CN112827370B - High-flux composite nanofiltration membrane and preparation method thereof - Google Patents

High-flux composite nanofiltration membrane and preparation method thereof Download PDF

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CN112827370B
CN112827370B CN202110069536.9A CN202110069536A CN112827370B CN 112827370 B CN112827370 B CN 112827370B CN 202110069536 A CN202110069536 A CN 202110069536A CN 112827370 B CN112827370 B CN 112827370B
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soybean protein
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polysulfone
layer
nanofiltration membrane
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CN112827370A (en
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孔新
单连杰
陈良
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Entai Environmental Technology Changzhou Co ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • 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
    • B01D67/0006—Organic membrane manufacture by chemical reactions
    • 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
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    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
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    • Y02A20/131—Reverse-osmosis

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Abstract

The invention discloses a high-flux composite nanofiltration membrane and a preparation method thereof. The nanofiltration membrane comprises a polysulfone supporting layer, a polyamide desalting layer and a soybean protein adhesive layer between the polysulfone supporting layer and the polyamide desalting layer; the soybean protein adhesive layer is formed by solidifying soybean protein liquid; the soybean protein liquid comprises the following components: 1.0-40.0 wt% of soybean protein powder, 0.01-5.0 wt% of alkaline substance, 0.01-3.0 wt% of surfactant and the balance of water. Preparation: (1) preparing a polysulfone supporting layer; (2) preparing soybean protein liquid according to the components, and then heating; (3) coating the soybean protein liquid on a polysulfone supporting layer, standing and drying to obtain a soybean protein adhesive layer; (4) adding piperazine and an acid absorbent into water, and stirring to obtain an aqueous phase liquid; (5) adding trimesoyl chloride into an organic solvent, and stirring to obtain an oil phase liquid; (6) and (3) soaking the polysulfone supporting layer containing the soy protein adhesive layer in aqueous phase liquid, then placing the polysulfone supporting layer in oil phase liquid for interfacial polymerization, drying and washing to obtain the high-flux composite nanofiltration membrane.

Description

High-flux composite nanofiltration membrane and preparation method thereof
Technical Field
The invention relates to the technical field of water treatment membranes, in particular to a high-flux composite nanofiltration membrane and a preparation method thereof.
Background
Nanofiltration is a pressure-driven membrane separation process between reverse osmosis and ultrafiltration, and is generally prepared by an interfacial polymerization technique, i.e., a water phase and an oil phase which are insoluble with each other are contacted at an interface to complete a cross-linking reaction of monomers in the two phases, and a formed dense desalination layer is attached to a porous support layer. In the early application stage of the membrane technology, nanofiltration is often regarded as a loose reverse osmosis membrane, and compared with the reverse osmosis technology, the reverse osmosis membrane has a similar preparation process, but has the advantages of higher water flux, lower rejection rate on salt ions, low operation pressure and less energy consumption, and simultaneously has selective screening capacity on macromolecules and micromolecules within the molecular weight of 200-1000, and monovalent salt and divalent salt.
The two aqueous phase monomers most commonly used in the preparation of commercial composite nanofiltration membranes at present are meta-phenylenediamine (MPD) and piperazine (PIP), respectively. Research shows that MPD and PIP have obvious difference in separating performance of corresponding nanofiltration membrane prepared through reaction with polyacyl chloride due to different molecular structures. MPD is generally used as a water-phase reaction monomer in the preparation process of the reverse osmosis membrane, the nanofiltration membrane prepared based on the MPD monomer has high overall desalination rate and is generally called as a desalination nanofiltration membrane, and the nanofiltration membrane prepared by using the reaction of PIP and trimesoyl chloride (TMC) has high selective screening capacity and is generally called as a salt separation nanofiltration membrane.
