阅读说明：本技术 一种聚偏氟乙烯超滤膜及其制备方法 (Polyvinylidene fluoride ultrafiltration membrane and preparation method thereof ) 是由 戴云帆 杨媛 樊少斌 谢长血 于 2021-07-23 设计创作，主要内容包括：本发明涉及化工技术领域,具体公开了一种聚偏氟乙烯超滤膜及其制备方法,所述聚偏氟乙烯超滤膜包括以下的原料：聚偏氟乙烯、改性石墨烯、还原铁粉粉料、偶联剂、聚乙烯吡咯烷酮、四氢呋喃、氨基化方解石。本发明实施例提供的聚偏氟乙烯超滤膜通过多种原料的复配,结合有机原料与无机原料复合增效原理,使得该超滤膜的抗拉强度和抗压强度大大提高,从而更好地适应用于处理污水或者废水时的恶劣运行状况和清洗条件,解决了现有聚偏氟乙烯超滤膜大多存在无法同时具有良好的抗拉强度和抗压强度的问题,具有广阔的市场前景。(The invention relates to the technical field of chemical industry, and particularly discloses a polyvinylidene fluoride ultrafiltration membrane and a preparation method thereof, wherein the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials: polyvinylidene fluoride, modified graphene, reduced iron powder, a coupling agent, polyvinylpyrrolidone, tetrahydrofuran and aminated calcite. The polyvinylidene fluoride ultrafiltration membrane provided by the embodiment of the invention greatly improves the tensile strength and the compressive strength by compounding various raw materials and combining the organic raw material and inorganic raw material composite synergistic principle, so that the polyvinylidene fluoride ultrafiltration membrane is better suitable for severe operating conditions and cleaning conditions during sewage or wastewater treatment, solves the problem that most of the existing polyvinylidene fluoride ultrafiltration membranes cannot simultaneously have good tensile strength and compressive strength, and has wide market prospect.)

1. The polyvinylidene fluoride ultrafiltration membrane is characterized by comprising the following raw materials: polyvinylidene fluoride, powder, a coupling agent, polyvinylpyrrolidone, tetrahydrofuran and aminated calcite; the powder material is prepared by mixing modified graphene and reduced iron powder according to a certain proportion; the modified graphene is prepared by adding ammonium fluotitanate and butyl titanate into nano graphene serving as a raw material, performing infrared radiation treatment, and then adding a modifier for modification.

2. The polyvinylidene fluoride ultrafiltration membrane of claim 1, wherein the modifier is a mixture of heptadecafluorodecyltriethoxysilane, isooctyltriethoxysilane, vinyltriethoxysilane, and absolute ethanol.

3. The polyvinylidene fluoride ultrafiltration membrane of claim 1, wherein the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials in parts by weight: 32-45 parts of polyvinylidene fluoride, 3-7 parts of powder, 0.05-0.25 part of coupling agent, 10-18 parts of polyvinylpyrrolidone, 30-50 parts of tetrahydrofuran and 5-12 parts of aminated calcite.

4. The polyvinylidene fluoride ultrafiltration membrane of claim 1, wherein the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials in parts by weight: 36-40 parts of polyvinylidene fluoride, 3-5 parts of powder, 0.08-0.12 part of coupling agent, 10-14 parts of polyvinylpyrrolidone, 36-42 parts of tetrahydrofuran and 7-9 parts of aminated calcite.

5. The polyvinylidene fluoride ultrafiltration membrane of claim 1, wherein the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials in parts by weight: 38 parts of polyvinylidene fluoride, 3.5 parts of powder, 0.1 part of coupling agent, 12 parts of polyvinylpyrrolidone, 40 parts of tetrahydrofuran and 8 parts of aminated calcite.

6. The polyvinylidene fluoride ultrafiltration membrane of claim 1, wherein the weight ratio of modified graphene to reduced iron powder in the powder lot is 10-30: 1-3.

7. The polyvinylidene fluoride ultrafiltration membrane of claim 1, wherein the preparation method of the modified graphene specifically comprises the following steps: the preparation method comprises the steps of dispersing nano-graphene in ethanol or water by ultrasonic waves to form a uniform solution, adding ammonium fluotitanate accounting for 4.5% of the weight of the nano-graphene and butyl titanate accounting for 12.5% of the weight of the nano-graphene under an acidic condition, uniformly mixing, carrying out infrared radiation treatment, adding a modifier, and carrying out vacuum pumping oscillation treatment at the temperature of 100-200 ℃ to complete modification, thereby obtaining the modified graphene.

