阅读说明：本技术 油水分离复合膜及其制备方法 (Oil-water separation composite membrane and preparation method thereof ) 是由 王栋 陈媛丽 樊辉 查新林 于 2020-09-27 设计创作，主要内容包括：本发明提供了一种油水分离复合膜及其制备方法。该油水分离复合膜由PVA-co-PE纳米纤维复合膜基层和均匀负载于所述PVA-co-PE纳米纤维复合膜基层表面和内部孔隙中的预定结构的二氧化硅纳米材料构成；所述二氧化硅纳米材料为辐射孔二氧化硅纳米球、空心二氧化硅纳米球、介孔结构二氧化硅纳米球、蠕虫状二氧化硅纳米管中的一种或多种。该制备方法为：采用溶胶-凝胶法,通过改变模板剂和三甲苯之间的比例,制备出不同形貌的亲水二氧化硅纳米材料,并将其喷涂在PVA-co-PE纳米纤维复合膜基层上,制备得到油水分离复合膜。该油水分离复合膜在空气和水下分别表现出优异的超亲水性和憎油特性,通过重力驱动过滤,能高效地分离油水混合物,分离效率大于98％。(The invention provides an oil-water separation composite membrane and a preparation method thereof. The oil-water separation composite membrane consists of a PVA-co-PE nanofiber composite membrane base layer and silica nano materials which are uniformly loaded on the surface of the PVA-co-PE nanofiber composite membrane base layer and in internal pores and have preset structures; the silicon dioxide nano material is one or more of a radiating hole silicon dioxide nanosphere, a hollow silicon dioxide nanosphere, a mesoporous structure silicon dioxide nanosphere and a worm-shaped silicon dioxide nanotube. The preparation method comprises the following steps: the oil-water separation composite membrane is prepared by adopting a sol-gel method, changing the proportion between a template agent and trimethylbenzene to prepare hydrophilic silicon dioxide nano materials with different shapes, and spraying the hydrophilic silicon dioxide nano materials on a PVA-co-PE nano fiber composite membrane base layer. The oil-water separation composite membrane respectively shows excellent super-hydrophilic and oleophobic properties in air and water, and can efficiently separate an oil-water mixture by gravity-driven filtration, wherein the separation efficiency is more than 98%.)

1. An oil-water separation composite membrane is characterized in that: the oil-water separation composite membrane consists of a PVA-co-PE nanofiber composite membrane base layer and silica nano materials which are uniformly loaded on the surface of the PVA-co-PE nanofiber composite membrane base layer and in three-dimensional micro-nano reticular pores inside the PVA-co-PE nanofiber composite membrane base layer;

the silicon dioxide nano material is one or more of a radiating hole silicon dioxide nanosphere, a hollow silicon dioxide nanosphere, a mesoporous silicon dioxide nanosphere and a worm-shaped silicon dioxide nanotube.

2. The oil-water separation composite membrane according to claim 1, characterized in that: in the air, the water contact angle of the oil-water separation composite membrane can be changed into 0 degree within 0.5 s-1.3 s;

the diameters of the radiating hole silicon dioxide nanospheres, the hollow silicon dioxide nanospheres and the mesoporous silicon dioxide nanospheres are 20nm-2 mu m, and the pore diameters are 0.5-20 nm;

the length of the vermicular silica nanotube is 50-500nm, and the diameter of the vermicular silica nanotube is 20-100 nm.

3. A method for producing the oil-water separation composite membrane according to claim 1 or 2, characterized in that: the method comprises the following steps:

s1, preparing a PVA-co-PE nanofiber composite membrane base layer: firstly, preparing PVA-co-PE nano-fiber by adopting a melt extrusion phase separation method; then, dispersing the PVA-co-PE nano-fiber in a solution, and carrying out high-speed shearing to prepare a nano-fiber suspension with a preset solid content; then, uniformly spraying the nanofiber suspension on a non-woven fabric substrate, and drying to obtain a PVA-co-PE nanofiber composite membrane base layer;

s2, preparing the silicon dioxide nano material: preparing a silicon dioxide nano material with a preset structure by adopting a preset template agent and a sol-gel method;

s3, preparing an oil-water separation composite membrane: dispersing the silicon dioxide nano material prepared in the step S2 in water according to a preset mass ratio, and performing ultrasonic treatment to prepare a uniformly mixed suspension solution; and spraying the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane base layer, and drying to obtain the PVA-co-PE/silica oil-water separation membrane, namely the oil-water separation composite membrane.

4. The method for producing an oil-water separation composite membrane according to claim 3, characterized in that: in step S2, the specific steps are:

p1, adding a template agent chiral amphiphilic micromolecule compound into an organic solvent, uniformly stirring at 60-100 ℃ and 100-1500 rpm, and then adding a predetermined amount of TMB under the action of ultrasonic dispersion to form a uniform first mixed solution;

p2, adding NaOH solution with preset concentration into the first mixed solution prepared in the step P1, and stirring; then adding a predetermined amount of TEOS, stirring for 1-3 h, and filtering and washing to obtain a first intermediate product;

and P3, calcining the first intermediate product obtained in the step P2 at 500-600 ℃ for 3-7 h, and removing the template agent to prepare the first silicon dioxide nano material.

5. The method for producing an oil-water separation composite membrane according to claim 4, characterized in that: in step S2, the specific steps are:

a1, dissolving a template CTAB in water, adding a predetermined amount of NaOH solution, and then adding TMB under ultrasonic dispersion to obtain a second mixed solution which is uniformly mixed;

a2, adding a predetermined amount of TEOS and ethyl acetate into the second mixed solution prepared in the step A1, reacting for 1-4 hours at the temperature of 25-70 ℃ and the stirring speed of 100-1500 rpm, and then filtering and washing to obtain a second intermediate product;

a3, calcining the second intermediate product obtained in the step A2 at 500-600 ℃ for 3-7 hours, and removing the template agent to obtain a second silicon dioxide nano material.