With the increase of water flux of commercial reverse osmosis membranes, especially the increasing popularization of high-flux household reverse osmosis membranes in recent two years, the advantages of salt separation nanofiltration membranes prepared based on PIP monomers in the aspect of water flux begin to disappear, and salt separation nanofiltration membranes with higher flux need to be developed to adapt to the development of markets. In order to improve the water flux of the salt separation nanofiltration membrane, the concentrations of the reactive monomers in the two phases can be reduced so as to reduce the crosslinking degree and the thickness of the formed desalting layer, but the reduction of the crosslinking degree and the thickness of the desalting layer can weaken the bonding strength between the desalting layer and the porous support layer, and the service life of the nanofiltration membrane is influenced. In addition, the addition of macromolecular substances and two/three-dimensional nano composite materials in the water phase is also a common method for preparing the high-flux composite nanofiltration membrane. Chinese patent CN 108176241A adds the aquaporin vesicles with macromolecular three-dimensional structures into aqueous phase solution, and embeds the aquaporin vesicles into a polyamide layer through interfacial polymerization reaction, thereby greatly improving the water flux of the nanofiltration membrane. Chinese patent CN 105617888A uses the same method to increase the water flux of the membrane by adding graphene oxide to the aqueous phase to embed it in the polyamide layer. The addition of water channel protein vesicles, graphene oxide and the like in the water phase similarly reduces the degree of crosslinking of the desalting layer, and the protein vesicles and the graphene oxide are easily separated from the polyamide layer during use, so that the membrane retention performance is remarkably reduced. Therefore, how to ensure the firm combination between the ultrathin desalination layer and the polysulfone supporting layer while improving the water flux of the nanofiltration membrane and not causing the reduction of the stability of the membrane is a problem which is urgently needed to be solved for preparing the high-flux composite nanofiltration membrane.
Disclosure of Invention
Compared with a commercial nanofiltration membrane, the nanofiltration membrane provided by the invention has the advantages of remarkable water flux advantage and stable performance; the invention also aims to provide a preparation method of the high-flux composite nanofiltration membrane, which has the advantages of simple process, safety, environmental protection, low cost of used materials and good commercial application prospect.
The invention is realized by the following technical scheme:
the high-flux composite nanofiltration membrane is characterized by comprising a polysulfone supporting layer, a soybean protein adhesive layer and a polyamide desalting layer; the soybean protein adhesive layer is arranged between the polysulfone supporting layer and the polyamide desalting layer; the soybean protein adhesive layer is formed by drying and solidifying soybean protein liquid prepared from soybean protein powder; and the soybean protein liquid comprises the following components in parts by weight: 1.0-40.0 wt% of soybean protein powder, 0.01-5.0 wt% of alkaline substance, 0.01-3.0 wt% of surfactant and the balance of water. Specifically, the soybean protein adhesive layer introduced by the invention can enhance the bonding strength between the polyamide desalting layer and the polysulfone supporting layer, and can also obviously improve the water flux of the nanofiltration membrane and obtain higher water permeability. The nanofiltration membrane prepared by the invention has a rejection rate of more than 97% to 2000ppm magnesium sulfate under standard test conditions, has a water flux of more than 45GFD, and has long-term use stability.
Further, the soybean protein liquid comprises the following components in parts by weight: 5.0-20.0 wt% of soybean protein powder, 0.02-1.0 wt% of alkaline substance, 0.1-1.0 wt% of surfactant and the balance of water.
Further, the alkaline substance is selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, calcium hydroxide and magnesium hydroxide; the surfactant is at least one selected from Sodium Dodecyl Sulfate (SDS), sodium dodecyl sulfate and Sodium Dodecyl Benzene Sulfonate (SDBS).
A preparation method of a high-flux composite nanofiltration membrane comprises the following steps:
(1) preparing a polysulfone support layer: dissolving polysulfone, stirring, and standing to obtain a polysulfone solution; uniformly coating the polysulfone solution on a support material, then carrying out phase separation in a water bath, and curing to form a polysulfone support layer;
(2) preparing soybean protein liquid: adding the soybean protein powder, the alkaline substance and the surfactant into water and stirring to obtain a soybean protein liquid; then heating the soybean protein liquid, and keeping the temperature for later use after heating;
(3) preparing a soy protein adhesive layer: uniformly coating the soybean protein liquid on the polysulfone supporting layer, standing, removing redundant liquid, drying, and curing on the polysulfone supporting layer to obtain a soybean protein adhesive layer;
(4) preparing a water phase liquid: adding piperazine and an acid absorbent into water, and stirring to obtain an aqueous phase liquid;
(5) preparing an oil phase liquid: adding trimesoyl chloride into an organic solvent and stirring to obtain an oil phase liquid; the organic solvent is at least one of n-hexane, cyclohexane, ethylcyclohexane, n-heptane and isoparaffin solvent;
(6) preparing a polyamide desalting layer: and (3) placing the polysulfone supporting layer containing the soybean protein adhesive layer in the water phase liquid for soaking, then placing the polysulfone supporting layer in the oil phase liquid for interfacial polymerization reaction, finally removing surface liquid, drying and washing to obtain the high-flux composite nanofiltration membrane.
