A conductive support layer reverse osmosis membrane for electrically assisted removal of ammonia nitrogen and a preparation method and application thereof
By constructing a conductive network in the reverse osmosis membrane support layer and applying an external voltage, the problem of insufficient ammonium ion retention by traditional reverse osmosis membranes is solved, achieving efficient and stable ammonia nitrogen removal while reducing system complexity and cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HARBIN INST OF TECH
- Filing Date
- 2026-05-25
- Publication Date
- 2026-07-21
AI Technical Summary
Traditional reverse osmosis membranes have insufficient retention of ammonium ions, and existing methods to improve this retention are complex and costly, making them difficult to apply effectively in high-standard reuse scenarios.
A continuous conductive network is constructed in the support layer of the reverse osmosis membrane. Combined with external voltage regulation, a conductive support layer reverse osmosis membrane with both mechanical support and electrical response capabilities is formed. A polyamide selective layer is formed through interfacial polymerization, thereby achieving active regulation of ammonium ions.
Without damaging the separation layer structure, the ammonia nitrogen removal rate was increased from 94.2% to 99.6%, and long-term stability was maintained, while reducing operating costs and system complexity.
Smart Images
Figure CN122424718A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water treatment, specifically relating to a conductive support layer reverse osmosis membrane for electrically assisted removal of ammonia nitrogen, its preparation method, and its application. Background Technology
[0002] Against the backdrop of escalating global water supply and demand imbalances and continuously growing demand for high-quality reclaimed water, reverse osmosis (RO) has become a crucial technological component for advanced reclaimed water treatment and high-quality reuse due to its high separation precision and stable product water quality. It has shown significant application potential, particularly in short-process reuse systems coupled with anaerobic membrane bioreactors (AnMBRs). However, this technology remains limited by the RO membrane's ability to effectively remove ammonium ions (NH4+) from wastewater. + The insufficient retention of ammonium ions is a key bottleneck that affects the improvement of permeate water quality and restricts its application in high-standard reuse scenarios. The root cause lies in the limited selective recognition capability of traditional polyamide (PA) RO membranes for small-sized monovalent ions. The RO process essentially still relies mainly on the inherent sieving capacity of the membrane structure and interfacial interactions to achieve passive separation, lacking the ability to actively regulate the migration behavior of ammonium ions. Existing methods to improve the ammonium removal efficiency of RO systems mostly rely on adsorption pretreatment or oxidation posttreatment. While these can improve the overall removal efficiency to some extent, they are usually accompanied by problems such as extended process time, increased operating costs, and more complex system integration. Therefore, improving the membrane's retention capacity for ammonium ions in situ within the RO system has greater engineering application value.
[0003] Against this backdrop, conductive RO membranes offer the possibility of introducing an external electric field and constructing new tunable interaction dimensions beyond traditional pressure-driven separation. This promises to regulate the local charge environment at the membrane interface, the distribution of ammonium ions in the near-membrane region, and their transmembrane transport behavior, providing a new technological path to enhance the ammonium ion removal capacity of the RO process. However, directly constructing conductive functionality around the PA dense separation layer often interferes with the interfacial polymerization process and the formation of the dense layer, increasing the risk of structural defects and weakening the membrane's high selectivity and long-term stability. Therefore, how to achieve conductivity in the RO membrane without destroying the basic separation structure of the PA separation layer is a key issue for the further development of this technology.
[0004] In fact, the final performance of an RO membrane is not solely determined by the PA separation layer. As a crucial component of the polyamide composite membrane, the support layer, in addition to providing mechanical support, also acts as a storage and transport channel for aqueous monomers during interfacial polymerization. Its pore size distribution, porosity, surface wettability, and interfacial characteristics affect monomer diffusion behavior and local concentration distribution, thereby influencing the formation process, structural uniformity, and overall separation performance of the PA separation layer. Therefore, compared to directly introducing conductivity into the PA separation layer, constructing a conductive structure starting from the support layer not only preserves the PA separation layer's primary role as a high-precision separation interface but also holds promise for achieving synergistic optimization of membrane structure construction and the introduction of conductivity by leveraging the support layer's regulatory role in the interfacial polymerization process.
