Method for preparing solar water evaporation material based on sunflower stalk core and application thereof

Abstract

This invention discloses a method for preparing solar water evaporation materials based on sunflower stalk pith and its application. It utilizes the closed yet selectively permeable cell walls of sunflower stalk pith, an agricultural byproduct, as raw material. A light-absorbing layer is constructed on its surface, and the material is then soaked in water to obtain solar water evaporation materials based on sunflower stalk pith. This invention utilizes the unique closed and selectively permeable cell walls of sunflower stalk pith to separate water and volatile organic pollutants. A simple soaking method fills the cell cavities of the thin-walled cells in the sunflower stalk pith with water, thereby forming a rapid water transport pathway using the fully wetted cell walls. This results in a solar water evaporation material with high evaporation efficiency and volatile organic compound separation and barrier properties, overcoming the problem of existing methods that struggle to simultaneously achieve high evaporation efficiency and volatile organic compound treatment functions.

Description

Technical Field

[0001] This invention belongs to the field of biomass resource utilization and solar water evaporation materials, specifically relating to a method for preparing solar water evaporation materials based on sunflower straw pith and its application. Background Technology

[0002] Freshwater is an essential resource for human production and development. Although the Earth possesses extremely abundant water resources, 96.5% of it is ocean water, and less than 0.4% is directly usable. With population growth and industrial development, the demand for freshwater resources is increasing daily, and insufficient freshwater supply has become a serious challenge for many countries and regions. Solar-powered interfacial water evaporation technology has attracted widespread attention in recent years due to its convenience, high efficiency, and low investment cost. The basic principle of solar-powered interfacial water evaporation technology is to confine the photothermal conversion and water evaporation process to the gas-liquid interface, thereby applying most of the heat energy generated by the photothermal conversion to water evaporation, thus achieving efficient seawater desalination and wastewater treatment.

[0003] However, regardless of whether they are based on natural biomass or artificially synthesized materials, most existing solar-driven water evaporation materials can only separate inorganic salts and non-volatile organic compounds in water, and are unable to treat and separate volatile organic pollutants (VOCs). This is because during the solar interfacial evaporation process, VOCs evaporate along with the water, and may even accumulate in the condensate. Some studies have prepared solar water evaporation materials with VOC treatment capabilities by loading materials that can catalytically degrade organic pollutants, using composite organic pollutant adsorbent materials, and selecting selectively permeable substrates. However, these solar interfacial water evaporation materials with VOC treatment capabilities suffer from problems such as cumbersome and complex preparation methods and high costs. Furthermore, the solar interfacial water evaporation materials prepared by the above methods are difficult to achieve both high evaporation efficiency and high VOC treatment capabilities. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for preparing solar water evaporation materials based on sunflower straw pith and its application. The resulting solar water evaporation materials can overcome the problem that existing methods cannot simultaneously achieve high evaporation efficiency and volatile organic pollutant treatment functions.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A sunflower stalk pith-based solar water evaporation material is prepared by utilizing the closed yet selectively permeable cell walls of sunflower stalk pith. Using sunflower stalk pith as raw material, a light-absorbing layer is constructed on its surface, followed by immersion in water to obtain a sunflower stalk pith-based solar water evaporation material with high evaporation efficiency and the ability to block and separate volatile organic pollutants. The specific preparation method includes the following steps:

[0007] (1) Separate the pith from the sunflower stalk;

[0008] (2) A light absorption layer is constructed on the surface of the sunflower straw pith obtained in step (1) to enhance light absorption and photothermal conversion.

[0009] (3) Soak the sunflower stalk pith with a light-absorbing layer on the surface obtained in step (2) in water for 0.5 to 60 days.

[0010] Furthermore, in step (2), the light absorption layer is constructed by loading a material with light absorption and photothermal conversion functions onto the surface of the sunflower straw pith by coating or soaking, or by carbonizing the surface of the sunflower straw pith by heating or laser direct writing.

[0011] Furthermore, the material with light absorption and photothermal conversion functions can be metal nanoparticles such as gold nanoparticles, silver nanoparticles and palladium metal nanoparticles, or carbon materials such as graphene, carbon nanotubes and carbon black, or semiconductor materials such as Ti2O3, black TiO2 and SiC.

[0012] Furthermore, the thickness of the light-absorbing layer can be 0.1~1000 μm.

[0013] The sunflower stalk pith-based solar water evaporation material can be used for the separation and purification of volatile organic compounds, as well as seawater desalination and wastewater treatment.

