It is estimated that over 660 million people in the world still do not have access to clean and safe drinking water — a number that is only expected to rise in the coming decades as water supplies begin to run dry. According to the United Nations, by 2025, 14 percent of the world’s population will face water scarcity.
This is despite Earth being a “pale blue dot,” 70 percent of whose surface is covered in water.
The problem is that the water held in our planet’s oceans, which accounts for over 96 percent of all water on Earth, is not potable. So far, efforts to make it drinkable have been either inefficient, dauntingly expensive, or both.
Now, in a study published Monday in the journal Nature Nanotechnology, a team of researchers from the University of Manchester have described a breakthrough that could open the door to the synthesis of an inexpensive desalination method — creation of a graphene oxide membrane that can be used as a sieve to remove salt from seawater.
“Realization 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,” study co-author Rahul Nair said in a statement released Monday. “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.”
Although previous experiments have shown that graphene-based membranes are capable of filtering out small nanoparticles, organic molecules, large salts, until now, scientists had been unable to create membranes with pore size small enough to filter out sodium chloride.
In order to overcome this hurdle, the researchers placed epoxy resin on either side of their graphene oxide membrane, stopping it from swelling up when immersed in water. When this was done, the membrane filtered out 97 percent of the sodium chloride, while allowing water molecules to pass through.
“The developed membranes are not only useful for desalination, but the atomic scale tunability of the pore size also opens new opportunity to fabricate membranes with on-demand filtration capable of filtering out ions according to their sizes,” Jijo Abraham, the study’s joint lead author, said in the statement.
Although the technology has the potential to revolutionize water filtration — especially in countries that sorely lack access to clean drinking water — more work is needed to scale up the production of these membranes to an industrial level.
“The ultimate goal is to create a filtration device that will produce potable water from seawater or wastewater with minimal energy input,” Ram Devanathan, a scientist at the Pacific Northwest National Laboratory in Richland, Washington, wrote in a commentary accompanying the Nature Nanotechnology study.