阅读说明：本技术 一种自驱动油水分离复合Janus膜材料及制备方法与应用 (Self-driven oil-water separation composite Janus membrane material and preparation method and application thereof ) 是由 于洋 苏芮琳 陈达 于�玲 于 2021-07-05 设计创作，主要内容包括：本发明属于化工分离、环境保护技术领域,具体公开了一种自驱动油水分离复合Janus膜材料及制备方法。本发明采用简便的化学氧化和多巴胺表面负载改性两步法制备具有三维结构的超亲水铜网,其表面所具有的高亲水性纳米针状氢氧化铜结构,能够贯穿或部分贯穿超水性纳米纤维层,形成水快速渗透通道。进而通过改变电纺丝制备时间调控超疏水纳米纤维层厚度,优化所制备膜材料在无重力等外部驱动力的条件下实现高效定向水渗透和油层下集水功能。(The invention belongs to the technical field of chemical separation and environmental protection, and particularly discloses a self-driven oil-water separation composite Janus membrane material and a preparation method thereof. The invention adopts a simple and convenient two-step method of chemical oxidation and dopamine surface loading modification to prepare the super-hydrophilic copper mesh with a three-dimensional structure, and the surface of the super-hydrophilic copper mesh has a high-hydrophilicity nano needle-shaped copper hydroxide structure which can penetrate through or partially penetrate through a super-aqueous nano fiber layer to form a water rapid permeation channel. And then the thickness of the super-hydrophobic nanofiber layer is regulated and controlled by changing the preparation time of the electrospinning, and the functions of efficient directional water permeation and water collection under an oil layer are realized by optimizing the prepared membrane material under the condition of no external driving force such as gravity.)

1. A method for self-driven oil-water separation of a composite Janus membrane material is characterized by comprising the following steps:

(1) preparing a super-hydrophilic three-dimensional copper net:

mixing a strong base with (NH)₄)₂S₂O₈Dissolving in water, and immersing copper net into the mixed solution to prepare Cu (OH) on the surface₂Nano thorns; then immersing the copper net into dopamine solution to make dopamine adhere to the surface to obtain PDA coated Cu @ Cu (OH)₂A net;

(2) preparing a super-hydrophobic electrospun nanofiber layer:

dissolving polyvinylidene fluoride-hexafluoropropylene in dimethylformamide to obtain a PVDF-HFP casting solution; hydrophobic SiO₂Dispersing the nano particles in acetone to obtain SiO₂An emulsion; PVDF-HFP membrane casting solution and SiO₂Mixing the emulsions to obtain an electrostatic spinning solution;

(3) preparing a self-driven oil-water separation composite Janus film material:

PDA was coated with Cu @ Cu (OH)₂The net is fixed on a roller of an electrostatic spinning instrument, and electrostatic spinning is carried out on the surface of the net to form PVDF-HFP/SiO₂And (5) a nanofiber layer to obtain the self-driven oil-water separation composite Janus membrane material.

2. The method of claim 1, wherein:

the molar concentration of the strong base in the mixed solution in the step (1) is 2-4 mol/L; (NH)₄)₂S₂O₈The molar concentration of (a) is 0.1-0.15 mol/L.

3. The method of claim 1, wherein:

the concentration of the dopamine solution in the step (1) is 1-4 g/L.

4. The method of claim 1, wherein: the mass ratio of the PVDF-HFP to the DMF in the step (2) is 2-8: 16.

5. The method of claim 1, wherein: the hydrophobic SiO in step (2)₂The mass ratio of the nano particles to the acetone is 0: 4-1: 4, and SiO is₂The amount is different from 0.

6. The method of claim 1, wherein: the PVDF-HFP and SiO in the step (2)₂In a mass ratio of 10:5 to 10:0, SiO₂The amount is different from 0.

7. The method of claim 1, wherein: the electrostatic spinning parameters in the step (3) are as follows: the rotating speed of the roller is 100-300 rpm, the receiving distance is 10-20 cm, the liquid feeding speed is 0.5-2.0 mL/h, and the voltage is 15-20 KV.

