CN109012183B - Preparation method of ultra-thin anti-pollution composite nanofiltration membrane assembled by phytic acid - Google Patents

Preparation method of ultra-thin anti-pollution composite nanofiltration membrane assembled by phytic acid Download PDF

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CN109012183B
CN109012183B CN201810741563.4A CN201810741563A CN109012183B CN 109012183 B CN109012183 B CN 109012183B CN 201810741563 A CN201810741563 A CN 201810741563A CN 109012183 B CN109012183 B CN 109012183B
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phytic acid
membrane
nanofiltration membrane
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composite nanofiltration
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CN109012183A (en
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吴洪
姜忠义
游昕达
苏延磊
余倩倩
袁锦秋
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Tianjin University
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    • 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
    • B01D61/027—Nanofiltration
    • 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
    • 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
    • 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
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/06—Organic material
    • B01D71/40—Polymers of unsaturated acids or derivatives thereof, e.g. salts, amides, imides, nitriles, anhydrides, esters
    • B01D71/42—Polymers of nitriles, e.g. polyacrylonitrile
    • 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
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    • B01D2325/36—Hydrophilic membranes

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Abstract

The invention discloses a method for preparing an ultrathin anti-pollution composite nanofiltration membrane assembled by phytic acid, which comprises the following steps of firstly, preparing a macromolecular porous base membrane by adopting a phase inversion method: preparing phytic acid assembly aqueous solution with the mass fraction of 0.5-2.0%; adding the ultrafiltration base membrane into phytic acid assembly aqueous solution to obtain an ultrafiltration base membrane adsorbed by phytic acid, adding 0.5-2.0% of transition metal salt by mass, standing and assembling at 25 ℃ for 40-80min to obtain an assembled composite membrane; and soaking the assembled composite membrane in deionized water for 10min, taking out the membrane, and performing heat treatment to obtain the phytic acid assembled ultrathin anti-pollution composite nanofiltration membrane. Compared with the traditional composite nanofiltration membrane, the phytic acid-transition metal ion separation layer prepared by the method is very thin, has super-hydrophilic characteristics, and has super-high water flux, separation performance and pollution resistance under super-low operation pressure (1 bar).

Description

Preparation method of ultra-thin anti-pollution composite nanofiltration membrane assembled by phytic acid
Technical Field
The invention relates to the technical field of composite membrane preparation, in particular to a preparation method of an ultrathin anti-pollution composite nanofiltration membrane assembled by phytic acid.
Background
The development of nanofiltration technology started in the end of the 80's 20 th century, and is a pressure-driven membrane separation technology with separation precision between reverse osmosis and ultrafiltration, which has higher permeation flux and higher separation precision than reverse osmosis membranesLow operation pressure (3-10bar), good interception performance to high-valence salt ions and small molecular organic matters, and wide application in fields of brackish water desalination, printing and dyeing wastewater treatment, biochemical preparation, medicine purification and the like[1-3]. However, the flux of the current commercial nanofiltration membrane is less than 3L m-2h- 1bar-1This greatly limits the separation efficiency of the nanofiltration membrane[4]。
At present, most scholars prepare a nano film with selective permeability on a porous substrate by using technologies such as interfacial polymerization and the like so as to obtain a composite nanofiltration membrane. The nano film is used as an active separation layer to determine the whole permeation flux and selectivity of the nanofiltration membrane, and the composite structure provides possibility for simultaneous optimization of the top active separation layer and the bottom support layer[5]. However, the thickness of the conventional composite nanofiltration membrane is often more than 100 nm, which severely restricts the permeation flux, and the ultra-thinning of the composite nanofiltration membrane has become an important issue in the field. In recent years, the regulation of the interfacial assembly behavior of molecules has become an effective strategy for preparing ultrathin polymer films. Currently, the scholars have optimized the physicochemical structure of the substrate[6-8]Control the diffusion of microphase[9,10]And the condensation polymerization reaction of the interface monomer is regulated and controlled by the technology, so that a series of ultrathin nanofiltration membranes with the thickness of dozens of nanometers are prepared, and the permeation flux is obviously improved. Levenston et al, the university of Imperial technology, England, used cadmium hydroxide nanowires as sacrificial layers to prepare for the first time self-supporting nanofiltration membranes with thicknesses of less than 10 nm[11]But with the risk of detachment from the substrate[7]. In addition, most of the preparation strategies of the ultrathin film are complicated in steps, and the organic solvent required for constructing the phase interface is also unfavorable for the environment. A simpler, more convenient and green preparation method of the ultrathin film is urgently needed to be developed.