[0005] Based on this, a continuous conductive network is constructed in the RO membrane support layer, giving it both support function and electroresponsiveness. Furthermore, by applying an external voltage during RO operation, electromodulation capabilities can be introduced into the membrane separation interface without damaging the surface PA separation layer structure, thereby enhancing the control of ammonium ion migration and transport processes. Therefore, developing a conductive support layer reverse osmosis membrane and its preparation method, and applying it to the efficient removal of ammonium ions under electro-assisted conditions, has significant technical importance and application prospects. Summary of the Invention
[0006] To address the aforementioned technical problems, this invention provides a conductive support layer reverse osmosis membrane for electrically assisted removal of ammonia nitrogen, its preparation method, and its application.
[0007] The present invention aims to construct a reverse osmosis membrane with a conductive support layer that combines high separation performance and electrical response capability, establish a stable preparation method for the membrane, and achieve efficient removal of ammonia nitrogen under electrically assisted conditions, so as to form a unified technical solution for membrane structure construction and separation application.
[0008] A conductive support layer reverse osmosis membrane for electrically assisted removal of ammonia nitrogen, comprising a porous conductive support layer and a polyamide selective layer located on the surface of the conductive support layer;
[0009] The conductive support layer comprises a matrix polymer, conductive carbon material, and conductive polymer to form a continuous conductive network inside the support layer, enabling the conductive support layer to have both mechanical support function and electrical response capability.
[0010] The polyamide selective layer is formed by interfacial polymerization.
[0011] A method for preparing a conductive support layer reverse osmosis membrane for electrically assisted removal of ammonia nitrogen is specifically carried out according to the following steps:
[0012] I. Preparation of the conductive support layer casting solution:
[0013] The pore-forming agent is dissolved in an organic solvent, then conductive carbon material is added and dispersed evenly. Next, a pore structure modifier and a conductive polymer are added, and finally the matrix polymer is added and stirred continuously to form a uniform conductive support layer casting solution.
[0014] II. Formation of the conductive support layer:
[0015] After degassing the casting solution of the conductive support layer, it is coated onto the surface of the support substrate. A porous conductive support layer is formed through non-solvent-induced phase transformation. The residual solvent is removed by immersion and washing, and then dried to obtain the conductive support layer.
[0016] III. Constructing a polyamide selective layer:
[0017] The conductive support layer is fixed in the mold and first comes into contact with the aqueous monomer solution for wetting. After wetting with the aqueous monomer solution, the excess aqueous monomer solution is poured off and the residual liquid on the membrane surface is removed. Then it comes into contact with the oil monomer solution for wetting. A polyamide selective layer is formed through interfacial polymerization. Subsequently, it is thermally cured and soaked and washed to obtain a conductive support layer reverse osmosis membrane for electrically assisted removal of ammonia nitrogen.
[0018] A conductive support layer reverse osmosis membrane for electrically assisted ammonia nitrogen removal is applied in the efficient removal of ammonia nitrogen under electrically assisted conditions. In application, the conductive support layer reverse osmosis membrane is assembled in a reverse osmosis membrane module, with its conductive support layer connected to the positive terminal of an external power source as the anode; a conductive feed spacer is provided on the feed side; the conductive feed spacer is connected to the negative terminal of the external power source as the cathode; an external voltage is applied during pressure-driven filtration to regulate the membrane interface charge environment and the migration behavior of ammonium ions in ammonia nitrogen, thereby improving the membrane's ammonia nitrogen rejection rate.
[0019] Compared with the prior art, the present invention has the following beneficial effects:
[0020] I. This invention introduces conductive functionality from the support layer rather than directly from the dense separation layer, thus taking into account conductivity, structural stability, and separation selectivity at the membrane construction level.
[0021] Second, the conductive support layer constructed by this invention not only provides mechanical support, but also promotes the construction of composite membrane structures by regulating monomer storage and transport during the interface polymerization process.
