A water treatment method and device based on saline-alkali water desalination membrane

Abstract

The present invention relates to a water treatment method and device based on a saline-alkali water desalination membrane. The water treatment method based on the saline-alkali water desalination membrane comprises the following steps: using the saline-alkali water desalination membrane to screen water molecules and ions in water, and applying an electric field to make the ions intermittently flow in a directional manner to delay scaling and clogging of the saline-alkali water desalination membrane; the preparation method of the saline-alkali water desalination membrane comprises the following steps: forming a substrate with columnar [5] aromatic hydrocarbons and polyethersulfone, the columnar [5] aromatic hydrocarbons on the substrate forming water channels, arranging carbon nanotubes in a directional manner on the substrate to form carbon nanotube water channels, the carbon nanotubes being interspersed in the gaps between adjacent columnar [5] aromatic hydrocarbons, and filling the gaps between the carbon nanotubes with graphene oxide, so that the saline-alkali water desalination membrane improves water flux and is not easy to be clogged.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation, and in particular relates to a water treatment method and device based on a saline-alkali water desalination membrane. Background Art

[0002] Under ion-hydration, Na + 、Cl - Plasma exists in the form of ions combined with water molecules. Under the action of ions, Na + 、Cl - Ions and H + OH - There are combined forms, ions combined with water molecules and ions combined with H + OH - The combined substances account for the majority, and there is a small amount of Na in the water. + 、Cl - Plasma, ions combined with water molecules and ions with H + OH - The size of the combined substance is 0.6-1 nm, and the size of water molecules and single ions is 0.1-0.4 nm. The existing saline water desalination membrane uses carbon nanotubes, graphene oxide, etc. to form ion screening channels. The size of the ion screening channels is adjusted to between 0.4-0.5 nm, which can make water molecules and a very small amount of Na + 、Cl - Plasma passes through the ion screening channel. Existing saline water desalination membrane carbon nanotubes are mostly disordered, and the water flux is limited. Saline water contains NaCl and is rich in CO3 2- 、SO4 2- , Ca 2+ Mg 2+ Due to hardness elements such as alkali metals, the saline water desalination membrane is very easy to be blocked, and the expensive desalination membrane equipment needs to be cleaned and replaced every 2-3 months. Summary of the Invention

[0003] The purpose of the present invention is to provide a water treatment method based on a saline-alkali water desalination membrane to increase the water flux of the saline-alkali water desalination and improve scaling and clogging.

[0004] Another object of the present invention is to provide a saline-alkali water desalination device based on a saline-alkali water desalination membrane.

[0005] In order to achieve the above objectives, the technical solution adopted by the present invention is:

[0006] A water treatment method based on a saline-alkali water desalination membrane comprises the following steps: using the saline-alkali water desalination membrane to screen water molecules and ions in water, and applying an electric field to make the ions flow intermittently and directional to delay scaling and clogging of the saline-alkali water desalination membrane; a preparation method of the saline-alkali water desalination membrane comprises the following steps: stirring columnar [5] aromatic hydrocarbons and polyethersulfone to form a substrate, the columnar [5] aromatic hydrocarbons on the substrate forming water channels, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, the carbon nanotubes being interspersed in the gaps between adjacent columnar [5] aromatic hydrocarbons, and filling the gaps between the carbon nanotubes with graphene oxide.

[0007] Furthermore, the method for aligning carbon nanotubes on a substrate to form carbon nanotube water channels includes the following steps: mixing carbon nanotubes, graphene oxide and a surfactant solution and performing ultrasound to evenly disperse the carbon nanotubes and graphene oxide, obtaining a mixed suspension of carbon nanotubes and graphene oxide after uniform dispersion, immersing a substrate in the mixed suspension of carbon nanotubes and graphene oxide, applying a vertical electric field to align the carbon nanotubes, removing the substrate with the aligned carbon nanotubes, drying it, and then washing it with water to remove the surfactant.

[0008] Furthermore, when applying the vertical electric field, a membrane strip is used to cover the substrate, carbon nanotubes are arranged in a direction on the exposed substrate, and there are no carbon nanotubes arranged in a direction on the covered substrate, forming an uneven grid structure on the substrate to disturb the water flow and prevent the hydrated ions in the saline water from directional aggregation.

[0009] Furthermore, the vertical electric field has an intensity of 300 to 500 V / mm, a frequency of 100 to 600 Hz, and an electric field application time of 10 to 30 minutes.