In addition, for the removal of small molecular organic matters, the ultra-thinning endows the nanofiltration membrane with high flux, and simultaneously, the nanofiltration membrane also faces more serious pollution problems. Since high flux will drive more contaminants to adsorb on the membrane surface, permeate flux is reduced during operation[12]. Theoretically, the attachment of contaminants to the membrane surface depends on a ternary system of "contaminants-water molecules-membrane surfaceMaximum gibbs free energy[13]. The super-hydrophilic membrane material has rich polar groups, is combined with water molecules through hydrogen bonds or electrostatic interaction, can combine a large number of water molecules on the surface of the membrane to form a hydration layer, increases the energy barrier of pollutants adsorbed on the surface of the membrane, and brings excellent pollution resistance[13]. In addition, the hydrophilic membrane is also helpful for water molecules to be adsorbed and dissolved on the surface of the membrane, and the water flux of the separation membrane is improved. Therefore, the ultra-hydrophilic ultra-thin nanofiltration membrane can ensure the lasting high flux of the nanofiltration separation process.
The organism assembles and prepares the ultrathin membrane with various functions through weak interaction between functional molecules. For example, the cell membrane is assembled by hydrophobic interaction of phosphate functional molecules, and the thickness of only two molecular layers (about 8 nm) can realize the selective permeation of the molecules[14]The outer hydrophilic phosphate ends also resist the attachment of external contaminants by hydration[13]The method provides a new idea for the design and preparation of the functional ultrathin film from bottom to top. The natural cereal contains a hydrophilic small molecule containing six phosphate groups, namely phytic acid[15]. Wherein the hydration free energy of the phosphate group is about 47.3kJ/mol, which is equivalent to the sulfonic acid group, and the phosphate group is applied to strengthening the water retention of the proton exchange membrane[16]. In addition, the abundant phosphate groups endow the film with excellent molecular assembly characteristics, and the molecular film can be assembled on a solid-liquid interface through the actions of hydrogen bonds, coordination and the like to prepare the molecular film[17]. However, no research is reported on the preparation of the ultrathin anti-pollution composite nanofiltration membrane by taking phytic acid as a construction unit.
[ reference documents ]
[1] The content is Congjie, Chenyiniang birchleaf nanofiltration membrane and the application thereof [ J ]. Chinese non ferrous metals academic newspaper, 2004, (S1): 310-.
[2] Li Megakui, Zhouyong, Zhu Jia, Kong from Congjie, development of nanofiltration membrane functional material research [ J ] water treatment technology, 2009,35(12):1-6.
[3] Wen Qin snow, Wang Qung, Zheng Ming and Chen Zhi Qiang, research progress and development trend of advanced treatment technology of printing and dyeing wastewater [ J ] chemical industry environmental protection, 2015,35(04): 363-.
[4]Soyekwo F,Zhang Q,Chen M,et al.Metal in-situ surface functionalization of polymer-grafted-carbon nanotube composite membranes for fast efficient nanofiltration[J].Journal of Materials Chemistry A,2016,5(2).
[5] The research on the structure, charge property, separation mechanism and electrokinetic property of nano-filter membrane pore is advanced [ J ]. Membrane science and technology, 2011,31(03): 127-.
