CN113788970B - Carbon nano tube/microcrystalline cellulose composite membrane and preparation method and application thereof - Google Patents
Carbon nano tube/microcrystalline cellulose composite membrane and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to a carbon nano tube/microcrystalline cellulose composite membrane and a preparation method and application thereof, belonging to the technical field of functional materials. The preparation method of the carbon nano tube/microcrystalline cellulose composite membrane comprises the steps of dispersing aldehyde microcrystalline cellulose and an aminated carbon nano tube in an aqueous solution to perform Schiff base reaction to obtain a suspension, and controlling the aldehyde microcrystalline cellulose in a reaction solution before the reaction: the mass ratio of the aminated carbon nano tube is (0.5-5) to (0.2-1); and (2) collecting solids in the suspension obtained in the step (1), and drying to obtain the carbon nano tube/microcrystalline cellulose composite membrane. The carbon nano tube/microcrystalline cellulose composite membrane obtained by the invention has excellent amphiphilic wettability, excellent photo-thermal property and water evaporation capacity, and can be used as a high-efficiency photo-thermal interface evaporation material for seawater desalination and emulsion separation.
Description
Technical Field
The invention relates to a carbon nano tube/microcrystalline cellulose composite membrane and a preparation method and application thereof, belonging to the technical field of functional materials.
Background
Over the past few years, shortage of drinking water and imbalanced distribution of fresh water resources have become an imminent crisis. Meanwhile, the leakage of ship fuel oil and the random discharge of industrial sewage and domestic sewage cause a great deal of sewage pollution mainly caused by oil-water mixed fuel. The solar heating is concentrated on the interface of air and water by utilizing a photo-thermal material, and the solar water-heating solar water heater is a new technology for obtaining clean water from seawater or sewage for daily use. The carbon-based membrane material generates steam through sunlight collection and heat localization, which brings great hope for sustainable seawater desalination and sewage treatment. Although the development of solar desalination has made effective progress, there is still a need to address the challenges presented by oil-containing seawater, particularly the treatment of nano/sub-micron emulsions. Since oily sewage not only destroys the ecological environment but also poses a serious threat to the health of organisms, the purification of sewage has attracted great attention of researchers.
There are few reports on effective purification of emulsified oily seawater or sewage. In the oily sewage treatment technology, the use of a super-infiltration system for effective filtration and separation of oil-water solution is considered to be a mature process. However, for a filter membrane with a single wettability (superhydrophilic/superhydrophobic), it is difficult to achieve on-demand separation of different types of aqueous oil solutions. Effective cleansing of surfactant stabilized emulsions remains a problem. Meanwhile, the existing preparation process of the photo-thermal film material is complex, expensive equipment is needed for generation, and the exploration of the preparation technology which is convenient to prepare and has the process becomes a research hotspot. Therefore, it is necessary to design a dual-functional core component with good wetting property and photothermal effect to purify oily sewage or seawater.
Disclosure of Invention
In order to solve the technical problems, the invention provides a carbon nano tube/microcrystalline cellulose composite membrane and a preparation method thereof, and the invention adopts the following technical scheme:
the first purpose of the invention is to provide a preparation method of a carbon nano tube/microcrystalline cellulose composite membrane, which comprises the following steps: (1) Dispersing aldehyde microcrystalline cellulose and an aminated carbon nano tube in an aqueous solution to perform Schiff base reaction to obtain a suspension, and controlling the aldehyde microcrystalline cellulose in a reaction solution before the reaction: the mass ratio of the aminated carbon nano tube is (0.5-5) to (0.2-1); (2) And (2) collecting solids in the suspension obtained in the step (1), and drying to obtain the carbon nano tube/microcrystalline cellulose composite membrane.
As an embodiment of the present invention, before the reaction in the step (1), the aldehyde-based microcrystalline cellulose in the reaction solution is controlled: the mass ratio of the aminated carbon nanotube is (0.5-2.5): 0.5. Preferably, the aldehyde-based microcrystalline cellulose: the mass ratio of the aminated carbon nanotube is 2.
As an embodiment of the present invention, before the reaction in the step (1), the aldehyde-based microcrystalline cellulose in the reaction solution is controlled: aminated carbon nanotubes: the mass ratio of the water is (0.5-5) to (0.5-100).
In one embodiment of the present invention, the aminated carbon nanotube in the step (1) has a length of 20-50 μm and a diameter of 8-15nm.
As an embodiment of the present invention, the conditions of the schiff base reaction in the step (1) are: the temperature is 30-50 ℃, and the reaction time is 2-6h.
As an embodiment of the present invention, the conditions of the schiff base reaction in step (1) are as follows: reacting for 2 hours under the ultrasonic condition of 50 ℃.
As an embodiment of the invention, the ultrasonic power in the step (1) is 50-100W.
