A multifunctional ag@nh2-uio-66 / paes-cooh self-supporting homogeneous hybrid forward osmosis membrane

Abstract

The application relates to the technical field of forward osmosis membranes, in particular to a multiple-function Ag@NH2-UI0-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membrane, which is synthesized by introducing hydrophilic Ag@NH2-UI0-66 nanomaterials with water molecule specific channels and antibacterial capacity into the molecular structure of a carboxyl-containing polyarylether sulfone matrix material with excellent mechanical properties through precise molecular design, finally synthesizing a series of Ag@NH2-UIO-66 / PAES-COOH hybrid materials, and then constructing a self-supporting homogeneous forward osmosis membrane system without ICP phenomenon. The Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis without ICP phenomenon realizes the ability of antibiosis and resistance to organic pollution while maintaining.

Description

Technical Field

[0001] The present invention relates to the technical field of forward osmosis membranes, and in particular to a multifunctional Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membrane. Background Art

[0002] Compared with traditional pressure-driven membrane technologies (such as ultrafiltration and reverse osmosis), forward osmosis (FO) membrane separation technology offers advantages such as low energy consumption, high recovery rates, and excellent separation performance. It is particularly suitable for water treatment processes with high pollutant concentrations and complex compositions, such as seawater desalination, advanced municipal wastewater treatment, and dyeing and printing wastewater treatment. The thin film composite (TFC) membrane commonly used in FO technology consists of a porous support layer and an ultrathin polyamide (PA) active separation layer. However, the presence of the porous support layer causes severe internal concentration polarization (ICP) during use, significantly reducing the osmotic separation efficiency and hindering the development of FO technology. Furthermore, when treating wastewater containing organic pollutants and microorganisms, the microscopic wrinkles of the PA active separation layer cause organic pollutants, microbial excretions of extracellular polymers (ECPs), and biofilm to easily deposit on the active layer surface, resulting in severe membrane fouling. This reduces the effective permeation area of ​​the FO membrane and increases the mass transfer resistance of water transport across the membrane, severely impacting the membrane's permeation flux and service life. In summary, the ideal forward osmosis membrane should have a low ICP or ICP-free membrane structure, while having excellent osmotic separation performance and good anti-pollution ability.

[0003] In recent years, researchers have proposed strategies to mitigate ICP by improving membrane structural properties (thickness, tortuosity, pore size distribution, and porosity of the membrane support layer). Many studies have achieved the goal of reducing ICP by adding hydrophilic nanomaterials or hydrophilic polymers to the support layer substrate as additives to increase the hydrophilicity and porosity of the support layer. Some studies have also used electrospinning to prepare high-porosity, low-tortuosity support layers to reduce the structural parameters of the support layer, thereby alleviating the ICP phenomenon. However, these methods cannot completely eliminate the ICP problem of asymmetric membranes. To this end, Zhang et al. proposed the concept of a self-supporting homogeneous forward osmosis membrane. Using a hydrophilic carboxyl-containing polyoxadiazole material with excellent mechanical properties, they prepared a self-supporting homogeneous forward osmosis membrane via solution casting, making it possible to achieve a forward osmosis membrane without ICP. In addition, due to the smooth and hydrophilic surface properties of this type of forward osmosis membrane, after treating dye wastewater, it can show an extremely high flux recovery rate after washing with a 40% ethanol solution, reflecting the excellent anti-fouling properties of this type of membrane.

[0004] Metal-organic frameworks (MOFs) are a class of porous materials with high surface area and tunable structural properties. Their incorporation into water separation membranes through appropriate methods can impart various functionalities. Bagherzade et al. fabricated a composite FO membrane with significantly enhanced water flux and selectivity by adding a GQDs@NH2-UIO-66-based MOF to the PA active layer of a TFC membrane. When using 1M NaCl as the draw solution, the composite membrane exhibited a water flux 102% higher than that of a commercial TFC membrane and a selectivity 1.5 times that of a control membrane without the GQDs@NH2-UIO-6 material. The composite membrane also exhibited excellent resistance to organic fouling. Wang et al. developed a bifunctional PA-TFC membrane modified with a Ti-UiO-66-based MOF. The modified membrane demonstrated significantly enhanced desalination and antifouling properties in a real-world water treatment process using seawater as the feed solution. Geng et al. incorporated NH2-MIL-125-based MOFs into polymer structures through molecular design and fabricated a series of self-supporting homogeneous hybrid forward osmosis membranes using a solution casting method. When using 1.5M Na2SO4 as the draw solution, the hybrid membranes exhibited significantly improved water flux and excellent water-salt separation performance. This study provides new insights into the integration of MOFs with self-supporting forward osmosis membranes. Furthermore, MOFs can serve as reservoirs or carriers for bactericidal metals, and thus, when combined with appropriate metal-MOFs, they can impart antibacterial properties to the membranes. Fatemeh Seyedpour used Ag-MOFs to functionalize the surface of TFC membranes, resulting in membranes exhibiting strong antibacterial activity, with an antibacterial rate exceeding 99%. Furthermore, in dynamic contamination tests with the organic pollutant sodium alginate, the modified membranes demonstrated high flux recovery rates. Therefore, it is very important to select MOFs materials with multiple functionalities and introduce them into the forward osmosis membrane system in an appropriate manner for the design and development of forward osmosis membranes with excellent osmotic separation performance and anti-pollution ability. Summary of the Invention

[0005] To solve the above problems, the present invention provides a multifunctional Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membrane, synthesizes hydrophilic Ag@NH2-UIO-66 nanomaterials with water molecule-specific channels and antibacterial ability, and introduces them into the molecular structure of carboxyl-containing polyarylethersulfone (PAES-COOH) matrix materials with excellent mechanical properties through precise molecular design. Finally, a series of Ag@NH2-UIO-66 / PAES-COOH hybrid materials are synthesized, and a self-supporting homogeneous forward osmosis membrane system without ICP phenomenon is constructed.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A multifunctional Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membrane is prepared by the following method:

[0008] S1. Synthesis of Ag@NH2-UIO-66 materials

[0009] 0.233 g ZrCl4, 0.181 g NH2-H2BPC, 7.2 mL CH3COOH, and 36 mL DMF were thoroughly mixed and stirred in a sealed beaker for 1 h. The uniformly dispersed mixed solution was then transferred to a reactor lined with polytetrafluoroethylene. The reactor was placed in an oven and heated at 120°C for 24 h. After the reactor was naturally cooled to room temperature, it was centrifuged at 8000 rpm for 10 min to separate a light yellow powder, which was then washed three times with DMF and anhydrous ethanol to obtain NH2-UIO-66 material.

[0010] 0.2 g of the NH2-UIO-66 material was dispersed in 100 mL of DI water by ultrasound, and then 2.8 mL of 0.1 mol L -1 The AgNO3 solution was stirred for 30 min and then irradiated under a 50W xenon light source for 30 min to make the Ag in the solution + Reduction to Ag 0 The Ag@NH2-UIO-66 material was loaded on the surface and framework structure of the NH2-UIO-66 material. Finally, the product was centrifuged and washed, and dried in a vacuum oven at 80°C for 12 h to obtain a brown powder Ag@NH2-UIO-66 material.

