A carbon quantum dots modulated active layer pore size to enhance water flux and salt rejection rate of forward osmosis membrane

Abstract

The application discloses a kind of carbon quantum dots regulation active layer pore size to enhance water flux and salt rejection rate of positive osmosis membrane, including support layer and active layer, active layer is by water phase solution and oil phase solution on the surface of support layer through interface polymerization reaction is formed, carbon quantum dots are incorporated in water phase solution, and active layer is modified once;After modification, active layer is again modified by carbon quantum dots solution twice;By twice modification of carbon quantum dots, the pore size of active layer is regulated, so that the pore size of active layer is reduced, and the porosity is increased, so that the water flux and salt rejection rate of positive osmosis membrane are simultaneously improved.The positive osmosis membrane obtained by the application not only has antibacterial ability, but also improves water flux and salt rejection rate.

Description

Technical Field

[0001] This invention relates to the field of forward osmosis (FO) membrane modification technology, specifically to a forward osmosis membrane in which carbon quantum dots regulate the pore size of the active layer to enhance water flux and salt rejection rate. Background Technology

[0002] Thin-layer composite (TFC) polyamide (PA) membranes, consisting of an active layer and a support layer, are high-performance desalination membranes widely used in forward osmosis processes, exhibiting excellent properties such as high water flux and high salt rejection rate. However, due to the strong hydrophobicity of the active layer and the large pore size of the support layer, TFC-PA membranes are highly susceptible to membrane fouling during practical use, hindering the further promotion and application of forward osmosis (FO) membranes.

[0003] Water flux and salt rejection rate are important indicators of membrane separation. In recent years, thin-film composite FO membranes have been widely studied due to their many advantages, including superior water permeability, high desalination rate, and ease of modification. TFC-FO membranes exhibit a characteristic two-layer structure consisting of a polyamide active layer and a porous support layer. The PA active layer is very thin and highly cross-linked, which is the main site of water osmotic pressure action; the support layer typically provides physical support for the thin PA layer. However, the highly cross-linked structure of the active layer may hinder water permeation, resulting in lower water flux; the porous structure of the support layer may cause concentration polarization during FO, especially internal concentration polarization (ICP), leading to actual separation efficiency lower than theoretical values. Therefore, modification of conventional TFC-FO membranes is essential to improve their performance in FO processes.

[0004] Generally, the modification methods for TFC-FO membranes mainly focus on adjusting the structure of the support layer and the selective layer. Specifically, optimizing the performance of the support layer primarily involves increasing its porosity and enhancing its hydrophilicity by coating it with hydrophilic materials, thereby improving water flux. Optimizing the selective layer mainly involves surface grafting and adding hydrophilic nanoparticles to the oil and aqueous phases involved in interfacial polymerization. However, while coating with hydrophilic materials increases the hydrophilicity of the support layer, it also reduces its porosity, resulting in a less significant effect. Grafting for selective layer optimization is complex, and introducing other polymers can lead to unstable product performance. Furthermore, traditional FO membrane technology struggles to overcome the trade-off effect during the FO process, where increased water flux is accompanied by increased reverse salt flux, resulting in low selective permeability. Therefore, a high-performance polyamide FO membrane is needed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a forward osmosis membrane in which carbon quantum dots regulate the pore size of the active layer to enhance water flux and salt rejection rate. While ensuring increased water flux, it can also effectively improve the salt rejection rate of the membrane and achieve antibacterial effect.

[0006] To achieve its objectives, the present invention employs the following technical solution:

[0007] A forward osmosis membrane that uses carbon quantum dots to regulate the pore size of the active layer to enhance water flux and salt rejection rate is disclosed. The forward osmosis membrane includes a support layer and an active layer. The active layer is formed by interfacial polymerization of an aqueous solution and an oil solution on the surface of the support layer. The membrane is characterized by: incorporating carbon quantum dots into the aqueous solution to modify the active layer initially; followed by a secondary modification of the active layer using a carbon quantum dot solution; and through these two modifications with carbon quantum dots, regulating the pore size of the active layer, thereby reducing the pore size and increasing the porosity, thus simultaneously improving the water flux and salt rejection rate of the forward osmosis membrane.

