CN112898628B - Leaf-like porous membrane composite PPy/PVA sponge and preparation method and application thereof - Google Patents

Leaf-like porous membrane composite PPy/PVA sponge and preparation method and application thereof Download PDF

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CN112898628B
CN112898628B CN202110154920.9A CN202110154920A CN112898628B CN 112898628 B CN112898628 B CN 112898628B CN 202110154920 A CN202110154920 A CN 202110154920A CN 112898628 B CN112898628 B CN 112898628B
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ppy
sponge
porous membrane
pva sponge
leaf
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CN112898628A (en
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金欣
李叶燃
王闻宇
李伟
韩幸
郑意德
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Tianjin Polytechnic University
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/36—After-treatment
    • C08J9/40—Impregnation
    • C08J9/405—Impregnation with polymerisable compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/02—Treatment of water, waste water, or sewage by heating
    • C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/14—Treatment of water, waste water, or sewage by heating by distillation or evaporation using solar energy
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/36—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
    • C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
    • C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2425/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an aromatic carbocyclic ring; Derivatives of such polymers
    • C08J2425/02—Homopolymers or copolymers of hydrocarbons
    • C08J2425/04—Homopolymers or copolymers of styrene
    • C08J2425/08—Copolymers of styrene
    • C08J2425/12—Copolymers of styrene with unsaturated nitriles
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2479/00—Characterised by the use of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen, or carbon only, not provided for in groups C08J2461/00 - C08J2477/00
    • C08J2479/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00—Water conservation; Efficient water supply; Efficient water use
    • Y02A20/20—Controlling water pollution; Waste water treatment
    • Y02A20/208—Off-grid powered water treatment
    • Y02A20/212—Solar-powered wastewater sewage treatment, e.g. spray evaporation

Abstract

The invention provides a leaf-like porous membrane composite PPy/PVA sponge, a preparation method and application thereof, and belongs to the technical field of photoelectrode materials. The method comprises the following steps: soaking PVA sponge in FeCl3Contacting the solution with pyrrole for chemical vapor deposition to obtain PPy/PVA sponge; dipping the PPy/PVA sponge into a styrene-acrylonitrile copolymer solution, and performing water drop template method film formation to obtain the leaf-like porous membrane composite PPy/PVA sponge. In the invention, the hydrophilicity of PVA sponge with communicated microporous structures ensures the water supply property and simultaneously forms small molecular water clusters in a polymer network so as to reduce the evaporation enthalpy of water, the SAN hydrophobic honeycomb porous membrane is prepared by using a styrene-acrylonitrile copolymer solution to carry out a water drop template method, and the SAN hydrophobic honeycomb porous membrane is used as the surface to enhance the escape speed of steam, and the surface of a base material has hydrophobicity and the function of salt crystallization resistance.

Description

Leaf-like porous membrane composite PPy/PVA sponge and preparation method and application thereof
Technical Field
The invention relates to the technical field of photoelectrode materials, in particular to a leaf-like porous membrane composite PPy/PVA sponge and a preparation method and application thereof.
Background
The traditional solar distillation utilizes the principle of heating the whole water, and the solar steam conversion efficiency is low (30-50%) due to large optical loss and thermal loss, thereby limiting the further utilization and development of the technology to a great extent. Through development, researchers find that solar energy is absorbed by metal nanofluid, and therefore, the photothermal steam conversion device is produced at the same time, and people pay attention to the photothermal steam conversion device due to the advantages of no consumption of conventional energy, no pollution, high purity of obtained fresh water and the like. The photothermal steam conversion fundamentally eliminates the defect of low energy conversion rate of the traditional solar distillation technology by heating water at a gas-liquid evaporation interface instead of heating the whole water body, so that the solar steam conversion efficiency is greatly improved (80%), the operation cost is greatly reduced, and the water purification cost is lower and more convenient.
The factors for improving the conversion efficiency of the photo-thermal steam mainly have four aspects, namely high-efficiency solar energy absorption rate, low heat loss, proper water supply rate and rapid water vapor diffusion. Based on these four factors, in the prior art, the metal nanoparticles (such as chinese patent CN202010058364.0), the carbon-based materials including carbon black, graphene and carbon nanotubes (such as CN201911199433.3) all can improve the solar energy absorption rate, thereby improving the light-heat conversion efficiency; the low-cost photothermal polymer-polypyrrole has excellent adhesive force, a controllable molecular structure and high solar energy absorption rate, and is regarded as the most potential material in the field of photothermal steam conversion. However, the prior art improves the photothermal steam conversion material from the aspect of two-dimensional structures (such as films, paper, felts and fabrics), and still has the problem of low photothermal steam conversion efficiency.
Disclosure of Invention
In view of the above, the invention aims to provide a leaf-like porous membrane composite PPy/PVA sponge, and a preparation method and application thereof. The leaf-like porous membrane composite PPy/PVA sponge prepared by the method has high photo-thermal steam conversion efficiency.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a leaf-like porous membrane composite PPy/PVA sponge, which comprises the following steps:
soaking polyvinyl alcohol sponge in FeCl3Obtaining pretreated polyvinyl alcohol sponge in the solution;
contacting the pretreated polyvinyl alcohol sponge with pyrrole, and carrying out in-situ chemical vapor deposition on the polypyrrole on the pretreated polyvinyl alcohol sponge to obtain PPy/PVA sponge;
dipping the PPy/PVA sponge in a styrene-acrylonitrile copolymer solution, and performing water drop template method film forming to obtain the leaf-like porous membrane composite PPy/PVA sponge.