[0022] Third, by introducing an external voltage during reverse osmosis operation, this invention can add a new adjustable field in addition to pressure drive, and actively regulate the membrane interface charge environment, ammonium ion distribution in the near-membrane region, and transmembrane migration behavior to achieve enhanced ammonia nitrogen retention.
[0023] IV. The ammonia nitrogen removal rate of the conductive support layer reverse osmosis membrane for electrically assisted ammonia nitrogen removal prepared using the present invention is as follows: when the external voltage is 0 V, the removal rate is 94.2%; at 2 V, it is 96.1%; at 4 V, it is 98.7%; at 6 V, it is 99.6%; and at 8 V, it is 98.3%. Attached Figure Description
[0024] Figure 1 The surface and cross-sectional SEM images of the conductive support layer reverse osmosis membrane for electrically assisted removal of ammonia nitrogen prepared in Example 1 are shown.
[0025] Figure 2 The graphs show the long-term performance test results of the conductive support layer reverse osmosis membranes used for electrically assisted removal of ammonia nitrogen in the application examples, with applied voltages of 0 V, 4 V, and 6 V, for the ammonia nitrogen rejection rate. Detailed Implementation
[0026] Specific Implementation Method 1: This implementation method is a conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen, characterized in that the conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen includes a porous conductive support layer and a polyamide selective layer located on the surface of the conductive support layer;
[0027] The conductive support layer comprises a matrix polymer, conductive carbon material, and conductive polymer to form a continuous conductive network inside the support layer, enabling the conductive support layer to have both mechanical support function and electrical response capability.
[0028] The polyamide selective layer is formed by interfacial polymerization.
[0029] In addition to providing mechanical support, the conductive support layer described in this embodiment also serves as a storage and transport channel for aqueous monomers during interfacial polymerization, thereby participating in the formation process of the polyamide selective layer and affecting its structural uniformity and separation performance.
[0030] The conductive carbon material described in this embodiment is used to construct the basic electron transport network within the support layer and can improve the response of the support layer to an applied electric field.
[0031] The conductive polymer described in this embodiment is used to enhance the conductivity continuity and electric field response characteristics of the support layer, and to improve the dispersion and synergistic construction effect of conductive carbon materials in the support layer.
[0032] The pore-forming agent and pore structure regulator described in this embodiment are used to regulate the pore structure, porosity and surface state of the support layer, so as to facilitate monomer diffusion regulation and polyamide layer formation during the interfacial polymerization process.
[0033] The conductive polymer and conductive carbon material described in this embodiment synergistically construct a conductive network within the support layer.
[0034] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the matrix polymer is one or more of polysulfone, polyvinylidene fluoride, polyethersulfone, or polyacrylonitrile; the conductive carbon material is one or more of carbon nanotubes, carboxylated carbon nanotubes, aminated carbon nanotubes, graphene, reduced graphene oxide, or conductive carbon black; and the conductive polymer is one or more of polyaniline, polypyrrole, or poly(3,4-ethylenedioxythiophene). Other steps are the same as in Specific Implementation Method One.
[0035] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the conductive support layer is formed by a non-solvent-induced phase transformation of the conductive support layer casting solution to create a porous conductive support layer; the conductive support layer casting solution is prepared from a matrix polymer, conductive carbon material, conductive polymer, pore-forming agent, pore structure regulator, and organic solvent; the conductive support layer casting solution comprises, by mass percentage: 10-18 wt% matrix polymer, 0.8-1.4 wt% conductive carbon material, 2-4 wt% conductive polymer, 0.5-2 wt% pore-forming agent, 5-10 wt% pore structure regulator, with the balance being organic solvent. Other steps are the same as in Specific Implementation Method One or Two.
[0036] Specific Embodiment Four: This embodiment differs from Specific Embodiments One to Three in that: the pore-forming agent is one or more of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol; the pore structure regulating agent is one or more of 4-methyl-2-pentanone, ethylene glycol methyl ether, and dimethylacetamide; and the organic solvent is one or more of N-methylpyrrolidone, dimethylformamide, and dimethyl sulfoxide. Other steps are the same as in Specific Embodiments One to Three.