[0008] Preferably, the aqueous phase solution is a m-phenylenediamine solution and the oil phase solution is a pyromellitic trimethylol chloride solution.

[0009] Preferably, the carbon quantum dots are synthesized using m-phenylenediamine as the carbon source via a one-pot hydrothermal method. The carbon quantum dots refer to dispersed, spherical carbon particles with extremely small sizes (below 10 nm) and exhibit fluorescence or phosphorescence emission properties. Commonly used carbon sources for preparing carbon quantum dots include citric acid, glucose, polyethylene glycol, urea, and ionic liquids. Common synthesis methods include chemical oxidation, combustion, hydrothermal / solvothermal, microwave synthesis, and template methods. This invention uses a solution of m-phenylenediamine (MPD)-based carbon quantum dots (C-dots) synthesized via a hydrothermal / solvothermal method. Compared to other carbon quantum dots, the C-dots selected in this invention can simultaneously enhance the pore size of the active layer and improve both water flux and salt rejection rate.

[0010] Preferably, in the primary modification, the concentration of carbon quantum dots in the aqueous solution is 0.05-0.1 wt%.

[0011] Preferably, in the secondary modification, the concentration of the carbon quantum dot solution is 0.15-0.2 wt%.

[0012] The unmodified active layer has a large pore size, containing numerous interconnected pores of 3-5 nm. This invention incorporates a carbon quantum dot (C-dots) solution into a m-phenylenediamine solution. During interfacial polymerization to form the active layer, the pore size of the active layer is initially controlled. A secondary interfacial polymerization is then performed on the surface with the C-dots solution, resulting in a C-dots coating on the surface, thus completing the pore size control of the active layer. After these two modifications, the pore size range of the numerous pores in the active layer is reduced from 3-5 nm to below 2 nm.

[0013] Preferably, the matrix material of the support layer is polyethersulfone (PES).

[0014] This invention also discloses a method for preparing the forward osmosis membrane, characterized by: interfacial polymerization of a polyethersulfone membrane on the surface using a carbon quantum dot-doped m-phenylenediamine solution and a trimesoyl chloride solution to form a modified polyamide active layer, followed by modification of the surface with an aqueous solution of carbon quantum dots, thus obtaining the forward osmosis membrane. Specifically, the method includes the following steps:

[0015] Step 1: Synthesize carbon quantum dots using m-phenylenediamine as a carbon source

[0016] m-Phenylenediamine and ethanol were mixed at a mass ratio of 1:100 and sonicated until the m-Phenylenediamine was completely dissolved. The resulting solution was then transferred to a reaction vessel and heated to 180°C at a heating rate of 5°C / min, and reacted for 12 h. After the reaction was completed, the solution was naturally cooled to room temperature, and then rotary evaporated in a vacuum rotary evaporator at 65°C and 100 r / min for 30 min to remove excess ethanol. After rotary evaporation, the solution was diluted with deionized water to obtain a carbon quantum dot solution with m-Phenylenediamine as the carbon source.

[0017] Step 2: Prepare the required solution

[0018] Add m-phenylenediamine to water, then add the carbon quantum dots obtained in step 1, and disperse evenly by ultrasonication to obtain an aqueous solution with a m-phenylenediamine concentration of 1.0 wt% and a carbon quantum dot concentration of 0.05-0.1 wt%.

[0019] Tristyrene chloride was added to n-hexane to obtain an oil phase solution with a tristyrene chloride concentration of 0.15 wt%.

[0020] The carbon quantum dot concentration in the carbon quantum dot solution obtained in step 1 is adjusted to 0.15-0.2 wt% to obtain a carbon quantum dot solution for secondary modification.

