Graphene oxide photo-thermal water evaporation material with plastic shape as well as preparation method and application of graphene oxide photo-thermal water evaporation material

Abstract

The invention relates to a shape-plastic graphene oxide water evaporation material as well as a preparation method and application thereof. A high-concentration graphene oxide dough-shaped material with plasticity is prepared through evaporation concentration and a directional freezing method. The three-dimensional porous graphene oxide dough evaporator is constructed by combining a directional freezing method with hydrogen-bond interaction between a high-concentration graphene oxide sheet layer and water molecules. The graphene oxide dough evaporator has high shape plasticity and efficient photo-thermal water evaporation rate, can effectively remove metal ions in real seawater and saline water, and is good in salt resistance and long-term stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of photothermal water evaporation, and specifically relates to a method for preparing a highly plastic graphene oxide photothermal water evaporation material, and the application of the material in solar-driven water evaporation and seawater desalination. Background Art

[0002] Currently, industrial desalination technologies primarily include distillation and membrane separation. However, their practical application is limited to a few regions due to high equipment costs and high energy consumption. Solar-driven desalination technology, which uses solar energy to evaporate seawater to produce crystallized fresh water, is an efficient, green, and low-cost technology considered an effective way to alleviate the freshwater shortage crisis.

[0003] Graphene oxide (GO) is a carbon-based two-dimensional sheet material obtained by oxidative exfoliation of graphite. Compared to a perfect graphene honeycomb lattice, graphene oxide retains graphene's high mechanical strength and excellent photothermal conversion performance. At the same time, through chemical oxidation, it introduces oxygen-containing functional groups such as hydroxyl, epoxy, carboxyl, and carbonyl groups, giving it excellent hydrophilicity and solution dispersibility, providing abundant chemical reaction sites and high controllability. With its unique physicochemical properties and controllable characteristics, graphene oxide has great application prospects in a variety of fields, including energy storage and conversion, flexible electronics, biomedicine, and composite materials. Currently, a large number of literature has been published on the use of graphene oxide to prepare composite materials for research in the field of solar-driven water evaporation.

[0004] Existing graphene oxide evaporators are mostly two-dimensional planar structures or simple three-dimensional structures. Those prepared directly from graphene oxide dispersions typically form thin films or porous sponges, which acquire a defined shape during the material preparation stage and cannot be reshaped. This hinders the graphene oxide evaporator's ability to absorb sunlight from all directions under natural conditions, thereby limiting its evaporation efficiency. Dough, a highly ductile and viscoelastic material, can be easily reshaped without breaking, making it highly advantageous for fabricating independent, complex structures. Therefore, developing a plastic, dough-like graphene oxide photothermal conversion material could address the challenges of evaporator macroscopic design. Because graphene oxide sheets tend to aggregate at the air-water interface, obtaining a uniform, high-concentration graphene oxide dispersion without any binder or crosslinker is difficult. High-concentration graphene oxide dough is obtained through evaporation and concentration, supplemented by sufficient stirring to prevent localized aggregation of graphene oxide sheets. The resulting high-viscosity graphene oxide dough, with a mass fraction between 4.5% and 26.6%, is easily processable and can be manually kneaded into any shape, making it easy to reshape, connect, pattern, and further process.

[0005] In addition, the problem of salt crystal accumulation also seriously affects the long-term stability of the material. In order to ensure that salt does not accumulate on the surface of the evaporator, it is necessary to ensure sufficient water supply, adjust the pore structure inside the photothermal conversion material, and adjust the hydrophilicity of the surface. In order to ensure that the photothermal conversion material has a stable water transmission channel, a nanosponge is used as a water supply device to provide sufficient water to the photothermal conversion material on the top, which can alleviate the problem of salt accumulation to a certain extent. The directional freezing method can form an interconnected pore structure inside the graphene oxide material, and the oxygen-containing functional groups can combine with water to form a large number of hydrogen bonds, ensuring the hydrophilicity of the material, thereby obtaining a photothermal conversion material with good salt crystallization resistance. Summary of the Invention

