Photo-isomerization metal organic framework interlayer forward osmosis membrane and preparation method thereof

Abstract

The invention relates to the technical field of membrane separation, in particular to an optical isomerization metal organic framework interlayer forward osmosis membrane and a preparation method thereof. The preparation method of the photo-isomerization metal organic framework interlayer forward osmosis membrane comprises the following steps: loading a UiO-67-SP nano material dispersion liquid on the surface of a nylon support layer under a light source irradiation condition or a dark condition to form a composite interlayer; under a light source irradiation condition or a dark condition, adding an amine monomer aqueous phase solution and an acyl chloride organic phase solution to the surface of the composite intermediate layer, so that an amine monomer in the amine monomer aqueous phase solution and an acyl chloride monomer in the acyl chloride organic phase solution are subjected to an interfacial polymerization reaction and a separation layer is formed; the spiropyrane / zirconium-based photo-isomerization metal organic framework intermediate layer forward osmosis membrane is obtained. According to the prepared forward osmosis membrane, the water flux and the salt ion interception effect are remarkably improved, namely, the reverse salt flux is reduced, and the problems that an existing forward osmosis membrane is poor in water permeability and ion recovery performance due to the fact that a separation layer is too thick and non-selective holes exist can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, and in particular to a photo-isomerized metal organic framework intermediate layer forward osmosis membrane and a preparation method thereof. Background Art

[0002] In many industrial production processes, such as electroplating and metallurgy, waste liquid and waste residue containing metal ions are generated. Valuable metal ions such as lithium, ruthenium, and selenium can be recovered from these wastes. Taking the recovery of precious metals from electronic waste as an example, the enrichment process can concentrate the trace precious metal ions dispersed in a large amount of waste, and then carry out subsequent purification, which greatly improves the resource recovery rate and reduces resource waste.

[0003] Forward osmosis does not require external energy consumption. Instead, it uses the osmotic pressure difference between the raw liquid and the draw liquid to cause water molecules to spontaneously pass through the forward osmosis membrane from the raw liquid side to the draw liquid side, and intercept the solutes in the raw liquid, thereby achieving the purpose of enriching and recovering the solutes in the raw liquid. The kinetic energy required for forward osmosis is provided by the draw liquid, and its low energy consumption makes it extremely valuable in the field of resource recovery.

[0004] The forward osmosis membrane is usually composed of a polymer porous support layer and a surface polyamide (PA) separation layer. However, the separation layer of the traditional composite forward osmosis membrane is too thick and has non-selective holes. The overly thick separation layer has high water permeation resistance. In addition, the separation layer has non-selective holes, which affects the enrichment and recovery performance of the forward osmosis membrane for the target metal ions. Therefore, there is an urgent need to regulate the membrane structure to improve the water permeability and separation performance of the forward osmosis membrane.

[0005] With the rapid development of nanotechnology, researchers have found that constructing an intermediate layer of nanomaterials between the support layer and the separation layer can effectively improve the water flux and separation performance of the forward osmosis membrane. Metal organic frameworks (MOFs) are a type of crystalline material formed by metal ions connected by bridging organic ligands. The preparation and application of copper-cobalt / carbon catalysts derived from metal organic framework materials have proposed that the structure and chemical properties of MOFs can be regulated by changing the organic ligand molecules of MOFs. Although the use of these modified MOFs materials as intermediate layers can slow down the diffusion rate of amine monomers and obtain a separation layer with an ideal structure. However, after the forward osmosis membrane is formed, the intermediate layer with specific physicochemical properties may produce resistance to the penetration of water molecules, which has an adverse effect on the membrane flux. Therefore, it is still urgent to explore the flexible regulation method of the physicochemical properties of the intermediate layer before and after interfacial polymerization and the new membrane preparation method to further improve the performance of the forward osmosis membrane. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane to solve the problem of poor water permeability and ion recovery of the forward osmosis membrane in the prior art due to the excessive thickness of the separation layer and the presence of non-selective holes.