As an embodiment of the present invention, the method further comprises a step of preparing the aldehyde-based microcrystalline cellulose: and (3) carrying out oxidation reaction on the microcrystalline cellulose and sodium periodate to prepare the aldehyde group microcrystalline cellulose.
As an embodiment of the present invention, the preparation steps of the aldehyde-based microcrystalline cellulose specifically include: dispersing microcrystalline cellulose in an aqueous solution, adjusting the pH value to acidity, adding sodium periodate under a light-tight condition to perform an oxidation reaction to obtain aldehyde microcrystalline cellulose, and cleaning and drying; controlling microcrystalline cellulose in the reaction solution before reaction: sodium periodate: the mass ratio of the water is (0.5-5) to (2-10) to (30-150). Microcrystalline cellulose: sodium periodate: the mass ratio of water is preferably 2.
As an embodiment of the present invention, the conditions of the oxidation reaction in the preparation step of the aldehyde-based microcrystalline cellulose are as follows: the pH value is 2-4, the temperature is 30-50 ℃, and the reaction time is 2-6h. Preferably: reacting in a constant temperature water bath at 40 ℃ for 3h with the pH value of 4. Preferably, it is carried out by means of an oil bath or a water bath.
As an embodiment of the present invention, in the step of preparing the aldehyde-based microcrystalline cellulose, the washing includes alcohol washing and water washing, the alcohol washing uses 95% ethanol or absolute ethanol, and the water washing uses deionized water.
As an embodiment of the present invention, the preparation steps of the aldehyde-based microcrystalline cellulose specifically include: weighing 2g of microcrystalline cellulose, dispersing the microcrystalline cellulose in 60mL of aqueous solution, adjusting the pH value to 4, adding 5g of sodium periodate under the condition of keeping out of the sun, placing the mixture in a constant-temperature water bath at 40 ℃ for 3 hours, adding ethanol and deionized water after the reaction is finished, cleaning (alcohol washing and water washing), and drying at 60 ℃ to obtain the aldehyde group microcrystalline cellulose.
In one embodiment of the present invention, the solid in the suspension obtained in step (1) is collected in step (2) by vacuum-assisted filtration.
As an embodiment of the present invention, the conditions of the vacuum assisted filtration method in the step (2): the pressure is 0.2-1bar, and the suction filtration time is 20-120min. Preferably, the pressure is 0.5bar and suction filtration is carried out for 30min.
As an embodiment of the present invention, the drying conditions in the step (2) and/or the preparation step of the aldehyde-based microcrystalline cellulose are: the drying temperature is 30-50 ℃, and the drying time is 2-6h. Preferably, the step (2) is dried at 50 ℃ for 2h.
The second object of the present invention is to provide a carbon nanotube/microcrystalline cellulose composite film having oil-water amphiphilic wettability, which is prepared by the above method.
The third purpose of the invention is to provide the application of the carbon nano tube/microcrystalline cellulose composite membrane in solar interface evaporation, seawater desalination and sewage purification.
The fourth purpose of the invention is to provide the application of the carbon nano tube/microcrystalline cellulose composite membrane in the separation of water-in-oil emulsion and oil-in-water emulsion.
The invention has the beneficial effects that:
(1) According to the preparation method of the carbon nano tube/microcrystalline cellulose composite membrane, aldehyde microcrystalline cellulose and the aminated carbon nano tube in a specific ratio are subjected to Schiff base reaction, so that the aldehyde microcrystalline cellulose and the aminated carbon nano tube are crosslinked, the dispersibility of the composite membrane material is improved, the solid in the suspension obtained by the Schiff base reaction is collected by means such as negative pressure suction filtration and the like, and the carbon nano tube/microcrystalline cellulose composite membrane is prepared by drying, so that the composite membrane material with good mechanical property, excellent wettability and excellent photo-thermal property is obtained. The preparation method has simple process and easy operation, and can be expanded to large-scale preparation.
