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Harvesting water from air: Copolymer solution uses water-loving differential to induce desorption

Harvesting water from the air and decreasing humidity are crucial to realizing a more comfortable life for humanity. Water-adsorption polymers have been playing a key part in atmospheric water harvesting and desiccant air conditioning, but desorption so that the polymers can be efficiently reused has been an issue.

Now, Osaka Metropolitan University researchers have found a way to make desorption of these polymers more efficient. The findings are in ACS ES&T Water.

Usually, heat of around 100°C is required to desorb these polymers, but Graduate School of Engineering student Daisuke Ikegawa, Assistant Professor Arisa Fukatsu, Associate Professor Kenji Okada, and Professor Masahide Takahashi developed a liquid moisture adsorbent that requires only a temperature of around 35°C to do so.

This became possible through the use of random copolymers of polyethylene glycol, which adsorbs water well, and polypropylene glycol, which adsorbs water slightly less well. The difference in their water-loving properties created a transfer mechanism that broke down the water clusters, freeing the water more easily.

"This technology has the potential to be applied not only to water supply in arid regions and places with limited energy resources, but also to ensuring access to water in times of disaster and emergency," Dr. Fukatsu said.

"Improvements to this technology are also expected to lead to reductions in greenhouse gases and more efficient use of water resources," Professor Takahashi added. "From now on, we will aim to improve the liquid moisture adsorbent and increase the efficiency of the entire system in order to make it practical."