阅读说明：本技术 一种nh2-mil-125/pod-cooh超薄均相杂化正渗透膜及其制备方法 (NH2-MIL-125/POD-COOH ultrathin homogeneous hybrid forward osmosis membrane and preparation method thereof ) 是由 耿直 何男 刘威 杨霞 赵永杰 刘楚汉 刘倩 梁世强 于 2019-11-12 设计创作，主要内容包括：本发明提供一种NH2-MIL-125/POD-COOH超薄均相杂化正渗透膜的制备方法,属于高分子材料技术领域。本发明首先制备了MOFs材料(NH<Sub>2</Sub>-MIL-125)、聚恶二唑(POD)材料和含羧基聚恶二唑(POD-COOH)材料,进一步通过分子设计将NH<Sub>2</Sub>-MIL-125材料通过化学键作用引入含羧基聚恶二唑材料的分子结构中,成功制备了系列NH<Sub>2</Sub>-MIL-125/POD-COOH杂化正渗透膜材料,如图1所示,进而利用上述材料通过溶液浇铸法制备超薄均质杂化正渗透膜。最终提供了一种NH2-MIL-125/POD-COOH杂化正渗透膜的制备方法。由于该类正渗透膜中不存在支撑层,因而可以消除正渗透分离操作过程中的内浓差极化现象,大幅提升正渗透水处理效率。此外,对水和盐具有高效筛分效能的多孔亲水性MOFs材料的引入增强了杂化膜在正渗透分离操作过程中的水渗透性能和脱盐性能。综上所述,该类材料在海水淡化、苦咸水处理等领域将具有广阔的应用前景。(The invention provides a preparation method of an NH2-MIL-125/POD-COOH ultrathin homogeneous hybrid forward osmosis membrane, belonging to the technical field of high polymer materials. The invention firstly prepares the MOFs material (NH) 2 MIL-125), Polyoxadiazole (POD) material and carboxyl-containing polyoxadiazole (POD-COOH) material, and further performing molecular design on NH 2 the-MIL-125 material is introduced into the molecular structure of the carboxyl-containing polyoxadiazole material through the chemical bond effect, and the series of NH is successfully prepared 2 -MIL-125/POD-COOH hybrid forward osmosis membrane material as shown in FIG. 1, and further using the sameThe ultrathin homogeneous hybrid forward osmosis membrane is prepared by a solution casting method. Finally provides a preparation method of the NH2-MIL-125/POD-COOH hybridized forward osmosis membrane. Because the forward osmosis membrane does not have a supporting layer, the phenomenon of internal concentration polarization in the forward osmosis separation operation process can be eliminated, and the forward osmosis water treatment efficiency is greatly improved. In addition, the introduction of porous hydrophilic MOFs materials with high sieving efficiency for water and salt enhances the water permeation and desalination performance of the hybrid membrane during forward osmosis separation operations. In conclusion, the material has wide application prospect in the fields of seawater desalination, brackish water treatment and the like.)

1. An NH2-MIL-125/POD-COOH ultrathin homogeneous hybrid forward osmosis membrane and a preparation method thereof comprise the following steps:

the method comprises the following steps: adding butyl titanate and 2-amino-terephthalic acid into a mixed solution of N, N-Dimethylformamide (DMF) and methanol, stirring for 3-5 hours at room temperature, transferring to a 40 ml polytetrafluoroethylene-lined stainless steel reaction kettle, and placing in a temperature programming box at 140-150 ℃ for 24-48 hours. Naturally cooling to room temperature, washing and drying to obtain MOFs material NH₂-MIL-125；

