Reverse osmosis membrane based on tannic acid solution activation and hydrophilic compound surface modification and preparation method thereof

Abstract

The invention discloses a reverse osmosis membrane based on tannic acid solution activation and hydrophilic compound surface modification and a preparation method thereof, and belongs to the technical field of composite reverse osmosis membrane preparation. The method comprises the following steps: after an interfacial polymerization reaction is finished, activating an RO membrane by adopting an aqueous solution containing tannic acid (TA); and meanwhile, a hydrophilic compound is selected to carry out surface modification on the activated RO membrane. The unique molecular structure of the TA can improve the surface structure of the RO membrane to improve the selective permeability of the membrane on one hand, and on the other hand, in the surface modification process, more anti-pollution groups can be fixed on the surface of the RO membrane in the presence of the TA, so that the anti-pollution performance of the RO membrane is improved, the activated RO membrane is subjected to surface modification by selecting a hydrophilic compound polyethylene glycol (PEG), and the anti-pollution performance of the RO membrane is improved. A smooth hydrophilic coating is added to the surface of the RO membrane through PEG modification, so that the selective permeability and the anti-pollution performance of the membrane are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of composite reverse osmosis membrane preparation, and particularly relates to a reverse osmosis membrane based on tannic acid solution activation and hydrophilic compound surface modification and a preparation method thereof. Background Art

[0002] At present, seawater desalination technology is mainly divided into three categories: voltage-driven method, distillation method and membrane desalination method. Among them, membrane desalination mainly includes reverse osmosis (RO), nanofiltration, forward osmosis, etc., especially RO is the most widely used. This method has the advantages of simple operation, easy integration and scale, and short investment cycle. RO technology will continue to be the leading technology for seawater desalination for a long time in the future due to its low energy consumption. The widespread application of RO technology has also led to the rapid development of RO membranes. RO membranes have developed asymmetric structures from the initial symmetric membranes to the current reverse osmosis mainly using polyamide (PA) composite membranes, which greatly improves the efficiency of RO. RO membranes have high application prospects in the desalination of seawater and brackish water, wastewater treatment, pure water preparation, drinking water manufacturing, etc.

[0003] RO membrane has been the main membrane used in RO process because of its extremely high separation efficiency. The main methods for preparing RO membrane include interfacial polymerization (IP), grafting and coating, among which interfacial polymerization is the main method. There are still some problems and challenges in the application of RO membrane, which need to be solved by researchers. First, the raw liquid will pollute the membrane during the filtration process, leading to problems such as increased operating costs, shortened membrane service life, reduced flux and increased demand for energy. Secondly, it is difficult to improve the selectivity and permeability of the membrane at the same time, resulting in increased separation costs. Therefore, in the process of membrane development, solving the problems of membrane anti-pollution and selective permeability has received widespread attention. At present, the main methods to improve membrane performance are adding additives during interfacial polymerization and post-treating the membrane after interfacial polymerization. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a reverse osmosis membrane based on tannic acid solution activation and hydrophilic compound surface modification and a preparation method thereof, so as to solve the problems of poor pollution resistance and low retention rate of the reverse osmosis membrane when treating organic pollutants and salt substances.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a reverse osmosis membrane based on tannic acid solution activation and hydrophilic compound surface modification comprises the following steps:

[0007] Step 1, immersing the basement membrane in an aqueous solution to form a process basement membrane 1, wherein the aqueous solution is a mixed solution of camphorsulfonic acid, triethylamine, m-phenylenediamine and water;

[0008] Step 2, immersing the process base film 1 in an organic phase solution to generate an interfacial polymerization reaction to form a process base film 2, wherein the organic phase solution is a mixed solution of dichloromethane and trimesoyl chloride n-heptane;

[0009] Step 3, immersing the process basement membrane 2 in a post-treatment solution for modification and activation to form a process basement membrane 3; the post-treatment solution is a mixed solution of tannic acid and PEG;

[0010] Step 4, subjecting the process base film to a three-heat treatment to obtain a polyamide film.

[0011] A further improvement of the present invention is:

[0012] Preferably, in step 1, the mass fractions of camphorsulfonic acid, triethylamine and m-phenylenediamine in the aqueous phase solution are 2.6%, 1.1% and 3%, respectively.

