Currently, about eleven percent of the electricity consumed in the world is generated by nuclear power plants. Nuclear waste contains many radioactive isotopes with different levels of toxicity and different half-lives. Any process which is able to remove specific isotopes from nuclear waste would be quite useful in dealing with the dangers of nuclear waste.
Adsorption is a chemical process where molecules attach themselves to the surface of solid objects or liquids. Porous materials have been used to capture radioactive molecules but the efficiency of existing adsorbent materials is too inefficient for wide use.
A group of researchers at the Department of Materials Science and Engineering at the Erik Jonsson School of Engineering and Computer Science at the University of Texas at Dallas are working on new filtration technology for removing radioactive isotopes from nuclear waste. Their efforts could help efforts to recycle nuclear waste and make it safer to store radioactive materials. The U of T project is dedicated to finding more efficient and cheaper ways of capturing radioactive iodine isotopes and the common byproducts from the reactors.
The researchers are working with tiny metal-organic frameworks (MOF). MOFs have metal ions in the center of a structure composed of organic parts. Their utility lies in the fact that specific gases and other molecules can be trapped in the center of the MOF. The work at the U of T is focusing on the ability of a group of MOFs to adsorb radioactive isotopes of iodine efficiently. There are existing MOFs containing silver that are efficient at high temperatures but they are expensive and difficult to recycle.
Dr. Kui Tan is one of the researchers on the U of T project. He said in a published paper, "In a spent radioactive fuel rod, there are several elements that decay at different rates. Radioactive iodine is one of the primary byproducts. By attaching a nitrogen-containing molecule to the MOFs, our colleagues showed they could capture these radioactive molecules very efficiently."
Tan and his coworkers “used spectroscopy to determine the interaction of molecular iodine and organic iodide within the functionalized lattice.” They were able to determine exactly how the iodine was bound to the MOF and why the process was so efficient. The team at Rutgers found out that MOFs were able to adsorb over three hundred and forty percent more radioactive materials that any current industrial absorbents. The U of T team and the team at Wake Forest were able to determine why and how the adsorbent worked so well. There are many potential applications.
Tan says, “Synthesis of these MOFs is scalable, and they have the potential of being produced on an industrial scale. We really understand better how these processes work, and we hope it opens up the possibility of finding new applications.” Collaborations between the Rutgers, U of T, Wake Forrest U and other universities and research organizations was necessary in order to carry out this research on MOFs.
