A salt-resistant biomass photothermal interface evaporation material, its preparation method and application

Abstract

This invention discloses a salt-tolerant biomass photothermal interface evaporation material, its preparation method, and its application. The method includes the following steps: S1, peeling a fresh cactus, cutting the pulp into chunks, and placing it in water, heating at 50-70°C under stirring; S2, removing the cactus chunks obtained in step S1 from the water and placing them on a heated plate so that one plane of the chunks contacts the high-temperature heating plate, until the treated surface becomes a black carbonized layer with a thickness of 0.8-1.2 mm; S3, uniformly coating pyrrole onto the carbonized layer of the cactus pulp, then uniformly coating the pyrrole-coated carbonized layer with a 50-80 mM oxidant aqueous solution, allowing for a complete polymerization reaction to obtain the salt-tolerant biomass photothermal interface evaporation material—polypyrrole@cactus. This salt-tolerant biomass photothermal interface evaporation material can be applied in solar-driven interface evaporation, photothermal seawater desalination, and wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of photothermal interface evaporation material preparation technology, specifically to a salt-resistant biomass photothermal interface evaporation material, its preparation method, and its application. Background Technology

[0002] Powered by green, recyclable solar energy, an emerging water purification process generates pure water through interfacial water evaporation, demonstrating environmental friendliness and sustainability. The unique aspect of this technology is that it facilitates rapid water evaporation without requiring additional energy input or large-scale infrastructure. A key challenge in solar interfacial evaporation is ensuring that the thermal conversion of solar energy occurs solely at the gas-liquid interface, maximizing the use of the generated heat for water evaporation in that area without transferring it to the entire water body and causing its temperature to rise.

[0003] To maximize the efficiency of solar energy utilization, a range of materials with photothermal conversion properties—including carbon-based compounds, metal nanoparticles, polymers, and plasma-absorbing materials—have been integrated into solar distillation systems. To reduce the cost of water acquisition, researchers are actively exploring an economical and ecologically balanced approach: converting renewable biomass into high-value materials with photothermal properties.

[0004] Given its ubiquity and abundant supply in nature, biomass, as a type of renewable energy, boasts low acquisition costs and a unique porous structure, facilitating rapid collection from a wide range of environments. Biomass feedstocks, processed through surface carbonization, are typically used as core components in the manufacture of solar steam generation equipment.

[0005] In other words, to improve the effective use of solar energy, various photothermal materials, such as carbon materials, nanoscale metal particles, polymer compounds, and plasma light-absorbing components, have been incorporated into solar evaporation technology. While pursuing reduced water resource acquisition costs, efforts are being made to develop a cost-effective and environmentally responsible strategy: transforming renewable biomass into value-added materials with photothermal functions. Considering that biomass is a widely available renewable energy source in nature, it is not only inexpensive but also possesses a unique porous structure, making it easy to collect from various sources. Therefore, biomass materials currently show great promise in seawater desalination. Zongxing Liu et al. (2024) reported on the carbonization of winter melon technology, disclosing Ti3C2T derived from winter melon. X / Carbon aerogel, exhibiting excellent photothermal conversion performance in solar vapor generation (Ti3C2Tx / carbonaerogels derived from winteretrolon for high-efficiency photothermal conversion, Desalination, Volume 573, 15 March 2024, 117207). Chinese Patent (Announcement No. CN113968994B) discloses a method for preparing photothermal biomass aerogels for solar interfacial evaporation using natural porous cellulose biomass materials (such as eggplant, loofah, sugarcane, radish, yam, bamboo, and straw). The obtained photothermal biomass aerogels for solar interfacial evaporation have excellent photothermal properties and can continuously and efficiently convert aqueous solutions into water vapor under sunlight. They can be used as photothermal interfacial evaporation materials for seawater desalination and wastewater purification.

