CN112516813B - Graphene-polyurethane composite filtering membrane for oil-water separation and preparation method thereof - Google Patents
Graphene-polyurethane composite filtering membrane for oil-water separation and preparation method thereof Download PDFInfo
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- 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
- B01D69/12—Composite membranes; Ultra-thin membranes
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- 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
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/40—Devices for separating or removing fatty or oily substances or similar floating material
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- 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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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/16—Nature of the water, waste water, sewage or sludge to be treated from metallurgical processes, i.e. from the production, refining or treatment of metals, e.g. galvanic wastes
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/26—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof
- C02F2103/28—Nature of the water, waste water, sewage or sludge to be treated from the processing of plants or parts thereof from the paper or cellulose industry
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/30—Nature of the water, waste water, sewage or sludge to be treated from the textile industry
Abstract
The invention discloses a graphene-polyurethane composite filtering membrane for oil-water separation and a preparation method thereof, and belongs to the field of oil-water separation. The technical scheme comprises the following steps: preparing polydopamine powder; preparing a graphene dispersion liquid; preparing polydopamine-graphene powder; adding nano zinc oxide to obtain dopamine-graphene-nano zinc oxide mixed powder; treating the filter screen; mixing polytetramethylene glycol and diisocyanate, adding dimethyl acetamide to dissolve to obtain a prepolymer dissolving solution; adding dopamine-graphene-nano zinc oxide mixed powder, and adding diethanolamine and ethylenediamine to obtain a membrane casting solution; and putting the filter screen into the membrane casting solution to obtain the graphene-polyurethane oil-water separation membrane. The invention has the beneficial effects that: the hydrophilicity of the surface of the filtering membrane is improved, the surface roughness of the membrane is improved, the oil-water separation effect is enhanced, the characteristic strength of the filtering membrane is enhanced, the adhesion degree of the filtering membrane attached to the filtering net is enhanced, and the use requirements of various environments are met.
Description
Technical Field
The invention relates to a filtering membrane used in the field of oil-water separation and a preparation method thereof, in particular to a graphene-polyurethane composite filtering membrane used for oil-water separation and a preparation method thereof.
Background
The purified water resource is becoming a precious and scarce resource, and the sewage resource is the most important way to increase the supply of purified water. Industrial sewage and urban domestic sewage are two main sewage resources in China. The industrial sewage recycling not only can save a large amount of fresh water resources, but also can reduce pollution discharge, thereby achieving the purpose of environmental protection. The total discharge amount of domestic sewage in cities of China is almost equal to the using amount of tap water, the part of water only contains about 0.1 percent of pollutants, and the rest of the water exists mostly in the form of water sources, so that the sewage becomes the second large sewage resource.
The membrane separation technology is a novel oil-water separation mode, and has the advantages of low energy consumption, high single-stage separation efficiency, flexible and simple process, low environmental pollution, strong universality and the like. Membranes are the core of membrane separation technology. With the development of material science, the research and development of surface materials based on special wettability are rapid in recent years, and the surface materials mainly comprise super-hydrophilic, super-hydrophobic, super-oleophilic, super-oleophobic, super-amphiphobic, super-amphiphilic surfaces and the like. The super-oleophobic or super-hydrophobic separation material is obtained by designing the special wettability of the surface of the material, which is undoubtedly the most effective means for improving the oil-water separation performance, especially a membrane with super-hydrophilic and underwater super-oleophobic performances.
The graphene assembly is used as a membrane material, large-scale low-cost preparation of the graphene material is realized in the early stage, and the graphene assembly prepared by using the graphene material as a raw material is low in cost, simple in preparation process, high in mechanical strength, high in chemical and thermal stability and capable of being further popularized and applied as an excellent membrane material. The graphene composite filtering membrane with excellent super-hydrophilicity and underwater super-lipophobicity at normal temperature can be prepared, and the graphene composite filtering membrane is high in separation efficiency, high in separation speed, green, environment-friendly, excellent in anti-fouling performance, recyclable and long in service life. The hydrophilic graphene oxide is successfully coated on different filter screens with different apertures, and the prepared filter screen has excellent super-hydrophilic and underwater super-oleophobic characteristics.