8. The polyvinylidene fluoride ultrafiltration membrane of claim 1, wherein the method of preparing the aminated calcite specifically comprises the steps of: ball-milling 40-50 parts of calcite to nanometer level according to the weight parts, adding water, ultrasonically dispersing into slurry, dripping 1-5 parts of glycerol and 0.1-0.6 part of amino silane coupling agent, reacting at 70-80 ℃, washing, and drying to obtain the amino calcite.

9. A method of making a polyvinylidene fluoride ultrafiltration membrane according to any of claims 1-8 comprising the steps of:

1) weighing polyvinylidene fluoride, powder and a coupling agent according to a ratio, and uniformly mixing to obtain a first mixture;

2) sequentially adding polyvinylpyrrolidone, aminated calcite and tetrahydrofuran into the first mixture, and uniformly mixing to obtain a second mixture;

3) heating the second mixture to 200-400 ℃, extruding, molding and cooling to obtain a cooling material;

4) heating the cooling material, introducing compressed nitrogen, performing activation treatment in a hexamethylenetetramine aqueous solution, standing in soda water with the mass concentration of 2% at the temperature of 40 ℃ for 30-90 minutes, and performing vacuum treatment to remove organic volatile components to obtain the polyvinylidene fluoride ultrafiltration membrane.

10. The method of preparing a polyvinylidene fluoride ultrafiltration membrane according to claim 9, wherein the activation treatment is a vacuum heating treatment at 50 ℃ or lower in an aqueous hexamethylenetetramine solution having a concentration of 5 wt%.

Technical Field

The invention relates to the technical field of chemical industry, in particular to a polyvinylidene fluoride ultrafiltration membrane and a preparation method thereof.

Background

With the increasing environmental problems, the demand for rational utilization of water resources is increasing. The ultrafiltration membrane is used as an artificial permeable membrane and can be used in the fields of drinking water treatment, domestic sewage treatment, industrial wastewater treatment and the like, and only low-molecular-weight solutes and water pass through the ultrafiltration membrane under the drive of pressure difference based on a membrane separation technology, so that the purposes of purification, separation and concentration are achieved.

At present, the preparation material of the ultrafiltration membrane mostly adopts one of the following raw materials: cellulose acetate based materials, Polyethersulfone (PES), polyvinylidene fluoride (PVDF), and the like. Among them, the polyethersulfone-based ultrafiltration membrane includes X-flow, HydraCap, KOCH, and the like. Polyvinylidene fluoride-based ultrafiltration membranes include OMEXELL, Memtec CMF, PALL Microza, and the like. Generally, PVDF ultrafiltration membranes have certain advantages in terms of preparation processes and the like, and therefore, the PVDF ultrafiltration membranes are widely used, and the PVDF ultrafiltration membranes can be prefabricated into membrane modules of various types such as tubular type, plate type, roll type, capillary type and the like, and then a plurality of modules are assembled together for use.

However, the above technical solutions have the following disadvantages in practical use: polyvinylidene fluoride ultrafiltration membranes in the prior art mostly have the defects of low tensile strength and low compressive strength, are not suitable for severe running conditions and cleaning conditions in sewage or wastewater treatment, and are easy to break and the like due to the operating environment.

Disclosure of Invention

The embodiment of the invention aims to provide a polyvinylidene fluoride ultrafiltration membrane, which is used for solving the problem that most of the existing polyvinylidene fluoride ultrafiltration membranes in the background technology cannot have good tensile strength and compressive strength at the same time.

In order to achieve the above purpose, the embodiments of the present invention provide the following technical solutions:

a polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials: polyvinylidene fluoride, powder, a coupling agent, polyvinylpyrrolidone, tetrahydrofuran and aminated calcite; the powder material is prepared by mixing modified graphene and reduced iron powder according to a certain proportion; the modified graphene is prepared by adding ammonium fluotitanate and butyl titanate into nano graphene serving as a raw material, performing infrared radiation treatment, and then adding a modifier for modification.

Another object of an embodiment of the present invention is to provide a method for preparing a polyvinylidene fluoride ultrafiltration membrane, which comprises the following steps:

1) weighing polyvinylidene fluoride, powder and a coupling agent according to a ratio, and uniformly mixing to obtain a first mixture;

2) sequentially adding polyvinylpyrrolidone, aminated calcite and tetrahydrofuran into the first mixture, and uniformly mixing to obtain a second mixture;

3) heating the second mixture to 200-400 ℃, extruding, molding and cooling to obtain a cooling material;

4) heating the cooling material, introducing compressed nitrogen, performing activation treatment in a hexamethylenetetramine aqueous solution, standing in soda water with the mass concentration of 2% at the temperature of 40 ℃ for 30-90 minutes, and performing vacuum treatment to remove organic volatile components to obtain the polyvinylidene fluoride ultrafiltration membrane.

