Confined-range conductive composite film, preparation method thereof and electrochemical method for in-situ hydrolysis of extracellular polymeric substance based on confined-range conductive composite film

Abstract

The invention provides a confinement conductive composite membrane, a preparation method thereof and an electrochemical method for in-situ hydrolysis of extracellular polymeric substances based on the confinement conductive composite membrane, and relates to the technical field of sewage treatment. The confinement conductive composite membrane comprises an ultrafiltration membrane carrier and a conductive layer formed on the surface of the ultrafiltration membrane carrier, the conductive layer is made of a carbon nano tube material, and at least one of nano Ni, Co, Fe and Mo catalysts is selectively loaded on the inner wall of a hollow tube or between two-dimensional layers of the carbon nano tube material. The structure effectively prevents agglomeration and loss of the catalyst through a confinement effect, and the dispersity and stability of the catalyst are improved; meanwhile, a continuous conductive network formed by the carbon nanotubes has excellent electron transmission capability, and electrons can be quickly transmitted to catalytic active sites. When the composite membrane is used as a cathode to work, the loaded nano-metal catalyst can remarkably reduce the overpotential of hydrogen evolution reaction, an interface can be induced to construct an alkaline microenvironment in situ under low voltage, and EPS attached to the surface of the membrane is promoted to be hydrolyzed and degraded.

Description

Confined conductive composite films, their preparation methods, and electrochemical methods based on their in-situ hydrolysis of extracellular polymers. Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a confined conductive composite membrane, its preparation method, and an electrochemical method for in-situ hydrolysis of extracellular polymers based thereon. Background Technology

[0002] With water scarcity becoming increasingly severe, wastewater reuse is a crucial way to alleviate water shortages. Compared to traditional physical or chemical methods, membrane technology, due to its high efficiency and good selectivity, has become a key technology for realizing wastewater resource utilization. However, during the filtration process, membrane materials trap pollutants in the water and form a filter cake layer on their surface, leading to a significant decrease in membrane flux, which in turn increases system operating energy consumption and maintenance costs.

[0003] In biological treatment systems such as membrane bioreactors (MBRs), microorganisms readily adhere to the membrane surface and continuously secrete extracellular polymeric substances (EPS). EPS possesses a complex three-dimensional network structure, exhibiting strong mechanical stability and resistance to chemical degradation. It can form a dense gel layer on the membrane surface, significantly enhancing the adhesion between contaminants and the membrane, thus leading to severe membrane fouling. Furthermore, as a protective barrier for microorganisms, EPS exhibits strong resistance to conventional cleaning methods, resulting in low cleaning efficiency.

[0004] Currently, physical, chemical, or biological methods are commonly used to clean EPS (expanded polystyrene) deposits on membrane surfaces. While physical methods such as backwashing are simple to operate, they are ineffective at removing highly adsorbed EPS. Chemical cleaning agents can decompose EPS to some extent, but long-term use can lead to membrane material aging, pore structure damage, and may inhibit microbial activity, affecting wastewater treatment efficiency. Biological cleaning suffers from long cycles and unstable efficiency. Therefore, existing cleaning methods generally have limitations such as poor long-term effectiveness and negative impacts on the environment or system ecology, making it difficult to meet the requirements of sustainable operation.

[0005] In recent years, electrochemical technology has been introduced into the field of membrane fouling control. By applying current or voltage to conductive membranes, the oxidative degradation of organic pollutants can be achieved, exhibiting in-situ self-cleaning potential. For example, using carbon nanotube (CNT) modified hollow fiber membranes as cathodes to construct electro-Fenton systems can effectively remove algal cells and extracellular organic matter in algal biofilm reactors, maintaining stable flux. However, such advanced oxidation processes typically rely on large amounts of external aeration to provide oxygen or require the addition of Fe²⁺. +Chemical agents such as H2O2 and NaCl lead to high operating costs and complex operations, and are difficult to promote and apply on a large scale in actual sewage treatment due to the large volume and complex composition of the water.

[0006] Carbon nanotubes (CNTs) are widely used in the fabrication of high-performance membrane materials due to their excellent chemical inertness, high mechanical strength, good water transport properties, and large specific surface area. The overlapping network structure formed between CNTs endows the membrane with high porosity and abundant interconnected channels, enabling high water flux even at low operating pressures. More importantly, CNTs possess excellent electrochemical properties, capable of rapidly transferring electrons, making them ideal electrochemically functionalized membrane substrates. Therefore, applying a negative voltage to CNT-based membranes is considered a promising method for mitigating membrane fouling and improving separation performance, as it can slow down the fouling process by inhibiting the deposition of planktonic microorganisms and EPS on the membrane surface.

[0007] Nevertheless, existing technologies still lack an integrated solution that can efficiently remove EPS without relying on chemical additives, while also ensuring energy conservation, environmental protection, and system stability.

[0008] In view of this, the present invention is hereby proposed. Summary of the Invention

[0009] The primary objective of this invention is to provide a confined conductive composite membrane that, through the synergistic effect of specific structures and materials, can significantly improve separation performance, mechanical strength, and antifouling ability, achieving excellent selectivity and long-term operational stability while ensuring high throughput.

[0010] The second objective of this invention is to provide a method for preparing a confined conductive composite film.