[0007] In order to solve the above problems, the present invention proposes a method for preparing a photo-isomerized metal organic framework intermediate layer forward osmosis membrane, and the technical solution adopted is: A method for preparing a photo-isomerized metal organic framework intermediate layer forward osmosis membrane comprises the following steps: The UiO-67-SP nanomaterial dispersion under light source irradiation or dark conditions is loaded on the surface of the nylon support layer to form a composite intermediate layer; Under light source irradiation conditions or dark conditions, an amine monomer aqueous solution and an acyl chloride organic solution are added to the surface of the composite intermediate layer, so that the amine monomer in the amine monomer aqueous solution and the acyl chloride monomer in the acyl chloride organic solution undergo interfacial polymerization reaction and form a separation layer, thereby obtaining a spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane.

[0008] Beneficial effects: The present invention is an improved invention. During the preparation process of the present invention, the UiO-67-SP nanomaterial under changing lighting conditions or dark conditions is loaded on the surface of the nylon support layer to form a composite intermediate layer. Compared with the traditional nanomaterial membrane, the pore size of the composite intermediate layer is smaller, and the UiO-67-SP intermediate layer reduces the loss of nanomaterials and increases the loading amount of nanomaterials. Compared with the traditional forward osmosis membrane, the separation layer is formed on the surface of the support layer with a larger pore size, and the separation layer has the disadvantages of high thickness and many non-selective pores. The separation layer of the spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane of the present application is formed on the intermediate layer with a smaller pore size, thereby avoiding the risk of separation layer formation defects, improving the membrane's interception performance for reverse solutes, optimizing the porous base membrane structure, and improving stability; at the same time, spiropyran isomerization can change the interaction force with MPD through pore size screening and changes in interaction force, thereby adjusting the structure of the forward osmosis membrane; at the same time, based on the retention effect of the intermediate layer on amine monomers, the interfacial polymerization self-termination is accelerated, which is conducive to forming a thinner separation layer and improving the membrane's water permeability; the preparation method of the photoisomerized metal organic framework intermediate layer forward osmosis membrane of the present invention has a simple preparation process and low cost, and the prepared forward osmosis membrane significantly improves the water flux and the interception effect on salt ions, that is, reduces the reverse salt flux, and can solve the problem of poor water permeability and ion recovery of the existing forward osmosis membrane due to the excessive thickness of the separation layer and the presence of non-selective pores.

[0009] Preferably, the average pore size of the nylon support layer is 0.1-0.25 μm, and the effective area of ​​the nylon support layer is 20 cm 2 .

[0010] In order to regulate the pore structure and chemical properties of the modified MOF material, thereby optimizing the adhesion and sustained release performance of the intermediate layer for the amine monomer and improving the performance of the forward osmosis membrane, preferably, the preparation method of the UiO-67-SP nanomaterial comprises the following steps: at room temperature, dispersing zirconium tetrachloride, 4,4'-biphenyldicarboxylic acid, and 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran in an N,N-dimethylformamide solvent and performing ultrasound to obtain a mixed solution; placing the mixed solution in an environment of 120° C. for reaction, cooling to room temperature after the reaction, and filtering to obtain a precipitate; washing, filtering, and drying the precipitate to obtain the UiO-67-SP nanomaterial.

[0011] In order to ensure that the spiropyran is grafted onto the MOF to obtain the photo-isomerized MOF material, preferably, the molar ratio of zirconium tetrachloride, 4,4'-biphenyldicarboxylic acid, and 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran is 1:(1-3):(0.5-2).

[0012] In order to further optimize the adhesion and sustained release performance of the intermediate layer to the amine monomer and improve the performance of the forward osmosis membrane, preferably, the mass of the UiO-67-SP nanomaterial in every 50-100 mL of the UiO-67-SP nanomaterial dispersion is 0.002-0.007 g.

[0013] In order to further optimize the isomerization of spiropyran, preferably, the light source is one of ultraviolet light, visible light, and natural light, and the irradiation time of the light source condition or the dark condition is 30 to 90 min.