[0014] Compared with existing technologies, the sunflower straw pith-based solar water evaporation material proposed in this invention has the following advantages:

[0015] (1) The present invention uses sunflower straw pith, an agricultural by-product, as raw material and utilizes its unique closed and selectively permeable cell wall to separate volatile organic pollutants in water;

[0016] (2) This invention uses soaking to form a water transport pathway, which enhances the water transport function of the sunflower stalk pith and overcomes the obstruction of water conduction by the closed structure. It can achieve water transport in one solar (1 kW m³) -2 Under light conditions, the water evaporation efficiency can reach 3.3 kg·m³. -2 ·h -1The above is superior to most currently reported solar water evaporation materials;

[0017] (3) The solar water evaporation material provided by the present invention uses sunflower straw pith as raw material, which is inexpensive and renewable. At the same time, the preparation process is simple and easy to implement, and has broad application prospects. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the sunflower straw pith core obtained in Example 1.

[0019] Figure 2 The sunflower straw-based solar evaporation materials prepared in Examples 1, 2, and 1 were tested under 1 solar (1 kW m) conditions. -2 Evaporation rate of photothermal water under illumination conditions.

[0020] Figure 3 The heat flow curves of the sunflower straw-based solar evaporation materials prepared in Examples 1, 3 and Comparative Example 1 are shown in the range of -20 to 20 °C.

[0021] Figure 4 The UV absorption spectra of the condensate obtained from the evaporation of phenol solution from the sunflower straw pith-based solar water evaporation materials prepared in Example 1 (A) and Comparative Example 2 (B) are shown. Detailed Implementation

[0022] The specific embodiments of the present invention will be described in further detail below with reference to specific examples. These examples are for illustrative purposes only and are not intended to limit the scope of protection of the present invention, which is defined by the claims.

[0023] Unless otherwise specified, all experimental reagents and materials used in the embodiments of the present invention are commercially available. Unless otherwise specified, all technical means used in the embodiments of the present invention are conventional means well known to those skilled in the art.

[0024] Example 1

[0025] The pith of the sunflower stalk was separated from the outer skin, and the obtained pith was processed into a strip shape of 10 mm × 10 mm × 15 mm (length × width × height), and then immersed in 10 mg·mL⁻¹ water. -1 After 10 minutes in an ethanol dispersion of carbon nanotubes, the material was removed and dried in a 60 °C oven to form a light-absorbing layer of carbon nanotubes on its surface. Subsequently, it was soaked in water for 30 days to obtain a sunflower straw-based solar water evaporation material.

[0026] Example 2

[0027] The pith of the sunflower stalk was separated from the outer skin, and the obtained pith was processed into a strip shape of 10 mm × 10 mm × 20 mm (length × width × height), and then immersed in 10 mg·mL⁻¹ water. -1 After 10 minutes in an ethanol dispersion of carbon nanotubes, the material was removed and dried in a 60°C oven to form a light-absorbing layer of carbon nanotubes on its surface. Subsequently, it was soaked in water for 30 days to obtain a sunflower straw-based solar evaporation material.

[0028] Example 3

[0029] The pith of the sunflower stalk was separated from the outer skin, and the obtained pith was processed into a strip shape of 10 mm × 10 mm × 15 mm (length × width × height), and then immersed in 10 mg·mL⁻¹ water. -1 After 10 minutes in an ethanol dispersion of carbon nanotubes, the material was removed and dried in a 60 °C oven to form a light-absorbing layer of carbon nanotubes on its surface. Subsequently, it was soaked in water for 10 days to obtain a sunflower straw-based solar evaporation material.

[0030] Example 4

[0031] The pith of the sunflower stalk was separated from the outer skin, and the obtained pith was processed into a strip shape of 10 mm × 10 mm × 15 mm (length × width × height). 5 mg·mL -1 A gold nanoparticle dispersion was uniformly sprayed onto the surface of sunflower stalk pith, and then dried in a 60 ℃ oven to form a light-absorbing layer of gold nanoparticles on the surface. Subsequently, it was soaked in water for 30 days to obtain a sunflower stalk-based solar evaporation material.

[0032] Example 5

[0033] The pith of the sunflower stalk was separated from the outer skin, and the obtained pith was processed into a strip shape of 10 mm × 10 mm × 15 mm (length × width × height). 50 mg·mL -1 Ti2O3 particle dispersion was uniformly sprayed onto the surface of sunflower stalk pith, and then dried in a 60 ℃ oven to form a light-absorbing layer of gold nanoparticles on its surface. Subsequently, it was soaked in water for 30 days to obtain sunflower stalk-based solar evaporation material.

[0034] Comparative Example 1

[0035] The pith of the sunflower stalk was separated from the outer skin, and the obtained pith was processed into a strip shape of 10 mm × 10 mm × 15 mm (length × width × height), and then immersed in 10 mg·mL⁻¹ water. -1After 10 minutes in an ethanol dispersion of carbon nanotubes, the material is removed and dried in a 60 °C oven to form a light-absorbing layer of carbon nanotubes on its surface, thus obtaining an unsoaked sunflower straw-based solar evaporation material.