[0021] Step 3: Prepare the primary modified active layer

[0022] The aqueous solution is poured onto the cleaned and dried polyethersulfone membrane surface and soaked at room temperature for 3 minutes. Then, the excess solution on the surface is removed. The oil phase solution is then poured onto the polyethersulfone membrane surface and soaked at room temperature for 2 minutes. After removing the excess solution on the surface, the membrane is dried in a drying oven at 60°C for 8 minutes, thus forming a modified polyamide active layer on the polyethersulfone membrane surface.

[0023] Step 4: Secondary modification of the active layer

[0024] The carbon quantum dot solution used for secondary modification was poured onto the surface of the modified polyamide active layer and reacted at room temperature for 20-30 minutes. After rinsing, a forward osmosis membrane was obtained.

[0025] The forward osmosis membrane obtained by this invention can be used for forward osmosis treatment or recycling of saline wastewater systems.

[0026] Compared with existing technologies, the beneficial effects of the present invention are as follows:

[0027] 1. Traditional forward osmosis (FO) membrane technology struggles to overcome the trade-off effect during the FO process, where an increase in water flux is accompanied by a corresponding increase in reverse salt flux, resulting in poor selective permeation performance. This invention incorporates C-dots prepared using m-phenylenediamine as a carbon source into an aqueous solution, undergoing interfacial polymerization to obtain an active layer. A further C-dots layer is coated onto this active layer to perform secondary modification of the FO membrane, reducing its pore size and increasing its porosity. This significantly improves the selective permeation performance of the prepared FO membrane, effectively mitigating the trade-off effect. The forward osmosis membrane obtained by this invention not only possesses antibacterial capabilities but also increases both water flux and salt rejection rate.

[0028] 2. The C-dots prepared by this invention contain a large number of hydrophilic groups such as amino and imino groups. When C-dots are distributed on the membrane, they can increase the hydrophilicity of the membrane and improve the water flux of the FO membrane.

[0029] 3. Traditional nanomodification methods typically involve directly adding nanoparticles to the casting solution, which makes it difficult to control nanoparticle aggregation. This invention, however, fixes C-dots onto the base film by incorporating a homogeneous C-dots solution into an aqueous solution and then subjecting it to ultrasonication. This process virtually eliminates aggregation, and the amount of C-dots can be controlled by adjusting the concentration, thereby precisely controlling the amount of bonding at the IP interface. By fixing C-dots onto the base film surface, this invention alters both the skin structure and the surface pore size and porosity, effectively mitigating dilution-induced concentration polarization and addressing issues such as low water flux and salt rejection.

[0030] 4. The method for preparing the forward osmosis membrane provided by this invention is simple, safe and environmentally friendly, and can effectively increase economic benefits. It has the potential to be applied to practical production industries such as water treatment and seawater desalination. Attached Figure Description

[0031] Figure 1 The water contact angle is the forward osmosis membrane obtained in Comparative Example 1 and Examples 1 and 2.

[0032] Figure 2 AFM (Atomic Force Microscopy) images of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2.

[0033] Figure 3 This is a comparison chart of the water flux of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2.

[0034] Figure 4 This is a comparison chart of the salt flux of NaCl through the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2.

[0035] Figure 5 The diagram shows the antibacterial effect of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2 on Escherichia coli. From left to right, they are the Comparative Example, Example 1, and Example 2.

[0036] Figure 6 The pore size distribution of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2 is shown.

[0037] Figure 7 For the porosity analysis of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2, from left to right are Comparative Example, Example 1, and Example 2. Detailed Implementation

[0038] To more clearly illustrate the present invention, a detailed description will be provided below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the scope of the present invention, but are merely for illustrative purposes. Any modifications made within the scope of the claims of the present invention are still within the scope of protection of the claims.