Step two: hydrazine sulfate (N)₂H₄·H₂SO₄) Adding polyphosphoric acid (PPA) into a three-neck bottle with mechanical stirring, a nitrogen gas port, a thermometer, a Dean-Stark water carrying device and a condensation pipe, mixing and heating to 160-180 ℃, adding a diacid monomer (4,4' -diphenyl ether dicarboxylic acid), reacting for 3-5 hours at 160-180 ℃ to generate a viscous substance, discharging the viscous substance into a NaOH aqueous solution with the mass fraction of 5%, and washing and drying a product to obtain a polyoxadiazole material (POD);

step three: dissolving the polyoxadiazole material obtained in the step two in an N-methylpyrrolidone solvent, adding p-aminobenzoic acid and polyphosphoric acid, reacting for 10-15 hours at 180-195 ℃, discharging in deionized water, and obtaining a polyoxadiazole material (POD-COOH) with a side chain containing carboxyl;

step four: dissolving the carboxyl-containing polyoxadiazole material obtained in the third step in an anhydrous solvent, and after the polymer is completely dissolved, dropwise adding the polymer into the anhydrous solvent in which 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), N-hydroxysuccinimide (NHS) and NH obtained in the first step are dissolved₂Adding an MIL-125 material (the mass of the MIL-125 material is 5% or 10% of that of the carboxyl-containing polyoxadiazole material) in an anhydrous solvent, after dropwise adding for 2-3 hours, continuously stirring for 48-72 hours at room temperature, discharging in n-hexane, and obtaining NH₂-MIL-125/POD-COOH hybrid material.

Step five: the polyoxadiazole material obtained in the step two, the carboxyl-containing polyoxadiazole material obtained in the step three and NH obtained in the step four₂Respectively dissolving MIL-125/POD-COOH hybrid materials in an organic solvent, standing and defoaming at room temperature for 24-48 hours to obtain a membrane casting solution;

step six: and D, respectively coating the casting solution obtained in the fifth step on the surface of a smooth and flat silicon wafer, placing the silicon wafer coated with the casting solution in an oven for heat treatment, forming a film by a solution casting method, and then immersing the film in water to separate the film, thereby finally obtaining the ultrathin homogeneous forward osmosis film.

2. The preparation method of the ultrathin homogeneous hybrid forward osmosis membrane according to claim 1, wherein the molar ratio of the butyl titanate to the 2-amino-terephthalic acid is 1:3 to 1: 5; the volume ratio of N, N-Dimethylformamide (DMF) to methanol was 1:1.

3. The method for preparing an ultrathin homogeneous hybrid forward osmosis membrane according to claim 1, wherein the molar ratio of hydrazine disulfide, 4' -diphenyl ether dicarboxylic acid and polyphosphoric acid is 1:1.2: 10.

4. The method for preparing an ultrathin homogeneous hybrid forward osmosis membrane according to claim 1, wherein the molar ratio of the polyoxadiazole material to the p-aminobenzoic acid in the step is 1:1.

5. The method for preparing an ultrathin homogeneous hybrid forward osmosis membrane according to claim 1, wherein the anhydrous solvent in step four is anhydrous N, N-Dimethylformamide (DMF).

6. The method for preparing an ultrathin homogeneous hybrid forward osmosis membrane according to claim 1, wherein the molar ratio of the carboxyl-containing polyoxadiazole material, N-hydroxysuccinimide (NHS) and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in the step four is 1:0.1: 1.2.

7. The method for preparing an ultrathin homogeneous hybrid forward osmosis membrane according to claim 1, wherein the organic solvent in the step five is N, N-Dimethylformamide (DMF).

8. The method for preparing an ultrathin homogeneous hybrid forward osmosis membrane according to claim 1, wherein the mass fraction of the solute in the membrane casting solution of the step five is between 0.2% and 0.4%.

9. The preparation method of the ultrathin homogeneous hybrid forward osmosis membrane according to claim 1, wherein the heat treatment temperature in the sixth step is 60-80 ℃ and the heat treatment time is 12-24 hours.

Technical Field

The invention belongs to the technical field of high polymer materials, and particularly relates to NH₂-MIL-125/POD-COOH ultrathin homogeneous hybrid forward osmosis membrane and preparation method thereof.