[0011] S2. Synthesis of PAES-COOH Matrix Materials

[0012] The carboxyl-containing hydrophilic PAES-COOH matrix material is synthesized by aromatic nucleophilic substitution polycondensation reaction. Specifically, first, a three-neck flask is fixed in the reaction system, and then 2.283 g of BPA, 4.805 g of PPL, 6.356 g of DFPS, 5.389 g of K2CO3, 46 mL of TMS, and 23 mL of TL are added to a 100 mL three-neck flask. The solvent and powdered medicine are uniformly mixed by stirring for 25 min under the protection of a mild argon stream. Then, the reaction system is heated to 135°C, and the water produced in the reaction system is removed under the condition of condensation reflux until no new liquid droplets fall into the water separator. The temperature is then increased to 180°C. After 6 h, the polymerization reaction is complete, the viscous material in the three-port bottle is poured into DI water, and the obtained tough strip material is crushed. Then, the material is washed with deionized water and anhydrous ethanol several times to remove unreacted monomers and solvents. Then, the material is dissolved in THF and acidified with concentrated hydrochloric acid. Then, the solution is poured into deionized water to obtain a white crude product. The crude product is washed and placed in a vacuum drying oven at 80°C for 24 h to obtain the PAES-COOH material.

[0013] S3, synthesis of a series of Ag@NH2-UIO-66 / PAES-COOH hybrid materials

[0014] The Ag@NH2-UIO-66 is introduced into the molecular structure of the PAES-COOH matrix material by chemical bonding to synthesize the Ag@NH2-UIO-66 / PAES-COOH hybrid material. Specifically, 2 g of the PAES-COOH synthesized above is dissolved in anhydrous THF at room temperature, and 0.4 mL of oxalyl chloride, which is 1.5 times the amount of carboxyl in the PAES-COOH material, is slowly added dropwise. The reaction is continued for 6 h. Then, the unreacted oxalyl chloride and THF are removed by evaporation under vacuum, and the obtained solid is dissolved again in anhydrous THF. At the same time, a certain amount of Ag@NH2-UIO-66 is dispersed in anhydrous THF to form a suspension, which is added dropwise to the above reaction system. Then, the reaction is stirred at room temperature for 24 h. The viscous reaction product is poured into deionized water to obtain a brown-yellow flocculent crude product, which is crushed into powder with a high-speed tissue crusher. Then, the powder is washed with deionized water and anhydrous ethanol several times, and dried in a vacuum drying oven at 80°C for 24 h to obtain a series of x% Ag@NH2-UIO-66 / PAES-COOH hybrid materials, where "x" represents the mass fraction of Ag@NH2-UIO-66 in the hybrid material.

[0015] S4, preparation of Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membrane

[0016] The forward osmosis membrane with a dense and homogeneous structure is obtained by solution casting and solvent evaporation. Specifically, the above-synthesized PAES-COOH and Ag@NH2-UIO-66 / PAES-COOH materials are respectively dissolved in DMF, stirred at room temperature for 12 h, and then left to stand for 6 h to remove bubbles. Then, a smooth silicon wafer is placed horizontally in a vacuum oven, and the above-prepared casting solution is added dropwise onto the silicon wafer, and then the liquid is cast onto the whole silicon wafer by using the surface tension of the liquid. Then, the silicon wafer is heated at 60°C in a vacuum state for 12 h, and then the membrane with a dense and homogeneous structure is formed on the silicon wafer after the solvent is completely evaporated. Finally, the silicon wafer is taken out and immersed in deionized water to separate the membrane from the silicon wafer.

[0017] Further, in the step S3, 0.02 g or 0.06 g or 0.10 g or 0.14 g of Ag@NH2-UIO-66 is added.

[0018] The above scheme successfully designs and prepares a series of Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membranes without ICP. Due to the tight combination between Ag@NH2-UIO-66 and the membrane matrix through chemical bonds, the good interfacial compatibility makes it play an active role in the forward osmosis process. The sub-nanometer cavities of Ag@NH2-UIO-66 / PAES-COOH particles become an additional transport channel for water and a barrier for salt ions, so that the prepared forward osmosis membrane shows an improved water flux while showing a decreased reverse salt flux. The hybrid forward osmosis membrane (U5) with a Ag@NH2-UIO-66 grafting amount of 5% shows a significantly improved water flux of 13.78 L m -2 h -1 and an ultra-high water-salt selectivity of 1724.7 mol L -1 Moreover, the introduction of Ag@NH2-UIO-66 significantly improves the sterilization performance and anti-organic pollution performance of the hybrid forward osmosis membrane. U5 shows an antibacterial property of 95.3% after being cultured with Escherichia coli for 24 h. At the same time, U5 shows a very low flux decline rate during the 24 h dynamic pollution test process with BSA or SA-containing synthetic wastewater as the feed liquid, and after hydraulic cleaning, the flux recovery rate is as high as 97.1% (BSA) and 98.5% (SA). In summary, we successfully prepare the Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis without ICP, which realizes the water flux while having the ability of antibacterial and resisting organic pollution. BRIEF DESCRIPTION OF DRAWINGS

[0019] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, when read in conjunction with the accompanying drawings:

[0020] Other features, objects, and advantages of the application will become more apparent from the following detailed description of non-limiting embodiments, when read in conjunction with the accompanying drawings:Figure 1 Schematic diagram of the preparation of MOFs materials, hybrid materials and self-supporting homogeneous forward osmosis membranes: (a) Synthesis of Ag@NH2-UIO-66 materials; (b) Synthesis of PAES-COOH matrix materials; (c) Synthesis of Ag@NH2-UIO-66 / PAES-COOH hybrid materials; (d) Preparation of self-supporting homogeneous forward osmosis membranes.

[0021] Figure 2 To synthesize carboxyl-containing hydrophilic PAES-COOH matrix materials through aromatic nucleophilic substitution condensation reaction.

[0022] Figure 3 In order to introduce Ag@NH2-UIO-66 into the molecular structure of PAES-COOH matrix material by chemical bonding, Ag@NH2-UIO-66 / PAES-COOH hybrid material was synthesized.

[0023] Figure 4 Schematic diagram of the cross-flow forward osmosis experimental device.

[0024] Figure 5 (a) XRD pattern of MOFs material (b) FT-IR spectrum of MOFs material.

[0025] Figure 6 (a) SEM image of Ag@NH2-UIO-66 (b)-(e) EDS element mapping images.

[0026] Figure 7 FT-IR spectra of Ag@NH2-UIO-66 / PAES-COOH series hybrid materials.

[0027] Figure 8 SEM images of the surface morphology and cross-sectional morphology of the forward osmosis membrane. A1-E1: upper surface morphology of U0, U1, U3, U5, U7, A2-E2: lower surface morphology of U0, U1, U3, U5, U7, A3-E3: cross-sectional morphology of U0, U1, U3, U5, U7.

[0028] Figure 9 (a) Water contact angles at the top and bottom of the forward osmosis membrane (b) Zeta potentials at the top and bottom of the forward osmosis membrane.

[0029] Figure 10 Mechanical properties of forward osmosis membrane.

