CN116139707A - Graphene oxide/phenolic resin composite nanofiltration membrane and preparation method and application thereof - Google Patents

Graphene oxide/phenolic resin composite nanofiltration membrane and preparation method and application thereof Download PDF

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CN116139707A
CN116139707A CN202310156560.5A CN202310156560A CN116139707A CN 116139707 A CN116139707 A CN 116139707A CN 202310156560 A CN202310156560 A CN 202310156560A CN 116139707 A CN116139707 A CN 116139707A
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graphene oxide
phenolic resin
nanofiltration membrane
resin composite
composite nanofiltration
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柯岩
王姣姣
谭皓坤
杜希
邱孝群
张玉高
张旋
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Guangdong Esquel Textiles Co Ltd
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
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    • B01D69/12—Composite membranes; Ultra-thin membranes
    • 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
    • B01D61/027—Nanofiltration
    • 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
    • B01D67/0079—Manufacture of membranes comprising organic and inorganic components
    • 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
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    • B01D69/12—Composite membranes; Ultra-thin membranes
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    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/72—Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, not provided for in a single one of the groups B01D71/46 - B01D71/70 and B01D71/701 - B01D71/702
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    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F1/00—Treatment of water, waste water, or sewage
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    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
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    • C02F2101/00—Nature of the contaminant
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    • C02F2101/308—Dyes; Colorants; Fluorescent agents
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Abstract

The invention provides a graphene oxide/phenolic resin composite nanofiltration membrane, and a preparation method and application thereof. The graphene oxide/phenolic resin composite nanofiltration membrane comprises: the graphene oxide/phenolic resin nanofiltration membrane comprises a base membrane and a graphene oxide/phenolic resin nanofiltration membrane on the surface of the base membrane. The preparation method of the graphene oxide/phenolic resin composite nanofiltration membrane comprises the following steps: and coating the mixed solution containing the graphene oxide material, the polyphenol monomer and the polyaldehyde monomer on the surface of a base film, and reacting to form a graphene oxide/phenolic resin nanofiltration membrane on the surface of the base film, thereby obtaining the graphene oxide/phenolic resin composite nanofiltration membrane. The invention provides application of the graphene oxide/phenolic resin composite nanofiltration membrane in treating dye-containing high-salt wastewater. The graphene oxide/phenolic resin composite nanofiltration membrane has the advantages of simple preparation process, easiness in mass production, stable structure, stable performance and excellent inorganic salt/dye separation performance.

Description

Graphene oxide/phenolic resin composite nanofiltration membrane and preparation method and application thereof
Technical Field
The invention relates to a graphene oxide/phenolic resin composite nanofiltration membrane and a preparation method and application thereof, and belongs to the technical field of nanofiltration membranes.
Background
The processing, weaving and dyeing processes of cotton spinning products are very complex and each process adds and produces different contaminant components. In particular, the waste water discharged from the dyeing process contains a large amount of salt (usually NaCl, na 2 CO 3 、Na 2 SO 4 One or more of the group consisting of, and the like), an undyed dye, and a hydrolysate thereof. The dyeing wastewater has high salinity and high chromaticity, and is difficult to biochemically treat. The traditional treatment method of the part of wastewater is to mix the wastewater with the wastewater produced in other production links, dilute the salt content and chromaticity, and then pass throughAdvanced treatment is carried out on the waste water in modes of physicochemical treatment, biochemical treatment or physicochemical-biochemical combination, and the waste water is discharged after reaching the standard. If the wastewater discharged after reaching the standard is recycled, the wastewater still needs to be subjected to advanced oxidation or activated carbon adsorption to be completely decolorized to meet the recycling requirement. However, these steps inevitably bring about secondary pollution of the environment.
The loose nanofiltration is a membrane separation technology with the aperture between ultrafiltration and nanofiltration, and most inorganic salt can permeate the membrane on the basis of ensuring high interception of organic dye, so that the high-efficiency separation of organic dye/brine in printing and dyeing wastewater is achieved, and the loose nanofiltration has high economic value and research significance. However, commercial nanofiltration membranes are mostly organic membranes, which have a wide pore size, poor selectivity and poor contamination resistance due to the inherent properties of the polymer network chain structure. When the organic membrane is used for treating high-salinity high-chromaticity wastewater, if the retention rate of dye is required to be high, the aperture of the organic membrane is required to be smaller, and the organic membrane also has certain retention on salt at the moment, and the flux of the membrane is small due to the osmotic pressure effect of the retained part of salt, so that the high flux and the high dye retention rate are difficult to obtain simultaneously.
Graphene oxide is a derivative of graphene and is also a single-layer two-dimensional sheet-like carbon material. Recent studies have shown that water molecules can flow rapidly on the surface of graphene oxide, which has excellent separation performance. The graphene oxide surface is rich in oxygen-containing functional groups such as hydroxyl, carboxyl, epoxy, carbonyl and the like, and has good hydrophilicity, so that the graphene oxide is easy to disperse in water to form uniform dispersion liquid, and the graphene oxide film is easy to prepare.
At present, the graphene oxide nanofiltration membrane can be prepared by vacuum filtration, dip coating, spray coating, layer-by-layer self-assembly, coating and other methods, and has excellent salt/dye separation performance. CN110523297a discloses a graphene oxide composite nanofiltration membrane and a preparation method thereof. The preparation method comprises the following steps: and uniformly coating graphene oxide dispersion liquid on one surface of a base film by using a coating rod, and then drying and partially reducing by ultraviolet irradiation to obtain the graphene oxide composite nanofiltration membrane. CN111821867a discloses a self-supporting reduced graphene oxide nanofiltration membrane, a preparation method and application thereof. The preparation method comprises the following steps: and uniformly coating the graphene oxide slurry on a polymer substrate, and then carrying out reduction through ultraviolet lamp irradiation to obtain the self-supporting reduced graphene oxide nanofiltration membrane.
Although the above documents provide an attempt to mass-produce graphene oxide nanofiltration membranes, the graphene oxide sheets lack rigid support, and water channels between the sheets may vary with the external environment. On the one hand, the graphene oxide film prepared by the document has good hydrophilicity because the surface of the graphene oxide contains a large number of carboxyl groups, hydroxyl groups and epoxy groups, the interlayer spacing is increased, the retention rate is reduced, the graphene oxide film can expand after being soaked for a long time, and the film can be damaged or even disintegrated. On the other hand, when the graphene oxide film is contacted with the reducing agent, the oxygen-containing group is reduced; or after acid treatment, carboxyl groups are protonated, the interlayer spacing between graphene oxide sheets is reduced, and the flux is greatly reduced. Therefore, the graphene oxide film prepared by the method has no practical application value.
Therefore, developing a graphene oxide nanofiltration membrane which is simple to prepare, easy to produce in batch, stable in structure, stable in performance and excellent in salt/dye separation performance becomes one of the problems to be solved in the field.
Disclosure of Invention
In order to solve the technical problems, the invention aims at providing a graphene oxide/phenolic resin composite nanofiltration membrane and a preparation method and application thereof. The graphene oxide/phenolic resin composite nanofiltration membrane has a stable structure and good salt/dye separation performance.
In order to achieve the above object, a first aspect of the present invention provides a graphene oxide/phenolic resin composite nanofiltration membrane, comprising: a base film, and a graphene oxide/phenolic resin nanofiltration membrane on the surface of the base film;
the graphene oxide/phenolic resin composite nanofiltration membrane is prepared by the following steps: and coating the mixed solution containing the graphene oxide material, the polyphenol monomer and the polyaldehyde monomer on the surface of a base film, and reacting to form a graphene oxide/phenolic resin nanofiltration membrane on the surface of the base film, thereby obtaining the graphene oxide/phenolic resin composite nanofiltration membrane.
