Ultraviolet crosslinking titanium dioxide nanometer interlayer assisted nanofiltration membrane, and preparation method and application thereof

Abstract

The application discloses a kind of nanofiltration membrane based on ultraviolet crosslinking titanium dioxide nano intermediate layer auxiliary and its preparation method and application, preparation method includes the following steps: photo initiator, methyl methacryloyl oxypropyl double-terminated polydimethylsiloxane and titanium dioxide are dissolved in solvent and are configured into coating liquid;The prepared coating liquid is coated on ultrafiltration membrane, is obtained after ultraviolet irradiation in light-proof place ultraviolet crosslinking titanium dioxide nano intermediate layer;After that, interface polymerization is carried out to obtain the nanofiltration membrane containing ultraviolet crosslinking titanium dioxide nano intermediate layer.The application promotes methyl methacryloyl oxypropyl double-terminated polydimethylsiloxane polymerization by using ultraviolet light crosslinking and is wrapped titanium dioxide nanoparticles to form super-hydrophilic intermediate layer, and the nanofiltration membrane containing ultraviolet crosslinking titanium dioxide nano intermediate layer with ultrathin defect is generated by using interface polymerization, while improving the retention of multivalent salt, the pure water permeability and the permeation rate of monovalent salt are increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanofiltration membranes, in particular to a nanofiltration membrane based on a UV cross-linked titanium dioxide intermediate layer and a preparation method and application thereof. BACKGROUND

[0002] Nanofiltration membranes have attracted much attention in water treatment due to their low energy consumption, high separation precision and low secondary pollution. However, the high selectivity of nanofiltration membranes is usually at the expense of permeability. Therefore, it is an ideal choice to improve the separation efficiency by preparing nanofiltration membranes with high permeability. Generally, polyamide (PA) nanofiltration membranes are prepared by the rapid interfacial polymerization (IP) reaction of water-soluble monomer piperazine (PIP) and oil-soluble monomer trimesoyl chloride (TMC) at the water / oil interface of a porous substrate. Since the IP reaction occurs instantaneously and the reaction rate is difficult to control, it often leads to the formation of a PA separation layer with a highly cross-linked structure and a large thickness, which greatly limits the transport of water molecules in the membrane pores.

[0003] In order to maintain the high retention of nanofiltration membranes while improving the permeability of water molecules, one feasible strategy is to add nanomaterials to the PA layer to construct a loose separation layer structure by generating a large number of interfacial voids. However, since the aggregation of nanomaterials can destroy the integrity of the selective layer, it is a more ideal method to introduce nanomaterials as an intermediate layer between the porous substrate and the active layer. First, the intermediate layer can effectively control the release of monomers during the IP process. In addition, the introduction of the intermediate layer can also induce monomer diffusion-driven instability to produce a rough PA separation layer, thereby increasing the effective permeation area and improving water permeability. However, most intermediate layers are deposited on the surface of the substrate by vacuum filtration, which not only makes it difficult to realize large-scale application on the production line, but also increases the risk of active layer detachment during long-term filtration due to the weak interaction between the intermediate layer and the substrate. Titanium dioxide (TiO2) is widely used in the modification of nanofiltration membranes due to its good hydrophilicity, low price, good chemical and physical stability and other advantages. Among them, the use of TiO2 as an intermediate layer for interfacial polymerization can greatly improve the controllability of the reaction rate, and also provide additional water transport channels to improve the overall permeability of the nanofiltration membrane. However, due to the inherent agglomeration of TiO2, the large aggregate size limits the extension of polymer chains during the IP process, and to some extent promotes the close packing of molecular chains, leading to the formation of interface defects during the film formation process. SUMMARY

[0004] In order to solve the problems in the prior art, the application provides a preparation method of a nanofiltration membrane based on an ultraviolet cross-linked titanium dioxide nanometer intermediate layer, which applies ultraviolet polymerization technology to the formation process of the intermediate layer, forms a continuous polymer network through ultraviolet light polymerization of methyl acryloxypropyl double-terminated polydimethylsiloxane, wraps the introduced titanium dioxide particles by using polymer chains, makes the titanium dioxide particles ultrafast freeze before polymerization, promotes uniform distribution of the titanium dioxide, thereby preventing accumulation of aggregates, produces a stable super-hydrophilic ultraviolet cross-linked titanium dioxide nanometer intermediate layer, and then performs an interfacial polymerization reaction to prepare a nanofiltration membrane with an ultrathin separation layer and super-hydrophilic / high negative electric property, which enhances selective separation of multivalent / monovalent salt and greatly improves overall permeability.

[0005] In order to achieve the above object, the application is implemented by the following technical scheme.

[0006] The nanofiltration membrane based on the ultraviolet cross-linked titanium dioxide nanometer intermediate layer is prepared by embedding titanium dioxide nanoparticles to form the ultraviolet cross-linked titanium dioxide nanometer intermediate layer through ultraviolet graft polymerization of methyl acryloxypropyl double-terminated polydimethylsiloxane, and then performing an interfacial polymerization reaction to form the nanofiltration membrane containing the ultraviolet cross-linked titanium dioxide nanometer intermediate layer.

[0007] The preparation method of the nanofiltration membrane based on the ultraviolet cross-linked titanium dioxide nanometer intermediate layer includes the following steps.

[0008] (1) The photoinitiator, methyl acryloxypropyl double-terminated polydimethylsiloxane and titanium dioxide are dissolved in a solvent to configure a coating liquid, and the solvent can be water or ultrapure water.

