CN116020286A - Graphene oxide composite nanofiltration membrane and preparation method and application thereof - Google Patents
Graphene oxide composite nanofiltration membrane and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a graphene oxide composite nanofiltration membrane and a preparation method and application thereof. The graphene oxide composite nanofiltration membrane comprises: a base film and a graphene oxide nanofiltration film embedded with a high polymer nano material on the surface of the base film; the graphene oxide nanofiltration membrane embedded with the high polymer nano material is obtained by embedding the high polymer nano material between the sheets of graphene oxide material in a crosslinking manner. The preparation method of the composite nanofiltration membrane comprises the following steps: and coating the mixed solution containing the graphene oxide material, the polymer nano material and the cross-linking agent on the surface of the base film, and carrying out a cross-linking reaction to obtain the graphene oxide composite nanofiltration membrane. The invention provides application of the graphene oxide composite nanofiltration membrane in treating dye-containing high-salt wastewater. The graphene oxide 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
Technical Field
The invention relates to a graphene oxide 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 method for treating the part of wastewater is to mix the part of wastewater with wastewater produced in other production links, dilute the salt content and chromaticity, and then deeply treat the part of wastewater in a manner of physical and chemical treatment, biochemical treatment or physical and chemical-biochemical combination and the like, and then discharge the wastewater reaching the standard. The waste water discharged after reaching the standard is recycled if necessary,advanced oxidation or activated carbon adsorption is still needed to completely decolorize 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 good 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 composite nanofiltration membrane and a preparation method and application thereof. The graphene oxide 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 composite nanofiltration membrane, comprising: a base film and a graphene oxide nanofiltration film embedded with a high polymer nano material on the surface of the base film; the graphene oxide nanofiltration membrane embedded with the high polymer nano material is obtained by embedding the high polymer nano material between the sheets of graphene oxide material in a crosslinking manner.
In the above graphene oxide composite nanofiltration membrane, preferably, the graphene oxide nanofiltration membrane embedded with the polymer nanomaterial is disposed on one surface of the base membrane.
In the graphene oxide composite nanofiltration membrane, preferably, the thickness of the graphene oxide nanofiltration membrane embedded with the polymer nanomaterial is 5-2000nm, and more preferably 50-500nm.
In the graphene oxide composite nanofiltration membrane, preferably, the interlayer spacing between the sheets of graphene oxide material in the graphene oxide nanofiltration membrane embedded with the polymer nano material is 0.8-2.0nm.
In the graphene oxide composite nanofiltration membrane, preferably, the molecular weight cut-off of the graphene oxide nanofiltration membrane embedded with the polymer nanomaterial is 500-3000 daltons, and more preferably 800-3000 daltons.
In the graphene oxide composite nanofiltration membrane, preferably, the weight ratio of the polymer nanomaterial to the graphene oxide material in the graphene oxide nanofiltration membrane embedded with the polymer nanomaterial is 0.125-16, and more preferably 0.5-8.
In the graphene oxide composite nanofiltration membrane, preferably, the polymer nanomaterial includes a polymer nanofiber and/or a polymer nanocrystal. More preferably, the polymer nanofiber has a diameter of 10 to 50nm and an aspect ratio of 10 to 100. More preferably, the diameter of the polymer nanocrystalline is 2-20nm, and the length-diameter ratio is 10-100. More specifically, the polymer nanomaterial includes one or a combination of several of cellulose nanofibers, cellulose nanocrystals, chitin nanofibers, chitin nanocrystals, chitosan nanofibers, chitosan nanocrystals, lignin nanofibers, lignin nanocrystals, and the like.
In the above graphene oxide composite nanofiltration membrane, preferably, the graphene oxide 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.
In the graphene oxide composite nanofiltration membrane described above, the sheet size of the graphene oxide and the modified graphene oxide is preferably 0.5 to 500 μm, more preferably 2 to 50 μm.
In the graphene oxide 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 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 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. According to the invention, the nylon micro-filtration membrane modified by positive charges is preferably used as a base membrane, the surface of the nylon micro-filtration membrane carries positive charges, and the nylon micro-filtration membrane is combined with the graphene oxide material with negative charges in a mode of electrostatic force, hydrogen bond, van der Waals force and the like, so that the binding force between the graphene oxide nano-filtration membrane embedded with the high polymer nano-material and the base membrane is improved, and the graphene oxide nano-filtration membrane is prevented from falling off from the base membrane in the membrane filtration process.