Compared with the prior art, the embodiment of the invention has the beneficial effects that:

according to the polyvinylidene fluoride ultrafiltration membrane provided by the embodiment of the invention, the polyvinylidene fluoride, the modified graphene, the reduced iron powder, the coupling agent, the polyvinylpyrrolidone, the tetrahydrofuran, the aminated calcite and other raw materials are compounded, and the polyvinylidene fluoride ultrafiltration membrane is prepared by combining the organic raw material and the inorganic raw material composite synergistic principle, so that the tensile strength and the compressive strength of the ultrafiltration membrane are greatly improved, and the polyvinylidene fluoride ultrafiltration membrane is better suitable for severe running conditions and cleaning conditions when being used for sewage or wastewater. Wherein, through the cooperation of modified graphite alkene with amination calcite, can make polyvinylidene fluoride milipore filter plays good ultrafiltration effect, and simultaneously, tensile strength and compressive strength improve greatly, have solved the problem that current polyvinylidene fluoride milipore filter mostly exists and can't have good tensile strength and compressive strength simultaneously, have wide market prospect.

Drawings

Fig. 1 is a diagram illustrating a result of detecting the COD removal rate of a polyvinylidene fluoride ultrafiltration membrane according to an embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples. The following examples will assist those skilled in the art in further understanding the embodiments of the present invention, but are not intended to limit the embodiments of the present invention in any way. It should be noted that various changes and modifications can be made by those skilled in the art without departing from the spirit of the embodiments of the present invention. These are all within the scope of the embodiments of the present invention.

In the embodiment of the invention, the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials: polyvinylidene fluoride, powder, a coupling agent, polyvinylpyrrolidone, tetrahydrofuran and aminated calcite; the powder material is prepared by mixing modified graphene and reduced iron powder according to a certain proportion; the modified graphene is prepared by adding ammonium fluotitanate and butyl titanate into nano graphene serving as a raw material, performing infrared radiation treatment, and then adding a modifier for modification.

As another preferred embodiment of the present invention, the modifier is a mixture of heptadecafluorodecyltriethoxysilane, isooctyltriethoxysilane, vinyltriethoxysilane, and absolute ethanol.

Preferably, the modifier is formed by mixing heptadecafluorodecyltriethoxysilane, isooctyltriethoxysilane, vinyltriethoxysilane and absolute ethyl alcohol according to the mass ratio of 12:6:3: 27.

As another preferred embodiment of the present invention, the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials in parts by weight: 32-45 parts of polyvinylidene fluoride, 3-7 parts of powder, 0.05-0.25 part of coupling agent, 10-18 parts of polyvinylpyrrolidone, 30-50 parts of tetrahydrofuran and 5-12 parts of aminated calcite; the powder material is prepared by mixing modified graphene and reduced iron powder according to a certain proportion; the modified graphene is prepared by adding a modifier formed by mixing heptadecafluorodecyltriethoxysilane, isooctyltriethoxysilane, vinyltriethoxysilane and absolute ethyl alcohol into nano-graphene serving as a raw material after adding ammonium fluotitanate and butyl titanate for infrared radiation treatment.

As another preferred embodiment of the present invention, the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials in parts by weight: 36-40 parts of polyvinylidene fluoride, 3-5 parts of powder, 0.08-0.12 part of coupling agent, 10-14 parts of polyvinylpyrrolidone, 36-42 parts of tetrahydrofuran and 7-9 parts of aminated calcite.

Preferably, the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials in parts by weight: 38 parts of polyvinylidene fluoride, 3.5 parts of powder, 0.1 part of coupling agent, 12 parts of polyvinylpyrrolidone, 40 parts of tetrahydrofuran and 8 parts of aminated calcite.

As another preferred embodiment of the present invention, in the powder lot, the weight ratio of the modified graphene to the reduced iron powder is 10 to 30: 1-3.

Preferably, the powder is prepared by mixing modified graphene and reduced iron powder according to the mass ratio of 15:1 and grinding the mixture to be nano-scale.

In another preferred embodiment of the present invention, the coupling agent is a mixture of heptadecafluorodecyltriethoxysilane, vinyltriethoxysilane, and isopropyl triisostearoyltitanate in equal mass ratios. Compared with the single coupling agent product, the composite difficulty of the material and the organic component can be effectively reduced.

