Aromatic polyamine nanofiltration membrane, preparation method thereof and application thereof in separation of antibiotics and inorganic salts

Abstract

The present application relates to the technical field of water treatment membrane, and particularly relates to a kind of aromatic polyamine nanofiltration membrane and its preparation method and its application in separating antibiotic and inorganic salt.The aromatic polyamine nanofiltration membrane includes base film and separation layer attached to the surface of the base film, the separation layer is composed of piperazine, 2,4,6-triaminotoluene and benzene tricarboxylic acid chloride by forming amide bond polymer, the mass ratio of piperazine and 2,4,6-triaminotoluene is (6.8~9.2):(0.8~3.2).The aromatic polyamine nanofiltration membrane provided by the present application not only has higher antibiotic retention rate, but also has better water permeability, so as to realize efficient separation of antibiotic in antibiotic inorganic salt system.

Description

Technical Field

[0001] This invention relates to the field of water treatment membrane technology, and in particular to an aromatic polyamine nanofiltration membrane, its preparation method, and its application in the separation of antibiotics and inorganic salts. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Currently, the main method for producing antibiotics is bio-fermentation. The fermentation broth of bio-fermentation contains both the target antibiotic and inorganic salts. This is primarily because inorganic salts such as sodium chloride play indispensable roles in bio-fermentation, maintaining osmotic pressure, regulating pH, and providing inorganic nutrients. To obtain high-purity antibiotics, efficient separation of inorganic salts and antibiotics from the fermentation broth is necessary. However, improper treatment of antibiotic fermentation wastewater can easily induce the emergence and spread of drug-resistant bacteria, posing a long-term threat to ecosystems and public health. Traditional separation methods mainly rely on ion exchange resin adsorption, but these methods are cumbersome and have limited separation efficiency. Nanofiltration technology, with its nanoscale membrane pore size and the synergistic effect of the Donnan effect, can achieve selective separation of ions with different valence states at lower operating pressures. This provides an energy-efficient and high-performance new approach for separating antibiotics from salts such as sodium chloride, and is of great significance for purifying antibiotic fermentation broth, curbing antibiotic diffusion, and promoting the development of green water treatment technologies.

[0004] Existing nanofiltration membrane materials still face performance bottlenecks in achieving antibiotic-salt separation. For example, negatively charged polyamide nanofiltration membranes prepared based on piperazine and trimesoyl chloride, while exhibiting high rejection rates for some antibiotics, typically have low water flux (<20 L·m). -2 ·h -1 ·bar -1 Furthermore, nanofiltration membranes have limited selectivity for high-valent salts. Introducing coamine monomers such as polyethyleneimine can enhance the positive charge on the membrane surface and improve antibiotic rejection, but this often leads to a significant decrease in flux and insufficient salt permeability, affecting separation efficiency. In addition, while using highly cross-linked monomers such as m-phenylenediamine can improve antibiotic rejection, their dense structure results in low flux. Therefore, there is an urgent need to develop nanofiltration membranes that combine high water flux and efficient antibiotic rejection. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an aromatic polyamine nanofiltration membrane, its preparation method, and its application in the separation of antibiotics and inorganic salts. The aromatic polyamine nanofiltration membrane provided by the present invention not only has a high antibiotic rejection rate but also better water permeability, thereby achieving efficient separation of antibiotics in an antibiotic-inorganic salt system.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In a first aspect, an aromatic polyamine nanofiltration membrane includes a base membrane and a separation layer attached to the surface of the base membrane, the separation layer being composed of a polymer of piperazine, 2,4,6-triaminotoluene and trimesoyl chloride forming amide bonds, wherein the mass ratio of piperazine to 2,4,6-triaminotoluene is (6.8~9.2):(0.8~3.2).

[0008] Secondly, a method for preparing an aromatic polyamine nanofiltration membrane includes the following steps:

[0009] The base membrane was immersed in an aqueous solution containing piperazine, 2,4,6-triaminotoluene, and alkaline compounds;

[0010] Remove the soaked base film and then remove the water from its surface;

[0011] The soaked and anhydrous base film is added to an organic phase solution containing trimesoyl chloride, so that piperazine, 2,4,6-triaminotoluene and trimesoyl chloride undergo interfacial polymerization on the base film surface to form a polymer separation layer connected by amide bonds.