(2) The invention is based on the Schiff base reaction of the aldehyde microcrystalline cellulose and the aminated carbon nano tube, and produces unexpected technical effects by optimizing the proportion of the aldehyde microcrystalline cellulose to the aminated carbon nano tube: in one aspect, the resulting carbon nanotube/microcrystalline fiberThe roughness of the cellulose composite membrane material is obviously improved, the dispersibility is good, the contact angle of the cellulose composite membrane material to water and an oil solvent is 0 degree, the excellent amphiphilic wettability is realized, and compared with a microcrystalline cellulose composite membrane, the oil-water amphiphilic wettability is obviously improved. Especially when the aldehyde group microcrystalline cellulose: when the mass ratio of the aminated carbon nanotube is 2:0.5, the obtained carbon nanotube/microcrystalline cellulose composite membrane shows super-hydrophilicity and super-lipophilicity (water drops/oil drops can be completely spread within 0.1 s). On the other hand, the obtained carbon nanotube/microcrystalline cellulose composite film material also has excellent photo-thermal properties: under the irradiation of sunlight, the temperature can be rapidly raised, water is converted into water vapor, high-efficiency interface evaporation is realized, and the interface evaporation rate can reach 1.58Kg m -2 h -1 Is higher than most of the reported existing solar interface evaporation materials (1-1.5 Kg m) -2 h -1 )。
(3) The carbon nanotube/microcrystalline cellulose composite membrane prepared by the method has excellent membrane forming performance, the dispersion performance of the carbon nanotube and the microcrystalline cellulose is improved through Schiff base reaction, the roughness of the composite membrane is improved, and the amphiphilic wettability of the composite membrane is further improved.
(4) The carbon nano tube/microcrystalline cellulose composite membrane can be used as a high-quality and high-efficiency super-wetting filter material for separating a water-in-oil emulsion and an oil-in-water emulsion.
(5) The carbon nano tube/microcrystalline cellulose composite membrane has good mechanical property, excellent amphiphilic wettability and excellent photo-thermal property, and can be used as a high-quality and high-efficiency photo-thermal interface evaporation material for seawater desalination and sewage purification. Has good application prospect in the fields of solar energy utilization, seawater desalination, oil/water emulsion separation and the like.
Drawings
FIG. 1 is SEM photographs of the morphology tests of the composite films obtained in examples 1 to 5 and comparative example 1, wherein FIG. 1 shows (a) CNT/microcrystalline cellulose composite film CNT @ DAC # 4, (b) microcrystalline cellulose composite film DAC, (c) CNT/microcrystalline cellulose composite film CNT @ DAC # 1, (d) CNT/microcrystalline cellulose composite film CNT @ DAC # 2, (e) CNT/microcrystalline cellulose composite film CNT @ DAC # 3, and (f) CNT/microcrystalline cellulose composite film CNT @ DAC # 5.
FIG. 2 shows the composite films obtained in examples 1 to 5 and comparative example 1, and pure water in one sun (1000W m) -2 ) Water evaporation rate in the beaker under irradiation was compared.
FIG. 3 shows the composite films of examples 1-5 and comparative example 1 in a sunlight (1000W m) -2 ) Temperature rise contrast of the irradiated lower surface.
FIG. 4 shows wettabilities of composite films obtained in examples 1 to 5 and comparative example 1, and FIG. 4 (a) shows wettabilities of microcrystalline cellulose composite films DAC # 2, (b) shows wettabilities of carbon nanotube/microcrystalline cellulose composite film CNT @ DAC # 1 to water, (c) shows wettabilities of carbon nanotube/microcrystalline cellulose composite film CNT @ DAC # 2 to water, (d) shows wettabilities of carbon nanotube/microcrystalline cellulose composite film CNT @ DAC #3 to water, (e) shows wettabilities of carbon nanotube/microcrystalline cellulose composite film CNT @ DAC # 4 to water, (f) shows wettabilities of carbon nanotube/microcrystalline cellulose composite film CNT @ DAC # 5 to water, and (g) shows wettabilities of carbon nanotube/microcrystalline cellulose composite film CNT @ DAC # 4 to oil (n-hexane).
FIG. 5 is a graph showing the emulsion separation ability of the composite membrane obtained in example 1. FIG. 5 (a) flux of carbon nanotube/microcrystalline cellulose composite membrane CNT @ DAC # 4 for separating oil-in-water emulsion and obtaining COD value of water, (b) flux of carbon nanotube/microcrystalline cellulose composite membrane CNT @ DAC # 4 for separating water-in-oil emulsion and obtaining purity of oil.
FIG. 6 is a photograph showing the separation of the emulsion of the composite membrane obtained in example 1. FIG. 6 (a) photo of separation of oil-in-water emulsion of carbon nanotube/microcrystalline cellulose composite membrane CNT @ DAC # 4, (b) photo of oil-in-water emulsion and water-in-oil emulsion before and after separation of carbon nanotube/microcrystalline cellulose composite membrane CNT @ DAC # 4.
Detailed Description
The following description of the preferred embodiments of the present invention is provided for the purpose of better illustrating the invention and is not intended to limit the invention thereto.
The test method comprises the following steps:
1. and (3) morphology testing: the morphology of the composite membrane samples was characterized by scanning electron microscopy (SEM, hitachi Su1510 co., ltd., japan).