As another preferred embodiment of the present invention, the preparation method of the modified graphene specifically includes the following steps:

performing ultrasonic dispersion on nano-graphene (placing a particle suspension in an ultra-strong sound field, treating the particle suspension with proper ultrasonic amplitude and high temperature conditions, forming a monomolecular structure by combining a cavitation effect, preferably performing ultrasonic dispersion under the conditions that the ultrasonic power is more than 50kHz and the temperature is more than 80 ℃) to form a uniform liquid in ethanol or water, then adding 4.5% of ammonium fluotitanate and 12.5% of butyl titanate by weight of the nano-graphene under an acidic condition, uniformly mixing, then performing infrared radiation treatment, adding a modifier, and performing vacuum pumping (nano-scale) oscillation treatment at the temperature of 100-200 ℃ to complete modification, thereby obtaining the modified graphene.

As another preferable example of the embodiment of the present invention, the system is made acidic under acidic conditions by using boric acid, hydrochloric acid, silicic acid, or the like.

As another preferred embodiment of the present invention, the method for preparing aminated calcite specifically comprises the following steps:

ball-milling 40-50 parts of calcite to nanometer level according to the weight parts, adding water, ultrasonically dispersing into slurry, dripping 1-5 parts of glycerol and 0.1-0.6 part of amino silane coupling agent, reacting at 70-80 ℃, washing, and drying to obtain the amino calcite.

Preferably, the preparation method of the aminated calcite comprises the steps of ball-milling 45 parts by weight of calcite into nanoscale calcite powder, adding water, performing ultrasonic dispersion to obtain slurry, dropwise adding 1-5 parts by weight of glycerol and 0.1-0.55 part by weight of an aminosilicone coupling agent, reacting at 75 ℃ for 3 hours, washing, and drying to obtain the aminated calcite.

As another preferred embodiment of the present invention, the ball milling is performed until the average size of the particles is below 10 nm.

In the embodiment of the invention, the polyvinylidene fluoride ultrafiltration membrane is prepared by adopting polyvinylidene fluoride as a base material and combining an organic raw material and an inorganic raw material composite synergistic principle, and the tensile strength and the compressive strength of the ultrafiltration membrane are greatly improved by a blending formula, so that the polyvinylidene fluoride ultrafiltration membrane is better suitable for severe operating conditions and cleaning conditions when being used for sewage or wastewater, and the defects of low tensile strength and compressive strength of other PVDF membranes are overcome. Wherein, modified graphene in the powder is modified through multiple raw materials and treatment means, has effectively improved its and organic material's combination effect, and simultaneously, the amino group that amination calcite self has can form complicated network structure with modified graphene, polyvinylidene fluoride combined action, can make polyvinylidene fluoride milipore filter plays good ultrafiltration effect, and simultaneously, tensile strength and compressive strength improve greatly, compare in single adoption graphite alkene, can guarantee the ultrafiltration effect when effectively improving mechanical strength.

The embodiment of the invention also provides a preparation method of the polyvinylidene fluoride ultrafiltration membrane, which comprises the following steps:

1) weighing polyvinylidene fluoride, powder and a coupling agent according to a ratio, and uniformly mixing to obtain a first mixture;

2) sequentially adding polyvinylpyrrolidone, aminated calcite and tetrahydrofuran into the first mixture, and uniformly mixing to obtain a second mixture;

3) heating the second mixture to 200-400 ℃, extruding, molding and cooling to obtain a cooling material;

4) heating the cooling material, introducing compressed nitrogen, performing activation treatment in a hexamethylenetetramine aqueous solution, standing in soda water with the mass concentration of 2% at the temperature of 40 ℃ for 30-90 minutes, and performing vacuum treatment to remove organic volatile components to obtain the polyvinylidene fluoride ultrafiltration membrane.

In another preferred embodiment of the present invention, in the method for preparing a polyvinylidene fluoride ultrafiltration membrane, the activation treatment is performed by putting the polyvinylidene fluoride ultrafiltration membrane into a 5 wt% aqueous solution of hexamethylenetetramine, and heating the mixture under vacuum at 50 ℃ or below, so that the material is rich in amino groups, and adverse effects such as easy caking and the like caused by adding inorganic materials are improved.

In another preferred embodiment of the present invention, the compressed nitrogen is used as a protective gas, and may be an inert gas such as helium, neon, or argon, or may be nitrogen, and the activation treatment is performed in the hexamethylenetetramine aqueous solution under a protective gas atmosphere, so that adverse effects of oxygen in the air on the activation can be avoided.

