A novel pH-responsive modified PTFE-based MABR membrane, a preparation method and application thereof

Abstract

The present application belongs to the technical field of functional modified membranes and membrane bioreactor, and relates to a novel pH-responsive modified PTFE-based MABR membrane and a preparation method and application thereof. The present application constructs a dynamic reversible pH-responsive cross-linked network, realizes intelligent regulation of oxygen permeability, and perfectly adapts to fluctuating conditions of printing and dyeing wastewater. The present application constructs a dense and pH-responsive dynamic cross-linked network on the membrane surface through double Schiff base reaction of aldehyde-containing compounds, amino nanoparticles and PDA transition layer; under acidic conditions, the imine bond reversibly dissociates, the cross-linking degree of the network decreases, the pore size moderately increases, and the oxygen permeation rate increases to match the oxygen supply demand under high pollution load; under neutral / alkaline conditions, the imine bond is regenerated, the network shrinks and is dense, and the oxygen permeation rate moderately decreases to adapt to low load conditions, solving the technical problems that the fixed pore size of traditional PTFE membranes cannot respond to pH fluctuations of water quality and cannot dynamically match mass transfer demand.

Description

Technical Field

[0001] This invention belongs to the field of functional modified membranes and membrane bioreactors, and relates to a novel pH-responsive modified PTFE-based MABR membrane, its preparation method, and its application. Background Technology

[0002] In the field of industrial wastewater treatment, membrane aerated biofilm reactor (MABR) technology has become a leading choice for treating recalcitrant industrial wastewater such as dyeing and printing wastewater due to its superior oxygen transfer efficiency and significant low energy consumption. As the core of this technology, the performance of the membrane material directly determines the efficiency and long-term operational stability of the treatment system. Polytetrafluoroethylene (PTFE) is considered an ideal substrate for constructing MABR membranes due to its excellent chemical inertness, high-temperature resistance, and mechanical strength.

[0003] However, the inherently strong hydrophobic surface of traditional PTFE membranes makes them highly susceptible to adsorbing dye molecules and organic pollutants from complex, high-concentration dyeing and printing wastewater. This leads to severe membrane pore blockage, decreased oxygen permeability, and consequently, increased operating and maintenance costs. More importantly, the pH value of dyeing and printing wastewater often fluctuates with the production process, and PTFE membranes with fixed pore sizes cannot dynamically adjust their oxygen permeability according to changes in water acidity or alkalinity. This static characteristic limits their adaptability to complex operating conditions.

[0004] While existing technologies attempt to improve the hydrophilicity of PTFE membranes to alleviate fouling through plasma treatment or coating modification, these modifications often result in fixed pore structures, losing their responsiveness to environmental changes. Other studies have focused on constructing pH-responsive porous coatings, but these often increase oxygen permeability resistance due to the introduction of additional porous structures, and the weak adhesion between the coating and the PTFE substrate makes it prone to peeling and failure under long-term operation. Therefore, maintaining high oxygen permeability and structural stability of a dense coating while ensuring the membrane material's pH responsiveness has become a pressing technical bottleneck. Developing a PTFE-based MABR membrane with a pH-responsive dense coating, dynamically adjustable oxygen permeability, and strong antifouling capabilities would not only overcome the limitations of existing technologies but also provide solid technical support and broad prospects for the large-scale application of MABR technology in the complex and ever-changing field of industrial wastewater treatment.

[0005] Chinese patent application document (CN108905649A) discloses a method for preparing a hydrophilic polytetrafluoroethylene microfiltration membrane. This method achieves hydrophilic modification of PTFE membrane by increasing the concentration of L-dopamine with surfactants and simple curing crosslinking. However, it can only improve the basic hydrophilic properties and shorten the modification time. It has defects such as single function, lack of intelligent responsiveness, and lack of nano-reinforced dense layer. It cannot be adapted to high-end and complex working conditions such as MABR. It is only suitable for conventional filtration scenarios, and its technical level and application value are limited. Summary of the Invention

[0006] To address the shortcomings of the prior art, this invention aims to provide a novel method for preparing a pH-responsive modified PTFE-based MABR membrane. Through a mild surface covalent modification process, a novel MABR membrane with resistance to biofouling, pH-responsive flux regulation, and high air permeability stability is obtained. This method can significantly improve the long-term operating efficiency of the MABR reactor, reduce operation and maintenance costs, and can be effectively applied in the field of recalcitrant industrial wastewater treatment.