[0012] The aromatic polyamine nanofiltration membrane provided by this invention, based on a negatively charged polyamide nanofiltration membrane prepared from piperazine and trimesoyl chloride, significantly optimizes the polyamide separation layer by introducing 2,4,6-triaminotoluene. First, the rigid benzene ring structure of 2,4,6-triaminotoluene enhances the rigidity and crosslinking density of the polymer network, contributing to the formation of a more stable free volume. Second, the polyamino groups carried by 2,4,6-triaminotoluene exhibit high reactivity, participating in interfacial polymerization and promoting the formation of a denser and more uniformly distributed separation layer, thereby achieving precise control over the nano-mass transfer channels. Furthermore, by adjusting the addition ratio of TAT, Marangoni flow during interfacial polymerization can be induced, resulting in a unique "crater" morphology on the membrane surface. This morphological evolution further modulates the membrane's permeability selectivity, ultimately achieving significant optimization between permeability and retention performance. Experiments show that the nanofiltration membrane provided by this invention not only significantly improves its separation factor for antibiotics such as doxorubicin hydrochloride and sodium chloride but also maintains a high water flux.

[0013] Thirdly, the application of an aromatic polyamine nanofiltration membrane as described in the first aspect of the present invention or an aromatic polyamine nanofiltration membrane obtained by the preparation method described in the second aspect of the present invention in the separation of antibiotics and inorganic salts.

[0014] The beneficial effects of this invention are as follows:

[0015] 1. The aromatic polyamine nanofiltration membrane provided by this invention significantly optimizes the pore size distribution, crosslinking density, and surface charge of the polyamide separation layer by introducing 2,4,6-triaminotoluene, which has a rigid benzene ring structure and high reactivity, as a monomer, and synergistically participating in interfacial polymerization with piperazine. The prepared aromatic polyamine nanofiltration membrane maintains a high water flux (up to 22.025 L·m³). -2 ·h -1 ·bar -1 While achieving high retention of antibiotics such as doxorubicin hydrochloride, it also significantly reduces the retention of NaCl. Compared with existing PIP / TMC systems (where the separation factor between antibiotics and NaCl is typically <20) and PEI-modified systems (where the separation factor between antibiotics and NaCl is <15), the aromatic polyamine nanofiltration membrane provided by this invention significantly improves the separation factor between antibiotics and NaCl, reaching 96.132.

[0016] 2. The aromatic polyamine nanofiltration membrane provided by this invention introduces an appropriate amount of TAT into the PIP / TMC membrane, which can improve the degree of crosslinking and form a separation layer with a "crater" morphology and a large free volume. This not only enhances the rigidity of the membrane but also expands the effective permeation area. This structure significantly improves water flux with almost no sacrifice in antibiotic rejection rate, overcoming the low flux (<20 L·m) of PIP / TMC membranes. -2 ·h -1 ·bar -1 Or the flux of the PEI modified membrane is too low (~10 L·m). -2 ·h -1 ·bar -1 The problem is...

[0017] 3. Experiments show that the aromatic polyamine nanofiltration membrane provided by this invention exhibits high retention rates for various antibiotics (such as chloramphenicol, tetracycline hydrochloride, ceftriaxone sodium, and doxorubicin hydrochloride), demonstrating good applicability in the treatment of complex fermentation broths or antibiotic-containing wastewater. Simultaneously, it exhibits tunable retention behavior for salts of different valence states (such as Na₂SO₄, MgCl₂, MgSO₄, and NaCl), broadening the selective window for the separation of monovalent and divalent salts, making it suitable for high-salinity wastewater treatment and resource recovery.

[0018] 4. The aromatic polyamine nanofiltration membrane provided by the present invention exhibits stable separation performance and water flux over a wide range of operating pressure (1~4 bar) and feed concentration (25~200 ppm), demonstrating strong antifouling ability, mechanical stability and engineering scale-up potential.

[0019] 5. The 2,4,6-triaminotoluene introduced into the aromatic polyamine nanofiltration membrane provided by this invention originates from the catalytic hydrogenation reduction of decommissioned TNT (2,4,6-trinitrotoluene), realizing the transformation of hazardous energetic materials into high-value-added chemical raw materials and endowing the membrane preparation process with significant green sustainability. Therefore, this invention not only provides a new approach for the energy-efficient purification of antibiotic fermentation broth, but also helps to curb antibiotic diffusion and promote the development of green water treatment technology. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0021] Figure 1 This is a schematic diagram illustrating the chemical reaction between piperazine, 2,4,6-triaminotoluene, and pyromellitic methyl chloride involved in the preparation of the nanofiltration membrane in this embodiment of the invention.