Background

In recent years, water safety issues and the development of low energy water treatment technologies have received a great deal of attention. Among the numerous water treatment technologies, membrane processes are considered to be a very promising class of water treatment technologies. Forward Osmosis (FO) membrane separation technology is a novel membrane method water treatment technology, water separation operation is carried out by taking solution osmotic pressure difference on two sides of a membrane as a driving force, the technology has the advantages of high water recovery rate, low pollution tendency, low energy requirement, simplicity and convenience in operation and the like, and good development prospects are shown in the fields of food concentration, drug release, seawater desalination and the like. Currently commercialized forward osmosis membranes are generally asymmetric membranes, i.e. the surface consists of an active layer and a bottom support layer. In the forward osmosis membrane separation process, the concentration polarization phenomenon in the bottom supporting layer becomes a main factor for limiting the wide application of forward osmosis technology at present, which causes the water flux of the forward osmosis membrane to be obviously reduced and the water production efficiency to be reduced. The method for alleviating the problems comprises the steps of reducing the thickness of the supporting layer, reducing the tortuosity of holes in the supporting layer and increasing the porosity of the supporting layer in the process of preparing the forward osmosis membrane, thereby reducing the internal concentration polarization phenomenon of the supporting layer in the forward osmosis process. However, the forward osmosis membrane with the characteristics is often poor in mechanical strength and easy to damage in the using process, and the internal concentration polarization phenomenon of the support layer is not fundamentally eliminated. In order to thoroughly eliminate the adverse effect of concentration polarization in the supporting layer on the forward osmosis separation process, the ultrathin homogeneous forward osmosis membrane without the supporting layer is prepared by selecting a high-strength polymer material and is worthy of attention. In addition, in order to further improve the water flux of the forward osmosis membrane and improve the water treatment efficiency of the forward osmosis membrane, a hybrid forward osmosis membrane can be prepared by introducing porous hydrophilic fillers (such as metal organic framework MOFs materials) into the chemical structure of a high-strength polymer material, so that a novel high-performance forward osmosis membrane is developed, and the forward osmosis separation technology is promoted to be further popularized and applied.

Disclosure of Invention

The invention aims to provide a preparation method of a novel ultrathin homogeneous hybrid forward osmosis membrane. Firstly, synthesizing a high-strength polymer matrix material, modifying the molecular structure of the high-strength polymer matrix material to introduce an active reaction group, and further introducing metal organic framework Materials (MOFs) into the molecular structure of the polymer through a side chain grafting reaction by utilizing a strong chemical bond effect, thereby designing and synthesizing the hybrid forward osmosis membrane material. Finally, the hybrid material is used for preparing a series of novel ultrathin homogeneous hybrid forward osmosis membranes by a solution casting method. A supporting layer does not exist in the homogeneous forward osmosis membrane structure, so that the adverse effect of concentration polarization phenomenon in the supporting layer on forward osmosis separation operation is avoided. In addition, the high water permeability of MOFs molecular pore canals and the high-efficiency screening capacity for water and salt can be utilized, and the hybrid membrane is endowed with excellent water permeability and salt retention performance in the water treatment process.

The invention provides a NH₂The preparation method of the-MIL-125/POD-COOH ultrathin homogeneous hybrid forward osmosis membrane comprises the following steps:

the method comprises the following steps: adding butyl titanate and 2-amino-terephthalic acid into a mixed solution of N, N-Dimethylformamide (DMF) and methanol, stirring for 3-5 hours at room temperature, transferring to a 40 ml polytetrafluoroethylene-lined stainless steel reaction kettle, and placing in a temperature programming box at 140-150 ℃ for 24-48 hours. Naturally cooling to room temperature, washing and drying to obtain MOFs material NH₂-MIL-125；

Step two: hydrazine sulfate (N)₂H₄·H₂SO₄) And Polyphosphoric Acid (PPA) is added into a three-neck bottle with mechanical stirring, a nitrogen gas port, a thermometer, a Dean-Stark water carrying device and a condensation pipe, the materials are mixed and heated to 160-180 ℃, then diacid monomer (4,4' -diphenyl ether dicarboxylic acid) is added, the reaction is carried out for 3-5 hours at 160-180 ℃, a viscous substance is generated, the material is discharged into a NaOH aqueous solution with the mass fraction of 5%, and the product is washed and dried to obtain polyoxadiazole material (POD), wherein the structural formula of the polyoxadiazole material is shown as formula I:

in the formula I, n is the polymerization degree, and n is 10-200.

