February 5, 2003

UPDATE on Materials That Expand Under Pressure

New Irreversible Expansion May Yield Better Pollution Trap

Scientists from Brookhaven National Laboratory and their collaborators have previously shown that certain zeolites -- materials in which oxygen atoms are shared between tetrahedra-containing silicon and/or aluminium -- can expand under pressure and take up more water to become superhydrated (see press release). These materials can exchange cations under pressure. Due to the pressure-induced expansion, larger molecules and cations -- possibly pollutants -- could be incorporated into the nano-sized pores of these "molecular sponges." When the pressure is released, the pollutants would become trapped.

However, in a reversible system, half of the water would be expelled again, making the sponges somewhat "leaky."

In a paper appearing in the December 5 issue of Nature, the scientists now describe a material that shows irreversible pressure-induced hydration. That is, when the pressure is released, the material stays superhydrated. This new finding opens up the possibility of using these "molecular sponges" to truly immobilize pollutants such as tritiated water.

"Our studies show that the irreversible pressure-induced hydration is associated with a rearrangement of the charge-balancing cations contained in the nanopores," says Brookhaven physicist Thomas Vogt, a co-author on the previous research and the new Nature paper. "By understanding these cation migrations and rearrangments under pressure, we hope to be able to reduce the pressure at which the pressure-induced hydration occurs, and thereby open up new ways to use zeolites as "molecular sponges" for pollutants or as transport vessels for medical applications."

The collaborators on this research include Vogt and Yongjae Lee of the Physics Department and Jonathan Hanson of the Chemistry Department at Brookhaven Lab; Joe Hriljac of the University of Birmingham, U.K.; John B. Parise of Stony Brook University; and Sun Jin Kim of the Korean Institute of Science & Technology. The research was funded by the U.S. Department of Energy, which supports basic research in a variety of scientific fields.

FOR MORE INFORMATION
Tom Vogt
Physics Department
Brookhaven National Laboratory
Email: tvogt@bnl.gov

SCIENCE WRITER: Mona S. Rowe