The method has the defects that the graphene oxide is simply accumulated on the surface of the filter screen, and the combination is not firm enough. The surface of the filter screen is coated with a layer of polydopamine film, and the prepared filter screen shows ultrahigh hydrophobicity and can be used for separating a series of oil/water mixtures. On the basis, in order to achieve the practical field application of the filter screen, the filter screen is generally required to be fixed on a filter device or a cross-flow filter device for use. In the process, the filter screen and the membrane body are subjected to huge pressure from a liquid column, so that the filter screen and the graphene and polydopamine membrane loaded on the filter screen are required to have certain mechanical strength and adhesive force. Therefore, how to improve the strength of the graphene-polydopamine film and improve the adhesion degree of the graphene-polydopamine film with a loaded filter screen is a problem to be solved urgently at present.
Disclosure of Invention
In order to solve the problems, the invention provides a graphene-polyurethane composite filtering membrane for oil-water separation and a preparation method thereof. The introduction of polydopamine into graphene also improves the hydrophilicity of the surface of the filtering membrane, and the introduction of nano zinc oxide improves the surface roughness of the membrane and enhances the oil-water separation effect. The graphene-polydopamine-nano zinc oxide is combined with polyurethane, so that the characteristic strength of the filtering membrane is enhanced, the adhesion degree of the filtering membrane with an attached filtering net is also enhanced, and certain impact force and shearing force can be borne, so that the filtering membrane can meet the use requirements of various environments.
In order to achieve the above object, the present invention provides a method for preparing a graphene-polyurethane composite filtration membrane for oil-water separation, comprising the steps of:
(A) Adding dopamine hydrochloride into a Tris-HCl buffer solution with the pH value of 8.5 to prepare a solution with the concentration of 2.0mg/ml, stirring for 24 hours under an aerobic condition, gradually changing the solution from colorless to brownish black, centrifuging by using a centrifugal machine at the rotating speed of 1000rpm, collecting precipitates, and drying at the temperature of 55 ℃ to obtain polydopamine powder;
(B) Drying graphene at 60 ℃ for 12h, dissolving in deionized water, and treating with ultrasonic waves for 30min to obtain a graphene dispersion liquid;
(C) Adding the polydopamine powder in the step (A) into a Tris-HCl buffer solution with the pH value of 8.5 to prepare a polydopamine buffer solution, dropwise adding the polydopamine buffer solution into the graphene dispersion liquid in the step (B) under magnetic stirring for 60min to react to obtain a black solution, centrifuging the black solution, collecting the precipitate, and drying at 65 ℃ to obtain polydopamine-graphene powder;
(D) Drying nano zinc oxide at 60 ℃ for 12H, dissolving polydopamine-graphene powder in deionized water, treating with ultrasonic waves for 30min to obtain a polydopamine-graphene solution, adding the dried nano zinc oxide into the polydopamine-graphene solution, treating with ultrasonic waves for 30min to form a uniform mixed solution, adding 1ml of H into the mixed solution 2 O 2 And 0.5ml NH 3 ·H 2 O, dispersing for 10min, mixing the mixture with H 2 O 2 And NH 3 ·H 2 Treating the mixture in a hot water bath at 180 ℃ for 5 hours at a ratio of O of 50;
(E) Soaking the filter screen in acetone and anhydrous ethanol, placing into deionized water, treating with ultrasonic wave for 30min, and drying at 60 deg.C;
(F) Carrying out a constant-temperature reaction on a mixture of polytetramethylene glycol and diisocyanate at 60 ℃ for 2h to carry out prepolymerization, then cooling to 50 ℃, and adding dimethylacetamide to dissolve to obtain a prepolymer dissolving solution;
(G) Cooling the prepolymer dissolving solution obtained in the step (F) to 45 ℃, adding the dopamine-graphene-nano zinc oxide mixed powder obtained in the step (D), treating for 1h by using ultrasonic waves, then slowly adding diethanolamine and ethylenediamine, and reacting for 30min to obtain a membrane casting solution;
(H) And (5) placing the filter screen treated in the step (E) into the membrane casting solution in the step (G), soaking for 5min, taking out, and curing at 100 ℃ for 12h to obtain the graphene-polyurethane oil-water separation membrane.