[0037] Specific Implementation Method 5: This implementation method is a method for preparing a conductive support layer reverse osmosis membrane for electrically assisted removal of ammonia nitrogen, specifically completed according to the following steps:
[0038] I. Preparation of the conductive support layer casting solution:
[0039] The pore-forming agent is dissolved in an organic solvent, then conductive carbon material is added and dispersed evenly. Next, a pore structure modifier and a conductive polymer are added, and finally the matrix polymer is added and stirred continuously to form a uniform conductive support layer casting solution.
[0040] II. Formation of the conductive support layer:
[0041] After degassing the casting solution of the conductive support layer, it is coated onto the surface of the support substrate. A porous conductive support layer is formed through non-solvent-induced phase transformation. The residual solvent is removed by immersion and washing, and then dried to obtain the conductive support layer.
[0042] III. Constructing a polyamide selective layer:
[0043] The conductive support layer is fixed in the mold and first comes into contact with the aqueous monomer solution for wetting. After wetting with the aqueous monomer solution, the excess aqueous monomer solution is poured off and the residual liquid on the membrane surface is removed. Then it comes into contact with the oil monomer solution for wetting. A polyamide selective layer is formed through interfacial polymerization. Subsequently, it is thermally cured and soaked and washed to obtain a conductive support layer reverse osmosis membrane for electrically assisted removal of ammonia nitrogen.
[0044] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in the following ways: The dispersion in step one is ultrasonic dispersion, with a power of 10-500 W and a dispersion time of 0.5-3 h; the matrix polymer is added in step one and continuously stirred for 2-48 h; the supporting substrate in step two is non-woven fabric or polyester non-woven fabric; the coating thickness in step two is 100-250 μm; the coagulation bath in the non-solvent-induced phase inversion in step two is ultrapure water at a temperature of 20-30 ℃, and the ambient temperature is 20-30 ℃; after phase separation in step two, the mixture is soaked in ultrapure water for at least 12-24 h and the water is changed at least twice. Other steps are the same as in Specific Implementation Methods One to Five.
[0045] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in the following ways: The concentration of the aqueous monomer solution in step three is 0.5-5 wt%, wherein the aqueous monomer is an amino-containing water-soluble monomer; the amino-containing water-soluble monomer is an aromatic diamine or aliphatic polyamine, preferably one or more of m-phenylenediamine, p-phenylenediamine, ethylenediamine, or diethylenetriamine; the concentration of the oil phase monomer solution in step three is 0.05-0.3 wt%, wherein the oil phase monomer is a polyfunctional acyl chloride monomer; the polyfunctional acyl chloride monomer is an aromatic polyacyl chloride, preferably one or more of pyromellitic trimethylolpropionate chloride, isophthaloyl chloride, or terephthaloyl chloride; in step three, the conductive support layer is fixed in the mold, first contacted and immersed in the aqueous monomer solution for 1-5 min, and then contacted and immersed in the oil phase monomer solution for 10-60 s; the thermosetting temperature in step three is 40-80 ℃, and the thermosetting time is 1-10 min. Other steps are the same as in Specific Implementation Methods One to Six.
[0046] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the aqueous monomer solution in step three may also contain one or more of the following: acid acceptor, wetting agent, surfactant, or interface control agent; the acid acceptor is sodium hydroxide, sodium carbonate, sodium bicarbonate, or triethylamine, with a concentration of 0.01-1 wt%; the wetting agent is ethanol or isopropanol, with a concentration of 0.1-5 wt%; the surfactant is sodium dodecyl sulfate, Tween 20, or Triton X-100, with a concentration of 0.005-0.5 wt%; the interface control agent is polyvinylpyrrolidone, polyethylene glycol, or triethylamine, with a concentration of 0.01-1 wt%; the oil phase monomer solution in step three may also contain one or more of the following: a cosolvent and an interface control agent; the cosolvent is toluene, cyclohexane, or isoalkanes, with a concentration of 1-20 wt%; the interface control agent is polyvinylpyrrolidone, polyethylene glycol, or triethylamine, with a concentration of 0.1-5 wt%. The other steps are the same as those in Specific Implementation Methods 1 to 7.
