阅读说明：本技术 一种针对膜蒸馏过程的耐摩擦、抗污染的超疏水膜及其制备方法 (Friction-resistant and pollution-resistant super-hydrophobic membrane for membrane distillation process and preparation method thereof ) 是由 廖园 黄津辉 郑广泰 于 2019-09-26 设计创作，主要内容包括：本发明公开了一种针对膜蒸馏过程的耐摩擦、抗污染的超疏水膜及其制备方法,该超疏水膜由纳米纤维支撑层和复合超疏水层两层结构构成的双层膜结构,所述超疏水膜具有耐摩擦性能。为提高膜蒸馏过程中膜的抗润湿性能,本研究通过静电纺丝以及静电喷涂制备了耐摩擦耐污染的新型超疏水膜。本发明应用于膜蒸馏过程中,可有效提高膜的超疏水性。该超疏水表面具有良好的稳定性以及抗摩擦性能。该超疏水表面可有效减轻膜蒸馏过程中的膜污染,使膜材料在长期测试过程中具有更优异的稳定性。(The invention discloses a friction-resistant and pollution-resistant super-hydrophobic membrane for a membrane distillation process and a preparation method thereof. In order to improve the anti-wetting property of the membrane in the membrane distillation process, the research prepares a novel friction-resistant and pollution-resistant super-hydrophobic membrane through electrostatic spinning and electrostatic spraying. The invention is applied to the membrane distillation process, and can effectively improve the super-hydrophobicity of the membrane. The super-hydrophobic surface has good stability and anti-friction performance. The super-hydrophobic surface can effectively reduce membrane pollution in the membrane distillation process, so that the membrane material has more excellent stability in the long-term test process.)

1. A rub resistant, anti-fouling, superhydrophobic membrane for membrane distillation processes, comprising: the super-hydrophobic membrane is a double-layer membrane structure consisting of a nanofiber supporting layer and a composite super-hydrophobic layer, wherein the two layers are overlapped together by an electrostatic spinning technology, and the super-hydrophobic membrane has friction resistance.

2. The superhydrophobic film of claim 1, wherein: the nanofiber supporting layer is a high-porosity polyvinylidene fluoride (PVDF) nanofiber supporting layer prepared by electrostatic spinning.

3. The superhydrophobic film of claim 1, wherein: the composite super-hydrophobic layer is a PVDF/Polydimethylsiloxane (PDMS)/silicon dioxide composite super-hydrophobic layer with a multi-layer structure, which is prepared by electrostatic spraying.

4. The superhydrophobic film of any of claims 1-3, wherein: the film thickness of the super-hydrophobic film is 60 +/-5 mu m.

5. A preparation method of a friction-resistant and pollution-resistant super-hydrophobic membrane for a membrane distillation process is characterized by comprising the following steps: the novel friction-resistant and pollution-resistant super-hydrophobic membrane is prepared through electrostatic spinning and electrostatic spraying, and the specific steps are as follows:

(1) preparing a nanofiber supporting layer: preparing a PVDF nanofiber supporting layer with high porosity by electrostatic spinning of 8 wt% of PVDF solution;

(2) preparing a composite super-hydrophobic layer: preparing a mixed solution by dissolving or dispersing PVDF, PDMS and silicon dioxide in N, N-Dimethylformamide (DMF) on the upper part of the nanofiber supporting layer in the step (1), and preparing a PVDF/PDMS/silicon dioxide composite super-hydrophobic layer by an electrostatic spraying method;

(3) preparing a super-hydrophobic membrane: and (2) electrostatically spraying a PVDF/PDMS/silicon dioxide composite super-hydrophobic layer on the surface of the PVDF nano-fiber supporting layer in the step (1) to obtain the super-hydrophobic membrane.

6. The method of preparing a rub resistant, anti-fouling, superhydrophobic membrane for membrane distillation process of claim 5, wherein: the concentration of PVDF in the step (2) is 2 wt%; the concentration of PDMS was 3 wt%.