[0011] The third objective of this invention is to provide an electrochemical method for in-situ hydrolysis of extracellular polymers based on the above-mentioned confined conductive composite film.

[0012] To achieve the above-mentioned objectives of this invention, the following technical solution is adopted: This invention provides a confined conductive composite membrane, comprising an ultrafiltration membrane carrier and a conductive layer formed on the surface of the ultrafiltration membrane carrier; the conductive layer is composed of carbon nanotube material loaded with a nano-metal catalyst, wherein the nano-metal catalyst is loaded on the hollow inner wall of the carbon nanotube material or in the two-dimensional interlayer; the nano-metal catalyst includes at least one of nano-Ni catalyst, nano-Co catalyst, nano-Fe catalyst, and nano-Mo catalyst.

[0013] Furthermore, the carbon nanotube material undergoes an oxidation treatment, forming a porous structure on the tube wall that allows ions to enter the tube cavity.

[0014] Furthermore, the particle size of the nano-metal catalyst is 0.4~100 nm.

[0015] Furthermore, the ultrafiltration membrane carrier is selected from any one of polyvinylidene fluoride (PVDF) membrane, polyethersulfone (PES) membrane, polypropylene (PP) membrane, or polytetrafluoroethylene (PTFE) membrane.

[0016] The present invention provides a method for preparing the above-mentioned confined conductive composite membrane, comprising the following steps: a1: immersing oxidized and opened carbon nanotubes in a solution containing metal salts, allowing metal ions to enter the hollow inner wall or interlayer of the carbon nanotubes; a2: heating in air to decompose the metal salts into metal oxides; a3: further heating in an inert atmosphere to retain the metal oxides within the confined space of the carbon nanotubes; then, heating in a reducing atmosphere to reduce the metal oxides into nano-metal catalysts; a4: dispersing the material treated in step a3 in deionized water and depositing it onto an ultrafiltration membrane carrier by vacuum filtration to form a conductive composite membrane.

[0017] Furthermore, the metal salt in step a1 is at least one of nickel nitrate, cobalt nitrate, ferric nitrate, or ammonium molybdate.

[0018] Furthermore, the specific conditions for heating in air in step a2 are: heating to 140~150℃ and holding for 6~8h; and / or the specific conditions for heating in an inert atmosphere in step a3 are: heating to 350~650℃ at a rate of 2~3℃ / min and holding for 3~8h.

[0019] This invention provides an electrochemical method for in-situ hydrolysis of extracellular polymeric substances (EPS) based on a confined conductive composite membrane, comprising the following steps: S1, placing the confined conductive composite membrane as a cathode in a liquid environment containing EPS; S2, setting an anode near the cathode and applying a DC voltage between the cathode and anode to induce a hydrogen evolution reaction at the cathode, forming an alkaline microenvironment on its surface or interface region, thereby achieving in-situ hydrolysis of EPS attached to the membrane surface; S3, physically backwashing the confined conductive composite membrane after hydrolysis in step S2 to remove the hydrolyzed EPS contaminants.

[0020] Furthermore, the distance between the anode and cathode is 2-5 cm, and the applied DC voltage is 0.5-2 V.

[0021] Furthermore, the alkaline microenvironment causes the local pH at the cathode interface to rise to 9-11.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The confined conductive composite membrane provided by the present invention includes an ultrafiltration membrane carrier and a conductive layer formed on its surface. The conductive layer is composed of carbon nanotube material, and at least one of nano-Ni, Co, Fe, and Mo catalysts is selectively loaded on the inner wall of the hollow tubes or in the two-dimensional interlayer. This structure effectively prevents catalyst aggregation and loss through the confinement effect, improving the dispersion and stability of the catalyst. At the same time, the continuous conductive network formed by carbon nanotubes has excellent electron transport capability, which can efficiently respond to the applied electric field and rapidly transfer electrons to the catalytic active site. When the composite membrane of the present application works as a cathode, the loaded nano-metal catalyst can significantly reduce the overpotential of the hydrogen evolution reaction. It can induce the local pH of the interface to rise to 9-11 at a low voltage of 0.5-2V, constructing an alkaline microenvironment in situ, and promoting the hydrolytic degradation of EPS attached to the membrane surface.

[0023] The present invention provides a method for preparing a confined conductive composite film. This method involves immersing oxidized, open-pore carbon nanotubes in a metal salt solution, allowing metal ions to diffuse into the hollow inner wall or two-dimensional interlayer. Combined with a stepwise heat treatment process, this achieves in-situ generation and stable encapsulation of the catalyst within the confined space. This method fully utilizes the porous structure and confinement effect of carbon nanotubes, effectively guiding the selective distribution of metal components on the inner wall, avoiding the problems of easy agglomeration and detachment associated with traditional surface-loaded catalysts, and significantly improving the dispersibility and long-term stability of the catalyst.

