CN116139712A - Preparation method and application of composite nano material modified organic film - Google Patents

Preparation method and application of composite nano material modified organic film Download PDF

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CN116139712A
CN116139712A CN202310041216.1A CN202310041216A CN116139712A CN 116139712 A CN116139712 A CN 116139712A CN 202310041216 A CN202310041216 A CN 202310041216A CN 116139712 A CN116139712 A CN 116139712A
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film
composite
dcn
pvdf
carbon nitride
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王锦
张清云
周朝煦
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Beijing Jiaotong University
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    • 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
    • B01D71/30—Polyalkenyl halides
    • B01D71/32—Polyalkenyl halides containing fluorine atoms
    • B01D71/34—Polyvinylidene fluoride
    • 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
    • B01D67/0002—Organic membrane manufacture
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • 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
    • B01D71/30—Polyalkenyl halides
    • B01D71/32—Polyalkenyl halides containing fluorine atoms
    • B01D71/36—Polytetrafluoroethene
    • 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
    • B01D71/40—Polymers of unsaturated acids or derivatives thereof, e.g. salts, amides, imides, nitriles, anhydrides, esters
    • B01D71/42—Polymers of nitriles, e.g. polyacrylonitrile
    • 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
    • B01D71/66—Polymers having sulfur in the main chain, with or without nitrogen, oxygen or carbon only
    • B01D71/68—Polysulfones; Polyethersulfones
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/14—Membrane materials having negatively charged functional groups
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/36—Hydrophilic membranes

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Abstract

The invention provides a preparation method and application of a novel composite nanomaterial modified organic membrane, which belongs to the technical field of filtering membranes for sewage treatment, wherein a modified carbon nitride nanocomposite prepared from a graphite-phase carbon nitride nanomaterial and a pore-forming agent are added into an organic solvent, a mixed solution is obtained by ultrasonic treatment, then a polymeric polymer membrane material is added into the mixed solution, and the mixed solution is stirred at constant temperature, kept stand and defoamed to form a membrane casting solution; preparing the composite nano material by using the prepared casting film liquidAnd (3) modifying the organic film. The invention improves C 3 N 4 The hydrophilicity and dispersibility of the nano material in the casting film liquid accelerate the phase inversion rate of the composite film, improve the porosity of the film, increase the electronegativity of the film, improve the anti-pollution performance of the film, and solve the problems of low flux, serious film pollution and the like in the operation of the composite organic film.

Description

Preparation method and application of composite nano material modified organic film
Technical Field
The invention relates to the technical field of filtering membranes for sewage treatment, in particular to a preparation method and application of a composite nano material modified organic membrane.
Background
The membrane technology has the advantages of high separation efficiency, low energy consumption and the like, and is widely applied to a plurality of fields. Organic membranes such as polyvinylidene fluoride (PVDF), polysulfone (PSF), polyethersulfone (PES), polyacrylonitrile (PAN) and Polytetrafluoroethylene (PTFE) membranes have been widely used in industrial microfiltration and ultrafiltration processes due to their excellent mechanical properties, thermal stability, chemical resistance and simple preparation process. However, the organic membrane has strong hydrophobicity and is easy to adsorb organic impurities to be polluted, so that the membrane resistance is increased, the membrane flux is reduced, and the membrane is frequently cleaned and replaced chemically. The method for constructing the mixed matrix ultrafiltration membrane by adding the hydrophilic nano material into the ultrafiltration membrane is a convenient and effective method for improving the antifouling performance of the membrane.
Graphite phase carbon nitride (g-C) 3 N 4 ) Having a plurality of nanopores, providing transport channels and providing a molecular sieving effect during solution transport. In g-C 3 N 4 On the basis, a series of C with larger specific surface area and better photocatalysis performance can be obtained through modification 3 N 4 For example mesoporous g-C 3 N 4 (MCN), nitrogen-enriched g-C 3 N 4 (NCN) and Defect g-C 3 N 4 (DCN). Nitrogen deficiency g-C 3 N 4 (DCN) has a higher surface area, more reactive sites and stronger interactions with the membrane matrix. However, DCN has insufficient hydrophilicity, which hinders the improvement of flux and anti-fouling performance of the composite membrane, and therefore, further modification is required.
Disclosure of Invention
The invention aims to provide a preparation method and application of a composite nano material modified organic film, which are used for solving at least one technical problem in the background technology.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the invention provides a preparation method of a composite nano material modified organic film, which comprises the following steps:
adding a modified carbon nitride nanocomposite prepared from a graphite-phase carbon nitride nanomaterial and a pore-forming agent into an organic solvent, performing ultrasonic treatment to obtain a mixed solution, adding a polymer membrane material into the mixed solution, stirring at a constant temperature, standing and defoaming to form a membrane casting solution;
and preparing the composite nano material modified organic film by using the prepared film casting solution.
Preferably, the modified carbon nitride nanocomposite is obtained by uniformly grinding graphite-phase carbon nitride nanomaterial and graphene oxide at a mass ratio of 1:1.