[0007] One objective of this invention can be achieved through the following technical solutions: A novel method for preparing a pH-responsive modified PTFE-based MABR membrane, the method comprising the following steps: S1. A modified membrane containing active groups is obtained by immersing a polytetrafluoroethylene membrane in a Tris-HCl buffer solution containing dopamine hydrochloride and a hydrophilic crosslinking compound. S2. Disperse aldehyde-containing hydrophilic compounds and amino-modified nanoparticles in a solvent to obtain a reaction precursor solution; S3. The modified membrane containing active groups from step S1 is immersed in the reaction precursor solution from step S2 to obtain an intermediate membrane. Finally, the intermediate membrane is washed and dried to obtain a novel pH-responsive modified PTFE-based MABR membrane.

[0008] In the above-mentioned method for preparing a novel pH-responsive modified PTFE-based MABR membrane, in step S1, the hydrophilic crosslinking compound is at least one of polyethyleneimine, sodium alginate, and polyacrylic acid.

[0009] In the above-mentioned method for preparing a novel pH-responsive modified PTFE-based MABR membrane, in step S1, the content of dopamine hydrochloride in the Tris-HCl buffer aqueous solution is 0.5-5 g / L, and the content of the hydrophilic crosslinking compound is 0.5-5 g / L.

[0010] Preferably, the mass ratio of dopamine hydrochloride to the hydrophilic crosslinking compound is 2:1 to 1:2.

[0011] In the above-mentioned method for preparing a novel pH-responsive modified PTFE-based MABR membrane, the pH of the Tris-HCl buffer solution is 8-9, and the Tris-HCl content is 5-15 mmol / L.

[0012] In the above-mentioned method for preparing a novel pH-responsive modified PTFE-based MABR membrane, in step S2, the aldehyde-containing hydrophilic compound is at least one of oxidized hyaluronic acid, poly(vinylbenzaldehyde), dialdehyde polyethylene glycol, and polyacrylaldehyde.

[0013] The aldehyde-containing hydrophilic compound in this invention provides excellent and stable hydrophilicity to PTFE membranes, effectively improving the wettability of the membrane surface. Furthermore, the aldehyde groups on its molecules provide key reactive sites for the system, serving as the core unit for constructing the pH-responsive functional structure. It also acts as a bridge molecule to achieve covalent bonding and stable cross-linking of various functional layers on the membrane surface. This aldehyde-containing hydrophilic compound can covalently bond and polymerize with active sites such as amino and phenolic hydroxyl groups in the dopamine active layer, firmly anchoring the functional layer to the membrane substrate and enhancing the stability of the surface structure. Simultaneously, it can react with the amino groups on the surface of amino nanoparticles, synergistically constructing a dense pH-responsive functional layer. This gives the membrane material a comprehensive advantage of hydrophilicity, antifouling, structural stability, and intelligent pH response, making it suitable for applications in the MABR field.

[0014] In the above-mentioned method for preparing a novel pH-responsive modified PTFE-based MABR membrane, in step S2, the average particle size of the amino-modified nanoparticles is 50-150 nm.

[0015] In the above-mentioned method for preparing a novel pH-responsive modified PTFE-based MABR membrane, in step S2, the mass ratio of the aldehyde-containing hydrophilic compound to the amino-modified nanoparticles is (2:1)-(1:3).

[0016] In the above-mentioned method for preparing a novel pH-responsive modified PTFE-based MABR membrane, the amino-modified nanoparticles are prepared by surface modification with γ-aminopropyltriethoxysilane using inorganic nanoparticles as the substrate; wherein the inorganic nanoparticles include at least one of silica nanoparticles, silicon carbide nanoparticles, and montmorillonite nanoparticles.

[0017] In the above-mentioned method for preparing a novel pH-responsive modified PTFE-based MABR membrane, in step S2, the solvent is a mixture of organic solvent and water in a volume ratio of 1:(0.5-1.5), wherein the organic solvent includes at least one of methanol, ethanol, and propylene glycol.

[0018] The second objective of this invention is achieved through the following technical solution: A novel MABR membrane is prepared by the above-described method for preparing a novel pH-responsive modified PTFE-based MABR membrane.

[0019] Preferably, the MABR membrane has a dense structure coating.

[0020] Preferably, the MABR membrane is pH responsive, and under acidic conditions, H + Attacking the nitrogen atom of the imine bond causes it to break through hydrolysis. This reduces the network cross-linking degree, increases the pore size, and increases oxygen permeability; under alkaline conditions, OH... - The water produced in the absorption reaction is absorbed, and the nucleophilic addition of amines to aldehydes is promoted, driving the reaction toward the formation of imine bonds. Increased network crosslinking leads to structural shrinkage, reduced pore size, and decreased oxygen permeability.

