XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3289
Mn. Hydrogen peroxide (H2O2) is the most commonly
used reductant as it possesses a low oxidation potential, low
reagent cost, and produces harmless byproducts (Larouche
et al., 2020).
The downside to using hydrometallurgical routes is
they evolve large quantities of toxic gases and require lon-
ger leaching periods to recover the desired metals. The use
of stronger leaching agents generate a substantial amount of
secondary pollutants (e.g., SO3,Cl2,NOx, etc.), which pose
significant environmental and health risks.
The next section describes the leaching systems used to
recycle cathode material.
Acid Leaching
Inorganic acids are commonly used due to their effec-
tiveness and low cost. Compared to HNO3, H2SO4, and
H3PO4, HCl leaching requires a lower concentration to
achieve high leaching rates and efficiency. This is ascribed
to:
• its stronger acidity (i.e., higher dissociation constant),
• the presence of corrosive Cl– anions that possess a
lower pitting potential compared to sulfate, nitrate,
and phosphate anions,
• Cl– can serve as a reductant for M3+/M4+. High
leaching efficiencies can be achieved for HCl without
the supplementation of a reducing agent. An upside
to coupling HCl with a reducing agent is it can lower
the concentration threshold of HCl required to reach
high efficiency.
That said, the industry preferred industrial leaching system
that generates the better grades and recovery is H2SO4 with
H2O2 as the reducing agent.
Figure 2. Examples of cathode material recycling via hydrometallurgical routes
Mn. Hydrogen peroxide (H2O2) is the most commonly
used reductant as it possesses a low oxidation potential, low
reagent cost, and produces harmless byproducts (Larouche
et al., 2020).
The downside to using hydrometallurgical routes is
they evolve large quantities of toxic gases and require lon-
ger leaching periods to recover the desired metals. The use
of stronger leaching agents generate a substantial amount of
secondary pollutants (e.g., SO3,Cl2,NOx, etc.), which pose
significant environmental and health risks.
The next section describes the leaching systems used to
recycle cathode material.
Acid Leaching
Inorganic acids are commonly used due to their effec-
tiveness and low cost. Compared to HNO3, H2SO4, and
H3PO4, HCl leaching requires a lower concentration to
achieve high leaching rates and efficiency. This is ascribed
to:
• its stronger acidity (i.e., higher dissociation constant),
• the presence of corrosive Cl– anions that possess a
lower pitting potential compared to sulfate, nitrate,
and phosphate anions,
• Cl– can serve as a reductant for M3+/M4+. High
leaching efficiencies can be achieved for HCl without
the supplementation of a reducing agent. An upside
to coupling HCl with a reducing agent is it can lower
the concentration threshold of HCl required to reach
high efficiency.
That said, the industry preferred industrial leaching system
that generates the better grades and recovery is H2SO4 with
H2O2 as the reducing agent.
Figure 2. Examples of cathode material recycling via hydrometallurgical routes