Freshwater from air using moisture-capturing hydrogels: Soft matter and sorption for sustainability and energy

Humidity in the air is a vast water resource representing 6 times more freshwater than all rivers and lakes. This humidity can be converted to drinking water via moisture sorption-desorption, serving as a potentially decentralized, passive, and low-cost pathway to mitigate the pressing water scarcity challenge. However, the productivity and potential of this approach has been severely limited by the performance, scalability, and durability of conventional moisture sorbent materials. In this talk, I will discuss the material-level to application-level development of low-cost (<$0.1/kg of material) hydrogel-salt composites that capture record amounts of water from the air and produce liquid water even in extreme conditions like the Atacama Desert, Chile.

Firstly, I will discuss the physics-based models I developed to elucidate the key thermodynamic interactions and transport mechanisms in hydrogel-salt composites. Through comprehensive synthesis and characterization, I demonstrated that these models accurately predict the sorption performance metrics (uptake, enthalpy, and kinetics) of hydrogel-salt composites from their composition. Secondly, I will present how these insights guided the synthesis of hydrogels with the highest capability ever demonstrated of any material to capture and store water from the air (~2 kg of water/kg of material), even in arid conditions (30% relative humidity) through an optimized swelling-based approach. Thirdly, I will discuss how my thermodynamic and transport models guided the design of a hydrogel-based atmospheric water harvesting device that was tested in the Atacama Desert, in Chile. Using these models, I tuned key design parameters to achieve ~1 L/m2/day water productivity even at ~30% relative humidity in the desert. Critically, through the demonstrated combination of low-cost, high productivity, and high material durability we provide a path towards <$0.01/L decentralized water production from the air.

Speaker: Carlos Diaz-Marin, Advanced Research Projects Agency - Energy (ARPA-E)