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Renewable Material Removes Toxic Pollutant From Drinking Water
August 25, 2017

According to information provided by Northwestern University, a research team led by William R. Dichtel, an expert in organic and polymer chemistry, has reported the development of an inexpensive and renewable material that rapidly removes perfluorooctanoic acid (PFOA), a highly toxic water pollutant, from drinking water supplies. PFOA contamination is considered to be a pervasive problem worldwide due to its long-term use in Teflon production and other industrial processes as well as its environmental persistence.

In research supported by a grant from the National Science Foundation (NSF) through the Center for Sustainable Polymers, the novel treatment has been shown to effectively eliminate the micropollutant to below 10 parts per trillion, far below the Environmental Protection Agency’s (EPA) 2016 advisory limit for the combined concentration of PFOA and perfluorooctanesulfonic acid (PFOS) in drinking water of 70 parts per trillion and all state health advisory limits.

“Our material fully extracts the pollutant out of water,” explained Dr. Dichtel, the Robert L. Letsinger Professor of Chemistry at Northwestern’s Weinberg College of Arts and Sciences. “The polymer contains sites that bind PFOA strongly, which strips this pollutant out of water even when present at extremely low concentrations. The binding sites are joined together by linkers that further enhance the affinity for PFOA.”

The polymer can be regenerated and reused multiple times because only a small amount of the material is required to capture and remove PFOA to less than 10 parts per trillion. The networked polymer is made from joining smaller molecules with tiny pores, and selectivity is programmed into the material through a crosslinked monomer. The main component, beta-cyclodextrin, is a naturally occurring bio-renewable sugar molecule derived from cornstarch.

“Our findings demonstrate the selectivity of this type of polymer can be tailored to target pollutants of interest, in this case PFOA,” Dr. Dichtel said. “The material has more than 10 times higher affinity for PFOA than activated carbon, a conventional treatment method with several known deficiencies.”

Co-authored by Dr. Dichtel, Damian Helbling, assistant professor of civil and environmental engineering at Cornell University, first author Leilei Xiao, along with contributions from members of research groups at Northwestern and Cornell, the study, “??Cyclodextrin Polymer Network Sequesters Perfluorooctanoic Acid at Environmentally Relevant Concentrations,” was published recently in the Journal of the American Chemical Society.

The PFOA material and Dr. Dichtel’s polymer technology are being developed for commercial use by CycloPure, Inc., a company co-founded by Dr. Dichtel. Serving on the scientific advisory board of CycloPure, Inc., both Dr. Dichtel and Prof. Helbling have a financial interest in the company. Cornell University has filed patent applications related to the cyclodextrin polymer that was the study’s focus.

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