Water treatment coating film and method for producing the same

Abstract

The present application relates to a kind of water treatment coating film and its preparation method, with polyethylene film as matrix, coating slurry containing nitrogen-doped hierarchical porous carbon is coated on surface, the water treatment coating film obtained, wherein, nitrogen element in nitrogen-doped hierarchical porous carbon is combined in the form of covalent bond on the surface of porous carbon material, enhance the treatment capacity of porous carbon to sewage;Nitrogen element enters the inside of porous carbon material, so that carbon atom and nitrogen atom form covalent bond, increase the active site of water treatment film in the process of filtering water, improve adsorption effect;At the same time, nitrogen-doped hierarchical porous carbon has larger specific surface area and high specific surface pore volume, pore size is controllable, using intermolecular force adsorbs pollutant, improve the adsorption performance of the prepared diaphragm, can be used in water filtration permeation etc.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of water treatment, and particularly relates to a water treatment coating film and a preparation method thereof. BACKGROUND

[0002] Water is the source of life and an important component of life. The discharge of sewage causes very serious pollution to the environment. The discharge of sewage not only pollutes surface water, but also pollutes underground water sources, and even affects the life and safety of human beings. There are many methods for sewage treatment, such as physical methods, chemical methods, biological methods, etc. Among them, the membrane treatment method is a new technology, and the high polymer water treatment membrane is usually used in a water treatment device. For example, polysulfone, polyvinylidene fluoride, polyethylene, polyvinyl alcohol, etc.

[0003] Polyethylene film has high mechanical strength, chemical resistance, impact resistance and other advantages, and is widely used. However, the surface energy of polyethylene film is low, so the interaction between polyethylene film and water is weak. The hydrophobic property of the surface of polyethylene film makes polyethylene film easy to be polluted, and reduces the filtration performance of the film. SUMMARY

[0004] The purpose of the present application is to provide a water treatment coating film based on the prior art. The water treatment coating film is prepared by coating a coating slurry containing nitrogen-doped hierarchical porous carbon on the surface of a polyethylene film (PE film). In the water treatment coating film, the nitrogen element in the nitrogen-doped hierarchical porous carbon is covalently bonded to the surface of the porous carbon material, which enhances the treatment capacity of the porous carbon for sewage. The nitrogen element enters the interior of the porous carbon material, and the carbon atoms and nitrogen atoms form covalent bonds, which increases the active sites of the water treatment film during the water filtration process and improves the adsorption effect. At the same time, the nitrogen-doped hierarchical porous carbon has a large specific surface area and high specific surface pore volume, and the pore size is controllable. The nitrogen-doped hierarchical porous carbon can adsorb pollutants by using intermolecular forces, and improve the adsorption performance of the prepared membrane. The prepared membrane can be used in the fields of water filtration and permeation.

[0005] Another purpose of the present application is to provide a preparation method of the water treatment coating film.

[0006] The technical solution of the present application is as follows:

[0007] A preparation method of a water treatment coating film, which comprises the following steps:

[0008] (1) Preparation of nitrogen-doped hierarchical porous carbon:

[0009] The potassium hydroxide, the ferric citrate and the purified water are mixed uniformly, and then dried at 80-120℃. After drying, the obtained mixture is ground, and then subjected to carbonization treatment to obtain an intermediate product carbon material. The obtained intermediate product carbon material is mixed with nitric acid, and then subjected to etching treatment at 60-80℃. After washing and drying, the obtained product is subjected to calcination treatment in an atmosphere containing ammonia gas to obtain a nitrogen-doped hierarchical porous carbon. In the carbonization treatment, the temperature rising procedure is as follows: the temperature rising rate is 3-7℃ / min, and the carbonization temperature is 700-900℃.

[0010] (2) Preparation of coating slurry:

[0011] The thickening agent is dissolved in deionized water, and then the nitrogen-doped hierarchical porous carbon prepared in step (1) is added. After uniform dispersion, the obtained mixture is added with a binder and a wetting agent to obtain a coating slurry.

[0012] (3) Preparation of water treatment coating film:

[0013] The coating slurry obtained in step (2) is coated on the surface of a polyethylene film, and then dried to obtain a water treatment coating film.

[0014] For the present application, in step (1), the mass ratio of potassium hydroxide to ferric citrate is 1:8-12, which can be but is not limited to 1:8, 1:9, 1:10, 1:11 or 1:12. In order to obtain better results, the mass ratio of potassium hydroxide to ferric citrate is 1:10.

[0015] In step (1), the drying temperature is 80-120℃, preferably 90-110℃, and more preferably 100℃. The drying time is 10-16h, preferably 12h.

