CN107715704B - Polyhexamethylene adipamide ultrafiltration membrane and preparation method thereof - Google Patents
Polyhexamethylene adipamide ultrafiltration membrane and preparation method thereof Download PDFInfo
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D71/06—Organic material
- B01D71/58—Other polymers having nitrogen in the main chain, with or without oxygen or carbon only
- B01D71/62—Polycondensates having nitrogen-containing heterocyclic rings in the main chain
- B01D71/64—Polyimides; Polyamide-imides; Polyester-imides; Polyamide acids or similar polyimide precursors
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0009—Organic membrane manufacture by phase separation, sol-gel transition, evaporation or solvent quenching
- B01D67/0013—Casting processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- 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
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
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Abstract
The invention belongs to the membrane filtration and purification technology, and particularly relates to a polyhexamethylene adipamide ultrafiltration membrane and a preparation method thereof. A polyhexamethylene adipamide ultrafiltration membrane comprises the following raw materials in parts by weight: 70-75 parts of solvent, 20-22 parts of polyhexamethylene adipamide and 5-8 parts of polyvinylpyrrolidone. Meanwhile, the invention also provides a preparation method of the polyhexamethylene adipamide ultrafiltration membrane, which comprises the following steps: stirring a solvent, keeping stirring, pouring polyhexamethylene adipamide, pouring polyvinylpyrrolidone after the polyhexamethylene adipamide is dissolved, stirring for 10-12 hours, vacuumizing until no bubbles are seen in the casting solution, pouring the casting solution on a smooth and flat plane, scraping the film by using a film scraping machine, standing at room temperature, and then putting the film and the plane into water at a constant speed to enable the film to naturally fall off. The invention has good hydrophilicity, heat resistance and long service life.
Description
Technical Field
The invention belongs to the membrane filtration and purification technology, and particularly relates to a polyhexamethylene adipamide ultrafiltration membrane and a preparation method thereof.
Background
The application prospect of the membrane filtration separation technology in wastewater treatment is very good. It has low energy consumption, high efficiency and easy operation. Compared with other separation processes, the advantages are more prominent: generally, no phase change occurs; secondly, the liquid separation efficiency is high; the operation and the maintenance are simple and convenient; fourthly, the equipment used for preparing the membrane has smaller volume and small occupied area.
The composite ultrafiltration membrane needs to have better hydrophilicity, and because the hydrophilicity is good, the lipophilicity is poor, so that oil and water in the oily sewage are separated more easily, and the effect is better. For example, the membrane filter made of polyvinylidene fluoride on the market has poor hydrophilic performance, so that the membrane filter is easy to separate incompletely. And the operating temperature of the ultrafiltration membrane used at present is generally low, and the ultrafiltration membrane cannot be used when the recovery temperature is high-temperature wastewater, so that certain limitation exists.
Therefore, there is a need for an ultrafiltration membrane that has good hydrophilicity and can be used at higher temperatures.
Disclosure of Invention
In order to solve the problems, the invention provides an ultrafiltration membrane which has good hydrophilicity and can be used at higher temperature, and the invention adopts the following technical scheme:
a polyhexamethylene adipamide ultrafiltration membrane comprises the following raw materials in parts by weight:
70-75 parts of solvent, 20-22 parts of polyhexamethylene adipamide and 5-8 parts of polyvinylpyrrolidone.
Preferably, the solvent comprises the following components in parts by weight: 30-35 parts of formic acid and 35-40 parts of dichloromethane.
The raw materials and the solvent of the invention are both materials with a large number of hydrophilic groups, so that the hydrophilic capability of the invention can be improved. Thereby improving the use efficiency and the anti-pollution capability of the invention. And the organic material adopted by the invention is beneficial to the repeated use of the material, and the cost is reduced.
Preferably, the polyhexamethylene adipamide is treated by the following method: the polyhexamethylene adipamide is treated by the following method: dissolving 20-30 parts by weight of polyhexamethylene adipamide with formic acid, precipitating with ethanol, adding organic acid salt accounting for 5-10% of the mass of the polyhexamethylene adipamide, mixing and stirring, adding 1-2 parts by weight of nano silicon dioxide, performing ultrasonic treatment at 85-95 ℃ for 20-25 min, heating at 180-190 ℃ for 3-5 h, extracting with methanol for 18-22 h, and vacuum-drying the product at 65-70 ℃ for 12-15 h.
The invention firstly modifies polyhexamethylene adipamide with organic acid salt, and the organic acid salt is dispersed in the polyhexamethylene adipamide, so that the thermal stability and yellowing resistance of the polyhexamethylene adipamide can be improved, the service life of the invention is prolonged, and the cost is reduced.