[6]Zhang X,Lv Y,Yang H C,et al.Polyphenol Coating as an Interlayer for Thin-Film Composite Membranes with Enhanced Nanofiltration Performance.[J].Acs Appl Mater Interfaces,2016,8(47):32512-32519.
[7]Wu M B,Lv Y,Yang H C,et al.Thin film composite membranes combining carbon nanotube intermediate layer and microfiltration support for high nanofiltration performances[J].Journal of Membrane Science,2016,515:238-244.
[8]Wang X,Yeh T M,Wang Z,et al.Nanofiltration membranes prepared by interfacial polymerization on thin-film nanofibrous composite scaffold[J].Polymer,2014,55(6):1358-1366.
[9]Shan L,Gu J,Fan H,et al.Micro-phase diffusion-controlled interfacial polymerization for an ultrahigh permeability nanofiltration membrane[J].Acs Applied Materials&Interfaces,2017,9(51)：44820-44827.
[10]Wang X,Fang D,Hsiao B S,et al.Nanofiltration membranes based on thin-film nanofibrous composites[J].Journal of Membrane Science,2014,469(11):188-197.
[11]Karan S,Jiang Z,Livingston A G.Sub-10nm polyamide nanofilms with ultrafast solvent transport for molecular separation[J].Science,2015,348(6241):1347-1351.
[12]Liu Y,Su Y,Cao J,et al.Synergy of the mechanical,antifouling and permeation properties of a carbon nanotube nanohybrid membrane for efficient oil/water separation.[J].Nanoscale,2017,9(22)：7508-7518.
[13]He M,Gao K,Zhou L,et al.Zwitterionic materials for antifouling membrane surface construction[J].Acta Biomaterialia,2016,40:142-152.
[14]Hochmuth R M,Evans C A,Wiles H C,et al.Mechanical measurement of red cell membrane thickness[J].Science,1983,220(4592):101.
[15]Song X,Chen Y,Rong M,et al.A Phytic Acid Induced Super‐Amphiphilic Multifunctional 3D Graphene-Based Foam[J].Angewandte Chemie,2016,55(12):3936-3941.
[16]Paddison S J,Kreuer K D,Maier J.About the choice of the protogenic group in polymer electrolyte membranes:Ab initio modelling of sulfonic acid,phosphonic acid,and imidazole functionalized alkanes[J].Physical Chemistry Chemical Physics,2006,8(39):4530-4542.
[17]Pujari S P,Scheres L,Marcelis A T,et al.Covalent surface modification of oxide surfaces.[J].Angewandte Chemie,2014,53(25):6322-6356.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a method for preparing an ultra-thin anti-pollution composite nanofiltration membrane assembled by phytic acid, wherein a polyacrylonitrile ultrafiltration base membrane or a polyether sulfone ultrafiltration base membrane is prepared by a phase inversion method, phytic acid is used as a functional molecular unit, transition metal ions are used as a cross-linking center, and the coordination of the phytic acid and the polyether sulfone ultrafiltration base membrane is utilized to prepare the ultra-thin hydrophilic composite nanofiltration membrane with the thickness of about 8 nanometers through green one-step assembly at a solid-liquid interface of an aqueous solution and a polymer substrate.
The technical scheme of the invention is that the preparation method of the ultra-thin anti-pollution composite nanofiltration membrane assembled by phytic acid comprises the following steps:
step one, preparing a high-molecular porous base membrane: dissolving polyacrylonitrile or polyether sulfone in N, N-dimethylformamide to prepare a casting solution with the mass concentration of 15-18%, stirring at 50-70 ℃, standing and defoaming for 12h, cooling to room temperature, pouring the casting solution on a glass plate to scrape a film, placing the glass plate in a water bath to solidify into a film, taking the glass plate down, and soaking the glass plate in deionized water;
step two, preparing phytic acid assembly solution: adding phytic acid with a certain mass into water to prepare a phytic acid assembling solution with the mass fraction of 0.5-2.0%;
step three, soaking the polyacrylonitrile-based membrane or polyether sulfone-based membrane prepared in the step one in the phytic acid assembly solution in the step two; then, adding 0.5-2.0% of transition metal salt by mass, standing and assembling for 40-80min at 25 ℃ to obtain an assembled composite membrane; soaking the assembled composite membrane in deionized water for 10min, taking out the membrane, and carrying out heat treatment at 50-80 ℃ for 5-15min to obtain the phytic acid assembled ultrathin anti-pollution composite nanofiltration membrane.