[0006] To address the structural design issues, salt accumulation issues, and complex preparation methods of existing graphene oxide-based solar-thermal water evaporation materials in applications in the field of solar-driven solar-thermal water evaporation, the present invention provides a shape-plastic graphene oxide solar-thermal water evaporation material, a preparation method, and applications. A dough-like graphene oxide solar-thermal water evaporation material with high plasticity and water transport properties is obtained through evaporation concentration and directional freezing. The preparation method of the present invention is easy to operate and has a simple process. The graphene oxide dispersion is converted into a highly plastic graphene oxide dough by evaporation concentration. The dough has high plasticity and can be manually kneaded into any shape, making it easy to reshape, connect, pattern the surface, and further process. The directional freezing method forms an interconnected pore structure within the graphene oxide dough, resulting in high hydrophilicity, high light absorption across the entire spectrum, and good water supply capacity. When applied to seawater desalination, the dough exhibits excellent water evaporation performance and salt tolerance, alleviating the problem of freshwater resource shortages.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] A method for preparing a shape-plastic graphene oxide (GO) material for photothermal evaporation comprises the following steps: evaporating and concentrating a 1% (mass) graphene oxide dispersion to obtain a high-concentration GO dough; shaping the dough, placing it on a copper cylinder immersed in liquid nitrogen for directionally freezing; and thawing the dough at room temperature to obtain the shape-plastic GO GO material for photothermal evaporation. The material is highly plastic and can be manually kneaded into any shape, making it easy to reshape, connect, pattern, and further process.

[0009] In a preferred embodiment of the present invention, the preparation method comprises the following steps:

[0010] (1) Measure a certain volume of graphene oxide dispersion, ultrasonically crush it and stir it continuously, and at the same time, slowly add a certain amount of anhydrous ethanol to the graphene oxide dispersion and stir it evenly;

[0011] (2) placing the dispersion obtained in step (1) and its beaker in a glass crystallizing dish filled with a certain amount of water to simulate water bath heating, and placing it on a magnetic heating stirrer for heating and stirring. After a period of time, the magnetic stirrer becomes difficult to stir. The magnetic stirrer and the water bath heating device are removed, and the dispersion and its beaker are placed directly on the magnetic heating stirrer for further heating and manual stirring until a dough-like graphene oxide material with a plastic shape is obtained;

[0012] (3) The dough-like graphene oxide material obtained in step (2) is manually shaped, placed on a copper column soaked in liquid nitrogen for directionally freezing, and then thawed at room temperature to obtain a graphene oxide photothermal water evaporation material.

[0013] In a preferred embodiment of the present invention, in step (1), the mass fraction of the graphene oxide dispersion is 1%, the volume ratio of the graphene oxide dispersion to anhydrous ethanol is 30:1, and the ultrasonic crushing time is 30 minutes.

[0014] In a preferred embodiment of the present invention, in step (2), the first waterbath heating and stirring step is performed at a temperature of 70-90°C, a rotation speed of 600-1400 rpm, and a duration of 2-4 hours. Preferably, the heating and stirring temperature is 80°C, and the waterbath heating device and the magnet are removed when the magnetic stirring device fails to stir the upper surface of the graphene oxide dispersion. Evaporation and concentration are then performed again at a hot plate temperature of 80-95°C for 1-2 hours. Preferably, the hot plate temperature is 90°C, and the duration is when the viscosity of the graphene oxide dispersion increases to the point where it becomes unable to flow and adheres to form dough-like lumps, thereby controlling the solid mass fraction of the resulting graphene oxide dough.

[0015] In a preferred embodiment of the present invention, in step (3), the dough-like graphene oxide is shaped by manual kneading, pressing, or using a mold for shaping, the liquid nitrogen temperature is -196°C, the directional freezing time is 10-20 minutes, preferably 15 minutes, and the thawing time at room temperature is greater than 1 hour.

[0016] The present invention also protects the use of the dough-shaped graphene oxide photothermal evaporation material for photothermal evaporation and seawater desalination. In a preferred embodiment of the present invention, a certain volume of salt water or seawater is placed inside an uncovered transparent glass container. A sponge block, as tall as the container, is soaked in the water to supply water to the upper surface. The upper lid of the container is covered with aluminum foil for insulation, with a hole cut in the center of the foil that is the same shape as the bottom of the graphene oxide dough evaporator. Finally, the graphene oxide dough evaporator is placed at the center hole of the aluminum foil at the top of the glass container, with water supplied upward by the sponge block. A xenon lamp is used to simulate sunlight and shine directly on the top of the evaporator. A densitometer is used to calibrate the intensity of sunlight. An electronic balance and computer software are used to record the change in water mass over time during the photothermal evaporation process.

