Seawater desalination method and seawater desalination system

Abstract

Provided are a seawater desalination method and a seawater desalination system. The seawater desalination method comprises the following steps: subjecting seawater to a filtration treatment to obtain a filtrate, wherein a filtration membrane used is a polymer membrane containing a photocatalyst, and the photocatalyst is porous polymer nanospheres containing a graphitized titanium-based frame material; subjecting the filtrate to a reverse osmosis treatment to obtain a reverse osmosis permeate, wherein the reverse osmosis membrane used comprises a support membrane, and also a polyamide layer and a porous polymer layer that are sequentially stacked on the surface of the support membrane, the polyamide layer containing a layered ionic covalent organic framework material, and the porous polymer layer containing a positively charged crystalline polymer; and subjecting the reverse osmosis permeate to a disinfection treatment to obtain desalinated water.

Description

Seawater desalination methods and systems

[0001] Related applications

[0002] This application claims priority to Chinese patent application filed on November 13, 2024, with application number 202411613770.3, entitled "Seawater Desalination Method and Seawater Desalination System", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of water treatment technology, and in particular to seawater desalination methods and systems. Background Technology

[0004] In reverse osmosis seawater desalination, seawater is typically pretreated to remove impurities such as silt, colloids, particles, suspended solids, and microorganisms to ensure the proper functioning of the subsequent membrane system. Traditional pretreatment methods include coagulation, sedimentation, and filtration. However, these pretreatment processes, due to limitations in hydraulic retention time, unit throughput, and membrane permeate flux, require a large land area, have long construction cycles, and involve high costs for chemicals and flocculants. Electricity and membrane replacement costs also increase the investment cost of seawater desalination. Furthermore, they suffer from poor resistance to fouling shocks and poor system stability.

[0005] Therefore, the seawater desalination methods and systems in related technologies still have problems such as long process flow, poor resistance to pollution shocks, large footprint, and poor system operation stability. Summary of the Invention

[0006] According to various embodiments of this application, a seawater desalination method and a seawater desalination system are provided.

[0007] A seawater desalination method includes the following steps:

[0008] Seawater is filtered to obtain a filtrate, wherein the filtration membrane used in the filtration process is a polymer membrane containing a photocatalyst, and the photocatalyst is a porous polymer nanosphere containing a graphitized titanium-based framework material.

[0009] The filtrate is subjected to reverse osmosis treatment to obtain reverse osmosis permeate. The reverse osmosis membrane used in the reverse osmosis treatment includes a support membrane and a polyamide layer and a porous polymer layer sequentially stacked on the surface of the support membrane. The polyamide layer contains a layered ionic covalent organic framework material, and the porous polymer layer contains a positively charged crystalline polymer.

[0010] The reverse osmosis permeate is disinfected to obtain desalinated water.

[0011] In one embodiment, the polymer film further contains ferrocene-modified magnesium titanate particles.

[0012] In one embodiment, the ferrocene-modified magnesium titanate particles in the polymer film have a mass fraction of 1%-5%;

[0013] And / or, the ferrocene in the ferrocene-modified magnesium titanate particles has a mass fraction of 0.05%-0.5%.

[0014] In one embodiment, the photocatalyst has a mass fraction of 0.5%-8% in the polymer film.

[0015] In one embodiment, the graphitized titanium-based framework material has a mass fraction of 40%-70% in the porous polymer nanospheres.

[0016] In one embodiment, the layered ionic covalent organic framework material has a mass fraction of 0.1%-3% in the polyamide layer.

[0017] In one embodiment, the positively charged crystalline polymer has a mass fraction of 5%-20% in the porous polymer layer.

[0018] In the seawater desalination method of this application, a polymer membrane containing a photocatalyst is used as the filter membrane. The photocatalyst is a porous polymer nanosphere containing a graphitized titanium-based framework material. The porous polymer nanospheres containing the graphitized titanium-based framework material have abundant nanochannel structures, providing space for nano-confined catalytic reactions. This allows the filter membrane to rapidly filter seawater while efficiently catalyzing and degrading organic pollutants in the seawater, improving pollutant removal efficiency. This effectively prevents pollutants from clogging the filter membrane even without pretreatment such as coagulation or sedimentation, exhibiting good anti-fouling performance and ensuring normal filtration. This significantly reduces the amount of pretreatment equipment, floor space, and operating costs of the treatment unit, while simultaneously improving seawater desalination efficiency. Furthermore, the polyamide layer of the reverse osmosis membrane contains a layered ionic covalent organic framework material. This layered ionic covalent organic framework material works synergistically with the polyamide layer, enabling the reverse osmosis membrane to possess both high efficiency and high performance. The layered ionic covalent organic framework material, with its own charge, is anchored in the functional separation layer through electrostatic and hydrogen bonding, preventing it from detaching during long-term use and ensuring the long-term operational stability of the reverse osmosis membrane. Furthermore, by incorporating positively charged crystalline polymers into the porous polymer layer of the reverse osmosis membrane, concentration polarization caused by high salt ion concentration at the membrane-seawater interface can be avoided or mitigated during seawater desalination, effectively ensuring high desalination rate and water flux during long-term use. On the other hand, it serves as a protective layer for the functional separation layer, intercepting residual contaminants and preventing fouling of the reverse osmosis membrane, further guaranteeing its long-term operational stability. Moreover, the positive charge inherent in the porous polymer layer of the positively charged crystalline polymers repels trace amounts of metal cations in seawater, further enhancing the membrane's anti-fouling performance and improving seawater desalination efficiency.