[0010] Furthermore, the surfactant is a sodium dodecylbenzenesulfonate solution, the mass ratio of carbon nanotubes to sodium dodecylbenzenesulfonate is 1:0.3 to 1:0.5, and the mass concentration of the surfactant solution is 3 to 5 g / L.

[0011] Furthermore, the mass ratio of the carbon nanotubes to the graphene oxide is 1:0.01 to 1:0.06.

[0012] Furthermore, the method of stirring the column [5] aromatic hydrocarbon and polyethersulfone to form a substrate comprises the following steps: dissolving polyethersulfone in solvent A to obtain a polyethersulfone solution, dissolving the column [5] aromatic hydrocarbon in solvent A to obtain a column [5] aromatic hydrocarbon suspension, gradually adding the polyethersulfone solution to the column [5] aromatic hydrocarbon suspension, stirring for 24 to 48 hours to obtain a membrane liquid, forming the membrane liquid into a membrane by casting, drying, and then washing with water.

[0013] Furthermore, the mass concentration of the polyethersulfone is 0.02-0.05 g / mL, and the mass concentration of the column [5] aromatic suspension is 5×103 ~8×10 3 g / mL; the volume ratio of the polyethersulfone solution to the column [5] aromatic hydrocarbon suspension is 3:1 to 5:1.

[0014] Furthermore, the diameter of the carbon nanotubes is 0.4 to 0.5 nm.

[0015] A saline-alkali water desalination device based on a saline-alkali water desalination membrane comprises a saline-alkali water desalination membrane and an electric field applying device, wherein the saline-alkali water desalination membrane comprises a substrate formed of columnar [5] aromatic hydrocarbons and polyethersulfone, a carbon nanotube mesh layer interspersed with carbon nanotubes, and a graphene oxide connecting layer, wherein the carbon nanotubes are interspersed between the columnar [5] aromatic hydrocarbons on the substrate, and the graphene oxide connects the carbon nanotubes to form a conductive structure.

[0016] Beneficial effects of the present invention:

[0017] In the water treatment method based on a saline-alkali water desalination membrane of the present invention, the pillars [5] arene are anchored on a substrate, forming water molecule channels to separate water from salt ions. Carbon nanotubes are interspersed between the pillars [5] and are also anchored on the substrate, increasing the density of the water molecule channels and improving water flux. The carbon nanotubes are arranged in a directional manner, overcoming the drawback of the previously disordered distribution of carbon nanotubes and greatly increasing the water molecule flux.

[0018] In the water treatment method based on the saline-alkali water desalination membrane of the present invention, after the membrane strips are covered, there are low-lying gaps between the carbon nanotube aggregation strips. This structure disturbs the water flow, making the salt particles anisotropic and not easy to gather at the entrance of the carbon nanotube and column [5] aromatic hydrocarbon water channel. In addition, in the case of gaps, the flexible carbon nanotubes will also swing back and forth to avoid the aggregation of salt particles.

[0019] The water treatment method based on saline-alkali water desalination membrane of the present invention uses a graphene oxide layer to connect carbon nanotubes to form a conductive layer. Under the action of alternating current, the carbon nanotube layer has a repulsive effect on the hydrated ions of salt with the same charge, causing the hydrated ions of the salt to move, causing the hydrated ions of the salt to continuously move away from the corresponding saline-alkali water desalination membrane and flow away. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a scanning electron microscope image of the saline water desalination membrane in Example 1;

[0021] Figure 2 The end of the membrane column after the water treatment method based on the saline-alkali water desalination membrane in Example 1 has been running for three months;

[0022] Figure 3 This is the end of the membrane column after the water treatment method based on saline-alkali water desalination membrane in Comparative Example 2 has been running for three months. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the embodiments of the present invention and the accompanying drawings.

[0024] Example 1

[0025] The water treatment method based on the saline-alkali water desalination membrane of this embodiment includes the following steps: using the saline-alkali water desalination membrane to screen water molecules and ions in water. The preparation method of the saline-alkali water desalination membrane is as follows: forming a substrate with columnar [5] aromatic hydrocarbons and polyethersulfone, the columnar [5] aromatic hydrocarbons on the substrate forming water channels, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, the carbon nanotubes being interspersed in the gaps between adjacent columnar [5] aromatic hydrocarbons, and filling the gaps between the carbon nanotubes with graphene oxide to form a saline-alkali water desalination membrane.