2. Water evaporation test: composite membrane samples were placed in beakers containing large amounts of water and irradiated with simulated sunlight using a xenon lamp (Cel-S500) equipped with an AM 1.5 filter. Meanwhile, a Solar energy meter (SM 206-Solar) is used for calibrating the sunlight intensity to maintain at one sunlight (1000W m) -2 ) The interfacial evaporation capacity of the samples was measured by recording the mass loss of water in a beaker on an electronic balance (AX 224 ZH/E), thermal imaging systems (Testo 871, testo Se&Kgaa) the sample surface temperature in the beaker was recorded.
3. Contact angle test: the contact angle of the composite membrane sample in air is measured by a contact angle measuring instrument (Powereach JC2000D 1) at room temperature, and the contact angle of the sample in air is measured by the contact angle measuring instrument (for example, oil can be selected from trichloromethane, normal hexane, silicone oil, soybean oil, olive oil and the like, and the selection of the type of the oil has little influence on the contact angle of the oil through the research of the invention, and the invention is described by taking the normal hexane as an example).
4. Emulsion separation test: the emulsion separation experiment was performed in a vacuum driven filtration system: the composite membrane samples were placed in a filtration device to act as a filter membrane, and a vacuum pump (Millipore, WP 6122050) was used to provide a pressure differential to separate the oil-in-water and water-in-oil emulsions. After separation of the oil-in-water emulsion, the organic content (COD value) in the collected water was measured by a multiparameter water quality tester (MI-88S). After separation of the water-in-oil emulsion, the purity of the separated oil was checked by means of a Karl Fischer titrator (Metrohm 831KF, switzerland).
Wherein the preparation of oil-in-water emulsion and water-in-oil emulsion: mixing water and oil (chloroform, n-hexane, silicone oil, soybean oil and olive oil) according to a volume ratio of 100:1 and 1:100, respectively adding 0.1g/L Tween 80 and 1g/L span 80, and rapidly stirring for 6h to obtain oil-in-water emulsion and water-in-oil emulsion. Wherein the original COD values of the oil-in-water emulsions are all more than 10000mg/L.
Example 1
A preparation method of a carbon nano tube/microcrystalline cellulose composite membrane comprises the following steps:
(1) 2g of microcrystalline cellulose is weighed and dispersed in 60mL of aqueous solution, the pH value is adjusted to 4, 5g of sodium periodate is added under the condition of keeping out of the sun, and the mixture is placed in a constant-temperature water bath at 40 ℃ for 3 hours. After the reaction is finished, adding ethanol and deionized water for cleaning and drying at 60 ℃ to obtain aldehyde group microcrystalline cellulose;
(2) Weighing 2g of aldehyde microcrystalline cellulose reacted in the step (1) and 0.5g of aminated carbon nanotube, dispersing in 50mL of aqueous solution, and carrying out Schiff base reaction for 2h under the ultrasonic condition at 50 ℃;
(3) And (3) carrying out suction filtration on the suspension reacted in the step (2) for 30min under the pressure of a 0.5bar vacuum pump, and drying at 50 ℃ for 2h to obtain the carbon nano tube/microcrystalline cellulose composite membrane which is marked as CNT @ DAC # 4.
Comparative example 1
A preparation method of a microcrystalline cellulose composite membrane comprises the following steps:
(1) 2g of microcrystalline cellulose is weighed and dispersed in 60mL of aqueous solution, the pH value is adjusted to 4, 5g of sodium periodate is added under the condition of keeping out of the sun, and the mixture is placed in a constant-temperature water bath at 40 ℃ for 3 hours. After the reaction is finished, adding ethanol and deionized water for cleaning and drying at 60 ℃ to obtain aldehyde group microcrystalline cellulose;
(2) And (2) weighing 2g of aldehyde microcrystalline cellulose reacted in the step (1), dispersing in 50mL of aqueous solution, carrying out suction filtration on the suspension for 30min under the pressure of a 0.5bar vacuum pump, and drying at 50 ℃ for 2h to obtain the microcrystalline cellulose composite membrane which is recorded as DAC.
Example 2
A preparation method of a carbon nano tube/microcrystalline cellulose composite membrane comprises the following steps:
(1) 2g of microcrystalline cellulose is weighed and dispersed in 60mL of aqueous solution, the pH value is adjusted to 4, 5g of sodium periodate is added under the condition of keeping out of the sun, and the mixture is placed in a constant-temperature water bath at 40 ℃ for 3 hours. After the reaction is finished, adding ethanol and deionized water for cleaning and drying at 60 ℃ to obtain aldehyde group microcrystalline cellulose;
(2) Weighing 0.5g of aldehyde microcrystalline cellulose reacted in the step (1) and 0.5g of aminated carbon nanotube, dispersing in 50mL of aqueous solution, and carrying out Schiff base reaction for 2h under the ultrasonic condition at 50 ℃;
(3) And (3) carrying out suction filtration on the suspension reacted in the step (2) for 30min under the pressure of a 0.5bar vacuum pump, and drying at 50 ℃ for 2h to obtain the carbon nano tube/microcrystalline cellulose composite membrane marked as CNT @ DAC # 1.