[0030] Figure 11(a) Water flux, reverse solute flux, and water-salt selectivity for a series of hybrid forward osmosis membranes (deionized water as the feed solution and 1 M NaCl as the draw solution). (b)-(d) Water flux, (c) reverse solute flux, and (d) water-salt selectivity for a series of hybrid forward osmosis membranes of a specific thickness (1.15 μm) using different concentrations of NaCl as the draw solution. Each membrane sample was tested three times and the average results were used to obtain the final test results.

[0031] Figure 12 (a) Plate count results and inhibition zone determination results of the Ag@NH2-UIO-66 / PAES-COOH membrane series after 24 h of contact and culture with bacteria (b) Antibacterial rates of each membrane (U1, U3, U5, U7) with U0 as the control (d) Results of Ag+ release from the U7 membrane structure.

[0032] Figure 13 24h dynamic fouling test results of original membrane U0 and modified membrane U5 (a) pollutant BSA (b) pollutant SA (c) flux recovery rate after hydraulic cleaning. DETAILED DESCRIPTION

[0033] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0034] Example

[0035] 1. Materials and preparation methods:

[0036] Silver nitrate (AgN03, 98%), zirconium tetrachloride (ZrCl4, 99.9%), acetic acid (CH3CH2OH, 99.7%), anhydrous tetrahydrofuran (THF, 99.9%), chloroxyl (C2Cl20, 98%), bisphenol A (BPA, 99%), tetramethylene sulfone (TMS, 98%), 2-amino terephthalic acid (H2BDC-NH2, 97%), bovine serum albumin (BSA, 99%), bis(4-fluorophenyl)sulfone (BFPS, 99%), N,N-dimethylformamide (DMF, 99.5%), anhydrous tetrahydrofuran (THF, 99%), calcium chloride (CaCl2, 98%), magnesium sulfate (MgS04, 99%), ethanol (CH3CH2OH, 99.7%), sodium chloride (NaCl, 99.5%), ammonium chloride (NH4Cl, 99%), sodium alginate (SA, 99%), LB broth and LB nutrient agar were purchased from Sigma-Aldrich. Escherichia coli (ATCC 25922) was purchased from Beijing Solabio Biotech Co., Ltd. Phenothalin (PPL, 98%) was obtained from TCI Development Co., Ltd. Toluene (TL, 99.5%) and hydrochloric acid (HC1, 38%) were supplied by Xilong Chemical Co., Ltd.

[0037] Synthesis of Ag@NH2-UIO-66 materials

[0038] NH2-UIO-66 nanoparticles were first synthesized by a classical solvothermal method Figure 1 a), ZrCl4(0.233 g, 1 mmol), NH2-H2BPC (0.181 g, 1 mmol), CH3COOH (7.2 mL), DMF (36 mL) were mixed thoroughly in a closed beaker and stirred for 1 h, then the uniformly dispersed mixed solution was transferred into a reaction kettle with a polytetrafluoroethylene liner, and the reaction kettle was placed in an oven for heating at 120 °C for 24 h. After the reaction kettle was naturally cooled to room temperature, the liquid therein was separated by centrifugation (8000 rpm, 10 min) to obtain a light yellow powder, which was washed with DMF and anhydrous ethanol for 3 times, respectively, to obtain the NH2-UIO-66 material. Further, Ag@NH2-UIO-66 materials were synthesized by a photoreduction method Figure 1 a). 0.2 g of the above NH2-UIO-66 material was dispersed in 100 mL of DI water by ultrasonic assistance, then 0.1 mol L -1 AgN03 solution (2.8 mL) was slowly added dropwise into the dispersion in a dark environment and stirred for 30 min. Then it was irradiated under a 50 W xenon light source for 30 min, so that Ag + in the solution was reduced to Ag 0The Ag@NH2-UIO-66 material is loaded on the surface and framework structure of the NH2-UIO-66 material. Finally, the product is centrifuged and washed, and a brownish powder Ag@NH2-UIO-66 material is obtained after drying in a vacuum oven at 80°C for 12h.

[0039] Synthesis of PAES-COOH matrix material

[0040] As shown in Figure 2 , a carboxyl-containing hydrophilic PAES-COOH matrix material is synthesized by aromatic nucleophilic substitution polycondensation reaction. The preparation process of the material is shown in Figure 1 (b). The reaction system is equipped with an intelligent digital constant temperature heating jacket, a mechanical stirrer, a thermometer, a water separator, a condenser tube and an argon gas inlet device. The synthesis steps are as follows: first, fix the three-necked flask in the reaction system, then add BPA (2.283g, 0.010mol), PPL (4.805g, 0.015mol), DFPS (6.356g, 0.0250mol), K2CO3 (5.389g, 0.039mol), TMS (46mL), TL (23mL) into the 100mL three-necked flask in sequence. Stir under the protection of gentle argon flow for 25min to mix the solvent and powdered chemicals uniformly. Then, the reaction system is heated to 135°C, and the water generated in the reaction system is removed under condensation reflux until there is no new liquid droplet in the water separator. Then, the temperature is increased to 180°C. After 6h, the polymerization reaction is completed, the viscous material in the three-necked flask is poured into DI water, and the obtained tough strip material is crushed, then washed with deionized water and anhydrous ethanol several times to remove unreacted monomers and solvents. Then, the material is dissolved in THF and acidified with concentrated hydrochloric acid, and then the solution is poured into deionized water to obtain a white crude product. The crude product is washed and placed in a vacuum drying oven at 80°C for 24h to obtain the PAES-COOH material.

[0041] Synthesis of Ag@NH2-UIO-66 / PAES-COOH hybrid material

[0042] As shown in Figure 3 , by precise molecular design, Ag@NH2-UIO-66 is introduced into the molecular structure of the PAES-COOH matrix material by chemical bonding to synthesize Ag@NH2-UIO-66 / PAES-COOH hybrid material. The preparation process of the hybrid material is shown in Figure 1As shown in Figure (c), the PAES-COOH synthesized above (2 g) was dissolved in anhydrous THF at room temperature with stirring. Oxalyl chloride (0.4 mL, 0.048 mol) equivalent to 1.5 times the calculated amount of carboxyl groups in the PAES-COOH material was slowly added dropwise, and the reaction was continued for 6 h. Subsequently, the unreacted oxalyl chloride and THF were evaporated under vacuum, and the resulting solid was redissolved in anhydrous THF. Simultaneously, a certain amount of Ag@NH2-UIO-66 (0.02 g, 0.06 g, 0.10 g, 0.14 g) was dispersed in anhydrous THF to form a suspension and added dropwise to the above reaction system. The suspension was then stirred at room temperature for 24 h. The viscous reactants were poured into deionized water to yield a brownish-yellow flocculent crude product. This product was then ground into a powder using a high-speed tissue grinder. The powder was then washed several times with deionized water and anhydrous ethanol, respectively. After drying in a vacuum oven at 80°C for 24 hours, a series of x% Ag@NH2-UIO-66 / PAES-COOH hybrid materials were obtained, where "x" represents the mass fraction of Ag@NH2-UIO-66 in the hybrid material. The mass fractions of Ag@NH2-UIO-66 in the hybrid materials prepared here were 1%, 3%, 5%, and 7%, respectively.

