CN114249374B - Plant bionic high-concentration-salt-resistant solar evaporation device and preparation method and application thereof - Google Patents

Plant bionic high-concentration-salt-resistant solar evaporation device and preparation method and application thereof Download PDF

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CN114249374B
CN114249374B CN202111652234.0A CN202111652234A CN114249374B CN 114249374 B CN114249374 B CN 114249374B CN 202111652234 A CN202111652234 A CN 202111652234A CN 114249374 B CN114249374 B CN 114249374B
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plant
evaporation device
stems
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CN114249374A (en
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肖娟秀
罗文琪
郭阳
蔡栋
赵芃
冯建波
吕荣鑫
李桂秋
谭琳惠
韩彩娜
沈义俊
王东
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Hainan University
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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
    • 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
    • C02F1/048—Purification of waste water by evaporation
    • 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
    • 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
    • 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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  • Hydrology & Water Resources (AREA)
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Abstract

The invention discloses a plant bionic high-concentration-salt-resistant solar evaporation device and preparation and application thereof; the invention first uses plant stems as plant bionics of the photo-thermal conversion material, recycles the waste plant stems, changes waste into valuable and effectively improves air pollution caused by burning the plant stems. The top surface of the stem of the plant is carbonized by the alcohol lamp, and a carbon black layer is formed through simple oxidation to prepare the bionic top carbonized plant pseudostem. Through carbonizing after the manual work is punched on the plant stem, penetrate the cotton thread drainage again, utilize the drive power that the difference in height and the concentration difference of solution produced, the capillary force through the cotton thread can realize one-way jet flow transmission, also can ensure when guaranteeing sufficient water supply that evaporimeter surface salt concentration can not reach the saturated condition to break through the limitation of traditional bionic solar energy evaporimeter of plant unstable, the easy salt that binds under high concentration salt water, waste water environment for a long time.

Description

Plant bionic high-concentration-salt-resistant solar evaporation device and preparation method and application thereof
Technical Field
The invention belongs to the technical field of desalination treatment of high-concentration salt water, and particularly relates to a plant bionic high-concentration salt resistant solar evaporation device and a preparation method and application thereof.
Background
However, the lack of resources has become an unsound fact, and especially in the modernization of industrial technology, the only fresh water resources are destroyed to a great extent. At present, fresh water which can be directly utilized by human beings is taken from underground water, lake fresh water and river water, and with the increasing deterioration of the environment, the fresh water resources are gradually deficient, especially in some arid regions and island regions. Arid regions are water-deficient due to too little ground water on the surface and shallow layers, and sea water is mostly stored in islands and coastal regions, so that fresh water resources are insufficient. Therefore, seawater desalination is one of the important means for solving the problem of water shortage of human beings.
At present, the photo-thermal driving interface evaporation is a novel solar seawater desalination technology, the technology has higher photo-thermal conversion efficiency and lower cost advantage, is suitable for small-scale domestic water desalination and portable water taking devices, is particularly suitable for fresh water acquisition in scenes such as isolated islands or field research and investigation, and becomes a research hotspot in the field of seawater desalination. However, the following problems still exist in the current solar evaporator:
(1) the conventional photothermal conversion materials are expensive, such as: noble metal materials such as platinum-nickel alloy, gold nanoparticles and silver nanoparticles.
(2) The preparation process is complex, the steps are complex, special equipment is often needed, and the preparation cost is high, so that the large-scale production and application of materials such as carbon nanotubes, MXenes, graphene and the like are hindered.
(3) Most of the photo-thermal materials have poor salt resistance in the evaporation process, and salt is crystallized and blocks a water transportation channel due to the fact that salt on the surface of the photo-thermal materials reaches supersaturated concentration in the evaporation process, so that water supply is affected, and even light absorption and water vapor escape are affected; leading the photo-thermal material to be unstable, finally greatly reducing the seawater desalination performance, and even leading the device to be invalid.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a plant bionic high-concentration salt resistant solar evaporation device;
the second purpose of the invention is to provide a preparation method of the plant bionic high-concentration salt resistant solar evaporation device;
the third purpose of the invention is to provide the application of the plant bionic high-concentration salt resistant solar evaporation device in high-concentration salt water and wastewater.