Example 3
A preparation method of a carbon nano tube/microcrystalline cellulose composite membrane comprises the following steps:
(1) Weighing 2g of microcrystalline cellulose, dispersing the microcrystalline cellulose in 60mL of aqueous solution, adjusting the pH value to 4, adding 5g of sodium periodate under the condition of keeping out of the sun, and placing the mixture in a constant-temperature water bath at 40 ℃ for 3h. After the reaction is finished, adding ethanol and deionized water for cleaning and drying at 60 ℃ to obtain aldehyde group microcrystalline cellulose;
(2) Weighing 1g of aldehyde microcrystalline cellulose reacted in the step (1) and 0.5g of aminated carbon nano tube, dispersing in 50mL of water solution, and carrying out Schiff base reaction for 2h under the ultrasonic condition at 50 ℃;
(3) And (3) carrying out suction filtration on the suspension reacted in the step (2) for 30min under the pressure of a 0.5bar vacuum pump, and drying at 50 ℃ for 2h to obtain the carbon nano tube/microcrystalline cellulose composite membrane marked as CNT @ DAC # 2.
Example 4
A preparation method of a carbon nano tube/microcrystalline cellulose composite membrane comprises the following steps:
(1) 2g of microcrystalline cellulose is weighed and dispersed in 60mL of aqueous solution, the pH value is adjusted to 4, 5g of sodium periodate is added under the condition of keeping out of the sun, and the mixture is placed in a constant-temperature water bath at 40 ℃ for 3 hours. After the reaction is finished, adding ethanol and deionized water for cleaning, and drying at 60 ℃ to obtain aldehyde group microcrystalline cellulose;
(2) Weighing 1.5g of aldehyde microcrystalline cellulose reacted in the step (1) and 0.5g of aminated carbon nanotube, dispersing in 50mL of aqueous solution, and carrying out Schiff base reaction for 2h under the ultrasonic condition at 50 ℃;
(3) And (3) carrying out suction filtration on the suspension reacted in the step (2) for 30min under the pressure of a 0.5bar vacuum pump, and drying at 50 ℃ for 2h to obtain the carbon nano tube/microcrystalline cellulose composite membrane which is marked as CNT @ DAC # 3.
Example 5
A preparation method of a carbon nano tube/microcrystalline cellulose composite membrane comprises the following steps:
(1) 2g of microcrystalline cellulose is weighed and dispersed in 60mL of aqueous solution, the pH value is adjusted to 4, 5g of sodium periodate is added under the condition of keeping out of the sun, and the mixture is placed in a constant-temperature water bath at 40 ℃ for 3 hours. After the reaction is finished, adding ethanol and deionized water for cleaning and drying at 60 ℃ to obtain aldehyde group microcrystalline cellulose;
(2) Weighing 2.5g of aldehyde microcrystalline cellulose reacted in the step (1) and 0.5g of aminated carbon nanotube, dispersing in 50mL of aqueous solution, and carrying out Schiff base reaction for 2h under the ultrasonic condition at 50 ℃;
(3) And (3) carrying out suction filtration on the suspension reacted in the step (2) for 30min under the pressure of a 0.5bar vacuum pump, and drying at 50 ℃ for 2h to obtain the carbon nano tube/microcrystalline cellulose composite membrane marked as CNT @ DAC # 5.
1. Topographical contrast
The results of the topography test were shown in fig. 1, in which fig. 1 (a) is the carbon nanotube/microcrystalline cellulose composite film cnt @ DAC # 4 of example 1, fig. 1 (b) is the microcrystalline cellulose composite film DAC of comparative example 1, fig. 1 (c) is the carbon nanotube/microcrystalline cellulose composite film cnt @ DAC # 1 of example 2, fig. 1 (d) is the carbon nanotube/microcrystalline cellulose composite film cnt @ DAC # 2 of example 3, fig. 1 (e) is the carbon nanotube/microcrystalline cellulose composite film cnt @ DAC # 3 of example 4, and fig. 1 (f) is the carbon nanotube/microcrystalline cellulose composite film cnt @ DAC # 5 of example 5.