Further, in the second step of the present invention, the mass fraction of the prepared phytic acid assembly solution is preferably 0.5%.
The transition metal salt in the third step is any one or the combination of more than two of silver nitrate, ferric chloride, zinc chloride, nickel chloride and zirconium nitrate. Preferably ferric chloride.
The mass fraction of the transition metal salt added in step three is preferably 1.5%.
The time for phytic acid assembly in step three is preferably 60 min.
Compared with the prior art, the invention has the advantages that:
the ultrathin anti-pollution composite nanofiltration membrane assembled by the phytic acid is prepared by mainly adopting a phase inversion method to prepare a macromolecular porous base membrane; preparing phytic acid assembly aqueous solution; adding the ultrafiltration basal membrane into phytic acid aqueous solution to obtain an ultrafiltration basal membrane adsorbed by phytic acid; and then adding a transition metal into the solution for coordination assembly to prepare the composite membrane assembled by the phytic acid. The phytic acid and the transition metal ions are assembled in the aqueous solution in one step, the process is simple and easy to operate, the method is green and environment-friendly, no organic solvent is used, and compared with the traditional composite nanofiltration membrane, the phytic acid-transition metal ion separation layer prepared by the method is very thin and has super-hydrophilic characteristics, and has higher water flux, separation performance and pollution resistance under the ultra-low operation pressure (1 bar).
Drawings
Fig. 1 is a graph showing pure water flux and methyl blue (mass fraction is 0.01%) retention rate of the phytic acid composite nanofiltration membranes prepared in examples 1 to 5 of the present invention.
Fig. 2 is an electron microscope image of the surface of the polyacrylonitrile-based film prepared in example 1.
Fig. 3-1 is a surface electron microscope image of the phytic acid assembled (iron ion) composite nanofiltration membrane prepared in example 1.
Fig. 3-2 is a sectional electron microscope image of the phytic acid assembled (iron ion) composite nanofiltration membrane prepared in example 1.
Fig. 4 is a graph of the cyclic pollution tolerance of the phytic acid assembled (iron ion) composite nanofiltration membrane prepared in example 1 to three model pollutants, namely humic acid, sodium alginate and bovine serum albumin.
Fig. 5 is an electron microscope image of the surface of the polyethersulfone-based film prepared in example 6.
Fig. 6 is a surface electron microscope image of the phytic acid assembled (iron ion) composite nanofiltration membrane prepared in example 6.
Detailed Description
The invention is further illustrated by the following specific examples and the accompanying drawings. The examples are intended to better enable those skilled in the art to better understand the present invention and are not intended to limit the present invention in any way.
Example 1, preparation of a phytic acid assembled composite nanofiltration membrane, the steps are as follows:
step one, preparation of a polyacrylonitrile-based film: dissolving polyacrylonitrile in N, N-dimethylformamide to prepare a casting solution containing polyacrylonitrile with the mass concentration of 15%, stirring at 60 ℃ for 12h, standing at 50 ℃ for defoaming for 12h, cooling to room temperature, pouring the casting solution on a glass plate to scrape a film, putting the glass plate into a water bath with the temperature of 25 ℃ for solidifying to form a film, taking the glass plate down, and soaking the glass plate in deionized water for 24h to obtain a polyacrylonitrile-based film, wherein the polyacrylonitrile-based film is shown in figure 2.
