CN114669204B - A kind of composite separation membrane and its preparation method and application - Google Patents

Abstract

The invention relates to a preparation method of a composite separation membrane. In the method, a metal salt solution, a polyphenol solution and an oxidant solution are used together to cause a complexation reaction and an oxidative polymerization reaction to occur on a polymer substrate, thereby forming a hydrophilic The highly resistant modified layer improves the flux, rejection rate and anti-pollution performance of the separation membrane. The preparation method is short in time, simple in operation, mild in reaction conditions, easy to realize large-scale industrial application, and has obvious promotion advantages. The preparation method of the invention can be carried out by inkjet printing, has high raw material utilization rate, no waste of resources, and is environmentally friendly. The invention also relates to the composite separation membrane obtained by the above preparation method, which has strong hydrophilicity, high flux, rejection rate and anti-pollution performance, good separation effect, and is of great significance in the separation of oil-water emulsion.

Description

A kind of composite separation membrane and its preparation method and application

technical field

The invention relates to the field of preparation of polymer separation membranes, in particular to a composite separation membrane and its preparation method and application.

Background technique

Membrane separation technology uses the selective permeability of the membrane to separate different components from the mixture under the action of external force, so as to achieve the purposes of separation, purification, concentration and classification. Membrane separation technology has the advantages of high efficiency, low cost, less secondary pollution, simple operation, and energy saving, and is playing an increasingly important role in water and wastewater treatment.

However, commonly used organic polymer membranes are easily contaminated by oil droplets due to their low surface energy and strong hydrophobicity, resulting in severely reduced flux and rejection rates and shortened membrane life. If the membrane surface is hydrophilic, it can form a hydration layer under water, thereby maintaining high permeate flux and excellent antifouling properties. Therefore, the hydrophilic modification of the surface of the organic polymer membrane is an effective way to improve the anti-fouling performance of the membrane and expand the application of membrane separation technology in the field of oil-water separation. A commonly used hydrophilic modification method is to load hydrophilic modified materials on the surface of organic polymer membranes. However, the existing organic polymer membranes loaded with hydrophilic modified materials still have the disadvantage of weak hydrophilicity.

Therefore, it is necessary to develop a method for preparing a separation membrane with strong hydrophilicity.

Contents of the invention

The purpose of the present invention is to overcome the shortcoming of prior art, provide a kind of preparation method of composite separation membrane, this method is by using metal salt solution, polyphenol solution and oxidizing agent solution in conjunction, make it to produce complexation reaction on polymer substrate And oxidative polymerization reaction, thereby forming a modified layer with strong hydrophilicity, which improves the flux, rejection rate and anti-fouling performance of the separation membrane.

Another object of the present invention is to provide a composite separation membrane obtained by the above preparation method, which has higher flux, rejection rate and anti-pollution performance.

Another object of the present invention is to provide the application of the composite separation membrane in the treatment of oily wastewater.

In order to achieve the above objectives, the present invention provides the following technical solutions.

A method for preparing a composite separation membrane, comprising:

The metal salt solution, the polyphenol solution and the oxidizing agent solution are reacted on the surface of the polymer base to form a modified layer on the surface of the polymer base to obtain a composite separation membrane.

In the present invention, the formation mechanism of the modified layer is as follows: a part of the phenolic hydroxyl groups of polyphenols undergoes a complex reaction with metal ions in the metal salt solution, and another part of the phenolic hydroxyl groups undergoes oxidative polymerization under the action of an oxidant, thereby forming a modified layer. sex layer.

Preferably, the preparation method of the metal salt solution comprises: dissolving the metal salt in a solvent, wherein the metal salt is ferric sulfate or ferric chloride, and the solvent is water, alcohol or a mixture thereof. Preferably, the alcohol is ethanol or propanol. Preferably, the solvent is a mixture of water and alcohol. Preferably, the concentration of alcohol in the mixture is 10-30%. If the alcohol concentration is too low, the contact angle between the mixture and the membrane surface will be larger, and it is not conducive to the penetration of droplets, resulting in uneven distribution of the coating. If the concentration is too high, it is not conducive to subsequent cleaning, and it will cause waste of reagents. Preferably, the concentration of the metal salt solution is below 23.5mmol/L, such as 4-23.5mmol/L. Excessive concentration can cause clogging of the ink cartridge, and excessive metal salts can accumulate on the membrane surface when the metal salts, polyphenols, and oxidants react, resulting in uneven distribution of the coating. If the concentration is too low, the printing effect is not obvious, and more printing times are required, and the time cost is high.