[0024] The electrochemical method provided by this invention involves placing a confined conductive composite membrane as the cathode in a liquid environment containing EPS (expanded polysaccharides). Under a low voltage (0.5~2V), a hydrogen evolution reaction is triggered at the cathode, generating an alkaline microenvironment in situ at the membrane surface interface. This effectively breaks the chemical bonds between proteins and polysaccharides in the EPS, achieving its efficient hydrolytic degradation. This process does not rely on exogenous chemical agents, avoiding the corrosion of membrane materials and inhibition of microbial activity caused by traditional cleaning methods. It has the advantages of being environmentally friendly, easy to operate, and low in energy consumption. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 shows the variation of EPS hydrolysis rate of the confined conductive composite membrane provided in Example 1 of the present invention under different voltages; Figure 2 shows the variation trend of EPS hydrolysis rate of the confined conductive composite membrane provided in Example 1 of the present invention under different initial pH conditions; Figure 3 shows the pH change of the confined conductive composite membrane provided in Example 1 of the present invention under constant voltage over time; Figure 4 shows the percentage of membrane flux recovery of the confined conductive composite membrane provided in Example 1 of the present invention after backwashing with electrolysis time; Figure 5 shows SEM images of Ni nanoparticle / CNTs composite material after different deposition times provided in Example 1 of the present invention; Figure 6 shows the linear sweep voltammetry (LSV) test results of the confined conductive composite membrane provided in Example 1 of the present invention; Figure 7 shows the variation of EPS hydrolysis rate of the confined conductive composite membrane provided in Example 2 of the present invention under different voltages. Figure 8 shows the trend of EPS hydrolysis rate of the confined conductive composite membrane provided in Example 2 of the present invention under different initial pH conditions; Figure 9 shows the pH change of the confined conductive composite membrane provided in Example 2 of the present invention under constant voltage with time; Figure 10 shows the percentage of membrane flux recovery of the confined conductive composite membrane provided in Example 2 of the present invention after backwashing with electrolysis time; Figure 11 shows the SEM cross-sectional morphology of the Mo-Fe bimetallic modified carbon nanotube composite material provided in Example 2 of the present invention; Figure 12 shows the comparison of X-ray photoelectron spectroscopy (XPS) of the two configuration catalysts, Mo-on-Fe and Fe-on-Mo, provided in Example 2 of the present invention; Figure 13 shows the electrochemical impedance spectroscopy (EIS) Nyquist plot of the Mo-Fe / CNT composite membrane provided in Example 2 of the present invention under different cathode potentials. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] According to one aspect of the present invention, a confined conductive composite membrane includes an ultrafiltration membrane carrier and a conductive layer formed on the surface of the ultrafiltration membrane carrier; the conductive layer is composed of a carbon nanotube material loaded with a nano-metal catalyst, wherein the nano-metal catalyst is loaded on the hollow inner wall of the carbon nanotube material or in the two-dimensional interlayer; the nano-metal catalyst includes at least one of nano-Ni catalyst, nano-Co catalyst, nano-Fe catalyst, and nano-Mo catalyst.

[0029] The present invention provides a confined conductive composite membrane, comprising an ultrafiltration membrane carrier and a conductive layer formed on its surface. The conductive layer is composed of carbon nanotubes, and at least one of nano-Ni, Co, Fe, and Mo catalysts is selectively loaded onto the inner wall of the hollow tubes or between the two-dimensional layers. This structure effectively prevents catalyst aggregation and loss through the confinement effect, improving the dispersion and stability of the catalyst. Simultaneously, the continuous conductive network formed by the carbon nanotubes possesses excellent electron transport capabilities, efficiently responding to an applied electric field and rapidly transferring electrons to the catalytic active sites. When the composite membrane of this application operates as a cathode, the loaded nano-metal catalyst can significantly reduce the overpotential of the hydrogen evolution reaction, inducing a local pH rise to 9-11 at a low voltage of 0.5-2V, constructing an alkaline microenvironment in situ, and promoting the hydrolytic degradation of EPS attached to the membrane surface.

[0030] It should be noted that, unlike traditional methods that rely on strong oxidizing free radicals (e.g., -OH) to destroy organic matter, this invention cleverly utilizes the OH generated by the efficient hydrogen evolution of a confined conductive film under low voltage. - This process constructs an alkaline microenvironment in situ at the membrane-solution interface, specifically breaking hydrogen and ester bonds between proteins and polysaccharides in EPS, achieving targeted hydrolysis under mild conditions. This process avoids membrane material corrosion and microbial inactivation problems caused by high-potential oxidation, and offers advantages in energy saving, environmental protection, and system compatibility.

[0031] In a preferred embodiment of the present invention, the carbon nanotube material is subjected to oxidation treatment to form a porous structure on the tube wall that allows ions to enter the tube cavity.

[0032] In a preferred embodiment of the present invention, the particle size of the nano-metal catalyst is 0.4~100 nm.

[0033] As an optional embodiment, the particle size of the nano-metal catalyst is 0.4~100 nm, for example, it can be 0.4 nm, 1 nm, 5 nm, 10 nm, 20 nm, 50 nm, 100 nm, or any value between 0.4~100 nm.

[0034] In a preferred embodiment of the present invention, the ultrafiltration membrane carrier is selected from any one of polyvinylidene fluoride (PVDF) membrane, polyethersulfone (PES) membrane, polypropylene (PP) membrane, or polytetrafluoroethylene (PTFE) membrane.

[0035] According to one aspect of the present invention, a method for preparing the above-mentioned confined conductive composite membrane includes the following steps: a1: immersing oxidized and opened carbon nanotubes in a solution containing metal salts, allowing metal ions to enter the hollow inner wall or interlayer of the carbon nanotubes; a2: heating in air to decompose the metal salts into metal oxides; a3: further heating in an inert atmosphere to retain the metal oxides within the confined space of the carbon nanotubes; then, heating in a reducing atmosphere to reduce the metal oxides into nano-metal catalysts; a4: dispersing the material treated in step a3 in deionized water and depositing it onto an ultrafiltration membrane carrier by vacuum filtration to form a conductive composite membrane.