[0043] Preparation of Ag@NH2-UIO-66 / PAES-COOH Self-Supported Homogeneous Hybrid Forward Osmosis Membrane

[0044] A forward osmosis membrane with a dense homogeneous structure is obtained by solution casting and solvent evaporation. The preparation process is as follows: Figure 1 (d) First, the synthesized PAES-COOH and Ag@NH2-UIO-66 / PAES-COOH materials were dissolved in DMF, stirred at room temperature for 12 hours, and then allowed to stand for 6 hours to degas. Subsequently, a smooth, flat silicon wafer was placed horizontally in a vacuum oven, and the prepared casting solution was added dropwise to the wafer. Using the surface tension of the liquid, the film was cast onto the entire wafer. The wafer was then heated at 60°C in a vacuum state for 12 hours. After the solvent completely evaporated, a dense, homogeneous film was formed on the wafer. Finally, the wafer was removed and immersed in deionized water to separate the membrane. For simplicity, the prepared series of x% Ag@NH2-UIO-66 / PAES-COOH (1%, 3%, 5%, 7%) hybrid forward osmosis membranes are designated as U1, U3, U5, and U7, respectively, and the PAES-COOH forward osmosis membrane is designated as U0.

[0045] 2. Characterization Methods

[0046] The crystal structure of MOFs was recorded using an X-ray diffractometer (XRD, Bruker, D8 Venture) using CuKα as the radiation source. The scanning speed was 5° / min, and the 2θ range was 5°-50°. A field emission scanning electron microscope (FE-SEM, Agilent 8500) equipped with an energy dispersive X-ray spectrometer (EDS) was used to observe the micromorphology of MOFs materials and forward osmosis membranes, and to detect the elemental composition of MOFs and membrane surfaces. Fourier transform infrared spectroscopy (FT-IR, Thermo, Nicolet IS50) was used to characterize the chemical structure of the materials. Before the test, the prepared powder sample was ground and pressed into a pellet with potassium bromide (KBr), and then fully dried under an infrared lamp. The water contact angle tester ( DSA255) was used to evaluate the hydrophilicity and hydrophobicity of the forward osmosis membrane. DI water was used as the test solution and the sessile drop method was selected as the test method. Each membrane sample was measured 5 times at different positions on the front and back sides, and the average value was calculated. The surface Zeta potential of the forward osmosis membrane was tested using an electrokinetic analyzer (Anton Paar, SurPASS3) based on the streaming potential method, and 1mM L -1 KCl was used as the background electrolyte solution and the (ζ) value was measured under neutral conditions. The mechanical properties of the forward osmosis membrane were evaluated using a universal testing machine (Shimadzu AG-I) with a tensile rate of 1 mm min -1 , the sample film size was 5 mm × 50 mm, and each film sample was measured 5 times to obtain the average value.

[0047] Permeation performance and structural parameter testing of forward osmosis membrane

[0048] Use as Figure 4 The laboratory-scale cross-flow forward osmosis test device shown is used to test the pure water flux (J) of the forward osmosis membrane. w ) and reverse salt flux (J s ) was tested at room temperature (25°C) and the effective area of ​​the membrane pool was 14.82 cm 2 1M NaCl and DI water were used as the draw solution (DS) and feed solution (FS) in the forward osmosis process, respectively. A peristaltic pump (PreFluid, BF200) was used to make DS and FS flow on both sides of the membrane. The flow rate was fixed at 12.5 cm -1 In addition, the volume change of FS was monitored by an electronic balance (SaiLun, YP502N), and the solute content change in FS was measured by a conductivity meter (TimePower, TP320) to calculate J w and J s . J of forward osmosis membrane w (L m -2 h -1 ) and J s (mmol m -2 h -1 ) value is calculated as follows:

[0049]

[0050] Where, ΔV represents the volume change of feed liquid (L), A m Represents the effective area of ​​the membrane pool (m 2 ), Δt represents the measurement time interval (s); C0 and C t represent the initial salt concentration of the feed solution and the salt concentration at time t (mmol L -1 ), V0 and V t are the initial volume of the feed solution and the volume at time t (L), respectively.

[0051] The membrane's water permeability coefficient (A), salt ion rejection rate (R), salt permeability coefficient (B), and structural parameters (S) were obtained by reverse osmosis testing with 7 mM Na2SO4 solution at a pressure of 15 bar. The test was performed at room temperature (25°C) with an effective membrane area of ​​14.82 cm 2 The specific calculation method is as follows:

[0052]

[0053] Where ΔP is the applied transmembrane pressure difference, is the pure water flow rate;

[0054]

[0055] where Cf and Cp are the salt concentrations in the feed and permeate, respectively;

[0056]

[0057] Where, k is the mass transfer coefficient, which is given by:

[0058]

[0059] Where D is the diffusion coefficient of Na2SO4, dh is the hydrodynamic diameter of the flow channel, and Sh is the Sherwood number, which is calculated as follows:

[0060]

[0061] Where L is the flow channel length, Re is the Reynolds number, and Sc is the Schmidt number. Re and Sc are calculated using the following formulas:

[0062]

[0063] Where ρ is the water density, μ is the dynamic viscosity of the solution, and u is the cross-flow velocity.

[0064] K reflects the membrane's resistance to solute diffusion and is determined by the following equation:

[0065]

[0066] where πd and πf are the osmotic pressures of DS and FS, respectively.

[0067] Finally, the membrane structure parameter (S) is determined by the following formula: S = KD (11) Antibacterial performance test of forward osmosis membrane

[0068] The antibacterial test of the forward osmosis membrane is carried out in a UV clean bench. Before testing, the membrane samples are soaked in anhydrous ethanol, washed with sterile water, and dried in a clean bench to avoid contamination by external bacteria.

[0069] Preparation of Escherichia coli suspension

[0070] Take the pre-activated E. coli colony and add it to LB liquid medium, place it in a constant temperature shaker at 37℃ and culture it for 10 hours to obtain E. coli with good biological activity. Then, dilute the bacterial solution in fresh LB medium and continue to shake culture at 37℃ until the optical density of the bacterial solution at 600nm (OD 600 ) reaches 1.0 (corresponding to 10 9 CFU mL -1 The bacterial suspension was centrifuged (1500 rpm, 2 min) to separate the nutrients from the bacterial cells, and then washed with sterile saline (0.9%) to remove the attached culture medium. A certain amount of sterile saline was added to the separated bacterial cell sediment to prepare a bacterial suspension of the desired concentration. 7 CFU mL -1 .

[0071] Static antibacterial test

[0072] The plate count method and inhibition zone test were used to evaluate the antibacterial properties of the forward osmosis membrane. The plate count method experiment process was as follows: the forward osmosis membrane (U0, U1, U3, U5, U7) was cut into 1 cm × 1.5 cm samples, and then mixed with 2 mL of bacterial suspension (10 7 CFU mL -1 ) were shaken and incubated at 37°C for 3 hours. The membrane sample was then removed and washed with sterile saline to remove bacteria not adhering to the sample surface. The cleaned membrane sample was placed in a centrifuge tube containing 10 mL of sterile saline and sonicated for 10 minutes to obtain a bacterial suspension. 0.2 mL of this bacterial suspension was applied to LB solid medium and incubated in a 37°C incubator for 12 hours. The number of surviving bacterial cells in the culture dish was determined by counting colony-forming units (CFU). The antibacterial rate, Eb, was calculated using the following formula:

[0073]

[0074] where N p and N m Represent the number of colonies formed on the original membrane and hybrid membrane, respectively.

