【摘要】 吸附式空气取水技术是解决干旱地区水资源短缺的有效技术手段.吸附材料的设计和选取直接决定吸附式空气取水的性能,物理吸附材料因其具有易于再生等诸多优越的性能得到了学者的广泛研究.本文简要介绍了基于吸附-脱附循环吸附式空气取水技术的工作原理和物理吸附材料3种不同的吸附机制,进一步提出了理想物理吸附材料的设计目标.通过对近些年来吸附式空气取水物理吸附材料的研究进展进行总结和分析,综述了硅胶、沸石、磷酸铝、有序介孔材料、金属有机骨架材料和共价有机骨架材料等不同物理吸附材料的特点和研究现状,总结对比了不同材料的吸附性能,最后着重分析了目前物理吸附材料在吸附量、动力学、循环稳定性和规模化应用等方面存在的问题,并提出了引入离子交换法、采用多孔基质、引入疏水性官能团和取消溶剂等技术路径,对新一代物理吸附材料的研发具有一定的借鉴意义.更多还原

【Abstract】 The issue of water shortage has become increasingly prominent in recent years due to human activities and natural disasters. As a clean and energy-saving technology, sorption-based atmospheric water harvesting technology(SAWH) can greatly relieve the pressure of water shortage. SAWH relies on the water vapor in the atmosphere and realizes the collection of liquid water through the process of adsorption, desorption, and condensation. The advantages of SAWH are as follows:Wide adaptability, low energy consumption, and environmentally friendly. Due to these excellent properties, SAWH is regarded as a new generation of important technologies to solve water scarcity. The performance of sorbents is the core subject of SAWH, which can be measured by indicators such as equilibrium water absorption, regeneration energy consumption, adsorption velocity, and desorption velocity. According to the interaction with water molecules, the sorbents can be divided into physical sorbents and chemical sorbents, the former has been widely studied by scholars because it is easier to complete the adsorption and regeneration process.This paper focuses on the physical sorbents for SAWH research. First, the principle of SAWH and the thermodynamic cycle process of sorbents are introduced through psychrometric chart. Second, the adsorption mechanisms of physical sorbents are illustrated, respectively, which are surface adsorption, micropore filling, capillary condensation, and absorption of ionic solutions.Besides, the adsorption characteristics and research status of several sorbents are described, including silica gel, zeolite,and ordered mesoporous materials, as well as novel physical sorbents: Aluminum phosphate, metal-organic frameworks(MOFs), covalent organic frameworks(COFs) and other novel physical sorbents. As one of the most commonly used adsorption materials, silica gel has been widely used in SAWH due to its low regeneration temperature and good adsorption kinetics, however, silica gel has the weakness of low adsorption capacity. In recent years, researchers have improved this shortcoming by reducing the pore size and adding heat-absorbing materials. Due to excellent sorption performance in low RH conditions, zeolites have also been utilized by researchers to study SAWH, however, the low sorption capacity and high regeneration temperature restrict its application. For mesoporous materials, the equilibrium adsorption point range of isothermal adsorption curve is 0.5–0.8, so it is only suitable for the study of SAWH in the area with high RH. Differently,porous aluminum phosphate usually has type I or type IV isothermal adsorption curve, it cannot only absorb vapor with low RH and fast kinetics, but also regenerate under low temperatures, whereas, it has the disadvantage of low water uptake.According to the pore size, MOFs can be divided into microporous and mesoporous types, which are suitable for SAWH under low and high RH conditions, respectively. MOFs are widely used in SAWH because of their high water uptake and high porosity, however, stability and cost are still factors that limit its large-scale application. COFs has the characteristic of low regeneration temperature and good stability, but its application in lower RH conditions needs further study.Finally, the issues of the existing sorbents are summarized, and the design directions of the next-generation sorbents are proposed, which are high water uptake under low relative humidity conditions, fast adsorption and desorption kinetics,excellent stability and viable scalability.更多还原