[0006] Although biomass-integrated solar steam generation systems have demonstrated significant technological leaps, practical applications still face challenges such as cumbersome production processes, low evaporation efficiency, difficulty in obtaining raw materials, susceptibility to seasonal limitations, and low evaporation rates in high-concentration brine. These factors constitute significant obstacles. Therefore, there is an urgent need to develop a novel solar interface evaporation material, characterized by a simple preparation process, excellent photothermal conversion efficiency, and economical production costs. Summary of the Invention

[0007] The purpose of this invention is to address the above-mentioned problems by providing a salt-resistant biomass photothermal interface evaporation material, its preparation method, and its application.

[0008] To achieve its objective, the present invention employs the following technical solution:

[0009] The first aspect of this invention provides a method for preparing a salt-resistant biomass photothermal interface evaporation material, comprising the following steps:

[0010] S1. Peel the fresh cactus, cut the pulp into chunks, put it in water, and heat it at 50-70°C with stirring to soften the pulp and remove sugars and impurities (such as cytoplasmic impurities on the surface of the pulp).

[0011] S2. Take the blocky cactus pulp obtained after step S1 out of the water and place it on a heating plate so that one plane of the blocky pulp is in contact with the high-temperature heating plate until the surface being treated becomes a black carbonized layer.

[0012] S3. Apply pyrrole evenly to the carbonized layer of cactus pulp, then apply an aqueous solution of oxidant with a concentration of 50-80mM evenly to the carbonized layer coated with pyrrole. Allow it to fully polymerize to obtain salt-resistant biomass photothermal interface evaporation material - polypyrrole@cactus.

[0013] Preferably, the oxidant is selected from one or more of ammonium persulfate, Fe2(SO4)3, and FeCl3.

[0014] Preferably, the concentration of the oxidant solution is 55–65 mM.

[0015] Preferably, in step S1, the stirring speed of the stir bar is 500-700 r / min, the heating time under stirring conditions is 32-40 h, and the water is changed every 3-6 h.

[0016] Preferably, in step S2, the cactus pulp is heated on a plate at a temperature of 300-500°C until the carbonized layer thickness reaches 0.8-1.2 mm (more preferably 0.9-1.1 mm); preferably, the plate is a metal plate, and the heating time is 3-5 minutes.

[0017] Preferably, in step S3, 40-60 microliters of pyrrole are used for coating per square centimeter of carbonized layer, and then 40-60 microliters of an oxidant aqueous solution are used for coating per square centimeter of carbonized layer.

[0018] The polymerization reaction time is 0.5 to 2 hours, preferably 0.7 to 1.3 hours.

[0019] Preferably, the blocky cactus pulp is rectangular, cylindrical, prismatic, conical, or other polyhedral.

[0020] Preferably, the blocky cactus pulp is rectangular in shape, with its length, width, and height set in the following proportions: length 0.5–1.5 cm, width 0.5–1.5 cm, and height 1–3 cm. The blocky cactus pulp is not limited to a rectangular shape, as long as it has a surface suitable for forming a carbonized layer.

[0021] A second aspect of the present invention provides a salt-resistant biomass photothermal interface evaporation material, which is prepared by any of the preparation methods described above.

[0022] A third aspect of the present invention provides the application of the above-mentioned salt-resistant biomass photothermal interface evaporation material in solar-driven interface evaporation, photothermal seawater desalination, and wastewater treatment.

[0023] The beneficial effects of this invention are:

[0024] 1. As a plant that grows in the desert, the pulp of the cactus has excellent hydrophilicity, but there is currently no research on using cactus pulp as an interfacial evaporation material for seawater desalination. This invention is the first to develop a novel, low-cost, salt-tolerant biomass interfacial evaporation material made from cactus, and its interfacial evaporation rate is higher than that of most biomass materials.

[0025] 2. The cactus used in this invention is not limited by season, has low cost, and the preparation process only requires simple water bath heating and top surface carbonization to obtain the substrate. There is no need for complicated and energy-consuming operation steps such as freeze drying. The process is simple and easy to operate, and can realize large-scale mass production.