The concentration of the polydopamine buffer solution prepared from the polydopamine powder and the Tris-HCL buffer solution in the step (C) is 0.2-0.5mg/ml.
The polydopamine modified graphene oxide serving as the surface coating of the filter screen can improve the cohesiveness of the coating, also improves the hydrophilicity of the surface of the mesh, enhances the hydrophilicity and underwater oil stain resistance of the surface of the steel wire mesh, and enables the filter screen to have a remarkable separation effect on an oil-water mixture.
The mass ratio of the nano zinc oxide to the dopamine-graphene powder in the step (D) is 1:1-10.
The rough structure of the nano zinc oxide can make the hydrophilic surface more hydrophilic so as to realize super-hydrophilicity, realize the removal of a small amount of or trace oil in water, improve the surface energy and strong polarity of the filter screen, and further realize the purpose of oil purification.
In the step (F), the mass ratio of the mixture of the polytetramethylene glycol and the diisocyanate is 3-7:1, and the total mass is 25-30g.
The addition amount of the dopamine-graphene-nano zinc oxide mixed powder is 0.1-0.7% of the total mass of the polytetramethylene glycol and the diisocyanate.
The amount of dimethylacetamide added in the step (F) is 1 to 20g.
And (G) adding diethanolamine and ethylenediamine in the mass ratio of 1:5 into the mixture in the step (G), wherein the total mass of the mixture is 0.6-1.0G.
The polyurethane is an elastic block copolymer which is formed by a flexible soft segment region and a rigid functional group hard segment region, and the special chemical structure endows the polyurethane material with the characteristics of high modulus, high strength and the like, and simultaneously has excellent elasticity and flexibility at low temperature.
The polydopamine-graphene and polyurethane have good interfacial bonding, and the interfacial covalent bond of the polydopamine-graphene and polyurethane causes good interfacial action of the polydopamine-graphene in the polyurethane and induced change of a polyurethane matrix micro-phase separation structure. The addition of the polydopamine-graphene can greatly improve the quantity of polyurethane hard phase micro-regions and reduce the size of the hard phase micro-regions, thereby playing a role in enhancing the mechanical property and enhancing the strength, the fracture strain and the toughness of the composite material.
The filter screen in the step (E) is a metal screen or a nylon screen.
In order to achieve the purpose of the invention, the invention also provides the graphene-polyurethane composite filtering membrane for oil-water separation, which is prepared by the preparation method.
The graphene-polyurethane composite filtering membrane for oil-water separation is applied to oil-water separation of oil fields and wastewater treatment of printing and dyeing, papermaking or electroplating industries.
The beneficial effects of the invention are: the introduction of polydopamine into graphene also improves the hydrophilicity of the surface of the filtering membrane, and the introduction of nano zinc oxide improves the surface roughness of the membrane and enhances the oil-water separation effect. The graphene-polydopamine-nano zinc oxide is combined with polyurethane, so that the characteristic strength of the filtering membrane is enhanced, the adhesion degree of the filtering membrane with an attached filtering net is also enhanced, and certain impact force and shearing force can be borne, so that the filtering membrane can meet the use requirements of various environments.
Detailed Description
In order to clearly illustrate the technical features of the present solution, the present solution is explained below by way of specific embodiments.