In addition, the invention adopts the silicon dioxide to treat the membrane, the silicon dioxide is added, the contact angle of the surface of the membrane can be reduced, the structure of the membrane is more compact, the hydrophilicity of the surface of the membrane is improved, the improvement of the filtering effect of the ultrafiltration membrane is facilitated, the adhesion acting force of the surface of the membrane and pollutants is reduced, the occurrence of the condition that the pollutants are adhered to the membrane to cause the blockage of filter pores on the membrane is reduced, the pollution resistance of the membrane is improved, and the service life of the membrane is prolonged.
Preferably, the organic acid salt is a mixture of lanthanum citrate and cerium butane tetraate, and the mass ratio of the lanthanum citrate to the cerium butane tetraate is 1: 2-2: 3.
The invention adopts the scheme of sharing lanthanum citrate and cerium butane tetraacetate, firstly, the lanthanum citrate has large molecular weight, the heat resistance of the invention can be improved, the invention can treat waste water with higher temperature, and the rare earth element is added, so that the toughness and the strength of the membrane can be improved, the application range of the membrane is strengthened, and the service life of the ultrafiltration membrane is prolonged. Then, cerium butane tetraacetate is added, and the lanthanum citrate is matched to improve the strength of the ultrafiltration membrane, relieve the degradation rate of the membrane, improve the corrosion resistance of the membrane and improve the heat resistance of the ultrafiltration membrane.
Preferably, the lanthanum citrate is prepared by the following steps: dissolving 3-4 parts by weight of lanthanum acetate in 10-15 parts by weight of water, dissolving 3-4 parts by weight of citric acid in 10-15 parts by weight of water, mixing the solutions, heating to 85-90 ℃, stirring for 1-2 hours at the rotating speed of 300-400 rpm, filtering, taking out solids, washing and drying; the butane cerium tetraacetate is prepared by the following method: adding 10-15 parts by weight of 10-15% sodium hydroxide solution into 4-5 parts by weight of 1,2,3, 4-butanetetracarboxylic acid, adding 5-10% dilute hydrochloric acid until the pH value of the solution is 6-7.5, then adding 4-5 parts by weight of cerium trichloride, preserving heat at 65-70 ℃ for 1.5-2.5 h, and washing and drying with clear water.
The lanthanum citrate prepared by the method is beneficial to forming bidentate chelation by oxyhydrogen and rare earth metal, and is beneficial to generating coordination of rare earth metal ions under ultrasound, so that the dispersibility of the lanthanum organic acid in the invention is improved, and the mechanical strength and the yellowing resistance of the invention are better improved.
The method for preparing the butane cerium tetraacetate can improve the dispersing capacity of the butane cerium tetraacetate, is beneficial to dispersing the butane cerium tetraacetate in the invention, and improves the corrosion resistance of the invention.
Preferably, the nano-silica is treated by the following method: soaking 2-3 parts by weight of nano silicon dioxide in water, adding hydrochloric acid, performing ultrasonic treatment for 20-25 min, standing for 24-48 h, performing centrifugal separation, performing vacuum drying at 150-160 ℃ for 18-20 h, adding 2, 4-toluene diisocyanate under the protection of nitrogen, performing ultrasonic treatment for 30-40 min, adding 3-4 drops of dibutyltin dilaurate, and performing reflux at 65-68 ℃ for 5-6 h.
Because the surface effect of the silicon dioxide is strong, the agglomeration phenomenon exists, the invention firstly activates the silicon dioxide, improves the dispersibility of the silicon dioxide, removes impurities adsorbed on the surface of the silicon dioxide, strengthens the grafting rate of the silicon dioxide on the polyhexamethylene adipamide, improves the utilization efficiency of the silicon dioxide and improves the anti-pollution capacity of the ultrafiltration membrane.
A preparation method of a polyhexamethylene adipamide ultrafiltration membrane comprises the following steps:
(1) preparing a casting solution: stirring a solvent, keeping stirring, pouring polyhexamethylene adipamide, pouring polyvinylpyrrolidone after the polyhexamethylene adipamide is dissolved, stirring for 10-12 hours, and vacuumizing until no bubbles are seen in a casting solution;
(2) and (3) synthesis of a membrane: pouring the casting film liquid on a smooth and flat plane, scraping the film by using a film scraping machine, standing at room temperature, and then putting the film and the plane into water at a constant speed to enable the film to naturally fall off.
Preferably, the stirring speed in the step (1) is 300 to 400 rpm.
Preferably, the standing time in the step (2) is 5-6 h, and the thickness of the scraping film is 0.3-0.5 mm.
