WO2023087481A1 - 一种超薄脱盐层反渗透复合膜及其制备方法 - Google Patents

一种超薄脱盐层反渗透复合膜及其制备方法 Download PDF

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WO2023087481A1
WO2023087481A1 PCT/CN2021/140077 CN2021140077W WO2023087481A1 WO 2023087481 A1 WO2023087481 A1 WO 2023087481A1 CN 2021140077 W CN2021140077 W CN 2021140077W WO 2023087481 A1 WO2023087481 A1 WO 2023087481A1
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layer
membrane
reverse osmosis
desalination
solution
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PCT/CN2021/140077
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English (en)
French (fr)
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梁松苗
曾焕
陈心笛
胡利杰
杨兴胜
方俊
郭玉阳
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沃顿科技股份有限公司
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Priority to US18/257,230 priority Critical patent/US20240091718A1/en
Publication of WO2023087481A1 publication Critical patent/WO2023087481A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction
    • B01D69/1251—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction by interfacial polymerisation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/66—Polymers having sulfur in the main chain, with or without nitrogen, oxygen or carbon only
    • B01D71/68—Polysulfones; Polyethersulfones
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/025—Reverse osmosis; Hyperfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0002—Organic membrane manufacture
    • B01D67/0006—Organic membrane manufacture by chemical reactions
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0079—Manufacture of membranes comprising organic and inorganic components
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0081—After-treatment of organic or inorganic membranes
    • B01D67/0095—Drying
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/10—Supported membranes; Membrane supports
    • B01D69/105—Support pretreatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/14—Dynamic membranes
    • B01D69/141—Heterogeneous membranes, e.g. containing dispersed material; Mixed matrix membranes
    • B01D69/1411—Heterogeneous membranes, e.g. containing dispersed material; Mixed matrix membranes containing dispersed material in a continuous matrix
    • B01D69/14111—Heterogeneous membranes, e.g. containing dispersed material; Mixed matrix membranes containing dispersed material in a continuous matrix with nanoscale dispersed material, e.g. nanoparticles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/56—Polyamides, e.g. polyester-amides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/76—Macromolecular material not specifically provided for in a single one of groups B01D71/08 - B01D71/74
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/08—Specific temperatures applied
    • B01D2323/081—Heating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/38—Graft polymerization
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/48—Influencing the pH
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/04—Characteristic thickness
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0039—Inorganic membrane manufacture
    • B01D67/0041—Inorganic membrane manufacture by agglomeration of particles in the dry state
    • B01D67/00413—Inorganic membrane manufacture by agglomeration of particles in the dry state by agglomeration of nanoparticles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
    • B01D67/0039—Inorganic membrane manufacture
    • B01D67/0051—Inorganic membrane manufacture by controlled crystallisation, e,.g. hydrothermal growth
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/024—Oxides
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/08—Seawater, e.g. for desalination
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124—Water desalination
    • Y02A20/131—Reverse-osmosis

Definitions

  • the disclosure belongs to the technical field of preparation of porous film materials, and in particular relates to an ultra-thin desalination layer reverse osmosis composite membrane and a preparation method thereof.
  • Reverse osmosis membrane water treatment technology has the characteristics of integration and convenience.
  • reverse osmosis membrane material is the direct factor determining the technical and economic indicators of water treatment. Reducing energy consumption is the focus of continuous attention in the application process of this technology. Increasing the flux can significantly reduce the energy consumption of the membrane under the same water treatment capacity. With the development of the market, the requirement for continuously increasing flux is increasingly becoming a reverse osmosis composite membrane. Hot issues in technology development.
  • the transmittance is an inherent characteristic parameter of the polyamide desalination layer material itself and cannot be changed
  • reducing the effective thickness of the desalination layer is an obvious way to increase the flux of the membrane.
  • the interfacial polymerization reaction is carried out on the basis of the intermediate layer formed on the surface of the base membrane to obtain an ultra-thin desalination layer. This reduces the length of the water channel in the membrane functional layer, which is beneficial to improving the water flux of the reverse osmosis composite membrane.
