XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 151
the gold glycinate onto the carbon in the ore. In such cases
the carbon in the ore needs to either pre-blinded (e.g., kero-
sene) or oxidized (e.g., roasting) to make the ore amenable
to leaching. For base metals leaching, where glycine is used
in the GlyLeach configuration, glycine is mostly suitable
for leaching ores, low grade concentrates (e.g., flotation
rougher concentrates without further cleaning) and tailings
rather than high grade concentrates. Such concentrates, as
typically prepared for pressure leaching or smelting, are not
the best candidates for glycine leaching. Ideally, ores that
are polymetallic, with fine dissemination of the base metal
minerals in the gangue matrix, and where significant losses
will be incurred in the concentrating process to meet the
grade requirement for smeltable or pressure leachable con-
centrates, are the best candidates for glycine leaching. For
nickel-cobalt-copper sulfide ores this would be with grades
ore/rougher concentrate grades ranging from 0.2% to 6%.
Key concerns are the solubility limit of base metal glycinates
at high concentrations, with the potential of unwanted
recrystallisation, although small amounts of additives such
as ammonia may act synergistically to significantly increase
the solvent capacity of the GlyLeach systems. Due to the
low concentration of precious metals, they are not con-
strained as base metals are. When rich base metal concen-
trates are leached, the %solids in the leach would need to
be reduced (e.g., down to 8–10%), or synergistic additives
need to be added to enhance the lixiviant capacity. Finally,
it should be noted that the leaching of base metals from sili-
cates (such as chrysotile, olivine, or serpentine) or hydrated
ferric oxides (e.g., limonite) doesn’t yield high recoveries
unless undergoing some form of pre-processing. While very
versatile, the glycine-based processes have limitations that
depend on ore mineralogy, carbon content, and grade (too
high grade for base metals being problematic).
PROCESS DEVELOPMENT, UPTAKE AND
COMMERCIALISATION
The process development of fully integrated hydrometal-
lurgical circuits that are feasible and incorporates a totally
new process chemistry is time-consuming and faces signifi-
cant resistance from a traditionally conservative industry,
no matter the positive credentials of the new proposed
process. This is often disheartening to the prospective met-
allurgical inventors who seldom see commercialization of
technologies within the period that a patent is valid. Often
the best opportunity for the uptake of a new metallurgical
technology is the application to legacy or current arising
tailings where the value has already been extracted using
conventional methods. Alternatively, the technology must
allow rapid retrofitting into existing circuits. This was par-
ticularly useful for the GlyCat ™ technology utilizing gly-
cine with cyanide at starvation concentrations, as it could
be deployed in existing CIP/CIL circuits without major
process changes. Many recent advances in hydrometallurgy
focused strongly on new bioleach technologies, or more
recently, ionic liquids and Deep Eutectic Solvent (DES)
technologies. While DES technologies promises very rapid
leach times for minerals that are often refractory, their
non-aqueous basis makes sufficient solvent-residue separa-
tion hard given that washing introduces a solvent that then
has to be separated from the DES chemicals (Binnemans
and Jones, 2023b). That said, DES may offer interesting
opportunities in very high-grade applications such as some
e-Waste applications, and the processing of some process
intermediates and residues, such as precious metal bearing
anode slimes from copper electrorefining.
CONCLUSIONS
This paper presented the process development towards sus-
tainable processing technologies with a focus on critical
metals such as nickel, cobalt, palladium, etc., using alkaline
glycine leaching as a case study. The proposed 12 Principles
of Sustainable Hydrometallurgy (Binnemans and Jones,
2023a) provides a useful template for evaluating new lix-
iviant technologies. This paper used alkaline glycine leach
technology as a case study how these objectives are satisfied
for a novel process technology.
Regenerate reagents Glycine is regenerated for reuse
during the metal recovery
processes (precipitation, IX, SX)
Close water loops The recovery of the glycine
automatically triggers the recovery
of water
Prevent waste Waste of reagents are minimized
while leach residues are inherently
less toxic than for many other
lixiviants (cyanide, ammonia,
sulfuric acid)
Maximize mass, energy,
space, and time efficiency
Glycine is a fit-for-purpose reagent
for low grade concentrates, ores
and tailings. Leaching timeframes
are comparable to other
hydrometallurgical processes at
atmospheric pressure.