In the graphene oxide composite nanofiltration membrane described above, preferably, the thickness of the base membrane is 50-200 μm.
In the graphene oxide composite nanofiltration membrane, preferably, the graphene oxide nanofiltration membrane embedded with the polymer nanomaterial is obtained by embedding the polymer nanomaterial between sheets of graphene oxide material by a crosslinking reaction using a crosslinking agent. More preferably, the graphene oxide nanofiltration membrane embedded with the polymer nano material is specifically obtained by the following steps: coating a mixed solution containing graphene oxide materials, polymer nano materials and a cross-linking agent on the surface of a base film, carrying out cross-linking reaction, embedding the polymer nano materials between the sheets of the graphene oxide materials in a cross-linking mode, and forming the graphene oxide nanofiltration membrane embedded with the polymer nano materials on the surface of the base film.
In the graphene oxide composite nanofiltration membrane, preferably, the crosslinking agent comprises a carboxyl crosslinking agent and/or a hydroxyl crosslinking agent and the like; more preferably, the carboxyl crosslinking agent includes an aziridine-based crosslinking agent and/or a polycarbodiimide-based crosslinking agent, etc.; more preferably, the hydroxyl crosslinking agent includes an isocyanate-based crosslinking agent and/or a polyaldehyde-based crosslinking agent, etc., and more specifically, the polyaldehyde-based crosslinking agent includes glyoxal and/or glutaraldehyde, etc.
In the graphene oxide composite nanofiltration membrane, the amount of the cross-linking agent is preferably 0.1% -30%, more preferably 0.5% -10%, and even more preferably 1% -8% of the total weight of the graphene oxide material and the polymer nanomaterial.
In the graphene oxide composite nanofiltration membrane, preferably, the temperature of the crosslinking reaction is 20-100 ℃, more preferably 50-70 ℃; preferably, the time of the crosslinking reaction is 2 minutes to one week. The crosslinking reaction can be performed by natural drying or thermal crosslinking.
The surface of the polymer nano material selected by the invention contains a large amount of carboxyl and/or hydroxyl, the surface of the graphene oxide material also contains rich carboxyl and hydroxyl, the invention adopts a carboxyl cross-linking agent and/or hydroxyl cross-linking agent, the graphene oxide material and the carboxyl and/or hydroxyl on the polymer nano material are cross-linked together, and the polymer nano material is embedded between the lamellar layers of the graphene oxide material; on one hand, the rigid support is provided, so that a water channel between graphene oxide materials can be maintained, the decline of membrane flux in practical application is avoided, and on the other hand, the structural stability of the membrane is improved. According to the preferred technical scheme, the contents of the polymer nano material and the cross-linking agent are optimized, so that the relation of the permeability and the selectivity of the graphene oxide nanofiltration membrane is broken through, and the dual increase of the flux and the dye retention rate is realized.
According to a particular embodiment of the invention, it is preferred thatThe flux of 2000ppm sodium sulfate solution filtered by the graphene oxide composite nanofiltration membrane is 5-30L/(m) 2 H. Bar), the desalination rate is 50-95%. Wherein, the desalination rate is the retention rate of inorganic salt (here, sodium sulfate) and is calculated by a conventional calculation method in the field.
According to a specific embodiment of the present invention, preferably, the graphene oxide 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 the specific embodiment of the invention, preferably, the flux of the mixed solution of 70g/L sodium sulfate and 2g/L reactive dye filtered by the graphene oxide composite nanofiltration membrane is 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 composite nanofiltration membrane, which comprises the following steps: coating a mixed solution containing graphene oxide materials, polymer nano materials and a cross-linking agent on the surface of a base film, carrying out cross-linking reaction, embedding the polymer nano materials between the sheets of the graphene oxide materials in a cross-linking mode, and forming a graphene oxide nanofiltration membrane embedded with the polymer nano materials on the surface of the base film to obtain the graphene oxide composite nanofiltration membrane.
In the above preparation method, preferably, in the mixed solution, the weight ratio of the polymer nanomaterial to the graphene oxide-based material is 0.125 to 16, and more preferably 0.5 to 8.
In the above preparation method, preferably, the amount of the crosslinking agent in the mixed solution is 0.1% to 30%, more preferably 0.5% to 10%, and even more preferably 1% to 8% of the total weight of the graphene oxide-based material and the polymer nanomaterial.
