Biochar-based hydrogel evaporator, preparation method and application

Abstract

The invention belongs to the technical field of solar seawater desalination, and particularly relates to a charcoal-based hydrogel evaporator, a preparation method and application, and the charcoal-based hydrogel evaporator is prepared from the following components: gellan gum, Siberian iris and polyethylene glycol. Compared with the prior art, the charcoal-based hydrogel evaporator for solar seawater desalination (SSD) is prepared by using a simple mixing method, the charcoal-based hydrogel evaporator is prepared by calcining Siberian iris wastes at high temperature, and the carbonized Siberian iris is used for reducing evaporation heat and increasing the evaporation rate of the Siberian iris. Meanwhile, the original network structure of the SGG is destroyed by adding PEG, so that a new pore structure is formed, and faster movement of water molecules is facilitated. Under the same reaction parameters, the evaporation rate is obviously improved by 0.21 kg.m <-2 >. H <-1 > compared with that of an evaporator without PEG, and the photothermal conversion efficiency is improved by 11.3%.

Description

Technical Field

[0001] This invention belongs to the field of solar seawater desalination technology, specifically relating to a biochar-based hydrogel evaporator, its preparation method, and its application. Background Technology

[0002] As people's living standards and development demands continue to rise, the problem of water scarcity may become even more severe in the future. Currently, directly usable clean water is extremely limited. Only 3% of the water on Earth is freshwater; the remaining 97% is trapped in the ocean and unsuitable for drinking. Solar desalination is an environmentally friendly, economical, and sustainable technology that offers a promising method for obtaining clean water from seawater without relying on electricity or complex infrastructure. However, a major challenge of solar desalination is salt accumulation on or inside the solar evaporator, which reduces solar evaporation efficiency and can lead to evaporator failure. Increasing research is focused on developing novel structural materials to improve the efficiency of solar desalination (SSD). To date, a variety of materials have been explored for SSD applications, including polymer-based materials, semiconductors, ceramic-based materials, plasma metals, and carbon dots. However, its widespread practical application is hindered by expensive raw materials, complex preparation processes, and a lack of biodegradability.

[0003] Previous studies have found that biomass can be used as a starting material to produce carbon materials with various morphologies and porous structures through carbonization, which can serve as ideal carbon-based photothermal materials. Previous research has shown that biochar made from corn stalks and other raw materials has moisture evaporation rates of 1.65, 1.7, and 1.57 kg·m³, respectively. -2 ·h -1 With a photothermal conversion efficiency as high as 87.26%, and 76% and 85.9% respectively under a single solar irradiation, it is higher than that of traditional materials. To a certain extent, various plants grow and are utilized on a large scale in many areas of my country. These plants generate a large amount of biomass waste during their growth and utilization. This waste is often disposed of haphazardly through incineration or landfill, leading to a waste of biomass energy and damage to the ecological environment, even increasing the risk of air pollution and soil degradation. However, if this waste biomass is converted into biochar through pyrolysis and used for solar-powered seawater desalination, it can promote the resource utilization of terrestrial plant waste biomass resources.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a biochar-based hydrogel evaporator, its preparation method, and its application, in order to solve the technical problems mentioned in the background section.

[0006] To achieve one of the above objectives, the present invention provides the following technical solution:

[0007] A biochar-based hydrogel evaporator is prepared from the following components: gellan gum, Siberian iris, and polyethylene glycol.

[0008] Preferably, by weight, the ingredients are 2-10 parts gellan gum, 1-5 parts Siberian iris, and 2-5 parts polyethylene glycol.

[0009] Preferably, by weight, the mixture comprises 4 parts gellan gum, 1 part Siberian iris, and 3 parts polyethylene glycol.

[0010] To achieve the second objective mentioned above, the present invention provides the following technical solution:

[0011] A method for preparing a biochar-based hydrogel evaporator includes the following steps:

[0012] S100. After washing and drying the Siberian iris, crush it and then sieve the crushed material to obtain biomass powder with uniform particle size.

[0013] S200. The screened biomass powder is calcined, and the calcined carbonized biomass powder is mixed with deionized water, stirred and ultrasonically vibrated to obtain Siberian iris biochar suspension.

[0014] S300: Heat the Siberian iris biochar suspension, add gellan gum and stir continuously. After stirring, add polyethylene glycol and continue stirring.

[0015] S400, add CaCl2 again and continue stirring until cooled. Pour the cooled mixture into a mold to cool and form a primary sample.

