Biosynthesis of nanocrystal akaganeite from FeCl2 solution oxidized by Acidithiobacillus ferrooxidans cells

Akaganeite (beta-FeOOH) is a major iron oxyhydroxide component in some soils, marine concretions, and acid mine drainage environments. Recently, synthetic beta-FeOOH has been found to be a promising absorbent in the treatment of metal-contaminated water. It has been recognized in previous study that akaganeite could be formed via FeCl2 chemical oxidation under specific conditions. Here we report a novel and simple method for akaganeite bioformation from FeCl2 Solution oxidized by Acidithiobacillus ferrooxidans LX5 cells at 28 degrees C. After acclimation in modified 9K medium containing 0.2 M chloride, Acidithiobacillus ferrooxidans cells had great potential for oxidization of Fe2+ as FeCl2 solution, and then resulted in the formation of precipitates. The resulting precipitates were identified by powder X-ray diffraction and transmission FT-IR analyses to be akaganeite. Scanning electron microscopy images showed the akaganeite was spindle-shaped, approximately 200 nm long with an axial ratio of about 5, and the spindles had a rough surface. X-ray energy-dispersive spectral analyses indicated the chemical formula of the crystalloid akaganeite could be expressed as Fe8O8(OH)(7.1)(Cl)(0.9) with Fe/Cl molar ratio of 8.93. The biogenetic akaganeite had a specific surface area of about 100 m(2) g(-1) determined by BET method.