[0009] The photoinitiator is one or more of 2-hydroxy-2-methylpropionyl ketone, ethyl (2,4,6-trimethylbenzoyl) phenyl phosphonate, diphenyl (2,4,6-trimethylbenzoyl) phosphorus oxide, 4-dimethylamino-benzoic acid ethyl ester and 4-chlorobenzophenone, which are mixed in any proportion.

[0010] The mass concentration of the photoinitiator in the coating solution is 0.05-0.5 g / L, and the mass concentration of the photoinitiator in the coating solution is 0.05 g / L, 0.08 g / L, 0.1 g / L, 0.12 g / L, 0.15 g / L, 0.2 g / L, 0.23 g / L, 0.25 g / L, 0.5 g / L, for example. The mass concentration of the methacryloxypropyl double-terminated polydimethylsiloxane is 0.1-0.5 g / L, and the mass concentration of the methacryloxypropyl double-terminated polydimethylsiloxane is 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.25 g / L, 0.3 g / L, 0.35 g / L, 0.4 g / L, 0.45 g / L, 0.5 g / L, for example. The mass concentration of titanium dioxide is 0.2-0.8 g / L, and the mass concentration of titanium dioxide is 0.2 g / L, 0.25 g / L, 0.3 g / L, 0.35 g / L, 0.4 g / L, 0.45 g / L, 0.5 g / L, 0.55 g / L, 0.6 g / L, 0.65 g / L, 0.7 g / L, 0.75 g / L, 0.8 g / L, for example. The titanium dioxide can be nano-titanium dioxide, and the particle size of the titanium dioxide is 10-100 nm, and the particle size of the titanium dioxide can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or the titanium dioxide can be a mixture of titanium dioxide with various particle sizes in the range of 10-100 nm.

[0011] (2) The coating solution is coated on the ultrafiltration membrane, and the ultraviolet cross-linked titanium dioxide nano-intermediate layer is obtained after ultraviolet irradiation in the dark.

[0012] The coating method for coating the coating solution on the ultrafiltration membrane is one or more of spraying, brushing, rolling or dipping, which can achieve uniform coating of the ultraviolet cross-linked titanium dioxide nano-intermediate layer; the coating time of the coating solution on the ultrafiltration membrane is 1-3 minutes, and the coating time is 1 minute, 90 seconds, 2 minutes, 150 seconds, 3 minutes, for example, and the ultraviolet irradiation time is 5-20 minutes, and the ultraviolet irradiation time is 5 minutes, 8 minutes, 10 minutes, 12 minutes, 15 minutes, 18 minutes, 20 minutes, for example.

[0013] The ultrafiltration membrane is one or more of polyacrylonitrile ultrafiltration membrane, polyether sulfone ultrafiltration membrane, polysulfone ultrafiltration membrane, polyvinylidene fluoride ultrafiltration membrane, sulfonated polyether sulfone ultrafiltration membrane.

[0014] (3) The aqueous solution and the oil phase solution are sequentially coated on the ultraviolet cross-linked titanium dioxide nano-intermediate layer, and the nanofiltration membrane containing the ultraviolet cross-linked titanium dioxide nano-intermediate layer is prepared by interfacial polymerization.

[0015] The coating method of the UV cross-linked titanium dioxide nanometer intermediate layer is one or more of spraying, brushing, rolling or dipping, and uniform coating can be achieved.

[0016] The solute in the aqueous solution is one or more of piperazine, m-phenylenediamine, polyethyleneimine and polyhydric alcohol, and the solvent in the aqueous solution is water; the solute in the oil phase solution is isophthaloyl chloride or / and m-phthaloyl chloride and isocyanate, and the solvent in the oil phase solution is one or more of n-hexane, toluene, n-heptane, cyclohexane and chloroform.

[0017] The coating time of the aqueous solution is 2-3 minutes, and the coating time of the aqueous solution is 2 minutes, 130 seconds, 140 seconds, 150 seconds, 160 seconds, 170 seconds or 3 minutes, for example; the coating time of the oil phase solution is 30 seconds-2 minutes, and the coating time of the oil phase solution is 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, 80 seconds, 90 seconds, 100 seconds, 110 seconds or 2 minutes, for example.

[0018] The mass concentration of the solute in the aqueous solution is 0.01-20 g / L, and the mass concentration of the solute in the aqueous solution is 0.01 g / L, 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, 1.0 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 15 g / L or 20 g / L, for example; the mass concentration of the solute in the oil phase solution is 0.01-2 g / L, and the mass concentration of the solute in the oil phase solution is 0.01 g / L, 0.05 g / L, 0.1 g / L, 0.15 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, 1 g / L, 1.5 g / L or 2 g / L, for example.

[0019] The nanofiltration membrane containing the UV cross-linked titanium dioxide nanometer intermediate layer prepared is one or more of polyamide nanofiltration membrane, polyester nanofiltration membrane, polyurethane nanofiltration membrane, polyurea nanofiltration membrane, poly-piperazine amide nanofiltration membrane, polysulfone nanofiltration membrane and polyether sulfone nanofiltration membrane. In the preparation of the above nanofiltration membrane, the solvent in the aqueous solution is water, and the solvent in the oil phase solution can be one or more of n-hexane, toluene, n-heptane, cyclohexane and chloroform.

[0020] When the polyamide nanofiltration membrane is prepared, the solute in the aqueous phase solution is m-phenylenediamine or / and polyethylene imine, and the solute in the oil phase solution is trimesoyl chloride or / and isophthaloyl chloride.

[0021] When the polyester nanofiltration membrane is prepared, the solute in the aqueous phase solution is polyol, and the solute in the oil phase solution is trimesoyl chloride or / and isophthaloyl chloride.

[0022] When the polyurethane nanofiltration membrane is prepared, the solute in the aqueous phase solution is polyol, and the solute in the oil phase solution is isocyanate.