[0026] 3. Currently, the production processes of most carbon-based biomass interface evaporation materials, such as carbonized winter melon and carbonized eggplant, are relatively complex, requiring expensive and energy-intensive equipment such as muffle furnaces and freeze dryers. However, the cactus pulp of this invention only requires placing its surface on a preheated iron plate, using a surface carbonization scheme to replace the traditional overall carbonization scheme of biomass materials. Furthermore, its evaporation rate is far higher than that of traditional biomass materials such as carbonized winter melon and carbonized eggplant.

[0027] 4. The polypyrrole@cactus of the present invention has good salt resistance and exhibits a relatively good water evaporation rate even in high-concentration salt water of 25 wt%.

[0028] 5. The polypyrrole@cactus of the present invention has excellent photothermal properties: it can rapidly heat up under sunlight and convert water into water vapor, achieving efficient interfacial evaporation. Under one ray of sunlight, its interfacial evaporation rate can reach 3.6 kg / m³. 2 / h, and as can be seen from Comparative Example 2, even without photothermal modification of the material, a high water evaporation rate can be obtained by simply performing surface carbonization treatment on the cactus pulp, with a water evaporation rate as high as 2.9 kg / m³. 2 / h, cactus is an excellent biomass material for seawater desalination interface evaporation.

[0029] 6. Compared to directly carbonizing cactus pulp to obtain photothermal properties, this invention uses a simple chemical polymerization method to grow polypyrrole on its top. This not only avoids a large amount of energy consumption but also retains the hydrophilicity of the cactus pulp itself, resulting in high evaporation efficiency, mild conditions, and strong operability. This invention uses cactus as a biomass material, which is environmentally friendly, green, and non-toxic (edible cactus), therefore, there are no concerns about water pollution when using it as an interfacial evaporation material. Attached Figure Description

[0030] Figure 1 The upper surface of the photothermal layer of cactus pulp ( Figure 1 a) and the lower surface of the aquifer ( Figure 1 (b) Water contact angle.

[0031] Figure 2 Example 2 ( Figure 2 a) and Comparative Example 2 Figure 2 b) Infrared thermal imaging changes over 1 hour under sunlight.

[0032] Figure 3 The products obtained in Examples 1-5 and Comparative Examples 1-2 were subjected to sunlight (1000 W / m²). 2 The curve showing the change in the mass of water in a beaker over time under irradiation.

[0033] Figure 4 The water evaporation rate of the product prepared in Example 2 in real seawater and at different salt concentrations.

[0034] Figure 5 The evaporation rate of the product prepared in Example 2 in deionized water, North Sea seawater, and 25 wt% NaCl aqueous solution during 30 cycles of the experiment. Detailed Implementation

[0035] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0037] Example 1:

[0038] 1. Peel the fresh cactus, cut it into chunks (1cm*1cm*1cm), and then put it into ultrapure water and heat and stir (temperature: 65℃, speed: 600r / min) for 36 hours, changing the water every four hours.

[0039] 2. Place the pulp obtained after heating and stirring in step 1 in a petri dish, wipe off the excess water on the surface with absorbent paper, and then place it on an iron plate at a temperature of about 400℃ and heat for 3-5 minutes until the treated surface is completely turned into a black carbonized layer with a thickness of about 1mm.

[0040] 3. Take 50 μL of 99% pure pyrrole (CAS No.: 109-97-7) solution and coat it evenly on the carbonized layer. Prepare a 60 mM ammonium persulfate solution, and then take 50 μL of the prepared ammonium persulfate solution and coat it evenly on the carbonized layer with pyrrole. Polymerize for 1 hour to obtain polypyrrole@cactus.

[0041] Using natural biomass cactus as the substrate, it is heated and stirred in a magnetic heating stirrer to soften the pulp, remove sugars and cytoplasmic impurities on the surface of the pulp, and open the water transport channels of the cactus pulp. Then, the upper surface is heated to form a carbonized layer, and polypyrrole is then uniformly grown on the surface of the carbonized layer. The excellent photothermal properties of polypyrrole, combined with the excellent hydrophilicity of the cactus pulp, achieve efficient interfacial water evaporation.