In the graphene oxide/phenolic resin composite nanofiltration membrane described above, preferably, the graphene oxide/phenolic resin nanofiltration membrane is disposed on one surface of the base membrane.
In the graphene oxide/phenolic resin composite nanofiltration membrane, the thickness of the graphene oxide/phenolic resin nanofiltration membrane is preferably 5-2000nm, and more preferably 50-500nm.
In the graphene oxide/phenolic resin composite nanofiltration membrane, preferably, the graphene oxide/phenolic resin nanofiltration membrane has a structure in which a sheet layer of graphene oxide material is embedded in a phenolic resin porous network.
In the graphene oxide/phenolic resin composite nanofiltration membrane, preferably, the interlayer spacing between the graphene oxide material sheets in the graphene oxide/phenolic resin nanofiltration membrane is 0.8-1.2nm.
In the graphene oxide/phenolic resin composite nanofiltration membrane, preferably, the molecular weight cut-off of the graphene oxide/phenolic resin nanofiltration membrane is 500-2000 daltons.
In the graphene oxide/phenolic resin composite nanofiltration membrane, preferably, the polyphenol monomer includes an organic matter containing at least 2 phenolic hydroxyl groups. More preferably, the polyphenol monomer comprises one or a combination of several of catechin, theaflavin, tannic acid, pyrogallol, gallic acid and the like.
In the graphene oxide/phenolic resin composite nanofiltration membrane described above, preferably, the polyaldehyde monomer comprises an organic matter containing at least 2 aldehyde groups. More preferably, the polyaldehyde monomer comprises one or a combination of several of glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, adipaldehyde, terephthalaldehyde, trimellitaldehyde and the like.
In one embodiment of the present invention, the structure of the graphene oxide/phenolic resin nanofiltration membrane in the composite nanofiltration membrane is shown in fig. 1 as an example. As can be seen from fig. 1, the lamellar layers 1 of the graphene oxide-based material are embedded in the porous network of the phenolic resin 2, stabilizing the interlayer spacing 3 between lamellar layers of the graphene oxide-based material.
In the graphene oxide/phenolic resin composite nanofiltration membrane, preferably, the graphene oxide material comprises graphene oxide and/or modified graphene oxide. More preferably, the graphene oxide-based material is graphene oxide. The graphene oxide and the modified graphene oxide may be a single-layer two-dimensional sheet structure. The modified graphene oxide may include various modified graphene oxides in the prior art, such as, but not limited to, carboxyl modified graphene oxide and/or amine modified graphene oxide, etc.
In the graphene oxide/phenolic resin composite nanofiltration membrane, the size of the graphene oxide and the modified graphene oxide is preferably 0.5-500 μm, and more preferably 2-50 μm.
In the graphene oxide/phenolic resin composite nanofiltration membrane, preferably, the material of the base membrane includes one or a combination of several of nylon (PA), polyvinylidene fluoride (PVDF), polysulfone (PSF), polyethersulfone (PES), polyacrylonitrile (PAN), cellulose Acetate (CA), and the like.
In the graphene oxide/phenolic resin composite nanofiltration membrane described above, the average pore diameter of the base membrane is preferably 0.02 to 10 μm, more preferably 0.1 to 0.22 μm, still more preferably 0.1 μm and/or 0.22 μm.
In the graphene oxide/phenolic resin composite nanofiltration membrane described above, preferably, the base membrane comprises a positively charge modified nylon microfiltration membrane. The positively charge-modified nylon microfiltration membrane can be obtained commercially or prepared by a method disclosed in the prior art, and is not particularly limited by the present invention.
In the graphene oxide/phenolic resin composite nanofiltration membrane, the thickness of the base membrane is preferably 50-200 μm, more preferably 80-120 μm.
According to a specific embodiment of the present invention, preferably, the graphene oxide/phenolic resin composite nanofiltration membrane filters 2000ppm sodium sulfate solution with a flux of 5-30L/(m 2 H. Bar), the desalination rate is 50-95%. The desalination rate is the rejection rate of salt, and is calculated by adopting a conventional calculation method in the field.
According to a specific embodiment of the present invention, preferably, the graphene oxide/phenolic resin composite nanofiltration membrane filters 2000ppm of the reactive dye solution with a flux of 5-30L/(m) 2 H Bar), rejection rate>98%. Wherein, the reactive dye is a reactive dye which is conventionally adopted in the textile field and is mainly used for cotton dyeing. More specifically, the reactive dyes include, but are not limited to, one or a combination of several of TQ Blue, yellow 3RF, red 7B, everzol Blue BB, novacron Red EC-2BL, and the like.
According to a specific embodiment of the present invention, preferably, the graphene oxide/phenolic resin composite nanofiltration membrane filters a mixed solution of 70g/L sodium sulfate and 2g/L reactive dye with a flux of 3-10L/(m) 2 H Bar), dye retention of 95-99.9%, desalination rate<15％。
The second aspect of the invention provides a preparation method of the graphene oxide/phenolic resin composite nanofiltration membrane, which comprises the following steps: and coating the mixed solution containing the graphene oxide material, the polyphenol monomer and the polyaldehyde monomer on the surface of a base film, and reacting to form a graphene oxide/phenolic resin nanofiltration membrane on the surface of the base film, thereby obtaining the graphene oxide/phenolic resin composite nanofiltration membrane.
In the above-mentioned production method, preferably, the polyphenol monomer includes an organic substance containing at least 2 phenolic hydroxyl groups. More preferably, the polyphenol monomer comprises one or a combination of several of catechin, theaflavin, tannic acid, pyrogallol, gallic acid and the like. Wherein catechin has a structural formula shown in formula I, theaflavin has a structural formula shown in formula II, tannic acid has a structural formula shown in formula III, pyrogallol has a structural formula shown in formula IV, and gallic acid has a structural formula shown in formula V:
Figure BDA0004092582680000041
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Figure BDA0004092582680000051
In the above preparation method, preferably, the polyaldehyde monomer comprises an organic matter having at least 2 aldehyde groups. More preferably, the polyaldehyde monomer comprises one or a combination of several of glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, adipaldehyde, terephthalaldehyde, trimellitaldehyde and the like.
In the above preparation method, preferably, the graphene oxide-based material includes graphene oxide and/or modified graphene oxide. More preferably, the graphene oxide-based material is graphene oxide. The graphene oxide and the modified graphene oxide may be a single-layer two-dimensional sheet structure. The modified graphene oxide may include various modified graphene oxides in the prior art, such as, but not limited to, carboxyl modified graphene oxide and/or amine modified graphene oxide, etc. More preferably, the platelet size of the graphene oxide and the modified graphene oxide is 0.5 to 500 μm, still more preferably 2 to 50 μm.
In the above preparation method, preferably, the material of the base film includes one or a combination of several of nylon (PA), polyvinylidene fluoride (PVDF), polysulfone (PSF), polyethersulfone (PES), polyacrylonitrile (PAN), cellulose Acetate (CA), and the like.
In the above-mentioned production method, the average pore diameter of the base film is preferably 0.02 to 10. Mu.m, more preferably 0.1 to 0.22. Mu.m, still more preferably 0.1 μm and/or 0.22. Mu.m.
In the above preparation method, preferably, the base membrane comprises a positively charge-modified nylon microfiltration membrane.
In the above-mentioned production method, the thickness of the base film is preferably 50 to 200 μm, more preferably 80 to 120 μm.
