CN109173730B - Method for in-situ preparation of MOFs @ f-GO hybrid membrane by freeze drying technology - Google Patents

Method for in-situ preparation of MOFs @ f-GO hybrid membrane by freeze drying technology Download PDF

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CN109173730B
CN109173730B CN201811076605.3A CN201811076605A CN109173730B CN 109173730 B CN109173730 B CN 109173730B CN 201811076605 A CN201811076605 A CN 201811076605A CN 109173730 B CN109173730 B CN 109173730B
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CN109173730A (en
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安全福
张文海
王乃鑫
殷明杰
纪树兰
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Beijing University of Technology
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/025—Reverse osmosis; Hyperfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B01D67/0095—Drying
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material

Abstract

A method for preparing MOFs @ f-GO hybrid membranes in situ by a freeze drying technology belongs to the field of nanofiltration membrane separation. The method comprises the following steps: preparing GO dispersion liquid, and adding a certain amount of metal coordination ions or organic ligands into the GO dispersion liquid; assembling the GO-based dispersion liquid on the surface of a porous base membrane in a suction filtration deposition mode to prepare a wet GO-based composite membrane; preparing the obtained wet GO-based composite membrane into a loose GO-based composite membrane by using a freeze drying technology; correspondingly immersing the obtained composite membrane into an organic ligand solution or a metal coordination ion solution to carry out MOFs in-situ hybrid growth, and preparing the metal organic framework @ graphene oxide (MOFs @ f-GO) hybrid nanofiltration membrane. The film can be used for separating dyes in water, high-valence salts and small molecules in an organic phase.

Description

Method for in-situ preparation of MOFs @ f-GO hybrid membrane by freeze drying technology
Technical Field
The invention relates to a method for preparing a metal organic framework @ graphene oxide hybrid membrane (MOFs @ f-GO) by the aid of a freeze drying technology and in-situ growth in a synergistic manner, and the membrane can be used for separating dyes, high-valence salts and small molecules in an organic phase in water and belongs to the field of nanofiltration membrane separation.
Background
The nanofiltration technology is regarded as an effective separation means of high-valence salts and organic micromolecules in a liquid phase system because of the advantages of simple operation, high efficiency, energy conservation, no secondary pollution and the like, and the nanofiltration membrane is the key of the nanofiltration technology. At present, polymer membranes are most widely applied in all nanofiltration membrane materials, and are easy to use in a large scale mainly due to simple preparation process and high mechanical strength, and are convenient to assemble into integrated membrane components. However, the polymeric nanofiltration membrane still has the disadvantages of poor chemical stability and thermal stability, easy pollution, short service life and the like.
Graphene Oxide (GO) as an oxidized derivative of graphene not only maintains the superior performance of partial graphene, but also is easy for large-scale preparation. Furthermore, GO can be assembled by simple suction filtration or spin coating into macroscopic membrane materials with abundant two-dimensional nanopore networks and is therefore considered to have very broad application potential in the field of membrane separation [ e.n.wang and r.karnik, Nature nanotechnology, 2012,7,552 ]. However, mass transfer of GO membranes relies primarily on inter-layer spacing, which greatly prolongs the mass transfer path, reducing permeation rates, and thus limiting the application of GO membranes. In addition, recent research shows that flux is greatly attenuated due to microstructure compaction of the GO membrane and is dissociated in water in the running process, so that the industrial application of the GO membrane is greatly limited [ Wei Y, Zhang Y, Gao X, et al. carbon,2016,108: 568-575; chong J Y, Wang B, Mattevi C, et al. journal of Membrane Science,2017,549 ]. To this end, a series of improved methods have been proposed.