The water flux of the film was 1.090 L.s-1·m-2The water flux of the thick film was 0.179 L.s-1.m-2. The water flux is greater for thin films relative to thick films. Thus, the thickness of the dried thin and thick films was measured by metallographic microscopy, the thickness of the thin film was about 0.3-0.5mm, and if the film was too thin, it would lead to a weaker film and would be more easily pulled apart, and several thicknesses were sought between them for testing, and finally it was found that the best film thickness was about 0.4mm, at which time the water flux was the greatest. The thickness of the film is selected to be 0.4mm for the experiment.
The invention has the beneficial effects that: (1) the invention has good hydrophilicity (2) and heat resistance (3), and has long service life.
Detailed Description
The invention is further explained below with reference to specific embodiments:
example 1
A polyhexamethylene adipamide ultrafiltration membrane comprises the following raw materials in parts by weight:
70 parts of solvent, 20 parts of polyhexamethylene adipamide and 5 parts of polyvinylpyrrolidone.
Wherein, the solvent comprises the following components in parts by weight: 30 parts of formic acid and 35 parts of dichloromethane.
Wherein the polyhexamethylene adipamide is treated by the following method: dissolving 20 parts by weight of polyhexamethylene adipamide with formic acid, precipitating with ethanol, adding a mixture of lanthanum citrate and cerium butane tetraacetate with the mass ratio of 1: 2, which is 5% of the mass of the polyhexamethylene adipamide, mixing and stirring, adding 1 part by weight of nano silicon dioxide, performing ultrasonic treatment at 85 ℃ for 20min, and heating at 180 ℃ for 3 h.
The lanthanum citrate is prepared by the following steps: dissolving 3 parts by weight of lanthanum acetate in 10 parts by weight of water, dissolving 3 parts by weight of citric acid in 10 parts by weight of water, then mixing the solutions, heating to 85 ℃, stirring for 2 hours at the rotating speed of 300rpm, filtering, taking out solids, washing and drying; the butane cerium tetraacetate is prepared by the following method: adding 10 parts by weight of 10% sodium hydroxide solution into 4 parts by weight of 1,2,3, 4-butanetetracarboxylic acid, adding 5% dilute hydrochloric acid until the pH value of the solution is 6, then adding 5 parts by weight of cerium trichloride, preserving the temperature at 70 ℃ for 2.5h, and washing and drying the product by using clean water.
Wherein, the nano silicon dioxide is processed by the following method: soaking 2 parts by weight of nano silicon dioxide in water, adding hydrochloric acid, performing ultrasonic treatment for 20min, standing for 24h, performing centrifugal separation, performing vacuum drying for 18h at 160 ℃, then adding 2, 4-toluene diisocyanate under the protection of nitrogen, performing ultrasonic treatment for 30min, adding 4 drops of dibutyltin dilaurate, and performing reflux for 5h at 65 ℃.
A preparation method of a polyhexamethylene adipamide ultrafiltration membrane comprises the following steps:
(1) preparing a casting solution: stirring a solvent at the stirring speed of 300rpm, keeping stirring, pouring polyhexamethylene adipamide, pouring polyvinylpyrrolidone after the polyhexamethylene adipamide is dissolved, stirring for 10 hours, and vacuumizing until no bubbles are seen in the casting solution;
(2) and (3) synthesis of a membrane: pouring the casting film liquid on a smooth and flat plane, scraping the film by using a film scraping machine, keeping the thickness of the film at 0.3mm, standing at room temperature for 5h, and then putting the film and the plane into water at a constant speed to enable the film to naturally fall off.
Example 2
A polyhexamethylene adipamide ultrafiltration membrane comprises the following raw materials in parts by weight:
75 parts of solvent, 22 parts of polyhexamethylene adipamide and 8 parts of polyvinylpyrrolidone.
Wherein, the solvent comprises the following components in parts by weight: 35 parts of formic acid and 30 parts of dichloromethane.
Wherein the polyhexamethylene adipamide is treated by the following method: dissolving 20 parts by weight of polyhexamethylene adipamide with formic acid, precipitating with ethanol, adding a mixture of lanthanum citrate and cerium butane tetraacetate with the mass ratio of 1: 2, which is 5% of the mass of the polyhexamethylene adipamide, mixing and stirring, adding 1 part by weight of nano silicon dioxide, performing ultrasonic treatment at 85 ℃ for 20min, and heating at 180 ℃ for 3 h.
