the sodium hydroxide solution is 15-25 mL, preferably 20 mL; the loading is carried out at 40-90°C, preferably 60°C; the loading time is 30-60 min, preferably 40 min; and the drying time is 10-40 min, preferably 30 min.

[0052] In this invention, in step 3), the diameter of the double-sided hydrophobic polytetrafluoroethylene (PTFE) membrane is 30-60 mm, preferably 50 mm; the pore size is 0.2-0.5 μm, preferably 0.45 μm.

[0053] In this invention, in step 4), the volume ratio of halloysite nanotube aqueous dispersion, lysozyme aqueous solution and L-cysteine ​​aqueous solution in the mixed solution is 1:0.5:0.5 to 1:2:2, preferably 1:1:1.

[0054] In this invention, in step 4), the mixed solution of halloysite nanotube aqueous dispersion, lysozyme aqueous solution and L-cysteine ​​aqueous solution is sonicated before culturing PTFE substrate. The sonication time is 10-30 min, preferably 30 min; the volume of the mixed solution is 20-40 mL, preferably 30 mL.

[0055] In this invention, in step 4), the PTFE substrate is cultured at 20-30°C, preferably 25°C; the culture time is 3-7 hours, preferably 5-7 hours, and more preferably 6 hours; the drying temperature is 20-60°C, preferably 20-40°C; and the drying time is 2-6 hours, preferably 2.5-5 hours.

[0056] In this invention, in step 5), the mass fractions of PAA solution and PVA solution are 1-5 wt%, preferably 2-4 wt%, and more preferably 3-4 wt%; the mixing volume ratio of PAA solution and PVA solution is 1:0.5-1:2, preferably 1:1-1:2; the culture temperature is 20-80℃, preferably 60℃; and the culture time is 0.5-3h, preferably 2h.

[0057] In this invention, in step 5), the ratio of the mixed solution to the double-sided hydrophobic polytetrafluoroethylene (PTFE) membrane is 1-3 mL (volume): 30-60 mm (diameter), preferably 2 mL (volume): 30-60 mm (diameter). For example, the amount of mixed solution used is 1-3 mL, preferably 2 mL.

[0058] In this invention, in step 5), the molecular weight of PAA is 8.0 × 10⁻⁶. 6 -1.5×10 7 g mol -1 Preferably 1.0×10 7 gmol -1 The molecular weight of PVA is 1.0 × 10⁻⁶. 5 -1.5×10 5 g mol -1 The preferred value is 1.2 × 10⁻⁶. 5 g mol -1 .

[0059] The present invention also provides a Janus distillation membrane for treating industrial high-salt and oily wastewater.

[0060] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0061] Example 1

[0062] 1) Dissolve 0.08g halloysite nanotubes (with an inner diameter of 20nm, an outer diameter of 60nm, a wall thickness of 40nm, and a length of 500nm) in 20mL of deionized water, and then treat them by sonication and cell disruption for 30min each, to prepare a halloysite nanotube aqueous dispersion with a concentration of 4mg / mL.

[0063] 2) Prepare 20 mL of L-cysteine ​​aqueous solution with a concentration of 14 mg / mL (L-cysteine ​​was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.) and 20 mL of lysozyme aqueous solution with a concentration of 8 mg / mL (lysozyme was purchased from Shanghai Yuanye Biochemical Reagent). Adjust the pH of the L-cysteine ​​aqueous solution to 9 using 1 mol / mL sodium hydroxide solution.

[0064] 3) One side of a double-sided hydrophobic polytetrafluoroethylene (PTFE) membrane (50 mm in diameter, 0.45 μm in pore size, purchased from Haining Delu New Material Technology Co., Ltd.) was loaded onto 20 mL of 7% sodium hydroxide solution at 60 °C for 40 min (one side of the membrane was left to float on the sodium hydroxide solution) and dried at 25 °C for 30 min to obtain a PTFE substrate treated with sodium hydroxide.

[0065] 4) Using a pipette, take 10 mL of halloysite nanotube aqueous dispersion, lysozyme aqueous solution and L-cysteine ​​aqueous solution respectively, mix them and sonicate for 30 min to obtain a mixed solution; load one side of the PTFE substrate treated with sodium hydroxide onto the above mixed solution at 25 °C (one side of the membrane is left to float on the mixed solution) for 6 h, and dry at 25 °C for 3 h to obtain HNTs / PTFE composite membrane.

[0066] 5) Prepare PAA (molecular weight 1.0 × 10⁻⁶) solutions, each with a volume of 20 mL and a mass fraction of 4 wt%. 7 g mol -1 ) solution and PVA (molecular weight 1.2 × 10⁻⁶) 5 g mol -1 The solution was prepared and mixed to obtain a mixed solution; 2 mL of the mixed solution was drop-coated onto the modified side of the HNTs / PTFE composite membrane at 25 °C, and loaded at 60 °C for 2 h to obtain a Janus distillation membrane, denoted as M2-H4-P.