In the above preparation method, preferably, in the mixed solution, the weight of the polyphenol monomer is 5% to 500% of the weight of the graphene oxide-based material, and more preferably 10% to 200%.
In the above preparation method, preferably, in the mixed solution, the weight of the polyaldehyde monomer is 5% to 500% of the weight of the graphene oxide-based material, and more preferably 10% to 100%.
In the above preparation method, preferably, the concentration of the graphene oxide-based material in the mixed solution is 0.5 to 10g/L, more preferably 1 to 4g/L.
In the above preparation method, preferably, the pH of the mixed solution is 2 to 4. Before the coating, an acid (e.g., hydrochloric acid solution, etc.) may be used to adjust the pH of the mixture within the above range to facilitate the subsequent reaction.
In the above preparation method, preferably, the mixed solution containing the graphene oxide material, the polyphenol monomer and the polyaldehyde monomer may be prepared by the following steps: preparing a dispersion liquid of graphene oxide materials; preparing a buffer solution of polyphenol monomers; dripping a proper amount of buffer solution of the polyphenol monomer into a proper amount of dispersion liquid of the graphene oxide material, and uniformly mixing to obtain a graphene oxide material/polyphenol monomer solution; dropping a proper amount of multi-aldehyde monomer solution into the graphene oxide material/polyphenol monomer solution and uniformly mixing; and then a proper amount of hydrochloric acid solution is dripped, the pH value of the solution is regulated to be 2-4, and the mixed solution containing the graphene oxide material, the polyphenol monomer and the polyaldehyde monomer is obtained. Among them, more specifically, the buffer solution of the polyphenol monomer may be Tris-HCl buffer solution or sodium dihydrogen phosphate-disodium hydrogen phosphate buffer solution or the like. The dispersion liquid of the graphene oxide-based material and the solvent in the polyaldehyde monomer solution are preferably water. The concentration of the graphene oxide material in the mixed solution containing the graphene oxide material, the polyphenol monomer and the polyaldehyde monomer, and the weight ratio of the polyphenol monomer to the polyaldehyde monomer to the graphene oxide material are not particularly limited, and the concentration of each raw material solution used in the preparation of the mixed solution can be adjusted according to the above content by a person skilled in the art.
In the above-described production method, the coating means preferably includes one or a combination of several of conventional coating processes such as wire bar coating, slot coating, and micro-gravure coating, as long as uniform coating of the mixed liquid on the base film is achieved.
In the above-described production method, the mixed solution containing the graphene oxide-based material, the polyphenol monomer, and the polyaldehyde monomer may be applied to one surface of the base film, or may be applied to both surfaces of the base film, and preferably to one surface of the base film.
In the above preparation method, preferably, the reaction is a phenol-formaldehyde polycondensation reaction performed under acid-catalyzed conditions. More specifically, the reaction is performed by placing the base film coated with the mixed solution in an acid solution. The acid solution used may include a hydrochloric acid solution, the concentration of which may be routinely adjusted by those skilled in the art, and the present invention is not particularly limited. More preferably, the reaction time may be 0.5 to 5 hours.
In one embodiment of the invention, the mechanism of the phenolic polycondensation reaction is shown by way of example as follows:
Figure BDA0004092582680000081
in the above equation, it can be seen that the polyphenol monomer is an organic compound containing at least 3 phenolic hydroxyl groups, and since specific organic compounds that can be included in the polyphenol monomer used in the present invention are already listed above, specific groups included in R are not described herein, wherein the polyaldehyde monomer is an organic compound containing 2 aldehyde groups, and n can be an integer of 0 to 4. It should be noted that the above equations are only for illustrating the mechanism of the phenolic polycondensation reaction of the present invention, and the polyphenol monomers and polyaldehyde monomers that can be used in the present invention are not limited to the monomers used in the above equations.
According to an embodiment of the present invention, the above preparation method may further include conventional steps such as drying after the reaction is performed. The drying manner is, for example but not limited to, natural drying, heating and drying, vacuum drying or air-flow blowing, etc., and the present invention is not particularly limited thereto, and may be routinely adjusted by those skilled in the art.
In the above preparation method, preferably, the dry film thickness of the graphene oxide/phenolic resin nanofiltration membrane formed on the surface of the base film is 5-2000nm, more preferably 50-500nm.
According to the preparation method of the graphene oxide/phenolic resin composite nanofiltration membrane, the graphene oxide material, the polyphenol monomer and the polyaldehyde monomer are mixed together and coated to form a film, then the polyphenol monomer and the polyaldehyde monomer are crosslinked through a phenolic polycondensation reaction to form the phenolic resin with a porous network structure, and the graphene oxide material is embedded in the porous network of the phenolic resin, so that the stability of the graphene oxide nanofiltration membrane is effectively improved, and meanwhile, the phenolic resin with the porous network structure has good permeability and selectivity, so that the performance of the nanofiltration membrane is improved.
The third aspect of the invention provides application of the graphene oxide/phenolic resin composite nanofiltration membrane in treating dye-containing high-salt wastewater.
According to a specific embodiment of the present invention, preferably, the application is an application of the graphene oxide/phenolic resin composite nanofiltration membrane in decolorization treatment of the dye-containing high-salt wastewater.
In the above application, preferably, the salt concentration in the dye-containing high-salt wastewater is 20-200g/L, and the dye concentration is 0.2-5g/L. Wherein the salt may comprise NaCl and/or Na 2 SO 4 Etc. The salt concentration is the total concentration of inorganic salts in the wastewater. The dye may comprise a reactive dye. The reactive dye is a reactive dye conventionally adopted in the textile field and is mainly used for cotton dyeing. More specifically, the reactive dyes include, but are not limited to, one or a combination of several of TQ Blue, yellow 3RF, red 7B, everzol Blue BB, novacron Red EC-2BL, and the like.
In the above application, preferably, the flux of the graphene oxide/phenolic resin composite nanofiltration membrane for treating the dye-containing high-salt wastewater is 2.5-10L/(m) 2 H Bar), dye retention of 90% -99.9%, desalination rate<15%. The graphene oxide/phenolic resin composite nanofiltration membrane can be used for filtering high-salt wastewater containing dye, can efficiently remove the dye, and allows most of inorganic salt to permeate.
The inventor of the scheme finds that the retention rate of the unique graphene oxide/phenolic resin composite nanofiltration membrane to salt is reduced along with the increase of the salt content through a large amount of experimental researches. Specifically, in some embodiments of the present invention, graphene oxide/phenolic resin composite nanofiltration membranes are used for low salt solutions (e.g., 2g/L Na 2 SO 4 Solution) is very high (50% or more, more specifically 50-95%) but has little retention (retention less than 15%) for salt solutions with a concentration exceeding 20 g/L. According to one embodiment of the invention, the graphene oxide/phenolic resin composite nanofiltration membrane is used for preparing sodium sulfate (namely Na 2 SO 4 ) The flux and salt rejection of the aqueous solution for filtration are shown in figure 2. In addition, in some specific embodiments of the invention, when the graphene oxide/phenolic resin composite nanofiltration membrane filters the mixed solution of the dye and the high-concentration salt, the retention rate of the salt is reduced to below 15%, but the retention rate of the dye can still be kept at a higher level, and the retention rate of the dye reaches 95% -99.9%. That is, the graphene oxide/phenolic resin composite nanofiltration membrane of the present invention has high rejection rate for low concentration salt and unlimited concentration of dye, and thus is not suitable for separating a system containing dye and low concentration salt (such as Na 2g/L 2 SO 4 +1g/L of reactive dye solution). However, the graphene oxide/phenolic resin composite nanofiltration membrane of the invention can effectively separate dye and high-concentration salt (such as 50g/L Na 2 SO 4 +1g/L of reactive dye solution). When the graphene oxide/phenolic resin composite nanofiltration membrane is adopted to filter a system containing dye and high-concentration salt, the retention rate of the salt is very low (lower than 15)The dye can still be effectively trapped (the dye trapping rate is 95% -99.9%), so that low-chroma brine can be obtained, further the decolorization treatment of high-salt wastewater containing the dye is realized, and inorganic salt is recycled.