[0075] The inhibition zone test process is similar to the plate counting method. 7 CFU mL -1 0.2 mL of bacterial suspension was coated on LB solid culture medium, and then the sterilized membrane sample (1 cm × 1.5 cm) was placed in LB solid culture medium and cultured in a constant temperature incubator at 37 ° C for 12 h. The width of the inhibition zone was measured by taking pictures to intuitively reflect the antibacterial performance of the membrane.

[0076] Ag in hybrid FO membrane + Release rate evaluation

[0077] Evaluation of Ag in Ag@NH2-UIO-66 / PAES-COOH hybrid forward osmosis membrane by leaching experiments + The test membrane (1cm×1.5cm) was immersed in 20ml of deionized water and stirred continuously for 7 days. The deionized water used to soak the membrane was replaced regularly every day. The collected water samples were acidified with nitric acid and then the Ag content in the water samples was detected by inductively coupled plasma optical emission spectroscopy (ICP-OES, LEEMAN Prodigy). + The concentration of Ag in the hybrid FO membrane was evaluated. + release rate.

[0078] Dynamic organic fouling test of forward osmosis membrane

[0079] A cross-flow forward osmosis experimental device was used. Bovine serum albumin (a protein) and sodium alginate (a polysaccharide) were selected as model pollutants to conduct a dynamic organic fouling test on the forward osmosis membrane. The purpose was to evaluate the organic fouling tendency of the forward osmosis membrane and the flux recovery after cleaning.

[0080] Before each experiment, the FO device was thoroughly washed and disinfected.

[0081] After the disinfection procedure was completed, a non-polluting baseline experiment was conducted to eliminate the effects of draw solution dilution and reverse solute diffusion on the decrease in water flux. 1 M NaCl and synthetic wastewater without organic pollutants (composition see Table 1) were selected as DS and FS, respectively, and the membrane was tested for 24 h to obtain a stable flux J. w0 .

[0082] After the baseline experiment, the feed solution was replaced with the prepared wastewater containing organic pollutants (Table 1), and 1M NaCl was used as DS to monitor the real-time water flux J wt Using normalized flux (J w0 / J wt )Evaluate the anti-fouling performance of forward osmosis membrane.

[0083] The dynamic anti-pollution test experimental conditions are the same as the above FO permeability test. The temperature is controlled at 25℃ throughout the experiment and the -1 The flux changes were monitored under cross-flow conditions. The digital balance and conductivity meter data were read every 30 minutes to calculate the flux changes during the entire cycle. After the dynamic contamination test, DI water was used as DS and FS for 30 minutes of cleaning, and then the water flux (J) was measured again under baseline test conditions. w1 ) to study the effect of membrane flushing on water flux recovery. The flux recovery rate (FRR) is calculated as follows:

[0084]

[0085] Table 1. Composition of synthetic wastewater

[0086]

[0087] Characterization of Ag@NH2-UIO-66

[0088] Figure 5 (a) shows the XRD patterns of NH2-UIO-66 and Ag@NH2-UIO-66. As shown in the figure, the characteristic diffraction peaks of NH2-UIO-66 are very consistent with the simulation patterns of the database (purple lines in Figure a). The characteristic diffraction peaks at 7.3°, 8.4°, 11.9°, 17.0°, 22.2°, and 25.6° correspond to the crystal planes (111), (002), (022), (004), (115), and (224), respectively. This shows that we have successfully synthesized a MOFs skeleton structure with good crystallinity. Compared with NH2-UIO-66, Ag@NH2-UIO-66 has new diffraction peaks at 38.2° and 44.4°, which correspond to the (111) and (200) crystal planes of Ag (JCPDS#04-0783), respectively. In addition, the intensity and position of other characteristic diffraction peaks of Ag@NH2-UIO-66 are not very different from those of NH2-UIO-66, which shows that we have successfully loaded silver nanoparticles (Ag NPs) into the skeleton structure of NH2-UIO-66 through photoreduction method, and the loading of Ag NPs does not destroy the integrity of the NH2-UIO-66 skeleton structure.

[0089] The infrared spectra of NH2-UIO-66 and Ag@NH2-UIO-66 are as follows: Figure 5As shown in (b), since Ag nanoparticles do not produce obvious characteristic peaks in the infrared spectrum, the infrared spectra of MOFs materials before and after Ag loading are almost the same. -1 and 3349cm -1 The characteristic peak at 1569 cm is attributed to the symmetric and asymmetric stretching vibrations of the primary amine group NH. -1 and 1379cm -1 The two sharp peaks are derived from the symmetric and asymmetric stretching of the carboxyl functional group CO. In addition, the peak at 1656 cm -1 The peak at corresponds to the metal ion (Zr +4 ) stretching vibration of C=O in the coordinated carboxyl group, 1502 cm -1 and 1429cm -1 The characteristic peak is attributed to the C=C stretching of the aromatic ring skeleton, located at 1260 cm -1 、757cm -1 and 660cm -1 The characteristic peaks correspond to the CN stretching vibration and Zr-O stretching vibration in aromatic amine.

[0090] Figure 6 (a) shows the SEM image of Ag@NH2-UIO-66. From the image, we can see that the MOFs particles are octahedral with a size of about 100-150nm. However, due to the presence of Ag NPs, the octahedral edges of the MOFs particles become slightly rounded. In addition, the EDS mapping image of the Ag element on the MOFs surface ( Figure 6 e), which also demonstrated that Ag NPs were uniformly loaded in the MOFs framework.

[0091] Chemical structure of forward osmosis membrane materials

[0092] The infrared spectra of PAES-COOH materials and series of Ag@NH2-UIO-66 / PAES-COOH hybrid materials are shown in Figure 2. Figure 7 As shown. 1581cm -1 and 1482cm -1 (C=C stretching vibration of benzene ring) 1319 cm -1 、1292cm -1 and 1144cm -1 (main chain sulfone group O=S=O stretching vibration), 1233cm -1 (Main chain ether oxygen bond Ar-O-Ar stretching vibration) 1103 cm -1 (Main chain sulfide bond Ar-S-Ar stretching vibration), 1710 cm -1(Side chain carboxyl C=O stretching vibration. The above shows that we have successfully synthesized PAES-COOH polymers with side chain carboxyl groups. For the infrared spectra of the series of hybrid materials, at 1633cm -1 and 1540cm -1 Two new characteristic peaks appeared near the amide bond, which were attributed to the stretching vibration of C=O and the bending vibration of NH. The appearance of these two peaks proved that we successfully grafted Ag@NH2-UIO-66 into the side chain of PAES-COOH polymer molecules through chemical bonding. In addition, the peak at 3470 cm -1 and 3363cm -1 The presence of two characteristic peaks derived from -NH2 also proves that the series of hybrid materials contain Ag@NH2-UIO-66.

