A cattail-based photothermal interface evaporation material and its preparation method and application

Abstract

The present invention provides a cattail-based photothermal interface evaporation material and a preparation method and application thereof. The preparation method of the photothermal interface evaporation material of the present invention comprises: placing cattail in a tubular furnace for carbonization to obtain carbon powder; adding cattail to a reactor, and then adding sodium hydroxide to react to obtain cattail leaf cellulose; adding cattail leaf cellulose to a container, and then adding water and carbon powder, filtering to obtain a cattail-based photothermal film, which is a photothermal interface evaporation material. The present invention uses cattail as a raw material to prepare a photothermal conversion cattail-based photothermal film, which has a three-dimensional pore structure, super hydrophilic and water-conducting ability, and good light absorption performance; cattail as a carbon source can effectively absorb sunlight to achieve photothermal conversion, and cattail leaves are used as hydrophilic and water-conducting materials to improve water evaporation efficiency and salt resistance. Compared with other solar light absorbers such as graphene, the low-priced cattail-based photothermal interface conversion material is easier to meet the application of seawater desalination in real life.

Description

Technical Field

[0001] The present invention relates to the technical fields of energy utilization, recycling of biomass resources and photothermal evaporation materials, and in particular to a cattail-based photothermal interface evaporation material and a preparation method and application thereof. Background Art

[0002] In recent years, the World Economic Forum has listed water shortage as one of the world's biggest crises in its risk reports. Therefore, the search for clean water has been included in the development plans of many countries and governments. Of all the water resources on the earth, 97% are salt water that cannot be drunk, so seawater desalination technology has become a key technology to solve water shortages. Seawater desalination treatment technologies mainly include membrane technology and thermal treatment technology. The main disadvantages of these technologies are high energy consumption, which affects the cost of seawater desalination and exacerbates the energy crisis. Therefore, it is urgent to find alternative clean energy for seawater desalination technology.

[0003] Solar energy is clean, effective and cheap, and can be used in seawater desalination technology. However, traditional solar desalination devices have low energy utilization and high investment costs, making them unsuitable for widespread use. In recent years, scientists have focused on more efficient, self-driven and portable solar-steam devices. These solar-steam systems use new solar absorbers to efficiently vaporize water, thereby purifying seawater or sewage. Solar-steam systems can be mainly divided into three categories: photothermal conversion materials at the bottom of the water, photothermal conversion materials suspended in water, and solar thermal steam conversion based on interface heating. Compared with the first two solar thermal-steam conversion systems, the interface heating photothermal-steam conversion system has received more attention due to its higher efficiency.

[0004] A typical interfacial solar evaporation system includes the following parts: a solar absorption layer, a thermal insulation layer, a water supply channel, and a steam escape channel. The incident sunlight is first absorbed by the solar absorption layer and converted into heat. At the same time, under the capillary action, water infiltrates the surface layer through the supply channel. At present, the absorbers in the interfacial solar evaporation system mainly include metal plasma materials, semiconductor materials, carbon-based materials, etc. The main disadvantages of metal plasma materials are that they are easily corroded by seawater and have a low reuse rate; semiconductor materials have a narrow absorption band, which leads to a complex preparation method for photothermal conversion materials; graphene in carbon-based materials is difficult to apply in actual production due to its high price. Biomass waste is cheap and renewable, and is an abundant carbon source. Therefore, membrane materials based on biomass waste are a good type of photothermal interfacial steam conversion material.

[0005] Cattail is a perennial herb, born in lakes, rivers or ponds in shallow water, widely distributed all over the world. Cattail grows rapidly, has a large output and is widely distributed. As a kind of aquatic plant, it can be used to beautify water surface and wetland, and has obvious purification effect on eutrophic water body simultaneously. Cattail leaf is the main part of cattail, its top is flat, middle part is slightly concave, lower part is gradually raised into convex shape, cross section is semicircular, intercellular space is large, aeration tissue is very developed, sponge-like, has strong ventilation capacity and water absorption capacity, can transport water and nutrients quickly and effectively. However, in my country, cattail is used for weaving, papermaking etc., and utilization rate is very low, and cattail is not utilized as raw material to be prepared into photothermal interface conversion material in the prior art. Summary of the invention

[0006] In view of this, the present invention proposes a cattail-based photothermal interface evaporation material and a preparation method and application thereof, in order to solve or partially solve the problems existing in the prior art.