[0042] Example 2:

[0043] 1. Peel the fresh cactus, cut it into chunks (1cm*1cm*2cm), and then put it into ultrapure water and heat and stir (temperature: 65℃, speed: 600r / min) for 36 hours, changing the water every four hours.

[0044] 2. Place the pulp obtained after heating and stirring in step 1 in a petri dish, wipe off the excess water on the surface with absorbent paper, and then place it on an iron plate at a temperature of about 400℃ and heat for 3-5 minutes until the treated surface is completely turned into a black carbonized layer with a thickness of about 1mm.

[0045] 3. Take 50 μL of 99% pyrrole solution and coat it evenly onto the carbonized layer. Prepare a 60 mM ammonium persulfate solution, and then take 50 μL of the prepared ammonium persulfate solution and coat it evenly onto the carbonized layer with added pyrrole. Polymerize for 1 hour to obtain polypyrrole@cactus.

[0046] Example 3:

[0047] 1. Peel the fresh cactus, cut it into chunks (1cm*1cm*3cm), and then put it into ultrapure water and heat and stir (temperature: 65℃, speed: 600r / min) for 36 hours, changing the water every four hours.

[0048] 2. Place the pulp obtained after heating and stirring in step 1 in a petri dish, wipe off the excess water on the surface with absorbent paper, and then place it on an iron plate at a temperature of about 400℃ and heat for 3-5 minutes until the treated surface is completely turned into a black carbonized layer with a thickness of about 1mm.

[0049] 3. Take 50 μL of 99% pyrrole solution and coat it evenly onto the carbonized layer. Prepare a 60 mM ammonium persulfate solution, and then take 50 μL of the prepared ammonium persulfate solution and coat it evenly onto the carbonized layer with added pyrrole. Polymerize for 1 hour to obtain polypyrrole@cactus.

[0050] The difference between Examples 1-3 lies in the varying heights of the cactus pulp. Different heights (representing the height of the water transport layer) mean different water transport distances, resulting in varying resistances that the same volume of water must overcome to travel from the bottom of the pulp to the top photothermal layer. This leads to different amounts of water reaching the top photothermal layer within the same timeframe, affecting evaporation efficiency. This difference is unrelated to the proportion of the carbonized layer thickness to the total height. The different heights in Examples 1-3 are designed to ensure varying amounts of water reach the top carbonized layer within the same timeframe, resulting in different evaporation rates.

[0051] Example 4:

[0052] 1. Peel the fresh cactus, cut it into chunks (1cm*1cm*2cm), and then put it into ultrapure water and heat and stir (temperature: 65℃, speed: 600r / min) for 36 hours, changing the water every four hours.

[0053] 2. Place the pulp obtained after heating and stirring in step 1 in a petri dish, wipe off the excess water on the surface with absorbent paper, and then place it on an iron plate at a temperature of about 400℃ and heat for 3-5 minutes until the treated surface is completely turned into a black carbonized layer with a thickness of about 1mm.

[0054] 3. Take 50 μL of 99% pyrrole solution and coat it evenly on the carbonized layer. Prepare a 60 mM ferric chloride solution. Then take 50 μL of the prepared ferric chloride solution and coat it evenly on the carbonized layer with added pyrrole. Polymerize for 1 hour to obtain polypyrrole@cactus.

[0055] Example 5:

[0056] 1. Peel the fresh cactus, cut it into chunks (1cm*1cm*2cm), and then put it into ultrapure water and heat and stir (temperature: 65℃, speed: 600r / min) for 36 hours, changing the water every four hours.

[0057] 2. Place the pulp obtained after heating and stirring in step 1 in a petri dish, wipe off the excess water on the surface with absorbent paper, and then place it on an iron plate at a temperature of about 400℃ and heat for 3-5 minutes until the treated surface is completely turned into a black carbonized layer with a thickness of about 1mm.