[0021] Preferably, the initial oxygen flux of the MABR membrane is ≥10.5 L / (m²). 3 ·h); Further optimization revealed that the prepared pH-responsive MABR membrane exhibited an oxygen flux of 4.6 gO under neutral conditions at pH=7. 2 / (m 2 ·h), under acidic conditions at pH=5, the oxygen flux can reach 6.2 g O. 2 / (m 2 The oxygen flux was increased by approximately 34.8% under neutral conditions (·h); under alkaline conditions (pH=9), the oxygen flux decreased to 2.9 g / (m³). 2 The pH value decreased by approximately 37% compared to neutral conditions, demonstrating a significant pH-responsive permeability. Further optimization was carried out using high COD dyeing and printing wastewater of 650 mg / L as the treatment target. A MABR experimental system with four compartments containing anaerobic and aerobic compartments was built. After 15 days of continuous operation, it was found that the MABR achieved a COD removal efficiency of 95% (effluent COD of only 12.99 ± 1.56 mg / L), which was much higher than the control system without MABR (55.6%).

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention breaks through the barriers to modifying inert PTFE substrates, simultaneously achieving strong adhesion hydrophilic modification and improved antifouling performance. Through the synergistic co-deposition of dopamine and hydrophilic crosslinking compounds, this invention constructs a highly active hydrophilic transition layer rich in amino and phenolic hydroxyl groups on the surface of a strongly hydrophobic PTFE hollow fiber membrane in one step. This not only overcomes the industry pain point of difficulty in covalent grafting onto inert PTFE surfaces, but also achieves chemical bonding between the functional layer and the substrate through subsequent double Schiff base covalent crosslinking, completely avoiding the problem of easy detachment during long-term operation of traditional coating modifications.

[0023] 2. This invention constructs a dynamic, reversible pH-responsive crosslinking network, achieving intelligent regulation of oxygen permeability and perfectly adapting to fluctuating conditions in dyeing and printing wastewater. Through a dual Schiff base reaction involving aldehyde-containing compounds, amino nanoparticles, and a PDA transition layer, this invention constructs a dense, pH-responsive dynamic crosslinking network on the membrane surface. Under acidic conditions, the imine bonds reversibly dissociate, reducing the network crosslinking degree and moderately increasing the pore size, thus improving oxygen permeability to match the oxygen supply requirements under high pollution loads. Under neutral / alkaline conditions, the imine bonds recombine, causing the network to shrink and become denser, moderately reducing the oxygen permeability to adapt to low-load conditions. This solves the technical problem of traditional PTFE membranes with fixed pore sizes being unable to respond to pH fluctuations and dynamically match mass transfer requirements.

[0024] 3. This invention achieves a synergistic balance between high oxygen permeability, structural stability, and pH responsiveness, overcoming the performance bottlenecks of existing modification technologies. The modified membrane prepared by this invention fully retains the excellent mechanical strength and chemical stability of the PTFE substrate, with a tensile strength at break ≥450N, and can withstand the complex water quality of dyeing and printing wastewater and long-term hydraulic scouring; the dense Schiff base cross-linked functional layer does not introduce additional oxygen permeability resistance, and the initial oxygen permeability flux is ≥9.2L / (m²). 2 The covalently cross-linked network structure gives the membrane excellent cycling response stability, and it can maintain stable response performance even after multiple pH cycles. This solves the inherent contradiction in the prior art that porous coatings increase oxygen permeability resistance and dense coatings cannot achieve response regulation.

[0025] 4. This invention combines excellent biocompatibility with advanced water treatment efficiency, making it precisely suited for dyeing and printing wastewater treatment scenarios. The modified membrane surface of this invention is hydrophilic and contains no antibacterial components, enabling the formation of a stable dissolved oxygen gradient on the membrane surface under bubble-free oxygen supply conditions. This spontaneously constructs a functional biofilm with an aerobic-anoxic-anaerobic stratified structure. Through the synergistic metabolic action of different functional microorganisms, it achieves simultaneous and efficient removal of azo dyes from dyeing and printing wastewater, including decolorization and ring-opening, aromatic hydrocarbon chain breaking and detoxification, and the simultaneous removal of COD and ammonia nitrogen. Simultaneously, the improved antifouling performance significantly extends the membrane's cleaning cycle and service life, substantially reducing the operation and maintenance costs of the MABR system. 5. The preparation process of this invention is mild and controllable, and the raw materials are universal and readily available, possessing excellent prospects for industrial scale-up. This invention employs room temperature / low temperature liquid-phase reaction throughout, eliminating the need for complex equipment and harsh conditions such as plasma and high-temperature sintering. The reaction conditions are mild and do not damage the original microporous permeable structure of the PTFE substrate. The process parameters at each step are highly controllable, exhibiting good batch stability. All raw materials used are industrially available reagents, ensuring cost control. It can be directly adapted to existing large-scale production lines for hollow fiber membranes, facilitating industrial mass production and widespread application. Attached Figure Description

[0026] Figure 1The flowchart for the preparation of the novel pH-responsive modified PTFE-based MABR membrane in Example 1 of this invention is as follows: 1. Tris-HCl buffer aqueous solution of dopamine hydrochloride and hydrophilic crosslinking compound; 2. Mixture of aldehyde hydrophilic compound and amino-modified nanoparticles.