The lanthanum citrate is prepared by the following steps: dissolving 3 parts by weight of lanthanum acetate in 10 parts by weight of water, dissolving 3 parts by weight of citric acid in 10 parts by weight of water, then mixing the solutions, heating to 85 ℃, stirring for 2 hours at the rotating speed of 300rpm, filtering, taking out solids, washing and drying; the butane cerium tetraacetate is prepared by the following method: adding 10 parts by weight of 10% sodium hydroxide solution into 4 parts by weight of 1,2,3, 4-butanetetracarboxylic acid, adding 5% dilute hydrochloric acid until the pH value of the solution is 6, then adding 5 parts by weight of cerium trichloride, preserving the temperature at 70 ℃ for 2.5h, and washing and drying the product by using clean water.
Wherein, the nano silicon dioxide is processed by the following method: soaking 2 parts by weight of nano silicon dioxide in water, adding hydrochloric acid, performing ultrasonic treatment for 20min, standing for 24h, performing centrifugal separation, performing vacuum drying for 18h at 160 ℃, then adding 2, 4-toluene diisocyanate under the protection of nitrogen, performing ultrasonic treatment for 30min, adding 4 drops of dibutyltin dilaurate, and performing reflux for 5h at 65 ℃.
A preparation method of a polyhexamethylene adipamide ultrafiltration membrane comprises the following steps:
(1) preparing a casting solution: stirring a solvent at the stirring speed of 300rpm, keeping stirring, pouring polyhexamethylene adipamide, pouring polyvinylpyrrolidone after the polyhexamethylene adipamide is dissolved, stirring for 10 hours, and vacuumizing until no bubbles are seen in the casting solution;
(2) and (3) synthesis of a membrane: pouring the casting film liquid on a smooth and flat plane, scraping the film by using a film scraping machine, keeping the thickness of the film at 0.3mm, standing at room temperature for 6h, and then putting the film and the plane into water at a constant speed to enable the film to naturally fall off.
Example 3
A polyhexamethylene adipamide ultrafiltration membrane comprises the following raw materials in parts by weight:
72 parts of solvent, 21 parts of polyhexamethylene adipamide and 6 parts of polyvinylpyrrolidone.
Wherein, the solvent comprises the following components in parts by weight: 32 parts of formic acid and 36 parts of dichloromethane.
Wherein the polyhexamethylene adipamide is treated by the following method: dissolving 20 parts by weight of polyhexamethylene adipamide with formic acid, precipitating with ethanol, adding a mixture of lanthanum citrate and cerium butane tetraacetate with the mass ratio of 1: 2, which is 5% of the mass of the polyhexamethylene adipamide, mixing and stirring, adding 1 part by weight of nano silicon dioxide, performing ultrasonic treatment at 85 ℃ for 20min, and heating at 180 ℃ for 3 h.
The lanthanum citrate is prepared by the following steps: dissolving 3 parts by weight of lanthanum acetate in 10 parts by weight of water, dissolving 3 parts by weight of citric acid in 10 parts by weight of water, then mixing the solutions, heating to 85 ℃, stirring for 2 hours at the rotating speed of 300rpm, filtering, taking out solids, washing and drying; the butane cerium tetraacetate is prepared by the following method: adding 10 parts by weight of 10% sodium hydroxide solution into 4 parts by weight of 1,2,3, 4-butanetetracarboxylic acid, adding 5% dilute hydrochloric acid until the pH value of the solution is 6, then adding 5 parts by weight of cerium trichloride, preserving the temperature at 70 ℃ for 2.5h, and washing and drying the product by using clean water.
Wherein, the nano silicon dioxide is processed by the following method: soaking 2 parts by weight of nano silicon dioxide in water, adding hydrochloric acid, performing ultrasonic treatment for 20min, standing for 24h, performing centrifugal separation, performing vacuum drying for 18h at 160 ℃, then adding 2, 4-toluene diisocyanate under the protection of nitrogen, performing ultrasonic treatment for 30min, adding 4 drops of dibutyltin dilaurate, and performing reflux for 5h at 65 ℃.
A preparation method of a polyhexamethylene adipamide ultrafiltration membrane comprises the following steps:
(1) preparing a casting solution: stirring a solvent at the stirring speed of 300rpm, keeping stirring, pouring polyhexamethylene adipamide, pouring polyvinylpyrrolidone after the polyhexamethylene adipamide is dissolved, stirring for 10 hours, and vacuumizing until no bubbles are seen in the casting solution;
(2) and (3) synthesis of a membrane: pouring the casting film liquid on a smooth and flat plane, scraping the film by using a film scraping machine, keeping the thickness of the film at 0.3mm, standing at room temperature for 4h, and then putting the film and the plane into water at a constant speed to enable the film to naturally fall off.
Example 4
A polyhexamethylene adipamide ultrafiltration membrane comprises the following raw materials in parts by weight:
72 parts of solvent, 21 parts of polyhexamethylene adipamide and 6 parts of polyvinylpyrrolidone.