In the present study, the ways to improve GO membrane flux and stability mainly include: a. chemical crosslinking, for example, chemical crosslinking is carried out on molecules such as polyamine, polyacyl chloride and the like and the sheet layer; b. and the construction of a GO interlayer nano mass transfer channel is realized by utilizing a nano particle filling technology. The method can support, stabilize and regulate the interlayer spacing. However, both approaches have their own drawbacks, such as small molecule chemical cross-linking does not contribute much to increase permeation flux; the filling hybridization of the nano particles (templates) introduced in a physical blending mode is difficult to realize the controllable construction of a nano transmission channel and the particle agglomeration is easy to generate defects to reduce the separation selectivity. For this reason, the development of an in situ hybridization method for porous materials is the key to solve the above problems.
Metal Organic Frameworks (MOFs) are a new porous material recently developed, and are widely applied to preparation of separation membranes due to their special pore structure characteristics, and all have relatively excellent separation performance [ CN106823854A, CN104209022A, CN104209021A ]. However, most of the existing hybrid methods are direct physical blending, so that the dispersions are uneven and easy to agglomerate when the addition amount is higher. While in-situ hybridization is a very powerful solution, pure GO films are difficult to grow in situ due to dense interlayer accumulation, and the premise of in-situ hybridization growth is to construct a nanoparticle growth space. The freeze-drying method, also called as an ice template technology, is a very effective method for preparing a porous material [ CN107200583A, CN106084302A and CN107185500A ] developed recently, so that the invention synergistically prepares a metal organic framework @ graphene oxide (MOFs @ f-GO) hybrid nanofiltration membrane with double separation channels by combining the freeze-drying technology and an in-situ hybrid growth approach, effectively improves the membrane mass transfer rate by the method, simultaneously maintains higher separation selectivity, has simple preparation process and good repeatability, and has great potential application prospect in the field of liquid phase separation.
Disclosure of Invention
The invention aims to construct a metal organic framework @ graphene oxide (MOFs @ f-GOm) hybrid nanofiltration membrane with double separation channels by adopting a freeze drying technology and an in-situ hybrid growth approach in a synergistic manner. And (3) carrying out direct in-situ hybridization on the f-GO membrane obtained by freeze drying treatment. The composite membrane prepared by the method has good separation performance and stability when being used in the field of nanofiltration separation.
The method comprises the following steps:
(1) pretreating the porous base membrane to remove organic matters, inorganic matters and microorganisms on the surface of the porous base membrane;
(2) dispersing GO powder in deionized water, and preparing a GO dispersion liquid in an ultrasonic centrifugation mode;
(3) adding a certain amount of metal coordination ions or organic ligands into the GO dispersion liquid;
(4) assembling the GO-based dispersion liquid on the surface of a porous base membrane in a suction filtration deposition mode to prepare a wet GO-based composite membrane;
(5) preparing the wet GO-based composite membrane obtained in the step (4) into a loose GO-based composite membrane by utilizing a freeze drying technology;
(6) correspondingly immersing the composite membrane obtained in the step (5) into an organic ligand solution or a metal coordination ion solution for MOFs in-situ hybrid growth, and preparing the metal organic framework @ graphene oxide (MOFs @ f-GO) hybrid nanofiltration membrane.
The substrate for preparing the polyelectrolyte composite membrane can be an inorganic porous membrane of a commercial tubular membrane or a flat membrane, the membrane material is alumina, silica and zirconia, and the pore diameter of the porous membrane is 0.1-1.0 mu m;
the mass percentage concentration of the GO dispersion liquid used for assembling in the step (2) is 0.001-0.5%; and (3) the concentration of the metal coordination ions or the organic ligands in the GO dispersion liquid in the step (3) is 0.01-1 mol/L.
In the step (4), the pressure range of suction filtration and deposition is 0.01-0.1 MPa, and the deposition time range is 0.1-10 min;
the freeze drying technology in the step (5) is that firstly, the frozen ice is crystallized and then is sublimated under reduced pressure, the freezing temperature is-10 to-50 ℃, the ice crystallization time is 0.5 to 3 hours, the pressure of the sublimation under reduced pressure is 1 to 10Pa, and the sublimation drying time is 1 to 10 hours;
the reaction temperature in the step (6) is 20-60 ℃, and the reaction time is 1-36 h; the corresponding organic ligand solution or the coordination metal ion solution has the molar concentration of 0.01-10 mol/L.
