Graphene could work wonders in water purification.
However, an innovative solution to this problem was proposed in this month’s issue of journal Nature Nanotechnology.
The authors, who belong to a group in the National Graphene Institute at the University of Manchester, developed graphene-oxide membranes capable of controlling pore size.
In order to avoid swelling, the sheets were stored under high humidity conditions and embedded in epoxy resin.
“This is the first clear-cut experiment in this regime.
We also demonstrate that there are realistic possibilities to scale up the described approach and mass produce graphene-based membranes with required sieve sizes.” The innovation is a low-cost, sustainable and reliable alternative to current bulky desalination systems.
When brought to fruition, it could be a game-changer in countries with poor access to drinking water.
This development could have far-reaching consequences including improving child health and empowering women who currently spend a significant part of their days gathering water.
Additionally, the United Nations forewarns that by 2025, 14% of the world will suffer from water scarcity.
Tunable graphene-oxide filters could potentially save the world from the impending water crisis.

Graphene-based sieve turns salt water into drinking water.
To make it, researchers turned to a chemical derivative known as graphene oxide.
Graphene is an allotrope consisting of a single layer of carbon atoms arranged in a hexagonal lattice.
This gives it a wide range of unique properties, such as extraordinary tensile strength and electrical conductivity.
However, manufacturing graphene-based membranes have proven difficult in the past.
In contrast, graphene oxide is much easier to produce.
“Graphene oxide can be produced by simple oxidation in the lab,” said co-author Dr. Rahul Nair, a professor at the University of Manchester, according to BBC News.
This then restricted the substance and allowed researchers to control how much salt passed through by changing the speed of water as it went through the membrane.
They hope that one day the sieve — or ones like it — could be used to help reduce that number.
While more work needs to be done before graphene-based membranes can be inexpensively produced at an industrial scale, this new device is the first time scientists have been able to control the spacing of pores in a membrane for desalination purposes.

This country lowered its hygiene test standards so 75 bottled water makers could pass.
Image: Shutterstock / Tarasyuk Igor You might want to be careful the next time you reach for a bottle of water in Myanmar.
Some 70 drinking water brands were granted brand licenses despite failing FDA-administered tests, after the government decided it was easier to lower test standards than for the brands to improve the quality of their water.
All water brands in Myanmar were previously required to contain less than 100 colonies per millilitre — the same standard used in places like the US and EU.
However, several of the brands that failed had over 300 colonies per millilitre.
"In U.S. and the E.U., the standard is 100 bacterial colonies.
Our standard was also [set at that level] but that was apparently too high for domestic brands," FDA director-general Dr Than Htut told news outlet Eleven.
Dr Htut added that the country "still won’t approve any brands whose drinking water contains coliform bacteria, including E.coli".
The FDA declined to reveal the brands that initially failed the microbial test.
Clean water is one of Myanmar’s biggest problems — in a country where it is unsafe to drink tap water, many still draw water from unprotected wells as they cannot afford or have no access to bottled water.

Researchers have tapped into graphene-oxide membranes as a new source to produce clean water.
A team from The University of Manchester have demonstrated the real-world potential of creating adequate clean water sources using graphene-oxide for new filtration technologies.
Graphene-oxide membranes have previously shown potential for gas separation and water filtration and graphene-oxide membranes developed at the National Graphene Institute at The University of Manchester have already demonstrated the potential of filtering out small nanoparticles, organic molecules and large salts.
However, prior to this study, graphene-oxide membranes could not be used for sieving common salts used in desalination technologies, which require very small sieves.
Previous research at The University of Manchester found that if immersed in water, graphene-oxide membranes become slightly swollen and smaller salts flow through the membrane along with water but larger ions or molecules were blocked.
The research team have now further developed the graphene membranes and found a strategy to avoid the swelling of the membrane when exposed to water.
The pore size in the membrane can be precisely controlled, allowing the sieving of common salts out of salty water, making it safe to drink.
When common salts are dissolved in water, they form a ‘shell’ of water molecules around the salt molecules, which allows the tiny capillaries of the graphene-oxide membranes to block the salt from flowing along with the water.
“This is the first clear-cut experiment in this regime.
However, the researchers believe that this technology has the potential to revolutionize water filtration across the world, particularly in countries that cannot afford large-scale desalination plants.