[0027] Figure 2 This is a schematic diagram of the structure of the novel pH-responsive modified PTFE-based MABR membrane prepared in Example 1 of the present invention; 1. PTFE base membrane; 2. Active layer; 3. pH-responsive layer. Detailed Implementation

[0028] The invention will be more fully understood by reading the following detailed description. However, it should be understood that the detailed description disclosed below is merely exemplary of the invention, which can be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as a representative basis for teaching those skilled in the art to employ the invention in different ways in any suitable detailed embodiment.

[0029] The present invention is further illustrated below by way of examples, but the invention is not limited to the scope of the examples described. All reagents and raw materials used in the following examples are commercially available, and test methods not specifically specified are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0030] Example 1: S1, according to Figure 1 As shown, the cleaned PTFE membrane (purchased from Zhejiang Jingyuan Membrane Technology Co., Ltd.) was immersed in 100 ml of Tris-HCl (10 mmol / L) buffer solution with a pH of 8.5 containing 0.5 g of dopamine hydrochloride and 0.5 g of polyethyleneimine. The mixture was magnetically stirred at room temperature for 6 h, and then rinsed three times with pure water to remove unpolymerized monomers, thus obtaining a hydrophilic modified base membrane with uniformly loaded anchor points on the surface. S2. 3g of silica nanoparticles were ultrasonically washed with 50ml of acetone and 50ml of ethanol for 10min each to remove surface oil, then rinsed with distilled water and dried at 120℃. Next, the treated particles were dispersed in 100ml of anhydrous ethanol, and then 3ml of APTES was added. The mixture was stirred and reacted in a 70℃ oil bath for 12h. After the reaction was complete, the supernatant was removed by centrifugation, and the unreacted APTES was repeatedly washed with ethanol. Finally, the mixture was vacuum dried at 60℃ until completely dry to obtain amino-modified silica nanoparticles with an average particle size of 120nm. S3. Disperse 1g of oxidized hyaluronic acid (purchased from Aladdin Company) and 0.5g of the amino-modified silica nanoparticles described in step S2 in 100ml of a 1:1 ethanol / water compound solvent, stir at room temperature for 30min to fully pre-disperse, and prepare a uniform and stable two-component reaction precursor solution. S4. Immerse the hydrophilic modified base film from step S1 into the reaction precursor solution from step S3, and stir magnetically at 30°C for 2 hours to achieve high-strength covalent anchoring of nanoparticles, thereby obtaining an intermediate film with stable cross-linking function. S5. The intermediate membrane is repeatedly rinsed 5 times with deionized water to remove free particles and unreacted small molecules, and then dried and cured at 60°C to finally obtain the final product. Figure 2 The diagram shows a smart modified PTFE functional separation membrane with stable covalent bonding and pH-responsive properties.

[0031] The modified pH-responsive MABR membrane was tested and found to have an initial oxygen flux of 12.3 L / m³. 3 Using high COD dyeing and printing wastewater of 650 mg / L as the treatment target, a MABR experimental system with four compartments containing anaerobic and aerobic compartments was built. After 15 days of continuous operation, it was found that the MABR achieved a COD removal efficiency of 95% (effluent COD of only 32.5 mg / L), which was much higher than the control system without MABR (55.6%).

[0032] Example 2:

[0033] S1. The cleaned PTFE membrane (purchased from Zhejiang Jingyuan Membrane Technology Co., Ltd.) was immersed in 100 ml of Tris-HCl (10 mmol / L) buffer solution with a pH of 8.5 containing 1.0 g of dopamine hydrochloride and 1.0 g of polyethyleneimine. The mixture was magnetically stirred at room temperature for 6 h. The membrane was rinsed three times with pure water to remove unpolymerized monomers, and a hydrophilic modified base membrane with uniformly loaded anchor points on the surface was obtained. S2. 3g of silica nanoparticles were ultrasonically washed with 50ml of acetone and 50ml of ethanol for 10min each to remove surface oil, then rinsed with distilled water and dried at 120℃. Next, the treated particles were dispersed in 100ml of anhydrous ethanol, and then 3ml of APTES was added. The mixture was stirred and reacted in a 70℃ oil bath for 12h. After the reaction was complete, the supernatant was removed by centrifugation, and the unreacted APTES was repeatedly washed with ethanol. Finally, the mixture was vacuum dried at 60℃ until completely dry to obtain amino-modified silica nanoparticles with an average particle size of 120nm. S3. Disperse 1.5g of poly(vinylbenzaldehyde) and 1.5g of the amino-modified silica nanoparticles described in step S2 in 100ml of a 1:1 ethanol / water compound solvent, stir at room temperature for 30min to fully pre-disperse, and prepare a uniform and stable two-component reaction precursor solution. S4. Immerse the hydrophilic modified base film from step S1 into the reaction precursor solution from step S3, and stir magnetically at 30°C for 2 hours to achieve high-strength covalent anchoring of nanoparticles, thereby obtaining an intermediate film with stable cross-linking function. S5. The intermediate membrane is repeatedly rinsed with deionized water 5 times to remove free particles and unreacted small molecules, and then dried and cured at 60°C to finally obtain a smart modified PTFE functional separation membrane with stable covalent bonding and pH response characteristics.