Preferably, the mass ratio of the modified carbon nitride nanocomposite to the pore-forming agent is 1:1-2.5:1, the mass ratio of the pore-forming agent to the organic solvent is 1:81-1:84, and the mass ratio of the modified carbon nitride nanocomposite to the polymeric polymer film material is 1:6-1:15.
Preferably, the modified carbon nitride nanocomposite is prepared by ultrasonically dispersing graphite-phase carbon nitride nanomaterial and dopamine hydrochloride in Tris buffer, centrifuging, washing, and drying to obtain polydopamine-coated C 3 N 4 A composite material.
Preferably, the mass ratio of the modified carbon nitride nanocomposite to the pore-forming agent ranges from 1:1 to 1:3, the mass ratio of the pore-forming agent to the organic solvent ranges from 1:27 to 1:83, and the mass ratio of the modified carbon nitride nanocomposite to the PFM ranges from 1:10 to 1:15.
Preferably, the pH value of the Tris buffer solution is 7.8-8.5, the concentration of dopamine is 1-10g/L, and the mass ratio of the graphite phase carbon nitride nano material to the dopamine is 1:0.2-1:2.
Preferably, the graphite phase carbon nitride nanomaterial is mesoporous g-C 3 N 4 Nitrogen-rich g-C 3 N 4 Or defect g-C 3 N 4 One of them.
Preferably, the polymeric polymer membrane material is one of polyvinylidene fluoride, polysulfone, polyethersulfone, polyacrylonitrile or polytetrafluoroethylene.
Preferably, the pore-forming agent is polyvinylpyrrolidone PVP or polyethylene glycol PEG.
Preferably, the organic solvent is one of 1-methyl-2-pyrrolidone NMP, dimethylformamide DMF or dimethylacetamide DMAc.
The invention has the beneficial effects that: c is improved 3 N 4 The hydrophilicity and dispersibility of the nano material in the casting film liquid accelerate the phase inversion rate of the composite film, improve the porosity of the film, increase the electronegativity of the film, improve the anti-pollution performance of the film, and solve the problems of low flux, serious film pollution and the like in the operation of the composite organic film.
The advantages of additional aspects of the invention will be set forth in part in the description which follows, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 shows a PVDF membrane and PVDF/GO@DCN according to an embodiment of the present invention 2.0 Surface SEM image of the composite film; wherein, (a) is a PVDF membrane; (b) The chart is PVDF/GO@DCN 2.0 And (3) a composite membrane.
Fig. 2 is a graph of contact angle measurements of GO and DCN modified composite membranes and PVDF membranes according to an embodiment of the invention.
Fig. 3 is a three-phase diagram of a GO and DCN modified composite membrane and PVDF membrane according to an embodiment of the invention.
FIG. 4 is a graph showing interactions of GO and DCN modified composite membranes and PVDF membranes with bovine serum albumin according to an embodiment of the present invention.
Fig. 5 is a schematic diagram showing interactions between go@dcn and a composite membrane according to an embodiment of the present invention. Wherein, (c) is a graph of RDG and electron density (ρ) of PVDF/go@dcn multiplied by the sign of the second Hessian eigenvalue (λ2), and (d) is the RDG isosurface of PVDF/go@dcn (s=0.5a.u.).
FIG. 6 is a graph showing the results of permeation (pure water flux) and bovine serum albumin entrapment experiments of GO and DCN modified composite membranes according to the examples of the present invention.
FIG. 7 is a graph showing the results of a cyclic experiment of the filtration of bovine serum albumin by the GO and DCN modified composite membrane according to the example of the present invention.
FIG. 8 is a PVDF according to an embodiment of the present invention 2 Membrane and PVDF 2 /PDA 2.5 Cross-section and surface SEM images of @ DCN composite membrane; (a) The figure is PVDF 2 A membrane; (b) The figure is PVDF 2 /PDA 2.5 @ DCN composite membrane.
FIG. 9 is a PVDF according to an embodiment of the present invention 2 /PDA 2.5 @ DCN composite membrane and PVDF 2 DCN composite membrane and PVDF 2 Contact angle measurement plot of the film.
FIG. 10 is a PVDF according to an embodiment of the present invention 2 /PDA 2.5 @ DCN composite membrane and PVDF 2 DCN composite membrane and PVDF 2 Three-phase diagram of the film.
FIG. 11 is a PVDF according to an embodiment of the present invention 2 /PDA 2.5 @DCN、PVDF 2 DCN and PVDF 2 Viscosity map of casting solution.
FIG. 12 is a PVDF according to an embodiment of the present invention 2 Membrane, PVDF 2 DCN composite membrane and PVDF 2 /PDA 2.5 Interaction energy between the @ DCN complex film and BSA.
FIG. 13 is a graph showing the permeability (pure water flux) and the entrapment test result of bovine serum albumin of the DCN and PDA@DCN modified composite membrane according to the example of the present invention.
FIG. 14 is a graph showing the results of a cyclic experiment of the filtration of bovine serum albumin by the DCN and PDA@DCN modified composite film according to the embodiment of the invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements throughout or elements having like or similar functionality. The embodiments described below by way of the drawings are exemplary only and should not be construed as limiting the invention.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless expressly stated otherwise, as understood by those skilled in the art. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and/or groups thereof.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
In order that the invention may be readily understood, a further description of the invention will be rendered by reference to specific embodiments that are illustrated in the appended drawings and are not to be construed as limiting embodiments of the invention.