Preferably, the preparation method of the polyphenol solution comprises: dissolving polyphenol in a solvent, wherein the polyphenol is tannic acid, and the solvent is water, alcohol or a mixture thereof. Preferably, the alcohol is ethanol or propanol. Preferably, the concentration of the polyphenol solution is below 47mmol/L, such as 7.8-47mmol/L. Excessive concentration can cause clogging of the ink cartridge, and excessive metal salts can accumulate on the membrane surface when the metal salts, polyphenols, and oxidants react, resulting in uneven distribution of the coating. Preferably, the solvent used to dissolve the polyphenols does not contain dissolved oxygen, thereby preventing polyphenols such as tannic acid from accumulating in the ink cartridge and clogging the ink cartridge. If the concentration is too low, the printing effect is not obvious, and more printing times are required, and the time cost is high.

Preferably, the preparation method of the oxidizing agent solution comprises: dissolving the oxidizing agent in a solvent, wherein the oxidizing agent is at least one of sodium periodate, potassium permanganate and potassium dichromate, and the solvent is water, Alcohol or mixtures thereof. Preferably, the alcohol is ethanol or propanol. Preferably, the concentration of the oxidant solution is below 94mmol/L, such as 15.7-94mmol/L. Excessive concentration can cause ink cartridge clogging. If the concentration is too low, the printing effect is not obvious, and more printing times are required, and the time cost is high.

Preferably, the polymer substrate is polyester, polypropylene, polyvinylidene fluoride, polysulfone or polyethylene. Preferably, prior to use, the polymeric substrate is soaked in ethanol to remove surface stains, ultrasonically cleaned, and then dried.

Preferably, the method for forming the modified layer includes: sequentially printing a metal salt solution, a polyphenol solution and an oxidizing agent solution on the surface of the polymer substrate by inkjet printing, and reacting the three to form the modified layer. Preferably, the reaction time is 5-60min.

In the present invention, the modified layer may be formed on one or both surfaces of the polymer substrate.

In some embodiments, before printing, one surface of the polymer substrate can be pasted on a substrate such as paper to form the modified layer on the other surface. Paper is easy to print on, is cheap and readily available, and can be reused if necessary.

Preferably, when the concentration ratio of the metal salt solution, the polyphenol solution and the oxidant solution is 1:(1.8-2.2):(3.8-4.2), preferably 1:2:4, the The ratio of the printing times of the metal salt solution, the polyphenol solution and the oxidant solution is (1-10):(1-5):(1-5), preferably (1-5):1:1, More preferably (2-3):1:1, most preferably 2:1:1. In some preferred embodiments, the printing times of the metal salt solution are 1-6 times, the printing times of the polyphenol solution are 1-3 times, and the printing times of the oxidant solution are 1-3 times.

Preferably, before printing, the metal salt solution, the polyphenol solution and the oxidant solution are respectively filled into different ink cartridges, and then the ink cartridges filled with the solutions are installed on the printer for testing.

Preferably, after the reaction is completed, the obtained composite separation membrane is washed with water to remove unreacted raw materials.

Preferably, the preparation method further includes: washing and drying after the reaction is completed. Preferably, washing can be performed with water. Preferably, drying includes air drying or drying. The drying temperature is 30-60°C.

The present invention also provides the composite separation membrane obtained by the above preparation method. The water contact angle of the composite separation membrane is 70° or less. Under the pressure of 0.4Mpa, the rejection rate of the composite separation membrane to the oil-containing emulsion reaches more than 98%, and the flux reaches more than 4968.4L·m ^-2 ·h ^-1 ·bar ^-1 . The flux recovery rate of the composite separation membrane reaches more than 89.1%. The composite separation membrane has low water contact angle and strong hydrophilicity, so it has high flux, rejection rate and anti-pollution performance.

The invention also provides the application of the composite separation membrane in the treatment of oily wastewater.

Compared with prior art, the beneficial effect of the present invention:

1. The present invention provides a method for preparing a composite separation membrane. In this method, a metal salt solution, a polyphenol solution and an oxidant solution are used together to cause a complexation reaction and an oxidative polymerization reaction to occur on a polymer substrate, thereby forming A modified layer with strong hydrophilicity was added, which improved the flux, rejection rate and anti-pollution performance of the separation membrane.