[0016] In a preferred embodiment, in step (1), in the carbonization treatment, the temperature rising procedure is as follows: the temperature rising rate is 5℃ / min, and the carbonization temperature is 800℃.

[0017] Further, the carbonization time is 0.5-1.5h, preferably 1h.

[0018] In a preferred embodiment, in step (1), the etching treatment temperature is 65-75℃, preferably 70℃, and the etching treatment time is 0.5-1.5h, preferably 1h.

[0019] For the present application, in step (2), the thickening agent is one or more of a fatty acid thickening agent, a cellulose thickening agent, an inorganic salt thickening agent or an amine oxide thickening agent, and is preferably sodium carboxymethyl cellulose.

[0020] In step (2), the binder is one or more of polyvinylidene fluoride, styrene butadiene rubber, polyacrylic acid, polyacrylonitrile or phenolic resin.

[0021] In step (2), the wetting agent is one or more of siloxanes, fatty alcohols, ethers or polyoxyethylenes.

[0022] For the present application, in step (2), the following components are made into 100% of the total weight of the coating slurry: the mass fraction of nitrogen-doped hierarchical porous carbon is 10-40wt%, the mass fraction of the binder is 3-8wt%, the mass fraction of the thickening agent is 5-10wt%, the mass fraction of the wetting agent is 0.1-0.5wt%, and the balance is water.

[0023] In a preferred embodiment, in step (2), the following components are made into 100% of the total weight of the coating slurry: the mass fraction of nitrogen-doped hierarchical porous carbon is 10wt%, the mass fraction of the binder is 4wt%, the mass fraction of the thickening agent is 5wt%, the mass fraction of the wetting agent is 0.2wt%, and the balance is water.

[0024] In a preferred embodiment, in step (2), the following components are made into 100% of the total weight of the coating slurry: the mass fraction of nitrogen-doped hierarchical porous carbon is 20wt%, the mass fraction of the binder is 5wt%, the mass fraction of the thickening agent is 8wt%, the mass fraction of the wetting agent is 0.2wt%, and the balance is water.

[0025] The present application uses potassium hydroxide for activation when preparing nitrogen-doped hierarchical porous carbon, so that the particles of the porous carbon are reduced and the surface becomes loose and porous, and then the hierarchical porous carbon is etched to form pores; and the hierarchical porous carbon is further calcined using ammonia gas, so that the preparation method is simple, the specific surface area and the specific pore volume are high, the pore size is controllable, pollutants are adsorbed by intermolecular forces, the adsorption performance of the prepared membrane is improved, and the membrane can be used in the fields of water filtration and permeation.

[0026] The present application also relates to a water treatment coating film obtained by the above preparation method.

[0027] The present application uses a polyethylene film (PE film) as a substrate, and the nitrogen-doped hierarchical porous carbon is coated on the surface of the polyethylene film (PE film), so that the present application has a two-layer structure, the structure is simple, the mechanical stability is high, the preparation method is mature, the price is low, the nitrogen-doped hierarchical porous carbon has a low bulk density, a large specific surface area and a controllable pore size, and has a strong adsorption performance.

[0028] The technical scheme of the present application has the following advantages:

[0029] The application takes polyethylene film (PE film) as a substrate, and a coating slurry containing nitrogen-doped hierarchical porous carbon is coated on the surface to obtain a water treatment coating film, wherein the nitrogen element in the nitrogen-doped hierarchical porous carbon is combined on the surface of the porous carbon material in the form of a covalent bond, thereby enhancing the treatment capacity of the porous carbon for sewage; the nitrogen element enters the interior of the porous carbon material, so that the carbon atoms and the nitrogen atoms form a covalent bond, thereby increasing the active sites of the water treatment film in the water filtration process and improving the adsorption effect; meanwhile, the nitrogen-doped hierarchical porous carbon has a large specific surface area and a high specific surface pore volume, the pore size is controllable, pollutants are adsorbed by using intermolecular forces, and the adsorption performance of the prepared diaphragm is improved, so that the diaphragm can be used in the fields of water filtration and permeation.

