Graphene Ox­ide Could Have the Power to Make Seawa­ter Drink­able

Could Have the Power to Make Seawa­ter Drink­able

Trillions - - In This Issue -

Graphene-ox­ide mem­branes are well known for their fil­ter­ing ca­pa­bil­i­ties. A new re­search study sug­gests that they might be able to turn seawa­ter into safe and clean drink­ing wa­ter.

The pos­si­bil­ity of this break­through came via a just-pub­lished pa­per by sci­en­tists at the Univer­sity of Manch­ester (United King­dom). It ap­peared in the jour­nal Na­ture Nan­otech­nol­ogy in an ar­ti­cle coau­thored by Jijo Abra­ham and Kalangi S. Vasu.

These unique mem­branes have pre­vi­ously been found to be very use­ful when at­tempt­ing to iso­late or­ganic mol­e­cules, large salts and small nanopar­ti­cles. They have also been used for gas sep­a­ra­tion. Us­ing them to re­move smaller salts such as those that nat­u­rally ap­pear in seawa­ter has been a tech­ni­cal dilemma so far. The rea­son is that when these mem­branes are im­mersed in wa­ter, the graphene-ox­ide struc­tures be­gin to swell. When the mem­branes swell, even though larger ions or mol­e­cules are suc­cess­fully blocked, the swelling is suf­fi­cient so that both wa­ter and the smaller salt mol­e­cules can flow through the ma­te­rial. It is also fur­ther com­pli­cated be­cause when seawa­ter is present, the dis­solved salts in it are sur­rounded nat­u­rally by a “shell” of wa­ter mol­e­cules that pro­tects the salt and blocks the ef­fi­cacy of any sep­a­ra­tion mem­brane.

The trick in­volved in the Univer­sity of Manch­ester group’s re­search in­volves man­u­fac­tur­ing graphene-ox­ide sieves with far more pre­cisely con­trolled mem­brane struc­tures. It also in­volves cre­at­ing mem­brane open­ings that have a uni­form pore size down to the atomic scale, in a more-or-less tun­able man­ner.

With these new struc­tures in place, the tiny cap­il­lar­ies of the graphene-ox­ide mem­branes keep the salt from pass­ing through the mem­brane along with the much smaller mol­e­cules of wa­ter. The re­sult is a sus­tained fresh-wa­ter out­put flow with­out any trace of the orig­i­nal in­com­ing salt­wa­ter sources.

The value of this break­through could be im­mense. Thanks to global warm­ing and re­lated con­tin­u­ing world­wide drought pat­terns, the United Na­tions es­ti­mates that by 2025 some 14% of the world’s pop­u­la­tion could be deal­ing with a ma­jor scarcity of fresh wa­ter. These po­ten­tially quite in­ex­pen­sive graphene-ox­ide sieves could be just the in­no­va­tion needed to save the world – from it­self – again.

Photo by Hin­kle Group, CC

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