[0058] 3. Take 50 μL of 99% pyrrole solution and coat it evenly onto the carbonized layer. Prepare a 60 mM ferric sulfate solution. Then take 50 μL of the prepared ferric sulfate solution and coat it evenly onto the carbonized layer with added pyrrole. Polymerize for 1 hour to obtain polypyrrole@cactus.

[0059] Comparative Example 1:

[0060] 1. Peel the fresh cactus and cut it into chunks (1cm*1cm*2cm).

[0061] 2. Place the pulp obtained after heating and stirring in step 1 in a petri dish, wipe off the excess water on the surface with absorbent paper, and then place it on an iron plate at a temperature of about 400℃ and heat for 3-5 minutes until the treated surface part turns into a black carbonized layer with a thickness of about 1mm. This will give you the original cactus interface evaporation material.

[0062] The difference between Comparative Example 1 and Example 2 is that the cactus was not subjected to water bath heating and stirring treatment or coated with pyrrole. The results showed that its evaporation rate in pure water was only 2.18 kg / m³. 2 / h.

[0063] Comparative Example 2:

[0064] 1. Peel the fresh cactus, cut it into chunks (1cm*1cm*2cm), and then put it into ultrapure water and heat and stir (temperature: 65℃, speed: 600r / min) for 36 hours, changing the water every four hours.

[0065] 2. Place the pulp obtained after heating and stirring in step 1 in a petri dish, wipe off the excess water on the surface with absorbent paper, and then place it on an iron plate at a temperature of about 400℃ and heat for 3-5 minutes until the treated surface part turns into a black carbonized layer with a thickness of about 1mm. This will give you the cactus interface evaporation material treated by water bath heating.

[0066] The difference between Comparative Example 2 and Example 2 is that polypyrrole was not grown on the carbonized layer of the cactus pulp; only a simple surface carbonization treatment was performed. The results showed that its evaporation rate in pure water was only 2.90 kg / m³. 2 / h.

[0067] Example 6 Performance Test

[0068] I. Contact Angle Test

[0069] Test methods: such as Figure 1 As shown, a contact angle measuring instrument (SDC-100, Dongguan Shengding Precision Instruments Co., Ltd.) was used to measure the photothermal layer of the upper surface of the cactus pulp. Figure 1 a) and the lower surface of the aquifer ( Figure 1 b) A water contact angle test was conducted.

[0070] Contact angle tests were performed on various parts of the product obtained in Example 2, and the results are as follows: Figure 1 As shown, where Figure 1 a represents the photothermal layer of the product. Figure 1 b represents the water delivery layer of the product.

[0071] from Figure 1 The contact angle image (b) shows that the cactus pulp, after being heated and stirred in a water bath, exhibits good hydrophilicity, with a contact angle of only 21.112°. Figure 1 As can be seen, the hydrophilicity of the cactus pulp after surface carbonization and photothermal modification is significantly reduced, changing from 21.112° to 70.957°. Without affecting the water supply, the reduction of the hydrophilicity of the photothermal layer is beneficial to enhance its surface roughness, thereby improving the light absorption capacity, and can also effectively inhibit the accumulation of salt.

[0072] II. Photothermal Heating Performance Test

[0073] Test method: Example 2 was recorded using a thermal imager (Testo 871, Testo Se&Co. Kgaa). Figure 2 a) and Comparative Example 2 Figure 2 b) The surface temperature change of the product under sunlight.

[0074] from Figure 2 As can be seen, obvious temperature stratification occurred in the water containing the products prepared in Example 2 and Comparative Example 2. The upper water in the beaker, i.e., the photothermal interface, showed a significant and concentrated temperature rise, exhibiting good thermal localization behavior. This indicates that the same amount of sunlight absorbed by the photothermal material can be more effectively converted into heat energy and concentrated at the interface to promote water evaporation, thereby reducing heat loss and increasing the evaporation rate. Figure 2 As can be seen, the product obtained in Example 2 under sunlight (1000W / m²) 2 Under irradiation, the surface temperature of the product prepared in Example 2 rapidly rose to 41°C within 10 minutes, while the surface temperature of the product prepared in Comparative Example 2 rose to 36°C within 10 minutes. The product prepared in Example 2 achieved a stable surface temperature of 44°C after 30 minutes, while the surface temperature of the product prepared in Comparative Example 2 rose more slowly and eventually stabilized at around 38°C. These results all indicate that the product prepared in Example 2 has excellent light absorption and photothermal conversion capabilities.