It will be appreciated by those skilled in the art that the drawings are merely schematic representations of examples and that the elements of the drawings are not necessarily required to practice the invention.
Example 1
In this embodiment 1, a method for preparing a go@dcn modified organic film is provided, including:
step 1) modified carbon nitride C 3 N 4 And graphene oxide GO is ground in a glass mortar for 50min in a mass ratio of 1:1 until completely uniform, denoted GO@C 3 N 4 A nanocomposite.
Step 2) GO@C 3 N 4 And a pore-forming agent are added into an organic solvent, wherein GO@C 3 N 4 The mass ratio of the polymer film material to the pore-forming agent is 1:1-2.5:1, the mass ratio of the pore-forming agent to the organic solvent is 1:81-1:84, the mixed solution is obtained by ultrasonic treatment, and then the polymer film material PFM, GO@C is added into the mixed solution 3 N 4 And PFM with a mass ratio of 1:6-1:15, stirring at constant temperature, standing and defoaming to form casting film liquid;
pouring the prepared casting solution to one side of a clean and dry glass plate, scraping a liquid film by using a square coater, immersing the glass plate with the scraped liquid film into deionized water for phase exchange, taking out the film after the casting solution is solidified to form a film, immersing in the deionized water, and removing residual organic solvent to obtain GO@C 3 N 4 And modifying the organic film.
Wherein, graphite phase carbon nitride C 3 N 4 Is mesoporous g-C 3 N 4 (MCN), nitrogen-enriched g-C 3 N 4 (NCN) or Defect g-C 3 N 4 (DCN). The Graphene Oxide (GO) is one of sulfonated graphene oxide and carboxylated graphene oxide. The PFM is one of polyvinylidene fluoride, polysulfone, polyethersulfone, polyacrylonitrile or polytetrafluoroethylene. The pore-forming agent is one of polyvinylpyrrolidone PVP and polyethylene glycol PEG, and the organic solvent is one of 1-methyl-2-pyrrolidone NMP, dimethylformamide DMF and dimethylacetamide DMAc.
In the step 1), the power of the ultrasonic wave is 500W, and the ultrasonic wave time is 1h; the constant temperature stirring temperature is 50 ℃, the rotating speed is 200rpm, and the stirring time is 12 hours; the standing and defoaming time is 12 hours. Before immersing the glass plate with the scraped liquid film in deionized water for exchange in the step 2), the glass plate with the scraped liquid film still needs to be kept stand in the air for 15s. The thickness of the liquid film in the step 2) is 250 mu m, and the liquid film is placed in deionized water for soaking for 24 hours.
PFM is polyvinylidene fluoride PVDF, and the mass ratio of GO@DCN to PVDF is 1:15.
In this embodiment, GO@C prepared by the method described above 3 N 4 Modified organic film and GO@C prepared by using same 3 N 4 The application of the modified organic film in catalyzing and degrading pollutants in water.
In this example 1, the oxygen-containing functionality of GO inhibits C 3 N 4 And C 3 N 4 And the covalent interactions between GO expand the interlayer spacing of GO. Ordered interlayer spacing increases the permeability and stability of the membrane. The flux of the prepared composite membrane is improved by 2.3 times, and the retention rate is improved by 91.6%; GO@C 3 N 4 The thermodynamic phase inversion of the modified organic film accelerates, resulting in an increase in porosity, thereby opening up the passage of water molecules. GO@C 3 N 4 The modified organic film is easy to recycle, and solves the problems of difficult material separation and recycling and easy secondary pollution generation; at the same time GO@C 3 N 4 The electronegativity of the modified organic film is increased, and the modified organic film has a repulsive interaction with electronegative pollutants in water, so that the anti-pollution performance of the film is improved; the removal efficiency of the modified film on pollutants in water is directly examined under the room temperature condition.
In this example 1, C was prepared 3 N 4 And GO modified organic membranes for use in the entrapment of target contaminants, C 3 N 4 And GO is combined with mechanical grinding to improve the film forming property, and meanwhile, the modified organic film solves the problems of low flux, serious film pollution and the like in the operation of an ultrafiltration film. C (C) 3 N 4 And the GO modified organic membrane flux is improved by 2.3 times, the BSA rejection rate is improved by 91.6 percent, the stability of the membrane structure and performance is good, the preparation method is simple to operate, the condition is mild, the production cost is low, the mass production is easy, and the application prospect is wide.
Example 2
In this example 2, a PDA@C is provided 3 N 4 A method for preparing a modified organic film comprising:
step 1) weighing a certain amount of C 3 N 4 Nanomaterial and dopamine hydrochloride are ultrasonically dispersed in Tris buffer (10 mmol.L) -1 pH is approximately equal to 8.5), stirring for 24 hours at 25 ℃, centrifuging, washing and drying the mixed solution to obtain the polydopamine-coated C 3 N 4 Composite material, named PDA@C 3 N 4 。
Step 2) PDA@C 3 N 4 And pore-forming agent are added into organic solvent, PDA@C 3 N 4 The mass ratio of the pore-forming agent to the pore-forming agent is in the range of 1:1-1:3, the mass ratio of the pore-forming agent to the organic solvent is in the range of 1:27-1:83, the mixed solution is obtained by ultrasonic treatment, and the polymeric polymer membrane material PFM and PDA@C are added into the mixed solution 3 N 4 And PFM with a mass ratio of 1:10-1:15, stirring at constant temperature, standing and defoaming to form casting film liquid;
pouring the casting solution on a glass plate to scrape a liquid film, exposing the glass plate in air for a period of time, immersing the glass plate in deionized water for curing to obtain PDA@C 3 N 4 And (3) a composite membrane.