[0019] Therefore, the seawater desalination method of this application can not only improve the desalination efficiency of seawater, but also eliminate the need for pretreatment of seawater, occupy a small area, have low cost, and have good anti-pollution performance, thus ensuring the long-term operational stability of the seawater desalination system.

[0020] A seawater desalination system, the seawater desalination system comprising:

[0021] A filtration device, wherein the filtration membrane used in the filtration device is a polymer membrane containing a photocatalyst, and the photocatalyst is a porous polymer nanosphere containing a graphitized titanium-based framework material;

[0022] A reverse osmosis device, which is connected to the filtration device, wherein the reverse osmosis membrane used in the reverse osmosis device includes a support membrane and a polyamide layer and a porous polymer layer sequentially stacked on the surface of the support membrane, wherein the polyamide layer contains a layered ionic covalent organic framework material and the porous polymer layer contains a positively charged crystalline polymer.

[0023] A disinfection device, wherein the reverse osmosis device is connected to the disinfection device.

[0024] In one embodiment, a security filter is also provided between the filtration device and the reverse osmosis device.

[0025] In one embodiment, the seawater desalination system further includes an energy recovery device connected to the reverse osmosis unit.

[0026] The seawater desalination system of this application can not only improve the desalination efficiency of seawater, but also eliminate the need for pretreatment of seawater. It has a simple process, small footprint, low cost, good anti-pollution performance, and can operate efficiently and stably.

[0027] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0028] To better describe and illustrate embodiments and / or examples of the inventions disclosed herein, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed inventions, the currently described embodiments and / or examples, or the best mode of these inventions as currently understood.

[0029] Figure 1 is a process flow diagram of a seawater desalination method provided in one embodiment of this application. Detailed Implementation

[0030] To facilitate understanding of this application, it will be described in more detail below. However, it should be understood that this application can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular implementations or embodiments only and is not intended to be limiting of this application. The optional range of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0032] As shown in Figure 1, the seawater desalination method provided in this application includes the following steps:

[0033] Seawater is filtered to obtain a filtrate, wherein the filtration membrane used in the filtration process is a polymer membrane containing a photocatalyst, and the photocatalyst is a porous polymer nanosphere containing a graphitized titanium-based framework material.

[0034] The filtrate is subjected to reverse osmosis treatment to obtain reverse osmosis permeate. The reverse osmosis membrane used in the reverse osmosis treatment includes a support membrane and a polyamide layer and a porous polymer layer sequentially stacked on the surface of the support membrane. The polyamide layer contains a layered ionic covalent organic framework material, and the porous polymer layer contains a positively charged crystalline polymer.

[0035] The reverse osmosis permeate is disinfected to obtain desalinated water.

[0036] Specifically, in this application, seawater is filtered. During this process, a polymer membrane containing a photocatalyst is used as the filter membrane. The photocatalyst is a porous polymer nanosphere containing a graphitized titanium-based framework material. Utilizing the abundant nanochannel structure of these porous polymer nanospheres, the permeability of the filter membrane is effectively enhanced, enabling rapid seawater filtration. Furthermore, it provides space for nano-confined catalytic reactions, allowing pollutants in the seawater to fully contact and efficiently degrade with the graphitized titanium-based framework material, effectively improving pollutant removal efficiency. This effectively prevents large amounts of pollutants from clogging the filter membrane without pretreatment such as coagulation or sedimentation, exhibiting excellent anti-fouling performance and ensuring normal filtration. This significantly reduces the amount of pretreatment equipment, floor space, and operating costs of the treatment device, while simultaneously improving seawater desalination efficiency.

[0037] In addition, since the graphitized titanium-based framework material is located inside porous polymer nanospheres, it can effectively prevent the risk of poisoning of the graphitized titanium-based framework material caused by the encapsulation of a large number of pollutants, thus further ensuring the photocatalytic efficiency of the graphitized titanium-based framework material and ensuring the efficient operation of the seawater desalination system.