[0014] In order to further enhance the retention effect of the intermediate layer on the amine monomer, reduce the diffusion rate of the amine monomer, and facilitate the formation of an ultra-thin separation layer, preferably, the amine monomer aqueous solution is prepared by dissolving an aqueous amine monomer in deionized water; wherein the aqueous amine monomer is one of m-phenylenediamine, piperazine, polyethyleneimine, and dopamine, and the mass percentage of the aqueous amine monomer in the amine monomer aqueous solution is 1.5-3%.

[0015] In order to promote the interfacial polymerization reaction between the amine monomer and the acyl chloride and form a separation layer, preferably, the acyl chloride organic phase solution is prepared by dissolving trimesoyl chloride in n-hexane; wherein the mass percentage of trimesoyl chloride in the acyl chloride organic phase solution is 0.1-0.5%.

[0016] After the interfacial polymerization is completed, the intermediate layer can be modified after synthesis by temperature control to further improve the performance of the forward osmosis membrane. Preferably, the preparation method of the photo-isomerized metal organic framework intermediate layer forward osmosis membrane also includes: The obtained spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane was placed in a temperature environment of 25 to 80°C for post-treatment for 2 to 8 minutes to obtain a modified spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane. The intermediate layer material used for the photoisomerized metal organic framework is modified after synthesis under different temperature environments. After the ultra-thin separation layer structure is obtained by interfacial polymerization, the interlayer material is isomerized again by temperature regulation. After heating treatment, the MC structure is transformed into the SP structure again. At this time, the free space inside the MOFs increases, and the penetration resistance of the intermediate layer to water molecules is reduced, which is conducive to further improving the water flux of the forward osmosis membrane.

[0017] In order to promote the formation of an ultra-thin separation layer with a high degree of cross-linking and further improve the permeability and separation performance of the membrane, preferably, under light source irradiation conditions or dark conditions, an amine monomer aqueous phase solution and an acyl chloride organic phase solution are added to the surface of the composite intermediate layer, so that the amine monomer and the acyl chloride undergo interfacial polymerization reaction and form a separation layer. The specific steps of obtaining a spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane include: Under light irradiation conditions or in darkness, an amine monomer aqueous solution is added to the surface of the composite intermediate layer for soaking, and excess solution is removed after soaking to obtain a dried membrane; an acyl chloride organic phase solution is added to the surface of the dried membrane to allow the amine monomer and the acyl chloride to undergo an interfacial polymerization reaction and form a separation layer, thereby obtaining a spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane; wherein the soaking time is 2 to 5 minutes, and the interfacial polymerization reaction time is 1 to 3 minutes.

[0018] Preferably, the step of loading the UiO-67-SP nanomaterial dispersion under light source irradiation conditions or dark conditions on the surface of the nylon support layer to form a composite intermediate layer specifically includes: loading the UiO-67-SP nanomaterial dispersion under light source irradiation conditions or dark conditions on the surface of the nylon support layer to form a composite intermediate layer by vacuum filtration.

[0019] The present invention also provides a photo-isomerized metal-organic framework intermediate layer forward osmosis membrane, which is prepared by adopting the above-mentioned method for preparing the photo-isomerized metal-organic framework intermediate layer forward osmosis membrane.

[0020] Beneficial effects: The photo-heterogeneous metal-organic framework intermediate layer forward osmosis membrane provided by the present invention significantly improves the water flux and the interception effect of salt ions, and can solve the problems of poor water permeability and ion recovery of the existing forward osmosis membrane due to the excessive thickness of the separation layer and the presence of non-selective pores. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic flow chart of the method for preparing the photo-isomerized metal organic framework intermediate layer forward osmosis membrane of the present invention. DETAILED DESCRIPTION

[0022] As cited in the background art, the water permeability and ion recovery of the forward osmosis membrane in the prior art are poor due to the excessive thickness of the separation layer and the presence of non-selective holes. Therefore, the present invention proposes a method for preparing a photo-isomerized metal organic framework intermediate layer forward osmosis membrane, comprising the following steps: The UiO-67-SP nanomaterial dispersion under light source irradiation or dark conditions is loaded on the surface of the nylon support layer to form a composite intermediate layer; Under light source irradiation conditions or dark conditions, an amine monomer aqueous solution and an acyl chloride organic solution are added to the surface of the composite intermediate layer, so that the amine monomer in the amine monomer aqueous solution and the acyl chloride monomer in the acyl chloride organic solution undergo interfacial polymerization reaction and form a separation layer, thereby obtaining a spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane.