[0039] The following examples and comparative examples all use polyethersulfone (PES) that has undergone solvent removal treatment as the base film material.

[0040] Testing of performance parameters of the forward osmosis membranes obtained in each embodiment and comparative example:

[0041] Membrane flux testing was conducted in a peristaltic pump unit, while membrane salt rejection was performed in a laboratory-scale reverse osmosis unit.

[0042] When testing the water flux of a membrane, the volume of pure water passing through the membrane is measured. The formula for calculating the pure water flux is:

[0043] In the formula J W (Unit: LMH) represents the pure water flux of the membrane, and As (unit: m³ / s) represents the pure water flux of the membrane. 2 ) represents the effective membrane area, and ΔV (in L) represents the change in permeate volume with test time Δt (in h).

[0044] During the salt rejection test, the pressure across the membrane was set to 3 bar, and the solution was roughly prepared with a concentration of 2000 ppm. The precise conductivity of the solution before passing through the membrane and the conductivity of the permeate after passing through the membrane were measured. The salt rejection rate was calculated using the following formula:

[0045]

[0046] In the formula, Rs (in %) is the salt rejection rate, and Cp and Cf (in ppm) are the concentrations of the solution after permeation and the initial feed solution, respectively.

[0047] The water contact angle test of the membrane was conducted at room temperature.

[0048] The static antibacterial test of the FO membrane was conducted as follows: the antibacterial activity of the membrane was determined using the colony counting method. The membrane (effective area 2.54cm × 7.62cm) was sterilized with ultraviolet light for 10 min and placed on a glass slide. First, 75μL of 10... 3 A bacterial suspension of CFU / mL was spread onto the modified side of the membrane. The membrane was covered with a glass slide at 37°C, placed in a petri dish, and sealed with plastic wrap to prevent moisture loss. It was then irradiated for 3 hours with an incandescent lamp (40W) 15cm away from the membrane. After irradiation, the membrane was transferred to physiological saline and sonicated for 5 minutes to remove the bacteria deposited on the membrane surface. Finally, the bacterial suspension was placed on a nutrient agar plate and incubated at 37°C for 12 hours, and the colony count was performed. The antibacterial activity was calculated using the following formula:

[0049] In the formula, Nb and Nm are the colony counts corresponding to the comparative example and the example, respectively.

[0050] Comparative Example

[0051] This comparative example prepared a forward osmosis membrane according to the following steps:

[0052] Step 1: Prepare the required solution

[0053] Add m-phenylenediamine to deionized water and sonicate for 30 minutes to obtain an aqueous solution with a m-phenylenediamine concentration of 1.0 wt%.

[0054] Tristyroyl chloride was added to n-hexane and sonicated for 30 min to obtain an oil phase solution with a tristyroyl chloride concentration of 0.15 wt%.

[0055] Step 2: Prepare the active layer

[0056] Take the PES membrane, rinse the membrane surface with deionized water, and then dry the PES base membrane in a 60℃ drying oven. After drying, remove the base membrane and allow it to cool naturally to room temperature.

[0057] Fix the base film with the smooth side facing up.

[0058] The aqueous phase solution was poured onto the cleaned and dried polyethersulfone membrane surface and immersed at room temperature for 3 minutes. The membrane was then removed, excess solution was removed from the surface, and the membrane was repositioned. The oil phase solution was then poured onto the polyethersulfone membrane surface and immersed at room temperature for 2 minutes. The membrane was removed, excess solution was removed from the surface, and the membrane was dried in a drying oven at 60°C for 8 minutes. After cooling to room temperature, a primary modified active layer was formed on the polyethersulfone membrane surface. The resulting forward osmosis membrane was stored in deionized water.

