High-efficiency deoxygenated pmp composite membrane with self-cleaning function and preparation method thereof

Abstract

This invention discloses a high-efficiency deoxygenating PMP composite membrane with self-cleaning function and its preparation method. The composite membrane, through a multi-layer structure design, sequentially includes a PMP / carbon nanotube composite substrate support layer, a Bi-modified g-C3N5 photocatalytic functional layer, and a superhydrophobic protective layer, possessing high-efficiency deoxygenation, photocatalytic self-cleaning, and anti-fouling properties. The photocatalytic functional layer uses Bi-modified g-C3N5 prepared by a solvothermal method as a modifier, and is prepared through electrospinning technology and coating modification process. This composite membrane has a superhydrophobic surface with a contact angle >150°, a deoxygenation rate of ≥95% for power plant boiler water, an oxygen permeation rate of 400-800 ml / (bar·min·m²), and good long-term operational stability.

Description

Technical Field

[0001] This invention belongs to the field of water treatment technology, specifically relating to a high-efficiency deoxygenation PMP composite membrane with photocatalytic self-cleaning function and its preparation method. The composite membrane, through a multi-layer functional design, integrates high-efficiency deoxygenation, photocatalytic self-cleaning, and anti-fouling properties, making it particularly suitable for high-temperature and high-pressure deoxygenation treatment of boiler water in power plants. It can effectively solve the performance degradation and fouling problems of traditional deoxygenation membrane materials under harsh operating conditions. Background Technology

[0002] In power plant boiler water treatment systems, dissolved oxygen removal is a crucial process for preventing corrosion of metal equipment and scaling of thermal systems. Currently, industrial applications mainly employ two technologies: thermal deoxygenation and chemical deoxygenation. Thermal deoxygenation requires heating the water to above saturation temperature, resulting in high energy consumption and complex equipment. Chemical deoxygenation, on the other hand, requires the continuous addition of reducing agents such as sodium sulfite, posing risks of reagent residue and secondary pollution.

[0003] Compared with traditional technologies, membrane deoxygenation technology has become a research hotspot due to its advantages such as low energy consumption and no chemical additives. In existing technologies, hollow fiber membrane materials such as polypropylene (PP) and polytetrafluoroethylene (PTFE) have been applied to the deoxygenation process. However, they are prone to polymer chain rearrangement in high-temperature environments above 80°C for a long time, which leads to the collapse of the membrane pore structure. Pollutants are also prone to deposit on the membrane surface to form a filter cake layer, which increases the resistance to oxygen mass transfer.

[0004] Poly(4-methyl-1-pentene) (PMP) is considered an ideal substrate for deoxidation membranes due to its excellent temperature resistance (melting point > 240℃) and chemical stability. Publication patent CN117414710A discloses a PMP hollow fiber membrane that exhibits good performance in degassing inks and electroplating solutions through an asymmetric pore design. However, this technology does not consider the membrane fouling problem caused by colloidal particles in boiler water, leading to strength degradation and performance decline over long-term operation.

[0005] To address the aforementioned problems, this invention innovatively constructs a composite structure consisting of a carbon nanotube (CNT) reinforced support layer, a Bi-C3N5 photocatalytic functional layer, and a PDMS superhydrophobic protective layer. This achieves breakthroughs in efficient deoxygenation and self-cleaning synergy, structural stability, and long-term anti-fouling properties. The Bi-C3N5 photocatalytic layer generates reactive oxygen species under light irradiation, promoting oxygen adsorption and removal while also degrading adsorbed organic matter. The CNT reinforced support layer enhances the structural stability of the composite membrane. The superhydrophobic modification layer reduces surface energy, significantly reducing pollutant adhesion and extending membrane lifespan. Compared to existing technologies, this invention is the first to integrate photocatalytic materials and hydrophobic modification technology into a PMP membrane system, solving the technical challenge of deoxygenation membrane performance degradation under high temperature and high pressure conditions, and providing a revolutionary solution for power plant boiler water treatment. Summary of the Invention

[0006] The purpose of this invention is to address the problems of structural degradation, decreased deoxygenation efficiency, and weak antifouling ability of existing deoxygenation membrane materials under high temperature and high pressure conditions. A PMP composite membrane for efficient deoxygenation of power plant boiler water has been prepared. This composite membrane achieves efficient deoxygenation, photocatalytic self-cleaning, and long-term antifouling functions by sequentially constructing a PMP / carbon nanotube composite substrate support layer, a photocatalytic functional layer, and a superhydrophobic protective layer. It is suitable for deoxygenation treatment of power plant boiler water, ensuring excellent deoxygenation effect and long-term stable operation.

[0007] The PMP composite membrane for efficient deoxygenation of boiler water in power plants prepared by this invention adopts an innovative three-dimensional composite structure design. Bi-modified g-C3N5 photocatalytic material is prepared via a solvothermal method, combined with electrospinning technology and coating modification processes, endowing the membrane material with excellent deoxygenation performance and environmental adaptability. Specifically, the process includes the following steps:

[0008] Step 1): Synthesis of g-C3N5: A certain amount of 3-amino-1,2,4-triazole was placed in a crucible and heated to 550℃ in a muffle furnace at a heating rate of 5℃ / min. The temperature was maintained at 550℃ for 3 hours. After cooling to room temperature, the sample was ground for later use.

[0009] Step 2) Preparation of Bi-C3N5

[0010] Bismuth nitrate pentahydrate, ethylene glycol, polyvinylpyrrolidone (PVP), and g-C3N5 were sequentially added to a dilute nitric acid solution and mixed with magnetic stirring. Bi-modified g-C3N5 was then synthesized via a solvothermal method. After centrifugation, washing with water and ethanol, drying, and grinding, Bi-C3N5 was obtained; the mass percentage of bismuth was 1%–5%.