Step two, preparing phytic acid assembly solution: adding phytic acid with the mass fraction of 0.5% into 40mL of aqueous solution to prepare phytic acid assembly solution;
step three, preparing a composite membrane assembled by phytic acid: soaking the polyacrylonitrile base membrane prepared in the first step in 40mL of the phytic acid assembly solution prepared in the second step for 5min to obtain a base membrane adsorbed by phytic acid, adding 1.5% by mass of ferric chloride, standing at 25 ℃ for assembly for 60min, soaking the assembled composite membrane in deionized water for 10min, taking out the membrane, and carrying out heat treatment on the membrane in an oven at 60 ℃ for 10min to obtain the phytic acid assembled composite nanofiltration membrane 1, wherein a surface electron microscope image of the composite nanofiltration membrane 1 is shown in figure 3.
The water flux of the phytic acid assembled composite nanofiltration membrane 1 prepared in example 1 at an operating pressure of 1bar is 109.8L m-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 95.3%.
Example 2, preparation of phytic acid assembled composite nanofiltration membrane, the preparation process was substantially the same as in example 1, except that: in the third step, the added transition metal salt is changed from ferric chloride with the mass fraction of 1.5% to silver nitrate with the mass fraction of 1.5%, and finally the composite nanofiltration membrane 2 assembled by the phytic acid is obtained.
The water flux of the phytic acid assembled composite nanofiltration membrane 2 prepared in example 2 at an operating pressure of 1bar is 266.1L m-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 41.7%.
Example 3, preparation of the phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, and the difference is only that: in the third step, the added transition metal salt is changed from ferric chloride with the mass fraction of 1.5% to nickel chloride with the mass fraction of 1.5%, and finally the phytic acid assembled composite nanofiltration membrane 3 is obtained.
The water flux of the phytic acid assembled composite nanofiltration membrane 3 prepared in the example 3 under the operation pressure of 1bar is 231.6L m- 2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 49.3%.
Example 4, preparation of the phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, and the difference is only that: in the third step, the added transition metal salt is changed from ferric chloride with the mass fraction of 1.5% to zinc chloride with the mass fraction of 1.5%, and finally the phytic acid assembled composite nanofiltration membrane 4 is obtained.
The water flux of the phytic acid assembled composite nanofiltration membrane 4 prepared in example 4 under the operation pressure of 1bar is 256.1L m- 2h-1bar-1Retention rate of methyl blue (mass fraction 0.01%) in water solutionThe content was found to be 51.9%.
Example 5, preparation of the phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, and the difference is only that: in the third step, the added transition metal salt is changed from ferric chloride with the mass fraction of 1.5% to zirconium nitrate with the mass fraction of 1.5%, and finally the phytic acid assembled composite nanofiltration membrane 5 is obtained.
The water flux of the phytic acid assembled composite nanofiltration membrane 5 prepared in the example 5 under the operation pressure of 1bar is 96.7L m- 2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 96.4%. FIG. 1 is a graph showing the retention rate of a phytic acid assembled composite nanofiltration membrane 1-5 to a methyl blue (the mass fraction of the methyl blue is 0.01%) aqueous solution.
Example 6 preparation of a phytic acid assembled composite nanofiltration membrane, the steps are as follows:
step one, preparation of a polyether sulfone base film: dissolving polyether sulfone in N, N-dimethylformamide to prepare a casting solution containing polyether sulfone with the mass concentration of 15%, stirring at 60 ℃ for 12h, standing at 50 ℃ for defoaming for 12h, cooling to room temperature, pouring the casting solution on a glass plate to scrape a film, putting the glass plate into a water bath at 25 ℃ for solidification to form a film, taking the glass plate down, and soaking the glass plate in deionized water for 24h to obtain a polyether sulfone-based film, wherein the polyether sulfone-based film is shown in figure 5;
step two, preparing phytic acid assembly aqueous solution: same as example 1;
step three, preparing a composite membrane assembled by phytic acid: soaking the polyether sulfone base film prepared in the first step in 40mL of the phytic acid assembly solution prepared in the second step for 5min to obtain a base film adsorbed by phytic acid, adding 1.5% by mass of ferric chloride, standing at 25 ℃ for assembly for 60min, soaking the assembled composite film in deionized water for 10min, taking out the film, and carrying out heat treatment at 60 ℃ for 10min to obtain a phytic acid assembled composite nanofiltration membrane 6, wherein a surface electron microscope image of the phytic acid assembled composite nanofiltration membrane 6 is shown in figure 6.