In the above preparation method, preferably, the content 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-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 of the graphene oxide-based material, the polymer nanomaterial, and the crosslinking agent 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 temperature of the crosslinking reaction is 20 to 100 ℃, more preferably 50 to 70 ℃; preferably, the time of the crosslinking reaction is 2 minutes to one week. The crosslinking reaction can be performed by natural drying or thermal crosslinking. The high polymer nano material is embedded between the sheets of the graphene oxide material through a crosslinking reaction, and the graphene oxide nanofiltration membrane embedded with the high polymer nano material is formed on the surface of the base membrane in the crosslinking reaction process.
The third aspect of the invention provides an application of the graphene oxide 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 composite nanofiltration membrane in decolorizing 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 TQ Blue, yellow 3RF, red E7B, evOne or a combination of several of erzol Blue BB and Novacron Red EC-2BL, etc.
In the above application, preferably, the flux of the graphene oxide 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 composite nanofiltration membrane can be used for filtering high-salt wastewater containing dye, can efficiently remove the dye, and allows most inorganic salt to permeate.
The inventor of the scheme finds that the rejection rate of the unique graphene oxide 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 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 composite nanofiltration membrane is used for preparing anhydrous sodium sulfate (namely Na 2 SO 4 ) The flux and salt rejection of the aqueous solution for filtration are shown in figure 1. In addition, in some specific embodiments of the invention, when the graphene oxide 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 composite nanofiltration membrane of the present invention has high rejection rate for low concentration of salt and unlimited concentration of dye, and thus is not suitable for separating a system containing dye and low concentration of salt (e.g., 2g/L Na 2 SO 4 +1g/L of reactive dye solution). However, the graphene oxide composite nanofiltration membrane can effectively separate dye and high-concentration salt (such as 50g/LNa 2 SO 4 +1g/L of reactive dye solution). When the graphene oxide 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 percent), but still can be achievedSo as to efficiently entrap dye (the dye entrapping rate is 95% -99.9%), thereby obtaining low-chroma brine, further realizing the decoloring treatment of high-salinity wastewater containing dye, and recycling inorganic salt.
The fourth aspect of the invention provides a wastewater treatment system comprising the graphene oxide 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; wherein, the nanofiltration unit comprises the graphene oxide 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 by rolling the graphene oxide composite nanofiltration membrane. 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 effect of fine protection of the graphene oxide composite nanofiltration membrane of a subsequent nanofiltration unit is achieved, finally, the wastewater after ultrafiltration treatment is treated by a two-stage graphene oxide composite nanofiltration membrane, dyes are trapped, most of inorganic salts such as sodium sulfate and the like are allowed to pass through, and finally, a low-color or colorless salt solution is obtained, namely reuse water which can be reused in the dyeing process of textiles.
The invention provides a graphene oxide composite nanofiltration membrane and a preparation method and application thereof. The preparation method of the graphene oxide composite nanofiltration membrane comprises the steps of coating a mixed solution containing graphene oxide materials, polymer nano materials and a cross-linking agent on the surface of a base membrane, carrying out a cross-linking reaction, embedding the polymer nano materials between the sheets of the graphene oxide materials in a cross-linking mode, and forming the graphene oxide nanofiltration membrane embedded with the polymer nano materials on the surface of the base membrane to obtain the graphene oxide composite nanofiltration membrane. According to the invention, the polymer nano material membrane is embedded between the sheets of the graphene oxide materials in a crosslinking manner, so that on one hand, a rigid support is provided, a water channel between the graphene oxide materials can be maintained, the decline of membrane flux in practical application is avoided, and on the other hand, due to the crosslinking structure between the polymer nano material and the graphene oxide materials, the structural stability of the membrane is improved. In addition, the preferable technical scheme of the invention can break through the relation of the permeability and the selectivity of the graphene oxide nanofiltration membrane by optimizing the contents of the polymer nano material and the cross-linking agent, so as to realize the dual increase of flux and dye retention rate. In addition, the nylon micro-filtration membrane modified by positive charges is preferably used as a base membrane, the surface of the nylon micro-filtration membrane is positively charged, and the nylon micro-filtration membrane and the graphene oxide material with negative charges can be combined together in the modes of electrostatic force, hydrogen bond, van der Waals force and the like, so that the bonding force between the graphene oxide nano-filtration membrane embedded with the high polymer nano-material and the base membrane is improved, and the graphene oxide nano-filtration membrane is prevented from falling off from the base membrane in the membrane filtration process.
