A single layer of graphene has been shown to filter hydrogen from its other isotopes. This technology could optimise the cleaning of nuclear waste and facilitate the production of heavy water.
The researchers, led by Nobel-prize winner Sir Andre Geim at the University of Manchester, used graphene membranes as a sieve to separate a mixture of hydrogen nuclei and deuterium nuclei. Deuterium is an isotope of hydrogen.
Isotopes are different types of the same element, meaning they show almost exactly the same chemical behaviour but have different mass. Deuterium, which is hydrogen with an extra neutron, is frequently used to study the mechanisms of chemical reactions and in 'heavy water' nuclear reactors.
Using graphene membranes to seperate deuterium from hydrogen could enable heavy water to be produced faster and more economically as it requires 10 times less energy than current methods. Nuclear Power plants often consumer thousands of tonnes of heavy water during their lifetime.
Tritium is a radioactive isotope of hydrogen which is heavier than deuterium. At nuclear fission plants ttritium is produced as a byproduct and it must be removed safely. It is hoped that the fusion of deuterium and tritium could be used in future nuclear power generation.
Tests were conducted on deuterons (atoms of deuterium) to determine if they could, like hydrogen, permeate single sheets of boron nitride or graphene. Existing theory predicted the same permeation for both hydrogen and deuterium; meaning the deuterons were expected to easily pass through the membranes. However, the atom-thick membranes of graphene and boron nitride prevented deuterons from passing.
Effectively this sieved the deuterons out, resulting in an efficient seperation of hydrogen and deuterium.
This finding demonstrates the potential of using atom-thick layers of boron nitride and graphene for the enrichment of deuterium and tritium mixtures.
Devices on the centimeter scale were built using chemical-vapor-deposited (CVD) graphene, and these were used to pump hydrogen out of a deuterium-hydrogen mixture.
This is really the first membrane shown to distinguish between subatomic particles, all at room temperature.
Now that we showed that it is a fully scalable technology, we hope it will quickly find its way into real world applications.
Dr Marcelo Lozada-Hidalgo - UoM
The research has been published in the journal Science.