Graphene composite aerogel and preparation method and application thereof
By constructing a gradient pore structure of graphene composite aerogel, the problem of low evaporation efficiency of interfacial solar evaporators in high-concentration brine treatment was solved, achieving efficient salt/water separation and zero liquid discharge.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANDONG FIRST MEDICAL UNIV & SHANDONG ACADEMY OF MEDICAL SCI
- Filing Date
- 2023-04-23
- Publication Date
- 2026-06-19
AI Technical Summary
Existing interface solar evaporators suffer from insufficient vertical absorption when processing high-concentration brine, resulting in low evaporation efficiency and an inability to achieve efficient and stable salt/water separation and zero liquid discharge.
By employing graphene composite aerogel, a gradient pore structure is constructed, and capillary pressure difference is used to create a concentration gradient of brine in the radial direction, which eventually crystallizes at the edge, achieving stable and efficient evaporation and salt/water separation.
It achieves long-term treatment and stable and efficient evaporation of high-concentration brine, and can efficiently and stably collect fresh water and salt, achieving the goal of zero liquid discharge.
Smart Images
Figure CN116474667B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water treatment technology, specifically relating to a graphene composite aerogel, its preparation method, and its application. Background Technology
[0002] People have begun to utilize seawater desalination technologies such as multi-stage flash distillation, multi-effect distillation, reverse osmosis membranes, and electroosmosis to address the freshwater shortage problem. However, seawater desalination plants discharge large amounts of concentrated brine wastewater into rivers, lakes, or the sea daily, adversely affecting the ecological environment and terrestrial vegetation. Recently, the ultimate goal of water treatment—"zero liquid discharge"—has been proposed, which involves the complete separation of salt and water to minimize ecological damage. However, when using traditional seawater desalination technologies (such as reverse osmosis membranes) to treat concentrated brine (greater than 7 wt.%), the energy required increases dramatically, and the membrane lifespan is significantly shortened. Therefore, there is an urgent need for an energy-saving and environmentally friendly new technology that can treat high-concentration brine and achieve zero liquid discharge.
[0003] In recent years, interfacial solar evaporation technology has attracted widespread attention due to its ability to rapidly evaporate water under solar power while minimizing carbon footprint when treating seawater or wastewater. Currently, interfacial solar evaporators employ two main strategies to reduce the impact of salt crystallization on the evaporation process when treating high-concentration brine: "salt-free" and "salt-out." The "salt-free" strategy prevents salt crystallization on the evaporator surface through structural design; however, it cannot separate water and salt, thus failing to achieve zero liquid discharge. The "salt-out" strategy regulates the direction of brine transport, causing salt to crystallize directionally outside the evaporation interface. However, the current one-dimensional water supply channel, as the sole water supply unit for directional crystallization evaporators, suffers from insufficient vertical absorption, reducing overall evaporation efficiency and hindering the use of directional crystallization evaporators for high-efficiency desalination. Therefore, achieving efficient, continuous, and stable simultaneous collection of salt and water, ultimately resulting in zero liquid discharge, remains a significant challenge for directional crystallization solar evaporation devices. Summary of the Invention
[0004] This invention proposes a graphene composite aerogel and its preparation method. By constructing and controlling a gradient pore structure, this invention creates a capillary pressure difference in the radial direction of the evaporator, causing the brine to spontaneously form a concentration gradient in the radial direction, eventually leading to crystallization at the edge. Therefore, it can process high-concentration brine for extended periods while maintaining a stable and efficient evaporation rate, ultimately enabling efficient and stable simultaneous collection of freshwater and saline with zero liquid discharge.
[0005] The graphene composite aerogel described in this invention has a gradient porous spiral structure.
[0006] The composite aerogel includes a melamine foam skeleton coated with graphene oxide and a hydrophilic substance; the hydrophilic substance includes, but is not limited to, MXene or cellulose nanocrystals.
[0007] The mass ratio of graphene oxide to hydrophilic material is (50-80):(50-20), preferably 50 / 50, 60 / 40, or 80 / 20. If too little hydrophilic material is added, the graphene aerogel will not be hydrophilic, leading to insufficient water supply and affecting the solar evaporation performance; if too little graphene is added, it will affect the photothermal conversion performance.
