| Co-Investigator(Kenkyū-buntansha) |
HIROYOSHI Naoki Hokkaido Univ., Grad.School. Of Eng., Inst., 大学院・工学研究科, 助手 (50250486)
HIRAJIMA Tsuyoshi Hokkaido Univ., Grad. School. Of Eng., Asso. Pro., 大学院・工学研究科, 助教授 (00175556)
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| Research Abstract |
Weathering of pyrite and chalcopyrite plays an important role in formation of acid mine drainage and releases toxic trace elements, such as Ni, Co, Zn and As from the minerals. In mine environments, and especially in aerobic environments, the pyrite and chalcopyrite weathering is accelerated by iron- and sulfur-oxidizing bacteria. This research was conducted on the weathering mechanism, inhibitor to the bacteria and remediation of acid contaminated sites.
In acid solutions the preferential dissolution of iron took place resulting in the formation of a surface layer enriched with sulfur. Natural organic acid, such as tannic acids, wood vinegar, fulvic acids, and humic acids, suppressed microbially mediated dissolution of pyrite. It was caused by adsorption of natural organic acids on pyrite, inhibition of cell growth, as well as reduction and complexation of Fe(III) ions.
Ferrous ions enhanced copper extraction in sulfuric acid solutions in air at ambient temperatures because they promoted chalcopyrite oxidation with dissolved oxygen. However iron-oxidizing bacteria consumed ferrous ions, suppressing copper extraction. Sodium lauryl sulfate and tannic acid suppressed not only the bacterial ferrous oxidation but also the chalcopyrite oxidation with dissolved oxygen, resulting in a suppression of copper extraction.
Dissolution of iron from high sulfur coal refuse by iron-oxidizing bacteria was depressed in the presence of sodium lauryl sulfate, which inhibited cell growth. However, the refuse contained some soluble iron species that could release into drainage. For decreasing iron concentration of drainage addition of lime was effective.
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