Preferably, the polyVinyl alcohol sponge and FeCl3FeCl in solution3The dosage ratio of the components is 1cm3：0.005～0.01mol。
Preferably, the FeCl3FeCl in solution3The dosage ratio of the pyrrole to the pyrrole is 0.005-0.01 mol: 2 mL.
Preferably, the vacuum degree of the in-situ chemical vapor deposition is 0.6-0.8, the temperature is 23-25 ℃, and the time is 4-6 hours.
Preferably, the dosage ratio of the PPy/PVA sponge dipping to the styrene-acrylonitrile copolymer in the styrene-acrylonitrile copolymer solution is 1cm3：0.008～0.012g。
Preferably, the water drop template method film forming is carried out in a closed reaction device, the closed reaction device is provided with a wet nitrogen gas injection port, and the humidity of the closed reaction device is enabled to be 75-90% by the injected wet nitrogen gas.
Preferably, the distance from the wet nitrogen blowing opening to the dipped styrene-acrylonitrile copolymer solution is 3-5 cm, and the speed of the wet nitrogen is 1-2L/min.
Preferably, the temperature of the water drop template film forming is 80-90 ℃, and the time is 30-60 min.
The invention also provides the leaf-imitated porous membrane composite PPy/PVA sponge prepared by the preparation method in the technical scheme, which comprises a base material and the styrene-acrylonitrile copolymer hydrophobic porous membrane loaded on the surface of the base material, wherein the base material comprises polyvinyl alcohol sponge and polypyrrole loaded in the polyvinyl alcohol sponge.
The invention also provides application of the leaf-like porous membrane composite PPy/PVA sponge in the technical scheme in photo-thermal steam conversion.
The invention provides a preparation method of a leaf-like porous membrane composite PPy/PVA sponge, which comprises the following steps: soaking polyvinyl alcohol sponge in FeCl3Taking out the solution to obtain pretreated polyvinyl alcohol sponge; contacting the pretreated polyvinyl alcohol sponge with pyrrole for chemical vapor deposition to obtain PPy/PVA sponge; dipping the PPy/PVA sponge into a styrene-acrylonitrile copolymer solution, and performing film formation by a water drop template method to obtain the PPy/PVA spongeThe leaf-like porous membrane is compounded with PPy/PVA sponge. In the present invention, FeCl is used3The solution and the pyrrole are subjected to chemical vapor deposition to obtain polypyrrole (PPy), the PPy has a wide spectral response range, high light absorption rate, a large specific surface area and good light resistance and heat resistance, and is used as a solar absorber; the molecular chain of the polyvinyl alcohol (PVA) sponge contains a large number of hydrogen bonds, so that the PVA sponge has excellent hydrophilicity, good flexibility and flexibility, high porosity and moisture absorption and heat insulation, the PVA sponge is used as a water supply channel of a photothermal steam conversion device, PPy and PVA are compounded to obtain PPy loaded PVA sponge with a 3D micro-channel, black PPy has excellent light absorption performance, the hydrophilicity of the PVA sponge with an intercommunicated microporous structure ensures the water supply performance, meanwhile, small molecular water clusters are formed in a polymer network, so that the evaporation enthalpy of water is reduced, a styrene-acrylonitrile copolymer (SAN) solution is used for a water drop template method to prepare the SAN hydrophobic honeycomb porous membrane, the styrene-acrylonitrile copolymer is a colorless and transparent hydrophobic polymer, has high temperature resistance and chemical medium resistance, excellent dimensional stability and higher bearing capacity, and the escape speed of steam is enhanced by taking the hydrophobic porous membrane as the surface, further improving the conversion efficiency of photo-thermal steam, and making the surface of the base material have hydrophobicity and salt crystallization resistance.
The data of the examples show that the leaf-like porous membrane composite PPy/PVA sponge prepared by the invention has one-time solar light intensity (1 kW.m)-2) The evaporation rate was 3.09kg · m-2·h-1。
The invention also provides a leaf-like porous membrane composite PPy/PVA sponge, which comprises a base material and the styrene-acrylonitrile copolymer hydrophobic porous membrane wrapping the base material, wherein the base material comprises polyvinyl alcohol sponge and polypyrrole loaded in the polyvinyl alcohol sponge. The invention is inspired by the leaf transpiration in nature, and provides a novel bionic leaf porous membrane composite PPy/PVA sponge, wherein the polyvinyl alcohol sponge is equivalent to a guard tissue in leaves and plays roles of supporting a framework and transporting water, the polypyrrole is equivalent to chlorophyll and plays roles of absorbing sunlight and carrying out heat collection, and the styrene-acrylonitrile copolymer hydrophobic porous membrane is equivalent to an air hole and is beneficial to water vapor diffusion.