6. The method for producing an oil-water separation composite membrane according to claim 5, characterized in that: in step S3, the specific steps are:

s31, mixing the first silica nano-material or the second silica nano-material prepared in the step S2 according to the weight ratio of 1: (100-200) dispersing in water according to the mass ratio, and performing ultrasonic treatment to prepare a uniformly mixed suspension solution;

s32, spraying the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane base layer, drying, uniformly and stably embedding and loading the first silica nano material or the second silica nano material on the surface and the inner three-dimensional micro-nano mesh pores of the PVA-co-PE nanofiber composite membrane base layer through hydrogen bonding, and preparing to obtain the oil-water separation composite membrane.

7. The method for producing an oil-water separation composite membrane according to claim 5, characterized in that: in step S3, the specific steps are:

s31, mixing the following components in percentage by mass (1-9): (1-9), uniformly mixing the first silicon dioxide nano material and the second silicon dioxide nano material prepared in the step S2, and mixing the mixture according to the ratio of 1: (100-200) dispersing in water according to the mass ratio, and performing ultrasonic treatment to prepare a uniformly mixed suspension solution;

s32, spraying the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane base layer, drying, uniformly and stably embedding and loading the first silica nanomaterial and the second silica nanomaterial on the surface of the PVA-co-PE nanofiber composite membrane base layer and the three-dimensional micro-nano reticular pores inside the PVA-co-PE nanofiber composite membrane base layer through hydrogen bonding, and preparing to obtain the oil-water separation composite membrane.

8. The method for producing an oil-water separation composite membrane according to claim 4, characterized in that: the chiral amphiphilic micromolecule compound is L-16Ala5PyF6, L-16Val6PyBr, D-16Val6PyBr, L-16Phe (NEt)₃、D-16Phe(NEt)₃、L-16PhePy6Br、D-16PhePy6Br、L-14Ala2BrN(Et)₃、D-14Ala2BrN(Et)₃、L-16Ala6BrN(Et)₃、D-16Ala6BrN(Et)₃、L-16IlePy6Br、D-16IlePy6Br、L-16Leu6Br N(Et)₃、D-16Leu6Br N(Et)₃One of (1); the mass volume ratio of the template to the TMB is 100 mg: (0.1-10) mL.

9. The method for producing an oil-water separation composite membrane according to claim 5, characterized in that: the mass volume ratio of the template CTAB to the TMB is 204 mg: (0.1-10) mL.

10. The method for producing an oil-water separation composite membrane according to claim 3, characterized in that: in step S3, the spraying density of the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane substrate is 0.1-0.8 mL/cm²(ii) a The material of the non-woven fabric substrate includes but is not limited to one or a mixture of more of PP, PET, PE, PVC, PAN and PA.

Technical Field

The invention relates to the technical field of preparation of separation membranes, in particular to an oil-water separation composite membrane and a preparation method thereof.

Background

With the rapid development of global economy and industrialization, a large amount of oily sewage is discharged, and meanwhile, the leakage events of marine crude oil are frequent, so that water resources are seriously polluted, the ecological environment and the health of human beings are seriously threatened, and the oil-water separation is always focused as a worldwide problem. The membrane separation technology is considered to be one of the most promising separation means, however, the traditional membrane separation material is easy to generate membrane pollution in the oil-water separation process, which leads to the rapid reduction of membrane flux and separation efficiency, and meanwhile, the traditional oil-water separation membrane has high production cost, which seriously hinders the further development and large-scale production and application of the membrane separation technology in the oil-water separation field. In the prior art, the traditional separation membrane is difficult to be comprehensively optimized in terms of performance and cost on the basis of excellent oil-water separation effect and low production cost, so that a novel oil-water separation membrane material needs to be developed urgently, antifouling performance is achieved, and the oil-water separation membrane with excellent separation efficiency and low price is the key place for achieving efficient oil-water separation on the premise of ensuring permeability.

The hydrophilic nano silicon dioxide material is adopted to carry out chemical and physical modification treatment on the surface of the oil-water separation membrane, and the method is an effective method for improving the oil-water separation performance of the separation membrane. The nano silicon dioxide materials with different shapes and sizes can improve the roughness of the surface of the separation membrane, so as to effectively improve the hydrophilic capacity of the oil-water separation membrane.

The invention patent with publication number CN107456879A discloses a nano-silica-nanofiber oil-water separation composite membrane and a preparation method thereof. The method comprises the following steps: 1) preparing a nano silicon dioxide solution: mixing nano silicon dioxide particles with a water-soluble polymer and dissolving the mixture in a solvent to obtain a nano silicon dioxide solution; 2) preparing a nanofiber suspension: dispersing the nano-fibers treated by the high-speed shearing machine in a solvent to obtain a nano-fiber suspension; 3) preparing a nano silicon dioxide/nanofiber oil-water separation composite membrane: and uniformly mixing the nano-silica solution and the nanofiber suspension to obtain a membrane making solution, coating the membrane making solution on the surface of a substrate, and drying to obtain the nano-silica/nanofiber oil-water separation composite membrane. However, the oil-water separation composite membrane has the disadvantages that the coated super-hydrophilic layer is easy to fall off after being dried, and the surface roughness is difficult to greatly improve.

The invention patent with the publication number of CN110721596A discloses a preparation method of a novel environment-friendly and efficient oil-water separation composite membrane. Dissolving cellulose acetate in a blending solvent of acetone, N-dimethylacetamide and deionized water, magnetically stirring at normal temperature until the solution is uniform and stable, and then carrying out electrostatic spinning on the spinning solution to prepare a basement membrane; then, silicon dioxide nano particles are loaded on the surface of a basement membrane in an electrostatic spraying mode to construct a nano-scale roughness prepared composite membrane; and finally, soaking the membrane in octyl trimethoxy silane hydrophobic modification liquid and drying to obtain the novel environment-friendly and efficient oil-water separation composite membrane with higher porosity and specific surface area. However, the preparation method of the oil-water separation composite membrane has the defects of complex preparation process, single nano-silicon loaded on the fiber and the like.

