Charged graphene foam acts as "uranium magnet" for water purification
Is there anything graphene can’t do? Researchers at MIT have found yet another use for the over-achieving wonder material, by making a reusable filter out of graphene oxide foam that acts like a magnet for uranium, effectively pulling the radioactive element out of drinking water.
Uranium can leach into water supplies from natural deposits in rock, or through waste from nuclear power plants or mining operations. Once there, it’s invisible to the naked eye and it doesn’t take very high doses to start causing harm to human health.
Enter everybody’s favorite material. Graphene oxide foam was found to be so well-suited to sponging uranium out of water that it became drinkable by EPA standards within hours. Better yet, the foam could be cleaned off and reused multiple times over without losing its efficiency.
To put the material to work, an electric charge is first sent through the foam. This splits the water around it and releases hydrogen, which increases the pH in the area. That in turn induces a chemical change that attracts the uranium ions to the surface of the foam. Strangely enough, the team found that the uranium was actually crystallizing into a previously unknown form of uranium hydroxide.
The graphene oxide foam is able to snare high amounts of the pollutant, and once enough of it has been collected, it can be easily removed by simply reversing the electric charge, causing it to slide right off. The foam is then ready to be reused.
“Each time it’s used, our foam can capture four times its own weight of uranium, and we can achieve an extraction capacity of 4,000 mg per gram, which is a major improvement over other methods,” says Ju Li, lead researcher on the study. “We’ve also made a major breakthrough in reusability, because the foam can go through seven cycles without losing its extraction efficiency.”
The team says that the method is low-cost and could be implemented along different stages of water infrastructure. The filters could also potentially be modified to target other heavy metal pollutants like lead, mercury and cadmium.
The research was published in the journal Advanced Materials.