[0026] The method for forming a base of column [5] aromatic hydrocarbon and polyethersulfone comprises the following steps:

[0027] S1: Dissolve polyethersulfone in N,N-dimethylformamide (DMF) to obtain a polyethersulfone solution with a mass concentration of 0.03 g / mL.

[0028] S2: Take column [5] and dissolve the aromatic hydrocarbon in DMF to obtain a mass concentration of 6×10 3 g / mL column[5] aromatic hydrocarbon suspension.

[0029] S3: Take 100 mL of column [5] aromatic hydrocarbon suspension, gradually add 400 mL of polyethersulfone solution into the column [5] aromatic hydrocarbon suspension, stir slowly, and stir for 36 hours to obtain membrane liquid.

[0030] S4: forming a membrane by casting the membrane liquid, drying to remove the solvent DMF, and then washing with water to obtain a membrane.

[0031] The method for aligning carbon nanotubes on a substrate to form carbon nanotube water channels comprises the following steps:

[0032] S1: Prepare sodium dodecylbenzenesulfonate (SDBS) solution: Take 40 g of SDBS and dissolve it in 1 L of water to obtain SDBS solution.

[0033] S2: 100 g of carbon nanotubes and 3 g of graphene oxide were mixed with the SDBS solution in step 1) and ultrasonicated to evenly disperse the carbon nanotubes. The ultrasonic power was 500 W and the ultrasonic time was 30 min. The diameter of the carbon nanotubes was 0.4-0.5 nm. After uniform dispersion, a carbon nanotube and graphene oxide suspension (CNTs-GO suspension) was obtained.

[0034] S3: Immerse the substrate in the CNTs-GO suspension and apply a vertical electric field to align the carbon nanotubes. The vertical electric field strength is 400 V / mm, the frequency is 500 Hz, and the electric field is applied for 20 minutes. During the application of the vertical electric field, the substrate is covered with a nanocellulose membrane strip. The exposed substrate has aligned carbon nanotubes, while the covered substrate does not. This creates an uneven structure on the substrate, disrupting the water flow and preventing the hydrated ions in the saline-alkali water from aligning.

[0035] S4: taking out the substrate with aligned carbon nanotubes, drying it, and then washing it with water to remove the surfactant.

[0036] In the process of desalination of saline-alkali water, the method of delaying the scaling and clogging of the saline-alkali water desalination membrane by applying an electric field to make the ions flow intermittently and directionally is to apply alternating current to make the ions move back and forth, thereby preventing the hydrated ions of salt from directionally gathering on the saline-alkali water desalination membrane.

[0037] The saline-alkali water desalination device based on the saline-alkali water desalination membrane of this embodiment includes a saline-alkali water desalination membrane and an electric field application device. The saline-alkali water desalination membrane includes a substrate formed by stirring columnar [5] aromatic hydrocarbons and polyethersulfone, a carbon nanotube grid layer interspersed with carbon nanotubes, and a graphene oxide connecting layer. The carbon nanotubes are interspersed between the columnar [5] aromatic hydrocarbons on the substrate, and the graphene oxide connects the carbon nanotubes to form a conductive structure.

[0038] Figure 1 This is an electron microscope image of the saline-alkali water desalination membrane of Example 1. It can be seen from the image that after being covered with the nanocellulose membrane strips, an uneven structure is formed on the substrate.

[0039] Example 2

[0040] The water treatment method based on the saline-alkali water desalination membrane of this embodiment includes the following steps: using the saline-alkali water desalination membrane to screen water molecules and ions in water. The preparation method of the saline-alkali water desalination membrane is as follows: forming a substrate with columnar [5] aromatic hydrocarbons and polyethersulfone, the columnar [5] aromatic hydrocarbons on the substrate forming water channels, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, the carbon nanotubes being interspersed in the gaps between adjacent columnar [5] aromatic hydrocarbons, and filling the gaps between the carbon nanotubes with graphene oxide to form a saline-alkali water desalination membrane.

[0041] The method for forming a substrate by stirring aromatic hydrocarbon and polyethersulfone comprises the following steps:

[0042] S1: Dissolve polyethersulfone in DMF to obtain a polyethersulfone solution with a mass concentration of 0.02 g / mL.