As can be seen from fig. 1 (a) in the high-magnification scanning electron microscope image, the carbon nanotube/microcrystalline cellulose composite film obtained after schiff base reaction and vacuum-assisted filtration can be observed to have a uniform (good dispersibility) and rough morphology, and a large number of carbon nanotubes crosslinked with fibers can also be found. As can be seen from fig. 1 (b), due to the lack of micro-nano scale carbon nanotube cross-linking, the surface topography of the microcrystalline cellulose composite film DAC is very dense and smooth. As shown in fig. 1 (c-f), with the addition of the carbon nanotubes, a large number of micro-nano-scale roughness structures appear on the surface of all the carbon nanotube/microcrystalline cellulose composite films. With the increase of the content of the microcrystalline cellulose, the surface appearance of the film tends to be flat and smooth. Compared with examples 2 to 5 and comparative example 1, example 1 has the coarsest morphology with good dispersibility; in examples 2 to 4, a large number of microcracks and gaps occurred due to the low proportion of aldehyde cellulose; the surfaces of the example 5 and the comparative example 1 are too dense and flat due to the high proportion of the aldehyde cellulose. Therefore, the combination of a moderate amount of microcrystalline cellulose and carbon nanotubes is more advantageous for building a film with a uniform and rough morphology (example 1).
2. Comparison of Water Evaporation test
The composite films obtained in examples 1 to 5 and comparative example 1 and a blank set (pure water to which no photothermal material was added) were subjected to water evaporation tests, and the results of the change in the mass of water in a beaker with the time of solar irradiation for different samples under the irradiation of sunlight are shown in FIG. 2, in which water (representing the blank set) is illustrated.
As shown in fig. 2, in the evaporation apparatus, the quality degradation of all the carbon nanotube/microcrystalline cellulose films was approximately linear to the solar irradiation time, while the quality degradation of the microcrystalline cellulose DAC film and the bulk water was non-linear with respect to time. This is because it lacks thermal localization of photothermal materials, and heat is not concentrated at the gas-liquid interface but diffused throughout the water, resulting in a very low water evaporation rate. After 60min of light irradiation, the water mass reduction of the CNT @ DAC # 4 and the DAC film is 1.58 and 0.66kg m respectively -2 4.8 times and 2.0 times of pure water respectively. The carbon nanotube/microcrystalline cellulose composite membrane was confirmed to have an excellent effect of increasing the water evaporation rate, with the optimal ratio being that of example 1.
3. Comparison of photothermal heating performance test
The photothermal temperature increase performance test was performed on the composite films prepared in examples 1 to 5 and comparative example 1, and the results of the surface temperature changes with the solar irradiation time in the beaker of different samples under the irradiation of sunlight are shown in fig. 3.
As can be seen from FIG. 3, in one sun (1000W m) -2 ) Under irradiation, the temperature of the carbon nanotube/microcrystalline cellulose composite membrane is continuously increased along with the increase of the irradiation time of sunlight. Meanwhile, the temperature of different carbon nanotube/microcrystalline cellulose composite membranes is slightly different. The surface temperature of the carbon nano tube/microcrystalline cellulose composite membrane CNT @ DAC # 4 is the highest and can reach 35.8 ℃, and the temperature is far higher than 24.7 ℃ of the carbon microcrystalline cellulose membrane DAC. The photo-thermal performance of the carbon nano tube/microcrystalline cellulose composite membrane is excellent, and the carbon nano tube/microcrystalline cellulose composite membrane is suitable for photo-thermal materials for solar interface evaporation, wherein the embodiment 1 is used as the optimal proportion. The carbon nano tube is introduced as a photo-thermal substrate, and the aldehyde microcrystalline cellulose and the aminated carbon nano tube in a specific range are matched and pass through the matThe thermal localization of the evaporated water can be effectively realized by the Schiff base reaction.
Under the same illumination condition, the carbon nano tube/microcrystalline cellulose CNT @ DAC # 1 film, the carbon nano tube/microcrystalline cellulose CNT @ DAC # 2 film, the carbon nano tube/microcrystalline cellulose CNT @ DAC # 3 film and the carbon nano tube/microcrystalline cellulose CNT @ DAC # 5 film are respectively heated to 31.7 ℃,33.7 ℃,33.9 ℃ and 29.5 ℃. The carbon nanotube/microcrystalline cellulose composite membrane can realize different photo-thermal heating effects by changing the content of microcrystalline cellulose, wherein the embodiment 1 is used as the optimal proportion.
3. Comparison of wetting Properties test
The composite membranes prepared in examples 1 to 5 and comparative example 1 were subjected to wettability tests, and the results of the spreading change of water droplets on the surfaces of different samples with time are shown in fig. 4 (a-f) in sequence.