The graphene oxide 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 composite nanofiltration membrane provided by the invention is particularly suitable for decoloring high-salt wastewater containing dyes, including industrial wastewater with high salt content and high chromaticity, has the advantages of high flux, high dye retention rate and the like, and can efficiently remove chromaticity and recycle inorganic salts.
Drawings
FIG. 1 is a graph showing flux and salt rejection rate of graphene oxide composite nanofiltration membranes for filtration of aqueous glauber salt solutions of different contents according to an embodiment of the present invention.
Fig. 2 is an optical diagram of the graphene oxide composite nanofiltration membrane of example 1.
FIG. 3 is an electron microscope image of graphene oxide composite nanofiltration membranes prepared with isocyanate crosslinker content of 0.1mg/mL and chitin nanofibers of 0, 0.5, 1, 2, 4 and 8mg/mL, respectively, in Table 1.
Fig. 4 is an optical comparison chart of the graphene oxide composite nanofiltration membrane obtained in example 1 without using the chitin nanofibers and the isocyanate crosslinking agent after application test.
Fig. 5 is a cross-sectional view of a graphene oxide nanofiltration membrane with lignin nanofibers embedded therein in the graphene oxide composite nanofiltration membrane of example 3.
Fig. 6 is a schematic diagram of the structure of the wastewater treatment system provided by the application example.
Fig. 7 is an optical view of a membrane element rolled by graphene oxide composite nanofiltration membranes in a wastewater treatment system of an application example.
FIG. 8 is an optical image of the actual dye-containing high-salt wastewater before and after treatment by the wastewater treatment system of the application example, and a comparative image of the recycled glauber salt reused for dyeing and directly dyed with fresh glauber salt.
Reference numerals illustrate:
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 composite nanofiltration membrane, which is prepared by the following steps:
(1) Adding graphene oxide (the sheet size is 5-50 mu m), chitin nanofiber (the average diameter is 30nm, the length-diameter ratio is 10-20) and 4,4' -diphenylmethane diisocyanate into deionized water, and uniformly stirring by a stirrer to obtain a mixed solution, wherein the content of graphene oxide in the mixed solution is 2mg/mL, and the content of chitin nanofiber and isocyanate crosslinking agent are shown in table 1;
(2) Spreading a positively charged modified nylon micro-filtration membrane with an average pore diameter of 0.1 mu m and a thickness of 50-200 mu m on an automatic coating machine, uniformly coating the mixed solution prepared in the step (1) on one surface of the nylon micro-filtration membrane by using a micro-concave coating mode to form a wet membrane containing graphene oxide, chitin nano-fibers and 4,4' -diphenylmethane diisocyanate, wherein the thickness of the wet membrane is 40 mu m, and obtaining a base membrane coated with the wet membrane;
(3) And (3) placing the base film coated with the wet film obtained in the step (2) in an oven, drying for 2 hours at the temperature of 80 ℃, embedding the chitin nanofiber between the sheet layers of the graphene oxide through a crosslinking reaction, and simultaneously forming a graphene oxide nanofiltration film embedded with the chitin nanofiber on the surface of the base film to obtain the graphene oxide composite nanofiltration film.
The graphene oxide composite nanofiltration membrane of the embodiment comprises: a positive charge modified nylon micro-filtration membrane with an average pore diameter of 0.1 mu m and a thickness of 50-200 mu m, and a graphene oxide nano-filtration membrane embedded with chitin nano-fibers on the surface of the positive charge modified nylon micro-filtration membrane; wherein, the thickness of the graphene oxide nanofiltration membrane (dry film) embedded with the chitin nanofiber is about 240nm.
The graphene oxide composite nanofiltration membrane of the embodiment is adopted to filter 2g/L (namely 2000 ppm) of sodium sulfate solution, and the rejection rate (namely the desalination rate) of sodium sulfate is more than 60%.
The graphene oxide composite nanofiltration membrane is adopted to filter 70g/L sodium sulfate solution, and the rejection rate of sodium sulfate is lower than 15%.
The graphene oxide composite nanofiltration membrane is adopted to filter 2g/L dye blue solution, and the retention rate of the dye is more than 99%.