In view of the above, there is a need for an improved composite membrane for oil-water separation and a method for preparing the same, which solves the above problems.

Disclosure of Invention

The invention aims to provide an oil-water separation composite membrane and a preparation method thereof.

In order to realize the purpose, the invention provides an oil-water separation composite membrane which is composed of a PVA-co-PE nanofiber composite membrane base layer and a PVA-co-PE nanofiber composite membrane uniformly loaded on the PVA-co-PE nanofiber composite membrane

The silicon dioxide nano material is one or more of a radiating hole silicon dioxide nanosphere, a hollow silicon dioxide nanosphere, a mesoporous silicon dioxide nanosphere and a worm-shaped silicon dioxide nanotube.

As a further improvement of the invention, in the air, the water contact angle of the oil-water separation composite membrane can be changed into 0 degree within 0.5 s-1.3 s;

the diameters of the radiating hole silicon dioxide nanospheres, the hollow silicon dioxide nanospheres and the mesoporous silicon dioxide nanospheres are 20nm-2 mu m, and the pore diameters are 0.5-20 nm;

the length of the vermicular silica nanotube is 50-500nm, and the diameter of the vermicular silica nanotube is 20-100 nm.

In order to achieve the purpose, the invention provides a preparation method of the oil-water separation composite membrane, which comprises the following steps:

s1, preparing a PVA-co-PE nanofiber composite membrane base layer: firstly, preparing PVA-co-PE nano-fiber by adopting a melt extrusion phase separation method; then, dispersing the PVA-co-PE nano-fiber in a solution, and carrying out high-speed shearing to prepare a nano-fiber suspension with a preset solid content; then, uniformly spraying the nanofiber suspension on a non-woven fabric substrate, and drying to obtain the PVA-co-PE nanofiber composite membrane base layer;

s2, preparing the silicon dioxide nano material: preparing a silicon dioxide nano material with a preset structure by adopting a template method;

s3, preparing an oil-water separation composite membrane: dispersing the silicon dioxide nano material prepared in the step S2 in water according to a preset mass ratio, and performing ultrasonic treatment to prepare a uniformly mixed suspension solution; and spraying the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane base layer, and drying to obtain the PVA-co-PE/silica oil-water separation membrane, namely the oil-water separation composite membrane.

As a further improvement of the present invention, in step S2, the template method specifically includes the steps of:

p1, adding a template agent chiral amphiphilic micromolecule compound into an organic solvent, uniformly stirring at 60-100 ℃ and 100-1500 rpm, and then adding a predetermined amount of TMB under the action of ultrasonic dispersion to form a uniform first mixed solution;

p2, adding NaOH solution with preset concentration into the first mixed solution prepared in the step P1, and stirring; then adding a predetermined amount of TEOS, stirring for 1-3 h, and filtering and washing to obtain a first intermediate product;

and P3, calcining the first intermediate product obtained in the step P2 at 500-600 ℃ for 3-7 h, and removing the template agent to prepare the silicon dioxide nano material.

As a further improvement of the present invention, in step S2, the template method specifically includes the steps of:

a1, dissolving CTAB in water, adding a predetermined amount of NaOH solution, and then adding TMB under ultrasonic dispersion to obtain a second mixed solution which is uniformly mixed;

a2, adding a predetermined amount of TEOS and ethyl acetate into the second mixed solution prepared in the step A1, reacting for 1-4 hours at the temperature of 25-70 ℃ and the stirring speed of 100-1500 rpm, and then filtering and washing to obtain a second intermediate product;

a3, calcining the second intermediate product obtained in the step A2 at 500-600 ℃ for 3-7 hours, and removing the template agent to obtain the silicon dioxide nano material.

As a further improvement of the present invention, in step S3, the specific steps are:

s31, mixing the first silica nano-material or the second silica nano-material prepared in the step S2 according to the weight ratio of 1: (100-200) dispersing in water according to the mass ratio, and performing ultrasonic treatment to prepare a uniformly mixed suspension solution;

s32, spraying the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane base layer, drying, uniformly and stably embedding and loading the first silica nano material or the second silica nano material on the surface and the inner three-dimensional micro-nano mesh pores of the PVA-co-PE nanofiber composite membrane base layer through hydrogen bonding, and preparing to obtain the oil-water separation composite membrane.

As a further improvement of the present invention, in step S3, the specific steps are:

s31, mixing the following components in percentage by mass (1-9): (1-9), uniformly mixing the first silicon dioxide nano material and the second silicon dioxide nano material prepared in the step S2, and mixing the mixture according to the ratio of 1: (100-200) dispersing in water according to the mass ratio, and performing ultrasonic treatment to prepare a uniformly mixed suspension solution;

s32, spraying the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane base layer, drying, uniformly and stably embedding and loading the first silica nanomaterial and the second silica nanomaterial on the surface of the PVA-co-PE nanofiber composite membrane base layer and the three-dimensional micro-nano reticular pores inside the PVA-co-PE nanofiber composite membrane base layer through hydrogen bonding, and preparing to obtain the oil-water separation composite membrane.

As a further improvement of the invention, the chiral amphiphilic small molecule compound is L-16Ala5PyF6, L-16Val6PyBr, D-16Val6PyBr, L-16Phe (NEt)₃、D-16Phe(NEt)₃、L-16PhePy6Br、D-16PhePy6Br、L-14Ala2BrN(Et)₃、D-14Ala2BrN(Et)₃、L-16Ala6BrN(Et)₃、D-16Ala6BrN(Et)₃、L-16IlePy6Br、D-16IlePy6Br、L-16Leu6Br N(Et)₃、D-16Leu6Br N(Et)₃One of (1); the mass volume ratio of the template to the TMB is 100 mg: (0.1-10) mL.