[0017] In a preferred embodiment of the present invention, the sponge is a high-density nanosponge, the aluminum foil is tinfoil aluminum foil, the uncovered transparent glass container is a cylindrical open glass cup, the certain volume of salt water or seawater is a liquid that is two-fifths of the solvent in the container, and the central opening of the aluminum foil should be consistent with the bottom area of the graphene oxide evaporator.

[0018] In summary, the shape-modifiable graphene oxide solar-heated water evaporation material prepared by the present invention exhibits high plasticity, excellent water transport properties, and a high solar-heated water evaporation rate. This shape-modifiable graphene oxide solar-heated water evaporation material is used for water evaporation and seawater desalination, and the resulting evaporator exhibits excellent salt tolerance and long-term stability. Compared to existing technologies, the present invention has the following advantages:

[0019] 1. The present invention utilizes the technical route of evaporation concentration and directional freezing to realize the preparation of shape-plastic graphene oxide photothermal water evaporation material.

[0020] 2. The shape-plastic graphene oxide photothermal water evaporation material prepared by the present invention has good plasticity and good hydrophilicity, can quickly transport water, and has excellent shape plasticity and water evaporation performance.

[0021] 3. The shape-molded graphene oxide photothermal evaporation material prepared by the present invention is used for water evaporation and seawater desalination, and has good salt resistance and long-term stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The following is further explained with reference to the accompanying drawings.

[0023] Figure 1 This is a schematic diagram of the preparation of Example 1 of the present invention;

[0024] Figure 2 This is a picture of the transition from dispersion to dough and the plastic shape in Example 1 of the present invention;

[0025] Figure 3 These are scanning electron microscope images of horizontal and vertical cross-sections of GO dough in Example 1 of the present invention;

[0026] Figure 4 The XRD pattern and infrared spectrum of GO dough in Example 1 of the present invention are shown;

[0027] Figure 5 The mass change curve and water evaporation rate diagram of GO dough with different solid contents at 1 sun in Example 1 of the present invention;

[0028] Figure 6 The images and SEM images of the horizontal and vertical sections of the bionic flower-shaped GO dough evaporator in Example 2 of the present invention are shown;

[0029] Figure 7 Graph showing mass change and water evaporation rate of GO dough at 1 sun after different freezing times in Example 2 of the present invention;

[0030] Figure 8 The water evaporation rate graph and infrared thermal imaging graph of GO-F2 in Example 2 of the present invention in 3.5wt% NaCl solution and pure water for 12 hours;

[0031] Figure 9 This is a diagram of the water evaporation rate of GO-2 in pure water, 3.5 wt% NaCl solution and seawater in Example 1 of the present invention, as well as the changes in metal ion concentration before and after seawater desalination. DETAILED DESCRIPTION

[0032] The following embodiments of the present invention are specifically described to make the technical content of the present invention more obvious and easy to understand, but this is only used to explain the present invention, and the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] A method for preparing a shape-plastic graphene oxide photothermal water evaporation material comprises the following steps:

[0035] (1) 150 mL of 1 wt% graphene oxide dispersion was measured and ultrasonically crushed for 30 min with continuous stirring. At the same time, 5 mL of anhydrous ethanol was slowly added dropwise to the graphene oxide dispersion and stirred evenly.

[0036] (2) placing the dispersion obtained in step (1) and its beaker in a glass crystallizing dish filled with a certain amount of water to simulate water bath heating, placing it on a magnetic heating stirrer and evaporating and concentrating it at 80°C for 4 hours, removing the magnetic stirrer and the water bath heating device when the magnetic stirrer is difficult to stir, placing the dispersion and its beaker directly on the magnetic heating stirrer to continue evaporating the water, maintaining the hot plate temperature at 90°C, and manually stirring until a dough-like graphene oxide material with a certain mass fraction is obtained;

[0037] (3) The dough-like graphene oxide material obtained in step (2) was kneaded and cut into blocks with a length, width, and height of 10 mm, 10 mm, and 5 mm, respectively, and placed on a copper column soaked in liquid nitrogen for directional freezing for 15 minutes. The block was then thawed at room temperature for 1 hour to obtain a graphene oxide photothermal water evaporation material.

