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First author: Xiao Qingbo Associate Researcher & Zhu Yan
Corresponding Author: Ye Xiaomei, Researcher Lin Hongzhen, Dr. Jian Wang
Communication unit: Jiangsu Academy of Agricultural Sciences
DOI: 10.1016/j.cej.2021.133019
Full text at a glance
Solar water evaporation technology using the light-heat conversion function of photothermal nanomaterials is a low-carbon and energy-saving water treatment technology, which shows good application prospects in the fields of sewage treatment and seawater desalination. However, the current photothermal nanomaterials are not yet well adapted to the slightly complex water quality environment. Among them, for sewage containing volatile harmful components, harmful small molecule substances can easily pass through the pore structure of photothermal nanomaterials during photothermal evaporation, and then escape into the air. In this paper, it is proposed that the dense structure hydrogel layer (PCH) containing high density charge is used as the interception layer, and the high-efficiency ammonia nitrogen interception in the photothermal evaporation process is realized based on the Donnan rejection effect of PCH on small molecule ammonia nitrogen (NH4+). By adjusting the charge density of the PCH layer, the 95% ammonia nitrogen interception efficiency in the photothermal evaporation process was achieved for the first time. In addition, the PCH layer was combined with the porous photothermal evaporation layer to obtain a Janus structure hydrogel, which increased the evaporation rate of photothermal water from ~1.2 Kgm-2h-1 to 3.3 Kgm-2h-1. Further using interface-selective and frequency vibration spectroscopy (SFG), the microscopic molecular mechanism of regulating the state of water molecules in the photothermal evaporation layer and thus enhancing water evaporation was elucidated.
Background
Under the national carbon peak and carbon neutrality strategic goals, it is particularly important to develop different forms of solar energy, wind energy and other clean energy efficient use technologies. The use of photothermal nanomaterials to absorb sunlight, convert it into thermal energy, and realize the rapid evaporation and purification of water at the interface of the material, which has the advantages of low carbon, energy saving and low cost in the fields of sewage treatment and seawater desalination. In recent years, the development of solar thermal evaporation technology has become a research hotspot in related fields. However, most of the current research on solar thermal evaporation materials focuses on water-salt separation systems such as desalination and desalination of bitter alkali water, and cannot adapt well to the slightly complex water quality environment. Most industrial and agricultural sewage water quality components are more complex, but also have urgent low-carbon, low-energy treatment needs. In addition to containing salts that are not volatile, these sewage also contain other contaminant components, often accompanied by volatile small molecule contaminants. Among them, ammonia nitrogen components (especially NH4+) are commonly present in industrial and agricultural sewage, which are close to water molecules in terms of molecular size and chemical properties, and are difficult to separate from water molecules. However, photothermal evaporation materials tend to have multi-stage micro-nano pore structures to obtain a large water evaporation area. In the process of photothermal evaporation, small molecules of ammonia nitrogen will also escape from the surface of the material along with the water vapor generated by the evaporation of light and heat, and cannot be effectively separated and purified. Previously, in order to inhibit the ammonia nitrogen volatilization in the process of photothermal evaporation, some researchers designed an organic light absorption layer with ammonia nitrogen response, which can be dynamically adjusted to a low-absorbing material when there is ammonia nitrogen component in the water body, terminating the evaporation process. However, in order to expand the application range of solar thermal evaporation materials/technologies, it is necessary to study and explore new materials that can also work effectively in water quality containing ammonia nitrogen.
In response to the above problems, Xiao Qingbo, associate researcher of Jiangsu Academy of Agricultural Sciences, in collaboration with Dr. Wang Jian and Lin Hongzhen of the Suzhou Institute of Nanotechnology of the Chinese Academy of Sciences, published a paper entitled "Highly Charged Hydrogel with Enhanced Donnan Exclusion toward Ammonium for Efficient" in the internationally renowned Journal chemical Engineering Journal Solar-driven Water Remediation" research work. In this paper, the densification effect of dense structure hydrogel layer (PCH) containing high density charge on NH4+ is proposed, and the efficient interception of ammonia nitrogen components in sewage during photothermal evaporation is realized for the first time. At the same time, by constructing a Janus structure composite hydrogel, the evaporation rate of photothermal water of 3.3 Kgm-2h-1 was achieved. Further combining interface-selective and frequency vibration spectroscopy (SFG) elucidates microscopic molecular mechanisms that enhance water evaporation.
Highlights
Point 1: It is proposed to use the Donnan rejection effect of charged hydrogels on ammonia nitrogen components to achieve the effective separation of water molecules from NH4+.
Point 2: By optimizing the charge density in the hydrogel, the interception efficiency of NH4+ can reach 95%.
Key point 3: Construct a Janus structure composite membrane to regulate the state of water molecules and obtain a higher evaporation rate of photothermal water.