[0034] The modified pH-responsive MABR membrane was tested and found to have an initial oxygen flux of 13.4 L / m³. 3 Using high COD dyeing and printing wastewater of 650 mg / L as the treatment target, a MABR experimental system with four compartments containing anaerobic and aerobic compartments was built. After 15 days of continuous operation, it was found that the MABR achieved a COD removal efficiency of 97% (effluent COD of only 19.5 mg / L), which was much higher than the control system without MABR (56.5%).

[0035] Example 3: S1. The cleaned PTFE membrane (purchased from Zhejiang Jingyuan Membrane Technology Co., Ltd.) was immersed in 100 ml of Tris-HCl (10 mmol / L) buffer solution with a pH of 8.5 containing 2.0 g of dopamine hydrochloride and 2.0 g of polyethyleneimine. The mixture was magnetically stirred at room temperature for 6 h. The membrane was rinsed three times with pure water to remove unpolymerized monomers, and a hydrophilic modified base membrane with uniformly loaded anchor points on the surface was obtained. S2. 3g of silicon carbide nanoparticles were ultrasonically washed with 50ml of acetone and 50ml of ethanol for 10min each to remove surface oil, then rinsed with distilled water and dried at 120℃. Next, the treated particles were dispersed in 100ml of anhydrous ethanol, and then 3ml of APTES was added. The mixture was stirred and reacted in an oil bath at 70℃ for 12h. After the reaction was completed, the supernatant was removed by centrifugation, and the unreacted APTES was repeatedly washed with ethanol. Finally, the mixture was vacuum dried at 60℃ until completely dry to obtain amino-modified silicon carbide nanoparticles with an average particle size of 120nm. S3. Disperse 1.0g of dialdehyde polyethylene glycol (purchased from Aladdin Company) and 1.5g of amino-modified silicon carbide nanoparticles described in step S2 in 100ml of ethanol / water 1:1 compound solvent, stir at room temperature for 30min to fully pre-disperse, and prepare a uniform and stable two-component reaction precursor solution. S4. Immerse the hydrophilic modified base film from step S1 into the reaction precursor solution from step S3, and stir magnetically at 30°C for 2 hours to achieve high-strength covalent anchoring of nanoparticles, thereby obtaining an intermediate film with stable cross-linking function. S5. The intermediate membrane is repeatedly rinsed with deionized water 5 times to remove free particles and unreacted small molecules, and then dried and cured at 60°C to finally obtain a smart modified PTFE functional separation membrane with stable covalent bonding and pH response characteristics.

[0036] The modified pH-responsive MABR membrane was tested and found to have an initial oxygen flux of 14.1 L / m³. 3 Using high COD dyeing and printing wastewater of 650 mg / L as the treatment target, a MABR experimental system with four compartments containing anaerobic and aerobic compartments was built. After 15 days of continuous operation, it was found that the COD removal efficiency of MABR reached 96% (only 26.2 mg / L in the effluent), which was much higher than that of the control system without MABR (55.7%).

[0037] Example 4: S1. The cleaned PTFE membrane (purchased from Zhejiang Jingyuan Membrane Technology Co., Ltd.) was immersed in 100 ml of Tris-HCl (10 mmol / L) buffer solution with a pH of 8.5 containing 3.5 g of dopamine hydrochloride and 3.5 g of polyethyleneimine. The mixture was magnetically stirred at room temperature for 7 h. The membrane was rinsed three times with pure water to remove unpolymerized monomers, and a hydrophilic modified base membrane with uniformly loaded anchor points on the surface was obtained. S2. 3g of silicon carbide nanoparticles were ultrasonically washed with 50ml of acetone and 50ml of ethanol for 10min each to remove surface oil, then rinsed with distilled water and dried at 120℃. Next, the treated particles were dispersed in 100ml of anhydrous ethanol, and then 3ml of APTES was added. The mixture was stirred and reacted in an oil bath at 70℃ for 12h. After the reaction was completed, the supernatant was removed by centrifugation, and the unreacted APTES was repeatedly washed with ethanol. Finally, the mixture was vacuum dried at 60℃ until completely dry to obtain amino-modified silicon carbide nanoparticles with an average particle size of 120nm. S3. Disperse 2g of polyacrylaldehyde and 2.0g of amino-modified silicon carbide nanoparticles described in step S2 in 100ml of a 1:1 ethanol / water compound solvent, stir at room temperature for 30min to fully pre-disperse, and prepare a uniform and stable two-component reaction precursor solution. S4. Immerse the hydrophilic modified base film from step S1 into the reaction precursor solution from step S3, and stir magnetically at 45°C for 2 hours to achieve high-strength covalent anchoring of nanoparticles, thereby obtaining an intermediate film with stable cross-linking function. S5. The intermediate membrane is repeatedly rinsed with deionized water 5 times to remove free particles and unreacted small molecules, and then dried and cured at 60°C to finally obtain a smart modified PTFE functional separation membrane with stable covalent bonding and pH response characteristics.