[0036] The present invention provides a method for preparing a confined conductive composite film. This method involves immersing oxidized, open-pore carbon nanotubes in a metal salt solution, allowing metal ions to diffuse into the hollow inner wall or two-dimensional interlayer. Combined with a stepwise heat treatment process, this achieves in-situ generation and stable encapsulation of the catalyst within the confined space. This method fully utilizes the porous structure and confinement effect of carbon nanotubes, effectively guiding the selective distribution of metal components on the inner wall, avoiding the problems of easy agglomeration and detachment associated with traditional surface-loaded catalysts, and significantly improving the dispersibility and long-term stability of the catalyst.

[0037] It should be noted that in the above preparation method, the metal salt is decomposed into metal oxide by low-temperature heating in air, followed by high-temperature reduction in an inert atmosphere. This ensures that the metal species are uniformly anchored at the nanoscale within the confined region of the carbon nanotubes, forming robust catalytic active centers. Finally, a vacuum filtration method is used to deposit functionalized carbon nanotubes onto the surface of the ultrafiltration membrane carrier, achieving tight integration between the conductive layer and the substrate. The entire process is simple, controllable, and highly reproducible, making it suitable for large-scale preparation. The resulting composite membrane exhibits excellent electrochemical response and interfacial reactivity, providing a solid material foundation for the subsequent efficient hydrolysis of EPS in an electrochemical environment.

[0038] In a preferred embodiment of the present invention, the metal salt in step a1 is at least one of nickel nitrate, cobalt nitrate, ferric nitrate, or ammonium molybdate.

[0039] In a preferred embodiment of the present invention, the specific conditions for the heating treatment in air in step a2 are: heating to 140~150℃ and holding at that temperature for 6~8 hours; as an optional embodiment, the specific conditions for the heating treatment in air in step a2 are: heating to 140~150℃, for example, 140℃, 141℃, 142℃, 143℃, 144℃, 145℃, 146℃, 147℃, 148℃, 149℃, 150℃, or any value between 140~150℃; and holding at that temperature for 6~8 hours, for example, 6 hours, 7 hours, 8 hours, or any value between 6~8 hours.

[0040] In a preferred embodiment of the present invention, the specific conditions for the heating treatment in step a3 in an inert atmosphere are as follows: heating to 350-650°C at a rate of 2-3°C / min and holding at that temperature for 3-8 hours.

[0041] As an optional implementation, the specific conditions for the heating treatment in the inert atmosphere in step a3 are as follows: the temperature is increased to 350-650℃ at a rate of 2-3℃ / min, for example, the heating rate is 2℃ / min, 2.5℃ / min, or 3℃ / min, the final temperature is 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, or 650℃, and the holding time is 3-8 h, for example, it can be 3h, 4h, 5h, 6h, 7h, or 8h, or any value between 3 and 8h.

[0042] According to one aspect of the present invention, an electrochemical method for in-situ hydrolysis of extracellular polymeric substances (EPS) based on a confined conductive composite membrane includes the following steps: S1: placing the above-mentioned confined conductive composite membrane as a cathode in a liquid environment containing EPS; S2: setting an anode near the cathode and applying a DC voltage between the anode and cathode to cause a hydrogen evolution reaction in the cathode, forming an alkaline microenvironment on its surface or interface region, thereby achieving in-situ hydrolysis of EPS attached to the membrane surface; S3: physically backwashing the confined conductive composite membrane after hydrolysis in step S2 to remove the hydrolyzed EPS contaminants.

[0043] The electrochemical method provided by this invention involves placing a confined conductive composite membrane as the cathode in a liquid environment containing EPS (expanded polysaccharides). Under a low voltage (0.5~2V), a hydrogen evolution reaction is triggered at the cathode, generating an alkaline microenvironment in situ at the membrane surface interface. This effectively breaks the chemical bonds between proteins and polysaccharides in the EPS, achieving its efficient hydrolytic degradation. This process does not rely on exogenous chemical agents, avoiding the corrosion of membrane materials and inhibition of microbial activity caused by traditional cleaning methods. It has the advantages of being environmentally friendly, easy to operate, and low in energy consumption.

[0044] In a preferred embodiment of the present invention, the distance between the anode and cathode is 2-5 cm, and the applied DC voltage is 0.5-2 V.

[0045] As an optional implementation, the distance between the anode and cathode is 2 to 5 cm, for example, it can be 2 cm, 3 cm, 4 cm, 5 cm, or any value between 2 and 5 cm; the applied DC voltage is 0.5 to 2 V, for example, it can be 0.5 V, 1 V, 1.5 V, 2 V, or any value between 0.5 and 2 V.

[0046] In a preferred embodiment of the present invention, the alkaline microenvironment causes the local pH at the cathode interface to rise to 9-11.

[0047] The technical solution of the present invention will be further described below with reference to the embodiments.

[0048] Example 1: A method for preparing a composite film based on a carbon nanotube (CNT) confined conductive film supporting a nano-Ni catalyst and its application in in-situ hydrolysis of extracellular polymeric substances (EPS).