[0013] Preferably, in step 1, the basement membrane is immersed in the aqueous solution for 10 to 60 seconds.

[0014] Preferably, in step 2, in the organic phase solution, the mass fraction of dichloromethane is 10%, and the mass fraction of n-heptane is 90%.

[0015] Preferably, in step 2, 0.1 g of trimesoyl chloride is also added to the organic phase solution.

[0016] Preferably, in step 2, the infiltration time of the process basement membrane 1 is 10 to 50 seconds.

[0017] Preferably, in step 3, the concentration of tannic acid in the post-treatment solution is 0.1% to 0.5% g / mL, and the concentration of PEG is 0.001% to 0.009% g / mL.

[0018] Preferably, in step 3, the infiltration time of the basement membrane 2 is 10 to 60 seconds.

[0019] Preferably, in step 4, the heat treatment temperature is 60-100° C., and the heat treatment time is 3-7 min.

[0020] A reverse osmosis membrane based on tannic acid solution activation and hydrophilic compound surface modification, prepared by any of the above preparation methods, consists of a support layer and a separation layer; the support layer is a polysulfone ultrafiltration membrane, and the polysulfone ultrafiltration membrane has a polyamide layer formed by the interfacial polymerization of metaphenylenediamine, metaphenylenediamine and trimesoyl chloride in its channel; and tannic acid and PEG are grafted on the surface of the separation layer.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The invention discloses the preparation of a reverse osmosis membrane based on activation of a tannic acid solution and surface modification of a hydrophilic compound. In the preparation process, after the interfacial polymerization reaction is completed, a tannic acid (TA) solution is used as an activator for activation, and a hydrophilic compound post-treatment solution is used for modification. The selective permeability and anti-pollution performance of the RO membrane are improved by modifying the membrane surface with tannic acid and a hydrophilic organic compound. The tannic acid structure contains a large amount of phenolic hydroxyl groups, which makes it have good adhesion, can coordinate with metal ions, and has antibacterial properties. Therefore, after the polymerization reaction process, a TA aqueous solution is used to activate the RO membrane, and the TA concentration is optimized. The hydrophilicity of the RO membrane is increased by increasing the density of phenolic hydroxyl groups on the membrane surface, thereby improving the selective permeability of the membrane. Then, different hydrophilic organic compounds, polyethylene glycol (PEG), are used as co-components to act on the membrane surface with TA to improve the surface physicochemical structure of the membrane. While providing phenolic hydroxyl groups, TA anchors the hydrophilic organic compound on the membrane surface through hydrogen bonding. PEG modification adds a smooth hydrophilic coating to the surface of the RO membrane, reduces the surface roughness of the membrane, and thus improves the selective permeability and anti-pollution performance of the membrane.

[0023] The present invention also discloses a reverse osmosis membrane based on tannic acid solution activation and hydrophilic compound surface modification. Compared with ordinary membranes, the reverse osmosis membrane significantly improves the retention rate of salt substances: under the test conditions of 0.5g / L sodium chloride solution as the raw material liquid, 15.5±0.1bar as the pressure and 25±1℃ as the temperature, when 0.3%w / v TA is used to activate the RO membrane, the obtained RO membrane has the highest selective permeability performance: the flux is 56.4L·m -2 ·h -1 , 29.7% higher than the original membrane, and the rejection rate was 98.67%, 5.8% higher than the original membrane. When 0.006% w / v PEG was added, the membrane flux reached 63.43 L·m -2 ·h -1 The interception rate is 99.43%, the flux reduction rate when intercepting pollutants is 8.19%, and the flux recovery rate is 93.41%. The present invention is not limited to the preparation of aromatic polyamide composite reverse osmosis membranes, but is also suitable for preparing other high-performance interfacial polymerization separation membranes. The present invention adds tannic acid and hydrophilic compounds in the post-treatment process, changes the hydrophilicity of the RO membrane, and improves the anti-pollution performance and selective separation performance of the reverse osmosis membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 : Scanning electron micrograph and atomic force micrograph of the polyamide composite reverse osmosis membrane prepared in Control Example 1; wherein (a) is a scanning electron micrograph, and (b) is an atomic force micrograph; it can be seen from the figure that the prepared reverse osmosis membrane has a typical ridge-valley structure.