As a further improvement of the invention, the mass-to-volume ratio of the template CTAB to the TMB is 204 mg: (0.1-10) mL.

As a further improvement of the invention, in step S3, the spraying density of the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane substrate is 0.1-0.8 mL/cm²(ii) a The material of the non-woven fabric substrate includes but is not limited to one or a mixture of more of PP, PET, PE, PVC, PAN and PA.

The invention has the beneficial effects that:

1. according to the preparation method of the oil-water separation composite membrane, the hydrophilic silicon dioxide nano materials with different appearances, namely the silicon dioxide nanospheres with the mesoporous structure, the silicon dioxide nanospheres with the radiation holes, the hollow silicon dioxide nanospheres and the worm-shaped silicon dioxide nanotubes are prepared by changing the proportion between the template agent and the Trimethylbenzene (TMB), and are respectively sprayed on the PVA-co-PE nanofiber composite membrane base layer. Based on the characteristic that the PVA-co-PE nanofiber surface has rich hydroxyl groups and the three-dimensional micro-nano net-shaped structure with the pores distributed in a mutually staggered mode, the silicon dioxide nano material can be uniformly and stably embedded and loaded on the surface and the inner pores of the PVA-co-PE nanofiber composite film base layer through the action of hydrogen bonds, namely, the silicon dioxide nano material is fixed and uniformly loaded in the three-dimensional micro-nano net-shaped pore structure of the surface and the inner part of the PVA-co-PE nanofiber composite film in a limited domain mode, and therefore the prepared oil-water separation composite film overcomes the technical defect that the nano silicon dioxide material in the traditional composite film is easy to fall off. The oil-water separation composite membrane respectively shows excellent super-hydrophilic and oleophobic properties in air and water, and can efficiently separate an oil-water mixture by gravity-driven filtration, wherein the separation efficiency is more than 98%.

2. According to the preparation method of the oil-water separation composite membrane, the composite membrane with excellent oil-water separation performance is prepared by compounding the silica nano material with different morphological structures and hydrophilicity and with the hollow and/or mesoporous and/or radiating pore structure with the PVA-co-PE nanofiber composite membrane base layer. The hollow and/or mesoporous and/or radiating pore structure of the silicon dioxide nano material can regulate and control the oil-water separation performance of the composite membrane, and the regulation and control mechanism is as follows:

the hollow and/or mesoporous and/or radiating pore structure of the silicon dioxide nano material can enable the silicon dioxide nano material to have excellent specific surface area, ordered pore structure and unique permeability, so that the roughness and specific surface area of the surface of the PVA-co-PE nano fiber can be obviously improved, and the selective separation performance and permeability of the composite membrane can be improved. The nano silicon dioxide prepared by the sol-gel method not only has excellent hydrophilic performance, but also has controllable appearance. The prepared silica nano particles with multiple morphologies such as radiating holes, hollows, mesopores, worms and the like have higher porosity, specific surface area and particle roughness than common silica nano particles, and can better improve the performance of the prepared composite film.

3. According to the preparation method of the oil-water separation composite membrane, the PVA-co-PE nanofiber composite membrane has the advantages of low cost and easiness in large-scale preparation, and the silica nano materials with different hollow and/or mesoporous structures can be stably loaded on the surface of the PVA-co-PE nanofiber composite membrane substrate through simple spraying treatment; the preparation method is simple, controllable in operation process, low in cost, easy for large-scale mass production and has a huge application prospect in the field of oil-water separation.

4. The oil-water separation composite membrane provided by the invention has excellent hydrophilic performance in air, and the water contact angle can be changed into 0 degree within 0.5-1.3 s (96 s is required for a pure PVA-co-PE nanofiber composite membrane). The hydrophilic performance of the composite membrane is obviously improved. Meanwhile, the oil is in a non-adhesion state on the surface of the composite film, which shows that the adhesion between the surface of the composite film and the oil is low, and the composite film has excellent oil pollution resistance. In addition, the diameter of the PVA-co-PE nanofiber composite membrane is of a nanometer size, so that the aperture of the oil-water separation composite membrane is of a micro-nano pore level, and granular impurities in water can be filtered while oil-water separation is realized.

Drawings

FIG. 1 is an infrared spectrum of examples 1 to 6 of the present invention and comparative example 1.

FIG. 2 is an electron microscope (with scale in nm) of the nano-silica material and the oil-water separation composite membrane prepared in examples 1 to 3 of the present invention.

FIG. 3 is a scanning electron microscope image of EDS elements of the oil-water separation composite membrane prepared in examples 1 to 3 of the present invention.

FIG. 4 is an electron microscope image (with scale in nm) of the nano-silica material and the oil-water separation composite membrane prepared in examples 4-6 of the present invention.

FIG. 5 is a scanning electron microscope image of EDS elements of the oil-water separation composite membrane prepared in examples 4 to 6 of the present invention.

FIG. 6 is a water contact angle test chart of examples 1 to 6 of the present invention and comparative example 1.

FIG. 7 is a water-oil separation experimental diagram of the oil-water separation composite membrane provided by the invention.

FIG. 8 is a graph showing different oil-water separation efficiencies of the oil-water separation composite membranes provided in examples 1 to 6 of the present invention.

FIG. 9 is a schematic diagram of a preparation process of the oil-water separation composite membrane provided by the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings and specific embodiments.

It should be noted that, in order to avoid obscuring the present invention with unnecessary details, only the structures and/or processing steps closely related to the aspects of the present invention are shown in the drawings, and other details not closely related to the present invention are omitted.