  • the patent document with the application number CN202110114270.5 discloses a preparation method of a polyamide composite reverse osmosis membrane and the obtained reverse osmosis membrane, which is to set a flexible chain cross-linked carbon quantum nanoporous layer on the polysulfone support layer as an interfacial polymerization The control layer, and finally the functional layer.
  • the interfacial polymerization control layer is formed by cross-linking and fixing the aminated carbon atoms with a flexible chain cross-linking agent, which can regulate the interfacial polymerization process and serve as an effective water channel after film formation; the formed aromatic polyamide layer is ultra-thin and dense, The water flux and desalination rate of the membrane material are improved at the same time.
  • the present disclosure provides an ultra-thin desalination layer reverse osmosis composite membrane and a preparation method thereof.
  • An ultra-thin desalination layer reverse osmosis composite membrane said reverse osmosis composite membrane is composed of a non-woven fabric, a modified polysulfone base membrane support layer, an intermediate layer and a desalination layer.
  • the modified polysulfone-based membrane support layer is obtained by grafting and modifying the polysulfone-based membrane with a chlorosulfonic acid solution with a concentration of 10wt.%-99wt.%.
  • the average pore size of the polysulfone-based membrane is 10-50 nm.
  • the middle layer is stacked on the surface of the modified polysulfone-based membrane support layer after the metal hydroxide nanowire solution is vacuum filtered. It is found through SEM photo inspection that its thickness is 1-10 ⁇ m.
  • the desalination layer is obtained by interfacial polymerization with polyamines as water phase monomers and polyacyl chlorides as oil phase monomers, and compounded on the polysulfone-based membrane support layer. It is found through SEM photo inspection that its thickness is ⁇ 10nm.
  • the preparation method of the metal hydroxide nanowire solution is as follows:
  • step (1) Centrifuge and wash the hydroxide precipitate until the pH value is neutral, then redisperse the precipitate in deionized water, add 1-10g of soluble metal salt corresponding to step (1), and carry out the process in a closed container at normal pressure 1.
  • the hydrothermal reaction is carried out under the temperature condition of 200-250 DEG C, and the reaction time is 10-15 hours to obtain the metal hydroxide nanowire solution.
  • the soluble metal salt is any one of sodium chloride, barium chloride, strontium chloride, and zinc chloride.
  • the method for preparing the above-mentioned ultra-thin desalination layer reverse osmosis composite membrane specifically includes the following steps:
  • Modification of the base membrane soak the polysulfone base membrane in the chlorosulfonic acid solution for 1-24h, the ratio of the polysulfone base membrane to the chlorosulfonic acid solution is 20cm 2 : 1L, and the concentration of the chlorosulfonic acid solution is 10wt.%. -99wt.%; and adding a palladium catalyst in the solution, the addition amount is 2g/L, after the soaking is completed, it is washed with ultrapure water and dried to obtain a modified polysulfone-based membrane support layer;
  • the metal hydroxide nanowire solution is stacked on the surface of the modified polysulfone base membrane support layer through vacuum filtration, and compacted;
  • the metal hydroxide nanowire is any one of cadmium hydroxide, barium hydroxide, strontium hydroxide, and zinc hydroxide, with a concentration of 1-10wt.%;
  • the aqueous phase solution is one or more of m-phenylenediamine, p-phenylenediamine, ethylenediamine, and piperazine, with a concentration of 3-5wt.%.
  • oil phase solution is one or more of trimesoyl chloride, terephthaloyl chloride, and oxalyl chloride, and the concentration is 0.15-0.25wt.%.
  • the solvent of the oil phase solution is one or more of methylene chloride, chloroform, ethylene dichloride, n-hexane, ethylcyclohexane, propylene oxide and the like.
  • Membrane preparation The modified polysulfone-based membrane support layer forming the desalination layer is subjected to surface drying and heat treatment at 50-70°C for 1-10 minutes to obtain an ultra-thin desalination layer reverse osmosis composite membrane.
  • the beneficial effect of the present disclosure lies in that: the present disclosure introduces the intermediate layer after modifying the polysulfone base membrane, and the modified polysulfone base membrane support layer can strengthen the connection with the desalination layer by covalent bonds, And reduce the thickness of the desalination layer, so that while the flux of the membrane is increased, the desalination rate of the membrane will not be greatly affected.
