Breakthrough made in nuclear-waste sequestration

A Venus flytrap-like response at the molecular level captures and sequesters radioactive waste in liquid while letting water pass through.

Mercouri G. Kanatzidis Northwestern University

Researchers at Northwestern University are developing a new method for removing radioactive materials from liquid nuclear waste.

The group of scientists led by Mercouri G. Kanatzidis, a Charles E. and Emma H. Morrison professor of Chemistry at Northwestern University, announced their breakthrough on Tuesday. The group's paper described the process metaphorically to how a Venus flytrap closes after absorbing a fly in its grip, while letting other objects pass by.

At the molecular level the radioactive ion cesium found in liquid nuclear waste passes through "holes" in a porous metal-sulfide material via an ion-exchange process. Meanwhile, harmless substances like sodium ions are allowed to pass through.

The cesium itself triggers a response in the material's structure causing its atoms, which are arranged in a layered and porous pattern, to "close up" around the cesium. Once the cesium is captured, the structure keeps its "holes" closed preventing the radioactive cesium from leaching out while letting other materials pass by.

"Seeing the windows close was completely unexpected. We expected ion exchange--we didn't expect the material to respond dynamically. This gives us a new mechanism to focus on," Kanatzidis said in a statement.

Kanatzidis published his group's results in the February issue of Nature Chemistry.

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