Example 1
The embodiment of the invention provides a preparation method of a graphene-polyurethane composite filtering membrane for oil-water separation, which comprises the following steps:
(A) Adding dopamine hydrochloride into a Tris-HCl buffer solution with the pH value of 8.5 to prepare a solution with the concentration of 2.0mg/ml, stirring for 24 hours under an aerobic condition, gradually changing the solution from colorless to brownish black, centrifuging by using a centrifugal machine at the rotating speed of 1000rpm, collecting precipitates, and drying at the temperature of 55 ℃ to obtain polydopamine powder;
(B) Drying graphene at 60 ℃ for 12 hours, dissolving the graphene in deionized water, and treating the graphene for 30min by using ultrasonic waves to obtain a graphene dispersion liquid;
(C) Adding the polydopamine powder in the step (A) into a Tris-HCl buffer solution with the pH value of 8.5 to prepare a polydopamine buffer solution, dropwise adding the polydopamine buffer solution into the graphene dispersion liquid in the step (B) under magnetic stirring for 60min to react to obtain a black solution, centrifuging the black solution, collecting the precipitate, and drying at 65 ℃ to obtain polydopamine-graphene powder;
(D) Drying nano zinc oxide at 60 ℃ for 12H, dissolving polydopamine-graphene powder in deionized water, treating for 30min with ultrasonic waves to obtain a polydopamine-graphene solution, adding the dried nano zinc oxide into the polydopamine-graphene solution, treating for 30min with ultrasonic waves to form a uniform mixed solution, adding 1ml of H into the mixed solution, and adding the H into the mixed solution 2 O 2 And 0.5ml NH 3 ·H 2 O, dispersing for 10min, mixing the mixture with H 2 O 2 And NH 3 ·H 2 The proportion of O is 50;
(E) Soaking the filter screen in acetone and anhydrous ethanol, placing into deionized water, treating with ultrasonic wave for 30min, and drying at 60 deg.C;
(F) Carrying out a constant-temperature reaction on a mixture of polytetramethylene glycol and diisocyanate at 60 ℃ for 2h to carry out prepolymerization, then cooling to 50 ℃, and adding dimethylacetamide to dissolve to obtain a prepolymer dissolving solution;
(G) Cooling the prepolymer dissolving solution in the step (F) to 45 ℃, adding the dopamine-graphene-nano zinc oxide mixed powder in the step (D), treating for 1h by ultrasonic waves, slowly adding diethanolamine and ethylenediamine, and reacting for 30min to obtain a casting solution;
(H) And (5) placing the filter screen treated in the step (E) into the membrane casting solution in the step (G), soaking for 5min, taking out, and curing at 100 ℃ for 12h to obtain the graphene-polyurethane oil-water separation membrane.
The concentration of the polydopamine buffer solution prepared from the polydopamine powder and the Tris-HCL buffer solution in the step (C) is 0.2mg/ml.
The mass ratio of the nano zinc oxide to the dopamine-graphene powder in the step (D) is 1:6.
The mass ratio of the polytetramethylene glycol and diisocyanate mixture in step (F) was 5:1 and the total mass was 30g.
The adding amount of the dopamine-graphene-nano zinc oxide mixed powder is 0.5 percent of the total mass of the polytetramethylene glycol and the diisocyanate.
Dimethylacetamide was added in an amount of 10g in step (F).
And (G) adding diethanolamine and ethylenediamine with the mass ratio of 1:5 into the mixture, wherein the total mass is 0.8G.
The filter screen in the step (E) is a metal screen.
Example 2
The embodiment of the invention provides a preparation method of a graphene-polyurethane composite filtering membrane for oil-water separation, which comprises the following steps, wherein the preparation method refers to the embodiment 1, but is different from the embodiment 1 in that:
the concentration of the polydopamine buffer solution prepared from the polydopamine powder and the Tris-HCL buffer solution in the step (C) is 0.3mg/ml.
The mass ratio of the nano zinc oxide to the dopamine-graphene powder in the step (D) is 1:4.
The mass ratio of the polytetramethylene glycol and diisocyanate mixture in step (F) was 3:1 with a total mass of 25g.