The purpose of the invention is realized by the following technical scheme: a preparation method of a plant bionic high-concentration-salt-resistant solar evaporation device comprises the following steps:
s1, pretreatment: selecting plant stems, cutting the plant stems into large blocks along the longitudinal growth direction, freezing for 45-52 hours, and freeze-drying in a freeze dryer for 70-80 hours to obtain freeze-dried stems;
s2, designing a stem: first, the freeze-dried stems are divided into small blocks; secondly, respectively punching holes close to the inner epidermis and the outer epidermis which are rich in cellulose and lignin to form artificial pores, and then carbonizing the top of the stem to form a carbon black layer with the thickness of 1-2 mm; finally, the cotton thread passes through the artificial small hole to be bridged with saline water with different solution heights and different concentrations on two sides.
Further, the plant in step S1 is any one of banana tree, reed, ramie or flax.
A preparation method of a plant bionic high-concentration-salt-resistant solar evaporation device comprises the following steps:
s1, pretreatment: selecting banana stems, cutting the banana stems into large blocks along the longitudinal growth direction, freezing for 45-52 hours, and freeze-drying in a freeze dryer for 70-80 hours to obtain freeze-dried banana stems;
s2, designing a stem: firstly, the sheath part of the outer ring of the freeze-dried banana stem is divided into the top surface area of 3.14cm 2 A cuboid with the height of 1 cm; secondly, respectively punching holes close to the inner epidermis and the outer epidermis which are rich in cellulose and lignin to form artificial pores, and carbonizing the top of the pseudostem to form a carbon black layer with the thickness of 1-2 mm; finally, the cotton thread is penetrated through the artificial pores to be bridged with saline water with different solution heights and different concentrations on two sides.
Further, the height of the small block in step S2 is 1 cm.
Further, the temperature of the freezing in the step S1 is-25 to-15 ℃.
Further, in step S2, small holes of 0.5mm in diameter were punched near the cellulose-and lignin-rich inner and outer skins, respectively.
Further, the carbon black layer is formed in step S2 by the following method: carbonizing the top of the pseudostem for 1-3 min by using an alcohol lamp outer flame to form a carbon black layer with the thickness of 1-2 mm.
The plant bionic high-concentration-salt-resistant solar evaporation device prepared by the method.
The plant bionic high-concentration-salt-resistant solar evaporation device is applied to high-concentration salt water and wastewater.
Furthermore, two ends of the cotton thread of the solar evaporation device are respectively immersed into a water body, the height difference of the liquid level and the concentration difference of the solution are adjusted, and one-way jet flow transportation of water and salt is constructed under the driving of pressure difference and concentration gradient.
The invention has the following advantages:
1. according to the invention, plant bionics taking plant stems as a photo-thermal conversion material is firstly carried out, and waste plant stems are recycled, so that waste is changed into valuable, and no cost is needed; meanwhile, the air pollution caused by burning the plant stems can be effectively improved.
2. The plant stalks have developed pore structures, are rich in cellulose and lignin, have strong capillary action force and low transmission resistance, and can realize the rapid transportation of water. Meanwhile, the porous structure of the plant stem can also enhance the absorption of light and accelerate the escape of steam. Utilize alcohol burner carbonization plant stem top surface, form the carbon black layer through simple oxidation, make bionical top carbonization plant stem, its simple process flow is its convenient operation, and its light absorption performance is good moreover, and light-heat conversion is efficient.
3. The plant stalk is punched and cotton thread is penetrated, the driving force generated by the height difference and the concentration difference of the solution is utilized, unidirectional jet flow transmission can be realized through the capillary force of the cotton thread, the sufficient water supply is ensured, the surface salt concentration of the evaporator can be ensured not to reach a saturated state, the salt resistance is improved, and the limitation that the traditional plant bionic solar evaporator is unstable and easy to salt under the high-concentration salt water and waste water environment for a long time is broken through.
Drawings
FIG. 1 is SEM pictures of natural banana stalks (a) and (c) are cross-section and longitudinal section of stellate parenchyma tissue, respectively; (b) and (d) are a cross-sectional and a longitudinal section, respectively, near the outer skin.
FIG. 2 is a full spectrum light absorption diagram of non-carbonized banana stem and carbonized banana stem.
