Preparation method and application of CNTs@SiO2@CeO2 composite film

Abstract

The application discloses a preparation method of a CNTs@SiO2@CeO2 composite membrane and application thereof, and comprises the following steps: preparing CNTs material; adding SiO2 and CeO2 nanoparticles into the CNTs solution, uniformly stirring, and then drying and grinding to form composite particles, which are then dispersed in an organic solvent to obtain a dispersion liquid; adding PVDF powder and a pore-forming agent into the dispersion liquid, heating and stirring to obtain a casting solution, and then defoaming, blade coating and obtaining a membrane; and placing the membrane into water to separate the membrane, and then soaking to remove residual organic solvents, so as to obtain the CNTs@SiO2@CeO2 composite membrane. The CNTs@SiO2@CeO2 composite membrane has excellent separation efficiency and flux recovery rate for five different oil-water mixtures of kerosene, gasoline, 1,2-dichloroethane, edible oil and n-hexane. The preparation process of the oil-water separation membrane is simple, the cost is low, the reaction condition is mild, and when the oil-water separation membrane is applied to organic wastewater separation, the oil-water separation membrane has the advantages of high efficiency, good removal performance and good recycling performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of membrane separation technology, and particularly relates to a preparation method of a CNTs@SiO2@CeO2 composite membrane and application thereof. BACKGROUND

[0002] With the development of industrial production, more and more oil-containing wastewater and oil spill accidents have caused serious water pollution, which threatens the ecological environment of human beings. Traditional oil removal technologies, such as gravity sedimentation, flotation, coagulation, adsorption, biological treatment and advanced oxidation process, have problems such as low efficiency, high cost, complex process and secondary pollution, and cannot cope with the increasing discharge of oil-containing wastewater. In comparison, membrane filtration is considered as the most effective method due to its low energy cost, high efficiency, simple operation and environmental friendliness.

[0003] In recent decades, membrane separation technology has been widely used in the treatment of oil-containing wastewater due to its low energy consumption, high efficiency and simple operation. Membrane separation technology removes pollutants of a certain particle size in water through specially designed porous materials.

[0004] However, the existing separation membranes generally have problems such as low separation efficiency, poor anti-pollution performance, easy plugging of pore channels by high-viscosity crude oil, and rapid decay of membrane flux. SUMMARY

[0005] This section aims to summarize some aspects of the embodiments of the application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, abstract and title, and such simplifications or omissions cannot be used to limit the scope of the application.

[0006] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0007] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art and provide a preparation method of a CNTs@SiO2@CeO2 composite membrane

[0008] To solve the above technical problems, the present application provides the following technical scheme: a preparation method of a CNTs@SiO2@CeO2 composite membrane, comprising,

[0009] Disperse CNTs into deionized water and stir to form a uniform CNTs dispersion solution;

[0010] Add SiO2 and CeO2 nanoparticles to the CNTs dispersion solution and ultrasonically mix uniformly, dry and grind the composite particles to obtain the composite particles;

[0011] The composite particles are added into an organic solvent and uniformly dispersed by ultrasonic to obtain a dispersion liquid;

[0012] The PVDF powder and a pore-forming agent are added into the dispersion liquid, and heated and stirred to obtain a casting solution, which is defoamed, blade-coated, and a film is obtained;

[0013] The obtained film is repeatedly cleaned in deionized water to remove the organic solvent remaining in the film, and the CNTs@SiO2@CeO2 composite film is obtained.

[0014] As a preferred scheme of the preparation method, the ratio of CNTs, SiO2 and CeO2 is 50-100 mg: 100-150 mg: 100-150 mg.

[0015] As a preferred scheme of the preparation method, the particle size of the composite particles is 0.5-1.5 μm.

[0016] As a preferred scheme of the preparation method, the organic solvent comprises a DMF solution.

[0017] As a preferred scheme of the preparation method, the ratio of the organic solvent and CNTs is 40-80 mL: 5-10 mg.

