Solar interface evaporation composite photothermal material and preparation method and application thereof

Abstract

This invention discloses a solar interface evaporation composite photothermal material, its preparation method, and its application, belonging to the field of solar energy utilization and wastewater treatment technology. The material uses cenospheres or hollow glass microspheres as a matrix, with a photothermal layer composed of carbon black and asphalt composited on the surface. The mass ratio of the three is 100:(3~7):(12~20), preferably 100:5:16. The preparation method includes: ultrasonically dispersing the matrix material, carbon black, and asphalt in petroleum ether, loading and drying them via rotary evaporation, and then subjecting them to air-blowing hydrophilication treatment. This material is used to improve the evaporation efficiency of calcium-containing industrial wastewater by forming a photothermal interface on the liquid surface. This invention further proposes a synergistic method: solar evaporation is performed using the material during the day, while gas is blown into the liquid at night to enhance evaporation. The material of this invention is low in cost and has good stability. Its synergistic method with nighttime bubbling can increase the evaporation efficiency by more than 40% compared to the blank, significantly outperforming single technologies, and providing an efficient solution for the energy-saving treatment of high-calcium, corrosive industrial wastewater.

Description

Technical Field

[0001] This invention belongs to the field of solar energy utilization and industrial wastewater treatment technology, specifically relating to a composite photothermal material for solar interface evaporation technology, its preparation method and application, especially suitable for the concentration treatment of high-salt, high-calcium, and corrosive industrial waste liquids (such as ammonia-calcium distillate). Background Technology

[0002] Solar interface evaporation technology utilizes photothermal materials to locally convert solar energy into thermal energy, directly driving water evaporation at the gas-liquid interface. It has advantages such as low energy consumption, simple equipment, and environmental friendliness, and shows great potential in the fields of seawater desalination and wastewater treatment.

[0003] Photothermal materials are the core of this technology. Currently, high-performance photothermal material systems mainly fall into the following categories: First, ceramic-based materials, represented by Ti2AlSnC MAX phase nanofiber membranes, exhibit good stability under extreme environments, but their synthesis process is complex, costly, and their texture is brittle (see Wang Y et al., Ti2AlSnC MAX Phase Nanofiber Membranes for Solar-Driven Interfacial Evaporation in Extreme Environments, ACS Nano, 2025). Second, layered MoS2 / Ti3C2T... x Two-dimensional materials, represented by heterojunctions, have high photothermal conversion efficiency, but Ti3C2T... x The components are easily oxidized and degraded under acidic conditions, and the uniformity of large-area preparation is difficult to control (see Rong, K. et al., Hierarchical MoS2 / Ti3C2T). x Heterostructure with excellent photothermal conversion performance for solar-driven vapor generation, Acta Phys. -Chim.Sin., 2025, 41(6), 100053). Thirdly, perovskite hybrid materials (such as Cs2SnI6 / graphene) have broad infrared spectral absorption, but they are easily decomposed and degraded by calcium liquid moisture and temperature. In addition, some materials contain heavy metals such as lead and tin, which pose a pollution risk (see Zhao, FY et al., Double perovskite Cs2AgInCl6:Cr 3+: broadband and near-infrared luminescent materials, Inorg. Chem. Front., 2019, 6, 3621).

[0004] In contrast, carbon-based materials have attracted widespread attention due to their low cost and wide spectral absorption range. For example, the carbon black / cellulose nanofiber (CNF) composite material developed by Li Jinbao's team has a high solar light absorption rate (92.05%) and good hydrophilicity, but its preparation depends on a time-consuming freeze-drying process, resulting in low mass production efficiency (see Li Jinbao, Xie Zhuhang, Yang Xue, et al., Preparation and performance study of carbon black / CNF composite photothermal conversion materials, China Pulp & Paper, 2020, 39(07):1-6). The carbon black / cellulose acetate nanofiber network material developed by Zhang Rui et al. of Nanjing University has excellent photothermal properties, but cellulose acetate may hydrolyze at pH < 4, and its mechanical strength is weak. Its long-term stability in complex industrial environments such as strong acid and high calcium salt has not been verified (see Zhang R, Zhou YW, Xiang B, et al. Scalable Carbon Black Enhanced Nanofiber Network Films for High-Efficiency Solar Steam Generation, Advanced Materials Interfaces, 2021, 8(21):2101160). In addition, other carbon-based composite materials such as basalt fiber fabric matrix (CDs / CB@BF), modified biochar matrix, and MOF-derived carbon matrix also have problems such as complicated preparation process, high raw material cost, easy coating peeling in high calcium salt environment, and unstable performance (see He, YL et al., Invasive plant-derived carbon dots and carbon black co-deposited basalt fiber fabric as an efficient solar interface evaporator for high salinity water purification, Separation and Purification Technology, 2025, 365, 132644).