[0043] S2: Take column [5] and dissolve the aromatic hydrocarbon in DMF to obtain a mass concentration of 5×10 3g / mL column[5] aromatic hydrocarbon suspension.

[0044] S3: Take 100 mL of column [5] aromatic hydrocarbon suspension, gradually add 300 mL of polyethersulfone solution into the column [5] aromatic hydrocarbon suspension, stir slowly, and stir for 48 hours to obtain membrane liquid.

[0045] S4: forming a membrane by casting the membrane liquid, drying to remove the solvent DMF, and then washing with water to obtain a membrane.

[0046] The method for aligning carbon nanotubes on a substrate to form carbon nanotube water channels comprises the following steps:

[0047] S1: Prepare SDBS solution: Take 50 g of SDBS and dissolve it in 1 L of water to obtain SDBS solution.

[0048] S2: 100 g of carbon nanotubes and 5 g of graphene oxide were mixed with the SDBS solution in step 1) and ultrasonicated to evenly disperse the carbon nanotubes. The ultrasonic power was 100 W and the ultrasonic time was 50 min. The diameter of the carbon nanotubes was 0.4-0.5 nm. After uniform dispersion, a carbon nanotube and graphene oxide suspension (CNTs-GO suspension) was obtained.

[0049] S3: Immerse the substrate in the CNTs-GO suspension and apply a vertical electric field to align the carbon nanotubes. The vertical electric field strength is 500 V / mm, the frequency is 100 Hz, and the electric field is applied for 30 minutes. During the application of the vertical electric field, the substrate is covered with a nanocellulose membrane strip. The exposed substrate has aligned carbon nanotubes, while the covered substrate does not. This creates an uneven structure on the substrate, disrupting the water flow and preventing the hydrated ions in the saline-alkali water from aligning.

[0050] S4: taking out the substrate with aligned carbon nanotubes, drying it, and then washing it with water to remove the surfactant.

[0051] In the process of desalination of saline-alkali water, the method of delaying the scaling and clogging of the saline-alkali water desalination membrane by applying an electric field to make the ions flow intermittently and directionally is to apply alternating current to make the ions move back and forth, thereby preventing the hydrated ions of salt from directionally gathering on the saline-alkali water desalination membrane.

[0052] The saline-alkali water desalination device based on the saline-alkali water desalination membrane of this embodiment includes a saline-alkali water desalination membrane and an electric field application device. The saline-alkali water desalination membrane includes a substrate formed by columnar [5] aromatic hydrocarbons and polyethersulfone, a carbon nanotube grid layer interspersed with carbon nanotubes, and a graphene oxide connecting layer. The carbon nanotubes are interspersed between the columnar [5] aromatic hydrocarbons on the substrate, and the graphene oxide connects the carbon nanotubes to form a conductive structure.

[0053] Example 3

[0054] The water treatment method based on the saline-alkali water desalination membrane of this embodiment includes the following steps: using the saline-alkali water desalination membrane to screen water molecules and ions in water. The preparation method of the saline-alkali water desalination membrane is as follows: forming a substrate with columnar [5] aromatic hydrocarbons and polyethersulfone, the columnar [5] aromatic hydrocarbons on the substrate forming water channels, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, the carbon nanotubes being interspersed in the gaps between adjacent columnar [5] aromatic hydrocarbons, and filling the gaps between the carbon nanotubes with graphene oxide to form a saline-alkali water desalination membrane.

[0055] The method for forming a substrate by stirring aromatic hydrocarbon and polyethersulfone comprises the following steps:

[0056] S1: Dissolve polyethersulfone in DMF to obtain a polyethersulfone solution with a mass concentration of 0.05 g / mL.

[0057] S2: Take column [5] and dissolve the aromatic hydrocarbon in DMF to obtain a mass concentration of 8×10 3 g / mL column[5] aromatic hydrocarbon suspension.

[0058] S3: Take 100 mL of column [5] aromatic hydrocarbon suspension, gradually add 500 mL of polyethersulfone solution into the column [5] aromatic hydrocarbon suspension, stir slowly, and stir for 48 hours to obtain membrane liquid.

[0059] S4: forming a membrane by casting the membrane liquid, drying to remove the solvent DMF, and then washing with water to obtain a membrane.

[0060] The method for aligning carbon nanotubes on a substrate to form carbon nanotube water channels comprises the following steps:

[0061] S1: Prepare SDBS solution: Dissolve 30 g of SDBS in 1 L of water to obtain SDBS solution.