[0038] It is understandable that, compared with traditional filter membranes, the filter membrane used in this application can simultaneously perform pretreatment functions such as coagulation, sedimentation, and filtration of seawater, reducing the pretreatment process and effectively improving the permeability of the filter membrane. It also has excellent organic pollutant removal effect and effectively prevents pollutants from clogging the filter membrane without pretreatment such as coagulation and sedimentation, thereby significantly reducing the amount of pretreatment equipment, floor space, and operating costs of the treatment device.

[0039] The filtrate obtained above is subjected to reverse osmosis treatment. In this process, the polyamide layer of the reverse osmosis membrane contains a layered ionic covalent organic framework material. The layered ionic covalent organic framework material has abundant ordered pores, which can provide additional water transport channels. Its two-dimensional structure can reduce the tortuous transport path, effectively reducing the resistance of the seawater reverse osmosis membrane and significantly increasing the water permeation flux. Furthermore, the layered ionic covalent organic framework material has good compatibility with the polyamide layer, which can avoid the formation of interfacial gaps and effectively ensure the desalination effect of the reverse osmosis membrane. Moreover, the charge carried by the layered ionic covalent organic framework material can anchor it in the functional separation layer through electrostatic and hydrogen bonding, preventing it from falling off during long-term use and ensuring the long-term operational stability of the reverse osmosis membrane.

[0040] Meanwhile, by incorporating positively charged crystalline polymers into the porous polymer layer of the reverse osmosis membrane, on the one hand, concentration polarization caused by the accumulation of high-concentration salt ions at the interface between the reverse osmosis membrane and seawater can be avoided or mitigated during seawater desalination, effectively ensuring high desalination rate and water flux during long-term use of the reverse osmosis membrane. On the other hand, it can serve as a protective layer for the functional separation layer, intercepting residual pollutants at the front end and preventing fouling of the reverse osmosis membrane, further ensuring the long-term operational stability of the reverse osmosis membrane. Moreover, the positive charge inherent in the porous polymer layer of the positively charged crystalline polymers can repel trace amounts of metal cations in seawater, further improving the antifouling performance of the reverse osmosis membrane and increasing the desalination efficiency of seawater.

[0041] The reverse osmosis permeate obtained above is disinfected to kill bacteria in the water, ensuring the hygiene and safety of the freshwater.

[0042] Therefore, the seawater desalination method of this application can not only improve the desalination efficiency of seawater, but also eliminate the need for pretreatment of seawater. The process is simple, requires little space, has low cost, and has good anti-pollution performance, which can ensure the long-term operational stability of the seawater desalination system.

[0043] As contaminants accumulate on the surface of the filter membrane, the transmembrane pressure difference increases during seawater desalination, affecting the membrane's antifouling performance. In this application, the polymer membrane containing the photocatalyst also contains ferrocene-modified magnesium titanate particles. With this configuration, when the transmembrane pressure difference increases during seawater filtration, the increased pressure on the filter membrane causes the magnesium titanate in the membrane to generate charges that capture protons from the ferrocene, producing more negative charges. This enhances the repulsion of contaminants, further improving the membrane's antifouling performance and ensuring its proper use.

[0044] Optionally, the ferrocene-modified magnesium titanate particles in the polymer membrane have a mass fraction of 1%-5%, wherein the ferrocene in the ferrocene-modified magnesium titanate particles has a mass fraction of 0.05%-0.5%. This setting helps to further improve the antifouling performance of the filter membrane and better ensure the normal operation of the filtration process.

[0045] It is understood that this application uses ferrocene-modified magnesium titanate particles to perform pressure-sensitive modification treatment on polymer films containing photocatalysts. In one embodiment, the ferrocene-modified magnesium titanate particles are heated and then sprayed onto the surface of the polymer film containing the photocatalyst.

[0046] Optionally, the photocatalyst in the polymer membrane has a mass fraction of 0.5%-8%. This configuration can further improve the photocatalytic degradation efficiency of the filter membrane for pollutants in seawater, better improve the removal efficiency of pollutants in seawater, and better avoid pollutants clogging the filter membrane without pretreatment such as coagulation and sedimentation of seawater, thus better ensuring the normal operation of the filtration process.

[0047] Optionally, the graphitized titanium-based framework material comprises 40%-70% by mass in the porous polymer nanospheres. This configuration can better improve the photocatalytic degradation efficiency of pollutants and further enhance the removal efficiency of pollutants by the filter membrane.