7. The method of preparing a rub resistant, anti-fouling, superhydrophobic membrane for membrane distillation process of claim 5, wherein: the specific method of the step (2) is as follows: dissolving a monomer of PDMS and a crosslinking curing agent in a mixed solvent of N, N-Dimethylformamide (DMF) and Tetrahydrofuran (THF) to obtain a PDMS solution with a concentration of 3 wt%; then 2 wt% of PVDF is added to obtain homogeneous PVDF/PDMS solution; dispersing 3 wt% of silicon dioxide powder in a homogeneous PVDF/PDMS solution to obtain the PVDF/PDMS/silicon dioxide composite super-hydrophobic layer.

8. The method of preparing a rub resistant, stain resistant, superhydrophobic membrane for membrane distillation process of claim 7, wherein: the mass ratio of the monomers of the PDMS to the crosslinking curing agent is 10: 1.

9. the method of preparing a rub resistant, stain resistant, superhydrophobic membrane for membrane distillation process of claim 7, wherein: the mass ratio of the mixed solvent N, N-Dimethylformamide (DMF) to Tetrahydrofuran (THF) is 1: 1.

10. The application of the friction-resistant and pollution-resistant super-hydrophobic membrane in the membrane distillation process is characterized in that: the super-hydrophobic membrane is applied to seawater desalination.

Technical Field

The invention belongs to the field of wastewater treatment and seawater desalination, and particularly relates to a friction-resistant and pollution-resistant super-hydrophobic membrane for a membrane distillation process and a preparation method thereof.

Background

Membrane Distillation (MD) is a Membrane separation process in which a hydrophobic Membrane material is used as a separation medium and a difference in steam pressure is used as a driving force. Different from reverse osmosis desalination, the membrane distillation process has phase change and high energy consumption. Therefore, the method is generally applied to the field that reverse osmosis cannot be applied and the treatment capacity is relatively small, and has potential application prospects in the directions of industrial sewage zero discharge, deep concentration of strong brine, movable small-sized purified water preparation and the like.

China is short of water resources, one of effective measures for solving the problem is wastewater recycling, and zero-liquid-discharge (ZLD) is achieved. Taking coal chemical industry as an example, sewage containing various organic matters and a large amount of salt needs to be subjected to complex pretreatment including flocculation, oxidation, precipitation, membrane filtration and concentration (such as ultra-microfiltration and reverse osmosis), the salt content of the formed strong brine reaches 50000-80000mg/L, and then crystallization and pure water are obtained through concentration. Compared with the existing concentration technology (such as natural evaporation, mechanical compression evaporation and multi-effect evaporation), the membrane distillation equipment has the advantages of relatively low cost, low operation pressure and temperature, mild operation condition and high water quality of produced water. If solar energy, waste heat and the like can be used as heat sources for distillation treatment, the distillation treatment device has strong competitive advantages. Membrane distillation can also be used as a core component of mobile water treatment equipment to provide a clean water source for many fresh water-deficient areas. However, when the membrane distillation process is used for treating a complex water system, the pollution, the scaling and the wetting of the hydrophobic membrane material can cause the process to be unstable, and the membrane is frequently replaced.

Contamination of the membrane material is a surface phenomenon. For ultrafiltration, microfiltration and reverse osmosis membrane materials, strong hydrophilicity and zwitterion on the surface of the material are expected. The membrane surface preferentially adsorbs water molecules, and the contact of pollutants and the membrane material needs to overcome stronger hydrogen bonds, so that the contact probability of the pollutants and the membrane material is reduced, and the membrane material is more resistant to pollution. Common sense tells us that: the hydrophobic membrane material is hydrophobic, and has no water molecule protective layer, and the membrane material is easy to adsorb organic matters (such as surfactant), thereby forming pollution, leading the membrane to be wetted, and losing the original separation performance. The resistance to wetting and fouling of the membrane material during membrane distillation is therefore of crucial importance for long-term stable operation of the process.

Disclosure of Invention

In order to solve the problems, the invention provides a friction-resistant and pollution-resistant super-hydrophobic membrane with good stability and friction resistance in a membrane distillation process and a preparation method thereof. Aiming at the membrane distillation process, the super-hydrophobic membrane material with friction resistance and pollution resistance is prepared by an electrostatic spinning method, so that the pollution resistance of the membrane material in the membrane distillation process is improved, a new scheme is provided for reducing the membrane pollution, and the practical application of the membrane distillation technology is promoted.

