NL2032535A - Composite nanofiltration membrane as well as preparation method and application thereof - Google Patents

Composite nanofiltration membrane as well as preparation method and application thereof Download PDF

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NL2032535A
NL2032535A NL2032535A NL2032535A NL2032535A NL 2032535 A NL2032535 A NL 2032535A NL 2032535 A NL2032535 A NL 2032535A NL 2032535 A NL2032535 A NL 2032535A NL 2032535 A NL2032535 A NL 2032535A
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membrane
phase solution
composite nanofiltration
nanofiltration membrane
present
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NL2032535A
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Dutch (nl)
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NL2032535B1 (en
Inventor
Han Fei
Gui Shuanglin
Wang Yiwen
Xiong Jihai
Fan Min
Jiang Qinliang
Lou Jianquan
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Institute Of Energy Res Jiangxi Academy Of Sciences
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    • 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
    • B01D71/58—Other polymers having nitrogen in the main chain, with or without oxygen or carbon only
    • B01D71/60—Polyamines
    • 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
    • B01D67/00793—Dispersing a component, e.g. as particles or powder, in another component
    • 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
    • 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
    • B01D69/10—Supported membranes; Membrane supports
    • 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
    • B01D69/108—Inorganic support material
    • 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
    • B01D69/12—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
    • 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
    • B01D69/148—Organic/inorganic mixed matrix 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
    • B01D71/56—Polyamides, e.g. polyester-amides
    • 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
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/12—Specific ratios of components used
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2323/00—Details relating to membrane preparation
    • B01D2323/50—Control of the membrane preparation process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/02—Details relating to pores or porosity of the membranes
    • B01D2325/022—Asymmetric membranes
    • B01D2325/023—Dense layer within the membrane
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2325/00—Details relating to properties of membranes
    • B01D2325/36—Hydrophilic membranes
    • 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
    • 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
    • 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
    • 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
    • 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
    • C02F2103/30—Nature of the water, waste water, sewage or sludge to be treated from the textile industry
    • 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

Abstract

The present invention relates to a composite nanofiltration membrane as well as a preparation method and an application thereof. The composite nanofiltration membrane includes a substrate layer, a base membrane layer and a polyamide separating layer which are stacked successively, wherein the base Hembrane layer includes a polysulfone membrane and molybdenum. disulfide oxide dispersed in the polysulfone membrane; the polyamide separating layer is prepared from a water—phase solution and an oil—phase solution through an in—situ interfacial polymerization reaction; the water—phase solution. contains piperazine, and. the oil—phase solution contains trimesoyl chloride. The molybdenum disulfide oxide with hydrophilicity and electronegativity not only increases an efficiency of water passing through the composite nanofiltration membrane, but also generates an electrostatic repulsion effect between the surface of the composite nanofiltration membrane and contaminants, so that the contamination. resistance of the surface of the composite nanofiltration membrane is improved.

Description

COMPOSITE NANOFILTRATION MEMBRANE AS WELL AS PREPARATION METHOD
AND APPLICATION THEREOF
TECHNICAL FIELD
The present invention belongs to the technical field of nano- filtration membranes, and particularly relates to a composite nan- ofiltration membrane as well as a preparation method and an appli- cation thereof.
BACKGROUND ART
With the rapid development of textile printing and dyeing in- dustry, a lot of textile wastewater is generated and discharged every year. The textile wastewater usually contains inorganic salts, dyes and other chemical substances, and these substances will be hazardous to the environment if not treated properly.
Therefore, the separation of dyes and salts from textile wastewater is the key to prevent the wastewater from polluting the ecological environment.
A nanofiltration membrane is a microporous filtration mem- brane with a structurally consistent pore size ranging from 1 nm to 2 nm. The nanofiltration membrane can effectively separate con- taminants with a diameter of between 200 Da and 1,000 Da. At pre- sent, the nanofiltration membrane is usually used in the fields of industrial wastewater treatment (e.g., removal of dyes in dye wastewater), seawater desalination and the like. Membrane separa- tion plays an important role in sewage treatment. It is recognized as an advanced separation technique because of its advantages of simple operation, low energy consumption, low maintenance costs and the like. Compared with other types of membranes, the nanofil- tration membrane has a good capability of intercepting multivalent ions and low molecular weight organic matters and has been uti- lized in a better way in the desalination and recovery of textile wastewater. However, the problem of membrane contamination is in- evitable in water treatment as the nanofiltration membrane is a pressure-driven membrane. In the operation process of the mem-
brane, contaminants (e.g., multivalent ions or dyes) are easily adsorbed on the surface of the membrane and inside membrane pores, the membrane pores are inevitably blocked. As a result, the pure water flux and the removal rate are decreased, the operation life of the membrane is reduced, and the usage cost of the membrane is increased.
SUMMARY
In view of this, the present invention provides a composite nancfiltration membrane as well as a preparation method and an ap- plication thereof. The composite nanofiltration membrane provided by the present invention has a high pure water flux and a good contamination resistance property, so that the service life of the composite nanofiltration membrane is prolonged.
In order to solve the above-mentioned technical problems, the present invention provides a composite nanofiltration membrane, including a substrate layer, a base membrane layer and a polyamide separating layer which are stacked successively, wherein the base membrane layer includes a polysulfone membrane and molybdenum disulfide oxide dispersed in the polysulfone membrane; the polyamide separating layer is prepared from a water-phase solution and an oil-phase solution through an in-situ interfacial polymerization reaction; the water-phase solution contains pipera- zine, and the oil-phase solution contains trimesoyl chloride.
Preferably, the water-phase solution includes the following components based on percentages: piperazine 1-2%; pH regulator 1.5-3.0%; sodium dodecyl sulfonate 0.58-0.62%; water Remaining amount. the oil-phase solution is an n-hexane solution of trimesoyl chloride, and a mass-to-concentration ratio of the trimesoyl chlo- ride to the n-hexane is 0.1-0.5g:1/100 mL.
Preferably, a particle diameter of the molybdenum disulfide oxide is 10-2,000 nm, and a water contact angle of the molybdenum disulfide oxide is 20-45°.
The present invention further provides a method for preparing the composite nanofiltration membrane of the above-mentioned tech- nical solution, including the following steps: mixing organic solvent, organic pore-forming agent, molyb- denum disulfide oxide and polysulfone to obtain a casting solu- tion; after defoaming the casting solution, forming a membrane on the surface of the substrate layer, then soaking the membrane to obtain a base membrane layer to obtain a primary composite nano- filtration membrane; and soaking the primary composite nanofiltration membrane succes- sively in a water-phase solution and an oil-phase solution, per- forming an in-situ interfacial polymerization reaction to obtain a composite nanofiltration membrane; wherein the water-phase solu- tion contains piperazine, and the oil-phase solution contains tri- mesoyl chloride.