The water flux of the phytic acid assembled composite nanofiltration membrane 6 prepared in the embodiment 6 under the operation pressure of 1bar is 73.0L m- 2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 96.5%.
Example 7 preparation of phytic acid assembled composite nanofiltration membrane, the preparation process was substantially the same as in example 1 except that: in the first step, the casting solution is changed from the casting solution containing 15% by mass of polyacrylonitrile to the casting solution containing 18% by mass of polyacrylonitrile; finally obtaining the composite nanofiltration membrane 7 assembled by the phytic acid.
The water flux of the phytic acid assembled composite nanofiltration membrane 7 prepared in the example 7 under the operation pressure of 1bar is 100.8L m- 2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 97.3%.
Example 8 preparation of phytic acid assembled composite nanofiltration membranes, the preparation process was substantially the same as in example 7, except that:
in the first step, the stirring temperature of the membrane casting solution is changed from stirring at 60 ℃ for 12 hours to stirring at 50 ℃ for 12 hours, and finally the composite nanofiltration membrane 8 assembled by the phytic acid is obtained.
The phytic acid assembled composite nanofiltration membrane 8 prepared in example 8 has a water flux of 108.8L m at an operating pressure of 1bar-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 94.3%.
Example 9 preparation of phytic acid assembled composite nanofiltration membranes, the preparation process was essentially the same as in example 7, except that:
in the first step, the stirring temperature of the membrane casting solution is changed from stirring at 60 ℃ for 12 hours to stirring at 70 ℃ for 12 hours, and finally the phytic acid assembled composite nanofiltration membrane 9 is obtained.
The phytic acid assembled composite nanofiltration membrane 9 prepared in example 9 has a water flux of 99.8L m at an operating pressure of 1bar-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 98.3%.
Example 10, preparation of phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, except that: in the second step, phytic acid with the mass fraction of 1.0 percent is added into 40mL of aqueous solution to prepare phytic acid assembly solution; finally obtaining the phytic acid assembled composite nanofiltration membrane 10.
The phytic acid assembled composite nanofiltration membrane 10 prepared in example 10 was operated at 1barWater flux at bottom 100.8L m-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 96.3%.
Example 11 preparation of phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, except that: in the second step, phytic acid with the mass fraction of 1.5 percent is added into 40mL of aqueous solution to prepare phytic acid assembly solution; finally obtaining the phytic acid assembled composite nanofiltration membrane 11.
The water flux of the phytic acid assembled composite nanofiltration membrane 11 prepared in the example 11 under the operation pressure of 1bar is 89.8L m-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 98.3%.
Example 12 preparation of phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, except that: in the second step, phytic acid with the mass fraction of 2.0 percent is added into 40mL of aqueous solution to prepare phytic acid assembly solution; finally obtaining the phytic acid assembled composite nanofiltration membrane 12.
The water flux of the phytic acid assembled composite nanofiltration membrane 12 prepared in example 12 under the operation pressure of 1bar is 79.8L m-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 99.9%.
Example 13 preparation of phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, except that: in the third step, the mass fraction of the added ferric chloride is changed from 1.5% to 0.5%, and the phytic acid assembled composite nanofiltration membrane 13 is finally obtained.
The water flux of the phytic acid assembled composite nanofiltration membrane 13 prepared in example 13 at an operating pressure of 1bar is 129.8L m-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 90.8%.