[0038] In order to evaluate the plasticity of dough-like graphene oxide materials, graphene oxide dough was prepared into different shapes without using a mold and with using a mold. Figure 2 Digital photos of graphene oxide transitioning from dispersion to dough and after shaping.

[0039] SEM scanning images ( Figure 3) It can be seen that there are many interconnected channels in the horizontal direction of the GO dough evaporator, with a size of 10-50μm. The channel structure in the vertical direction has a certain degree of orientation. There are many interconnected micron-level pores between the tightly stacked graphene oxide. These channels can quickly transfer moisture from the bottom to the surface and the entire dough, which is conducive to moisture evaporation and reduces salt crystal aggregation.

[0040] In order to evaluate the changes in the chemical composition and crystal structure of each sample in Example 1, XRD and FTIR tests were performed ( Figure 4 ). From the XRD pattern, it can be seen that GO has two characteristic peaks, namely the 001 diffraction peak at 12.2° and the 100 diffraction peak at 41.5°. The position of the 001 peak can be used to calculate that the interlayer spacing of graphene oxide is 0.782nm, which is larger than the interlayer spacing of natural graphite (0.34nm). The low intensity of the (100) peak further confirms that the sp2 domain is highly fragmented and GO has many defects. Similarly, the Fourier transform infrared spectrum of GO shows that GO has a high density at 3405cm -1 There is a significant absorption peak at 1726 cm -1 The peak is the stretching vibration peak of C=O on the carboxyl group, at 1619 cm -1 The absorption peak at 1045 cm belongs to the bending vibration peak of C-OH. -1 、876cm -1 The absorption peaks at correspond to the vibrations of CH and COC, respectively. This indicates that the GO surface contains abundant oxygen-containing functional groups such as hydroxyl and carboxyl groups, which can form a large number of hydrogen bonds with water molecules, ensuring the hydrophilicity and water transfer rate of GO.

[0041] Example 2

[0042] A method for preparing a shape-plastic graphene oxide photothermal water evaporation material comprises the following steps:

[0043] (1) 150 mL of 1 wt% graphene oxide dispersion was measured and ultrasonically crushed for 30 min with continuous stirring. At the same time, 5 mL of anhydrous ethanol was slowly added dropwise to the graphene oxide dispersion and stirred evenly.

[0044] (2) placing the dispersion obtained in step (1) and its beaker in a glass crystallizing dish filled with a certain amount of water to simulate water bath heating, placing it on a magnetic heating stirrer and evaporating and concentrating it at 80°C for 4 hours, removing the magnetic stirrer and the water bath heating device when the magnetic stirrer is difficult to stir, placing the dispersion and its beaker directly on the magnetic heating stirrer to continue evaporating the water, maintaining the hot plate temperature at 90°C, and manually stirring until a dough-like graphene oxide material with a certain mass fraction is obtained;

[0045] (3) The dough-like graphene oxide material obtained in step (2) was manually processed into oval petals using a glass rod. Multiple layers of petals were stacked to form a biomimetic flower-shaped GO dough evaporator with a diameter of 18 mm and a height of approximately 15 mm at the highest point of the petals. The prepared biomimetic flower-shaped GO dough evaporator was placed on a copper column soaked in liquid nitrogen and subjected to directionally frozen for 15 minutes. It was then thawed at room temperature for 1 hour to return to room temperature. A single freeze-thaw cycle was designated as GO-F1; two cycles of the same freeze-thaw cycle were designated as GO-F2, and three cycles were designated as GO-F3.

[0046] Figure 6 The SEM image of the bionic flower-shaped GO dough evaporator obtained in Example 2 is shown. It can be seen that within the petals of the GO dough evaporator, the GO sheets appear in a layered structure with local parallel arrangement along the direction of applied external force. This structure forms a layered structure further in the part of the petals of the GO dough evaporator close to the outer layer. This can shorten the water transmission path inside the bionic flower-shaped GO dough evaporator to a certain extent, making it possible to prepare evaporators with larger areas.