[0048] In this application, the porous polymer nanospheres containing graphitized titanium-based framework material can be prepared by the following method: specifically, graphitized titanium-based framework material is added to an ethanol solvent, then cyanuric chloride, dinitrobenzene, and sodium hydroxide are added and mixed and reacted for 20-25 hours, followed by the addition of terephthalaldehyde and heating at 110-130°C for 65-80 hours to obtain porous polymer nanospheres containing graphitized titanium-based framework material; wherein the molar ratio of cyanuric chloride, dinitrobenzene, sodium hydroxide, and terephthalaldehyde is 1:3:3:1-4, and in some embodiments, it is 1:3:3:1.5.

[0049] It should be noted that the graphitized titanium-based framework material in this application can be prepared by the following method: specifically, a mixed solution is prepared by mixing trimellitic acid, tetraethoxytitanium, and N,N-dimethylformamide, and then the mixed solution is reacted at 120℃-150℃ for 45h-50h, washed and dried, and then heat-treated at 800℃-1000℃ for 4h-6h to obtain the graphitized titanium-based framework material. The mass fraction of trimellitic acid in the mixed solution is 2%-3%, and the mass fraction of tetraethoxytitanium in the mixed solution is 2%-4%, optionally 3%.

[0050] In one embodiment, the polymer membrane is selected from polyacrylonitrile membrane, polysulfone membrane, polyvinylidene fluoride membrane, polyethylene membrane, or polypropylene membrane.

[0051] In one embodiment, the preparation method of the polymer film containing the photocatalyst is as follows: the photocatalyst is added to the polymer film liquid, and the film is prepared by phase inversion or direct curing followed by pore drilling.

[0052] Optionally, the layered ionic covalent organic framework material has a mass fraction of 0.1%-3% in the polyamide layer. This configuration is beneficial for further improving the water flux and desalination rate of the reverse osmosis membrane, as well as better ensuring the long-term operational stability of the reverse osmosis membrane.

[0053] In one embodiment, the method for preparing the polyamide layer includes the following steps: preparing an aqueous solution by mixing an amine monomer and water; preparing an oil solution by mixing a layered ionic covalent organic framework material, an acyl chloride monomer, and an alkane solvent; placing the aqueous solution and the oil solution sequentially on the same surface of a support film, and heat-treating to form a polyamide layer, wherein the polyamide layer contains a layered ionic covalent organic framework material.

[0054] Wherein, the amine monomer is selected from at least one of phenylenediamine, o-phenylenediamine, m-phenylenediamine, pyromellitic triamine, ethylenediamine, propylenediamine, butanediamine, hexamethylenediamine, and piperazine; the acyl chloride monomer is selected from at least one of pyromellitic tricarboxylic acid chloride, terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, adipic acid chloride, and biphenyl dicarboxylic acid chloride; and the supporting membrane is selected from polyacrylonitrile membrane, polysulfone membrane, polyvinylidene fluoride membrane, polyethylene membrane, or polypropylene membrane.

[0055] It should be noted that, in this application, the layered ionic covalent organic framework material can be prepared by the following method: specifically, the layered ionic covalent organic framework material is obtained by reacting triaminoguanidine hydrochloride and trimesin in tetrahydrofuran at 110℃-125℃ for 4 to 5 days, followed by cleaning and drying.

[0056] In some embodiments, the layered ionic covalent organic framework material in this application is prepared in accordance with the above-described manner.

[0057] Optionally, the positively charged crystalline polymer has a mass fraction of 5%-20% in the porous polymer layer. This configuration can better avoid or mitigate concentration polarization caused by the enrichment of high-concentration salt ions at the interface between the reverse osmosis membrane and seawater during the seawater desalination process, better ensure the desalination rate and water flux of the reverse osmosis membrane, and better ensure the long-term operational stability of the reverse osmosis membrane, thereby improving the seawater desalination efficiency.

[0058] In one embodiment, the porous polymer layer comprises a positively charged crystalline polymer and a porous polymer, wherein the porous polymer is selected from at least one of polysulfone and polyethersulfone.

[0059] In one embodiment, a positively charged crystalline polymer and a porous polymer are formulated into a mixed solution, and then the mixed solution is applied to the surface of a polyamide layer containing a layered ionic covalent organic framework material, and cured to obtain a porous polymer layer containing a positively charged crystalline polymer.