[0022] Figure 2 The figures show the chemical composition characterization results of the nanofiltration membrane prepared in the embodiments of the present invention; a is the FT-IR spectrum, b is the XPS photoelectron spectrum, c is the fine spectrum of N1, and d is the fine spectrum of O1s.

[0023] Figure 3 Figure 1 shows the separation performance of the nanofiltration membrane prepared in the embodiments of the present invention; Figure 2 shows the effect of the amount of 2,4,6-triaminotoluene added on the separation performance and flux; Figure 3 shows the comparison of separation factors under different 2,4,6-triaminotoluene doping conditions; Figure 4 shows the retention performance of nanofiltration membrane PTA-1 for other antibiotics; and Figure 5 shows the separation ability of nanofiltration membrane PTA-1 for seawater salt.

[0024] Figure 4The images show the surface and cross-sectional morphology of the nanofiltration membranes prepared in the embodiments of the present invention; a is the surface of nanofiltration membrane PA (scale bar 500 nm), b is the surface of nanofiltration membrane PTA-1 (scale bar 500 nm), c is the surface of nanofiltration membrane PTA-2 (scale bar 500 nm), d is the surface of nanofiltration membrane PTA-3 (scale bar 500 nm), e is the surface of nanofiltration membrane TA (scale bar 500 nm), f is the cross-section of nanofiltration membrane PA (scale bar 200 nm), g is the cross-section of nanofiltration membrane PTA-1 (scale bar 200 nm), h is the cross-section of nanofiltration membrane PTA-2 (scale bar 200 nm), i is the cross-section of nanofiltration membrane PTA-3 (scale bar 200 nm), and j is the cross-section of nanofiltration membrane TA (scale bar 200 nm).

[0025] Figure 5 The diagram shows the physical properties of the nanofiltration membrane prepared in the embodiments of the present invention; a is the water contact angle, b is the Zeta potential, c is the cutoff curve, and d is the pore size distribution. Detailed Implementation

[0026] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0027] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0028] Given that existing nanofiltration membranes struggle to simultaneously achieve high water flux and efficient antibiotic retention, this invention proposes an aromatic polyamine nanofiltration membrane, its preparation method, and its application in separating antibiotics and inorganic salts to address the aforementioned technical problems.

[0029] A typical embodiment of the present invention provides an aromatic polyamine nanofiltration membrane, comprising a base membrane and a separation layer attached to the surface of the base membrane. The separation layer is composed of a polymer of piperazine, 2,4,6-triaminotoluene and pyromellitic acid chloride forming amide bonds, wherein the mass ratio of piperazine to 2,4,6-triaminotoluene is (6.8~9.2):(0.8~3.2).

[0030] In the process of forming the polymer with amide bonds, the mass ratio of piperazine to 2,4,6-triaminotoluene can be arbitrary, and the amount of trimesoyl chloride added is in excess. In some embodiments, the mass ratio of piperazine to 2,4,6-triaminotoluene in the process of forming the polymer with amide bonds is 8.8~9.2:1. Studies have shown that the aromatic polyamine nanofiltration membrane formed under these conditions has better performance.

[0031] In some embodiments, the thickness of the separation layer is 65.00–88.00 nm. Specifically, the thickness of the separation layer is 65.00–66.00 nm. Studies have shown that aromatic polyamine nanofiltration membranes perform better under these conditions.

[0032] In some embodiments, the pore size is 0.368–0.825 nm. Specifically, the pore size is 0.373–0.728 nm. Studies have shown that aromatic polyamine nanofiltration membranes perform better under these conditions.

[0033] In some embodiments, the base membrane is a polyethersulfone ultrafiltration membrane. Polyethersulfone ultrafiltration membranes possess good chemical stability, high mechanical strength, good thermal stability, tunable microstructure, and good compatibility with the separation layer. Therefore, aromatic polyamine nanofiltration membranes formed using polyethersulfone ultrafiltration membranes as the base membrane exhibit better performance.

[0034] Another embodiment of the present invention provides a method for preparing an aromatic polyamine nanofiltration membrane, comprising the following steps:

[0035] The base membrane was immersed in an aqueous solution containing piperazine, 2,4,6-triaminotoluene, and alkaline compounds;

[0036] Remove the soaked base film and then remove the water from its surface;

[0037] The soaked and anhydrous base film is added to an organic phase solution containing trimesoyl chloride, so that piperazine, 2,4,6-triaminotoluene and trimesoyl chloride undergo interfacial polymerization on the base film surface to form a polymer separation layer connected by amide bonds.

