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

Abstract

The invention relates to a water treatment method and device based on a saline-alkaline water desalination membrane, and the water treatment method based on the saline-alkaline water desalination membrane comprises the following steps: screening water molecules and ions in water by using the saline-alkaline water desalination membrane, and enabling the ions to intermittently and directionally flow in a manner of applying an electric field to delay scaling and blocking of the saline-alkaline water desalination membrane; the preparation method of the saline-alkali water desalination film comprises the following steps: forming a substrate by column [5] arene and polyethersulfone, forming a water channel by the column [5] arene on the substrate, directionally arranging carbon nanotubes on the substrate to form a carbon nanotube water channel, and inserting the carbon nanotubes into gaps of adjacent column [5] arene to obtain the saline-alkali water desalination film. Meanwhile, gaps of the carbon nanotubes are filled with graphene oxide, so that the saline-alkali water desalination film improves the water flux and is not easy to block.

Description

Technical Field

[0001] The 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 combined 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-alkali water desalination membrane uses carbon nanotubes, graphene oxide, etc. to form ion screening channels, and adjusts the size of the ion screening channels to between 0.4-0.5nm, 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. The saline water in Xinjiang Uygur Autonomous Region contains NaCl and is rich in CO3 2- 、SO4 2- , Ca 2+ Mg 2+ Due to hardness elements such as chlorinated carbon dioxide, the saline-alkali 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 purpose, 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 column [5] aromatic hydrocarbons and polyethersulfone to form a substrate, the column [5] aromatic hydrocarbons on the substrate forming water channels, arranging carbon nanotubes on the substrate in a directional manner to form carbon nanotube water channels, the carbon nanotubes being interspersed in the gaps between adjacent column [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 a carbon nanotube water channel comprises 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 even dispersion, immersing a substrate in the mixed suspension of carbon nanotubes and graphene oxide, applying a vertical electric field to align the carbon nanotubes, taking out the substrate with the aligned carbon nanotubes, drying it, and then washing it with water to remove the surfactant.

[0008] Furthermore, when the vertical electric field is applied, a membrane strip is used to cover the substrate, the exposed substrate has carbon nanotubes arranged in a direction, and the covered substrate has no carbon nanotubes arranged in a direction, and an uneven grid structure is formed 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 min.

[0010] Furthermore, the surfactant is a sodium dodecylbenzene sulfonate solution, the mass ratio of carbon nanotubes to sodium dodecylbenzene sulfonate 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 a membrane by casting the membrane liquid, and drying and washing the membrane.

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

[0014] Furthermore, the diameter of the carbon nanotube is 0.4-0.5 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 application device. The saline-alkali water desalination membrane comprises a substrate formed of 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.

[0016] Beneficial effects of the present invention:

[0017] In the water treatment method based on saline-alkali water desalination membrane of the present invention, the column [5] aromatic hydrocarbons are anchored on the substrate to form water molecule channels to separate water from salt ions. Carbon nanotubes are interspersed between the column [5] aromatic hydrocarbons and are also anchored on the substrate, which increases the density of the water molecule channels and improves the water flux. The carbon nanotubes are arranged in a directional manner, overcoming the defect of the conventional disorderly distribution of carbon nanotubes and greatly increasing the water molecule flux.

[0018] In the water treatment method based on 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 water channel. In addition, in the presence 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 repels 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-alkali water desalination membrane in Example 1;

[0021] Figure 2 The end of the membrane column after the water treatment method based on 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 in conjunction with the embodiments of the present invention and the accompanying drawings.

[0024] Example 1

[0025] The water treatment method based on saline-alkali water desalination membrane of this embodiment comprises 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: forming a substrate with column [5] aromatic hydrocarbons and polyethersulfone, the column [5] aromatic hydrocarbons on the substrate form water channels, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, the carbon nanotubes are inserted into the gaps between adjacent column [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 of forming a substrate from 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 the aromatic suspension of column [5], gradually add 400 mL of polyethersulfone solution into the aromatic suspension of column [5], stir slowly, and stir for 36 hours to obtain a membrane solution.

[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 a carbon nanotube water channel comprises the following steps:

[0032] S1: Prepare sodium dodecylbenzene sulfonate (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 even 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 has an intensity of 400 V / mm, a frequency of 500 Hz, and an electric field application time of 20 min. When applying the vertical electric field, the substrate is covered with a membrane strip, which is a nanocellulose membrane strip. The exposed substrate has oriented carbon nanotubes, and the covered substrate has no oriented carbon nanotubes. An uneven structure is formed on the substrate to disturb the water flow and prevent the hydrated ions in the saline-alkali water from oriented aggregation.