According to the specific embodiment of the invention, as an illustration, the interception mechanism of the graphene oxide/phenolic resin nanofiltration membrane in the composite nanofiltration membrane for treating the high-salt wastewater containing the dye is shown in fig. 3. As can be seen from fig. 3, most of the salt ions 5 in the dye-containing high-salt wastewater can pass through the graphene oxide/phenolic resin nanofiltration membrane of the present invention, while the dye clusters 4 are trapped.
The fourth aspect of the invention provides a wastewater treatment system comprising the graphene oxide/phenolic resin composite nanofiltration membrane.
According to a specific embodiment of the present invention, preferably, the wastewater treatment system includes: the device comprises a pH value adjusting unit, a coarse filtering unit, an ultrafiltration unit and a nanofiltration unit; the inlet of the pH value adjusting unit is connected with a wastewater conveying pipeline, the outlet of the pH value adjusting unit is connected with the inlet of the coarse filtering unit through a pipeline, the outlet of the coarse filtering unit is connected with the inlet of the ultrafiltration unit through a pipeline, the outlet of the ultrafiltration unit is connected with the inlet of the nanofiltration unit through a pipeline, and the water producing port of the nanofiltration unit produces reuse water; the nanofiltration unit comprises the graphene oxide/phenolic resin composite nanofiltration membrane.
In the above-described wastewater treatment system, preferably, the pH adjusting unit includes a pH adjusting tank for adjusting the pH of the wastewater to neutral. The pH adjusting tank used may be a pH adjusting tank conventional in the art.
In the above-described wastewater treatment system, preferably, the coarse filtration unit includes one or a combination of several of a sand filter, a filter bag, a cartridge filter, and the like. More preferably, the coarse filtration unit comprises a sand filter and a filter bag connected in series, or a sand filter and a cartridge filter connected in series. The sand filter, filter bag and cartridge filter employed may be any conventional filtration device in the art.
In the above-described wastewater treatment system, preferably, the ultrafiltration unit comprises a hollow fiber ultrafiltration membrane or a tubular ceramic ultrafiltration membrane. More preferably, the pore size of the ultrafiltration unit is 10-100nm.
In the above wastewater treatment system, preferably, the nanofiltration unit includes a first-stage nanofiltration membrane element and a second-stage nanofiltration membrane element connected in series, an outlet of the ultrafiltration unit is connected to an inlet of the first-stage nanofiltration membrane element through a pipeline, a water producing port of the first-stage nanofiltration membrane element is connected to an inlet of the second-stage nanofiltration membrane element through a pipeline, and a water producing port of the second-stage nanofiltration membrane element produces reuse water; the first-stage nanofiltration membrane element and the second-stage nanofiltration membrane element are membrane elements which are made of the graphene oxide/phenolic resin composite nanofiltration membrane roll. The method of rolling the nanofiltration membrane into the membrane element may be performed according to a conventional method in the art, and the present invention is not particularly limited thereto.
In the above wastewater treatment system, preferably, the nanofiltration unit further includes a first concentrate return line, and the first concentrate return line is used for returning a part of concentrate generated after the treatment by the first stage nanofiltration membrane element, and treating the concentrate again by the first stage nanofiltration membrane element.
In the above wastewater treatment system, preferably, the nanofiltration unit further includes a second concentrated water backflow line, and the second concentrated water backflow line is used for backflow of the concentrated water generated after the treatment by the second stage nanofiltration membrane element, and the concentrated water is treated again by the first stage nanofiltration membrane element.
The method for treating wastewater by adopting the wastewater treatment system of the invention can comprise the following steps: enabling the wastewater to enter the pH value adjusting unit, and adjusting the pH value of the wastewater in the pH value adjusting unit by utilizing acid to obtain wastewater with neutral pH value; then the wastewater with neutral pH value is treated by the coarse filtering unit, and large particles and/or fine substances and the like in the wastewater are removed to obtain wastewater after coarse filtering; treating the wastewater after coarse filtration by the ultrafiltration unit to further remove fine substances and/or partial COD (chemical oxygen demand) and the like in the wastewater to obtain wastewater after ultrafiltration treatment; and then the wastewater after ultrafiltration treatment is treated by the nanofiltration unit, the dye in the wastewater is trapped and most of inorganic salt is allowed to pass through, and the reuse water is obtained. Wherein, preferably, the wastewater comprises high-salt wastewater containing dye.
The wastewater treatment system and method of the present invention are particularly useful for treating high salt wastewater containing dyes, especially high salt and high color wastewater. The high-salt wastewater containing the dye contains a large amount of inorganic salts such as anhydrous sodium sulfate (i.e., sodium sulfate) and/or sodium carbonate, and the dye, and is thus alkaline. According to the specific embodiment of the invention, the wastewater treatment system and the method firstly adopt a pH adjusting unit to adjust the wastewater to be neutral by utilizing acid (preferably sulfuric acid), sodium carbonate is converted into sodium sulfate, then large particles, fine suspended matters and the like in the wastewater are removed by a coarse filtering unit, then fine substances, partial COD and the like in the wastewater are further removed by an ultrafiltration unit, meanwhile, the graphene oxide/phenolic resin composite nanofiltration membrane of a subsequent nanofiltration unit is subjected to fine protection, finally, the wastewater after ultrafiltration treatment is subjected to treatment by a two-stage graphene oxide/phenolic resin composite nanofiltration membrane, dyes are trapped, most inorganic salts such as sodium sulfate and the like are allowed to pass through, and finally, a low-color or colorless salt solution, namely reuse water, can be reused in the dyeing process of textiles, is obtained.
The invention provides a graphene oxide/phenolic resin composite nanofiltration membrane, and a preparation method and application thereof. The graphene oxide layered material is creatively embedded into the porous network of the phenolic resin, so that the lamellar layers of the graphene oxide layered material in the nanofiltration membrane have proper and stable interlayer spacing, the stability of the graphene oxide nanofiltration membrane is effectively improved, the problems that the retention rate is reduced due to the fact that the interlayer spacing is increased in the application process and the flux is reduced due to the fact that the graphene oxide lamellar layers of the graphene oxide nanofiltration membrane in the prior art lack rigid support are solved, and the porous network of the phenolic resin has good water permeability and selectivity, and the performance of the nanofiltration membrane is improved. The graphene oxide/phenolic resin composite nanofiltration membrane provided by the invention has the advantages of simple preparation process, easiness in mass production, stable structure, stable performance and excellent inorganic salt/dye separation performance. The graphene oxide/phenolic resin composite nanofiltration membrane provided by the invention is particularly suitable for decoloring high-salt wastewater containing dyes, including high-salt and high-chroma industrial wastewater, has the advantages of large flux, high dye retention rate and the like, and can efficiently remove chroma and recycle inorganic salts.
Drawings
Fig. 1 is a block diagram of a graphene oxide/phenolic resin nanofiltration membrane in a composite nanofiltration membrane according to an embodiment of the present invention.
FIG. 2 is a graph showing flux and desalination rate of graphene oxide/phenolic resin composite nanofiltration membranes for filtering aqueous solutions of anhydrous sodium sulfate with different contents according to an embodiment of the present invention.
