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

Abstract

This invention provides a confined conductive composite membrane, its preparation method, and an electrochemical method for in-situ hydrolysis of extracellular polymeric substances (EPS) based thereon, relating to the field of wastewater treatment technology. The confined conductive composite membrane comprises an ultrafiltration membrane carrier and a conductive layer formed on its surface. The conductive layer is composed of carbon nanotubes, with at least one of nano-Ni, Co, Fe, and Mo catalysts 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 catalyst's dispersibility and stability. Simultaneously, the continuous conductive network formed by the carbon nanotubes possesses excellent electron transport capabilities, enabling rapid electron transfer to the catalytically active sites. When the composite membrane of this application operates as a cathode, the loaded nano-metal catalyst significantly reduces the overpotential of the hydrogen evolution reaction, inducing the in-situ construction of an alkaline microenvironment at low voltage, promoting the hydrolytic degradation of EPS attached to the membrane surface.

Description

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] Compared to traditional physical or chemical methods, membrane technology has become a key technology for realizing the resource utilization of wastewater due to its high efficiency and good selectivity. However, during the filtration process, membrane materials trap pollutants in the water and form a filter cake layer on their surface, resulting in a significant decrease in membrane flux, which in turn increases the system's 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] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0013] The present 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;

[0014] 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 between two-dimensional layers.

[0015] The nano-metal catalyst includes at least one of nano-Ni catalyst, nano-Co catalyst, nano-Fe catalyst, and nano-Mo catalyst.

[0016] 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.

[0017] Furthermore, the particle size of the nano-metal catalyst is 0.4~100 nm.

[0018] 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.

[0019] The present invention provides a method for preparing the above-mentioned confined conductive composite film, comprising the following steps:

[0020] 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.

[0021] a2: Heating in air decomposes the metal salt into metal oxides;

[0022] a3: Further heating in an inert atmosphere allows the metal oxide to remain within the confined space of the carbon nanotubes; then, heating in a reducing atmosphere reduces the metal oxide to a nano-metal catalyst.

[0023] a4: Disperse the material treated in step a3 in deionized water and deposit it onto an ultrafiltration membrane carrier by vacuum filtration to form a conductive composite membrane.

[0024] Furthermore, the metal salt in step a1 is at least one of nickel nitrate, cobalt nitrate, ferric nitrate, or ammonium molybdate.

[0025] Furthermore, 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;

[0026] And / or, the specific conditions for the heating treatment in step a3 in an inert atmosphere are: heating to 350~650℃ at a rate of 2~3℃ / min and holding at that temperature for 3~8h.

[0027] This invention provides an electrochemical method for in-situ hydrolysis of extracellular polymeric substances (EPS) based on a confined conductive composite film, comprising the following steps:

[0028] S1. Place the above-mentioned confined conductive composite film as a cathode in a liquid environment containing EPS.

[0029] S2. An anode is placed near the cathode, and a DC voltage is applied between the cathode and anode to cause the cathode to undergo a hydrogen evolution reaction, forming an alkaline microenvironment on its surface or interface region, thereby realizing the in-situ hydrolysis of EPS attached to the membrane surface.

[0030] S3. Perform physical backwashing on the confined conductive composite membrane after hydrolysis in step S2 to remove EPS contaminants after hydrolysis.

[0031] Furthermore, the distance between the anode and cathode is 2-5 cm, and the applied DC voltage is 0.5-2 V.

[0032] Furthermore, the alkaline microenvironment causes the local pH at the cathode interface to rise to 9-11.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 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.

[0035] 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.

[0036] 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

[0037] 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.

[0038] Figure 1 The relationship between the EPS hydrolysis rate of the confined conductive composite film provided in Embodiment 1 of the present invention under different voltages is shown.

[0039] Figure 2 The variation trend of EPS hydrolysis rate of the confined conductive composite membrane provided in Embodiment 1 of the present invention under different initial pH conditions;

[0040] Figure 3 This is a graph showing the pH change over time under constant voltage in the confined conductive composite membrane provided in Embodiment 1 of the present invention;

[0041] Figure 4 The percentage of membrane flux recovery after backwashing with electrolysis time for the confined conductive composite membrane provided in Embodiment 1 of the present invention;

[0042] Figure 5 SEM images of Ni nanoparticle / CNTs composite materials after different deposition times provided in Example 1 of this invention;

[0043] Figure 6 The graph shows the linear sweep voltammetry (LSV) test results of the confined conductive composite film provided in Embodiment 1 of the present invention.

[0044] Figure 7 The relationship between the EPS hydrolysis rate of the confined conductive composite film provided in Embodiment 2 of the present invention under different voltages is shown.