Wherein, the solvent comprises the following components in parts by weight: 32 parts of formic acid and 36 parts of dichloromethane.
Wherein the polyhexamethylene adipamide is treated by the following method: dissolving 20 parts by weight of polyhexamethylene adipamide with formic acid, precipitating with ethanol, adding a mixture of lanthanum citrate and cerium butane tetraacetate with the mass ratio of 1: 2, which is 5% of the mass of the polyhexamethylene adipamide, mixing and stirring, adding 1 part by weight of nano silicon dioxide, performing ultrasonic treatment at 85 ℃ for 20min, and heating at 180 ℃ for 3 h.
The lanthanum citrate is prepared by the following steps: dissolving 3 parts by weight of lanthanum acetate in 10 parts by weight of water, dissolving 3 parts by weight of citric acid in 10 parts by weight of water, then mixing the solutions, heating to 85 ℃, stirring for 2 hours at the rotating speed of 300rpm, filtering, taking out solids, washing and drying; the butane cerium tetraacetate is prepared by the following method: adding 10 parts by weight of 10% sodium hydroxide solution into 4 parts by weight of 1,2,3, 4-butanetetracarboxylic acid, adding 5% dilute hydrochloric acid until the pH value of the solution is 6, then adding 5 parts by weight of cerium trichloride, preserving the temperature at 70 ℃ for 2.5h, and washing and drying the product by using clean water.
Wherein, the nano silicon dioxide is processed by the following method: soaking 2 parts by weight of nano silicon dioxide in water, adding hydrochloric acid, performing ultrasonic treatment for 20min, standing for 24h, performing centrifugal separation, performing vacuum drying for 18h at 160 ℃, then adding 2, 4-toluene diisocyanate under the protection of nitrogen, performing ultrasonic treatment for 30min, adding 4 drops of dibutyltin dilaurate, and performing reflux for 5h at 65 ℃.
A preparation method of a polyhexamethylene adipamide ultrafiltration membrane comprises the following steps:
(1) preparing a casting solution: stirring a solvent at the stirring speed of 300rpm, keeping stirring, pouring polyhexamethylene adipamide, pouring polyvinylpyrrolidone after the polyhexamethylene adipamide is dissolved, stirring for 10 hours, and vacuumizing until no bubbles are seen in the casting solution;
(2) and (3) synthesis of a membrane: pouring the casting film liquid on a smooth and flat plane, scraping the film by using a film scraping machine, keeping the thickness of the film at 0.3mm, standing at room temperature for 6h, and then putting the film and the plane into water at a constant speed to enable the film to naturally fall off.
Example 5
A polyhexamethylene adipamide ultrafiltration membrane comprises the following raw materials in parts by weight:
72 parts of solvent, 21 parts of polyhexamethylene adipamide and 6 parts of polyvinylpyrrolidone.
Wherein, the solvent comprises the following components in parts by weight: 32 parts of formic acid and 36 parts of dichloromethane.
Wherein the polyhexamethylene adipamide is treated by the following method: dissolving 20 parts by weight of polyhexamethylene adipamide with formic acid, precipitating with ethanol, adding a mixture of lanthanum citrate and cerium butane tetraacetate with the mass ratio of 1: 2, which is 5% of the mass of the polyhexamethylene adipamide, mixing and stirring, adding 1 part by weight of nano silicon dioxide, performing ultrasonic treatment at 85 ℃ for 20min, and heating at 180 ℃ for 3 h.
The lanthanum citrate is prepared by the following steps: dissolving 3 parts by weight of lanthanum acetate in 10 parts by weight of water, dissolving 3 parts by weight of citric acid in 10 parts by weight of water, then mixing the solutions, heating to 85 ℃, stirring for 2 hours at the rotating speed of 300rpm, filtering, taking out solids, washing and drying; the butane cerium tetraacetate is prepared by the following method: adding 10 parts by weight of 10% sodium hydroxide solution into 4 parts by weight of 1,2,3, 4-butanetetracarboxylic acid, adding 5% dilute hydrochloric acid until the pH value of the solution is 6, then adding 5 parts by weight of cerium trichloride, preserving the temperature at 70 ℃ for 2.5h, and washing and drying the product by using clean water.
Wherein, the nano silicon dioxide is processed by the following method: soaking 2 parts by weight of nano silicon dioxide in water, adding hydrochloric acid, performing ultrasonic treatment for 20min, standing for 24h, performing centrifugal separation, performing vacuum drying for 18h at 160 ℃, then adding 2, 4-toluene diisocyanate under the protection of nitrogen, performing ultrasonic treatment for 30min, adding 4 drops of dibutyltin dilaurate, and performing reflux for 5h at 65 ℃.