[0038] The modified pH-responsive MABR membrane was tested and found to have an initial oxygen flux of 12.3 L / m³. 3Using high COD dyeing and printing wastewater of 650 mg / L as the treatment target, a MABR experimental system with four compartments containing anaerobic and aerobic compartments was built. After 15 days of continuous operation, it was found that the MABR achieved a COD removal efficiency of 95% (effluent COD of only 12.99 mg / L), which was much higher than the control system without MABR (57.2%).

[0039] Example 5: S1. The cleaned PTFE membrane (purchased from Zhejiang Jingyuan Membrane Technology Co., Ltd.) was immersed in 100 ml of Tris-HCl (10 mmol / L) buffer solution with a pH of 8.5 containing 4.5 g of dopamine hydrochloride and 4.5 g of polyethyleneimine. The mixture was magnetically stirred at room temperature for 8 h. The membrane was rinsed three times with pure water to remove unpolymerized monomers, and a hydrophilic modified base membrane with uniformly loaded anchor points on the surface was obtained. S2. 3g of montmorillonite nanoparticles were ultrasonically washed with 50ml of acetone and 50ml of ethanol for 10min each to remove surface oil, then rinsed with distilled water and dried at 120℃. Next, the treated particles were dispersed in 100ml of anhydrous ethanol, and then 3ml of APTES was added. The mixture was stirred and reacted in a 70℃ oil bath for 12h. After the reaction was complete, the supernatant was removed by centrifugation, and the unreacted APTES was repeatedly washed with ethanol. Finally, the mixture was vacuum dried at 60℃ until completely dry to obtain amino-modified montmorillonite nanoparticles with an average particle size of 100nm. S3. Disperse 2.5g of oxidized hyaluronic acid and 2.5g of amino-modified montmorillonite nanoparticles from step S2 in 100ml of a 1:1 ethanol / water compound solvent, stir at room temperature for 30min to fully pre-disperse, and prepare a uniform and stable two-component reaction precursor solution. S4. Immerse the hydrophilic modified base film from step S1 into the reaction precursor solution from step S3, and stir magnetically at 30°C for 2 hours to achieve high-strength covalent anchoring of nanoparticles, thereby obtaining an intermediate film with stable cross-linking function. S5. The intermediate membrane is repeatedly rinsed with deionized water 5 times to remove free particles and unreacted small molecules, and then dried and cured at 60°C to finally obtain a smart modified PTFE functional separation membrane with stable covalent bonding and pH response characteristics.

[0040] The modified pH-responsive MABR membrane was tested and found to have an initial oxygen flux of 12.7 L / m³. 3 Using high COD dyeing and printing wastewater of 650 mg / L as the treatment target, a MABR experimental system with four compartments containing anaerobic and aerobic compartments was built. After 15 days of continuous operation, it was found that the COD removal efficiency of MABR reached 96% (only 25.8 mg / L in the effluent), which was much higher than that of the control system without MABR (58.2%).

