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

• DOI: 10.1071/en11119
• Publication Date: 2012-05-04T02:35:36Z
• Authors: Xiaodong Gao; Jon Chorover
• Keywords: Perfluorooctanoic acid; Attenuated total reflection; Carboxylate

Environmental contextPerfluoroalkyl compounds are organic contaminants that exhibit strong resistance to chemical- and microbial-degradation. As partitioning between solid aqueous phases is expected control the transport of perfluoroalkyl compounds, we studied molecular mechanisms their adsorption–desorption at a representative Fe oxide surface using in situ spectroscopy. The results provide valuable information on types bonds formed, enable better understanding fate these natural environments. AbstractThe kinetics perfluorooctanoic acid (PFOA) perfluorooctanesulfonic (PFOS) adsorption nanoparticulate hematite (α-Fe2O3) from solutions were examined situ, flow-through attenuated total reflection Fourier-transform infrared (ATR-FTIR) Results indicate both PFOA PFOS molecules retained hydrophilic shows pH dependence. However, ATR-FTIR data reveal bound iron by different mechanisms. Specifically, addition electrostatic interactions, forms inner-sphere Fe–carboxylate complexes ligand exchange, whereas sulfonate group outer-sphere possibly hydrogen-bonds mineral surface. Both solution loading affect kinetics. Faster was observed low high initial PFC concentrations. Sorption for can be described pseudo-second-order rate law (pH 3.0 4.5) pseudo-first-order 6.0). isotherm derived spectroscopic features characteristic ionic surfactant charged surfaces.