Graphene sieve that turns seawater into drinking water could be a game-changer.
By using a graphene sieve to turn seawater into drinking water, millions of lives could be saved all over the world.
Time and time again, the ‘wonder material’ graphene has shown itself to be a potential game-changer for many industries due to its superconductive properties, at only one atom in thickness.
A new discovery by a team from the University of Manchester (UM) – the very place that gave birth to graphene in its latest form – has found that its applications in the real world could have even greater effects.
Controlling the pores In a research paper published in the journal Nature Nanotechnology, Jijo Abraham and Dr Vasu Siddeswara Kalangi, along with their team, have shown that a graphene-oxide membrane has exciting potential for gas separation and water filtration.
While graphene-oxide membranes have already proved to be promising in filtering out small nanoparticles and organic molecules, they couldn’t be used for sieving common salts used in desalination technologies, which require even smaller sieves.
With this latest breakthrough, however, salt water can be sieved through the graphene membrane to create clean, potable drinking water that could potentially benefit millions of people around the world.
Timely in face of climate change The graphene membrane would originally swell allowing smaller salts to flow through, but the team found a way to prevent this by precisely controlling the pore size.
Prof Rahul Raveendran-Nair of UM said: “Realisation of scalable membranes with uniform pore size down to atomic scale is a significant step forward, and will open new possibilities for improving the efficiency of desalination technology.
We also demonstrate that there are realistic possibilities to scale up the described approach and mass produce graphene-based membranes with required sieve sizes.” By creating smaller-scale graphene sieves, the hope is that more drinking water will be available, with predictions that 14pc of the world’s population will experience water scarcity by 2025 in the face of climate change.

In a paper published in the journal Nature Nanotechnology, scientists from the University of Manchester revealed how they were able to create a graphene-based filter that can make saltwater drinkable.
According to a report from BBC News, this new graphene oxide sieve can actually remove salt from seawater.
"As an ink or solution, we can compose it on a substrate or porous material," Nair said.
"Then we can use it as a membrane.
In terms of scalability and the cost of the material, graphene oxide has a potential advantage over single-layered graphene."
However, when these membranes are immersed in water, they swell up, causing smaller salts to flow through the membrane with the water while larger ions or molecules are blocked.
Common salts dissolve in water and create a "shell" of water molecules around the salt molecules, according to a report from Phys Org.
Then, the capillaries of the membrane can keep the salt from flowing with the water.
"Realisation of scalable membranes with uniform pore size down to atomic scale is a significant step forward and will open new possibilities for improving the efficiency of desalination technology," Nair explained.
"This is the first clear-cut experiment in this regime."

Graphene-based sieve turns seawater into drinking water.
A UK-based team of researchers has created a graphene-based sieve capable of removing salt from seawater.
The promising graphene oxide sieve could be highly efficient at filtering salts.
Reporting their results in the Nature Nanotechnology journal, University of Manchester scientists, led by Dr Rahul Nair, show how they used a chemical derivative called graphene oxide to solve some of the challenges.
Until now, they could not be used to filter out common salts, which require smaller sieves.
Previous work had shown that graphene oxide membranes became slightly swollen when immersed in water, allowing smaller salts to flow through the pores along with water molecules.
By contrast, water molecules flowed fast through the membrane barrier, which made it ideal for use in desalination.
Current desalination plants around the world use polymer-based membranes.
"The next step is to compare this with the state-of-the-art material available on the market," Dr Nair said.
Ram Devanathan, from the Pacific Northwest National Laboratory in Richland, US, said more work was needed to produce graphene oxide membranes inexpensively at industrial scales.