[0093] Forward osmosis membrane morphology

[0094] The SEM images of the self-supporting homogeneous hybrid forward osmosis membrane prepared by solution casting are shown in Figure 2. Figure 8 As shown in the figure, we can observe no significant difference between the top and bottom surfaces (the interface between the membrane and the silicon wafer) of each membrane, all exhibiting a dense, non-porous structure. Notably, compared to U0 (A1, A2), the SEM images of U1-U5 (B1-D1, B2-D2) reveal a uniform distribution of MOF particles at the nanoscale within the hybrid forward osmosis membrane. Furthermore, the membrane surface becomes increasingly rougher with increasing MOF grafting loading. This demonstrates that chemical bonding of the MOFs to the membrane matrix creates strong interfacial compatibility, preventing the formation of non-selective gaps. The uniform distribution of N, Zr, and Ag elements in the EDS mapping image of the U5 membrane surface also indirectly confirms the successful grafting of Ag@NH2-UIO-66. However, when the MOF grafting loading in the hybrid material reaches 7%, surface defects due to MOF self-agglomeration appear on the surface of membrane U7 (E1, E2). Furthermore, cross-sectional SEM images of the hybrid membranes (B3-E3) show that the average thickness of each membrane is approximately 1.15 μm, and MOF particles are uniformly distributed within the cross-section. Furthermore, the membrane cross-sectional structure is homogeneous and free of pores.

[0095] Surface electrical and hydrophilic properties of the membrane

[0096] By testing the water contact angle, we explored the effect of MOFs materials introduced into the hybrid membrane on the hydrophilicity of the membrane surface. Figure 9As shown in (a), the series of hybrid forward osmosis membranes have lower water contact angles compared to the PAES-COOH forward osmosis membrane. Furthermore, with the increase in the amount of Ag@NH2-UIO-66 grafted, the water contact angle of the forward osmosis membrane gradually decreases from 72.3 in U0 to 64.5 in U7. The enhanced hydrophilicity of the series of hybrid forward osmosis membranes can be attributed to the large number of hydrophilic groups (-NH2 and -COOH) contained in the introduced MOFs material, which gives the hybrid membrane a more hydrophilic membrane surface. Secondly, the nanoscale pores provided by the MOFs particles may enhance the membrane's wetting behavior through capillary effects. In addition, in this study, it was found that the water contact angles at the top and bottom of the same membrane were almost the same, which indirectly indicates that the MOFs particles introduced through chemical bonding have good stability and dispersion in the membrane matrix, avoiding the occurrence of MOFs particles settling to the bottom of the membrane as the solvent evaporates during the membrane preparation process.

[0097] The successful grafting of MOFs materials will not only improve the hydrophilicity of the hybrid membrane surface, but also affect the surface electrical properties of the membrane. We conducted surface Zeta potential tests on a series of forward osmosis membranes under neutral conditions. The membrane surfaces of U0-U7 all have negative charges under neutral conditions ( Figure 9 b), primarily due to the deprotonation of the carboxyl groups, which imparts a significant negative charge on the membrane surface. Furthermore, we observed that the hybrid forward osmosis membranes exhibited lower zeta potentials than the PAES-COOH forward osmosis membrane. Furthermore, as the degree of MOF grafting increased, the zeta potential decreased from -52.2 mV in U0 to -64.9 mV in U7. This result is closely related to the ionization of the carboxyl groups in the organic ligands of the MOFs.

[0098] Mechanical properties of membranes

[0099] In order to ensure the long-term stable operation of forward osmosis, the mechanical properties of the self-supporting forward osmosis membrane are particularly important. Here, we evaluate the mechanical properties of a series of forward osmosis membranes by measuring the Young's modulus, tensile strength, and elongation at break of the forward osmosis membranes. Figure 10 As shown in the figure, compared with U0, when the MOFs material grafting amount is between 1% and 5%, the Young's modulus, tensile strength, and elongation at break of the series of hybrid forward osmosis membranes only decrease to a very small extent. This is mainly due to the close chemical bonding between the MOFs material and the membrane matrix material, which creates a strong interfacial compatibility between the two. Therefore, the series of hybrid forward osmosis membranes still maintain excellent mechanical properties to meet the stability of long-term operation. However, when the MOFs material grafting amount exceeds 5%, the mechanical properties of membrane U7 drop drastically. At this time, the agglomeration of MOFs particles reduces its interfacial compatibility with the membrane matrix, thereby affecting the mechanical properties of the forward osmosis membrane.

[0100] Table 2. Mechanical properties of a series of forward osmosis membranes with a thickness of approximately 1.15 μm

[0101]

[0102] Membrane permeability and transport properties

[0103] DI water and 1M NaCl were used as feed and draw solutions to evaluate the permeability of the series of forward osmosis membranes. The water permeation flux (J w ) and reverse solute diffusion flux (J s ) and water-salt selectivity (J w / J s ) test results are as follows Figure 11 As shown in (a), it can be observed that when the grafting amount of MOFs material in the hybrid membrane increases from 0 to 5%, the water flux of the hybrid forward osmosis membrane increases from 3.29 L m -2 h -1 Significantly increased to 13.78L m -2 h -1 This is due to the sub-nanometer pore size of Ag@NH2-UIO-66. It can serve as a specific transport channel for water molecules. As the amount of MOFs grafted increases, the number of additional transport channels for water molecules in the membrane matrix gradually increases. At the same time, the hydrophilic groups in the MOF material enhance the hydrophilicity of the membrane matrix, thereby improving the membrane's permeability and generating a higher water flux. However, when the MOF grafting amount reaches 7%, the water flux actually decreases. This may be due to the agglomeration of MOF particles, which prevents some of the water molecule-specific channels from performing their transport function. At the same time, external concentration polarization also affects the water flux.

[0104] In addition, when the MOFs content in the hybrid membrane increased from 0 to 5%, the reverse solute flux decreased slightly, from 11.1 mmolm -2 h -1 Down to 8 mmol m -2 h -1 This is determined by the size screening effect and the electrostatic repulsion effect. First, the successful grafting of Ag@NH2-UIO-66 provides a large number of salt ion retention barriers in the membrane matrix. It can screen Na + and Cl - Secondly, combined with the Zeta potential test results of the membrane surface, the increase in the amount of MOFs material grafted can give the hybrid forward osmosis membrane surface a lower negative charge, which can -This produces a stronger electrostatic repulsion effect, thereby inhibiting reverse solute diffusion. In addition, the MOFs particles stably bound to the membrane matrix also increase steric hindrance to the transport of salt ions, enhancing the mass transfer resistance of solute reverse diffusion. However, membrane U7 showed a sharp increase in reverse solute diffusion flux. This undesirable phenomenon is mainly due to the reduced compatibility of the agglomerated MOFs particles with the membrane matrix material, which easily forms non-selective gaps at the edges of the MOFs particles. This opens up new channels for the transport of salt ions, leading to an intensification of the reverse solute diffusion phenomenon.