[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 the salt from directional aggregation 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 various 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 saline-alkali water desalination membrane of this embodiment comprises 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: forming a substrate with column [5] aromatic hydrocarbons and polyethersulfone, the column [5] aromatic hydrocarbons on the substrate form water channels, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, the carbon nanotubes are inserted into the gaps between adjacent column [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 of stirring aromatic hydrocarbon and polyethersulfone to form a substrate 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 suspension, gradually add 300 mL of polyethersulfone solution into the column [5] aromatic suspension, slowly stir, stir for 48 hours, and obtain membrane solution.

[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 a carbon nanotube water channel 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 evenly dispersing, a carbon nanotube and graphene oxide suspension (CNTs-GO suspension) was obtained.

[0049] S3: The substrate is immersed in the CNTs-GO suspension and a vertical electric field is applied to align the carbon nanotubes. The vertical electric field has an intensity of 500 V / mm, a frequency of 100 Hz, and an electric field application time of 30 min. When the vertical electric field is applied, the substrate is covered with a membrane strip, which is a nanocellulose membrane strip. The exposed substrate has oriented carbon nanotubes, and the covered substrate has no oriented carbon nanotubes. An uneven structure is formed on the substrate to disturb the water flow and prevent the hydrated ions in the saline-alkali water from oriented aggregation.

[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 the salt from directional aggregation 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 various carbon nanotubes to form a conductive structure.

[0053] Example 3

[0054] The water treatment method based on saline-alkali water desalination membrane of this embodiment comprises 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: forming a substrate with column [5] aromatic hydrocarbons and polyethersulfone, the column [5] aromatic hydrocarbons on the substrate form water channels, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, the carbon nanotubes are inserted into the gaps between adjacent column [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 of stirring aromatic hydrocarbon and polyethersulfone to form a substrate 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 suspension, gradually add 500 mL of polyethersulfone solution into the column [5] aromatic suspension, slowly stir, stir for 48 hours, and obtain membrane solution.

[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 a carbon nanotube water channel comprises the following steps:

[0061] S1: Prepare SDBS solution: Take 30 g of SDBS and dissolve it 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 evenly 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 even 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 has an intensity of 300 V / mm, a frequency of 600 Hz, and an electric field application time of 10 min. When applying the vertical electric field, use a membrane strip to cover the substrate. The membrane strip is a nanocellulose membrane strip. The exposed substrate has carbon nanotubes aligned in an aligned manner, 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 hydrated ions in the saline-alkali water from oriented aggregation.

[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 the salt from directional aggregation 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 various carbon nanotubes to form a conductive structure.

[0067] Example 4

[0068] The water treatment method based on saline-alkali water desalination membrane of this embodiment comprises 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: forming a substrate with column [5] aromatic hydrocarbons and polyethersulfone, the column [5] aromatic hydrocarbons on the substrate form water channels, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, the carbon nanotubes are inserted into the gaps between adjacent column [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 of stirring aromatic hydrocarbon and polyethersulfone to form a substrate 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 suspension, gradually add 300 mL of polyethersulfone solution into the column [5] aromatic suspension, slowly stir, stir for 24 h, and obtain membrane solution.

[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 a carbon nanotube water channel 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 evenly dispersing, 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 has an intensity of 500 V / mm, a frequency of 300 Hz, and an electric field application time of 30 min. When applying the vertical electric field, the substrate is covered with a membrane strip, which is a nanocellulose membrane strip. The exposed substrate has oriented carbon nanotubes, and the covered substrate has no oriented carbon nanotubes. An uneven structure is formed on the substrate to disturb the water flow and prevent the hydrated ions in the saline-alkali water from oriented aggregation.

[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 the salt from directional aggregation 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 various carbon nanotubes to form a conductive structure.

[0081] Example 5

[0082] The water treatment method based on saline-alkali water desalination membrane of this embodiment comprises 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: forming a substrate with column [5] aromatic hydrocarbons and polyethersulfone, the column [5] aromatic hydrocarbons on the substrate form water channels, aligning carbon nanotubes on the substrate to form carbon nanotube water channels, the carbon nanotubes are inserted into the gaps between adjacent column [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 of stirring aromatic hydrocarbon and polyethersulfone to form a substrate 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 suspension, gradually add 500 mL of polyethersulfone solution into the column [5] aromatic suspension, slowly stir, stir for 48 hours, and obtain membrane solution.