Preferably, the defoaming refers to standing at a constant temperature under a vacuum condition, a temperature of the defoam- ing is 25-70°C, a degree of the vacuum is 0.3-0.8 MPa, and a time of the defoaming is 1-8 h.
Preferably, the membrane forming includes membrane casting, air bathing and coagulation bathing; a speed of the membrane cast- ing is 2-5m/ min, and a thickness of the membrane casting is 50- 200um; a temperature of the air bathing is 25-80°C, and a time is 10-240s; and a temperature of the coagulation bathing is 15-40°C, and a time is 4-48h.
Preferably, a time of soaking in the water-phase solution is 10-30 s, and a time of soaking in the oil-phase solution is 10-30 s; and a temperature of the in-situ interfacial polymerization reac- tion is 50-70°C, and a time is 1-5 min.
Preferably, the organic solvent includes one or more of N,N- dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone.
Preferably, the organic pore-forming agent includes one or more of polyethylene glycol, glycerin, propylene glycol and ace-
tone.
The present invention further provides an application of the composite nanofiltration membrane of the above-mentioned technical solution, or the composite nanofiltration membrane obtained by the preparation method of the above-mentioned technical solution in water treatment, dye concentration or seawater desalination.
The present invention provides a composite nanofiltration membrane, including a substrate layer, a base membrane layer and a polyamide separating layer which are stacked successively, wherein the base membrane layer includes a polysulfone membrane and molyb- denum disulfide oxide dispersed in the polysulfone membrane; the polyamide separating layer is prepared from a water-phase solution and an oil-phase solution through an in-situ interfacial polymeri- zation reaction; the water-phase solution contains piperazine, and the oil-phase solution contains trimesoyl chloride. The molybdenum disulfide oxide contained in the base membrane layer of the compo- site nanofiltration membrane provided by the present invention not only adjusts a hydrophilicity of the surface of the composite nan- ofiltration membrane effectively, but also increases an efficiency of water passing through the composite nanofiltration membrane.
Moreover, the molybdenum disulfide oxide realizes relatively high electronegativity of the surface of the composite nanofiltration membrane, so that an electrostatic repulsion is generated between the surface of the composite nanofiltration membrane and contami- nants to reduce accumulation of the contaminants on the surface of the composite nanofiltration membrane, so that a contamination re- sistance of the surface of the composite nanofiltration membrane is improved; the molybdenum disulfide oxide features a layered structure, there are pores between molecular layers of the molyb- denum disulfide oxide, and these pores can act as water channels to enable water molecules to pass through the channels rapidly, thus further improving a pure water flux of the composite nanofil- tration membrane. The polyamide separating layer obtained through the in-situ interfacial polymerization reaction has relatively high compactness, so that a removal rate of the composite nanofil- tration membrane for contaminants (multivalent ions and dyes in wastewater) is improved. In the present invention, a hydrogen bond is formed between the molybdenum disulfide oxide and polyamide, thus compacting a skin layer and further improving the removal rate of the composite nanofiltration membrane for contaminants.
The results of the embodiments show that the removal rate of the 5 modified composite nanofiltration membrane for dye rose Bengal is 99.8%, the removal rate for Na,S0, is 95.3%, and the pure water flux is 27.7 Lm “h'bar™* when a content of the molybdenum disulfide oxide in a PSF ultrafiltration base membrane provided by the pre- sent invention is 0.06 wt.% under an operating pressure of 0.4
MPa.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a structural view of the composite nanofiltration membranes prepared and obtained in example 1 and comparative exam- ple.
FIG. 2 is a membrane pore size distribution graph of the com- posite nanofiltration membranes prepared and obtained in example 2 and comparative example 1.
FIG. 3 is SEM images of a plan and a section of the composite nanofiltration membranes prepared and obtained in example 2 and comparative example 1.
FIG. 4 is a comparative curve graph of normalized fluxes for long-time operation of the composite nanofiltration membranes pre- pared and obtained in example 2 and comparative example 1.
DETAILED DESCRIPTION OF THE EMBODIMENTS
The present invention provides a composite nanofiltration membrane, including a substrate layer, a base membrane layer and a polyamide separating layer which are stacked successively, wherein the base membrane layer includes a polysulfone membrane and molybdenum disulfide oxide dispersed in the polysulfone membrane; the polyamide separating layer is prepared from a water-phase solution and an oil-phase solution through an in-situ interfacial polymerization reaction; the water-phase solution contains pipera- zine, and the oil-phase solution contains trimesoyl chloride.
Unless specially specified, all the raw materials and compo- nents in the present invention are commercially available products well known to those skilled in the art.
In the present invention, the composite nanofiltration mem- brane includes a substrate layer; the substrate layer preferably includes a non-woven fabric. In the present invention, a thickness of the non-woven fabric is preferably 75-150 um, more preferably 80-100 um, and further more preferably 97 um; and a density of the non-woven fabric is preferably 0.73-0.85 g/m’, and more preferably 0.77 g/m’. In the present invention, the non-woven fabric supports the base membrane layer.
In the present invention, the composite nanofiltration mem- brane includes a base membrane layer; a thickness of the base mem- brane layer is preferably 106-118 pm, and more preferably 110-115 um. In the present invention, the base membrane layer is prefera- bly obtained by preparing a membrane from a casting solution in- cluding the following components based on parts by weight: polysulfone 15-30 parts organic solvent 64-90.1 parts molybdenum disulfide oxide 0.01-3 parts organic pore-forming agent 0.01-6 parts
In the present invention, the raw materials for preparing the casting solution for the base membrane layer include 15-30 parts (by weight) of polysulfone (PSF), and preferably 20-25 parts (by weight). In the present invention, the polysulfone is used as a base membrane material, so that a mechanical property of the com- posite nanofiltration membrane is improved.
The parts by weight of the polysulfone are used as a bench- mark, and the raw materials for preparing the casting solution for the base membrane layer include 64-90.1 parts of organic solvent, preferably 70-85 parts, and more preferably 75-81 parts. In the present invention, the organic solvent preferably includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide and N- methylpyrrolidone, and more preferably N,N-dimethylacetamide; when the organic solvent is more than one of the specific substances, there is no special limitation to the proportion of the specific substances in the present invention.