Step three: dissolving the polyoxadiazole material obtained in the step two in an N-methylpyrrolidone (NMP) solvent, adding p-aminobenzoic acid and polyphosphoric acid, reacting at 180-195 ℃ for 10-15 hours, discharging in deionized water, and obtaining a polyoxadiazole material (POD-COOH) with a side chain containing an active reaction group, namely carboxyl, wherein the structural formula of the polyoxadiazole material is shown as a formula II:

in formula II, m is 0.2, n is the degree of polymerization, and n is 10 to 200.

Step four: dissolving the carboxyl-containing polyoxadiazole material obtained in the third step in an anhydrous solvent, and after the polymer is completely dissolved, dropwise adding the polymer into the anhydrous solvent in which 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), N-hydroxysuccinimide (NHS) and NH obtained in the first step are dissolved₂And (2) after dropwise adding the MIL-125 material (the mass of the MIL-125 material is 5% or 10% of that of the carboxyl-containing polyoxadiazole material) in an anhydrous solvent for about 2-3 hours, continuously stirring for 48-72 hours at room temperature, and discharging in n-hexane to obtain the hybrid material. According to NH₂-mass fraction of MIL-125 in the hybrid material, naming the synthesized series of hybrid materials as: 5% NH₂-MIL-125/POD-COOH or 10% NH₂-MIL-125/POD-COOH having the formula III:

in formula III, m is 0.2, n is the degree of polymerization, and n is 10 to 200.

Step five: mixing the polyoxadiazole material (POD) obtained in the step two, the carboxyl-containing polyoxadiazole material (POD-COOH) obtained in the step three and the 5% NH obtained in the step four₂-MIL-125/POD-COOH and 10% NH₂Respectively dissolving MIL-125/POD-COOH hybrid materials in an organic solvent, standing and defoaming at room temperature for 24-48 hours to obtain a membrane casting solution;

step six: and D, respectively coating the casting solution obtained in the fifth step on the surface of a smooth and flat silicon wafer, placing the silicon wafer coated with the casting solution in an oven for heat treatment, forming a film by a solution casting method, and then immersing the film in water to separate the film, thereby finally obtaining the ultrathin homogeneous forward osmosis film.

Preferably, the molar ratio of the butyl titanate to the 2-amino-terephthalic acid in the step is 1:3 to 1: 5; the volume ratio of N, N-Dimethylformamide (DMF) to methanol was 1:1.

Preferably, the molar ratio of hydrazine disulfide, 4' -diphenylether dicarboxylic acid and polyphosphoric acid is 1:1.2: 10.

Preferably, the molar ratio of the polyoxadiazole material to the p-aminobenzoic acid in the step is 1:1.

Preferably, the anhydrous solvent of step four is anhydrous N, N-Dimethylformamide (DMF).

Preferably, the molar ratio of the carboxyl group-containing polyoxadiazole material, N-hydroxysuccinimide (NHS) and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in step four is 1:0.1: 1.2.

Preferably, the organic solvent of step five is N, N-Dimethylformamide (DMF).

Preferably, the mass fraction of the solute in the step five membrane casting solution is between 0.2% and 0.5%.

Preferably, the heat treatment temperature in the sixth step is 60-80 ℃, and the heat treatment time is 12-24 hours.