[0011] Step 3) Preparation of spinning solution

[0012] The first spinning solution, by mass percentage, includes 5-10% PMP, 0.5-2% carbon nanotubes (CNTs), 0.1-2% sodium dodecyl sulfate, and the remainder is solvent. Dissolve PMP in the solvent, stir magnetically at 60°C for 4 hours until transparent, add sodium dodecyl sulfate and CNTs, disperse ultrasonically for 30 minutes, and continue stirring for 1.5-3.5 hours until completely dissolved.

[0013] The second spinning solution, by mass percentage, includes 3-5% PMP, 1-3% Bi-C3N5, 2-10% PVP, with the remainder being solvent. Dissolve PMP in the solvent, stir magnetically at 60°C for 4 hours until transparent, add Bi-C3N5, ultrasonically disperse for 1 hour, and continue stirring for 1.5-3.5 hours until completely dissolved.

[0014] Step 4) Preparation of composite membrane

[0015] Using electrospinning technology, the first spinning solution is spun for 5-20 h at a DC voltage of 15-18 kV, a flow rate of 1-2 ml / h, and a receiving distance of 10-15 cm to form a nanofiber base film with a thickness of 180-220 μm and a pore size of 1-5 μm.

[0016] A second spinning solution was spun on the base membrane for 1.5-4 h to form a Bi-C3N5 / PMP composite membrane with a total thickness of 185-220 μm and a pore size of 1-3 μm.

[0017] After cleaning and drying the obtained composite film with ethanol, a hexane solution consisting of 5% PDMS and 0.5% perfluorooctyltrimethoxysilane was sprayed onto it and cured at room temperature for 24 h to form a superhydrophobic protective layer.

[0018] Preferably, the concentration of the dilute nitric acid solution in step 2) is 1 mol / L.

[0019] Preferably, the solvent in step 3) is one or more of acetone, ethyl acetate, dichloroethane, and xylene;

[0020] The PMP composite membrane prepared by this invention achieves the following comprehensive performance through a three-level synergistic structure of "PMP / carbon nanotube reinforced support layer - Bi-C3N5 photocatalytic functional layer - PDMS superhydrophobic protective layer": deoxygenation rate ≥95%; oxygen permeation rate 400-800 ml / (bar·min·m²); stable operation for >1 h under 0.4 kPa high pressure; superhydrophobic and antifouling properties with a contact angle greater than 150°; no pore collapse under high temperature conditions above 80℃; and long-term deoxygenation efficiency decay rate <5%.

[0021] Technical solution

[0022] The self-cleaning, high-efficiency deoxygenating PMP composite membrane provided by this invention achieves its deoxygenation function through a three-stage synergistic mechanism:

[0023] 1. Physical sieving - adsorption layer

[0024] The base film layer composed of PMP / carbon nanotubes (thickness 180-220 μm, pore size 1-5 μm) functions through the following mechanisms: the PMP matrix provides a high-temperature resistant framework, carbon nanotubes (CNTs) form a conductive network, optimize the pore size distribution, and enable oxygen permeation rate of 400-800 mL / (bar·min·m²); the nanoscale pores generate a surface adsorption effect on dissolved oxygen, thereby improving mass transfer efficiency.

[0025] 2. Photocatalytic reaction layer

[0026] Bi-modified g-C3N5 functional layers (thickness 5-20 μm) achieve catalytic deoxygenation through the following pathways: Bi doping causes a red shift in the light absorption edge, expands the light absorption range, and improves the utilization rate of visible light; the construction of heterojunctions improves the electron-hole separation efficiency, continuously generates active oxygen species, decomposes residual dissolved oxygen, and simultaneously degrades organic pollutants, thereby achieving self-cleaning of the membrane surface.

[0027] 3. Superhydrophobic protective layer

[0028] The PDMS / perfluorooctyltrimethoxysilane coating (thickness 1-3 μm) has the following characteristics: low surface energy, static contact angle >150°, and stable operation for >1 h under a pressure difference of 0.4 kPa.

[0029] Beneficial effects:

[0030] 1. Structural innovation and performance improvement

[0031] For the first time, photocatalytic oxidation reaction is coupled with membrane separation technology. Through the photocatalytic synergistic deoxygenation of active species such as ·OH and O2⁻, the deoxygenation rate reaches more than 95%, and the oxygen permeation rate reaches 400-800 mL / (bar·min·m²). The CNT three-dimensional network enhances the strength of the base membrane and solves the problem of PMP being brittle and easily broken under high pressure.

[0032] 2. Technological innovation and long-term stability

[0033] The electrospinning-spraying combined technology is used to achieve precise construction of functional layers and improve the interfacial bonding strength; photocatalytic adsorption and degradation of organic pollutants avoid membrane pore blockage and maintain long-term deoxygenation efficiency; PDMS / perfluorinated superhydrophobic layer protection significantly reduces pollutant adhesion.

[0034] 3. Multifunctional integrated design

[0035] Through a three-in-one design of "physical sieving-photocatalysis-superhydrophobicity", it simultaneously achieves efficient deoxygenation, self-cleaning and anti-fouling, solving the pain point of performance degradation of traditional membranes under complex working conditions. Attached Figure Description

[0036] Figure 1 Different proportions of Bi-C3N5 in this invention

[0037] Figure 2 Cross-sectional view of the composite membrane in this invention Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments.

