Freshwater Harvester with Ultra-High Yield by Super-Hygroscopic Composite Under Extremely Low Humidity Environment

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Atmospheric water harvesting (AWH) is crucial for freshwater production, but faces challenges with low daily water output at low relative humidity (RH).
• Existing AWH technologies struggle to efficiently capture moisture in arid environments with RH below 30%.

Purpose of the Study:

• To develop a high-performance super-hygroscopic composite (CHG) for efficient atmospheric water harvesting.
• To enhance water harvesting capacity and freshwater yield, particularly under extremely low RH conditions.

Main Methods:

• Fabrication of a composite using chitosan (CS), hyaluronic acid (HA), MOF-303, graphene oxide (GO), and calcium chloride (CaCl2).
• Characterization of the composite's water uptake and sorption-desorption properties under varying RH and illumination.
• Evaluation of large-scale freshwater yield using a self-made device.

Main Results:

• The CHG composite demonstrated a high water uptake of approximately 0.78 g g⁻¹ at 20% RH.
• Under 0.50-sun illumination, the material achieved 0.93 g g⁻¹ after absorbing water at 45% RH.
• Large-scale CHG achieved a freshwater yield of 9.95 L kg⁻¹ day⁻¹ at 25% RH and 30°C.

Conclusions:

• The developed CHG composite shows significant potential for efficient atmospheric water harvesting, especially in water-scarce and arid regions.
• The synergistic combination of CS-HA, MOF-303, GO, and CaCl2 enhances water capture and material stability.
• This work provides a new material design strategy for high-performance AWH applications.