[0045] Figure 8 The following is a trend of EPS hydrolysis rate variation of the confined conductive composite membrane provided in Embodiment 2 of the present invention under different initial pH conditions;

[0046] Figure 9 This is a graph showing the pH change over time under constant voltage in the confined conductive composite membrane provided in Embodiment 2 of the present invention;

[0047] Figure 10 The percentage of membrane flux recovery after backwashing with electrolysis time for the confined conductive composite membrane provided in Embodiment 2 of the present invention;

[0048] Figure 11 This is a SEM cross-sectional morphology image of the Mo-Fe bimetallic modified carbon nanotube composite material provided in Example 2 of the present invention.

[0049] Figure 12 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;

[0050] Figure 13 The Nyquist plots of the electrochemical impedance spectroscopy (EIS) of the Mo-Fe / CNT composite film provided in Example 2 of this invention at different cathode potentials are shown. Detailed Implementation

[0051] 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.

[0052] 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.

[0053] 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 between two-dimensional layers.

[0054] The nano-metal catalyst includes at least one of nano-Ni catalyst, nano-Co catalyst, nano-Fe catalyst, and nano-Mo catalyst.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] In a preferred embodiment of the present invention, the particle size of the nano-metal catalyst is 0.4~100 nm.

[0059] 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.

[0060] 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.

[0061] According to one aspect of the present invention, a method for preparing the above-mentioned confined conductive composite film includes the following steps:

[0062] 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.

[0063] a2: Heating in air decomposes the metal salt into metal oxides;

[0064] a3: Further heating in an inert atmosphere allows the metal oxide to remain within the confined space of the carbon nanotubes; then, heating in a reducing atmosphere reduces the metal oxide to a nano-metal catalyst.

[0065] a4: Disperse the material treated in step a3 in deionized water and deposit it onto an ultrafiltration membrane carrier by vacuum filtration to form a conductive composite membrane.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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°C and holding at that temperature for 6~8 hours;

[0070] As an optional implementation, the specific conditions for the heating treatment in air in step a2 are as follows: the temperature is raised to 140~150℃, for example, it can be 140℃, 141℃, 142℃, 143℃, 144℃, 145℃, 146℃, 147℃, 148℃, 149℃, or 150℃, or any value between 140~150℃; the holding time is 6~8 h, for example, it can be 6 h, 7 h, 8 h, or any value between 6~8 h.

[0071] 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.

[0072] 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.

[0073] 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 film includes the following steps:

[0074] S1: Place the above-mentioned confined conductive composite film as a cathode in a liquid environment containing EPS.

[0075] S2: An anode is placed near the cathode, and a DC voltage is applied between the cathode and anode to cause the cathode to undergo a hydrogen evolution reaction, forming an alkaline microenvironment on its surface or interface region, thereby realizing the in-situ hydrolysis of EPS attached to the membrane surface;

[0076] S3: Perform physical backwashing on the confined conductive composite membrane after hydrolysis in step S2 to remove EPS contaminants after hydrolysis.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] In a preferred embodiment of the present invention, the alkaline microenvironment causes the local pH at the cathode interface to rise to 9-11.

[0081] The technical solution of the present invention will be further described below with reference to the embodiments.

[0082] Example 1

[0083] A method for preparing a composite membrane based on a carbon nanotube (CNT) confined conductive membrane supporting a nano-Ni catalyst and its application in in-situ hydrolysis of extracellular polymeric substances (EPS).

[0084] The specific plan is as follows:

[0085] (I) Preparation of composite membranes:

[0086] 1. The carbon nanotubes after oxidation and pore opening treatment are added to a nickel nitrate [Ni(NO3)2] solution under stirring, and simultaneously subjected to ultrasonic treatment for 2 hours to allow metal ions to fully enter the hollow inner wall and two-dimensional interlayer space of the carbon nanotubes.

[0087] 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.

[0088] 3. Then, the temperature was further increased to 350°C in a helium atmosphere at a heating rate of 2°C / min, and maintained at this temperature for 3 hours. This allowed nickel nitrate to thermally decompose inside the carbon nanotubes to generate nickel oxide (NiO) particles, thus achieving catalyst loading within the confined space and obtaining the NiO / CNTs composite material. (See...) Figure 5 ).

[0089] 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.

[0090] 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.

[0091] Material characterization:

[0092] Figure 5 SEM images of Ni nanoparticle / CNTs composite materials after different deposition times provided in Example 1 of this invention.

[0093] in: Figure 5 (a) is a SEM image of the Ni nanoparticle / CNTs composite material after 1 min of deposition. Figure 5 (b) is a SEM image of the Ni nanoparticle / CNTs composite material after a deposition time of 3 min; Figure 5 (c) is a SEM image of the Ni nanoparticle / CNTs composite material after a deposition time of 5 min; Figure 5 Image d shows a SEM image of the Ni nanoparticle / CNTs composite material after 7 min of deposition. Figure 5 (e) is a SEM image of the Ni nanoparticle / CNTs composite material after 15 min of deposition time; Figure 5 (f) is a TEM image of Ni nanoparticles.