[0023] When the polyurea nanofiltration membrane is prepared, the solute in the aqueous phase solution is m-phenylenediamine, and the solute in the oil phase solution is diisocyanate.

[0024] When the polypiperazine amide nanofiltration membrane is prepared, the solute in the aqueous phase solution is piperazine, and the solute in the oil phase solution is trimesoyl chloride or / and isophthaloyl chloride.

[0025] Application of a nanofiltration membrane based on an ultraviolet cross-linked titanium dioxide nanometer intermediate layer in underground water purification.

[0026] The underground water filtered by the nanofiltration membrane prepared by the application contains beneficial mineral elements and / or trace elements.

[0027] Compared with the prior art, the application has the beneficial effects that:

[0028] 1、The application uses methacryloxypropyl double-terminated polydimethylsiloxane as a photosensitive monomer, which can undergo addition reaction and realize rapid polymerization within several seconds under ultraviolet irradiation, and an ultraviolet cross-linked titanium dioxide nanometer intermediate layer with ultra-thin and no defects is finally formed due to the addition of titanium dioxide, and compared with conventional chemical synthesis process, the UV polymerization processing time is shorter, the energy consumption is lower, and pollution is less likely to occur.

[0029] 2. The present invention relates to a method for preparing nanofiltration membranes based on ultraviolet cross-linked titanium dioxide nanolayers. This method does not require changing the original formulation of the interfacial polymerization monomer solution, i.e., it does not require dissolving methacryloyloxypropyl-terminated polydimethylsiloxane and titanium dioxide in the interfacial polymerization aqueous solution, nor does it change the interfacial polymerization reaction conditions for generating polyamide nanofiltration membranes, polyester nanofiltration membranes, polyurethane nanofiltration membranes, polyurea nanofiltration membranes, polypiperazine amide nanofiltration membranes, polysulfone nanofiltration membranes, and polyethersulfone nanofiltration membranes. Instead, it only requires a one-step intermediate layer modification before the IP reaction. The intermediate layer modification is based on the photosensitizing properties of methacryloxypropyl double-terminated polydimethylsiloxane. Under UV irradiation, a self-polymerization reaction occurs, promoting the polymerization of the polymer network. This encapsulates TiO2 particles within the polymer chains, transforming unmodified, easily agglomerated particles into a uniformly distributed nano-intermediate layer. Simultaneously, the photocatalytic effect of TiO2 under UV irradiation generates free radicals and numerous hydrophilic groups, enhancing interfacial hydrophilicity and endowing the nanofiltration membrane with catalytic efficiency, thus strengthening its ability to remove organic pollutants in actual natural water bodies. Regarding the mass transfer of water molecules within the membrane, the presence of the superhydrophilic intermediate layer promotes the enrichment of aqueous monomers such as piperazine and m-phenylenediamine during interfacial polymerization and accelerates their diffusion to the interface, significantly improving polymerization efficiency and promoting the formation of an ultrathin and smooth polyamide active layer. On the one hand, the enrichment of aqueous monomers can promote rapid cross-linking of the polyamide layer in a relatively short time. The resulting dense separation layer prevents further diffusion of monomers, causing the reaction to terminate prematurely and avoiding the stacking of subsequent reaction products in the vertical direction. Therefore, it can effectively reduce the thickness of the polyamide layer and significantly reduce the mass transfer resistance of water molecules. On the other hand, the residual acyl chloride groups on the membrane surface enhance the hydrophilicity. The combined effect of these two effects promotes the ultrafast transport of water molecules within the membrane. In addition, nanofiltration membranes have poor retention of monovalent salt ions, and the increase in flux indirectly promotes the permeation of monovalent ions. Nanofiltration mainly relies on the electrostatic repulsion of charged membrane surfaces to retain divalent salt ions. Due to the premature termination of the interfacial polymerization reaction, more unreacted TMC hydrolyzes to generate a large number of negatively charged carboxyl groups, which significantly improves the electrostatic repulsion ability of the membrane surface. Therefore, while promoting the permeation of monovalent ions, the enhancement of the negative charge on the membrane surface simultaneously strengthens the electrostatic repulsion effect on divalent ions, thereby improving the permeability of nanofiltration membranes and enhancing their ability to selectively separate polyvalent / monovalent salts. The membrane-making method and process of the present invention can be perfectly matched with existing commercial membrane-making processes, and has good application prospects in the fields of comprehensive water resource utilization and groundwater purification. Attached Figure Description

[0030] Appendix Figure 1 This is a flowchart of the nanofiltration membrane preparation process based on ultraviolet cross-linked titanium dioxide nanolayers.

[0031] AppendixFigure 2 is a filtration effect diagram of the nanofiltration membrane of application example 1 on groundwater. DETAILED DESCRIPTION

[0032] The present application will be further described with reference to the following examples. It should be understood that these examples are intended to illustrate the present application and are not intended to limit the scope of the present application. Furthermore, since various modifications and changes can be made to the present application as will be understood by those of ordinary skill in the art upon reading the description of the present application, it is intended to cover any and all such modifications and changes as fall within the scope of the present application.

[0033] Before further description of the present application, it should be understood that the scope of the present application is not limited to specific specific embodiments described below; it should also be understood that the terminology used in the present application is used for the purpose of describing particular specific embodiments only and is not intended to limit the scope of the present application. Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by those skilled in the art. Unless otherwise noted, the test methods used in the following examples were conducted under conventional conditions or under conditions recommended by the respective manufacturers. In addition to the specific methods, devices, materials used in the examples, any methods, devices and materials similar or equivalent to those described in the examples of the present application can be used to implement the present application according to the knowledge of those skilled in the art and the description of the present application.

