CN114212851A - Solar seawater desalination material based on natural plant rods and preparation method and application thereof - Google Patents
Solar seawater desalination material based on natural plant rods and preparation method and application thereof Download PDFInfo
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- CN114212851A CN114212851A CN202110235144.5A CN202110235144A CN114212851A CN 114212851 A CN114212851 A CN 114212851A CN 202110235144 A CN202110235144 A CN 202110235144A CN 114212851 A CN114212851 A CN 114212851A
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- 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
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/08—Seawater, e.g. for desalination
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- 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
- Y02A20/124—Water desalination
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- 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
- Y02A20/124—Water desalination
- Y02A20/138—Water desalination using renewable energy
- Y02A20/142—Solar thermal; Photovoltaics
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- 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 discloses a solar seawater desalination material based on natural plant rods and a preparation method and application thereof. The sunflower stem pith is a porous structure with a gradient structure, has extremely low thermal conductivity (the thermal conductivity of the sunflower stem is 0.04W/m/K, and the thermal conductivity of wood is 0.2W/m/K), and can efficiently utilize heat to evaporate water. The heat conductivity is reduced, namely the heat loss of the bulk water is limited, and the heat after photo-thermal conversion is fully utilized to evaporate water so as to improve the efficiency. And the special structure of the inner surface of the sunflower stalk pith provides a special water channel, so that the evaporation of water is accelerated, the evaporation efficiency of water is obviously improved, and the material is endowed with excellent antibacterial and anti-mildew properties, so that the durability and the service life of the material are improved.
Description
Technical Field
The invention belongs to the technical field of seawater desalination, and particularly relates to a solar seawater desalination material based on natural plant rods, and a preparation method and application thereof.
Background
The shortage of fresh water resources is one of the biggest concerns in the development of our modern human society. Various seawater desalination technologies, such as reverse osmosis and multi-effect distillation technologies, have increased the supply of clean water over decades. However, due to the high energy consumption limitations and the need for complex infrastructure, many countries and regions still cannot afford to use these new technologies at a cost. Solar desalination is considered to be the most promising application, using clean solar energy and the vast ocean as water resources.
Wood as a natural plant can be used as a novel solar seawater desalination material due to the special water channel structure, three-dimensional porosity and good biocompatibility, and in addition, the special existence of interlayer water in the three-dimensional network porous hydrogel can reduce the evaporation break of water so as to improve the evaporation efficiency of seawater desalination, so that the material is also widely concerned. However, solar seawater desalination based on the above materials still has the following technical drawbacks:
1. the thermal conductivity of the wood and the hydrogel material is relatively high, and the evaporation efficiency is greatly reduced due to heat loss in the solar seawater desalination evaporation process.
2. In a high salinity environment, the precipitation of salt blocks the porous structure during evaporation, greatly reducing the evaporation efficiency.
3. After long-term durable use, the hydrogel and the wood are easy to be stained by marine organisms, so that the service life of the hydrogel and the wood is greatly shortened, and evaporated water can be polluted by bacteria and the like.
Disclosure of Invention
In order to improve the technical problem, the invention provides a modified natural plant pith, which comprises a natural plant pith, a zwitter-ion hydrogel which forms an interpenetrating network topology with the natural plant pith, and a photothermal conversion layer loaded at one end of the natural plant pith.
According to an embodiment of the invention, the natural plant pith may be a sunflower stalk pith, a maize stalk pith or a sorghum stalk pith, preferably a sunflower stalk pith.
The sunflower stalk pith, the sorghum stalk pith and the corn stalk pith are low-density natural foams with good mechanical properties and excellent heat insulation capability.
According to an embodiment of the invention, the natural plant medulla is the inner body remaining after removal of the outer wall of the natural plant. For example, the medullary center of a sunflower stem is the medullary center of the sunflower stem after the outer wall of the sunflower stem is peeled off.
According to an embodiment of the invention, the structure of the sunflower stalk pith in the pith cross section shows a gradient porous structure from the center to the edge. Specifically, the structure of the sunflower stem pith is as follows: the center of the medullary heart of the sunflower stem is a regular hexagonal honeycomb structure, the aperture of the medullary heart of the sunflower stem is enlarged towards the outer edge in sequence and presents an elongated approximately rectangular structure, the whole sunflower stem is arranged in order in a radial mode, two structures exist in the longitudinal section direction of the medullary heart of the sunflower stem, a catheter which is arranged longitudinally is arranged along the fiber direction of the stem, and the two sides of the catheter are mainly in an elongated or flattened hexagon and are arranged in a row in an overlapping mode along the axial direction of the stem. Preferably, the sunflower stem pith has a topography substantially as shown in fig. 1.