[0049] The specific plan is as follows: (I) Preparation of composite membrane: 1. The carbon nanotubes after oxidation and pore opening treatment are added to the nickel nitrate [Ni(NO3)2] solution under stirring conditions, and ultrasonic treatment is carried out for 2 hours at the same time to allow metal ions to fully enter the hollow inner wall and two-dimensional interlayer space of the carbon nanotubes.

[0050] 2. Subsequently, the solvent was slowly evaporated at room temperature, and the resulting solid mixture was gradually heated to 140°C in air and kept at that temperature for 8 hours.

[0051] 3. Then, the temperature was increased to 350°C in a helium atmosphere at a heating rate of 2°C / min and held at this temperature for 3 hours to allow nickel nitrate to thermally decompose inside the carbon nanotubes to generate nickel oxide (NiO) particles, thereby achieving catalyst loading in the confined space and obtaining NiO / CNTs composite material. (See Figure 5).

[0052] 4. The NiO / CNTs composite material obtained in step 3 is reduced under a reducing atmosphere: Under the protection of an argon-hydrogen mixture (hydrogen gas fraction of 5%~10%), the temperature is increased to 400~450℃ at a rate of 2℃ / min and held for 1~3 hours. This reduces the NiO nanoparticles confined within the hollow tube wall and two-dimensional interlayer of the carbon nanotubes to metallic Ni nanoparticles in situ, yielding the Ni nanoparticle / CNTs composite material. This reduction step ensures that the catalyst is in a highly active metallic state and is stably anchored within the confined space, preventing agglomeration and loss.

[0053] 5. Disperse 10 mg of the above Ni nanoparticle / CNT composite material and 100 mg of sodium dodecylbenzenesulfonate in 100 mL of deionized water. Sonicate the resulting mixture in an ultrasonic disperser for 8 hours, then centrifuge at 10000 r / min for 1 hour. Collect the supernatant as the Ni-CNT dispersion. Filter a certain amount of the Ni-CNT dispersion onto a polyvinylidene fluoride (PVDF) ultrafiltration membrane using vacuum filtration to obtain a confined conductive composite membrane with catalytic function.

[0054] Material characterization: Figure 5 shows SEM images of Ni nanoparticle / CNTs composite materials after different deposition times provided in Example 1 of this invention.

[0055] In Figure 5: (a) is the SEM image of the Ni nanoparticle / CNTs composite material after 1 min of deposition; (b) is the SEM image of the Ni nanoparticle / CNTs composite material after 3 min of deposition; (c) is the SEM image of the Ni nanoparticle / CNTs composite material after 5 min of deposition; (d) is the SEM image of the Ni nanoparticle / CNTs composite material after 7 min of deposition; (e) is the SEM image of the Ni nanoparticle / CNTs composite material after 15 min of deposition; and (f) is the TEM image of the Ni nanoparticles.

[0056] As shown in Figure 5, the morphology of the above Ni nanoparticle / CNTs composite material was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

[0057] The results showed that the nanoparticles were uniformly distributed on the surface of the carbon nanotubes and in their network structure, with a particle size of about 100 nm. The carbon nanotubes intertwined to form a continuous conductive pathway, and the film surface had a porous structure with uniform pore distribution and an average pore size of 1-2 nm, which was beneficial for the contact between EPS molecules and the active sites of the catalyst.

[0058] Using the composite membrane prepared above as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl as the reference electrode, linear sweep voltammetry (LSV) tests were performed in simulated wastewater containing EPS. The scan rate was 10 mV / s, and the potential range was -0.70 V to -1.0 V. The test results show that the composite membrane has excellent electrochemical catalytic activity (see Figure 6).

[0059] Figure 6 shows the linear scan voltammetry (LSV) test results of the confined conductive composite film provided in Example 1 of the present invention; wherein, Figure 6(a) shows the linear scan voltammetry (LSV) curves of pure nickel-based materials at different scan rates; Figure 6(b) shows the LSV comparison curves of composite materials with different CNT contents at a scan rate of 10 mV / s.

[0060] (II) Electrochemical Hydrolysis of EPS Experiment: The composite membrane prepared in step (I) was used as the cathode, and a stainless steel mesh was used as the anode. Both were placed in a simulated wastewater membrane bioreactor containing EPS. The distance between the anode and cathode was controlled to be 2-5 cm. A DC voltage of 1 V was applied between them, the reaction temperature was maintained at 20℃, and the solution flow rate was 0.3 L / min. After energization, hydrogen evolution reaction occurred at the cathode, generating an alkaline microenvironment at its interface, which promoted the hydrolysis of EPS attached to the membrane surface.

[0061] Furthermore, the hydrolysis effect of the composite membrane in this embodiment was verified, as shown in Figures 1 to 4.

[0062] Figure 1 shows the relationship between the EPS hydrolysis rate of the confined conductive composite film in this embodiment under different voltages.

[0063] Figure 2 shows the trend of EPS hydrolysis rate of the confined conductive composite film in this embodiment under different initial pH conditions.

[0064] Figure 3 shows the pH change over time in the confined conductive composite membrane of this embodiment under constant voltage.

[0065] Figure 4 shows the percentage of membrane flux recovery of the confined conductive composite membrane in this embodiment after backwashing with electrolysis time.

