Water harvesting from air with a hygroscopic salt in a hydrogel–derived matrix

Abstract

The extraction of water from air is a promising way to supply fresh water, especially in remote, arid regions. This process can be supported by desiccant materials such as zeolites, metal−organic frameworks, or hygroscopic salts. Here we present a composite material that is able to absorb 660 kg of water per cubic meter of bulk material from air at 10 mbar water vapor pressure and 28°C. The material consists of calcium chloride incorporated into an alginate-derived matrix. A simple synthesis route leads to spherical beads of the composite with a diameter of approximately 2 mm. This macroscopic structure allows for good vapor permeability through packed beds. The collected water can be released at 100°C, potentially enabling a solar-driven application. In addition, the synthetic route uses cheap, non-toxic, and easily accessible materials allowing for widespread application.

Water recycling efficacies of extremely hygroscopic, antifouling hydrogels

“…The development of novel materials with superior water absorption and storage capabilities, in well-dened threedimensional architectures, is a topic of great interest in science, nanotechnology, biomedicine, agriculture, and the food industry. [1][2][3][4][5][6][7][8][9] Superabsorbent hydrogels are an example of highly permeable, and biocompatible, three-dimensional network of polymeric materials, capable of holding large amount of water in comparison to their own molecular weight. [2][3][4][5][6][7] The water releasing hydrogels are a specialized class of superabsorbent hydrogels, which exhibit superior water absorbing and release efficacies, in the presence of external stimulus, such as the temperature.…”

“…[1][2][3][4][5][6][7][8][9] Superabsorbent hydrogels are an example of highly permeable, and biocompatible, three-dimensional network of polymeric materials, capable of holding large amount of water in comparison to their own molecular weight. [2][3][4][5][6][7] The water releasing hydrogels are a specialized class of superabsorbent hydrogels, which exhibit superior water absorbing and release efficacies, in the presence of external stimulus, such as the temperature. [4][5][6][7] These water releasing hydrogels, capable of harvesting clean water from rivers, mist, dew, fog and dry air, are generally comprised of hygroscopic natural polysaccharides in the presence of organic salts or are cross-linked in the presence of stimuli responsive polymer chains to aid the release of water at high temperatures.…”

Efficient Solar‐Driven Water Harvesting from Arid Air with Metal–Organic Frameworks Modified by Hygroscopic Salt

“…In recent years, research on new porous matrix materials with large pore volumes inspired the design and development of new composite sorbents to achieve high sorption capacity by filling with large amount of salts. Similar to the CSPMs, several composite sorbents of salt@matrix were reported to achieve high‐performance AWH, of which CaCl 2 @polyacrylamide showed 0.70 g g −1 water sorption capacity at 1.1 kPa vapor pressure (35 % RH at 25 °C), CaCl 2 @alginate showed 1.0 g g −1 water uptake at 1.0 kPa vapor pressure (26 % RH at 28 °C), and chloride‐doped polypyrrole@N‐isopropylacrylamide showed 0.7 g g −1 water sorption capacity at 0.8 kPa vapor pressure (30 % RH at 25 °C) . Although hydrogels can supply large pore volumes to encapsulate hygroscopic salts, they suffer from several drawbacks including serious swelling, low specific surface area, and low mechanical strength .…”

Efficient Solar‐Driven Water Harvesting from Arid Air with Metal–Organic Frameworks Modified by Hygroscopic Salt

“…In recent years,r esearch on new porous matrix materials with large pore volumes inspired the design and development of new composite sorbents to achieve high sorption capacity by filling with large amount of salts.S imilar to the CSPMs, several composite sorbents of salt@matrix were reported to achieve high-performance AW H, of which CaCl 2 @polyacrylamide showed 0.70 gg À1 water sorption capacity at 1.1 kPa vapor pressure (35 %R Ha t2 5 8 8C), [17] CaCl 2 @alginate showed 1.0 gg À1 water uptake at 1.0 kPa vapor pressure (26 %R Ha t2 8 8 8C), [18] and chloride-doped polypyrrole@N-isopropylacrylamide showed 0.7 gg À1 water sorption capacity at 0.8 kPa vapor pressure (30 %R Ha t 25 8 8C). [19] Although hydrogels can supply large pore volumes to encapsulate hygroscopic salts,t hey suffer from several drawbacks including serious swelling, [19] low specific surface area, and low mechanical strength.…”