[0047] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that it applies a conductive support layer reverse osmosis membrane for electrically assisted ammonia nitrogen removal in the efficient removal of ammonia nitrogen under electrically assisted conditions. In application, the conductive support layer reverse osmosis membrane is assembled in a reverse osmosis membrane module, with its conductive support layer connected to the positive terminal of an external power source as the anode; a conductive feed spacer is provided on the feed side; the conductive feed spacer is connected to the negative terminal of the external power source as the cathode; an external voltage is applied during pressure-driven filtration to regulate the membrane interface charge environment and the migration behavior of ammonium ions in ammonia nitrogen, thereby improving the membrane's ammonia nitrogen rejection rate. Other steps are the same as in Specific Implementation Methods One to Eight.
[0048] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: the conductive feed spacer is one or more of a metal conductive mesh, carbon cloth, and graphite felt; the conductive feed spacer is used to establish a stable electrode interface on the feed side and together with the conductive support layer forms an electro-assisted separation system; the reverse osmosis membrane module adopts a flat-plate, spiral-wound, or other membrane module configuration suitable for conductive connection; the filtration process is carried out at a pressure of 5-20 bar and an operating temperature of 15-35 ℃; the external voltage is 0-10 V; the application is suitable for systems with an ammonia nitrogen concentration of 40-500 mg / L in the influent; the application is suitable for the removal of ammonia nitrogen from municipal wastewater deep treatment effluent, anaerobic membrane bioreactor effluent, aquaculture wastewater, fertilizer wastewater, leachate, or other water bodies containing ammonium ions. Other steps are the same as in Specific Implementation Methods One to Nine.
[0049] The beneficial effects of the present invention are verified using the following embodiments:
[0050] Example 1: A method for preparing a conductive support layer reverse osmosis membrane for electrically assisted removal of ammonia nitrogen, specifically comprising the following steps:
[0051] I. Preparation of conductive polymer polyaniline:
[0052] 1.86 g of aniline monomer was dissolved in 50 mL of 1 mol / L HCl solution at 4 °C, and then 50 mL of 0.50 mol / L ammonium persulfate solution was added dropwise to induce an oxidative polymerization reaction for 48 h, yielding conductive polyaniline. The reaction product was filtered, and the resulting solid product was washed with deionized water to remove residual ammonium persulfate, and then dried to obtain a solid powder. 1.0 g of the obtained solid powder was placed in 100 mL of 0.1 mol / L ammonia solution and stirred for 12 h to induce reverse doping, yielding intrinsic polyaniline. The product was then filtered, and residual ammonia was washed away with deionized water, followed by washing away oligomers with methanol. The product was then vacuum dried at 60 °C for 24 h and ground to obtain polyaniline.
[0053] II. Preparation of the conductive support layer casting solution:
[0054] Polyvinylpyrrolidone was dissolved in N-methylpyrrolidone, then carboxylated carbon nanotubes were added, and the mixture was ultrasonically dispersed at an ultrasonic power of 220 W for 1 h. Then 4-methyl-2-pentanone and the polyaniline prepared in step one were added, and finally polysulfone was added and stirred continuously at room temperature for 24 h to form a uniform conductive support layer casting solution.
[0055] The conductive support layer casting solution comprises, by mass percentage: 13 wt% polysulfone, 1.2 wt% carboxylated carbon nanotubes, 3 wt% polyaniline, 1 wt% polyvinylpyrrolidone, 8 wt% 4-methyl-2-pentanone, with the balance being N-methylpyrrolidone.
[0056] III. Formation of the conductive support layer:
[0057] The conductive support layer casting solution was degassed under vacuum for 20 min, then coated onto the surface of a nonwoven fabric and formed a film at an ambient temperature of 25±1 ℃ and a relative humidity of 40±1%. Subsequently, it was rapidly immersed in ultrapure water at 25±1 ℃, where a non-solvent-induced phase transformation occurred to form the conductive support layer. The resulting conductive support layer was soaked in ultrapure water for more than 24 h with the water changed twice, and then stored in ultrapure water at 4 ℃ for later use.
