Adsorption of perfluorooctanoic acid and perfluorooctanesulfonic acid to iron oxide surfaces as studied by flow-through ATR-FTIR spectroscopy

Xiaodong Gao, Jon Chorover

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

The kinetics and mechanisms of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) adsorption to nanoparticulate hematite (α-Fe2O3) from aqueous solutions were examined using in situ, flow-through attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. Results indicate that both PFOA and PFOS molecules are retained at the hydrophilic hematite surface and the adsorption shows strong pH dependence. However, ATR-FTIR data reveal that PFOA and PFOS are bound to the iron oxide by different mechanisms. Specifically, in addition to electrostatic interactions, PFOA forms inner-sphere Fecarboxylate complexes by ligand exchange, whereas the PFOS sulfonate group forms outer-sphere complexes and possibly hydrogen-bonds at the mineral surface. Both solution pH and surface loading affect adsorption kinetics. Faster adsorption was observed at low pH and high initial PFC concentrations. Sorption kinetics for both compounds can be described by a pseudo-second-order rate law at low pH (pH 3.0 and 4.5) and a pseudo-first-order rate law at high pH (pH 6.0). Sorption isotherm data for PFOA derived from spectroscopic results exhibit features characteristic of ionic surfactant adsorption to hydrophilic charged solid surfaces.

Original languageEnglish (US)
Pages (from-to)148-157
Number of pages10
JournalEnvironmental Chemistry
Volume9
Issue number2
DOIs
StatePublished - 2012

Fingerprint

perfluorooctanoic acid
FTIR spectroscopy
iron oxide
adsorption
Adsorption
acid
Kinetics
Sorption
kinetics
hematite
Coulomb interactions
Surface-Active Agents
Minerals
Isotherms
sorption
Fourier transforms
Hydrogen bonds
perfluorooctane sulfonic acid
ferric oxide
Ligands

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Chemistry (miscellaneous)
  • Environmental Chemistry

Cite this

@article{03aba4706f744ed69de6d627a997c25d,
title = "Adsorption of perfluorooctanoic acid and perfluorooctanesulfonic acid to iron oxide surfaces as studied by flow-through ATR-FTIR spectroscopy",
abstract = "The kinetics and mechanisms of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) adsorption to nanoparticulate hematite (α-Fe2O3) from aqueous solutions were examined using in situ, flow-through attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. Results indicate that both PFOA and PFOS molecules are retained at the hydrophilic hematite surface and the adsorption shows strong pH dependence. However, ATR-FTIR data reveal that PFOA and PFOS are bound to the iron oxide by different mechanisms. Specifically, in addition to electrostatic interactions, PFOA forms inner-sphere Fecarboxylate complexes by ligand exchange, whereas the PFOS sulfonate group forms outer-sphere complexes and possibly hydrogen-bonds at the mineral surface. Both solution pH and surface loading affect adsorption kinetics. Faster adsorption was observed at low pH and high initial PFC concentrations. Sorption kinetics for both compounds can be described by a pseudo-second-order rate law at low pH (pH 3.0 and 4.5) and a pseudo-first-order rate law at high pH (pH 6.0). Sorption isotherm data for PFOA derived from spectroscopic results exhibit features characteristic of ionic surfactant adsorption to hydrophilic charged solid surfaces.",
author = "Xiaodong Gao and Jon Chorover",
year = "2012",
doi = "10.1071/EN11119",
language = "English (US)",
volume = "9",
pages = "148--157",
journal = "Environmental Chemistry",
issn = "1448-2517",
publisher = "CSIRO",
number = "2",

}

TY - JOUR

T1 - Adsorption of perfluorooctanoic acid and perfluorooctanesulfonic acid to iron oxide surfaces as studied by flow-through ATR-FTIR spectroscopy

AU - Gao, Xiaodong

AU - Chorover, Jon

PY - 2012

Y1 - 2012

N2 - The kinetics and mechanisms of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) adsorption to nanoparticulate hematite (α-Fe2O3) from aqueous solutions were examined using in situ, flow-through attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. Results indicate that both PFOA and PFOS molecules are retained at the hydrophilic hematite surface and the adsorption shows strong pH dependence. However, ATR-FTIR data reveal that PFOA and PFOS are bound to the iron oxide by different mechanisms. Specifically, in addition to electrostatic interactions, PFOA forms inner-sphere Fecarboxylate complexes by ligand exchange, whereas the PFOS sulfonate group forms outer-sphere complexes and possibly hydrogen-bonds at the mineral surface. Both solution pH and surface loading affect adsorption kinetics. Faster adsorption was observed at low pH and high initial PFC concentrations. Sorption kinetics for both compounds can be described by a pseudo-second-order rate law at low pH (pH 3.0 and 4.5) and a pseudo-first-order rate law at high pH (pH 6.0). Sorption isotherm data for PFOA derived from spectroscopic results exhibit features characteristic of ionic surfactant adsorption to hydrophilic charged solid surfaces.

AB - The kinetics and mechanisms of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) adsorption to nanoparticulate hematite (α-Fe2O3) from aqueous solutions were examined using in situ, flow-through attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. Results indicate that both PFOA and PFOS molecules are retained at the hydrophilic hematite surface and the adsorption shows strong pH dependence. However, ATR-FTIR data reveal that PFOA and PFOS are bound to the iron oxide by different mechanisms. Specifically, in addition to electrostatic interactions, PFOA forms inner-sphere Fecarboxylate complexes by ligand exchange, whereas the PFOS sulfonate group forms outer-sphere complexes and possibly hydrogen-bonds at the mineral surface. Both solution pH and surface loading affect adsorption kinetics. Faster adsorption was observed at low pH and high initial PFC concentrations. Sorption kinetics for both compounds can be described by a pseudo-second-order rate law at low pH (pH 3.0 and 4.5) and a pseudo-first-order rate law at high pH (pH 6.0). Sorption isotherm data for PFOA derived from spectroscopic results exhibit features characteristic of ionic surfactant adsorption to hydrophilic charged solid surfaces.

UR - http://www.scopus.com/inward/record.url?scp=84860680989&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84860680989&partnerID=8YFLogxK

U2 - 10.1071/EN11119

DO - 10.1071/EN11119

M3 - Article

AN - SCOPUS:84860680989

VL - 9

SP - 148

EP - 157

JO - Environmental Chemistry

JF - Environmental Chemistry

SN - 1448-2517

IS - 2

ER -