Adv. Funct. Mater.｜Vertical Yarn Array Stereo-Fabric Evaporator with Multistage Pores for Efficient Continuous Water Evaporation

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Research abstract

In recent years, the interfacial water evaporation technology driven by solar thermal conversion has been regarded as an excellent way to solve the shortage of freshwater resources, and has broad application prospects in the fields of seawater desalination and sewage treatment. In order to improve the evaporation rate and efficiency of evaporators, researchers have been working on synthesizing efficient photothermal conversion materials and improving the functional structure of evaporators, so as to obtain efficient photothermal conversion, good thermal management, water transport, interfacial wetting and Salt resistance equals an all-in-one evaporator. However, the current evaporation rate of two-dimensional (2D) planar evaporators is already close to the theoretical limit for solar steam generation (1.47 kg m-2 h-1); three-dimensional (3D) stereo evaporator sidewalls with a certain height usually have cold evaporation characteristics, causing the sidewall temperature to be lower than the ambient temperature, thereby effectively extracting additional energy from the surrounding environment, resulting in evaporation rates above the theoretical limit. However, most of the current 3D evaporators mainly focus on improving the evaporation surface area, ignoring the problem that a large amount of steam is stagnant inside the pores and cannot be diffused. The balance between the effective evaporation surface area and the diffusion space is crucial for efficient evaporation rate. In addition, the antibacterial, anti-oil, anti-salt and other characteristics of the evaporator also determine the service life of the evaporator. At the same time, the condensation enthalpy generated during the condensation of steam into liquid water is lost to the environment, resulting in a greatly reduced energy utilization rate.

Introduction

Recently, Associate Professor Zhang Xiansheng, Associate Professor Wang Lili, Professor Qu Lijun of Qingdao University and Professor Liang Kun of Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences cooperated, and innovatively prepared MXene and polydopamine/polyethyleneimine (PDA/PEI) modified with multi-level Porous hemp yarn vertical array structure 3D evaporator, and further designed a condensation device with recyclable evaporation enthalpy, which was successfully assembled into a solar "desalination-thermoelectric-irrigation" integrated platform to maximize energy use. The evaporation rate of the evaporator under one sunlight is as high as 3.95 kg m-2 h-1, and the freshwater collection volume of 47.04 kg m-2 can be achieved in the continuous 8-hour outdoor test. Because the macropores between the evaporator yarns and the micropores between the fibers synergistically promote the convection and diffusion of salt water, even if the evaporator is irradiated with sunlight for 120 hours continuously in 14% salt water, no salt crystals are precipitated on the surface of the evaporator, showing excellent performance. salt tolerance. In addition, the intrinsic antibacterial properties of hemp fibers and the efficient bactericidal properties of MXene endow the evaporator with excellent antibacterial and anti-biofouling properties. The hydration layer formed by the PDA/PEI coating on the surface of the hemp fiber exhibits stable hydrophilicity and underwater superoleophobicity, which can not only speed up the transportation of water, but also exhibit good oil pollution resistance, which further ensures that the evaporator can be used in Long-term stability in different complex environments. Finally, through the innovative multi-module design of the condenser in the water collection device, the steam enthalpy is applied to the thermoelectric conversion, and the waste heat further preheats the circulating seawater to be evaporated, realizing the multiple utilization of energy.

The result was published online in the top international journal Advanced Functional Materials (impact factor 19.924), titled: A Multiscale Porous 3D-Fabric Evaporator with Vertically Aligned Yarns Enables Ultra-Efficient and Continuous Water Desalination.

Lei Zhiwei and Zhu Shifeng are the first authors of this article.

Graphical guide

Figure 1. Schematic diagram of the "desalination-thermoelectric-irrigation" integrated platform of the vertical array three-dimensional evaporator.

Figure 2. Structural characterization and thermal positioning performance of a 3D three-dimensional fabric evaporator. (a) Schematic diagram of the fabrication process of PP/M/PP-H, (b) photographs of vertically aligned hemp yarn evaporators, (c–d) Pristine-H, PP-H, M/PP-H, PP/M/PP -H (sample name: H = hemp, PP = PDA/PEI, M = MXene) SEM image and XPS spectrum, (e) picture of PP/M/PP-H that can withstand 100 g weight, (f) water contact Angle, (g) absorption spectrum of PP/M/PP-H, (h) IR image of PP/M/PP-H on a hot plate.

