1995 Fiscal Year Final Research Report Summary
Recovery of Valuable Metals from Marine Mineral Resources by Autotrophic Bacteria
| Project/Area Number |
06454038
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
生物・生体工学
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| Research Institution | University of Osaka Prefecture |
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Principal Investigator |
ASAI Satoru Univ.of Osaka Pref., Col.of Eng., Professor, 工学部, 教授 (90081348)
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| Co-Investigator(Kenkyū-buntansha) |
KONISHI Yasuhiro Univ.of Osaka Pref., Col.of Eng., Associate Professor, 工学部, 助教授 (90167403)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Marine mineral resources / Manganese nodules / Sulfur-oxidizing bacteria / Hydrogen sulfide / Thermophile / Sulfate-reducing bacteria / Leaching / Valuable metals |
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| Research Abstract |
This report describes results on the microbial treatment of manganese nodules using a 3-stage bioprocess which consists of the bioleaching of nodule, the precipitation and recovery of leached metals by biogenic H_2S,and the microbial treatment of waste H_2S.
1. Manganese nodules were solubilized during the growth of acidophilic sulfur-oxidizing bacteria using elemental sulfur as their energy sources. The thermophile Acidianus brierleyi was more effective for the nodule leaching than the mesophiles Thiobacillus ferrooxidans and Thiobacillus thiooxidans. The experimental data for the leaching with A.brierleyi were used to optimize various process parameters, such as medium pH,initial cell concentration, initial sulfur-liquid loading ratio and initial nodule-liquid loading ratio.
2. For the utilization of biogenic H_2S to recover leached metals as insoluble sulfides, we measured the rates of batch growth of Desulfovibrio desulfuricans on sulfate and subsequent H_2S desorption in a H_2-sparg
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ed and stirred reactor. The experimental data were analyzed to determine kinetic and stoichiometric parameters for the microbial H_2S formation. Predictions based on the theory of mass transfer with reaction indicated that the desorption of biogenic H_2S is a mass transfer process with negligible film reaction. The observed desorption rates were interpreted quantitatively by using the developed kinetics of bacterial growth and subsequent H_2S formation, the dissociation equilibria of dissolved H_2S,and the mass transfer characteristics in the bioreactor.
3. To treat waste H_2S,the liquid-phase oxidation of H_2S by T.thiooxidans was studied in continuous culture. The observed data were analyzed to evaluate the growth yield and the kinetic parameters in the Monod equation.
4. From the above results it was found that the bioleaching of nodules is a rate-limiting step in the 3-stage bioprocess. Thus we can conclude that under the conditions determined as optimum, the proposed microbial processing yields the 100% recovery of copper and zinc from nodules within 3 days, and high recoveries of nickel (85%) and cobalt (70%) for 10 days. Less
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