[0038] The steps provided by this invention control the interface between the aqueous phase and the organic phase on the surface of the base film, so that the interfacial polymerization reaction of piperazine, 2,4,6-triaminotoluene and pyromellitic acid chloride on the base film surface can be carried out on the base film surface, thereby forming a separation layer on the base film surface.

[0039] Since the interfacial polymerization reaction in this invention mainly involves the amidation reaction between acyl chloride and amine groups, the generation of HCl during the amidation reaction can affect the reaction process. Therefore, it is necessary to add an alkaline compound to remove the generated HCl. Thus, the alkaline compound described in this invention is a compound that can react with HCl to form a salt, such as sodium hydroxide, potassium hydroxide, or ammonia. In some embodiments, the concentration of the alkaline compound in the aqueous solution is 0.2~0.6 wt%, or 0.45~0.55 wt%, etc.

[0040] In some embodiments, the total concentration of piperazine and 2,4,6-triaminotoluene in the aqueous solution is 0.45~0.55 wt%. Under these conditions, it is not only beneficial to ensure that there is a sufficient amount of piperazine and 2,4,6-triaminotoluene on the base membrane surface to form a separation membrane, but also to avoid losses caused by excessive amounts of piperazine and 2,4,6-triaminotoluene.

[0041] The mass ratio of piperazine to 2,4,6-triaminotoluene can be arbitrary, and the amount of trimesoyl chloride added is in excess. In some embodiments, the mass ratio of piperazine to 2,4,6-triaminotoluene in the aqueous solution is 8.8–9.2:1. Studies have shown that the aromatic polyamine nanofiltration membrane formed under these conditions exhibits better performance.

[0042] In some embodiments, the concentration of pyromellitic acid chloride in the organic phase solution is 0.09~0.11 wt%. This condition ensures the reaction rate.

[0043] In some embodiments, the solvent for the organic phase solution is n-hexane. This solvent is more favorable for interfacial polymerization reactions.

[0044] In some embodiments, the base membrane is a polyethersulfone ultrafiltration membrane. Polyethersulfone ultrafiltration membranes possess good chemical stability, high mechanical strength, good thermal stability, tunable microstructure, and good compatibility with the separation layer. Therefore, aromatic polyamine nanofiltration membranes formed using polyethersulfone ultrafiltration membranes as the base membrane exhibit better performance.

[0045] A third embodiment of the present invention provides the application of the above-described aromatic polyamine nanofiltration membrane or the aromatic polyamine nanofiltration membrane obtained by the above preparation method in the separation of antibiotics and inorganic salts.

[0046] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0047] Example

[0048] All raw materials used in the embodiments of this invention were commercially available or donated. For example: the polyethersulfone ultrafiltration membrane (PES-based membrane, molecular weight cutoff of 50 kDa) was purchased from Harbin Ruiste Biotechnology Development Co., Ltd. (Germany, Menard); Na2SO4, MgCl2, MgSO4, NaCl, piperazine (PIP), n-hexane (AR: analytical grade), doxorubicin hydrochloride (MV=579.98 Da), tetracycline hydrochloride (MW=480.9 Da), chloramphenicol (MW=323.13 Da), ceftriaxone sodium (MW=661.59 Da), sodium hydroxide (granular), polyethylene glycol (PEG, 200~1000 Da), and bovine serum albumin (BSA) were purchased from Aladdin. 2,4,6-triaminotoluene (TAT) was donated by China Rongtong Resources Development Group Co., Ltd. Tristyrene chloride (TMC) was purchased from TCI (Japan).

[0049] experiment

[0050] A representative method for preparing the nanofiltration membrane of this invention is described in this experiment.

[0051] 1. Pretreatment of PES base film

[0052] The main purpose of PES base film pretreatment is to remove any residual organic impurities, dust, or processing aids from the surface and pores of the base film. The process involves immersing the PES base film in a 35wt% isopropanol aqueous solution (or any concentration of isopropanol aqueous solution in the range of 20-50wt%), shaking for 5 minutes (or any time from 2 to 10 minutes) during immersion. The soaked PES base film is then placed in a cleaning box and rinsed three times with deionized water (or 2-5 times).

