Carbon to the Water Rescue?

Water Wonk Wednesdays

A weekly column on water news, tips, and innovations.

GrapheneSieve_1024

Image Credit: University of Manchester. 

by Erik Baard
(apologies for the publication delay)

Carbon is unloved these days, with carbon emissions from industry and livestock rightly identified as a chief cause of global climate chaos, melting glaciers, and ocean acidification. This core element of life, however, is also a tool of fantastic invention and innovation. The latest example: Researchers from the University of Manchester report in the peer-reviewed journal Nature Nanotechnology that they’ve developed membranes of carbon and oxygen that passively and rapidly sieve saltwater to produce drinking water. The honeycomb-shaped (hexagonal) pores of this form of graphene oxide are small enough to block salt and other impurities without slowing H2O molecules.

This new work builds on earlier graphene membranes gas separation and water filtration, but those earlier renditions were unable to screen out sodium chloride, which is a relatively small molecule. Salt attracts a coating of water molecules that makes it a larger blob, but the pores themselves in earlier graphines grew larger too when soaked.

New York City’s mountain reservoirs fill up with generous rain and snowfall, forests protect almost all of this bounty from pollution and soiling, and gravity powers the flow without pumping. That makes for an astonishingly inexpensive water system. What a contrast with many other cities, which depends on the sea for drinking water. Perhaps global climate change will one day rob New York City too of its water wealth. Desalination plants have proven a boon to humanity, turning enough saltwater into potable supplies each day to slake the thirst of New York City 23-times over.  Bu it’s terribly expensive. Energy is a great component of this cost, and when desalination depends on fossil fuels the result is carbon emissions that only worsen the world’s water crises. This graphene membrane technology could be coupled with solar, wind, tidal, or current power to make clean water more affordable and reliable.

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