Waste plastics become molecular sponges that capture water from air

Source materials like discarded packaging, old CDs, and LEGO bricks can be repurposed to create substances capable of pulling significant amounts of moisture from the atmosphere, according to researchers at the University of Vienna. Materials chemists Anastasiia Naryshkina, Paul Schweng, and Robert Woodward transformed various types of plastic waste into polymer networks that readily absorb water, even in arid environments.

The study, published in Chem Circularity, represents a potential solution to the dual issues of plastic waste and water scarcity. Atmospheric water harvesting, which captures water vapor from the air and releases it later, offers a decentralized water source. To develop suitable adsorbents for this process, the researchers explored the use of aromatic polymers found in certain plastics.

These polymers, featuring six-membered carbon rings, form porous structures that can hold substantial quantities of water. By treating the plastic waste with sulfuric acid, the team created water-attracting molecular sponges from polystyrene packaging, polycarbonate CDs, and acrylonitrile butadiene styrene LEGO bricks. The resulting sponges demonstrated the ability to adsorb up to 60% of their mass in water from humid air and up to 20% in dry conditions, with the water releasing readily upon mild heating from sources such as sunlight.

The materials have shown resilience through repeated capture-and-release cycles, making them viable for continuous water generation. While the study lays the groundwork for utilizing mixed plastic feedstocks as water-absorbing materials, further research is needed to evaluate the long-term performance and resource demands of these innovative sponges.