Surface Chemistry and Dissolution of α-FeOOH Nanorods and Microrods: Environmental Implications of Size-Dependent Interactions with Oxalate†

Although recent evidence suggests that particle size plays an important role in the dissolution of iron from mineral dust aerosol, a fundamental understanding of how particle size influences the rate and extent of iron oxide dissolution processes remains unclear. In this study, surface spectroscopic methods are combined with solution phase measurements to explore ligand-promoted dissolution and photochemical reductive dissolution of goethite (α-FeOOH) of different particle sizes in the presence of oxalate at pH 3 and 298 K. Both X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) revealed differences between α-FeOOH particles in the nanometer-size range as compared to α-FeOOH particles in the micrometer-size range (nanorods and microrods, respectively). ATR-FTIR spectra showed a significant presence of surface hydroxyl groups as well as differences in surface complexes formed on nanorod surfaces. Furthermore, the saturation coverage of oxala...