Well, OK, it’s not exactly a sponge, but it is spongelike. And, of course, it didn’t eat Three-Mile Island — but it COULD… maybe… eventually. (Not that it needs it.) What the heck am I talking about?
Researchers from Northwestern University and Claflin University have developed an inorganic solid that is also porous, flexible, and absorbs cesium-137. Better than that, it actually traps the nasty cesium ions, rendering them ineffective. How nasty are they? “Of all the radioactive isotopes left over from nuclear weapons testing and nuclear power plants, cesium-137 is among the most dangerous. The soft, silvery-white metal has a half-life of 30 years, enters the body quickly, and can trigger cancer even decades after exposure.” And it’s notoriously hard to remove from the environment.
But, as reported online last month in Nature Chemistry, there may be a solution. The substance is actually stacked sheets of a framework of mixed gallium, tin, and sulphur, dosed with dimethylammonium (DMA) ions. Originally, the researchers thought the cesium-137, which is swapped with the like-charged DMA ions, would just be flushed out with other charged ions. But, the cesium surprised them by bonding to the sulphur. The result is that the holes in the framework are nudged closed, locking in the cesium.
Because the new material has an affinity for cesium even when similar alkali metals are present, it may eventually be useful at nuclear cleanup sites. One problem, however, is that gallium is rather expensive. So, the search is on to find cheaper components (perhaps the chemically-similar aluminum?) that will give the same results.