[0039] Example 1:

[0040] Step 1): Synthesis of g-C3N5: 2.0 g of 3-amino-1,2,4-triazole (3-AT) was placed in a crucible, the lid was fully closed, and the crucible was placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min. The mixture was held at 550°C for 3 hours. After cooling to room temperature, the sample was ground for later use.

[0041] Step 2) Preparation of Bi-C3N5

[0042] Using 5 mL of nitric acid solution (1 mol / L) as a solvent, 0.058 g of bismuth nitrate pentahydrate (Bi(NO3)3 5H2O) was weighed and dissolved in it. 55 mL of ethylene glycol was added under magnetic stirring, and the mixture was stirred for 30 minutes. Then, 0.1 g of polyvinylpyrrolidone (PVP) was added, and stirring continued. Next, 0.5 g of the prepared g-C3N5 was added, and the mixture was stirred for 2 hours. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor, and the reaction was carried out at 160 °C for 12 hours. After natural cooling, the product was transferred to centrifuge tubes, and the synthesized sample was collected by centrifugation. The sample was washed multiple times with double-distilled water and anhydrous ethanol. The centrifuge used for collection and washing was set at 8000 r / min for 10 min. The resulting sample was labeled as 5%Bi-C3N5, where 5% represents the mass percentage of Bi relative to g-C3N5 in the composite.

[0043] Step 3) Preparation of spinning solution

[0044] The first spinning solution, by mass percentage, includes 5% PMP, 0.5% carbon nanotubes (CNTs), 0.1% sodium dodecyl sulfate, and the remainder is solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Sodium dodecyl sulfate and CNTs are added, and the mixture is ultrasonically dispersed for 30 minutes and then stirred for another 2 hours until completely dissolved.

[0045] The second spinning solution, by mass percentage, includes 3% PMP, 1% Bi-C3N5, and 2% PVP, with the remainder being solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Bi-C3N5 is then added, and the solution is ultrasonically dispersed for 1 hour, followed by stirring for another 2 hours until completely dissolved.

[0046] Step 4) Preparation of composite membrane

[0047] Electrospinning technology was used to spin the first spinning solution for 5 hours at a DC voltage of 15 kV, a flow rate of 1 ml / h and a receiving distance of 10 cm to form a nanofiber base film with a thickness of 180 μm and a pore size of 1 μm.

[0048] A second spinning solution was spun on the base film for 1.5 h to form a Bi-C3N5 / PMP composite film with a total film thickness of 190 μm and a pore size of 1 μm.

[0049] After cleaning and drying the obtained composite film with ethanol, a hexane solution consisting of 5% PDMS and 0.5% perfluorooctyltrimethoxysilane was sprayed onto it and cured at room temperature for 24 h to form a superhydrophobic protective layer.

[0050] The PMP composite membrane prepared by this invention achieves the following comprehensive performance through a three-level synergistic structure of "PMP / carbon nanotube reinforced support layer - Bi-C3N5 photocatalytic functional layer - PDMS superhydrophobic protective layer": deoxygenation rate ≥95.3%; oxygen permeation rate 450 ml / (bar·min·m²); stable operation for >1 h under 0.4 kPa high pressure; superhydrophobic and antifouling properties (contact angle >150°); no pore collapse under high temperature conditions above 80℃; and a long-term deoxygenation efficiency decay rate of 4%.

[0051] Example 2:

[0052] Step 1): Synthesis of g-C3N5: 2.0 g of 3-amino-1,2,4-triazole (3-AT) was placed in a crucible, the lid was fully closed, and the crucible was placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min. The mixture was held at 550°C for 3 hours. After cooling to room temperature, the sample was ground for later use.

[0053] Step 2) Preparation of Bi-C3N5

[0054] Using 5 mL of nitric acid solution (1 mol / L) as a solvent, 0.058 g of bismuth nitrate pentahydrate (Bi(NO3)3 5H2O) was weighed and dissolved in it. 55 mL of ethylene glycol was added under magnetic stirring, and the mixture was stirred for 30 minutes. Then, 0.1 g of polyvinylpyrrolidone (PVP) was added, and stirring continued. Next, 0.5 g of the prepared g-C3N5 was added, and the mixture was stirred for 2 hours. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor, and the reaction was carried out at 160 °C for 12 hours. After natural cooling, the product was transferred to centrifuge tubes, and the synthesized sample was collected by centrifugation. The sample was washed multiple times with double-distilled water and anhydrous ethanol. The centrifuge used for collection and washing was set at 8000 r / min for 10 min. The resulting sample was labeled as 5%Bi-C3N5, where 5% represents the mass percentage of Bi relative to g-C3N5 in the composite.

[0055] Step 3) Preparation of spinning solution

[0056] The first spinning solution, by mass percentage, includes 5-10% PMP, 1.5% carbon nanotubes (CNTs), 1% sodium dodecyl sulfate, and the remainder is solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Sodium dodecyl sulfate and CNTs are added, and the mixture is ultrasonically dispersed for 30 minutes and then stirred for another 2 hours until completely dissolved.

[0057] The second spinning solution, by mass percentage, includes 4% PMP, 2% Bi-C3N5, and 5% PVP, with the remainder being solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Bi-C3N5 is then added, and the solution is ultrasonically dispersed for 1 hour, followed by stirring for another 2 hours until completely dissolved.

[0058] Step 4) Preparation of composite membrane

[0059] Electrospinning technology was used to spin the first spinning solution for 7 hours at a DC voltage of 16 kV, a flow rate of 1.6 ml / h, and a receiving distance of 12 cm to form a nanofiber base film with a thickness of 185 μm and a pore size of 3 μm.