The leaf-like porous membrane composite PPy/PVA sponge provided by the invention has good desalting and purifying capabilities (salt water and seawater), provides a new idea for the field of water treatment by utilizing sustainable energy, and can relieve global energy and the crisis of fresh water shortage.
Drawings
FIG. 1 is a flow chart of a method for preparing a leaf-like porous membrane composite PPy/PVA sponge;
FIG. 2 is a field emission scanning electron micrograph of the PVA sponge of example 1;
FIG. 3 is a scanning electron micrograph of PPy/PVA sponge of example 1;
FIG. 4 is a scanning electron microscope spectrum of the field emission of the leaf-like porous membrane composite PPy/PVA sponge in example 1;
FIG. 5 is a comparison of the structure of a leaf-like porous membrane composite PPy/PVA sponge and the structure of a leaf;
FIG. 6 is a diagram of a test device for simulating solar radiation evaporation experiments;
FIG. 7 is a standard solar absorption spectrum of PVA sponge, PPy/PVA sponge and the leaf-like porous membrane composite PPy/PVA sponge of example 1;
FIG. 8 is a graph comparing thermal conductivity coefficients of PVA sponge, PPy/PVA sponge and the leaf-like porous membrane composite PPy/PVA sponge of example 1 in a dry and wet state;
FIG. 9 is an electron microscope image of the leaf-like porous membrane composite PPy/PVA sponge prepared in examples 1 to 5, wherein a is HPF-1, b is HPF-2, c is HPF-3, d is HPF-4, and e is HPF-5;
FIG. 10 is a comparison graph of the most probable pore size and equivalent perimeter per unit area of the leaf-like porous membrane composite PPy/PVA sponges prepared in examples 1-5;
FIG. 11 is a graph showing the water loss of free liquid surface water under 1 time of sunlight irradiation and the leaf-like porous membrane composite PPy/PVA sponges prepared in examples 1 to 5;
FIG. 12 is a graph showing the evaporation rate and the photothermal steam conversion efficiency of free liquid surface water and the leaf-like porous membrane composite PPy/PVA sponges prepared in examples 1 to 5 under 1-fold sunlight irradiation;
FIG. 13 is a graph of the transverse relaxation times of free liquid surface water, PVA sponge, PPy/PVA sponge, and the leaf-like porous membrane composite PPy/PVA sponge made in example 3;
FIG. 14 thermogravimetric curves of free surface water, PVA sponge, PPy/PVA sponge and the simulated leaf porous membrane composite PPy/PVA sponge made in example 3;
FIG. 15 is a schematic illustration of the edge effect of leaf pore transpiration;
FIG. 16 is a water molecule distribution diagram of the leaf-like porous membrane composite PPy/PVA sponge prepared in example 3 after surface collision and diffusion;
FIG. 17 is a probability chart of different distribution ranges of water molecules after the surface of the leaf-like porous membrane composite PPy/PVA sponge prepared in example 3 is collided and diffused;
FIG. 18 is a test chart of the solar seawater desalination capability of the leaf-imitated porous membrane composite PPy/PVA sponge prepared in example 3, wherein a is a comparison chart of salinity before and after solar seawater desalination, and b is a comparison chart of contents of sodium ions, magnesium ions, potassium ions and calcium ions before and after solar seawater desalination; c is a real image of the solar water purification equipment based on the leaf-imitated porous membrane composite PPy/PVA sponge prepared in the example 3; d is a schematic structural diagram of the solar water purification equipment based on the leaf-imitated porous membrane composite PPy/PVA sponge prepared in example 3; e is a schematic diagram of the solar water purification equipment connecting the brine bottle and the purified water bottle; f is a daily irradiance curve; g is the curve of the air temperature inside the evaporation cavity, the surface temperature of the condenser and the surface temperature of HPF-3; h is a schematic diagram of resistance test of different water qualities.
Detailed Description
The invention provides a preparation method of a leaf-like porous membrane composite PPy/PVA sponge, which comprises the following steps:
soaking polyvinyl alcohol sponge in FeCl3Obtaining pretreated polyvinyl alcohol sponge in the solution;
contacting the pretreated polyvinyl alcohol sponge with pyrrole, and carrying out in-situ chemical vapor deposition on the polypyrrole on the pretreated polyvinyl alcohol sponge to obtain PPy/PVA sponge;
dipping the PPy/PVA sponge in a styrene-acrylonitrile copolymer solution, and performing water drop template method film forming to obtain the leaf-like porous membrane composite PPy/PVA sponge.
In the present invention, the starting materials used are all commercial products in the art unless otherwise specified.
The invention soaks polyvinyl alcohol (PVA) sponge in FeCl3And taking out the solution to obtain the pretreated polyvinyl alcohol sponge.
In the invention, the polyvinyl alcohol sponge and FeCl3FeCl in solution3The dosage ratio of (A) is preferably 1cm3: 0.005 to 0.01 mol. In the invention, the ferric trichloride can react with pyrrole monomer to generate polypyrrole (PPy).
