Scalable super hygroscopic polymer films for sustainable moisture harvesting in arid environments

Abstract

Extracting ubiquitous atmospheric water is a sustainable strategy to enable decentralized access to safely managed water but remains challenging due to its limited daily water output at low relative humidity (≤30% RH). Here, we report super hygroscopic polymer films (SHPFs) composed of renewable biomasses and hygroscopic salt, exhibiting high water uptake of 0.64–0.96 g g−1 at 15–30% RH. Konjac glucomannan facilitates the highly porous structures with enlarged air-polymer interfaces for active moisture capture and water vapor transport. Thermoresponsive hydroxypropyl cellulose enables phase transition at a low temperature to assist the release of collected water via hydrophobic interactions. With rapid sorption-desorption kinetics, SHPFs operate 14–24 cycles per day in arid environments, equivalent to a water yield of 5.8–13.3 L kg−1. Synthesized via a simple casting method using sustainable raw materials, SHPFs highlight the potential for low-cost and scalable atmospheric water harvesting technology to mitigate the global water crisis.

Environmentally adaptive MOF-based device enables continuous self-optimizing atmospheric water harvesting

“…Compared with other adsorbent-driven water harvesting devices, our MOF-801-based adaptive device reduces the amount of adsorbent material required for producing enough water required to fulfill daily personal consumption needs (3.5 L) by 75%, 73%, and 57% with respect to devices based on super moisture-absorbent gels, super hygroscopic polymer films, and hygroscopic salts in a hydrogel-derived matrix, respectively (Table 1) [26][27][28] . Furthermore, our adaptive device drastically reduces energy consumption by 60% compared to the benchmark device based on super hygroscopic polymer films while maintaining a smaller physical footprint (Table 1).…”

Sustainable water generation: grand challenges in continuous atmospheric water harvesting

“…13,[29][30][31]46 Encouraging sorption-desorption uptake ratios at 4 : 1 in the 30-60% RH range have been very recently reported for polymer films composed of biomass and LiCl. 47 Therefore, the progress of future sorbent materials used for continuous AWH should be further oriented towards equalized sorption vs. desorption time. The above discussed topic illustrates current mismatch between sorption and desorption rates, exposing a meaningful challenge for sorbent materials.…”

“…50 Moreover, special care should be dedicated to composite sorbents using hygroscopic salts, as high salt wt% has a detrimental effect on sorption kinetics. 47 Additional insight into sorption kinetics of hygroscopic hydrogels can be provided by a mechanistic model, showing the importance of the interdependence between the liquid transport through the nanopores in addition to the vapor transport through micropores of the polymer network. 51 Similar mechanistic models illuminating chief design parameters for all kinds of sorbents are severely needed for future development of sorbents for continuous AWH.…”

Marine biomass-derived, hygroscopic and temperature-responsive hydrogel beads for atmospheric water harvesting and solar-powered irrigation

“…[18][19][20][21][22][23] Compared to typical passive approaches (i.e., fog and dew condensers), sorbent-based AWGs signicantly reduce geographical and climatic effects (i.e., sky emissivity, humidity, wind speed and topographic location), boosting water production yields in relatively dry air and low temperature. [24][25][26][27] Incorporating hygroscopic materials with photothermal or radiative cooling materials, sorbent-based AWGs can release water and regenerate under natural sunlight with low energy intake. [28][29][30][31][32] Sunlight is the largest energy source for our planet.…”

“…, sky emissivity, humidity, wind speed and topographic location), boosting water production yields in relatively dry air and low temperature. 24–27 Incorporating hygroscopic materials with photothermal or radiative cooling materials, sorbent-based AWGs can release water and regenerate under natural sunlight with low energy intake. 28–32…”