[0047] Example 3

[0048] In order to evaluate the water evaporation performance of the GO dough evaporator and the GO-F dough evaporator obtained in step (3) of Example 1 and Example 2, water evaporation tests in pure water and salt water were carried out. The specific test methods are as follows:

[0049] Two-fifths of the total volume of a transparent glass container without a lid is filled with pure water or a 3.5% NaCl solution by mass. A sponge block as high as the container is soaked in the water to supply water to the upper surface. The upper lid of the container is covered with aluminum foil for insulation, and a hole in the center of the aluminum foil is cut out in the same shape as the bottom of the graphene oxide dough evaporator. Finally, the graphene oxide dough evaporator is placed on the center hole of the aluminum foil at the top of the glass container, and water is supplied upward by the sponge block. A xenon lamp is used to simulate sunlight directly on the top of the evaporator. A densitometer is used to calibrate the intensity of sunlight. An electronic balance and computer software are used to record the change in water mass over time during the photothermal water evaporation process.

[0050] Figure 5 The mass change curves and water evaporation rates corresponding to evaporating pure water for 1 h under one sun are shown in Example 1 for GO-1, GO-2, and GO-3 evaporators with different graphene oxide mass fractions;

[0051] Figure 7 The mass change curves and water evaporation rates corresponding to evaporating pure water for 1 h under one sun are shown for GO-F1, GO-F2, and GO-F3 evaporators corresponding to different freeze-thaw times in Example 3.

[0052] Figure 8The water evaporation rate of GO-F2 in 3.5wt% NaCl solution and pure water for 12 hours in Example 3 and the infrared thermal imaging of the top surface during water evaporation indicate the long-term stability of GO-F3 in salt water and that the evaporation rate is not much different from that in pure water.

[0053] Example 4

[0054] In order to evaluate the performance of the GO-2 dough evaporator obtained in step (3) of Example 1 in evaporating desalinated seawater, Bohai seawater was purchased and tested for water evaporation rate and metal ion concentration before and after evaporation. The specific test methods are as follows:

[0055] The steam condensation apparatus is based on the existing evaporation apparatus in Example 3. A custom-made glass container is attached to a suitably sized crystallizing dish, and the opening is sealed with plastic wrap. When evaporating under a xenon lamp, the generated water vapor condenses on the cooler glassware, flows down the walls of the container, and is collected in the crystallizing dish. The collected evaporated seawater is then analyzed by ICP-MS to determine the ion concentration in the desalinated seawater.

[0056] Figure 9 The following graph shows the evaporation rate of GO-2 in pure water, a 3.5wt% NaCl solution, and Bohai Seawater, as well as its ability to desalinate metal ions from seawater, as described in Example 4. As can be seen from the graph, the evaporation rate of the GO-2 evaporator in seawater is slightly lower than that in pure water, but higher than that in a 3.5wt% NaCl solution. The ion concentration in seawater after evaporation by the GO-2 drops by more than two orders of magnitude, meeting the World Health Organization's standards for drinking water.

[0057] The specific embodiments listed in this specification are primarily intended to help understand the technical implementation path of the present invention. The detailed descriptions should not be construed as limiting the scope of patent protection, and modifications or improvements may be made. Therefore, any implementation that does not deviate from the spirit of the present invention is within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a shape-plastic graphene oxide light-heat water evaporation material, characterized in that: The preparation method is an evaporation concentration method. After the graphene oxide dispersion is evaporated and concentrated, a plastic graphene oxide dough is obtained. After shaping, it is placed in liquid nitrogen for directionally freezing, and then thawed at room temperature to obtain a graphene oxide photothermal water evaporation material with shape plasticity.

2. The graphene oxide light-heat water evaporation material according to claim 1, characterized in that: The mass fraction of the graphene oxide dispersion gradually increases during the evaporation and concentration process, and the state changes from a dilute dispersion to a gel state and finally to a solid dough state. The mass fraction of graphene oxide in the dough state graphene oxide material is between 4.5% and 26.6%.

3. The graphene oxide light-heat water evaporation material according to claim 1, characterized in that: The graphene oxide photothermal water evaporation material has shape plasticity and can be placed in a mold to form different shapes. The shape remains stable after the mold is removed. It can also be made into various complex structures by manual methods such as kneading and pressing. Multiple structures can be quickly bonded together.

4. The graphene oxide light-heat water evaporation material according to claim 1, characterized in that: After directional freezing and room temperature thawing, the graphene oxide photothermal water evaporation material has a pore structure inside, the pores are interconnected, and the graphene oxide sheets are tightly stacked together.

