1754 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Grosse, A.C., Dicinoski, G.W, Shaw, M.J., Haddad, P.R.,
2003. Leaching and recovery of gold using ammonia-
cal thiosulfate leach liquors (a review). Hydrometallurgy
69 (1–3): 1–21.
Jeon, S., Tabelin, C.B., Park, I., Nagata, Y., Ito, M.,
Hiroyoshi, N., 2020. Ammonium thiosulfate extrac-
tion of gold from printed circuit boards (PCBs) of end-
of-life mobile phones and its recovery from pregnant
leach solution by cementation. Hydrometallurgy 191:
105214.
Lin, Y.-T., Kumar, G., Chen, F.-C., 2020. Interfacial plas-
monic effects of gold nanoparticle-decorated graphene
oxides on the performance of perovskite photovoltaic
devices. Solar Energy 211: 822–830.
Mhandu, T.J., Park, I., Jeon, S., Hamatsu, S., Elakneswaran,
Y., Ito, M., Hiroyoshi, N. 2023. A Pretreatment of
Refractory Gold Ores Containing Sulfide Minerals to
Improve Gold Leaching by Ammonium Thiosulfate: A
Model Experiment Using Gold Powder and Arsenic-
Bearing Sulfide Minerals. Metals 13(8): 1357.
Park, I., Tabelin, C.B., Magaribuchi, K., Seno, K., Ito,
M., Hiroyoshi, N. 2018. Suppression of the release of
arsenic from arsenopyrite by carrier-microencapsula-
tion using Ti-catechol complex. Journal of Hazardous
Materials 344: 322–332.
Park, I., Tabelin, C.B., Jeon, S., Li, X., Seno, K., Ito, M.,
Hiroyoshi, N., 2019. A review of recent strategies for
acid mine drainage prevention and mine tailings recy-
cling. Chemosphere 219: 588–606.
Park, I., Higuchi, K., Tabelin, C.B., Jeon, S., Ito, M.,
Hiroyoshi, N., 2021. Suppression of arsenopyrite oxi-
dation by microencapsulation using ferric-catecholate
complexes and phosphate. Chemosphere 269: 129413.
Statista Research Department, 2023. Demand for gold
worldwide from 1st quarter of 2016 to 2nd quarter of
2023, by purpose. https://www.statista.com/statistics
/274684/global-demand-for-gold-by-purpose
-quarterly-figures. Accessed 15th Jan 2024.
World Gold Council, 2018. Gold and climate change: An
introduction. https://www.gold.org/goldhub/research
/gold-and-climate-change-introduction. Accessed 15th
Jan 2024.
Xu, B., Kong, W., Li, Q., Yang, Y., Jiang, T., Liu, X., 2017.
A Review of Thiosulfate Leaching of Gold: Focus on
Thiosulfate Consumption and Gold Recovery from
Pregnant Solution. Metals 7(6), 222.
Xu, Y., Schoonen, M.A.A., 1995. The stability of thiosul-
fate in the presence of pyrite in low-temperature aque-
ous solutions. Geochim. Cosmochim. Acta 59(22),
4605–4622.
Zoleta, J., Jeon, S., Kuze, A., Okada, N., Park, I., Ito,
M., Elakneswaran, Y., Hiroyoshi, N., 2023. Selective
Cementation of Gold Using an Iron Oxide and Zero-
Valent Aluminum Galvanic System from Gold–
Copper Ammoniacal Thiosulfate Solutions. Metals
13(7): 1289.

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Extracted Text (may have errors)