[0060] It should be noted that, in this application, the positively charged crystalline polymer can be prepared by means of the following method: specifically, the positively charged crystalline polymer is prepared by polymerization reaction of p-methanesulfonylbenzenepropene and chloroplatinic acid under the action of an alkylaluminum catalyst, wherein the molar ratio of p-methanesulfonylbenzenepropene and chloroplatinic acid is 4:1-5:1. The positively charged crystalline polymer obtained by this method can, in addition to avoiding or mitigating concentration polarization caused by the enrichment of high-concentration salt ions at the interface between the reverse osmosis membrane and seawater during seawater desalination, effectively ensuring high desalination rate and water flux during long-term use of the reverse osmosis membrane, preventing fouling of the reverse osmosis membrane by residual pollutants at the front end, and improving the antifouling performance of the reverse osmosis membrane, also allows the non-covalent bonds (including metal-π bonds, hydrogen bonds, and weak coordination bonds) in the positively charged crystalline polymer molecules to undergo reversible dissociation under high-pressure operating conditions. This increases the interfacial porosity between the positively charged crystalline polymer and the porous polymer layer, effectively preventing the porous polymer layer containing the positively charged crystalline polymer from becoming dense under high pressure, thereby affecting the water flux of the reverse osmosis membrane.

[0061] Therefore, the positively charged crystalline polymer in this application can be prepared using the above-described preparation method.

[0062] In one embodiment, before subjecting the filtrate to reverse osmosis treatment, the filtrate is further filtered to improve seawater desalination efficiency and better ensure the stable operation of the reverse osmosis treatment.

[0063] In one embodiment, the reverse osmosis treatment of the filtrate also yields reverse osmosis concentrate. It should be noted that in seawater desalination, the filtrate needs to be pumped to a reverse osmosis unit for treatment using a high-pressure pump. Therefore, the reverse osmosis concentrate obtained in the reverse osmosis treatment step contains high pressure. To address this, in this application, energy recovery is performed on the reverse osmosis concentrate to reduce its pressure, thereby increasing the pressure of the reverse osmosis feed water.

[0064] In this application, reverse osmosis permeate can be disinfected and sterilized by using liquid chlorine, chlorine dioxide, ozone or ultraviolet light to obtain safe and hygienic desalinated water.

[0065] In one embodiment, the desalinated water obtained in this application can be used for domestic water use, fish farming, or water supply for related industries.

[0066] Meanwhile, this application also provides a seawater desalination system, the seawater desalination system comprising: a filtration device, wherein the filtration device uses a polymer membrane containing a photocatalyst, and the photocatalyst is a porous polymer nanosphere containing a graphitized titanium-based framework material; a reverse osmosis device, wherein the reverse osmosis device is connected to the filtration device, and the reverse osmosis device uses a reverse osmosis membrane comprising a support membrane and a polyamide layer and a porous polymer layer sequentially stacked on the surface of the support membrane, wherein the polyamide layer contains a layered ionic covalent organic framework material, and the porous polymer layer contains a positively charged crystalline polymer; and a disinfection device, wherein the reverse osmosis device is connected to the disinfection device.

[0067] In the seawater desalination system of this application, porous polymer nanospheres containing graphitized titanium-based framework materials are used as photocatalysts in the filter membrane. The synergistic effect of the polyamide layer containing layered ionic covalent organic framework materials and the porous polymer layer containing positively charged crystalline polymers in the reverse osmosis membrane enables the seawater desalination system of this application to not only improve the desalination efficiency of seawater, but also eliminate the need for seawater pretreatment. The process is simple, occupies a small area, has low cost, and has good anti-fouling performance, enabling efficient and stable operation.

[0068] Optionally, the polymer film further contains ferrocene-modified magnesium titanate particles, wherein the mass fraction of the ferrocene-modified magnesium titanate particles in the polymer film is 1%-5%, and the mass fraction of ferrocene in the ferrocene-modified magnesium titanate particles is 0.05%-0.5%.

[0069] Optionally, the photocatalyst has a mass fraction of 0.5%-8% in the polymer film.

[0070] Optionally, the graphitized titanium-based framework material has a mass fraction of 40%-70% in the porous polymer nanospheres.

[0071] Optionally, the layered ionic covalent organic framework material has a mass fraction of 0.1%-3% in the polyamide layer.

[0072] Optionally, the positively charged crystalline polymer has a mass fraction of 5%-20% in the porous polymer layer.

[0073] It should be noted that in this application, the filtration device is connected to the reverse osmosis device via a high-pressure pump.

[0074] Optionally, a security filter is provided between the filtration device and the reverse osmosis device to remove residual contaminants in the filtrate. Specifically, the outlet of the security filter is connected to the inlet of the high-pressure pump.

[0075] Optionally, the seawater desalination system further includes an energy recovery device connected to the reverse osmosis unit, which recovers energy from the reverse osmosis concentrate extracted from the reverse osmosis unit.

[0076] Specifically, in one embodiment, the product water side of the filtration device is connected to the inlet water side of the reverse osmosis membrane device, the product water side of the reverse osmosis membrane device is connected to the inlet water side of the disinfection device, the concentrate water side of the reverse osmosis membrane device is connected to the high-pressure inlet water side of the energy recovery device, the low-pressure outlet water side of the energy recovery device is connected to the reverse osmosis concentrate treatment device and / or connected to the backwash water tank, and the product water side of the disinfection device is used to output fresh water.