The principle of the technical scheme of the invention is as follows: preparing a wet GO-based composite membrane by using a suction filtration deposition method, freezing at a low temperature, solidifying the solvent to generate a solvent crystal nucleus with a nanometer size when the temperature is lower than the freezing point of the solvent, and removing the solvent by using a negative pressure sublimation method to construct a space with a special microporous structure so as to perform in-situ hybrid growth of MOFs on the basis of the space. The method greatly improves the structural stability and the mass transfer rate of the GO membrane and simultaneously maintains high separation selectivity.
Technical advantages
According to the invention, the MOFs @ f-GO hybrid nanofiltration membrane with double separation channels is constructed by adopting a freeze drying technology, so that the retention rate is maintained while the stability and the permeation flux of the membrane structure are improved; the method is a typical in-situ hybridization technology, is simple to operate and stable in structure, and has industrial popularization potential. The MOFs @ f-GO hybrid nanofiltration membrane prepared by the technology is used for separating a 0.1g/L methyl blue aqueous solution system, a 0.1g/L chrome black T aqueous solution system, a 0.1g/L sodium sulfate aqueous solution system and a 0.1g/L Evans blue methanol aqueous solution system, and when the operating pressure is 0.1MPa, the flux is respectively 30.9L/m2h bar、29.2L/m2h bar、38.6L/m2h bar and 34.2L/m2h bar; the retention rates were 99.8%, 99.0%, 66.2% and 90.2% in this order.
Drawings
FIG. 1 is a scanning electron microscope image of the cross section of the ZIF-8@ f-GO hybrid nanofiltration membrane subjected to freeze drying in example 1,
FIG. 2 is a scanning electron microscope image of the surface of the ZIF-8@ f-GO hybrid nanofiltration membrane in example 1.
Detailed Description
The present invention will be described in detail with reference to specific examples, but the present invention is not limited to the examples.
Example 1
The commercial porous membrane is made of alumina material and is in the form of tubular ultrafiltration membrane, the pore diameter of the membrane is 0.1 mu m, and the area of the membrane is 10cm2The selected GO dispersing agent is deionized water, and the concentration of the GO dispersing liquid is 0.003 g/L.
Preparation method of ZIF-8@ f-GO hybrid nanofiltration membrane
(1) Washing an alumina film with the length of about 5cm by using deionized water for pretreatment, removing organic matters, inorganic matters and microorganisms on the surface of the alumina film, and then drying the alumina film in a 50 ℃ drying oven;
(2) dispersing a certain amount of GO powder in deionized water, preparing GO dispersion liquid with a concentration ratio of 0.003g/L by an ultrasonic centrifugation mode, and adding 2-methylimidazole with the concentration of 1 mol/L;
(3) assembling the GO-based dispersion liquid prepared in the step (2) on the treated alumina membrane in a suction filtration and deposition mode, wherein the suction filtration pressure is 0.1MPa, and the suction filtration time is 3 min;
(4) directly putting the wet GO composite membrane prepared in the step (3) into a freeze drying box, wherein the temperature is-50 ℃, and the ice crystallization time is 3 hours; then carrying out sublimation drying for 10 h; finally taking out and putting into a 50 ℃ oven for drying for 12 h;
(5) and (3) soaking the prepared f-GO composite membrane in 0.01mol/L zinc nitrate hexahydrate solution for 6 hours, taking out and drying. When the operating pressure is 0.1MPa, the retention rate and the flux of the sodium sulfate are respectively 66.2 percent and 38.6L/m2h bar。
Example 2
The commercial porous membrane is made of alumina material and is in the form of tubular ultrafiltration membrane, the pore diameter of the membrane is 0.1 mu m, and the area of the membrane is 10cm2The selected GO dispersing agent is deionized water, and the concentration of the GO dispersing liquid is 0.003 g/L.