  • the water flux can be increased by about 0.5 times, while the desalination rate changes little.
  • the introduction of the intermediate layer can change the solvent environment in the miscible zone of the reaction between the water phase monomer and the oil phase monomer during the interfacial polymerization reaction, thereby obtaining an ultra-thin desalination layer. This is because only the water phase introduced in the intermediate layer can participate in the formation of the miscible region during the interfacial polymerization process, and the intermediate layer formed by vacuum filtration and stacking of metal hydroxide nanowires on the surface of the base film can be formed at the interface. While the polymerization reaction proceeds, it is removed by the neutralization reaction of the generated hydrogen chloride.
  • the amount of the water phase in the middle layer transferred to the miscible region is very limited, and the water phase monomers participating in the interfacial polymerization reaction to form the functional layer are very few.
  • the interfacial polymerization reaction initially forms a very thin layer of polyamide functional layer nascent film, which will be fixed and no longer thicken, resulting in a composite film with an ultra-thin desalination layer structure.
  • the present disclosure conducts sulfonation of the polysulfone benzene ring of the base membrane.
  • the acid chloride group is grafted, so that when the interface polymerizes the polyaniline of the water phase monomer and the polyacyl chloride of the oil phase monomer to form a desalination layer, at the same time, part of the polyaniline of the water phase monomer reacts with the sulfonyl chloride group on the surface of the group, so as to realize The basement membrane and the desalination layer are strengthened by covalent bonds.
  • the polyamide functional layer (i.e. the desalination layer) of the reverse osmosis composite membrane prepared by the disclosed method can reach a thickness of ⁇ 10nm, and by comparing with the diaphragm of the polyamide functional layer of the traditional thickness, it is found that the diaphragm is under the following conditions: 1500ppm When the NaCl aqueous solution is operated at an operating pressure of 0.70MPa (concentrated water circulation), the water flux increases from about 42gfd to about 60gfd, an increase of about 0.5 times, and the desalination rate only drops from 99.2% to 98.8%.
  • 0.70MPa concentrated water circulation
  • the water-effect solution is prepared by adding 11.10g CaCl 2 , 10.75g NaHCO 3 , and 2.00g NaCl to 40L of pure water, and then adding 40ml of dilute solution according to the ratio of 6-8ml of hypochlorous acid dissolved in 1L of pure water.
  • Hypochlorous acid solution when the operating pressure is 0.70MPa (concentrated water circulation), the water flux is increased from about 36gfd to about 56gfd, which is also increased by about 0.5 times, and the desalination rate is only reduced from 96.2% to 95.0%.
  • connection strength between the base membrane of the reverse osmosis composite membrane prepared by the disclosed method and the desalination layer is basically the same as that of the reverse osmosis composite membrane obtained by the conventional method.
  • the method of characterizing the connection strength between the base film and the desalination layer is to measure the peel strength of the film (or called the average peel force), which means that when the width is fixed, there is a force of 180° continuous peeling between the base film and the desalination layer. size.
  • the peeling strengths of the membrane prepared by the disclosed method and the conventional membrane are all in the range of 0.3N-0.5N, and both belong to a better range of connection strength between the base membrane and the desalination layer.
  • the water flux of the membrane prepared by the disclosed method has a greater improvement effect. This technology is expected to be applied to the production of reverse osmosis membranes in large quantities, and it is easy to implement factory production.
  • An ultra-thin desalination layer reverse osmosis composite membrane said reverse osmosis composite membrane is composed of a non-woven fabric, a modified polysulfone base membrane support layer, an intermediate layer and a desalination layer.
  • the average pore size of the polysulfone-based membrane is 10 nm.
  • the middle layer is stacked on the surface of the modified polysulfone-based membrane support layer after the metal hydroxide nanowire solution is vacuum filtered.
