- Title: Graphene sieve could make sea water drinkable
- Date: 30th May 2017
- Summary: ARUSHA, TANZANIA (FILE) (REUTERS) VARIOUS OF WOMEN CARRYING WATER IN BUCKETS VARIOUS OF SCHOOL CHILDREN PICKING UP CUPS AND DRINKING WATER FROM FILTER CARLSBAD, CALIFORNIA, UNITED STATES (FILE) (REUTERS) VARIOUS OF PIPES OUTSIDE THE PLANT CLOSE UP PIPES, METERS AND OTHER INSTRUMENTS VIEW FROM THE ROOFTOP OF THE DESALINATION PLANT
- Embargoed: 13th June 2017 10:53
- Keywords: graphene University of Manchester water filtration graphene sieve
- Location: MANCHESTER, ENGLAND, UK / FILE LOCATIONS
- City: MANCHESTER, ENGLAND, UK / FILE LOCATIONS
- Country: United Kingdom
- Topics: Science
- Reuters ID: LVA0026J15QVV
- Aspect Ratio: 16:9
- Story Text: Scientists have developed a 'sieve' made from an oxidised form of 'wonder material' graphene that can filter dirty water and seawater to provide drinking water.
The researchers from the UK's University of Manchester developed a membrane using graphene oxide with pores small enough to filter out common salts.
Graphene, which is just one atom thick, is strong, highly flexible, electrically conductive and transparent.
Like current commercial polymer membranes used in desalination processes, graphene oxide membranes developed in the past were unable to filter salts because they swell when immersed in water. This made the pores in the membrane too large.
Now, the scientists say they have developed the 'sieve' further, so that nanoparticles like salts can be filtered out of water.
"This membrane works on a physical sieving principle and the sieve is so small, in principle we can use one membrane to filter out all molecules including large and small molecules. We only need one unit to remove all the contamination including the smallest sodium chloride," said Professor Rahul Nair, who led the research.
The researchers made the membrane by layering flakes of graphene oxide and coating them with epoxy resin to prevent swelling in water.
They pumped an oily water mixture through the graphene oxide membrane to filter out larger molecules. Then the remaining salty water was pumped through a second filter to sieve out smaller sodium chloride and other salt molecules.
Water forms what the scientists call a shell of water molecules around the salt molecules and the tiny pores of the graphene membrane are small enough to block the salt molecule while allowing the water to flow through, making the membrane ideal for desalination.
"Water filtration through the graphene membrane is much faster than the commercial polymer membrane which means you get more drinking water in a short period of time, and the pressure required to make that drinking water is smaller," he told Reuters.
Nair said that the fabrication of the membrane can be scaled up to an industrial level, which should see a fall in the cost of the materials. Its efficiency and low energy requirements could lead to a revolution in desalination technology.
The researchers hope that the 'sieve' could play a part in providing clean drinking water for millions of people around the world who do not have access to safe drinking water.
Nair envisages a smaller filtration unit for use in developing countries, where expensive large-scale desalination plants are not an option.
"It would be really nice if we could come up with a portable water filtration device. If you can have a hand pump or something like that then we can filter out dirty water from clean water. That is probably our long term goal," he said.
The challenge for researchers is to find a partner in industry to scale up production of the membrane and combine the two stages of filtration used in the lab in one unit.
The United Nations predicts that globally 1.8 billion people will experience water scarcity by 2025.
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