A synthetic clay, sodium-4 mica, was found to effectively remove radium from water and soil.
The clay contains tiny spaces that capture water and radium. Once the mica fills with radium, a shift in the layers occurs and the atoms of radium are trapped between the layered structure.
This method is inexpensive compared to current radium removal methods that are more costly and complicated.
Dr. Sridhar Komarneni, professor of clay mineralogy both with Penn State's College of Agricultural Sciences and Materials Research Institute, worked with Naofumi Kozai, a visiting scientist from the Japan Atomic Energy Research Institute and William Paulus, master's degree recipient, now at General Motors Corp., worked together and reported this finding in the journal Nature.
"Once the radium is trapped, it will not leave the mica," said Komarneni. "Disposal and storage requirements would then depend only on the radioactivity of the material and not whether radium could leach out of the clay. Very low level radioactive clay could simply be buried."
To immobilize radium from mine or mill tailings, simply mixing the clay with the tailings is sufficient. The clay could also line ponds that receive radium containing tailing water to prevent migration from the pond, or clay curtains around tailings could keep the radium inside.
Radium, a natural decay product of uranium, often is found in the southwestern U.S. where large deposits of uranium are mined, and also is present in rocks and soils. Coal and phosphate processing also produce tailings that contain radium.
Federal regulations limit the amount of radium in drinking water to five pico Curies per liter of water. A pico Curie is a trillionth of a Curie and is a million times less than the radiation produced by the radium on a wristwatch face.