Graphite-phase carbon nitride C 3 N 4 Is mesoporous g-C 3 N 4 (MCN), nitrogen-enriched g-C 3 N 4 (NCN) or Defect g-C 3 N 4 (DCN).
In step 1), the pH of the Tris buffer solution is 7.8-8.5, the concentration of dopamine is 1-10g/L, and the carbon nitride C 3 N 4 The mass ratio of the compound to the dopamine is 1:0.2-1:2; the reaction time is 24 hours; the temperature is controlled at 25 ℃; centrifuging at 10000rpm for 5-10min; washing with deionized water for 3 times; drying by placing in an oven at 60 ℃ for 8-12h.
In the step 2), the power of the ultrasonic wave is 500W, and the ultrasonic wave time is 1h; the constant temperature stirring temperature is 50 ℃, the rotating speed is 200rpm, and the stirring time is 12 hours; the standing and defoaming time is 12 hours.
The PFM is one of polyvinylidene fluoride, polysulfone, polyethersulfone, polyacrylonitrile or polytetrafluoroethylene.
The pore-forming agent is one of polyvinylpyrrolidone PVP and polyethylene glycol PEG, and the organic solvent is one of 1-methyl-2-pyrrolidone NMP, dimethylformamide DMF and dimethylacetamide DMAc.
Before immersing the glass plate with the scraped liquid film in deionized water for exchange in the step 3), the glass plate with the scraped liquid film still needs to be kept stand in the air for 15s.
The thickness of the liquid film in the step 3) is 250 mu m, and the liquid film is placed in deionized water for soaking for 24 hours.
PFM is polyvinylidene fluoride PVDF, PDA@C 3 N 4 The mass ratio of the PVDF to the PVDF is 1:10-1:15.
In this example 2, PDA can be attached to C by covalent, non-covalent interactions and pi-pi bonds 3 N 4 On the surface. PDA attached to C 3 N 4 The surface can provide more hydrophilic groups, and C is increased 3 N 4 Dispersibility in solution and enhanced interfacial compatibility such that PDA@C 3 N 4 The dispersion is more uniform in the film matrix. The prepared composite membrane has more outstanding hydrophilicity, interception capability and anti-pollution performance, the pure water flux can be improved by 77% at most compared with the pure membrane, and the BSA interception rate can reach more than 90%. Can realize self-cleaning under the irradiation of visible light, has flux recovery rate up to 84 percent, and has good stability of membrane structure and performance. The method has the advantages of simple operation, mild condition, low production cost, easy mass production and wide application prospect.
In this example 2, C was prepared 3 N 4 And PDA modified organic film, applied in catalyzing and degrading organic pollutant in water, and prepared C 3 N 4 And the pure water flux of the PDA modified organic film is improved by 77% compared with that of the pure film, and the retention rate of BSA reaches more than 90%; and the self-cleaning can be realized under the illumination condition, and the flux recovery rate reaches 84%. In addition, the modification of the PDA improves the ultraviolet resistance of the composite film, reduces the damage of illumination to the film structure, prolongs the service life of the film, has good stability of the film structure and performance, and has the advantages of simple operation, mild condition, low production cost, easy mass production and wide application prospect.
Example 3
The embodiment 3 provides a preparation method of a GO modified defective carbon nitride DCN modified PVDF ultrafiltration membrane, in particular to a preparation method of a PVDF/GO@DCN composite membrane, which comprises the following steps:
step 1) 500mg of defective carbon nitride DCN and 500mg of Graphene Oxide (GO) are ground in a mortar for 50min until uniform, and the mixture is marked as GO@DCN composite material.
Step 2) adding 33mgGO@DCN and 33mg polyvinylpyrrolidone PVP into 3000mg 1-methyl-2-pyrrolidone NMP, performing ultrasonic treatment in a 500W ultrasonic cleaner for 1h to obtain a mixed solution, adding 500mgPVDF (i.e. polymeric polymer membrane material PFM) into the mixed solution, stirring at a constant temperature of 50 ℃ for 12h, standing and defoaming for 12h to form a membrane casting solution;
pouring the prepared casting solution to one side of a clean and dry glass plate, scraping a liquid film with the thickness of 250 mu m by using a square coater, standing the glass plate with the scraped liquid film in air for 15 seconds, quickly immersing the glass plate in deionized water to complete a phase conversion process, taking out the film after the casting solution is solidified to form a film, immersing the film in the deionized water for 24 hours, and removing residual NMP solvent to obtain the PVDF/GO@DCN composite film.