[0062] S2: 100 g of carbon nanotubes and 3 g of graphene oxide were mixed with the SDBS solution in step 1) and ultrasonicated to uniformly disperse the carbon nanotubes. The ultrasonic power was 500 W and the ultrasonic time was 300 min. The diameter of the carbon nanotubes was 0.4-0.5 nm. After uniform dispersion, a carbon nanotube and graphene oxide suspension (CNTs-GO suspension) was obtained.

[0063] S3: Immerse the substrate in the CNTs-GO suspension and apply a vertical electric field to align the carbon nanotubes. The vertical electric field strength is 300 V / mm, the frequency is 600 Hz, and the electric field is applied for 10 minutes. During the application of the vertical electric field, the substrate is covered with a nanocellulose membrane strip. The exposed substrate has aligned carbon nanotubes, while the covered substrate does not. This creates an uneven structure on the substrate, disrupting the water flow and preventing the hydrated ions in the saline-alkali water from aligning.

[0064] S4: taking out the substrate with aligned carbon nanotubes, drying it, and then washing it with water to remove the surfactant.

[0065] In the process of desalination of saline-alkali water, the method of delaying the scaling and clogging of the saline-alkali water desalination membrane by applying an electric field to make the ions flow intermittently and directionally is to apply alternating current to make the ions move back and forth, thereby preventing the hydrated ions of salt from directionally gathering on the saline-alkali water desalination membrane.

[0066] The saline-alkali water desalination device based on the saline-alkali water desalination membrane of this embodiment includes a saline-alkali water desalination membrane and an electric field application device. The saline-alkali water desalination membrane includes a substrate formed by columnar [5] aromatic hydrocarbons and polyethersulfone, a carbon nanotube grid layer interspersed with carbon nanotubes, and a graphene oxide connecting layer. The carbon nanotubes are interspersed between the columnar [5] aromatic hydrocarbons on the substrate, and the graphene oxide connects the carbon nanotubes to form a conductive structure.

[0067] Example 4

[0068] The water treatment method based on the saline-alkali water desalination membrane of this embodiment includes the following steps: using the saline-alkali water desalination membrane to screen water molecules and ions in water. The preparation method of the saline-alkali water desalination membrane is as follows: forming a substrate with columnar [5] aromatic hydrocarbons and polyethersulfone, the columnar [5] aromatic hydrocarbons on the substrate forming water channels, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, the carbon nanotubes being interspersed in the gaps between adjacent columnar [5] aromatic hydrocarbons, and filling the gaps between the carbon nanotubes with graphene oxide to form a saline-alkali water desalination membrane.

[0069] The method for forming a substrate by stirring aromatic hydrocarbon and polyethersulfone comprises the following steps:

[0070] S1: Dissolve polyethersulfone in DMF to obtain a polyethersulfone solution with a mass concentration of 0.03 g / mL.

[0071] S2: Take column [5] and dissolve the aromatic hydrocarbon in DMF to obtain a mass concentration of 6×10 3 g / mL column[5] aromatic hydrocarbon suspension.

[0072] S3: Take 100 mL of column [5] aromatic hydrocarbon suspension, gradually add 300 mL of polyethersulfone solution into the column [5] aromatic hydrocarbon suspension, stir slowly, and stir for 24 h to obtain membrane liquid.

[0073] S4: forming a membrane by casting the membrane liquid, drying to remove the solvent DMF, and then washing with water to obtain a membrane.

[0074] The method for aligning carbon nanotubes on a substrate to form carbon nanotube water channels comprises the following steps:

[0075] S1: Prepare SDBS solution: Take 40 g of SDBS and dissolve it in 1 L of water to obtain SDBS solution.

[0076] S2: 100 g of carbon nanotubes and 4 g of graphene oxide were mixed with the SDBS solution in step 1) and ultrasonicated to evenly disperse the carbon nanotubes. The ultrasonic power was 200 W and the ultrasonic time was 50 min. The diameter of the carbon nanotubes was 0.4-0.5 nm. After uniform dispersion, a carbon nanotube and graphene oxide suspension (CNTs-GO suspension) was obtained.