[0034] Example 1

[0035] A non-homogeneous mixed solution was prepared as a coating solution by dissolving 0.01 g of a photoinitiator (the photoinitiator was 2-hydroxy-2-methylpropionenone), 0.02 g of methacryloxypropyl bis-blocked polydimethylsiloxane, and 0.02 g of titanium dioxide powder into ultrapure water at room temperature, and ultrasonic dissolution, wherein the mass concentration of the photoinitiator was 0.1 g / L, the mass concentration of the methacryloxypropyl bis-blocked polydimethylsiloxane was 0.1 g / L, and the mass concentration of the titanium dioxide was 0.2 g / L; 1 g of piperazine (PIP) powder was added into a volumetric flask, and ultrapure water was poured to prepare a water phase solution with a piperazine mass concentration of 10 g / L; 0.1 g of trimesoyl chloride (TMC) powder was added into a volumetric flask, and n-hexane was poured to prepare an oil phase solution with a trimesoyl chloride mass concentration of 1 g / L; the coating solution was poured onto the surface of a commercial polyether sulfone ultrafiltration membrane fixed in a mold at room temperature; after being immersed for 3 minutes, the coating solution was discharged, and the ultrafiltration membrane was placed in a dark place and irradiated with ultraviolet light for 5 minutes; the ultraviolet cross-linked titanium dioxide nano intermediate layer was obtained; then the water phase solution was poured into the mold; after being immersed for 2 minutes, the water phase solution was discharged, and the membrane surface was blown dry with an air knife; then the oil phase solution was poured into the mold; after being immersed for 30 seconds, the oil phase solution was discharged and placed in an oven at 60°C for 10 minutes; then the sample was taken out and rinsed with ultrapure water to obtain a piperazine nanofiltration membrane containing the ultraviolet cross-linked titanium dioxide nano intermediate layer.

[0036] The prepared nanofiltration membrane was tested for performance, and a water solution containing NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L) was subjected to membrane filtration at an operating pressure of 0.4 MPa and a temperature of 25°C; the water flux was 18.55 L / m 2 The NaCl rejection rate was 23.45%, the MgCl2 rejection rate was 51.28%, the MgSO4 rejection rate was 92.51%, and the Na2SO4 rejection rate was 98.79%. The selectivity coefficient of the membrane can be calculated according to the rejection rates of NaCl and Na2SO4 using the following formula:

[0037]

[0038] wherein, α is the selectivity coefficient, R NaCl is the NaCl rejection rate, is the Na2SO4 rejection rate;

[0039] The calculation showed that the selectivity of the modified nanofiltration membrane to the negatively charged multivalent / single-valent ions was about 63.26.

[0040] In addition, the membrane surface under the preparation condition has negative charge, the potential of the membrane surface is determined by solid surface Zeta potential analyzer, the Zeta potential of the membrane surface is -34.25 mV; the molecular weight cut-off is 298 Da.

[0041] Example 2

[0042] The difference between this example 2 and example 1 is that the ultraviolet irradiation is 8 minutes.

[0043] The prepared nanofiltration membrane is tested for performance, and the results are as follows:

[0044] Under the operation pressure of 0.4 Mpa and the temperature of 25℃, the membrane filtration experiment is carried out on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solution, and the water flux is 24.73 L / m 2 hbar, the NaCl rejection rate is 22.69%, the MgCl2 rejection rate is 53.41%, the MgSO4 rejection rate is 94.38%, the Na2SO4 rejection rate is 99.12%, and the selectivity of negative multivalent / single-valent ion is about 87.85. In addition, the membrane surface under the preparation condition has negative charge, the Zeta potential of the membrane surface is -38.34 mV; the molecular weight cut-off is 321 Da.

[0045] Example 3

[0046] The difference between this example 3 and example 1 is that the ultraviolet irradiation is 10 minutes.

[0047] The prepared nanofiltration membrane is tested for performance, and the results are as follows:

[0048] Under the operation pressure of 0.4 Mpa and the temperature of 25℃, the membrane filtration experiment is carried out on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solution, and the water flux is 28.96 L / m 2 hbar, the NaCl rejection rate is 25.77%, the MgCl2 rejection rate is 58.83%, the MgSO4 rejection rate is 95.78%, the Na2SO4 rejection rate is 99.56%, and the selectivity of negative multivalent / single-valent ion is about 168.7. In addition, the membrane surface under the preparation condition has negative charge, the Zeta potential of the membrane surface is -43.78 mV; the molecular weight cut-off is 345 Da.

[0049] Example 4

[0050] The difference between this example 4 and example 1 is that the ultraviolet irradiation is 15 minutes.

[0051] The prepared nanofiltration membrane was tested for performance, and the results were as follows:

[0052] Under the operation pressure of 0.4 Mpa and the temperature of 25℃, the membrane filtration experiment was carried out on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solution, and the water flux was 26.31 L / m 2 hbar, the rejection rate of NaCl was 21.32%, the rejection rate of MgCl2 was 51.25%, the rejection rate of MgSO4 was 90.86%, the rejection rate of Na2SO4 was 95.41%, and the selectivity to the negatively charged multivalent / single-valent ion was about 17.14. In addition, the membrane surface under this preparation condition was negatively charged, the membrane surface Zeta potential was -36.38 mV, and the molecular weight cut-off was 396 Da.

[0053] Example 5

[0054] The difference between this example 5 and example 1 was that the ultraviolet irradiation was 20 minutes.