1754 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
Grosse, A.C., Dicinoski, G.W, Shaw, M.J., Haddad, P.R.,
2003. Leaching and recovery of gold using ammonia-
cal thiosulfate leach liquors (a review). Hydrometallurgy
69 (1–3): 1–21.
Jeon, S., Tabelin, C.B., Park, I., Nagata, Y., Ito, M.,
Hiroyoshi, N., 2020. Ammonium thiosulfate extrac-
tion of gold from printed circuit boards (PCBs) of end-
of-life mobile phones and its recovery from pregnant
leach solution by cementation. Hydrometallurgy 191:
105214.
Lin, Y.-T., Kumar, G., Chen, F.-C., 2020. Interfacial plas-
monic effects of gold nanoparticle-decorated graphene
oxides on the performance of perovskite photovoltaic
devices. Solar Energy 211: 822–830.
Mhandu, T.J., Park, I., Jeon, S., Hamatsu, S., Elakneswaran,
Y., Ito, M., Hiroyoshi, N. 2023. A Pretreatment of
Refractory Gold Ores Containing Sulfide Minerals to
Improve Gold Leaching by Ammonium Thiosulfate: A
Model Experiment Using Gold Powder and Arsenic-
Bearing Sulfide Minerals. Metals 13(8): 1357.
Park, I., Tabelin, C.B., Magaribuchi, K., Seno, K., Ito,
M., Hiroyoshi, N. 2018. Suppression of the release of
arsenic from arsenopyrite by carrier-microencapsula-
tion using Ti-catechol complex. Journal of Hazardous
Materials 344: 322–332.
Park, I., Tabelin, C.B., Jeon, S., Li, X., Seno, K., Ito, M.,
Hiroyoshi, N., 2019. A review of recent strategies for
acid mine drainage prevention and mine tailings recy-
cling. Chemosphere 219: 588–606.
Park, I., Higuchi, K., Tabelin, C.B., Jeon, S., Ito, M.,
Hiroyoshi, N., 2021. Suppression of arsenopyrite oxi-
dation by microencapsulation using ferric-catecholate
complexes and phosphate. Chemosphere 269: 129413.
Statista Research Department, 2023. Demand for gold
worldwide from 1st quarter of 2016 to 2nd quarter of
2023, by purpose. https://www.statista.com/statistics
/274684/global-demand-for-gold-by-purpose
-quarterly-figures. Accessed 15th Jan 2024.
World Gold Council, 2018. Gold and climate change: An
introduction. https://www.gold.org/goldhub/research
/gold-and-climate-change-introduction. Accessed 15th
Jan 2024.
Xu, B., Kong, W., Li, Q., Yang, Y., Jiang, T., Liu, X., 2017.
A Review of Thiosulfate Leaching of Gold: Focus on
Thiosulfate Consumption and Gold Recovery from
Pregnant Solution. Metals 7(6), 222.
Xu, Y., Schoonen, M.A.A., 1995. The stability of thiosul-
fate in the presence of pyrite in low-temperature aque-
ous solutions. Geochim. Cosmochim. Acta 59(22),
4605–4622.
Zoleta, J., Jeon, S., Kuze, A., Okada, N., Park, I., Ito,
M., Elakneswaran, Y., Hiroyoshi, N., 2023. Selective
Cementation of Gold Using an Iron Oxide and Zero-
Valent Aluminum Galvanic System from Gold–
Copper Ammoniacal Thiosulfate Solutions. Metals
13(7): 1289.

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XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1753
under which arsenopyrite is completely coated with FePO4
precipitates.
Effect of FePO4 Coating on the Leachability of
Arsenopyrite
After extracting gold from arsenopyritic ores, leach residue
containing high content of arsenopyrite will be disposed
of at a landfill site. When this leach residue is exposed to
atmospheric conditions, arsenopyrite is oxidized, resulting
in the formation of acid mine drainage (AMD) as well as
the release of toxic arsenic into the environment (Park et
al., 2019). The previous study of the authors investigated
the effect of FePO4 coating on the leachability of arseno-
pyrite (Park et al., 2021). Figure 6 shows the dissolved As
concentrations released from uncoated and FePO4-coated
arsenopyrite after leaching with DI water for 24 h. As can
be seen, ~0.36 mM of As was leached out from uncoated
arsenopyrite, while arsenic release was limited to ~0.09
mM in the case of FePO4-coated arsenopyrite (Figure 6).
This result implies that the application of ME treatment
can not only improve the efficiency of thiosulfate leaching
in extracting gold from arsenopyritic ores but also reduce
arsenic release from leach residues.
CONCLUSIONS
This study investigated the applicability of ME treatment
to improve the efficiency of gold extraction from a simu-
lated gold-bearing arsenopyrite ores by thiosulfate leaching.
The findings of this study are summarized as follows:
1. Arsenopyrite enhanced the decomposition of thio-
sulfate, and as a result, gold extraction decreased
from 99% to ~10%.
2. Microencapsulation using ferrous and phosphate
ions could create FePO4 coating on the surface of
arsenopyrite.
3. The application of ME treatment prior to thio-
sulfate leaching improved the efficiency of gold
extraction from ~10% to 52%, and moreover, arse-
nopyrite oxidation releasing toxic arsenic into the
environment was suppressed after ME treatment.
4. After ME treatment under the studied condition,
the surface of arsenopyrite was not completely
passivated, and thus gold extraction was limited
to ~52%. Therefore, further study is necessary to
improve the efficiency of gold extraction by opti-
mizing ME treatment conditions.
REFERENCES
Aylmore, M.G., 2005. Alternative lixiviants to cyanide for
leaching gold ores. Developments in Mineral Processing
15: 501–539.
Energy Industry Review, 2018. Gold’s role in improving
energy efficiency and developing low carbon technolo-
gies. https://energyindustryreview.com/metals-mining
/golds-role-in-improving-energy-efficiency-and
-developing-low-carbon-technologies. Accessed 15th
Jan 2024.
Figure 5. The effect of microencapsulation treatment on the
extraction of gold by thiosulfate leaching in the presence of
arsenopyrite
Figure 6. Dissolved As concentration released from untreated
and ME-treated arsenopyrite (Park et al., 2021)