Integrate materials and
energy flows
The process happens at
atmospheric pressure and mild
temperatures (from ambient to 70
°C)
the gold glycinate onto the carbon in the ore. In such cases
the carbon in the ore needs to either pre-blinded (e.g., kero-
sene) or oxidized (e.g., roasting) to make the ore amenable
to leaching. For base metals leaching, where glycine is used
in the GlyLeach configuration, glycine is mostly suitable
for leaching ores, low grade concentrates (e.g., flotation
rougher concentrates without further cleaning) and tailings
rather than high grade concentrates. Such concentrates, as
typically prepared for pressure leaching or smelting, are not
the best candidates for glycine leaching. Ideally, ores that
are polymetallic, with fine dissemination of the base metal
minerals in the gangue matrix, and where significant losses
will be incurred in the concentrating process to meet the
grade requirement for smeltable or pressure leachable con-
centrates, are the best candidates for glycine leaching. For
nickel-cobalt-copper sulfide ores this would be with grades
ore/rougher concentrate grades ranging from 0.2% to 6%.
Key concerns are the solubility limit of base metal glycinates
at high concentrations, with the potential of unwanted
recrystallisation, although small amounts of additives such
as ammonia may act synergistically to significantly increase
the solvent capacity of the GlyLeach systems. Due to the
low concentration of precious metals, they are not con-
strained as base metals are. When rich base metal concen-
trates are leached, the %solids in the leach would need to
be reduced (e.g., down to 8–10%), or synergistic additives
need to be added to enhance the lixiviant capacity. Finally,
it should be noted that the leaching of base metals from sili-
cates (such as chrysotile, olivine, or serpentine) or hydrated
ferric oxides (e.g., limonite) doesn’t yield high recoveries
unless undergoing some form of pre-processing. While very
versatile, the glycine-based processes have limitations that
depend on ore mineralogy, carbon content, and grade (too
high grade for base metals being problematic).
PROCESS DEVELOPMENT, UPTAKE AND
COMMERCIALISATION
The process development of fully integrated hydrometal-
lurgical circuits that are feasible and incorporates a totally
new process chemistry is time-consuming and faces signifi-
cant resistance from a traditionally conservative industry,
no matter the positive credentials of the new proposed
process. This is often disheartening to the prospective met-
allurgical inventors who seldom see commercialization of
technologies within the period that a patent is valid. Often
the best opportunity for the uptake of a new metallurgical
technology is the application to legacy or current arising
tailings where the value has already been extracted using
conventional methods. Alternatively, the technology must
allow rapid retrofitting into existing circuits. This was par-
ticularly useful for the GlyCat ™ technology utilizing gly-
cine with cyanide at starvation concentrations, as it could
be deployed in existing CIP/CIL circuits without major
process changes. Many recent advances in hydrometallurgy
focused strongly on new bioleach technologies, or more
recently, ionic liquids and Deep Eutectic Solvent (DES)
technologies. While DES technologies promises very rapid
leach times for minerals that are often refractory, their
non-aqueous basis makes sufficient solvent-residue separa-
tion hard given that washing introduces a solvent that then
has to be separated from the DES chemicals (Binnemans
and Jones, 2023b). That said, DES may offer interesting
opportunities in very high-grade applications such as some
e-Waste applications, and the processing of some process
intermediates and residues, such as precious metal bearing
anode slimes from copper electrorefining.
CONCLUSIONS
This paper presented the process development towards sus-
tainable processing technologies with a focus on critical
metals such as nickel, cobalt, palladium, etc., using alkaline
glycine leaching as a case study. The proposed 12 Principles
of Sustainable Hydrometallurgy (Binnemans and Jones,
2023a) provides a useful template for evaluating new lix-
iviant technologies. This paper used alkaline glycine leach
technology as a case study how these objectives are satisfied
for a novel process technology.
Regenerate reagents Glycine is regenerated for reuse
during the metal recovery
processes (precipitation, IX, SX)
Close water loops The recovery of the glycine
automatically triggers the recovery
of water
Prevent waste Waste of reagents are minimized
while leach residues are inherently
less toxic than for many other
lixiviants (cyanide, ammonia,
sulfuric acid)
Maximize mass, energy,
space, and time efficiency
Glycine is a fit-for-purpose reagent
for low grade concentrates, ores
and tailings. Leaching timeframes
are comparable to other
hydrometallurgical processes at
atmospheric pressure.
Integrate materials and
energy flows
The process happens at
atmospheric pressure and mild
temperatures (from ambient to 70
°C)