  • the preparation method of the metal hydroxide nanowire solution is as follows:
  • the method for preparing the above-mentioned ultra-thin desalination layer reverse osmosis composite membrane specifically includes the following steps:
  • the cadmium hydroxide nanowire solution is stacked on the surface of the modified polysulfone base membrane support layer through vacuum filtration, and compacted to a thickness of about 2 ⁇ m;
  • Membrane preparation the modified polysulfone-based membrane support layer forming the desalination layer was heat-treated at 70° C. for 5 minutes to obtain an ultra-thin desalination layer reverse osmosis composite membrane.
  • the preparation method is the same as in Example 1, the difference is that in the modification step of the base membrane, the polysulfone base membrane is soaked in 75% chlorosulfonic acid solution for 2 hours, and a palladium catalyst is added to the solution. Washing with water and drying to obtain a modified polysulfone-based membrane support layer.
  • the other preparation steps and conditions are exactly the same and will not be repeated here.
  • the preparation method is the same as in Example 1, the difference is that the barium hydroxide nanowires are stacked by vacuum filtration on the modified polysulfone base membrane support layer, and the preparation method of the barium hydroxide nanowire solution is similar to that of the hydroxide nanowires solution.
  • the other preparation steps and conditions are exactly the same and will not be repeated here.
  • the reverse osmosis composite membrane was prepared by the method of Example 1, the difference being that there was no base membrane modified by immersion in chlorosulfonic acid solution and no metal hydroxide nanowire intermediate layer was introduced.
