This monthly discussion series features presentations from EPA’s innovative early career researchers in addition to an invited speaker from industry or academia.
February 2, 12-1:00 PM ET
For the month of February, we will be joined by John Sloop, an ORISE participant from USEPA’s Office of Research and Development, and William Dichtel, Robert L. Letsinger Professor of Chemistry from Northwestern University
USEPA Office of Research and Development
John Sloop received a Bachelor of Science in chemistry and mathematics from Barton College in Wilson, NC, and then received his PhD in chemistry from Wake Forest University in Winston Salem, NC. While his PhD focused on atomic spectrometry and non-traditional calibration techniques, his postdoc on non-targeted analysis at the EPA has been quite a shift in gears, but an excellent learning experience at the same time. In his spare time, he enjoys making music, playing video games, and spending time with his wife, Emily, their daughter, Valerie, and their dog, Parker.
Non-targeted analysis of drinking water samples from 46 homes across five regions of California
Many chemicals can be found in drinking water samples across the US, most of which occur at very low concentrations. Point-of-use (POU) drinking water filters are useful tools from a consumer perspective; they can also serve as a viable sampling tool, sampling hundreds of gallons of water while filtering and concentrating chemicals onto the filters. In this study, participants across California were provided with POU drinking water filters and most participants sampled between 100-200 gallons. Chemicals were extracted from the filters, and non-targeted analysis techniques were used to identify these chemicals, with an emphasis on potential carcinogens.
Robert L. Letsinger Professor of Chemistry
William Dichtel received a B.S. degree in Chemistry from MIT, where he performed research with Prof. Tim Swager. Dichtel obtained his Ph.D. degree from UC-Berkeley under Prof. Jean M. J. Fréchet. He was a joint postdoctoral researcher with Prof. Fraser Stoddart, UCLA, and Prof. James Heath, Caltech. He began his independent academic career at Cornell University in 2008 and was promoted to Associate Professor in 2014. In 2016, he moved to Northwestern University as the Robert L. Letsinger Professor of Chemistry. The unifying theme of Dichtel’s research is the use of organic synthesis and noncovalent assembly to control the structure and reactivity of molecules, materials, and interfaces across chemical environments. His research has expanded the study of polymerization processes into the second and third dimensions in an emerging class of polymers known as covalent organic frameworks (COFs), porous polymers for water purification, and new approaches to polymer recycling.
Dichtel’s research has been recognized nationally and internationally. Dichtel has received a MacArthur Fellowship, a Guggenheim Fellowship, the Leo Hendrik Baekeland Award of the North Jersey Section of the ACS, and he was named the 2020 National Laureate in Chemistry by the Blavatnik Awards for Young Scientists.
Porous Polymer Adsorbents Remove Perfluorinated Pollutants and Enable Their Mineralization
Per- and polyfluoroalkyl substances (PFASs) pollute water at concentrations harmful to human health. Crosslinked polymers containing β-cyclodextrin (β-CD) are promising adsorbents with demonstrated removal performances for PFASs from contaminated water sources. Despite the promising performance of some β-CD-based adsorbents for PFAS removal, many of these materials are not amenable for rational performance improvement or addressing fundamental questions about the PFAS adsorption mechanisms. These ambiguities arise from the poorly defined structure of the crosslinked polymers, especially with respect to the random substitution patterns of the cyclodextrins, as well as side reactions that modify the structures of some crosslinkers. A new β-CD polymer platform in which styrene groups are covalently attached to β-CD will be presented. These adsorbents also provide an opportunity to degrade PFAS at high concentrations in non-aqueous solvents because they can be regenerated by a simple solvent wash. The mineralization of perfluoroalkyl carboxylic acids (PFCAs) through a previously unrecognized sodium hydroxide-mediated defluorination pathway will be presented. This strategy is generalizable to branched perfluoroether carboxylic acids and operates via previously unrecognized mechanistic pathways.