FIG. 3 is a graph of the temperature rise of top carbonized banana stalks in 1 kW.m sunlight -2 Under irradiation, the change curve of the banana stalk top and the water body temperature along with time.
Fig. 4 is a water absorption diagram of the top carbonized banana stalk and a static contact angle diagram of the stalk surface, wherein (a) is the speed of the top carbonized banana stalk absorbing the colored dye along the vascular bundle direction; (b) is the static contact angle of the top carbonized banana stalk surface.
Fig. 5 is a graph of the water mass loss of a top carbonized banana stalk solar evaporator.
Fig. 6 shows evaporation rate and photothermal conversion efficiency of top carbonized banana stalks in different solutions; wherein, the water sources (a) are respectively east slope lake water, acid/alkali solution and sea mouth meadow river seawater of the Hainan university, and the water sources (b) are solutions with different salt concentrations.
FIG. 7 is a diagram of a plant bionic high-concentration salt resistant solar evaporation device and a salt resistant performance test; wherein (a) the experiment device diagram of the top carbonized banana stem solar evaporator after the salt resistance improvement treatment is that the number 1 is 3.5 wt% seawater; 2, 15 wt% high strength brine; 3, white cotton threads; 4, polystyrene foam; 5, a banana stem solar evaporator; 6, tin paperboard; 7, simulating sunlight; (b) the change of the beaker mass of 1 and 2 and the evaporation amount of 5 in 100h continuous evaporation experiments are obtained; (c) change in salt concentration for 1, 2 and 5 in 100h continuous evaporation experiments; (d) the photo-thermal evaporation performance of the mixed solution is 200 hours in 15 wt% high-concentration saline water.
FIG. 8 is the ion concentration in water before and after desalination using the evaporation device of the present invention; wherein (a) is heavy metal ion (Cu) 2+ 、Zn 2+ 、Pb 2+ 、Cd 2+ ) The waste water is a water source; (b) the water source is the seawater of the Haikou Diandihe, and the black bar chart is the ions (Na) in the drinking water of the world health organization + 、K + 、Ca 2+ 、Mg 2+ ) And (4) concentration standard.
Detailed Description
The invention is further described with reference to the following examples and figures, without limiting the scope of the invention to the following:
example 1: a preparation method of a plant bionic high-concentration-salt-resistant solar evaporation device comprises the following steps:
s1, pretreatment: selecting a stem of a reed, cutting the stem into large blocks along the longitudinal growth direction, freezing the large blocks at the temperature of-25 ℃ for 45 hours, and freeze-drying the large blocks in a freeze dryer for 70 hours after freezing to obtain the stem;
s2, stem design: firstly, the reed stalks are bundled to have the top surface area of 3.14cm 2 A cylinder with a height of 1 cm; secondly, respectively punching 8 small holes with the diameter of 0.5mm on the reed stems at the outermost circle to form artificial small holes, and carbonizing the top of the pseudostem for 3min by using an alcohol burner outer flame to form a carbon black layer with the thickness of 1 mm; finally, the cotton thread passes through the artificial small hole to be bridged with saline water with different solution heights and different concentrations on two sides.
Example 2: a preparation method of a plant bionic high-concentration-salt-resistant solar evaporation device comprises the following steps:
s1, pretreatment: selecting stems of plant ramie, cutting the stems into large blocks along the longitudinal growth direction, freezing the large blocks at the temperature of 15 ℃ below zero for 52 hours, and freeze-drying the large blocks in a freeze dryer for 80 hours after freezing to obtain the stems;
s2, stem design: first, ramie stalks are bundled to have a top surface area of 3.14cm 2 A cylinder with a height of 1 cm; secondly, respectively drilling 8 small holes with the diameter of 0.5mm on the ramie stalks on the outermost circle to form artificial small holes, and carbonizing the top of the pseudostem for 4min by using an alcohol lamp outer flame to form a carbon black layer with the thickness of 2 mm; finally, the cotton thread passes through the artificial small hole to be bridged with saline water with different solution heights and different concentrations on two sides.