[0007] In a first aspect, the present invention provides a method for preparing a cattail-based photothermal interface evaporation material, comprising the following steps:

[0008] Placing cattail in a tube furnace and heating it to 350-950°C at 3-10°C / min, carbonizing it for 1-3 hours to obtain carbon powder;

[0009] Add cattail into a reaction kettle, then add sodium hydroxide solution and react at 150-180° C. for 10-15 hours, and wash to obtain cattail leaf cellulose;

[0010] Add cattail leaf cellulose into a container, then add water, stir, then add carbon powder, and filter to obtain a cattail-based photothermal film, which is a cattail-based photothermal interface evaporation material.

[0011] Preferably, the method for preparing the cattail-based photothermal interface evaporation material comprises placing the cattail in a tubular furnace for carbonization, washing the carbonized cattail with a 1-3M hydrochloric acid solution, washing with water until neutral, and drying and then ball-milling to obtain carbon powder.

[0012] Preferably, in the method for preparing the cattail-based photothermal interface evaporation material, the concentration of the sodium hydroxide solution is 1-3M.

[0013] Preferably, in the method for preparing the cattail-based photothermal interface evaporation material, in the step of adding cattail leaf cellulose into a container, adding water, stirring, adding carbon powder, and filtering to obtain a cattail-based photothermal film, the mass volume ratio of cattail leaf cellulose, carbon powder and water is (1-2) g: (0.1-0.3) g: (20-30) ml.

[0014] Preferably, the method for preparing the cattail-based photothermal interface evaporation material further comprises bundling the cattail leaves into bundles as a water-conducting material, and placing the prepared cattail-based photothermal film on the cattail leaf water-conducting material to obtain the cattail-based photothermal interface evaporation material.

[0015] Preferably, in the method for preparing the cattail-based photothermal interface evaporation material, the carbon powder is obtained by ball milling after drying, wherein the ball milling time is 20 to 40 minutes.

[0016] In a second aspect, the present invention further provides a cattail-based photothermal interface evaporation material, which is prepared by the preparation method.

[0017] In a third aspect, the present invention also provides an application of the cattail-based photothermal interface evaporation material in seawater desalination and sewage treatment.

[0018] The cattail-based photothermal interface evaporation material of the present invention and its preparation method and application have the following beneficial effects compared with the prior art:

[0019] 1. The preparation method of the cattail-based photothermal interface evaporation material of the present invention uses cattail as raw material to prepare a cattail-based photothermal film for photothermal conversion. The prepared cattail-based photothermal film has a three-dimensional pore structure, super hydrophilic and water-conducting ability, and good light absorption performance; cattail as a carbon source can effectively absorb sunlight to achieve photothermal conversion, and at the same time, cattail leaves are used as hydrophilic and water-conducting materials to improve water evaporation efficiency and salt resistance. Compared with other solar light absorbers such as graphene, the low-priced cattail-based photothermal interface conversion material is easier to meet the application of seawater desalination in real life. The cattail-based photothermal interface evaporation material prepared by this application has the following advantages: it can effectively desalinate seawater, purify groundwater and dye wastewater; it has good recycling stability; it has a higher photothermal conversion efficiency, which can reach 75% to 85%; the raw materials are renewable, the cost is low, and it can be applied on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 This is a flow chart of the preparation method of the cattail-based photothermal interface evaporation material of the present invention;

[0022] Figure 2 This is a photo of the cattail-based photothermal film prepared in Example 1 of the present invention;

[0023] Figure 3 This is a surface morphology of the cattail-based photothermal film prepared in Example 1 of the present invention;

[0024] Figure 4 This is the ultraviolet-visible-near-infrared absorption spectrum of the cattail-based photothermal film prepared in Example 1 of the present invention;

[0025] Figure 5 The hydrophilic property of the cattail-based photothermal film prepared in Example 1 of the present invention;

[0026] Figure 6 The cattail-based photothermal interface evaporation material prepared in Example 1 of the present invention is used to desalinate seawater outdoors;

[0027] Figure 7 Comparison of cation concentrations in seawater and in water vapor collected from desalinated seawater;

[0028] Figure 8 This is a comparison chart of the ultraviolet spectra of dye wastewater and the collected purified dye wastewater. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] The present application embodiment provides a method for preparing a cattail-based photothermal interface evaporation material, such as Figure 1 As shown, the following steps are included:

[0032] S1, placing cattail in a tube furnace, heating it to 350-950°C at 3-10°C / min, and carbonizing it for 1-3h to obtain carbon powder;

[0033] S2, adding cattail into a reaction kettle, then adding sodium hydroxide solution to react at 150-180° C. for 10-15 hours, and washing to obtain cattail leaf cellulose;

[0034] S3, adding cattail leaf cellulose into a container, then adding water, stirring, then adding carbon powder, filtering to obtain a cattail-based photothermal film, that is, a cattail-based photothermal interface evaporation material.