[0025] Figure 2: are scanning electron micrographs and atomic force micrographs of the polyamide composite reverse osmosis membrane obtained in Example 2; wherein, (a) is a scanning electron micrograph, and (b) is an atomic force micrograph; it can be seen from the figure that the prepared reverse osmosis membrane, after TA activation, the membrane containing tannic acid is compared with the membrane not containing tannic acid, and the reverse osmosis membrane with tannic acid added has more leaves and becomes tighter.

[0026] Figure 3 : are scanning electron micrographs and atomic force micrographs of the polyamide composite reverse osmosis membrane obtained in Example 5; wherein, (a) is a scanning electron micrograph, and (b) is an atomic force micrograph; it can be seen from the figure that the prepared reverse osmosis membrane, after the reverse osmosis membrane is modified by hydrophilic organic matter PEG after TA activation, the connection structure between the reverse osmosis membrane blades containing the hydrophilic organic matter increases therewith, and the membrane surface structure gradually becomes flat.

[0027] Figure 4 : are scanning electron micrographs and atomic force micrographs of the polyamide composite reverse osmosis membranes obtained in Examples 2 to 4 and Examples 5 to 8; wherein, (a) is the water contact angle of the reverse osmosis membrane to which TA is added, and (b) is the water contact angle of the reverse osmosis membrane to which the hydrophilic compound PEG is added; it can be seen from the figures that the water contact angle of the prepared reverse osmosis membrane is larger and larger after being activated by TA and modified by the hydrophilic compound, and the membrane becomes more and more hydrophilic, and a good water film will be formed during the filtration process, thereby improving the anti-pollution performance of the membrane.

[0028] Figure 5 : It is a curve diagram of the retention rate of the membranes prepared in Examples 1 to 5, Examples 6 to 9 and Comparative Examples over time, wherein (a) is for Examples 1 to 5 and Comparative Examples; (b) is for Examples 6 to 9 and Comparative Examples. It can be seen from the figure that the anti-fouling performance of the reverse osmosis membrane has been significantly improved by tannic acid activation and modification of hydrophilic compounds, and the retention rate and flux have also been greatly improved, and the retention rate of the membrane containing 0.3% TA and 0.006% PEG is higher and the anti-fouling performance is the best.

[0029] Figure 6 : is a curve diagram of the pure water flux of the membranes prepared in Examples 7 to 8 and the comparative example over time. It can be seen intuitively from the figure that the flux of the membrane is significantly improved by modification with tannic acid and hydrophilic compounds. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0031] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0032] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0033] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0034] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0035] A method for preparing a reverse osmosis membrane based on activation with a tannic acid solution and surface modification with a hydrophilic compound, characterized in that the reverse osmosis membrane based on activation with a tannic acid solution and surface modification with a hydrophilic compound has higher anti-pollution performance and selectivity.

[0036] The method of the present invention for preparing a polyamide membrane having high anti-pollution performance and high selectivity by using tannic acid and a hydrophilic compound as a post-treatment solution comprises the following steps:

[0037] 1) The basement membrane is immersed in an aqueous solution containing camphorsulfonic acid, triethylamine and m-phenylenediamine for 10 to 60 seconds so that the basement membrane is fully infiltrated by the aqueous solution, and a process basement membrane 1 is obtained; the mass fractions of camphorsulfonic acid, triethylamine and m-phenylenediamine in water are 2.6%, 1.1% and 3%, respectively, and the basement membrane is a polyethersulfone ultrafiltration membrane. In this process, m-phenylenediamine in the aqueous phase enters into the membrane pores of the basement membrane, and triethylamine and camphorsulfonic acid play a promoting role.

[0038] 2) Immersing the process base membrane 1 in an organic phase solution containing dichloromethane and trimesoyl chloride and n-heptane for 10 to 50 seconds to initiate interfacial polymerization to form a polyamide separation layer, thereby obtaining the process base membrane 2; in terms of volume fraction, the organic phase solution is added with a solution composed of 10% dichloromethane and 90% n-heptane, and 0.1 g of trimesoyl chloride is also added to 100 ml of the organic phase solution; in this process, the trimesoyl chloride undergoes an interfacial polymerization reaction with the aqueous phase monomer m-phenylenediamine in the process 1.

