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Specific Anion Nanoengineered Sorbents (SANS)
Initiated: October 2000
Team: Patrick V. Brady, Nadim R. Khandaker, James L. Krumhansl, Malcolm D. Siegel
Implementation of a new drinking water standard of 10 ppb for arsenic in 2006 will require water treatment approaches that are substantially more effective than existing ones which tend to rely on filtration and/or coagulation by iron or aluminum hydroxides. The most direct way to reduce treatment outlays is to develop filtration/coagulation media that remove arsenic better than iron and aluminum hydroxides. At the molecular level this requires increasing the number of positively charged sites present at metal hydroxide surfaces, decreasing surface acidity, or (ideally) both so that sorption of negatively charged arsenate species can be maximized.

At the same time, media selectivity for arsenate - as opposed to carbonate, silicate, or sulfate - must be assured under natural conditions where the latter anions are overwhelmingly more abundant in solution.

molecular model
Molecular model of arsenate sorption on sorbent surface.
The goal of this project was to use state-of-the-art molecular modeling techniques to identify suites of candidate medias which were subsequently tested under laboratory conditions for their ability to remove arsenic from drinking water at the ppb level. The 3-year effort has resulted in identification of "next-generation" media that perform better than existing media for most drinking waters. The fundamental features of media-As interaction that were identified in the course of the project have also been applied to develop means for improving both coagulation and lime-softening removal of arsenic, as well as for in situ immobilization of arsenic in aquifers and at hazardous waste sites. The results also suggest paths for selecting sorption media able to remove perchlorate from drinking water.
Patent application has been filed on this technology.

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