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Extracted Text (may have errors)

XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1753
under which arsenopyrite is completely coated with FePO4
precipitates.
Effect of FePO4 Coating on the Leachability of
Arsenopyrite
After extracting gold from arsenopyritic ores, leach residue
containing high content of arsenopyrite will be disposed
of at a landfill site. When this leach residue is exposed to
atmospheric conditions, arsenopyrite is oxidized, resulting
in the formation of acid mine drainage (AMD) as well as
the release of toxic arsenic into the environment (Park et
al., 2019). The previous study of the authors investigated
the effect of FePO4 coating on the leachability of arseno-
pyrite (Park et al., 2021). Figure 6 shows the dissolved As
concentrations released from uncoated and FePO4-coated
arsenopyrite after leaching with DI water for 24 h. As can
be seen, ~0.36 mM of As was leached out from uncoated
arsenopyrite, while arsenic release was limited to ~0.09
mM in the case of FePO4-coated arsenopyrite (Figure 6).
This result implies that the application of ME treatment
can not only improve the efficiency of thiosulfate leaching
in extracting gold from arsenopyritic ores but also reduce
arsenic release from leach residues.
CONCLUSIONS
This study investigated the applicability of ME treatment
to improve the efficiency of gold extraction from a simu-
lated gold-bearing arsenopyrite ores by thiosulfate leaching.
The findings of this study are summarized as follows:
1. Arsenopyrite enhanced the decomposition of thio-
sulfate, and as a result, gold extraction decreased
from 99% to ~10%.
2. Microencapsulation using ferrous and phosphate
ions could create FePO4 coating on the surface of
arsenopyrite.
3. The application of ME treatment prior to thio-
sulfate leaching improved the efficiency of gold
extraction from ~10% to 52%, and moreover, arse-
nopyrite oxidation releasing toxic arsenic into the
environment was suppressed after ME treatment.
4. After ME treatment under the studied condition,
the surface of arsenopyrite was not completely
passivated, and thus gold extraction was limited
to ~52%. Therefore, further study is necessary to
improve the efficiency of gold extraction by opti-
mizing ME treatment conditions.
REFERENCES
Aylmore, M.G., 2005. Alternative lixiviants to cyanide for
leaching gold ores. Developments in Mineral Processing
15: 501–539.
Energy Industry Review, 2018. Gold’s role in improving
energy efficiency and developing low carbon technolo-
gies. https://energyindustryreview.com/metals-mining
/golds-role-in-improving-energy-efficiency-and
-developing-low-carbon-technologies. Accessed 15th
Jan 2024.
Figure 5. The effect of microencapsulation treatment on the
extraction of gold by thiosulfate leaching in the presence of
arsenopyrite
Figure 6. Dissolved As concentration released from untreated
and ME-treated arsenopyrite (Park et al., 2021)