[0016] S500: The primary sample is repeatedly immersed in liquid nitrogen and then frozen and dried sequentially to finally obtain a biochar-based hydrogel evaporator.

[0017] Preferably, in step S100:

[0018] The Siberian iris was crushed twice; the crushed material was then passed through a 100-mesh sieve.

[0019] Preferably, in step S200:

[0020] The calcination of the screened biomass powder specifically includes: heating to 900℃ under nitrogen atmosphere and maintaining for 2 hours;

[0021] The stirring and ultrasonic oscillation time was 2 hours.

[0022] Preferably, in step S300:

[0023] The Siberian iris biochar suspension was heated to 90°C; the stirring time after adding gellan gum was 1 hour; and the stirring time after adding polyethylene glycol was 20 minutes.

[0024] Preferably, in step S400:

[0025] After adding CaCl2 again, continue stirring for 10 minutes, then stir the mixture until it cools to 50°C.

[0026] Preferably, in step S500:

[0027] The primary sample was immersed in liquid nitrogen for 15 seconds, then frozen at -18°C for 6 hours, and this process was repeated 3 times. Finally, it was frozen in a freeze dryer for 36 hours to obtain a biochar-based hydrogel evaporator.

[0028] To achieve the third objective mentioned above, the present invention provides the following technical solution:

[0029] Application of a biochar-based hydrogel evaporator as described above and a method for preparing the biochar-based hydrogel evaporator as described above in solar-powered seawater desalination.

[0030] Compared with existing technologies, this invention provides a biochar-based hydrogel evaporator, its preparation method, and its application. A biochar-based hydrogel evaporator for solar desalination (SSD) is prepared using a simple mixing method. This biochar-based hydrogel evaporator is prepared by high-temperature calcination of Siberian iris waste. The carbonization of the Siberian iris reduces the heat of vaporization and increases its evaporation rate. Simultaneously, the addition of PEG disrupts the original network structure of SGG, leading to the formation of new porous structures, which facilitates faster water molecule movement. Under the same reaction parameters, the evaporation rate is significantly increased by 0.21 kg·m³ compared to the evaporator without PEG. -2 ·h -1 The photothermal conversion efficiency was improved by 11.3%. In addition, the inventors unexpectedly discovered that no significant changes were observed when the biochar-based hydrogel evaporator was exposed to a 7% brine solution for 10 hours, and the biochar-based hydrogel evaporator exhibited excellent seawater desalination and wastewater treatment capabilities.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a process flow diagram of a method for preparing solar thermal conversion materials provided in an embodiment of the present invention.

[0034] Figure 2 This is a scanning electron microscope image of the hydrogel evaporator prepared in Example 1 of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment constructs a photothermal conversion system with a hierarchical porous structure by precisely controlling the mass ratio of gellan gum, Siberian iris biochar, and polyethylene glycol to 4:1:3. First, plant tissue was pulverized twice and passed through a 100-mesh sieve, then calcined at 900℃ under a nitrogen atmosphere for 2 hours to prepare biochar material with a rich pore structure. Subsequently, the biochar dispersion was heated to 90℃ and subjected to a thermally induced gelation reaction with gellan gum for 1 hour. Polyethylene glycol was then introduced as a pore structure regulator for 20 minutes of interface modification. Next, ionic crosslinking with CaCl2 solution was used to form a three-dimensional network structure. Finally, after three cycles of rapid freezing at -196℃ and deep cryogenic treatment at -18℃ using liquid nitrogen, followed by 36 hours of freeze-drying, a hydrogel evaporator with vertical channels was constructed. This evaporator operates at 1 kW·m³. -2 Under illumination, it exhibits a yield of 2.05 kg·m. -2 ·h -1With its high evaporation rate and 89.5% photothermal conversion efficiency, its unique pore structure enables rapid water transport through capillary action. At the same time, the polyethylene glycol-modified interface effectively reduces the enthalpy of water evaporation. The photothermal conversion layer of biochar and the water transport layer of hydrogel form a synergistic effect, enabling the evaporator to maintain a stable state of salt-free crystallization even after continuous operation in 3.5% brine for 10 hours.

[0038] In this embodiment, the prepared hydrogel evaporator was scanned by electron microscopy, and the results are as follows: Figure 2 As shown, through Figure 2 It can be seen that the hydrogel evaporator prepared in this embodiment has a rich pore structure. In the unique pore structure, rapid water transport is achieved through capillary action, which can improve the water evaporation performance, salt resistance and photothermal conversion efficiency of the hydrogel evaporator.