[0041] Example 6: S1. The cleaned PTFE membrane (purchased from Zhejiang Jingyuan Membrane Technology Co., Ltd.) was immersed in 100ml of Tris-HCl (10mmol / L) buffer solution with a pH of 8.5 containing 5g of dopamine hydrochloride and 5g of polyacrylic acid. The mixture was magnetically stirred at room temperature for 6h. The membrane was rinsed three times with pure water to remove unpolymerized monomers, and a hydrophilic modified base membrane with uniformly loaded anchor points on the surface was obtained. S2. 3g of montmorillonite nanoparticles were ultrasonically washed with 50ml of acetone and 50ml of ethanol for 10min each to remove surface oil, then rinsed with distilled water and dried at 120℃. Next, the treated particles were dispersed in 100ml of anhydrous ethanol, and then 3ml of APTES was added. The mixture was stirred and reacted in a 70℃ oil bath for 12h. After the reaction was complete, the supernatant was removed by centrifugation, and the unreacted APTES was repeatedly washed with ethanol. Finally, the mixture was vacuum dried at 60℃ until completely dry to obtain amino-modified montmorillonite nanoparticles with an average particle size of 100nm. S3. Disperse 3.0g of polyacrylaldehyde and 3.0g of amino-modified montmorillonite nanoparticles from step S2 in 100ml of a 1:1 ethanol / water mixture and stir at room temperature for 30min to fully pre-disperse them, thus preparing a uniform and stable two-component reaction precursor solution. S4. Immerse the hydrophilic modified base film from step S1 into the reaction precursor solution from step S3, and stir magnetically at 30°C for 2 hours to achieve high-strength covalent anchoring of nanoparticles, thereby obtaining an intermediate film with stable cross-linking function. S5. The intermediate membrane is repeatedly rinsed with deionized water 5 times to remove free particles and unreacted small molecules, and then dried and cured at 60°C to finally obtain a smart modified PTFE functional separation membrane with stable covalent bonding and pH response characteristics.

[0042] The modified pH-responsive MABR membrane was tested and found to have an initial oxygen flux of 13.5 L / m³. 3 Using high COD dyeing and printing wastewater of 650 mg / L as the treatment target, a MABR experimental system with four compartments containing anaerobic and aerobic compartments was built. After 15 days of continuous operation, it was found that the COD removal efficiency of MABR reached 97% (only 19.3 mg / L in the effluent), which was much higher than that of the control system without MABR (57.7%).

[0043] Comparative Example 1: The only difference from Example 1 is that oxidized hyaluronic acid was not added in step S3.

[0044] When aldehyde-free hydrophilic compounds are added, the dopamine active layer and amino nanoparticles will lack a key reaction bridge, and a stable Schiff base covalent cross-linked structure cannot be formed. At the same time, a continuous and dense pH-responsive functional network cannot be constructed on the membrane surface. It can only rely on the weak physical adsorption and hydrogen bonding between dopamine and amino nanoparticles. The interlayer binding force is extremely weak, and the overall surface structure is loose and easy to fall off.

[0045] Comparative Example 2: The difference from Example 1 is that in step S3, 0.1g of oxidized hyaluronic acid (purchased from Aladdin) and 0.5g of the amino-modified silica nanoparticles described in step S2 are dispersed in 100ml of a 1:1 ethanol / water compound solvent.

[0046] When the amount of aldehyde hydrophilic compound added is too small, there are insufficient aldehyde active sites in the system to participate in the reaction. On the one hand, it cannot fully covalently bond and polymerize with the dopamine active layer, resulting in a significant decrease in the anchoring strength of the functional layer on the membrane substrate. On the other hand, it is also difficult to fully form a stable Schiff base structure with amino nanoparticles, which will cause a large number of amino nanoparticles to fail to bond effectively and thus detach and aggregate, ultimately forming a discontinuous, loose and defective surface structure on the membrane surface.

[0047] Comparative Example 3: The difference from Example 1 is that in step S3, 5g of oxidized hyaluronic acid (purchased from Aladdin Company) and 0.5g of the amino-modified silica nanoparticles described in step S2 are dispersed in 100ml of a 1:1 ethanol / water compound solvent.

[0048] When too much aldehyde hydrophilic compound is added, a large number of unreacted free aldehyde groups will exist in the system. On the one hand, they are prone to excessive cross-linking and polymerization with the dopamine active layer, resulting in an excessively thick and uneven cross-linked layer on the membrane surface, which can easily block the pores of the PTFE membrane. On the other hand, excessive aldehyde groups will cause the amino nanoparticles to be over-coated and wrapped, resulting in severe aggregation between particles. They cannot form a uniform and dense pH-responsive functional layer on the membrane surface, but instead cause an increase in surface structural defects and a decrease in binding stability.

[0049] Comparative Example 4: The only difference from Example 1 is that step S1 modification was not performed, and the original PTFE membrane was directly immersed in the reaction precursor solution.

[0050] If a dopamine active layer is not pre-constructed on the PTFE membrane surface, due to the extremely inert nature of the PTFE surface and the absence of any active reaction sites, neither aldehyde hydrophilic compounds nor amino nanoparticles can achieve effective covalent anchoring on the membrane surface. They can only adhere to the membrane surface through weak physical adsorption. Under this modification method, the improvement effect on the hydrophilicity of the membrane is extremely poor and extremely unstable, and the surface substances will be quickly lost in water flow or acidic or alkaline environments.

[0051] The initial oxygen flux of the membranes prepared in Examples 1-6 and Comparative Examples 1-5 was tested. A MABR experimental system with four compartments containing anaerobic and aerobic components was built using 650 mg / L high COD dyeing and printing wastewater as the treatment object. The COD removal efficiency was tested after 15 days of continuous operation.