In addition, it is also to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

The invention provides a preparation method of an oil-water separation composite membrane, which comprises the following steps:

s1, preparing a PVA-co-PE nanofiber composite membrane base layer: firstly, preparing PVA-co-PE nano-fiber by adopting a melt extrusion phase separation method; then, dispersing the PVA-co-PE nano-fiber in a solution, and carrying out high-speed shearing to prepare a nano-fiber suspension with a preset solid content; then, uniformly spraying the nanofiber suspension on a non-woven fabric substrate, and drying to obtain the PVA-co-PE nanofiber composite membrane base layer;

s2, preparing the silicon dioxide nano material: preparing a silicon dioxide nano material with a preset structure by adopting a template method;

s3, preparing an oil-water separation composite membrane: dispersing the silicon dioxide nano material prepared in the step S2 in water according to a preset mass ratio, and performing ultrasonic treatment to prepare a uniformly mixed suspension solution; and spraying the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane base layer, and drying to obtain the PVA-co-PE/silica oil-water separation membrane, namely the oil-water separation composite membrane.

Preferably, in step S2, the specific steps are:

p1, adding a template agent chiral amphiphilic micromolecule compound into an organic solvent, uniformly stirring at 60-100 ℃ and 100-1500 rpm, and then adding a predetermined amount of TMB under the action of ultrasonic dispersion to form a uniform first mixed solution;

p2, adding NaOH solution with preset concentration into the first mixed solution prepared in the step P1, and stirring; then adding a predetermined amount of TEOS, stirring for 1-3 h, and filtering and washing to obtain a first intermediate product;

and P3, calcining the first intermediate product obtained in the step P2 at 500-600 ℃ for 3-7 h, and removing the template agent to prepare the silicon dioxide nano material.

Preferably, in step S2, the specific steps are:

a1, dissolving CTAB in water, adding a predetermined amount of NaOH solution, and then adding TMB under ultrasonic dispersion to obtain a second mixed solution which is uniformly mixed;

a2, adding a predetermined amount of TEOS and ethyl acetate into the second mixed solution prepared in the step A1, reacting for 1-4 hours at the temperature of 25-70 ℃ and the stirring speed of 100-1500 rpm, and then filtering and washing to obtain a second intermediate product;

a3, calcining the second intermediate product obtained in the step A2 at 500-600 ℃ for 3-7 hours, and removing the template agent to obtain the silicon dioxide nano material.

Preferably, in step S3, the specific steps are:

s31, mixing the first silica nano-material or the second silica nano-material prepared in the step S2 according to the weight ratio of 1: (100-200) dispersing in water according to the mass ratio, and performing ultrasonic treatment to prepare a uniformly mixed suspension solution;

s32, spraying the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane base layer, drying, uniformly and stably embedding and loading the first silica nano material or the second silica nano material on the surface and the inner three-dimensional micro-nano mesh pores of the PVA-co-PE nanofiber composite membrane base layer through hydrogen bonding, and preparing to obtain the oil-water separation composite membrane.

Preferably, in step S3, the specific steps are:

s31, mixing the following components in percentage by mass (1-9): (1-9), uniformly mixing the first silicon dioxide nano material and the second silicon dioxide nano material prepared in the step S2, and mixing the mixture according to the ratio of 1: (100-200) dispersing in water according to the mass ratio, and performing ultrasonic treatment to prepare a uniformly mixed suspension solution;

s32, spraying the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane base layer, drying, uniformly and stably embedding and loading the first silica nanomaterial and the second silica nanomaterial on the surface of the PVA-co-PE nanofiber composite membrane base layer and the three-dimensional micro-nano reticular pores inside the PVA-co-PE nanofiber composite membrane base layer through hydrogen bonding, and preparing to obtain the oil-water separation composite membrane.

Preferably, the chiral amphiphilic small molecule compound is L-16Ala5PyF6, L-16Val6PyBr, D-16Val6PyBr, L-16Phe (NEt)₃、D-16Phe(NEt)₃、L-16PhePy6Br、D-16PhePy6Br、L-14Ala2BrN(Et)₃、D-14Ala2BrN(Et)₃、L-16Ala6BrN(Et)₃、D-16Ala6BrN(Et)₃、L-16IlePy6Br、D-16IlePy6Br、L-16Leu6Br N(Et)₃、D-16Leu6Br N(Et)₃One of (1); the mass volume ratio of the template to the TMB is 100 mg: (0.1-10) mL.

Preferably, the mass-to-volume ratio of the template CTAB to the TMB is 204 mg: (0.1-10) mL.

Preferably, in step S3, the spraying density of the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane substrate is 0.1-0.8 mL/cm²(ii) a The material of the non-woven fabric substrate includes but is not limited to one or a mixture of more of PP, PET, PE, PVC, PAN and PA.

Example 1

The embodiment 1 of the invention provides a preparation method of an oil-water separation composite membrane, which comprises the following steps:

s1, mixing PVA-co-PE and CAB at a ratio of 80:20, and melt-extruding the mixture on a twin-screw extruder. The mixture was soaked in acetone solution for 24 hours to remove CAB. Then, PVA-The co-PE nano-fiber is further dispersed in the water solution, and a stable suspension is formed by a high-speed mixer; finally, the PVA-co-PE nanofiber suspension is evenly sprayed on a PP matrix and naturally dried to form the PVA-co-PE film. Wherein the spraying density of the PVA-co-PE nanofiber suspension with the solid content of 3 percent on the PP substrate is 0.38mL/cm²。

S2, adopting a sol-gel method: 204mg of CTAB template was dissolved in a mixture of 90mL of deionized water and 0.7mL of 2M/L NaOH solution, and 1.0mL of 1,3, 5-Trimethylbenzene (TMB) was added to the mixture under ultrasonic dispersion to form a homogeneous solution. After 20 minutes, adding 1.0mL TEOS and 0.8mL ethyl acetate into the uniform solution, and reacting for two hours under the conditions of keeping the temperature at 50 ℃ and stirring speed of 800 rpm; after the reaction was complete, the solution was filtered to give an intermediate product, which was washed with ethanol and concentrated hydrochloric acid and further calcined at 550 ℃ for 5h to remove the template, thereby obtaining radiative pore silica nanospheres, noted C-SiO₂-1。