The mixed solution of 70g/L sodium sulfate and 2g/L dye blue is filtered by adopting the graphene oxide composite nanofiltration membrane of the embodiment, the flux and the dye retention rate are shown in the table 1, and the retention rate of sodium sulfate is less than 15%.
Table 1 flux and dye retention of graphene oxide composite nanofiltration membranes prepared from mixed solutions of different chitin nanofiber contents and isocyanate crosslinking agent contents.
It should be noted that, the graphene oxide composite nanofiltration membrane prepared in table 1 with the chitin nanofiber content and the isocyanate crosslinking agent content outside the scope of the present invention is used as a comparison, but not an example of the present invention. As can be seen from table 1, as the crosslinker content increases, the membrane flux decreases and the dye retention increases; with the increase of the content of chitin nano-fibers, the flux of the membrane is increased, and the dye retention rate is reduced. According to the invention, the weight ratio of the high polymer nano material to the graphene oxide is 0.5-8 by optimizing the contents of the high polymer nano material and the graphene oxide, the amount of the cross-linking agent is 0.5% -10% (more preferably 1% -8%) of the total weight of the graphene oxide and the high polymer nano material, the increase of flux and retention rate can be realized, and the trade-off relation of the permeability and selectivity of the separation membrane is broken through.
The preparation process of the graphene oxide composite nanofiltration membrane in the embodiment is simple, the mass production is easy, and an optical diagram of the graphene oxide composite nanofiltration membrane is shown in fig. 2, which shows photographs of a rolled membrane and a rolled membrane element of the graphene oxide composite nanofiltration membrane. FIG. 3 is an electron micrograph of graphene oxide composite nanofiltration membranes prepared with isocyanate crosslinker content of 0.1mg/mL, chitin nanofibers of 0 (a in FIG. 3), 0.5 (b in FIG. 3), 1 (c in FIG. 3), 2 (d in FIG. 3), 4 (e in FIG. 3) and 8mg/mL (f in FIG. 3), respectively, in Table 1. Fig. 4 is an optical comparison graph of a graphene oxide composite nanofiltration membrane obtained without using chitin nanofibers and an isocyanate crosslinking agent after application test. As can be seen from fig. 4, due to the effects of the chitin nanofiber and the cross-linking agent, the graphene oxide composite nanofiltration membrane is not damaged at the contact place with the rubber ring after the test, which indicates that the structural stability of the membrane is greatly improved.
The graphene oxide composite nanofiltration membrane prepared by the isocyanate crosslinking agent content of the embodiment is 0.1mg/mL, the chitin nanofiber content is 4mg/mL, and the graphene oxide composite nanofiltration membrane prepared by the chitin nanofiber and the isocyanate crosslinking agent is not adopted for comparison, and after being treated by acid liquor or reducing agent, the mixed solution of 70g/L sodium sulfate and 2g/L dye BlueR is subjected to filtration test, and the results are shown in Table 2. Wherein, the acid liquor adopts hydrochloric acid with pH=3, the treatment mode is soaking, and the time is 8 hours; the reducing agent adopts 1% hydroiodic acid, and the treatment mode is soaking for 8 hours.
TABLE 2
As can be seen from table 2, the graphene oxide composite nanofiltration membrane obtained by adopting the chitin nanofiber and the isocyanate crosslinking agent in the embodiment is treated by the acid liquor or the reducing agent, the flux is not significantly attenuated, and the performance stability of the membrane is greatly improved.
Example 2
The embodiment provides a graphene oxide composite nanofiltration membrane, which is prepared by the following steps:
(1) Adding graphene oxide (the sheet size is 5-50 mu m), cellulose nanocrystalline (the average diameter is 10nm, the length-diameter ratio is 20-50) and glutaraldehyde into deionized water, and uniformly stirring by a stirrer to obtain a mixed solution, wherein the content of graphene oxide in the mixed solution is 1mg/mL, the content of cellulose nanocrystalline is 8mg/mL and the content of glutaraldehyde is 0.72mg/mL;
(2) Spreading a positive charge modified nylon micro-filtration membrane with an average pore diameter of 0.22 mu m on an automatic coating machine, uniformly coating the mixed solution 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, cellulose nanocrystalline and glutaraldehyde, wherein the thickness of the wet membrane is 10 mu m, and obtaining a base membrane coated with the wet membrane;
(3) And (3) naturally drying the base film coated with the wet film obtained in the step (2) for three days at room temperature, embedding cellulose nanocrystals between the graphene oxide sheets through a crosslinking reaction, and forming a graphene oxide nanofiltration membrane embedded with the cellulose nanocrystals on the surface of the base film to obtain the graphene oxide composite nanofiltration membrane.