[0030] In the preparation of the nitrogen-doped hierarchical porous carbon, potassium hydroxide is used for activation, so that the particles of the porous carbon are reduced and the surface becomes loose and porous, and then the hierarchical porous carbon is etched to form pores; and then the hierarchical porous carbon is calcined by using ammonia gas, so that the preparation method is simple, the hierarchical porous carbon has a large specific surface area and a high specific surface pore volume, the pore size is controllable, pollutants are adsorbed by using intermolecular forces, and the adsorption performance of the prepared diaphragm is improved, so that the diaphragm can be used in the fields of water filtration and permeation. DETAILED DESCRIPTION

[0031] The application will be further explained and described through specific examples and comparative examples, but this is not a limitation of the application. Any modification, equivalent replacement or improvement made by a person skilled in the art according to the basic idea of the application should be included in the scope of the application

[0032] Example 1

[0033] (1) Preparation of nitrogen-doped hierarchical porous carbon:

[0034] 1g of potassium hydroxide was dissolved in 50mL of pure water, and then 10g of ferric citrate was added, and the mixture was uniformly mixed and then dried in a 100℃ oven for 12h. After drying, the obtained mixture was ground and then placed in a tube furnace for carbonization treatment, and the intermediate product carbon material was obtained, wherein, during the carbonization treatment, the temperature rising program was as follows: the temperature rising rate was 5℃ / min, the carbonization temperature was 800℃, and the carbonization time was 1h.

[0035] 0.5g of the obtained intermediate product carbon material was added into 30mL of nitric acid, and etching treatment was carried out by water bath heating to 70℃, and the etching treatment time was 1h, and the condensation reflux was maintained during the etching treatment. The obtained product was washed with pure water until neutral, and then dried in an oven, and then calcined under the gas atmosphere containing argon gas and ammonia gas after drying, and the calcination treatment time was 2h, and the nitrogen-doped hierarchical porous carbon was obtained.

[0036] (2) Preparation of coating slurry:

[0037] The thickening agent (sodium carboxymethyl cellulose, CMC) was dissolved in deionized water to obtain a CMC aqueous solution. The nitrogen-doped hierarchical porous carbon prepared in step (1) was added to deionized water, stirred for 30 min, and then added to the above CMC aqueous solution. The mixture was uniformly dispersed using a planetary ball mill, with the ball mill parameters set to 400 rpm / min, and the stirring time was 30-60 min. The binder was added and the ball milling was continued for 30 min. The wetting agent was added and the ball milling was continued for 30 min to obtain a coating slurry. The coating slurry was prepared from the following components by mass fraction, based on 100% of the total weight of the coating slurry: 10 wt% of nitrogen-doped hierarchical porous carbon, 4 wt% of binder, 5 wt% of thickening agent, 0.2 wt% of wetting agent, and the balance being water.

[0038] (3) Preparation of water treatment coating film:

[0039] The coating slurry obtained in step (2) was coated on the surface of a polyethylene film (PE film), and dried to obtain a water treatment coating film.

[0040] Example 2

[0041] (1) Preparation of nitrogen-doped hierarchical porous carbon:

[0042] 1 g of potassium hydroxide was weighed and dissolved in 50 mL of pure water, and then 10 g of ferric citrate was added. After mixing, the mixture was placed in a 100°C oven for drying, with a drying time of 12 h. After drying, the obtained mixture was ground and placed in a tube furnace for carbonization treatment. During the carbonization treatment, the temperature program was as follows: a carbonization temperature of 800°C at a heating rate of 5°C / min, and a carbonization time of 1 h.

[0043] 0.5 g of the obtained intermediate product carbon material was weighed and added to 30 mL of nitric acid. The etching treatment was carried out by heating in a water bath to 70°C for 1 h, with condensation reflux maintained during the etching treatment. The obtained product was washed with pure water until neutral, and then dried in an oven. After drying, the product was calcined under a gas atmosphere containing a mixture of argon and ammonia gas for 2 h to obtain nitrogen-doped hierarchical porous carbon.

[0044] (2) Preparation of coating slurry:

[0045] A thickening agent (sodium carboxymethyl cellulose, CMC) was dissolved in deionized water to obtain a CMC aqueous solution. The nitrogen-doped hierarchical porous carbon prepared in step (1) was added into deionized water, stirred for 30 min, and then added into the above CMC aqueous solution. A planetary ball mill was used to uniformly disperse the mixture, with the ball mill parameters set to 400 rpm / min and the stirring time set to 30-60 min. A binder was added and ball milling was continued for 30 min. A wetting agent was then added and ball milling was continued for another 30 min to obtain a coating slurry. The coating slurry was prepared from the following components in the indicated mass fractions, with the total weight of the coating slurry taken as 100%: 20 wt% of the nitrogen-doped hierarchical porous carbon, 5 wt% of the binder, 8 wt% of the thickening agent, 0.2 wt% of the wetting agent, and the balance being water.

[0046] (3) Preparation of a water treatment coating film:

[0047] The coating slurry obtained in step (2) was coated onto the surface of a polyethylene film (PE film), and dried to obtain a water treatment coating film.