FIG. 3 is a graph showing the retention mechanism of graphene oxide/phenolic resin nanofiltration membrane in the composite nanofiltration membrane for treating high-salt wastewater containing dye according to an embodiment of the invention.
Fig. 4 is an optical comparison graph of the composite nanofiltration membranes provided in example 1, example 2 and comparative example 1.
Fig. 5a is an SEM image of the composite nanofiltration membrane provided in comparative example 1, and fig. 5b is an SEM image of the composite nanofiltration membrane provided in example 1.
Fig. 6 is an optical diagram of the graphene oxide/phenolic resin composite nanofiltration membrane provided in example 1 after continuous testing for 1 month.
Fig. 7 is a schematic diagram of a structure of a wastewater treatment system provided by an application example.
Reference numerals illustrate:
1: a sheet of graphene oxide-based material; 2: a phenolic resin; 3: interlayer spacing between sheets of graphene oxide-based material; 4: dye clusters; 5: salt ions;
11: a pH value adjusting unit; 12: a coarse filtration unit; 13: an ultrafiltration unit; 14: a nanofiltration unit; 141: a first stage nanofiltration membrane element; 142: a second stage nanofiltration membrane element; 143: a first concentrate return line; 144: a concentrate discharge line; 145: a second concentrate return line; 146: a first water production line; 147: and a second water production line.
Detailed Description
The technical solution of the present invention will be described in detail below for a clearer understanding of technical features, objects and advantageous effects of the present invention, but should not be construed as limiting the scope of the present invention.
Example 1
The embodiment provides a graphene oxide/phenolic resin composite nanofiltration membrane, which is prepared by the following steps:
(1) Preparing a mixed solution containing graphene oxide, polyphenol monomers and polyaldehyde monomers
(a) Preparation of Graphene Oxide (GO) dispersion: adding 1g of GO powder (the size of a lamellar layer of the GO powder is 5-50 mu m) into 400mL of deionized water, and performing ultrasonic dispersion to obtain a uniform graphene oxide dispersion liquid with the concentration of 2.5 mg/mL;
(b) Preparing a polyphenol monomer buffer solution: 2g of tannic acid is dissolved in 100mL of Tris-HCl buffer solution to obtain tannic acid solution;
(c) Dripping 100mL of tannic acid solution into 400mL of GO dispersion liquid, and uniformly stirring and mixing to obtain GO/tannic acid solution;
(d) Dropwise adding 0.6mL of 50wt% glutaraldehyde water solution into the GO/tannic acid solution, and uniformly stirring and mixing;
(e) Then a proper amount of hydrochloric acid solution is added dropwise, and the mixture is stirred and mixed uniformly, and the pH value of the solution is regulated to be 2.5, so that the mixed solution containing graphene oxide, polyphenol monomers and polyaldehyde monomers, hereinafter referred to as slurry, is obtained; graphene oxide in slurry: tannic acid: the weight ratio of glutaraldehyde is 1:2:0.3;
(2) Coating
Spreading a positive charge modified nylon micro-filtration membrane with an average pore diameter of 0.1 mu m on an automatic coater, uniformly coating the slurry prepared in the step (1) on one surface of the nylon micro-filtration membrane by using a wire rod coating mode to form a wet membrane containing graphene oxide, wherein the thickness of the wet membrane is 25 mu m, and obtaining a base membrane coated with the slurry;
(3) Phenolic polycondensation reaction under acid catalysis
Soaking the base film coated with the slurry obtained in the step (2) in hydrochloric acid solution with pH=2 for 2 hours, and in the process, carrying out polycondensation on tannic acid and glutaraldehyde under the catalysis of acid to form phenolic resin, so as to obtain a graphene oxide/phenolic resin composite nanofiltration membrane crude product;
(4) Drying
And (3) placing the crude product of the graphene oxide/phenolic resin composite nanofiltration membrane obtained in the step (3) in an oven, and drying at 60 ℃ for 30 minutes to obtain the graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment.
The graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment comprises: a positively charge-modified nylon microfiltration membrane having an average pore size of 0.1 μm, and a graphene oxide/phenolic resin nanofiltration membrane on the surface of the positively charge-modified nylon microfiltration membrane. Wherein the thickness of the graphene oxide/phenolic resin nanofiltration membrane is about 150nm. The graphene oxide/phenolic resin nanofiltration membrane has a structure that graphene oxide sheets are embedded into a phenolic resin porous network, and a structural schematic diagram of the graphene oxide/phenolic resin nanofiltration membrane is shown in figure 1.
2g/L (i.e., 2000 ppm) of sodium sulfate solution was filtered using the graphene oxide/phenolic resin composite nanofiltration membrane of this example, with a flux of 9.93L/(m) 2 H Bar), the rejection of sodium sulfate was 87%.
The graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment is adopted to filter 70g/L sodium sulfate solution, and the flux is 6.32L/(m) 2 H Bar), the rejection of sodium sulfate was 13.2%.
2g/L dye blue R solution is filtered by adopting the graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment, and the flux is 8.72L/(m) 2 H Bar), the dye retention was 99.8%.
The graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment is adopted to filter 70g/L sodium sulfate and 2g/L dye blue mixed solution, and the flux is 5.52L/(m) 2 H Bar), the rejection of the dye was 99.1% and the rejection of sodium sulfate was 12.8%.
Example 2
The embodiment provides a graphene oxide/phenolic resin composite nanofiltration membrane, which is prepared by the following steps:
(1) Preparing a mixed solution containing graphene oxide, polyphenol monomers and polyaldehyde monomers
(a) Preparation of Graphene Oxide (GO) dispersion: adding 2g of GO powder (the size of a lamellar layer of the GO powder is 5-50 mu m) into 400mL of deionized water, and performing ultrasonic dispersion to obtain a uniform graphene oxide dispersion liquid with the concentration of 5 mg/mL;
(b) Preparing a polyphenol monomer buffer solution: 0.5g of gallic acid is dissolved in 100mL of Tris-HCl buffer solution to obtain gallic acid solution;
(c) Dripping 100mL of gallic acid solution into 400mL of GO dispersion liquid, and uniformly stirring and mixing to obtain GO/gallic acid solution;
(d) 1mL of 50wt% terephthalaldehyde aqueous solution is dripped into the GO/gallic acid solution, and the mixture is stirred and mixed uniformly;
(e) Then a proper amount of hydrochloric acid solution is added dropwise, and the mixture is stirred and mixed uniformly, and the pH value of the solution is regulated to be 2.5, so that the mixed solution containing graphene oxide, polyphenol monomers and polyaldehyde monomers, hereinafter referred to as slurry, is obtained; graphene oxide in slurry: gallic acid: the weight ratio of terephthalaldehyde is 2:0.5:0.5;
(2) Coating
Spreading a positive charge modified nylon micro-filtration membrane with an average pore diameter of 0.1 mu m on an automatic coater, uniformly coating the slurry prepared in the step (1) on one surface of the nylon micro-filtration membrane by using a wire rod coating mode to form a wet membrane containing graphene oxide, wherein the thickness of the wet membrane is 25 mu m, and obtaining a base membrane coated with the slurry;
(3) Phenolic polycondensation reaction under acid catalysis
Soaking the base film coated with the slurry obtained in the step (2) in hydrochloric acid solution with pH=2 for 2 hours, and carrying out polycondensation on gallic acid and terephthalaldehyde under the catalysis of acid to form phenolic resin in the process, so as to obtain a graphene oxide/phenolic resin composite nanofiltration membrane crude product;
(4) Drying
And (3) placing the crude product of the graphene oxide/phenolic resin composite nanofiltration membrane obtained in the step (3) in an oven, and drying at 60 ℃ for 30 minutes to obtain the graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment.
The graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment comprises: a positively charge-modified nylon microfiltration membrane having an average pore size of 0.1 μm, and a graphene oxide/phenolic resin nanofiltration membrane on the surface of the positively charge-modified nylon microfiltration membrane. Wherein the thickness of the graphene oxide/phenolic resin nanofiltration membrane is about 75nm. The graphene oxide/phenolic resin nanofiltration membrane has a structure that a graphene oxide sheet layer is embedded into a phenolic resin porous network.
2g/L (i.e., 2000 ppm) of sodium sulfate solution was filtered using the graphene oxide/phenolic resin composite nanofiltration membrane of this example, with a flux of 13.8L/(m) 2 H Bar), the rejection of sodium sulphate was 69%.
The graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment is adopted to filter 70g/L sodium sulfate solution, and the flux is 9.32L/(m) 2 H Bar), the rejection of sodium sulfate was 8.6%.
2g/L dye blue R solution is filtered by adopting the graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment, and the flux is 11.9L/(m) 2 H Bar), the dye retention was 99.2%.
The graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment is adopted to filter 70g/L sodium sulfate and 2g/L dye blue mixed solution, and the flux is 8.12L/(m) 2 H Bar), the retention of dye was 97.2%, and the retention of sodium sulfate was 7.7%.
Example 3
The embodiment provides a graphene oxide/phenolic resin composite nanofiltration membrane, which is prepared by the following steps:
(1) Preparing a mixed solution containing graphene oxide, polyphenol monomers and polyaldehyde monomers
(a) Preparation of Graphene Oxide (GO) dispersion: adding 1g of GO powder (the size of a lamellar layer of the GO powder is 5-50 mu m) into 400mL of deionized water, and performing ultrasonic dispersion to obtain a uniform graphene oxide dispersion liquid with the concentration of 2.5 mg/mL;
(b) Preparing a polyphenol monomer buffer solution: 1g of catechin was dissolved in 100mL of a sodium dihydrogen phosphate-disodium hydrogen phosphate buffer solution to obtain a catechin solution;
(c) Dropwise adding 100mL of catechin solution into 400mL of GO dispersion liquid, and uniformly stirring and mixing to obtain GO/catechin solution;
(d) Dropwise adding 0.6ml of 50wt% glyoxal water solution into the GO/catechin solution, and uniformly stirring and mixing;
(e) Then a proper amount of hydrochloric acid solution is added dropwise, and the mixture is stirred and mixed uniformly, and the pH value of the solution is regulated to be 2.5, so that the mixed solution containing graphene oxide, polyphenol monomers and polyaldehyde monomers, hereinafter referred to as slurry, is obtained; graphene oxide in slurry: catechin: the weight ratio of the glyoxal is 2:1:0.3;
(2) Coating
Spreading a positive charge modified nylon micro-filtration membrane with an average pore diameter of 0.1 mu m on an automatic coater, uniformly coating the slurry prepared in the step (1) on one surface of the nylon micro-filtration membrane by using a wire rod coating mode to form a wet membrane containing graphene oxide, wherein the thickness of the wet membrane is 10 mu m, and obtaining a base membrane coated with the slurry;
(3) Phenolic polycondensation reaction under acid catalysis
Soaking the base film coated with the slurry obtained in the step (2) in hydrochloric acid solution with pH=2 for 2 hours, and carrying out polycondensation on catechin and glyoxal under the catalysis of acid to form phenolic resin in the process, so as to obtain a graphene oxide/phenolic resin composite nanofiltration membrane crude product;
(4) Drying
And (3) placing the crude product of the graphene oxide/phenolic resin composite nanofiltration membrane obtained in the step (3) in an oven, and drying at 60 ℃ for 30 minutes to obtain the graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment.
The graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment comprises: a positively charge-modified nylon microfiltration membrane having an average pore size of 0.1 μm, and a graphene oxide/phenolic resin nanofiltration membrane on the surface of the positively charge-modified nylon microfiltration membrane. Wherein the thickness of the graphene oxide/phenolic resin nanofiltration membrane is about 35nm. The graphene oxide/phenolic resin nanofiltration membrane has a structure that a graphene oxide sheet layer is embedded into a phenolic resin porous network.
2g/L (i.e., 2000 ppm) of sodium sulfate solution was filtered using the graphene oxide/phenolic resin composite nanofiltration membrane of this example, with a flux of 15.8L/(m) 2 H Bar), the rejection of sodium sulfate was 65%.
The graphene oxide/phenolic resin composite nanofiltration membrane is adopted to filter 70g/L sodium sulfate solution, and the flux is 10.72L/(m) 2 H Bar), the rejection of sodium sulfate was 8.9%.
2g/L dye blue R solution is filtered by adopting the graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment, and the flux is 13.8L/(m) 2 H Bar), the dye retention was 98.9%.
The graphene oxide/phenolic resin composite nanofiltration membrane of the embodiment is adopted to filter 70g/L sodium sulfate and 2g/L dye blue mixed solution, and the flux is 9.82L/(m) 2 H Bar), the rejection of dye was 96.8% and the rejection of sodium sulfate was 8.6%.
Comparative example 1
The comparative example provides a graphene oxide composite nanofiltration membrane, which is prepared by the following steps:
(1) Preparing graphene oxide dispersion liquid
Adding 1g of GO powder (the size of a lamellar layer of the GO powder is 5-50 mu m) into 400mL of deionized water, and performing ultrasonic dispersion to obtain a uniform graphene oxide dispersion liquid with the concentration of 2.5mg/mL, which is hereinafter referred to as slurry;
(2) Coating
Spreading a positive charge modified nylon micro-filtration membrane with an average pore diameter of 0.1 mu m on an automatic coating machine, uniformly coating the slurry prepared in the step (1) on one surface of the nylon micro-filtration membrane by using a wire rod coating mode to form a graphene oxide wet membrane, wherein the thickness of the wet membrane is 25 mu m, and obtaining a base membrane coated with the slurry;
(3) Drying
And (3) placing the base film coated with the slurry obtained in the step (2) in an oven, and drying at 60 ℃ for 30 minutes to obtain the graphene oxide composite nanofiltration membrane of the comparative example.
The graphene oxide composite nanofiltration membrane of this comparative example includes: a positively charge-modified nylon microfiltration membrane having an average pore size of 0.1 μm, and a graphene oxide nanofiltration membrane on the surface of the positively charge-modified nylon microfiltration membrane. Wherein the thickness of the graphene oxide nanofiltration membrane is about 65nm.
2g/L (i.e., 2000 ppm) of sodium sulfate solution was filtered using the graphene oxide composite nanofiltration membrane of the present comparative example, with a flux of 9.8L/(m) 2 H Bar), the rejection of sodium sulfate was 82%.
70g/L sodium sulfate solution is filtered by adopting the graphene oxide composite nanofiltration membrane of the comparative example, and the flux is 5.3L/(m) 2 H Bar), the rejection of sodium sulfate was 9.8%.
2g/L dye blue R solution is filtered by adopting the graphene oxide composite nanofiltration membrane of the comparative example, and the flux is 9.2L/(m) 2 H Bar), the dye retention was 96.3%.
The graphene oxide composite nanofiltration membrane of the comparative example is adopted to filter 70g/L sodium sulfate and 2g/L dye blue mixed solution, and the flux is 4.8L/(m) 2 H Bar), the rejection of dye was 92.8% and the rejection of sodium sulfate was 9.6%.