[0018] As a preferred scheme of the preparation method, the pore-forming agent comprises polyethylene glycol and polyvinylpyrrolidone.

[0019] As a preferred scheme of the preparation method, the ratio of the PVDF powder and the pore-forming agent is 3-5 g: 0.1-0.3 g.

[0020] As a preferred scheme of the preparation method, the heating and stirring to obtain the casting solution is performed at a temperature of 50-70 ℃ for 6-8 h.

[0021] Another object of the present application is to provide a CNTs@SiO2@CeO2 composite film prepared by the preparation method.

[0022] Another object of the present application is to provide an application of the CNTs@SiO2@CeO2 composite film in oil-water mixture separation.

[0023] The present application has the following advantages:

[0024] (1) The CNTs@SiO2@CeO2 composite film prepared by the method has the advantages of good oil filtration effect, good recycling performance, and economic practicability.

[0025] (2) The application provides a preparation method of a CNTs@SiO2@CeO2 composite film, and the CNTs@SiO2@CeO2 composite material is prepared and dispersed in an organic solvent, so that the composite effect is achieved, and the filtration performance of the film is improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor. Among them:

[0027] Figure 1 It is the physical map of the composite film prepared in the embodiment of the application.

[0028] Figure 2 It is the filtration effect diagram of the composite film prepared in the embodiment of the application on different types of oil. DETAILED DESCRIPTION

[0029] In order to make the above-mentioned purposes, features and advantages of the application more obvious and easy to understand, the specific embodiments of the application will be described in detail in the following description.

[0030] In the following description, many specific details are set forth in order to provide a thorough understanding of the application, but the application can also be implemented in other ways different from those described herein, and those skilled in the art can make similar generalizations without departing from the connotation of the application, therefore the application is not limited to the specific embodiments disclosed below.

[0031] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the application. In this specification, "in one embodiment" does not mean the same embodiment, nor is it an independent or alternative embodiment that excludes other embodiments.

[0032] SiO2 nanoparticles in the application are purchased from Bisley New Materials; dimethylacetamide is purchased from the National Pharmaceutical Group; polyvinylpyrrolidone (PVP-K30) is of superior purity and is purchased from the National Pharmaceutical Group, CNTs are purchased from Chengdu Organic Chemical Co., Ltd., and CeO2 nanoparticles are purchased from Suzhou Yuan Te New Material.

[0033] The composite separation membrane in the application is used to test the separation performance of oil-water mixture:

[0034] (1) Water flux test method: the time for 100ml pure water to pass through the composite membrane using a vacuum filtration device is used to determine the water flux of the membrane, and the specific formula is:

[0035] In the formula, V (L), A (m 2 ), Δt (h) are the filtrate volume, effective membrane permeation area, and filtration time, respectively.

[0036] (2) Oil flux test method: the time for 100ml oil-in-water emulsion (kerosene emulsion, the preparation method is: 990mL of deionized water is added to a container, 30mg of SDS is taken as an emulsifier; then, 10mL of kerosene is added to the above solution, ultrasonic stirring for 30min, and then strong stirring for 6h to obtain a surfactant-stabilized emulsion) to pass through the composite membrane using a vacuum filtration device is used to determine the water flux of the membrane, and the specific formula is

[0037] In the formula, V (L), A (m2), Δt (h), ΔP (bar) are the filtrate volume, effective membrane permeation area, filtration time, and transmembrane pressure, respectively.

[0038] (3) Retention rate test method: after 100ml of oil-in-water emulsion (kerosene emulsion, the preparation method is the same as above) passes through the composite membrane using a vacuum filtration device, then the concentration of the solution before and after filtration is measured using an infrared oil measuring instrument, and the specific formula is

[0039] Wherein C i (mg / L) and C0(mg / L) are the oil content in the filtrate after and in the original feed emulsion, respectively.

