At least 25 water systems in Wisconsin have had problems with radium in their drinking water. Federal regulations limit the amount of radium in drinking water to 5 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. Current methods to remove radium are complicated and expensive. Komarneni, working with Naofumi Kozai, a visiting scientist from the Japan Atomic Energy Research Institute and William J. Paulus, master's degree recipient, now at General Motors Corporation, tested a variety of synthetic micas for radium removal, but found that sodium-4 mica was the best synthetic clay for this purpose.
Natural mica is a mineral containing a combination of aluminum, silica, magnesium and potassium.
The mineral is found in sheets and has a structure like the pages of a book. The sheets are bonded to each other to form a solid, layered mass. Natural mica has a closed structure with all the spaces between layers filled and is not a good ion exchange media, says Komarneni. Sodium-4 mica, like natural mica, contains aluminum, silica and magnesium, but each potassium atom is replaced by two sodium ions, and fluorine is also added. The two sodium ions take up more space than the potassium ion and the layers of mica become offset, creating a space to capture water and radium.