The invention has the beneficial effects that:

the invention provides a NH₂The preparation method of the-MIL-125/POD-COOH ultrathin homogeneous hybrid forward osmosis membrane is simple, the raw materials are easy to obtain, and the yield is high. The method is to design NH through molecules₂the-MIL-125 material is introduced into the chemical structure of the carboxyl-containing high-strength polyoxadiazole substrate material by side chain grafting reaction and chemical bond action, so as to synthesize a series of NH₂-MIL-125/POD-COOH hybrid material, and a novel series of ultrathin homogeneous hybrid forward osmosis membranes are obtained by using the material through a solution casting method. NH (NH)₂Strong chemical bond action between-MIL-125 material and polyoxadiazole substrate material ensures NH₂The MIL-125 is uniformly dispersed in the polymer matrix in a nanometer scale, so that the strong hydrophilicity, high water permeability and high-efficiency water-salt screening performance of the MIL-125 are fully exerted in the hybrid membrane, and the hybrid membrane is endowed with excellent water permeability and salt retention performance in the water treatment process. In addition, a supporting layer does not exist in the homogeneous forward osmosis membrane structure obtained by the solution casting method, so that the adverse effect of concentration polarization phenomenon in the supporting layer on forward osmosis separation operation is avoided. The ultrathin homogeneous hybrid forward osmosis membrane has wide application prospect in the fields of seawater desalination, brackish water treatment and the like.

Drawings

FIG. 1 shows NH prepared in example 1 of the present invention₂-MIL-125/POD-COOH hybrid material structural formula diagram;

FIG. 2 shows the MOFs material NH prepared in the embodiment 1 of the present invention₂-XRD pattern of MIL-125;

FIG. 3 is a nuclear magnetic spectrum of the polyoxadiazole material prepared in example 1 of the present invention;

FIG. 4 is a nuclear magnetic spectrum of the carboxyl group-containing polyoxadiazole material prepared in example 1 of the present invention;

FIG. 5 shows polyoxadiazole material, carboxyl group-containing polyoxadiazole material, and 5% NH prepared in example 1 of the present invention₂MIL-125/POD-COOH hybrid and 10% NH prepared in example 2₂Infrared Spectrum of-MIL-125/POD-COOH hybrid MaterialA drawing;

FIG. 6 shows a polyoxadiazole forward osmosis membrane (POD), a carboxyl group-containing polyoxadiazole forward osmosis membrane (POD-COOH) and 5% NH with a membrane thickness of about 5 μm prepared in example 1 of the present invention ₂10% NH with the same thickness of 5 μm for the-MIL-125/POD-COOH hybrid forward osmosis membrane and the membrane prepared in example 2₂Forward osmosis water flux (J) of MIL-125/POD-COOH hybrid forward osmosis membrane_w) And reverse salt flux (J)_s) A test result graph;

FIG. 7 is a 10% NH film thickness of about 5 microns prepared in example 2, about 8 microns prepared in example 3, and about 12 microns prepared in example 4, according to the invention₂-graph of forward osmosis water flux test results of MIL-125/POD-COOH hybrid forward osmosis membrane against sodium sulfate draw solution;

FIG. 8 is a 10% NH film thickness of about 5 microns prepared in example 2, about 8 microns prepared in example 3, and about 12 microns prepared in example 4, according to the invention₂-graph of forward osmosis reverse salt flux test results for MIL-125/POD-COOH hybrid forward osmosis membrane versus sodium sulfate draw solution;

Detailed Description

The invention provides a NH₂The preparation method of the-MIL-125/POD-COOH ultrathin homogeneous hybrid forward osmosis membrane comprises the following steps:

the method comprises the following steps: adding butyl titanate and 2-amino-terephthalic acid into a mixed solution of N, N-Dimethylformamide (DMF) and methanol, stirring for 3-5 hours at room temperature, transferring to a 40 ml polytetrafluoroethylene-lined stainless steel reaction kettle, and placing in a temperature programming box at 140-150 ℃ for 24-48 hours. Naturally cooling to room temperature, washing with N, N-Dimethylformamide (DMF) for 3-5 times, then washing with methanol for 3-5 times, wherein each time the solution is 20-30 ml, and the time is 2-3 hours, thus obtaining the MOFs material NH₂-MIL-125；