Preparation method of ZIF-8@ f-GO hybrid nanofiltration membrane
(1) Washing an alumina film with the length of about 5cm by using deionized water for pretreatment, removing organic matters, inorganic matters and microorganisms on the surface of the alumina film, and then drying the alumina film in a 50 ℃ drying oven;
(2) dispersing a certain amount of GO powder in deionized water, preparing GO dispersion liquid with a concentration ratio of 0.003g/L by an ultrasonic centrifugation mode, and adding 2-methylimidazole with the concentration of 1 mol/L;
(3) assembling the GO-based dispersion liquid prepared in the step (2) on the treated alumina membrane in a suction filtration and deposition mode, wherein the suction filtration pressure is 0.1MPa, and the suction filtration time is 3 min;
(4) directly putting the wet GO composite membrane prepared in the step (3) into a freeze drying box, wherein the temperature is-50 ℃, and the ice crystallization time is 3 hours; then carrying out sublimation drying for 10 h; finally taking out and putting into a 50 ℃ oven for drying for 12 h;
(5) and (3) soaking the prepared f-GO composite membrane in 0.01mol/L zinc nitrate hexahydrate solution for 6 hours, taking out and drying. When the operating pressure is 0.1MPa, the rejection rate and the flux of the methyl blue are respectively 99.8 percent and 30.9L/m2h bar。
Example 3
The commercial porous membrane is made of alumina material and is in the form of tubular ultrafiltration membrane, the pore diameter of the membrane is 0.1 mu m, and the area of the membrane is 10cm2The selected GO dispersing agent is deionized water, and the concentration of the GO dispersing liquid is 0.003 g/L.
Preparation method of ZIF-8@ f-GO hybrid nanofiltration membrane
(1) Washing an alumina film with the length of about 5cm by using deionized water for pretreatment, removing organic matters, inorganic matters and microorganisms on the surface of the alumina film, and then drying the alumina film in a 50 ℃ drying oven;
(2) dispersing a certain amount of GO powder in deionized water, preparing GO dispersion liquid with a concentration ratio of 0.003g/L by an ultrasonic centrifugation mode, and adding 2-methylimidazole with the concentration of 1 mol/L;
(3) assembling the GO-based dispersion liquid prepared in the step (2) on the treated alumina membrane in a suction filtration and deposition mode, wherein the suction filtration pressure is 0.1MPa, and the suction filtration time is 3 min;
(4) directly putting the wet GO composite membrane prepared in the step (3) into a freeze drying box, wherein the temperature is-50 ℃, and the ice crystallization time is 3 hours; then carrying out sublimation drying for 10 h; finally taking out and putting into a 50 ℃ oven for drying for 12 h;
(5) and (3) soaking the prepared f-GO composite membrane in 0.01mol/L zinc nitrate hexahydrate solution for 6 hours, taking out and drying. When the operation pressure is 0.1MPa, the retention rate and the flux of the chromium black T are respectively 99.0 percent and 29.2L/m2h bar。
Example 4
The commercial porous membrane is made of alumina material and is in the form of tubular ultrafiltration membrane, the pore diameter of the membrane is 0.1 mu m, and the area of the membrane is 10cm2The selected GO dispersing agent is deionized water, and the concentration of the GO dispersing liquid is 0.003 g/L.