[0077] The seawater desalination method and system will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0078] It should be noted that the preparation methods of the graphitized titanium-based framework material and porous polymer nanospheres containing the graphitized titanium-based framework material involved in the embodiments and comparative examples of this application are as follows: Tristyrene, tetraethoxytitanium, and N,N-dimethylformamide are mixed to obtain a mixed solution. The mixed solution is reacted at 130°C for 48 hours, then washed and dried, and finally heat-treated at 900°C for 5 hours to obtain the graphitized titanium-based framework material. The mass of the tristyrene in the mixed solution is... The mass fraction of the graphitized titanium-based framework material is 2%, and the mass fraction of the tetraethoxytitanium in the mixed solution is 3%. The graphitized titanium-based framework material obtained above is added to an ethanol solvent, then cyanuric chloride, dinitrobenzene and sodium hydroxide are added and mixed and reacted for 24 h. Then, terephthalaldehyde is added and reacted at 120 °C for 72 h to obtain porous polymer nanospheres containing graphitized titanium-based framework material. The molar ratio of cyanuric chloride, dinitrobenzene, sodium hydroxide and terephthalaldehyde is 1:3:3:1.5.

[0079] Example 1

[0080] Seawater (conductivity 397600 μS / cm, turbidity 20.5 NTU, COD 13.8 mg / L) was passed through a filtration device to obtain filtrate. The filtration device used a polypropylene membrane containing a photocatalyst. The photocatalyst was a porous polymer nanosphere containing a graphitized titanium-based framework material. The mass fraction of the photocatalyst in the polypropylene membrane was 0.5%, and the mass fraction of the graphitized titanium-based framework material in the porous polymer nanosphere was 40%. The polypropylene membrane also contained ferrocene-modified magnesium titanate particles, and the mass fraction of the ferrocene-modified magnesium titanate particles in the polypropylene membrane was 1%, and the mass fraction of ferrocene in the ferrocene-modified magnesium titanate particles was 0.05%.

[0081] The filtrate obtained above is passed through a security filter and a high-pressure pump before being fed into a reverse osmosis membrane device for treatment, resulting in reverse osmosis permeate and reverse osmosis concentrate. The reverse osmosis membrane used in the reverse osmosis device includes a polysulfone supported membrane and a polyamide layer and a porous polysulfone layer sequentially stacked on the surface of the polysulfone supported membrane. The polyamide layer contains a layered ionic covalent organic framework material, and the porous polysulfone layer contains a positively charged crystalline polymer. The mass fraction of the layered ionic covalent organic framework material in the polyamide layer is 0.1%, and the mass fraction of the positively charged crystalline polymer in the porous polysulfone layer is 5%. The positively charged crystalline polymer is prepared by polymerization of p-methanesulfonylbenzenepropylene and chloroplatinic acid in a molar ratio of 5:1 under the action of an alkylaluminum catalyst.

[0082] The reverse osmosis concentrate obtained above is fed into an energy recovery device for treatment; the reverse osmosis permeate obtained above is fed into a disinfection device for sterilization treatment to obtain desalinated water.

[0083] Testing revealed that the turbidity of the filtrate was 0.16 NTU and the COD was <0.5 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 5.2 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 82%.

[0084] Example 2

[0085] Compared with Example 1, Example 2 differs only in that the photocatalyst has a mass fraction of 4% in the polypropylene film, the graphitized titanium-based framework material has a mass fraction of 55% in the porous polymer nanospheres, the ferrocene-modified magnesium titanate particles have a mass fraction of 3% in the polypropylene film, the ferrocene has a mass fraction of 0.25% in the ferrocene-modified magnesium titanate particles, the layered ionic covalent organic framework material has a mass fraction of 1.5% in the polyamide layer, and the positively charged crystalline polymer has a mass fraction of 12% in the porous polysulfone layer. All other conditions are the same.

[0086] Tests showed that the turbidity of the filtrate was 0.15 NTU and the COD was <0.5 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 5.6 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 85%.

[0087] Example 3

[0088] Example 3 differs from Example 1 only in that the photocatalyst has a mass fraction of 8% in the polypropylene film, the graphitized titanium-based framework material has a mass fraction of 70% in the porous polymer nanospheres, the ferrocene-modified magnesium titanate particles have a mass fraction of 5% in the polypropylene film, the ferrocene has a mass fraction of 0.5% in the ferrocene-modified magnesium titanate particles, the layered ionic covalent organic framework material has a mass fraction of 3% in the polyamide layer, and the positively charged crystalline polymer has a mass fraction of 20% in the porous polysulfone layer. All other conditions are the same.

[0089] Tests showed that the turbidity of the filtrate was 0.11 NTU and the COD was <0.5 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 4.8 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 83%.

[0090] Example 4

[0091] The only difference between Example 4 and Example 1 is that the photocatalyst has a mass fraction of 0.1% in the polypropylene film, while all other conditions are the same.

[0092] Testing revealed that the turbidity of the filtrate was 0.25 NTU and the COD was 0.8 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 6.3 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 78%.

[0093] Example 5

[0094] The only difference between Example 5 and Example 1 is that the photocatalyst has a mass fraction of 10% in the polypropylene film, while all other conditions are the same.

[0095] Tests showed that the turbidity of the filtrate was 0.64 NTU and the COD was 0.7 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 6.1 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 76%.

[0096] Example 6

[0097] The only difference between Example 6 and Example 1 is that the mass fraction of the layered ionic covalent organic framework material in the polyamide layer is 0.05%, while all other conditions are the same.

[0098] Tests showed that the turbidity of the filtrate was 0.21 NTU and the COD was <0.5 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 6.7 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 75%.

[0099] Example 7

[0100] The only difference between Example 7 and Example 1 is that the mass fraction of the layered ionic covalent organic framework material in the polyamide layer is 5%, while all other conditions are the same.

[0101] Tests showed that the turbidity of the filtrate was 0.15 NTU and the COD was <0.5 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 9.4 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 76%.

[0102] Example 8

[0103] The only difference between Example 8 and Example 1 is that the positively charged crystalline polymer has a mass fraction of 2% in the porous polysulfone layer, while all other conditions are the same.

[0104] Tests showed that the turbidity of the filtrate was 0.17 NTU and the COD was <0.5 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 5.7 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 78%.

[0105] Example 9

[0106] The only difference between Example 9 and Example 1 is that the positively charged crystalline polymer has a mass fraction of 25% in the porous polysulfone layer, while all other conditions are the same.

[0107] Tests showed that the turbidity of the filtrate was 0.18 NTU and the COD was <0.5 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 6.1 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 77%.

[0108] Example 10

[0109] The only difference between Example 10 and Example 1 is that the polypropylene film containing the photocatalyst does not contain ferrocene-modified magnesium titanate particles; all other conditions are the same.

[0110] Testing revealed that the turbidity of the filtrate was 0.41 NTU and the COD was 0.7 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 6.4 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 79%.

[0111] Comparative Example 1

[0112] The only difference between Comparative Example 1 and Example 1 is that the filter membrane used in the filter device is a polypropylene membrane without photocatalyst; all other conditions are the same.

[0113] Testing revealed that the turbidity of the filtrate was 1.55 NTU and the COD was 8.6 mg / L. The conductivity of the reverse osmosis permeate was 8.3 μS / cm. The desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 65%.

[0114] Comparative Example 2

[0115] The only difference between Comparative Example 2 and Example 1 is that the photocatalyst is a graphitized titanium-based framework material, while all other conditions are the same.

[0116] Testing revealed that the turbidity of the filtrate was 0.67 NTU and the COD was 3.4 mg / L. The conductivity of the reverse osmosis permeate was 7.8 μS / cm. The desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 67%.

[0117] Comparative Example 3

[0118] The only difference between Comparative Example 3 and Example 1 is that titanium dioxide was used instead of the photocatalyst in Example 1, while all other conditions were the same.

[0119] Testing revealed that the turbidity of the filtrate was 0.93 NTU and the COD was 6.5 mg / L. The conductivity of the reverse osmosis permeate was 8.9 μS / cm. The desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 67%.

[0120] Comparative Example 4

[0121] The only difference between Comparative Example 4 and Example 1 is that the polyamide layer of the reverse osmosis membrane used in the reverse osmosis treatment does not contain layered ionic covalent organic framework material, i.e., ordinary polyamide layer; all other conditions are the same.

[0122] Testing revealed that the turbidity of the filtrate was 0.20 NTU and the COD was <0.5 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 6.1 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 63%.

[0123] Comparative Example 5

[0124] The only difference between Comparative Example 5 and Example 1 is that the porous polysulfone layer does not contain a positively charged crystalline polymer; all other conditions are the same.

[0125] Tests showed that the turbidity of the filtrate was 0.14 NTU and the COD was <0.5 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 6.3 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 62%.

[0126] Comparative Example 6

[0127] The only difference between Comparative Example 6 and Example 1 is that the reverse osmosis membrane does not contain a porous polysulfone layer; all other conditions are the same.

[0128] Tests showed that the turbidity of the filtrate was 0.16 NTU and the COD was <0.5 mg / L, indicating that almost all pollutants in the seawater had been removed. The conductivity of the reverse osmosis permeate was 7.3 μS / cm, and the desalinated water met the water quality requirements for reuse. Furthermore, calculations showed that the water recovery rate was 60%.

[0129] Meanwhile, after verification, under the same seawater composition, inlet water temperature, inlet water flow rate, and inlet water pressure, after the filter membrane in the filtration device of Comparative Example 1 became clogged, the desalination system of Comparative Example 2 could still continue to operate stably for 4 days, and the desalination system of Comparative Example 3 could continue to operate stably for 2 days. This is because none of Comparative Examples 1 to 3 used porous polymer nanospheres containing graphitized titanium-based framework materials as photocatalysts, resulting in a significant reduction in the removal efficiency of pollutants during filtration, thus leading to a decrease in the stability of the subsequent reverse osmosis system. The desalination system of Comparative Example 4 could continue to operate stably for 12 days. This is because the polyamide layer of the reverse osmosis membrane in Comparative Example 4 did not contain layered ionic covalent organic framework materials, resulting in unstable water flux of the reverse osmosis membrane and a severe decrease over operating time. The desalination system of Comparative Example 5... The system can continue to operate stably for 9 days, and the desalination system of Comparative Example 6 can continue to operate stably for 7 days. The reason is that, since Comparative Examples 5 and 6 did not set a porous polymer layer containing positively charged crystalline polymer on the polyamide layer of the reverse osmosis membrane, the reverse osmosis membrane is prone to concentration polarization and fouling during operation, reducing the operational stability of the reverse osmosis membrane. The desalination systems of Examples 1 to 10 can continue to operate stably for more than 30 days. Among them, the desalination systems of Examples 8 to 9 can continue to operate stably for more than 35 days, and the desalination systems of Examples 1 to 7 can continue to operate stably for more than 45 days. Moreover, during the period when the desalination systems of Examples 1 to 10 continue to operate stably, no fouling occurs during the entire water production process, the flux of the filter membrane and the reverse osmosis membrane does not change significantly, and the water production flow and water quality remain stable.

[0130] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0131] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method of desalination of sea water, characterized in that, Includes the following steps: Seawater is filtered to obtain a filtrate, wherein the filtration membrane used in the filtration process is a polymer membrane containing a photocatalyst, and the photocatalyst is a porous polymer nanosphere containing a graphitized titanium-based framework material. The filtrate is subjected to reverse osmosis treatment to obtain reverse osmosis permeate. The reverse osmosis membrane used in the reverse osmosis treatment includes a support membrane and a polyamide layer and a porous polymer layer sequentially stacked on the surface of the support membrane. The polyamide layer contains a layered ionic covalent organic framework material, and the porous polymer layer contains a positively charged crystalline polymer. The reverse osmosis permeate is disinfected to obtain desalinated water.

2. The method of seawater desalination according to claim 1, wherein, The polymer film also contains ferrocene-modified magnesium titanate particles.

3. The method of seawater desalination according to claim 2, wherein, The ferrocene-modified magnesium titanate particles in the polymer film have a mass fraction of 1%-5%. And / or, the ferrocene in the ferrocene-modified magnesium titanate particles has a mass fraction of 0.05%-0.5%.

4. The method of seawater desalination according to claim 1, wherein, The photocatalyst has a mass fraction of 0.5%-8% in the polymer film.

5. The method of seawater desalination according to claim 4, wherein, The graphitized titanium-based framework material comprises 40%-70% by mass in the porous polymer nanospheres.

6. The method of seawater desalination according to claim 1, wherein, The layered ionic covalent organic framework material has a mass fraction of 0.1%-3% in the polyamide layer.

7. The method of seawater desalination according to claim 1, wherein, The positively charged crystalline polymer has a mass fraction of 5%-20% in the porous polymer layer.

8. A sea water desalination system characterized by, The seawater desalination system includes: A filtration device, wherein the filtration membrane used in the filtration device is a polymer membrane containing a photocatalyst, and the photocatalyst is a porous polymer nanosphere containing a graphitized titanium-based framework material; A reverse osmosis device, which is connected to the filtration device, wherein the reverse osmosis membrane used in the reverse osmosis device includes a support membrane and a polyamide layer and a porous polymer layer sequentially stacked on the surface of the support membrane, wherein the polyamide layer contains a layered ionic covalent organic framework material and the porous polymer layer contains a positively charged crystalline polymer. A disinfection device, wherein the reverse osmosis device is connected to the disinfection device.

9. The system for desalination of seawater according to claim 8, wherein, A security filter is also provided between the filtration device and the reverse osmosis device.

10. The seawater desalination system of claim 8 or claim 9, wherein, The seawater desalination system also includes an energy recovery device, which is connected to the reverse osmosis device.

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