A preparation method of a polyhexamethylene adipamide ultrafiltration membrane comprises the following steps:
(1) preparing a casting solution: stirring a solvent at the stirring speed of 300rpm, keeping stirring, pouring polyhexamethylene adipamide, pouring polyvinylpyrrolidone after the polyhexamethylene adipamide is dissolved, stirring for 10 hours, and vacuumizing until no bubbles are seen in the casting solution;
(2) and (3) synthesis of a membrane: pouring the casting film liquid on a smooth and flat plane, scraping the film by using a film scraping machine, keeping the thickness of the film at 0.3mm, standing at room temperature for 8h, and then putting the film and the plane into water at a constant speed to enable the film to naturally fall off.
Example 6
A polyhexamethylene adipamide ultrafiltration membrane comprises the following raw materials in parts by weight:
72 parts of solvent, 21 parts of polyhexamethylene adipamide and 6 parts of polyvinylpyrrolidone.
Wherein, the solvent comprises the following components in parts by weight: 32 parts of formic acid and 36 parts of dichloromethane.
Wherein the polyhexamethylene adipamide is treated by the following method: dissolving 20 parts by weight of polyhexamethylene adipamide with formic acid, precipitating with ethanol, adding a mixture of lanthanum citrate and cerium butane tetraacetate with the mass ratio of 1: 2, which is 5% of the mass of the polyhexamethylene adipamide, mixing and stirring, adding 1 part by weight of nano silicon dioxide, performing ultrasonic treatment at 85 ℃ for 20min, and heating at 180 ℃ for 3 h.
The lanthanum citrate is prepared by the following steps: dissolving 3 parts by weight of lanthanum acetate in 10 parts by weight of water, dissolving 3 parts by weight of citric acid in 10 parts by weight of water, then mixing the solutions, heating to 85 ℃, stirring for 2 hours at the rotating speed of 300rpm, filtering, taking out solids, washing and drying; the butane cerium tetraacetate is prepared by the following method: adding 10 parts by weight of 10% sodium hydroxide solution into 4 parts by weight of 1,2,3, 4-butanetetracarboxylic acid, adding 5% dilute hydrochloric acid until the pH value of the solution is 6, then adding 5 parts by weight of cerium trichloride, preserving the temperature at 70 ℃ for 2.5h, and washing and drying the product by using clean water.
Wherein, the nano silicon dioxide is processed by the following method: soaking 2 parts by weight of nano silicon dioxide in water, adding hydrochloric acid, performing ultrasonic treatment for 20min, standing for 24h, performing centrifugal separation, performing vacuum drying for 18h at 160 ℃, then adding 2, 4-toluene diisocyanate under the protection of nitrogen, performing ultrasonic treatment for 30min, adding 4 drops of dibutyltin dilaurate, and performing reflux for 5h at 65 ℃.
A preparation method of a polyhexamethylene adipamide ultrafiltration membrane comprises the following steps:
(1) preparing a casting solution: stirring a solvent at the stirring speed of 300rpm, keeping stirring, pouring polyhexamethylene adipamide, pouring polyvinylpyrrolidone after the polyhexamethylene adipamide is dissolved, stirring for 10 hours, and vacuumizing until no bubbles are seen in the casting solution;
(2) and (3) synthesis of a membrane: pouring the casting film liquid on a smooth and flat plane, scraping the film by using a film scraping machine, keeping the thickness of the film at 0.3mm, standing at room temperature for 12h, and then putting the film and the plane into water at a constant speed to enable the film to naturally fall off.