[0059] Example 1

[0060] In this embodiment, the forward osmosis membrane is prepared according to the following steps:

[0061] Step 1: Synthesize carbon quantum dots using m-phenylenediamine as a carbon source

[0062] m-Phenylenediamine and ethanol were mixed at a mass ratio of 1:100 and sonicated until the m-Phenylenediamine was completely dissolved. The resulting solution was then transferred to a reaction vessel and heated to 180°C at a heating rate of 5°C / min for 12 h. After the reaction was completed, the solution was allowed to cool to room temperature naturally. The resulting solution was then rotary evaporated in a vacuum rotary evaporator at 65°C and 100 r / min for 30 min to remove excess ethanol. After rotary evaporation, the solution was diluted with deionized water to obtain a carbon quantum dot solution with m-Phenylenediamine as the carbon source.

[0063] Step 2: Prepare the required solution

[0064] Add m-phenylenediamine to deionized water, then add the carbon quantum dots obtained in step 1, and sonicate for 30 min to obtain an aqueous solution with a m-phenylenediamine concentration of 1.0 wt% and a carbon quantum dot concentration of 0.1 wt%.

[0065] Tristyroyl chloride was added to n-hexane and sonicated for 30 min to obtain an oil phase solution with a tristyroyl chloride concentration of 0.15 wt%.

[0066] Step 3: Prepare the active layer

[0067] Take the PES membrane, rinse the membrane surface with deionized water, and then dry the PES base membrane in a 60℃ drying oven. After drying, remove the base membrane and allow it to cool naturally to room temperature.

[0068] Fix the base film with the smooth side facing up.

[0069] The aqueous phase solution was poured onto the cleaned and dried polyethersulfone membrane surface and immersed at room temperature for 3 minutes. The membrane was then removed, excess solution was removed from the surface, and the membrane was repositioned. The oil phase solution was then poured onto the polyethersulfone membrane surface and immersed at room temperature for 2 minutes. The membrane was removed, excess solution was removed from the surface, and the membrane was dried in a drying oven at 60°C for 8 minutes. After cooling to room temperature, a primary modified active layer was formed on the polyethersulfone membrane surface. The resulting forward osmosis membrane was stored in deionized water.

[0070] Example 2

[0071] Step 1: Synthesize carbon quantum dots using m-phenylenediamine as a carbon source

[0072] m-Phenylenediamine and ethanol were mixed at a mass ratio of 1:100 and sonicated until the m-Phenylenediamine was completely dissolved. The resulting solution was then transferred to a reaction vessel and heated to 180°C at a heating rate of 5°C / min for 12 h. After the reaction was completed, the solution was allowed to cool to room temperature naturally. The resulting solution was then rotary evaporated in a vacuum rotary evaporator at 65°C and 100 r / min for 30 min to remove excess ethanol. After rotary evaporation, the solution was diluted with deionized water to obtain a carbon quantum dot solution with m-Phenylenediamine as the carbon source.

[0073] Step 2: Prepare the required solution

[0074] Add m-phenylenediamine to deionized water, then add the carbon quantum dots obtained in step 1, and sonicate for 30 min to obtain an aqueous solution with a m-phenylenediamine concentration of 1.0 wt% and a carbon quantum dot concentration of 0.1 wt%.

[0075] Tristyroyl chloride was added to n-hexane and sonicated for 30 min to obtain an oil phase solution with a tristyroyl chloride concentration of 0.15 wt%.

[0076] The carbon quantum dot concentration in the carbon quantum dot solution obtained in step 1 was adjusted to 0.2 wt%, and the solution was sonicated for 10 min to obtain a carbon quantum dot solution for secondary modification.

[0077] Step 3: Prepare the active layer

[0078] Take the PES membrane, rinse the membrane surface with deionized water, and then dry the PES base membrane in a 60℃ drying oven. After drying, remove the base membrane and allow it to cool naturally to room temperature.

[0079] Fix the base film with the smooth side facing up.