According to an embodiment of the invention, there is also an ionic interaction between the zwitterionic hydrogel and the natural plant medulla.
According to the embodiment of the invention, the zwitterionic hydrogel is obtained by soaking and polymerizing a zwitterionic compound monomer, and the interpenetrating network structure of the zwitterionic hydrogel is utilized to be compounded with the medulla of the natural plant. Preferably, the zwitterionic compound monomer may be selected from one, two or more of N, N-dimethyl (methacryloyloxyethyl), ammonio propanesulfonate inner salt (DMAPS), methacrylethyl Sulfobetaine (SBMAA), carboxybetaine methyl methacrylate (CBMAA) and Phosphocholine (PCMA).
According to an embodiment of the present invention, the photothermal conversion layer contains a photothermal conversion material. For example, the photothermal conversion material may be selected from one, two or more of polypyrrole, carbon black, carbon nanotube, activated carbon, graphene oxide, and polyaniline.
According to an embodiment of the present invention, the photothermal conversion layer is black in color.
According to an embodiment of the present invention, the thickness of the photothermal conversion layer is 0.2 to 2mm, and is exemplified by 0.2mm, 0.5mm, 0.7mm, and 1 cm.
According to an embodiment of the present invention, the light-to-heat conversion layer is modified at one end of the natural plant's medulla. When in use, one end decorated with the photo-thermal conversion layer floats on the water surface to receive the illumination of the sun.
According to an exemplary embodiment of the present invention, the modified natural plant pith is a modified sunflower stem pith, which includes a sunflower stem pith, a zwitterionic hydrogel forming an interpenetrating network topology with the sunflower stem pith, and a photothermal conversion layer supported at one end of the sunflower stem pith.
The photothermal conversion layer contains polypyrrole, carbon black, carbon nanotubes, activated carbon, graphene oxide or polyaniline;
there is also an ionic interaction between the zwitterionic hydrogel and the sunflower stem pith.
The invention also provides a preparation method of the modified natural plant pith, which comprises the following steps: firstly, modifying natural plant medulla with zwitter-ion hydrogel, and then compounding a photo-thermal conversion layer to obtain the modified natural plant medulla.
According to an embodiment of the invention, the method for preparing the modified natural plant pith comprises the following steps:
(1) soaking the natural plant medulla in the zwitterionic hydrogel pre-polymerization solution, and then heating and polymerizing to obtain the natural plant medulla containing the zwitterionic hydrogel;
(2) coating a photo-thermal conversion material on one end of the natural plant pith containing the zwitterion hydrogel, then soaking the end coated with the photo-thermal conversion material in a dispersion liquid of the photo-thermal conversion material, and compounding a photo-thermal conversion layer to obtain the modified natural plant pith.
According to the embodiment of the invention, the zwitterionic hydrogel pre-polymerization solution comprises the following components in percentage by mass: 5-60 wt% of a zwitterionic compound monomer, 0.5-5 wt% of a cross-linking agent, 0.5-2 wt% of an initiator and the balance of water. For example, the zwitterionic hydrogel pre-polymerization solution comprises the following components in percentage by mass: 10-50 wt% of a zwitterionic compound monomer, 0.8-4 wt% of a cross-linking agent, 0.8-1.5 wt% of an initiator and the balance of water.
Preferably, the zwitterionic compound monomer is selected as described above.
Preferably, the crosslinking agent may be polyethylene glycol dimethacrylate (PEGDMA) or N, N' -methylenebisacrylamide, preferably polyethylene glycol dimethacrylate (PEGDMA).
Preferably, the initiator may be one or both of ammonium persulfate and tetramethylethylenediamine, preferably ammonium persulfate and tetramethylethylenediamine. Preferably, the mass ratio of the ammonium persulfate to the tetramethylethylenediamine is 1 (0.8-1.5), and is exemplarily 1:0.8, 1:1, 1:1.2, and 1: 1.5.
According to the embodiment of the invention, the soaking time is 1-30 min, preferably 5-20min, and exemplary times are 1min, 5min, 10min, 15min, 20min and 30 min.
According to an embodiment of the present invention, in step (1), the soaking comprises: placing the natural plant medulla in the zwitterionic hydrogel pre-polymerization solution, and performing ultrasonic dispersion. For example, the time for ultrasonic dispersion is 5 to 20min, preferably 10 min.
According to an embodiment of the present invention, in the step (1), the temperature of the thermal polymerization is 35 to 50 ℃, illustratively 35 ℃, 40 ℃, 45 ℃, 50 ℃, preferably 40 ℃. Further, the time for heating polymerization is 10 to 60min, preferably 15 to 30min, exemplary 10min, 15min, 20min, 25min, 30min, preferably 20 min.