[0067] Example 2

[0068] The difference between this embodiment and Example 1 is that the halloysite nanotube solution prepared in step 1) and the PAA and PVA mixed solution prepared in step 5) are not required. Everything else is the same as in Example 1. The prepared membrane is denoted as M1-H4.

[0069] Example 3

[0070] The difference between this embodiment and Example 1 is that in step 1), 0.072 g of halloysite nanotubes were weighed, while the rest was the same as in Example 1. The Janus distillation membrane prepared was designated as M3-H. 3.6 -P.

[0071] Example 4

[0072] The difference between this embodiment and Example 1 in the preparation process is that in step 1), 0.096 g of halloysite nanotubes were weighed, while the rest was the same as in Example 1. The Janus distillation membrane prepared was designated as M4-H. 4.8 -P.

[0073] Example 5

[0074] Contact angle testing of Janus distillation membranes. The distillation membranes prepared in Examples 1, 2, 3, and 4 were subjected to water contact angle (WCA) testing. The results are as follows: Figure 2 As shown, when the membrane modified with cysteine ​​and lysozyme was further modified with halloysite nanotubes, PAA, and PVA, its water contact angle decreased significantly; the water contact angle of M2-H4-P (with halloysite nanotube concentration of 4 mg / mL) was lower than that of M3-H 3.6 -P (haloysite nanotube concentration of 3.6 mg / mL) and M4-H 4.8 The water contact angle of M2-H4-P (with halloysite nanotube concentration of 4.8 mg / mL) is only 45.3°. This is because halloysite nanotubes, PAA, and PVA are rich in hydrophilic functional groups (hydroxyl groups, OH), which can reduce the surface energy of the M1-H4 membrane and thus enhance its hydrophilicity. However, when the content of halloysite nanotubes is further increased, the halloysite nanotubes will aggregate, thereby increasing the contact angle. This indicates that M2-H4-P with a halloysite nanotube concentration of 4 mg / mL has the best hydrophilicity.

[0075] Example 6

[0076] The salt rejection capacity of the distillation membranes prepared in Examples 1, 2, 3, and 4 was tested for 2 hours. A 3.5 wt% sodium chloride solution was used as the feed liquid for membrane distillation. The flux and salt rejection rate are as follows: Figure 3 As shown in the diagram, the apparatus for membrane distillation is as follows: Figure 6As shown, the operation process is as follows: A peristaltic pump delivers the feed solution, heated to 60°C in a water bath, to the feed side of the membrane module at a flow rate of 0.10 L / min. Volatile components in the feed solution permeate through the membrane under the vapor pressure difference caused by the temperature difference, entering the permeate side of the membrane module. The fluid on the permeate side is then pumped at a flow rate of 0.10 L / min by the peristaltic pump. A chiller (maintained at 20°C) controls the temperature of the effluent, causing the permeated vapor to condense into liquid water. The condensed liquid water is collected, and the mass of the collected permeate is weighed using an electronic balance to calculate the flux. A conductivity meter is used to detect the conductivity to calculate the salt rejection rate. The water flux of the M1-H4 membrane is 16.58 kg·m³. 2 ·h 1 With the addition of halloysite nanotubes, the porosity of the membrane increases. Compared with the M1-H4 membrane, the Janus membrane with added halloysite nanotubes, PAA, and PVA significantly improves the hydrophilicity of the M1-H4 membrane, allowing more water to pass through in the same amount of time, thus increasing the water flux of the membrane. The M2-H4-P prepared in Example 1 has the highest flux, at 24.49 kg·m³. 2 ·h 1 Excessive halloysite nanotube content can lead to aggregation in the membrane matrix, resulting in decreased porosity and hydrophilicity, thus reducing flux. Furthermore, M2-H4-P exhibits an optimal salt rejection rate of 99.84%, indicating that the prepared Janus distillation membrane possesses excellent salt rejection capabilities and shows promising application prospects in brine purification.

[0077] Example 7

[0078] Scaling experiments were conducted on the Janus distillation membrane. A 2-hour scaling experiment was performed using a mixture of 40 mM calcium chloride, 40 mM sodium sulfate, and 3.5 wt% sodium chloride solution as the feed liquid for membrane distillation to evaluate the anti-scaling performance of the Janus distillation membrane M2-H4-P prepared in Example 1. Calcium chloride and sodium sulfate ions have relatively large diameters, making it difficult for them to pass through the tiny channels and pores of halloysite nanotubes; moreover, the cations (Ca) of calcium chloride and sodium sulfate... 2 The Na+ and Na+ ions interact electrostatically with the negative charge of halloysite nanotubes. This electrostatic interaction hinders the passage of cations, thereby enabling Ca2+ to pass through. 2 Retention of + and Na+. The results are as follows: Figure 4 As shown, the flux of M2-H4-P remained consistently at 21 kg·m. 2 ·h 1 The salt rejection rate consistently exceeded 99.9%, indicating that the prepared Janus distillation membrane has good application prospects in anti-fouling.