In addition, PVDF/GO, PVDF/DCN and PVDF/GO@DCN composite films with the following mass ratios are respectively prepared: 33mg of GO nano material is added and accounts for 1% of the total casting solution mass, and the mixture is recorded as PVDF/GO 1.0 The method comprises the steps of carrying out a first treatment on the surface of the 33mg of DCN nano material is added and accounts for 1% of the total casting solution mass, and the obtained product is recorded as PVDF/DCN 1.0 The method comprises the steps of carrying out a first treatment on the surface of the 33mg of GO@DCN nano material is added, and the mass of the nano material accounts for 1% of the total casting solution, and is recorded as PVDF/GO@DCN 1.0 The method comprises the steps of carrying out a first treatment on the surface of the 49.5mg of GO@DCN nano material is added and accounts for 1.5% of the total casting solution in mass, and the mixture is recorded as PVDF/GO@DCN 1.5 The method comprises the steps of carrying out a first treatment on the surface of the 66mg of GO@DCN nano material is added, and the mass of the nano material accounts for 2% of the total casting solution, and is recorded as PVDF/GO@DCN 2.0 The method comprises the steps of carrying out a first treatment on the surface of the 82.5mg of GO@DCN nano material is added and accounts for 2.5% of the total casting solution in mass, and the mixture is marked as PVDF/GO@DCN 2.5 . The PVDF is added in proportion to the other materials.
And performing application experiments on the PVDF/GO@DCN composite film obtained by the different proportions. The specific contents are as follows:
fig. 1 is an SEM image of the present embodiment: wherein, (a) is an SEM image of the PVDF film surface, and the film surface is smooth and has small porosity; (b) PVDF/GO@DCN 2.0 SEM images of the composite membrane surface, a significant increase in porosity can be seen due to the addition of GO@DCN nanocomposites to the polymer solutionThe composite material may increase the phase inversion rate by increasing the thermodynamic instability, such that the porosity of the membrane increases.
FIG. 2 is a graph showing the comparative measurement of contact angles of GO and DCN modified PVDF composite membrane and PVDF membrane of this example, and referring to FIG. 1, it can be seen that the contact angle of the resulting nanocomposite membrane is reduced and follows PVDF>PVDF/DCN 1.0 >PVDF/GO 1.0 >PVDF/GO@DCN 1.0 >PVDF/GO@DCN 2.0 Is a sequence of (a). This indicates PVDF/GO@DCN 2.0 Nanocomposite membranes become more hydrophilic. Compared with the water contact angle 72.37 DEG of an unmodified pure PVDF film, PVDF/GO@DCN 2.0 The water contact angle of the composite film is reduced to 64.12 degrees, which shows that the hydrophilicity of the film is greatly improved after the nano material GO@DCN is added. Covalent interactions between DCN and GO alter the interlayer spacing, increase surface roughness, and increase the hydrophilicity of the membrane. Furthermore, the addition of GO@DCN significantly increases the hydrophilicity of the membrane by exposing the oxygen containing functional groups and enhancing the transition of the PVDF polar structure from the alpha phase to the beta phase.
Fig. 3 is a three-phase diagram of the GO and DCN modified PVDF composite membrane and PVDF membrane of this example, where the miscibility gap (distance between the polymer-solvent axis and the cloud point curve) decreases gradually with the addition of GO, DCN, and go@dcn, indicating that the thermodynamic conversion rate of the liquid-liquid phase separation increases, resulting in an increase in the porosity of the composite membrane. Wherein PVDF/GO@DCN 2.0 The phase inversion rate is the fastest, exhibiting the highest porosity.
FIG. 4 is a graph showing interactions of GO and DCN modified PVDF composite membranes and PVDF membranes of the present embodiment with bovine serum albumin, a contaminant in water. It can be seen that the GO, DCN and GO@DCN modified PVDF composite membrane added has less attraction to BSA, wherein PVDF/DCN 2.0 The repulsive force of the composite membrane on bovine serum albumin is greatly improved after the nano material GO@DCN is added.
FIG. 5 is the electrostatic potential distribution of DCN and GO calculated by DFT and the interaction of PVDF/GO@DCN. Fig. 5 (a) and (b) show that the oxygen-containing functional group region of GO and the nitrogen-deficient region in the DCN structure have strong positive and negative electrical properties. Therefore, strong electrostatic potential penetration is formed between the graphene oxide and the DCN, and the dispersibility of GO@DCN is enhanced. Furthermore, analysis of the non-covalent interactions between go@dcn and PVDF molecules with RDG as shown in fig. 5 (c), the presence of low density green spikes indicates the presence of strong van der waals interactions in the PVDF/go@dcn system. Meanwhile, the red region of low density represents weak repulsive force inside the system. Finally, FIG. 5 (d) shows the determination of the location of the interaction using VMD software. There is van der Waals interaction of the interaction layer between GO and DCN and the interaction region between PVDF and GO@DCN. Thus, the strong interactions inside the PVDF/go@dcn system promote membrane permeability and antifouling properties, consistent with the conclusions of thermodynamics and XDLVO.