Example 14, preparation of phytic acid assembled composite nanofiltration membrane, the preparation process was substantially the same as in example 1, except that: in the third step, the mass fraction of the added ferric chloride is changed from 1.5% to 1.0%, and the phytic acid assembled composite nanofiltration membrane 14 is finally obtained.
Phytic acid prepared in example 14The water flux of the assembled composite nanofiltration membrane 14 at an operating pressure of 1bar is 119.0L m-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 92.3%.
Example 15 preparation of phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, except that: in the third step, the mass fraction of the added ferric chloride is changed from 1.5% to 2.0%, and the phytic acid assembled composite nanofiltration membrane 15 is finally obtained.
The phytic acid assembled composite nanofiltration membrane 14 prepared in example 15 has a water flux of 95.8L m at an operating pressure of 1bar-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 97.3%.
Example 16 preparation of phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, except that: in the third step, the assembly time after adding the ferric chloride with the mass fraction of 1.5 percent is changed from standing and assembling at 25 ℃ for 60min to 40min, and finally the phytic acid assembled composite nanofiltration membrane 16 is obtained.
The phytic acid assembled composite nanofiltration membrane 16 prepared in example 16 has a water flux of 149.8L m at an operating pressure of 1bar-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 91.3%.
Example 17 preparation of phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, except that: in the third step, the assembly time after adding the ferric chloride with the mass fraction of 1.5 percent is changed from standing at 25 ℃ for assembly for 60min to 80min, and finally the phytic acid assembled composite nanofiltration membrane 17 is obtained.
The phytic acid assembled composite nanofiltration membrane 17 prepared in example 17 has a water flux of 89.8L m at an operating pressure of 1bar-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 98.3%.
Example 18 preparation of phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, except that: in the third step, the heat treatment condition of the membrane taken out of the ionized water is changed from heat treatment at 60 ℃ for 10min to heat treatment at 50 ℃ for 10min, and finally the phytic acid assembled composite nanofiltration membrane 18 is obtained.
The phytic acid assembled composite nanofiltration membrane 18 prepared in example 18 has a water flux of 119.5L m at an operating pressure of 1bar-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 94.3%.
Example 19, preparation of phytic acid assembled composite nanofiltration membrane, the preparation process was substantially the same as in example 1, except that: in the third step, the heat treatment condition of the membrane taken out of the ionized water is changed from heat treatment at 60 ℃ for 10min to heat treatment at 70 ℃ for 10min, and finally the phytic acid assembled composite nanofiltration membrane 19 is obtained.
The phytic acid assembled composite nanofiltration membrane 19 prepared in example 19 has a water flux of 100.8L m at an operating pressure of 1bar-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 96.3%.
Example 20 preparation of phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, except that: in the third step, the heat treatment condition of the membrane taken out of the ionized water is changed from heat treatment at 60 ℃ for 10min to heat treatment at 80 ℃ for 10min, and finally the phytic acid assembled composite nanofiltration membrane 20 is obtained.
The phytic acid assembled composite nanofiltration membrane 20 prepared in example 20 has a water flux of 79.8L m at an operating pressure of 1bar-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 99.3%.
Example 21 preparation of phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, except that: in the third step, the heat treatment condition of the membrane taken out of the ionized water is changed from heat treatment at 60 ℃ for 10min to heat treatment at 60 ℃ for 5min, and finally the phytic acid assembled composite nanofiltration membrane 21 is obtained.
The water flux of the phytic acid assembled composite nanofiltration membrane 21 prepared in the example 21 under the operation pressure of 1bar is 119.8L m-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 92.3%.
Example 22 preparation of phytic acid assembled composite nanofiltration membrane, the preparation process is basically the same as that of example 1, except that: in the third step, the heat treatment condition of the membrane taken out of the ionized water is changed from heat treatment at 60 ℃ for 10min to heat treatment at 60 ℃ for 15min, and finally the phytic acid assembled composite nanofiltration membrane 22 is obtained.