Example 3: a preparation method of a plant bionic high-concentration-salt-resistant solar evaporation device comprises the following steps:
s1, pretreatment: selecting flax stems, cutting the flax stems into large blocks along the longitudinal growth direction, freezing the large blocks at the temperature of 18 ℃ below zero for 48 hours, and freeze-drying the large blocks in a freeze dryer for 75 hours after freezing to obtain stems;
s2, stem design: firstly, the flax stalks are bundled to have a top surface area of 3.14cm 2 A cylinder with a height of 1 cm; secondly, respectively drilling 8 small holes with the diameter of 0.5mm on the flax stalks at the outermost circle to form artificial small holes, and carbonizing the top of the pseudostem for 2min by using an alcohol lamp outer flame to form a carbon black layer with the thickness of 1.5 mm; finally, the cotton thread passes through the artificial small hole to be bridged with saline water with different solution heights and different concentrations on two sides.
The following experiments illustrate the beneficial effects of the present invention:
a preparation method of a plant bionic high-concentration-salt-resistant solar evaporation device comprises the following steps:
s1, pretreatment: cutting stems of bananas into large blocks along the longitudinal growth direction, freezing for 48 hours at the temperature of-18 ℃, and freeze-drying for 78 hours in a freeze dryer to obtain the stems;
s2, stem design: first, the stalks were divided into pieces having a top surface area of 3.14cm 2 A cuboid with the height of 1 cm; secondly, respectively drilling 8 small holes with the diameter of 0.5mm at the positions close to the inner epidermis and the outer epidermis which are rich in cellulose and lignin to form artificial small holes, and then carbonizing the top of the stem for 2min by using an alcohol lamp outer flame to form a carbon black layer with the thickness of 1 mm; finally, the cotton thread passes through the artificial small hole to be bridged with saline water with different solution heights and different concentrations on two sides.
2. Microscopic morphology of natural banana stalk
Observing the microscopic morphology of the material by using a field emission scanning electron microscope and taking a picture for recording, as shown in fig. 1, it can be known from fig. 1 that: the leaf sheath of the natural banana stem has smooth two surfaces, the inner epidermis mainly consists of cellulose, and the outer epidermis is rich in lignin. The leaf sheath is mainly composed of a stellate thin-walled tissue and a vascular bundle, the stellate thin-walled tissue forms a layer space and separates air pipelines, so that the heat insulation effect of the banana stalks is good, and the vascular sheath is mainly used for transporting water. The star-shaped parenchyma of the leaf sheath is distributed with a large number of micropores with the pore diameter of 30-50 μm, as shown in figure 1 a; the star-shaped thin-walled tissue blocks the air duct layer by layer, playing a role of heat insulation, and the interval of the star-shaped thin-walled tissue between layers is about 1.40mm, as shown in fig. 1 c. As can be seen from FIG. 1b, the part near the outer skin is also composed of vertical vascular bundles and parenchyma cells, and the aperture of the vascular bundles is in the range of 190-420 μm; the length of parenchymal cells is in the range of 50-250 μm, as shown in FIG. 1 d.
3. Light absorption of Top-carbonized Banana stalks
The experimental method comprises the following steps: measuring the optical reflection and transmission spectrum of the surface of the top carbonized banana stem by using an ultraviolet visible near-infrared spectrometer within the range of 200-2500nm, collecting reflected light by using an integrating sphere, and calculating the light absorption efficiency by using A ═ 1-R-T, wherein R is the reflection efficiency and T is the transmission efficiency.
The experimental results are as follows: as shown in fig. 2, the ultraviolet-visible-near infrared spectrometer is used to measure the absorbance of the top carbonized banana stalk, and it can be seen that the absorbance of the natural banana stalk is only about 30%; after flame carbonization, the light absorption rate of the material is improved to 85 percent. Carbon black is an excellent photo-thermal material with an absorption range that spans the ultraviolet, visible, and even near infrared regions. Therefore, the carbonized banana stalks prepared by the flame carbonization method can obtain high light absorption rate, concentrate heat in the evaporation area at the top, and improve evaporation efficiency.
4. Raising temperature property of top carbonized banana stem
The experimental method comprises the following steps: aligning the top of the material by using an infrared imager; shooting is carried out once per minute under the irradiation of one piece of sunlight, and the surface temperature of the top carbonized banana stalks is recorded.