[0040] (4) Flux recovery rate test method: after the membrane is filtered with 100ml of kerosene using a vacuum filtration device, the water flux is measured again after simple cleaning, and the formula is

[0041] Wherein, J W1 and J W2 are the pure water fluxes before and after filtering the emulsion, respectively.

[0042] Example 1

[0043] (1) 50 mg of CNTs were dispersed into 50 ml of deionized water and stirred at 25°C for 100 min to form a uniform CNTs dispersion.

[0044] (2) Then 100 mg of SiO2 and 100 mg of CeO2 nanoparticles were added to the solution of the CNTs dispersion, mixed uniformly by ultrasonic, and then the composite particles were dried and ground to prevent particle agglomeration.

[0045] (3) The composite particles CNTs@SiO2@CeO2 were added to 40 ml of an organic solvent DMF and then dispersed uniformly by ultrasonic at 60 W for 60 min.

[0046] (4) Then 3 g of PVDF powder and 0.1 g of PVP were added to the dispersion, heated and stirred for 6 h to obtain a casting solution, and left to stand for 12 h to degas.

[0047] (5) The casting solution was scraped with a doctor blade, and the obtained membrane was immediately placed into deionized water for phase inversion. The membrane needed to be soaked in deionized water for more than 24 h, and the water was changed every 2 h to fully exchange the solvent and non-solvent. Finally, a composite separation membrane with a thickness of 100 um was obtained. The physical map of the composite membrane is shown in Figure 1 .

[0048] Example 2

[0049] (1) 80 mg of CNTs were dispersed into 50 ml of deionized water and stirred at 25°C for 120 min to form a uniform CNTs dispersion.

[0050] (2) Then 120 mg of SiO2 nanoparticles and 120 mg of CeO2 were added to the solution of the CNTs dispersion, mixed uniformly by ultrasonic, and then the composite particles were dried and ground to prevent particle agglomeration.

[0051] (3) The composite particles CNTs@SiO2@CeO2 were added to 50 ml of an organic solvent DMF and then dispersed uniformly by ultrasonic at 60 W for 60 min.

[0052] (4) Then 3 g of PVDF powder and 0.1 g of PVP were added to the dispersion, heated and stirred for 6 h to obtain a casting solution, and left to stand for 12 h to degas.

[0053] (5) The casting solution was scraped with a doctor blade, and the obtained membrane was immediately placed into deionized water for phase inversion. The membrane needed to be soaked in deionized water for more than 24 h, and the water was changed every 2 h to fully exchange the solvent and non-solvent. Finally, a composite separation membrane with a thickness of 100 um was obtained.

[0054] Example 3

[0055] (1) 100 mg CNTs were dispersed into 50 ml deionized water and stirred at 25 °C for 130 min to form a uniform CNTs dispersion.

[0056] (2) Then 130 mg of SiO2 and 130 mg of CeO2 nanoparticles were added into the solution of CNTs dispersion, mixed uniformly by 60 W ultrasonic, and then the composite particles were dried and ground to prevent particle agglomeration.

[0057] (3) The obtained yellow crystals and SiO2 nanoparticles were added into 60 ml of ethanol solution, and then treated by ultrasonic for 90 min. The mixed solution after ultrasonic was baked at 90 °C for 12 h to obtain a composite material, and then ground to 1300 mesh by a mortar to reduce its agglomeration, and then the CNTs@SiO2@CeO2 material was collected.

[0058] (4) Then 3 g of PVDF powder and 0.1 g of PVP were added into the dispersion, and heated and stirred for 6 h to obtain a casting solution, and then stood for 12 h to degas.

[0059] (5) The casting solution was scraped by a doctor blade, and then the obtained membrane was immediately put into deionized water for phase inversion. The membrane was soaked in deionized water for more than 24 h, and the water was changed every 2 h to make the solvent and non-solvent fully exchange. Finally, a composite separation membrane with a thickness of 100 um was obtained.