Graphic and text analysis
Fig. 1 Schematic diagram and material characteristics of the synthesis of the PCH layer and the Janus composite film
Figure 2 Detection and optimization of ammonia nitrogen interception performance of photothermal film
Fig. 3 Characterization of water evaporation rate of composite photothermal film and microscopic mechanism of chitosan regulating the state of water molecules
Fig. 4 Characterization of photothermal evaporation membrane on ammonia nitrogen interception performance of biogas slurry
Summary and outlook
In summary, this work proposes an effective strategy for intercepting ammonia nitrogen components in sewage by using the rejection effect of charged hydrogel Donnan. The results show that by optimizing the charge density to enhance the Donnan repulsion effect on NH4+, the interception efficiency of 95% of the ammonia nitrogen component in the photothermal evaporation process is achieved for the first time. A recent construction of the Janus structural composite membrane obtained a photothermal evaporation rate of up to 3.3 Kgm-2h-1. The test results of the agricultural sewage biogas slurry as the model system show that the prepared photothermal evaporation film also has a good ammonia nitrogen interception effect in the actual water body. This work explores a new strategy for separating volatile harmful components from sewage using charged photothermal gels, which is instructive for the preparation of relevant membrane treatment materials.
Literature source
Qingbo Xiao, Yan Zhu, Yonglan Xi, Xiangping Kong, Xiaomei Ye, Zhiyang Zhang, Cunpu Qiu, Wenlong Xu, Shuang Cheng, Jing Zhang, Mingli Jia, Enhui Sun, Hongzhen Lin, Jian Wang, Highly Charged Hydrogel with Enhanced Donnan Exclusion toward Ammonium for Efficient Solar-driven Water Remediation, Chemical Engineering Journal 2021, DOI: 10.1016/j.cej.2021.133019, 2021
Article links:
About the author
Dr. Qingbo Xiao
Associate researcher of Jiangsu Academy of Agricultural Sciences, leader of discipline. He received his Ph.D. from the Fujian Institute of Material Structure of the Chinese Academy of Sciences in 2011, worked at the Suzhou Institute of Nanotechnology and Nanobionics of the Chinese Academy of Sciences in the same year, and joined the Jiangsu Academy of Agricultural Sciences in 2019. Mainly engaged in the development and utilization of agricultural new energy materials research, including the development of agricultural solar thermal materials, low-energy consumption agricultural sewage treatment, etc. Currently, in Chem. Eng. J.、Small 、Nano. Lett.、 J. Mater. Chem. He has published more than 30 SCI papers in A and other journals, applied for more than 10 invention patents and authorized 4 projects, and undertaken 7 research projects such as the National Natural Science Foundation of China and the Natural Science Foundation of Jiangsu Province as the project leader.
Dr. Jian Wang
He is currently supported by the Alexander von Humboldt Foundation Fund to carry out research work at the Karlsruher Institute of Technology, Helmholtz Institute Ulm. He has presided over the Jiangsu Provincial Natural Science Foundation and the Jiangsu Provincial Talent Project, and participated in the National Natural Science Foundation of China and key R&D projects. His research interests are the design and synthesis of high-performance secondary electrodes and in situ characterization methods, and the relevant working mechanisms of batteries are explored. So far, he has published more than 37 papers, of which the first/corresponding author is in Nano Lett., Energy Storage Mater., Adv. Funct. Mater., Nano Energy, Energy Environment. Mater., Chem. Eng. J, J. Mater. Chem. A, ChemSusChem, J. Power Sources, ACS Appl. Mater. Interface and other journals published 18 articles (including IF> 10, a total of 11), authorized 5 national invention patents, and made oral reports on research progress at international conferences ChinaNano 2017 and ChinaNano 2019.
E-mail: [email protected] or [email protected]。
Lin Hongzhen researcher
He is currently the doctoral supervisor and research leader of the Suzhou Institute of Nanotechnology and Nanobionics, Chinese Academy of Sciences. His research interests include the development and application of in situ interface and frequency vibration spectroscopy technology, the electrode design and preparation of high-energy secondary batteries, and the related application of graphene materials. Focusing on the development of in situ and frequency vibration spectroscopy technology, the construction of instruments and equipment to expand their in situ (working conditions) characterization function of related spectroscopic technology, at the molecular level to clarify the microscopic mechanism of the key interface physical and chemical processes in a series of functional materials and devices. In Nat. Commun.、JACS、Nano Lett. Adv. Funct. Mater.、Angew.Chem. Int. Ed.、Nano Energy、Energy Storage Mater.、J. Phys. Chem. Nearly 80 academic papers have been published in important international journals in the field of physical chemistry and nano research, such as Lett., Small, ACS Nano, and Nanoscale.