Preparation method of ZIF-8@ f-GO hybrid nanofiltration membrane
(1) Washing an alumina film with the length of about 5cm by using deionized water for pretreatment, removing organic matters, inorganic matters and microorganisms on the surface of the alumina film, and then drying the alumina film in a 50 ℃ drying oven;
(2) dispersing a certain amount of GO powder in deionized water, preparing GO dispersion liquid with a concentration ratio of 0.003g/L by an ultrasonic centrifugation mode, and adding 2-methylimidazole with the concentration of 1 mol/L;
(3) assembling the GO-based dispersion liquid prepared in the step (2) on the treated alumina membrane in a suction filtration and deposition mode, wherein the suction filtration pressure is 0.1MPa, and the suction filtration time is 3 min;
(4) directly putting the wet GO composite membrane prepared in the step (3) into a freeze drying box, wherein the temperature is-50 ℃, and the ice crystallization time is 3 hours; then carrying out sublimation drying for 10 h; finally taking out and putting into a 50 ℃ oven for drying for 12 h;
(5) and (3) soaking the prepared f-GO composite membrane in 0.01mol/L zinc nitrate hexahydrate solution for 6 hours, taking out and drying. When the operating pressure is 0.1MPa, the retention rate and the flux of the evans blue are respectively 902 percent and 34.2L/m2h bar。
Example 5
The commercial porous membrane is alumina material and is in the form of tubular ultrafiltration membrane, the pore diameter of the membrane is 0.1 μm,the membrane area is 10cm2The selected GO dispersing agent is deionized water, and the concentration of the GO dispersing liquid is 0.003 g/L.
Preparation method of ZIF-11@ f-GO hybrid nanofiltration membrane
(1) Washing an alumina film with the length of about 5cm by using deionized water for pretreatment, removing organic matters, inorganic matters and microorganisms on the surface of the alumina film, and then drying the alumina film in a 50 ℃ drying oven;
(2) dispersing a certain amount of GO powder in deionized water, preparing GO dispersion liquid with a concentration ratio of 0.003g/L by an ultrasonic centrifugation mode, and adding benzimidazole into the GO dispersion liquid with the concentration of 1 mol/L;
(3) assembling the GO-based dispersion liquid prepared in the step (2) on the treated alumina membrane in a suction filtration and deposition mode, wherein the suction filtration pressure is 0.1MPa, and the suction filtration time is 3 min;
(4) directly putting the wet GO composite membrane prepared in the step (3) into a freeze drying box, wherein the temperature is-50 ℃, and the ice crystallization time is 3 hours; then carrying out sublimation drying for 10 h; finally taking out and putting into a 50 ℃ oven for drying for 12 h;
(5) and (3) soaking the prepared f-GO composite membrane in 0.01mol/L zinc nitrate hexahydrate solution for 6 hours, taking out and drying. When the operating pressure is 0.1MPa, the rejection rate and the flux of the methyl blue are respectively 99.8 percent and 25.9L/m2h bar。
Example 6
The commercial porous membrane is made of alumina material and is in the form of tubular ultrafiltration membrane, the pore diameter of the membrane is 0.1 mu m, and the area of the membrane is 10cm2The selected GO dispersing agent is deionized water, and the concentration of the GO dispersing liquid is 0.003 g/L.
Preparation method of ZIF-90@ f-GO hybrid nanofiltration membrane
(1) Washing an alumina film with the length of about 5cm by using deionized water for pretreatment, removing organic matters, inorganic matters and microorganisms on the surface of the alumina film, and then drying the alumina film in a 50 ℃ drying oven;
(2) dispersing a certain amount of GO powder in deionized water, preparing GO dispersion liquid with a concentration ratio of 0.003g/L by using an ultrasonic centrifugation mode, and adding zinc nitrate tetrahydrate with a concentration of 0.01 mol/L;
(3) assembling the GO-based dispersion liquid prepared in the step (2) on the treated alumina membrane in a suction filtration and deposition mode, wherein the suction filtration pressure is 0.1MPa, and the suction filtration time is 3 min;
(4) directly putting the wet GO composite membrane prepared in the step (3) into a freeze drying box, wherein the temperature is-50 ℃, and the ice crystallization time is 3 hours; then carrying out sublimation drying for 10 h; finally taking out and putting into a 50 ℃ oven for drying for 12 h;
(5) and (3) soaking the prepared f-GO composite membrane in 1mol/L imidazole-2-formaldehyde solution for 6 hours, taking out and drying. When the operating pressure is 0.1MPa, the rejection rate and the flux of the methyl blue are respectively 99.6 percent and 21.8L/m2h bar。
Example 7
The method adopts a commercialized porous membrane as a zirconia material and is in the form of a tubular ultrafiltration membrane, the pore diameter of the membrane is 0.1 mu m, and the area of the membrane is 10cm2The selected GO dispersing agent is deionized water, and the concentration of the GO dispersing liquid is 0.003 g/L.