As shown in fig. 4, it can be seen from comparative examples 1 to 5 and comparative example 1 that the dense structure of the microcrystalline cellulose film DAC makes it difficult for water to diffuse on the surface. And due to the introduction of the carbon nano tube, the aldehyde microcrystalline cellulose with a specific ratio and the aminated carbon nano tube are subjected to Schiff base reaction, so that the aldehyde microcrystalline cellulose and the aminated carbon nano tube are crosslinked, the roughness of the film is obviously increased, and the affinity of the film to water and oil is improved. The carbon nano tube/microcrystalline cellulose CNT @ DAC # 4 composite membrane shows super-hydrophilicity, and water drops can be completely spread within 0.1 s. After the ratio of the aldehyde microcrystalline cellulose to the aminated carbon nanotube is adjusted, for example, the carbon nanotube/microcrystalline cellulose composite films of comparative example 1 and examples 2 to 5 require a spreading time of 0.2s or more. The carbon nanotube/microcrystalline cellulose CNT @ DAC # 4 composite membrane also achieves rapid spreading in an oil solvent as shown in FIG. 4g, and shows that the composite membrane has excellent amphiphilic wettability. The carbon nano tube/microcrystalline cellulose composite membranes prepared in examples 1-5 all have good oil-water amphiphilic wetting performance, wherein the optimal proportion is in example 1, so that the composite membrane prepared in example 1 is very suitable for being used as a filter membrane for emulsion separation, and is especially suitable for oil-water separation of oil-in-water emulsion and water-in-oil emulsion systems which are difficult to treat by conventional filter membranes.
3. Emulsion separation Performance test
The composite membrane prepared in example 1 was subjected to an emulsion separation performance test, and the separation results of different oil-in-water emulsions and water-in-oil emulsions sequentially obtained by using the carbon nanotube/microcrystalline cellulose CNT @ DAC # 4 composite membrane as a filter membrane under a vacuum filtration pressure of 0.5bar by a vacuum pump are shown in FIG. 5 (a-b); the photographs of the emulsion separation experiment are shown in FIG. 6 (a), and the photographs of the oil-in-water emulsion and the water-in-oil emulsion before and after separation are shown in FIG. 6 (b).
As shown in FIG. 5 (a), the separation flux of the CNT/microcrystalline cellulose CNT @ DAC # 4 composite membrane of example 1 for different oil-in-water emulsions is about 300L m -2 h -1 The COD value of the collected water is lower than 40mg/L and is far smaller than that of the original emulsion (the COD value of the original oil-in-water emulsion is about more than 10000 mg/L), and the excellent oil-water separation and purification capacity is proved. In addition, as shown in FIG. 5 (b), the separation flux of the carbon nanotube/microcrystalline cellulose composite membrane to different water-in-oil emulsions was about 320L m -2 h -1 The purity of the collected oil can reach more than 99.9 percent, and the oil-water separation and purification capability is proved to be excellent.
As shown in fig. 6 (a), after separating the oil-in-water emulsion with the carbon nanotube/microcrystalline cellulose composite membrane under a pressure of 0.5bar and passing the milky emulsion through the composite membrane, a clear and transparent aqueous solution was obtained. As shown in fig. 6 (b), the turbid emulsions containing a large number of micron-sized droplets, including oil-in-water and water-in-oil emulsions, became transparent after separation, and no droplets were observed.
The composite membranes prepared in comparative example 1 and examples 2-5 were tested for emulsion separation performance under the same conditions, and the test results showed that: the composite membrane prepared in the comparative example 1 can not be separated from oil-in-water emulsion and water-in-oil emulsion to obtain pure water or oil by being used as a filter membrane; although the composite membranes prepared in examples 2 to 5 have the effect of separating oil-in-water emulsion from water-in-oil emulsion to some extent, the purity of the collected filtrate (water or oil) is reduced to different extents, which means that when the oil-in-water emulsion is separated, the COD value of water in the obtained filtrate is increased to different extents compared with that of example 1; when the water-in-oil emulsion was isolated, the purity of the oil in the filtrate was reduced to a different extent from that of example 1. The composite membrane with different wettabilities can be constructed by changing the proportion of the aldehyde microcrystalline cellulose to the aminated carbon nano tube, so that the emulsion separation with different capabilities is realized.
The analysis shows that:
(1) Based on the Schiff base reaction of the aldehyde microcrystalline cellulose and the aminated carbon nano tube, the invention generates unexpected technical effects by optimizing the proportion of the aldehyde microcrystalline cellulose to the aminated carbon nano tube: on one hand, the roughness of the obtained carbon nanotube/microcrystalline cellulose composite film material is obviously improved, the dispersibility is good, the contact angle of the carbon nanotube/microcrystalline cellulose composite film material to water and an oil solvent is 0 degree, excellent amphiphilic wettability is realized, and compared with a microcrystalline cellulose composite film, the oil-water amphiphilic wettability is obviously improved. Especially when the aldehyde group microcrystalline cellulose: when the mass ratio of the aminated carbon nanotube is 2:0.5, the obtained carbon nanotube/microcrystalline cellulose composite membrane shows super-hydrophilicity and super-lipophilicity (water drops/oil drops can be completely spread within 0.1 s). On the other hand, the obtained carbon nanotube/microcrystalline cellulose composite film material also has excellent photo-thermal performance: under the irradiation of sunlight, the temperature can be rapidly raised, water is converted into water vapor, high-efficiency interface evaporation is realized, and the interface evaporation rate can reach 1.58Kg m -2 h -1 Is higher than most of the reported existing solar interface evaporation materials (1-1.5 Kg m) -2 h -1 )。
(2) The carbon nanotube/microcrystalline cellulose composite membrane prepared by the method has excellent membrane forming performance, the dispersion performance of the carbon nanotube and the microcrystalline cellulose is improved through Schiff base reaction, the roughness of the composite membrane is improved, and the amphiphilic wettability of the composite membrane is further improved.