1755
Establishment of a Sustainable and Eco-Friendly Scheme for
Recovery of Gold from Double Refractory Ores
Azizbek Buronov, Sanghee Jeon, Labone Godirilwe,
Kazutoshi Haga, Atsushi Shibayama
Department of Geosciences, Geotechnology, and Materials Engineering for Resources,
Graduate School of International Resource Sciences, Akita University, Akita, Japan
ABSTRACT: A novel green-hydrometallurgy scheme was established for sustainable Au extraction from low-
grade refractory ores. Pyrite oxidation with a ferric solution obtained from a bio-oxidation plant with sustainable
catalysts gained from natural ores was executed, and Au was extracted in an eco-friendly thiosulfate solvent. The
results showed that Au extraction was enhanced three-fold compared with direct leaching. Subsequently, the
recovery/upgrading of Au was carried out by utilizing tailings (e.g., pyrite) with a thiosulfate decomposition
reaction. The results showed that Au was recovered and upgraded by 500–700 folds. Therefore, the results
indicate that this sustainable green-mining scheme is effective in improving Au extraction from low-grade
refractory ores to achieve a carbon-neutral society.
Keywords: Green mining, Refractory ores, Gold, Pyrite oxidation, Thiosulfate, Flotation
INTRODUCTION
One important concern is the increasing level of green-
house gases resulting from industrial activities (Hegerl et
al., 2019), which leads to climate change. This situation
initiated global efforts to achieve a carbon-neutral soci-
ety, where the mitigation of climate change is maintained
(Chen et al., 2022).
Renewable energy technologies are increasingly impor-
tant for reducing fossil fuels and minimizing greenhouse
gas emissions. Key to this sustainable transition are tech-
nologies such as solar panels, wind turbines, and fuel cells.
However, these technologies require a significant amount
of critical metals, highlighting the necessity for sustainable
extraction and processing methods.
Gold (Au), known for its outstanding conductivity
and resistance to corrosion, is integral in various electronic
devices, particularly in renewable energy applications.
In solar energy, gold is utilized in thin-film photovolta-
ics, enhancing the efficiency of organic photovoltaic cells
(Wadams et al., 2014), which is crucial for next-generation
solar technology. This is due to gold’s ability to facilitate
efficient energy conduction and electron transfer. Similarly,
in wind energy systems, the conductive properties of gold
are essential for the electrical interfaces and components in
wind turbines (Dudem et al., 2018).
In gold-hydrometallurgy, the first stage is to dissolve
gold using suitable lixiviants, followed by the recovery of
extracted gold ions from pregnant leach solutions (Jeon et
al., 2019, 2020). Historically, in the leaching stage, cya-
nide is the most commonly used lixiviants to extract gold.
Over time, there has been an increasing development of
double refractory gold ores (DRGO), and when those con-
ventional methods are employed for the DRGO, unfortu-
nately, these are resistant to conventional processing due to

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Extracted Text (may have errors)

1755
Establishment of a Sustainable and Eco-Friendly Scheme for
Recovery of Gold from Double Refractory Ores
Azizbek Buronov, Sanghee Jeon, Labone Godirilwe,
Kazutoshi Haga, Atsushi Shibayama
Department of Geosciences, Geotechnology, and Materials Engineering for Resources,
Graduate School of International Resource Sciences, Akita University, Akita, Japan
ABSTRACT: A novel green-hydrometallurgy scheme was established for sustainable Au extraction from low-
grade refractory ores. Pyrite oxidation with a ferric solution obtained from a bio-oxidation plant with sustainable
catalysts gained from natural ores was executed, and Au was extracted in an eco-friendly thiosulfate solvent. The
results showed that Au extraction was enhanced three-fold compared with direct leaching. Subsequently, the
recovery/upgrading of Au was carried out by utilizing tailings (e.g., pyrite) with a thiosulfate decomposition
reaction. The results showed that Au was recovered and upgraded by 500–700 folds. Therefore, the results
indicate that this sustainable green-mining scheme is effective in improving Au extraction from low-grade
refractory ores to achieve a carbon-neutral society.
Keywords: Green mining, Refractory ores, Gold, Pyrite oxidation, Thiosulfate, Flotation
INTRODUCTION
One important concern is the increasing level of green-
house gases resulting from industrial activities (Hegerl et
al., 2019), which leads to climate change. This situation
initiated global efforts to achieve a carbon-neutral soci-
ety, where the mitigation of climate change is maintained
(Chen et al., 2022).
Renewable energy technologies are increasingly impor-
tant for reducing fossil fuels and minimizing greenhouse
gas emissions. Key to this sustainable transition are tech-
nologies such as solar panels, wind turbines, and fuel cells.
However, these technologies require a significant amount
of critical metals, highlighting the necessity for sustainable
extraction and processing methods.
Gold (Au), known for its outstanding conductivity
and resistance to corrosion, is integral in various electronic
devices, particularly in renewable energy applications.
In solar energy, gold is utilized in thin-film photovolta-
ics, enhancing the efficiency of organic photovoltaic cells
(Wadams et al., 2014), which is crucial for next-generation
solar technology. This is due to gold’s ability to facilitate
efficient energy conduction and electron transfer. Similarly,
in wind energy systems, the conductive properties of gold
are essential for the electrical interfaces and components in
wind turbines (Dudem et al., 2018).
In gold-hydrometallurgy, the first stage is to dissolve
gold using suitable lixiviants, followed by the recovery of
extracted gold ions from pregnant leach solutions (Jeon et
al., 2019, 2020). Historically, in the leaching stage, cya-
nide is the most commonly used lixiviants to extract gold.
Over time, there has been an increasing development of
double refractory gold ores (DRGO), and when those con-
ventional methods are employed for the DRGO, unfortu-
nately, these are resistant to conventional processing due to