The phytic acid assembled composite nanofiltration membrane 22 prepared in example 22 has a water flux of 99.8L m at an operating pressure of 1bar-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 98.3%.
And (3) preparing a polyacrylonitrile-based membrane in the mode of the first step in the example 1, namely obtaining a comparison membrane.
The comparative membrane prepared in the comparative example had a water flux of 270.1L m at an operating pressure of 1bar-2h-1bar-1The retention rate of the aqueous solution of methyl blue (mass fraction of 0.01%) was 40.1%.
The flux and separation performance of the membranes prepared in the examples and comparative examples of the present invention are compared with those of the comparative membrane prepared in the comparative example as shown in table 1:
TABLE 1
Figure BDA0001723338730000081
Figure BDA0001723338730000091
As can be seen from the data in table 1: in the preparation process of the phytic acid assembled composite nanofiltration membrane, 1, when the mass fraction of the phytic acid is increased, the water flux of the membrane is increased, and the methyl blue rejection rate is reduced; 2. when different types of transition metal salts are added, the membrane water flux is ordered as follows: silver nitrate, zinc chloride, nickel chloride, ferric chloride and zirconium nitrate, and the methyl blue retention rates are ordered as follows: silver nitrate < zinc chloride < nickel chloride < ferric chloride < zirconium nitrate; 3. when the mass fraction of the ferric perchlorate is increased, the water flux of the membrane is reduced, and the methyl blue retention rate is increased; 4. as the assembly time increased, the membrane water flux decreased and the methyl blue rejection increased.
It should be understood that the embodiments and examples discussed herein are illustrative only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.

Claims (5)

1. A method for preparing an ultrathin anti-pollution composite nanofiltration membrane assembled by phytic acid is characterized by comprising the following steps:
step one, preparing a high-molecular porous base membrane: dissolving polyacrylonitrile or polyether sulfone in N, N-dimethylformamide to prepare a casting solution with the mass concentration of 15-18%, stirring at 50-70 ℃, standing and defoaming for 12h, cooling to room temperature, pouring the casting solution on a glass plate to scrape a film, placing the glass plate in a water bath to solidify into a film, taking the glass plate down, and soaking the glass plate in deionized water;
step two, preparing phytic acid assembly solution: adding phytic acid with a certain mass into water to prepare a phytic acid assembling solution with the mass fraction of 0.5-2.0%;
step three, soaking the polyacrylonitrile-based membrane or polyether sulfone-based membrane prepared in the step one in the phytic acid assembly solution in the step two; then adding 0.5-2.0% by mass of transition metal salt, wherein the transition metal salt is any one or combination of more than two of silver nitrate, ferric chloride, zinc chloride, nickel chloride and zirconium nitrate, and standing and assembling at 25 ℃ for 40-80min after adding the transition metal salt to obtain an assembled composite membrane; soaking the assembled composite membrane in deionized water for 10min, taking out the membrane, and carrying out heat treatment at 50-80 ℃ for 5-15min to obtain the phytic acid assembled ultrathin anti-pollution composite nanofiltration membrane.
2. The method for preparing the ultra-thin anti-pollution composite nanofiltration membrane assembled by the phytic acid as claimed in claim 1, wherein in the second step, the mass fraction of the prepared phytic acid assembly solution is 0.5%.
3. The method for preparing the ultra-thin anti-pollution composite nanofiltration membrane assembled by the phytic acid as claimed in claim 1, wherein the transition metal salt in the third step is ferric chloride.
4. The method for preparing the ultra-thin anti-pollution composite nanofiltration membrane assembled by the phytic acid as claimed in claim 1, wherein in the third step, the mass fraction of the added transition metal salt is 1.5%.
5. The method for preparing the ultra-thin anti-pollution composite nanofiltration membrane assembled by the phytic acid as claimed in claim 1, wherein the assembly time in the third step is 60 min.
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