Synthesis and preliminary characterization of 2-line ferrihydrite containing different amounts of Si

Abstract

Ferrihydrite ($Fe_{5}HO_{8} \cdot 4H_{2}O$) is the reddish-brown, nearly amorphous hydrous ferric oxyhydroxide mineral with variable composition, widespread in various near-surface environments. Being thermodynamically unstable, it transforms with time into goethite ($\alpha-FeOOH$) or hematite ($\alpha-Fe_{2}O_{3}$). Due to its low crystallinity and high surface area, ferrihydrite is highly reactive and plays, through coprecipitation and adsorption reactions, an essential role in e.g. geochemical cycling of various trace elements and capturing of contaminants from streams and groundwater in such environments as ironladen springs, mine wastes and acid mine drainage.