Step two: hydrazine sulfate (N)₂H₄·H₂SO₄) And Polyphosphoric Acid (PPA) are added into a three-neck flask with mechanical stirring, a nitrogen gas port, a thermometer, a Dean-Stark water carrying device and a condensing tube, mixed and heated to 160-180 ℃, and then diacid monomer (4,4' -diphenyl ether dimethyl ether) is addedAcid), reacting for 3-5 hours at 160-180 ℃ to generate a viscous substance, discharging the viscous substance into a NaOH aqueous solution with the mass fraction of 5%, and washing and drying a product to obtain a polyoxadiazole material (POD);

step three: dissolving the polyoxadiazole material obtained in the step two in an N-methylpyrrolidone solvent, adding p-aminobenzoic acid and polyphosphoric acid, reacting for 10-15 hours at 180-195 ℃, discharging in deionized water, and obtaining a polyoxadiazole material (POD-COOH) with a side chain containing carboxyl;

step four: dissolving the carboxylated polyoxadiazole material obtained in the third step into an anhydrous solvent, and after the polymer is completely dissolved, dropwise adding the solution containing 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), N-hydroxysuccinimide (NHS) and NH obtained in the first step₂Adding an MIL-125 material (the mass of the MIL-125 material is 5% or 10% of that of the carboxyl-containing polyoxadiazole material) in an anhydrous solvent, continuously stirring for 48-72 hours at room temperature after dropwise adding for about 2-3 hours, discharging in n-hexane to obtain 5% NH₂-MIL-125/POD-COOH or 10% NH₂-MIL-125/POD-COOH hybrid material;

step five: respectively dissolving the polyoxadiazole material obtained in the step two, the carboxylated polyoxadiazole material obtained in the step three and the hybrid material obtained in the step four in an organic solvent, standing and defoaming at room temperature for 24-48 hours to respectively obtain a polyoxadiazole membrane casting solution, a carboxylated polyoxadiazole membrane casting solution and a hybrid material membrane casting solution;

step six: respectively coating the casting solution obtained in the fifth step on the surface of a smooth and flat silicon wafer, placing the silicon wafer coated with the casting solution in an oven for heat treatment, forming a film by a solution casting method, and then immersing the film in water to separate the film, thereby finally obtaining the ultrathin homogeneous polyoxadiazole forward osmosis film (POD), the carboxylated polyoxadiazole forward osmosis film (POD-COOH) and 5% NH respectively₂-MIL-125/POD-COOH and 10% NH₂-MIL-125/POD-COOH hybrid forward osmosis membrane.

According to the invention, the molar ratio of the butyl titanate and the 2-amino-terephthalic acid in the first step is preferably 1:3 to 1: 5; the volume ratio of N, N-Dimethylformamide (DMF) to methanol is preferably 1:1.

According to the present invention, the molar ratio of hydrazine sulfate, 4' -diphenyletherdicarboxylic acid and polyphosphoric acid in step two is preferably 1:1.2: 10. The reaction process is as follows:

according to the invention, the molar ratio of the polyoxadiazole material and the p-aminobenzoic acid in the third step is preferably 1:1.

The reaction process is as follows:

according to the present invention, the anhydrous solvent described in the fourth step is preferably anhydrous N, N-Dimethylformamide (DMF); the molar ratio of carboxylated polyoxadiazole material, N-hydroxysuccinimide (NHS) and 1-ethyl- (3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) is preferably 1:0.1: 1.2. the reaction process is as follows:

according to the invention, the organic solvent in step five is preferably N, N-Dimethylformamide (DMF); the mass fraction of solute in the dope solution is preferably between 0.2% and 0.5%.

According to the invention, the heat treatment temperature in the sixth step is preferably 60-80 ℃, and the heat treatment time is preferably 12-24 hours; the thickness of the obtained ultrathin homogeneous forward osmosis membrane is preferably 5-12 microns.

The present invention is described in further detail below with reference to specific examples, in which the starting materials are all commercially available.