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Download fileSorption of Perfluoroalkyl Acids to Fresh and Aged Nanoscale Zerovalent Iron Particles
journal contribution
posted on 2018-04-30, 00:00 authored by Yanyan Zhang, Yue Zhi, Jinxia Liu, Subhasis GhoshalThe sorption of perfluoroalkyl acids
(PFAAs), particularly perfluorooctanesulfonic
acid (PFOS), to freshly synthesized nanoscale zerovalent iron (nZVI)
and aged (oxidized) and sulfidated nZVI, was investigated under anaerobic
conditions. The sorption of PFAAs to nZVI was 2–4 orders of
magnitude higher than what has been reported for sediments, soils,
and iron oxides. The hydrophobicity of the perfluorocarbon chain dominated
the sorption, although FTIR spectra indicated specific interactions
between sulfonate and carboxylate head groups and nZVI. The contributions
from electrostatic interactions depended on the surface charge and
pH. Humic acids influenced sorption only at concentrations above 50
mg/L. nZVI aged in deoxygenated water up to 95 days showed similar
sorption isotherms for PFOS to fresh nZVI, because Fe(OH)2 was the predominant phase on the nZVI surface independent of aging
time. Sulfidation of nZVI reduced sorption of PFOS by 1 log unit owing
to the FeS deposited, but the sorption affinity was restored after
aging because of formation of Fe(OH)2. Oxidation of nZVI
by water and dissolved oxygen also resulted in similar sorption of
PFOS as fresh nZVI at environmentally relevant concentrations. The
results suggest that injection of nZVI could reduce PFAA concentrations
in groundwater despite changes to its surface chemistry with aging.
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sulfidated nZVIPerfluoroalkyl Acidssurface chemistryFTIR spectranZVI surfaceAged Nanoscale Zerovalent Iron Particlesdeoxygenated watersorption affinityiron oxidessurface charge95 days1 log unitnanoscale zerovalent ironsorption isothermsperfluorooctanesulfonic acidPFOSHumic acidsperfluorocarbon chainperfluoroalkyl acidscarboxylate head groupsPFAA concentrations