FIG. 6 shows the flux of the sample and its retention properties for bovine serum albumin (BSA, molecular weight 66.430 kDa) in water. After hydrophilic materials GO, DCN and GO@DCN are added, the water flux is obviously improved; in particular PVDF/GO@DCN 2.0 The water flux of (a) reaches 387.80L/m -2 h -1 . The addition of GO@DCN can effectively improve the hydrophilicity and the surface roughness of the membrane; thus, the membrane can absorb more water molecules. Addition of go@dcn resulted in transient phase separation; this increases the porosity of the membrane, resulting in a better water flux. At the same time, all nanocomposite membranes showed higher BSA rejection than the pure PVDF membrane. PVDF/GO@DCN 2.0 The rejection rate of (2) is highest and reaches 91.6%.
The membrane was hydraulically backwashed after one cycle (90 min) and then the contaminants were filtered a second time to evaluate the membrane for reusability, with the membrane being evaluated for 5 complete filtration cycles. Referring to FIG. 7, PVDF/GO@DCN in this embodiment 2.0 The composite membrane still exhibits reusability superior to that of pure PVDF membrane after 5 uses. Therefore, the PVDF/GO@DCN composite film has good stability and practical applicability.
Example 4
The embodiment provides a polydopamine PDA modified carbon nitride PDA@C 3 N 4 The preparation method of the modified organic film, in particular to a preparation method of a PVDF/PDA@DCN composite film, which comprises the following steps:
step 1) weighing a certain amount of DCN nano material and dopamine hydrochloride, and ultrasonically dispersing the DCN nano material and the dopamine hydrochloride in a Tris buffer solution (10 mmol.L) -1 pH ≡ 8.5) such that the concentration of DCN in the solution is 5g +.L, the concentration of dopamine is 2.5g/L, stirring is carried out for 24 hours at 25 ℃, the stirring speed is 750rpm, and then the mixed solution is centrifuged for 6 minutes at 10000 rpm; washing with deionized water for 3 times; drying the obtained polydopamine-attached DCN composite material was dried in an oven at 60℃for 12 hours, and the obtained polydopamine-attached DCN composite material was named PDA@DCN.
Step 2) adding 33mgPDA@DCN and 33mg polyvinylpyrrolidone (PVP) into 3000mg 1-methyl-2-pyrrolidone (NMP), carrying out ultrasonic treatment for 1h to obtain a mixed solution, and adding 500mgPVDF (namely a polymer membrane material PFM) into the mixed solution, wherein the mass ratio of the PDA@DCN to the PFM is 1:15, stirring for 12h at 50 ℃, standing and defoaming for 12h to form a casting solution;
casting the defoamed casting solution on a glass plate, scraping a liquid film with the thickness of 250 mu m by using a square coater, standing the glass plate with the scraped liquid film in air for 15 seconds, quickly immersing the glass plate in deionized water to complete the cross-conversion process, taking out the glass plate after the liquid film is solidified, immersing the glass plate in the deionized water for 24 hours, and removing residual solvent to obtain the PVDF/PDA@DCN composite film.
PVDF/PDA@DCN composite films with different dopamine and carbon nitride and PVP mass ratios are prepared respectively and named PVDF X /PDA Y @ DCN, wherein X represents PVP addition in step 2 and Y represents dopamine concentration in step 1. The concentration of PDA is 1, 2.5, 5, 10g/L, PVP is 1-3% of total casting solution. The PDA@DCN was added in an amount of 33mg. And performing application experiments on PVDF/PDA@DCN composite films obtained by different proportions. The specific contents are as follows:
fig. 8 is an SEM image of the present embodiment. a, a 1 And b 1 Is PVDF 2 And PVDF (polyvinylidene fluoride) 2 /PDA 2.5 Cross-section SEM pictures @ DCN. Adding PDA 2.5 After @ DCN, the composite membrane fingers Kong Bianchang widen, reducing the water transport resistance in the membrane. a, a 2 And b 2 PVDF is shown therein 2 And PVDF (polyvinylidene fluoride) 2 /PDA 2.5 @ DCN surface SEM image. PVDF (polyvinylidene fluoride) 2 /PDA 2.5 The number of pores on the surface of the @ DCN is obviously increased, and the distribution is more uniform.
The hydrophilicity of a composite membrane surface is usually expressed by the static contact angle of pure water on the membrane surface, the contact angleSmaller represents better hydrophilicity of the membrane surface. FIG. 9 is a PVDF of the present example 2 /PDA 2.5 @ DCN composite membrane and PVDF 2 DCN composite membrane and PVDF 2 Water contact angle measurement plot of the film. In FIG. 9, PVDF 2 /PDA 2.5 @ DCN composite membrane and PVDF 2 DCN composite membrane and PVDF 2 The water contact angles of the films are 64.2 degrees, 73.2 degrees and 73.6 degrees respectively, which shows that the hydrophilicity of the films is greatly improved after the nano material PDA@DCN is added.
PVDF as shown in FIG. 10 2 And PVDF (polyvinylidene fluoride) 2 PVDF as compared to DCN 2 /PDA 2.5 The double-pitch line of @ DCN was closer to the polymer-solvent axis, indicating PVDF 2 /PDA 2.5 The casting solution at DCN requires minimal non-solvent (water) for phase inversion and is thermodynamically least stable. The faster the cast film with poor thermodynamic stability is transformed into liquid phase, the higher porosity composite film is formed.