[0075] III. Water Evaporation Test

[0076] Test method: The prepared product was placed in a beaker containing 100ml of water and irradiated with a xenon lamp (Cel-S500) equipped with an AM 1.5 filter to simulate sunlight. Simultaneously, a solar energy meter (SM206-Solar) was used to calibrate and maintain the sunlight intensity at a level of 1000W / m². 2An electronic balance (AX224ZH / E) was used to record the mass loss of water in the beaker to measure the interfacial evaporation capacity of the sample. Another beaker containing 100 ml of water was placed in the balance and placed in a dark environment. The amount of natural evaporation of the system after 1 hour was recorded as a control group to calculate its actual evaporation efficiency.

[0077] Water evaporation tests were conducted on the products prepared in Examples 1, 2, 3, 4, 5, Comparative Example 1, and Comparative Example 2, respectively. The changes in the mass of water in the beakers of different samples under sunlight irradiation time are shown in the following results. Figure 3 As shown, under sunlight irradiation, the water mass in the beaker continuously changes with increasing irradiation time for pure water and different samples. In Example 2, the product obtained exhibits a water evaporation rate and efficiency of 3.6 kg / m³. 2 / h and 91.67% demonstrate that the polypyrrole@cactus of the present invention has excellent water evaporation effect.

[0078] IV. Salt Tolerance Test

[0079] Test method: In order to study the effect of aqueous solutions with different salt concentrations on the evaporation performance of polypyrrole@cactus, aqueous solutions of sodium chloride with mass fractions of 5 wt%, 10 wt%, 15 wt%, 20 wt%, and 25 wt% were prepared using deionized water and sodium chloride, respectively, and water evaporation experiments were conducted with the product prepared in Example 2. In addition, seawater from Beihai, Guangxi Zhuang Autonomous Region was collected in this study and water evaporation experiments were conducted with the product prepared in Example 2. The average salinity of the seawater was about 3.5 wt%.

[0080] To investigate the effect of different salt concentrations of aqueous solutions on the evaporation performance of polypyrrole@cactus, water evaporation experiments were conducted using deionized water and sodium chloride aqueous solutions with mass fractions of 5 wt%, 10 wt%, 15 wt%, 20 wt%, and 25 wt%, respectively, and the product prepared in Example 2. In addition, seawater from Beihai, Guangxi Zhuang Autonomous Region, was collected for water evaporation experiments with the product prepared in Example 2. The average salinity of the seawater was approximately 3.5 wt%.

[0081] from Figure 4 It can be seen that the product obtained in Example 2 still exhibits a water evaporation rate as high as 3.21 kg / m³ in real seawater. 2 / h, and also showed 1.54 kg / m in 25 wt% saline solution. 2 The water evaporation rate of / h demonstrates the excellent salt resistance of polypyrrole@cactus.

[0082] Evaporation rate is given by the formula The values ​​are: Δm (kg) represents the mass change of the evaporation system, t (h) represents the evaporation time, and S (m 2(This refers to the effective evaporation area of ​​the evaporator).

[0083] V. Durability Testing

[0084] Test method: The previous experiments showed that the polypyrrole@cactus of the present invention has good photothermal properties, water transport properties and salt resistance. In order to further understand the durability of polypyrrole@cactus, the product in Example 2 was subjected to 30 cycles of solar interface evaporation experiment (each experiment was conducted for 1 hour of light exposure, and after the experiment was completed, the product was placed in a dark environment for a period of time until the evaporation surface temperature of the material returned to room temperature before the next experiment was conducted).

