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The Daily Wildcat

The Daily Wildcat


    Scientists discover new way to dispose of radioactive waste

    CHICAGO — It may be oversimplifying to suggest that the microscopic mechanism that Mercouri Kanatzidis andNan Dinghave developed resembles a roach motel of nuclear waste, where the ghastly undesirable checks in but doesn’t check out. Kanatzidis prefers to call it a Venus flytrap.

    Either way, the results are the same. The pinkish, powdery material the two researchers created traps caesium-137, a prevalent, stubborn radioactive contaminant. And trapping it could make clearing it from toxic sites immensely easier.

    That discovery has created a buzz in the scientific community.

    “”The science is really cool,”” saidKarl Rockne, a University of Illinois at Chicago associate professor of civil and materials engineering who specializes in cleaning toxic sites.

    Essentially, the sulfide framework acts as a “”very tiny, tiny building with rooms,”” Kanatzidis said. The caesium enters the building then bonds to the “”sulfide walls”” of the interior. At that point, the building begins “”making all the doors and windows smaller so the caesium cannot get out,”” he added.

    In a more scientific context, the flexible sulfide structure contains organic, positively charged ions that can change positions with caesium in a watery solution. That reaction prompts the structure of the framework to close only on the caesium ions, preventing them from escaping. Other similar ions are not trapped.

    Kanatzidis, a professor at Northwestern University and a senior scientist at Argonne National Laboratory, and Ding, an assistant chemistry professor at Claflin University in Orangeburg, S.C., made the discovery in 2007. Ding was at Northwestern working on her Ph.D. with Kanatzidis. She was focusing on the discovery and evaluation of new ion exchange material when she noticed the caesium-137 Venus flytrap.

    Between then and now, Kanatzidis said, he and Ding were conducting ion exchange testing and making sure they could produce the Venus flytrap effects again and again. Then they needed several months to research and write an academic paper on their discovery, which was published in the peer-reviewed journal Nature Chemistry on Jan. 24.

    “”I’m proud of it,”” Ding said by phone from South Carolina. “”It’s definitely something that will be useful or lead to useful things. Nuclear waste is a big issue, and we need new materials and new mechanisms to get rid of it as soon as possible.””

    Scientists maintain that caesium-137 is among the most dangerous radioactive isotopes, largely because the soft, silvery-white metal has a half-life of 30 years, easily enters the body and can bring on cancer decades after exposure. A remnant from nuclear weapons testing and nuclear power plants, caesium-137 is believed to be the main source of radiation still present from the notorious nuclear power plant explosion in 1986 in Chernobyl, Ukraine.

    And pulling the deadly isotopes from waste is a difficult undertaking. Most materials are unable to distinguish between toxic and nontoxic ions.

    But one of the critical challenges to widespread use of the sulfide framework is cost, UIC’s Rockne and others said. The sulfide framework includes gallium, a very expensive metallic chemical element.

    “”This is really cool, but how much will it cost on a large scale?”” Rockne said. “”I have to think it might be expensive, relatively speaking.

    “”If he can do this inexpensively, this is a super big deal,”” he added, in part because scientists may be able to tweak the structure to capture a wider array of metal pollutants.

    Kanatzidis agreed that the process remains too costly and said he is searching for material that is less expensive than gallium but can perform the same function. He also is “”looking to test it on a big scale with big companies so we can evaluate it in more realistic situations.

    “”It’s hard to say”” when his Venus flytrap or roach motel for radioactive waste will be ready for widespread use, Kanatzidis said. “”We need to wait for testing and then we need to make comparisons between this and other materials. If everything goes right, you’re talking about three to four years.””

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