[0039] 3) The process base film II is dissolved in a post-treatment solution containing tannic acid and a hydrophilic compound PEG for 10 to 60 seconds to post-treat the film to obtain the process base film III; 0.01 to 0.09 g of PEG and 0.1 to 0.5 g of TA are added to 100 mL of the post-treatment solution containing tannic acid and a hydrophilic compound PEG; in this process, the phenolic hydroxyl groups in the tannic acid and PEG react with the acyl chloride group in trimesoyl chloride.

[0040] 4) Then, the process base membrane is placed at 60-100° C. for heat treatment for 3-7 minutes to increase the cross-linking degree of the polyamide layer, thereby obtaining an aromatic polyamide composite reverse osmosis membrane.

[0041] Through the above process, a polyamide composite reverse osmosis membrane is formed, which is a highly cross-linked network structure formed by the interfacial polymerization of the water phase and the oil phase, and then modified by TA and PEG. The polyamide composite reverse osmosis membrane is mainly composed of a support layer and a separation layer, the support layer is a polysulfone ultrafiltration membrane, and the separation layer is a polyamide layer formed by the interfacial polymerization of m-phenylenediamine and trimesoyl chloride; there is m-phenylenediamine in the channel of the polysulfone ultrafiltration membrane, and it forms a separation layer with trimesoyl chloride, and tannic acid and PEG are grafted on the surface of the separation layer.

[0042] The supporting layer supports the membrane and increases the mechanical strength and stability of the membrane. The separation layer plays a role of separation by adjusting the pore size and surface charge density of the membrane. During the production process of the membrane, the water phase containing m-phenylenediamine is infiltrated into the base membrane, so that the m-phenylenediamine smoothly enters the base membrane pores and adheres tightly to the surface of the base membrane, and then reacts with the oil phase containing trimesoyl chloride to form a cross-linked network structure containing amide bonds, which plays a role of separation. The surface of the formed composite membrane is then modified by TA and PEG to improve the anti-pollution property and retention rate of the reverse osmosis membrane.

[0043] The following is further described in conjunction with specific embodiments.

[0044] Example 1

[0045] The surface of the base membrane was immersed in the aqueous solution for 60 seconds so that the base membrane was fully infiltrated by the aqueous solution. Subsequently, the solution was poured out. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a 100 mL mixed solution containing 10 wt% dichloromethane and 90 wt% n-heptane solution for 30 seconds to initiate interfacial polymerization. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a post-treatment solution containing 0.1% tannic acid for 30 seconds for activation. Finally, the membrane was placed at 80°C for heat treatment for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane.

[0046] The composite reverse osmosis membrane flux and rejection rate were 49.5 L·m -2 ·h -1 and 98.23%.

[0047] Example 2

[0048] The surface of the base membrane was immersed in the aqueous solution for 60 seconds so that the base membrane was fully infiltrated by the aqueous solution. Subsequently, the solution was poured out. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a 100 mL mixed solution containing 10 wt% dichloromethane and 90 wt% n-heptane solution for 30 seconds to initiate interfacial polymerization. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a post-treatment solution containing 0.2% tannic acid for 30 seconds for activation. Finally, the membrane was placed at 80°C for heat treatment for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane.

[0049] The flux and rejection rate of the composite reverse osmosis membrane were 56.4 L·m -2 ·h -1 and 98.67%.

[0050] Example 3

[0051] The surface of the base membrane was immersed in the aqueous solution for 60 seconds so that the base membrane was fully infiltrated by the aqueous solution. Subsequently, the solution was poured out. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a 100 mL mixed solution containing 10 wt% dichloromethane and 90 wt% n-heptane solution for 30 seconds to initiate interfacial polymerization. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a post-treatment solution containing 0.3% tannic acid for 30 seconds for activation. Finally, the membrane was placed at 80°C for heat treatment for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane.

[0052] The composite reverse osmosis membrane flux and rejection rate were 51.2 L·m-2 ·h -1 and 98.44%.