In the present invention, the FeCl3The concentration of the solution is preferably 0.5-1 mol/L, and the FeCl3The solvent of the solution is preferably ethanol (CH)3CH2OH). The FeCl is preferably used in the invention3Adding ethanol into a conical flask, and stirring for 1h at 25 ℃ to obtain FeCl3And (3) solution.
In the present invention, the porosity of the polyvinyl alcohol (PVA) sponge is preferably 45 to 50%, and more preferably 48%.
The specific parameters of the soaking are not specially limited, and the ferric trichloride can be attached to the PVA sponge framework so as to prepare for the next step of reacting the ferric trichloride with pyrrole to generate polypyrrole.
After the pretreated polyvinyl alcohol sponge is obtained, the pretreated polyvinyl alcohol sponge is contacted with pyrrole, and the polypyrrole is deposited on the pretreated polyvinyl alcohol sponge in an in-situ chemical vapor deposition manner, so that the PPy/PVA sponge is obtained.
In the present invention, the FeCl3FeCl in solution3The dosage ratio of the pyrrole to the pyrrole is preferably 0.005-0.01 mol: 2 mL.
In the invention, the vacuum degree of the in-situ chemical vapor deposition is preferably 0.6-0.8, the temperature is preferably 23-25 ℃, and the time is preferably 4-6 h.
In the present invention, the in situ chemical vapor deposition is preferably performed in a vacuum oven.
After the in-situ chemical vapor deposition is finished, the obtained chemical vapor deposition product is preferably washed and dried by absolute ethyl alcohol in sequence to obtain the PPy/PVA sponge. In the invention, the number of times of washing with the absolute ethyl alcohol is preferably 3-5, and the dosage of the absolute ethyl alcohol in each time of washing with the absolute ethyl alcohol is not particularly limited. In the invention, the drying is preferably carried out in a forced air drying oven, and the invention has no special limitation on the specific parameters of the drying and can completely remove the ethanol.
The invention preferably produces the PPy/PVA sponge in a vacuum oven.
After the PPy/PVA sponge is obtained, the PPy/PVA sponge is dipped in a styrene-acrylonitrile copolymer solution and subjected to water drop template method film forming to obtain the leaf-like porous membrane composite PPy/PVA sponge.
In the present invention, the ratio of the amount of the PPy/PVA sponge dipped in the styrene-acrylonitrile copolymer solution (SAN solution) to the amount of the styrene-acrylonitrile copolymer in the styrene-acrylonitrile copolymer solution is preferably 1cm3: 0.008 to 0.012g, more preferably 1cm3：0.008g、1cm3：0.009g、1cm3：0.010g、1cm3: 0.011g and 1cm3：0.012g。
In the present invention, the concentration of the styrene-acrylonitrile copolymer solution is preferably 0.016 to 0.024g/mL, more preferably 0.016, 0.018, 0.020, 0.022 and 0.024g/mL, and the solvent of the styrene-acrylonitrile copolymer solution is preferably chloroform (CHCl)3). The styrene-acrylonitrile copolymer and CHCl are preferably used in the invention3Putting the mixture into an erlenmeyer flask, and stirring the mixture for 1h at 25 ℃ to obtain the SAN solution. In the present invention, the number average molecular mass of the styrene-acrylonitrile copolymer is preferably 180000 to 185000.
In the invention, the water drop template method film forming is carried out in a closed reaction device, the closed reaction device is provided with a wet nitrogen gas injection port, and the humidity of the closed reaction device is preferably 75-90% by the injected wet nitrogen gas.
In the invention, the distance from the wet nitrogen blowing opening to the obtained dipped styrene-acrylonitrile copolymer solution is preferably 3-5 cm, and the speed of the wet nitrogen is preferably 1-2L/min.
In the invention, the film forming temperature of the water drop template method is preferably 80-90 ℃, the time is preferably 30-60 min, and the water drop template method (breakthrough figure method) takes condensed water drops as templates to prepare the honeycomb ordered porous membrane with uniform pore size and compact arrangement, namely the styrene-acrylonitrile copolymer hydrophobic porous membrane, on the solid substrate in a high humidity environment.
After the film forming by the water drop template method is finished, the method preferably further comprises the steps of drying, vacuumizing and curing in sequence, wherein the drying time is preferably 1-2 hours, and the temperature is preferably 60-65 ℃; the vacuumizing time is preferably 30-45 min; the curing time is preferably 30-45 min.
FIG. 1 is a flow chart of the preparation of the leaf-like porous membrane composite PPy/PVA sponge of the present invention. Pyrrole and ferric trichloride are subjected to chemical vapor deposition in a pore structure of the PVA sponge to form PPy/PVA sponge, and styrene-acrylonitrile copolymer and chloroform are formed into a styrene-acrylonitrile copolymer hydrophobic porous membrane on the surface of the PPy/PVA sponge by a water drop template method, so that the leaf-like porous membrane composite PPy/PVA sponge is finally obtained.
The invention also provides the leaf-imitated porous membrane composite PPy/PVA sponge prepared by the preparation method in the technical scheme, which comprises a base material and the styrene-acrylonitrile copolymer hydrophobic porous membrane loaded on the surface of the base material, wherein the base material comprises polyvinyl alcohol sponge and polypyrrole loaded in the polyvinyl alcohol sponge.