[0023] The technical concept of the present invention is that MOF materials are flexible and easy to adjust, and the structure and chemical properties of MOF can be further adjusted by grafting other chemical substances. Spiropyran has photoisomerization characteristics, and spiropyran is grafted onto MOF to obtain photoisomerization MOF materials. Through different light source irradiation conditions or dark conditions, the pore structure and chemical properties of the modified MOF material can be adjusted, thereby optimizing the adhesion and sustained release performance of the intermediate layer for amine monomers and improving the performance of the forward osmosis membrane. In addition, spiropyran can also achieve structural transformation under the influence of temperature.

[0024] This method of constructing the intermediate layer of the photoisomerized metal-organic framework is based on the fact that the CO bond in the closed-ring spiropyran (SP) structure is rapidly broken under light conditions or dark conditions, the molecule rotates locally and forms a planar conjugated merocyanine (MC) structure with indole. Compared with the SP structure, the MC projection diameter is larger, which makes the internal space in MOFs smaller; and the MC morphology is an open-ring structure, which usually exposes more polar groups, such as hydroxyl (-OH) and amine (-NH), and the MC morphology has different charge distributions. Based on hydrogen bonds and electrostatic interactions, the MC structure has a stronger effect on amine monomers. The spiropyran (SP) in MOF gradually transforms into an amphiphilic merocyanine (MC) structure, which can enhance the retention effect of the intermediate layer on the amine monomer, reduce the diffusion rate of the amine monomer, and facilitate the formation of an ultra-thin separation layer, that is, the spiropyran / zirconium-based metal-organic framework (UiO-67-SP) nanomaterial isomerized under light irradiation conditions or dark conditions to obtain the spiropyran / zirconium-based photoisomerized metal-organic framework nanomaterial. In addition, the projected diameter of merocyanine is larger than that of spiropyran, so under light, the effective pore size of the modified MOF is reduced, thereby increasing the spatial resistance to the diffusion of amine monomers. This also contributes to reducing the diffusion rate of amine monomers. Appropriate light conditions or dark conditions can also enhance the attachment behavior of the spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer to amine monomers, thereby facilitating the formation of an ultra-thin separation layer with a high degree of cross-linking, and simultaneously improving the permeability and separation performance of the membrane.