The adding amount of the dopamine-graphene-nano zinc oxide mixed powder is 0.1 percent of the total mass of the polytetramethylene glycol and the diisocyanate.
Dimethylacetamide was added in an amount of 1g in step (F).
And (G) adding diethanolamine and ethylenediamine in the mass ratio of 1:5 into the mixture, wherein the total mass of the mixture is 0.6G.
The filter screen in the step (E) is a nylon screen.
Example 3
The embodiment of the invention provides a preparation method of a graphene-polyurethane composite filtering membrane for oil-water separation, which comprises the following steps, wherein the preparation method refers to the embodiment 1, but the preparation method is different from the embodiment 1 in that:
the concentration of the polydopamine buffer solution prepared from the polydopamine powder and the Tris-HCL buffer solution in the step (C) is 0.5mg/ml.
The mass ratio of the nano zinc oxide to the dopamine-graphene powder in the step (D) is 1:8.
The mass ratio of the polytetramethylene glycol and diisocyanate mixture in step (F) was 7:1 and the total mass was 30g.
The adding amount of the dopamine-graphene-nano zinc oxide mixed powder is 0.3 percent of the total mass of the polytetramethylene glycol and the diisocyanate.
Dimethylacetamide was added in an amount of 20g in step (F).
And (G) adding diethanolamine and ethylenediamine with the mass ratio of 1:5 into the mixture, wherein the total mass is 1.0G.
The filter screen in the step (E) is a metal screen.
Example 4
The embodiment of the invention provides a preparation method of a graphene-polyurethane composite filtering membrane for oil-water separation, which comprises the following steps, wherein the preparation method refers to the embodiment 1, but is different from the embodiment 1 in that:
the concentration of the polydopamine buffer solution prepared from the polydopamine powder and the Tris-HCL buffer solution in the step (C) is 0.4mg/ml.
The mass ratio of the nano zinc oxide to the dopamine-graphene powder in the step (D) is 1.
The mass ratio of the polytetramethylene glycol and diisocyanate mixture in step (F) was 4:1 and the total mass was 27g.
The adding amount of the dopamine-graphene-nano zinc oxide mixed powder is 0.7 percent of the total mass of the polytetramethylene glycol and the diisocyanate.
Dimethylacetamide was added in an amount of 5g in step (F).
And (G) adding diethanolamine and ethylenediamine with the mass ratio of 1:5 into the mixture, wherein the total mass is 0.7G.
The filter screen in the step (E) is a nylon screen.
Example 5
The embodiment of the invention provides a preparation method of a graphene-polyurethane composite filtering membrane for oil-water separation, which comprises the following steps, wherein the preparation method refers to the embodiment 1, but is different from the embodiment 1 in that:
the concentration of the polydopamine buffer solution prepared from the polydopamine powder and the Tris-HCL buffer solution in the step (C) is 0.3mg/ml.
The mass ratio of the nano zinc oxide to the dopamine-graphene powder in the step (D) is 1:2.
In step (F), the mass ratio of the polytetramethylene glycol to the diisocyanate mixture was 6:1 and the total mass was 28g.
The adding amount of the dopamine-graphene-nano zinc oxide mixed powder is 0.2 percent of the total mass of the polytetramethylene glycol and the diisocyanate.
Dimethylacetamide was added in an amount of 15g in step (F).
And (G) adding diethanolamine and ethylenediamine with the mass ratio of 1:5 into the mixture, wherein the total mass is 0.6G.
The filter screen in the step (E) is a metal screen.
Example 6
The embodiment of the invention provides a preparation method of a graphene-polyurethane composite filtering membrane for oil-water separation, which comprises the following steps, wherein the preparation method refers to the embodiment 1, but is different from the embodiment 1 in that:
the concentration of the polydopamine buffer solution prepared from the polydopamine powder and the Tris-HCL buffer solution in the step (C) is 0.3mg/ml.
The mass ratio of the nano zinc oxide to the dopamine-graphene powder in the step (D) is 1:1.