According to an embodiment of the present invention, the step (1) further comprises washing the heated and polymerized natural plant pith containing the zwitterionic hydrogel with water to remove unpolymerized zwitterionic compound monomer. For example, the washing may be performed by immersing the natural plant pith containing the zwitterionic hydrogel after the thermal polymerization in water. For another example, the soaking time is more than 2 h.
According to an embodiment of the present invention, the step (1) further comprises a step of drying the washed natural plant pith containing the zwitterionic hydrogel. Preferably, the drying manner may be vacuum drying. For example, the temperature of the vacuum drying is 40 to 60 ℃, exemplary 40 ℃, 50 ℃, 60 ℃, and preferably 40 ℃.
According to an embodiment of the present invention, in the step (2), the coating may be spin coating. For example, a dispersion of the photothermal conversion material is spin-coated on the surface of the natural plant core.
Preferably, the photothermal conversion material has the selection as described above.
According to an embodiment of the present invention, the dispersion of the photothermal conversion material has a concentration of 1 to 5 wt%, illustratively 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%.
Preferably, the number of spin coating may be one, two or more, preferably 5 or more, for example 10.
According to an embodiment of the invention, in step (2), the soaking time is at least 1 hour, such as at least 2 hours. Wherein the soaking temperature is room temperature.
According to an embodiment of the present invention, the preparation method further comprises a step of pre-treating the natural plant pith before the step (1). For example, the outer wall of the natural plant medulla is stripped to obtain a foamed medulla.
According to an embodiment of the invention, step (1) further comprises cutting the natural plant medulla before soaking. For example, it is cut into a disk-like shape having a thickness of 2 to 15mm and a diameter of about 2cm, and exemplified by a disk-like shape having a thickness of 2mm, 5mm, 7mm, 10mm or 15mm and a diameter of about 2 cm.
According to an embodiment of the present invention, the step (1) further comprises grinding a cross-section of the cut natural plant pith to make the surface thereof uniform and smooth.
According to an embodiment of the invention, the method for preparing the modified natural plant pith comprises the following steps:
(S1) peeling the outer wall of the natural plant stem, taking the medulla of the natural plant stem, cutting the medulla into required size, and grinding the cross section of the medulla until the surface is uniform and smooth;
(S2) soaking the natural plant medulla in the zwitterionic hydrogel pre-polymerization solution, heating for polymerization, immersing the polymerized natural plant medulla in water, removing unpolymerized zwitterionic compound monomer, and drying to obtain the natural plant medulla containing the zwitterionic hydrogel;
(S3) coating a photothermal conversion material on one end of the natural plant pith containing the zwitterionic hydrogel, and then soaking the end coated with the photothermal conversion material in a dispersion of the photothermal conversion material to form a composite photothermal conversion layer, thereby obtaining the modified natural plant pith.
The invention also provides application of the modified natural plant pith as a seawater desalination material, preferably application as a solar seawater desalination material.
According to an embodiment of the present invention, the seawater may be normal seawater, seawater contaminated with oil stains, or seawater contaminated with heavy metals.
The invention also provides application of the modified natural plant pith in heavy metal sewage treatment. Wherein the heavy metal is one, two or more of Ni, Pb, Cu, Zn, Cr and Cd. Wherein, in the heavy metal sewage, the heavy metal exists in an ion form.
The invention also provides a seawater desalination material which contains the modified natural plant pith.
According to an embodiment of the invention, the seawater has the choice as described above.
The invention also provides a heavy metal sewage treatment material which contains the modified natural plant pith.
According to an embodiment of the invention, the heavy metal has the choice as described above.
The invention has the beneficial effects that:
the invention takes the natural plant medulla as a modified matrix, and modifies the natural plant medulla by using a zwitterion hydrogel layer and a photo-thermal conversion layer. Taking the modified sunflower stem pith as an example:
(1) the sunflower stem pith is a porous structure with a gradient structure, has extremely low thermal conductivity (the thermal conductivity of the sunflower stem is 0.04W/m/K, and the thermal conductivity of wood is 0.2W/m/K), can limit the heat loss of the bulk water, and fully utilizes the heat after photo-thermal conversion to evaporate the water so as to improve the efficiency.
(2) The special structure of the inner surface of the sunflower stem pith provides a special water channel, so that the evaporation of water is accelerated, and the evaporation efficiency of water is obviously improved.
(3) According to the invention, the zwitter-ion hydrogel is modified on the surface of the medulla of the sunflower stalk, and zwitter-ions have strong water binding capacity, so that a hydration film can be formed on the surface of the medulla of the sunflower stalk to prevent salt from being separated out after crystallization, and the evaporation efficiency of solar seawater desalination can be obviously improved; meanwhile, the anti-biological fouling performance of the material is improved, and the material is endowed with excellent antibacterial and anti-mildew performance so as to improve the durability and the service life of the material.
