FERRIHYDRITE DISSOLUTION AND REACTION IN THE PRESENCE OF ASCORBIC ACID AND WITH ADSORBED PHOSPHOLIPID

The dissolution and reprecipitation of ferrihydrite plays a role in the cycling and mobility of iron in aqueous environments. The interaction and reaction of ascorbic acid with nano-ferrihydrite (2-8 nm diameter) with and without adsorbed phosphochloine lipid has been investigated with atomic force microscopy (AFM), attenuated total reflection infra-red spectroscopy (ATR-IR), and aqueous batch reaction experiments. In situ AFM and aqueous batch reactions showed that the dissolution of the particles induced by the presence of ascorbic acid was a function of the morphology of the nanomaterial. ATR-IR experiments showed that the ascorbic acid or fragments thereof were strongly speciated to the nanoparticles. Exposure of the nanoparticles to phosphochloine lipid resulted in a strong suppression in their dissolution rate. AFM showed that the lipid layers that formed on the particles were typically relatively thin (5-10 nm) and ATR-IR suggested that the primary interaction of the lipid with the ferrihydrite was through the phosphate group.