The mass ratio of the polytetramethylene glycol and diisocyanate mixture in step (F) was 5:1 and the total mass was 26g.
The adding amount of the dopamine-graphene-nano zinc oxide mixed powder is 0.6 percent of the total mass of the polytetramethylene glycol and the diisocyanate.
Dimethylacetamide was added in an amount of 18g in step (F).
And (G) adding diethanolamine and ethylenediamine with the mass ratio of 1:5 into the mixture, wherein the total mass is 0.9G.
The filter screen in the step (E) is a metal screen.
Example 7
The embodiment of the invention provides a graphene-polyurethane composite filtering membrane for oil-water separation, which is prepared by the preparation method in the embodiment 6.
Example 8
The embodiment of the invention provides a graphene-polyurethane composite filtering membrane for oil-water separation, which is applied to oil-water separation in an oil field and wastewater treatment in printing and dyeing, papermaking or electroplating industries.
The oil-water separation efficiency test of the filtering membrane obtained by the invention
The test method comprises the following steps: the oil-water separation test adopts a funnel filtering device. And (4) removing the sand core of the sand core funnel, placing the sample to be detected, and fixing the whole by using a clamp. In the oil-water separation test, the reagents used were oil of various oils and deionized water. The mixing ratio of the oil and the deionized water is 1:1, and the oil and the deionized water are used as oil-water mixed liquid for separation. When the liquid level above the filter screen is stable and no water drops drop any more, the part of liquid (oil) is poured back into the measuring cylinder to measure the volume of the liquid after separation, and the volume is recorded. This was repeated a number of times and the test was performed on each sample. And finally, calculating the obtained result to obtain the oil-water separation efficiency, wherein the formula is as follows:
R＝V ob /V oa x100％
wherein R is the oil-water separation efficiency (%), vob is the volume of the oil after separation (m L), voa is the volume of the oil before separation (m L)
And (3) experimental design: adopts metal net and nylon net, two kinds of filter net. The aperture of the filter screen is 300 meshes.
Soaking the filter screen in acetone and anhydrous ethanol, placing into deionized water, treating with ultrasonic wave for 30min, and drying at 60 deg.C.
TABLE 1 Effect of Polydopamine dosage on omentum oil-water separation efficiency
As shown in Table 1, the oil-water separation efficiency of the filter screen without addition polymerization of dopamine is only 96%, while the oil-water filtration efficiency of the filter screen with addition of polydopamine exceeds 99%, which shows that the polydopamine modified graphene oxide serving as a surface coating of the filter screen can improve the hydrophilicity of the mesh surface, enhance the hydrophilicity and the oil stain resistance of the steel wire mesh surface and ensure that the filter screen has a remarkable separation effect on an oil-water mixture.
Soaking the filter screen in acetone and anhydrous ethanol, placing into deionized water, treating with ultrasonic wave for 30min, and drying at 60 deg.C.
TABLE 2 influence of nano-zinc oxide on the oil-water separation efficiency of omentum
As shown in Table 2, the oil-water separation efficiency of the filter screen without the added nano zinc oxide is only 95%, and the oil-water separation efficiency with the added nano oxidizing property exceeds 99% by adopting the method of the invention, which indicates that the hydrophilic surface can be more hydrophilic due to the coarse structure of the nano zinc oxide, so that super-hydrophilicity is realized, the removal of a small amount of or trace oil in water is realized, the surface energy and strong polarity of the filter screen are improved, and the purpose of oil purification is realized.
Soaking the filter screen in acetone and anhydrous ethanol, placing into deionized water, treating with ultrasonic wave for 30min, and drying at 60 deg.C.
TABLE 3 influence of polyurethane on the oil-water separation efficiency of omentum
In the table, the mass percentages are: the adding amount of the polydopamine-graphene-nano zinc oxide mixed powder is the percentage of the total mass of the polytetramethylene glycol and the diisocyanate.