The parts by weight of the polysulfone are used as a bench- mark, and the raw materials for preparing the casting solution in-
clude 0.01-6 parts of organic pore-forming agent, and preferably 1-5 parts. In the present invention, the organic pore-forming agent preferably includes one or more of polyethylene glycol, glycerin, propylene glycol and acetone, and more preferably poly- ethylene glycol, and the polyethylene glycol is preferably poly- ethylene glycol 400; when more than two of the specific options are available for the organic pore-forming agent, there is no spe- cial limitation to the proportion of the specific substances in the present invention, and any proportion may be used.
In the present invention, the organic pore-forming agent can improve a viscosity of the casting solution, so that a compactness of the composite nanofiltration membrane is improved, and a remov- al rate of the composite nanofiltration membrane is increased.
The parts by weight of the polysulfone are used as a bench- mark, and the raw materials for preparing the casting solution for the base membrane layer include 0.01-3 parts of molybdenum disul- fide oxide, preferably 0.03-0.5 part, and more preferably 0.06- 0.12 part. In the present invention, a particle size of the molyb- denum disulfide oxide is preferably 10-2,000 nm, and more prefera- bly 100-800 nm, and a water contact angle of the molybdenum disul- fide oxide is preferably 20-45°, and more preferably 30-40°.
In the present invention, the molybdenum disulfide oxide is preferably prepared and obtained by a Hummers oxidation method.
The method for preparing the molybdenum disulfide oxide pref- erably includes the following steps: performing a first mixing step on molybdenum disulfide and sodium nitrate to obtain a mixture; performing a second mixing step on concentrated sulfuric acid and the mixture to obtain a dispersion solution; performing a third mixing step on the dispersion solution and potassium permanganate for an oxidation reaction to obtain a mo- lybdenum disulfide oxide dispersion solution; and removing impurities from the molybdenum disulfide oxide dis- persion solution, filtering and drying the molybdenum disulfide oxide dispersion solution to obtain molybdenum disulfide oxide.
In the present invention, the first mixing step is performed on molybdenum disulfide and sodium nitrate to obtain a mixture. In the present invention, a mass ratio of the molybdenum disulfide to the sodium nitrate is preferably 2.8-3.2:1, and more preferably 3:1. In the present invention, there is no special limitation to the first mixing step, and an acceptable way is to use a process well known to those skilled in the art and ensure that the molyb- denum disulfide and the sodium nitrate are mixed fully and evenly.
In the present invention, after the mixture is obtained, the second mixing step is performed on concentrated sulfuric acid and the mixture to obtain a dispersion solution. In the present inven- tion, a mass concentration of the concentrated sulfuric acid is preferably 98%; a mass-to-concentration ratio of the molybdenum disulfide to the concentrated sulfuric acid is preferably 2.8-3.2 g:50 mL, and more preferably 3 g:50 mL; a mode of the second mix- ing step is preferably stirring, a speed of the stirring is pref- erably 430-470 r/min, and more preferably 450 r/min, and the time is preferably 11-13 h, and more preferably 12 h.
After the dispersion solution is obtained, the third mixing step is performed on the dispersion solution and potassium perman- ganate for an oxidation reaction to obtain a molybdenum disulfide oxide dispersion solution. In the present invention, a mass ratio of the potassium permanganate to the molybdenum disulfide is pref- erably 1.8-2.2:1, and more preferably 2:1. In the present inven- tion, there is no special limitation to the third mixing step, and an acceptable way is to use a process well known to those skilled in the art and ensure that the potassium permanganate is fully dispersed in the dispersion solution.
In the present invention, the oxidation reaction preferably includes two steps, a temperature of the first step of the oxida- tion reaction is preferably 0-5°C, and more preferably 0-1°C, and a time of the first step of the oxidation reaction is preferably 0.2-1 h, and more preferably 0.5-0.6 h; a temperature of the sec- ond step of the oxidation reaction is preferably 33-37°C, and more preferably 35°C, and a time of the second step of the oxidation reaction is preferably 2.8-3.2 h, and more preferably 3 h. In the present invention, the first step of the oxidation reaction is preferably performed in an ice bath; the second step of the oxida-
tion reaction is preferably performed in an oil bath, and a pro- cess of the oil bathing is preferably performed under a stirring condition. In the present invention, there is no special limita- tion to the stirring, and an acceptable way is to use a process well known to those skilled in the art.
After the molybdenum disulfide oxide dispersion solution is obtained, impurity removal, filtration and drying are performed on the molybdenum disulfide oxide dispersion solution to obtain mo- lybdenum disulfide oxide. In the present invention, the impurity removal preferably includes: adding hydrogen peroxide and hydro- chloric acid successively after the ice bathing of the molybdenum disulfide oxide dispersion solution; in the present invention, de- ionized water is preferably added in the process of the ice bath- ing and after the ice bathing is finished, and a volume-to-mass ratio of the deionized water to the molybdenum disulfide is pref- erably 148-152 mL:3 g, and more preferably 150 mL:3 g. In the pre- sent invention, deionized water accounting for 30-35% of the total amount is preferably added in the process of the ice bathing, and the purpose of adding the deionized water is to dilute concentrat- ed sulfuric acid; after the ice bathing is finished, the remaining deionized water is added, and a temperature of the molybdenum di- sulfide oxide dispersion solution is controlled below 60°C. In the present invention, the process of the ice bathing is preferably performed under a stirring condition. In the present invention, there is no special limitation to the stirring, and an acceptable way 1s to use a process well known to those skilled in the art to achieve the purpose of even stirring.
In the present invention, a mass concentration of the hydro- gen peroxide is preferably 28-32%, and more preferably 30%; a vol- ume-to-mass ratio of the hydrogen peroxide to the molybdenum di- sulfide is preferably 7.8-8.2 mL:3 g, and more preferably 8 mL:3 g. In the present invention, the purpose of adding deionized water and hydrogen peroxide is to remove the excessive potassium perman- ganate in the product system in a more effective way. In the pre- sent invention, a mass concentration of the hydrochloric acid is preferably 0.08-1.2%, and more preferably 0.1%; a volume-to-mass ratio of the hydrogen peroxide to the molybdenum disulfide is preferably 248-252 mL:3 g, and more preferably 250 mL:3 g. In the present invention, the purpose of adding the hydrochloric acid is to remove the metallic elements in the product system.
The present invention has no special restrictions on the fil- tration and drying, and an acceptable way is to use a process well known to those skilled in the art.
In the present invention, a particle size of the molybdenum disulfide oxide is preferably 10-2,000 nm, and more preferably 100-800 nm, and a water contact angle of the molybdenum disulfide oxide is preferably 20-45°, and more preferably 30-40°. In the present invention, the molybdenum disulfide oxide has an excellent hydrophilicity, electronegativity and mechanical property. The ad- dition of molybdenum disulfide oxide can improve the compactness of the composite nanofiltration membrane, and further the removal rate of the composite nancfiltration membrane; the addition of mo- lybdenum disulfide oxide makes the surface of the nanofiltration membrane more hydrophilic and negatively charged, so that a pure water flux of the composite nanofiltration membrane with the modi- fied base membrane is improved; in addition, pores exist between molybdenum disulfide oxide molecules and can act as water channels to enable water molecules to pass through the channels rapidly, thus further improving a pure water flux of the nanofiltration membrane.
In the present invention, a porosity of the base membrane layer is preferably 70-90%, and more preferably 75-85%.
In the present invention, the composite nanofiltration mem- brane further includes a polyamide separating layer; a thickness of the base membrane layer is preferably 80-120 nm, and more pref- erably 100-110 nm. In the present invention, the polyamide sepa- rating layer is prepared from a water-phase solution and an oil- phase solution through an in-situ interfacial polymerization reac- tion. In the present invention, the water-phase solution prefera- bly includes the following components based on mass percentages: piperazine 1-23; pH regulator 1.5-3.0%; sodium dodecyl sulfonate 0.58-0.62%;
water Remaining amount. the water-phase solution preferably includes 1-2% (by weight) of piperazine (PIP), and more preferably 1.3-1.6% (by weight).
The water-phase solution preferably includes 1.5-3.0% (by weight) of pH regulator, and more preferably 2.0-2.5% (by weight).
In the present invention, a pH value of the water-phase solution is preferably 9.8-10.2, and more preferably 10. In the present in- vention, there is no special limitation to the type and dosage of the pH regulator, as long as a pH value of the water-phase solu- tion can satisfy the requirements. In the embodiments of the pre- sent invention, the pH regulator is a mixture of camphorsulfonic acid and triethylamine, and a mass ratio of the camphorsulfonic acid to the triethylamine is 1:1.
The water-phase solution preferably includes 0.58-0.62% (by weight) of sodium dodecyl sulfonate, and more preferably 0.6% (by weight). In the present invention, the sodium dodecyl sulfonate can reduce a surface tension of the base membrane.
The water-phase solution preferably further includes a re- maining amount (percentage by weight) of water. In the present in- vention, the water is preferably deionized water.
In the present invention, the oil-phase solution is prefera- bly an n-hexane solution of trimesoyl chloride (TMC), and a mass- to-concentration ratio of the trimesoyl chloride to the n-hexane is preferably 0.1-0.5 g/100 mL, and more preferably 0.2-0.35 g/100 mL.
In the present invention, a temperature of the in-situ inter- facial polymerization reaction is preferably 50-70°C, and more preferably 55-65°C; a time of the in-situ interfacial polymeriza- tion reaction is preferably 1-5 min, and more preferably 2-4 min.
In the present invention, the interfacial reaction is prefer- ably a reaction between piperazine and trimesoyl chloride to gen- erate polyamide, and a reaction equation is as shown in formula 1:
0 EO 3 ; end W fu 8 smd Ne! x Se] En : i To iF et 3 ox 3 © : . . . .
NH # & i Fully cross-linked pelypiperszine snide oF Ny or” Nong — Noe :
Set Sa : oo SE gy ey pi is oy 3 i ; i Teen Nd AT
Piperazine Lo Co i Hed Ty i Ea Bed Eo
PeIRLIse Triwesoyl chloride Re SR jj Ng Po EER ke 3% SN 1 : SUN gh ; x xv
Wetwork cross-linked past Linear cross-linked part
Formula 1.
In the present invention, the polyamide includes two compo- nents: one is a fully cross-linked polypiperazine amide, and the 5 other is a polypiperazine amide including a network cross-linked part and a linear cross-linked part; in the present invention, there is no special limitation to contents of the two components.
In the present invention, a pH value of the water-phase solu- tion is limited to 9.8-10.2, so that HCl generated in the interfa- cial reaction can be neutralized to promote the interfacial polymerization reaction towards the direction of a positive reac- tion.
The present invention further provides a method for preparing the composite nanofiltration membrane as described in the above- mentioned technical solution, including the following steps: mixing organic solvent, organic pore-forming agent, molyb- denum disulfide oxide and polysulfone to obtain a casting solu- tion; after defoaming the casting solution, forming a membrane on the surface of the substrate layer, then soaking the membrane to obtain a base membrane layer to obtain a primary composite nano- filtration membrane; and soaking the primary composite nanofiltration membrane succes- sively in a water-phase solution and an oil-phase solution, per- forming an in-situ interfacial polymerization reaction to obtain a composite nanofiltration membrane; wherein the water-phase solu- tion contains piperazine, and the oil-phase solution contains tri-
mesoyl chloride.
In the present invention, the organic solvent, organic pore- forming agent, molybdenum disulfide oxide and polysulfone are mixed to obtain the casting solution. In the present invention, the mixing preferably includes the following steps: performing a fourth mixing step on the organic solvent and organic pore-forming agent to obtain a pore-forming agent solu- tion; performing a fifth mixing step on the pore-forming agent so- lution and molybdenum disulfide oxide to obtain a mixed dispersion solution; and performing a sixth mixing step on the mixed dispersion solu- tion and polysulfone to obtain a casting solution.
In the present invention, a fourth mixing step is performed on the organic solvent and organic pore-forming agent to obtain a pore-forming agent solution. In the present invention, the fourth mixing step is preferably performed under a stirring condition, and a speed of the stirring is preferably 300-600 r/min, more preferably 400-500 r/min, and further more preferably 450 r/min; a time of the stirring is preferably 1-5 h, and more preferably 2-3 h. In the present invention, after the fourth mixing step per- formed on the organic solvent and organic pore-forming agent, the organic pore-forming agent can be mixed with the organic solvent uniformly to ensure that the organic pore-forming agent is dis- tributed in the casting solution uniformly, thus enabling the base membrane to have membrane pores distributed in a more uniform man- ner.