(4) According to the invention, the zwitterionic hydrogel is modified on the surface of the medullary heart of the sunflower stem, and the modified medullary heart of the sunflower has special infiltration performance: the material can still perform efficient water evaporation in a water environment with oil stain fouling due to the characteristics of underwater super-oleophobic property and oil-underwater super-hydrophilic property, and a new method strategy is provided for solar water evaporation in a special environment.
(5) Because of the existence of components such as polysaccharide in natural plant materials, the complex of heavy metal ions is facilitated; meanwhile, a large number of inherent adsorption sites can be provided based on the larger specific surface area of the natural plant material, so that the modified material can be applied to a heavy metal polluted water source, and purified water is obtained by solar evaporation.
Drawings
FIG. 1 shows SEM representation results of the center portion (a) of the medullary cross section of a sunflower stem, the edge portion (b) of the medullary cross section, the horizontal channel (c) of the medullary side wall, and the vertical channel (d) of the medullary side wall.
FIG. 2 is a diagram showing the distribution of the aperture at the center of the cross section of the medullary center of a sunflower stem.
FIG. 3 shows the results of the light absorption measurements of the medulla of the modified sunflower stem of example 1.
FIG. 4 is a thermal infrared image of the core of a modified sunflower stem of example 1 at two solar intensities.
FIG. 5 shows wettability test results of sunflower stalk pith modified zwitterionic hydrogel in air super-hydrophilic (left), underwater super-oleophobic (middle) and oil super-hydrophilic (right).
FIG. 6 shows the results of the water evaporation rate test of sunflower under different simulated solar light intensities after the zwitterionic hydrogel is modified by the medullary center of the sunflower.
FIG. 7 shows the effect of the modified sunflower stem pith on the ion content for desalination of sea water in example 1.
FIG. 8 shows the effect of the modified sunflower stem pith purification of example 1 in simulating heavy metal ion industrial wastewater.
In FIG. 9, SP is the stem pith of sunflower stem obtained in step (1) of this example, and SPH is the anti-Pseudomonas aeruginosa test result of the stem pith of sunflower stem obtained after the composite zwitterionic gel obtained in step (3) of this example.
FIG. 10 is a graph of the effect of sunflower stem pith on the resistance to salt-out crystallization with and without the complex zwitterionic hydrogel, where SP is the sunflower stem pith of the uncomplexed zwitterionic hydrogel prepared in comparative example 1 and SPH is the modified sunflower stem pith after the complex zwitterionic hydrogel prepared in example 1.
Detailed Description
The technical solution of the present invention will be further described in detail with reference to specific embodiments. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
Unless otherwise indicated, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.
Example 1
The preparation method of the modified sunflower stem pith comprises the following steps:
(1) peeling sunflower straw (purchased from Liaoning, China) lightly to leave pith, cutting into discs with height of 10mm by a blade, polishing the cross section with sand paper until smooth, taking four discs, taking the area of 11.1368mm measured by Adobe Photoshop pixel statistical counting method after photographing2；
(2) Preparing a zwitterionic hydrogel pre-polymerization solution: mixing 2g of DMAPS, 8g of deionized water, 40mg of PEGDMA, 20mg of ammonium persulfate and 20mg of tetramethylethylenediamine to prepare a zwitterionic hydrogel pre-polymerization solution;
(3) placing the sunflower stem pith obtained in the step (1) in the zwitterionic hydrogel pre-polymerization solution obtained in the step (2) for ultrasonic dispersion for 2min, taking out the pith, placing in a 40 ℃ oven for thermal polymerization for 20min, taking out the pith, placing in deionized water for soaking for at least 2h to remove unpolymerized monomers, and then placing in a vacuum oven for drying;
(4) and (3) uniformly dispersing carbon black in water by using a high-speed shearing machine to form a carbon black dispersion liquid with the concentration of 3 wt%, spin-coating the carbon black dispersion liquid on one end face of the sunflower pith prepared in the step (3) for 10 times (the spin-coating speed is 600r/min, and the time is 20s), and then soaking the cross section of the coating end in a carbon black solution for adsorption for 2 hours to obtain a stable photo-thermal conversion coating, so that the modified sunflower stalk pith is obtained.
The pith of the four modified sunflower stems prepared in this example was placed in a petri dish or beaker containing 20mL of seawater, and subjected to a solar seawater desalination evaporation experiment. The calculation was started after 20 minutes of equilibration by simulated solar irradiation before measurement. And the mass change was recorded by weighing with a balance and the temperature was monitored with an infrared camera.