The polyvinylidene fluoride ultrafiltration membrane provided by the embodiment of the invention can be widely applied to water treatment, can be used in the fields of drinking water treatment, domestic sewage treatment, industrial wastewater treatment and the like, has good tensile strength and compressive strength, is suitable for severe running conditions and cleaning conditions in sewage or wastewater treatment, and is not easy to break and the like.

The technical effects of the polyvinylidene fluoride ultrafiltration membrane of the embodiment of the present invention will be further described below by referring to specific examples.

Example 1

The preparation method of the modified graphene specifically comprises the following steps:

performing ultrasonic dispersion on nano-graphene (ultrasonic dispersion is performed under the conditions that the ultrasonic power is more than 50kHz and the temperature is more than 80 ℃) to ethanol or water to form uniform liquid, then adding ammonium fluotitanate with the weight of 4.5% of the nano-graphene and butyl titanate with the weight of 12.5% of the nano-graphene under an acidic condition to uniformly mix, then performing infrared radiation treatment, then adding a modifier, and performing vacuumizing (nano-scale) oscillation treatment at 100 ℃ to complete modification, thereby obtaining the modified graphene. The modifier is formed by mixing heptadecafluorodecyltriethoxysilane, isooctyltriethoxysilane, vinyl triethoxysilane and absolute ethyl alcohol according to the mass ratio of 12:6:3: 27.

Example 2

The preparation method of the modified graphene specifically comprises the following steps:

performing ultrasonic dispersion on nano-graphene (ultrasonic dispersion is performed under the conditions that the ultrasonic power is more than 50kHz and the temperature is more than 80 ℃) to ethanol or water to form uniform liquid, then adding ammonium fluotitanate with the weight of 4.5% of the nano-graphene and butyl titanate with the weight of 12.5% of the nano-graphene under an acidic condition to uniformly mix, then performing infrared radiation treatment, then adding a modifier, and performing vacuumizing (nano-scale) oscillation treatment at 200 ℃ to complete modification, thereby obtaining the modified graphene. The modifier is formed by mixing heptadecafluorodecyltriethoxysilane, isooctyltriethoxysilane, vinyl triethoxysilane and absolute ethyl alcohol according to the mass ratio of 12:6:3: 27.

Example 3

The modification was performed in the same manner as in example 2 except that the modification was performed by vacuum (nano-scale) shaking treatment at 150 ℃.

Example 4

A polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials: 36 parts of polyvinylidene fluoride, 3 parts of powder, 0.08 part of coupling agent dimethyl dioxysilane, 10 parts of polyvinylpyrrolidone, 36 parts of tetrahydrofuran and 7 parts of aminated calcite. The powder material is prepared by mixing modified graphene and reduced iron powder according to the mass ratio of 15:1 and grinding the mixture to be nano-scale.

In this embodiment, the preparation method of the modified graphene specifically includes the following steps:

performing ultrasonic dispersion on nano-graphene (ultrasonic dispersion is performed under the conditions that the ultrasonic power is more than 50kHz and the temperature is more than 80 ℃) to ethanol or water to form uniform liquid, then adding ammonium fluotitanate with the weight of 4.5% of the nano-graphene and butyl titanate with the weight of 12.5% of the nano-graphene under an acidic condition to uniformly mix, then performing infrared radiation treatment, then adding a modifier, and performing vacuumizing (nano-scale) oscillation treatment at 140 ℃ to complete modification, thereby obtaining the modified graphene. The modifier is formed by mixing heptadecafluorodecyltriethoxysilane, isooctyltriethoxysilane, vinyl triethoxysilane and absolute ethyl alcohol according to the mass ratio of 12:6:3: 27.

In this example, the preparation method of the aminated calcite includes ball-milling 45 parts by weight of calcite into nanoscale calcite powder, adding water, ultrasonically dispersing the calcite powder into slurry, adding 2.5 parts by weight of glycerol and 0.3 part by weight of an aminosilicone coupling agent dropwise, reacting at 75 ℃ for 3 hours, washing, and drying to obtain the aminated calcite.

In this embodiment, the preparation method of the polyvinylidene fluoride ultrafiltration membrane comprises the following steps:

1) weighing the polyvinylidene fluoride, the powder and the coupling agent dimethyl dioxysilane, and uniformly mixing to obtain a first mixture;

2) sequentially adding polyvinylpyrrolidone, aminated calcite and tetrahydrofuran into the first mixture, and uniformly mixing to obtain a second mixture;

3) heating the second mixture to 250 ℃, extruding, molding and cooling to obtain a cooling material;

4) heating the cooling material, introducing compressed nitrogen, performing activation treatment in a hexamethylenetetramine aqueous solution (specifically, heating in 5 wt% hexamethylenetetramine aqueous solution at the temperature of below 50 ℃ in vacuum), standing in soda water with the mass concentration of 2% at the temperature of 40 ℃ for 30 minutes, and performing vacuum treatment to remove organic volatile components to obtain the polyvinylidene fluoride ultrafiltration membrane.