8. The method of claim 1, wherein: immersing the copper mesh in the mixed solution for 5-15 min in the step (1); and (2) immersing the copper mesh in the dopamine solution for 12-48 h.

9. A self-driven oil-water separation composite Janus membrane material prepared by the method of any one of claims 1-8.

10. The application of the self-driven oil-water separation composite Janus membrane material as claimed in claim 9 in the field of oil-water separation.

Technical Field

The invention belongs to the technical field of chemical separation and environmental protection, and particularly relates to a self-driven oil-water separation composite Janus membrane material and a preparation method thereof.

Background

Inspired by the wettability phenomenon of animals and plants (such as cactus, lotus leaves, spider silk, desert beetle and the like) in nature, a plurality of Janus membranes with the liquid spontaneous transport capability are disclosed, and the Janus membranes are applied to low-cost and high-efficiency oil-water separation. The currently reported methods for preparing Janus films mainly include surface grafting, dip coating, spraying, atomic layer deposition and the like. Compared with the Janus film preparation method, the electrostatic spinning technology has the advantages of easiness in batch production, controllable wettability, capability of doping other active materials and the like. Hydrophilic polyvinyl alcohol (PVA) is electrospun onto a hydrophobic Polyurethane (PU) film, and water droplets can penetrate unidirectionally from the PU side to the PVA side. A Janus membrane prepared by electrospinning hydrophobic polyvinylidene fluoride (PVDF) on one side of a hydrophilic copper mesh can collect water droplets under oil. However, the Janus membrane only relates to the one-way permeation of water drops and cannot show self-driven oil-water separation performance, so that the wide application of the Janus membrane in the field of oil-water separation is not facilitated.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention mainly aims to provide a preparation method of a self-driven oil-water separation composite Janus membrane material.

The invention also aims to provide the self-driven oil-water separation composite Janus membrane material prepared by the method.

The invention further aims to provide application of the self-driven oil-water separation composite Janus membrane material in the field of oil-water separation.

The purpose of the invention is realized by the following scheme:

a method for self-driven oil-water separation of a composite Janus membrane material comprises the following steps:

(1) preparing a super-hydrophilic three-dimensional copper net:

mixing strong alkali and ammonium persulfate ((NH)₄)₂S₂O₈) Dissolving in water, and immersing copper net into the mixed solution to obtain copper hydroxide (Cu (OH)₂) Nano thorns; then immersing the copper net into dopamine (PDA) solution to make dopamine adhere to the surface, thus obtaining PDA coated Cu @ Cu (OH)₂A net;

(2) preparing a solution of the super-hydrophobic electrospun nanofiber layer:

dissolving polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) in dimethyl formamide (DMF) to obtain a PVDF-HFP casting solution; hydrophobic Silica (SiO)₂) Dispersing the nano particles in acetone to obtain SiO₂An emulsion; PVDF-HFP membrane casting solution and SiO₂Mixing the emulsions to obtain an electrostatic spinning preparation solution;

(3) preparing a self-driven oil-water separation composite Janus film material:

PDA coated Cu @ Cu (OH)₂The net is fixed on a roller of an electrostatic spinning instrument, electrostatic spinning is carried out on the surface of the net to form PVDF-HFP/SiO₂And (5) a nanofiber layer to obtain the self-driven oil-water separation composite Janus membrane material.

The molar concentration of the strong base in the mixed solution in the step (1) is 2-4 mol/L, and preferably 2.5 mol/L; said (NH)₄)₂S₂O₈The molar concentration of (b) is 0.1 to 0.15mol/L, preferably 0.13 mol/L.

Before the copper mesh in the step (1) is used, in order to remove impurities on the surface of the copper mesh, the copper mesh is ultrasonically cleaned by ethanol, water and hydrochloric acid aqueous solution respectively.