[0005] At the application level, treating high-concentration calcium solutions (such as ammonia-distilled calcium solutions) generated by industries like steel and chemicals faces unique challenges: these solutions are characterized by high temperatures, strong corrosiveness, and a tendency to scale. Traditional multi-effect distillation methods for treating such solutions consume extremely high energy (approximately 200 kg of standard coal equivalent per ton), and suffer from severe equipment corrosion and scaling, resulting in high maintenance costs. Applying solar interfacial evaporation technology to this field holds the promise of significantly reducing energy consumption. However, existing solar thermal materials are either too expensive to be industrialized or lack stability under the highly corrosive and easily crystallizing conditions of calcium solutions, limiting the practical application of this technology.

[0006] Therefore, developing a low-cost, simple-process, chemically stable, and highly efficient photothermal material that can withstand long-term exposure to high-calcium and corrosive industrial wastewater environments, and matching it with an efficient and low-energy-consumption enhanced evaporation strategy, has become the key to promoting the application of solar interfacial evaporation technology in this field. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-cost, simple-to-prepare, and stable solar interfacial evaporation composite photothermal material suitable for the treatment of calcium-containing waste liquid in high-salt industries, as well as its preparation method and application.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a solar interfacial evaporation composite photothermal material. The material uses lightweight porous cenospheres or hollow glass microspheres as a matrix, and a photothermal functional layer composed of carbon black and asphalt is uniformly laminated onto the surface of the matrix. The mass ratio of the matrix material, carbon black, and asphalt is 100:(3~7):(12~20). Preferably, the mass ratio is 100:5:16, at which the photothermal conversion performance and cost of the material are optimally balanced. More preferably, the material undergoes a hydrophilic treatment to make its surface hydrophilic, thereby enabling better moisture transport during application.

[0009] Secondly, the present invention provides a method for preparing the composite photothermal material, comprising the following steps: (1) Ingredients: Weigh the matrix material, carbon black and pitch according to the above mass ratio; (2) Dispersion: Add the above materials together to a low-boiling-point organic solvent (such as petroleum ether) and sonicate them to disperse and mix them initially; (3) Loading and molding: Organic solvents are removed by rotary evaporation. During this process, the molten pitch firmly adheres to and coats the carbon black onto the surface of the matrix material to form a primary composite material. (4) Drying: The obtained primary composite material is dried to obtain a hydrophobic basic photothermal material.

[0010] Furthermore, to enhance its hydrophilicity, the method further includes step (5) hydrophilic modification: immersing the dried primary composite material in an electrolyte aqueous solution (such as sodium chloride aqueous solution) and continuously blowing air into the solution for surface oxidation treatment for 0.5 to 48 hours; then filtering and drying to obtain a hydrophilic composite photothermal material.

[0011] Thirdly, this invention provides the application of the composite photothermal material in improving the evaporation efficiency of calcium-containing industrial waste liquid (especially calcium liquid with ammonia stripping). Specifically, the application involves laying the hydrophilically treated composite photothermal material on the surface of the calcium liquid to be treated, forming a photothermal evaporation interface, and utilizing solar energy to drive evaporation.

[0012] Furthermore, to overcome the bottleneck of a single technology and achieve efficient evaporation in all weather conditions, this invention proposes a synergistic enhancement method. Specifically, during the day or when there is sunshine, the composite photothermal material laid on the liquid surface is used for solar interface evaporation; at night or when there is no sunshine, gas (such as air) is bubbled into the calcium solution. The bubbling effect removes saturated vapor from the liquid surface and disturbs the water, further enhancing water evaporation. This spatiotemporal synergistic mode of "daytime photothermal + nighttime bubbling" can significantly improve the overall evaporation efficiency.