[0060] A second spinning solution was spun on the base membrane for 3 hours to form a Bi-C3N5 / PMP composite membrane with a total thickness of 200 μm and a pore size of 2 μm.

[0061] After cleaning and drying the obtained composite film with ethanol, a hexane solution consisting of 5% PDMS and 0.5% perfluorooctyltrimethoxysilane was sprayed onto it and cured at room temperature for 24 h to form a superhydrophobic protective layer.

[0062] The PMP composite membrane prepared by this invention achieves the following comprehensive performance through a three-level synergistic structure of "PMP / carbon nanotube reinforced support layer - Bi-C3N5 photocatalytic functional layer - PDMS superhydrophobic protective layer": deoxygenation rate ≥95.7%; oxygen permeation rate 600 ml / (bar·min·m²); stable operation for >1 h under 0.4 kPa high pressure; superhydrophobic and antifouling properties (contact angle >150°); no pore collapse under high temperature conditions above 80℃; and a long-term deoxygenation efficiency decay rate of 4.5%.

[0063] Example 3:

[0064] Step 1): Synthesis of g-C3N5: 2.0 g of 3-amino-1,2,4-triazole (3-AT) was placed in a crucible, the lid was fully closed, and the crucible was placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min. The mixture was held at 550°C for 3 hours. After cooling to room temperature, the sample was ground for later use.

[0065] Step 2) Preparation of Bi-C3N5

[0066] Using 5 mL of nitric acid solution (1 mol / L) as a solvent, 0.058 g of bismuth nitrate pentahydrate (Bi(NO3)3 5H2O) was weighed and dissolved in it. 55 mL of ethylene glycol was added under magnetic stirring, and the mixture was stirred for 30 minutes. Then, 0.1 g of polyvinylpyrrolidone (PVP) was added, and stirring continued. Next, 0.5 g of the prepared g-C3N5 was added, and the mixture was stirred for 2 hours. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor, and the reaction was carried out at 160 °C for 12 hours. After natural cooling, the product was transferred to centrifuge tubes, and the synthesized sample was collected by centrifugation. The sample was washed multiple times with double-distilled water and anhydrous ethanol. The centrifuge used for collection and washing was set at 8000 r / min for 10 min. The resulting sample was labeled as 5%Bi-C3N5, where 5% represents the mass percentage of Bi relative to g-C3N5 in the composite.

[0067] Step 3) Preparation of spinning solution

[0068] The first spinning solution, by mass percentage, includes 10% PMP, 2% carbon nanotubes (CNTs), 2% sodium dodecyl sulfate, and the remainder is solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Sodium dodecyl sulfate and CNTs are added, and the mixture is ultrasonically dispersed for 30 minutes and then stirred for another 2 hours until completely dissolved.

[0069] The second spinning solution, by mass percentage, includes 5% PMP, 3% Bi-C3N5, 10% PVP, with the remainder being solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Bi-C3N5 is then added, and the solution is ultrasonically dispersed for 1 hour, followed by stirring for another 2 hours until completely dissolved.

[0070] Step 4) Preparation of composite membrane

[0071] Electrospinning technology was used to spin the first spinning solution for 13 h at a DC voltage of 18 kV, a flow rate of 2 ml / h and a receiving distance of 15 cm to form a nanofiber base film with a thickness of 200 μm and a pore size of 5 μm.

[0072] A second spinning solution was spun on the base membrane for 4 hours to form a Bi-C3N5 / PMP composite membrane with a total thickness of 220 μm and a pore size of 3 μm.

[0073] After cleaning and drying the obtained composite film with ethanol, a hexane solution consisting of 5% PDMS and 0.5% perfluorooctyltrimethoxysilane was sprayed onto it and cured at room temperature for 24 h to form a superhydrophobic protective layer.

[0074] The PMP composite membrane prepared by this invention achieves the following comprehensive performance through a three-level synergistic structure of "PMP / carbon nanotube reinforced support layer - Bi-C3N5 photocatalytic functional layer - PDMS superhydrophobic protective layer": deoxygenation rate ≥95.6%; oxygen permeation rate 500 ml / (bar·min·m²); stable operation for >1 h under 0.4 kPa high pressure; superhydrophobic and antifouling properties (contact angle >150°); no pore collapse under high temperature conditions above 80℃; and a long-term deoxygenation efficiency decay rate of 4.7%.

[0075] Example 4:

[0076] Step 1): Synthesis of g-C3N5: 2.0 g of 3-amino-1,2,4-triazole (3-AT) was placed in a crucible, the lid was fully closed, and the crucible was placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min. The mixture was held at 550°C for 3 hours. After cooling to room temperature, the sample was ground for later use.

[0077] Step 2) Preparation of Bi-C3N5

[0078] Using 5 mL of nitric acid solution (1 mol / L) as a solvent, 0.035 g of bismuth nitrate pentahydrate (Bi(NO3)3 5H2O) was dissolved in it. 55 mL of ethylene glycol was added under magnetic stirring, and the mixture was stirred for 30 minutes. Then, 0.1 g of polyvinylpyrrolidone (PVP) was added, and stirring continued. Next, 0.5 g of the prepared g-C3N5 was added, and the mixture was stirred for 2 hours. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor, and the reaction was carried out at 160 °C for 12 hours. After natural cooling, the product was transferred to centrifuge tubes, and the synthesized sample was collected by centrifugation. The sample was washed multiple times with double-distilled water and anhydrous ethanol. The centrifuge used for collection and washing was set at 8000 r / min for 10 min. The resulting sample was labeled as 3%Bi-C3N5, where 3% represents the mass percentage of Bi relative to g-C3N5 in the composite.