Fig. 5 is a comparison diagram of the structure of the leaf-imitated porous membrane composite PPy/PVA sponge and the structure of the leaves, wherein the polyvinyl alcohol sponge is equivalent to a guard tissue in the leaves and plays a role in supporting a framework and transporting water, the polypyrrole is equivalent to chlorophyll and plays a role in absorbing sunlight and performing heat aggregation, and the styrene-acrylonitrile copolymer hydrophobic porous membrane is equivalent to pores and is beneficial to water vapor diffusion. On the left side of fig. 5 are leaf structures of a rainforest of tropical rain, with a layered network and interconnected channels, which structures pump and transport water by transpiration. The leaf structure includes three parts with different features and functions: (1) the air holes on the surface of the blade are used for water vapor diffusion. (2) The lower layer contains rich chlorophyll, and the solar energy is absorbed to provide energy for photosynthesis and transpiration. (3) The lowermost layer is the guard tissue, mesophyll tissue, which contains a large number of mesophyll cells that absorb water from the roots and stems of the plant like a sponge, providing sufficient water for evaporation; in order to simulate the blade structure, the invention designs the following characteristics (as shown on the right side of FIG. 5): (1) PVA sponge (equivalent layer of mesophyll tissue) as the skeleton of a solar evaporator has hydrophilicity, high porosity and low thermal conductivity, provides excellent mechanical properties and facilitates rapid water transport. (2) The PPy layer (chlorophyll equivalent layer) is coated on the upper side of the PVA sponge by chemical vapor deposition for capturing solar energy and converting sunlight into heat, and heating the water clusters in the PVA sponge network, thereby realizing thermal aggregation of the upper layer. (3) SAN layer (equivalent layer of air holes): SAN is assembled as a hydrophobic polymer on the surface of a double-layer sponge by a water drop template method, and the structure forms a porous hydrophobic surface, and the accelerated escape of water vapor can lead to higher vapor diffusion and effective solar vapor generation.
In the invention, the mass ratio of the styrene-acrylonitrile copolymer hydrophobic porous membrane to the polypyrrole to the polyvinyl alcohol sponge is preferably 4-6: 5: 23.
The invention also provides application of the leaf-like porous membrane composite PPy/PVA sponge in the technical scheme in the field of photo-thermal steam conversion.
The invention preferably uses the leaf-like porous membrane composite PPy/PVA sponge as a solar photo-thermal steam conversion device.
The invention preferably applies the leaf-like porous membrane composite PPy/PVA sponge to purify water, and the invention has no special limitation on the specific mode of application and can adopt a mode which is well known by the technical personnel in the field.
In order to further illustrate the present invention, the leaf-like porous membrane composite PPy/PVA sponge provided by the present invention, the preparation method and application thereof are described in detail below with reference to examples, but they should not be construed as limiting the scope of the present invention.
Example 1
PPy/PVA sponge was prepared using a vacuum oven. Ferric trichloride and ethanol are put into a conical flask and stirred for 1h at 25 ℃ to prepare FeCl with the FeCl concentration of 1mol/L3And (3) solution. PVA sponge (1 cm)3) Put into FeCl3The solution (1mL) was soaked, then taken out and placed in a vacuum oven containing 2mL of pyrrole, and the vacuum degree of the vacuum oven was maintained at 0.6 and the temperature at 25 ℃ for 4 h. And after the reaction is finished, taking out the sample, washing the sample for 3 times by using absolute ethyl alcohol, and drying the sample in a blast drying oven to obtain black sponge, which indicates that the PPy is successfully loaded on the PVA sponge to obtain the PPy/PVA sponge.
Scanning electron microscopy of the uncoated PPy PVA sponge and the prepared PPy/PVA sponge are shown in FIGS. 2 and 3, respectively. As can be seen from FIGS. 2 to 3, polypyrrole (PPy) was successfully attached to the PVA sponge skeleton.
Styrene-acrylonitrile copolymer and chloroform are put into a conical flask and stirred for 6 hours at 25 ℃ to prepare SAN solution with the SAN concentration of 0.016 g/mL. PPy/PVA sponge (1 cm)3) Dipping SAN solution (0.5mL) and placing the SAN solution under a wet nitrogen gas blowing port of a closed reaction device, and adjusting reaction parameters: the blowing distance was 3cm, the nitrogen gas flow rate was 2L/min, the water bath temperature was 80 ℃ and the humidity in the closed apparatus was 75%. After film forming, the sponge is taken out and dried: the drying time is 1h, the temperature is 60 ℃, the vacuumizing time is 30min, and the curing time is 30min, so that the leaf-like porous membrane composite PPy/PVA sponge is obtained and is marked as HPF-1, a scanning electron microscope is shown in figure 4, as can be seen from figure 4, the SAN hydrophobic porous membrane is successfully attached to the PPy/PVA sponge, and water drops are condensed and grow on the surface of the cold SAN casting membrane liquid to form an ordered cellular porous membrane and are attached to the surface of the PPy/PVA sponge through the blowing of the humid air flow.