Fig. 1 is a scanning electron microscope characterization result of the central portion (a) of the medullary cross section, the edge portion (b) of the medullary cross section, the horizontal channel (c) of the medullary sidewall, and the vertical channel (d) of the medullary sidewall of the sunflower stem obtained in step (1) of this example. From the results in the figure, it can be seen that: the cross section of the medullary core of the sunflower stem presents a gradient porous structural characteristic from inside to outside. Specifically, the central part of the honeycomb structure is a regular hexagonal honeycomb structure, the pore diameters of the honeycomb structure become larger from the central part to the outer edge in sequence, the honeycomb structure is in an elongated approximate rectangular structure, and the honeycomb structure is arranged in a radial and ordered mode as a whole; in addition, two structures exist in the longitudinal section direction of the medullary heart, a duct which is longitudinally arranged is presented along the fiber direction of the stem, and the two sides of the duct are mainly in the shape of an elongated or flattened hexagon and are overlapped and arranged in a row along the axial direction of the stem. The microstructure of the sunflower stem pith is beneficial to heat insulation so as to reduce the heat conductivity, thereby limiting the heat loss of the bulk water, and fully utilizing the heat after photo-thermal conversion to evaporate the water so as to improve the seawater desalination efficiency; the special structure of the inner surface of the water-saving evaporator provides a special water transmission channel, so that the evaporation of water is accelerated, and the evaporation efficiency of water is obviously improved.
Fig. 2 is a pore size distribution diagram of the center of the cross section of the medullary center of the sunflower stem in this embodiment, and the result shows that a porous structure with larger pores exists in the medullary center of the sunflower stem, thereby facilitating the escape of water vapor in the solar seawater desalination process to significantly improve the evaporation efficiency of water.
FIG. 3 is a result of a light absorption property test of the carbon black modified sunflower stem pith prepared in this example, and the result shows that: the photo-thermal conversion layer is modified on the medulla of the sunflower stem, so that the utilization rate of the modified natural plant medulla to sunlight is improved, the heat after photo-thermal conversion is fully utilized to evaporate water, and the seawater desalination efficiency is improved.
FIG. 4 is a thermal infrared image of the pith of the carbon black-modified sunflower stem prepared in this example under two solar intensities, showing that: the modified sunflower pith has excellent photo-thermal conversion effect.
Wherein, the wettability is measured by a DCAT-21 contact angle instrument, and the specific method is as follows:
mu.L of water drops and 1, 2-dichloroethane were slowly applied dropwise to the pitted surface of the sunflower stems after modification of the zwitterionic hydrogel, and then measured by a DCAT-21 contact goniometer.
Fig. 5 shows the results of wettability tests of the modified zwitterionic hydrogel obtained in step (3) of this example on the sunflower stalk pith in air super-hydrophilic (left), underwater super-oleophobic (middle) and oil super-hydrophilic (right). The results in the figure show that: after the sunflower stem pith is modified by the zwitter-ion hydrogel, the sunflower stem pith has better hydrophilicity in the air and has super oleophobic property to underwater oil, and even an oil layer can be discharged to reach a water layer in an underwater environment, so that the excellent super-hydrophilicity characteristic is shown. The modified sunflower stem pith prepared by the invention can be evaporated in complex oil-polluted seawater without blocking the pore canal inside the sunflower stem pith to reduce the seawater evaporation efficiency.
Fig. 6 is a water evaporation rate test result of the sunflower pith after the modified zwitterionic hydrogel prepared in step (3) of this example under the intensity of simulated sunlight, and the result shows that the modified sunflower pith has higher water evaporation efficiency.
In order to verify the desalting effect of the modified sunflower pith on metal ions in seawater, the test method comprises the following steps:
placing the four modified sunflower pith prepared in the embodiment into a glass culture dish containing 20mL of yellow sea water, placing the glass culture dish under a xenon lamp simulating sunlight, wherein the light intensity is the radiation intensity of the sunlight, measuring the evaporation rate for 1 hour after the irradiation reaches the balance for 20 minutes, and testing Na in the seawater before and after evaporation by using a precise electronic balance and ICP-MS+、K+、Mg2 +、Ca2+Ion content.
FIG. 7 shows the effect of ion content desalination on modified sunflower stem pith seawater prepared in this example, and the results in the figure confirm that Na in seawater is obtained after seawater desalination by the material+、K+、Mg2+、Ca2+The ion content reaches the standard of the world health organization.
In order to further verify the purification effect of the modified sunflower pith on the wastewater containing heavy metal ions, the preparation method comprises the following steps: lead chloride, zinc chloride, nickel chloride, copper nitrate, cadmium chloride and chromium chloride are used as heavy metal ion salts, solutions containing metal ions with the content of about one hundred thousand ppb are prepared respectively, and then the modified sunflower pith prepared in the four embodiments is placed in each group of culture dishes containing 20mL of the simulated industrial wastewater.