[0077] S3: Immerse the substrate in the CNTs-GO suspension and apply a vertical electric field to align the carbon nanotubes. The vertical electric field strength is 500 V / mm, the frequency is 300 Hz, and the electric field is applied for 30 minutes. During the application of the vertical electric field, the substrate is covered with a nanocellulose membrane strip. The exposed substrate has aligned carbon nanotubes, while the covered substrate does not. This creates an uneven structure on the substrate, disrupting the water flow and preventing the hydrated ions in the saline-alkali water from aligning.

[0078] S4: taking out the substrate with aligned carbon nanotubes, drying it, and then washing it with water to remove the surfactant.

[0079] In the process of desalination of saline-alkali water, the method of delaying the scaling and clogging of the saline-alkali water desalination membrane by applying an electric field to make the ions flow intermittently and directionally is to apply alternating current to make the ions move back and forth, thereby preventing the hydrated ions of salt from directionally gathering on the saline-alkali water desalination membrane.

[0080] The saline-alkali water desalination device based on the saline-alkali water desalination membrane of this embodiment includes a saline-alkali water desalination membrane and an electric field application device. The saline-alkali water desalination membrane includes a substrate formed by columnar [5] aromatic hydrocarbons and polyethersulfone, a carbon nanotube grid layer interspersed with carbon nanotubes, and a graphene oxide connecting layer. The carbon nanotubes are interspersed between the columnar [5] aromatic hydrocarbons on the substrate, and the graphene oxide connects the carbon nanotubes to form a conductive structure.

[0081] Example 5

[0082] The water treatment method based on the saline-alkali water desalination membrane of this embodiment includes the following steps: using the saline-alkali water desalination membrane to screen water molecules and ions in water. The preparation method of the saline-alkali water desalination membrane is as follows: forming a substrate with columnar [5] aromatic hydrocarbons and polyethersulfone, the columnar [5] aromatic hydrocarbons on the substrate forming water channels, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, the carbon nanotubes being interspersed in the gaps between adjacent columnar [5] aromatic hydrocarbons, and filling the gaps between the carbon nanotubes with graphene oxide to form a saline-alkali water desalination membrane.

[0083] The method for forming a substrate by stirring aromatic hydrocarbon and polyethersulfone comprises the following steps:

[0084] S1: Dissolve polyethersulfone in DMF to obtain a polyethersulfone solution with a mass concentration of 0.05 g / mL.

[0085] S2: Take column [5] and dissolve the aromatic hydrocarbon in DMF to obtain a mass concentration of 5×10 3 g / mL column[5] aromatic hydrocarbon suspension.

[0086] S3: Take 100 mL of column [5] aromatic hydrocarbon suspension, gradually add 500 mL of polyethersulfone solution into the column [5] aromatic hydrocarbon suspension, stir slowly, and stir for 48 hours to obtain membrane liquid.

[0087] S4: forming a membrane by casting the membrane liquid, drying to remove the solvent DMF, and then washing with water to obtain a membrane.

[0088] The method for aligning carbon nanotubes on a substrate to form carbon nanotube water channels comprises the following steps:

[0089] S1: Prepare SDBS solution: Dissolve 30 g of SDBS in 1 L of water to obtain SDBS solution.

[0090] S2: 100 g of carbon nanotubes and 3 g of graphene oxide were mixed with the SDBS solution in step 1) and ultrasonicated to uniformly disperse the carbon nanotubes. The ultrasonic power was 100 W and the ultrasonic time was 40 min. The diameter of the carbon nanotubes was 0.4-0.5 nm. After uniform dispersion, a carbon nanotube and graphene oxide suspension (CNTs-GO suspension) was obtained.

[0091] S3: Immerse the substrate in the CNTs-GO suspension and apply a vertical electric field to align the carbon nanotubes. The vertical electric field strength is 300 V / mm, the frequency is 200 Hz, and the electric field is applied for 15 minutes. During the application of the vertical electric field, the substrate is covered with a nanocellulose membrane strip. The exposed substrate has aligned carbon nanotubes, while the covered substrate does not. This creates an uneven structure on the substrate, disrupting the water flow and preventing the hydrated ions in the saline-alkali water from aligning.

[0092] S4: taking out the substrate with aligned carbon nanotubes, drying it, and then washing it with water to remove the surfactant.

[0093] In the process of desalination of saline-alkali water, the method of delaying the scaling and clogging of the saline-alkali water desalination membrane by applying an electric field to make the ions flow intermittently and directionally is to apply alternating current to make the ions move back and forth, thereby preventing the hydrated ions of salt from directionally gathering on the saline-alkali water desalination membrane.

