| Project/Area Number |
23KJ1718
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| Research Category |
Grant-in-Aid for JSPS Fellows
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| Allocation Type | Multi-year Fund |
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| Section | 国内 |
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| Review Section |
Basic Section 31020:Earth resource engineering, Energy sciences-related
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| Research Institution | Kyushu University |
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Principal Investigator |
CINDY 九州大学, 工学府, 特別研究員(DC1)
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| Project Period (FY) |
2023-04-25 – 2026-03-31
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| Project Status |
Granted (Fiscal Year 2023)
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| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 2025: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2024: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2023: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Keywords | Refractory gold ore / Carbonaceous matter / Laccase-mediator system / Sequential treatment / Enzymatic degradation / Au extraction |
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| Outline of Research at the Start |
Free native gold is rapidly depleted, so treatments to recover gold from double refractory gold ores are demanded. Environmentally friendly treatments, including laccase from agriculture waste and surfactant, then thiourea to replace toxic cyanide will be aimed to meet sustainable development goals.
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| Outline of Annual Research Achievements |
Double refractory gold ores (DRGOs), in which gold (Au(0)) is encapsulated in sulfide minerals with carbonaceous matter, has generally been abandoned for economic reasons, although it has a relatively higher Au content than other types of Au ores. To enhance Au extraction from DRGOs, sulfides must be dissolved to release locked Au grains, and carbonaceous matter must be degraded to reduce Au(CN)2- adsorption during cyanidation. Laccase, aided by a mediator in a laccase-mediator system (LMS), has been applied to degrade carbonaceous matter in DRGOs. In this study, to sustain enzyme activity over 7 days treatment, LMS was added in multiple divided doses with the same final concentration. Results show decreased Au(CN)2- adsorption, leading to improved Au extraction. Characterization of solid residues using thermogravimetry/differential thermal analysis, Raman spectroscopy, three-dimensional fluorescence spectrometry, and CHN elemental analysis observed carbonaceous matter degradation. In the case of the present DRGO, the total dose of laccase was optimized to 11.87 U/100 mL, divided into four additions to treat 5 g of FW containing 5.2% C. This LMS method offers a promising, environmentally friendly approach for further exploration, particularly in advancing our understanding of carbon science in biohydrometallurgy. Some parts of this work have been presented at conferences, leading to the receipt of the CINEST Award for Best Presentation at the International Symposium on Earth Science and Technology at Kyushu University, and the Young Researcher Award from MMIJ Kyushu.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
To increase the efficiency of the biotechnological process, the study began by focusing on replacing purified laccase with laccase extracted from agricultural waste. Some agricultural waste from mushroom species may be utilizable due to its wide availability. Laccase harvested from agricultural waste underwent enzyme activity assay and was then applied for degrading carbonaceous matter in double refractory gold ores. However, the biomass of the agricultural waste itself could passivate the ore's surface, thereby hindering Au extraction. Therefore, another approach involves optimizing the laccase-mediator system by adding it in multiple divided doses with the same final concentration, while investigating the effect of different mediators in the reaction.
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| Strategy for Future Research Activity |
Numerous natural and synthetic mediators have been identified, and laccases obtained from different mushrooms have been reported to interact differently with these mediators. According to the latest research findings, the only compound applied as a mediator in the laccase-mediator system (LMS) for the biodegradation of carbonaceous matter in double refractory gold ores (DRGOs) is 1-hydroxybenzotriazole hydrate (HBT). This study examines the effects of typical mediators, specifically HBT, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), 2,6-dimethoxyphenol, violuric acid, and guaiacol, in LMS on degrading the carbonaceous matter in DRGOs, thus improving the extraction of Au from DRGOs.
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