[0066] As described above, the increase in pH at the cathode interface with electrolysis time under constant voltage confirms the gradual establishment of the alkaline microenvironment in this embodiment. The detection results after 1 hour of reaction show that the membrane flux recovery rate increased by approximately 40%, and the recovery of membrane flux with electrolysis time after backwashing is shown in Figure 4.

[0067] Example 2: A method for preparing a composite membrane based on a carbon nanotube (CNT) confined conductive membrane and a nano-Mo-Fe bimetallic catalyst supported thereon, and its application in in-situ hydrolysis of extracellular polymeric substances (EPS).

[0068] (I) Preparation of composite membrane: 1. The multi-walled carbon nanotubes after oxidation and pore opening treatment are added to a mixed solution of ammonium molybdate and ferric nitrate under stirring conditions (where the molar ratio of Mo to Fe is 1:2). Then, the mixture is ultrasonically treated for 2 hours to allow the metal ions of Mo and Fe to fully enter the hollow inner wall and two-dimensional interlayer space of the carbon nanotubes, thereby achieving the confined distribution of the precursor.

[0069] 2. The solvent is slowly evaporated at room temperature to obtain a solid mixture. The mixture is placed in a muffle furnace and gradually heated to 150°C in air, and held at this temperature for 6 hours to allow ammonium molybdate and ferric nitrate to completely decompose into molybdenum trioxide (MoO3) and ferric oxide (Fe2O3), thus initially forming metal oxide particles anchored within the CNT confinement space.

[0070] 3. Subsequently, the above materials were transferred to a tube furnace and heated to 650°C at a heating rate of 3°C / min under a nitrogen atmosphere, and held at that temperature for 3 hours. Then, the mixture of hydrogen and nitrogen (H2:N2 = 10%:90%) was switched, and the temperature was maintained for another 2 hours to allow MoO3 and Fe2O3 to be reduced in situ to zero-valent Mo and Fe nanoparticles, thus obtaining a Mo-Fe bimetallic modified carbon nanotube composite material (Mo-Fe / CNT) with high hydrogen evolution activity.

[0071] 4. Disperse 10 mg of the above Mo-Fe / CNT composite material and 120 mg of sodium dodecylbenzenesulfonate in 100 mL of deionized water. Sonicate the resulting mixture in an ultrasonic disperser for 6 hours, then centrifuge at 9000 r / min for 1.5 hours. Collect the supernatant as the Mo-Fe~CNT dispersion. Filter a certain amount of this dispersion using vacuum filtration and deposit it onto the surface of a polyethersulfone (PES) ultrafiltration membrane to obtain a confined conductive composite membrane with synergistic catalytic function.

[0072] Material characterization: The cross-sectional morphology of the prepared Mo-Fe / CNT composite material was analyzed by scanning electron microscopy (SEM) (see Figure 11).

[0073] Figure 11 shows the SEM cross-sectional morphology of the Mo-Fe bimetallic modified carbon nanotube composite material provided in Example 2 of the present invention. In Figure 11(a), the reference Fe (0.4 nm) is shown; in Figure 11(b-d), the ordered "nanoforest" structure formed by the "Mo-on-Fe" catalyst is shown; and in Figure 11(e-g), the irregular growth morphology of the "Fe-on-Mo" catalyst is shown.

[0074] It should be noted that in Figures 11 and 12 of this invention, molybdenum loaded on iron (Mo-on-Fe) and iron loaded on molybdenum (Fe-on-Mo) refer to the Mo-Fe bimetallic modified carbon nanotube composite materials of this embodiment prepared by different processes. Among them, molybdenum loaded on iron (Mo-on-Fe) refers to the preparation of Mo-on-Fe / CNTs by adopting the loading order of "Mo first and then Fe" and the reduction temperature is 400~450℃. Specifically, the preparation method of the molybdenum loaded on iron (Mo-on-Fe) material in Figures 11 and 12 is as follows: 1. Carbon nanotube pretreatment: Weigh 10 g of multi-walled carbon nanotubes (CNTs), add 200 mL of mixed acid system (concentrated nitric acid: concentrated sulfuric acid = 1:3, volume ratio), and stir magnetically at 60 ℃ for 6 h to introduce oxygen-containing functional groups (-OH, -COOH) on the surface and enhance the adsorption sites of metal species. After the reaction was completed, the filtrate was vacuum filtered, washed with deionized water until it was neutral, dried at 100 °C for 12 h, and then ground to obtain purified modified CNTs for later use.

[0075] 2. Loading and calcination of Mo in the bottom layer: 0.02 mol of ammonium heptamolybdate was dissolved in 100 mL of deionized water, and 0.01 mol of citric acid was added as a complexing agent. After stirring until completely dissolved, the pH of the system was adjusted to 2-3 with dilute nitric acid. 5 g of pretreated CNTs were added to the solution, ultrasonically dispersed for 30 min, and then magnetically stirred at room temperature for 12 h to allow Mo species to be fully adsorbed onto the CNT surface. Subsequently, the mixture was vacuum dried at 60 ℃ for 12 h to obtain the Mo / CNT precursor. The precursor was placed in a muffle furnace and calcined at 500 ℃ under a nitrogen atmosphere (50 mL / min) at a heating rate of 2 ℃ / min for 3 h to convert Mo species into MoO3 and anchor them on the CNT surface. After natural cooling, the mixture was ground into powder for later use.