Further, step (1) preparing a polysulfone support layer: adding polysulfone into a polymer solvent for dissolving, mechanically stirring for 1-3 hours, and then standing for 8-12 hours to obtain a polysulfone solution; uniformly coating the polysulfone solution on a support material, then carrying out phase separation for 15-25 seconds in a water bath at the temperature of 20-30 ℃, and curing to form a polysulfone support layer; the polymer solvent is any one of N, N-dimethylacetamide and N, N-dimethylformamide; the polysulfone accounts for 10-20 wt% of the sulfone solution; the supporting material is non-woven fabric.
Further, preparing the soybean protein liquid in the step (2): adding the soybean protein powder, the alkaline substance and the surfactant into water, and uniformly stirring at room temperature to obtain a soybean protein liquid; and then heating the soybean protein liquid to 50-70 ℃, and preserving heat for 1-4 hours for later use after the temperature is raised.
Further, step (3) preparing a soy protein adhesive layer: and uniformly coating the soybean protein liquid on the polysulfone supporting layer, standing for 20-60 seconds, removing redundant liquid on the surface, drying at 40-60 ℃ for 2-10 minutes, and curing on the polysulfone supporting layer to obtain the soybean protein adhesive layer after drying.
Further, preparing a water phase liquid in the step (4): adding piperazine and an acid absorbent into water, and uniformly stirring to obtain an aqueous phase liquid; wherein said piperazine comprises 0.2 to 4.0 wt% of said aqueous liquid; the acid absorbent accounts for 1.0 to 3.0 weight percent of the aqueous phase; and the acid scavenger is at least one selected from trisodium phosphate, sodium hydroxide, sodium carbonate and triethylamine.
Further, in the step (5), the trimesoyl chloride accounts for 0.05-0.5 wt% of the oil phase liquid.
Further, step (6) prepares a polyamide desalting layer: and (2) placing the polysulfone supporting layer containing the soybean protein adhesive layer in the water phase liquid for soaking for 1-3 minutes, then placing the polysulfone supporting layer in the oil phase liquid for interfacial polymerization for 40-60 seconds, finally removing surface liquid, drying for 2-10 minutes at 60-110 ℃, and washing with water to obtain the high-flux composite nanofiltration membrane. Generally, the key to the preparation of the nanofiltration membrane by the interfacial polymerization method is the selection of a porous support layer and the control of the distribution coefficient and diffusion rate of the reaction monomers in two phases, compared with the MPD monomer, the PIP monomer has poor dispersibility on the surface of a hydrophobic polysulfone support layer, and the polysulfone support layer modification or the addition of a hydrophilic component in an aqueous solution is generally required. According to the invention, the soybean protein adhesive layer is introduced between the hydrophobic polysulfone supporting layer and the polyamide desalting layer as the porous intermediate layer, so that the bonding strength between the polyamide desalting layer and the polysulfone supporting layer can be enhanced, and high water permeability can be obtained. The soybean protein is a complex macromolecule containing 18 amino acids, has a specific primary structure and a high-order space structure, is modified through alkaline degradation, changes the internal molecular structure thereof, changes amino acid residues and polypeptide chains, and destroys hydrogen bonds, thereby loosening chemical bonds in protein molecules and among molecules and playing a role in the adhesiveness thereof. After the soybean protein is subjected to alkali degradation and modification, the aggregation structure of soybean protein molecules becomes loose, and polar groups and nonpolar groups hidden in the soybean spherical protein can be exposed, on one hand, the soybean protein with viscosity is uniformly dispersed on the surface of a hydrophobic polysulfone supporting layer, and a porous middle layer formed after drying is firmly combined with the polysulfone supporting layer. On the other hand, the polar groups (such as hydroxyl, carboxyl, amino and the like) contained in the intermediate layer are beneficial to improving the dispersibility of the PIP monomer on the surface of the support layer, and can participate in the process of forming a desalting layer by polyamine/polybasic acyl chloride to perform dehydration condensation reaction with partial acyl chloride groups, so that the ultrathin polypiperazine amide desalting layer is firmly combined with the intermediate layer, meanwhile, the distribution coefficient and the diffusion speed of the PIP monomer at a two-phase interface are influenced by the polar groups, the crosslinking degree and the thickness of the formed desalting layer are reduced, and the water flux of the nanofiltration membrane is remarkably improved.