[0013] Furthermore, to fully utilize solar energy, sinking photothermal materials such as carbon black can be dispersed and added at the bottom of the calcium solution or in the water body as a bottom photothermal layer, forming a double-layer photothermal structure with the composite photothermal material on the liquid surface, thereby realizing the three-dimensional absorption and utilization of solar energy.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. Extremely low cost and easy industrialization: This invention uses industrial by-product cenospheres or inexpensive hollow glass microspheres as the matrix, and widely available and inexpensive carbon black and pitch as photothermal functional raw materials. The preparation process is simple, involving only conventional dispersion, evaporation, and drying steps, requiring no complex equipment or harsh conditions, making it very suitable for large-scale production.

[0015] 2. Excellent and stable performance: The hollow structure inside the material provides excellent thermal insulation and reduces the density of the composite material, which is beneficial for its floating on the surface of calcium liquid. The surface-coated carbon black and asphalt layer achieves broad-spectrum and efficient absorption. The asphalt coating effectively enhances the adhesion of the carbon black and the overall chemical inertness of the material, making it exhibit excellent long-term stability in corrosive environments with high temperature, high salt, and high calcium, and it is not easy to decompose or fail.

[0016] 3. Significantly Improved Evaporation Efficiency: Laboratory tests show that when this material is applied to ammonia-calcium liquid evaporation, the solar evaporation efficiency can be increased by more than 30% compared to the control group. When a synergistic mode of "daytime solar thermal material evaporation + nighttime bubbling" is adopted, the overall evaporation efficiency of the system can be increased by more than 40%, or even higher, providing a new, highly efficient, and energy-saving approach to solving the problem of high-energy-consuming calcium liquid treatment.

[0017] 4. Highly innovative application strategy: The proposed "spatiotemporal synergy" application method cleverly combines the technical characteristics of solar energy (intermittent) and bubbling (continuous). It maximizes the use of free solar energy during the day and maintains a high evaporation rate at night using low-energy bubbling, thereby maximizing the system's energy efficiency. It has strong practicality and innovation. Attached Figure Description

[0018] Figure 1 These are photographs of various composite photothermal materials prepared in the embodiments of the present invention.

[0019] Figure 2 A scanning electron microscope (SEM) image of the beaded material (material 1) used as the matrix.

[0020] Figure 3 SEM image of material 2 prepared in Example 1.

[0021] Figure 4 SEM image of material 3 prepared in Example 1.

[0022] Figure 5 SEM image of material 4 prepared in Example 1.

[0023] Figure 6 SEM image of material 5 prepared in Example 1.

[0024] Figure 7 SEM image of material 6 prepared in Example 1.

[0025] Figure 8 SEM image of material 7 prepared in Example 1.

[0026] Figure 9 SEM image of material 8 prepared in Example 1.

[0027] Figure 10 The graph shows the relationship between the vapor pressure of calcium solution and the height of the bubbling liquid column at 15℃.

[0028] Figure 11 The graph shows the relationship between the vapor pressure of calcium solution at 25℃ and the height of the bubbling liquid column.

[0029] Figure 12 The graph shows the relationship between the vapor pressure of calcium solution at 60℃ and the height of the bubbling liquid column.

[0030] Figure 13 The diagram shows an experiment using photothermal materials and bubbling in tandem, where (a) shows only photothermal materials used and (b) shows both photothermal materials and bubbling used simultaneously. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0032] Example 1: Preparation and Characterization of Composite Photothermal Materials This embodiment details various specific preparation methods of the composite photothermal material described in the claims, and its physical form is as follows: Figure 1 As shown, its microstructure was characterized by scanning electron microscopy (SEM), such as... Figures 2-9 As shown.

[0033] Material 1 (Comparison Matrix): Commercially available cenospheres were purchased directly. Its SEM image ( Figure 2 The data shows that the matrix material consists of spherical particles with a rough surface and pinhole-like pores, exhibiting good adsorption properties.

[0034] Material 2: Weigh 100g of cenospheres, 3g of carbon black, and 16g of asphalt, mix them, and add 1000mL of petroleum ether. Sonicate for 0.5 hours. Then remove the petroleum ether by rotary evaporation. After drying, immerse the primary composite material in an electrolyte aqueous solution (such as sodium chloride aqueous solution) and continuously bubble air into the solution for surface treatment for 48 hours. After filtration and drying, the hydrophilic composite photothermal material 2 is obtained. Its SEM image (… Figure 3 The results show that the photothermal material has adhered to the substrate surface, but still retains some porous structure.