S3, SiO preparation of S2₂According to the mass ratio of 1: 150 were sonicated in deionized water for 2 hours to form a homogeneous suspension. Finally, the suspension solution was sprayed onto the surface of the powder particles and dried at room temperature. Obtaining the silicon dioxide/PVA-co-PE oil-water separation membrane which is marked as C-SiO₂-1/PM. Wherein the spraying density of the suspension solution on the surface of the PVA-co-PE nanofiber composite membrane substrate is 0.38mL/cm²。

Examples 2 to 3

The difference from example 1 is that: the CTAB and TMB are added in different proportions, the other steps are the same as those in embodiment 1, and are not repeated herein, and the oil-water separation composite membranes prepared in embodiments 2 and 3 are respectively denoted as C-SiO₂-2/PM and C-SiO₂-3/PM。

Table 1 shows the process parameter settings and composite film performance parameters of examples 1-3

Examples	Ratio of CTAB to TMB
		Example 1	204mg：1.0mL
Example 2	204mg：3.0mL
		Example 3	204mg：6.0mL

Example 4

The embodiment 4 of the invention provides a preparation method of an oil-water separation composite membrane, which comprises the following steps:

s1, mixing PVA-co-PE and CAB at a ratio of 80:20, and melt-extruding the mixture on a twin-screw extruder. The mixture was soaked in acetone solution for 24 hours to remove CAB. Then, further dispersing the PVA-co-PE nano-fiber in an aqueous solution, and forming a stable suspension by a high-speed mixer; finally, the PVA-co-PE nanofiber suspension is evenly sprayed on a PP matrix and naturally dried to form the PVA-co-PE film. Wherein the spraying density of the PVA-co-PE nanofiber suspension with the solid content of 3 percent on the PP substrate is 0.38mL/cm²。

S2, 100mg of template L-16Ala5PyF6, 3mL of methanol, and 100mL of deionized water were mixed at 80 ℃ and stirred at 1000rpm to form a clear solution. Then, 0.5ml of TMB was added to the mixture under ultrasonic dispersion to form a homogeneous solution. After 5 minutes, 350uL of 2M/L NaOH were added and the stirring was maintained. Subsequently, 1ml of tetraethyl orthosilicate (TEOS) was added and stirred for 2 hours to effect a reaction. Finally, the solution was filtered to give an intermediate product, which was washed with ethanol and concentrated hydrochloric acid and further calcined at 550 ℃ for 5h to removeRemoving the template to obtain the vermicular hollow silica nanotube with spherical structures at two ends, which is marked as L-SiO₂-1。

S3, mixing SiO2 prepared by S2 according to the mass ratio of 1: 150 were sonicated in deionized water for 2 hours to form a homogeneous suspension. Finally, the suspension solution was sprayed onto the surface of the powder particles and dried at room temperature. Obtaining PVA-co-PE/silica oil-water separation membrane which is marked as L-SiO₂-1/PM. The spraying density of the suspension solution on the surface of the PVA-co-PE nanofiber composite film substrate layer is 0.38mL/cm²。

Examples 5 to 6

The difference from example 4 is that: the addition ratio of the template L-16Ala5PyF6 to TMB was different, and the other steps were the same as in example 4, and are not repeated herein. And the oil-water separation composite membranes prepared in examples 5 and 6 were respectively designated as L-SiO₂-2/PM and L-SiO₂-3/PM。

Table 2 shows the process parameter settings and composite film performance parameters of examples 4-6

Examples	Ratio of L-16Ala5PyF6 to TMB
		Example 4	100mg：0.5mL
Example 5	100mg：1.5mL
		Example 6	100mg：3.0mL

Comparative example 1

Blank comparative example, preparation of PVA-co-PE film prepared directly by step S1 without performing steps S2 and S3, i.e., without adding silica nanospheres, the steps were as follows:

a mixture of PVA-co-PE and CAB was mixed at a mass ratio of 80:20 and melt-extruded on a twin-screw extruder. The mixture was soaked in acetone solution for 24 hours to remove CAB. The PVA-co-PE nanofibers were then further dispersed in an aqueous solution and passed through a high speed mixer to form a stable suspension. Finally, uniformly spraying the PVA-co-PE nanofiber suspension on a PP matrix, and naturally drying to form a PVA-co-PE film which is marked as PM. Wherein the spraying density of the PVA-co-PE nanofiber suspension with the solid content of 3 percent on the PP substrate is 0.38mL/cm²。

Comparative example 2

The difference from example 1 is that: in step S2, conventional nano silica particles (solid structure) are adopted to prepare an oil-water separation composite membrane formed by compounding conventional nano silica particles and a PVA-co-PE nanofiber membrane, which is marked as SiO₂/PM。

Example 7

Referring to fig. 9, embodiment 7 is different from embodiment 1 in that: in step S2, the C-SiO prepared in example 1 is used as the silica nanomaterial₂L-SiO prepared in-1 and example 4₂1 according to 1: 1 to prepare two oil-water separation composite membranes of silica nano materials with different morphological structures and loaded with PVA-co-PE nanofiber membranes.

The performance parameters of the oil-water separation membrane prepared by the embodiment are tested as follows:

referring to the infrared spectrum shown in FIG. 1, it is shown that characteristic peaks of silica including 457cm are present in the oil-water separation composite membranes, i.e., silica/PM, prepared in examples 1 to 6 of the present invention, as compared to the pure PVA-co-PE membrane substrate provided in comparative example 1^-1Bending vibration of Si-O-Si of 810cm^-1Si-O-Si symmetrical stretching vibration, 1075cm^-1Asymmetric vibration sum of Si-O1635 cm^-1H-O-H bending vibration, thereby showing thatIn the oil-water separation composite membranes provided in examples 1 to 6, the combination between the silica nanomaterial and the PVA-co-PE membrane is stable, and the silica nanomaterial is stably supported by the PVA-co-PE membrane.

