XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 1275
the TDF. Alternatively, producing a commercial Bi product
could meet a domestic demand and reduce the amount of
metal hydroxides sent to waste. We are exploring three pos-
sible ways to produce Bi commercially.
Option 1
Neutralization with an alternative alkaline source involves
raising the pH of a Bi-rich solution until it precipitates as a
solid (Gao, Xu, Yang et al., 2021). We anticipate complet-
ing Bi recovery within a pH range of 2 to 4. The expected
reaction with hydrochloric acid is presented in equation
(1). It is expected that the resulting Bi oxychloride (BiOCl)
will be filtered, dried, and bagged.
Option 2
Cementation with copper, where copper powder is added
to a heated solution containing dissolved Bi. Triggering a
reaction whereby copper replaces Bi in solution, with Bi
depositing as fine metallic solids that can be recovered by
filtration (Shen, Zhang, Cao et al., 2019). The expected
reaction is shown in equation (2). The resulting cement-Bi
product would be filtered, dried, and bagged.
Option 3
Electrowinning, where the goal is to plate Bi metal directly
from the selenium effluent solution in the precious metals
plant (Canizares, Gladkovas, and Mezei 2009). The reac-
tion involved in the Bi reduction is shown in equation (3).
BiCl3 +H2O → BiOCl(s) +2HCl (1)
Bi3+ +3Cu0 → Bi0 +3Cu+ (2)
Bi3+ +3e– → Bi0(s) EVSSHEat
50˚ C =0.335V (3)
The main uncertainty is whether the final products pro-
duced are suitable for further refining. The selected method
will be used to produce enough material at a pilot scale to
conduct trial refining campaigns.
Indium, Gallium, and Germanium
Indium (In), Gallium (Ga), and Germanium (Ge) are
critical materials with strategic importance for the United
States due to their essential roles in advanced technolo-
gies. Indium is a key component of In tin oxide (ITO),
which enables touchscreens, flat-panel displays, and solar
panels (Frenzel, Hirsch, and Gutzmer 2016). Indium also
has applications in the aerospace and defense industries.
Gallium’s importance stems from its use in Ga arsenide and
Ga nitride semiconductors, which are vital for 5G wire-
less communications, high-performance electronics, and
light-emitting diodes (LEDs) (Musumeci and Barba 2023).
Germanium is used in fiber optic systems, infrared optics,
solar cells, and LEDs. (Bosi and Attolini 2010). The U.S.
government has designated Ge as a critical material, call-
ing for a stockpile to support national defense needs (Fink
and Culver-Hopper 1991). China currently dominates the
global supply of these metals, making it crucial for the U.S.
to develop domestic resources and recycling capabilities to
ensure a stable and secure supply chain (Huang, Wang, and
Liu et al., 2024).
Recent export restrictions imposed by China on
Ge have raised concerns about potential supply disrup-
tions and highlighted the need for the U.S. to diversify
its sources and invest in domestic production capabilities
(Reuters 2023). Germanium concentrations reported in
zinc and coal fly ash residue range between 200–3600 ppm
(Arroyo, Font, Chimenos et al., 2014 Liu, Liu, Li et al.,
2017). Germanium concentrations across the Kennecott
process streams are significantly lower at around 5–20 ppm.
Figure 8 reveals that there seems to be no clear increase
in concentration throughout the downstream process.
Notably, the refinery streams do not appear to concentrate
Figure 8. Kennecott current processing flow with bismuth flow path
the TDF. Alternatively, producing a commercial Bi product
could meet a domestic demand and reduce the amount of
metal hydroxides sent to waste. We are exploring three pos-
sible ways to produce Bi commercially.
Option 1
Neutralization with an alternative alkaline source involves
raising the pH of a Bi-rich solution until it precipitates as a
solid (Gao, Xu, Yang et al., 2021). We anticipate complet-
ing Bi recovery within a pH range of 2 to 4. The expected
reaction with hydrochloric acid is presented in equation
(1). It is expected that the resulting Bi oxychloride (BiOCl)
will be filtered, dried, and bagged.
Option 2
Cementation with copper, where copper powder is added
to a heated solution containing dissolved Bi. Triggering a
reaction whereby copper replaces Bi in solution, with Bi
depositing as fine metallic solids that can be recovered by
filtration (Shen, Zhang, Cao et al., 2019). The expected
reaction is shown in equation (2). The resulting cement-Bi
product would be filtered, dried, and bagged.
Option 3
Electrowinning, where the goal is to plate Bi metal directly
from the selenium effluent solution in the precious metals
plant (Canizares, Gladkovas, and Mezei 2009). The reac-
tion involved in the Bi reduction is shown in equation (3).
BiCl3 +H2O → BiOCl(s) +2HCl (1)
Bi3+ +3Cu0 → Bi0 +3Cu+ (2)
Bi3+ +3e– → Bi0(s) EVSSHEat
50˚ C =0.335V (3)
The main uncertainty is whether the final products pro-
duced are suitable for further refining. The selected method
will be used to produce enough material at a pilot scale to
conduct trial refining campaigns.
Indium, Gallium, and Germanium
Indium (In), Gallium (Ga), and Germanium (Ge) are
critical materials with strategic importance for the United
States due to their essential roles in advanced technolo-
gies. Indium is a key component of In tin oxide (ITO),
which enables touchscreens, flat-panel displays, and solar
panels (Frenzel, Hirsch, and Gutzmer 2016). Indium also
has applications in the aerospace and defense industries.
Gallium’s importance stems from its use in Ga arsenide and
Ga nitride semiconductors, which are vital for 5G wire-
less communications, high-performance electronics, and
light-emitting diodes (LEDs) (Musumeci and Barba 2023).
Germanium is used in fiber optic systems, infrared optics,
solar cells, and LEDs. (Bosi and Attolini 2010). The U.S.
government has designated Ge as a critical material, call-
ing for a stockpile to support national defense needs (Fink
and Culver-Hopper 1991). China currently dominates the
global supply of these metals, making it crucial for the U.S.
to develop domestic resources and recycling capabilities to
ensure a stable and secure supply chain (Huang, Wang, and
Liu et al., 2024).
Recent export restrictions imposed by China on
Ge have raised concerns about potential supply disrup-
tions and highlighted the need for the U.S. to diversify
its sources and invest in domestic production capabilities
(Reuters 2023). Germanium concentrations reported in
zinc and coal fly ash residue range between 200–3600 ppm
(Arroyo, Font, Chimenos et al., 2014 Liu, Liu, Li et al.,
2017). Germanium concentrations across the Kennecott
process streams are significantly lower at around 5–20 ppm.
Figure 8 reveals that there seems to be no clear increase
in concentration throughout the downstream process.
Notably, the refinery streams do not appear to concentrate
Figure 8. Kennecott current processing flow with bismuth flow path