In order to achieve the purpose, the invention is obtained by the following technical scheme:

the utility model provides a antifriction, antipollution's super hydrophobic membrane to membrane distillation process, this super hydrophobic membrane is by the bilayer membrane structure that nanofiber supporting layer and compound super hydrophobic layer two-layer structure constitute, super hydrophobic membrane has antifriction performance.

Further, the nanofiber supporting layer is a high-porosity polyvinylidene fluoride (PVDF) nanofiber supporting layer prepared by electrostatic spinning.

Further, the composite super-hydrophobic layer is a PVDF/Polydimethylsiloxane (PDMS)/silicon dioxide composite super-hydrophobic layer with a multi-layer structure, which is prepared by electrostatic spraying.

Further, the film thickness of the super-hydrophobic film is 60 +/-5 μm.

A preparation method of a friction-resistant and pollution-resistant super-hydrophobic membrane for a membrane distillation process is characterized in that a novel friction-resistant and pollution-resistant super-hydrophobic membrane is prepared through electrostatic spinning and electrostatic spraying, and the specific steps are as follows:

(1) preparing a nanofiber supporting layer: preparing a PVDF nanofiber supporting layer with high porosity by electrostatic spinning of 8 wt% of PVDF solution;

(2) preparing a composite super-hydrophobic layer: preparing a mixed solution by dissolving or dispersing PVDF, PDMS and silicon dioxide in N, N-Dimethylformamide (DMF) on the upper part of the nanofiber supporting layer in the step (1), and preparing a PVDF/PDMS/silicon dioxide composite super-hydrophobic layer by an electrostatic spraying method;

(3) preparing a super-hydrophobic membrane: and (2) electrostatically spraying a PVDF/PDMS/silicon dioxide composite super-hydrophobic layer on the surface of the PVDF nano-fiber supporting layer in the step (1) to obtain the super-hydrophobic membrane.

The concentration of PVDF in the step (2) is 2 wt%; the concentration of PDMS was 3 wt%.

The specific method of the step (2) is as follows: dissolving a monomer of PDMS and a crosslinking curing agent (in a mass ratio of 10: 1) in a mixed solvent of N, N-Dimethylformamide (DMF) and Tetrahydrofuran (THF) (in a mass ratio of 1: 1) to obtain a PDMS solution with a concentration of 3 wt%; then 2 wt% of PVDF is added to obtain homogeneous PVDF/PDMS solution; dispersing 3 wt% of silicon dioxide powder in a homogeneous PVDF/PDMS solution to obtain the PVDF/PDMS/silicon dioxide composite super-hydrophobic layer.

The invention has the beneficial effects that:

the invention is applied to the membrane distillation process, and can effectively improve the super-hydrophobicity of the membrane. The super-hydrophobic surface has good stability and anti-friction performance. The super-hydrophobic surface can effectively reduce membrane pollution in the membrane distillation process, so that the membrane material has more excellent stability in the long-term test process.

Drawings

In order to make the purpose, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation:

FIG. 1: schematic diagram of preparation process of the super-hydrophobic membrane;

FIG. 2: scanning Electron Microscope (SEM) images of membrane distillation membranes;

wherein A is a nanofiber support layer; b is a commercial PVDF membrane; c is a super-hydrophobic membrane;

FIG. 3: schematic diagram of bounce image of water drop on the surface of the super-hydrophobic film;

FIG. 4: long-term performance test plots for nanofiber PVDF membranes, superhydrophobic membranes, and commercial PVDF membranes in DCMD processes with different feed solutions;

wherein: a: 35g/L NaCl,3g/L CaCl₂,3g/L NaSO₄；B：35g/L NaCl,10mg/L HA；C：35g/LNaCl,10mg/L DTAB；(D)35g/L NaCl,10mg/L SLS(T_f＝333K,T_p293K, both sides flow rate 0.5Lmin^-1)。

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer.