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Scientists May Just Have Solved the Earth’s Freshwater Problem

graphene sieve

Source: http://www.bbc.com/news/science-environment-39482342

[DIGEST: Phys.org, BBC, Nature]

As water resources become scarcer around the world due to climate change, desalination technology has grown more popular. The UN anticipates that 14% of the world’s population will experience water scarcity by 2025. However, taking the salt out of water to drink it, or even use it for crop irrigation, is expensive; a thousand gallons of freshwater from a desalination plant costs the average US consumer anywhere from $2.50 to $5, compared to just $2 for regular freshwater, according to Tom Pankratz, editor of the Water Desalination Report. It’s also a huge energy consumer. Desalination plants around the world consume more than 200 million kilowatt-hours each day, an estimated 55 percent of plants’ total operation and maintenance costs. These plants can also cause environmental issues such as displacing ocean creatures and negatively altering salt concentrations in their habitats.

A relatively new technology has taken the field of desalination by storm: graphene-oxide membranes can filter common salts, rendering water clean, and likely save energy and money, too. These new findings came from a group of scientists at t he University of Manchester and were published in the journal Nature Nanotechnology. The technology has been around for some years, but researchers have been refining it.

Graphene membranes are comprised of a single layer of carbon atoms laid out in a hexagonal lattice. Due to its remarkable tensile strength and electrical conductivity, it has been considered one of the most promising materials for filtration. Graphene is not only durable and incredibly thin, but it’s not sensitive to water treatment chemicals like chlorine.

Graphene-oxide membranes previously developed at the National Graphene Institute have been shown to filter out nanoparticles, organic molecules and even large salts. Until recently, however, they had not yet perfected the technique for filtering out common salts used in desalination technologies, which are even smaller.

One of the early problems was that the graphene membranes would swell slightly when immersed in water, allowing the smaller salts to escape. The Manchester group has now perfected a strategy to avoid the swelling of the membrane when exposed to water. They

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