As can be seen from table 3, the filter screen prepared by combining polydopamine-graphene-nano zinc oxide and polyurethane still maintains high 99% oil-water separation efficiency, which indicates that the polydopamine-graphene-nano zinc oxide and polyurethane have good synergistic effect in oil-water separation, and the oil-water separation efficiency is not reduced by mutual influence, but is promoted.
Carrying out an adhesion test on the graphene-polyurethane composite filtering membrane for oil-water separation:
comparative test example the preparation procedure was as follows, using steps (a) - (D) of the preparation method of example 3, wherein step (D) was drying nano zinc oxide at 60 ℃ for 12H, dissolving poly dopamine-graphene powder in deionized water, treating with ultrasound for 30min to obtain poly dopamine-graphene solution, adding dried nano zinc oxide to poly dopamine-graphene solution, treating with ultrasound for 30min to form a uniform mixed solution, adding 1ml H to the mixed solution 2 O 2 And 0.5ml NH 3 ·H 2 O, dispersing for 10min, mixing the liquid with H 2 O 2 And NH 3 ·H 2 And (3) treating the mixture in a hot water bath at 180 ℃ for 5 hours according to the proportion of O being 50.
Soaking the filter screen in acetone and absolute ethyl alcohol in the step (E) in the embodiment 3, putting the filter screen into deionized water, treating the filter screen for 30min by using ultrasonic waves, and drying the filter screen at the temperature of 60 ℃ for later use;
and (5) placing the filter screen treated in the step (E) into a polydopamine-graphene-nano zinc oxide casting solution, and soaking for 5min to obtain a comparative test example.
And (3) carrying out an adhesion test on the filtering membrane:
and (3) placing the filter screen into test liquid, soaking the filter screen in the test liquid for different time, different temperature and different test liquids, and then testing the oil-water separation efficiency of the filter screen.
TABLE 4 Filter Membrane adhesion test
Standard test solutions: mixture of oil and deionized water 1:1 and mixture of 1:1 in oil-water separation efficiency test experiment
As shown in table 4, when polydopamine-graphene-nano zinc oxide is not combined with polyurethane, the oil-water separation efficiency decreases with the increase of the soaking time, which indicates that the polydopamine-graphene-nano zinc oxide is separated from the polyurethane, while the oil-water separation efficiency of the graphene-polyurethane composite filter membrane remains substantially unchanged within 12 hours and slightly decreases within 24-48 hours; when polydopamine-graphene-nano zinc oxide is not combined with polyurethane, the filtering membrane is greatly influenced by the temperature, the oil-water separation efficiency is reduced to 98% from the original 99% along with the increase of the temperature, and the oil-water separation efficiency of the graphene-polyurethane composite filtering membrane is still kept to be over 99%, so that the stability of the filtering membrane to the temperature at different temperatures is improved by adding the polyurethane. The polydopamine-graphene-nano zinc oxide shows different oil-water separation efficiencies in the environments of various test solutions when not combined with polyurethane, which indicates the instability of the polydopamine-graphene-nano zinc oxide in different solvents and adhesion with a filter screen, and the graphene-polyurethane composite filter membrane keeps a relatively stable state. Because the polyurethane has excellent physical properties and chemical properties such as aging resistance. The polyurethane is an elastic block copolymer consisting of a flexible soft segment region and a rigid functional group hard segment region, and the special chemical structure endows the polyurethane material with the characteristics of high modulus, high strength and the like, and also has excellent elasticity and flexibility at low temperature.
The polydopamine-graphene and polyurethane have good interfacial bonding, and the interfacial covalent bond of the polydopamine-graphene and polyurethane causes good interfacial action of the polydopamine-graphene in the polyurethane and induced change of a polyurethane matrix micro-phase separation structure. The addition of the polydopamine-graphene can greatly improve the quantity of polyurethane hard phase micro-regions and reduce the size of the hard phase micro-regions, thereby playing a role in enhancing the mechanical property and enhancing the strength, the fracture strain and the toughness of the composite material. The two interact with each other to improve the adhesiveness with the filter screen and the stability in various environments.
