Analytical Sciences

Roles of Microbial Activity and Anthraquinone-2,7-disulfonate as a Model of Humic Substances in Leaching of Iron from Hematite into Seawater

Apichaya ANEKSAMPANT,*1 Atsushi TANAKA,*2 Xuefei TU,*1 Hisanori IWAI,*3 Mitsuo YAMAMOTO,*4 Kazunori NAKASHIMA,*1 and Masami FUKUSHIMA*1

*1 Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan
*2 Graduate School of Environment Science, Hokkaido University, Sapporo 060-0810, Japan
*3 Department of Marine System Engineering, Graduate School of Engineering, Osaka Prefecture University, Sakai 599-8531, Japan
*4 Ocean Alliance, The University of Tokyo, Kashiwa, Chiba 277-8564, Japan

Fertilization with a mixture of steelmaking slag and compost can affect the supply of dissolved iron used to restore seaweed beds, however, the mechanisms of iron elution from the fertilizer are not well understood. In the present study, the microorganism was isolated from Fe-fertilizer incubated in coastal seawater for 6 months, and was identified as Exiguobacterium oxidotolerans by 16S rDNA sequencing. The iron elutability of the bacteria was proved based on the increasing of dissolved iron by incubation with Fe₂O₃ (hematite) under a seawater-like condition. The value of ORP was changed by inoculated of the bacteria from ca. 0 to ca. –400 mV, which is anticipated concerning to reduction of Fe. The concentration of eluted iron was largely depended on those of organic acids produced by bacteria. From the results, it was proved that E. oxidotolerans is capable of Fe reductive eluting of iron from Fe₂O₃ into seawater. Anthraquinone-2,7-disulfonate (AQDS), which can play as an electron acceptor/donor between microbe and insoluble Fe₂O₃ particles, enhanced the effect of iron bio-leaching.

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