Figure 3. Water evaporation performance. (a) Temperature map of the top surface and bottom of the evaporator (left), steam generation image (right), (b) schematic diagram of the evaporator, (c) PP/M/PP-H-D1, D2, D3, D4 evaporation Evaporation rates of the evaporator (D for different yarn gaps), (d) water mass loss of the PP/M/PP-HD2 evaporator under various convections under 1 sun, (e) measured PP/M/PP- Evaporation cycle performance of H-D2 in 10 cycles, (f) evaporation rates of 3D evaporators with different heights in dark and sunlight, (g) comparison of efficiency and evaporation rates of different 3D evaporators, (h) PP Infrared thermal images of /M/PP-HD2 under 0° and 45° sunlight exposure, (i) water loss of PP/M/PP-HD2 under 0° and 45° sunlight exposure.

Figure 4. Antibacterial, oil and salt resistance. (a) Digital images of agar plates with colony cell growth in different samples, (b) antimicrobial efficiency of different samples, (c) underwater oil contact angle of PP/M/PP-H, (d) PP/M/PP -H good oil stain resistance, (e) schematic diagram of PP/M/PP-H excellent oil stain resistance performance under water, (f) PP/M/PP-H evaporated water (test solutions: soybean, kerosene and gasoline in water) oil emulsion), (g) image of salt tolerance of PP/M/PP-H, (h) schematic diagram of salt-water exchange.

Figure 5. Desalination-thermoelectric-irrigation integrated platform. (a) The concentration of ions before and after desalination, (b) the absorption spectrum of the solution, (c) the open-circuit voltage of the TEG module, (d) the schematic diagram of the experimental setup of the desalination-thermoelectric-cultivation system, (e) the open-circuit voltage of the TEG module Images, (f) images of outdoor rooftop desalination-thermoelectric-irrigation system installations, (g) images of outdoor evaporative light intensity, ambient temperature, and collected water.

Summarize

In this paper, an integrated 3D evaporator system is designed and developed, which successfully achieves excellent evaporation performance, anti-biological/oil pollution performance, and salt tolerance in actual seawater desalination, and recovers the evaporation enthalpy to obtain electricity. The multi-scale pore (macropores and micropores) structure of the vertical array of 3D evaporators facilitates light trapping (97.5% light absorption) by increasing the multiple reflections of incident light, facilitating photothermal conversion. This structure also increases the effective air/water interface and vapor diffusion space, while the sidewall has the property of absorbing energy from the environment, enabling full-dimensional water evaporation. Based on the above performance, the evaporation rate of the evaporator under one sunlight illumination is 3.95 kg m−2 h−1, and the evaporation rate reaches 13.25 kg m−2 h−1 under the convection of 4 m s−1, and the evaporation rate reaches 13.25 kg m−2 h−1. The evaporation is as high as 47.04 kg m−2. At the same time, this unique structure promotes the convection and diffusion of water. Even if the evaporator is continuously irradiated in 14% salt water for 120 h (1 sunlight), no salt crystals are precipitated on the surface, showing excellent salt resistance. . In addition, the inherent antibacterial effect of hemp fibers and the efficient bactericidal properties of MXene inhibit bacterial growth near the evaporator, showing superior anti-biofouling performance. The stable hydration layer formed on the fiber surface by the PDA/PEI coating protects the evaporator from oily contaminants. Finally, an integrated evaporation system of "seawater desalination-thermoelectricity-irrigation" is innovatively designed, and the steam enthalpy recovered by the multi-module condenser is used for thermoelectric power generation (TEG) and preheating the circulating seawater to be evaporated, realizing the available energy The multiple uses of and desalinated water are used for real-time and on-demand crop growth through irrigated cultivation platforms. The integrated design of this evaporator system provides new ideas for developing sustainable, durable and scalable solar evaporation systems.

Literature link

https://doi.org/10.1002/adfm.202205790

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