The experimental results are as follows: FIG. 3 shows the concentration of 1 kW.m in a single sunlight -2 Under irradiation, the change curve of the banana stem top and the water body temperature along with time; the temperature of the top carbonized banana stalk is raised from 25 ℃ to 41 ℃ within 20 min; the temperature of the water body rises from 25 ℃ to 27 ℃ within 20 min. Furthermore, it can be observed that polystyrene foamThe heat insulation performance of the evaporator is good, heat is concentrated on the evaporator and does not diffuse to the water body, and the heat loss is reduced.
5. Hydrophilicity of top carbonized banana stalks
The experimental method comprises the following steps: placing paper towels with the same area on the surface of the dried carbonized banana stem, then placing the paper towels into a surface dish filled with 10ml of rhodamine B, and simultaneously taking a picture to record the time for the rhodamine B to be absorbed on the top surface of the banana stem; the measurement of the contact angle of water was measured using a contact angle measuring instrument.
The experimental results are as follows: as shown in fig. 4, fig. 4a shows the speed of the top carbonized banana stalk absorbing the colored dye along the vascular bundle direction, and it can be observed that only 30s rhodamine B is needed to cover 100% of the surface. This is because banana stalks contain more vascular bundles, and water is rapidly transported to the top thereof by the capillary action of the vascular bundles. Fig. 4b shows the hydrophilicity of the sample, which is analyzed by static contact angle, and the liquid drops disappear from the surface of the stalk only after 0.2s, which is a super-hydrophilic material due to the fact that the banana stalk is rich in hydrophilic cellulose.
6. Evaporation rate of top carbonized banana stalks
The experimental method comprises the following steps: the banana stalks have developed pore structures, and the top of the material is carbonized by a flame carbonization method to form a carbon black layer with excellent light absorption performance. Under the irradiation of sunlight, the weight change of water within 60min is collected by a computer, an evaporation curve of the quality of the photo-thermal material along with the change of time is obtained, and the evaporation rate of the top carbonized banana stalks is researched.
The experimental results are as follows: as shown in FIG. 5, under a sunlight irradiation, since there is no photothermal material to efficiently convert solar energy into heat energy, the evaporation rate of pure water is very low, only 0.14kg/m -2 ·h -1 . After simple carbonization, the evaporation rate of the top carbonized banana stalks is improved to 2.388kg/m -2 ·h -1 The evaporation rate is improved by 17 times compared with that of pure water; the inner and outer skins of the banana stalks are perforated and carbonized, and then are penetrated with cotton threads, the convection effect is increased by using the height difference of the solution and the capillary force of the cotton threads, and the evaporation rate is increased to 2.645kg/m -2 ·h -1 The evaporation rate is improved by 19 times compared with that of pure water.
7. Seawater desalination and wastewater application of top carbonized banana stalks
The experimental method comprises the following steps: to demonstrate that top-carbonized banana stalks can be used in different water environments, their evaporation in lake water, acid, alkali, real seawater and solutions of different salt concentrations (Copt ═ 1 kW/m) was tested -2 )。
The experimental results are as follows: as shown in FIG. 6, the evaporation rates in lake water, alkali, true seawater and acid were 2.081, 2.126, 2.144 and 2.166kg/m, respectively -2 ·h -1 The photothermal conversion rates were 89.17%, 91.12%, 91.87%, and 92.81%, respectively. The pH of the solution before and after evaporation under acid/base conditions was tested and found to be neutral and consistent with the pH range of drinking water after evaporation, as shown in figure 6 a. To investigate the salt resistance, the evaporation rate of the above evaporator was tested in solutions of different salt concentrations, as shown in fig. 6 b: the evaporation rates of the above evaporators at simulated seawater salinity of 3.5,7, 15 and 25 wt% were 2.134, 2.123, 2.114 and 1.932kg/m, respectively -2 ·h -1 The corresponding photothermal conversion efficiency was also slightly decreased, which was 91.43%, 90.99%, 90.61% and 82.76%, respectively. Since the higher the concentration of brine, the greater the surface tension, resulting in a slight decrease in the evaporation rate.