FIG. 8 is a graph showing the effect of the modified sunflower stalk pith prepared in this example on the purification of simulated heavy metal ion industrial wastewater, and the result shows that the modified sunflower pith prepared in the present invention can be used for the purification of Ni-containing heavy metal ions2+、Pb2+、Zn2+、Cu2+、Cr3+、Cd2+The desalting treatment of the wastewater shows excellent heavy metal ion desalting treatment effect.
In FIG. 9, SP is the stem pith of sunflower stem obtained in step (1) of this example, and SPH is the anti-Pseudomonas aeruginosa test result of the stem pith of sunflower stem obtained after the composite zwitterionic gel obtained in step (3) of this example. The results in the figure show that: under the same experimental conditions, the colony number of the sunflower stem pith group compounded with the zwitter-ion gel is obviously less than that of the SP group, and the antibacterial rate of the sunflower stem pith compounded with the zwitter-ion gel is as high as 97%. Therefore, after the zwitterionic hydrogel is modified on the surface of the medullary heart of the sunflower stem, the anti-biological fouling performance of the medullary heart of the sunflower stem can be obviously enhanced, so that the excellent antibacterial and anti-mildew performance is provided for the medullary heart of the sunflower stem, and the durability and the service life of the material are improved.
Example 2
The preparation method of the modified sunflower stem pith comprises the following steps:
(1) peeling sunflower stalk (purchased from Liaoning, China) to obtain pulp core, cutting into discs with thickness of 5mm and diameter of 2cm, polishing cross section with sand paper to smooth surface, taking four discs, and measuring area of 11.2552mm by photographing pixel counting method2；
(2) Preparing a zwitterionic hydrogel pre-polymerization solution: sequentially mixing 1g of DMAPS, 9g of deionized water, 20mg of PEGDMA, 20mg of ammonium persulfate and 30mg of tetramethylethylenediamine to prepare a zwitterionic hydrogel pre-polymerization solution;
(3) placing the sunflower pith obtained in the step (1) in the zwitterionic hydrogel pre-polymerization solution obtained in the step (2) for ultrasonic dispersion for 2min, taking out the pith, placing in a 40 ℃ oven for thermal polymerization for 20min, taking out the pith, soaking in deionized water for more than 2h to remove unpolymerized monomers, and then placing in a vacuum oven for drying;
(4) and (3) dispersing polypyrrole in water by using a high-speed shearing machine to form a polypyrrole dispersion liquid with the concentration of 3 wt%, spin-coating the polypyrrole dispersion liquid on one end face of the sunflower pith prepared in the step (3) for 10 times (the spin-coating speed is 600r/min, and the time is 20s), and then soaking the cross section of the coating end in the polypyrrole dispersion liquid for adsorption for 2 hours to obtain a stable coating, so that the modified sunflower stem pith is obtained.
Example 3
The preparation method of the modified sunflower stem pith comprises the following steps:
(1) peeling sunflower stalk (purchased from Liaoning, China) to obtain pulp core, cutting into discs with diameter of 7mm with a blade, polishing the cross section with sand paper until smooth, taking four discs, and measuring the area of 11.3883mm by using a photographing pixel counting method2；
(2) Preparing a zwitterionic hydrogel pre-polymerization solution: mixing 5g of DMAPS, 5g of deionized water, 20mg of PEGDMA, 75mg of ammonium persulfate and 70mg of tetramethylethylenediamine in sequence to prepare a zwitterionic hydrogel pre-polymerization solution;
(3) placing the sunflower pith obtained in the step (1) in the zwitterionic hydrogel pre-polymerization solution obtained in the step (2) for ultrasonic dispersion for 2min, taking out the pith, placing in a 40 ℃ oven for thermal polymerization for 20min, taking out the pith, soaking in deionized water for more than 2h to remove unpolymerized monomers, and then placing in a vacuum oven for drying;
(4) and (3) uniformly dispersing graphene oxide in water by using a high-speed shearing machine to form a graphene oxide dispersion liquid with the concentration of 3 wt%, spin-coating the graphene oxide dispersion liquid on one end face of the sunflower pith prepared in the step (3) for 10 times (the spin-coating speed is 600r/min, and the time is 20s), and then soaking the cross section of the coating end in the graphene oxide solution for adsorption for 2h to obtain a stable coating, so that the modified sunflower stalk pith is obtained.