  • the water efficiency solution was used to test the salt rejection rate and flux of the membrane under the conditions of operating pressure of 0.70MPa and temperature of 25°C. The results are shown in Table 2 (concentrated water circulation).
  • the preparation method of the water-effect solution add 11.10g CaCl 2 , 10.75g NaHCO 3 , 2.00g NaCl to 40L of pure water respectively, and then add 40ml of hypochlorite diluted according to the ratio of 6-8ml of hypochlorous acid dissolved in 1L of pure water acid solution.
  • a high-performance ultra-thin desalination layer reverse osmosis composite membrane can be prepared by adopting the method within the scope of the claims of the present disclosure, and the thickness of the functional layer is relatively thin.
  • the flux can be increased by about 0.5 times with little change in the rejection rate.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Manufacturing & Machinery (AREA)
  • Nanotechnology (AREA)
  • Inorganic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
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Abstract

一种超薄脱盐层反渗透复合膜及其制备方法，属于多孔薄膜材料制备技术领域，通过对聚砜基膜进行改性后引入中间层，经改性后的聚砜基膜支撑层可与脱盐层以共价键加强连接，并降低脱盐层的厚度至≤10nm，使得在提高膜片通量的同时，膜片的脱盐率不受较大影响。与传统厚度脱盐层的膜片对比，水通量可提高约0.5倍，而脱盐率变化较小。

Description

一种超薄脱盐层反渗透复合膜及其制备方法 技术领域
本公开属于多孔薄膜材料制备技术领域，具体涉及一种超薄脱盐层反渗透复合膜及其制备方法。
背景技术
反渗透膜水处理技术具有集成、便捷的特点，反渗透膜材料作为膜法海水淡化技术的基础和核心材料，其性能是决定水处理技术经济指标的直接因素。降低能耗是该技术应用过程中持续关注的重点，提升通量能够显著降低膜片在同等水处理能力下的能量消耗，随着市场发展，对通量不断提升的要求日益成为反渗透复合膜技术开发的热点问题。
其中，由于透过率作为聚酰胺脱盐层材料本身固有的特征参数无法改变，故减少脱盐层的有效厚度是一种显而易见的提高膜片通量的办法。为了制备得到一种高性能的反渗透复合膜，从功能层的厚度改造角度出发，选择在基膜表面形成的中间层基础上进行界面聚合反应，得到超薄脱盐层。这使得在膜片功能层中的水通道长度减小，利于提高反渗透复合膜的水通量。
申请号为CN202110114270.5的专利文件公开了一种聚酰胺复合反渗透膜的制备方法及所得反渗透膜，其是在聚砜支撑层上设置柔性链交联的碳量子纳米多孔层作为界面聚合调控层，最后再制作功能层。界面聚合调控层由柔性链交联剂将氨基化的碳原子交联固定形成，能对界面聚合过程进行调控并在成膜后作为有效水通道；使形成的芳香聚酰胺层超薄且致密，膜材料的水通量和脱盐率同时提高。
另外，文献如Journal of Membrane Science 576(2019)131–141、Journal of Membrane Science 564(2018)813–819等也给出过在覆膜过程中于基膜和功能层之间引入中间层的报道。由以上专利和文献可知，在支撑层上覆膜得到脱 盐层之前引入中间层来调控界面聚合反应的条件已有相关研究。但现有技术中所制备的功能层厚度还达不到理想程度，或者是厚度与功能性无法同时兼顾。