[0053] Example 4

[0054] The surface of the base membrane was immersed in the aqueous solution for 60 seconds so that the base membrane was fully infiltrated by the aqueous solution. Subsequently, the solution was poured out. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a 100 mL mixed solution containing 10 wt% dichloromethane and 90 wt% n-heptane solution for 30 seconds to initiate interfacial polymerization. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a post-treatment solution containing 0.4% tannic acid by volume for 30 seconds for activation to modify the polyamide separation layer. Finally, the membrane was heat treated at 80°C for 5 minutes to increase the cross-linking degree of the polyamide separation layer, and an aromatic polyamide composite reverse osmosis membrane was obtained.

[0055] The composite reverse osmosis membrane flux and rejection rate were 51.1 L·m -2 ·h -1 and 98.40%.

[0056] Example 5

[0057] The surface of the base membrane was immersed in the aqueous solution for 60 seconds so that the base membrane was fully infiltrated by the aqueous solution. Subsequently, the solution was poured out. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a 100 mL mixed solution containing 10 wt% dichloromethane and 90 wt% n-heptane solution for 30 seconds to initiate interfacial polymerization. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a post-treatment solution containing 0.5% tannic acid by volume for 30 seconds for activation to modify the polyamide separation layer. Finally, the membrane was heat treated at 80°C for 5 minutes to increase the cross-linking degree of the polyamide separation layer, and an aromatic polyamide composite reverse osmosis membrane was obtained.

[0058] The composite reverse osmosis membrane flux and rejection rate were 51.1 L·m -2 ·h -1 and 98.40%.

[0059] Comparative Example 1

[0060] The surface of the base membrane was immersed in the aqueous solution for 60 seconds to allow the base membrane to be fully infiltrated by the aqueous solution. Subsequently, the solution was poured off. Next, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a solution containing 0.1% trimesoyl chloride, 10% dichloromethane and 90% n-heptane for 30 seconds to initiate interfacial polymerization. Finally, the membrane was heat treated at 80°C for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane.

[0061] The composite reverse osmosis membrane flux and rejection rate were 45.8 m -2 ·h -1 and 98.01%.

[0062] From the experimental data, we can get Figure 5 As shown in Figure (a), the results show that the rejection rate of the reverse osmosis membrane with 0.3% TA for sodium chloride salt solution is greater than that of the reverse osmosis membrane with 0.1% TA and 0.5% TA, and greater than that of the reverse osmosis membrane without TA. In summary, using TA as a post-treatment solution to prepare a polyamide reverse osmosis membrane can significantly improve the salt rejection effect of the membrane and improve the high selectivity performance of the reverse osmosis membrane.

[0063] Example 6

[0064] The surface of the base membrane was immersed in the aqueous solution for 60 seconds so that the base membrane was fully infiltrated by the aqueous solution. Subsequently, the solution was poured out. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a 100 mL mixed solution containing 10 wt% dichloromethane and 90 wt% n-heptane solution for 30 seconds to initiate interfacial polymerization. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a post-treatment solution containing 0.3% tannic acid and 0.001% PEG for 30 seconds for activation and modification. Finally, the membrane was placed at 80°C for heat treatment for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane.

[0065] The composite reverse osmosis membrane flux and rejection rate were 55.1 m / s and 55.1 m / s, respectively, when filtered through a 0.5 g / L sodium chloride solution at 15.5 bar and 25 °C. -2 ·h -1 and 98.75%.

[0066] Example 7

[0067] The surface of the base membrane was immersed in the aqueous solution for 60 seconds so that the base membrane was fully infiltrated by the aqueous solution. Subsequently, the solution was poured out. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a 100 mL mixed solution containing 10 wt% dichloromethane and 90 wt% n-heptane solution for 30 seconds to initiate interfacial polymerization. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a post-treatment solution containing 0.3% tannic acid and 0.003% PEG for 30 seconds for activation and modification. Finally, the membrane was placed at 80°C for heat treatment for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane.

[0068] The composite reverse osmosis membrane flux and rejection rate were 57.2 m -2 ·h -1 and 99.01%.