[0105] Excellent water-salt selectivity (J w / J s ) is the key performance of an ideal forward osmosis membrane. w / J s The higher the value, the stronger the membrane's selectivity for ions and the better the retention effect. Figure 11 As shown in (a), when the MOFs content in the hybrid forward osmosis membrane is in the range of 0-5%, as the amount of MOFs grafted increases, the water and salt screening performance of the membrane gradually increases, and U5 shows the highest J w / J s Value (1724.7 mol L -1 This is attributed to the successful grafting of Ag@NH2-UIO-66, which increases the water flux of the hybrid forward osmosis membrane while reducing the reverse salt flux of the membrane. w and J s This special relationship helps us to study and overcome the classic permeation-selectivity trade-off. Unfortunately, the presence of nonselective gaps in U7 reduces its water-salt selectivity.

[0106] At the same time, we also evaluated the FO performance of a series of hybrid forward osmosis membranes by using different concentrations of NaCl as the draw solution. The water flux, reverse salt flux, and water-salt selectivity of the series of membranes vary with the draw solution concentration. Figure 11 (b)-(d) are shown. From the figure, we can see that the water flux of all membranes increases linearly with the increase of the draw solution concentration. The linear relationship between water flux and draw solution concentration proves that the series of self-supporting homogeneous hybrid forward osmosis membranes we prepared have almost no ICP phenomenon in the FO process, so the osmotic pressure generated by the draw solution can be effectively utilized. Accordingly, due to

[0107] Solution-diffusion mechanism, the higher the concentration of ions in the draw solution, the reverse solute flux of all membranes increases linearly with the increase of DS concentration. Figure 11(d) It can also be observed that the water-salt selectivity of the hybrid forward osmosis membranes is unaffected by changes in the draw solution concentration. These results demonstrate that our series of self-supporting homogeneous hybrid forward osmosis membranes possess an ideal ICP-free structure, effectively utilizing the osmotic pressure generated by the draw solution. Furthermore, the optimal MOF particle content plays a role in water and salt sieving during the osmotic process. Consequently, the hybrid forward osmosis membranes maintain excellent permselectivity regardless of changes in the draw solution concentration.

[0108] In addition, we evaluated the key performance parameters of the membrane series through reverse osmosis testing (Table 3). The structural parameters of U1, U3, U5, and U7 were 0.83μm, 0.69μm, 0.56μm, and 1.9μm, respectively. Considering the potential for errors in the testing process, these values ​​can be statistically considered to be close to zero. This demonstrates that the self-supporting homogeneous hybrid forward osmosis membrane we designed and prepared has an ideal symmetrical structure, ensuring that the forward osmosis membrane does not produce ICP during operation, allowing the effective osmotic pressure to infinitely approach the theoretical osmotic pressure.

[0109] Table 3. Key performance parameters of a series of Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membranes in forward osmosis and reverse osmosis systems

[0110]

[0111] Antibacterial properties of forward osmosis membranes

[0112] In this study, Escherichia coli (Ecoli) was selected as a biofouling model, and the plate count method and inhibition zone determination experiment were used to evaluate the effect of successful grafting of Ag@NH2-UIO-66 on the antibacterial properties of a series of hybrid forward osmosis membranes. Figure 12 a) It can be observed that as the amount of Ag@NH2-UIO-66 grafted increases, the number of colonies on the culture medium gradually decreases. When the MOFs grafting amount reaches 7%, the sterilization rate of the membrane is as high as 98% ( Figure 12 b) The phenomenon observed in the inhibition zone experiment is as follows: no inhibition zone was observed around membrane U0, while a clear inhibition zone without colonies was formed around the series of hybrid forward osmosis membranes modified with Ag@NH2-UIO-66. Moreover, with the increase of the amount of MOFs grafted, the area of ​​the inhibition zone gradually expanded. The maximum inhibition area formed around membrane U7 was 1.89cm×1.76cm. The antibacterial property of Ag@NH2-UIO-66 is mainly attributed to the broad-spectrum bactericidal effect of the Ag NPs loaded in its structure. The MOFs skeleton acts as a carrier of Ag NPs, avoiding the problem of rapid loss of NPs due to poor aggregation of NPs, ensuring the + Stable release ( Figure 12c) The bactericidal mechanism of AgNPs includes several pathways: (1) After AgNPs attach to the cell wall, they degrade lipopolysaccharide, causing the cell wall to collapse and destroying the cell structure. (2) AgNPs release + They can interact with thiol groups in DNA or proteins, disrupting DNA replication. (3) Reactive oxygen species (ROS) generated by Ag NPs can react with cellular substances that carry out basic metabolic activities, inactivating respiratory enzymes.

[0113] Anti-organic pollution performance of forward osmosis membrane

[0114] Combined with previous literature reports, considering that polysaccharides, proteins and humus are the main components of organic matter in wastewater, sodium alginate (polysaccharide) and bovine serum albumin (protein) were selected as simulated organic pollutants for 24h dynamic pollution experiments. Based on the results of the above FO performance test and antibacterial test, the membrane U5 with the best water-salt selectivity and excellent antibacterial performance was selected as the research object of the 24h dynamic pollution test, and the original membrane U0 was used as a control to further explore the effect of Ag@NH2-UIO-66 on the anti-organic pollution performance of the hybrid membrane. During the test, 1M NaCl was selected as the draw liquid and synthetic wastewater was used as the feed liquid (Table 1). Figure 13 As shown in (a) and (b), the normalized water flux reduction rate of U5 after 24h dynamic fouling test of BSA and SA was 10.1% and 13.3%, respectively, which was lower than 20.7% (BSA) and 24.1% (SA) of the control membrane U0. This result shows that the successful grafting of Ag@NH2-UIO-66 has a positive effect on the anti-organic fouling performance of the forward osmosis membrane. The improvement of the anti-fouling performance of the hybrid membrane may be attributed to the following factors: (1) The MOFs material contains a large number of polar groups (-NH2, -COOH), which enhances the hydrophilicity of the membrane surface. The highly hydrophilic membrane surface can build a dense hydration layer barrier through hydrogen bonding, thereby generating a strong spatial repulsion effect to prevent dirt adhesion. (2) The surface charge of the membrane also plays a vital role in anti-fouling. The characteristic organic substances SA and BSA faced in this study are negatively charged in natural solution. Combined with the discussion of the above Zeta potential, it can be seen that the successful grafting of MOFs makes the membrane surface carry abundant negative charges, which can prevent the adhesion of organic pollutants through electrostatic repulsion. (3) The excellent water-salt screening performance of MOFs also plays a positive role in resisting membrane fouling. According to previous studies, reversely diffused salt ions will weaken the electrostatic repulsion between organic foulants, thereby promoting the formation of a dense fouling layer. The MOFs introduced into the hybrid membrane can act as a barrier to intercept salt ions, inhibiting the reverse solute diffusion phenomenon, thereby avoiding the formation of a compact fouling layer, and thus preventing a more serious decrease in water flux.

[0115] After the dynamic pollution test, the feed liquid and the draw liquid were replaced with fresh deionized water, the membrane was cleaned for half an hour, and then the flux recovery rate test was performed. The test results of the flux recovery rate are as follows: Figure 13 As shown in (c), both U0 and U5 exhibit excellent flux recovery due to their smooth, hydrophilic membrane surfaces. Combined with the water contact angle test results, the introduction of MOFs imparts a more hydrophilic membrane surface, making it easier to remove surface-attached dirt through hydraulic cleaning. Consequently, the hybrid membrane's flux recovery is slightly improved compared to U0.

