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CN-122006478-A - Janus film with sandwich structure and preparation method

CN122006478ACN 122006478 ACN122006478 ACN 122006478ACN-122006478-A

Abstract

The invention discloses a Janus membrane with a sandwich structure and a preparation method thereof, wherein the Janus membrane comprises a base membrane, a super-hydrophobic layer and a hydrophilic layer, wherein the base film is positioned between the super-hydrophobic layer and the hydrophilic layer and is tightly attached. The Janus membrane has superhydrophobic surface and hydrophilic surface, so that the multi-element interface with asymmetric infiltration characteristic is formed, namely, the membrane hydrophobicity requirement for the membrane distillation process, especially for the air gap membrane distillation process is met, the water contact angle in the air of the superhydrophobic layer is larger than 150 degrees, and the water contact angle in the air of the hydrophilic layer is smaller than 90 degrees; the Janus membrane has the characteristics of high heat efficiency and acceleration of gas phase condensation, has good infiltration resistance and high interception efficiency, has good heat efficiency, namely membrane distillation efficiency, has wide application prospect, and has simple film forming process, convenient operation and easy realization of industrial production.

Inventors

  • HOU DEYIN
  • Mou Yuxin
  • LI FENG

Assignees

  • 中国科学院生态环境研究中心

Dates

Publication Date
20260512
Application Date
20260128

Claims (10)

  1. 1. A Janus membrane with a sandwich structure is characterized by comprising a base membrane, a super-hydrophobic layer and a hydrophilic layer, wherein the base membrane is positioned between the super-hydrophobic layer and the hydrophilic layer and is tightly attached.
  2. 2. The Janus membrane of claim 1, wherein said base membrane is a hydrophobic membrane.
  3. 3. The Janus film according to claim 1 or 2, wherein the super-hydrophobic layer is prepared by dispersing inorganic nano particles in absolute ethyl alcohol to prepare inorganic nano particle dispersion liquid, adding super-pure water, ammonia water and heptadecafluorodecyl trimethoxysilane into the dispersion liquid, stirring and mixing uniformly to prepare super-hydrophobic layer spraying liquid, spraying the super-hydrophobic layer spraying liquid on the surface of one side of a base film, and drying to form the super-hydrophobic layer.
  4. 4. The Janus film according to claim 1 or 2, wherein the hydrophilic layer is formed by mixing an organic polymer, a high thermal conductivity nanomaterial dispersion with an organic solvent, stirring, dissolving, and spraying the hydrophilic layer spray solution onto the surface of the other side of the base film, and drying.
  5. 5. The preparation method of the Janus film with the sandwich structure is characterized by comprising the following steps of: 1) Preparing the super-hydrophobic layer spraying liquid Adding ultrapure water, ammonia water and heptadecafluorodecyl trimethoxysilane FAS-17 into the dispersion liquid of the inorganic nano particles, stirring and mixing uniformly to prepare a super-hydrophobic layer spraying liquid for later use; 2) Preparing hydrophilic layer spraying liquid Mixing organic polymer, high heat conductivity nano material dispersion liquid and organic solvent, stirring, dissolving and preparing hydrophilic layer spraying liquid for standby; 3) Spraying super-hydrophobic and hydrophilic layers And respectively spraying super-hydrophobic layer spraying liquid and hydrophilic layer spraying liquid on two sides of the base film, and drying to obtain the Janus film with the sandwich structure.
  6. 6. The method of claim 5, wherein the inorganic nanoparticles in step 1) are nanosilica, nanosilica or nanosilica particles.
  7. 7. The method according to claim 5 or 6, wherein the content of the inorganic nanoparticles in the super-hydrophobic layer spraying liquid in the step 1) is 0.2wt% to 0.6wt%, and the content of FAS-17 in the super-hydrophobic layer spraying liquid is 1.4wt% to 1.8wt%.
  8. 8. The process according to claim 5 or 6, wherein the organic polymer in step 2) is Polyacrylonitrile (PAN) or AN Acrylonitrile (AN) copolymer, preferably polyacrylonitrile.
  9. 9. The method of claim 5 or 6, wherein the high thermal conductivity nanomaterial of step 2) is single-layer Graphene Oxide (GO) or Carbon Nanotubes (CNTs), preferably GO.
  10. 10. The method according to claim 5 or 6, wherein the hydrophilic layer spraying liquid in step 2) has an organic polymer content of 2wt% to 4wt%, the hydrophilic layer spraying liquid has a high thermal conductivity nanomaterial content of 0.1wt% to 0.2wt%, and the ratio of the organic polymer in the hydrophilic layer spraying liquid to the high thermal conductivity nanomaterial is 100 (2.5 to 10), preferably 100 (5 to 5.5).