In the present invention, after the pore-forming agent solu- tion is obtained, a fifth mixing step is performed on the pore- forming agent solution and molybdenum disulfide oxide to obtain a mixed dispersion solution. In the present invention, the fifth mixing step preferably includes ultrasonic treatment and stirring which are performed successively; a power of the ultrasonic treat- ment is preferably 500-10,000 W, and more preferably 500-2,000W, and a time of the ultrasonic treatment is preferably 2-36 h, and more preferably 4-12 h; a speed of the stirring is preferably 100- 600 r/min, more preferably 300-500 r/min, and further more prefer-
ably 400 r/min; a time of the stirring is preferably 0.5-4 h, and more preferably 1-2 h. In the present invention, the ultrasonic treatment and stirring allow the molybdenum disulfide oxide to be dispersed in the dispersion solution in a more uniform manner.
In the present invention, after the mixed dispersion solution is obtained, a sixth mixing step is performed on the mixed disper- sion solution and polysulfone to obtain a casting solution. In the present invention, the sixth mixing step is preferably performed under a stirring condition, and a speed of the stirring is prefer- ably 50-200 r/min, and more preferably 100-150 r/min; a time of the stirring is preferably 0.5-5 h, and more preferably 1-2 h. In the present invention, the stirring enables polysulfone to be ful- ly dissolved.
In the present invention, all the components can be mixed uniformly by means of mixing step by step, and agglomeration be- tween the components and that between the components and molyb- denum disulfide oxide can be avoided.
In the present invention, after the casting solution is ob- tained and defoamed, a membrane is formed on the surface of the substrate layer, then the membrane is soaked to obtain a base mem- brane layer to obtain a primary composite nanofiltration membrane.
In the present invention, the defoaming is preferably standing un- der the condition of constant temperature and vacuum, and a tem- perature of the defoaming is preferably 25-80°C, and more prefera- bly 50°C; a degree of the vacuum is preferably 0.2-0.9 MPa, more preferably 0.5-0.85 MPa, and further more preferably 0.8 MPa; a time of the defoaming is preferably 1-12 h, more preferably 3-10 h, and further more preferably 4-6 h. In the present invention, the defoaming can remove air bubbles from the casting solution, prevent large cavities from being generated in the composite nano- filtration membrane with modified base membrane, and further re- duce a removal rate.
In the present invention, the membrane forming preferably in- cludes membrane casting, air bathing and coagulation bathing. In the present invention, the membrane casting is preferably per- formed by a scraper on the surface of the substrate layer, and a thickness of the membrane casting is preferably 20-300 um, more preferably 30-150 um, and further more preferably 50-100 um. In the present invention, an ambient temperature of the membrane casting is preferably 24-26°C, and more preferably 25°C, and an am- bient relative humidity of the membrane casting is preferably 30- 80%, and more preferably 30-50%. In the present invention, a speed of the membrane casting is preferably 1-5 m/min, and more prefera- bly 1.5-3 m/min, the scraper preferably contains a groove, and a depth of the groove is preferably 50-350 um, specifically 50 pum, 100 um, 150 Hm, 200 pm, 250 pm and 300 um. In the present inven- tion, the process after the membrane casting preferably further includes the following steps: evaporating the product obtained af- ter membrane casting in air at 70-80°C for 0.45-0.55 min, then cur- ing the product in water. In the present invention, the water is preferably tap water, and a temperature of the water is preferably normal temperature, and more preferably 23-25°C; a time of the cur- ing is preferably 0.4-0.6 min, and more preferably 0.5 min.
In the present invention, a temperature of the air bathing is preferably 25-90°C, more preferably 60-90°C, and further more pref- erably 80°C, and a time is preferably 5-320 s, more preferably 20- 60 s, and further more preferably 30 s. A temperature of the coag- ulation bath is preferably 15-50°C, more preferably 20-30°C, and further more preferably 25°C, and a time is preferably 0.1-48 h, more preferably 0.5-24 h, and further more preferably 10-12 h. The coagulation bath preferably includes one or more of tap water, ethanol, acetone and dimethylacetamide, and more preferably a mixed solution of tap water, dimethylacetamide, ethanol and ace- tone, or tap water. In the present invention, when more than two of the specific substances are included in the coagulation bath, there is no special limitation to the proportion of the specific substances, and any proportion is acceptable.
In the present invention, the soaking treatment preferably includes the following steps: soaking the product after membrane forming in pure water and a glycerol water-phase solution with a mass concentration of 30% successively, taking the product out and drying the product in the air to obtain the primary composite nan- ofiltration membrane. In the present invention, a time of scaking in the pure water is preferably 47-49 h, and more preferably 48 h, a time of soaking in the glycerol water-phase solution is prefera- bly 12-48 h, and more preferably 24 h, and a temperature of the soaking is preferably 24-28°C, and more preferably 25°. In the present invention, the product after membrane forming is soaked in pure water for the purpose of dissolving the organic pore-forming agent in the pure water and ensuring the formation of membrane pores in the primary composite nanofiltration membrane; in the present invention, the product after membrane forming is scaked in the glycerin water-phase solution with a mass concentration of 30% for the purpose of preventing decrease in the pure water flux due to contraction of the membrane pores in the base membrane.
In the present invention, after the primary composite nano- filtration membrane is obtained and soaked in a water-phase solu- tion and an oil-phase solution successively, an in-situ interfa- cial polymerization reaction is performed to obtain the composite nanofiltration membrane. Before soaking, the method of the present invention further preferably includes the following steps: soaking the primary composite nanofiltration membrane in water, and then rinsing and drying the primary composite nanofiltration membrane.
In the present invention, the water is preferably deionized water; a time of the soaking is preferably 1-6 h, and more preferably 2-5 h. In the present invention, a solvent for the rinsing is prefera- bly deionized water. In the present invention, the drying is pref- erably drying in the air. In the present invention, residual poly- ethylene glycol on a surface of the nanofiltration membrane can be removed by soaking and rinsing.
In the present invention, the water-phase solution preferably includes 1-2% (by weight) of piperazine (PIP), and more preferably 1.3-1.6% (by weight); preferably includes 1.5-3.0% (by weight) of camphorsulfonic acid, and more preferably 2.0-2.5% (by weight); preferably includes 1.5-3.0% (by weight) of triethylamine, and more preferably 2.0-2.5% (by weight); preferably includes 0.58- 0.62% (by weight) of sodium dodecyl sulfonate, and more preferably 0.6% (by weight); and further preferably includes a remaining amount of water. In the present invention, the water is preferably deionized water. In the present invention, a time of soaking the primary composite nanofiltration membrane in the water-phase solu- tion is preferably 10-30 s, and more preferably 20-30 s. In the present invention, there is no special limitation to the amount of the water-phase solution, as long as the primary composite nano- filtration membrane can be immersed. After the primary composite nanofiltration membrane is scaked in the water-phase solution and taken out, the method of the present invention preferably further includes the following step: removing excessive water-phase solu- tion from the surface of the primary composite nanofiltration mem- brane after soaking is completed. In the present invention, the removal of excessive water-phase solution from the surface of the primary composite nanofiltration membrane preferably includes the following three modes: the first mode is blow-drying of excessive water-phase solution; the second mode is natural drying in the air; and the third mode is adsorption of excessive water-phase so- lution with facial tissues.