[0008] The preparation method of the graphene composite aerogel includes the following steps:
[0009] (1) Melamine foam is hot-pressed to obtain a foam film;
[0010] (2) The foam film is rolled and wound into a melamine foam skeleton; the melamine foam skeleton is a gradient porous spiral structure skeleton;
[0011] (3) Spray a mixed aqueous solution of graphene oxide and hydrophilic substances onto the melamine foam skeleton, dry under normal pressure and reduce under sunlight to obtain graphene composite aerogel.
[0012] In step (1), the compression ratio during hot pressing is 0, 2, 4, 6, 8, or 10.
[0013] Step (2) is based on the fact that the membrane pressed out in step (1) has a pore structure with different sizes, so it has a gradient pore structure after being rolled up.
[0014] The formation process of the gradient porous spiral structure skeleton is as follows: foam films obtained with different compression ratios are rolled into spiral rolls from the inside to the outside. By adjusting the inner and outer heights of the spiral rolls, a gradient porous spiral structure skeleton with a low inner height and a gradually increasing outer height is formed; from the inside to the outside, the compression ratio of the foam film gradually increases.
[0015] In step (3), the content of graphene oxide in the mixed aqueous solution is 5 mg / mL-10 mg / mL.
[0016] The graphene composite aerogel can be used to assemble solar evaporation devices for treating high-concentration brine.
[0017] This invention utilizes low-cost polymer gradient porous foam as a framework to achieve a malleable, resilient graphene / MXene network structure with synergistic control over its microporous structure and macroscopic shape. This allows salt to crystallize directionally only on the sides, enabling efficient water evaporation and simultaneous salt / water collection, ultimately achieving zero liquid discharge. The presence of foam also enhances the mechanical properties of the graphene composite aerogel. By controlling the microporous structure and macroscopic shape of graphene / MXene, this invention elucidates the directional crystallization mechanism and the enhanced evaporation performance mechanism, providing new theoretical basis for the design and development of high-efficiency solar desalination devices. Attached Figure Description
[0018] Figure 1 This is a schematic diagram comparing the gradient porous graphene composite aerogel multidimensional water supply channel described in this invention with other one-dimensional water supply channels.
[0019] Figure 2 This is a schematic diagram comparing salt crystallization in a one-dimensional water supply channel after the gradient porous graphene composite aerogel described in this invention has been continuously treated with high-concentration brine (25 wt.%, near-saturated salt solution) for 48 hours.
[0020] Figure 3 This is a schematic diagram of the gradient porous spiral structure graphene composite aerogel described in this invention;
[0021] Figure 4 This is a side-oriented crystallization diagram of the graphene composite aerogel described in this invention when treating high-concentration brine;
[0022] Figure 5 This is a comparison chart of the evaporation rates of the graphene composite aerogel and the bulk graphene aerogel described in this invention.
[0023] Figure 6 for Figure 1 Color images;
[0024] Figure 7 for Figure 2 Color images;
[0025] Figure 8 for Figure 3 Color illustrations. Detailed Implementation
[0026] Example 1
[0027] A graphene composite aerogel, wherein the composite aerogel has a gradient porous helical structure;
[0028] The composite aerogel comprises a melamine foam skeleton coated with graphene oxide and a hydrophilic substance; the hydrophilic substance is MXene.
[0029] The specific preparation process is as follows:
[0030] (1) Melamine foam is hot-pressed to obtain foam films with different compression ratios;
[0031] (2) The foam film is rolled and wound into a melamine foam skeleton; the melamine foam skeleton is a gradient porous spiral structure skeleton; the formation process of the gradient porous spiral structure skeleton is as follows: the foam film obtained with different compression ratios is rolled into a spiral roll from the inside to the outside, the height of the spiral roll is controlled to be 1cm, and the compression ratio of the foam film gradually increases from the inside to the outside.
[0032] (3) A mixed aqueous solution of graphene oxide and hydrophilic substance was sprayed onto the melamine foam skeleton, dried at normal pressure and reduced by sunlight to obtain graphene composite aerogel; the content of graphene oxide in the mixed aqueous solution was 5 mg / mL, and the mass ratio of graphene oxide to hydrophilic substance was 80 / 20.
[0033] The prepared graphene composite aerogel was assembled into a solar evaporation device.