[0076] 3. Loading and Reduction Activation of Upper Fe Layer: 0.02 mol of ferric nitrate nonahydrate was dissolved in 80 mL of deionized water. The pH was adjusted to 2-3, and after stirring to dissolve, 3 g of the above Mo / CNTs powder was added. The mixture was ultrasonically dispersed for 30 min and magnetically stirred at room temperature for 12 h to complete the loading of Fe species on the Mo layer surface. The precursor was obtained by vacuum drying at 60 ℃ for 12 h. It was then placed in a tube furnace, and nitrogen gas (100 mL / min) was first introduced to purge the air for 30 min. Then, a 5 vol% H2 / Ar mixed gas (100 mL / min) was introduced, and the temperature was increased to 400-450 ℃ at a heating rate of 2 ℃ / min. The temperature was reduced for 2 h, preferentially reducing the outer Fe species while retaining the higher valence states of Mo. After natural cooling to room temperature, the mixture was ground to obtain Mo-on-Fe bimetallic modified carbon nanotubes.

[0077] Iron-on-Mo (Fe-on-Mo) refers to Fe-on-Mo / CNTs prepared by a "Fe first, then Mo" loading sequence and a reduction temperature of 650~700 ℃. Specifically, the preparation method of the Fe-on-Mo material in Figures 11 and 12 is as follows: 1a. Carbon nanotube pretreatment: same as the above for molybdenum-on-iron (Mo-on-Fe); 2a. Loading and calcination of the bottom Fe layer: Weigh 0.02 mol of ferric nitrate nonahydrate and dissolve it in 100 mL of deionized water, add 0.01 mol of citric acid, adjust the pH to 2~3, stir to dissolve, add 5 g of pretreated CNTs, ultrasonically disperse for 30 min, and magnetically stir at room temperature for 12 h to make the Fe species uniformly adsorbed on the surface of CNTs. Fe / CNTs precursors were obtained by vacuum drying at 60 °C for 12 h. The precursors were placed in a muffle furnace and heated to 500-550 °C at 2 °C / min under a nitrogen atmosphere (50 mL / min) for 3 h to convert Fe species into Fe2O3 and form a stable matrix. After cooling, the precursors were ground for later use.

[0078] 3a. Loading and Reduction Activation of Upper Mo Layer: 0.02 mol of ammonium heptamolybdate was dissolved in 80 mL of deionized water, and the pH was adjusted to 2-3. After stirring and dissolving, 3 g of the above Fe / CNTs powder was added, and the mixture was ultrasonically dispersed for 30 min and magnetically stirred at room temperature for 12 h to achieve loading of Mo species on the Fe layer surface. The Fe-on-Mo / CNTs precursor was obtained by vacuum drying at 60 ℃ for 12 h. It was then placed in a tube furnace, purged with nitrogen for 30 min, and then a 5 vol% H2 / Ar mixed gas (100 mL / min) was introduced. The temperature was increased to 650-700 ℃ at 2 ℃ / min and reduced for 2 h to fully reduce the outer Mo species and form a capping layer, inhibiting the aggregation of internal Fe particles. After natural cooling to room temperature, Fe-on-Mo bimetallic modified carbon nanotubes were obtained by grinding.

[0079] The results showed that a highly ordered "nanoforest" structure was formed on the "Mo-on-Fe" catalyst (Figure 11, b-d), while the "Fe-on-Mo" sample exhibited a more irregular growth morphology (Figure 11, e-g), indicating that Mo, as the bottom layer, can effectively guide the uniform nucleation and directional growth of Fe. This structure significantly increased the specific surface area and the number of exposed active sites of the catalyst, which is beneficial to improving the interfacial reaction efficiency.

[0080] To further reveal the electronic structure characteristics of the catalyst surface, X-ray photoelectron spectroscopy (XPS) was used to characterize the two configurations, Mo-on-Fe and Fe-on-Mo (see Figure 12).

[0081] Figure 12 shows a comparison of X-ray photoelectron spectroscopy (XPS) spectra of the two catalyst configurations, Mo-on-Fe and Fe-on-Mo, provided in Example 2 of this invention. The shifts in the Fe 2p and Mo 3d peaks indicate electron transfer from Mo to Fe.

[0082] The results show that in the Mo-on-Fe structure, the Fe 2p3 / 2 peak undergoes a negative shift of approximately 0.3 eV, while the Mo 3d5 / 2 peak shows a positive shift. This indicates that electrons are transferred from Mo to Fe, modulating the d-band center position of Fe and optimizing the hydrogen adsorption free energy (ΔG_H*), thereby enhancing the kinetics of the hydrogen evolution reaction (HER). This electronic modulation effect helps reduce the reaction overpotential, enabling efficient hydrogen production at lower voltages.

[0083] In addition, electrochemical impedance spectroscopy (EIS) was performed on the Mo-Fe / CNT composite membrane using an electrochemical workstation (see Figure 13).

[0084] Figure 13 shows the electrochemical impedance spectroscopy (EIS) Nyquist plots of the Mo-Fe / CNT composite film provided in Example 2 of the present invention at different cathode potentials.