(3) The carbon nano tube/microcrystalline cellulose composite membrane can be used as a high-quality and high-efficiency oil-water amphiphilic infiltration filtering material and is used for separating a water-in-oil emulsion and an oil-in-water emulsion.
(4) The carbon nano tube/microcrystalline cellulose composite membrane has good mechanical property, excellent amphiphilic wettability and excellent photo-thermal property, and can be used as a high-quality and high-efficiency photo-thermal interface evaporation material for seawater desalination and sewage purification. Has good application prospect in the fields of solar energy utilization, seawater desalination, oil/water emulsion separation and the like.
(5) The carbon nano tube/microcrystalline cellulose composite membrane prepared by the method is simple in preparation process and easy for industrial production.
(6) The invention can use microcrystalline cellulose as raw material, generate aldehyde microcrystalline cellulose by sodium periodate oxidation, introduce aldehyde group as action site, further use aldehyde microcrystalline cellulose and aminated carbon nano tube to carry out Schiff base reaction to improve the dispersibility (uniformity) of the composite membrane material, finally prepare the carbon nano tube/microcrystalline cellulose composite membrane by vacuum auxiliary filtration technology, suction filtration and drying to improve the mechanical property.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by one skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (6)
1. A preparation method of a carbon nano tube/microcrystalline cellulose composite membrane is characterized by comprising the following steps:
(1) Dispersing aldehyde microcrystalline cellulose and an aminated carbon nano tube in an aqueous solution, carrying out Schiff base reaction for 2h under the ultrasonic condition of 50 ℃ to obtain a suspension, and controlling the aldehyde microcrystalline cellulose in a reaction solution before the reaction: the mass ratio of the aminated carbon nanotube is 2.5; the preparation method of the aldehyde microcrystalline cellulose comprises the following steps: dispersing microcrystalline cellulose in an aqueous solution, adjusting the pH value to 4, adding sodium periodate under the condition of keeping out of the sun, and placing the mixture in a constant-temperature water bath at 40 ℃ for reaction for 3 hours; after the reaction is finished, adding ethanol and deionized water for cleaning and drying to obtain aldehyde group microcrystalline cellulose; controlling microcrystalline cellulose in the reaction solution before reaction: sodium periodate: the mass ratio of water is 2;
(2) And (2) collecting solids in the suspension obtained in the step (1), and drying to obtain the carbon nano tube/microcrystalline cellulose composite membrane.
2. The method according to claim 1, wherein the aminated carbon nanotubes in step (1) have a length of 20-50 μm and a diameter of 8-15nm.
3. The method of claim 1, comprising the steps of:
(1) Weighing 2g of microcrystalline cellulose, dispersing the microcrystalline cellulose in 60mL of aqueous solution, adjusting the pH value to 4, adding 5g of sodium periodate under the condition of keeping out of the sun, placing the mixture in a constant-temperature water bath at 40 ℃ for 3 hours, adding ethanol and deionized water after the reaction is finished, cleaning the mixture, and drying the mixture at 60 ℃ to obtain aldehyde microcrystalline cellulose;
(2) Weighing 2g of aldehyde microcrystalline cellulose reacted in the step (1) and 0.5g of aminated carbon nanotube, dispersing in 50mL of aqueous solution, and carrying out Schiff base reaction for 2h under the ultrasonic condition at 50 ℃;
(3) And (3) carrying out suction filtration on the suspension reacted in the step (2) for 30min under the pressure of a 0.5bar vacuum pump, and drying at 50 ℃ for 2h to obtain the carbon nano tube/microcrystalline cellulose composite membrane.
4. The carbon nanotube/microcrystalline cellulose composite membrane prepared by the method of any one of claims 1 to 3, wherein the carbon nanotube/microcrystalline cellulose composite membrane has oil-water amphiphilic wettability.
5. The carbon nanotube/microcrystalline cellulose composite membrane of claim 4, for use in solar interfacial evaporation, seawater desalination, and sewage purification.
6. Use of the carbon nanotube/microcrystalline cellulose composite membrane according to claim 4 for water-in-oil emulsion and/or oil-in-water emulsion separation.
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