In the present invention, the oil-phase solution is prefera- bly an n-hexane solution of trimesoyl chloride (TMC), and a mass- to-concentration ratio of the trimesoyl chloride to the n-hexane is preferably 0.1-0.5 g/100 mL, and more preferably 0.2-0.35 g/100 mL. In the present invention, a time of soaking the primary compo- site nanofiltration membrane (soaked in the water-phase solution) in the oil-phase solution is preferably 10-30 s, and more prefera- bly 15-20 s. In the present invention, there is no special limita- tion to the amount of the oil-phase solution, as long as the pri- mary composite nanofiltration membrane can be immersed in the oil- phase solution. After the primary composite nanofiltration mem- brane is soaked in the oil-phase solution and taken out, the meth- od of the present invention preferably further includes the fol- lowing step: removing excessive oil-phase solution from the sur- face of the primary composite nanofiltration membrane after soak- ing is completed. In the present invention, the mode for removing excessive oil-phase solution is the same as that for removing ex- cessive water-phase solution, which will not be repeated here.
In the present invention, a temperature of the in-situ inter- facial polymerization reaction is preferably 50-70°C, and more preferably 55-65°C; a time is preferably 1-5 min, and more prefera-
bly 2-3 min.
After the composite nanofiltration membrane is obtained, the composite nanofiltration membrane is preferably stored in deion- ized water in the present invention.
In the present invention, a formation rate of the polyamide separating layer is controlled by controlling the concentrations and reaction times of the water-phase and oil-phase, so that the strength of the polyamide separating layer is improved. In the present invention, the higher the formation rate of polyamide is, the easier a dense skin layer is formed, but too fast formation will produce skin layer defects.
The present invention further provides an application of the composite nanofiltration membrane of the above-mentioned technical solution, or the composite nanofiltration membrane obtained by the preparation method of the above-mentioned technical solution in water treatment, dye concentration or seawater desalination. In the present invention, there is no special requirement for the mode of the application, and a conventional mode in the art may be used.
In order to further explain the present invention, the tech- nical solution provided by the present invention will be described below in detail in conjunction with the embodiments, but these em- bodiments cannot be construed as a limitation to the protection scope of the present invention.
Example 1
Preparation of molybdenum disulfide oxide: 3 g of molybdenum disulfide and 1 g of sodium nitrate were mixed to obtain a mixture. 50 mL of concentrated sulfuric acid with a mass concentration of 98% was mixed with the mixture and stirred at a speed of 450 r/min for 12 h to obtain a dispersion solution.
Under ice bathing condition, 6 g of potassium permanganate was added to the dispersion solution to perform a first step of oxidation reaction; after reaction for 30 min, a second step of oxidation reaction was performed in an oil bath at 35°C for 3 h to obtain a molybdenum disulfide oxide dispersion solution; the oil bathing process is accompanied by stirring.
Impurity removal, filtration and drying were performed on the molybdenum disulfide oxide dispersion solution successively to ob- tain molybdenum disulfide oxide; the impurity removal included the following steps: under a stirring condition, ice bathing was per- formed on the molybdenum disulfide oxide dispersion solution, 50 mL of deionized water was added to the molybdenum disulfide oxide dispersion solution in the process of ice bathing, and after stir- ring for 30 min, the ice bathing was stopped; 100 mL of deionized water was continuously added to the molybdenum disulfide oxide dispersion solution, and a temperature of the dispersion solution was controlled below 60°C; after 8 mL of hydrogen peroxide with a mass concentration of 30% was added, 250 mL of hydrochloric acid with a mass concentration of 0.1% was added.
N,N-dimethylacetamide and polyethylene glycol 400 were mixed, and the mixture was stirred for 2 h at a speed of 450 r/min to ob- tain a mixed solution; ultrasonic treatment and stirring were per- formed on the mixed solution and molybdenum disulfide oxide suc- cessively to obtain a dispersion solution, wherein a power of the ultrasonic treatment was 500 W, a time of the ultrasonic treatment was 4 h, a speed of the stirring was 400 r/min, and a time of the stirring was 2 h; the dispersion solution was mixed with polysul- fone, and the mixture was stirred for 2 h at a speed of 150 r/min to obtain a casting solution; in the casting solution, a mass per- centage of the polyethylene glycol 400 was 1%, a mass percentage of the molybdenum disulfide oxide was 0.03%, a mass percentage of the polysulfone was 18%, and a mass percentage of the N,N- dimethylacetamide was 80.97%.
After the casting solution stood at a temperature of 50°C and a vacuum degree of 0.8 MPa for 4 h, the casting solution was ap- plied to a non-woven fabric surface with a thickness of 97 um and a density of 0.77 g/m’ in an environment with a temperature of 25°C and a relative humidity of 50% by using a scraper with a groove depth of 100 um, membrane casting was performed at a speed of 1.5 m/ min, the casting solution was evaporated in the air at 80°C for 0.5 min, and then the product was put into tap water at 25°C for curing for 0.5 h before scaking treatment. The soaking treatment was performed according to the following steps: the cured product was put into pure water at 25°C and soaked for 48 h, then put into a glycerin aqueous solution with a mass concentration of 30% and a temperature of 25°C and soaked for 24 h, and finally a membrane was taken out and dried in the air to obtain a primary composite nano- filtration membrane.
A water-phase solution was prepared, wherein a mass concen- tration of camphorsulfonic acid was 1.5%, a mass concentration of triethylamine was 1.5%, a mass concentration of piperazine was 1.63, and a mass concentration of sodium dodecyl sulfonate was 0.6%; an oil-phase solution was prepared, wherein a mass-to- concentration ratio of the trimesoyl chloride to the n-hexane was 0.35 g:100 mL.
After being soaked in deionized water for 2 h, the primary composite nanofiltration membrane was rinsed with deionized water, and the rinsed primary composite nanofiltration membrane was dried in the air; after being soaked in a water-phase solution for 30 s, the dried primary composite nanofiltration membrane was taken out, excessive water-phase solution on the surface of the nanofiltra- tion membrane was adsorbed with facial tissue, the nanofiltration membrane was soaked in an oil-phase solution for 20 s and taken out, excessive oil-phase solution on the surface of the nanofil- tration membrane was adsorbed with facial tissue, and an in-situ interfacial polymerization reaction was performed at 60°C for 2 min to obtain a composite nanofiltration membrane.