Preparation method of Cu-BTC @ f-GO hybrid membrane
(1) Washing an alumina film with the length of about 5cm by using deionized water for pretreatment, removing organic matters, inorganic matters and microorganisms on the surface of the alumina film, and then drying the alumina film in a 50 ℃ drying oven;
(2) dispersing a certain amount of GO powder in deionized water, preparing GO dispersion liquid with a concentration ratio of 0.003g/L by an ultrasonic centrifugation mode, and adding copper nitrate with the concentration of 0.01 mol/L;
(3) assembling the GO-based dispersion liquid prepared in the step (2) on the treated alumina membrane in a suction filtration and deposition mode, wherein the suction filtration pressure is 0.1MPa, and the suction filtration time is 3 min;
(4) directly putting the wet GO composite membrane prepared in the step (3) into a freeze drying box, wherein the temperature is-50 ℃, and the ice crystallization time is 3 hours; then carrying out sublimation drying for 10 h; finally taking out and putting into a 50 ℃ oven for drying for 12 h;
(5) and (3) soaking the prepared f-GO composite membrane in 0.06mol/L trimellitic acid for 6h, taking out and drying. When the operation pressure is 0.1MPa, the retention rate and the flux of the chromium black T are respectively 96.9 percent and 31.6L/m2h bar。
Example 8
The commercial porous membrane is made of alumina material and is in the form of tubular ultrafiltration membrane, the pore diameter of the membrane is 0.1 mu m, and the area of the membrane is 10cm2The selected GO dispersing agent is deionized water, and the concentration of the GO dispersing liquid is 0.003 g/L.
Preparation method of ZIF-8@ f-GO hybrid nanofiltration membrane
(1) Washing an alumina film with the length of about 5cm by using deionized water for pretreatment, removing organic matters, inorganic matters and microorganisms on the surface of the alumina film, and then drying the alumina film in a 50 ℃ drying oven;
(2) dispersing a certain amount of GO powder in deionized water, preparing GO dispersion liquid with a concentration ratio of 0.003g/L by an ultrasonic centrifugation mode, and adding 2-methylimidazole with the concentration of 10 mol/L;
(3) assembling the GO-based dispersion liquid prepared in the step (2) on the treated alumina membrane in a suction filtration and deposition mode, wherein the suction filtration pressure is 0.1MPa, and the suction filtration time is 3 min;
(4) directly putting the wet GO composite membrane prepared in the step (3) into a freeze drying box, wherein the temperature is-50 ℃, and the ice crystallization time is 3 hours; then carrying out sublimation drying for 10 h; finally taking out and putting into a 50 ℃ oven for drying for 12 h;
(5) and (3) soaking the prepared f-GO composite membrane in 1mol/L zinc nitrate hexahydrate solution for 6 hours, taking out and drying. When the operating pressure is 0.1MPa, the rejection rate and the flux of the methyl blue are respectively 99.8 percent and 18.1L/m2h bar。
Example 9
The commercial porous membrane is made of alumina material and is in the form of tubular ultrafiltration membrane, the pore diameter of the membrane is 0.1 mu m, and the area of the membrane is 10cm2The selected GO dispersing agent is deionized water, and the concentration of the GO dispersing liquid is 0.003 g/L.