Israeli firm to provide drinking water — from the air — for India and Vietnam.
Water Gen inked an agreement last week with India’s second largest solar company to produce purified water for remote villages in the country.
“The government of Vietnam greatly esteems the technological developments in Israel, and I hope that the Israeli technology that we supply to Vietnam will significantly help to improve water conditions in the country,” Water Gen President Mikhael Mirilashvili said after the signing in Hanoi, according to a statement.
Harvard Law professor Alan Dershowitz demonstrated Water Gen’s technology on stage at the American Israel Public Affairs Committee’s annual policy conference in Washington, D.C., on March 26.
He touted the device, which he said can produce 15-20 liters of drinkable water a day, as a weapon against worldwide water scarcity and the Boycott, Divestment and Sanctions movement against Israel.
“There is no weapon more powerful in the fight against BDS than for Israel to develop technologies that the world cannot live without,” he told the crowd.
“You cannot boycott products that you can’t live without.” About 1.2 billion people, nearly one-fifth of the world’s population, live in areas of water scarcity, according to the United Nations Department of Economic and Social Affairs.
Of India’s 1.25 billion people, 75 million lack access to clean water, the Water Aid nonprofit found last year.
Water Gen devices use thin plastic leaves to condensed water from warm, humid air.
In India, Water Gen is to deploy its technology to supply drinking water to remote villages in India with solar power from Vikar Solar.

Graphene sieve could make seawater drinkable.
(CNN)Researchers in the United Kingdom have developed a graphene-based sieve that can filter salt out of seawater, a development that could provide drinking water to millions of people around the globe.
Graphene — an ultra-thin sheet of carbon atoms organized in a hexagonal lattice — was first identified at the University of Manchester in 2002 and has since been hailed as a "wonder material," with scientists racing to develop inexpensive graphene-based barriers for desalination on an industrial scale.
Now, the team at Manchester has used a compound of graphene, known as graphene oxide, to create a rigid sieve that could filter out salt using less energy.
But researchers had struggled to move forward after finding that the membrane’s pores would swell up when immersed in water, allowing particles to continue to pass through.
Writing Monday in the Nature Nanotechnology journal, the team revealed it was able to restrict pore-swelling by coating the material with epoxy resin composite that prevented the sieve from expanding.
"This is the first clear-cut experiment in this regime.
We also demonstrate that there are realistic possibilities to scale up the described approach and mass produce graphene-based membranes with required sieve sizes," he added.
Boosting global access to water is critical.
Cities have been investing heavily in diversifying their water supplies, including developing new desalination technologies to make seawater potable.

Nitrogen, phosphorus from fertilizers and pet waste polluting urban water.
The study—published in the Proceedings of the National Academy of Sciences—is the first to compare the urban watershed budgets of nitrogen and phosphorus.
And the results can be applied to urban watersheds around the world impaired by excess nutrients.
The research team—led by Sarah Hobbie, Distinguished McKnight University Professor in the Department of Ecology, Evolution & Behavior and an Institute on the Environment Fellow—discovered households are the main sources of nutrient pollutants in the Twin Cities urban watershed.
Urban watersheds are highly "leaky" with regard to nutrient pollution because of their dense networks of streets and storm drains, which are designed to readily move water off the landscape to avoid flooding.
As a result, most of the phosphorus entering urban watersheds ends up being carried away by stormwater that drains into surface waters and thus contributes to pollution and eutrophication.
Nitrogen tends to disperse through more diverse pathways—about one-fifth is transported via stormwater into surface water while much of the rest ends up either being released into the atmosphere or moving through soil into groundwater.
"Urban waters—lakes, streams, rivers, coastal waters—continue to be impaired by nutrient pollution, especially phosphorus, despite long-running efforts to clean them up," said Hobbie.
"Not only is this a concern for water resource managers tasked with cleaning up urban pollution, but also urban and downstream residents who depend on clean water for drinking water, recreation and aesthetic value."
More information: Contrasting nitrogen and phosphorus budgets in urban watersheds and implications for managing urban water pollution, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1618536114