[0053] 2. Preparation of Aqueous Solutions

[0054] Add a small amount of water and appropriate amounts of PIP and TAT to the reagent bottle, then add more water to prepare an aqueous solution. The concentrations of PIP and TAT in each aqueous solution are shown in Table 1, and the concentration of sodium hydroxide in each aqueous solution is 0.5 wt% (the concentration of sodium hydroxide can also be any value from 0.2% to 0.6 wt%). The key to the aqueous solution is controlling the concentration of PIP and TAT, which is independent of the order in which the reagents are added. Other methods of preparing the solution can also be used, such as directly adding an appropriate amount of water to the reagent bottle containing appropriate amounts of PIP and TAT.

[0055] 3. Preparation of organic phase solutions

[0056] Add a small amount of n-hexane and 0.1 g of TMC to a reagent bottle, then add an appropriate amount of n-hexane to prepare an organic phase solution with a TMC concentration of 0.1 wt%. The key to the organic phase solution is controlling the TMC concentration, which is independent of the order in which the reagents are added. Other methods can also be used to prepare the solution, such as directly adding an appropriate amount of n-hexane to a reagent bottle containing a suitable amount of TMC. The TMC concentration in the organic phase solution can fluctuate by up to 10%.

[0057] 4. Preparation of aromatic polyamine nanofiltration membranes (nanofiltration membranes for short)

[0058] 4.1. Place the PES base membrane after pretreatment in step 1 into the reactor, add the aqueous solution prepared in step 2, and soak the pretreated PES base membrane in the aqueous solution for 2 minutes (the aqueous solution is sufficient to saturate the PES base membrane, or it can be 1 minute or 3 minutes).

[0059] 4.2. Take out the PES base film after soaking in step 4.1, and then dry it with an air gun until there are no visible droplets on the surface of the PES base film.

[0060] 4.3. The PES substrate membrane dried by air gun in step 4.2 and the organic phase solution prepared in step 3 are added to the reactor and reacted for 20 seconds to form a separation layer on the surface of the PES substrate membrane. After the reaction, the organic phase solution is discarded, and the membrane is placed in a forced-air drying oven at 60°C for 5 minutes. The purpose of drying is to remove the organic solvent; therefore, the drying temperature can be 40~70°C, and the drying time can be 5~10 minutes.

[0061] The nanofiltration membranes prepared from aqueous solutions of PIP and TAT at different concentrations are shown in Table 1.

[0062] Table 1. Concentrations of PIP and TAT in the aqueous solutions used to prepare different nanofiltration membranes

[0063]

[0064] Separation performance test

[0065] Dead-end filtration system employed (operating temperature: room temperature 25℃, pressure: 3 bar, area: 36 cm²) 2 The separation performance was evaluated. All samples were pre-pressurized for 60 minutes before the start of data collection. The flux (F, L m) was obtained from the equation. -2 h -1 ) and performance (P, L m) -2 h -1 bar -1 )

[0066] ;

[0067] ;

[0068] In the formula, V (L) represents the permeation volume of the filter, and Am (m 2 ) represents the effective filtration area, Δt (H) represents the filtration time, and Δp (Bar) represents the applied pressure.

[0069] The retention capacity (R,%) and separation factor (S) of the nanofiltration membrane for antibiotic inorganic salts, using 50 ppm doxorubicin hydrochloride solution and 1000 ppm salt solution as indicators, were derived from the following formulas:

[0070] ;

[0071] ;

[0072] Where Cp and Cf represent the solute concentrations in the feed solution and permeate solution, respectively. Antibiotic concentrations were determined using a UV-Vis spectrophotometer. Salt concentrations were measured using a conductivity meter (DDS-307, LEICI). Neutral solute concentrations were measured using a total organic carbon analyzer (Shimadu TOC-L CPH, Japan). The average pore size of the membrane (μp) is calculated from the solute diameter (d) at 50% rejection. s The aperture distribution (nm) and pore size distribution are obtained by the following formula:

[0073] ;

[0074] ;

[0075] In the formula, Mw(Da) is the molecular weight of diethylene glycol and polyethylene glycol, and σp represents the geometric standard deviation.