Referring to FIG. 2, a and d in FIG. 2 are C-SiO prepared in example 1₂Electron micrograph of-1, g in FIG. 2 is C-SiO₂-electron micrograph of 1/PM. In FIG. 2, b and e are C-SiO prepared in example 2₂Electron micrograph of-2, and h in FIG. 2 is C-SiO₂Electron micrograph of 2/PM. In FIG. 2, C and f are C-SiO prepared in example 3₂Electron micrograph of-3, i in FIG. 2 is C-SiO₂-electron micrograph of 3/PM.

As can be seen in fig. 2, as the ratio of CTAB to TMB increases, the size of the nanosilica spheres increases. And in examples 1-3, the diameters of the nano-silica spheres were respectively between 30-70nm, 62-72nm, and 0.5-1.5 μm.

In example 1, when 1mL of TMB was added, the silica sample was C-SiO₂The surface of-1 presents a plurality of radiating pore-like structures (shown as d in FIG. 3), with a pore size of about 1 nm.

In example 2, when 3mL of TMB was added, the silica sample was C-SiO₂2 presents a radiating pore structure. The pore diameter and the thickness of the mesoporous structure are respectively about 3.5nm and 8 nm.

In example 3, when 6ml of ltmb was added, the diameter of the nanosilica spheres increased dramatically and collapse of the shell wall occurred. In the silica sample C-SiO₂-3 hollow nanostructures and radial pore-like structures were observed on the surface. C-SiO₂The diameter, pore size and thickness of-3 were 200-800nm, 6nm and 25nm, respectively.

In the invention, in the process of preparing the silicon dioxide nanosphere with the radiation hole structure and/or the hollow structure by adopting a sol-gel method, the regulation and control mechanism of the mass volume ratio of CTAB and TMB to the structure of the silicon dioxide nanomaterial is as follows:

in the reaction system, at a lower content of TMB, TMB firstly diffuses into hydrophobic micelle cores of CTAB to swell the micelles, and the expanded micelle size reduces the charge density of hydrolyzed silicon TEOS, thereby reducing the condensation rate and being CTAB/SiO₂2 ofThe sub-self-assembly provides sufficient time to form a certain radiating hole structure. However, at higher levels of TMB, the TMB is linked to the hydrophilic head of the CTAB by cationic interaction, reducing the polarity of the CTAB and favoring SiO₂And thus the diameter of the prepared silica becomes significantly large. Then, the hydrolysis and condensation rate of TEOS is influenced by controlling the temperature, and finally, the silica nanospheres with different forms and different radiation hole structures and/or hollow structures are formed.

It can also be seen from fig. 2 that the silica nanosphere materials prepared in examples 1-3 are uniformly supported on the surface and inside of the PVA-co-PE membrane and uniformly embedded in the three-dimensional micro-nano mesh pores of the PVA-co-PE membrane (shown in g, h, i in fig. 3).

Please refer to the scanning electron microscope image of EDS element shown in fig. 3. In FIG. 3, a, b and C represent C-SiO prepared in example 1₂EDS elemental scanning electron micrographs of-1/PM. In FIG. 3, d, e and f are C-SiO prepared in example 2₂EDS elemental scanning electron micrographs of-2/PM. In FIG. 3, g, h and i are C-SiO prepared in example 3₂EDS elemental scanning electron micrographs of-3/PM.

As can be seen from FIG. 3, in the oil-water separation composite membranes prepared in examples 1 to 3, silica nanoballs are uniformly dispersed on the surface and inside of the PVA-co-PE membrane.

Referring to FIG. 4, a and d in FIG. 4 are L-SiO prepared in example 4₂Electron micrograph of-1, and g in FIG. 4 is L-SiO₂-electron micrograph of 1/PM. In FIG. 4, b and e are L-SiO prepared in example 5₂Electron micrograph of-2, and h in FIG. 4 is L-SiO₂Electron micrograph of 2/PM. In FIG. 4, c and f are L-SiO prepared in example 6₂Electron micrograph of-3, i in FIG. 4 is L-SiO₂-electron micrograph of 3/PM.

As shown in FIG. 4, L-16AlaPyPF6 is used as a template agent, and vermicular silica nanotubes and hollow silica nanospheres with different structures, which are respectively marked as L-SiO, are obtained by setting the template agent and TMB in different proportions₂-1、L-SiO₂-2、L-SiO₂-3。

In example 4, worms with spherical structures at both ends were obtained after addition of 0.5mL of TMBShaped silicon dioxide nanorod L-SiO₂-1 (shown as a in figure 4). TEM image confirmed L-SiO₂-1 is a hollow nanotube structure (shown as d in fig. 4). The length and diameter of the nanotubes are about 130-350nm and 30-45 nm.

In example 5, when TMB was increased to 1.5mL, uniform silica nanotubes L-SiO with worm-like structure were obtained₂-2 (shown in fig. 4 as b and e). L-SiO₂The length and diameter of-2 are about 100-325nm and 47-63nm, respectively.

In example 6, after addition of 3.0mL of TMB, silica nanoparticles (shown in panel c) were obtained. As shown in f of fig. 4, the silica nanoparticles have a hollow structure, and the outer shell collapses. The diameter of the hollow nanospheres is about 58-600nm and many porous structures are found on the nanosphere surface.

It can also be seen from fig. 4 that the silica nanomaterials prepared in examples 4 to 6 are uniformly supported on the surface and inside of the PVA-co-PE film, and are uniformly embedded into the three-dimensional micro-nano mesh pores of the PVA-co-PE film (shown in g, h, i in fig. 4).