The invention has the beneficial effects that:
the high-flux composite nanofiltration membrane prepared by the invention comprises a polysulfone supporting layer, a soybean protein adhesive layer and a polyamide desalting layer, and compared with a commercial nanofiltration membrane, the nanofiltration membrane has remarkable water flux advantage and performance stability; according to the nanofiltration membrane, the soybean protein adhesive layer is introduced between the polysulfone supporting layer and the polyamide desalting layer, so that the binding force between the polyamide desalting layer and the polysulfone supporting layer can be enhanced, the long-term service performance stability of the nanofiltration membrane is ensured, the water flux of the nanofiltration membrane can be obviously improved, the rejection rate of the prepared nanofiltration membrane on 2000ppm magnesium sulfate under standard test conditions is more than 97%, the water flux is more than 45GFD, and the water flux is 50% higher than that of the current commercial nanofiltration membrane NF270 of the same type. In addition, the preparation method of the high-flux composite nanofiltration membrane provided by the invention has the advantages of simple process, safety, environmental protection, low cost of the used modified material and high commercial application value, and the soybean protein powder used in the preparation method has the advantages of sufficient raw materials, low price, low viscosity, easiness in processing and the like.
Drawings
Fig. 1 is an SEM image of the high-flux composite nanofiltration membrane prepared in example 1 of the present invention;
figure 2 is an SEM image of the nanofiltration membrane prepared in comparative example 1 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
A high-flux composite nanofiltration membrane comprises a polysulfone supporting layer, a soy protein adhesive layer and a polyamide desalting layer; the soybean protein adhesive layer is arranged between the polysulfone supporting layer and the polyamide desalting layer; the soybean protein adhesive layer is formed by drying and solidifying soybean protein liquid prepared from soybean protein powder; and the soybean protein liquid comprises the following components in parts by weight: 10.0 wt% of soybean protein powder, 0.04 wt% of sodium hydroxide, 0.06 wt% of Sodium Dodecyl Benzene Sulfonate (SDBS) and 89.9 wt% of water.
The preparation method of the high-flux composite nanofiltration membrane comprises the following steps:
(1) preparing a polysulfone support layer: adding polysulfone into N, N-dimethylformamide to dissolve, mechanically stirring for 2 hours, standing and degassing for 8 hours to obtain a polysulfone solution; then uniformly coating the polysulfone solution on a support material (non-woven fabric), carrying out phase separation for 20 seconds in a water bath at 25 ℃, and curing to form a polysulfone support layer; and polysulfone accounts for 15 wt% of the polysulfone solution;
(2) preparing soybean protein liquid: adding the soybean protein powder, sodium hydroxide and sodium dodecyl benzene sulfonate into water according to the weight percentage, and uniformly stirring to obtain a soybean protein liquid; then heating the soybean protein liquid to 60 ℃, and preserving heat for 2 hours after heating for later use;
(3) preparing a soy protein adhesive layer: uniformly coating the soybean protein liquid on the polysulfone supporting layer, standing for 30 seconds, removing redundant liquid on the surface, drying at 50 ℃ for 3 minutes, and curing on the polysulfone supporting layer to obtain a soybean protein adhesive layer;
(4) preparing a water phase liquid: adding piperazine and trisodium phosphate into water, and uniformly stirring to obtain an aqueous phase liquid; and the piperazine accounts for 0.6 wt% of the aqueous phase liquid, and the trisodium phosphate accounts for 2.0 wt% of the aqueous phase liquid;
(5) preparing an oil phase liquid: adding trimesoyl chloride into ethylcyclohexane and uniformly stirring to obtain an oil phase liquid; and the trimesoyl chloride accounts for 0.15 wt% of the oil phase liquid;
(6) preparing a polyamide desalting layer: and (3) placing the polysulfone supporting layer containing the soybean protein adhesive layer in the water phase liquid for soaking for 2 minutes, then placing the polysulfone supporting layer in the oil phase liquid for interfacial polymerization reaction for 50 seconds, then removing surface liquid, placing the polysulfone supporting layer in an oven at 80 ℃ for drying for 5 minutes, finally taking out the membrane and washing the membrane with water to obtain the high-flux composite nanofiltration membrane.
Example 2
A high-flux composite nanofiltration membrane comprises a polysulfone supporting layer, a soy protein adhesive layer and a polyamide desalting layer; the soybean protein adhesive layer is arranged between the polysulfone supporting layer and the polyamide desalting layer; the soybean protein adhesive layer is formed by drying and solidifying soybean protein liquid prepared from soybean protein powder; and the soybean protein liquid comprises the following components in parts by weight: 5.0 wt% of soybean protein powder, 0.04 wt% of sodium bicarbonate, 0.06 wt% of Sodium Dodecyl Sulfate (SDS) and 94.9 wt% of water.
