Biomineralization of Vivianite on Carbon Steel Surface Attacked by the Iron Reducing Bacteria
- PDF / 502,070 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 8 Downloads / 169 Views
1265-AA06-01
Biomineralization of Vivianite on Carbon Steel Surface Attacked by the Iron Reducing Bacteria S. Lee1, H. Yoshikawa2, and T. Matsui1 1
World Cultural Heritage Studies, University of Tsukuba, Tennodai 1-1-1, Tsukuba-shi, Ibarakiken 305-8574, Japan 2 Geological Isolation Research and Development Directorate, Japan Atomic Energy Agency, Muramatsu 4-33, Tokai-mura, Naka-gun, Ibaraki-ken 319-1194, Japan ABSTRACT Experiments were carried out to investigate the corrosion and mineralization of carbon steel samples exposed to iron reducing bacteria cultured in a liquid medium. Specifically iron reducing bacteria were cultured under static conditions for 41 days with carbon steel samples. The result showed that a complex (biofilm, bacteria, etc.) was generated by the bacteria and covered the surface of the carbon steel sample. By using a microscope, the corrosion products were revealed to be formed of green and white crystals, or needle-shaped and lozenge crystals by SEM observation. The crystals were vivianite (Fe2+3(PO4)2・8H2O) measuring 50~250 μm. In a corrosion process of an iron material surface, ferrous ion (Fe2+) is dissolved from the iron in a cathode reaction, and generates Fe3+ oxide as corrosion product. It appears that vivianite can be also generated as corrosion product in an environment rich in Fe2+ and phosphate by activity of the iron reducing bacteria. Some data on the morphological feature of these corrosion products were obtained. INTRODUCTION Carbon steel is a candidate for overpack material in the multi-barrier system adopted for the Japanese high level radioactive waste (HLW) disposal concept. The metal material such as carbon steel is expected to be exposed to corrosion factors in the soil over a long-term. Therefore, stability of the overpack (carbon steel) is important for the safety of geological disposal of high level radioactive wastes. The overpack is installed in the deep underground which is regarded as being an anaerobic environment. Iron reducing bacteria can inhabit this environment and its influence is important for overpack stability. The present study revealed that iron reducing bacteria (IRB) were involved in the generation of vivianite ((Fe2+3 (PO4)2・8H2O) [1]. Also revealed is the anticorrosion effect of vivianite on archeological iron remains [2]. Archaeological samples, such as iron remains, which have been corroded underground over several hundred years under aerobic or anaerobic conditions, provide good examples for studying of this purpose [3]. The iron remains of cultural heritage, however, have not been examined for MIC so far. The purpose of this study is to investigate the formation mechanism of vivianite by iron reducing bacteria. This information is useful for overpack stability and conservation of iron remains. EXPERIMENTAL DETAILS Specimens of carbon steel, 20x20x5mm in size, were polished and sterilized at 120℃for 20minutes. Then they were immersed in 30 mL of a liquid medium which contained iron
reducing bacteria or 30 mL of a liquid medium which did not
Data Loading...