[0079] Step 3) Preparation of spinning solution

[0080] The first spinning solution, by mass percentage, includes 5% PMP, 0.5% carbon nanotubes (CNTs), 0.1% sodium dodecyl sulfate, and the remainder is solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Sodium dodecyl sulfate and CNTs are added, and the mixture is ultrasonically dispersed for 30 minutes and then stirred for another 2 hours until completely dissolved.

[0081] The second spinning solution, by mass percentage, includes 3% PMP, 1% Bi-C3N5, and 2% PVP, with the remainder being solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Bi-C3N5 is then added, and the solution is ultrasonically dispersed for 1 hour, followed by stirring for another 2 hours until completely dissolved.

[0082] Step 4) Preparation of composite membrane

[0083] Electrospinning technology was used to spin the first spinning solution for 5 hours at a DC voltage of 15 kV, a flow rate of 1 ml / h and a receiving distance of 10 cm to form a nanofiber base film with a thickness of 180 μm and a pore size of 1 μm.

[0084] A second spinning solution was spun on the base film for 1.5 h to form a Bi-C3N5 / PMP composite film with a total film thickness of 190 μm and a pore size of 1 μm.

[0085] After cleaning and drying the obtained composite film with ethanol, a hexane solution consisting of 5% PDMS and 0.5% perfluorooctyltrimethoxysilane was sprayed onto it and cured at room temperature for 24 h to form a superhydrophobic protective layer.

[0086] The PMP composite membrane prepared by this invention achieves the following comprehensive performance through a three-level synergistic structure of "PMP / carbon nanotube reinforced support layer - Bi-C3N5 photocatalytic functional layer - PDMS superhydrophobic protective layer": deoxygenation rate ≥95.6%; oxygen permeation rate 550 ml / (bar·min·m²); stable operation for >1 h under 0.4 kPa high pressure; superhydrophobic and antifouling properties (contact angle >150°); no pore collapse under high temperature conditions above 80℃; and a long-term deoxygenation efficiency decay rate of 4.9%.

[0087] Example 5:

[0088] Step 1): Synthesis of g-C3N5: 2.0 g of 3-amino-1,2,4-triazole (3-AT) was placed in a crucible, the lid was fully closed, and the crucible was placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min. The mixture was held at 550°C for 3 hours. After cooling to room temperature, the sample was ground for later use.

[0089] Step 2) Preparation of Bi-C3N5

[0090] Using 5 mL of nitric acid solution (1 mol / L) as a solvent, 0.035 g of bismuth nitrate pentahydrate (Bi(NO3)3 5H2O) was dissolved in it. 55 mL of ethylene glycol was added under magnetic stirring, and the mixture was stirred for 30 minutes. Then, 0.1 g of polyvinylpyrrolidone (PVP) was added, and stirring continued. Next, 0.5 g of the prepared g-C3N5 was added, and the mixture was stirred for 2 hours. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor, and the reaction was carried out at 160 °C for 12 hours. After natural cooling, the product was transferred to centrifuge tubes, and the synthesized sample was collected by centrifugation. The sample was washed multiple times with double-distilled water and anhydrous ethanol. The centrifuge used for collection and washing was set at 8000 r / min for 10 min. The resulting sample was labeled as 3%Bi-C3N5, where 3% represents the mass percentage of Bi relative to g-C3N5 in the composite.

[0091] Step 3) Preparation of spinning solution

[0092] The first spinning solution, by mass percentage, includes 5-10% PMP, 1.5% carbon nanotubes (CNTs), 1% sodium dodecyl sulfate, and the remainder is solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Sodium dodecyl sulfate and CNTs are added, and the mixture is ultrasonically dispersed for 30 minutes and then stirred for another 2 hours until completely dissolved.

[0093] The second spinning solution, by mass percentage, includes 4% PMP, 2% Bi-C3N5, and 5% PVP, with the remainder being solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Bi-C3N5 is then added, and the solution is ultrasonically dispersed for 1 hour, followed by stirring for another 2 hours until completely dissolved.

[0094] Step 4) Preparation of composite membrane

[0095] Electrospinning technology was used to spin the first spinning solution for 7 hours at a DC voltage of 16 kV, a flow rate of 1.6 ml / h, and a receiving distance of 12 cm to form a nanofiber base film with a thickness of 185 μm and a pore size of 3 μm.

[0096] A second spinning solution was spun on the base membrane for 3 hours to form a Bi-C3N5 / PMP composite membrane with a total thickness of 200 μm and a pore size of 2 μm.

[0097] After cleaning and drying the obtained composite film with ethanol, a hexane solution consisting of 5% PDMS and 0.5% perfluorooctyltrimethoxysilane was sprayed onto it and cured at room temperature for 24 h to form a superhydrophobic protective layer.

[0098] The PMP composite membrane prepared by this invention achieves the following comprehensive performance through a three-level synergistic structure of "PMP / carbon nanotube reinforced support layer - Bi-C3N5 photocatalytic functional layer - PDMS superhydrophobic protective layer": deoxygenation rate ≥95.0%; oxygen permeation rate 700 ml / (bar·min·m²); stable operation for >1 h under 0.4 kPa high pressure; superhydrophobic and antifouling properties (contact angle >150°); no pore collapse under high temperature conditions above 80℃; and a long-term deoxygenation efficiency decay rate of 4.1%.