The preparation method of the high-flux composite nanofiltration membrane comprises the following steps:
(1) preparing a polysulfone support layer: adding polysulfone into N, N-dimethylacetamide, dissolving, mechanically stirring for 1 hour, standing and degassing for 10 hours to obtain a polysulfone solution; then uniformly coating the polysulfone solution on a support material (non-woven fabric), carrying out phase separation for 15 seconds in a water bath at 20 ℃, and curing to form a polysulfone support layer; and polysulfone accounts for 10 wt% of the polysulfone solution;
(2) preparing soybean protein liquid: adding the soybean protein powder, sodium bicarbonate and sodium dodecyl sulfate into water according to the weight percentage, and uniformly stirring to obtain a soybean protein liquid; then heating the soybean protein liquid to 50 ℃, and preserving heat for 2 hours for later use;
(3) preparing a soy protein adhesive layer: uniformly coating the soybean protein liquid on the polysulfone supporting layer, standing for 20 seconds, removing redundant liquid on the surface, drying at 40 ℃ for 5 minutes, and curing on the polysulfone supporting layer after drying to obtain a soybean protein adhesive layer;
(4) preparing a water phase liquid: adding piperazine and triethylamine into water, and uniformly stirring to obtain an aqueous phase liquid; the piperazine accounts for 0.6 wt% of the aqueous phase, and the triethylamine accounts for 2.0 wt% of the aqueous phase;
(5) preparing an oil phase liquid: adding trimesoyl chloride into n-hexane and uniformly stirring to obtain an oil phase liquid; and the trimesoyl chloride accounts for 0.15 wt% of the oil phase liquid;
(6) preparing a polyamide desalting layer: and (2) placing the polysulfone supporting layer containing the soybean protein adhesive layer in the water phase liquid for soaking for 1 minute, then placing the polysulfone supporting layer in the oil phase liquid for interfacial polymerization reaction for 60 seconds, then removing surface liquid, placing the polysulfone supporting layer in a 60 ℃ drying oven for drying for 10 minutes, and finally taking out the membrane and washing the membrane with water to obtain the high-flux composite nanofiltration membrane.
Example 3
A high-flux composite nanofiltration membrane comprises a polysulfone supporting layer, a soy protein adhesive layer and a polyamide desalting layer; the soybean protein adhesive layer is arranged between the polysulfone supporting layer and the polyamide desalting layer; the soybean protein adhesive layer is formed by drying and solidifying soybean protein liquid prepared from soybean protein powder; and the soybean protein liquid comprises the following components in parts by weight: 40.0 wt% of soybean protein powder, 0.04 wt% of magnesium hydroxide, 0.06 wt% of sodium dodecyl sulfate and 59.9 wt% of water.
The preparation method of the high-flux composite nanofiltration membrane comprises the following steps:
(1) preparing a polysulfone support layer: adding polysulfone into N, N-dimethylformamide to dissolve, mechanically stirring for 3 hours, standing and degassing for 12 hours to obtain a polysulfone solution; then uniformly coating the polysulfone solution on a support material (non-woven fabric), carrying out phase separation for 25 seconds in a water bath at 30 ℃, and curing to form a polysulfone support layer; and polysulfone accounts for 20 wt% of the polysulfone solution;
(2) preparing soybean protein liquid: adding the soybean protein powder, the magnesium hydroxide and the lauryl sodium sulfate into water according to the weight percentage, and uniformly stirring to obtain a soybean protein liquid; then heating the soybean protein liquid to 70 ℃, and preserving heat for 2 hours for later use;
(3) preparing a soy protein adhesive layer: uniformly coating the soybean protein liquid on the polysulfone supporting layer, standing for 60 seconds, removing redundant liquid on the surface, drying at 60 ℃ for 10 minutes, and curing on the polysulfone supporting layer to obtain a soybean protein adhesive layer;
(4) preparing aqueous phase liquid: adding piperazine and sodium hydroxide into water, and uniformly stirring to obtain an aqueous phase liquid; the piperazine accounts for 0.6 wt% of the aqueous phase, and the sodium hydroxide accounts for 2.0 wt% of the aqueous phase;
(5) preparing an oil phase liquid: adding trimesoyl chloride into an isoparaffin solvent and uniformly stirring to obtain an oil phase liquid; and the trimesoyl chloride accounts for 0.15 wt% of the oil phase liquid;
(6) preparing a polyamide desalting layer: and (3) placing the polysulfone supporting layer containing the soybean protein adhesive layer in the water phase liquid for soaking for 3 minutes, then placing the polysulfone supporting layer in the oil phase liquid for interfacial polymerization for 40 seconds, then removing surface liquid, placing the polysulfone supporting layer in a drying oven at 110 ℃ for drying for 3 minutes, finally taking out the membrane and washing the membrane with water to obtain the high-flux composite nanofiltration membrane.
