1704 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
also become a significant focus for research and commercial
processing (Panda, Jha, and Pathak 2018 Steinlechner and
Antrekowitsch 2013).
The current players in PGMs recycling include
Umicore (Belgium), Heraeus (Germany), BASF (USA),
Johnson Matthey (England), and Nippon/Mitsubishi
(Japan) (Panda, Jha, and Pathak 2018). Recycling from
EOL sources contributed over 25% of Pt, Pd, and Rh to the
PGMs supply from 2018 to 2022 (Johnson Matthey 2023).
The PGMs vrecycling process typically involves a combina-
tion of pyrometallurgical and hydrometallurgical methods,
with a standard flowsheet for recycling SACs encompassing
dismantling, crushing, milling, smelting, casting, dissolu-
tion, separation, and purification (Taninouchi and Okabe
2023). During smelting, the PGMs are concentrated. In
smelting, SACs are mixed with a flux, base metal collec-
tor, and reducing agent, heated at 1500–2000 °C, form-
ing a metal phase rich in PGMs and a slag phase rich in
base metal through density differences (Ding et al. 2020
Morcali 2020). The metal phase is collected, cast, and
treated by hydrometallurgical means to produce pure Pt,
Pd, and Rh products.
Despite its prevalence, the smelting process used in
commercial PGMs recycling faces challenges. It cannot
produce final PGM products independently, requiring
substantial energy and investment in process control and
off-gas treatment. Additionally, there is a considerable gen-
eration of slag waste, and the process is not suitable for co-
extraction of other valuable metals present in SACs, such as
Cerium, resulting in a loss of potential revenue. Moreover,
the production cycle for PGMs is long (Ge et al., 2023).
The challenges and high investment associated with
the hybrid pyro and hydrometallurgy process have spurred
research on a purely hydrometallurgical route for PGMs
recovery (Ge et al., 2023). Purely hydrometallurgical pro-
cesses offer advantages such as the extraction of other valu-
able metals from SACs, affordability, and lower energy
costs due to lower process temperatures compared to pyro-
metallurgical processes (Kolbadinejad and Ghaemi 2023).
However, a major drawback is the production of large
amounts of wastewater, resulting in increased treatment
costs (Steinlechner and Antrekowitsch 2013).
While the exclusive use of hydrometallurgy for com-
mercial PGMs recycling is rare, there is a notable focus on
researching PGMs recycling from EOL products through
hydrometallurgical methods. These methods involve the
formation of soluble PGM complexes through leaching
EOL products using hydrochloric acid and robust oxidiz-
ing agents such as chlorine gas, usually conducted at tem-
peratures and pressures of 65–120 °C and 70–400 kPa,
respectively (Saguru 2018 Crundwell 2019). Commercial
PGMs extraction primarily involves leaching concentrates
containing 50–70% PGMs in chloride media to form
anionic chloro-complexes, followed by PGMs recovery
through SX and PPT (Sole, Mooiman, and Hardwick
2017). However, applying PPT to recover PGMs from
leach solutions obtained from EOL sources becomes chal-
lenging due to significantly lower PGMs concentrations
(500 ppm) in these solutions (Shen et al., 2010). PPT
shows poor selectivity, requiring numerous recycle streams
that extend the PGMs hold-up time in the refinery and
increase operating costs (Bernardis, Grant, and Sherrington
2005 Shen et al., 2010). Solvents used in SX processes
are expensive, flammable, toxic, generate fumes, and pose
disposal challenges, necessitating environmentally friendly
and efficient methods for PGMs extraction, particularly at
very low metal concentrations. Although CPE has primar-
ily served as a preconcentration technique for analytes, it
could offer an alternative. Some advantages that CPE offers
include lower costs, reduced toxicity, and decreased envi-
ronmental impact compared to conventional liquid-liquid
extraction methods (Samaddar and Sen 2014).
CPE and IX have exhibited effective recovery of PGMs
at trace levels, minimizing environmental impact (Makua
et al. 2019 Gaita and Al-Bazi 1995). CPE, a liquid-liq-
uid extraction method, utilizes surfactants and complex-
ing agents for metal ion extraction (Makua et al., 2019).
Surfactants, featuring a polar head and a long hydrophobic
tail, are adsorbed at the aqueous solution-air or aqueous
solution-organic solution interface. The water-loving part
faces the aqueous phase, while the hydrophobic part faces
the hydrophobic phase (Melnyk, Namiesnik, and Wolska
2015). Exceeding a surfactant concentration known as the
critical micelle concentration (CMC) leads to the forma-
tion of colloidal like structures known as micelles. These
are capable of bonding with dissolved substances, whether
hydrophilic or hydrophobic (Melnyk, Namiesnik, and
Wolska 2015).
In the CPE process, non-ionic surfactants are induced
to the CMC through change in temperature (Melnyk,
Namiesnik, and Wolska 2015). The procedure involves
mixing a solution containing target metal ions with a com-
plexing agent and a surfactant, followed by heating to a
temperature known as the Cloud Point Temperature where
micelle formation occurs. This results in two liquid phases—
one rich in the surfactant containing complexed target ions
and the other without (Yamini, Feizi, and Moradi, 2020).