发明内容
本公开为解决上述问题，提供了一种超薄脱盐层反渗透复合膜及其制备方法。
具体是通过以下技术方案来实现的：
1、一种超薄脱盐层反渗透复合膜，所述的反渗透复合膜是由无纺布、改性聚砜基膜支撑层、中间层和脱盐层组成。
进一步，所述的改性聚砜基膜支撑层，是采用浓度为10wt.％-99wt.％的氯磺酸溶液对聚砜基膜进行接枝改性处理得到。
进一步，通过SEM照片检测发现，所述的聚砜基膜平均孔径大小为10-50nm。
进一步，所述的中间层，是由金属氢氧化合物纳米线溶液经真空过滤后堆叠于改性聚砜基膜支撑层表面的。通过SEM照片检测发现，其厚度为1-10μm。
进一步，所述的脱盐层，是以多元胺作为水相单体，以多元酰氯作为油相单体，通过界面聚合反应得到，复合在聚砜基膜支撑层上的。通过SEM照片检测发现，其厚度为≤10nm。
2、所述金属氢氧化合物纳米线溶液的制备方法如下：
(1)将可溶性金属盐溶解在去离子水中，形成浓度为1-10wt.％的溶液，再加入碱或氨水溶液调节pH值为10-14，搅拌生成金属氢氧化物沉淀；
(2)将氢氧化物沉淀离心洗涤至pH值为中性，再将沉淀重新分散在去离子水中，加入1-10g与步骤(1)相应的可溶性金属盐，在密闭容器内进行在常压、200-250℃温度条件下进行的水热反应，反应时间为10-15h，得到金属氢氧化物纳米线溶液。
进一步，所述的可溶性金属盐为氯化隔、氯化钡、氯化锶、氯化锌中的任意一种。
3、上述超薄脱盐层反渗透复合膜的制备方法，具体包括以下步骤：
(1)基膜改性：将聚砜基膜浸泡在氯磺酸溶液中1-24h，聚砜基膜与氯磺 酸溶液的比例为20cm 2：1L，氯磺酸溶液浓度为10wt.％-99wt.％；并在溶液中加入钯催化剂，加入量为2g/L，浸泡完成后经超纯水洗涤、晾干，得到改性聚砜基膜支撑层；
(2)形成中间层：将金属氢氧化合物纳米线溶液经真空过滤堆叠于改性聚砜基膜支撑层表面，压实；
进一步，所述的金属氢氧化合物纳米线为氢氧化镉、氢氧化钡、氢氧化锶、氢氧化锌中的任意一种，浓度为1-10wt.％；
(3)形成脱盐层：将覆盖有中间层的改性聚砜基膜支撑层浸入含多元胺的水相溶液中，处理5-300s，取出，除去表面水滴，再浸入含多元酰氯的油相溶液中，处理5-300s，形成聚酰胺脱盐层；
进一步，所述的水相溶液为间苯二胺、对苯二胺、乙二胺、哌嗪中的一种或几种，浓度为3-5wt.％。
进一步，所述的油相溶液为苯三甲酰氯、对苯二甲酰氯、草酰氯中的一种或几种，浓度为0.15-0.25wt.％。
进一步，所述油相溶液的溶剂为二氯甲烷、氯仿、二氯乙烷、正己烷、乙基环己烷、环氧丙烷等中的一种或几种。
(4)成膜制备：将形成脱盐层的改性聚砜基膜支撑层在50-70℃条件下进行表面烘干热处理1-10min，即得到超薄脱盐层反渗透复合膜。
综上所述，本公开的有益效果在于：本公开通过对聚砜基膜进行改性后引入中间层，经改性后的聚砜基膜支撑层可与脱盐层以共价键加强连接，并降低脱盐层的厚度，使得在提高膜片通量的同时，膜片的脱盐率不受较大影响。与传统厚度脱盐层的膜片对比，水通量可提高约0.5倍，而脱盐率变化较小。
引入中间层可以改变界面聚合反应过程中的水相单体与油相单体反应的混溶区溶剂环境，从而得到超薄脱盐层。这是因为在界面聚合过程中只有中间层中引入的水相才能参与形成混溶区，而且，采用金属氢氧化合物纳米线经过真空过滤堆叠于基膜表面压密形成的中间层，可在界面聚合反应进行的同时被生成的氯 化氢中和反应去除。所以，显然的，在中间层中的水相传递至混溶区的量就很受限制，参与界面聚合反应形成功能层的水相单体很少。综上所述，界面聚合反应最初形成很薄的一层聚酰功能层初生膜会被固定下来不再增厚，从而导致复合膜具有超薄的脱盐层结构。
由于引入了中间层会导致基膜与脱盐层之间的连接变弱，为了在提高反渗透复合膜通量的同时保证较高的脱盐率，本公开通过对基膜的聚砜苯环进行磺酰氯基团接枝，使得在界面聚合水相单体多元苯胺与油相单体多元酰氯反应生成脱盐层的同时，部分水相单体多元苯胺与基团表面的磺酰氯基团反应，从而实现基膜与脱盐层以共价键的方式加强连接。这保证了功能层在复合膜上的强度，使得在提高膜片通量的同时，膜片脱盐率不受较大影响。不过引入可牺牲的中间层只是手段，而以此来制备厚度≤10nm的超薄功能层才是本公开的核心内容，在此基础上又为保证功能层与支撑层之间的连接强度而引进基膜支撑层改性过程。