[0079] Example 8

[0080] Membrane distillation fouling experiment of Janus distillation membrane. A fouling experiment was conducted for 10 h using a solution containing 2000 ppm n-hexadecane and 3.5 wt% sodium chloride as feed liquid to evaluate the antifouling performance of the Janus distillation membrane M2-H4-P prepared in Example 1. The hydrophilic groups on the PAA and PVA layers of the hydrophilic layer bind to water molecules, accelerating the rate of water molecule permeation through the membrane. Simultaneously, a protective layer is formed on the membrane surface, acting as a protective barrier against fouling, thus giving it excellent oil resistance. The results are as follows... Figure 5 As shown, M2-H4-P consistently maintains excellent flux (>22 kg·m). 2 ·h 1 The high salt rejection rate (>99.9%) indicates that the prepared Janus distillation membrane has good application prospects in resisting oil contamination.

[0081] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A method for preparing a Janus distillation membrane for treating industrial high-salt and oily wastewater, characterized in that, The method includes the following steps: 1) One side of a double-sided hydrophobic polytetrafluoroethylene membrane is loaded onto a sodium hydroxide solution and dried to obtain a PTFE substrate treated with sodium hydroxide. 2) Mix halloysite nanotube aqueous dispersion, lysozyme aqueous solution and L-cysteine ​​aqueous solution to obtain a mixed solution; load one side of the PTFE substrate treated with sodium hydroxide onto the mixed solution, incubate for a certain time, and dry to obtain the modified film; 3) Mix polyacrylic acid and polyvinyl alcohol solutions, and coat the mixed solution onto the modified side of the above-mentioned modified film to obtain a composite Janus film.

2. The method for preparing the Janus distillation membrane for treating industrial high-salt and oily wastewater according to claim 1 or 2, characterized in that, In step 2), the time for both ultrasound and cell wall disruption is 20–40 min.

3. The method for preparing the Janus distillation membrane for treating industrial high-salt and oily wastewater according to claim 1, characterized in that, In step 2), the concentration of the halloysite nanotube aqueous dispersion is 2-8 mg / mL; the halloysite nanotube has an inner diameter of 10-30 nm, an outer diameter of 50-70 nm, a wall thickness of 20-60 nm, and a length of 200-1500 nm.

4. The method for preparing the Janus distillation membrane for industrial high-salt and oily wastewater according to claim 1, characterized in that, In step 2), the concentration of the L-cysteine ​​aqueous solution is 10–18 mg / mL, and the pH is 8.5–10.5; the concentration of the lysozyme aqueous solution is 2–8 mg / mL; the concentration of the sodium hydroxide solution is 0.8–1.2 mol / mL; and the volume ratio of halloysite nanotube aqueous dispersion, lysozyme aqueous solution, and L-cysteine ​​aqueous solution in the mixed solution is 1:0.5:0.5 to 1:2:

2.

5. The method for preparing the Janus distillation membrane for treating industrial high-salt and oily wastewater according to claim 1, characterized in that, In step 1), the diameter of the double-sided hydrophobic polytetrafluoroethylene (PTFE) membrane is 30-60 mm and the pore size is 0.2-0.5 μm; the mass fraction of the sodium hydroxide solution used to treat the double-sided hydrophobic PTFE membrane is 5-10%; the loading is carried out at 40-90°C for 30-60 min; the drying time is 10-40 min and the drying temperature is 20-30°C.

6. The method for preparing the Janus distillation membrane for treating industrial high-salt and oily wastewater according to claim 1, characterized in that, In step 2), the mixed solution of halloysite nanotube aqueous dispersion, lysozyme aqueous solution and L-cysteine ​​aqueous solution is subjected to ultrasonic treatment before culturing PTFE substrate, and the ultrasonic treatment time is 10-30 min.

7. The method for preparing the Janus distillation membrane for treating industrial high-salt and oily wastewater according to claim 1, characterized in that, In step 2), the PTFE substrate is cultured at 20–30°C for 3–7 hours; the drying temperature is 20–60°C for 2–6 hours.

8. The method for preparing the Janus distillation membrane for treating high-salt, oily industrial wastewater according to claim 7, wherein in step 3), the mass fraction of both the polyacrylic acid solution and the polyvinyl alcohol solution is 1-5 wt%, and the mixing volume ratio of the polyacrylic acid solution and the polyvinyl alcohol solution is 1:0.5 to 1:2; the culture temperature is 20-80℃, and the culture time is 0.5-3 h; the molecular weight of the polyacrylic acid is 8.0 × 10⁻⁶. 6 -1.5×10 7 g mol -1 The molecular weight of polyvinyl alcohol is 1.0 × 10⁻⁶. 5 -1.5×10 5 g mol -1 .

9. The Janus distillation membrane for treating industrial high-salt oily wastewater prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the Janus distillation membrane according to claim 9 in the treatment of industrial high-salt and oily wastewater.

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