Examples 2-4
The composite nanofiltration membrane was prepared according to the method of example 1, and the difference was that the raw materials of the casting solution were added according to the pro- portion in Table 1;
Table 1 Raw Material Proportion of Casting Solution in Exam- ples 1-4 and Comparative Example 1
Base Mem- Polyethylene Molybdenum Polysulfone (%) | Dimethylacetamide brane No. Glycol 400 (%) Disulfide Oxide (%) (%)
Comparative 1 0 18 81
Comparative Example 1
The composite nanofiltration membrane was prepared according to the method of example 1, and the difference was that molybdenum disulfide oxide was not added to the casting solution, a mass per- centage of the polyethylene glycol 400 in the casting solution was 1%, a mass percentage of the polysulfone was 18%, and a mass per- centage of the N,N-dimethylacetamide was 81%.
Comparative Example 2
The composite nanofiltration membrane was prepared according to the method of example 1, and the difference was that the inter- facial polymerization reaction was not performed on the surface of the base membrane layer, that is, the obtained composite nanofil- tration membrane did not contain the polyamide separating layer.
In the present invention, the results of the pure water flux, pore size, contact angle and removal rate for sodium sulfate, so- dium chloride and rose Bengal of the composite nanofiltration mem- brane prepared in examples 1-4 and comparative examples 1 and 2 as tested according to GB/T 34242-2017 are listed in Table 2. In the present invention, the composite nanofiltration membrane prepared and obtained in examples 1-4 and comparative examples 1 and 2 was pre-pressed at a pressure of 0.25 MPa for 1 h before the removal rate was tested.
Table 2 Performance of Composite Nanofiltration Membrane Pre- pared and Obtained in Examples 1-4 and Comparative Examples 1 and 2
Example Pure Wa- | Pore Contact Retention Rate (%) ter Flux Size Angle (°) Rose Ben- | Na,SO, Nacl (500 (LM?H%) | (nm) gal (500 (500 ppm) | ppm) ppm)
Comparative | 14.3 0.56 64.20 99.0 84.0 18.4 er | co
Comparative | 164.3 12.0 59.3 0.61 1.42 0.54 me
According to the results in Table 2, a pure water flux of the composite nanofiltration membrane provided in the present inven- tion was 13.4-27.7 Lmh'ibar'*, a removal rate for sodium sulfate was 84-95.6%, a removal rate for rose Bengal was 66.2-99.8%, the composite nanofiltration membrane had a good pure water flux and dye removal rate, and the composite nanofiltration membrane pro- vided in the present invention has a good separation performance.
A structural view of the composite nanofiltration membranes prepared and obtained in example 1 and comparative example 1 is shown in FIG. 1. In the figure, an upper route shows a structural view of the base membrane and composite nanofiltration membrane prepared and obtained in comparative example 1; a lower route shows a structural view of the base membrane and composite nano- filtration membrane prepared and obtained in example 1.
A membrane pore size distribution graph obtained by testing the membrane pore size distribution of the composite nanofiltra- tion membrane prepared and obtained in example 2 and comparative example 1 is shown in FIG. 2. According to FIG. 2, the pore size distribution of the composite nanofiltration membrane prepared and obtained in example 2 was narrower, mainly concentrated between 0.1 nm and 0.5 nm, so the composite nanofiltration membrane showed a better interception performance.
SEM images obtained by scanning electron microscopy of the plane and section of the composite nanofiltration membranes pre-
pared and obtained in example 2 and comparative example 1 are shown in FIG. 3. According to FIG. 3, both the surface and the section of the composite nanofiltration membrane prepared and ob- tained in example 2 changed greatly as compared with those in com- parative example 1. More bulges appeared on the surface of the composite nanofiltration membrane prepared and obtained in the present invention because there were more hydrophilic lamellar structures of molybdenum disulfide oxide on the surface of the base membrane.
A long-time operation status of the composite nanofiltration membranes prepared and obtained in example 2 and comparative exam- ple 1 in separation of actual wastewater was tested according to the following method by taking the actual wastewater of industrial rare earth as the wastewater to be treated: a rare earth wastewater solution was continuously filtered under a pressure of 0.4 MPa, and a flux was recorded every 1 h. The results are listed in Table 3.
Table 3 Fluxes of Rare Earth Wastewater Filtered by Composite
Nanofiltration Membranes Prepared and Obtained in Example 2 and
Comparative Example 1
Example Example 2 Comparative Example - mm 7 wo fw ew mo few ow
A comparative curve graph of long-time operation fluxes of the composite nanofiltration membranes prepared and obtained in example 2 and comparative example 1 was drawn according to data in
Table 3, as shown in FIG. 4. According to FIG. 4, the flux of the composite nanofiltration membrane provided by the present inven- tion was higher than that of the composite nanofiltration membrane in comparative example 1 in the long-time operation process of ra- re earth metallurgy wastewater filtration, and the composite nano- filtration membrane provided by the present invention had higher contamination resistance.
Although the above-mentioned embodiments provide a detailed description of the present invention, such embodiments are only a part of, not all of, the embodiments of the present invention.
Other embodiments may also be obtained according to these embodi- ments without making creative efforts, and all the embodiments shall fall into the protection scope of the present invention.