The graphene oxide composite nanofiltration membrane of the embodiment comprises: a positively charged modified nylon microfiltration membrane with an average pore size of 0.22 mu m, and a graphene oxide nanofiltration membrane with cellulose nanocrystals embedded in the surface of the positively charged modified nylon microfiltration membrane; wherein, the thickness of the graphene oxide nanofiltration membrane (dry film) embedded with cellulose nanocrystals is about 90nm.
2g/L sulfur is filtered by adopting the graphene oxide composite nanofiltration membrane of the embodiment Sodium acid solution with flux of 8.35L/(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 embodiment, and the flux is 4.87L/(m) 2 H Bar), the rejection of sodium sulfate was 9.2%.
2g/L dye blue R solution is filtered by adopting the graphene oxide composite nanofiltration membrane of the embodiment, and the flux is 7.46L/(m) 2 H Bar), the dye retention was 99.9%.
The graphene oxide 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 4.64L/(m) 2 H Bar), the rejection of the dye was 99.2% and the rejection of sodium sulfate was 13.2%.
Example 3
The embodiment provides a graphene oxide composite nanofiltration membrane, which is prepared by the following steps:
(1) Adding graphene oxide (with the lamellar size of 5-50 mu m), lignin nanofiber (with the average diameter of 30nm and the length-diameter ratio of 20-50) and an aziridine crosslinking agent (You En chemical SAC-100) into deionized water, and uniformly stirring by a stirrer to obtain a mixed solution, wherein the content of graphene oxide is 3mg/mL, the content of lignin nanofiber is 2mg/mL, and the content of the aziridine crosslinking agent is 0.06mg/mL;
(2) Spreading a positively charge modified nylon micro-filtration membrane with an average pore diameter of 0.1 mu m on an automatic coating machine, uniformly coating the mixed solution prepared in the step (1) on one surface of the nylon micro-filtration membrane by using a micro-concave coating mode to form a wet membrane containing graphene oxide, lignin nanofibers and an aziridine cross-linking agent, wherein the thickness of the wet membrane is 10 mu m, and obtaining a base membrane coated with the wet membrane;
(3) And (3) placing the base film coated with the wet film obtained in the step (2) in an oven, drying for 15 minutes at 70 ℃, embedding lignin nanofibers between graphene oxide sheets through a crosslinking reaction, and forming a graphene oxide nanofiltration film embedded with lignin nanofibers on the surface of the base film to obtain the graphene oxide composite nanofiltration film.
The graphene oxide composite nanofiltration membrane of the embodiment comprises: a positively charged modified nylon microfiltration membrane with an average pore size of 0.1 μm, and a graphene oxide nanofiltration membrane embedded with lignin nanofibers on the surface of the positively charged modified nylon microfiltration membrane; wherein the thickness of the graphene oxide nanofiltration membrane (dry film) embedded with lignin nanofibers is about 40nm. The cross-sectional view of the graphene oxide nanofiltration membrane embedded with lignin nanofibers in the graphene oxide composite nanofiltration membrane of the embodiment is shown in fig. 5.
2g/L sodium sulfate solution is filtered by adopting the graphene oxide composite nanofiltration membrane of the embodiment, and the flux is 16.3L/(m) 2 H Bar), the rejection of sodium sulfate was 91%.
70g/L sodium sulfate solution is filtered by adopting the graphene oxide composite nanofiltration membrane of the embodiment, and the flux is 9.82L/(m) 2 H Bar), the rejection of sodium sulfate was 11.2%.
2g/L dye blue R solution is filtered by adopting the graphene oxide composite nanofiltration membrane of the embodiment, and the flux is 14.2L/(m) 2 H Bar), the dye retention was 99.8%.
The graphene oxide 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 9.04L/(m) 2 H Bar), the rejection of dye was 96.3% and the rejection of sodium sulfate was 11.2%.