[0099] Example 6:

[0100] Step 1): Synthesis of g-C3N5: 2.0 g of 3-amino-1,2,4-triazole (3-AT) was placed in a crucible, the lid was fully closed, and the crucible was placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min. The mixture was held at 550°C for 3 hours. After cooling to room temperature, the sample was ground for later use.

[0101] Step 2) Preparation of Bi-C3N5

[0102] Using 5 mL of nitric acid solution (1 mol / L) as a solvent, 0.035 g of bismuth nitrate pentahydrate (Bi(NO3)3 5H2O) was dissolved in it. 55 mL of ethylene glycol was added under magnetic stirring, and the mixture was stirred for 30 minutes. Then, 0.1 g of polyvinylpyrrolidone (PVP) was added, and stirring continued. Next, 0.5 g of the prepared g-C3N5 was added, and the mixture was stirred for 2 hours. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor, and the reaction was carried out at 160 °C for 12 hours. After natural cooling, the product was transferred to centrifuge tubes, and the synthesized sample was collected by centrifugation. The sample was washed multiple times with double-distilled water and anhydrous ethanol. The centrifuge used for collection and washing was set at 8000 r / min for 10 min. The resulting sample was labeled as 3%Bi-C3N5, where 3% represents the mass percentage of Bi relative to g-C3N5 in the composite.

[0103] Step 3) Preparation of spinning solution

[0104] The first spinning solution, by mass percentage, includes 10% PMP, 2% carbon nanotubes (CNTs), 2% sodium dodecyl sulfate, and the remainder is solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Sodium dodecyl sulfate and CNTs are added, and the mixture is ultrasonically dispersed for 30 minutes and then stirred for another 2 hours until completely dissolved.

[0105] The second spinning solution, by mass percentage, includes 5% PMP, 3% Bi-C3N5, 10% PVP, with the remainder being solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Bi-C3N5 is then added, and the solution is ultrasonically dispersed for 1 hour, followed by stirring for another 2 hours until completely dissolved.

[0106] Step 4) Preparation of composite membrane

[0107] Electrospinning technology was used to spin the first spinning solution for 13 h at a DC voltage of 18 kV, a flow rate of 2 ml / h and a receiving distance of 15 cm to form a nanofiber base film with a thickness of 200 μm and a pore size of 5 μm.

[0108] A second spinning solution was spun on the base membrane for 4 hours to form a Bi-C3N5 / PMP composite membrane with a total thickness of 220 μm and a pore size of 3 μm.

[0109] After cleaning and drying the obtained composite film with ethanol, a hexane solution consisting of 5% PDMS and 0.5% perfluorooctyltrimethoxysilane was sprayed onto it and cured at room temperature for 24 h to form a superhydrophobic protective layer.

[0110] The PMP composite membrane prepared by this invention achieves the following comprehensive performance through a three-level synergistic structure of "PMP / carbon nanotube reinforced support layer - Bi-C3N5 photocatalytic functional layer - PDMS superhydrophobic protective layer": deoxygenation rate ≥95.1%; oxygen permeation rate 800 ml / (bar·min·m²); stable operation for >1 h under 0.4 kPa high pressure; superhydrophobic and antifouling properties (contact angle >150°); no pore collapse under high temperature conditions above 80℃; and a long-term deoxygenation efficiency decay rate of 3.9%.

[0111] Example 7:

[0112] Step 1): Synthesis of g-C3N5: 2.0 g of 3-amino-1,2,4-triazole (3-AT) was placed in a crucible, the lid was fully closed, and the crucible was placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min. The mixture was held at 550°C for 3 hours. After cooling to room temperature, the sample was ground for later use.

[0113] Step 2) Preparation of Bi-C3N5

[0114] Using 5 mL of nitric acid solution (1 mol / L) as a solvent, 0.012 g of bismuth nitrate pentahydrate (Bi(NO3)3 5H2O) was dissolved in it. 55 mL of ethylene glycol was added under magnetic stirring, and the mixture was stirred for 30 minutes. Then, 0.1 g of polyvinylpyrrolidone (PVP) was added, and stirring continued. Next, 0.5 g of the prepared g-C3N5 was added, and the mixture was stirred for 2 hours. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor, and the reaction was carried out at 160 °C for 12 hours. After natural cooling, the product was transferred to centrifuge tubes, and the synthesized sample was collected by centrifugation. The sample was washed multiple times with double-distilled water and anhydrous ethanol. The centrifuge used for collection and washing was set at 8000 r / min for 10 min. The resulting sample was labeled as 1%Bi-C3N5, where 1% represents the mass percentage of Bi relative to g-C3N5 in the composite.

[0115] Step 3) Preparation of spinning solution

[0116] The first spinning solution, by mass percentage, includes 5% PMP, 0.5% carbon nanotubes (CNTs), 0.1% sodium dodecyl sulfate, and the remainder is solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Sodium dodecyl sulfate and CNTs are added, and the mixture is ultrasonically dispersed for 30 minutes and then stirred for another 2 hours until completely dissolved.

[0117] The second spinning solution, by mass percentage, includes 3% PMP, 1% Bi-C3N5, and 2% PVP, with the remainder being solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Bi-C3N5 is then added, and the solution is ultrasonically dispersed for 1 hour, followed by stirring for another 2 hours until completely dissolved.

[0118] Step 4) Preparation of composite membrane

[0119] Electrospinning technology was used to spin the first spinning solution for 5 hours at a DC voltage of 15 kV, a flow rate of 1 ml / h and a receiving distance of 10 cm to form a nanofiber base film with a thickness of 180 μm and a pore size of 1 μm.