[0076] Example 1: Effect of the ratio of PIP to TAT in aqueous solution on the chemical composition of nanofiltration membrane

[0077] PIP monomer is a planar cyclic aliphatic diamine with an amine group at each end of the closed ring. TAT is a rigid, non-coplanar, highly reactive monomer with three amino groups oriented in opposite directions. Introducing TAT significantly increases the free space of the system, generating a more porous separation layer. The chemical reactions of PIP, TAT, and TMC are as follows: Figure 1 As shown. The Fourier transform infrared spectra of each nanofiltration membrane are as follows. Figure 2 As shown in a, this demonstrates the successful preparation of the separation layer. At 1647 cm⁻¹ -1 There are stretching vibration peaks of the generated amide bonds on both sides. At 1440 cm⁻¹ -1 Left and right and 3200~3600cm -1The range represents the stretching vibration peaks of hydroxyl, amino, and carboxyl groups.

[0078] Furthermore, the bonding of the prepared nanofiltration membrane and the changes in bonding after the introduction of TAT were characterized using XPS. The main focus was on identifying C1s, N1s, and O1s atoms. Characterization of the chemical states of these three elements further confirmed the successful preparation of the nanofiltration membrane. Figure 2 As shown in b in the diagram. (By...) Figure 2 In the c and d diagrams, it is clear that as the TAT doping ratio increases, the proportion of amide bonds increases as shown in XPS. Figure 2 As shown in c, with the increase of TAT, the proportion of amide bonds increases from 94.05% to 98.93%, indicating that the degree of amide bond formation in the selective layer of the nanofiltration membrane increases with the increase of TAT.

[0079] Example 2: Effect of the ratio of PIP to TAT in aqueous solution on the separation performance of nanofiltration membranes

[0080] like Figure 3 As shown in Figure a, the flux of the modified nanofiltration membrane was significantly improved, reaching its peak at a mass ratio of 1:9, which also resulted in the highest retention rate of doxorubicin hydrochloride (ADR). The flux increased from 11.325 L·m⁻¹. -2 ·h -1 ·bar -1 Rising to 22.025 L·m -2 ·h -1 ·bar -1 This is because TAT has high reactivity, which increases the crosslinking degree of the system after its introduction. TAT is a rigid aromatic triamine, and its introduction significantly increases the crosslinking density and reduces the effective pore size, thereby inhibiting water molecule passage. However, in PTA-1, the TAT dosage is low; only a small amount of TAT is needed to form a highly crosslinked, ultrathin selective layer on the PIP matrix, while retaining the good hydrophilicity and flexibility of PIP and possessing a high degree of free space. Therefore, a significant increase in water flux, reaching 22.025 L·m, is achieved with almost no sacrifice in ADR retention. -2 ·h -1 ·bar -1 The flux was reduced to 12.1 L·m⁻¹ when the TAT content was further increased, due to the excessively high crosslinking density and the thicker / more rigid active layer. -2 ·h -1 ·bar -1 .like Figure 3As shown in b, the separation factor of PTA-1 exhibits a peak. While maintaining near-quantitative ADR rejection, NaCl rejection is effectively suppressed, thus maximizing the selectivity of both. In pure PA or pure TA systems, the relatively loose PA network leads to slightly lower ADR rejection and higher NaCl rejection. The overly dense TA membrane layer increases NaCl rejection but sacrifices water flux and some selectivity. When TAT is in excess, NaCl rejection increases and the separation factor decreases due to excessive network contraction. Low-doped TAT acts as a "local crosslinking center" during interfacial polymerization, resulting in a more concentrated pore size distribution, a more stable interfacial layer, and higher free space. Therefore, it almost saturates the rejection of large molecular ADRs while maintaining a high throughput for smaller NaCl molecules.

[0081] System pressure and feed concentration may also affect the system. PTA-1 maintains a nearly constant high ADR rejection and stable water flux within a wide concentration window of 25-200 ppm, revealing its good structural tolerance to concentration polarization and organic contamination. The rejection peak at 50 ppm reflects that a moderate solute concentration is beneficial for achieving a better balance between mass transfer and concentration polarization. Within an engineering-feasible operating window of 1-4 bar, PTA-1 exhibits both linearly adjustable water flux and pressure-independent high separation performance, demonstrating good structural integrity and mechanical stability, providing a foundation for scale-up under actual operating conditions.

[0082] Antibiotic desalination is a crucial step in purifying and extracting antibiotics from fermentation broth, and is key to obtaining high-purity antibiotics. Retention tests were conducted on four antibiotics (chloramphenicol, tetracycline hydrochloride, ceftriaxone sodium, and doxorubicin hydrochloride) as a model for antibiotic purification. Retention tests were also conducted on four salts (Na₂SO₄, MgCl₂, MgSO₄, and NaCl) as an experimental model for seawater desalination. Figure 3 As shown in c and d, thanks to the synergistic regulation of pore size distribution and surface chemistry, PTA-1 can simultaneously and efficiently retain multiple antibiotic molecules with different molecular sizes, charges and hydrophobicities, demonstrating its broad applicability in the treatment of complex pharmaceutical wastewater.