[0034] Example 2
[0035] A graphene composite aerogel, wherein the composite aerogel has a gradient porous helical structure;
[0036] The composite aerogel comprises a melamine foam skeleton coated with graphene oxide and a hydrophilic substance; the hydrophilic substance is MXene.
[0037] The specific preparation process is as follows:
[0038] (1) Melamine foam is hot-pressed to obtain foam films with different compression ratios;
[0039] (2) The foam film is rolled and wound into a melamine foam skeleton; the melamine foam skeleton is a ring-shaped gradient porous structure skeleton; the specific process of forming the gradient porous spiral structure skeleton is as follows: the foam film obtained with different compression ratios is rolled into a spiral roll from the inside to the outside, the height of the spiral roll is controlled to be 3cm, and the compression ratio of the foam film gradually increases from the inside to the outside.
[0040] (3) A mixed aqueous solution of graphene oxide and hydrophilic substance was sprayed onto the melamine foam skeleton, dried at normal pressure and reduced by sunlight to obtain graphene composite aerogel; the content of graphene oxide in the mixed aqueous solution was 5 mg / mL, and the mass ratio of graphene oxide to hydrophilic substance was 80 / 20.
[0041] The prepared graphene composite aerogel was assembled into a solar evaporation device.
[0042] Example 3
[0043] A graphene composite aerogel, wherein the composite aerogel has a ring-shaped gradient porous structure;
[0044] The composite aerogel comprises a melamine foam skeleton coated with graphene oxide and a hydrophilic substance; the hydrophilic substance is MXene.
[0045] The specific preparation process is as follows:
[0046] (1) Melamine foam is hot-pressed to obtain foam films with different compression ratios;
[0047] (2) The foam film is rolled and wound into a melamine foam skeleton; the melamine foam skeleton is a ring-shaped gradient porous structure skeleton; the specific process of forming the gradient porous spiral structure skeleton is as follows: the foam film obtained with different compression ratios is rolled into a spiral roll from the inside to the outside, the height of the spiral roll is controlled to be 5cm, and the compression ratio of the foam film gradually increases from the inside to the outside.
[0048] (3) A mixed aqueous solution of graphene oxide and hydrophilic substance was sprayed onto the melamine foam skeleton, dried at normal pressure and reduced by sunlight to obtain graphene composite aerogel; the content of graphene oxide in the mixed aqueous solution was 5 mg / mL, and the mass ratio of graphene oxide to hydrophilic substance was 80 / 20.
[0049] The prepared graphene composite aerogel was assembled into a solar evaporation device.
[0050] Example 4
[0051] A graphene composite aerogel, wherein the composite aerogel has a three-dimensional helical porous structure;
[0052] The composite aerogel comprises a melamine foam skeleton coated with graphene oxide and a hydrophilic substance; the hydrophilic substance is cellulose nanocrystals.
[0053] The specific preparation process is as follows:
[0054] (1) Melamine foam is hot-pressed to obtain a foam film with the same pore structure;
[0055] (2) The foam film is rolled and wound into a melamine foam skeleton; the melamine foam skeleton is a three-dimensional spiral porous structure skeleton; the specific process of forming the gradient porous spiral structure skeleton is as follows: the foam film obtained with different compression ratios is rolled into a spiral roll from the inside to the outside, the height of the spiral roll is controlled to be 3cm, and the compression ratio of the foam film gradually increases from the inside to the outside;
[0056] (3) Spray a mixed aqueous solution of graphene oxide and hydrophilic substance onto the melamine foam skeleton, dry under normal pressure and reduce under sunlight to obtain graphene composite aerogel; the content of graphene oxide in the mixed aqueous solution is 10 mg / mL, and the mass ratio of graphene oxide to hydrophilic substance is 50 / 50.
[0057] The prepared graphene composite aerogel was assembled into a solar evaporation device.
[0058] Example 5
[0059] A graphene composite aerogel, wherein the composite aerogel has a three-dimensional helical porous structure;
[0060] The composite aerogel comprises a melamine foam skeleton coated with graphene oxide and a hydrophilic substance; the hydrophilic substance is cellulose nanocrystals.
