Graphene as a Nuclear Waste Filter

Tuesday, January 12, 2016 @ 03:01 PM gHale

Graphene can now see action in an effort to clean up nuclear waste by filtering different isotopes of hydrogen, a new study has found.

By using membranes made from graphene, they can act as a sieve, separating protons — nuclei of hydrogen – from heavier nuclei of hydrogen isotope deuterium, said Andre Geim from University of Manchester in UK.

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The process could mean producing heavy water for nuclear power plants could be ten times less energy intensive, simpler and cheaper using graphene.

One of the hydrogen isotopes, deuterium, sees widespread use in analytical and chemical tracing technologies and, also, as heavy water required in thousands of metric tons for operation of nuclear power stations.

The heaviest isotope, tritium, is radioactive and needs to end up safely removed as a byproduct of electricity generation at nuclear fission plants. The basis of future nuclear technology comes from fusion of the two heavy isotopes.

The current separation technologies for production of heavy water are extremely energy intensive, and have presented a major scientific and industrial problem. Now graphene shows great promise in solving the problem.

Researchers tested whether deuterons — nuclei of deuterium — can pass through graphene and its sister material boron nitride. They fully expected deuterons to easily pass through, as existing theory did not predict any difference in permeation for both isotopes.

The researchers found deuterons were not only effectively sieved out by their one atom thick membranes, but sieved with a high separation efficiency.

The discovery makes monolayers of graphene and boron nitride attractive as separation membranes to enrich mixtures of deuterium and tritium.

Furthermore, the researchers showed the separation is fully scalable. Using chemical-vapor-deposited (CVD) graphene, they built centimeter-sized devices to effectively pump out hydrogen from a mixture of deuterium and hydrogen.

“This is really the first membrane shown to distinguish between subatomic particles, all at room temperature,” said first author Marcelo Lozada-Hidalgo, a postdoctoral researcher at University of Manchester.

“Now that we showed that it is a fully scalable technology, we hope it will quickly find its way to real applications,” Lozada-Hidalgo said.

“We were stunned to see that a membrane can be used to separate subatomic particles,” said co-author Irina Grigorieva, from the University of Manchester.

“It is a really simple set up. We hope to see applications of these filters not only in analytical and chemical tracing technologies but also in helping to clean nuclear waste from radioactive tritium,” Grigorieva said.