[0069] Example 8

[0070] The surface of the base membrane was immersed in the aqueous solution for 60 seconds so that the base membrane was fully infiltrated by the aqueous solution. Subsequently, the solution was poured out. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a 100 mL mixed solution containing 10 wt% dichloromethane and 90 wt% n-heptane solution for 30 seconds to initiate interfacial polymerization. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a post-treatment solution containing 0.3% tannic acid and 0.006% PEG for 30 seconds for activation and modification. Finally, the membrane was placed at 80°C for heat treatment for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane.

[0071] The composite reverse osmosis membrane flux and rejection rate were 61.5 m -2 ·h -1 and 99.32%.

[0072] Example 9

[0073] The surface of the base membrane was immersed in the aqueous solution for 60 seconds so that the base membrane was fully infiltrated by the aqueous solution. Subsequently, the solution was poured out. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a 100 mL mixed solution containing 10 wt% dichloromethane and 90 wt% n-heptane solution for 30 seconds to initiate interfacial polymerization. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a post-treatment solution containing 0.3% tannic acid and 0.009% PEG for 30 seconds for activation and modification. Finally, the membrane was placed at 80°C for heat treatment for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane.

[0074] The composite reverse osmosis membrane flux and rejection rate were tested by filtering 0.5 g / L sodium chloride solution at 15.5 bar and 25°C, and were 61.9 m-2·h-1 and 99.41%, respectively.

[0075] Example 10

[0076] The surface of the base membrane was immersed in the aqueous solution for 10 seconds so that the base membrane was fully infiltrated by the aqueous solution. Subsequently, the solution was poured out. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a 100 mL mixed solution containing 10 wt% dichloromethane and 90 wt% n-heptane solution for 10 seconds to initiate interfacial polymerization. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a post-treatment solution containing 0.1% tannic acid and 0.006% PEG for 10 seconds for activation and modification. Finally, the membrane was placed at 60°C for heat treatment for 7 minutes to obtain an aromatic polyamide composite reverse osmosis membrane.

[0077] The composite reverse osmosis membrane flux and rejection rate were tested by filtering 0.5 g / L sodium chloride solution at 15.5 bar and 25°C, and were 58.8 m-2·h-1 and 98.93%, respectively.

[0078] Embodiment 11

[0079] The surface of the base membrane was immersed in the aqueous solution for 30 seconds so that the base membrane was fully infiltrated by the aqueous solution. Subsequently, the solution was poured out. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a 100 mL mixed solution containing 10 wt% dichloromethane and 90 wt% n-heptane solution for 50 seconds to initiate interfacial polymerization. Then, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a post-treatment solution containing 0.5% tannic acid and 0.006% PEG for 60 seconds for activation and modification. Finally, the membrane was placed at 100°C for heat treatment for 3 minutes to obtain an aromatic polyamide composite reverse osmosis membrane.

[0080] The composite reverse osmosis membrane flux and rejection rate were tested by filtering 0.5 g / L sodium chloride solution at 15.5 bar and 25°C, and were 52.1 m-2·h-1 and 98.33%, respectively.

[0081] Comparative Example 2

[0082] The surface of the base membrane was immersed in the aqueous solution for 60 seconds to allow the base membrane to be fully infiltrated by the aqueous solution. Subsequently, the solution was poured off. Next, after ensuring that there was no visible liquid on the membrane surface, the membrane surface was immersed in a solution containing 0.1% trimesoyl chloride, 10% dichloromethane and 90% n-heptane for 30 seconds to initiate interfacial polymerization. Finally, the membrane was heat treated at 80°C for 5 minutes to obtain an aromatic polyamide composite reverse osmosis membrane.

[0083] The composite reverse osmosis membrane flux and rejection rate were 2.86 mg / L and 80.28% respectively when filtered through a 0.5 g / L sodium chloride solution at 15.5 bar and 25° C.