[0055] The prepared nanofiltration membrane was tested for performance, and the results were as follows:

[0056] Under the operation pressure of 0.4 Mpa and the temperature of 25℃, the membrane filtration experiment was carried out on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solution, and the water flux was 15.21 L / m 2 hbar, the rejection rate of NaCl was 11.05%, the rejection rate of MgCl2 was 40.15%, the rejection rate of MgSO4 was 82.14%, the rejection rate of Na2SO4 was 85.41%, and the selectivity to the negatively charged multivalent / single-valent ion was about 6.09. In addition, the membrane surface under this preparation condition was negatively charged, the membrane surface Zeta potential was -13.78 mV, and the molecular weight cut-off was 429 Da.

[0057] Example 6

[0058] The difference between this example 6 and example 1 was that the mass concentration of the photoinitiator 2-hydroxy-2-methylpropionone in the coating solution was 0.2 g / L.

[0059] The prepared nanofiltration membrane was tested for performance, and the results were as follows:

[0060] Under the operation pressure of 0.4 Mpa and the temperature of 25℃, the membrane filtration experiment was carried out on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solution, and the water flux was 27.81 L / m 2hbar, NaCl rejection rate was 27.23%, MgCl2 rejection rate was 61.55%, MgSO4 rejection rate was 96.28%, Na2SO4 rejection rate was 99.75%, and the selectivity for negatively charged multivalent / monovalent ions was about 291.08. In addition, the membrane surface under the preparation condition was negatively charged, the membrane surface Zeta potential was -41.23 mV; the molecular weight cut-off was 312 Da.

[0061] Example 7

[0062] The difference between this example 7 and example 1 is that the mass concentration of the photoinitiator 2-hydroxy-2-methylpropionone in the coating solution is 0.25 g / L.

[0063] The performance test of the prepared nanofiltration membrane is as follows:

[0064] Under the operation pressure of 0.4 MPa and the temperature of 25℃, the membrane filtration experiment was carried out on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solution, and the water flux was 20.15 L / m 2 hbar, NaCl rejection rate was 27.23%, MgCl2 rejection rate was 61.55%, MgSO4 rejection rate was 96.28%, Na2SO4 rejection rate was 99.75%, and the selectivity for negatively charged multivalent / monovalent ions was about 291.08. In addition, the membrane surface under the preparation condition was negatively charged, the membrane surface Zeta potential was -41.23 mV; the molecular weight cut-off was 312 Da.

[0065] Example 8

[0066] The difference between this example 8 and example 1 is that the mass concentration of the methacryloyloxypropyl bis-blocked polydimethylsiloxane in the coating solution is 0.35 g / L.

[0067] The performance test of the prepared nanofiltration membrane is as follows:

[0068] Under the operation pressure of 0.4 MPa and the temperature of 25℃, the membrane filtration experiment was carried out on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solution, and the water flux was 20.15 L / m 2 hbar, NaCl rejection rate was 27.23%, MgCl2 rejection rate was 61.55%, MgSO4 rejection rate was 96.28%, Na2SO4 rejection rate was 99.75%, and the selectivity for negatively charged multivalent / monovalent ions was about 291.08. In addition, the membrane surface under the preparation condition was negatively charged, the membrane surface Zeta potential was -41.23 mV; the molecular weight cut-off was 312 Da.

[0069] Example 9

[0070] The difference between this example 9 and example 1 is that the mass concentration of methacryloxypropyl bis-terminated polydimethylsiloxane in the coating solution is 0.5 g / L.

[0071] The prepared nanofiltration membrane was tested for performance, and the results were as follows:

[0072] Under the operating pressure of 0.4 MPa and the temperature of 25℃, the membrane filtration experiment was carried out on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solution, and the water flux was 18.47 L / m 2 hbar, the rejection rate of NaCl was 17.96%, the rejection rate of MgCl2 was 58.64%, the rejection rate of MgSO4 was 91.22%, the rejection rate of Na2SO4 was 94.91%, and the selectivity of negatively charged multivalent / single-valent ions was about 16.12. In addition, the membrane surface under this preparation condition was negatively charged, the membrane surface Zeta potential was -29.98 mV; the molecular weight cut-off was 411 Da.

[0073] Example 10

[0074] The difference between this example 10 and example 1 is that the mass concentration of TiO2 in the coating solution is 0.4 g / L.

[0075] The prepared nanofiltration membrane was tested for performance, and the results were as follows:

[0076] Under the operating pressure of 0.4 MPa and the temperature of 25℃, the membrane filtration experiment was carried out on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solution, and the water flux was 26.35 L / m 2 hbar, the rejection rate of NaCl was 22.15%, the rejection rate of MgCl2 was 59.35%, the rejection rate of MgSO4 was 93.21%, the rejection rate of Na2SO4 was 97.33%, and the selectivity of negatively charged multivalent / single-valent ions was about 29.16. In addition, the membrane surface under this preparation condition was negatively charged, the membrane surface Zeta potential was -32.41 mV; the molecular weight cut-off was 374 Da.

[0077] Example 11

[0078] The difference between this example 11 and example 1 is that the mass concentration of TiO2 in the coating solution is 0.8 g / L.

[0079] The prepared nanofiltration membrane was tested for performance, and the results were as follows:

[0080] The membrane filtration experiment was carried out on the aqueous solution of NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) under the operating pressure of 0.4 MPa and the temperature of 25℃, and the water flux was 11.45 L / m 2 The rejection rate of NaCl was 10.76%, the rejection rate of MgCl2 was 41.23%, the rejection rate of MgSO4 was 75.15%, the rejection rate of Na2SO4 was 80.37%, and the selectivity to the negatively charged multivalent / monovalent ions was about 4.55. In addition, the membrane surface under the preparation condition was negatively charged, the membrane surface Zeta potential was -21.37 mV, and the molecular weight cut-off was 456 Da.

[0081] Example 12

[0082] The difference between this example 12 and example 1 is that the photoinitiator is ethyl (2,4,6-trimethylbenzoyl) phenyl phosphonate.

