MIT Engineers Develop Superabsorbent Material for Water Harvesting in Desert-Like Conditions

Significance 

In the face of global water scarcity and the need for energy-efficient technologies, Dr. Gustav Graeber, Dr.  Carlos D. Díaz-Marín, Dr.  Leon C. Gaugler, Dr.  Yang Zhong, Dr.  Bachir El Fil, Dr. Xinyue Liu, and led by Professor Evelyn N. Wang at the Massachusetts Institute of Technology (MIT) have achieved a significant engineering breakthrough. They have successfully synthesized a superabsorbent material with unprecedented moisture absorption capabilities, even in arid conditions resembling deserts. This transparent and rubbery material, made from a hydrogel infused with lithium chloride, has the potential to revolutionize water harvesting and energy-saving applications.

Hygroscopic hydrogels are a type of hydrogel material that has the ability to absorb and retain large amounts of water from the surrounding environment. These hydrogels contain hydrophilic (water-attracting) polymers, which enable them to swell and retain water molecules within their structure. The term “hygroscopic” refers to the ability of a substance to attract and hold water molecules from the air, making hygroscopic hydrogels useful for applications such as moisture control, humidity sensing, drug delivery, and tissue engineering.

The research team set out to optimize hydrogels, which are already known for their exceptional absorbent properties in applications such as disposable diapers. By infusing hydrogels with lithium chloride, a powerful desiccant salt, the researchers were able to significantly enhance their absorbency. Previous attempts at infusing hydrogels with salts were limited in the amount of salt that could be loaded. However, the authors surpassed previous achievements by synthesizing hydrogels that incorporated an impressive 24 grams of salt per gram of polymer.

The salt-loaded hydrogels demonstrated remarkable moisture uptake across various humidity levels, including extremely dry conditions with only 30% relative humidity. Even in such challenging environments, the material captured a record-breaking 1.79 grams of water per gram of material. This breakthrough opens up possibilities for passive water harvesting, especially in desert and drought-prone regions, where the material could continuously absorb vapor and subsequently condense it into ultra-pure drinking water.

The potential applications of this superabsorbent material are vast. The researchers envision integrating it into air conditioning units as an energy-saving and dehumidifying element. By using the material’s ability to capture moisture from the air, the energy consumption of air conditioning systems can be reduced significantly. Additionally, the harvested water could be collected, heated, and condensed, providing a sustainable source of clean water.

The authors’ findings, published in the journal Advanced Materials, signify a significant step forward in the development of scalable and low-cost sorbents for atmospheric water harvesting, dehumidification, passive cooling, and thermal energy storage. By pushing the boundaries of water vapor uptake in hygroscopic hydrogels, this research paves the way for the realization of sorption-based devices that can tackle water scarcity and contribute to solving the global energy crisis.

One of the key innovations in this research lies in the synthesis process itself. The MIT team extended the duration of salt infusion into the hydrogels, allowing for significantly higher salt loadings and, consequently, superior moisture absorption. By manipulating the concentration of the salt solution and the cross-linking properties of the hydrogel, they optimized the material’s swelling dynamics and achieved maximum water uptake. This breakthrough contributes to the field of hygroscopic hydrogels and sets new standards for their water absorption capacity.

The superabsorbent material developed by MIT has tremendous potential to address critical sustainability challenges. Water scarcity and energy efficiency are pressing global concerns, and this innovation offers a promising solution. By enabling the efficient harvesting of water from the atmosphere, particularly in arid regions, the material can alleviate water stress and promote self-sufficiency. Moreover, its integration into air conditioning units can enhance energy efficiency and reduce the environmental impact of cooling systems.

The authors acknowledged the vast potential of this material and are actively exploring various applications. Their focus now shifts towards improving the kinetics of the material’s superabsorbent properties to enable faster cycling for water harvesting. By maximizing the efficiency of water recovery, it may be possible to harvest water multiple times a day, ensuring a constant supply even in challenging environments.

The synthesis of a superabsorbent material with exceptional moisture uptake capabilities represents a significant engineering breakthrough. The MIT engineers have demonstrated the immense potential of this hydrogel infused with lithium chloride, paving the way for scalable and low-cost solutions to address water scarcity and enhance energy efficiency. The material’s ability to absorb water vapor and retain moisture without leakage, even in desert-like conditions, opens up new possibilities for passive water harvesting and energy-saving applications. With further advancements and optimization, this technology could make a profound impact on global water sustainability and the mitigation of water and energy crises.

MIT Engineers Develop Superabsorbent Material for Water Harvesting in Desert-Like Conditions - Advances in Engineering

About the author

Dr. Gustav Graeber
Massachusetts Institute of Technology

Gustav joined the DRL in March 2021 as a postdoctoral fellow on a Postdoc Mobility Grant by the Swiss National Science Foundation. After studying mechanical engineering at TU Berlin (Germany), KTH Stockholm (Sweden), and RWTH Aachen (Germany), he graduated as a PhD from ETH Zurich (Switzerland). His doctoral research focused on freezing physics and derived surface nano-engineering for spontaneous deicing. After his PhD, Gustav joined the Swiss Federal Laboratories for Materials Science and Technology (Empa) as a postdoc to study wetting and phase change in electrochemical systems. At the DRL, Gustav investigates adsorption on tailored nanostructures and the rational design of hydrogels for atmospheric water harvesting.

About the author

Evelyn N. Wang
Ford Professor of Engineering
Massachusetts Institute of Technology

RESEARCH INTERESTS

  • Thermal management, energy conversion, and storage
  • Nanoengineered surfaces and materials
  • Water harvesting, purification, and conservation

Reference

Graeber G, Díaz-Marín CD, Gaugler LC, Zhong Y, El Fil B, Liu X, Wang EN. Extreme Water Uptake of Hygroscopic Hydrogels through Maximized Swelling-Induced Salt Loading. Adv Mater. 2023:e2211783. doi: 10.1002/adma.202211783.

Go To Adv Mater.

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