PVDF is shown in FIG. 11 2 ，PVDF 2 DCN and PVDF 2 /PDA 2.5 Viscosity of casting solution @ DCN. PDA 2.5 @DCN/PVDF 2 The viscosity of the casting solution is less than that of PVDF 2 DCN slightly greater than PVDF 2 Casting solution, indicating PDA 2.5 The @ DCN reduces the viscosity increase compared to DCN while due to the nanomaterial PDA 2.5 The @ DCN improves the hydrophilicity of the casting solution, so that the exchange rate of the solvent and the non-solvent is accelerated, and the porosity is increased.
FIG. 12 is PVDF 2 ，PVDF 2 DCN and PVDF 2 /PDA 2.5 Interaction diagram of @ DCN with BSA. With PVDF 2 And PVDF (polyvinylidene fluoride) 2 BSA compared to PVDF 2 /PDA 2.5 The total interaction between @ DCN can be reduced by 33% and 25%, respectively. This indicates that PVDF 2 /PDA 2.5 The attracting effect of the @ DCN composite membrane on BSA is reduced, and the anti-fouling capability is stronger.
The performance of the composite membrane samples was evaluated by the permeability and contaminant rejection. The average pure water flux was measured after pre-pressing the membrane for 1h at a pressure of 0.15MPa before testing. The contaminant rejection experiment was filtered using a bovine serum albumin solution (BSA, 500 ppm) at a pressure of 0.10 MPa. Detection using ultraviolet spectrophotometersComparison of the ratio of ABS values before and after BSA solution filtration to evaluate the filtration performance of the membrane, the permeability of the composite membrane and the retention effect on BSA are shown in fig. 13. PVDF of optimal Performance 1 /PDA 2.5 @ DCN composite membranes compared to PVDF 1 The membrane improves the pure water flux by 77 percent, PVDF 2 /PDA 2.5 Comparative PVDF @ DCN composite membranes 2 The pure water flux of the DCN composite membrane is improved by 34 percent. The retention rate of PVDF/PDA@DCN composite membrane to BSA is higher while the flux of pure water is kept higher, and the PVDF has optimal performance 2 /PDA 2.5 The retention rate of BSA of the @ DCN composite membrane reaches 94%, while PVDF 2 DCN composite membrane and PVDF 2 The membrane BSA rejection was 87% and 85%, respectively.
The membrane was hydraulically backwashed after one cycle (90 min) and then the contaminants were filtered a second time to evaluate the membrane's reusability using 5 complete filtration cycles. Referring to FIG. 14, PVDF of the present invention 2 /PDA 2.5 After 5 uses of the @ DCN composite membrane, the BSA removal effect still reaches 91.7%. PVDF of optimal Performance 2 /PDA 2.5 Flux recovery rate of the @ DCN composite membrane is 62.7%, compared with PVDF 1 The film was improved by about 12.7%. PVDF (polyvinylidene fluoride) 2 /PDA 2.5 The @ DCN composite membrane still has the highest pure water flux and BSA flux after multiple cycles, indicating PVDF 2 /PDA 2.5 The @ DCN composite film has good stability and practical applicability.
Photocatalytic self-cleaning properties of samples the self-cleaning ability of the membranes was evaluated by filtering BSA with the prepared membranes for 1 hour, then exposing it to visible light under a 300W xenon lamp that filtered out wavelengths below 420nm for 2 hours, measuring again the flux of the membranes, and using the FRR values. Each group of experiments are repeated three times, so that the accuracy of the experiments is ensured. FIG. 14 is a graph of the photocatalytic self-cleaning results of composite membranes against BSA. After irradiation with visible light for 2 hours, compared with pure PVDF 1 Membrane flux recovery of 47.7%, PVDF 2 /PDA 2.5 The flux recovery rate of the @ DCN composite membrane can reach 84.6%, and the flux recovery rate is improved by 36.9%. Meanwhile, FIG. 14 shows PVDF 2 /PDA 2.5 The composite film still maintains good separation performance after 5 times of illumination, which indicates that the PDA@DCN nano particles not only have photocatalytic activity, but also endowThe pre-film has self-cleaning capability, and the polymer film has higher performance stability and service life in the visible light irradiation process.