Please refer to the scanning electron micrograph of EDS shown in fig. 5. In FIG. 5, a, b and c represent the L-SiO prepared in example 4₂EDS elemental scanning electron micrographs of-1/PM. In FIG. 5, d, e and f are the L-SiO prepared in example 5₂EDS elemental scanning electron micrographs of-2/PM. In FIG. 5, g, h and i are L-SiO prepared in example 6₂EDS elemental scanning electron micrographs of-3/PM.

As can be seen from FIG. 5, in the oil-water separation composite membranes prepared in examples 4 to 6, the silica nanomaterial was uniformly dispersed on the surface and inside of the PVA-co-PE membrane.

Please refer to the water contact angle test chart shown in fig. 6. Fig. 6a is a water contact angle test chart of the pristine PVA-co-PE film provided in comparative example 1, and b to g in fig. 6 represent water contact angle test charts of the oil-water separation composite films provided in examples 1 to 6, respectively.

The hydrophilicity of the various membrane surfaces was tested by a Water Contact Angle (WCA) experiment and the results are shown in fig. 6. The contact angle of the PM film provided in comparative example 1 was about 96s from 79.5 ° to 0 °.

The contact angle experiment results of the silica/PM oil-water separation composite membrane provided in embodiments 1 to 6 show that after the PM membrane is embedded with the silica nanospheres, the radiation hole silica nanospheres, the hollow silica nanospheres and the worm-like silica nanotubes having the mesoporous structure, the hydrophilicity is significantly improved, the contact angle of the silica/PM oil-water separation composite membrane can be changed to 0 ° within 1.3s, and only 0.5s is needed at the fastest, so that the hydrophilicity of the composite membrane is significantly improved.

Please refer to the experimental diagram of water-oil separation shown in fig. 7. (Note: chloroform, n-hexane (red color); and water (blue color)). In FIG. 7, a is chloroform (bottom, heavier than water) on the silica/PM oil-water separation composite membrane, and b is n-hexane (top, lighter than water) on the silica/PM oil-water separation composite membrane in FIG. 7. In fig. 7, c to e are non-adhesion images of chloroform droplets on the surface of the silica/PM oil-water separation composite membrane. In FIG. 7, f to g are photographs showing the measurement of the oil-water separation performance of the silica/PM oil-water separation composite membrane (f in FIG. 7 is before separation and g is after separation).

As can be seen from fig. 7, the silica/PM oil-water separation composite membrane provided by the present invention has a superhydrophilic property in air (shown as a in fig. 7) and a superoleophobic property under water (shown as b in fig. 7), so that oil is in a non-adhesive state on the surface of the composite membrane, which indicates that the adhesion between the surface of the composite membrane and oil is low and the composite membrane has excellent oil contamination resistance.

During the underwater oleophobic treatment (shown in c in fig. 7), when the dropper sucks oil drops (shown in d in fig. 7) adhered to the membrane surface, the membrane surface does not have the color of one drop of oil drop molecules (shown in e in fig. 7).

During gravity-driven filtration (shown as f in fig. 7), oil is completely isolated above the membrane due to the existence of the silica/PM oil-water separation composite membrane, and after standing overnight, an oil layer continues to be isolated above the membrane (shown as g in fig. 7), thereby showing excellent oil repellency of the membrane.

As can be seen from FIG. 7, the silica/PM oil-water separation composite membrane provided by the invention can effectively separate oil-water mixtures by gravity-driven filtration.

Referring to fig. 8, the separation efficiency of different oil and water (n-hexane/water, silicone oil/water, and peanut oil/water mixtures) of the silica/PM oil-water separation composite membranes provided in examples 1 to 6 is shown. The results show that the silica/PM oil-water separation composite membranes of examples 1 to 6 provided by the present invention all have high separation efficiency (> 98%) for oil-water mixtures.

Upon testing, SiO prepared in comparative example 2₂The oil-water separation efficiency of the PM oil-water separation composite membrane is 94%, which is lower than that of the oil-water separation composite membranes prepared in the embodiments 1-6, and the oil-water separation performance of the composite membrane can be remarkably improved by adopting the nano silica material with the hollow structure and the mesoporous structure.

The oil-water separation composite membrane prepared in example 7 has an oil-water separation efficiency of more than 99% and excellent oil-water separation performance.

It should be noted that, in the embodiments of the present invention, the process parameters of the preparation process of the silica nanomaterial can be adjusted according to actual requirements to prepare the silica nanomaterial with a predetermined structure. The spraying amount of the silicon dioxide nano material on the PVA-co-PE film base layer can be adjusted according to actual requirements, and the prepared composite film has excellent oil-water separation performance. The nonwoven fabric substrate used in the embodiment may also be, but is not limited to, one or more of PP, PET, PE, PVC, PAN, and PA mixed.

In summary, the invention provides an oil-water separation composite membrane and a preparation method thereof. The oil-water separation composite membrane consists of a PVA-co-PE nanofiber composite membrane base layer and silica nano materials which are uniformly loaded on the surface of the PVA-co-PE nanofiber composite membrane base layer and in internal pores and have preset structures; the silicon dioxide nano material is one or more of a radiating hole silicon dioxide nanosphere, a hollow silicon dioxide nanosphere, a mesoporous structure silicon dioxide nanosphere and a worm-shaped silicon dioxide nanotube. The preparation method comprises the following steps: the oil-water separation composite membrane is prepared by adopting a sol-gel method, changing the proportion between a template agent and trimethylbenzene to prepare hydrophilic silicon dioxide nano materials with different shapes, and spraying the hydrophilic silicon dioxide nano materials on a PVA-co-PE nano fiber composite membrane base layer. The oil-water separation composite membrane respectively shows excellent super-hydrophilic and oleophobic properties in air and water, and can efficiently separate an oil-water mixture by gravity-driven filtration, wherein the separation efficiency is more than 98%.

Although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the spirit and scope of the present invention.