[0061] The specific preparation process is as follows:
[0062] (1) Melamine foam is hot-pressed to obtain a foam film with the same pore structure;
[0063] (2) The foam film is rolled and wound into a melamine foam skeleton; the melamine foam skeleton is a three-dimensional spiral porous structure skeleton; the specific process of forming the gradient porous spiral structure skeleton is as follows: the foam film obtained with different compression ratios is rolled into a spiral roll from the inside to the outside, the height of the spiral roll is controlled to be 3cm, and the compression ratio of the foam film gradually increases from the inside to the outside;
[0064] (3) Spray a mixed aqueous solution of graphene oxide and hydrophilic substance onto the melamine foam skeleton, dry under normal pressure and reduce under sunlight to obtain graphene composite aerogel; the content of graphene oxide in the mixed aqueous solution is 10 mg / mL, and the mass ratio of graphene oxide to hydrophilic substance is 60 / 40.
[0065] The prepared graphene composite aerogel was assembled into a solar evaporation device.
[0066] Example 6
[0067] A graphene composite aerogel, wherein the composite aerogel has a three-dimensional helical porous structure;
[0068] The composite aerogel comprises a melamine foam skeleton coated with graphene oxide and a hydrophilic substance; the hydrophilic substance is cellulose nanocrystals.
[0069] The specific preparation process is as follows:
[0070] (1) Melamine foam is hot-pressed to obtain a foam film with the same pore structure;
[0071] (2) The foam film is rolled and wound into a melamine foam skeleton; the melamine foam skeleton is a three-dimensional spiral porous structure skeleton; the specific process of forming the gradient porous spiral structure skeleton is as follows: the foam film obtained with different compression ratios is rolled into a spiral roll from the inside to the outside, the height of the spiral roll is controlled to be 3cm, and the compression ratio of the foam film gradually increases from the inside to the outside;
[0072] (3) Spray a mixed aqueous solution of graphene oxide and hydrophilic substance onto the melamine foam skeleton, dry under normal pressure and reduce under sunlight to obtain graphene composite aerogel; the content of graphene oxide in the mixed aqueous solution is 10 mg / mL, and the mass ratio of graphene oxide to hydrophilic substance is 80 / 20.
[0073] The prepared graphene composite aerogel was assembled into a solar evaporation device.
[0074] Experimental Example 1
[0075] The graphene composite aerogel obtained in this invention can be used to treat high-concentration brine, such as... Figure 4 As shown, during continuous 48-hour treatment of high-concentration brine (25 wt.%, near-saturated salt solution), salt only crystallized directionally on the sides, while no salt deposition occurred at the top evaporation interface. Therefore, the graphene composite aerogel of this structure described in this invention can maintain long-term, stable, high-speed evaporation. Furthermore, the evaporation rate gradually increases with salt deposition, reaching a maximum of 15.1 kgm³ under sunlight. -2 h -1 Furthermore, a self-accelerating phenomenon is observed. Compared to bulk graphene aerogels, the evaporation rate is significantly increased (see...). Figure 5 This indicates that the difference in capillary forces between the porous structures of the gradient porous helical graphene composite aerogel can promote the radial transport of brine, thereby enabling the salt to crystallize oriented on the side of the sample.
Claims
1. A method for preparing graphene composite aerogel, characterized in that, Includes the following steps: (1) Melamine foam is hot-pressed to obtain a foam film; (2) The foam film from step (1) is rolled and wound into a melamine foam skeleton; the melamine foam skeleton is a gradient porous spiral skeleton; (3) Spray a mixed aqueous solution of graphene oxide and hydrophilic substance onto the melamine foam skeleton, dry under normal pressure and reduce under sunlight to obtain graphene composite aerogel. In the mixed aqueous solution, the content of graphene oxide is 5 mg / mL-10 mg / mL, and the mass ratio of graphene oxide to hydrophilic substance is (50-80):(50-20). The hydrophilic substance is MXene or cellulose nanocrystals.
2. The method for preparing a graphene composite aerogel according to claim 1, characterized in that, In step (1), the compression ratio during hot pressing is 0, 2, 4, 6, 8, or 10.
3. A graphene composite aerogel, characterized in that, The graphene composite aerogel was prepared using the preparation method described in claim 1 or 2.
4. The application of the graphene composite aerogel according to claim 3 in the treatment of high-concentration brine.