[0035] In some embodiments, after placing the cattail in a tubular furnace for carbonization, the method further includes washing the carbonized cattail with a 1-3M hydrochloric acid solution, then washing with water until neutral, and then drying and ball milling to obtain carbon powder.

[0036] In some embodiments, the concentration of the sodium hydroxide solution is 1-3M.

[0037] In some embodiments, in the step of adding cattail leaf cellulose into a container, then adding water, stirring, adding carbon powder, and filtering to obtain a cattail-based photothermal film, the mass volume ratio of cattail leaf cellulose, carbon powder and water is (1-2) g: (0.1-0.3) g: (20-30) ml.

[0038] In some embodiments, the method further includes bundling cattail leaves into bundles as water-conducting materials, and placing the prepared cattail-based photothermal film on the cattail leaf water-conducting materials to obtain the cattail-based photothermal interface evaporation material.

[0039] In some embodiments, the carbon powder is obtained by ball milling after drying, wherein the ball milling time is 20 to 40 minutes.

[0040] Specifically, in some embodiments, the method for preparing the cattail-based photothermal interface evaporation material comprises the following steps:

[0041] S1, cut the cattail leaves into 0.5-1 cm small segments for standby use, put 8-12 g of the cut cattail leaves into a crucible and place it in a tube furnace, heat it to 350-950 ° C at 3-10 ° C / min, keep carbonizing for 1-3 hours, cool it to room temperature, wash the carbonized cattail leaves with 10-20 ml 1M hydrochloric acid, wash the carbonized cattail carbon with tap water and deionized water until neutral, dry it, and then put it into a ball mill for 20-40 minutes to obtain carbon powder;

[0042] S2, adding 1-3 g of cattail leaves into a 100 ml reactor, then adding 60-80 ml of 1-3 M NaOH solution, reacting at 150-180° C. for 12 hours, washing with tap water and deionized water until neutral, and filtering under reduced pressure to obtain cattail leaf cellulose;

[0043] S3, taking 1-2 g of the cattail leaf cellulose prepared in step S2 into a 50 ml beaker, then adding 20-30 ml of deionized water, magnetically stirring for 30 min to completely disperse the cattail leaf cellulose, then adding 0.1-0.3 g of carbon powder, ultrasonicating for 30 minutes to completely adhere the carbon powder to the cattail leaf cellulose, and finally filtering under reduced pressure to obtain a cattail-based photothermal film that can evaporate water under sunlight;

[0044] S4, cutting cattail leaves into small segments of 3 to 10 cm, bundling them side by side into bundles as water-conducting materials, and placing the cattail-based photothermal film prepared in step S3 on the cattail leaf water-conducting materials to form a photothermal interface evaporation system.

[0045] Based on the same inventive concept, the present application also provides the application of the cattail-based photothermal interface evaporation material prepared by the above preparation method in seawater desalination and sewage treatment.

[0046] The preparation method of the cattail-based photothermal interface evaporation material of the present application uses cattail as raw material to prepare a cattail-based photothermal film for photothermal conversion. The prepared cattail-based photothermal film has a three-dimensional pore structure, super hydrophilic and water-conducting ability, and good light absorption performance; cattail as a carbon source can effectively absorb sunlight to achieve photothermal conversion, and at the same time, cattail leaves are used as hydrophilic and water-conducting materials to improve water evaporation efficiency and salt resistance. Compared with other solar light absorbers such as graphene, the low-priced cattail-based photothermal interface conversion material is easier to meet the application of seawater desalination in real life. The cattail-based photothermal interface evaporation material prepared by the present application has the following advantages: it can effectively desalinate seawater, purify groundwater and dye wastewater; it has good recycling stability; it has a higher photothermal conversion efficiency, which can reach 75% to 85%; the raw materials are renewable, the cost is low, and it can be applied on a large scale.

[0047] The preparation method and application of the cattail-based photothermal interface evaporation material of the present application are further described below with specific examples.