The technical features of the present invention which are not described in the above embodiments may be implemented by or using the prior art, and are not described herein again, of course, the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and variations, modifications, additions or substitutions which may be made by those skilled in the art within the spirit and scope of the present invention should also fall within the protection scope of the present invention.
Claims (2)
1. A preparation method of a graphene-polyurethane composite filtering membrane for oil-water separation comprises the following steps:
(A) Adding dopamine hydrochloride into a Tris-HCl buffer solution with the pH value of 8.5 to prepare a solution with the concentration of 2.0mg/ml, stirring for 24 hours under an aerobic condition, gradually changing the solution from colorless to brownish black, centrifuging by using a centrifuge at the rotation speed of 1000rpm, collecting precipitates, and drying at the temperature of 55 ℃ to obtain polydopamine powder;
(B) Drying graphene at 60 ℃ for 12h, dissolving in deionized water, and treating with ultrasonic waves for 30min to obtain a graphene dispersion liquid;
(C) Adding the polydopamine powder in the step (A) into Tris-HCl buffer solution with the pH value of 8.5 to prepare polydopamine buffer solution, dropwise adding the polydopamine buffer solution into the graphene dispersion liquid in the step (B) under magnetic stirring, reacting for 60min to obtain black solution, centrifuging the black solution, collecting precipitate, and drying at 65 ℃ to obtain polydopamine-graphene powder;
(D) Drying nano zinc oxide at 60 ℃ for 12h, dissolving polydopamine-graphene powder in deionized water, treating with ultrasonic waves for 30min to obtain a polydopamine-graphene solution, adding the dried nano zinc oxide into the polydopamine-graphene solution, treating with ultrasonic waves for 30min to form a uniform mixed solution, adding 1ml H into the mixed solution 2 O 2 And 0.5ml NH 3 ·H 2 O, dispersing for 10min, mixing the mixture with H 2 O 2 And NH 3 ·H 2 O volume ratio 50Drying for 1h at 100 ℃ to obtain polydopamine-graphene-nano zinc oxide mixed powder;
(E) Soaking the filter screen in acetone and anhydrous ethanol, placing into deionized water, treating with ultrasonic wave for 30min, and drying at 60 deg.C;
(F) Carrying out a constant-temperature reaction on polytetramethylene glycol and diisocyanate at 60 ℃ for 2h to carry out prepolymerization, then cooling to 50 ℃, and adding dimethylacetamide to dissolve to obtain a prepolymer dissolving solution;
(G) Cooling the prepolymer dissolving liquid in the step (F) to 45 ℃, adding the polydopamine-graphene-nano zinc oxide mixed powder in the step (D), treating for 1h by ultrasonic waves, slowly adding diethanolamine and ethylenediamine, and reacting for 30min to obtain a casting solution;
(H) Placing the filter screen treated in the step (E) into the membrane casting solution in the step (G), soaking for 5min, taking out, and curing at 100 ℃ for 12h to obtain a graphene-polyurethane oil-water separation membrane;
the concentration of the polydopamine buffer solution prepared by the polydopamine powder and the Tris-HCL buffer solution in the step (C) is 0.2-0.5mg/ml;
the mass ratio of the nano zinc oxide to the polydopamine-graphene powder in the step (D) is 1:1-10;
in the step (F), the mass ratio of the polytetramethylene glycol to the diisocyanate is 3-7:1, and the total mass is 25-30g;
the adding amount of the polydopamine-graphene-nano zinc oxide mixed powder is 0.1-0.7 percent of the total mass of the polytetramethylene glycol and the diisocyanate;
adding 1-20g of dimethylacetamide in the step (F);
adding diethanolamine and ethylenediamine in the mass ratio of 1:5 into the step (G), wherein the total mass is 0.6-1.0G;
the filter screen in the step (E) is a metal screen or a nylon screen.
2. A graphene-polyurethane composite filtration membrane for oil-water separation prepared according to the preparation method of claim 1.
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