[0084] From the experimental data, we can get Figure 5 Figure (b) shows that the separation performance of the membrane modified with PEG at different concentrations was tested. It was found that when the concentration was 0.006% w / v, the water / salt selectivity and water permeability of the PEG-modified membrane were the highest, which were increased by 160% and 13.13% respectively compared with the unmodified membrane. That is, the surface modification of the TA-activated membrane with 0.006% w / v PEG resulted in the greatest improvement in the selectivity. In the anti-fouling performance test of BSA, the membrane modified with PEG at a concentration of 0.003% w / v had the highest anti-fouling performance, with a flux decline rate of 8.84%. After physical washing, the flux recovery rate was 94.12%. Comprehensive analysis of the selectivity and anti-fouling performance showed that the modified membrane obtained by surface modification of the TA-activated membrane with 0.006% w / v PEG had the best performance. In summary, the use of tannic acid and PEG as post-treatment solutions to prepare polyamide reverse osmosis membranes can significantly improve the membrane's anti-fouling performance, while the retention rate and flux have both increased significantly.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a reverse osmosis membrane based on activation with tannic acid solution and surface modification with hydrophilic compounds, characterized in that: The following steps are involved: Step 1, immersing the basement membrane in an aqueous solution to form a process basement membrane 1, wherein the aqueous solution is a mixed solution of camphorsulfonic acid, triethylamine, m-phenylenediamine and water; Step 2, immersing the process base film 1 in an organic phase solution to generate an interfacial polymerization reaction to form a process base film 2, wherein the organic phase solution is a mixed solution of dichloromethane and trimesoyl chloride n-heptane; Step 3, immersing the process basement membrane 2 in a post-treatment solution for modification and activation to form a process basement membrane 3; the post-treatment solution is a mixed solution of tannic acid and PEG; Step 4, subjecting the process base film to a three-heat treatment to obtain a polyamide film.

2. The method for preparing a reverse osmosis membrane based on activation of tannic acid solution and surface modification of hydrophilic compounds according to claim 1, characterized in that: In step 1, the mass fractions of camphorsulfonic acid, triethylamine and m-phenylenediamine in the aqueous phase solution are 2.6%, 1.1% and 3%, respectively.

3. The method for preparing a reverse osmosis membrane based on activation of tannic acid solution and surface modification of hydrophilic compounds according to claim 1, characterized in that: In step 1, the base film is immersed in the aqueous solution for 10 to 60 seconds.

4. The method for preparing a reverse osmosis membrane based on activation of tannic acid solution and surface modification of hydrophilic compounds according to claim 1, characterized in that: In step 2, in the organic phase solution, the mass fraction of dichloromethane is 10%, and the mass fraction of n-heptane is 90%.

5. The method for preparing a reverse osmosis membrane based on activation of tannic acid solution and surface modification of hydrophilic compound according to claim 4, characterized in that: In step 2, 0.1 g of trimesoyl chloride is also added to the organic phase solution.

6. The method for preparing a reverse osmosis membrane based on activation of tannic acid solution and surface modification of hydrophilic compounds according to claim 1, characterized in that: In step 2, the infiltration time of the process basement membrane 1 is 10 to 50 seconds.

7. The method for preparing a reverse osmosis membrane based on activation of tannic acid solution and surface modification of hydrophilic compounds according to claim 1, characterized in that: In step 3, the concentration of tannic acid in the post-treatment solution is 0.1% to 0.5% g / mL, and the concentration of PEG is 0.001% to 0.009% g / mL.

8. The method for preparing a reverse osmosis membrane based on activation of tannic acid solution and surface modification of hydrophilic compounds according to claim 1, characterized in that: In step 3, the infiltration time of the basement membrane 2 is 10 to 60 seconds.

9. The method for preparing a reverse osmosis membrane based on activation of tannic acid solution and surface modification of hydrophilic compounds according to claim 1, characterized in that: In step 4, the heat treatment temperature is 60-100° C., and the heat treatment time is 3-7 minutes.

10. A reverse osmosis membrane based on activation with tannic acid solution and surface modification with hydrophilic compound prepared by the preparation method according to any one of claims 1 to 9, characterized in that: It consists of a support layer and a separation layer; the support layer is a polysulfone ultrafiltration membrane, and in the channel of the polysulfone ultrafiltration membrane there is a polyamide layer formed by the interfacial polymerization of metaphenylenediamine, metaphenylenediamine and trimesoyl chloride; and tannic acid and PEG are grafted on the surface of the separation layer.

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