[0080] The aqueous phase solution was poured onto the cleaned and dried polyethersulfone membrane surface and immersed at room temperature for 3 minutes. The membrane was then removed, excess solution was removed from the surface, and the membrane was repositioned. The oil phase solution was then poured onto the polyethersulfone membrane surface and immersed at room temperature for 2 minutes. The membrane was removed, excess solution was removed from the surface, and the membrane was dried in a drying oven at 60°C for 8 minutes. After cooling to room temperature, a primary modified active layer was formed on the polyethersulfone membrane surface. The resulting forward osmosis membrane was stored in deionized water.

[0081] Step 4: Secondary modification of the active layer

[0082] The carbon quantum dot solution used for secondary modification was poured onto the surface of the active layer modified in the first stage. The reaction was carried out at room temperature for 30 minutes. After rinsing, a forward osmosis membrane was obtained and stored in deionized water.

[0083] Figure 1 The figure shows the water contact angles of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2. It can be seen from the figure that the contact angle of the comparative example is 76.35°±2.75°, the contact angle of Example 1 is 58.9°±1.2°, and the contact angle of Example 2 is 43.8°±1.5°. It can be seen that the contact angle of the membrane was reduced to different degrees through primary and secondary modification, and the hydrophilicity of the membrane was enhanced.

[0084] Figure 2 The images show AFM (Atomic Force Microscopy) images of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2. It can be seen from the images that Ra = 60.7 nm in Comparative Example 1, Ra = 57.8 nm in Example 1, and Ra = 41.4 nm in Example 2. It can be seen that the roughness of the membrane was reduced to different degrees and the wettability of the membrane was enhanced through one modification and two modifications.

[0085] Figure 3 The graph shows a comparison of the water flux of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2. It can be seen from the graph that the water flux Jw of the comparative example is 22.29 L / m². 2 h, the water flux Jw in Example 1 is 27.44 L / m 2 h, the water flux Jw in Example 2 is 33.31 L / m 2 h.

[0086] Figure 4 The graph shows a comparison of the salt flux of the forward osmosis membranes for NaCl obtained in Comparative Example 1 and Examples 1 and 2. It can be seen from the graph that the salt flux Js of the comparative example is 6.17 L / m². 2 h, In Example 1, the salt flux Js was 6.99 L / m 2 h, In Example 2, the salt flux Js was 3.84 L / m 2 h.

[0087] Table 1

[0088]

[0089] Table 1 shows the performance and structural parameters of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2. As can be seen from the figure, the structural parameter S = 266.58 μm in the comparative example, S = 196.94 μm in Example 1, and S = 147.75 μm in Example 2. It can be seen that through primary and secondary modification, the structural parameters of the membrane were reduced and the performance was improved.

[0090] Figure 5 This diagram illustrates the antibacterial effect of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2 against Escherichia coli. The diagram shows that the comparative example had the highest number of colonies, while Example 2 had the lowest, indicating that the antibacterial effect of the membrane continuously increases with each subsequent modification.

[0091] Figure 6 The figure shows the pore size distribution of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2. It can be seen from the figure that the comparative example contains a large number of pores with a diameter of 2.74-3.14 nm, Example 1 contains a large number of pores with a diameter of 1.74-2.01 nm, and Example 2 contains a large number of pores with a diameter of 1.54-1.72 nm. This indicates that through primary and secondary modification, the significant pore size of the membrane was reduced.

[0092] Table 2

[0093] Membrane name membrane area in the figure Hole area Porosity (%) Comparative Example 100.0296 53.762 53.75 Example 1 100.0296 44.205 44.19 Example 2 100.0296 63.806 63.79

[0094] Figure 7 For the porosity analysis of the forward osmosis membranes obtained in Comparative Example 1 and Examples 1 and 2, the specific results are shown in Table 2. Figure 7 As can be seen from Table 2, the porosity of the comparative example is 53.75%, the porosity of Example 1 is 44.19%, and the porosity of Example 2 is 63.79%. It can be seen that the porosity of the membrane was increased through secondary modification.

