APS X-rays target selenium remediation
by Payal Marathe, Communications, Education and Public Affairs
A team from Argonne’s X-ray Science Division (XSD) provided expertise in structure characterization for recent research on selenium remediation, or the removal of selenium compounds from water.
Chemist Karena Chapman (XSD) and postdoctoral fellow Ana Platero-Prats (XSD) used Argonne’s Advanced Photon Source (APS) to probe the local atomic structure of a porous metal-organic framework developed at Northwestern.
Their contribution shed light on how selenite and selenate are bound by the framework, which paves the way toward an optimal system for selenium removal. Chapman and Platero-Prats are exploring how these frameworks can be used in designing effective catalysts as part of the Inorganometallic Catalyst Design Center.
For selenium remediation and catalysis alike, these frameworks must be highly stable. As a real-world device for selenium removal, the framework may have to withstand harsh water conditions varying in pH, temperature and pressure. The Northwestern team, led by Professor Omar Farha, tested different materials to identify a robust framework that was both efficient in absorbing selenium compounds and also chemically stable in a range of environments.
Chapman and Platero-Prats then closely analyzed this system using the high energy X-rays at APS. They were able to see how the framework captured selenium compounds.
Once you have a system that can bind a lot of selenite and selenate, you want to understand how it’s doing that so you can estimate long-term stability. For catalysis, you need a framework that won’t fall apart in highly reactive, even aggressive conditions.
Chemist Karena Chapman (XSD)
This project was funded by the DOE’s Energy Frontier Research Centers Program, which promotes synergistic research, often across institutions.
A series of zirconium-based, Metal-organic Frameworks (MOFs) were tested for their ability to adsorb and remove selenate and selenite ani-ons from aqueous solutions. MOFs were tested for adsorption capacity and uptake time at different concentrations. NU-1000 was shown to have the highest adsorption capacity, and fastest uptake rates for both selenate and selenite, of all zirconium-based MOFs studied here. Here-in, the mechanism of selenate and selenite adsorption on NU-1000 is explored to determine the important features that make NU-1000 a supe-rior adsorbent for this application.
Ashlee J. Howarth, Michael J. Katz, Timothy C. Wang, Ana E. Platero-Prats, Karena W Chapman, Joseph T. Hupp and Omar K. Farha, “High Efficiency Adsorption and Removal of Selenate and Selenite from Water using Metal Organic Frameworks,” The Journal of the American Chemical Society, Just Accepted Manuscript. DOI: 10.1021/jacs.5b03904, Published Online May 22, 2015.