Test example 1
The composite nanofiltration membranes provided in the above examples and comparative examples were subjected to optical comparison, SEM detection, stability test, etc., and the results are described below.
Optical contrast diagrams of the composite nanofiltration membranes provided in example 1, example 2 and comparative example 1 are shown in fig. 4. As can be seen from fig. 4, compared with the graphene oxide composite nanofiltration membrane of comparative example 1, the graphene oxide/phenolic resin composite nanofiltration membranes of examples 1 and 2 showed the gloss of plastics, and the place contacted with the membrane pool sealing ring was not damaged, indicating that the stability of the membrane was improved after GO was embedded into the phenolic resin.
An SEM image of the composite nanofiltration membrane provided in comparative example 1 is shown in fig. 5a, and an SEM image of the composite nanofiltration membrane provided in example 1 is shown in fig. 5 b. As can be seen from fig. 5a and 5b, the unique fold structure of graphene oxide becomes smoother due to the embedded phenolic resin.
The membrane elements rolled by the graphene oxide/phenolic resin composite nanofiltration membrane provided in examples 1-3 are tested by adopting a mixed solution of 70g/L sodium sulfate and 2g/L dye blue, and after continuous testing for 1 month, the membrane elements are cleaned and disassembled, and no damage to the membrane is found, so that the graphene oxide/phenolic resin composite nanofiltration membrane provided by the invention has high stability and can be applied to practical tests. Wherein, the optical diagram of the graphene oxide/phenolic resin composite nanofiltration membrane provided in example 1 after continuous test for 1 month is shown in fig. 6.
Application examples
The application example provides application of the graphene oxide/phenolic resin composite nanofiltration membrane of the example 1 to decolorization treatment of high-salt wastewater containing dye and recycling of salt (especially anhydrous sodium sulphate).
The embodiment of the application provides a wastewater treatment system, the structure of which is shown in fig. 7, the wastewater treatment system comprises: a pH adjusting unit 11, a coarse filtration unit 12, an ultrafiltration unit 13, and a nanofiltration unit 14;
the nanofiltration unit 14 comprises a first stage nanofiltration membrane element 141 and a second stage nanofiltration membrane element 142 which are connected in series, and a first concentrate return line 143, a concentrate discharge line 144, a second concentrate return line 145, a first water production line 146 and a second water production line 147;
the inlet of the pH value adjusting unit 11 is connected with a wastewater conveying pipeline, the outlet of the pH value adjusting unit 11 is connected with the inlet of the coarse filtering unit 12 through a pipeline, the outlet of the coarse filtering unit 12 is connected with the inlet of the ultrafiltration unit 13 through a pipeline, the outlet of the ultrafiltration unit 13 is connected with the inlet of the first-stage nanofiltration membrane element 141 through a pipeline, the water outlet of the first-stage nanofiltration membrane element 141 is connected with the inlet of the second-stage nanofiltration membrane element 142 through the first water outlet pipeline 146, and the water outlet of the second-stage nanofiltration membrane element 142 is connected with the second water outlet pipeline 147 for producing high-salt reuse water without or with low chromaticity;
The first concentrated water backflow pipeline 143 is connected to a concentrated water outlet of the first stage nanofiltration membrane element 141, and is used for partially backflow of the concentrated water generated after the treatment of the first stage nanofiltration membrane element 141, and the concentrated water is treated again by the first stage nanofiltration membrane element 141, and the other part of the concentrated water is discharged through the concentrated water discharge pipeline 144;
the second concentrated water backflow pipeline 145 is connected to a concentrated water outlet of the second stage nanofiltration membrane element 142, and is used for backflow of the concentrated water generated after the treatment of the second stage nanofiltration membrane element 142, and the concentrated water is treated again by the first stage nanofiltration membrane element 141;
wherein the pH value adjusting unit 11 comprises a pH value adjusting tank for adjusting the pH value of the wastewater to be neutral; the pH value adjusting tank can be a pH value adjusting tank which is conventional in the field;
the coarse filtration unit 12 comprises a sand filter and a filter bag connected in series; the sand filter and the filter bag can be all conventional filtering devices in the field;
the ultrafiltration unit 13 comprises a hollow fiber ultrafiltration membrane, and the pore diameter of the hollow fiber ultrafiltration membrane is 10nm;
the first stage nanofiltration membrane element 141 and the second stage nanofiltration membrane element 142 are membrane elements (which are obtained by rolling in a conventional manner) formed by rolling graphene oxide/phenolic resin composite nanofiltration membranes provided in example 1.
The high-salt wastewater containing the dye treated in this application example contains a large amount of anhydrous sodium sulfate (i.e., sodium sulfate) and sodium carbonate as well as the dye, and is thus alkaline.
The method for treating wastewater by adopting the wastewater treatment system of the application embodiment can comprise the following steps: the high-salt wastewater containing dye enters the pH value adjusting unit 11, the pH value of the wastewater is adjusted to be neutral by sulfuric acid in the pH value adjusting unit 11, and sodium carbonate is converted into sodium sulfate to obtain wastewater with neutral pH value; then the wastewater with neutral pH value is treated by the coarse filtering unit 12, and large particles and/or fine suspended matters and the like in the wastewater are removed, so that wastewater after coarse filtration is obtained; then the wastewater after coarse filtration is treated by the ultrafiltration unit 13 to further remove fine substances, partial COD and the like, and simultaneously plays a role in fine protection of the graphene oxide/phenolic resin composite nanofiltration membrane of the subsequent nanofiltration unit 14 to obtain wastewater after ultrafiltration treatment; and then the wastewater after ultrafiltration treatment is treated by the nanofiltration unit 14, the dye in the wastewater is trapped and most of sodium sulfate is allowed to pass through, so that a low-color or colorless sodium sulfate solution is obtained, namely reuse water, and the reuse water can be reused in the dyeing process of textiles.
Comparative examples of application
The present application comparative example provides the application of a conventional commercial loose nanofiltration membrane (Suez, product model Suez GK) to decolorize high salt wastewater containing dye and reuse salt (especially anhydrous sodium sulphate).
The wastewater treatment system of the present application comparative example was substantially the same as in the above application example, except that the first stage nanofiltration membrane element 141 and the second stage nanofiltration membrane element 142 in the application example were each replaced with a membrane element made of a commercial loose nanofiltration membrane roll of the present application comparative example.
Test example 2
The mixed solution of 70g/L sodium sulfate and 2g/L dye blue was filtered by using the membrane element made of graphene oxide/phenolic resin composite nanofiltration membrane roll provided in example 1 and the membrane element made of commercial loose nanofiltration membrane roll in comparative example, respectively, and the results are shown in Table 1.
TABLE 1
Figure BDA0004092582680000201
The wastewater treatment system of the above application examples and comparative examples was used to treat the actual dye-containing high-salt wastewater, and the results are shown in Table 2. The concentration of anhydrous sodium sulfate in the high-salt wastewater containing the dye is 20-100g/L, and the concentration of the dye is 0.2-2g/L.
TABLE 2
Figure BDA0004092582680000202
The retention rate of the traditional commercial loose nanofiltration membrane to the dye in the dyeing wastewater is only 85-88%, and the flux is 2L/(m) 2 H Bar). In practical application, the stable flux is only 0.5-1.5L/(m) under the condition of 85% of water recovery rate of the membrane element 2 H Bar) single stage nanofiltration membranes can only remove 65-75% of the dye. The dyeing wastewater is treated by the two-stage nanofiltration membrane, so that only 90% of dye can be removed. Further activated carbon adsorption or advanced oxidation techniques are then required to further remove the remaining dye and reuse the produced water containing anhydrous sodium sulfate, greatly increasing the cost of the process.