Simulating the sun illumination evaporation experiment, and FIG. 6 is a diagram of a testing device for simulating the sun illumination evaporation experimentThe leaf-like porous membrane composite PPy/PVA sponge prepared in the example has a unit area (1 m)2) 3.09 kg.h of water vapor is produced-1。
FIG. 7 shows the standard sunlight absorption spectrum of the PVA sponge, the PPy/PVA sponge and the leaf-like porous membrane composite PPy/PVA sponge, and it can be seen from FIG. 7 that the light absorption performance of the PPy/PVA sponge is obviously improved compared with that of the PVA sponge, and the PPy/PVA sponge reaches more than 99% in the full solar spectrum range, which indicates that the PPy/PVA sponge has excellent light absorption performance, the light absorption performance of the leaf-like porous membrane composite PPy/PVA sponge reaches more than 99%, and indicates that the load of the SAN porous membrane has little influence on the light absorption performance.
FIG. 8 is a comparison graph of thermal conductivity coefficients of PVA sponge, PPy/PVA sponge and leaf-like porous membrane composite PPy/PVA sponge in a dry and wet state, and it can be seen from FIG. 8 that the thermal conductivity coefficients of PVA sponge, PPy/PVA sponge and leaf-like porous membrane composite PPy/PVA sponge are 0.03, 0.10 and 0.06 W.m respectively in a dry state-1·K-1All of them exhibit excellent heat insulating properties, and in a wet state (the sponge contains water in the operating environment of photothermal steam conversion), the thermal conductivity of the PVA sponge, the PPy/PVA sponge and the composite PPy/PVA sponge of the leaf-like porous membrane are 0.4, 0.64 and 0.53 Wm.m.-1·K-1In the dry state and the wet state, the thermal insulation performance of the PVA sponge was decreased after the PPy was supported, and the thermal insulation performance was increased after the SAN hydrophobic porous film was further supported. (Note that the smaller the thermal conductivity, the more heat-insulating).
From fig. 7 to 8, it can be seen that the leaf-like porous membrane composite PPy/PVA sponge prepared in the present example shows superior light absorption performance and heat insulation performance compared to PVA sponges with the same size.
The porous membrane composite PPy/PVA sponge of the present invention showed higher evaporation rate and photothermal vapor conversion efficiency compared to free-standing water and PPy/PVA sponge under the same area and illumination conditions (see fig. 10).
Examples 2 to 5
Similar to example 1, except that SAN concentrations in the SAN solution were adjusted to 0.018, 0.020, 0.022, and 0.024g/mL, respectively, the resulting leaf-like porous membrane composite PPy/PVA sponges were designated as HPF-2, HPF-3, HPF-4, and HPF-5, respectively.
FIG. 9 is an electron microscope image of the leaf-like porous membrane composite PPy/PVA sponge prepared in examples 1 to 5, wherein a is HPF-1, b is HPF-2, c is HPF-3, d is HPF-4, and e is HPF-5. FIG. 10 is a comparison graph of the mode pore size and equivalent perimeter per unit area of the leaf-like porous membrane composite PPy/PVA sponges prepared in examples 1-5. As can be seen from FIG. 10, as the concentration of SAN solution increases, the pore size of the porous membrane layer of the leaf-like porous membrane composite PPy/PVA sponge (HPF) decreases and the equivalent perimeter per unit area increases, with 8.4, 7.9, 3.0, 2.7 and 4.4 μm for HPF-1, HPF-2, HPF-3, HPF-4 and HPF-5, respectively. At the same time, each 100X 100 μm2The total perimeter of the wells of (a) is 2104.8, 3439.9, 4615.6, 2411.4 and 1151.7 μm, respectively. Explained by Herry theory: the solvent in the higher concentration solution has a lower vapor pressure and the surface temperature of the solution rises, so water droplets condense and slowly grow, eventually leading to a decrease in the pore size of the membrane. However, when the viscosity of the high-concentration polymer solution is too high, it is difficult for water droplets to be immersed in the solution, resulting in a decrease in the number of pores and the circumference per unit area on the film surface.
TABLE 1 most probable pore diameter and Unit area (100X 100 μm) of leaf-like porous membrane composite PPy/PVA sponges prepared in examples 1 to 52) Equivalent circumference of the inner
Figure BDA0002933009500000101
FIG. 11 is a graph showing the water loss of the free surface water under 1 time of sunlight irradiation and the leaf-like porous membrane composite PPy/PVA sponges prepared in examples 1 to 5, and it can be seen that the evaporation rate of HPF-3 is the highest and is as high as 3.09 kg.m-2·h-1In contrast, HPF-1 was 1.38kg · m-2·h-1HPF-2 of 2.87kg · m-2·h-1HPF-4 of 2.56kg · m-2·h-1And HPF-5 is 1.14kg m-2·h-1All are significantly higher than the control sample (i.e., 0.55 kg. m for pure water without HPF)-2·h-1)。
The corresponding solar heat conversion efficiency (η) was calculated using the following formulath)：
Figure BDA0002933009500000102
Wherein
Figure BDA0002933009500000111
Is the evaporation flux, hVIs the enthalpy of vaporization of water, P0Is 1 time of solar radiation power (1 kW.m)-2)，CoptRefers to the absorber surface solar optical concentration. The photothermal conversion efficiency is shown in fig. 12. The solar heat conversion efficiencies of HPF-1, HPF-2, HPF-3, HPF-4 and HPF-5 were 44%, 91%, 98%, 81% and 36%, respectively, at 1 times the solar intensity. The photothermal conversion efficiency of the HPF-3 under 1 time of sunlight intensity is as high as 98%, which shows that the leaf-like porous membrane composite PPy/PVA sponge has great potential as a solar photothermal steam conversion device.