[0036] Comparative Example 2

[0037] The pith of sunflower stalks was separated from the outer skin, and the resulting pith was processed into a strip shape of 10 mm × 10 mm × 15 mm (length × width × height). A steel needle was then used to pierce the pith, creating a perforated porous structure similar to that of corn stalks. The pith was then immersed in 10 mg·mL⁻¹ water. -1 After 10 minutes in an ethanol dispersion of carbon nanotubes, the material was removed and dried in a 60 °C oven to form a light-absorbing layer of carbon nanotubes on its surface. Subsequently, it was immersed in water for 30 days to obtain a solar water evaporation material with interconnected pores.

[0038] Figure 1 This is a scanning electron micrograph of the sunflower stalk pith obtained in Example 1. As can be clearly observed from the image, unlike most wood and plant stalks, the sunflower stalk pith lacks interconnected pores such as vessels and sieve tubes, and is entirely composed of thin-walled cells with a closed structure.

[0039] Figure 2 The sunflower straw-based solar evaporation materials prepared in Examples 1, 2, and 1 were tested under 1 solar (1 kW m) conditions. -2 The evaporation rate of photothermal water under illumination. As shown in the figure, the evaporation rate of the unsoaked sunflower straw-based solar evaporation material obtained in Comparative Example 1 was only 1.37 ± 0.02 kg m³ under one sun. -2 h -1 The sunflower straw pith-based solar water evaporation materials prepared in Examples 1 and 2 achieved evaporation rates of 3.39 ± 0.10 kg m³ under one sun, respectively. -2 h -1 and 3.21±0.07 kg m -2 h -1 This is superior to most reported biomass-based solar evaporation materials, indicating that prolonged soaking can significantly improve the evaporation performance of sunflower straw pith-based solar water evaporation materials.

[0040] Figure 3The figures show the heat flow curves of the sunflower straw-based solar evaporation materials prepared in Examples 1, 3, and Comparative Example 1 within the range of -20 to 20 °C. As can be seen from the figures, no endothermic peak was observed at around 0 °C in the sunflower straw-based solar evaporation material prepared in Comparative Example 1, indicating that the water contained therein is all bound water. In contrast, two distinct endothermic peaks were observed at around 0 °C in the sunflower straw-based solar evaporation materials prepared in Examples 1 and 3, which are attributed to intermediate water and free water in the material. Furthermore, the intensity and position of the endothermic peaks changed significantly with soaking time. This demonstrates that soaking in liquid water can change the water state in the sunflower straw pith-based solar water evaporation material, thereby altering the enthalpy of evaporation and making the water more easily evaporated under the same light conditions, thus improving the evaporation performance of the material.

[0041] Figure 4 The UV absorption spectra of the condensate obtained from the evaporation of sunflower stalk pith-based solar water evaporation materials prepared in Example 1 (A) and Comparative Example 2 (B) in a phenol solution are shown. As can be seen from the figures, the sunflower stalk pith-based solar water evaporation material obtained in Example 1 has a significant interception effect on phenol, a volatile pollutant in water, while the sunflower stalk pith-based solar water evaporation material obtained in Comparative Example 2 clearly loses its interception effect on volatile pollutants. This result indicates that the unique closed structure of the sunflower stalk pith can achieve the interception of volatile pollutants, which is not possessed by other existing solar water evaporation materials.

[0042] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing solar water evaporation materials based on sunflower straw pith, characterized in that, Taking advantage of the closed and selectively permeable cell walls of sunflower stalk pith, a light-absorbing layer is constructed on its surface and then soaked in water to produce a sunflower stalk pith-based solar water evaporation material with high evaporation efficiency and the ability to block and separate volatile organic pollutants. The method for constructing the absorption layer is to load a material with light absorption and photothermal conversion functions onto the surface of the sunflower straw pith by coating or soaking, or to carbonize the surface of the sunflower straw pith by heating or laser direct writing. The soaking time is 30 days.

2. The method for preparing solar water evaporation materials based on sunflower straw pith according to claim 1, characterized in that, The material with light absorption and photothermal conversion functions includes any one of metal nanoparticles, carbon materials, or semiconductor materials.

3. A sunflower straw pith-based solar water evaporation material prepared by the method described in claim 1.

4. The application of a sunflower straw pith-based solar water evaporation material as described in claim 3 in the separation and purification of volatile organic compounds.

5. The application of a sunflower straw pith-based solar water evaporation material as described in claim 3 in seawater desalination.

6. The application of a sunflower straw pith-based solar water evaporation material as described in claim 3 in wastewater treatment.

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