Example 4
The preparation method of the modified sunflower stem pith comprises the following steps:
(1) peeling sunflower stalk (purchased from Liaoning, China) to obtain pulp core, cutting into discs with diameter of 10mm with a blade, polishing the cross section with sand paper until smooth, taking four discs, and measuring the area of 11.1723mm by using a photographing pixel counting method2；
(2) Preparing a zwitterionic hydrogel pre-polymerization solution: mixing 6g of methacryloyl ethyl Sulfobetaine (SBMAA), 4g of deionized water, 30mg of PEGDMA, 180mg of ammonium persulfate and 180mg of tetramethylethylenediamine in sequence to prepare a zwitterionic hydrogel pre-polymerization solution;
(3) placing the sunflower pith obtained in the step (1) in the zwitterionic hydrogel pre-polymerization solution obtained in the step (2) for ultrasonic dispersion for 2min, taking out the pith, placing in a 40 ℃ oven for thermal polymerization for 20min, taking out the pith, soaking in deionized water for more than 2h to remove unpolymerized monomers, and then placing in a vacuum oven for drying;
(4) and (3) uniformly dispersing carbon black in water by using a high-speed shearing machine to form a carbon black dispersion liquid with the concentration of 3 wt%, spin-coating the carbon black dispersion liquid on one end face of the sunflower pith prepared in the step (3) for 10 times (the spin-coating rotating speed is 600r/min, the time is 20s), and then soaking the cross section of the coating end in a carbon black solution for adsorption for 2h to obtain a stable coating, so that the modified sunflower stem pith is obtained.
Example 5
The preparation method of the modified sunflower stem pith comprises the following steps:
(1) peeling sunflower stalk (purchased from Liaoning, China) to obtain pulp core, cutting into discs with diameter of 10mm with a blade, polishing the cross section with sand paper until smooth, taking four discs, and measuring the area of 11.2733mm by using a photographing pixel counting method2；
(2) Preparing a zwitterionic hydrogel pre-polymerization solution: sequentially mixing 2g of carboxyl betaine methyl methacrylate (CBMAA), 6g of deionized water, 30mg of PEGDMA, 180mg of ammonium persulfate and 120mg of tetramethylethylenediamine to prepare a zwitterionic hydrogel pre-polymerization solution;
(3) placing sunflower medulla in solution, ultrasonically dispersing for 2min, taking out the medulla, placing in 40 deg.C oven, thermally polymerizing for 20min, taking out the medulla, soaking in deionized water for more than 2 hr to remove unpolymerized monomer, and drying in vacuum oven;
(4) and (3) uniformly dispersing carbon black in water by using a high-speed shearing machine to form a carbon black dispersion liquid with the concentration of 3 wt%, spin-coating the carbon black dispersion liquid on one end face of the sunflower pith prepared in the step (3) for 10 times (the spin-coating rotating speed is 600r/min, the time is 20s), and then soaking the cross section of the coating end in a carbon black solution for adsorption for 2h to obtain a stable coating, so that the modified sunflower stem pith is obtained.
Comparative example 1
The preparation method of the modified sunflower stem pith comprises the following steps:
(1) peeling sunflower stalk (purchased from Liaoning, China) to obtain pulp core, cutting into discs with diameter of 10mm with a blade, polishing the cross section with sand paper until smooth, taking four discs, and measuring the area of 11.3712mm by using a photographing pixel counting method2；
(2) Ultrasonically dispersing sunflower medulla in deionized water for 2min, taking out the medulla, placing in a 40 deg.C oven for 20min, taking out the medulla, soaking in deionized water for at least 2h, and drying in a vacuum oven;
(3) and (3) uniformly dispersing carbon black in water by using a high-speed shearing machine to form a carbon black dispersion liquid with the concentration of 3 wt%, spin-coating the carbon black dispersion liquid on one end face of the sunflower pith prepared in the step (3) for 10 times (the spin-coating rotating speed is 600r/min, and the time is 20s), and then soaking the cross section of one end of the coating in the carbon black solution for adsorption for 2h to obtain a stable photo-thermal conversion coating, so that the modified sunflower pith which is not compounded with the zwitter-ion hydrogel is obtained.
FIG. 10 shows the results of experiments with and without complex zwitterionic hydrogels against salt precipitation, under conditions simulating seawater desalination in high salinity environment, specifically: the seawater evaporation test was performed in simulated saline at a concentration of 20 wt% under simulated solar light intensity while placing about 2g of sodium chloride on the surface of the photothermal conversion layer of the sample.
The experimental results show that: comparative example 1 sodium chloride salt on the surface of sunflower Stem Pith (SP) sample without the compounded zwitterionic hydrogel was caked, while the (SPH) sample after compounding the zwitterionic hydrogel of example 1 according to the present invention was not salted and caked. Therefore, the zwitter-ion hydrogel is modified on the surface of the medulla of the sunflower stalk, and based on the strong water binding capacity of zwitter-ions, a hydration film can be formed on the surface of the medulla of the sunflower stalk to prevent salt from being separated out after crystallization, so that the evaporation efficiency of solar seawater desalination can be obviously improved.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The modified natural plant medulla, which is characterized in that the modified natural plant medulla comprises a natural plant medulla, a zwitter-ion hydrogel which forms an interpenetrating network topology with the natural plant medulla, and a photothermal conversion layer loaded at one end of the natural plant medulla.