[0035] Material 3 (preferred ratio): The preparation method is the same as that of Material 2, except that the amount of carbon black is adjusted to 5g to obtain Material 3. Its SEM image ( Figure 4 The surface pores are basically filled, formed by the agglomeration and stacking of small particles.

[0036] Material 4: The preparation method is the same as that of Material 2, except that the amount of carbon black is adjusted to 7g, thus obtaining Material 4. Its SEM image ( Figure 5 The surface appears relatively smooth, but there are some deep pits and holes.

[0037] Material 5 (carbon black-free comparison): 100g of cenospheres and 16g of asphalt were weighed and prepared according to the above method to obtain Material 5. Its SEM image ( Figure 6 The surface appears smooth and dense.

[0038] Material 6 (with a different matrix): The matrix was replaced with 100g of hollow glass microspheres, and 5g of carbon black and 16g of pitch were added. The mixture was prepared according to the method described in Material 2 to obtain Material 6. Its SEM image (…) Figure 7 The surface appears smooth.

[0039] Material 7 (Short-term hydrophilicization): First, a primary composite material was prepared according to the formulation of Material 3. Then, it was bubbled with air in an electrolyte aqueous solution (such as sodium chloride aqueous solution) for 0.5 hours, filtered, and dried to obtain Material 7. Its SEM image ( Figure 8 The surface is uneven, and the photothermal material is attached to the substrate surface.

[0040] Material 8 (unhydrophilized): A primary composite material was prepared according to the formulation of Material 3, but after removing petroleum ether by rotary evaporation, it was not subjected to gas-blowing hydrophilization treatment, resulting in Material 8. Its SEM image ( Figure 9 The surface appears relatively smooth and dense.

[0041] Example 2: Test on the performance improvement of calcium liquid evaporation by composite photothermal materials This embodiment tests the effect of the material prepared in Example 1 on improving the evaporation rate of calcium distillate solution under natural sunlight. An evaporation experiment was conducted using a crystallizing dish to hold the calcium solution. The evaporation amount was calculated by measuring the mass loss, and the improvement rate was calculated based on a blank experiment.

[0042] 1. The necessity of hydrophilic treatment: Test data are shown in Table 1 below. Unmodified hydrophobic material 8 reduced evaporation by 11%, while material 3, after hydrophilic treatment, increased evaporation by more than 36%. This proves that surface hydrophilicity is a prerequisite for efficient evaporation.

[0043] Table 1. Effect of surface modification and non-modification on evaporation rate of material 8 2. Evaporation efficiency of different photothermal materials The performance comparison data of various materials at the same addition amount (12g) are shown in Table 2 below.

[0044] Table 2 Evaporation efficiency of different photothermal materials 3. The effect of usage amount on evaporation efficiency For the preferred materials 3 and 7, the effect of dosage was examined. The data are shown in Table 3 below. In an evaporation system with a diameter of 20 cm, increasing the dosage from 12 g to 15 g further increased the daytime evaporation rate from 33%-36% to 41%-43%, indicating the existence of an optimal dosage range.

[0045] Table 3. Effect of Photothermal Material Usage on Evaporation Efficiency 4. The effect of single-layer or double-layer photothermal materials on evaporation efficiency A bilayer photothermal structure was constructed by combining 15g of surface-floating material 3 or material 7 with 5g of bottom carbon black (powder material 1). The effect data are shown in Table 4 below. The evaporation rate increase of the bilayer structure (58%) was significantly better than that of using the surface material (43%) or the bottom material alone (26%), confirming the synergistic effect of the structure.

[0046] Table 4. Effect of Single-Layer or Double-Layer Photothermal Materials on Evaporation Efficiency Example 3: Synergistic Method of Photothermal Materials and Bubbling This embodiment demonstrates that combining photothermal materials with bubbling technology, especially the synergistic method of "daytime photothermal evaporation + nighttime bubbling enhancement", can significantly improve the overall evaporation efficiency of the system.

[0047] 1. Synergistic Effect Verification: Under the same experimental conditions, the comparison data of the effects of using only Material 3 and "Material 3 + Bubbling" are shown in Table 5 below. The coupled mode further increased the evaporation rate from 43% to 70%, proving that the two have a synergistic enhancement effect.

