Hierarchical Micro/nanoporous Ion Exchangeable Sponge
Inspired by versatile properties of a sponge, we proposed an ion exchangeable sponge composed of hierarchical micro/nanopores for water treatment. Sodium ions in brackish water (10 ~ 300 mM) absorbed in the sponge were exchanged to hydrogen ions in short incubation time and the desalted water was released out by squeezing the sponge in a single hand grip. This simple desalination was attributed to the multiscale porous structures in the sponge. A number of nanoporous thin films were formed like a bubble rimmed by the closed backbone of a microporous sponge. The hierarchical micro/nanopores maximized contacting area of ion-exchanging surface for saline solution so that scaled-up desalination was able to be achieved. Furthermore, we demonstrated, for the first time, the growth of wheat was demonstrated in vivo using this micro/nanofluidic based water-treatment by the sponges. Wheat shoots grown from NaHCO3/Na2CO3 solutions treated by the sponges were 110 to 226.45 % longer than those grown from the original salty water. This implied that the ion-exchangeable sponge would serve as an appropriate technology to the treatment of ground water exacerbated by acid rain and weathered alkaline rocks.