Biosynthesis of Nanocrystal Akaganeite from FeCI_2 Solution Oxidized by Acidithiobacillus ferrooxidans Cells

摘要

Akaganeite (β-FeOOH) is a major iron oxyhydroxide component in some soils, marine concretions, and acid mine drainage environments. Recently, synthetic β-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 FeCI_2 chemical oxidation under specific conditions. Here we report a novel and simple method for akaganeite bioformation from FeCl_2 solution oxidized by Acidithiobacillus ferrooxidans LX5 cells at 28 ℃. After acclimation in modified 9K medium containing 0.2 M chloride, Acidithiobacillus ferrooxidans cells had great potential for oxidization of Fe~(2+) as FeCI_2 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 Fe_8O_8(OH)_(7.1)(CI)_(0.9) with Fe/CI molar ratio of 8.93. The biogenetic akaganeite had a specific surface area of about 100 m~2 g~(-1) determined by BET method.