[0094] See Figure 5 It can be seen that the morphology of the above Ni nanoparticle / CNTs composite material was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

[0095] 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.

[0096] 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 ).

[0097] Figure 6 The graph shows the linear sweep voltammetry (LSV) test results of the confined conductive composite film provided in Embodiment 1 of the present invention.

[0098] in, Figure 6 (a) shows the linear sweep 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.

[0099] (II) Electrochemical hydrolysis of EPS experiment:

[0100] The composite membrane prepared in step (I) was used as the cathode, and the stainless steel mesh as the anode, both placed in a simulated wastewater membrane bioreactor containing EPS. The distance between the anode and cathode was controlled to be 2-5 cm, and a 1 V DC voltage 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.

[0101] Furthermore, the hydrolysis effect of the composite membrane in this embodiment was verified; see details below. Figures 1-4 .

[0102] Figure 1 This diagram illustrates the variation of EPS hydrolysis rate under different voltages in the confined conductive composite film of this embodiment.

[0103] Figure 2 The figure shows the variation trend of EPS hydrolysis rate of the confined conductive composite film in this embodiment under different initial pH conditions.

[0104] Figure 3 This is a graph showing the pH change over time in the confined conductive composite membrane of this embodiment under constant voltage.

[0105] Figure 4 This represents the percentage of membrane flux recovery after backwashing of the confined conductive composite membrane in this embodiment over time during electrolysis.

[0106] 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%. The recovery of membrane flux with electrolysis time after backwashing is as follows... Figure 4 As shown.

[0107] Example 2

[0108] A method for preparing a composite membrane based on a carbon nanotube (CNT) confined conductive membrane supporting a nano-Mo-Fe bimetallic catalyst and its application in in-situ hydrolysis of extracellular polymeric substances (EPS).

[0109] (I) Preparation of composite membranes:

[0110] 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 solution 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] Material characterization:

[0115] The cross-sectional morphology of the prepared Mo-Fe / CNT composite material was analyzed using scanning electron microscopy (SEM) (see [link to SEM]). Figure 11 ).

[0116] Figure 11 This is a SEM cross-sectional image of the Mo-Fe bimetallic modified carbon nanotube composite material provided in Example 2 of the present invention. Figure 11 In the middle (a), Fe (0.4 nm) is the reference Fe. Figure 11 The structures shown in (b~d) represent the ordered "nanoforest" structure formed by the "Mo-on-Fe" type catalyst. Figure 11 The values ​​in (e~g) represent the irregular growth morphology of the "Fe-on-Mo" type catalyst.

[0117] It should be noted that the present invention Figure 11 , Figure 12 The terms "Mo-on-Fe" and "Fe-on-Mo" refer to the Mo-Fe bimetallic modified carbon nanotube composite materials prepared in this embodiment using different processes.

[0118] Molybdenum supported on iron (Mo-on-Fe) refers to the preparation of Mo-on-Fe / CNTs using a "Mo first, then Fe" loading sequence and a reduction temperature of 400~450℃. (Specific details are as described above.) Figure 11 , 12 The preparation method of molybdenum-supported iron (Mo-on-Fe) materials is as follows:

[0119] 1. Carbon nanotube pretreatment: Weigh 10 g of multi-walled carbon nanotubes (CNTs) and add them to 200 mL of a mixed acid system (concentrated nitric acid:concentrated sulfuric acid = 1:3, volume ratio). Stir magnetically at 60 ℃ for 6 h to introduce oxygen-containing functional groups (-OH, -COOH) on the surface, thereby increasing the adsorption sites of metal species. After the reaction, filter under vacuum, wash with deionized water until the filtrate is neutral, dry in a forced-air environment at 100 ℃ for 12 h, and grind to obtain purified modified CNTs for later use.

[0120] 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.

[0121] 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.

[0122] Iron-supported molybdenum (Fe-on-Mo) refers to Fe-on-Mo / CNTs prepared by using a "Fe first, then Mo" loading sequence and a reduction temperature of 650~700 ℃. (Specific details are as described above.) Figure 11 , 12 The preparation method of Fe-on-Mo material is as follows:

[0123] 1a. Carbon nanotube pretreatment: Same as above, molybdenum loaded onto iron (Mo-on-Fe).

[0124] 2a. Loading and calcination of Fe substrate: 0.02 mol of ferric nitrate nonahydrate was dissolved in 100 mL of deionized water. 0.01 mol of citric acid was added to adjust the pH to 2-3. After stirring and dissolving, 5 g of pretreated CNTs were added. The mixture was ultrasonically dispersed for 30 min and magnetically stirred at room temperature for 12 h to ensure uniform adsorption of Fe species onto the CNT surface. The Fe / CNT precursor was obtained by vacuum drying at 60 ℃ for 12 h. The precursor was then placed in a muffle furnace and calcined at 500-550 ℃ under a nitrogen atmosphere (50 mL / min) at a rate of 2 ℃ / min for 3 h to convert the Fe species into Fe2O3 and form a stable substrate. After cooling, the precursor was ground for later use.