Claims (10)

CONCLUSIESCONCLUSIONS 1. Composiet nanofiltratiemembraan, omvattende een substraatlaag, een basismembraanlaag en een scheidingslaag van polyamide die ach- tereenvolgens zijn gestapeld, waarbij de basismembraanlaag omvat een polysulfonmembraan en molybdeen- disulfideoxide gedispergeerd in de polysulfonmembraan; de scheidingslaag van polyamide wordt bereid uit een oplossing in de waterfase en een oplossing in de oliefase door een in-situ grensvlakpolymerisatiereactie; de waterfase-oplossing bevat pi- perazine en de oliefase-oplossing bevat trimesoylchloride.A composite nanofiltration membrane comprising a substrate layer, a base membrane layer and a polyamide separation layer stacked sequentially, the base membrane layer comprising a polysulfone membrane and molybdenum disulfide oxide dispersed in the polysulfone membrane; the polyamide separating layer is prepared from an aqueous phase solution and an oil phase solution by an in-situ interfacial polymerization reaction; the aqueous phase solution contains piperazine and the oil phase solution contains trimesoyl chloride. 2. Composiet nanofiltratiemembraan volgens conclusie 1, waarbij de waterfase-oplossing de volgende componenten omvat op basis van ge- wichtspercentages: piperazine 1 tot 2%; pH-regelaar 1,5 tot 3,0%; natriumdodecylsulfonaat 0,58 tot 0,623; water Resterende hoeveelheid; de oliefase-oplossing is een n-hexaanoplossing van trimesoylchlo- ride en een massa-tot-concentratie verhouding van het trimesoyl- chloride tot het n-hexaan is (0,1 tot 0,5) g:1/100 ml.A composite nanofiltration membrane according to claim 1, wherein the aqueous phase solution comprises the following components by weight percentage: piperazine 1 to 2%; pH adjuster 1.5 to 3.0%; sodium dodecyl sulfonate 0.58 to 0.623; water Remaining amount; the oil phase solution is an n-hexane solution of trimesoyl chloride and a mass-to-concentration ratio of the trimesoyl chloride to the n-hexane is (0.1 to 0.5) g:1/100 ml. 3. Composiet nanofiltratiemembraan volgens conclusie 1, waarbij een deeltjesdiameter van het molybdeendisulfideoxide 10 tot 2.000 nm is, en een watercontacthoek van het molybdeendisulfideoxide 20 tot 45° is.The composite nanofiltration membrane according to claim 1, wherein a particle diameter of the molybdenum disulfide oxide is 10 to 2,000 nm, and a water contact angle of the molybdenum disulfide oxide is 20 to 45°. 4. Werkwijze voor het vervaardigen van de composiet nanofiltratie- membraan volgens een van de conclusies 1 tot 3, omvattende de vol- gende stappen: het mengen van organisch oplosmiddel, organisch porievormend mid- del, molybdeendisulfideoxide en polysulfon om een gietoplossing te verkrijgen; na het ontschuimen van de gietoplossing, het vormen van een mem- braan op het oppervlak van de substraatlaag, het vervolgens onder-A method for manufacturing the composite nanofiltration membrane according to any one of claims 1 to 3, comprising the steps of: mixing organic solvent, organic pore-forming agent, molybdenum disulfide oxide and polysulfone to obtain a casting solution; after defoaming the casting solution, forming a membrane on the surface of the substrate layer, then sub- dompelen van de membraan om een basismembraanlaag te verkrijgen om een primair composiet nanofiltratiemembraan te verkrijgen; en het achtereenvolgens onderdompelen van de primaire composiet nano- filtratiemembraan in een waterfase-oplossing en een oliefase- oplossing, het uitvoeren van een in-situ grensvlakpolymerisatiere- actie om een composiet nanofiltratiemembraan te verkrijgen; waar- bij de waterfase-oplossing piperazine bevat en de oliefase- oplossing trimesoylchloride bevat.dipping the membrane to obtain a base membrane layer to obtain a primary composite nanofiltration membrane; and sequentially immersing the primary composite nanofiltration membrane in an aqueous phase solution and an oil phase solution, conducting an in-situ interfacial polymerization reaction to obtain a composite nanofiltration membrane; wherein the aqueous phase solution contains piperazine and the oil phase solution contains trimesoyl chloride. 5. Werkwijze voor het vervaardigen volgens conclusie 4, waarbij het ontschuimen verwijst naar het laten staan bij een constante temperatuur onder vacuüm, een temperatuur van het ontschuimen 25 tot 70 °C is, een vacuümgraad 0,3 tot 0,8 MPa is en een tijd van de ontschuiming 1 tot 8 uur is.The manufacturing method according to claim 4, wherein the defoaming refers to standing at a constant temperature under vacuum, a defoaming temperature is 25 to 70°C, a vacuum degree is 0.3 to 0.8 MPa, and a defoaming time is 1 to 8 hours. 6. Werkwijze voor het vervaardigen volgens conclusie 4, waarbij de membraanvorming membraangieten, luchtbaden en coagulatiebaden om- vat; een snelheid van het membraangieten 2 tot 5 m/min is, en een dikte van het membraanafgietsel 50 tot 200 pm is; een temperatuur van het luchtbad 25 tot 80 °C is, en een tijd 10 tot 240 s is; en een temperatuur van het coagulatiebad 15 tot 40 °C is, en een tijd 4 tot 48 uur is.The manufacturing method according to claim 4, wherein the membrane formation comprises membrane casting, air baths and coagulation baths; a membrane molding speed is 2 to 5 m/min, and a membrane molding thickness is 50 to 200 µm; a temperature of the air bath is 25 to 80°C, and a time is 10 to 240 s; and a temperature of the coagulation bath is 15 to 40°C, and a time is 4 to 48 hours. 7. Werkwijze voor het vervaardigen volgens conclusie 4, waarbij een onderdompelingstijd in de waterfase-oplossing 10 tot 30 s is en een onderdompelingstijd in de oliefase-oplossing 10 tot 30 s is; en een temperatuur van de in-situ grensvlakpolymerisatiereactie 50 tot 70 °C is, en een tijd 1 tot 5 min is.The manufacturing method according to claim 4, wherein an immersion time in the aqueous phase solution is 10 to 30 s and an immersion time in the oil phase solution is 10 to 30 s; and a temperature of the in-situ interfacial polymerization reaction is 50 to 70°C, and a time is 1 to 5 minutes. 8. Werkwijze voor het vervaardigen volgens conclusie 4, waarbij het organische oplosmiddel een of meer van N,N-dimethylformamide, N,N-dimethylaceetamide en N-methylpyrrolidon omvat.The manufacturing process according to claim 4, wherein the organic solvent comprises one or more of N,N-dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone. 9. Werkwijze voor het vervaardigen volgens conclusie 4, waarbij het organische poriënvormende middel een of meer van polyethyleen-The manufacturing process of claim 4, wherein the organic pore-forming agent is one or more of polyethylene glycol, glycerine, propyleenglycol en aceton omvat.glycol, glycerin, propylene glycol and acetone. 10. Toepassing van de composiet nanofiltratiemembraan volgens een van de conclusies 1 tot 3 of de composiet nanofiltratiemembraan bereid en verkregen door de werkwijze voor het vervaardigen vol- gens een van de conclusies 4 tot 9 bij waterbehandeling, kleur- stofconcentratie of zeewaterontzilting.Use of the composite nanofiltration membrane according to any one of claims 1 to 3 or the composite nanofiltration membrane prepared and obtained by the manufacturing method according to any one of claims 4 to 9 in water treatment, dye concentration or sea water desalination.
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