And (2) immersing the copper mesh in the mixed solution in the step (1) for 5-15 min, preferably 6 min.

The concentration of the dopamine solution in the step (1) is 1-4 g/L, and preferably 2 g/L. The immersion time of the copper net in the dopamine solution is 12-48 h, and preferably 24 h.

The mass ratio of PVDF-HFP to DMF in the step (2) is 2-8: 16, preferably 4-6: 16, and more preferably 5: 16;

the hydrophobic SiO in step (2)₂The nanoparticles are prepared by reacting hydrophilic SiO with Vinyltriethoxysilane (VTES)₂Carrying out hydrophobic modification on the nanoparticles;

the hydrophobic SiO in step (2)₂The mass ratio of the nano particles to the acetone is 0: 4-1: 4, and SiO is₂The dosage is different from 0, and is preferably 0.5: 4;

the PVDF-HFP and the hydrophobic SiO in the step (2)₂The mass ratio of the nano particles is 10: 5-10: 0, and SiO is₂The amount is other than 0, preferably 10: 1.

The electrostatic spinning parameters in the step (3) are as follows: the rotating speed of the roller is 100-300 rpm, the receiving distance is 10-20 cm, the liquid feeding speed is 0.5-2.0 mL/h, and the voltage is 15-20 KV; preferably, the parameters of the electrostatic spinning are as follows: the roller speed is 200rpm, the receiving distance is 15cm, the liquid feeding speed is 1.5mL/h, and the voltage is 16 KV.

A self-driven oil-water separation composite Janus membrane material is prepared by the method.

The self-driven oil-water separation composite Janus membrane material is applied to the field of oil-water separation.

Compared with the prior art, the invention has the following advantages and beneficial effects:

the invention adopts a simple and convenient two-step method of chemical oxidation and dopamine surface loading modification to prepare the super-hydrophilic copper mesh with a three-dimensional structure, and the surface of the super-hydrophilic copper mesh has a high-hydrophilicity nano needle-shaped copper hydroxide structure which can penetrate through or partially penetrate through a super-aqueous nano fiber layer to form a water rapid permeation channel. And then the thickness of the super-hydrophobic nanofiber layer is regulated and controlled by changing the preparation time of the electrospinning, and the functions of efficient directional water permeation and water collection under an oil layer are realized by optimizing the prepared membrane material under the condition of no external driving force such as gravity.

Drawings

FIG. 1 is a graph of the ability of the composite Janus membrane prepared in example 1 to separate oil from water and to orient permeation without external driving force; wherein (a) the composite Janus film faces the hydrophobic side of the oil-water mixture; (b) composite Janus membrane with hydrophilic side towards oil water mixture: (c) coating Cu @ Cu (OH) for PDA without Janus film₂

FIG. 2 is a water-collecting picture under the oil layer of the prepared composite Janus membrane; wherein (a) is a schematic diagram of water collection; (b) and (d) is a composite Janus membrane water-retention plot; (c) and (e) PDA coated Cu @ Cu (OH) without Janus film₂Net catchment diagram.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

The reagents used in the examples are commercially available without specific reference.

Example 1

1) Preparation of super-hydrophilic three-dimensional copper mesh

In order to remove impurities on the surface of the copper mesh, the copper mesh is ultrasonically cleaned by ethanol, deionized water and hydrochloric acid aqueous solution respectively. The copper mesh was then immersed in 2.5M NaOH and 0.13M (NH) at 25 deg.C₄)₂S₂O₈Mixing the solution for 6min to obtainCu (OH) grows on the surface₂Nano thorn, mixing the obtained hydrophilic Cu @ Cu (OH)₂The mesh was washed with deionized water and dried in an oven at 60 ℃. Finally, Cu @ Cu (OH)₂The web was immersed in a 2g/L dopamine solution (pH 8.5) for 24h and a thin layer of PDA was coated on its surface.

