Study on adsorption kinetics of thermosensitive adsorbents and its application in dehumidification and atmospheric water harvesting

With the continuous development of the economy, the world is facing a growing crisis of freshwater shortage and energy scarcity. Reducing the energy consumption of handling heat and moisture loads in air-conditioning systems and solving the global water scarcity problem have become major issues that we need to pay urgent attention to. The dynamic adsorption and desorption properties of adsorbents have a significant impact on the heat and moisture transfer characteristics of adsorptive atmospheric water harvesting systems and dehumidifying heat exchanger air-conditioning systems. In this paper, the dynamic adsorption and desorption properties of thermosensitive composites doped with different thermally conductive materials, such as nano-copper powder, nano-silver powder and nano-graphene, are investigated, and the theoretical daily water production capacity of the optimal materials is analyzed. The results show that the thermosensitive materials doped with graphene nanopowder have good adsorption/desorption kinetics, and their equilibrium adsorption reaches 2.51 g/g, which is 1.46 times higher than that of the undoped thermally conductive materials; and the desorption within 60 min is 1.17 times higher than that of the undoped thermally conductive materials. In addition, when the cycle time is 3h and the adsorption/desorption time ratio is 2:1, the thermosensitive material doped with nanographene can achieve a theoretical daily water volume of 7.02 kg/(kg·d), which is 21% higher than that of the undoped material.