[0060] The CNTs@SiO2@CeO2 composite separation membrane prepared in Example 1 was taken for oil-water mixture separation performance test. Edible oil, n-hexane, kerosene, petroleum ether, 1,2 dichloroethane were used as oil-in-water emulsion (990 mL of deionized water was added to the container, 30 mg of SDS was taken as an emulsifier; then 10 mL of the corresponding oil was added to the above solution, and ultrasonic stirring was performed for 30 min, and then strong stirring was performed for 6 h to obtain a surfactant-stabilized emulsion), and the results are shown in Table 1. Figure 2 ;

[0061] The CNTs@SiO2@CeO2 composite separation membrane prepared in Example was taken for water flux, oil filtration effect and flux recovery rate test, and the results are shown in Table 1.

[0062] Table 1

[0063] Water flux (L / m 2 ·h) Oil flux (L / m 2 • h) Retention (%) Flux recovery (%) Example 1 2355 650.2 99.5 99.2 Example 2 2201 586.2 99.4 98.7 Example 3 2050 535.4 99.2 98.6

[0064] Comparative Example 1

[0065] (1) 50 mg CNTs were dispersed into 50 ml deionized water and stirred at 25 °C for 100 min to form a uniform CNTs dispersion.

[0066] (2) Then 3 g of PVDF powder and 0.1 g of PVP were added to the dispersion, and heated stirring was performed for 6 h to obtain a casting solution, which was left to stand for 12 h to remove bubbles.

[0067] (3) After the casting solution was scraped with a doctor blade, the obtained membrane was immediately put into deionized water for phase inversion, and the membrane was soaked in deionized water for more than 24 h, and the water was changed every 2 h to enable sufficient exchange between the solvent and the non-solvent, and finally a composite separation membrane with a thickness of 100 um was obtained.

[0068] Comparative Example 2

[0069] (1) 100 mg of SiO2 and 100 mg of CeO2 nanoparticles were added to 50 ml of deionized water, and the mixture was uniformly dispersed by ultrasonic treatment, and the composite particles were dried and ground to prevent particle agglomeration.

[0070] (2) The composite particles SiO2@CeO2 were added to 40 ml of an organic solvent DMF, and then ultrasonic treatment was performed at 60 W for 60 min to uniformly disperse the composite particles.

[0071] (3) Then 3 g of PVDF powder and 0.1 g of PVP were added to the dispersion, and heated stirring was performed for 6 h to obtain a casting solution, which was left to stand for 12 h to remove bubbles.

[0072] (4) After the casting solution was scraped with a doctor blade, the obtained membrane was immediately put into deionized water for phase inversion, and the membrane was soaked in deionized water for more than 24 h, and the water was changed every 2 h to enable sufficient exchange between the solvent and the non-solvent, and finally a composite separation membrane with a thickness of 100 um was obtained.

[0073] Comparative Example 3

[0074] (1) 50 mg of CNTs were dispersed in 50 ml of deionized water, and stirring was performed at 25°C for 100 min to form a uniform CNTs dispersion.

[0075] (2) Then 100 mg of SiO2 and 100 mg of CeO2 nanoparticles were added to the CNTs dispersion solution, and the mixture was uniformly dispersed by ultrasonic treatment, and then the composite particles were dried and ground to prevent particle agglomeration.

[0076] (3) The composite particles CNTs@SiO2@CeO2 were added to 40 ml of an organic solvent DMF, and then ultrasonic treatment was performed at 60 W for 60 min to uniformly disperse the composite particles.

[0077] (4) Then 3 g of PVDF powder was added to the dispersion, and heated stirring was performed for 6 h to obtain a casting solution, which was left to stand for 12 h to remove bubbles.