The following tests were performed on the examples of the present invention with different film forming time, and the test results are as follows:
water flux of the Membrane (example 3)
| Number of times | Time(s) | Volume (L) | Water flux (L.s)-1.m-2) |
| 1 | 140.55 | 0.250 | 0.462 |
| 2 | 143.66 | 0.250 | 0.452 |
| 3 | 130.92 | 0.250 | 0.496 |
Water flux of the Membrane (example 4)
| Number of times | Time(s) | Volume (L) | Water flux (L.s)-1.m-2) |
| 1 | 53.23 | 0.250 | 1.220 |
| 2 | 55.60 | 0.250 | 1.168 |
| 3 | 51.33 | 0.250 | 1.265 |
Water flux of the Membrane (example 5)
| Number of times | Time(s) | Volume (L) | Water flux (L.s)-1.m-2) |
| 1 | 58.50 | 0.250 | 1.110 |
| 2 | 51.41 | 0.250 | 1.263 |
| 3 | 52.79 | 0.250 | 1.230 |
Water flux of Membrane (example 6)
| Number of times | Time(s) | Volume (L) | Water flux (L.s)-1.m-2) |
| 1 | 95.63 | 0.250 | 0.679 |
| 2 | 85.22 | 0.250 | 0.762 |
| 3 | 82.72 | 0.250 | 0.785 |
The water flux of the membrane obtained by leaving the membrane in the air for 4 hours after scraping the membrane and then adding water is 0.47 L.s-1.m-2The water flux of the membrane obtained by leaving the membrane in the air for 6 hours after scraping the membrane and then introducing water is 1.218 L.s-1.m-2The water flux of the membrane obtained by leaving the membrane in the air for 8 hours after scraping the membrane and then introducing water is 1.201 L.s-1.m-2The water flux of the membrane obtained by leaving the membrane in the air for 12 hours after scraping the membrane and then introducing water was 0.742L · s-1.m-2. On the comparison of water flux, the state of the ultrafiltration membrane obtained after the membrane casting solution is scraped and placed in the air for 6 hours is the best, and the maximum state can reach 1.265 L.s-1.m-2。
The following water flux test was performed for the preferred embodiment 3 of the present invention, and the test results are shown below:
| number of times | Time(s) | Volume (L) | Water flux (L.s)-1.m-2) |
| 1 | 53.21 | 0.250 | 1.220 |
| 2 | 66.94 | 0.280 | 1.086 |
| 3 | 56.91 | 0.255 | 1.164 |
| 4 | 60.24 | 0.210 | 0.905 |
| 5 | 59.35 | 0.225 | 0.985 |
| 6 | 52.11 | 0.243 | 1.211 |
| 7 | 61.35 | 0.265 | 1.122 |
| 8 | 58.21 | 0.238 | 1.062 |
| 9 | 56.33 | 0.229 | 1.056 |
The tensile strength of the film of example 3 was tested as follows:
cross section of membrane
| Film sample 1 | Thickness (mm) | Cross sectional area (mm)2) |
| First measurement | 0.3 | 4.5 |
| Second measurement | 0.31 | 4.65 |
| Measuring the weight for the third time | 0.32 | 4.8 |
| Mean value | 0.31 | 4.65 |
The tensile strength of the film reached 4.1MPa, the force required being 19.05N maximum. The strength required by the invention is above 4MPa, the strength is very high, the fracture is not easy to occur, and the invention is worthy of use.
The films of example 3 were tested for thermal stability as follows:
the ultrafiltration membrane, PA66 and PVP of example 3 were tested on a differential scanning calorimeter, respectively, and the experimental results obtained were as follows: the PA66 composite ultrafiltration membrane is tested, the first one is an evaporation peak, because some formic acid still remains in the membrane, the surplus formic acid is gradually evaporated along with the increase of the temperature, the evaporation temperature is between 50 ℃ and 92 ℃, the weight loss occurs, and then other impurities in the membrane are gradually evaporated along with the increase of the temperature, and the evaporation temperature is between 210 ℃ and 230 ℃. The invention melts between 255 ℃ and 265 ℃. Therefore, the invention has good heat resistance and can treat industrial wastewater with higher temperature.
The membranes of the examples were tested for their oleophilic and hydrophilic properties as follows:
table 3.12 contact angle data:
| number of times | Left contact angle | Right contact angle |
| Example 1 | 32.9° | 38.2° |
| Example 2 | 25.5° | 26.6° |
| Example 3 | 23.7° | 28.0° |
| Example 4 | 25.5° | 28.3° |
| Example 5 | 26.5° | 33.9° |
| Example 6 | 22.9° | 24.7° |
The measurement shows that the water contact angle value of the film is smaller on the left and right, the average value of the left angle is 26.17 degrees, the average value of the right angle is 29.97 degrees, the left angle and the right angle are smaller than 90 degrees, and the hydrophilic performance of the film is good according to the experimental measurement result.
The membrane of example 3 was used to filter the wastewater as follows:
| crude oil-containing sewage (mg/L) | Water sample after filtration (mg/L) | Removal rate | |
| 424.02 | 14.26 | 96.64％ | |
| 424.02 | 9.56 | 97.75％ | |
| 424.02 | 17.63 | 95.84％ | |
| Mean value of | 424.02 | 13.82 | 98％ |
The oily sewage taken in the experiment is industrial wastewater, wherein the oil content is 424.02mg/L, a water sample with low oil content shown in the figure is obtained after the oily sewage is subjected to membrane filtration, and the average value of the water sample is 13.82mg/L after multiple times of measurement. The removal rate of oil reaches 98 percent, which shows that the effect of filtering the oily sewage is good.
In view of the above, it is desirable to provide,
the water flux of the membrane is high and can reach 1.265 L.s at most-1·m-2This indicates that more water can pass through the membrane filtration.