[0048] Comparative Example 1

[0049] (1) Preparation of a coating slurry:

[0050] A thickening agent (sodium carboxymethyl cellulose, CMC) was dissolved in deionized water to obtain a CMC aqueous solution. Commercial carbon black was added into deionized water, stirred for 30 min, and then added into the above CMC aqueous solution. A planetary ball mill was used to uniformly disperse the mixture, with the ball mill parameters set to 400 rpm / min and the stirring time set to 30-60 min. A binder was added and ball milling was continued for 30 min. A wetting agent was then added and ball milling was continued for another 30 min to obtain a coating slurry. The coating slurry was prepared from the following components in the indicated mass fractions, with the total weight of the coating slurry taken as 100%: 10 wt% of the commercial carbon black, 4 wt% of the binder, 5 wt% of the thickening agent, 0.2 wt% of the wetting agent, and the balance being water.

[0051] (2) Preparation of a water treatment coating film:

[0052] The coating slurry obtained in step (1) was coated onto the surface of a polyethylene film (PE film), and dried to obtain a water treatment coating film.

[0053] A series of performance tests were conducted on the coating films prepared in the examples and the comparative example, and the obtained data are shown in Table 1 below:

[0054] Table 1 Effect data of examples and comparative example

[0055] Example Example 1 Example 2 Comparative Example 1 Thickness / pm 20 22 20 Average pore size / nm 4.5 5.1 1.8 Specific surface area / m 2 ·g -1 ]]> 2112 2546 1332 Mesoporosity in carbon material 78.04 82.87 21.3 Pure water flux 20.2 23.2 19.2

[0056] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a water treatment coated membrane, characterized in that, It includes the following steps: (1) Preparation of nitrogen-doped hierarchical porous carbon: Potassium hydroxide, ferric citrate, and purified water were mixed evenly and dried at 90-110°C. The resulting mixture was then ground and carbonized to obtain an intermediate carbon material. This intermediate carbon material was mixed with nitric acid and etched at 65-75°C for 0.5-1.5 h. The resulting product was washed, dried, and then calcined in an ammonia-containing atmosphere to obtain nitrogen-doped hierarchical porous carbon. During the carbonization process, the heating program is as follows: the heating rate is 5℃ / min, the carbonization temperature is 800℃, and the carbonization time is 0.5~1.5 h; the mass ratio of potassium hydroxide to ferric citrate is 1:8~12. (2) Preparation of coating slurry: The thickener was dissolved in deionized water, and the nitrogen-doped hierarchical porous carbon prepared in step (1) was added. After being dispersed evenly, the binder and wetting agent were added to the resulting mixture to obtain the coating slurry. The thickener is sodium carboxymethyl cellulose; the binder is one or more of polyvinylidene fluoride, styrene-butadiene rubber, polyacrylic acid, polyacrylonitrile, or phenolic resin; the wetting agent is one or more of siloxanes, fatty alcohol ethers, or polyoxyethylene; and the coating slurry is made of the following components in the following mass fractions, based on 100% of the total weight: nitrogen-doped hierarchical porous carbon in the mass fraction of 10-40 wt%, binder in the mass fraction of 3-8 wt%, thickener in the mass fraction of 5-10 wt%, wetting agent in the mass fraction of 0.1-0.5 wt%, with the balance being water; (3) Preparation of water treatment coating membrane: The coating slurry obtained in step (2) is coated onto the surface of a polyethylene film and dried to obtain a water treatment coated film.

2. The method for preparing the water treatment coating membrane according to claim 1, characterized in that, In step (1), the mass ratio of potassium hydroxide to ferric citrate is 1:10; the drying temperature is 100℃; and the drying time is 10~16 h.

3. The method for preparing the water treatment coating membrane according to claim 2, characterized in that, In step (1), the drying time is 12 h.

4. The method for preparing the water treatment coating membrane according to claim 1, characterized in that, In step (1), the carbonization time is 1 hour during the carbonization process.

5. The method for preparing the water treatment coating membrane according to claim 1, characterized in that, In step (1), the etching temperature is 70°C and the etching time is 1 hour.

6. The method for preparing the water treatment coating membrane according to claim 1, characterized in that, In step (2), the coating slurry is made of the following components by mass fraction, based on the total weight of 100% of the slurry: 10 wt% nitrogen-doped hierarchical porous carbon, 4 wt% binder, 5 wt% thickener, 0.2 wt% wetting agent, and the balance being water; or, 20 wt% nitrogen-doped hierarchical porous carbon, 5 wt% binder, 8 wt% thickener, 0.2 wt% wetting agent, and the balance being water.

7. The water treatment coating membrane obtained by the preparation method according to any one of claims 1-6.