[0078] (5) The casting solution is scraped with a doctor blade and the obtained membrane is immediately placed in deionized water for phase inversion. The membrane needs to be soaked in deionized water for more than 24 h, and the water is changed every 2 h to make the solvent and non-solvent fully exchange. Finally, a composite separation membrane with a thickness of 100 um is obtained.

[0079] The water flux, oil filtration effect and flux recovery rate are as shown in Table 2.

[0080] Table 2

[0081]

[0082] As can be seen from Table 2, the CNTs@SiO2@CeO2 composite separation membrane prepared in Example 1 is subjected to oil-water mixture separation performance test, kerosene is used as an oil-in-water emulsion, and as shown in Table 2, the CNTs material is a continuous and uniform two-dimensional porous network, which can load nanoparticles in the network and on the inside thereof, so that the oil-water separation performance of the composite membrane and the stability of the membrane are greatly improved.

[0083] The carbon nanotubes (CNTs) are compounded with SiO2@CeO2 due to their unique nano-scale pore structure and controllable surface chemical properties. The charged sites on the surface of the composite particles will match each other, so that the composite particles will become very firm and durable.

[0084] Comparative Example 4

[0085] (1) 100 mg of CNTs is dispersed in 50 ml of deionized water and stirred at 25°C for 100 min to form a uniform CNTs dispersion.

[0086] (2) Then 100 mg of SiO2 and 100 mg of CeO2 nanoparticles are added to the CNTs dispersion solution, and the mixture is uniformly mixed by ultrasonic, and then the composite particles are dried and ground to prevent particle agglomeration.

[0087] (3) The composite particles CNTs@SiO2@CeO2 are added to 40 ml of organic solvent DMF, and then dispersed uniformly at 60 W for 60 min;

[0088] (4) Then 3 g of PVDF powder and 0.1 g of PVP are added to the dispersion, and heated and stirred for 6 h to obtain a casting solution, which is left standing for 12 h to degas.

[0089] (5) The casting solution is scraped with a doctor blade and the obtained membrane is immediately placed in deionized water for phase inversion. The membrane needs to be soaked in deionized water for more than 24 h, and the water is changed every 2 h to make the solvent and non-solvent fully exchange. Finally, a composite separation membrane with a thickness of 100 um is obtained.

[0090] Comparative Example 5

[0091] (1) 25 mg of CNTs were dispersed into 50 ml of deionized water and stirred at 25°C for 100 min to form a uniform CNTs dispersion.

[0092] (2) Then, 100 mg of SiO2 and 100 mg of CeO2 nanoparticles were added to the solution of the CNTs dispersion, mixed uniformly by ultrasonic, and then the composite particles were dried and ground to prevent particle agglomeration.

[0093] (3) The composite particles CNTs@SiO2@CeO2 were added to 40 ml of an organic solvent DMF and then dispersed uniformly by ultrasonic at 60 W for 60 min.

[0094] (4) Then, 3 g of PVDF powder and 0.1 g of PVP were added to the dispersion, heated and stirred for 6 h to obtain a casting solution, and left to stand for 12 h to degas.

[0095] (5) After the casting solution was scraped by a doctor blade, the obtained membrane was immediately put into deionized water for phase inversion, and the membrane needed to be soaked in deionized water for more than 24 h, and the water was changed every 2 h to fully exchange the solvent and the non-solvent, and finally a composite separation membrane with a thickness of 100 um was obtained.

[0096] Comparative Example 6 (200 mg of CNTs)

[0097] (1) 200 mg of CNTs were dispersed into 50 ml of deionized water and stirred at 25°C for 100 min to form a uniform CNTs dispersion.

[0098] (2) Then, 100 mg of SiO2 and 100 mg of CeO2 nanoparticles were added to the solution of the CNTs dispersion, mixed uniformly by ultrasonic, and then the composite particles were dried and ground to prevent particle agglomeration.

[0099] (3) The composite particles CNTs@SiO2@CeO2 were added to 40 ml of an organic solvent DMF and then dispersed uniformly by ultrasonic at 60 W for 60 min.