Description

Janus film with sandwich structure and preparation method Technical Field The invention relates to a preparation technology of a membrane distillation membrane material, in particular to an anti-infiltration high-thermal-efficiency sandwich structure composite Si-PVDF-GO/PAN Janus membrane and a preparation method thereof. Background Membrane Distillation (MD) is a novel membrane separation technology, organically integrating the evaporation process and the membrane process. The driving force for the membrane distillation process is the vapor pressure differential across the membrane. The membrane used in membrane distillation is a hydrophobic membrane which is porous and is not wetted by feed liquid, one side of the membrane is a hot water solution to be treated which is in direct contact with the membrane, the water solution does not pass through the membrane pores due to the hydrophobicity of the membrane, but the volatile components are vaporized at the surface of the membrane on the feed liquid (high temperature) side due to the pressure difference of the volatile components vapor on both sides of the membrane, and the vapor is transferred to the other side of the membrane (low vapor pressure side) through the membrane pores and condensed into liquid. The membrane distillation process is carried out almost under normal pressure, the equipment is simple, the operation is convenient, the retention rate of pollutants in the membrane distillation process can almost reach 100 percent because only water vapor can permeate through the membrane holes, the produced water is quite pure, and in addition, the membrane distillation process can treat high-concentration salt-containing water and even concentrate the solution to a supersaturated state to crystallize and separate out, namely the membrane distillation crystallization technology. The membrane material used in the membrane distillation process should meet both basic requirements of hydrophobicity and porosity to ensure that water does not penetrate into the micropores and has a higher permeation flux. At the same time, the wettability resistance and high thermal efficiency should also be satisfied to improve MD stability and efficiency. Along with the continuous expansion of the application field of the membrane technology, the requirements on the membrane performance are higher and higher, the single membrane material can not meet the industrial water treatment requirements, and the preparation of the composite membrane material has important significance. At present, the preparation of the composite membrane generally adopts the thought of a substrate membrane and a functional layer, wherein the substrate membrane is prepared by a phase inversion method or electrospinning to obtain the required pore structure and mechanical properties, and the functional layer is usually introduced by an interfacial polymerization method, a coating method, electrospraying, sol-gel or in-situ reaction, such as a hydrophobic layer is constructed to improve the wettability, or a hydrophilic/heat-conducting layer is loaded to reduce the temperature polarization and improve the thermal efficiency. Nanofiller doping (e.g., siO 2、TiO2, GO, MOFs, etc.) is also widely used to improve the hydrophobicity, contamination resistance, and heat transfer properties of the films. Although the methods can effectively realize multifunctional integration and performance optimization, the method has the defects that the phase inversion and electrospinning processes are difficult to completely accurate in aperture and structure regulation and control, the large-scale cost is high, the interfacial polymerization and coating processes are highly sensitive to operation conditions, the film uniformity or stability is easily reduced, the sol-gel and in-situ deposition have stronger heat resistance and catalysis performance, but the processes are complex, the energy consumption and the cost are high, and the dispersion non-uniformity or agglomeration phenomenon of nano fillers can cause the film performance attenuation. Therefore, the preparation of composite membranes in the field of membrane distillation still faces challenges on how to combine membrane performance improvement with preparation process controllability, scale and cost effectiveness. The Janus film is an asymmetric functional film material with two surfaces and different physical or chemical properties, and the film body at least comprises a first functional layer and a second functional layer along the thickness direction, wherein the first functional layer and the second functional layer have obvious differences in at least one of wettability, heat conductivity, pore structure, surface energy or chemical composition, so that the two sides of the film respectively bear different functional effects. In the prior art, janus membranes for membrane distillation are generally realized by constructing functional layers with different sur