采用本公开方法制备得到反渗透复合膜的聚酰胺功能层(即脱盐层)可以达到≤10nm的厚度，且通过与传统厚度聚酰胺功能层的膜片对比，发现膜片在以下条件下：1500ppm的NaCl水溶液，在操作压力为0.70MPa下(浓水循环)运行时，水通量从42gfd左右提升至60gfd左右，增加了约0.5倍，且脱盐率仅从99.2％降至98.8％；在水效条件下：水效溶液的配制是在40L纯水中分别添加11.10g CaCl 2、10.75g NaHCO 3、2.00g NaCl，然后加入40ml的按照6-8ml次氯酸溶解在1L纯水中比例稀释的次氯酸溶液，在操作压力为0.70MPa下(浓水循环)运行时，水通量从36gfd左右提升至56gfd左右，亦增加了约0.5倍，且脱盐率仅从96.2％降至95.0％。
此外，采用本公开方法制备得到的反渗透复合膜基膜与脱盐层之间的连接强度与常规方法得到的反渗透复合膜基本一致。表征基膜和脱盐层之间的连接强度的方法为测量膜片剥离强度(或称为平均剥离力)，它表示的是宽度尺寸固定时基膜和脱盐层之间呈180°连续剥离时用力大小。而采用本公开方法制备得到的膜片与常规膜片的剥离强度均在0.3N-0.5N的范围之内变化，均属于基膜与脱盐层之间的连接强度较好范围。相较而言，本公开方法制备得到的膜片水通量有较 大的提升效果，此技术有望应用到大批量的反渗透膜生产中，易于推行工厂化生产。
具体实施方式
下面对本公开的具体实施方式作进一步详细的说明，但本公开并不局限于这些实施方式，任何在本实施例基本精神上的改进或代替，仍属于本公开权利要求所要求保护的范围。
一、实施例与对比例
实施例1
1、一种超薄脱盐层反渗透复合膜，所述的反渗透复合膜是由无纺布、改性聚砜基膜支撑层、中间层和脱盐层组成。
进一步，通过SEM照片检测发现，所述的聚砜基膜平均孔径大小为10nm。
进一步，所述的中间层，是由金属氢氧化合物纳米线溶液经真空过滤后堆叠于改性聚砜基膜支撑层表面的。
2、所述金属氢氧化合物纳米线溶液的制备方法如下：
(1)将氯化镉溶解在去离子水中形成10wt.％的溶液，再缓慢加入氨水溶液调节pH值为14，搅拌生成氢氧化镉沉淀；
(2)将氢氧化镉沉淀离心洗涤至pH值为中性，再将沉淀重新分散在去离子水中，加入适量无机盐氯化镉，在密闭容器内进行在200℃下进行水热反应10h，得到5wt.％的氢氧化镉纳米线溶液。
3、上述超薄脱盐层反渗透复合膜的制备方法，具体包括以下步骤：
(1)基膜改性：将聚砜基膜(10cm×10cm)浸泡在5L氯磺酸溶液中2h，氯磺酸溶液的浓度为50wt.％，并在溶液中加入10g钯催化剂，浸泡完成后经超纯水洗涤、晾干，得到改性聚砜基膜支撑层；
(2)形成中间层：将氢氧化镉纳米线溶液经真空过滤堆叠于改性聚砜基膜支撑层表面，压实，厚度约2μm；
(3)形成脱盐层：将覆盖有中间层的改性聚砜基膜支撑层浸入含3.0wt.％间苯二胺的水相溶液中，处理20s，取出，除去表面水滴，再浸入含0.15wt.％ 均苯三甲酰氯的油相溶液中，处理20s，形成聚酰胺脱盐层；进一步，所述的水相溶液中含有浓度为4wt.％的樟脑磺酸、2wt.％的三乙胺。进一步，所述油相溶液的溶剂为乙基环己烷。
(4)成膜制备：将形成脱盐层的改性聚砜基膜支撑层在70℃条件下热处理5min，即得到超薄脱盐层反渗透复合膜。
实施例2
与实施例1的制备方法相同，区别在于，在基膜改性步骤中，将聚砜基膜采用75％的氯磺酸溶液浸泡2h，并在溶液中加入钯催化剂，浸泡完成后经超纯水洗涤、晾干，得到改性聚砜基膜支撑层。其他制备步骤和条件完全相同，此不赘述。
实施例3
与实施例1的制备方法相同，区别在于，在改性聚砜基膜支撑层上真空过滤堆叠的是氢氧化钡纳米线，其中氢氧化钡纳米线溶液的制备方法类似于氢氧化隔纳米线溶液。其他制备步骤和条件完全相同，此不赘述。
对比例1
采用实施例1的方法制备反渗透复合膜，区别在于，没有基膜的经氯磺酸溶液浸泡改性和不引入金属氢氧化合物纳米线中间层。
二、膜片性能测试
2.1实验材料
采用实施例1-3及对比例1的方法制备的反渗透复合膜。
2.2实验方法
用1500ppm的NaCl水溶液，在操作压力为0.70MPa、温度为25℃的条件下测试膜片的脱盐率和通量，结果如表1所示(浓水循环)。
用水效溶液，在操作压力为0.70MPa、温度为25℃的条件下测试膜片的脱盐率和通量，结果如表2所示(浓水循环)。