[0100] (4) Then, 3 g of PVDF powder and 0.1 g of PVP were added to the dispersion, heated and stirred for 6 h to obtain a casting solution, and left to stand for 12 h to degas.

[0101] (5) After the casting solution was scraped by a doctor blade, the obtained membrane was immediately put into deionized water for phase inversion, and the membrane needed to be soaked in deionized water for more than 24 h, and the water was changed every 2 h to fully exchange the solvent and the non-solvent, and finally a composite separation membrane with a thickness of 100 um was obtained.

[0102] The performance test results are shown in Table 3.

[0103] Table 3

[0104]

[0105] From Table 3, it can be concluded that too much or too little addition of CNTs will affect the separation effect and water flux of the composite membrane. When too little CNTs are added, the water flux of the membrane will increase due to fewer particles blocking the water channels of the membrane, but the separation effect of the oil-containing wastewater will be poor, which is because the oil contact angle of the composite particles is too small, and the resistance to oil will be weak. However, too many particles will cause the particles to block the water flux of the membrane, and although the separation efficiency will be improved, in general, moderate addition of CNTs will make the overall separation effect best.

[0106] The preparation method of the CNTs@SiO2@CeO2 separation membrane provided by the application mainly has the following principle: in the pore forming mode, a pore former polyvinylpyrrolidone is used to form pores, and particles are embedded in the pore sites of the membrane. Since the zeta potential of the silica particles is negative and the zeta potential of the cerium dioxide particles is positive, there is an attractive force between SiO2 and CeO2. Since the CNTs material is a continuous and uniform two-dimensional porous network, the SiO2 nanoparticles and CeO2 can be loaded in the grid of the CNTs, so that the coating becomes firm and stable, and therefore the composite membrane prepared can achieve good results in oil-water separation.

[0107] It should be noted that the above examples are only used to illustrate the technical solutions of the application and are not limiting. Although the application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the application, and all should be included in the scope of the application.

Claims

1. A method for preparing a CNTs@SiO2@CeO2 composite film, characterized in that: The method comprises the steps of: dispersing CNTs into deionized water and stirring to form a uniform CNTs dispersion solution; adding SiO2 and CeO2 nanoparticles into the CNTs dispersion solution, ultrasonically mixing to be uniform, drying and grinding the composite particles to obtain the composite particles; adding the composite particles into an organic solvent, ultrasonically dispersing to be uniform to obtain a dispersion liquid; adding PVDF powder and a pore-forming agent into the dispersion liquid, heating and stirring to obtain a casting solution, defoaming, blade coating to obtain a film; placing the obtained film into deionized water for repeated cleaning to remove the organic solvent remaining in the film, and obtaining the CNTs@SiO2@CeO2 composite film.

2. The production method according to claim 1, characterized by: The ratio of CNTs, SiO2 and CeO2 is 50-100 mg: 100-150 mg: 100-150 mg.

3. The production method according to claim 1 or 2, characterized by: The particle size of the composite particles is 2-6 nm.

4. The production method according to claim 1, wherein: The organic solvent comprises a DMF solution.

5. The production method according to claim 4, characterized by: The ratio of the organic solvent to CNTs is 40-80 mL: 5-10 mg.

6. The production method according to claim 1, wherein: The pore-forming agent comprises polyethylene glycol and polyvinylpyrrolidone.

7. The production method according to claim 1 or 6, characterized by: The ratio of the PVDF powder to the pore-forming agent is 3-5 g: 0.1-0.3 g.

8. The production method according to claim 1, wherein: The heating and stirring to obtain the casting solution is performed at a temperature of 50-70 °C for 6-8 h.

9. The CNTs@SiO2@CeO2 composite film prepared by the method of any one of claims 1-8.

10. The CNTs@SiO2@CeO2 composite film of claim 9 for use in separating an oil-water mixture.

Images