Application examples
The application example provides application of the graphene oxide composite nanofiltration membrane (the graphene oxide composite nanofiltration membrane prepared by mixing liquid with isocyanate crosslinking agent content of 0.1mg/mL and chitin nanofiber content of 4 mg/mL) in the application of the dye-containing high-salt wastewater to decolorization treatment 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. 6, 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 (obtained by rolling in a conventional manner) formed by rolling the graphene oxide composite nanofiltration membrane provided in example 1.
Fig. 7 is an optical diagram of a membrane element rolled by graphene oxide composite nanofiltration membrane in the wastewater treatment system of this application example, the upper two are used two-stage membrane elements, and the lower two are unused membrane elements.
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 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 case
The results are shown in Table 3, using the membrane element prepared by rolling the graphene oxide composite nanofiltration membrane provided in example 1 (the graphene oxide composite nanofiltration membrane prepared by mixing the solution with isocyanate crosslinking agent in an amount of 0.1mg/mL and the chitin nanofiber in an amount of 4 mg/mL), and using the membrane element prepared by rolling the commercial loose nanofiltration membrane in comparative example, the mixed solution of 70g/L sodium sulfate and 2g/L dye BlueR was filtered.
TABLE 3 Table 3
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 4. 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 4 Table 4
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 composite nanofiltration membrane, the graphene oxide composite nanofiltration membrane has unique advantages for separating salt and the dye. The flux of the graphene oxide composite nanofiltration membrane is 3-10L/(m) 2 H Bar) is about 2-4 times that of commercial loose nanofiltration membranes, andthe retention rate of dye is>95%) was much better than commercial loose nanofiltration membranes. In practical application, the stable flux is 2.5-3.6L/(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 99% of the dye can be removed after the dyeing wastewater is treated by the two-grade graphene oxide composite nanofiltration membrane, and the produced water containing anhydrous sodium sulfate can be recycled without post-treatment.
Fig. 8 is an optical diagram (a in fig. 8) of the actual dye-containing high-salt wastewater before and after treatment by the wastewater treatment system (two-stage graphene oxide composite nanofiltration membrane) of the above application example, and a comparative diagram (b in fig. 8) of the reused anhydrous sodium sulfate for dyeing and the directly used fresh anhydrous sodium sulfate for dyeing. As can be seen from fig. 8, the recycled anhydrous sodium sulphate is reused for dyeing, and the cloth has no obvious chromatic aberration. Therefore, the membrane element rolled by the graphene oxide composite nanofiltration membrane is used for separating actual high-salt dyeing wastewater, has large membrane flux and excellent separation effect, can be used for efficiently decoloring the high-salt dyeing wastewater, has high anhydrous sodium sulfate recycling rate (more than 85 percent), and has excellent dyeing effect when the recycled anhydrous sodium sulfate is reused in textile dyeing process.
In conclusion, the graphene oxide 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 composite nanofiltration membrane provided by the invention is particularly suitable for decoloring industrial wastewater with high salt and high chromaticity, has the advantages of high flux, high dye retention rate and the like, and can efficiently remove chromaticity and recycle inorganic salts such as anhydrous sodium sulfate.
Claims (10)
1. A graphene oxide composite nanofiltration membrane, the graphene oxide composite nanofiltration membrane comprising: a base film and a graphene oxide nanofiltration film embedded with a high polymer nano material on the surface of the base film; the graphene oxide nanofiltration membrane embedded with the high polymer nano material is obtained by embedding the high polymer nano material between the sheets of graphene oxide material in a crosslinking manner.
2. The graphene oxide composite nanofiltration membrane according to claim 1, wherein the graphene oxide nanofiltration membrane embedded with the polymer nanomaterial has a thickness of 5-2000nm, preferably 50-500nm;
preferably, the molecular weight cut-off of the graphene oxide nanofiltration membrane embedded with the high molecular nano material is 500-3000 daltons.
3. The graphene oxide composite nanofiltration membrane according to claim 1, wherein the weight ratio of the polymer nanomaterial to the graphene oxide-based material in the graphene oxide nanofiltration membrane embedded with the polymer nanomaterial is 0.125-16, preferably 0.5-8.
