"Although difficult to imagine, these pores provide a large surface area for selective trapping of metal ions in solution," Liu said. "In fact, a mere tablespoon of this material in powder form has the surface area equivalent to that of a football field."
Upon release in water, demonstrations have shown that SAMMS quickly immobilizes the targeted metal, reducing the concentration to far below drinking water standards. The small pore size also precludes the metal from leaving and resolubilizing into a more toxic and/or mobile form.
"The SAMMS material has demonstrated the highest metal-loading capacity reported by anyone so far," Liu said. "Part of the reason is we have found an effective way to create a seating chart, so to speak, for the molecules, and have established a proficient method for getting the molecules into their proper seats."
Liu credits Pacific Northwest chemist Glen Fryxell with developing a process for attaching the monolayers to the mesoporous supports so that the density of the functional molecules can be optimized without blocking the tiny pore channels.
"I think the most exciting thing about SAMMS is that we not only have the ability to change pore size but also to custom design the molecular properties on the surface so that the molecules can recognize certain species and reject others," said Liu. "That kind of molecular recognition has tremendous potential."
SAMMS' versatility is reflected in the fact that it also can serve as a waste storage medium
following absorption of the metal. Essentially, the metal is encapsulated within the ceramic material.
When subjected to the Toxic Leaching Characteristic Test, a regulatory benchmark which measures
release under environmental
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Contact: Tim Ledbetter
tim.ledbetter@pnl.gov
509-375-5953
DOE/Pacific Northwest National Laboratory
18-Aug-1998