[0116] in conclusion

[0117] In this study, we started from the forward osmosis membrane structure design and membrane material modification, and successfully designed and prepared a series of ICP-free Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membranes. Since Ag@NH2-UIO-66 is tightly bonded to the membrane matrix through chemical bonds, its good interfacial compatibility enables it to play a positive role in the forward osmosis process. The sub-nanoscale cavities of Ag@NH2-UIO-66 / PAES-COOH particles become additional transmission channels for water and isolation barriers for salt ions, so that the prepared forward osmosis membrane shows a decreased reverse salt flux while increasing the water flux. The hybrid forward osmosis membrane (U5) with a 5% Ag@NH2-UIO-66 grafting amount showed a significantly improved water flux of 13.78L m -2 h -1 And ultra-high water-salt selectivity of 1724.7 mol L -1 . In addition, the introduction of Ag@NH2-UIO-66 significantly improved the bactericidal performance and anti-organic pollution performance of the hybrid forward osmosis membrane. U5 showed an antibacterial property of 95.3% after 24 hours of contact and cultivation with Escherichia coli. At the same time, U5 showed an extremely low flux decline rate during the 24-hour dynamic pollution test with synthetic wastewater containing BSA or SA as the feed liquid, and after hydraulic cleaning, the flux recovery rate was as high as 97.1% (BSA) and 98.5% (SA). In summary, we successfully prepared Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis without ICP phenomenon, which achieved the ability to maintain both antibacterial and resistance to organic pollution. It proves the potential of self-supporting homogeneous hybrid forward osmosis membranes in sewage and wastewater treatment, which will further promote the application of self-supporting forward osmosis membranes in sewage and wastewater treatment.

[0118] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A multifunctional Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membrane, characterized by: The forward osmosis membrane is a series of Ag@NH2-UIO-66 / PAES-COOH hybrid materials synthesized by introducing hydrophilic Ag@NH2-UIO-66 nanomaterials with water molecule-specific channels and antibacterial ability into the molecular structure of a carboxyl-containing polyarylethersulfone matrix material with excellent mechanical properties through precise molecular design. The synthesis steps of Ag@NH2-UIO-66 nanomaterials are as follows: 0.233 g ZrCl4, 0.181 g NH2-H2BPC, 7.2 mL CH3COOH, and 36 mL DMF were thoroughly mixed and stirred in a sealed beaker for 1 h. The uniformly dispersed mixed solution was then transferred to a polytetrafluoroethylene-lined reactor, which was placed in an oven and heated at 120°C for 24 h. After the reactor was naturally cooled to room temperature, it was centrifuged at 8000 rpm for 10 min to separate a light yellow powder, which was then washed three times with DMF and anhydrous ethanol to obtain NH2-UIO-66 material. 0.2 g of the NH2-UIO-66 material was dispersed in 100 mL of DI water by ultrasound, and then 2.8 mL of 0.1 mol L -1 The AgNO3 solution was stirred for 30 min and then irradiated under a 50W xenon light source for 30 min to make the Ag in the solution + Reduction to Ag 0 The product was loaded on the surface and framework of NH2-UIO-66 material. Finally, the product was centrifuged and washed, and then dried in a vacuum oven at 80 o After drying at C for 12 h, the brown powder Ag@NH2-UIO-66 material was obtained; The steps for the synthesis of a series of Ag@NH2-UIO-66 / PAES-COOH hybrid materials are as follows: Ag@NH2-UIO-66 was introduced into the molecular structure of the PAES-COOH matrix material by chemical bonding to synthesize the Ag@NH2-UIO-66 / PAES-COOH hybrid material. Specifically, 2 g of PAES-COOH was dissolved in anhydrous THF at room temperature with stirring, and 0.4 mL of oxalyl chloride (1.5 times the calculated amount of carboxyl groups in the PAES-COOH material) was slowly added dropwise, and the reaction was continued for 6 h. Subsequently, the unreacted oxalyl chloride and THF were evaporated under vacuum conditions, and the obtained solid was dissolved in anhydrous THF again. At the same time, a certain amount of Ag@NH2-UIO-66 was dispersed in anhydrous THF to form a suspension, which was then dropped into the above reaction system and stirred at room temperature for 24 h. The viscous reactant was poured into deionized water to obtain a brown-yellow flocculent crude product, which was crushed into powder with a high-speed tissue grinder, washed several times with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 80°C for 24 h. h, a series of x% Ag@ NH2-UIO-66 / PAES-COOH hybrid materials were obtained, where "x" represents the mass fraction of Ag@NH2-UIO-66 in the hybrid material; The preparation steps of Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membrane are as follows: A forward osmosis membrane with a dense homogeneous structure was obtained by solution casting and solvent evaporation.

2. The multifunctional Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membrane according to claim 1, characterized in that: The steps for synthesizing the PAES-COOH matrix material are: The carboxyl-containing hydrophilic PAES-COOH matrix material was synthesized by aromatic nucleophilic substitution polycondensation. Specifically, a three-necked flask was first fixed in the reaction system, and then 2.283 g BPA, 4.805 g PPL, 6.356 g DFPS, 5.389 g K2CO3, 46 mL TMS, and 23 mL TL were added to the 100 mL three-necked flask in sequence. The mixture was stirred for 25 min under a gentle argon flow to uniformly mix the solvent and the powdered drug. Subsequently, the reaction system was heated to 135 o C, remove the water produced by the reaction system under condensation reflux until no new liquid droplets drip from the water separator, and then raise the temperature to 180°C; after 6 hours, the polymerization reaction is completed, the viscous material in the three-necked flask is poured into DI water, and the obtained tough strip material is crushed, and then washed several times with deionized water and anhydrous ethanol to remove unreacted monomers and solvents; then, the material is dissolved in THF and acidified with concentrated hydrochloric acid, and then the solution is poured into deionized water to obtain a white crude product. After washing, the crude product is placed in a vacuum drying oven at 80°C for 24 hours to finally obtain PAES-COOH material; The preparation steps of Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membrane are as follows: The synthesized PAES-COOH and Ag@NH2-UIO-66 / PAES-COOH materials were dissolved in DMF respectively, stirred at room temperature for 12 hours, and then allowed to stand for degassing for 6 hours. Subsequently, a smooth and flat silicon wafer was placed horizontally in a vacuum oven, and the prepared casting liquid was added to the silicon wafer. The liquid was cast onto the entire silicon wafer using the surface tension of the liquid, and then heated at 60°C in a vacuum state for 12 hours. After the solvent was completely evaporated, a film with a dense and homogeneous structure was formed on the silicon wafer. Finally, the silicon wafer was taken out and immersed in deionized water to separate the film from the silicon wafer.

3. The multifunctional Ag@NH2-UIO-66 / PAES-COOH self-supporting homogeneous hybrid forward osmosis membrane according to claim 1, characterized in that: In the synthesis steps of a series of Ag@NH2-UIO-66 / PAES-COOH hybrid materials, 0.02 g or 0.06 g or 0.10 g or 0.14 g of Ag@NH2-UIO-66 was added.

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