5. The method for preparing the graphene oxide light-heat water evaporation material according to claim 1, wherein: The following steps are involved: (1) Measure a certain volume of graphene oxide dispersion, ultrasonically crush it and stir it continuously, and at the same time, slowly add a certain amount of anhydrous ethanol to the graphene oxide dispersion and stir it evenly; (2) placing the dispersion obtained in step (1) and its beaker in a glass crystallizing dish filled with a certain amount of water to simulate water bath heating, and placing it on a magnetic heating stirrer for heating and stirring. After a period of time, the magnetic stirrer becomes difficult to stir. The magnetic stirrer and the water bath heating device are removed, and the dispersion and its beaker are placed directly on the magnetic heating stirrer for further heating and manual stirring until a dough-like graphene oxide material with a plastic shape is obtained; (3) The dough-like graphene oxide material obtained in step (2) is manually shaped, placed on a copper column soaked in liquid nitrogen for directionally freezing, and then thawed at room temperature to obtain a graphene oxide photothermal water evaporation material.

6. The preparation method according to claim 5, characterized in that In step (1), the mass fraction of the graphene oxide dispersion is 1%, the volume ratio of the graphene oxide dispersion to anhydrous ethanol is 30:1, and the ultrasonic crushing time is 30 minutes.

7. The preparation method according to claim 5, characterized in that The following conditions should be met in step (2): (1) The temperature during the first water bath heating and stirring is 70-90°C, preferably, the heating and stirring temperature is 80°C; (2) The speed used during the first water bath heating and stirring is 600-1400 rpm; (3) The first water bath heating and stirring time is 2-4 hours, and the time limit is when the magnetic stirring cannot stir the upper surface of the graphene oxide dispersion; (4) In the process of removing the water bath heating and the magnetic evaporation concentration, the evaporation concentration temperature is set to the hot plate temperature of the magnetic heating stirrer, which is 80-95°C. The upper limit of the temperature is that the graphene oxide dispersion at the bottom of the beaker does not aggregate and precipitate due to thermal reduction due to excessive temperature when heated; preferably, the hot plate temperature is 90°C; (5) The water bath heating and magnetic evaporation and concentration process were removed, and manual stirring was performed using a custom-made polytetrafluoroethylene rod; (6) The time for removing the water bath heating and magnetic evaporation concentration process is 1-2 hours, and the time limit is when the viscosity of the graphene oxide dispersion increases to the point where it cannot flow and adheres to form dough-like lumps. The viscosity is related to the mass fraction of graphene oxide. By controlling the viscosity of the graphene oxide dough, dough-like graphene oxide materials with different mass fractions can be obtained.

8. The preparation method according to claim 5, characterized in that In step (3), the dough-like graphene oxide is shaped by manual kneading, pressing, or using a mold for shaping, the liquid nitrogen temperature is -196°C, the directional freezing time is 10-20 minutes, preferably, the directional freezing time is 20 minutes, and the thawing time at room temperature is greater than 1 hour.

9. A shape-modifiable graphene oxide dough evaporator, characterized in that: By using different molds or manual methods in the preparation method according to any one of claims 1 to 8, graphene oxide light-heat water evaporation materials of different shapes, namely graphene oxide dough evaporators, can be prepared.

10. Use of the graphene oxide water evaporation material according to any one of claims 1 to 4, or the graphene oxide water evaporation material prepared by the preparation method according to any one of claims 5 to 9, in solar thermal water evaporation and seawater desalination.

11. The use according to claim 10, characterized in that A certain volume of salt water or seawater is placed inside a transparent glass container without a lid. A sea sponge as tall as the container is soaked in the water to supply water to the upper surface. The upper lid of the container is covered with aluminum foil for insulation, and a hole in the center of the aluminum foil is cut out in the same shape as the bottom of the graphene oxide dough evaporator. Finally, the graphene oxide dough evaporator is placed on the hole in the center of the aluminum foil at the top of the glass container. Water is supplied upward by the sponge. A xenon lamp is used to simulate sunlight light directly on the top of the evaporator. A densitometer is used to calibrate the intensity of sunlight. An electronic balance and computer software are used to record the change in water mass over time during the photothermal water evaporation process.

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