Example 4
Example 4 differs from example 1 in that the soybean protein liquid of example 4 contains 0.01 wt% sodium hydroxide, and the rest is the same as example 1.
Example 5
Example 5 differs from example 1 in that the soy protein solution of example 5 contains 0.01 wt% Sodium Dodecylbenzenesulfonate (SDBS), the remainder being the same as in example 1.
Example 6
Example 6 is different from example 1 in that the soybean protein liquid of example 6 was kept at elevated temperature for 1 hour, and the rest was the same as example 1.
Example 7
Example 7 is different from example 1 in that piperazine contained in the aqueous liquid of example 7 is 0.2 wt%, and the rest is the same as example 1.
Example 8
Example 8 is different from example 1 in that piperazine contained in the aqueous liquid of example 8 is 2.0 wt%, and the rest is the same as example 1.
Example 9
Example 9 is different from example 1 in that trisodium phosphate is 1.0 wt% in the aqueous liquid of example 9, and the rest is the same as example 1.
Example 10
Example 10 is different from example 1 in that trimesoyl chloride in the oil phase of example 10 is 0.05 wt%, and the rest is the same as example 1.
Comparative example 1
A preparation method of a nanofiltration membrane comprises the following steps:
(1) preparing a polysulfone support layer: adding polysulfone into N, N-dimethylformamide to dissolve, mechanically stirring for 2 hours, standing and degassing for 8 hours to obtain a polysulfone solution; then uniformly coating the polysulfone solution on a support material (non-woven fabric), carrying out phase separation for 20 seconds in a water bath at 25 ℃, and curing to form a polysulfone support layer; and polysulfone accounts for 15 wt% of the polysulfone solution;
(2) preparing a water phase liquid: adding piperazine and trisodium phosphate into water, and uniformly stirring to obtain an aqueous phase liquid; and the piperazine accounts for 0.6 wt% of the aqueous phase liquid, and the trisodium phosphate accounts for 2.0 wt% of the aqueous phase liquid;
(3) preparing an oil phase liquid: adding trimesoyl chloride into ethylcyclohexane and uniformly stirring to obtain an oil phase liquid; and the trimesoyl chloride accounts for 0.15 wt% of the oil phase liquid;
(4) preparing a polyamide desalting layer: and (2) soaking the polysulfone support layer in the water-phase liquid for 2 minutes, then placing the polysulfone support layer in the oil-phase liquid for interfacial polymerization for 50 seconds, removing surface liquid, drying the polysulfone support layer in an oven at 80 ℃ for 5 minutes, and finally taking out the membrane and washing the membrane with water to obtain the nanofiltration membrane.
Comparative example 1 is different from example 1 in that comparative example 1 does not incorporate the soy protein adhesive layer of the present invention, and the rest is the same as example 1.
Comparative example 2
Comparative example 2 is different from comparative example 1 in that piperazine was 2.0 wt% and trisodium phosphate was 1.0 wt% in the aqueous liquid of comparative example 2, and the rest of homogeneous comparative example 1 was the same.
Comparative example 3
Comparative example 3 is different from comparative example 1 in that piperazine accounts for 2.0 wt% in the aqueous liquid of comparative example 3, and the rest of homogeneous comparative example 1 is the same.
Comparative example 4
Comparative example 4 is different from comparative example 1 in that trimesoyl chloride is 0.05 wt% in the oil-phase liquid of comparative example 4, and the rest of homogeneous comparative example 1 is the same.
The amounts of the components added in the above examples 1 to 10 and comparative examples 1 to 4 are shown in Table 1:
table 1 shows the mass percentages of the components in examples 1 to 10 and comparative examples 1 to 4
Figure BDA0002905517610000131
Test example 1
The nanofiltration membranes prepared in the above examples 1 to 10 and comparative examples 1 to 4 were subjected to performance tests, and the test results are shown in table 2; the invention discloses a performance evaluation method for a high-flux composite nanofiltration membrane, which comprises the following steps:
the separation performance of the prepared nanofiltration membrane is evaluated and mainly characterized by two characteristic parameters, namely the water flux and the salt rejection rate of the membrane.
Water flux (LMH) is defined as: the volume of water per unit time that permeates the active membrane area under certain operating pressure conditions.