[0039] Example 2

[0040] This embodiment achieves further improvement in evaporation performance by precisely controlling the synergistic effect of each component. The evaporator uses gellan gum, Siberian iris biochar, and polyethylene glycol in a mass ratio of 5:1.5:4. In the preparation process, Siberian iris plant tissue is first pulverized twice and passed through a 100-mesh sieve. Then, under nitrogen protection, the temperature is programmed to rise to 900°C at a rate of 5°C / min and calcined for 2 hours to prepare a biochar material with a rich porous structure. The obtained biochar is mixed with deionized water at a mass ratio of 1:20 and ultrasonically dispersed for 2 hours to form a uniform suspension. The biochar suspension is heated to 90°C, gellan gum is added, and stirring is continued for 1 hour to ensure full gelation. Subsequently, polyethylene glycol is added, and stirring is performed under high-speed shear emulsification conditions for 20 minutes to achieve more uniform interface modification. Then, a 0.2 mol / L CaCl2 solution is added dropwise for crosslinking, with the crosslinking time controlled at 10 minutes. The obtained gel precursor was subjected to a cycle of rapid liquid nitrogen freezing (15 seconds each time) followed by cryogenic treatment at -18°C (8 hours each time), and finally freeze-dried at -50°C for 36 hours to obtain a hydrogel evaporator with a superior vertical pore structure. Performance tests showed that this evaporator could achieve a speed of 1 kW·m³. -2 Under light conditions, the evaporation rate reaches 2.32 kg·m³. -2 ·h -1 The photothermal conversion efficiency was increased to 91.8%. After running continuously for 10 hours in a 7% high-concentration brine solution, no salt crystallization was observed on the evaporator surface, demonstrating excellent salt resistance and long-term operational stability.

[0041] Example 3

[0042] This embodiment aims to develop a hydrogel evaporator with both high evaporation performance and excellent mechanical stability by optimizing the component ratio and preparation process. Gellan gum, Siberian iris biochar, and polyethylene glycol were composited at a mass ratio of 6:1:3.5, significantly increasing the proportion of gellan gum to construct a denser three-dimensional network framework. The biomass precursor was pulverized twice through a 100-mesh sieve and then calcined at 850°C for 3 hours under a nitrogen atmosphere at a rate of 5°C / min to obtain mechanically enhanced layered biochar. The biochar and deionized water were ultrasonically dispersed at a mass ratio of 1:18 for 3 hours to form a stable suspension. Subsequently, gellan gum was added sequentially in an 85°C water bath with stirring for 90 minutes, followed by polyethylene glycol with stirring for 25 minutes, and then crosslinked with 0.25 mol / L CaCl2 solution for 15 minutes. The evaporator underwent four cycles of rapid freezing with liquid nitrogen (20 seconds / cycle) and deep freezing at -18°C (8 hours / cycle), and was finally freeze-dried for 40 hours to form the final product. This evaporator operates at a power output of 1 kW·m³. -2 The evaporation rate under light reaches 2.28 kg·m -2 ·h -1 It has a photothermal efficiency of 90.5%, and its compression modulus is increased to 1.8 times that of the original formula. It also maintains structural integrity after running continuously in 3.5% brine for 14 hours.

[0043] Example 4

[0044] This embodiment uses a gradient ratio of gellan gum, biochar, and polyethylene glycol in a 4.5:2:4 ratio. The increased proportion of biochar enhances photothermal conversion efficiency, and the constructed gradient pore structure improves water transport rate. A two-step calcination process is employed: Siberian iris powder is pre-carbonized at 500℃ for 1 hour, followed by final calcination at 900℃ for 1.5 hours to form hierarchical porous biochar with large-medium-micro pores. The biochar suspension (1:22 mass ratio) is then combined with gellan gum at 95℃ and stirred for 70 minutes. After introducing polyethylene glycol, ultrasonic-assisted stirring is performed for 15 minutes. Staged crosslinking is achieved by controlling the CaCl2 gradient concentration (0.1-0.3 mol / L). Finally, the evaporator undergoes five cycles of liquid nitrogen freezing (15 seconds / cycle) and -18℃ deep freezing (8 hours / cycle) followed by freeze-drying for 48 hours. Tests show that this evaporator operates at 1 kW·m³. -2 The evaporation rate under light is as high as 2.07 kg·m³. -2 ·h -1 The photothermal efficiency was 88.2%, and no salt deposition was observed on the surface for 10 consecutive hours.