[0083] Example 3: Effect of the ratio of PIP to TAT in aqueous solution on the morphology of nanofiltration membranes

[0084] Figure 4 The surface and cross-sectional morphology of polyamide selective layers formed under different TAT / PIP ratios are shown. The PA forms a nodular structure on its surface, a typical characteristic of rapid diffusion of aliphatic diamines to the organic phase interface and interfacial polymerization, such as... Figure 4 As shown in 'a'.

[0085] When a small amount of TAT (PTA-1, TAT:PIP = 1:9) is introduced, the surface morphology changes significantly, exhibiting a "cellular" morphology with a wider size distribution, such as... Figure 4 As shown in b. This morphology typically originates from Marangoni flow caused by differences in diffusion rates in polyamine mixtures, i.e., local convection in the aqueous phase induced by interfacial tension gradients, resulting in periodic collapse and expansion of the reaction interface, thus producing large-scale cellular textures. The cross-sectional thickness of PTA-1 is 65.52 nm, only slightly higher than that of PA, as shown in b. Figure 4 As shown in f and g, the introduction of a small amount of TAT effectively improves the non-uniformity of the interfacial reaction. It is noteworthy that the microstructure formed by PTA-1 is beneficial for increasing the effective permeable area, which is consistent with its highest water flux observed in flux tests.

[0086] As the TAT content further increases (PTA-2, PTA-3), the surface gradually exhibits a continuous "wrinkled" morphology, accompanied by a distinct network crack pattern, such as... Figure 4 As shown in c and d in the figure. This transformation stems from the rapid film formation and high intrafilm shrinkage stress resulting from the interfacial polymerization dominated by highly functional aromatic amines (TAT), causing tensile stress-driven wrinkle formation on the selective layer surface during polymerization shrinkage. For example... Figure 4 As shown in h and i, the selective layer thickness of PTA-2 increases to 75.12 nm, and that of PTA-3 reaches 87.12 nm, indicating that the degree of crosslinking and polymerization rate increase significantly with increasing TAT content. The surface texture tends to be smoother, lacking the cellular microporous characteristics of PTA-1, suggesting that high TAT content leads to a weakening of interfacial tension differences, and Marangoni flow is no longer significant. At this point, polymerization is more concentrated in the local interface, making the PA layer tend to be dense and continuous, which is not conducive to the effective transport of water molecules.

[0087] When the system is entirely composed of TAT (TA), the surface exhibits a uniform, dense, finely wrinkled structure, lacking obvious protruding granules or cellular features, such as... Figure 4 As shown in e. Due to the trifunctionality and aromatic structure of TAT, its interfacial reaction is highly rapid and highly cross-linked, resulting in a TA layer thickness maintained at around 76 nm, but with the most dense structure, as shown in... Figure 4 As shown in j in the figure. These highly cross-linked aromatic polyamide membranes typically have higher intrinsic structural rigidity and smaller free volume, and their compactness is the fundamental reason for the significant decrease in flux of the TA system.

[0088] In summary, when PIP dominates (pure PIP system), the interfacial polymerization rate is much greater than the diffusion rate, and the system exhibits a typical "nodular" surface structure. With the introduction of a small amount of TAT (PIP:TAT = 9:1), the reaction rate decreases slightly, and the surface tension gradient competes with the reaction kinetics, inducing Marangoni flow and generating a large-area "crater" morphology. At this point, the membrane surface area increases significantly, which is beneficial for improving water flux. Further increasing the TAT ratio (PIP:TAT = 7:3), the highly cross-linked network generates intralayer shrinkage stress during drying. When the stress exceeds the interfacial adhesion force, the membrane surface wrinkles. In the pure TAT system, diffusion is extremely slow and the reaction is confined, forming a regularly arranged microscale "crater array". This series of morphological evolutions reflects the balance transfer relationship between reaction rate, diffusion rate, and stress release in interfacial polymerization.

