Preparation and characterization of thermo-responsive composite for adsorption-based dehumidification and water harvesting

• Thermo-responsive composite adsorbents P-SG and P-SG-L are prepared. • Adsorption capacity of P-SG-L is 5 ∼ 10 times higher than that of dry silica gel. • Composite adsorbents can be regenerated under low temperature such as 40 °C. • Grafting can enhance the desorption rate and capacity of the adsorbents. Adsorption technologies for adsorption-based dehumidification and water harvesting from the atmosphere have great potential for energy-saving and environmental protection. The key to successful utilization of these technologies is desired properties of adsorbents. However, most existing adsorbents fail to have the characteristic of both high adsorption capacity and good desorption ability under low regeneration temperature such as at 40 °C. In this work, we grafted a thermo-responsive polymer (Poly(N-isopropylacrylamide) PNIPAM) to silica gel and impregnated with lithium chloride to prepare a composite adsorbent. The adsorption capacity of this composite can reach 1.70 g g −1 at 20 °C&70%RH, and 56% of adsorbed moisture can be released within 60 min at 40 °C&10%RH. This method offers a promising route to develop high-performance thermo-responsive composite adsorbents for desiccant coated heat exchanger (DCHE)-based dehumidification and adsorption-based atmospheric water harvesting (ABAWH).