[0058] IV. Constructing a polyamide selective layer:
[0059] Prepare an aqueous solution of 2 wt% m-phenylenediamine and a hexane solution of 0.1 wt% trimesoyl chloride. Fix the conductive support layer in a flat mold, ensuring a smooth surface and sealing around the edges. First, add the aqueous solution of 2 wt% m-phenylenediamine to the membrane surface, soak for 2 min, then pour off the excess liquid and blow away any remaining liquid on the surface with an air knife. Next, add the hexane solution of 0.1 wt% trimesoyl chloride to the membrane surface, contact for 30 s, then pour off the excess liquid and rinse the surface with hexane. After the hexane on the surface evaporates, heat-cur it at 60 ℃ for 5 min to obtain a conductive support layer reverse osmosis membrane for electro-assisted ammonia nitrogen removal. Soak the obtained membrane in ultrapure water for more than 24 h and change the water twice before use.
[0060] Figure 1 The images show the surface and cross-sectional SEM characterization of the conductive support layer reverse osmosis membrane prepared in Example 1 for electrically assisted removal of ammonia nitrogen.
[0061] from Figure 1 It can be seen that the surface of the prepared conductive support layer is relatively continuous and uniform, with no obvious macroscopic defects; its cross-section has a typical porous structure, indicating that a complete porous conductive support layer can be successfully formed through non-solvent-induced phase transformation, and can be used as a substrate for subsequent interfacial polymerization to construct polyamide selective layers.
[0062] Application Examples: System construction for electrically assisted ammonia nitrogen removal, and the effect of applied voltage on ammonia nitrogen removal performance:
[0063] 1. The conductive support layer reverse osmosis membrane for electrically assisted ammonia nitrogen removal prepared in Example 1 is loaded into a cross-flow membrane cell, with the polyamide selective layer facing the feed side, and the filtration area is 33.34 cm². 2 A conductive feed spacer is installed on the feed side of the membrane, and the conductive feed spacer is connected to the negative terminal of the DC power supply as the cathode; the conductive support layer is connected to the positive terminal of the DC power supply as the anode; the cross-flow membrane tank containing the reverse osmosis membrane with the conductive support layer and the conductive feed spacer is connected to the feed water pump, the pressure control valve and the permeate collection unit respectively to construct an electric-assisted reverse osmosis ammonia nitrogen removal device; the temperature is controlled at 25±1 ℃ and the feed side flow rate is 20 L / h during the test;
[0064] 2. Simulated feed water containing ammonia nitrogen (feed pH ~7, concentration 60 mg / L) was used under the same operating conditions. Voltages of 0V, 2V, 4V, 6V, and 8V were applied respectively to investigate the ammonia nitrogen removal rate of the conductive support layer reverse osmosis membrane. The results showed that the ammonia nitrogen removal rate first increased and then decreased with increasing voltage. The ammonia nitrogen removal rate was 94.2% at 0V, 96.1% at 2V, 98.7% at 4V, 99.6% at 6V, and 98.3% at 8V.
[0065] Long-term performance tests were conducted on the ammonia nitrogen rejection rates of three sets of conductive support layer reverse osmosis membranes used for electrically assisted ammonia nitrogen removal at applied voltages of 0 V, 4 V, and 6 V. (See attached figures.) Figure 2 As shown;
[0066] from Figure 2 The results show that the ammonia nitrogen rejection rate remained relatively stable in the 6 V group, while it decreased significantly in the 0 V group, rapidly dropping from 94.1% to 86.7%. The 6 V group maintained an ammonia nitrogen rejection rate of over 98% throughout the entire cycle. These results indicate that the applied voltage helps improve the long-term stable rejection performance of the conductive support layer reverse osmosis membrane used for electrically assisted ammonia nitrogen removal, with the regulatory effect being more significant under the 6 V condition, maintaining a stable and efficient rejection effect over a longer operating period.
