Robert L. Letsinger Professor of Chemistry
William Dichtel is the Robert L. Letsinger Professor of Chemistry at Northwestern University. His research on polymers has been recognized by more than a dozen national awards, including a 2015 MacArthur Fellowship. Based on promising results for removing emerging contaminants from water by cyclodextrin polymers, he co-founded CycloPure in 2016 to commercialize these materials and serves as his Chief Science Officer. Dichtel earned his BS and PhD degrees, both in chemistry, from MIT and UC-Berkeley, respectively, and performed postdoctoral research at UCLA and Caltech. In 2008, he joined the faculty of Cornell University and moved to Northwestern in 2016.
Remediation of PFASs from Water using Cyclodextrin-based Adsorbents
Anionic PFASs present a particular environmental problem because of their resistance to biodegradation or chemical transformation and association with negative health effects. PFASs have been used in the formulations of thousands of consumer goods and are present in aqueous film-forming foam formulations used to suppress aviation fires in training scenarios. As a result, they have contaminated surface and ground waters near thousands of airports and military installations. A ?-cyclodextrin polymer linked with tetrafluoroterephthalonitrile (TFN-CDP) has high affinity for cationic and many neutral MPs from contaminated water because of anionic groups incorporated during the polymerization. But TFN-CDP does not bind many anionic MPs strongly, including anionic PFASs. To address this shortcoming, we reduced the nitrile groups in TFN-CDP to primary amines, which reverses its affinity towards charged MPs. TFN-CDP exhibits adsorption distribution coefficients (log KD values) of 2-3 for cationic MPs and -0.5-1.5 for anionic MPs, whereas the reduced TFN-CDP exhibits log KD values of -0.5-1.5 for cationic MPs and 2-4 for anionic MPs, with especially high affinity towards anionic PFASs. Kinetic studies of the removal of 10 anionic PFASs at environmentally relevant concentrations showed 80-98% removal of all contaminants after 30 min and was superior to commercial granular activated carbon. The development of these adsorbents will be presented, along with progress towards their commercialization by a startup company, CycloPure, will be presented.