Example 5

A polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials: 40 parts of polyvinylidene fluoride, 5 parts of powder, 0.12 part of coupling agent dimethyl dioxysilane, 14 parts of polyvinylpyrrolidone, 42 parts of tetrahydrofuran and 9 parts of aminated calcite. The powder material is prepared by mixing modified graphene and reduced iron powder according to the mass ratio of 15:1 and grinding the mixture to be nano-scale.

In this embodiment, the preparation method of the modified graphene specifically includes the following steps:

performing ultrasonic dispersion on nano-graphene (ultrasonic dispersion is performed under the conditions that the ultrasonic power is more than 50kHz and the temperature is more than 80 ℃) to ethanol or water to form uniform liquid, then adding ammonium fluotitanate with the weight of 4.5% of the nano-graphene and butyl titanate with the weight of 12.5% of the nano-graphene under an acidic condition to uniformly mix, then performing infrared radiation treatment, then adding a modifier, and performing vacuumizing (nano-scale) oscillation treatment at 140 ℃ to complete modification, thereby obtaining the modified graphene. The modifier is formed by mixing heptadecafluorodecyltriethoxysilane, isooctyltriethoxysilane, vinyl triethoxysilane and absolute ethyl alcohol according to the mass ratio of 12:6:3: 27.

In this example, the preparation method of the aminated calcite includes ball-milling 45 parts by weight of calcite into nanoscale calcite powder, adding water, ultrasonically dispersing the calcite powder into slurry, adding 2.5 parts by weight of glycerol and 0.3 part by weight of an aminosilicone coupling agent dropwise, reacting at 75 ℃ for 3 hours, washing, and drying to obtain the aminated calcite.

In this example, the polyvinylidene fluoride ultrafiltration membrane was prepared in the same manner as in example 4.

Example 6

Compared with example 5, except that the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials: 38 parts of polyvinylidene fluoride, 3.5 parts of powder, 0.1 part of coupling agent dimethyl dioxysilane, 12 parts of polyvinylpyrrolidone, 40 parts of tetrahydrofuran and 8 parts of aminated calcite. The rest is the same as in example 5.

Example 7

A polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials: 32-45 parts of polyvinylidene fluoride, 3-7 parts of powder, 0.05-0.25 part of coupling agent dimethyl dioxysilane, 10-18 parts of polyvinylpyrrolidone, 30-50 parts of tetrahydrofuran and 5-12 parts of aminated calcite. Wherein the powder material is prepared from modified graphene and reduced iron powder according to a mass ratio of 10-30: 1-3, and grinding into nanometer level.

In this embodiment, the preparation method of the modified graphene specifically includes the following steps:

performing ultrasonic dispersion on nano-graphene (ultrasonic dispersion is performed under the conditions that the ultrasonic power is more than 50kHz and the temperature is more than 80 ℃) to ethanol or water to form uniform liquid, then adding ammonium fluotitanate with the weight of 4.5% of the nano-graphene and butyl titanate with the weight of 12.5% of the nano-graphene under an acidic condition to uniformly mix, then performing infrared radiation treatment, then adding a modifier, and performing vacuumizing (nano-scale) oscillation treatment at 140 ℃ to complete modification, thereby obtaining the modified graphene. The modifier is formed by mixing heptadecafluorodecyltriethoxysilane, isooctyltriethoxysilane, vinyl triethoxysilane and absolute ethyl alcohol according to the mass ratio of 12:6:3: 27.

In the embodiment, the preparation method of the aminated calcite comprises the steps of ball-milling 40-50 parts by weight of calcite to a nanometer level, adding water, performing ultrasonic dispersion to obtain slurry, dropwise adding 1-5 parts by weight of glycerol and 0.1-0.6 part by weight of an aminosilicone coupling agent, reacting at 70-80 ℃ for 3 hours, washing, and drying to obtain the aminated calcite.