[0083] The prepared nanofiltration membrane was tested for performance, and the results were as follows:

[0084] The membrane filtration experiment was carried out on the aqueous solution of NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) under the operating pressure of 0.4 MPa and the temperature of 25℃, and the water flux was 24.33 L / m 2 The rejection rate of NaCl was 20.18%, the rejection rate of MgCl2 was 52.13%, the rejection rate of MgSO4 was 92.30%, the rejection rate of Na2SO4 was 97.24%, and the selectivity to the negatively charged multivalent / monovalent ions was about 28.92. In addition, the membrane surface under the preparation condition was negatively charged, the membrane surface Zeta potential was -37.15 mV, and the molecular weight cut-off was 394 Da.

[0085] Example 13

[0086] The difference between this example 13 and example 1 is that the photoinitiator is diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide.

[0087] The prepared nanofiltration membrane was tested for performance, and the results were as follows:

[0088] The membrane filtration experiment was carried out on the aqueous solution of NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) under the operating pressure of 0.4 MPa and the temperature of 25℃, and the water flux was 21.27 L / m 2hbar, NaCl rejection rate was 22.35%, MgCl2 rejection rate was 55.82%, MgSO4 rejection rate was 91.41%, Na2SO4 rejection rate was 96.63%, and the selectivity for negatively charged multivalent / monovalent ions was about 23.04. In addition, the membrane surface under the preparation condition was negatively charged, and the membrane surface Zeta potential was -39.35 mV; the molecular weight cut-off was 387 Da.

[0089] Example 14

[0090] The difference between this example 14 and example 1 is that the photoinitiator is 4-dimethylamino-benzoic acid ethyl ester.

[0091] The performance test of the prepared nanofiltration membrane was carried out, and the results were as follows:

[0092] Under the operation pressure of 0.4 Mpa and the temperature of 25℃, the membrane filtration experiment was carried out on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solution, and the water flux was 23.51 L / m 2 hbar, NaCl rejection rate was 20.21%, MgCl2 rejection rate was 60.61%, MgSO4 rejection rate was 93.24%, Na2SO4 rejection rate was 97.83%, and the selectivity for negatively charged multivalent / monovalent ions was about 36.78. In addition, the membrane surface under the preparation condition was negatively charged, and the membrane surface Zeta potential was -40.11 mV; the molecular weight cut-off was 351 Da.

[0093] Example 15

[0094] The difference between this example 15 and example 1 is that the photoinitiator is 4-chlorobenzophenone.

[0095] The performance test of the prepared nanofiltration membrane was carried out, and the results were as follows:

[0096] Under the operation pressure of 0.4 Mpa and the temperature of 25℃, the membrane filtration experiment was carried out on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solution, and the water flux was 23.51 L / m 2 hbar, NaCl rejection rate was 20.21%, MgCl2 rejection rate was 60.61%, MgSO4 rejection rate was 93.24%, Na2SO4 rejection rate was 97.83%, and the selectivity for negatively charged multivalent / monovalent ions was about 36.78. In addition, the membrane surface under the preparation condition was negatively charged, and the membrane surface Zeta potential was -40.11 mV; the molecular weight cut-off was 351 Da.

[0097] Example 16

[0098] This example 16 is different from example 1 in that the water phase monomer is polyvinyl alcohol.

[0099] The prepared nanofiltration membrane was tested for performance, and the results were as follows:

[0100] Under an operating pressure of 0.4 MPa and a temperature of 25°C, membrane filtration experiments were performed on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L) aqueous solutions, and the water flux was 28.22 L / m 2 hbar, the NaCl rejection rate was 15.23%, the MgCl2 rejection rate was 31.25%, the MgSO4 rejection rate was 82.25%, the Na2SO4 rejection rate was 85.33%, and the selectivity for negatively charged multivalent / monovalent ions was about 5.78. In addition, the membrane surface under this preparation condition was negatively charged, with a membrane surface Zeta potential of -20.17 mV; the molecular weight cut-off was 523 Da.

[0101] Example 17

[0102] This example 17 is different from example 1 in that the water phase monomer is polyethyleneimine.

[0103] The prepared nanofiltration membrane was tested for performance, and the results were as follows:

[0104] Under an operating pressure of 0.4 MPa and a temperature of 25°C, membrane filtration experiments were performed on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L), and Na2SO4 (2 g / L) aqueous solutions, and the water flux was 19.85 L / m 2 hbar, the NaCl rejection rate was 17.21%, the MgCl2 rejection rate was 70.78%, the MgSO4 rejection rate was 91.32%, the Na2SO4 rejection rate was 30.16%, and the selectivity for negatively charged multivalent / monovalent ions was about 1.19. In addition, the membrane surface under this preparation condition was positively charged, with a membrane surface Zeta potential of 19.35 mV; the molecular weight cut-off was 478 Da.

[0105] Example 18

[0106] This example 18 is different from example 1 in that the water phase monomer is polyvinyl alcohol, and the oil phase monomer is isophthaloyl chloride.

[0107] The prepared nanofiltration membrane was tested for performance, and the results were as follows:

[0108] The membrane filtration experiment was carried out on the aqueous solution of NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) at an operating pressure of 0.4 MPa and a temperature of 25°C, and the water flux was 30.79 L / m 2 hbar, the rejection rates of NaCl, MgCl2, MgSO4 and Na2SO4 were 10.13%, 30.41%, 50.72% and 81.41% respectively, and the selectivity for the negatively charged multivalent / single-valent ions was about 4.83. In addition, the membrane surface was negatively charged under the preparation condition, the membrane surface Zeta potential was -28.92 mV, and the molecular weight cut-off was 645 Da.