2) Preparation of super-hydrophobic electrospun nanofiber layer

And dissolving PVDF-HFP powder in Dimethylformamide (DMF), and stirring at 50 ℃ for 6 hours to obtain the PVDF-HFP casting solution. To make hydrophilic SiO₂Hydrophobic modification of nano-particles by taking 1g of SiO₂15mL of VTES and 100mL of absolute ethanol were mixed and stirred at room temperature for 30 min. To the mixture was added 10mL of 25% aqueous ammonia, and the mixture was stirred at room temperature for 24 hours. The resulting mixture was centrifuged three times with absolute ethanol and then freeze-dried for 10 h. Subjecting the obtained hydrophobic SiO₂Dissolving the mixture in Acetone (Acetone) solvent by ultrasonic dispersion to obtain SiO₂An emulsion. The emulsion and the PVDF-HFP solution are mixed and stirred uniformly to obtain the electrostatic spinning solution, and the ratio of the spinning solution is shown in Table 1.

PDA coated Cu @ Cu (OH)₂The net is fixed on a roller of an electrostatic spinning instrument, and PVDF-HFP/SiO is electrospun on the surface of the net₂The nanofiber layer, electrospinning parameters are shown in table 2.

TABLE 1 PVDF-HFP/SiO₂Spinning solution ratio

TABLE 2 Electrostatic spinning parameters

PVDF-HFP/SiO obtained in this example₂The water contact angle of the nanofiber layer is about 144 degrees, and the surface of the membrane is uniform.

Example 2

Referring to example 1, the copper mesh of step 1) was ultrasonically cleaned with water and aqueous hydrochloric acid, respectively, before use.

Macroscopic impurities still remain on the surface of the copper mesh obtained in the embodiment, and the subsequent preparation process is influenced.

Example 3

Referring to example 1, step 2) of PVDF-HFP and SiO₂The mass ratio of (2) was changed to 10: 5.

PVDF-HFP/SiO obtained in this example₂The water contact angle of the nanofiber layer is about 145 degrees, and irregular white spots are randomly scattered on the surface of the membrane.

Example 4

Referring to example 1, step 2) of PVDF-HFP and SiO₂The mass ratio of (a) to (b) is changed to 10: 3.

PVDF-HFP/SiO obtained in this example₂The water contact angle of the nanofiber layer is about 144 degrees, and the surface of the membrane is relatively uniform.

Comparative example 1

With reference to example 1, no SiO was added in step 2)₂。

The PVDF-HFP nanofiber layer obtained in the example has a water contact angle of about 141 degrees, the membrane surface is more uniform, but the hydrophobicity is lower than that of the PVDF-HFP nanofiber layer obtained in the example 1.

Application examples

1) The oil-water separation experiment process uses a self-made dead-end filter device to carry out an oil-water separation experiment, and the device consists of two cylindrical glass tubes with the diameter of 3 cm. Before the oil-water separation experiment, the hydrophilic and hydrophobic sides of the membrane were wetted with water and oil, respectively. 50mL of oil and 50mL of water were stained with oil Red and methylene blue, respectively, and mixed, a glass tube closed at the bottom was added, a Janus membrane was fixed in the middle of the two tubes with the hydrophobic side facing the oil-water mixture, and the device was then placed horizontally. Referring to the experimental procedure described above, the Janus film was coated with Cu @ Cu (OH) with the hydrophilic side facing the oil water mixture and PDA₂The mesh was sequentially fixed between the two tubes for comparison.

2) Test procedure for water collection under oil reservoir

The oil was first added to a beaker and drops of water stained with methylene blue were added dropwise. The hydrophobic side of the Janus membrane was fixed outward to one end of the plastic tube as a Janus collector and the hydrophilic side of the Janus membrane was inward and pre-wetted with water. PDA coating with Cu @ Cu (OH) according to the Experimental procedure described above₂The net is also fixed at one end of the plastic pipeThe collector was used as a control. And (4) putting the collector under oil to collect water drops, and lifting the collector to be above the oil liquid level.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.