Per- and polyfluoroalkyl substances (PFAS), a class of ~5,000 compounds that are toxic and persistent, have been detected in drinking water across the country. Activated carbon (AC) is a widely used sorbent to remove PFAS. One challenge of using AC is its limited adsorption capacity for some PFAS, especially short-chain species. Manipulating the electrical behavior of AC may provide a solution to overcome these limitations. At environmentally relevant pH values, many PFAS occur as anions and are highly soluble in water. We therefore hypothesized that applying a small voltage to AC would increase adsorption capacities of anionic PFAS. Our results show that compared to uncharged controls (open circuit voltage), treatments with an applied voltage (1 V) always improved PFAS adsorption. The increase was dependent on PFAS chain length and acidic functional group (i.e., sulfonate or carboxylate). For example, with an applied voltage, adsorption increased upwards of 2.4 times for perfluorobutanesulfonic (PFBS; C4; sulfonate), but only up to 1.3 times for perfluorononanoic acid (PFNA; C9; carboxylate) compared to the no-voltage control. Preliminary tests with the background anion chloride (Cl-) were conducted to determine the competitive effect of this common environmental matrix component. In the presence of low-levels of Cl- typical of most groundwaters (1 mM), PFBS adsorption was enhanced up to 2.7 times with an applied voltage when compared to the open circuit control. At higher Cl- concentrations, however, an enhancement was not observed suggesting that the competitive effect of Cl- was concentration dependent. In summary, these results indicate that small inputs of electricity can enhance the adsorption of PFAS onto activated carbon, but that the degree of enhancement is dependent on PFAS species and background matrix components.

Electrosorption of perfluoroalkyl substances onto activated carbon

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.