水效溶液的配制方法：在40L纯水中分别添加11.10g CaCl 2、10.75g NaHCO 3、2.00g NaCl，然后加入40ml的按照6-8ml次氯酸溶解在1L纯水中比例稀释的次氯酸溶液。
2.3实验结果
表1
Figure PCTCN2021140077-appb-000001
表2
Figure PCTCN2021140077-appb-000002
由以上表1和表2的实验结果可知，在实施例1、实施例2和实施例3中分别采用本公开方法制备得到的超薄脱盐层反渗透复合膜，无论在NaCl溶液或是在水效溶液中运行时，通量均大大提高，同时脱盐率几乎不变。长时间运行条件 下，膜片在NaCl溶液中运行的脱盐率略有提升，而通量稳定；在水效溶液中运行的脱盐率亦略有提升，而通量衰减较快。但水效运行条件下，实施例1、2、3与对比例1均保持相同的通量衰减趋势，且实施例1、2、3的膜片通量始终高于对比例1的膜片通量。
亦即，采用本公开所述的权利要求范围内的方法可以制备得到一种高性能的超薄脱盐层反渗透复合膜，其功能层厚度较薄，与传统厚度脱盐层的膜片对比，水通量可提高约0.5倍，而脱盐率变化较小。

Claims (10)

  1. 一种超薄脱盐层反渗透复合膜，其特征在于，所述的反渗透复合膜是由无纺布、改性聚砜基膜支撑层、中间层和脱盐层组成；其中，所述的中间层，是由金属氢氧化合物纳米线溶液经真空过滤后堆叠于改性聚砜基膜支撑层表面的，厚度为1-10μm；所述的脱盐层，是以多元胺作为水相单体，以多元酰氯作为油相单体，通过界面聚合反应得到，复合在聚砜基膜支撑层上的，厚度≤10nm。
  2. 如权利要求1所述的一种超薄脱盐层反渗透复合膜，其特征在于，所述的改性聚砜基膜支撑层，是采用浓度为10wt.％-99wt.％的氯磺酸溶液对聚砜基膜进行接枝改性处理得到。
  3. 一种超薄脱盐层反渗透复合膜的制备方法，其特征在于，包括以下步骤：
    (1)基膜改性：将聚砜基膜浸泡在氯磺酸溶液中1-24h，聚砜基膜与氯磺酸溶液的比例为20cm 2：1L；并在溶液中加入钯催化剂，加入量为2g/L，浸泡完成后经超纯水洗涤、晾干，得到改性聚砜基膜支撑层；
    (2)形成中间层：将金属氢氧化合物纳米线溶液经真空过滤堆叠于改性聚砜基膜支撑层表面，压实；
    (3)形成脱盐层：将覆盖有中间层的改性聚砜基膜支撑层浸入含多元胺的水相溶液中，处理5-300s，取出，除去表面水滴，再浸入含多元酰氯的油相溶液中，处理5-300s，形成聚酰胺脱盐层；
    (4)成膜制备：将形成脱盐层的改性聚砜基膜支撑层在50-70℃条件下进行表面烘干热处理，处理时间为1-10min，即得到超薄脱盐层反渗透复合膜。
  4. 如权利要求3所述的一种超薄脱盐层反渗透复合膜的制备方法，其特征在于，所述的氯磺酸溶液，其浓度为10wt.％-99wt.％。
  5. 如权利要求3所述的一种超薄脱盐层反渗透复合膜的制备方法，其特征在于，所述的金属氢氧化合物纳米线为氢氧化镉、氢氧化钡、氢氧化锶、氢氧化锌中的任意一种，其中氢氧化物的浓度为1-10wt.％。
  6. 如权利要求3所述的一种超薄脱盐层反渗透复合膜的制备方法，其特征 在于，所述的水相溶液为间苯二胺、对苯二胺、乙二胺、哌嗪中的一种或几种，浓度为3-5wt.％。
  7. 如权利要求3所述的一种超薄脱盐层反渗透复合膜的制备方法，其特征在于，所述的油相溶液为苯三甲酰氯、对苯二甲酰氯、草酰氯中的一种或几种，浓度为0.15-0.25wt.％。
  8. 如权利要求3或5所述的一种超薄脱盐层反渗透复合膜的制备方法，其特征在于，所述的金属氢氧化物纳米线溶液的制备方法如下：
    (1)将可溶性金属盐溶解在去离子水中，形成浓度为1-10wt.％的溶液，再在其中加入碱或氨水溶液调节pH值为10-14，搅拌生成金属氢氧化物沉淀；
    (2)将氢氧化物沉淀离心洗涤至pH值为中性，再将沉淀重新分散在去离子水中，加入1-10g与步骤(1)相应的可溶性金属盐，在密闭容器内进行水热反应，得到金属氢氧化物纳米线溶液。
  9. 如权利要求8所述的一种超薄脱盐层反渗透复合膜的制备方法，其特征在于，所述的可溶性金属盐为氯化隔、氯化钡、氯化锶、氯化锌中的任意一种。
  10. 如权利要求8所述的一种超薄脱盐层反渗透复合膜的制备方法，其特征在于，所述的水热反应，是在常压下，于200-250℃条件下反应10-15h。
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