Salt rejection calculation formula: r ═ 1-Cp/Cf) X 100% in the formulaR represents the rejection rate, CfAnd CpThe concentrations of the salts (ppm) in the permeate and in the feed, respectively.
The test conditions of the separation performance of the membrane are as follows: the feed solution was 2000ppm magnesium sulfate in water, the feed temperature was 25 ℃ and the operating pressure was 70psi (0.48 MPa).
The method comprises the following steps of testing the water flux of a membrane before and after back pressure and the change rate of the desalination rate by back pressure of the membrane, and indirectly evaluating the bonding strength between a desalination layer of a nanofiltration membrane and a polysulfone supporting layer, wherein the steps are as follows:
(1) taking the prepared nanofiltration membrane, and testing the salt rejection rate R according to a normal test method0And water flux J0；
(2) Taking out the membrane from the membrane pool, reversely installing the membrane, and carrying out back pressure on the nanofiltration membrane for at least half an hour under the pressure of 1.0 MPa;
(3) taking the membrane out of the membrane pool, and testing the salt rejection rate R according to the method in the step (1)1And water flux J1；
(4) Respectively calculating the difference value delta R and delta J of the desalination rate and the water flux before and after the back pressure of the nanofiltration membrane, wherein the calculation formula is as follows: Δ R ═ R1-R0；ΔJ＝(J1-J0)/J0。
Table 2 shows the results of the performance tests of the nanofiltration membranes prepared in the above examples 1 to 10 and comparative examples 1 to 4
Figure BDA0002905517610000151
As can be seen from the test results in table 2, compared with the nanofiltration membranes prepared in comparative examples 1 to 4, the composite nanofiltration membranes prepared in examples 1 to 10 and containing the soy protein adhesive layer have the advantages that the water flux is improved by about 50% on the whole, but the desalination rate is not significantly reduced, and it is noted that the desalination rate of the nanofiltration membranes prepared in examples 1 to 10 is reduced to a small extent after being subjected to back pressure, which indicates that the back pressure resistance of the nanofiltration membranes can be significantly improved by introducing the soy protein adhesive layer.
Test example 2
The nanofiltration membranes prepared in the embodiment 1 and the comparative example 1 are respectively taken and observed through a scanning electron microscope, the scanning electron microscope image of the nanofiltration membrane prepared in the embodiment 1 is shown in figure 1, the scanning electron microscope image of the nanofiltration membrane prepared in the comparative example 1 is shown in figure 2, and it can be seen from the figure that a polyamide desalting layer which plays a decisive role in membrane separation performance is uniformly covered on the surface of the prepared nanofiltration membrane; from the comparison between FIG. 1 and FIG. 2, it can be seen that the introduction of the soy protein adhesive layer has a certain effect on the surface morphology of the polyamide desalting layer.
The sources of the raw materials used in the above examples and test examples are shown in table 3:
table 3 shows the sources of the materials used in the examples and the test examples
Name of raw materials Parameter index Manufacturer of the product
Piperazine derivatives The purity is more than or equal to 99 percent Aladdin reagent
Trisodium phosphate The purity is more than or equal to 98 percent Reagent for treating west longas
Trimesoyl chloride The purity is more than or equal to 99 percent Three-strength bennoco
Soybean protein powder The crude protein is more than or equal to 50 percent Hagaoke soybean food
Sodium hydroxide The purity is more than or equal to 99 percent Beijing YinuoKai
Sodium dodecyl benzene sulfonate The purity is more than or equal to 96 percent Beijing YinuoKai
Magnesium sulfate The purity is more than or equal to 98 percent Beijing YinuoKai
The above-mentioned preferred embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention. Obvious variations or modifications of the present invention are within the scope of the present invention.

Claims (10)

1. The high-flux composite nanofiltration membrane is characterized by comprising a polysulfone supporting layer, a soybean protein adhesive layer and a polyamide desalting layer; the soybean protein adhesive layer is arranged between the polysulfone supporting layer and the polyamide desalting layer; the soybean protein adhesive layer is formed by drying and solidifying soybean protein liquid prepared from soybean protein powder; and the soybean protein liquid comprises the following components in parts by weight: 1.0-40.0 wt% of soybean protein powder, 0.01-5.0 wt% of alkaline substance, 0.01-3.0 wt% of surfactant and the balance of water.
2. The high-flux composite nanofiltration membrane according to claim 1, wherein the soybean protein liquid comprises the following components in parts by weight: 5.0-20.0 wt% of soybean protein powder, 0.02-1.0 wt% of alkaline substance, 0.1-1.0 wt% of surfactant and the balance of water.
