Graphene, the much-hailed wonder material, may be the solution to the world’s water crisis. One in nine people around the world do not have access to clean, safe water close to their homes and at least 2 billion people are forced to use a drinking water source contaminated with faeces. Dirty water is a serious public health concern, and drinking or washing in dirty water spreads diseases such as diarrhoea, cholera and typhoid. Contaminated drinking water causes over 500,000 deaths each year from diarrhoea, a leading killer of children under five. First developed by scientists at the University of Manchester in 2004, graphene, an ultra-strong material composed of a single layer of carbon atoms, has been tipped for many uses from hair dye to super long-life batteries. But one of the material’s most exciting properties may be its ability to filter out even the tiniest impurities in water.
Researchers at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Sydney have recently found a way to turn ordinary cooking oil into graphene to create what they believe is a much more effective filter than standard methods. Their breakthrough consists of a thin graphene film that attaches to a conventional filter. Dr Michael Dong Han Seo, a research scientist at CSIRO, said that the filter contains microscopic nano-channels which block contaminants making it possible to filter out 99.9 percent of contaminants, he says. “We have developed a narrow channel to allow water to pass through while rejecting different contaminants – without failing,” said Dr Seo. The team tested their innovation, GraphAir on what Dr Seo calls an “extreme” case: Sydney harbour’s heavily contaminated water. The GraphAir filter was able to filter out virtually all the pollutants in the water, including heavy metals and dioxides, making it drinkable in one step.
Currently, conventional water purification involves chemical treatment and filtration of water in a seven to eight-step process. The CSIRO research is at an early stage, and the GraphAir membrane currently costs six or seven times more than a conventional polymer membrane – used most commonly for water filtration – but Dr Seo believes that the uses for GraphAir are potentially huge. “We can generate clean water virtually from anything,” he said. The team is planning to test their innovation on a larger scale pilot in a low-income country at the end of this year. Rahul Nair, professor of materials physics at Manchester University, is also exploring the potential of graphene to bring clean drinking water to millions of people. Last year, Prof Nair led a research team at the university which showed that a graphene oxide membrane could filter salt from seawater more quickly and more effectively than existing methods. Their ground-breaking discovery overcame graphene’s tendency to swell when wet – one of the sticking points with the material. The filters are the size of an A4 piece of paper, although Prof Nair said that some companies could manufacture them on a large scale. “If we can scale up the tech, then there are advantages to graphene,” he said.
While the team’s long-term goal is to use graphene filters in desalination plants to make seawater drinkable, Prof. Nair acknowledges this could be some time away. “There are two to three hurdles. One problem is making large membranes, and another challenge is making them defect free. Also, existing plants have invested quite heavily in existing technologies,” he said. In the more immediate term, the team at Manchester is focusing on finding a commercial application for their graphene oxide technology by using it to remove a broad range of pollutants from water on a smaller scale. Prof Nair and the team are currently working with British company Icon Lifesaver to create a portable version of their graphene filter that can be attached to a drinking bottle or larger mobile water unit. Prof Nair is hopeful that a product will be on the market soon. “Ideally, we would like to get everything done in 24 months,” he said.
Icon Lifesaver’s existing non-graphene filters have been used in humanitarian emergencies to filter out bacteria and viruses. Joe Lovegrove, the company’s technical manager, believes that graphene will allow them to create “the ultimate filter” by also filtering out heavy metals such as arsenic and cadmium in a one-step process. “You can filter these things out now, but you need four or five different filters,” said Mr Lovegrove. “What we’re trying to form is a one-stop shop.” He said that a great benefit of graphene was that there was no need to test the water to identify the existing impurities. Icon Lifesaver’s current water filtration bottles retail at over £100, meaning that the new graphene filter bottles are likely to be too costly to be deployed by NGOs or governments in low-income countries. But the company’s larger water filtration cubes are more cost-effective and have been used by Oxfam and the Department for International Development.
Remi Kaupp, an adviser on urban sanitation and resilience at Water Aid, is encouraged by graphene’s potential to tackle global water issues. “It’s exciting when there are new technological developments and graphene is exciting for some reasons,” he said. “We could see it applied to desalination. Desalination is currently very expensive, and it’s not used for this reason.” Cape Town is one city that is exploring desalination as an answer to the city’s crippling water crisis in the face of Day Zero – the point when the authorities will have to turn off the taps. But the high cost of desalination means that the city resorted to a more low tech solution: residents were encouraged to slash their water consumption to save the city from drying up. Mr Kaupp warns that new technologies such as graphene are unlikely to solve the world’s water crisis alone. “850 million are without access to clean water,” he said. “But often the issue is not the technology – some people without water live in cities where people one kilometre away have access to water. The real issues are political, social and financial.”
Fact box | Graphene
- Graphene is thought to be one of the strongest materials in the world: it is 200 times stronger than steel and harder than a diamond.
- Graphene was the first two-dimensional material discovered.
- It is made from a single layer of graphite, just one atom thick.
- Although there has been a lot of excitement about graphene, its practical uses so far have been few.
- Electricity can flow through graphene with zero resistance meaning it could be used one day as a super battery that won’t need recharging.
- Mobile phone companies are exploring using graphene to make bendable screens for smartphones and tablets.
- Graphene’s filtering properties means it can sieve the colour out of whiskey.
- Graphene has several promising biomedical uses including drug delivery, cancer therapies, biosensing and wound dressing.
Need to know | Global water facts
- 844 million people in the world – one in nine – do not have clean water close to home
- 3 billion people in the world – almost one in three – do not have a decent toilet of their own
- Around 289,000 children under five die every year from diarrhoeal diseases caused by poor water and sanitation. That’s almost 800 children a day, or one child every two minutes
- Every £1 invested in water and toilets returns an average of £4 in increased productivity
- Just £24 can provide one person with clean water.
To find out if countries are keeping their promises on water and sanitation, see the online database washwatch.org Source: WaterAid.
Credit: Aisha Majid for The Telegraph, 3 May 2018.