[0025] Specifically, Figure 1 As shown, the method for preparing the photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane of the present invention comprises the following steps: (1) A certain mass of UiO-67-SP nanomaterials was added to deionized water and ultrasonically dispersed to obtain a dispersion. The dispersion was irradiated with different types of light sources for a certain period of time or placed in a dark condition for 30 to 90 min to obtain an intermediate layer material dispersion. The mass of UiO-67-SP nanomaterials in each 50 to 100 mL of the intermediate layer material dispersion was 0.002 to 0.007 g. The average pore size of the nylon support layer was 0.1 to 0.25 μm, and the effective area of ​​the nylon support layer was 20 cm. 2 ; (2) dissolving an aqueous amine monomer in deionized water to prepare an amine monomer aqueous solution, wherein the mass percentage of the aqueous amine monomer in the amine monomer aqueous solution is 1.5-3%; dissolving trimesoyl chloride (TMC) in n-hexane to prepare a trimesoyl chloride organic solution, wherein the mass percentage of trimesoyl chloride in the trimesoyl chloride organic solution is 0.1-0.5%; (3) The intermediate layer material dispersion prepared in step (1) is loaded on the surface of the nylon support layer (Nylon base membrane) by vacuum filtration to form a composite intermediate layer, thereby obtaining a UiO-67-SP coated base membrane; (4) under light irradiation or dark conditions, adding the amine monomer aqueous solution prepared in step (2) to the surface of the composite intermediate layer obtained in step (3) and soaking for 2 to 5 minutes, removing excess solution after soaking, and obtaining a dried membrane; then pouring the trimesoyl chloride organic solution prepared in step (2) onto the surface of the dried membrane, so that m-phenylenediamine and trimesoyl chloride undergo interfacial polymerization reaction for 1 to 3 minutes, and forming a separation layer, thereby obtaining a spiropyran / zirconium-based photoisomerization metal organic framework intermediate layer forward osmosis membrane; (5) The spiropyran / zirconium-based photoisomerization metal organic framework intermediate layer forward osmosis membrane obtained in step (4) is placed in a temperature environment of 25 to 80° C. for post-treatment for 2 to 8 minutes, and the photoisomerization metal organic framework intermediate layer material is modified after heat treatment synthesis at different temperature environments to obtain a modified spiropyran / zirconium-based photoisomerization metal organic framework intermediate layer forward osmosis membrane; wherein the obtained modified spiropyran / zirconium-based photoisomerization metal organic framework intermediate layer forward osmosis membrane is stored under corresponding temperature conditions.

[0026] Preferably, the surface of the composite intermediate layer obtained in step (3) is added with the aqueous amine monomer solution prepared in step (2) and soaked for 3 to 5 minutes, and excess solution is removed after soaking; Preferably, the spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane obtained in step (4) is placed in a 60° C. temperature environment for post-treatment for 2 minutes.

[0027] Specifically, the light source is one of ultraviolet light (UV), visible light (Vis), and natural light.

[0028] Specifically, the preparation method of the UiO-67-SP nanomaterial of the present invention comprises the following steps: At room temperature, 4,4'-biphenyl dicarboxylic acid, zirconium tetrachloride and 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran in a molar ratio of 1:(1-3):(0.5-2) are dissolved in N,N-dimethylformamide solvent and subjected to light-protected ultrasonication for 10-40 minutes to obtain a mixed solution; the obtained mixed solution is placed in a polytetrafluoroethylene-lined stainless steel autoclave for heating reaction at 120°C for 24 hours, cooled to room temperature after the reaction, and filtered to obtain a precipitate; the precipitate is washed alternately with N,N-dimethylformamide and ethanol for 3-5 times to remove unreacted 4,4'-biphenyl dicarboxylic acid; the precipitate is filtered and dried at 80°C, and the spiropyran / zirconium-based metal organic framework powder, i.e., UiO-67-SP nanomaterial, is obtained after grinding.

[0029] Preferably, the N,N-dimethylformamide solvent is prepared by dissolving N,N-dimethylformamide in deionized water, wherein the volume ratio of N,N-dimethylformamide to deionized water is 1070:1.

[0030] The implementation process of the present invention is described in detail below in conjunction with specific embodiments.

[0031] In the following examples and comparative examples, the average pore size of the nylon support layer in the raw materials used is 0.1-0.25 μm, and the effective area of ​​the nylon support layer is 20 cm 2 ; The CAS number of 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran is 16111-07-2, and the CAS number of 4,4'-biphenyldicarboxylic acid is 787-70-2; the remaining raw materials used are all common commercial products that can be directly purchased or can be prepared according to conventional techniques in the art.

