Reductive dissolution of ferrihydrite by ascorbic acid and the inhibiting effect of phospholipid

• Published in: Journal of colloid and interface science Vol. 341; no. 2; pp. 215 - 223
• Main Authors: Debnath, Sudeep, Hausner, Douglas B., Strongin, Daniel R., Kubicki, James
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.01.2010
• Subjects: Amorphous iron hydroxide; Ascorbic acid; Atomic force microscopy; ATR-FTIR; Attenuation; Colloidal ferric hydroxide; DFT; Dissolution; Ferrihydrite; Geochemistry; HFO; Iron oxyhydroxide; Lipids; Mathematical analysis; Phospholipids; Reductive dissolution; HFO; Ferrihydrite; Ascorbic acid; DFT; ATR-FTIR; Reductive dissolution; Iron oxyhydroxide; Colloidal ferric hydroxide; Amorphous iron hydroxide
• ISSN: 0021-9797; 1095-7103; 1095-7103
• DOI: 10.1016/j.jcis.2009.09.035

Reductive dissolution of ferrihydrite nanoparticles induced by ascorbic acid is explored in the presence and absence of adsorbed phospholipid. The presence of adsorbed phospholipid reduces the otherwise facile dissolution process. The interaction of ascorbic acid with ferrihydrite nanoparticles with and without adsorbed phospholipid has been investigated with atomic force microscopy (AFM), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), density functional theory (DFT) cluster calculations, and batch geochemical methods. Both batch geochemical rate measurements and in situ AFM showed that ferrihydrite particles dissolved in the presence of ascorbic acid over a period of hours. The area-normalized dissolution rate derived from AFM measurements of isolated ferrihydrite particles was relatively constant over the period of dissolution and was faster than the dissolution rate derived from batch reaction methods. Results from ATR-FTIR interpreted in view of theoretical calculations suggested that exposure of ferrihydrite to ascorbic acid led to an adsorbed monodentate ascorbate surface complex. Ferrihydrite dissolution was suppressed if particles were exposed to an organic lipid prior to or during exposure to ascorbic acid. AFM analysis of the lipid layer showed that its thickness was close to 7 nm, the expected value for lipid assembled into a bilayer structure.