[0109] Example 19

[0110] The difference between this example 19 and example 1 is that the aqueous monomer is polyethyleneimine and the oil monomer is isophthaloyl dichloride.

[0111] The performance test of the prepared nanofiltration membrane was carried out, and the results were as follows:

[0112] The membrane filtration experiment was carried out on the aqueous solution of NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) at an operating pressure of 0.4 MPa and a temperature of 25°C, and the water flux was 21.37 L / m 2 hbar, the rejection rates of NaCl, MgCl2, MgSO4 and Na2SO4 were 24.54%, 54.47%, 81.64% and 29.22% respectively, and the selectivity for the negatively charged multivalent / single-valent ions was about 1.07. In addition, the membrane surface was positively charged under the preparation condition, the membrane surface Zeta potential was 15.98 mV, and the molecular weight cut-off was 556 Da.

[0113] Comparative Example 1

[0114] 0.01 g of a photoinitiator (the photoinitiator was 2-hydroxy-2-methylpropionyl ketone) and 0.02 g of titanium dioxide TiO2 were dissolved in 100 ml of ultrapure water at room temperature, ultrasonic dissolution was carried out, and a heterogeneous mixed solution was prepared; 1 g of PIP and 0.1 g of TMC were dissolved in ultrapure water and n-hexane respectively to prepare an aqueous solution and an oil solution; the heterogeneous mixed solution was poured onto the surface of a commercial polyether sulfone ultrafiltration membrane fixed in a mold at room temperature; after immersion for 3 minutes, the mixed solution was discharged and placed in the dark, and UV irradiation was carried out for 8 minutes; then the aqueous solution was poured into the mold; after immersion for 2 minutes, the solution was discharged and the membrane surface was blown dry with an air knife; then the oil solution was poured into the mold; after immersion for 30 seconds, the solution was discharged and placed in an oven at 60 degrees for 10 minutes; then the sample was taken out and rinsed with ultrapure water, and a nanofiltration membrane was prepared.

[0115] The performance of the nanofiltration membrane was determined, and the results were as follows: under the conditions of an operating pressure of 0.4 MPa and a temperature of 25 DEG C, the membrane filtration experiment was conducted on NaCl (2 g / L), MgCl2 (2 g / L), MgSO4 (2 g / L) and Na2SO4 (2 g / L) aqueous solutions, and the water flux was 12.35 L / m 2 hbar, the NaCl rejection rate was 21.35%, the MgCl2 rejection rate was 22.63%, the MgSO4 rejection rate was 43.58%, the Na2SO4 rejection rate was 52.26%, and the selectivity to the negatively charged multivalent / monovalent ions was about 1.22. The low ion rejection rate indicated that significant defects were generated in the PA active layer. In addition, the Zeta point of the membrane surface was -15.35 mV.

[0116]

[0117] The photoinitiator is a precondition for generating the ultraviolet photopolymerization reaction, and the content thereof determines the difficulty and reaction rate of the polymerization reaction; the methacryloxypropyl double-terminated polydimethylsiloxane is the main body of the ultraviolet photopolymerization reaction, and the content thereof determines the amount of substance of the reaction product and the completeness of the intermediate layer; the TiO2 is a modified material of the ultraviolet photopolymerization reaction, and the content thereof determines the hydrophilicity, crosslinking degree and roughness of the prepared intermediate layer product; the ultraviolet irradiation time determines the completeness of the polymerization reaction and the physicochemical properties of the prepared intermediate layer; the water-phase monomer is one of the prerequisites for preparing the nanofiltration membrane, and the type and content thereof determine the surface charge property and selective separation coefficient of the prepared nanofiltration membrane; and the oil-phase monomer is one of the prerequisites for preparing the nanofiltration membrane, and the type and content thereof determine the crosslinking degree and pore size of the prepared nanofiltration membrane. In the application, the methacryloxypropyl double-terminated polydimethylsiloxane is used as the main body of the ultraviolet photopolymerization reaction, and under ultraviolet irradiation, a self-polymerization reaction occurs, so that the titanium dioxide nanoparticles are wrapped in the polymer chain, so that the titanium dioxide is changed from unmodified easy-agglomerated particles into modified uniformly distributed nanometer intermediate layers. At the same time, under UV irradiation, free radicals and a large number of hydrophilic groups are generated due to the existence of the photocatalytic effect of titanium dioxide, which enhances the interfacial hydrophilicity and also endows the nanofiltration membrane with certain catalytic efficiency, and can strengthen the removal capacity of organic pollutants in the treatment of actual natural water bodies.

[0118] Application example

[0119] The polyamide nanofiltration membrane prepared in Example 1 was used for purification test of underground water (TOC: 4.13 mg / L, TDS: 1000 mg / L, Ca 2+ : 448 mg / L, Mg 2+ : 526 mg / L), and a single cycle was conducted.