[0089] Example 4: Effect of the ratio of PIP to TAT in aqueous solution on the chemical composition of nanofiltration membrane

[0090] like Figure 5 As shown in Figure a, compared with the PES-based membrane, the introduction of TAT or PIP significantly reduced the water contact angle, indicating that the hydrophilicity of the membrane surface was significantly improved after interfacial polymerization. The PA membrane prepared by pure PIP showed the lowest contact angle, while the introduction of a small amount of TAT slightly increased the contact angle, but it was still significantly stronger than that of the PES-based membrane. With further increases in the proportion of TAT (PTA-2, PTA-3), the contact angle gradually increased, which is consistent with the higher aromatic ring content and increased surface rigidity brought about by TAT.

[0091] like Figure 5 As shown in b, all membranes exhibited a gradually increasing negative surface charge as the pH value increased, a typical characteristic of polyamide membranes. Notably, the isoelectric point (IEP) shifted from 3.61 for the pure PIP system (PA) to 3.54 for PTA-1, indicating that the introduction of low TAT content had only a limited effect on the surface charge. Systems with higher TAT content further altered the isoelectric point, reflecting a change in the balance between protonable amino groups and deprotonable amide / phenolic hydroxyl groups. The surface charge distribution of the PTA-1 membrane was similar to that of the control group PA membrane, while the PTA-3 and TA membranes exhibited significantly more negative potentials in the neutral to alkaline pH range, consistent with their higher aromatic crosslinking degree and reduced amino accessibility.

[0092] The retention curve and pore size distribution analysis together show that, Figure 5As shown in c and d, the introduction of a small amount of TAT moderately modulates the microstructure of the polyamide network. Compared to the pure PIP system (PA, MWCO≈339 Da), the PTA-1 membrane exhibits a slightly higher molecular weight cutoff (≈403 Da) and a slightly increased average pore size (μp increases from 0.521 nm to 0.551 nm), while the pore size distribution is broadened (σp increases from 0.3355 to 0.403). These structural changes indicate that the copolymerization of a low proportion of TAT to some extent perturbs the interfacial polymerization kinetics, forming a relatively loose but still nanoscale homogeneous cross-linked network, thereby slightly expanding the effective mass transfer channels and achieving an increase in flux.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An aromatic polyamine nanofiltration membrane for separating antibiotics and inorganic salts, characterized in that, The product includes a base film and a separation layer attached to the surface of the base film. The separation layer is composed of a polymer of piperazine, 2,4,6-triaminotoluene, and trimesoyl chloride formed by amide bonds, wherein the mass ratio of piperazine to 2,4,6-triaminotoluene is (6.8~9.2):(0.8~3.2). The separation layer has a thickness of 65.00~66.00 nm and a pore size of 0.373~0.728 nm.

2. The aromatic polyamine nanofiltration membrane as described in claim 1, characterized in that, In the process of forming amide bonds in polymers, the mass ratio of piperazine to 2,4,6-triaminotoluene is 8.8~9.2:

1.

3. The aromatic polyamine nanofiltration membrane as described in claim 1, characterized in that, The base membrane is a polyethersulfone ultrafiltration membrane.

4. A method for preparing an aromatic polyamine nanofiltration membrane, wherein the prepared membrane is used to separate antibiotics and inorganic salts, characterized in that, Includes the following steps: The base membrane was immersed in an aqueous solution containing piperazine, 2,4,6-triaminotoluene, and alkaline compounds; Remove the soaked base film and then remove the water from its surface; The soaked and anhydrous base film is added to an organic phase solution containing trimellityl chloride, so that piperazine, 2,4,6-triaminotoluene and trimellityl chloride undergo interfacial polymerization on the base film surface to form a polymer separation layer connected by amide bonds. The separation layer has a thickness of 65.00~66.00 nm and a pore size of 0.373~0.728 nm. In the aqueous solution, the total concentration of piperazine and 2,4,6-triaminotoluene is 0.45~0.55 wt%. In the aqueous solution, the mass ratio of piperazine to 2,4,6-triaminotoluene is 8.8~9.2:

1.

5. The preparation method according to claim 4, characterized in that, The concentration of pyromellitic acid chloride in the organic phase solution is 0.09~0.11wt%.

6. The preparation method according to claim 4, characterized in that, The solvent for the organic phase solution is n-hexane.

7. The preparation method according to claim 4, characterized in that, The base membrane is a polyethersulfone ultrafiltration membrane.

8. The use of an aromatic polyamine nanofiltration membrane according to any one of claims 1 to 3 or an aromatic polyamine nanofiltration membrane obtained by any one of claims 4 to 7 in the separation of antibiotics and inorganic salts.

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