In summary, the embodiment of the invention provides a Graphene Oxide (GO) or dopamine (PDA) modified C 3 N 4 The preparation method and application of the composite material modified organic ultrafiltration membrane are used for solving the defects existing in the prior art. Graphene Oxide (GO) is a product of graphite powder after chemical oxidation and stripping, has the advantages of being resistant to organic solvents, rich in oxygen-containing functional groups, capable of reducing energy between interfaces, easy to modify and the like, and meanwhile, the GO cost is relatively low. Hydrophilic GO material and modified C 3 N 4 The preparation method is simple by combining mechanical grinding, and can improve the electronegativity and film forming property of the material. Polydopamine (PDA) is formed by automatic oxidation polymerization of Dopamine (DA) under weak base condition, and can be stably deposited on various inorganic materials through forming strong covalent and non-covalent bonds with a matrix between interfaces. Hydrophilic functional groups in PDA disrupt g-C 3 N 4 The van der Waals acting force among the particles enhances the compatibility with the solvent, and improves the dispersibility of the composite material in the solvent. The hydroxyl (-OH) and amino (-NH) groups in the polydopamine can be used as electron donors to provide hydrogen atoms to replace free radicals generated in the photodegradation stage to abstract hydrogen in polymer chains, so that photodegradation of the polymer is limited and the photoaging resistance of the composite membrane is improved. Through the DCN nano material modified and modified by GO and PDA, the exchange rate between the solvent and the non-solvent in the non-solvent phase conversion process is promoted, the thermodynamic instability of the casting solution is increased, and the enhancement of the performance of the composite membrane is facilitated in the aspects of membrane preparation dynamics and thermodynamics. The main solution strategy for membrane pollution is to reduce the interaction force between the pollutant and the membrane surface and improve the self-cleaning performance of the membrane surface pollutant. The hydrophilic modification modified carbon nitride nano material is introduced to enhance the hydrophilicity and the surface electronegativity of the composite membrane, so that the interaction between pollutants and the membrane surface is reduced, and the adhesion of the pollutants on the membrane surface is reduced.
While the foregoing description of the embodiments of the present invention has been presented in conjunction with the drawings, it should be understood that it is not intended to limit the scope of the invention, but rather, it should be understood that various changes and modifications could be made by one skilled in the art without the need for inventive faculty, which would fall within the scope of the invention.

Claims (10)

1. The preparation method of the composite nano material modified organic film is characterized by comprising the following steps:
adding a modified carbon nitride nanocomposite prepared from a graphite-phase carbon nitride nanomaterial and a pore-forming agent into an organic solvent, performing ultrasonic treatment to obtain a mixed solution, adding a polymer membrane material into the mixed solution, stirring at a constant temperature, standing and defoaming to form a membrane casting solution;
and preparing the composite nano material modified organic film by using the prepared film casting solution.
2. The method for preparing the composite nanomaterial modified organic film of claim 1, wherein the modified carbon nitride nanocomposite is obtained by uniformly grinding graphite-phase carbon nitride nanomaterial and graphene oxide in a mass ratio of 1:1.
3. The method for preparing the composite nanomaterial modified organic film according to claim 2, wherein the mass ratio of the modified carbon nitride nanocomposite to the pore-forming agent is 1:1-2.5:1, the mass ratio of the pore-forming agent to the organic solvent is 1:81-1:84, and the mass ratio of the modified carbon nitride nanocomposite to the polymeric polymer film material is 1:6-1:15.
4. The method for preparing the composite nanomaterial modified organic film according to claim 1, wherein the modified carbon nitride nanocomposite is prepared by ultrasonically dispersing graphite-phase carbon nitride nanomaterial and dopamine hydrochloride in Tris buffer solution, centrifuging the mixed solution, washing, and drying to obtain polydopamine-coated C 3 N 4 A composite material.
5. The method for preparing a composite nanomaterial modified organic film as claimed in claim 4, wherein the mass ratio of the modified carbon nitride nanocomposite to the pore-forming agent is in the range of 1:1-1:3, the mass ratio of the pore-forming agent to the organic solvent is in the range of 1:27-1:83, and the mass ratio of the modified carbon nitride nanocomposite to the PFM is in the range of 1:10-1:15.
6. The method for preparing the composite nanomaterial modified organic film according to claim 4, wherein the pH of the Tris buffer solution is 7.8-8.5, the concentration of dopamine is 1-10g/L, and the mass ratio of the graphite phase carbon nitride nanomaterial to the dopamine is 1:0.2-1:2.
7. The method for preparing a composite nanomaterial modified organic film as claimed in claim 1, wherein the graphite phase carbon nitride nanomaterial is mesoporous g-C 3 N 4 Nitrogen-rich g-C 3 N 4 Or defect g-C 3 N 4 One of them.
8. The method for preparing a composite nanomaterial modified organic membrane as claimed in claim 1, wherein the polymeric polymer membrane material is one of polyvinylidene fluoride, polysulfone, polyethersulfone, polyacrylonitrile or polytetrafluoroethylene.
9. The method for preparing the composite nanomaterial modified organic film of claim 1, wherein the pore-forming agent is polyvinylpyrrolidone PVP or polyethylene glycol PEG.
10. The method for preparing the composite nanomaterial modified organic film according to claim 1, wherein the organic solvent is one of 1-methyl-2-pyrrolidone NMP, dimethylformamide DMF, and dimethylacetamide DMAc.
CN202310041216.1A 2023-01-11 2023-01-11 Preparation method and application of composite nano material modified organic film Pending CN116139712A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117181023A (en) * 2023-11-06 2023-12-08 深圳格立菲环境科技有限公司 Anti-pollution hollow fiber ultrafiltration membrane and preparation method thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117181023A (en) * 2023-11-06 2023-12-08 深圳格立菲环境科技有限公司 Anti-pollution hollow fiber ultrafiltration membrane and preparation method thereof
CN117181023B (en) * 2023-11-06 2024-01-26 深圳格立菲环境科技有限公司 Anti-pollution hollow fiber ultrafiltration membrane and preparation method thereof

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