In this embodiment, the preparation method of the polyvinylidene fluoride ultrafiltration membrane comprises the following steps:

1) weighing the polyvinylidene fluoride, the powder and the coupling agent dimethyl dioxysilane, and uniformly mixing to obtain a first mixture;

2) sequentially adding polyvinylpyrrolidone, aminated calcite and tetrahydrofuran into the first mixture, and uniformly mixing to obtain a second mixture;

3) heating the second mixture to 200-400 ℃, extruding, molding and cooling to obtain a cooling material;

4) heating the cooling material, introducing compressed nitrogen, performing activation treatment in a hexamethylenetetramine aqueous solution (specifically, heating in 5 wt% hexamethylenetetramine aqueous solution at the temperature of below 50 ℃ in vacuum), standing in soda water with the mass concentration of 2% at the temperature of 40 ℃ for 30-90 minutes, and performing vacuum treatment to remove organic volatile components to obtain the polyvinylidene fluoride ultrafiltration membrane.

Example 8

A polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials: 32-45 parts of polyvinylidene fluoride, 3-7 parts of powder, 0.05-0.25 part of coupling agent dimethyl dioxysilane, 10-18 parts of polyvinylpyrrolidone, 30-50 parts of tetrahydrofuran and 5-12 parts of aminated calcite. Wherein the powder material is prepared from modified graphene and reduced iron powder according to a mass ratio of 10-30: 1-3, and grinding into nanometer level.

In this embodiment, the preparation method of the modified graphene specifically includes the following steps:

performing ultrasonic dispersion on nano-graphene (ultrasonic dispersion is performed under the conditions that the ultrasonic power is more than 50kHz and the temperature is more than 80 ℃) to ethanol or water to form uniform liquid, then adding ammonium fluotitanate with the weight of 4.5% of the nano-graphene and butyl titanate with the weight of 12.5% of the nano-graphene under an acidic condition to uniformly mix, then performing infrared radiation treatment, then adding a modifier, and performing vacuumizing (nano-scale) oscillation treatment at 140 ℃ to complete modification, thereby obtaining the modified graphene. The modifier is formed by mixing heptadecafluorodecyltriethoxysilane, isooctyltriethoxysilane, vinyl triethoxysilane and absolute ethyl alcohol according to the mass ratio of 12:6:3: 27.

In the embodiment, the preparation method of the aminated calcite comprises the steps of ball-milling 40-50 parts by weight of calcite to a nanometer level, adding water, performing ultrasonic dispersion to obtain slurry, dropwise adding 1-5 parts by weight of glycerol and 0.1-0.6 part by weight of an aminosilicone coupling agent, reacting at 70-80 ℃ for 3 hours, washing, and drying to obtain the aminated calcite.

In this embodiment, the preparation method of the polyvinylidene fluoride ultrafiltration membrane comprises the following steps:

1) weighing the polyvinylidene fluoride, the powder and the coupling agent dimethyl dioxysilane, and uniformly mixing to obtain a first mixture;

2) sequentially adding polyvinylpyrrolidone, aminated calcite and tetrahydrofuran into the first mixture, and uniformly mixing to obtain a second mixture;

3) heating the second mixture to 200-400 ℃, extruding, molding and cooling to obtain a cooling material;

4) heating the cooling material, introducing compressed nitrogen, performing activation treatment in a hexamethylenetetramine aqueous solution (specifically, heating in 5 wt% hexamethylenetetramine aqueous solution at the temperature of below 50 ℃ in vacuum), standing in soda water with the mass concentration of 2% at the temperature of 40 ℃ for 30-90 minutes, and performing vacuum treatment to remove organic volatile components to obtain the polyvinylidene fluoride ultrafiltration membrane.

Example 9

The same as example 5, except that the second compound was heated to 230 c, as compared to example 5.

Example 10

The same as example 5, except that the second compound was heated to 280 c, as compared to example 5.

Example 11

The same as example 5, except that the second compound was heated to 380 c, as compared to example 5.

Example 12

The same as example 4 except that helium was used instead of nitrogen, as compared with example 4.

Example 13

The same as example 4 except that the nitrogen gas was replaced with argon gas as compared with example 4.

Example 14

The same procedure as in example 5 was repeated, except that the amount of the aminosilane coupling agent added was 0.55 part as compared with example 5.

Comparative example 1

A polyvinylidene fluoride ultrafiltration membrane, compared to example 5, except that the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials: 38 parts of polyvinylidene fluoride, 3.5 parts of powder, 0.1 part of coupling agent dimethyl dioxysilane, 12 parts of polyvinylpyrrolidone and 40 parts of tetrahydrofuran. The rest is the same as in example 5.

Comparative example 2

A polyvinylidene fluoride ultrafiltration membrane, compared to example 5, except that the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials: 38 parts of polyvinylidene fluoride, 3.5 parts of powder, 0.1 part of coupling agent dimethyl dioxysilane, 12 parts of polyvinylpyrrolidone, 40 parts of tetrahydrofuran and 8 parts of aminated calcite. Wherein, only reduced iron powder is adopted in the powder material. The rest is the same as in example 5.