[0067] In summary: carbon nanotubes in the conductive support layer are used to construct the basic conductive network, while polyaniline is used to enhance the membrane support layer's sensitive response to the applied electric field. When the conductive support layer is connected to the positive terminal of the power supply and the conductive feed spacer on the feed side is connected to the negative terminal of the power supply, the applied voltage establishes a directional electric field near the membrane interface. This electric field can regulate the distribution and migration behavior of ammonium ions in ammonia nitrogen in the near-membrane region and change the charge environment at the membrane interface, thereby enhancing the membrane's repulsion of ammonium ions and inhibiting their transmembrane permeation.
Claims
1. A conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen, characterized in that... The conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen includes a porous conductive support layer and a polyamide selective layer located on the surface of the conductive support layer. The conductive support layer comprises a matrix polymer, conductive carbon material, and conductive polymer to form a continuous conductive network inside the support layer, enabling the conductive support layer to have both mechanical support function and electrical response capability. The polyamide selective layer is formed by interfacial polymerization.
2. The conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen according to claim 1, characterized in that... The matrix polymer is one or more of polysulfone, polyvinylidene fluoride, polyethersulfone, or polyacrylonitrile; the conductive carbon material is one or more of carbon nanotubes, carboxylated carbon nanotubes, aminated carbon nanotubes, graphene, reduced graphene oxide, or conductive carbon black; and the conductive polymer is one or more of polyaniline, polypyrrole, or poly(3,4-ethylenedioxythiophene).
3. The conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen according to claim 1, characterized in that... The conductive support layer is formed by a non-solvent-induced phase transformation of a conductive support layer casting solution to create a porous conductive support layer. The conductive support layer casting solution is prepared from a matrix polymer, conductive carbon material, conductive polymer, pore-forming agent, pore structure regulator, and organic solvent. The conductive support layer casting solution comprises, by mass percentage: 10-18 wt% matrix polymer, 0.8-1.4 wt% conductive carbon material, 2-4 wt% conductive polymer, 0.5-2 wt% pore-forming agent, 5-10 wt% pore structure regulator, and the balance being organic solvent.
4. The conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen according to claim 3, characterized in that... The pore-forming agent is one or more of polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol; the pore structure regulator is one or more of 4-methyl-2-pentanone, ethylene glycol methyl ether, and dimethylacetamide; and the organic solvent is one or more of N-methylpyrrolidone, dimethylformamide, and dimethyl sulfoxide.
5. A method for preparing a conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen as described in any one of claims 1 to 4, characterized in that... The preparation method is specifically carried out according to the following steps: I. Preparation of the conductive support layer casting solution: The pore-forming agent is dissolved in an organic solvent, then conductive carbon material is added and dispersed evenly. Next, a pore structure modifier and a conductive polymer are added, and finally the matrix polymer is added and stirred continuously to form a uniform conductive support layer casting solution. II. Formation of the conductive support layer: After degassing the conductive support layer casting solution, it is scraped onto the surface of the support substrate. A porous conductive support layer is formed through non-solvent-induced phase transformation. The residual solvent is removed by immersion washing and drying to obtain the conductive support layer. III. Constructing a polyamide selective layer: The conductive support layer is fixed in the mold and first comes into contact with the aqueous monomer solution for wetting. After wetting with the aqueous monomer solution, the excess aqueous monomer solution is poured off and the residual liquid on the membrane surface is removed. Then it comes into contact with the oil monomer solution for wetting. A polyamide selective layer is formed through interfacial polymerization. Subsequently, it is thermally cured and soaked and washed to obtain a conductive support layer reverse osmosis membrane for electrically assisted removal of ammonia nitrogen.
6. The method for preparing a conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen according to claim 5, characterized in that... The dispersion described in step one is ultrasonic dispersion, with a power of 10-500 W and a dispersion time of 0.5-3 h; the matrix polymer is added in step one and stirred continuously for 2-48 h; the supporting substrate described in step two is non-woven fabric or polyester non-woven fabric; the coating thickness described in step two is 100-250 μm; the coagulation bath in the non-solvent-induced phase transformation in step two is ultrapure water, with a temperature of 20-30 ℃ and an ambient temperature of 20-30 ℃; after phase separation in step two, the mixture is soaked in ultrapure water for more than 12-24 h and the water is changed at least twice.
