Graphene Sieve Makes Seawater Drinkable
If there’s an early contender for the word of 2017, it has to be ‘graphene’. Scientists, from the University of Manchester, first developed graphene in 2004 as the world’s first 2D material. Graphene is just one atom thick – one million times thinner than a human hair – and is 200 times stronger than steel. In the years since graphene was first developed scientists around the world have been trying to develop practical applications for this revolutionary new material and one of these applications hit the headlines in April 2017 with the announcement of the “graphene sieve”.
Worldwide Water Shortage
In developed parts of the world, we take clean, safe drinking water for granted. We turn on the tap, fill a glass and know that the water we drink isn’t going to give us an upset stomach or something more serious. Across the globe though, almost one billion people do not have access to safe, clean water, with the issue being particularly concentrated in sub-Saharan Africa. The issues also run deeper than simply just water for drinking; there are complex related issues such as children being taken out of school to walk miles to collect the family’s water, increased pressure on stretched medical services due to avoidable illnesses and scarce water resources being directed to agriculture rather than for drinking. Given that two thirds of the planet’s surface is covered with oceans, desalination could be the answer.
The idea of removing salts and other minerals from sea water and making it safe for drinking is not a new idea. Desalination plants already exists in areas of the world with large populations and a small supply of fresh water – the Canary Islands, Singapore and the Gulf States for example. Many desalination plants use thermal distillation, which is the process of boiling the sea water and then condensing the vapour back to water. Others use reverse osmosis, forcing the water through a membrane which separates out the salt. Done on an industrial scale, these processes are very energy hungry and expensive and are therefore out of the budget of many countries in the very areas of the world where water shortages are most acute. Desalination is twice as expensive as processes for treating rainwater or waste water to make it safe to drink.
Advantages of the Graphene Sieve
Graphene has not been used before now as a filter for salt water as it had been found that, when placed in water, the graphene swelled slightly and this was enough to let some of the salt particles flow through the membrane along with the water. Further research has allowed scientists to develop a technique which allows them to control the pore size in the graphene sieve and therefore stop the salts flowing through. This ability to control the size of the pores in the graphene means that researchers will be able to custom-build membranes to filter out a range of ions depending on requirements. Using a graphene sieve to filter water uses a lot less energy than more traditional desalination methods and if the technology proves that it is durable under prolonged contact with seawater, it could open the door for cost-effective, small scale desalination in every town or village. The same technology can also be used to filter water from other sources, removing bacteria and other minerals from rivers, streams or lakes.
Potential Stumbling Blocks
Graphene sieves seem like the answer to the world’s water problems but the road to commercialisation will not be without its bumps. Technology which works perfectly in the lab doesn’t always work perfectly in a field setting, especially in areas with poor infrastructure and unreliable power. Graphene is still a very expensive material and large scale production, on the scale needed to run multiple water treatment plants, is not practical at present. Investment on a large scale will be needed to commercialise the idea of using graphene to treat water and with the countries which are most affected being some of the poorest in the world, it’s not clear where the money is going to come from.