[0052] Table 1: Performance test results of membranes prepared in Examples 1-6 and Comparative Examples 1-4

[0053] In summary, this invention constructs a dynamic and reversible pH-responsive crosslinking network, achieving intelligent regulation of oxygen permeability and perfectly adapting to fluctuating conditions in dyeing and printing wastewater. This invention utilizes a dual Schiff base reaction between aldehyde-containing compounds, amino nanoparticles, and a PDA transition layer to construct a dense, pH-responsive dynamic crosslinking network on the membrane surface. Under acidic conditions, the imine bonds reversibly dissociate, reducing the network crosslinking degree and moderately increasing the pore size, thus improving oxygen permeability to match the oxygen supply requirements under high pollution loads. Under neutral / alkaline conditions, the imine bonds recombine, causing the network to shrink and become denser, moderately reducing the oxygen permeability to adapt to low-load conditions. This solves the technical problem of traditional PTFE membranes with fixed pore sizes being unable to respond to pH fluctuations and dynamically match mass transfer requirements.

[0054] The embodiments herein cover any points not exhaustively within the scope of the technical claims of this invention, as well as new technical solutions formed by equivalent substitutions of one or more technical features in the embodiments. These are all within the scope of the claims of this invention. Furthermore, in all listed or unlisted embodiments of this invention, each parameter in the same embodiment merely represents an instance (i.e., a feasible solution) of its technical solution, and there is no strict coordination or limitation relationship between the parameters. The parameters can be substituted for each other without violating axioms and the claims of this invention, unless otherwise stated.

[0055] The technical means disclosed in this invention are not limited to those described above, but also include technical solutions composed of any combination of the above technical features. The above descriptions are specific embodiments of this invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

[0056] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for preparing a novel pH-responsive modified PTFE-based MABR membrane, characterized in that, The method includes the following steps: S1. A modified membrane containing active groups is obtained by immersing a polytetrafluoroethylene membrane in a Tris-HCl buffer solution containing dopamine hydrochloride and a hydrophilic crosslinking compound. S2. Disperse aldehyde-containing hydrophilic compounds and amino-modified nanoparticles in a solvent to obtain a reaction precursor solution; S3. The modified membrane containing active groups from step S1 is immersed in the reaction precursor solution from step S2 to obtain an intermediate membrane. Finally, the intermediate membrane is washed and dried to obtain a novel pH-responsive modified PTFE-based MABR membrane.

2. The method for preparing a novel pH-responsive modified PTFE-based MABR membrane according to claim 1, characterized in that, In step S1, the hydrophilic crosslinking compound is at least one of polyethyleneimine, sodium alginate, and polyacrylic acid.

3. The method for preparing a novel pH-responsive modified PTFE-based MABR membrane according to claim 1, characterized in that, In step S1, the content of dopamine hydrochloride in the Tris-HCl buffer solution is 0.5-5 g / L, and the content of the hydrophilic crosslinking compound is 0.5-5 g / L.

4. The method for preparing a novel pH-responsive modified PTFE-based MABR membrane according to claim 1, characterized in that, The pH of the Tris-HCl buffer solution is 8-9, and the Tris-HCl content is 5-15 mmol / L.

5. The method for preparing a novel pH-responsive modified PTFE-based MABR membrane according to claim 1, characterized in that, In step S2, the aldehyde-containing hydrophilic compound is at least one of oxidized hyaluronic acid, poly(vinylbenzaldehyde), dialdehyde polyethylene glycol, and polyacrylaldehyde.

6. The method for preparing a novel pH-responsive modified PTFE-based MABR membrane according to claim 1, characterized in that, In step S2, the mass ratio of the aldehyde-containing hydrophilic compound to the amino-modified nanoparticles is (2:1)-(1:3).

7. The method for preparing a novel pH-responsive modified PTFE-based MABR membrane according to claim 6, characterized in that, Amino-modified nanoparticles are prepared by surface modification of inorganic nanoparticles with γ-aminopropyltriethoxysilane; wherein the inorganic nanoparticles include at least one of silica nanoparticles, silicon carbide nanoparticles and montmorillonite nanoparticles.

8. The method for preparing a novel pH-responsive modified PTFE-based MABR membrane according to claim 1, characterized in that, In step S2, the solvent is a mixture of organic solvent and water in a volume ratio of 1:(0.5-1.5), wherein the organic solvent includes at least one of methanol, ethanol, and propylene glycol.

9. A novel pH-responsive modified PTFE-based MABR membrane, characterized in that, The novel pH-responsive modified PTFE-based MABR membrane is prepared by the method described in any one of claims 1-8.

10. The application of a novel pH-responsive modified PTFE-based MABR membrane as described in claim 9 in the treatment of recalcitrant industrial wastewater.

Images