7. The method for preparing a conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen according to claim 5, characterized in that... In step three, the concentration of the aqueous monomer solution is 0.5-5 wt%, wherein the aqueous monomer is an amino-containing water-soluble monomer; the amino-containing water-soluble monomer is an aromatic diamine or an aliphatic polyamine, preferably one or more of m-phenylenediamine, p-phenylenediamine, ethylenediamine, or diethylenetriamine; the concentration of the oil phase monomer solution in step three is 0.05-0.3 wt%, wherein the oil phase monomer is a polyfunctional acyl chloride monomer; the polyfunctional acyl chloride monomer is an aromatic polyacyl chloride, preferably one or more of pyromellitic trimethylolpropionate chloride, isophthaloyl chloride, or terephthaloyl chloride; in step three, the conductive support layer is fixed in the mold, first contacted and immersed in the aqueous monomer solution for 1-5 min, and then contacted and immersed in the oil phase monomer solution for 10-60 s; the thermosetting temperature in step three is 40-80 ℃, and the thermosetting time is 1-10 min.
8. The method for preparing a conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen according to claim 5, characterized in that... The aqueous monomer solution in step three may also contain one or more of the following: acid acceptor, wetting agent, surfactant, or interface regulating agent; the acid acceptor is sodium hydroxide, sodium carbonate, sodium bicarbonate, or triethylamine, with a concentration of 0.01-1 wt%; the wetting agent is ethanol or isopropanol, with a concentration of 0.1-5 wt%; the surfactant is sodium dodecyl sulfate, Tween 20, or Triton X-100, with a concentration of 0.005-0.5 wt%; the interface regulating agent is polyvinylpyrrolidone, polyethylene glycol, or triethylamine, with a concentration of 0.01-1 wt%; the oil phase monomer solution in step three may also contain one or more of the following: co-solvent and interface regulating agent; the co-solvent is toluene, cyclohexane, or isoalkanes, with a concentration of 1-20 wt%; the interface regulating agent is polyvinylpyrrolidone, polyethylene glycol, or triethylamine, with a concentration of 0.1-5 wt%.
9. The application of a conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen as described in any one of claims 1 to 4, characterized in that... A conductive support layer reverse osmosis membrane for electrically assisted ammonia nitrogen removal is applied in the efficient removal of ammonia nitrogen under electrically assisted conditions. In application, the conductive support layer reverse osmosis membrane is assembled in a reverse osmosis membrane module, with its conductive support layer connected to the positive terminal of an external power source as the anode; a conductive feed spacer is provided on the feed side; the conductive feed spacer is connected to the negative terminal of the external power source as the cathode; an external voltage is applied during pressure-driven filtration to regulate the membrane interface charge environment and the migration behavior of ammonium ions in ammonia nitrogen, thereby improving the membrane's ammonia nitrogen rejection rate.
10. The application of the conductive support layer reverse osmosis membrane for electro-assisted removal of ammonia nitrogen according to claim 9, characterized in that... The conductive feed spacer is one or more of a metal conductive mesh, carbon cloth, and graphite felt; the conductive feed spacer is used to establish a stable electrode interface on the feed side and together with the conductive support layer to form an electro-assisted separation system; the reverse osmosis membrane module adopts a flat-plate, spiral-wound, or other membrane module configuration suitable for conductive connection; the filtration process is carried out at a pressure of 5-20 bar and an operating temperature of 15-35 ℃; the external voltage is 0-10 V; the application is suitable for systems with an ammonia nitrogen concentration of 40-500 mg / L in the influent; the application is suitable for the removal of ammonia nitrogen from municipal wastewater deep treatment effluent, anaerobic membrane bioreactor effluent, aquaculture wastewater, fertilizer wastewater, leachate, or other water bodies containing ammonium ions.