Post-Doctoral Research Assistant of Environmental Chemistry
Purdue University, Department of Agronomy
Mahsa is a post-doctoral research assistant in Environmental Chemistry at Purdue University and in the department of Agronomy, under the guidance of Dr. Linda Lee. She joined this research group after completing her Ph.D. in Environmental Engineering at Purdue University. She is also holding a B.Sc. degree in Civil Engineering and M.Sc. degree in Water Engineering. Currently, her research focuses on the fate, transport, and remediation of per- and polyfluoroalkyl substances (PFAS) in different media
Mineralization of Per- and Polyfluoroalkyl Substances (PFAS) with nNiFe0-AC
Linda S. Lee1,2*, Mahsa Modiri-Gharehveran1*, Jenny E. Zenobio1,2,3, and Younjeong Choi4 1 Department of Agronomy, 2Interdisciplinary Ecological Sciences & Engineering, Purdue University, West Lafayette, IN 3Current: The Henry Samueli School of Engineering, University of California-Irvine, Irvine, CA 4Current: Colorado School of Mines, Golden, CO
Per- and polyfluoroalkyl substances (PFAS) are highly fluorinated aliphatic chemicals with unique hydro- and oleo-phobic properties which have led to their extreme use in industrial and military facilities. The environmentally persistence and chemically recalcitrant nature of PFAS coupled to the recognized adverse effects PFAS can have on humans and biota have resulted in a global and rapidly growing interest in their fate, transport, and remediation. Preferred technologies lead to the destruction of PFAS, but current destructive technologies are often limited by not addressing all PFAS, being energy intensive or not being amenable for in-situ application. For example, oxidative processes have been found to be unsuccessful in treating perfluorooctane sulfonate (PFOS) while some reductive techniques like UV-activated sulfite have shown transformation of PFOS. However, such reductive approaches are not amenable for use in-situ. We found that one of the most effective PFAS reductive transformation technology with in-situ potential that can transform both L- and Br-PFOS is bimetal nanoscale zero valent iron particles (nNiFe0) synthesized onto activated carbon (AC). Column and batch reactor data will be presented that exemplify transformation and mineralization by nNiFe0-AC with generation of fluoride and sulfite where applicable of perfluoroalkyl sulfonates (PFSAs, C4-C8) and perfluoroalkyl carboxylates (PFCAs, C4-C8) as well as 6:2 and 8:2 fluorotelomer sulfonates in single solute and mixed solute solutions at temperatures up to 60 ?C. Batch studies were conducted in nNiFe0-AC:solution ratio of ~0.2 g:10 mL at reaction times up to 5 days. For column studies, columns were packed with different ratios like 1:10 nNiFe0-AC:sand mix and conducted with flow rates that translate to ~ 0.2 to 2 d residence times. In batch systems with single solute at 60 ?C, ? 50% of the PFOS initially presented was transformed with fluoride and sulfite generation with up to 90% being mineralized. With 6:2 FTS at 60 ?C, the degradation rate was 57 ± 5.1% while generating relatively low levels of several PFCAs (~0.9 ± 0.05% relative to initial moles of 6:2 FTS) and F- (~9.5 ± 0.5 % relative to initial moles of 6:2 FTS) as products of transformation. Interestingly, higher transformation magnitude of 89 ± 0.31%, and 84 ± 1.9 % at 50 and 60 °C, respectively, were observed with 8:2 FTS. Batch reactors with both single and mixed solute solutions indicated that chain length and head group affect transformation rates of PFSAs and PFCAs. For example, higher transformation rates were observed for PFSAs than PFCAs. Trends are consistent with a recent study using irradiated sulfite that degraded PFAS through the generation of hydrated electrons. In light of the latter, mechanism involved in PFAS transformation in our nNiFe0-AC work will be discussed along with potential optimization and limitations for their use in permeable reactive barriers.