8. Salt resistance test
In order to improve the salt resistance, the banana stalks are improved with treatment. As shown in FIG. 7, in FIG. 7a, the cotton thread was inserted into 1 at one end and simulated seawater (3.5 wt% NaCl) and into 2 at the other end, and the initial height difference between No. 1 beaker and No. 2 beaker was 7cm in high concentration salt solution (15 wt% NaCl). The pressure difference that liquid level difference formed in two beakers and the concentration difference between two kinds of different concentration solutions make the salt solution constantly flow to 2 from 1 through solar evaporator, guarantee to supply water sufficient, form the route after the cotton thread is moist for the convection current of water. Meanwhile, the polystyrene foam is used for separating the evaporator main body from water, so that heat dissipation is reduced. Through the experimental device, the salt concentration change of the whole system can be measured, and the change of 1 and 2 volumes can be monitored in real time to evaluate the evaporation rate of the solar evaporator. Under the irradiation of a sunlight, the top carbonized banana stalks continuously work for 100 hours, the height difference and the concentration difference of the solution cause unidirectional jet water transportation, so that the volume in 1 is reduced, the volume in 2 is increased, and the mass loss of the whole system is the amount of generated steam, as shown in fig. 7 b.
From fig. 7c it can be observed that the concentration of the whole system is monitored by means of optical refractometer tracking, and after the solar evaporator is operated for 100h continuously, the salt concentration in 1 is always 3.5 wt%, the salt concentration in 2 is decreased from 15 wt% to 9.8 wt%, and the concentration in the top 5 of the material is increased from 0 to 15 wt%. We note that the difference in solution height causes the cotton to have an increased convective flux, which is greater than the diffusive flux of the salt ions, which cannot diffuse from 2 through 5 into 1, and the salt concentration remains unchanged in 1. The low-concentration brine flows into the high-concentration brine in a single direction, so that the salt concentration in the solution in the step 2 is reduced obviously in the initial stage, but salt ions can be remained in the evaporator due to evaporation of moisture, the salt ions can be brought back to the step 2 by the flow of the solution, the reduction amplitude of the salt concentration in the later stage is small, and the salt concentration in the step 2 is basically unchanged after the evaporator works for 80 hours.
Below the saturation concentration of the salt solution (26 wt%) is the key to salt resistance, the convection effect of the cotton thread causes the water in the evaporator 1 to continuously flow to the evaporator 5, and the concentration of the surface of the evaporator does not exceed the crystallization concentration of the salt, so that the evaporator can continuously work. As shown in fig. 7d, the solutions with the corresponding concentrations in 1 and 2 were replaced every 12h to ensure that the initial height difference and concentration difference of the solutions were unchanged, the evaporator was cycled for 200h under a sunlight irradiation, and from the digital photograph in fig. 7d, it can be observed that the surface of the evaporator did not salt, and the evaporation rate remained substantially unchanged (2.645 kg/m) -2 ·h -1 ) And excel in the evaporation rate of banana stalks of different carbonization thickness, both of which are 2cm in diameter and height, thanks to sufficient water supply and reduced heat loss.
9. Desalination capacity of top carbonized banana stalks
The experimental method comprises the following steps: the solar simulator is used as a light source, polystyrene foam wrapped by paper towel is plugged into the beaker, and the beaker is extended into a beaker filled with seawater or solution containing heavy metal ions to play a role in drainage, and then the wet material is wettedThe moistened top carbonized banana stem is placed above the polystyrene foam, the whole device is placed on a balance, and evaporation is carried out under illumination; collecting condensed water by using a self-made collecting device; testing Na in seawater and collected condensed water by inductively coupled plasma mass spectrometer + 、K + 、Ca 2+ 、Mg 2+ The concentration of (c); and respectively testing the concentrations of the heavy metal ions in the heavy metal ion original solution and the condensed water collected respectively.