3. The nanofiltration membrane according to claim 1, wherein the alkaline substance is at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, calcium hydroxide, and magnesium hydroxide; the surfactant is selected from at least one of sodium dodecyl sulfate, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate.
4. The method for preparing the high-flux composite nanofiltration membrane according to any one of claims 1 to 3, wherein the method comprises the following steps:
(1) preparing a polysulfone support layer: dissolving polysulfone, stirring, and standing to obtain a polysulfone solution; uniformly coating the polysulfone solution on a support material, then carrying out phase separation in a water bath, and curing to form a polysulfone support layer;
(2) preparing soybean protein liquid: adding the soybean protein powder, the alkaline substance and the surfactant into water and stirring to obtain a soybean protein liquid; then heating the soybean protein liquid, and keeping the temperature for later use after heating;
(3) preparing a soy protein adhesive layer: uniformly coating the soybean protein liquid on the polysulfone supporting layer, standing, removing redundant liquid, drying, and curing on the polysulfone supporting layer to obtain a soybean protein adhesive layer;
(4) preparing a water phase liquid: adding piperazine and an acid absorbent into water, and stirring to obtain an aqueous phase liquid;
(5) preparing an oil phase liquid: adding trimesoyl chloride into an organic solvent and stirring to obtain an oil phase liquid; the organic solvent is at least one of n-hexane, cyclohexane, ethylcyclohexane, n-heptane and isoparaffin solvent;
(6) preparing a polyamide desalting layer: and (3) placing the polysulfone supporting layer containing the soybean protein adhesive layer in the water phase liquid for soaking, then placing the polysulfone supporting layer in the oil phase liquid for interfacial polymerization reaction, finally removing surface liquid, drying and washing to obtain the high-flux composite nanofiltration membrane.
5. The preparation method of the high-flux composite nanofiltration membrane according to claim 4, wherein the step (1) of preparing the polysulfone support layer comprises the following steps: adding polysulfone into a polymer solvent for dissolving, mechanically stirring for 1-3 hours, and then standing for 8-12 hours to obtain a polysulfone solution; uniformly coating the polysulfone solution on a support material, then carrying out phase separation for 15-25 seconds in a water bath at the temperature of 20-30 ℃, and curing to form a polysulfone support layer; the polymer solvent is any one of N, N-dimethylacetamide and N, N-dimethylformamide; the polysulfone accounts for 10-20 wt% of the sulfone solution; the supporting material is non-woven fabric.
6. The method for preparing the high-flux composite nanofiltration membrane according to claim 4, wherein the step (2) of preparing the soy protein solution comprises the following steps: adding the soybean protein powder, the alkaline substance and the surfactant into water, and uniformly stirring at room temperature to obtain a soybean protein liquid; and then heating the soybean protein liquid to 50-70 ℃, and preserving heat for 1-4 hours for later use after the temperature is raised.
7. The method for preparing the high-flux composite nanofiltration membrane according to claim 4, wherein the step (3) is to prepare a soy protein adhesive layer: and uniformly coating the soybean protein liquid on the polysulfone supporting layer, standing for 20-60 seconds, removing redundant liquid on the surface, drying at 40-60 ℃ for 2-10 minutes, and curing on the polysulfone supporting layer to obtain the soybean protein adhesive layer after drying.
8. The method for preparing the high-flux composite nanofiltration membrane according to claim 4, wherein the step (4) is to prepare a water phase liquid: adding piperazine and an acid absorbent into water, and uniformly stirring to obtain an aqueous phase liquid; wherein said piperazine comprises 0.2 to 4.0 wt% of said aqueous liquid; the acid absorbent accounts for 1.0 to 3.0 weight percent of the aqueous phase; and the acid scavenger is at least one selected from trisodium phosphate, sodium hydroxide, sodium carbonate and triethylamine.
9. The method for preparing a high-flux composite nanofiltration membrane according to claim 4, wherein in the step (5), the trimesoyl chloride accounts for 0.05-0.5 wt% of the oil phase liquid.
10. The preparation method of the high-flux composite nanofiltration membrane according to claim 4, wherein the polyamide desalination layer prepared in the step (6): and (2) placing the polysulfone supporting layer containing the soybean protein adhesive layer in the water phase liquid for soaking for 1-3 minutes, then placing the polysulfone supporting layer in the oil phase liquid for interfacial polymerization for 40-60 seconds, finally removing surface liquid, drying for 2-10 minutes at 60-110 ℃, and washing with water to obtain the high-flux composite nanofiltration membrane.
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