[0095] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A forward osmosis membrane that uses carbon quantum dots to regulate the pore size of the active layer to enhance water flux and salt rejection, the forward osmosis membrane comprising a support layer and an active layer, wherein the active layer is formed by an interfacial polymerization reaction of an aqueous solution and an oil solution on the surface of the support layer, characterized in that: Carbon quantum dots are incorporated into the aqueous solution to modify the active layer once; the modified active layer is then modified again by passing a carbon quantum dot solution; through the two modifications of carbon quantum dots, the pore size of the active layer is controlled, making the pore size smaller and the porosity larger, thereby simultaneously improving the water flux and salt rejection rate of the forward osmosis membrane. The aqueous phase solution is a m-phenylenediamine solution, and the oil phase solution is a trimesoyl chloride solution; the carbon quantum dots are synthesized using m-phenylenediamine as the carbon source via a one-pot hydrothermal method; in the primary modification, the concentration of carbon quantum dots in the aqueous phase solution is 0.05-0.1 wt%; in the secondary modification, the concentration of the carbon quantum dot solution is 0.15-0.2 wt%.

2. The forward osmosis membrane according to claim 1, characterized in that: The matrix material of the support layer is polyethersulfone.

3. A method for preparing the forward osmosis membrane according to any one of claims 1 to 2, characterized in that: Interfacial polymerization of a polyethersulfone membrane with a solution of m-phenylenediamine containing carbon quantum dots and a solution of trimesoyl chloride is carried out to form a modified polyamide active layer. The active layer is then modified with an aqueous solution of carbon quantum dots to obtain a forward osmosis membrane.

4. The preparation method according to claim 3, characterized in that, Includes the following steps: Step 1: Synthesize carbon quantum dots using m-phenylenediamine as a carbon source m-Phenylenediamine and ethanol were mixed at a mass ratio of 1:100 and sonicated until the m-Phenylenediamine was completely dissolved. The resulting solution was then transferred to a reaction vessel and heated to 180°C at a heating rate of 5°C / min, and reacted for 12 h. After the reaction was completed, the solution was naturally cooled to room temperature, and then rotary evaporated in a vacuum rotary evaporator at 65°C and 100 r / min for 30 min to remove excess ethanol. After rotary evaporation, the solution was diluted with deionized water to obtain a carbon quantum dot solution with m-Phenylenediamine as the carbon source. Step 2: Prepare the required solution Add m-phenylenediamine to water, then add the carbon quantum dots obtained in step 1, and disperse evenly by ultrasonication to obtain an aqueous solution with a m-phenylenediamine concentration of 1.0 wt% and a carbon quantum dot concentration of 0.05-0.1 wt%. Tristyrene chloride was added to n-hexane to obtain an oil phase solution with a tristyrene chloride concentration of 0.15 wt%. The carbon quantum dot concentration in the carbon quantum dot solution obtained in step 1 is adjusted to 0.15-0.2 wt% to obtain a carbon quantum dot solution for secondary modification. Step 3: Prepare the primary modified active layer The aqueous solution is poured onto the cleaned and dried polyethersulfone membrane surface and soaked at room temperature for 3 minutes. Then, the excess solution on the surface is removed. The oil phase solution is then poured onto the polyethersulfone membrane surface and soaked at room temperature for 2 minutes. After removing the excess solution on the surface, the membrane is dried in a drying oven at 60 °C for 8 minutes, thus forming a modified polyamide active layer on the polyethersulfone membrane surface. Step 4: Secondary modification of the active layer The carbon quantum dot solution used for secondary modification was poured onto the surface of the modified polyamide active layer and reacted at room temperature for 20-30 minutes. After rinsing, a forward osmosis membrane was obtained.

5. An application of the forward osmosis membrane according to any one of claims 1 to 2, characterized in that: Forward osmosis treatment or recycling of saline wastewater systems.

Images