[0085] The preceding experiments demonstrated the photothermal properties, water transport properties, and salt tolerance of the polypyrrole@cactus of this invention. To further investigate the durability of the polypyrrole@cactus, a solar interfacial evaporation experiment was conducted on the product from Example 2 in deionized water, North Sea seawater, and a 25wt% NaCl solution, with 30 cycles of each experiment (each cycle involving 1 hour of light exposure, followed by a period in darkness until the material's evaporation surface temperature returned to room temperature before the next cycle). The evaporation rates obtained from the experiments are as follows: Figure 5 As shown, in 30 consecutive cycles of solar interface evaporation experiments, the evaporation rate of the material prepared in this invention did not change significantly in pure water and North Sea water, with an average evaporation rate of 3.53 kg / m³. 2 / h and 3.14kg / m 2 The evaporation rate was 1.46 kg / m³ / h, and almost no salt crystallization was observed on the material surface in each experiment. However, as the salt concentration of the NaCl aqueous solution increased, salt precipitation occurred and the evaporation rate decreased. The average evaporation rate of the 25 wt% NaCl aqueous solution in 30 cycles of solar interface evaporation experiments was only 1.46 kg / m³. 2 The evaporation rate was measured at / h, and it decreased significantly with increasing cycle number, indicating that high-concentration brine has a certain impact on the evaporation rate of the material. Figure 5 It can be seen that, regardless of the salt concentration, the evaporation rate of this material changes little in 30 cycles of evaporation experiments, which demonstrates the good durability of polypyrrole@cactus.

Claims

1. A method for preparing a salt-tolerant biomass photo-thermal interface evaporation material, characterized in that, It comprises the following steps: S1, peeling fresh cactus, cutting the flesh into blocks and putting it into water, heating under stirring condition at 50-70℃ to soften the flesh and remove sugars and impurities; S2, taking the blocky cactus flesh treated in step S1 out of the water and putting it on a heated flat plate so that one plane of the blocky flesh contacts the high-temperature heated flat plate until the treated surface becomes a black carbonized layer; S3, taking pyrrole and uniformly coating it on the carbonized layer of the cactus flesh, then uniformly coating an oxidizing agent aqueous solution with a concentration of 50-80 mM on the carbonized layer coated with pyrrole, and fully polymerizing to obtain the salt-resistant biomass photo-thermal interface evaporation material polypyrrole@cactus.

2. The method of claim 1, wherein: The oxidizing agent is selected from one or more of ammonium persulfate, Fe2(SO4)3 and FeCl3.

3. The method of claim 1, wherein: The concentration of the oxidizing agent aqueous solution is 55-65 mM.

4. The method of claim 1, wherein: In step S1, the stirring speed of the stirring condition is 500-700 r / min, and the heating time under stirring condition is 32-40 h; the water is changed every 3-6 h.

5. The method of claim 1, wherein: In step S2, the cactus flesh is heated on a flat plate with a temperature of 300-500℃ until the carbonized layer reaches a thickness of 0.8-1.2 mm; the flat plate is a metal plate, and the heating time is 3-5 min.

6. The method of claim 1, wherein: In step S3, 40-60 microliters of pyrrole per square centimeter of carbonized layer are used for coating, and then 40-60 microliters of oxidizing agent aqueous solution per square centimeter of carbonized layer are used for coating; The polymerization reaction time is 0.5-2 h.

7. The method of claim 1, wherein: The blocky cactus pulp is rectangular parallelepiped, cylindrical, Prism, pyramid or other polyhedron.

8. The method of claim 7, wherein: The blocky cactus flesh is a rectangular cuboid, and the length, width and height are set in the following proportions: length 0.5-1.5 cm, width 0.5-1.5 cm, and height 1-3 cm.

9. A salt-tolerant bio-organic photothermal interface evaporation material, characterized in that: Prepared by the preparation method of any one of claims 1-8.

10. The salt-resistant biomass photo-thermal interface evaporation material of claim 9 is applied in solar-driven interface evaporation, photo-thermal seawater desalination and wastewater treatment.

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