The preparation method is short in time, simple in operation, mild in reaction conditions, easy to realize large-scale industrial application, and has obvious promotion advantages.

2. The preparation method of the present invention can be carried out by inkjet printing, the utilization rate of raw materials is high, there is no waste of resources, and the environment is friendly. However, the existing method for preparing the modified layer is usually carried out by soaking the polymer substrate in a solution, the utilization rate of raw materials is very low, and most of the solution is not used, resulting in serious waste of resources and environmental pollution.

3. The composite separation membrane of the present invention has strong hydrophilicity, high flux, rejection rate and anti-pollution performance, good separation effect, and is of great significance in the separation of oil-water emulsion.

4. The present invention is applicable to a wide range of objects, and can realize polyphenol coating on various polymer substrates.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings according to the provided drawings without creative work.

Fig. 1 is a flow chart of the preparation of the composite separation membrane of the present invention.

Figure 2 is the SEM image of (a) blank PVDF membrane, (b) Fe-TA composite separation membrane, (c) TA-SP composite separation membrane and (d) Fe-TA-SP composite separation membrane of Example 1.

Fig. 3 is a diagram of the oil-water separation efficiency of different oil-water emulsions by the blank PVDF membrane and the Fe-TA-SP composite separation membrane of Example 1.

Fig. 4 is a graph of the flux recovery rate of the blank PVDF membrane and the Fe-TA-SP composite separation membrane of Example 1 after 8 separation cycles of different oil-water emulsions.

Detailed ways

In order to make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific examples, but the present invention is not limited thereto. All technologies realized based on the above contents of the present invention are covered within the scope of protection intended by the present invention. Unless otherwise stated, the raw materials and reagents used in the examples are commercially available. Reagents, instruments or operation steps not described herein are those that can be routinely determined by those of ordinary skill in the art.

Embodiment 1: the preparation of hydrophilic Fe-TA-SP composite separation membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use 11.75mM Fe ₂ (SO ₄ ) ₃ solution and 47mM NaIO ₄ solution were prepared from the above solutions respectively to obtain Fe ink and SP ink;

(3) Equip ink cartridges: Inject the three kinds of inks prepared in (2) into three commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 4 times of Fe ink, then 2 times of TA ink, and finally 2 times of SP ink, and put the resulting film at room temperature The Fe-TA-SP composite separation membrane was prepared by keeping it for 15 min.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Embodiment 2: the preparation of hydrophilic Fe-TA-SP composite separation membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use 11.75mM Fe ₂ (SO ₄ ) ₃ solution and 47mM NaIO ₄ solution were prepared from the above solutions respectively to obtain Fe ink and SP ink;

(3) Equip ink cartridges: Inject the three kinds of inks prepared in (2) into three commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 4 times of Fe ink, then 2 times of TA ink, and finally 2 times of SP ink, and put the resulting film at room temperature The Fe-TA-SP composite separation membrane was prepared by keeping it for 5 min.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Embodiment 3: the preparation of hydrophilic Fe-TA-SP composite separation membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use 11.75mM Fe ₂ (SO ₄ ) ₃ solution and 47mM NaIO ₄ solution were prepared from the above solutions respectively to obtain Fe ink and SP ink;

(3) Equip ink cartridges: Inject the three kinds of inks prepared in (2) into three commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 4 times of Fe ink, then 2 times of TA ink, and finally 2 times of SP ink, and put the resulting film at room temperature The Fe-TA-SP composite separation membrane was prepared by keeping it for 10 min.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Embodiment 4: the preparation of hydrophilic Fe-TA-SP composite separation membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use 11.75mM Fe ₂ (SO ₄ ) ₃ solution and 47mM NaIO ₄ solution were prepared from the above solutions respectively to obtain Fe ink and SP ink;

(3) Equip ink cartridges: Inject the three kinds of inks prepared in (2) into three commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 4 times of Fe ink, then 2 times of TA ink, and finally 2 times of SP ink, and put the resulting film at room temperature The Fe-TA-SP composite separation membrane was prepared by keeping it for 30 min.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Embodiment 5: the preparation of hydrophilic Fe-TA-SP composite separation membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use 11.75mM Fe ₂ (SO ₄ ) ₃ solution and 47mM NaIO ₄ solution were prepared from the above solutions respectively to obtain Fe ink and SP ink;