[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 a carbon nanotube water channel comprises the following steps:

[0089] S1: Prepare SDBS solution: Take 30 g of SDBS and dissolve it 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 evenly 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 even 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 has an intensity of 300 V / mm, a frequency of 200 Hz, and an electric field application time of 15 min. When applying the vertical electric field, the substrate is covered with a membrane strip, which is a nanocellulose membrane strip. The exposed substrate has carbon nanotubes aligned in an aligned manner, while the covered substrate has no aligned carbon nanotubes. An uneven structure is formed on the substrate to disturb the water flow and prevent the hydrated ions in the saline-alkali water from oriented aggregation.

[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 the salt from directional aggregation 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 various carbon nanotubes to form a conductive structure.

[0095] Comparative Example 1

[0096] The water treatment method based on saline-alkali water desalination membrane of this comparative example comprises 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: polyethersulfone is made into a substrate, carbon nanotubes are oriented and arranged on the substrate to form carbon nanotube water channels, the carbon nanotubes are interspersed on the substrate, and the gaps between the carbon nanotubes are filled with graphene oxide to form a saline-alkali water desalination membrane.

[0097] The method for aligning carbon nanotubes on a substrate to form a carbon nanotube water channel 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 even 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 has an intensity of 400 V / mm, a frequency of 500 Hz, and an electric field application time of 20 min. When applying the vertical electric field, the substrate is covered with a membrane strip, which is a nanocellulose membrane strip. The exposed substrate has oriented carbon nanotubes, and the covered substrate has no oriented carbon nanotubes. An uneven structure is formed on the substrate to disturb the water flow and prevent the hydrated ions in the saline-alkali water from oriented aggregation.

[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 the salt from directional aggregation 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 a carbon nanotube water channel, no membrane strip is used to cover the substrate.

[0106] Test Example 1

[0107] The pure water flux of the saline-alkali water desalination membrane of Example 1, Comparative Example 1 and Comparative Example 2 was 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 column [5] aromatics is not 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 decreased slightly. 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 make the ions flow intermittently 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 includes the following steps: column [5] aromatic hydrocarbons and polyethersulfone are stirred to form a substrate, the column [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 column [5] aromatic hydrocarbons, and the gaps between the carbon nanotubes are filled with graphene oxide.

2. The water treatment method based on saline-alkali water desalination membrane according to claim 1 is characterized in that: The method for aligning carbon nanotubes on a substrate to form a carbon nanotube water channel comprises 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 even dispersion, immersing a substrate in the mixed suspension of carbon nanotubes and graphene oxide, applying a vertical electric field to align the carbon nanotubes, taking out the substrate with the aligned carbon nanotubes, and washing with water to remove the surfactant after drying.

3. The water treatment method based on saline-alkali water desalination membrane according to claim 2 is characterized in that: When applying the vertical electric field, the substrate is covered with a membrane strip, the exposed substrate has carbon nanotubes arranged in a directional manner, and the covered substrate has no carbon nanotubes arranged in a directional manner, and an uneven structure is formed on the substrate to disturb the water flow and prevent the hydrated ions in the saline-alkali water from directional aggregation.

4. The water treatment method based on saline-alkali water desalination membrane according to claim 2 or 3, 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 min.

5. The water treatment method based on saline-alkali water desalination membrane according to claim 2 or 3, characterized in that: The surfactant is a sodium dodecylbenzene sulfonate solution, the mass ratio of carbon nanotubes to sodium dodecylbenzene sulfonate is 1:0.3-1:0.5, and the mass concentration of the surfactant solution is 3-5 g / L.

6. The water treatment method based on saline-alkali water desalination membrane according to claim 2 or 3, characterized in that: The mass ratio of the carbon nanotubes to graphene oxide is 1:0.01 to 1:0.

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7. The water treatment method based on saline-alkali water desalination membrane according to claim 1 is characterized in that: The method of stirring 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 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, and drying and washing with water to obtain a membrane.

8. The water treatment method based on saline-alkali water desalination membrane according to claim 7 is characterized in that: The mass concentration of the polyethersulfone is 0.02-0.05 g / mL, and the mass concentration of the aromatic 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 suspension is 3:1 to 5:

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9. The water treatment method based on saline-alkali water desalination membrane according to any one of claims 1 to 3 and 7, characterized in that: The diameter of carbon nanotubes is 0.4 to 0.5 nm.

10. A saline-alkali water desalination device based on a saline-alkali water desalination membrane, comprising a saline-alkali water desalination membrane and an electric field application device, characterized in that: The saline-alkali water desalination membrane includes a substrate formed of 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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