The state of the presence of moisture in HPF-3 and the edge effect of the surface of the hydrophobic porous membrane were investigated.
The different water states in HPF were verified and the transverse relaxation times of the samples were measured by low field nuclear magnetic resonance (LNMR), and fig. 13 is a graph of the transverse relaxation times of free liquid level water, PVA sponge, PPy/PVA sponge and the simulated leaf porous membrane composite PPy/PVA sponge made in example 3 (HPF-3), which represents the mobility of water. The three peaks from left to right represent bound water, Intermediate Water (IW) and Free Water (FW), respectively. It is known that the signal amplitude of IW in PVA sponge, PPy/PVA sponge and HPF is higher than that of free liquid surface water, indicating the presence of water clusters in the molecular network of the PVA sponge skeleton. Furthermore, the IW interacts weakly with the polymer chains and with the adjacent water molecules. Thus, forming IW via the PVA polymer network results in a reduced energy barrier for water evaporation. FIG. 14 shows thermogravimetric curves of free liquid surface water, PVA sponge, PPy/PVA sponge and the composite PPy/PVA sponge of the leaf-imitated porous membrane prepared in example 3, and Table 2 shows thermogravimetric data of the free liquid surface water, the PVA sponge, the PPy/PVA sponge and the composite PPy/PVA sponge of the leaf-imitated porous membrane prepared in example 3, and it can be seen from FIG. 14 and Table 2 that the evaporation enthalpy of HPF-3 is reduced.
TABLE 2 thermogravimetric data of free liquid surface water, PVA sponge, PPy/PVA sponge and HPF-3
Figure BDA0002933009500000112
In a typical leaf transpiration process, liquid water is carried into the mesophyll cells and evaporates into water vapor in the lower cavities of the pores, eventually diffusing through the pores into the atmosphere, following a "fringe effect". Fig. 15 is a schematic diagram showing the edge effect of the leaf pore transpiration, and it is understood that when water molecules pass through the pores, the probability of collision between water molecules at the edges of the pores is low, and the diffusion resistance near the edges is low. The edge is higher than near the center. It is worth noting that in the same area, the evaporation rate caused by the pore transpiration is about tens of times higher than that of the free surface.
The method is characterized in that MATLAB software is utilized to simulate the collision behavior of water molecules in the composite PPy/PVA sponge membrane pores of the leaf-like porous membrane, and the water molecules are supposed to disappear after collision, so that a calculation model is simplified, and the distribution state of the water molecules which move upwards to the top layer at random is recorded to represent the molecular collision probability in different pore ranges. FIG. 16 is a distribution diagram of water molecules after surface collision and diffusion of the leaf-like porous membrane composite PPy/PVA sponge prepared in example 3, and FIG. 17 is a probability diagram of different distribution ranges of water molecules after surface collision and diffusion of the leaf-like porous membrane composite PPy/PVA sponge prepared in example 3. it can be seen that the edge range shows a lower chance of collision and thus has a higher diffusion rate, which explains the phenomenon per unit area (100X 100 μm. mu.m)2) The reason why the evaporation rate of HPF-3 with the longest equivalent circumference inside is the greatest.
Example 3 solar seawater desalination capability of leaf-like porous membrane composite PPy/PVA sponge
Three samples of brine having representative simulated salinity (grams of dissolved salt per kilogram of seawater (@ o)) of 8%, 36% and 100% respectively were tested.
A solar water purification apparatus (d in FIG. 18) based on the leaf-imitated porous membrane composite PPy/PVA sponge prepared in example 3 was placed under a solar simulator with one-time solar intensity, and a sample of the leaf-imitated porous membrane composite PPy/PVA sponge prepared in example 3, which has a diameter of 14cm and a thickness of 2cm, was floated in a container containing 200mL of a saline solution sample, which was disposed at the center of the solar water purification apparatus. The evaporated water vapor is condensed on a transparent condenser and the condensed water flows to the bottom edge of the apparatus to effect desalination (see d in fig. 18). After desalination, the salinity of the brine samples was significantly reduced (see a in FIG. 18) and was about an order of magnitude lower than the drinking water standard (1% o) defined by the World Health Organization (WHO).
FIG. 18 b is a graph showing the comparison of the contents of sodium ions, magnesium ions, potassium ions and calcium ions before and after the desalination of seawater by solar energy, and it can be seen that when a real seawater sample (from the yellow sea of China) is desalinated using the leaf-like porous membrane composite PPy/PVA sponge prepared in example 3, all four primary ions (Na) originally present in seawater+，Mg2+，K+And Ca2+) The concentration of (B) is remarkably reduced and is lower than the typical value (1-50 mg. L) obtained by a membrane distillation method-1) Table 3 shows the ion concentration change data before and after HPF-3 desalting.