(3) Equip ink cartridges: Inject the three kinds of inks prepared in (2) into three commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 1 time of Fe ink, then 1 time of TA ink, and finally 1 time of SP ink, and put the obtained film at room temperature The Fe-TA-SP composite separation membrane was prepared by keeping it for 15 min.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Embodiment 6: the preparation of hydrophilic Fe-TA-SP composite separation membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use 11.75mM Fe ₂ (SO ₄ ) ₃ solution and 47mM NaIO ₄ solution were prepared from the above solutions respectively to obtain Fe ink and SP ink;

(3) Equip ink cartridges: Inject the three kinds of inks prepared in (2) into three commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 2 times of Fe ink, then 1 time of TA ink, and finally 1 time of SP ink, and put the resulting film at room temperature The Fe-TA-SP composite separation membrane was prepared by keeping it for 15 min.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Embodiment 7: the preparation of hydrophilic Fe-TA-SP composite separation membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use 11.75mM Fe ₂ (SO ₄ ) ₃ solution and 47mM NaIO ₄ solution were prepared from the above solutions respectively to obtain Fe ink and SP ink;

(3) Equip ink cartridges: Inject the three kinds of inks prepared in (2) into three commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 3 times with Fe ink, then 1 time with TA ink, and finally 1 time with SP ink, and put the resulting film at room temperature The Fe-TA-SP composite separation membrane was prepared by keeping it for 15 min.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Embodiment 8: the preparation of hydrophilic Fe-TA-SP composite separation membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use 11.75mM Fe ₂ (SO ₄ ) ₃ solution and 47mM NaIO ₄ solution were prepared from the above solutions respectively to obtain Fe ink and SP ink;

(3) Equip ink cartridges: Inject the three kinds of inks prepared in (2) into three commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 5 times of Fe ink, then 1 time of TA ink, and finally 1 time of SP ink, and put the obtained film at room temperature The Fe-TA-SP composite separation membrane was prepared by keeping it for 15 min.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Embodiment 9: the preparation of hydrophilic Fe-TA-SP composite separation membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use 11.75mM Fe ₂ (SO ₄ ) ₃ solution and 47mM NaIO ₄ solution were prepared from the above solutions respectively to obtain Fe ink and SP ink;

(3) Equip ink cartridges: Inject the three kinds of inks prepared in (2) into three commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 4 times of Fe ink, then 1 time of TA ink, and finally 2 times of SP ink, and put the resulting film at room temperature The Fe-TA-SP composite separation membrane was prepared by keeping it for 15 min.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Embodiment 10: the preparation of hydrophilic Fe-TA-SP composite separation membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use 11.75mM Fe ₂ (SO ₄ ) ₃ solution and 47mM NaIO ₄ solution were prepared from the above solutions respectively to obtain Fe ink and SP ink;

(3) Equip ink cartridges: Inject the three kinds of inks prepared in (2) into three commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 6 times of Fe ink, then print 1 time of TA ink, and finally print 3 times of SP ink, and put the resulting film at room temperature The Fe-TA-SP composite separation membrane was prepared by keeping it for 15 min.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Example 11: Preparation of hydrophilic Fe-TA-SP composite separation membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use 11.75mM Fe ₂ (SO ₄ ) ₃ solution and 47mM NaIO ₄ solution were prepared from the above solutions respectively to obtain Fe ink and SP ink;

(3) Equip ink cartridges: Inject the three kinds of inks prepared in (2) into three commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 6 times of Fe ink, then print 3 times of TA ink, and finally print 3 times of SP ink, and put the resulting film at room temperature The Fe-TA-SP composite separation membrane was prepared by keeping it for 15 min.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Comparative Example 1: Preparation of Fe-TA Composite Separation Membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use Prepare 11.75mM Fe ₂ (SO ₄ ) ₃ solution from the above solution to obtain Fe ink;

(3) Equip ink cartridges: Inject the two kinds of inks prepared in (2) into two commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 4 times of Fe ink, then print 2 times of TA ink, and keep the obtained film at room temperature for 15min to obtain Fe -TA composite separation membrane.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