[0120] A second spinning solution was spun on the base film for 1.5 h to form a Bi-C3N5 / PMP composite film with a total film thickness of 190 μm and a pore size of 1 μm.

[0121] After cleaning and drying the obtained composite film with ethanol, a hexane solution consisting of 5% PDMS and 0.5% perfluorooctyltrimethoxysilane was sprayed onto it and cured at room temperature for 24 h to form a superhydrophobic protective layer.

[0122] The PMP composite membrane prepared by this invention achieves the following comprehensive performance through a three-level synergistic structure of "PMP / carbon nanotube reinforced support layer - Bi-C3N5 photocatalytic functional layer - PDMS superhydrophobic protective layer": deoxygenation rate ≥95.4%; oxygen permeation rate 470 ml / (bar·min·m²); stable operation for >1 h under 0.4 kPa high pressure; superhydrophobic and antifouling properties (contact angle >150°); no pore collapse under high temperature conditions above 80℃; and a long-term deoxygenation efficiency decay rate of 4.2%.

[0123] Example 8:

[0124] Step 1): Synthesis of g-C3N5: 2.0 g of 3-amino-1,2,4-triazole (3-AT) was placed in a crucible, the lid was fully closed, and the crucible was placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min. The mixture was held at 550°C for 3 hours. After cooling to room temperature, the sample was ground for later use.

[0125] Step 2) Preparation of Bi-C3N5

[0126] Using 5 mL of nitric acid solution (1 mol / L) as a solvent, 0.012 g of bismuth nitrate pentahydrate (Bi(NO3)3 5H2O) was dissolved in it. 55 mL of ethylene glycol was added under magnetic stirring, and the mixture was stirred for 30 minutes. Then, 0.1 g of polyvinylpyrrolidone (PVP) was added, and stirring continued. Next, 0.5 g of the prepared g-C3N5 was added, and the mixture was stirred for 2 hours. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor, and the reaction was carried out at 160 °C for 12 hours. After natural cooling, the product was transferred to centrifuge tubes, and the synthesized sample was collected by centrifugation. The sample was washed multiple times with double-distilled water and anhydrous ethanol. The centrifuge used for collection and washing was set at 8000 r / min for 10 min. The resulting sample was labeled as 1%Bi-C3N5, where 1% represents the mass percentage of Bi relative to g-C3N5 in the composite.

[0127] Step 3) Preparation of spinning solution

[0128] The first spinning solution, by mass percentage, includes 5-10% PMP, 1.5% carbon nanotubes (CNTs), 1% sodium dodecyl sulfate, and the remainder is solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Sodium dodecyl sulfate and CNTs are added, and the mixture is ultrasonically dispersed for 30 minutes and then stirred for another 2 hours until completely dissolved.

[0129] The second spinning solution, by mass percentage, includes 4% PMP, 2% Bi-C3N5, and 5% PVP, with the remainder being solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Bi-C3N5 is then added, and the solution is ultrasonically dispersed for 1 hour, followed by stirring for another 2 hours until completely dissolved.

[0130] Step 4) Preparation of composite membrane

[0131] Electrospinning technology was used to spin the first spinning solution for 7 hours at a DC voltage of 16 kV, a flow rate of 1.6 ml / h, and a receiving distance of 12 cm to form a nanofiber base film with a thickness of 185 μm and a pore size of 3 μm.

[0132] A second spinning solution was spun on the base membrane for 3 hours to form a Bi-C3N5 / PMP composite membrane with a total thickness of 200 μm and a pore size of 2 μm.

[0133] After cleaning and drying the obtained composite film with ethanol, a hexane solution consisting of 5% PDMS and 0.5% perfluorooctyltrimethoxysilane was sprayed onto it and cured at room temperature for 24 h to form a superhydrophobic protective layer.

[0134] The PMP composite membrane prepared by this invention achieves the following comprehensive performance through a three-level synergistic structure of "PMP / carbon nanotube reinforced support layer - Bi-C3N5 photocatalytic functional layer - PDMS superhydrophobic protective layer": deoxygenation rate ≥95.7%; oxygen permeation rate 400 ml / (bar·min·m²); stable operation for >1 h under 0.4 kPa high pressure; superhydrophobic and antifouling properties (contact angle >150°); no pore collapse under high temperature conditions above 80℃; and a long-term deoxygenation efficiency decay rate of 4.3%.

[0135] Example 9:

[0136] Step 1): Synthesis of g-C3N5: 2.0 g of 3-amino-1,2,4-triazole (3-AT) was placed in a crucible, the lid was fully closed, and the crucible was placed in a muffle furnace and heated to 550°C at a heating rate of 5°C / min. The mixture was held at 550°C for 3 hours. After cooling to room temperature, the sample was ground for later use.

[0137] Step 2) Preparation of Bi-C3N5

[0138] Using 5 mL of nitric acid solution (1 mol / L) as a solvent, 0.012 g of bismuth nitrate pentahydrate (Bi(NO3)3 5H2O) was dissolved in it. 55 mL of ethylene glycol was added under magnetic stirring, and the mixture was stirred for 30 minutes. Then, 0.1 g of polyvinylpyrrolidone (PVP) was added, and stirring continued. Next, 0.5 g of the prepared g-C3N5 was added, and the mixture was stirred for 2 hours. The resulting mixture was transferred to a 100 mL polytetrafluoroethylene-lined reactor, and the reaction was carried out at 160 °C for 12 hours. After natural cooling, the product was transferred to centrifuge tubes, and the synthesized sample was collected by centrifugation. The sample was washed multiple times with double-distilled water and anhydrous ethanol. The centrifuge used for collection and washing was set at 8000 r / min for 10 min. The resulting sample was labeled as 1%Bi-C3N5, where 1% represents the mass percentage of Bi relative to g-C3N5 in the composite.