[0048] Example 1

[0049] The present application provides a method for preparing a cattail-based photothermal interface evaporation material, comprising the following steps:

[0050] S1, put 10g of cattail leaves into a crucible and place it in a tube furnace, heat it to 700℃ at 5℃ / min, keep carbonizing for 2h, cool it to room temperature, wash the carbonized cattail leaves with 10ml 1M hydrochloric acid, wash the carbonized cattail carbon with tap water and deionized water until neutral, dry it, and then put it into a ball mill and mill it for 30min to obtain carbon powder;

[0051] S2, adding 2 g of cattail leaves into a 100 ml reactor, then adding 80 ml of 3M NaOH solution, reacting at 180° C. for 12 hours, washing with tap water and deionized water until neutral, and filtering under reduced pressure to obtain cattail leaf cellulose;

[0052] S3, taking 1 g of the cattail leaf cellulose prepared in step S2 into a 50 ml beaker, then adding 30 ml of deionized water, magnetically stirring for 30 min to completely disperse the cattail leaf cellulose, then adding 0.1 g of carbon powder, ultrasonicating for 30 minutes to completely adhere the carbon powder to the cattail leaf cellulose, and finally filtering under reduced pressure to obtain a cattail-based photothermal film that can evaporate water under sunlight;

[0053] S4, cutting cattail leaves into 3 cm small segments, bundling them side by side into bundles as water-conducting materials, placing the cattail-based photothermal film prepared in step S3 on the cattail leaf water-conducting materials, and forming a photothermal interface evaporation system.

[0054] Comparative Example 1

[0055] This comparative example provides a method for preparing a cattail film, comprising the following steps:

[0056] S1, adding 2 g of cattail leaves into a 100 ml reactor, then adding 80 ml of 3M NaOH solution, reacting at 180° C. for 12 hours, washing with tap water and deionized water until neutral, and filtering under reduced pressure to obtain cattail leaf cellulose;

[0057] S2. Take 1 g of the cattail leaf cellulose prepared in step S1 and put it into a 50 ml beaker, then add 30 ml of deionized water, stir magnetically for 30 min to completely disperse the cattail leaf cellulose, and finally obtain a cattail film by vacuum filtration.

[0058] Performance Testing

[0059] The photo of the cattail-based photothermal film prepared in Example 1 is shown in FIG. Figure 2 shown.

[0060] The surface morphology of the cattail-based photothermal film prepared in Example 1 is as follows: Figure 3 Shown, magnification is 220.

[0061] The ultraviolet-visible-near-infrared absorption spectra of the cattail-based photothermal film prepared in Example 1, the carbon powder prepared in Example 1, and the cattail film prepared in Comparative Example 1 were tested. The results are as follows: Figure 4 Specifically, Figure 4 CT-C is the cattail-based photothermal film in Example 1, C is the carbon powder in Example 1, and CT is the cattail film in Comparative Example 1. Figure 4 Solar radiance refers to the curves of different bands of the solar spectrum.

[0062] The above-mentioned different materials were put into a UV-Vis-NIR spectrometer (Shimadzu, Japan, model SolidSpec-3700), and the light absorption properties of the materials were tested within the wavelength range of 250-2500nm. It was found that the light absorption property of the cattail film CT in Comparative Example 1 was relatively low, at about 40%, while the carbon powder C in Example 1 and the cattail-based photothermal film CT-C in Example 1 had very strong and similar light absorption properties, at about 98%, indicating that the cattail-based photothermal film is a potential high-efficiency photothermal interface evaporation material.

[0063] The cattail-based photothermal film CT-C prepared in Example 1 and the cattail film CT prepared in Comparative Example 1 were respectively adhered to a smooth glass sheet, and the glass sheet was placed on a glass plate of German Defei (model OAC25), and the hydrophilicity of the material was tested by the static drop method. The results are as follows: Figure 5 As shown. Figure 5 It can be seen that the material absorbs water droplets in a very short time, proving that the cattail-based photothermal film CT-C and the cattail membrane CT have strong hydrophilic properties.

[0064] The evaporation rate of water in the cattail-based photothermal interface evaporation material prepared in Example 1 was 1.3-1.8 kg m under 1 standard sunlight. -2 h -1 .

[0065] Specifically, during the interfacial evaporation process, sunlight irradiates the photothermal film, water is locally heated and evaporated, and the water-conducting material continuously transports the water at the bottom to the surface of the photothermal film to maintain the interfacial evaporation process. The specific experiment is as follows: Bundle the cattail leaves into bundles as a water-conducting material, wrap the outer surface with polystyrene foam as an insulation layer, place the prepared cattail-based photothermal film on the cattail leaf water-conducting material, and then place the entire material in a beaker filled with seawater or wastewater, and then place the entire beaker on a balance connected to a computer. When sunlight irradiates the photothermal material, the mass change of the water in the beaker is immediately recorded on the electronic balance and computer, and the water evaporation rate is tested for 60 minutes under stable conditions to evaluate the water evaporation rate of the material.