Comparative Example 2: Preparation of TA-SP Composite Separation Membrane

(1) Treatment of the blank film: first soak the polyvinylidene fluoride film in ethanol for 30 minutes to remove the stains on the film surface, then ultrasonically clean the film with pure water for 2-3 times, and finally dry it at 60°C to obtain a blank film ;

(2) Ink preparation: prepare 17% n-propanol solution with cooled distilled water after boiling, add a certain amount of tannic acid to form a 23.5mM tannic acid solution, and obtain TA ink; prepare 17% n-propanol solution with distilled water, use Above-mentioned solution prepares _47mMNaIO Solution, obtains SP ink;

(3) Equip ink cartridges: Inject the two kinds of inks prepared in (2) into two commercial HP ink cartridges with syringes respectively, and equip them on HP desktop 1112 printers for testing;

(4) Inkjet printing: Paste the blank film processed in (1) on A4 paper, first print 2 times with TA ink, then print 2 times with SP ink, and keep the obtained film at room temperature for 15 minutes to obtain TA -SP composite separation membrane.

(5) Washing and drying: The composite separation membrane prepared in (4) was thoroughly washed 2-3 times with pure water, dried at 40°C and stored in a sealed bag.

In order to further illustrate that the composite separation membrane prepared by the present invention has an excellent effect, the inventor has also carried out the following tests:

(1) Determination of water contact angle of Fe-TA-SP composite separation membrane

Table 1 has provided the water contact angle measurement result of the Fe-TA-SP composite separation membrane that embodiment 1-11 makes

Table 1

As can be seen from Table 1, the tannic acid coating can be successfully coated on the surface of the polymer substrate by the method of the present invention, so that the hydrophilicity of the modified membrane is significantly improved compared with the blank PVDF membrane (the contact angle of the blank PVDF membrane is respectively 87.8°), which fully meets the requirements for oil-water separation applications.

In addition, it can be seen from Table 1 that the number of printing times of ferric salt, tannic acid, and sodium periodate has a great influence on the hydrophilicity of the modified membrane, and the best parameter is ferric salt printing 4 2 times, tannic acid printing 2 times, sodium periodate printing 2 times.

(2) Study on the morphology of the separation membrane

Scanning electron microscopy (SEM) of different magnifications was used to study the morphology of the Fe-TA-SP composite separation membrane prepared in Example 1, and compared with the separation membrane of blank PVDF membrane and unprinted sodium periodate (i.e. The morphology of the Fe-TA composite separation membrane of ratio 1) and the separation membrane of unprinted ferric salt (ie the TA-SP composite separation membrane of comparative example 2) were compared, as shown in Figure 2.

It can be seen from Figure 2 that the surface of the blank PVDF membrane is a porous and interconnected fiber network structure; compared with the blank PVDF membrane, the appearance of the other three composite separation membranes presents a uniform and obvious coating color. The surface of the Fe-TA composite separation membrane of comparative example 1 appears purple, and the surface of the TA-SP composite separation membrane of comparative example 2 appears light yellow, while the surface of the Fe-TA-SP composite separation membrane obtained in Example 1 then appears brown, indicating that Tannic acid polymer coatings were successfully applied on PVDF membranes by inkjet printing. It can be seen from the SEM images that the deposition on the surface of the Fe-TA-SP composite separation membrane printed simultaneously with Fe, TA and SP is significantly more than that of the Fe-TA composite separation membrane and the TA-SP composite separation membrane, and its membrane pores are in three The seed film was the smallest, and the deposits on the film surface were uniformly distributed and tightly bound to the film matrix, and no aggregation of large particles was observed. The above results indicate that the joint action of Fe and SP can increase the deposition amount of TA.

(3) Application of oil-water separation

Add 10ml oil dyed with oil red to 990ml ultrapure water, and add 20mg Tween80 as an emulsifier, then stir at 10000rpm for 2h to obtain a diesel/water emulsion.

The Fe-TA-SP composite separation membrane that embodiment 1 is made is installed in the filtering device, carries out the separation test of oil-water emulsion under 0.4Mpa pressure, investigates the membrane flux and the rejection rate of composite separation membrane to different oil-water emulsions, so The inspection situation includes:

① Filtration of gasoline emulsion, ② filtration of diesel emulsion; ③ filtration of soybean oil emulsion; ④ flux recovery rate test after 8 filtration cycles in the above ①, ② and ③.