[0125] 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.

[0126] The results showed that a highly ordered "nanoforest" structure was formed on the "Mo-on-Fe" type catalyst. Figure 11 (b~d), while in the "Fe-on-Mo" type samples, a more irregular growth morphology is observed ( Figure 11 The presence of e~g indicates that Mo, as the underlying layer, can effectively guide the uniform nucleation and directional growth of Fe. This structure significantly increases the specific surface area and the number of exposed active sites of the catalyst, which is beneficial for improving the efficiency of interfacial reactions.

[0127] To further reveal the electronic structure characteristics of the catalyst surface, X-ray photoelectron spectroscopy (XPS) was used to characterize the Mo-on-Fe and Fe-on-Mo configurations (see [link to XPS]). Figure 12 ).

[0128] Figure 12 The image shows a comparison of X-ray photoelectron spectroscopy (XPS) spectra of the Mo-on-Fe and Fe-on-Mo catalysts provided in Example 2 of this invention. The shifts in the Fe 2p and Mo 3d peaks indicate electron transfer from Mo to Fe.

[0129] 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.

[0130] In addition, electrochemical impedance spectroscopy (EIS) was performed on the Mo-Fe / CNT composite film using an electrochemical workstation (see [link to EIS]). Figure 13 ).

[0131] Figure 13 The Nyquist plots of the electrochemical impedance spectroscopy (EIS) of the Mo-Fe / CNT composite film provided in Example 2 of this invention at different cathode potentials are shown.

[0132] See Figure 13 The tests were 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 showed that the semicircle diameter decreased significantly with a negative potential shift, indicating a significant reduction in interfacial charge transfer resistance (Rct) and an acceleration of electron transfer rate, further confirming that the bimetallic synergistic effect effectively enhanced the material's electrochemical response capability.

[0133] (II) Electrochemical hydrolysis of EPS experiment:

[0134] The confined conductive composite membrane prepared in step (I) was used as the cathode, and a titanium mesh as the anode, both 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.

[0135] To further verify the hydrolysis effect of this embodiment, please refer to [link / reference needed]. Figures 7-10 .

[0136] Figure 7 This diagram illustrates the variation of EPS hydrolysis rate under different voltages in the confined conductive composite film of this embodiment.

[0137] Figure 8 The figure shows the variation trend of EPS hydrolysis rate of the confined conductive composite film in this embodiment under different initial pH conditions.

[0138] Figure 9 This is a graph showing the pH change over time in the confined conductive composite membrane of this embodiment under constant voltage.

[0139] Figure 10 This represents the percentage of membrane flux recovery after backwashing of the confined conductive composite membrane in this embodiment over time during electrolysis.

[0140] 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.

[0141] 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. An electrochemical method for in-situ hydrolysis of extracellular polymers based on a confined conductive composite membrane, characterized in that, Includes the following steps: S1: Place the confined conductive composite film as the cathode in a liquid environment containing EPS. The 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 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 between two-dimensional layers; the nano-metal catalyst includes at least one of nano-Ni catalyst, nano-Co catalyst, nano-Fe catalyst, and nano-Mo catalyst. The method for preparing the confined conductive composite film 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. S2: An anode is placed near the cathode, and a DC voltage is applied between the cathode and anode to cause the cathode to undergo a hydrogen evolution reaction, forming an alkaline microenvironment on its surface or interface region, thereby realizing the in-situ hydrolysis of EPS attached to the membrane surface; The distance between the anode and cathode is 2-5 cm, and the applied DC voltage is 0.5-2 V; The alkaline microenvironment causes the local pH at the cathode interface to rise to 9-11. S3: Perform physical backwashing on the confined conductive composite membrane after hydrolysis in step S2 to remove EPS contaminants after hydrolysis.

2. The electrochemical method 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 electrochemical method according to claim 1, characterized in that, The particle size of the nano-metal catalyst is 0.4~100 nm.

4. The electrochemical method 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. The electrochemical method according to claim 1, characterized in that, In step a1, the metal salt is at least one of nickel nitrate, cobalt nitrate, ferric nitrate, or ammonium molybdate.

6. The electrochemical method according to claim 1, characterized in that, 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.

7. The electrochemical method according to claim 1, characterized in that, The specific conditions for the heating treatment in step a3 in an inert atmosphere are as follows: the temperature is increased to 350-650℃ at a rate of 2-3℃ / min, and held for 3-8 hours.

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