[0032] 1. Embodiment of the method for preparing the photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane of the present invention Example 1 The method for preparing the photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane provided in this embodiment comprises the following steps: (1) UiO-67-SP nanomaterials were added to deionized water, and ultrasonicated for 30 min to uniformly disperse the nanomaterials to obtain a dispersion, and the dispersion was irradiated with visible light for 60 min to obtain an intermediate layer material dispersion; wherein the mass of the UiO-67-SP nanomaterials in every 100 mL of the intermediate layer material dispersion was 0.006 g; (2) dissolving m-phenylenediamine in deionized water to prepare a m-phenylenediamine solution, wherein the mass percentage of m-phenylenediamine in the m-phenylenediamine solution is 2.5%; dissolving trimesoyl chloride in n-hexane to prepare a trimesoyl chloride organic solution, wherein the mass percentage of trimesoyl chloride in the trimesoyl chloride organic solution is 0.5%; (3) The intermediate layer material dispersion prepared in step (1) is loaded on the surface of the nylon support layer by vacuum filtration to form a composite intermediate layer; (4) Under visible light irradiation conditions, the surface of the composite intermediate layer obtained in step (3) is added with the aqueous amine monomer solution prepared in step (2) and soaked for 3 minutes, and the excess solution is removed after soaking to obtain a dried membrane; then, the organic solution of trimesoyl chloride prepared in step (2) is poured onto the surface of the dried membrane, so that m-phenylenediamine and trimesoyl chloride undergo interfacial polymerization reaction for 2 minutes and form a separation layer, thereby obtaining a spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane; (5) The spiropyran / zirconium-based photoisomerization metal organic framework intermediate layer forward osmosis membrane obtained in step (4) is placed in a 60° C. temperature environment for post-treatment for 2 minutes, and the photoisomerization metal organic framework intermediate layer material is modified after synthesis in different temperature environments to obtain a modified spiropyran / zirconium-based photoisomerization metal organic framework intermediate layer forward osmosis membrane.

[0033] The preparation method of the UiO-67-SP nanomaterial provided in this embodiment comprises the following steps: At room temperature, 4,4'-biphenyldicarboxylic acid, zirconium tetrachloride and 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran in a molar ratio of 1:1:1 were dissolved in N,N-dimethylformamide solvent and subjected to light-proof ultrasonication to obtain a mixed solution after 30 minutes of ultrasonication. The obtained mixed solution was placed in a polytetrafluoroethylene-lined stainless steel autoclave and heated at 120°C for 24 hours. After the reaction, it was cooled to room temperature and filtered to obtain a precipitate. The precipitate was washed alternately with N,N-dimethylformamide and ethanol for 3 times to remove unreacted 4,4'-biphenyldicarboxylic acid. The precipitate was filtered and dried at 80°C, and then ground to obtain a spiropyran / zirconium-based metal organic framework powder, i.e., UiO-67-SP nanomaterial.

[0034] Example 2 The method for preparing the photo-heterogeneous metal-organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 1 in that the light source used is 365 nm ultraviolet light.

[0035] Example 3 The method for preparing the photo-heterogeneous metal-organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 1 in that the light source used is natural light.

[0036] Example 4 The method for preparing the photo-heterogeneous metal-organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 1 in that the dispersion is placed in darkness and allowed to stand for 60 minutes.

[0037] Example 5 The method for preparing the photo-isomerized metal organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 2 in that the aqueous phase amine monomer used is piperazine.

[0038] Example 6 The method for preparing the photo-isomerized metal organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 2 in that the aqueous phase amine monomer used is dopamine.

[0039] Example 7 The preparation method of the photo-isomerized metal-organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 2 in that the spiropyran / zirconium-based photo-isomerized metal-organic framework intermediate layer forward osmosis membrane is post-treated at 25° C. for 2 minutes.

[0040] Example 8 The preparation method of the photo-isomerized metal-organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 1 in that the spiropyran / zirconium-based photo-isomerized metal-organic framework intermediate layer forward osmosis membrane is post-treated at 80° C. for 2 minutes.

[0041] Example 9 The preparation method of the photo-heterogeneous metal-organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 1 in that the mass of the UiO-67-SP nanomaterial in each 50 mL of the intermediate layer material dispersion is 0.002 g.

[0042] Example 10 The method for preparing the photo-isomerized metal organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 2 in that the molar ratio of zirconium tetrachloride, 4,4'-biphenyldicarboxylic acid and 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran is 1:3:2.