[0085] Referring to Figure 13, the test was conducted in simulated wastewater containing EPS, with 0.1 M PBS buffer solution (pH 7.2) as the electrolyte and 5 mM L-cysteine ​​added as a model organic compound. Nyquist plots measured at different cathode potentials show that the semicircle diameter significantly decreases with a negative potential shift, indicating a significant reduction in interfacial charge transfer resistance (Rct) and an accelerated electron transfer rate, further confirming that the bimetallic synergistic effect effectively enhances the material's electrochemical response capability.

[0086] (II) Electrochemical hydrolysis of EPS experiment: The confined conductive composite membrane prepared in step (I) was used as the cathode, and a titanium mesh was used as the anode. Both were placed in a simulated wastewater membrane bioreactor containing EPS. The distance between the anode and cathode was controlled at 3 cm. A DC voltage of 1.0 V was applied between them, the reaction temperature was maintained at 35℃, and the solution flow rate was 0.4 L / min. After energization, hydrogen evolution reaction (2H₂O + 2e⁻) occurred at the cathode. - → H2↑ + 2OH - OH continues to be generated in its interface region. - This causes the local pH to gradually rise to the alkaline range (pH ≈ 9–10.5), thereby disrupting the hydrogen bond network and polysaccharide chain structure of proteins in EPS and achieving its in-situ hydrolysis.

[0087] The hydrolysis effect of this embodiment was further verified, as shown in Figures 7 to 10.

[0088] Figure 7 shows the relationship between the EPS hydrolysis rate of the confined conductive composite film in this embodiment under different voltages.

[0089] Figure 8 shows the trend of EPS hydrolysis rate of the confined conductive composite membrane in this embodiment under different initial pH conditions.

[0090] Figure 9 shows the pH change over time in the confined conductive composite membrane of this embodiment under constant voltage.

[0091] Figure 10 shows the percentage of membrane flux recovery after backwashing of the confined conductive composite membrane in this embodiment over electrolysis time.

[0092] The comprehensive experimental results show that the Mo-Fe bimetallic confined catalytic system in this embodiment not only possesses excellent hydrogen evolution activity and electron transport capabilities, but also effectively promotes the non-oxidative hydrolysis of EPS, significantly alleviating membrane fouling problems. Furthermore, since no chemical reagents are required and the operating conditions are mild (low pressure, room temperature), it has promising prospects for engineering applications.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A confined conductive composite film, characterized in that, The invention includes an ultrafiltration membrane carrier and a conductive layer formed on the surface of the ultrafiltration membrane carrier; the conductive layer is composed of a carbon nanotube material loaded with a nano-metal catalyst, wherein the nano-metal catalyst is loaded on the hollow inner wall of the carbon nanotube material or in the two-dimensional interlayer; the nano-metal catalyst includes at least one of nano-Ni catalyst, nano-Co catalyst, nano-Fe catalyst, and nano-Mo catalyst.

2. The confined conductive composite film according to claim 1, characterized in that, The carbon nanotube material undergoes an oxidation treatment, forming a porous structure on the tube wall that allows ions to enter the tube cavity.

3. The confined conductive composite film according to claim 1, characterized in that, The particle size of the nano-metal catalyst is 0.4~100 nm.

4. The confined conductive composite film according to claim 1, characterized in that, The ultrafiltration membrane carrier is selected from any one of polyvinylidene fluoride membrane, polyethersulfone membrane, polypropylene membrane, or polytetrafluoroethylene membrane.

5. A method for preparing a confined conductive composite film according to any one of claims 1 to 4, characterized in that, Includes the following steps: a1: Immerse the oxidized and opened carbon nanotubes in a solution containing metal salts to allow metal ions to enter the hollow inner wall or interlayer of the carbon nanotubes. a2: Heating in air decomposes the metal salt into metal oxides; a3: Heating in an inert atmosphere to retain the metal oxide within the confined space of the carbon nanotubes; then heating in a reducing atmosphere to reduce the metal oxide to a nano-metal catalyst; a4: Disperse the metal oxides treated in step a3 in deionized water and deposit them onto an ultrafiltration membrane carrier by vacuum filtration to form a conductive composite membrane.

6. The preparation method according to claim 5, characterized in that, The metal salt is at least one of nickel nitrate, cobalt nitrate, ferric nitrate, or ammonium molybdate.

7. The preparation method according to claim 5, characterized in that, The specific conditions for heating in air in step a2 are: heating to 140~150℃ and holding for 6~8h; and / or the specific conditions for heating in an inert atmosphere in step a3 are: heating to 350~650℃ at a rate of 2~3℃ / min and holding for 3~8h.

8. An electrochemical method for in-situ hydrolysis of extracellular polymers based on the confined conductive composite membrane according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1: Place the confined conductive composite membrane as the cathode in a liquid environment containing EPS; S2: Set an anode near the cathode and apply a DC voltage between the cathode and anode to cause the cathode to undergo a hydrogen evolution reaction, forming an alkaline microenvironment on its surface or interface, thereby achieving in-situ hydrolysis of EPS attached to the membrane surface; S3: Perform physical backwashing on the confined conductive composite membrane after hydrolysis in step S2 to remove the hydrolyzed EPS contaminants.

9. The electrochemical method according to claim 8, characterized in that, The distance between the anode and cathode is 2-5 cm, and the applied DC voltage is 0.5-2 V.

10. The electrochemical method according to claim 8, characterized in that, The alkaline microenvironment causes the local pH at the cathode interface to rise to 9-11.

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