Preparation method of ZIF-8@ f-GO hybrid nanofiltration membrane
(1) Washing an alumina film with the length of about 5cm by using deionized water for pretreatment, removing organic matters, inorganic matters and microorganisms on the surface of the alumina film, and then drying the alumina film in a 50 ℃ drying oven;
(2) dispersing a certain amount of GO powder in deionized water, preparing GO dispersion liquid with a concentration ratio of 0.003g/L by an ultrasonic centrifugation mode, and adding 2-methylimidazole with the concentration of 1 mol/L;
(3) assembling the GO-based dispersion liquid prepared in the step (2) on the treated alumina membrane in a suction filtration and deposition mode, wherein the suction filtration pressure is 0.1MPa, and the suction filtration time is 3 min;
(4) directly putting the wet GO composite membrane prepared in the step (3) into a freeze drying box, wherein the temperature is-50 ℃, and the ice crystallization time is 3 hours; then carrying out sublimation drying for 10 h; finally taking out and putting into a 50 ℃ oven for drying for 12 h;
(5) and (3) soaking the prepared f-GO composite membrane in 10mol/L zinc nitrate hexahydrate solution for 6 hours, taking out and drying. When the operating pressure is 0.1MPa, the rejection rate and the flux of the methyl blue are respectively 98.9 percent and 16.2L/m2h bar。

Claims (10)

1. A method for preparing MOFs @ f-GO hybrid membranes in situ by using a freeze drying technology is characterized by comprising the following steps:
(1) pretreating the porous base membrane to remove organic matters, inorganic matters and microorganisms on the surface of the porous base membrane;
(2) dispersing GO powder in deionized water, and preparing a GO dispersion liquid in an ultrasonic centrifugation mode;
(3) adding a certain amount of metal coordination ions or organic ligands into the GO dispersion liquid;
(4) assembling the GO-based dispersion liquid on the surface of a porous base membrane in a suction filtration deposition mode to prepare a wet GO-based composite membrane;
(5) preparing the wet GO-based composite membrane obtained in the step (4) into a loose GO-based composite membrane by utilizing a freeze drying technology;
(6) correspondingly immersing the composite membrane obtained in the step (5) into an organic ligand solution or a metal coordination ion solution for MOFs in-situ hybrid growth, and preparing the metal organic framework @ graphene oxide (MOFs @ f-GO) hybrid nanofiltration membrane.
2. The method according to claim 1, wherein the base membrane is an inorganic porous membrane of a tubular membrane or a flat membrane, the membrane material is alumina, silica or zirconia, and the pore diameter of the porous membrane is 0.1 to 1.0 μm.
3. The process according to claim 1, wherein the GO dispersion used for assembly in step (2) has a concentration of 0.001-0.5% by mass.
4. The process according to claim 1, wherein the concentration of metal coordinating ions or organic ligands in the GO dispersion in step (3) is 0.01 to 1 mol/L.
5. The method according to claim 1, wherein in the step (4), the pressure range of the suction filtration deposition is 0.01-0.1 MPa, and the deposition time range is 0.1-10 min.
6. The method according to claim 1, wherein the freeze drying technology in the step (5) comprises the steps of firstly freezing ice for crystallization and then carrying out sublimation under reduced pressure, wherein the freezing temperature is-10 to-50 ℃, the ice crystallization time is 0.5 to 3 hours, the sublimation pressure under reduced pressure is 1 to 10Pa, and the sublimation drying time is 1 to 10 hours.
7. The method according to claim 1, wherein the reaction temperature in the step (6) is 20 to 60 ℃ and the reaction time is 1 to 36 hours.
8. The method according to claim 1, wherein the molar concentration of the organic ligand solution or the coordinated metal ion solution corresponding to step (6) is 0.01 to 10 mol/L.
9. A MOFs @ f-GO hybrid membrane prepared according to the process of any one of claims 1 to 8.
10. Use of a MOFs @ f-GO hybrid membrane prepared according to any one of claims 1 to 8 for the separation of dyes in water, higher salts and small molecules in organic phase.
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CN107413204A (en) * 2017-07-17 2017-12-01 大连理工大学 The method for preparing highly oriented two-dimensional metallic organic backbone nanometer chip film using the inducing zinc growth of graphene oxide confinement

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