[0043] Embodiment 11 The method for preparing the photo-heterogeneous metal-organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 2 in that the irradiation time of 365 nm ultraviolet light is 90 min.

[0044] Example 12 The preparation method of the photo-isomerized metal-organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 2 in that the spiropyran / zirconium-based photo-isomerized metal-organic framework intermediate layer forward osmosis membrane is post-treated at 60° C. for 8 minutes.

[0045] Embodiment 13 The method for preparing the photo-isomerized metal organic framework intermediate layer forward osmosis membrane provided in this embodiment is different from that in Embodiment 2 in that the molar ratio of zirconium tetrachloride, 4,4'-biphenyldicarboxylic acid and 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran is 1:3:0.5.

[0046] The technical effect obtained when the aqueous phase amine monomer in the present application is polyethyleneimine is the same as the technical effect obtained in the embodiment.

[0047] The technical effect obtained when the mass percentage of trimesoyl chloride in the acyl chloride organic phase solution in the present application is 0.1% is the same as the technical effect obtained in the embodiment.

[0048] The technical effect obtained when the mass percentage of the aqueous amine monomer in the aqueous amine monomer solution of the present application is 1.5% is the same as the technical effect obtained in the embodiment.

[0049] The technical effect achieved in the present application when the light source irradiation condition or the dark condition time is 30 minutes is the same as the technical effect achieved in the embodiment.

[0050] 2. Comparison Comparative Example 1 The preparation method of the forward osmosis membrane of this comparative example 1 is different from that of Example 1 in that the UiO-67-SP nanomaterial is not used, and comprises the following steps: The base membrane is a nylon membrane. Under a constant temperature of 25°C, the base membrane is immersed in a 2.5% by mass aqueous solution of m-phenylenediamine for 3 minutes. After drying, a 0.5% by mass organic solution of trimesoyl chloride is poured on the surface of the base membrane. After 60 seconds, the excess organic solution is poured off, and finally heat treated at 60°C for 2 minutes.

[0051] 3. Experimental Examples The test conditions of the modified spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane prepared in Examples 1-13 of the present invention and the forward osmosis membrane prepared in Comparative Example 1 are as follows: deionized water is used as the raw material liquid, 1 mol / L NaCl is used as the draw liquid, and the performance of the prepared forward osmosis membrane is tested under the condition that the flow rate on both sides of the membrane surface is 12.5 cm / s at room temperature, the test time is 30 min, and the water flux J V and reverse salt flux J S , calculated according to the following formulas:

[0052]

[0053] Where △V represents the permeation volume (L), A eff Indicates the effective area of ​​the membrane (㎡), C t Indicates the salt concentration of the raw water at time t (g / L), V t It represents the volume of the raw water side at time t (L), and △t represents the penetration time (h).

[0054] Table 1 Performance of forward osmosis membranes prepared in Examples 1-13 and Comparative Example 1

[0055] It can be seen from Table 1 that the average water flux of the photo-isomerized metal-organic framework intermediate layer forward osmosis membrane prepared in Examples 1-13 of the present application is above 15.41LMH, and the highest can reach 29.23LMH; the reverse salt flux is below 2.88 gMH, and the lowest is 1.32gMH. The water flux of the forward osmosis membrane prepared in Comparative Example 1 is 9.11L LMH, and the reverse salt flux is 2.99 gMH. It can be seen that the photo-isomerized metal-organic framework intermediate layer forward osmosis membrane prepared in the present invention significantly improves the water flux and the interception of salt ions, that is, it reduces the reverse salt flux, and can solve the problems of poor water permeability and ion recovery of the existing forward osmosis membrane due to the excessive thickness of the separation layer and the presence of non-selective holes.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. The patent protection scope of the present invention shall be based on the claims. All equivalent structural changes made using the contents of the description and drawings of the present invention should also be included in the protection scope of the present invention.