[0066] According to the existing solar energy conversion efficiency formula, the photothermal conversion efficiency of the photothermal interface evaporation material prepared by the present invention can reach 65% to 85%.

[0067] The solar energy conversion efficiency formula is:

[0068] Where η represents the solar energy conversion efficiency, m (kg m -2 h -1 ) is the water evaporation rate, ΔH v is the enthalpy of evaporation of water, which is 2260 (kJ kg -1 ), Cop t is the optical concentration, q0 is the radiant power of one sun (1kW m -2 ).

[0069] In 1 standard sunlight (1kW m -2 ) under irradiation, the photothermal interface evaporation material prepared in Example 1 was used repeatedly for 20 times, and the water evaporation efficiency did not decrease significantly, indicating that the photothermal conversion material prepared by the method of the present invention can be repeatedly used.

[0070] Under natural light intensity, the seawater desalination performance of the photothermal interface evaporation material prepared in Example 1 is evaluated as follows: Figure 6 and Figure 7 shown.

[0071] The specific test method is as follows: In order to collect the evaporated water, the cattail-based photothermal film is placed in a transparent hemispherical glass cover. The cattail-based photothermal film is placed on the cattail leaf water-conducting material. The water-conducting material is located in a container filled with water (simulating original seawater or dye wastewater). During the interface evaporation process, sunlight irradiates the photothermal film, and the water is locally heated and evaporated. The water-conducting material continuously transports the water at the bottom to the surface of the photothermal film to maintain the interface evaporation process; under the irradiation of sunlight ( Figure 6 The temperature of the surface of the cattail-based photothermal film measured by an infrared thermal imager before and after sunlight irradiation was 16.6°C and 33.9°C respectively. A large number of water droplets condensed on the spherical glass cover. The evaporated water droplets were collected and analyzed and compared with the original seawater or dye (specifically methylene blue) wastewater to determine the ability of the photothermal film to desalinate seawater and purify dye wastewater. Take the purification of dye wastewater as an example: the water evaporated by the cattail-based photothermal film and the original dye wastewater were placed in a UV-visible spectrophotometer (Beijing Puxi, model TU-1950) respectively. The characteristic absorption peak of methylene blue can be clearly found in the dye wastewater, while the characteristic absorption peak of methylene blue disappears in the water obtained by photothermal distillation, proving that the cattail-based photothermal film can effectively purify dye wastewater.

[0072] from Figure 7 It can be seen that the Na in the collected water vapor + , K + Mg 2+ , Ca 2+ The concentration is compared to the original Na + , K + Mg 2+ , Ca 2+ The concentration is significantly reduced and the ion concentration meets the WHO standard.

[0073] from Figure 8It can be seen that the absorbance of methylene blue in the collected water vapor is significantly reduced compared with the absorbance of methylene blue in the original water, indicating that the cattail-based photothermal membrane of the present application can effectively purify dye wastewater.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. Application of a cattail-based photothermal interface evaporation material in seawater desalination and sewage treatment, and a method for preparing the cattail-based photothermal interface evaporation material, comprising the following steps: S1, put 10g of cattail leaves into a crucible and place it in a tube furnace, heat it to 700℃ at 5℃ / min, keep carbonizing for 2h, cool it to room temperature, wash the carbonized cattail leaves with 10ml 1M hydrochloric acid, wash the carbonized cattail carbon with tap water and deionized water until neutral, dry it, and then put it into a ball mill and mill it for 30min to obtain carbon powder; S2, adding 2 g of cattail leaves into a 100 ml reactor, then adding 80 ml of 3M NaOH solution, reacting at 180° C. for 12 hours, washing with tap water and deionized water until neutral, and filtering under reduced pressure to obtain cattail leaf cellulose; S3, taking 1 g of the cattail leaf cellulose prepared in step S2 into a 50 ml beaker, then adding 30 ml of deionized water, magnetically stirring for 30 min to completely disperse the cattail leaf cellulose, then adding 0.1 g of carbon powder, ultrasonicating for 30 minutes to completely adhere the carbon powder to the cattail leaf cellulose, and finally filtering under reduced pressure to obtain a cattail-based photothermal film that can evaporate water under sunlight; S4, cutting cattail leaves into 3 cm small segments, bundling them side by side into bundles as water-conducting materials, placing the cattail-based photothermal film prepared in step S3 on the cattail leaf water-conducting materials, and forming a photothermal interface evaporation system.

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