TABLE 3 ion concentration before and after HPF-3 desalination
Figure BDA0002933009500000121
A solar water purification apparatus (d in fig. 18) based on the leaf-imitated porous membrane composite PPy/PVA sponge prepared in example 3 was placed outdoors (on the roof of the institute of textile science and engineering, campus of the tianjin industry university) as shown in c in fig. 18, and a sample of the leaf-imitated porous membrane composite PPy/PVA sponge prepared in example 3, which had a diameter of 14cm and a thickness of 2cm, was floated in a saline water container, which was disposed at the center of the solar water purification apparatus. The evaporated water vapour condenses on the transparent condenser and the condensed water flows to the bottom edge of the apparatus (see d in figure 18). The water collector of the device is connected to the brine bottle and the purified water bottle through pipes (d-e in fig. 18), so that the water purification is continuously performed. The purification process is carried out under natural sunlight at 08: 00-20: 00, and the average sunshine amount is 0.6 kW.m-2Daily irradiance is as shown in the figure18, the air temperature inside the evaporation chamber, the surface temperature of the condenser and the surface temperature of the leaf-like porous membrane composite PPy/PVA sponge are shown as g in fig. 18, to quantitatively evaluate the solar energy utilization efficiency under natural illumination conditions. Enough sunlight enables the average water purification rate to reach 1.4 L.m-2·h-1(as in g in fig. 18), it can be seen from g in fig. 18 that the surface temperature of the simulated leaf porous membrane composite PPy/PVA sponge is increased to 50 ℃ compared to the laboratory test conditions, indicating that the evaporative cooling effect is reduced and thus evaporation is reduced, a phenomenon that is due to the saturated internal humidity of the closed system, which is likely to limit the evaporation of water. When the inside air is heated to 40 ℃, the condenser maintains a relatively low temperature of about 34 ℃, indicating that the device has sustainable evaporation and condensation, showing great potential in practical applications.
The leaf-like porous membrane composite PPy/PVA sponge prepared in example 3 was placed in a beaker containing natural seawater, purified water, and tap water, and the water quality was characterized by an ohmic value obtained by resistance test using a multimeter with a constant electrode distance, as shown in h in fig. 18, it was found that the actual resistance values of natural seawater (from the yellow sea), purified water, and tap water (from the city water supply system of tianjin, china) were 75.3K Ω, 1.047M Ω, and 0.914M Ω, respectively, indicating that the natural seawater was effectively purified.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be construed as the protection scope of the present invention.

Claims (10)

1. A preparation method of a leaf-like porous membrane composite PPy/PVA sponge is characterized by comprising the following steps:
soaking polyvinyl alcohol sponge in FeCl3Obtaining pretreated polyvinyl alcohol sponge in the solution;
contacting the pretreated polyvinyl alcohol sponge with pyrrole, and carrying out in-situ chemical vapor deposition on the polypyrrole on the pretreated polyvinyl alcohol sponge to obtain PPy/PVA sponge;
dipping the PPy/PVA sponge in a styrene-acrylonitrile copolymer solution, and performing water drop template method film forming to obtain the leaf-like porous membrane composite PPy/PVA sponge.
2. The method of claim 1, wherein the polyvinyl alcohol sponge and FeCl are combined3FeCl in solution3The dosage ratio of the components is 1cm3：0.005~0.01mol。
3. The method of claim 1 or 2, wherein the FeCl is3FeCl in solution3The dosage ratio of the pyrrole to the pyrrole is 0.005-0.01 mol: 2 mL.
4. The method according to claim 1, wherein the temperature of the in-situ chemical vapor deposition is 23-25 ℃ and the time is 4-6 h.
5. The method according to claim 1, wherein the ratio of the amount of the styrene-acrylonitrile copolymer in the PPy/PVA sponge and the styrene-acrylonitrile copolymer solution is 1cm3：0.008~0.012g。
6. The preparation method of claim 1, wherein the water drop template film formation is performed in a closed reaction device, the closed reaction device is provided with a wet nitrogen gas injection port, and the humidity of the closed reaction device is 75-90% by injecting wet nitrogen gas.
7. The method according to claim 6, wherein the distance from the wet nitrogen gas injection port to the obtained dipped styrene-acrylonitrile copolymer solution is 3 to 5cm, and the wet nitrogen gas injection rate is 1 to 2L/min.
8. The preparation method according to claim 1 or 6, wherein the temperature of the water drop template film forming is 80-90 ℃ and the time is 30-60 min.
9. The leaf-like porous membrane composite PPy/PVA sponge prepared by the preparation method of any one of claims 1 to 8, which is characterized by comprising a substrate and a styrene-acrylonitrile copolymer hydrophobic porous membrane loaded on the surface of the substrate, wherein the substrate comprises polyvinyl alcohol sponge and polypyrrole loaded in the polyvinyl alcohol sponge.
10. The use of the leaf-like porous membrane composite PPy/PVA sponge of claim 9 in photothermal steam conversion.
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