New de­vice can har­vest drink­ing wa­ter from dry desert air, sci­en­tists sug­gest

Tehran Times - - SCIENCE -

Our en­vi­ron­ment is chang­ing, and chang­ing fast, putting pres­sure on our hard­work­ing sci­en­tists to come up with ever more in­ge­nious ways of meet­ing the needs of hu­mankind – like pulling drink­able wa­ter right out of the air, in this case.

A new pro­to­type de­vice, de­vel­oped at the King Ab­dul­lah Univer­sity of Science and Tech­nol­ogy (KAUST) in Saudi Ara­bia, is able to ab­sorb wa­ter and then re­lease it on de­mand. It’s the sort of in­ven­tion that could prove in­valu­able to peo­ple liv­ing in arid, desert re­gions, where wa­ter is al­ready scarce.

Key to the de­vice is a spe­cial hy­dro­gel based on the salt cal­cium chlo­ride. It can prove ir­re­sistible to wa­ter, but usu­ally turns into a salty liq­uid as it ab­sorbs va­por. But thanks to the en­gi­neers’ in­no­va­tion, here the hy­dro­gel mix­ture keeps the whole thing in solid form un­til the wa­ter is needed.

With an es­ti­mated 13 tril­lion tons of wa­ter va­por in the at­mos­phere, be­ing able to har­vest some of that wa­ter to keep peo­ple hy­drated would be a ma­jor break­through, es­pe­cially for the hun­dreds of mil­lions with­out a suitable wa­ter source. It’s some­thing numer­ous re­search teams are busy in­ves­ti­gat­ing.

Stor­ing wa­ter

And while cal­cium chlo­ride has been looked at be­fore, mak­ing it prac­ti­cal as a ma­te­rial for stor­ing wa­ter has been dif­fi­cult. Here the team helped solve the prob­lem by con­vert­ing the salt into a poly­mer so it keeps its shape un­til heated; ad­di­tion­ally, car­bon nan­otubes would then help re­lease the wa­ter.

The idea is the de­vice could cap­ture wa­ter from the air overnight, then re­lease it when heated dur­ing the day.

That’s ex­actly how the pro­to­type tested by the re­searchers op­er­ated: 35 grams (1.23 ounces) of the hy­dro­gel was able to cap­ture 37 grams (1.31 ounces) of wa­ter dur­ing a night with a rel­a­tive hu­mid­ity of around 60 per­cent.

The next day, 2.5 hours of sun­shine was enough to re­lease 20 grams (0.71 ounces) of the wa­ter, which was col­lected in the de­vice ready to drink. The hy­dro­gel is then ready to use again, the re­searchers re­port.

How­ever the sci­en­tists aren’t sat­is­fied yet – they’re hop­ing to tweak the de­sign so that wa­ter is re­leased con­tin­u­ously.

There’s plenty of com­pe­ti­tion out there for these po­ten­tially life-sav­ing de­vices, which we think is a good thing.

An­other in­ven­tion

Ear­lier this year teams from the U.S. demon­strated a de­vice that used a spe­cially en­gi­neered me­tal to cap­ture wa­ter – this is an­other in­ven­tion that doesn’t need a sep­a­rate en­ergy source to work.

An­other team of sci­en­tists have cre­ated a syn­thetic ma­te­rial in­spired by the Namib desert bee­tles, which also shows prom­ise as a way of con­dens­ing and cap­tur­ing liq­uid wa­ter from the air where needed.

With all these ini­tia­tives, the chal­lenge is to get them from lab pro­to­type into com­mer­cial prod­uct, but this new hy­dro­gel-based de­vice is tick­ing a lot of the nec­es­sary boxes.

“This type of at­mo­spheric wa­ter gen­er­a­tor is cheap and af­ford­able, works per­fectly with a broad range of hu­mid­ity, does not need any elec­tric­ity, and thus is es­pe­cially suitable for clean wa­ter pro­duc­tion in re­mote ar­eas,” write the re­searchers.

Sci­en­tists have cre­ated a syn­thetic ma­te­rial in­spired by the Namib desert bee­tles, which also shows prom­ise as a way of con­dens­ing and cap­tur­ing liq­uid wa­ter from the air where needed.

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