4. The graphene oxide composite nanofiltration membrane according to claim 1, wherein the polymeric nanomaterial comprises polymeric nanofibers and/or polymeric nanocrystals;
preferably, the diameter of the polymer nanofiber is 10-50nm, and the length-diameter ratio is 10-100;
preferably, the diameter of the macromolecule nanocrystalline is 2-20nm, and the length-diameter ratio is 10-100;
preferably, the polymer nanomaterial comprises one or a combination of several of cellulose nanofibers, cellulose nanocrystals, chitin nanofibers, chitin nanocrystals, chitosan nanofibers, chitosan nanocrystals, lignin nanofibers and lignin nanocrystals.
5. The graphene oxide composite nanofiltration membrane according to claim 1, wherein the graphene oxide-based material comprises graphene oxide and/or modified graphene oxide;
preferably, the graphene oxide 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.
6. The graphene oxide 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;
preferably, the thickness of the base film is 50-200 μm.
7. The graphene oxide composite nanofiltration membrane according to claim 1, wherein the graphene oxide nanofiltration membrane embedded with the polymer nanomaterial is obtained by embedding the polymer nanomaterial between sheets of graphene oxide material by a crosslinking reaction using a crosslinking agent;
preferably, the crosslinking agent comprises a carboxyl crosslinking agent and/or a hydroxyl crosslinking agent; more preferably, the carboxyl crosslinking agent comprises an aziridine-based crosslinking agent and/or a polycarbodiimide-based crosslinking agent; more preferably, the hydroxyl crosslinking agent comprises an isocyanate-based crosslinking agent and/or a polyaldehyde crosslinking agent;
Preferably, the amount of the cross-linking agent is 0.1% -30%, more preferably 0.5% -10% of the total weight of the graphene oxide-based material and the polymer nanomaterial;
preferably, the temperature of the crosslinking reaction is 20-100 ℃, more preferably 50-70 ℃;
preferably, the time of the crosslinking reaction is 2 minutes to one week.
8. The graphene oxide composite nanofiltration membrane according to claim 1, wherein the flux of the graphene oxide composite nanofiltration membrane for filtering 2000ppm sodium sulfate solution is 5-30L/(m) 2 H Bar), the desalination rate is 50-95%;
preferably, the flux of 2000ppm of active dye solution filtered by the graphene oxide composite nanofiltration membrane 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 composite nanofiltration membrane is 3-10L/(m) 2 H Bar), dye retention of 95-99.9%, desalination rate<15％。
9. A method for preparing the graphene oxide composite nanofiltration membrane according to any one of claims 1 to 8, comprising the steps of: coating a mixed solution containing graphene oxide materials, polymer nano materials and a cross-linking agent on the surface of a base film, performing a cross-linking reaction, embedding the polymer nano materials between the sheets of the graphene oxide materials in a cross-linking manner, and forming a graphene oxide nanofiltration film embedded with the polymer nano materials on the surface of the base film to obtain the graphene oxide composite nanofiltration film;
Preferably, in the mixed solution, the weight ratio of the polymer nano material to the graphene oxide material is 0.125-16, more preferably 0.5-8;
preferably, in the mixed solution, the amount of the cross-linking agent is 0.1% -30% of the total weight of the graphene oxide-based material and the polymer nanomaterial, and more preferably 0.5% -10%;
preferably, in the mixed solution, the content of the graphene oxide material is 0.5-10g/L, more preferably 1-4g/L;
preferably, the coating mode comprises one or a combination of a plurality of wire rod coating, slot coating and micro-concave coating;
preferably, the temperature of the crosslinking reaction is 20-100 ℃, more preferably 50-70 ℃;
preferably, the time of the crosslinking reaction is 2 minutes to one week.
10. Use of the graphene oxide composite nanofiltration membrane of any one of claims 1-8 for treating high-salt wastewater containing dye;
preferably, the application is the application of the graphene oxide 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 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％。
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| CN117482759A (en) * | 2023-11-10 | 2024-02-02 | 浙江大学绍兴研究院 | Biomass-based nanofiltration membrane, preparation method and application |
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| CN117000045A (en) * | 2023-06-01 | 2023-11-07 | 贵州省材料产业技术研究院 | Loose nanofiltration membrane for removing heavy metals and preparation method thereof |
| CN117000045B (en) * | 2023-06-01 | 2024-02-20 | 贵州省材料产业技术研究院 | Loose nanofiltration membrane for removing heavy metals and preparation method thereof |
| CN117482759A (en) * | 2023-11-10 | 2024-02-02 | 浙江大学绍兴研究院 | Biomass-based nanofiltration membrane, preparation method and application |
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