Claims

1. A method for preparing a photo-isomerized metal organic framework intermediate layer forward osmosis membrane, characterized in that: The following steps are involved: The UiO-67-SP nanomaterial dispersion under light source irradiation or dark conditions is loaded on the surface of the nylon support layer to form a composite intermediate layer; Under light source irradiation conditions or dark conditions, an amine monomer aqueous solution and an acyl chloride organic solution are added to the surface of the composite intermediate layer, so that the amine monomer in the amine monomer aqueous solution and the acyl chloride monomer in the acyl chloride organic solution undergo interfacial polymerization reaction and form a separation layer, thereby obtaining a spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane.

2. The method for preparing the photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane according to claim 1, characterized in that: The preparation method of the UiO-67-SP nanomaterial comprises the following steps: at room temperature, dispersing zirconium tetrachloride, 4,4'-biphenyl dicarboxylic acid, and 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran in an N,N-dimethylformamide solvent and performing ultrasound to obtain a mixed solution; placing the mixed solution in an environment of 120° C. for reaction, cooling to room temperature after the reaction, and filtering to obtain a precipitate; and washing, filtering, and drying the precipitate to obtain the UiO-67-SP nanomaterial.

3. The method for preparing the photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane according to claim 2, characterized in that: The molar ratio of zirconium tetrachloride, 4,4'-biphenyl dicarboxylic acid and 1-(2-hydroxyethyl)-3,3-dimethylindoline-6'-nitrobenzospiropyran is 1:(1-3):(0.5-2).

4. The method for preparing the photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane according to claim 1, characterized in that: The mass of the UiO-67-SP nanomaterial in each 50-100 mL of the UiO-67-SP nanomaterial dispersion is 0.002-0.007 g.

5. The method for preparing the photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane according to claim 1, characterized in that: The light source is one of ultraviolet light, visible light, and natural light; the time of the light source irradiation condition or dark condition is 30 to 90 minutes.

6. The method for preparing the photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane according to claim 1, characterized in that: The amine monomer aqueous solution is prepared by dissolving an aqueous amine monomer in deionized water; wherein the aqueous amine monomer is one of m-phenylenediamine, piperazine, polyethyleneimine, and dopamine, and the mass percentage of the aqueous amine monomer in the amine monomer aqueous solution is 1.5-3%.

7. The method for preparing the photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane according to claim 1, characterized in that: The acyl chloride organic phase solution is prepared by dissolving trimesoyl chloride in n-hexane; wherein the mass percentage of trimesoyl chloride in the acyl chloride organic phase solution is 0.1-0.5%.

8. The method for preparing a photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane according to any one of claims 1 to 7, characterized in that: The method for preparing the photo-isomerized metal organic framework intermediate layer forward osmosis membrane also includes: The obtained spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane is placed in a temperature environment of 25 to 80° C. for post-treatment for 2 to 8 minutes to obtain a modified spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane.

9. The method for preparing the photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane according to claim 8, characterized in that: Under light irradiation conditions or dark conditions, an amine monomer aqueous phase solution and an acyl chloride organic phase solution are added to the surface of the composite intermediate layer, so that the amine monomer and the acyl chloride undergo interfacial polymerization reaction and form a separation layer, and the specific steps of obtaining a spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane include: Under light irradiation conditions or in darkness, an amine monomer aqueous solution is added to the surface of the composite intermediate layer for soaking, and excess solution is removed after soaking to obtain a dried membrane; an acyl chloride organic phase solution is added to the surface of the dried membrane to allow the amine monomer and the acyl chloride to undergo an interfacial polymerization reaction and form a separation layer, thereby obtaining a spiropyran / zirconium-based photoisomerized metal organic framework intermediate layer forward osmosis membrane; wherein the soaking time is 2 to 5 minutes, and the interfacial polymerization reaction time is 1 to 3 minutes.

10. A photo-heterogeneous metal organic framework intermediate layer forward osmosis membrane, characterized in that: The film is prepared by the method for preparing the photo-heterogeneous metal-organic framework intermediate layer forward osmosis membrane according to any one of claims 1 to 9.

Images