[0048] Table 5. Effect of Bubbling and Photothermal Material Coupling on Evaporation Rate 2. Key findings regarding the timing of bubbling use: such as Figure 13 As shown, bubbling during the day disturbs the photothermal material layer on the liquid surface, affecting its light absorption. The effect data for different bubbling times are shown in Table 6. Under the condition of using material 3, bubbling only at night results in an overall 24-hour evaporation increase of up to 84%; while bubbling only during the day results in an increase of only 15%. This finding indicates that scheduling bubbling operations primarily at night (during periods without sunlight) avoids interfering with the photothermal process and utilizes the residual heat accumulated in the water during the day to achieve efficient evaporation around the clock. This "spatiotemporal synergy" strategy is one of the core application methods of this invention.

[0049] Table 6. The effect of the coupling method of bubbling and photothermal materials on evaporation rate. 3. Guidance on the optimization of bubbling parameters: Bubbling kinetics research ( Figures 10-12The data shows that increasing the bubbling gas flow rate, gas temperature, or calcium solution temperature can all improve the evaporation efficiency of the bubbling process. For example, data (see Table 7-9) shows that increasing the gas flow rate from 0.5 L / min to 2 L / min increases the evaporation efficiency by 118%; heating the gas to 49°C further increases the evaporation efficiency by 92%. Meanwhile, at higher temperatures, the bubbling point (liquid column height) has a more significant impact on the evaporation effect. Figure 12 To reduce energy consumption, the bubbling position should be as close to the liquid surface as possible. These parameters provide specific guidance for optimizing the synergistic method.

[0050] Table 7 Effect of gas flow rate on evaporation efficiency Note: Liquid column height 15 cm, tube inner diameter 93 mm, gas temperature 25 ℃, calcium solution temperature 25 ℃ Table 8 Effect of gas temperature on bubbling evaporation rate Note: Liquid column height 15 cm, tube inner diameter 93 mm, calcium solution temperature 25 ℃, gas flow rate 1.0 L·min -1 Table 9. Effect of calcium solution temperature on bubbling evaporation rate Note: Liquid column height 15 cm, tube inner diameter 93 mm, gas temperature 25 ℃, gas flow rate 1.0 L·min -1 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 present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a solar interface evaporative composite photothermal material, characterized in that, Includes the following steps: (1) Weigh the matrix, carbon black and pitch in a mass ratio of 100:(3~7):(12~20; the matrix is ​​cenospheres or hollow glass microspheres; (2) Add the above materials together to petroleum ether solvent and perform ultrasonic dispersion treatment; (3) The petroleum ether solvent is removed by rotary evaporation, so that the asphalt and carbon black are blended and adhered to the surface of the matrix material; (4) The obtained material is dried to obtain a primary composite material; (5) The dried primary composite material is placed in an electrolyte aqueous solution and air is blown into the solution for surface treatment. Then it is filtered and dried to obtain a hydrophilic composite photothermal material.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the matrix material, carbon black, and pitch is 100:5:

16.

3. The application of a composite photothermal material prepared by the method described in claim 1 in improving the evaporation efficiency of calcium-containing industrial waste liquid.

4. The application according to claim 3, characterized in that, The application involves laying the composite photothermal material on the surface of calcium-containing industrial waste liquid and using solar energy for interfacial evaporation.

5. The application according to claim 4, characterized in that, The application also includes introducing a bubbling operation into the calcium-containing industrial waste liquid to synergistically enhance evaporation.

6. The application according to claim 5, characterized in that, The bubbling operation is mainly scheduled to be carried out during periods without sunlight.

7. The application according to claim 4 or 5, characterized in that, While laying the composite photothermal material as the surface photothermal layer, carbon black or hydrophilic particles loaded with carbon black are also added to the calcium-containing industrial waste liquid as the bottom photothermal layer, forming a double-layer photothermal evaporation structure.

8. A synergistic method for improving the evaporation efficiency of ammonia-calcium distillation solution, characterized in that, include: During the day, the composite photothermal material prepared by the method described in claim 1 is laid on the surface of the calcium ammonia vaporization solution, and solar energy is used for photothermal interface evaporation; At night, gas is bubbled into the calcium ammonia solution to further enhance water evaporation through the bubbling effect.

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