[0094] The saline-alkali water desalination device based on the saline-alkali water desalination membrane of this embodiment includes a saline-alkali water desalination membrane and an electric field application device. The saline-alkali water desalination membrane includes a substrate formed by columnar [5] aromatic hydrocarbons and polyethersulfone, a carbon nanotube grid layer interspersed with carbon nanotubes, and a graphene oxide connecting layer. The carbon nanotubes are interspersed between the columnar [5] aromatic hydrocarbons on the substrate, and the graphene oxide connects the carbon nanotubes to form a conductive structure.

[0095] Comparative Example 1

[0096] The water treatment method based on a saline-alkali water desalination membrane in this comparative example comprises the following steps: using the saline-alkali water desalination membrane to screen water molecules and ions in the water. The saline-alkali water desalination membrane is prepared by using a polyethersulfone substrate, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, interspersing the carbon nanotubes on the substrate, and filling the gaps between the carbon nanotubes with graphene oxide to form the saline-alkali water desalination membrane.

[0097] The method for aligning carbon nanotubes on a substrate to form carbon nanotube water channels comprises the following steps:

[0098] S1: Prepare SDBS solution: Take 40 g of SDBS and dissolve it in 1 L of water to obtain SDBS solution.

[0099] S2: 100 g of carbon nanotubes and 3 g of graphene oxide were mixed with the SDBS solution in step 1) and ultrasonicated to evenly disperse the carbon nanotubes. The ultrasonic power was 500 W and the ultrasonic time was 30 min. The diameter of the carbon nanotubes was 0.4-0.5 nm. After uniform dispersion, a carbon nanotube and graphene oxide suspension (CNTs-GO suspension) was obtained.

[0100] S3: Immerse the substrate in the CNTs-GO suspension and apply a vertical electric field to align the carbon nanotubes. The vertical electric field strength is 400 V / mm, the frequency is 500 Hz, and the electric field is applied for 20 minutes. During the application of the vertical electric field, the substrate is covered with a nanocellulose membrane strip. The exposed substrate has aligned carbon nanotubes, while the covered substrate does not. This creates an uneven structure on the substrate, disrupting the water flow and preventing the hydrated ions in the saline-alkali water from aligning.

[0101] S4: taking out the substrate with aligned carbon nanotubes, drying it, and then washing it with water to remove the surfactant.

[0102] In the process of desalination of saline-alkali water, the method of delaying the scaling and clogging of the saline-alkali water desalination membrane by applying an electric field to make the ions flow intermittently and directionally is to apply alternating current to make the ions move back and forth, thereby preventing the hydrated ions of salt from directionally gathering on the saline-alkali water desalination membrane.

[0103] The saline-alkali water desalination device based on the saline-alkali water desalination membrane of this comparative example includes a saline-alkali water desalination membrane and an electric field application device. The saline-alkali water desalination membrane includes a polyethersulfone substrate, a carbon nanotube grid layer interspersed with carbon nanotubes, and a graphene oxide connecting layer. The carbon nanotubes are interspersed on the substrate, and the graphene oxide connects the individual carbon nanotubes to form a conductive structure.

[0104] Comparative Example 2

[0105] The scheme of this comparative example is substantially the same as that of Example 1, except that, in the method of aligning carbon nanotubes on a substrate to form carbon nanotube water channels, no membrane strips are used to cover the substrate.

[0106] Test Example 1

[0107] The pure water flux of the saline-alkali water desalination membranes of Example 1, Comparative Example 1 and Comparative Example 2 were tested respectively, and the results are shown in Table 1.

[0108] Table 1 Pure water flux test results of saline-alkali water desalination membranes of Example 1, Comparative Example 1 and Comparative Example 2

[0109]

[0110] As can be seen from Table 1, in the initial operation, the pure water flux of Example 1 is larger than that of Comparative Examples 1 and 2. Because no column [5] aromatic hydrocarbons are used and membrane strips are used to cover the substrate, under the same conditions, the pure water flux of Comparative Example 1 is smaller. After three months of use, the pure water flux of the embodiment is slightly reduced. Figure 2 It can be seen that the scaling of the membrane column in Example 1 is not serious. The pure water flux of Comparative Example 1 is also reduced. The pure water flux of Comparative Example 2 is significantly reduced. Figure 3 It can be seen that the membrane column of Comparative Example 2 has more yellow scale at the end, which blocks the membrane column, so the pure water flux is reduced.