In the process of treating the high-salt wastewater containing the dye by the graphene oxide/phenolic resin composite nanofiltration membrane, the graphene oxide/phenolic resin composite nanofiltration membrane has unique advantages for separating the salt and the dye. The flux of the graphene oxide/phenolic resin composite nanofiltration membrane is 3-10L/(m) 2 H Bar) is about 2-4 times that of commercial bulk nanofiltration membranes and the rejection rate for dye is better than commercial bulk nanofiltration membranes. In practical application, the stable flux is 2.5-3.5L/(m) under the condition of 85% of water recovery rate of the membrane element 2 H Bar, the retention rate of each grade of nanofiltration membrane to the dye exceeds 90%, more than 98.5% of the dye can be removed after the dyeing wastewater is treated by the two-grade graphene oxide/phenolic resin composite nanofiltration membrane, and the produced water containing anhydrous sodium sulfate can be recycled without post-treatment.

Claims (10)

1. A graphene oxide/phenolic resin composite nanofiltration membrane, the graphene oxide/phenolic resin composite nanofiltration membrane comprising: a base film, and a graphene oxide/phenolic resin nanofiltration membrane on the surface of the base film;
the graphene oxide/phenolic resin composite nanofiltration membrane is prepared by the following steps: and coating the mixed solution containing the graphene oxide material, the polyphenol monomer and the polyaldehyde monomer on the surface of a base film, and reacting to form a graphene oxide/phenolic resin nanofiltration membrane on the surface of the base film, thereby obtaining the graphene oxide/phenolic resin composite nanofiltration membrane.
2. The graphene oxide/phenolic resin composite nanofiltration membrane according to claim 1, wherein the graphene oxide/phenolic resin nanofiltration membrane has a thickness of 5-2000nm, preferably 50-500nm.
3. The graphene oxide/phenolic resin composite nanofiltration membrane according to claim 1, wherein the graphene oxide/phenolic resin nanofiltration membrane has a structure in which a sheet layer of graphene oxide-based material is embedded into a phenolic resin porous network;
preferably, the polyphenol monomer comprises an organic matter comprising at least 2 phenolic hydroxyl groups;
more preferably, the polyphenol monomers comprise one or a combination of several of catechin, theaflavin, tannic acid, pyrogallol and gallic acid;
Preferably, the polyaldehyde monomer comprises an organic compound comprising at least 2 aldehyde groups;
more preferably, the polyaldehyde monomer comprises one or a combination of several of glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, adipaldehyde, terephthalaldehyde and trimesic aldehyde;
preferably, the graphene oxide-based material comprises graphene oxide and/or modified graphene oxide; more preferably, the graphene oxide-based material is graphene oxide;
preferably, the platelet size of the graphene oxide and the modified graphene oxide is 0.5 to 500 μm, more preferably 2 to 50 μm.
4. The graphene oxide/phenolic resin composite nanofiltration membrane according to claim 1, wherein the material of the base membrane comprises one or a combination of more of nylon, polyvinylidene fluoride, polysulfone, polyethersulfone, polyacrylonitrile and cellulose acetate;
preferably, the average pore size of the base film is 0.02 to 10 μm, more preferably 0.1 to 0.22 μm, still more preferably 0.1 μm and/or 0.22 μm;
preferably, the base membrane comprises a positively charge modified nylon microfiltration membrane.
5. According to the weightsThe graphene oxide/phenolic resin composite nanofiltration membrane of any one of claims 1 to 4, wherein the graphene oxide/phenolic resin composite nanofiltration membrane filters 2000ppm sodium sulfate solution with a flux of 5-30L/(m) 2 H Bar), the desalination rate is 50-95%;
preferably, the flux of the graphene oxide/phenolic resin composite nanofiltration membrane for filtering 2000ppm of active dye solution is 5-30L/(m) 2 H Bar), rejection rate>98％；
Preferably, the flux of the mixed solution of 70g/L sodium sulfate and 2g/L reactive dye filtered by the graphene oxide/phenolic resin composite nanofiltration membrane is 3-10L/(m) 2 H Bar), dye retention of 95-99.9%, desalination rate<15％。
6. A method for preparing the graphene oxide/phenolic resin composite nanofiltration membrane according to any one of claims 1 to 5, comprising the steps of: and coating the mixed solution containing the graphene oxide material, the polyphenol monomer and the polyaldehyde monomer on the surface of a base film, and reacting to form a graphene oxide/phenolic resin nanofiltration membrane on the surface of the base film, thereby obtaining the graphene oxide/phenolic resin composite nanofiltration membrane.
7. The method of claim 6, wherein the polyphenol monomer comprises an organic compound comprising at least 2 phenolic hydroxyl groups;
preferably, the polyphenol monomer comprises one or a combination of more of catechin, theaflavin, tannic acid, pyrogallol and gallic acid;
preferably, the polyaldehyde monomer comprises an organic compound comprising at least 2 aldehyde groups;
More preferably, the polyaldehyde monomer comprises one or a combination of several of glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, adipaldehyde, terephthalaldehyde and trimesic aldehyde;
preferably, the graphene oxide-based material comprises graphene oxide and/or modified graphene oxide; more preferably, the graphene oxide-based material is graphene oxide;
preferably, the platelet size of the graphene oxide and the modified graphene oxide is 0.5 to 500 μm, more preferably 2 to 50 μm;
preferably, the material of the base film comprises one or a combination of more of nylon, polyvinylidene fluoride, polysulfone, polyethersulfone, polyacrylonitrile and cellulose acetate;
preferably, the average pore size of the base film is 0.02 to 10 μm, more preferably 0.1 to 0.22 μm, still more preferably 0.1 μm and/or 0.22 μm;
preferably, the base membrane comprises a positively charge modified nylon microfiltration membrane.
8. The preparation method according to claim 6, wherein the weight of the polyphenol monomer in the mixed solution is 5% -500%, preferably 10% -200% of the weight of the graphene oxide-based material;
preferably, in the mixed solution, the weight of the polyaldehyde monomer is 5% -500%, more preferably 10% -100% of the weight of the graphene oxide-based material;
Preferably, in the mixed solution, the concentration of the graphene oxide material is 0.5-10g/L, more preferably 1-4g/L;
preferably, the pH value of the mixed solution is 2-4.
9. The method of claim 6, wherein the coating comprises one or a combination of several of bar coating, slot coating and micro-gravure coating;
preferably, the reaction is a phenolic polycondensation reaction carried out under acid-catalyzed conditions; more preferably, the reaction is carried out by placing the base film coated with the mixed solution in an acid solution.
10. Use of the graphene oxide/phenolic resin composite nanofiltration membrane of any one of claims 1-5 for treating high-salt wastewater containing dye;
preferably, the application is the application of the graphene oxide/phenolic resin composite nanofiltration membrane in the decolorization treatment of the dye-containing high-salt wastewater;
preferably, the salt concentration in the high-salt wastewater containing the dye is 20-200g/L, and the dye concentration is 0.2-5g/L; more preferably, the salt comprises NaCl and/or Na 2 SO 4 ；
Preferably, the flux of the graphene oxide/phenolic resin composite nanofiltration membrane for treating the dye-containing high-salt wastewater is 2.5-10L/(m) 2 H Bar), dye retention of 90% -99.9%, desalination rate <15％。
CN202310156560.5A 2023-02-23 2023-02-23 Graphene oxide/phenolic resin composite nanofiltration membrane and preparation method and application thereof Pending CN116139707A (en)

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