When water molecules
(red and white) and sodium and chlorine ions (green and purple) in saltwater,
on the right,
encounter a sheet of graphene (pale blue, center) perforated by holes of the
right size,
the water passes
through (left side), but the sodium and chlorine of the salt are blocked.
Graphic: David
Cohen-Tanugi
(July 2,
2012) Graphene
sheets with precisely controlled pores have potential to purify water more
efficiently than existing methods.
The
availability of fresh water is dwindling in many parts of the world, a problem
that is expected to grow with populations. One promising source of potable
water is the world’s virtually limitless supply of seawater, but so far
desalination technology has been too expensive for widespread use.
Now, MIT
researchers have come up with a new approach using a different kind of
filtration material: sheets of graphene, a one-atom-thick form of the element
carbon, which they say can be far more efficient and possibly less expensive
than existing desalination systems.
“There are
not that many people working on desalination from a materials point of view,”
says Jeffrey Grossman, the Carl Richard Soderberg Associate Professor of Power
Engineering in MIT’s Department of Materials Science and Engineering, who is
the senior author of a paper describing the new process in the journal Nano Letters.
Grossman and graduate student David Cohen-Tanugi, who is the lead author of the paper, aimed to “control the properties of the material down to the atomic level,” producing a graphene sheet perforated with precisely sized holes. They also added other elements to the material, causing the edges of these minuscule openings to interact chemically with water molecules — either repelling or attracting them.