Membrane flux (J), rejection rate (R) and flux recovery rate (FRR) were calculated by formulas (1)-(3):

J＝V/(A×Δt) (1)

R=(1-C ₁ /C ₀ )×100% (2)

FRR=(J _p2 /J _p1 )×100% (3)

Among them, V is the volume of the filtrate (L), A is the effective area of the membrane (m ² ), Δt is the sampling time interval (h), C ₁ and C ₀ are the oil concentrations in the filtrate and stock solution (mg·mL ^-1 ), J _p1 and J _p2 are the initial water flux and recovery water flux (L·m ^-2 ·h ^-1 ·bar ^-1 ), respectively.

As shown in Figure 3, the rejection rate of the Fe-TA-SP composite separation membrane prepared in Example 1 to gasoline or diesel emulsion can reach 98%, and the flux can reach 7340.4L·m ^-2 ·h ^-1 ·bar ^-1 and 4968.4L·m ^-2 ·h ^-1 ·bar ^-1 , the rejection rate of soybean oil emulsion can reach 99.3%, and the flux can reach 5501.8L·m ^-2 ·h ^-1 ·bar ^-1 , compared with blank PVDF membrane has been significantly improved. It can be seen that the Fe-TA-SP composite separation membrane prepared by the present invention exhibits excellent performance in the separation of oily wastewater.

As shown in Figure 4, the final FRR of the Fe-TA-SP composite separation membrane prepared in Example 1 to gasoline, diesel oil and soybean oil emulsions for eight filtrations reached 98.0%, 89.1% and 93.4%, respectively, much higher than the blank PVDF The FRR of the film to the three emulsions are 51.3% (gasoline), 43.2% (diesel), 36.0% (soybean oil). It can be seen that the Fe-TA-SP composite separation membrane prepared by the present invention exhibits excellent anti-pollution performance for oily wastewater.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed in the present invention can easily think of changes or Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (8)

1. A method of making a composite separation membrane, comprising:

sequentially printing a metal salt solution, a polyphenol solution and an oxidant solution on the surface of a polymer substrate by ink-jet printing, and reacting the metal salt solution, the polyphenol solution and the oxidant solution to form a modified layer on the surface of the polymer substrate to obtain a composite separation membrane;

the concentration ratio of the metal salt solution, the polyphenol solution and the oxidant solution is 1 (1.8-2.2) to 3.8-4.2, and the printing frequency ratio of the metal salt solution, the polyphenol solution and the oxidant solution is 1-10 to 1-5;

the metal salt used in the metal salt solution is ferric sulfate or ferric chloride.

2. The production method according to claim 1, wherein the concentration of the metal salt solution is 23.5mmol/L or less; the concentration of the polyphenol solution is below 47 mmol/L; the concentration of the oxidant solution is less than 94mmol/L.

3. The manufacturing method according to claim 1, wherein the number of printing of the metal salt solution is 1 to 6 passes, the number of printing of the polyphenol solution is 1 to 3 passes, and the number of printing of the oxidant solution is 1 to 3 passes.

4. The production method according to claim 1,

the preparation method of the metal salt solution comprises the following steps: dissolving the metal salt in a solvent, the solvent being water, an alcohol or a mixture thereof;

the preparation method of the polyphenol solution comprises the following steps: dissolving a polyphenol in a solvent, wherein the polyphenol is tannic acid and the solvent is water, alcohol or a mixture thereof;

the preparation method of the oxidant solution comprises the following steps: an oxidizing agent is dissolved in a solvent, the oxidizing agent is at least one of sodium periodate, potassium permanganate and potassium dichromate, and the solvent is water, alcohol or a mixture thereof.

5. The production method according to claim 1,

the polymer substrate is polyester, polypropylene, polyvinylidene fluoride, polysulfone or polyethylene;

the reaction time is 5-60min.

6. The method of claim 1, further comprising: after the reaction is completed, washing and drying are performed.

7. The composite separation membrane obtained by the production method according to any one of claims 1 to 6, characterized in that a water contact angle is 70 ° or less; the retention rate of the oil-containing emulsion under the pressure of 0.4Mpa reaches more than 98 percent, and the flux reaches 4968.4 L.m ^-2 ·h ^-1 ·bar ^-1 The above; the flux recovery rate reaches more than 89.1 percent.

8. Use of the composite separation membrane of claim 7 in the treatment of oily wastewater.

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