2. The modified natural plant pith according to claim 1, wherein the natural plant pith is a sunflower stalk pith, a maize stalk pith or a sorghum stalk pith, preferably a sunflower stalk pith.
Preferably, the zwitterionic hydrogel is obtained by soaking and polymerizing a zwitterionic compound monomer, and an interpenetrating network structure of the zwitterionic hydrogel is utilized to be compounded with the natural plant pith.
Preferably, the zwitterionic compound monomer is selected from one, two or more of N, N-dimethyl (methacryloyloxyethyl), ammonio propanesulfonate inner salt (DMAPS), methacryloyl ethyl Sulfobetaine (SBMAA), carboxybetaine methyl methacrylate (CBMAA) and Phosphocholine (PCMA).
Preferably, the photothermal conversion layer contains a photothermal conversion material. For example, the photothermal conversion material is selected from one, two or more of polypyrrole, carbon black, carbon nanotube, activated carbon, graphene oxide, and polyaniline.
Preferably, the thickness of the photothermal conversion layer is 0.2-2 mm.
Preferably, the photothermal conversion layer is modified at one end of the natural plant medulla.
3. A method for preparing a modified natural plant pith according to claim 1 or 2, comprising the steps of: firstly, modifying natural plant medulla with zwitter-ion hydrogel, and then compounding a photo-thermal conversion layer to obtain the modified natural plant medulla.
4. The method of claim 3, comprising the steps of:
(1) soaking the natural plant medulla in the zwitterionic hydrogel pre-polymerization solution, and then heating and polymerizing to obtain the natural plant medulla containing the zwitterionic hydrogel;
(2) coating a photo-thermal conversion material on one end of the natural plant pith containing the zwitterion hydrogel, then soaking the end coated with the photo-thermal conversion material in a dispersion liquid of the photo-thermal conversion material, and compounding a photo-thermal conversion layer to obtain the modified natural plant pith.
5. The method according to claim 4, wherein the zwitterionic hydrogel pre-polymerization solution comprises the following components in percentage by mass: 5-60 wt% of a zwitterionic compound monomer, 0.5-5 wt% of a cross-linking agent, 0.5-2 wt% of an initiator and the balance of water.
Preferably, the crosslinker is polyethylene glycol dimethacrylate (PEGDMA) or N, N' -methylenebisacrylamide.
Preferably, the initiator is one or two of ammonium persulfate and tetramethylethylenediamine, preferably ammonium persulfate and tetramethylethylenediamine.
Preferably, the preparation method further comprises the step of pretreating the natural plant medulla before the step (1).
6. The method according to any one of claims 3 to 5, wherein the modified natural plant pith is prepared by a method comprising the steps of:
(S1) peeling the outer wall of the natural plant stem, taking the medulla of the natural plant stem, cutting the medulla into required size, and grinding the cross section of the medulla until the surface is uniform and smooth;
(S2) soaking the natural plant medulla in the zwitterionic hydrogel pre-polymerization solution, heating for polymerization, immersing the polymerized natural plant medulla in water, removing unpolymerized zwitterionic compound monomer, and drying to obtain the natural plant medulla containing the zwitterionic hydrogel;
(S3) coating a photothermal conversion material on one end of the natural plant pith containing the zwitterionic hydrogel, and then soaking the end coated with the photothermal conversion material in a dispersion of the photothermal conversion material to form a composite photothermal conversion layer, thereby obtaining the modified natural plant pith.
7. Use of the modified natural plant pith according to claim 1 or 2 and/or the modified natural plant pith obtained by the preparation method according to any one of claims 3 to 6 as a material for seawater desalination, preferably as a material for solar seawater desalination.
Preferably, the seawater is normal seawater, seawater polluted by oil stains, or seawater polluted by heavy metals.
8. Use of the modified natural plant pith according to claim 1 or 2 and/or the modified natural plant pith produced by the method according to any one of claims 3 to 6 in heavy metal wastewater treatment. Wherein the heavy metal is one, two or more of Ni, Pb, Cu, Zn, Cr and Cd.
9. A seawater desalination material comprising the modified natural plant pith of claim 1 or 2 and/or the modified natural plant pith obtained by the production method of any one of claims 3 to 6.
10. A heavy metal wastewater treatment material comprising the modified natural plant pith according to claim 1 or 2 and/or the modified natural plant pith obtained by the production method according to any one of claims 3 to 6.
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