[0045] Example 5

[0046] This embodiment employs a special formulation of gellan gum, biochar, and polyethylene glycol in a ratio of 5:1.2:4.5. The appropriately increased polyethylene glycol content effectively improves the hydrophilic-hydrophobic balance of the material surface. During biochar preparation, after calcination at 900℃ for 2 hours, an additional 1-hour activation treatment with steam at 800℃ is performed to obtain superhydrophilic surface properties. The biochar suspension (1:25 mass ratio) is composited with gellan gum and stirred for 80 minutes at 85℃. After adding polyethylene glycol, magnetic-ultrasonic co-stirring is used for 30 minutes. A crosslinking system of 0.15 mol / L CaCl2 is introduced, and the mixture undergoes three liquid nitrogen freezing cycles (15 seconds / cycle) and -18℃ deep freezing cycles (8 hours / cycle), ultimately freeze-drying for 48 hours. The evaporator operates at 1 kW·m³. -2 Maintained at 1.93 kg·m under illumination -2 ·h -1 The evaporation rate is high, the photothermal efficiency is 89.5%, and no salt crystallization or membrane fouling was observed after 12 hours of continuous operation in 3.5% high-salt wastewater, demonstrating self-cleaning characteristics and long-term operational stability.

[0047] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0048] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0049] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

Claims

1. A biochar-based hydrogel evaporator, characterized in that, It is prepared from the following ingredients: gellan gum, Siberian iris, and polyethylene glycol.

2. The biochar-based hydrogel evaporator according to claim 1, characterized in that, By weight, 2-10 parts gellan gum, 1-5 parts Siberian iris, and 2-5 parts polyethylene glycol.

3. The biochar-based hydrogel evaporator according to claim 2, characterized in that, By weight, it contains 4 parts gellan gum, 1 part Siberian iris, and 3 parts polyethylene glycol.

4. A method for preparing a biochar-based hydrogel evaporator, characterized in that, Includes the following steps: S100. After washing and drying the Siberian iris, crush it and then sieve the crushed material to obtain biomass powder with uniform particle size. S200. The screened biomass powder is calcined, and the calcined carbonized biomass powder is mixed with deionized water, stirred and ultrasonically vibrated to obtain Siberian iris biochar suspension. S300: Heat the Siberian iris biochar suspension, add gellan gum and stir continuously. After stirring, add polyethylene glycol and continue stirring. S400, add CaCl2 again and continue stirring until cooled. Pour the cooled mixture into a mold to cool and form a primary sample. S500: The primary sample is repeatedly immersed in liquid nitrogen and then frozen and dried sequentially to finally obtain a biochar-based hydrogel evaporator.

5. The method for preparing a biochar-based hydrogel evaporator according to claim 4, characterized in that, In step S100: The Siberian iris was crushed twice; the crushed material was then passed through a 100-mesh sieve.

6. The method for preparing a biochar-based hydrogel evaporator according to claim 5, characterized in that, In step S200: The calcination of the screened biomass powder specifically includes: heating to 900℃ under nitrogen atmosphere and maintaining for 2 hours; The stirring and ultrasonic oscillation time was 2 hours.

7. The method for preparing a biochar-based hydrogel evaporator according to claim 6, characterized in that, In step S300: The Siberian iris biochar suspension was heated to 90°C; the stirring time after adding gellan gum was 1 hour; and the stirring time after adding polyethylene glycol was 20 minutes.

8. The method for preparing a biochar-based hydrogel evaporator according to claim 7, characterized in that, In step S400: After adding CaCl2 again, continue stirring for 10 minutes, then stir the mixture until it cools to 50°C.

9. The method for preparing a biochar-based hydrogel evaporator according to claim 8, characterized in that, In step S500: The primary sample was immersed in liquid nitrogen for 15 seconds, then frozen at -18°C for 6 hours, and this process was repeated 3 times. Finally, it was frozen in a freeze dryer for 36 hours to obtain a biochar-based hydrogel evaporator.

10. The application of a biochar-based hydrogel evaporator as described in claims 1-3 and a method for preparing a biochar-based hydrogel evaporator as described in claims 4-9 in solar-powered seawater desalination.

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