[0120] The specific steps are as follows:

[0121] a. Groundwater pretreatment by microfiltration membrane: The groundwater is filtered by using commercial microfiltration membrane, which aims to remove impurities and suspended particles in raw water and prevent the blocking of nanofiltration membrane. The operating pressure is 0.01 MPa, wherein the microfiltration membrane pore size is 0.45 μm, which is much larger than the nanofiltration membrane pore size and cannot intercept the dissolved substances and ions in water, thus not affecting the interception experiment data of Ca 2+ , Mg 2+ ions. The permeate obtained by microfiltration is used as the feed water of the nanofiltration membrane system;

[0122] b. The groundwater pretreated by microfiltration is introduced into the feed tank, and is subjected to deep filtration treatment by using the nanofiltration membrane with the UV crosslinked titanium dioxide nanometer intermediate layer prepared in the application under the pressure of 0.4 MPa;

[0123] The nanofiltration membrane effluent is collected, and the sample solution is measured and analyzed for TOC and TDS, and the Ca 2+ , Mg 2+ contents in the raw water and the permeate are detected and calculated by using the ion chromatograph, wherein the selectivity removal of the membrane for the organic matter and ions in the groundwater is mainly the ratio of the difference between the concentrated solution and the permeate obtained in the nanofiltration membrane filtration process. The following formula is used for calculation:

[0124]

[0125] wherein, R is the removal rate, C p is the permeate mass concentration, C f is the concentrated solution mass concentration;

[0126] According to Figure 2 results, the removal efficiency of the nanofiltration membrane for TOC is 72.1%, the removal efficiency for the dissolved solids TDS in water is 53.4%, the removal efficiency for Ca 2+ is 61.7%, and the removal efficiency for Mg 2+ is 74.5%. The separation efficiency of the nanofiltration membrane can be further improved by adjusting the UV irradiation time (5-20 minutes) and adjusting the mass concentration of the photoinitiator (0.1-0.5 g / L).

[0127] The above merely describes the preferred embodiments of the application and is not intended to limit the application, and any modification, equivalent replacement and improvement made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A nanofiltration membrane based on ultraviolet cross-linked titania nanolayer assisted, characterized by, The ultrafiltration membrane, the ultraviolet cross-linked titanium dioxide nano intermediate layer arranged on the ultrafiltration membrane, and the interfacial polymerization layer formed through the interfacial polymerization reaction; the ultraviolet cross-linked titanium dioxide nano intermediate layer is formed by embedding titanium dioxide nanoparticles on the ultrafiltration membrane through ultraviolet graft polymerization using methacryloyloxypropyl bis-blocked polydimethylsiloxane; and the interfacial polymerization layer is directly formed on the ultraviolet cross-linked titanium dioxide nano intermediate layer through the interfacial polymerization reaction.

2. The nanofiltration membrane based on UV-crosslinked titania nanolayer assisted by claim 1, characterized in that, The nanofiltration membrane is one or more of a polyamide nanofiltration membrane, a polyester nanofiltration membrane, a polyurethane nanofiltration membrane, a polyurea nanofiltration membrane, a poly-piperazine amide nanofiltration membrane, a polysulfone nanofiltration membrane, and a polyether sulfone nanofiltration membrane.

3. A method for preparation of nanofiltration membrane based on UV crosslinked titania nanolayer assisted as claimed in claim 1, wherein, The method comprises the following steps: The coating solution is prepared by dissolving a photoinitiator, methacryloyloxypropyl bis-blocked polydimethylsiloxane, and titanium dioxide in a solvent; wherein the photoinitiator is one or more of 2-hydroxy-2-methylpropionyl ketone, ethyl (2,4,6-trimethylbenzoyl) phenyl phosphonate, diphenyl (2,4,6-trimethylbenzoyl) phosphorus oxide, 4-dimethylamino-benzoic acid ethyl ester, and 4-chlorobenzophenone, which are mixed in any proportion; The coating solution is coated on the ultrafiltration membrane, and the ultraviolet cross-linked titanium dioxide nano intermediate layer is obtained after ultraviolet irradiation in a dark place; The water-phase solution and the oil-phase solution are sequentially coated on the ultraviolet cross-linked titanium dioxide nano intermediate layer to prepare the nanofiltration membrane containing the ultraviolet cross-linked titanium dioxide nano intermediate layer through the interfacial polymerization reaction; wherein the solute in the water-phase solution is one or more of piperazine, m-phenylenediamine, polyethyleneimine, and polyhydric alcohol, and the solvent in the water-phase solution is water; the solute in the oil-phase solution is one or more of isophthaloyl chloride, m-phenylenediamine, and isocyanate, and the solvent in the oil-phase solution is one or more of n-hexane, toluene, n-heptane, cyclohexane, and chloroform.

4. The method for preparing a nanofiltration membrane based on an ultraviolet cross-linked titania nanolayer interlayer according to claim 3, characterized in that, The ultrafiltration membrane is one or more of a polyacrylonitrile ultrafiltration membrane, a polyether sulfone ultrafiltration membrane, a polysulfone ultrafiltration membrane, a polyvinylidene fluoride ultrafiltration membrane, and a sulfonated polyether sulfone ultrafiltration membrane.

5. The method for preparation of nanofiltration membrane based on UV-crosslinked titania nanolayer interlayer assistance according to claim 3, characterized in that, The mass concentration of the photoinitiator in the coating solution is 0.05-0.5 g / L, the mass concentration of the methacryloyloxypropyl bis-blocked polydimethylsiloxane is 0.1-0.5 g / L, and the mass concentration of the titanium dioxide is 0.2-0.8 g / L.

6. The method for preparation of nanofiltration membrane based on UV-crosslinked titania nanolayer interlayer assistance according to claim 3, characterized in that, The mass concentration of the solute in the water-phase solution is 0.01-20 g / L, and the mass concentration of the solute in the oil-phase solution is 0.01-2 g / L.

7. The method for preparation of nanofiltration membrane based on UV-crosslinked titania nanolayer assisted by claim 3, characterized in that, The coating time of the coating solution on the ultrafiltration membrane is 1-3 minutes, the ultraviolet irradiation time is 5-20 minutes, the coating time of the water-phase solution is 2-3 minutes, and the coating time of the oil-phase solution is 30 seconds-2 minutes.

8. Application of the nanofiltration membrane based on the ultraviolet cross-linked titanium dioxide nano intermediate layer or prepared by the method of any one of claims 3-7 in underground water purification.

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