The experimental results are as follows: as shown in FIG. 8, in order to evaluate the desalting capacity of the top carbonized banana stalks on the wastewater containing heavy metal ions and seawater, the ion concentration of the collected fresh water was measured by ICP-MS and Cu was found 2+ From 256 mg.L -1 Reduce to 0.009 mg.L -1 ，Zn 2+ From 226.5 mg.L -1 Reduced to 0.11 mg.L -1 ，Pb 2+ From 774.8 mg.L -1 Reduced to 0.125 mg.L -1 ，Cd 2+ From 363.6mg.L -1 Reduced to 0.015mg.L -1 Far below the ion concentration level required for wastewater discharge, as shown in figure 8 a. Four major ions (Na) were collected in the water after evaporation + 、K + 、Ca 2+ 、Mg 2+ ) The concentration of (A) is greatly reduced from 17420.19, 1400, 14730 and 430 mg.L -1 Reduced to 67.36, 0.76, 16.9 and 0.169 mg.L -1 It is shown that the collected water meets the World Health Organization (WHO) drinking water standard, and that the top carbonized banana stalks not only have seawater desalination capability, but also have wastewater treatment and purification capability, as shown in fig. 8 b.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can substitute or change the technical solution of the present invention and the inventive concept within the technical scope of the present invention.

Claims (10)

1. A preparation method of a plant bionic high-concentration-salt-resistant solar evaporation device is characterized by comprising the following steps:
s1, pretreatment: selecting plant stems, cutting the plant stems into large blocks along the longitudinal growth direction, freezing for 45-52 hours, and freeze-drying in a freeze dryer for 70-80 hours to obtain freeze-dried stems;
s2 stem design: first, the freeze-dried stems are divided into small blocks; secondly, respectively punching holes close to the inner epidermis and the outer epidermis which are rich in cellulose and lignin to form artificial pores, and then carbonizing the top of the stem to form a carbon black layer with the thickness of 1-2 mm; finally, the cotton thread penetrates through the artificial small hole, one end of the cotton thread extends into the container filled with the low-concentration salt solution, and the other end of the cotton thread extends into the container filled with the high-concentration salt solution; the two different solutions have height difference, and the surface of the low-concentration salt solution is higher than that of the high-concentration salt solution; so that the salt solutions of different solution heights and different concentrations on both sides are bridged by cotton threads.
2. The method for preparing a plant bionic high-concentration-salt-resistant solar evaporation device according to claim 1, wherein the plant in the step S1 is any one of banana tree, reed, ramie or flax.
3. The preparation method of the plant bionic high-concentration-salt-resistant solar evaporation device according to claim 1, characterized by comprising the following steps of:
s1, pretreatment: selecting banana stems, cutting the banana stems into large blocks along the longitudinal growth direction, freezing for 45-52 hours, and freeze-drying in a freeze dryer for 70-80 hours to obtain freeze-dried banana stems;
s2 stem design: firstly, the sheath part of the outer ring of the freeze-dried banana stem is divided into the top surface area of 3.14cm 2 A cuboid with the height of 1 cm; secondly, respectively punching holes close to the inner epidermis and the outer epidermis which are rich in cellulose and lignin to form artificial pores, and carbonizing the top of the pseudostem to form a carbon black layer with the thickness of 1-2 mm; finally, the cotton thread is penetrated through the artificial pores to be bridged with saline water with different solution heights and different concentrations on two sides.
4. The method for preparing a plant bionic high-concentration-salt-resistant solar evaporation device according to claim 1, wherein the height of the small block in the step S2 is 1 cm.
5. The method for preparing a plant bionic high-concentration-salt-resistant solar evaporation device according to claim 1 or 3, wherein the freezing temperature in the step S1 is-25 to-15 ℃.
6. The method for preparing a plant bionic solar evaporation device resisting high-concentration salt according to claim 1 or 3, wherein in step S2, 8 small holes with the diameter of 0.5mm are respectively punched at the positions close to the inner skin and the outer skin rich in cellulose and lignin.
7. The method for preparing the plant bionic high-concentration-salt-resistant solar evaporation device according to claim 1 or 3, wherein the carbon black layer in the step S2 is formed by adopting the following method: carbonizing the top of the pseudostem for 1-3 min by using an alcohol lamp outer flame to form a carbon black layer with the thickness of 1-2 mm.
8. A plant biomimetic high-salt resistant solar evaporation device prepared by the method of any of claims 1-4.
9. The use of the plant biomimetic high-concentration salt resistant solar evaporation device according to claim 8 in high-concentration salt water and wastewater.
10. The application of claim 9, wherein the two ends of the cotton thread of the solar evaporation device are respectively immersed into the water body, the height difference of the liquid level and the concentration difference of the solution are adjusted, and the unidirectional jet transportation of water and salt is constructed under the driving of the pressure difference and the concentration gradient.
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