Cell-shape assemblage and nanostructure of akaganeite bioformed in FeCl2 solutions

Akaganeite (beta-FeOOH) with a tunnel structure typically occupied by chloride can undergo anion-exchange reactions in aqueous solutions for pollutant removal. In this work, we studied bioformation of akaganeite in FeCl2 solutions with Acidithiobacillus ferrooxidans cells at pH 2.9, during 36-h incubation. The obtained products were analyzed and characterized by XRD, FTIR, EDS, FETEM, and HRTEM. Results showed that in acidic media with pH 2.9, the cells facilitated ferrous biooxidation and ferric precipitation. The resulting ferric precipitates were identified as polycrystalline akaganeite powders and had a morphology of nanospindles with a length of less 100 nm. The correlatively chemical formula for akaganeite collected at 1 h was reckoned as Fe8O8(OH)(6.71)(Cl)(1.29) with 6.6% Cl. It was observed that ferric precipitates along exterior structures of cells or their extruded organic polymers grew and assembled into cellular shape. The evolved cell-shape akaganeite assemblages were twice of cells (about 2 mu m) in size. These results could contribute to understanding of laboratorial bioformation of akaganeite and its biomineralization in acidic environments and promoting its practical applications.

Automated summary

In this study, the bioformation of akaganeite in FeCl2 solutions mediated by Acidithiobacillus ferrooxidans cells was investigated. The obtained products were characterized, revealing the formation of nanospindle-shaped akaganeite powders. It was observed that the ferric precipitates grew along the exterior structures of cells, resulting in the formation of cellular-shaped assemblages.