XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 3179
8.0, respectively. A recovery in the overflow product of
99.6% graphite and 4.2% NMC was attained. Meanwhile,
flotation of Cyrene-treated MBM resulted in a recovery of
93.7% graphite and only 0.4% NMC in the overflow prod-
uct. These results demonstrated that Cyrene does not affect
the ideal flotation behavior of these particles. In the case
of pyrolysis pre-treatment of pristine materials, the previ-
ous works (Salces et al., 2022 Vanderbruggen et al., 2022)
suggest no deterioration of graphite and NMC flotation
behavior after exposure to thermal treatment.
Flotation Efficiency
Figure 4 shows the grade and recovery curve of NMC and
carbon (assumed as graphite) and their upgrading curve
in the overflow (O/F) product. The flotation of mechani-
cal and Cyrene pre-treated IBM exhibited a comparable
recovery of 93.3% and 88.3%, respectively, and grade of
50.7% C and 56.2% C, respectively. Meanwhile, the flota-
tion with pyrolysis pre-treatment attained the best result
with a graphite recovery and grade of 97.8% and 73.7% C,
respectively. The impact of Cyrene pre-treatment is more
relevant to the Ni+Co+Mn (NMC) recovery in the O/F
product. With C-IBM, the NMC recovery is 41.0% with a
grade of 19.0% while with M-IBM, the NMC recovery is
58.3% with a grade of 21.5%. P-IBM obtained the lowest
NMC recovery of 21.1% with a grade of 11.6%.
Overall, the upgrading curve highlights that Cyrene
pre-treatment with attrition resulted in a slight improve-
ment in flotation selectivity compared to mechanical
pre-treatment. Thermal treatment by pyrolysis has been
established as the one of most effective pre-treatment for
the flotation of black mass components in the conditions
tested. The main challenge in Cyrene pre-treatment is the
separation of the Cyrene-PVDF mixture from the black
mass after heating. The PVDF dissolution only occurs at
temperatures exceeding 80°C and PVDF segregates out of
the solution upon cooling. To prevent PVDF re-deposition,
researchers such as Bai et al. (2020) employed centrifuga-
tion to recover the cathode powders while the mixture was
hot. In this work, hot filtration was performed inside a dry-
ing oven. Since Cyrene has a relatively high viscosity, the
filtration took around 5–10 min, which may have led to
the redeposition of some PVDF. Water could be added dur-
ing filtration to reduce the viscosity of the PVDF-Cyrene
mixture but this would hydrate the Cyrene and inhibit its
re-use. Furthermore, important operating parameters such
as temperature, time, Cyrene-solids ratio, and washing after
filtration were fixed and therefore not optimized.
Dissolution of Lithium in Flotation Water
Cathode active materials, particularly NMC, can be
carbothermically reduced when subjected to pyrolysis
resulting in the formation of reduced compounds of Ni, Co,
Mn, and water-soluble lithium compounds. After flotation,
the different pHs of the process water—9.7, 8.5, and 11.7
for M-IBM, C-IBM, and P-IBM respectively, can be indic-
ative the relative content of lithium. The analysis of flota-
tion process water revealed a high concentration of lithium
after flotation. In P-IBM, about 55–56% of lithium dis-
solved into the process water, with lithium concentration in
the process water between 1100–1250 mg/L. Meanwhile,
mechanical and Cyrene pre-treatment show a similar extent
of lithium dissolution of about 12–16%, with lithium con-
centration between 200–270 mg/L. This lithium could be
derived from the electrolyte salt and CAMs, which can be
in their original form or chemically altered during battery
Figure 3. Outotec GTK LabCell® and progression of flotation experiment
8.0, respectively. A recovery in the overflow product of
99.6% graphite and 4.2% NMC was attained. Meanwhile,
flotation of Cyrene-treated MBM resulted in a recovery of
93.7% graphite and only 0.4% NMC in the overflow prod-
uct. These results demonstrated that Cyrene does not affect
the ideal flotation behavior of these particles. In the case
of pyrolysis pre-treatment of pristine materials, the previ-
ous works (Salces et al., 2022 Vanderbruggen et al., 2022)
suggest no deterioration of graphite and NMC flotation
behavior after exposure to thermal treatment.
Flotation Efficiency
Figure 4 shows the grade and recovery curve of NMC and
carbon (assumed as graphite) and their upgrading curve
in the overflow (O/F) product. The flotation of mechani-
cal and Cyrene pre-treated IBM exhibited a comparable
recovery of 93.3% and 88.3%, respectively, and grade of
50.7% C and 56.2% C, respectively. Meanwhile, the flota-
tion with pyrolysis pre-treatment attained the best result
with a graphite recovery and grade of 97.8% and 73.7% C,
respectively. The impact of Cyrene pre-treatment is more
relevant to the Ni+Co+Mn (NMC) recovery in the O/F
product. With C-IBM, the NMC recovery is 41.0% with a
grade of 19.0% while with M-IBM, the NMC recovery is
58.3% with a grade of 21.5%. P-IBM obtained the lowest
NMC recovery of 21.1% with a grade of 11.6%.
Overall, the upgrading curve highlights that Cyrene
pre-treatment with attrition resulted in a slight improve-
ment in flotation selectivity compared to mechanical
pre-treatment. Thermal treatment by pyrolysis has been
established as the one of most effective pre-treatment for
the flotation of black mass components in the conditions
tested. The main challenge in Cyrene pre-treatment is the
separation of the Cyrene-PVDF mixture from the black
mass after heating. The PVDF dissolution only occurs at
temperatures exceeding 80°C and PVDF segregates out of
the solution upon cooling. To prevent PVDF re-deposition,
researchers such as Bai et al. (2020) employed centrifuga-
tion to recover the cathode powders while the mixture was
hot. In this work, hot filtration was performed inside a dry-
ing oven. Since Cyrene has a relatively high viscosity, the
filtration took around 5–10 min, which may have led to
the redeposition of some PVDF. Water could be added dur-
ing filtration to reduce the viscosity of the PVDF-Cyrene
mixture but this would hydrate the Cyrene and inhibit its
re-use. Furthermore, important operating parameters such
as temperature, time, Cyrene-solids ratio, and washing after
filtration were fixed and therefore not optimized.
Dissolution of Lithium in Flotation Water
Cathode active materials, particularly NMC, can be
carbothermically reduced when subjected to pyrolysis
resulting in the formation of reduced compounds of Ni, Co,
Mn, and water-soluble lithium compounds. After flotation,
the different pHs of the process water—9.7, 8.5, and 11.7
for M-IBM, C-IBM, and P-IBM respectively, can be indic-
ative the relative content of lithium. The analysis of flota-
tion process water revealed a high concentration of lithium
after flotation. In P-IBM, about 55–56% of lithium dis-
solved into the process water, with lithium concentration in
the process water between 1100–1250 mg/L. Meanwhile,
mechanical and Cyrene pre-treatment show a similar extent
of lithium dissolution of about 12–16%, with lithium con-
centration between 200–270 mg/L. This lithium could be
derived from the electrolyte salt and CAMs, which can be
in their original form or chemically altered during battery
Figure 3. Outotec GTK LabCell® and progression of flotation experiment