The role of the complexing agent is to form hydrophobic
metal complexes that combine with the hydrophobic part of
the surfactant resulting in metal extraction to the surfactant
also become a significant focus for research and commercial
processing (Panda, Jha, and Pathak 2018 Steinlechner and
Antrekowitsch 2013).
The current players in PGMs recycling include
Umicore (Belgium), Heraeus (Germany), BASF (USA),
Johnson Matthey (England), and Nippon/Mitsubishi
(Japan) (Panda, Jha, and Pathak 2018). Recycling from
EOL sources contributed over 25% of Pt, Pd, and Rh to the
PGMs supply from 2018 to 2022 (Johnson Matthey 2023).
The PGMs vrecycling process typically involves a combina-
tion of pyrometallurgical and hydrometallurgical methods,
with a standard flowsheet for recycling SACs encompassing
dismantling, crushing, milling, smelting, casting, dissolu-
tion, separation, and purification (Taninouchi and Okabe
2023). During smelting, the PGMs are concentrated. In
smelting, SACs are mixed with a flux, base metal collec-
tor, and reducing agent, heated at 1500–2000 °C, form-
ing a metal phase rich in PGMs and a slag phase rich in
base metal through density differences (Ding et al. 2020
Morcali 2020). The metal phase is collected, cast, and
treated by hydrometallurgical means to produce pure Pt,
Pd, and Rh products.
Despite its prevalence, the smelting process used in
commercial PGMs recycling faces challenges. It cannot
produce final PGM products independently, requiring
substantial energy and investment in process control and
off-gas treatment. Additionally, there is a considerable gen-
eration of slag waste, and the process is not suitable for co-
extraction of other valuable metals present in SACs, such as
Cerium, resulting in a loss of potential revenue. Moreover,
the production cycle for PGMs is long (Ge et al., 2023).
The challenges and high investment associated with
the hybrid pyro and hydrometallurgy process have spurred
research on a purely hydrometallurgical route for PGMs
recovery (Ge et al., 2023). Purely hydrometallurgical pro-
cesses offer advantages such as the extraction of other valu-
able metals from SACs, affordability, and lower energy
costs due to lower process temperatures compared to pyro-
metallurgical processes (Kolbadinejad and Ghaemi 2023).
However, a major drawback is the production of large
amounts of wastewater, resulting in increased treatment
costs (Steinlechner and Antrekowitsch 2013).
While the exclusive use of hydrometallurgy for com-
mercial PGMs recycling is rare, there is a notable focus on
researching PGMs recycling from EOL products through
hydrometallurgical methods. These methods involve the
formation of soluble PGM complexes through leaching
EOL products using hydrochloric acid and robust oxidiz-
ing agents such as chlorine gas, usually conducted at tem-
peratures and pressures of 65–120 °C and 70–400 kPa,
respectively (Saguru 2018 Crundwell 2019). Commercial
PGMs extraction primarily involves leaching concentrates
containing 50–70% PGMs in chloride media to form
anionic chloro-complexes, followed by PGMs recovery
through SX and PPT (Sole, Mooiman, and Hardwick
2017). However, applying PPT to recover PGMs from
leach solutions obtained from EOL sources becomes chal-
lenging due to significantly lower PGMs concentrations
(500 ppm) in these solutions (Shen et al., 2010). PPT
shows poor selectivity, requiring numerous recycle streams
that extend the PGMs hold-up time in the refinery and
increase operating costs (Bernardis, Grant, and Sherrington
2005 Shen et al., 2010). Solvents used in SX processes
are expensive, flammable, toxic, generate fumes, and pose
disposal challenges, necessitating environmentally friendly
and efficient methods for PGMs extraction, particularly at
very low metal concentrations. Although CPE has primar-
ily served as a preconcentration technique for analytes, it
could offer an alternative. Some advantages that CPE offers
include lower costs, reduced toxicity, and decreased envi-
ronmental impact compared to conventional liquid-liquid
extraction methods (Samaddar and Sen 2014).
CPE and IX have exhibited effective recovery of PGMs
at trace levels, minimizing environmental impact (Makua
et al. 2019 Gaita and Al-Bazi 1995). CPE, a liquid-liq-
uid extraction method, utilizes surfactants and complex-
ing agents for metal ion extraction (Makua et al., 2019).
Surfactants, featuring a polar head and a long hydrophobic
tail, are adsorbed at the aqueous solution-air or aqueous
solution-organic solution interface. The water-loving part
faces the aqueous phase, while the hydrophobic part faces
the hydrophobic phase (Melnyk, Namiesnik, and Wolska
2015). Exceeding a surfactant concentration known as the
critical micelle concentration (CMC) leads to the forma-
tion of colloidal like structures known as micelles. These
are capable of bonding with dissolved substances, whether
hydrophilic or hydrophobic (Melnyk, Namiesnik, and
Wolska 2015).
In the CPE process, non-ionic surfactants are induced
to the CMC through change in temperature (Melnyk,
Namiesnik, and Wolska 2015). The procedure involves
mixing a solution containing target metal ions with a com-
plexing agent and a surfactant, followed by heating to a
temperature known as the Cloud Point Temperature where
micelle formation occurs. This results in two liquid phases—
one rich in the surfactant containing complexed target ions
and the other without (Yamini, Feizi, and Moradi, 2020).
The role of the complexing agent is to form hydrophobic
metal complexes that combine with the hydrophobic part of
the surfactant resulting in metal extraction to the surfactant