Claims

1. A water treatment method based on saline-alkali water desalination membrane, characterized in that: The following steps are involved: A saline-alkali water desalination membrane is used to screen water molecules and ions in water, and an electric field is applied to cause the ions to intermittently flow in a directional manner to delay scaling and clogging of the saline-alkali water desalination membrane; a method for preparing a saline-alkali water desalination membrane comprises the following steps: columnar [5] aromatic hydrocarbons and polyethersulfone are stirred to form a substrate, the columnar [5] aromatic hydrocarbons on the substrate form water channels, carbon nanotubes are oriented on the substrate to form carbon nanotube water channels, the carbon nanotubes are interspersed in the gaps between adjacent columnar [5] aromatic hydrocarbons, and graphene oxide is used to fill the gaps between the carbon nanotubes; the method for orientedly arranging carbon nanotubes on the substrate to form carbon nanotube water channels comprises the following steps: the carbon nanotubes, graphene oxide, Graphene is mixed with a surfactant solution and ultrasonicated to uniformly disperse carbon nanotubes and graphene oxide. After uniform dispersion, a mixed suspension of carbon nanotubes and graphene oxide is obtained. A substrate is immersed in the mixed suspension of carbon nanotubes and graphene oxide, and a vertical electric field is applied to align the carbon nanotubes. The substrate with the aligned carbon nanotubes is removed, dried, and then washed with water to remove the surfactant. When applying the vertical electric field, a film strip is used to cover the substrate, so that the exposed substrate has aligned carbon nanotubes and the covered substrate has no aligned carbon nanotubes. An uneven structure is formed on the substrate to disturb the water flow and prevent the oriented aggregation of hydrated ions in saline-alkali water.

2. The water treatment method based on saline-alkali water desalination membrane according to claim 1, characterized in that: The vertical electric field has an intensity of 300 to 500 V / mm, a frequency of 100 to 600 Hz, and an electric field application time of 10 to 30 minutes.

3. The water treatment method based on saline-alkali water desalination membrane according to claim 1, characterized in that: The surfactant is a sodium dodecylbenzenesulfonate solution, the mass ratio of carbon nanotubes to sodium dodecylbenzenesulfonate is 1:0.3 to 1:0.5, and the mass concentration of the surfactant solution is 3 to 5 g / L.

4. The water treatment method based on saline-alkali water desalination membrane according to claim 1, characterized in that: The mass ratio of the carbon nanotubes to graphene oxide is 1:0.01 to 1:0.

06.

5. The water treatment method based on saline-alkali water desalination membrane according to claim 1, characterized in that: The method for forming a substrate by stirring column [5] aromatic hydrocarbon and polyethersulfone comprises the following steps: dissolving polyethersulfone in solvent A to obtain a polyethersulfone solution, dissolving column [5] aromatic hydrocarbon in solvent A to obtain a column [5] aromatic hydrocarbon suspension, gradually adding the polyethersulfone solution to the column [5] aromatic hydrocarbon suspension, stirring for 24 to 48 hours to obtain a membrane liquid, forming a membrane by casting the membrane liquid, drying, and then washing with water.

6. The water treatment method based on saline-alkali water desalination membrane according to claim 5, characterized in that: The mass concentration of the polyethersulfone is 0.02-0.05 g / mL, and the mass concentration of the aromatic hydrocarbon suspension in column [5] is 5×10 3 ~8×10 3 g / mL; the volume ratio of the polyethersulfone solution to the column [5] aromatic hydrocarbon suspension is 3:1 to 5:

1.

7. The water treatment method based on saline-alkali water desalination membrane according to claim 1, characterized in that: The diameter of carbon nanotubes is 0.4 to 0.5 nm.

8. A saline-alkali water desalination device based on a saline-alkali water desalination membrane, applied to the water treatment method based on a saline-alkali water desalination membrane as claimed in claim 1, comprising a saline-alkali water desalination membrane and an electric field applying device, characterized in that: The saline-alkali water desalination membrane includes a substrate formed by columnar [5] aromatic hydrocarbons and polyethersulfone, a carbon nanotube grid layer interspersed with carbon nanotubes, and a graphene oxide connecting layer. The carbon nanotubes are interspersed between the columnar [5] aromatic hydrocarbons on the substrate, and the graphene oxide connects the carbon nanotubes to form a conductive structure.

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