Comparative example 3

A polyvinylidene fluoride ultrafiltration membrane, compared to example 5, except that the polyvinylidene fluoride ultrafiltration membrane comprises the following raw materials: 38 parts of polyvinylidene fluoride, 3.5 parts of powder, 0.1 part of coupling agent dimethyl dioxysilane, 12 parts of polyvinylpyrrolidone and 40 parts of tetrahydrofuran. Wherein, only reduced iron powder is adopted in the powder material. The rest is the same as in example 5.

Comparative example 4

The existing commercial polyvinylidene fluoride ultrafiltration membrane product.

The modified graphene prepared by the method in examples 1 to 3 was subjected to performance testing. In particular, the wear resistance test is carried out in a ball mill. Through detection, the modified graphene in the embodiments 1 to 3 has good wear resistance, and reaches the wear resistance index of graphene sold in the market.

The products prepared by the methods of examples 4-14 were tested for properties. Specifically, the detection is carried out by referring to methods in an HYT 112-2008 ultrafiltration membrane and components thereof, wherein the test methods of the pressure resistance, the corrosion resistance and the leakage resistance of the ultrafiltration membrane are carried out according to the regulations of GB/T13922.1. The polyvinylidene fluoride ultrafiltration membranes in examples 4-6 all meet the GB/T13922.1 specification.

And (3) pressure resistance test: the ultrafiltration membrane is pressurized by a water pump by taking water permeating through the ultrafiltration membrane at room temperature as a medium. The specific results are as follows: the operation is carried out for 0.5h to 1h under the nominal maximum water inlet pressure, and the polyvinylidene fluoride ultrafiltration membrane in the embodiment 4 to 6 has no breakage, fracture and leakage phenomena and is kept complete and undamaged; the membrane is operated for 12-24 h under the nominal maximum transmembrane pressure difference, and the membrane is kept intact.

Next, the ultrafiltration membrane product having a porosity of 70% and a separation pore size of 0.05 μm prepared by the method of example 6 was subjected to a COD removal rate test, specifically, the product water was subjected to ultrafiltration using domestic sewage having an influent COD of 385mg/L under the test conditions of 0.1MPa and 25 ℃, and the product water had a good COD removal rate. Meanwhile, the specific COD removal results are shown in Table 1 by using the product of comparative example 4 as a control.

Table 1 COD removal rate test results table

Group of	COD removal rate
		Example 6	88.5％
Comparative example 4	87.5％

The data in the table 1 are plotted to obtain a graph 1, and as can be seen from the data in the graph 1, the polyvinylidene fluoride ultrafiltration membrane provided by the embodiment of the invention can effectively ensure the COD removal rate which is equivalent to the performance of a product sold in the market. The above results are obtained by setting at least 10 groups of parallel tests respectively and taking the average value, P is less than 0.05, and the difference has statistical significance.

The products prepared by the methods of examples 4 to 6 and comparative examples 1 to 3 were subjected to mechanical property testing. Specifically, the compressive strength, tensile strength and elongation at break of the material were tested separately. Specific results are shown in table 2.

TABLE 2 table of mechanical property test results

As can be seen from the data in Table 2, in the embodiment of the invention, the polyvinylidene fluoride ultrafiltration membrane is prepared by adopting polyvinylidene fluoride as a base material, and the tensile strength and the compressive strength of the ultrafiltration membrane are greatly improved by the blending formula, so that the polyvinylidene fluoride ultrafiltration membrane is better suitable for severe running conditions and cleaning conditions when being used for sewage or wastewater. Wherein, through the cooperation of modified graphene with amination calcite, can make polyvinylidene fluoride milipore filter plays good ultrafiltration effect, and simultaneously, tensile strength and compressive strength improve greatly, compare in single adoption modified graphene, can guarantee the ultrafiltration effect when effectively improving mechanical strength.

The polyvinylidene fluoride ultrafiltration membrane prepared in example 6 is characterized by electron microscope images, and the result shows that the polyvinylidene fluoride ultrafiltration membrane has abundant pore structures on the surface, has uniform structure, good mechanical strength and high tensile strength and compressive strength, and is suitable for severe running conditions and cleaning conditions when used for sewage or wastewater.

While the preferred embodiments of the present invention have been described in detail, the embodiments of the present invention are not limited to the above embodiments, and various changes can be made without departing from the spirit of the embodiments of the present invention within the knowledge of those skilled in the art. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the embodiments of the present invention are still within the scope of the embodiments of the present invention as thus claimed.