The tensile strength of the membrane reaches 4.69MPa, which indicates that the membrane is not easy to crush when treating oily sewage and has good compressive capacity.
The water contact angle of the membrane is 26.17 degrees on the average for the left angle, 29.97 degrees on the average for the right angle, and less than 90 degrees on both sides, indicating that the membrane has good hydrophilic performance.
After the oily sewage is filtered by the method, the oil phase ratio in the filtered water sample begins to remove by 98 percent, which shows that the membrane has good oil stain removal effect on the oily sewage.
From the above, the invention has good effects on water flux, tensile resistance of the membrane, hydrophilic oleophilic property, thermal stability and oil stain removal capability, the oil-water separation capability is very high, and the filtered water sample can be obtained without too complex treatment. The membrane is simple to manufacture, few in raw materials and simple in process, can be manufactured in batches, is easy to degrade after being used, does not need to consume large manpower and material resources, and does not pollute the environment.
Claims (6)
1. The polyhexamethylene adipamide ultrafiltration membrane is characterized by comprising the following raw materials in parts by weight:
70 to 75 parts of solvent, 20 to 22 parts of polyhexamethylene adipamide, 5 to 8 parts of polyvinylpyrrolidone,
the polyhexamethylene adipamide is treated by the following method: dissolving 20-30 parts by weight of polyhexamethylene adipamide with formic acid, precipitating with ethanol, adding organic acid salt accounting for 5-10% of the mass of the polyhexamethylene adipamide, mixing and stirring, adding 1-2 parts by weight of nano silicon dioxide, performing ultrasonic treatment at 85-95 ℃ for 20-25 min, and heating at 180-190 ℃ for 3-5 h;
the organic acid salt is a mixture of lanthanum citrate and cerium butane tetraacetate, and the mass ratio of the lanthanum citrate to the cerium butane tetraacetate is 1: 2-2: 3;
the lanthanum citrate is prepared by the following steps: dissolving 3-4 parts by weight of lanthanum acetate in 10-15 parts by weight of water, dissolving 3-4 parts by weight of citric acid in 10-15 parts by weight of water, mixing the solutions, heating to 85-90 ℃, stirring for 1-2 hours at the rotating speed of 300-400 rpm, filtering, taking out solids, washing and drying;
the butane cerium tetraacetate is prepared by the following method: adding 10-15 parts by weight of 10-15% sodium hydroxide solution into 4-5 parts by weight of 1,2,3, 4-butanetetracarboxylic acid, adding 5-10% dilute hydrochloric acid until the pH value of the solution is 6-7.5, then adding 4-5 parts by weight of cerium trichloride, preserving heat at 65-70 ℃ for 1.5-2.5 h, and washing and drying the product by using clear water.
2. The polyhexamethylene adipamide ultrafiltration membrane according to claim 1, wherein the solvent comprises the following components in parts by weight: 30-35 parts of formic acid and 35-40 parts of dichloromethane.
3. The polyhexamethylene adipamide ultrafiltration membrane according to claim 1, wherein the nanosilica is treated by the following method: soaking 2-3 parts by weight of nano silicon dioxide in water, adding hydrochloric acid, performing ultrasonic treatment for 20-25 min, standing for 24-48 h, performing centrifugal separation, performing vacuum drying at 150-160 ℃ for 18-20 h, adding 2, 4-toluene diisocyanate under the protection of nitrogen, performing ultrasonic treatment for 30-40 min, adding 3-4 drops of dibutyltin dilaurate, and performing reflux at 65-68 ℃ for 5-6 h.
4. A method of preparing a polyhexamethylene adipamide ultrafiltration membrane according to any one of claims 1 to 3, comprising the steps of:
(1) preparing a casting solution: stirring a solvent, keeping stirring, pouring polyhexamethylene adipamide, pouring polyvinylpyrrolidone after the polyhexamethylene adipamide is dissolved, stirring for 10-12 hours, and vacuumizing until no bubbles are seen in a casting solution;
(2) and (3) synthesis of a membrane: pouring the casting film liquid on a smooth and flat plane, scraping the film by using a film scraping machine, standing at room temperature, and then putting the film and the plane into water at a constant speed to enable the film to naturally fall off.
5. The method for preparing the polyhexamethylene adipamide ultrafiltration membrane according to claim 4, wherein the ultrafiltration membrane comprises the following steps: the stirring speed in the step (1) is 300-400 rpm.
6. The method for preparing the polyhexamethylene adipamide ultrafiltration membrane according to claim 4, wherein the ultrafiltration membrane comprises the following steps: and (3) standing for 5-6 h in the step (2), wherein the thickness of the scraping film is 0.3-0.5 mm.
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