[0139] Step 3) Preparation of spinning solution

[0140] The first spinning solution, by mass percentage, includes 10% PMP, 2% carbon nanotubes (CNTs), 2% sodium dodecyl sulfate, and the remainder is solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Sodium dodecyl sulfate and CNTs are added, and the mixture is ultrasonically dispersed for 30 minutes and then stirred for another 2 hours until completely dissolved.

[0141] The second spinning solution, by mass percentage, includes 5% PMP, 3% Bi-C3N5, 10% PVP, with the remainder being solvent. PMP is dissolved in the solvent and magnetically stirred at 60°C for 4 hours until transparent. Bi-C3N5 is then added, and the solution is ultrasonically dispersed for 1 hour, followed by stirring for another 2 hours until completely dissolved.

[0142] Step 4) Preparation of composite membrane

[0143] Electrospinning technology was used to spin the first spinning solution for 13 h at a DC voltage of 18 kV, a flow rate of 2 ml / h and a receiving distance of 15 cm to form a nanofiber base film with a thickness of 200 μm and a pore size of 5 μm.

[0144] A second spinning solution was spun on the base membrane for 4 hours to form a Bi-C3N5 / PMP composite membrane with a total thickness of 220 μm and a pore size of 3 μm.

[0145] After cleaning and drying the obtained composite film with ethanol, a hexane solution consisting of 5% PDMS and 0.5% perfluorooctyltrimethoxysilane was sprayed onto it and cured at room temperature for 24 h to form a superhydrophobic protective layer.

[0146] The PMP composite membrane prepared by this invention achieves the following comprehensive performance through a three-level synergistic structure of "PMP / carbon nanotube reinforced support layer - Bi-C3N5 photocatalytic functional layer - PDMS superhydrophobic protective layer": deoxygenation rate ≥95.1%; oxygen permeation rate 500 ml / (bar·min·m²); stable operation for >1 h under 0.4 kPa high pressure; superhydrophobic and antifouling properties (contact angle >150°); no pore collapse under high temperature conditions above 80℃; and a long-term deoxygenation efficiency decay rate of 4.8%.

Claims

1. A method for preparing a power plant boiler water efficient deoxidation PMP composite membrane with photocatalytic self-cleaning function, characterized in that, Includes the following steps: (1) Preparation of g-C3N5 3-Amino-1,2,4-triazole was placed in a crucible and heated to 550°C in a muffle furnace at a heating rate of 5°C / min. The temperature was maintained for 3 h, cooled to room temperature, and then ground to obtain g-C3N5 powder. (2) Preparation of Bi-C3N5 Bismuth nitrate pentahydrate, ethylene glycol, polyvinylpyrrolidone, and g-C3N5 were sequentially added to a dilute nitric acid solution and mixed with magnetic stirring. Bi-modified g-C3N5 was then synthesized via a solvothermal method. After centrifugation, washing with water and ethanol, drying, and grinding, Bi-C3N5 was obtained; the mass percentage of bismuth was 1%–5%. (3) Preparation of spinning solution The first spinning solution, by mass percentage, includes 5-10% PMP, 0.5-2% carbon nanotubes, and 0.1-2% sodium dodecyl sulfate, with the remainder being solvent. Dissolve PMP in the solvent and stir magnetically at 60°C for 4 hours until transparent. Add sodium dodecyl sulfate and carbon nanotubes, disperse ultrasonically for 30 minutes, and continue stirring for 1.5-3.5 hours until completely dissolved. The second spinning solution, by mass percentage, includes 3-5% PMP, 1-3% Bi-C3N5, 2-10% polyvinylpyrrolidone, with the remainder being solvent. Dissolve PMP in the solvent, stir magnetically at 60°C for 4 hours until transparent, add Bi-C3N5, ultrasonically disperse for 1 hour, and continue stirring for 1.5-3.5 hours until completely dissolved. (4) Preparation of composite membrane Using electrospinning technology, the first spinning solution is spun for 5-20 h at a DC voltage of 15-18 kV, a flow rate of 1-2 ml / h, and a receiving distance of 10-15 cm to form a nanofiber base film with a thickness of 180-220 μm and a pore size of 1-5 μm. A second spinning solution was spun on the base film for 1.5-4 h to form a Bi-C3N5 / PMP composite film with a total film thickness of 185-220 μm and a pore size of 1-3 μm. After cleaning and drying the obtained composite film with ethanol, a hexane solution consisting of 5% PDMS and 0.5% perfluorooctyltrimethoxysilane was sprayed onto it and cured at room temperature for 24 h to form a superhydrophobic protective layer.

2. The method for preparing the power plant boiler water efficient deoxidation PMP composite membrane with photocatalytic self-cleaning function according to claim 1, characterized in that: The solvent of the spinning solution in step (3) is one or more of acetone, ethyl acetate, dichloroethane or xylene.

3. A high-efficiency PMP composite membrane for deoxygenation of power plant boiler water with photocatalytic self-cleaning function, obtained by the preparation method according to any one of claims 1 to 2, characterized in that: Deoxygenation rate ≥95%; oxygen permeation rate 400-800 ml / (bar·min·m 2 It can operate stably for more than 1 hour under a high pressure of 0.4 kPa; it has superhydrophobic and antifouling properties with a contact angle greater than 150°; it does not collapse pores under high temperature conditions above 80℃, and the long-term deoxygenation efficiency decay rate is less than 5%.

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