XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 25
The Limonite sample is mainly comprised of quartz, goe-
thite, montmorillonite, followed by enstatite, olivine, and
talc (Mg3Si4O10(OH)2), and contains 1.16% nickel and
0.041% cobalt. The mineral carbonation capacity is 0.36 t
and 0.29 t CO2 per t Saprolite and Limonite, respectively.
CO2 mineralization and selective leaching was carried
out at 175 °C, CO2 pressure (PCO2) =34.5 bar, 1.5 m
NaHCO3, and 5% solids for the Olivine and 0.5% solids
for the Saprolite and Limonite. A 600 mL stainless steel
autoclave (Model 5103, Parr Instrument) with 400 mL
solution volume and 21 g Olivine sample (or 2.01 g the
laterite sample) was used for each CO2 mineralization and
leaching test. The P80 of the Olivine, the Saprolite and the
Limonite samples was 30 ± 3 µm. NTA was also added as
a complexing reagent into the CO2 mineralization step at
the molar ratio of NTA versus total nickel (NTA/Ni) in the
natural samples. Since the raw Saprolite and Limonite may
not be reactive for CO2 mineralization due to the high con-
tent of serpentine and goethite, the laterites were calcined
as a pre-treatment in a rotary electric furnace (Nabertherm
RSRB 80–750/11, Germany) at 700 °C, 300 mL/min gas
mixture flow containing 5% CO and 95% N2 for 1 h.
The pre-treatment converts all hydrated silicate minerals
(including serpentine) and ferric oxide to olivine and fer-
rous oxide so that the treated laterites can be suitable for
the CO2 mineralization step. The mineral analysis (XRD)
after calcination is shown in Figure 2. The P80 of the lat-
erites after pre-treatment sightly increased to 35 ± 3 µm.
The elemental analysis of the laterites also increased due to
the loss of –OH as loss on ignition (L.O.I.). After the CO2
mineralization, the slurry was filtered to obtain an aqueous
solution for analysis by inductively coupled plasma atomic
Table 3. Raw Material Analysis
Sample SiO
2 MgO Fe
2 O
3 Al
2 O
3 Cr
2 O
3 Ni Co MnO CaO TiO
2 LOI
Olivine 44.4 45.5 10.1 0.17 0.31 0.22 0.0055 0.1 0.15 0.01 0.18
Saprolite 38.3 24.2 17.3 1.8 1.9 2.28 0.063 0.35 0.28 0.02 12.97
Limonite 43.9 13.4 22.9 3.8 1.2 1.16 0.041 0.37 2.4 0.1 10.48
Figure 1. X-Ray Diffraction Analysis of Olivine, Saprolite and Limonite Samples
The Limonite sample is mainly comprised of quartz, goe-
thite, montmorillonite, followed by enstatite, olivine, and
talc (Mg3Si4O10(OH)2), and contains 1.16% nickel and
0.041% cobalt. The mineral carbonation capacity is 0.36 t
and 0.29 t CO2 per t Saprolite and Limonite, respectively.
CO2 mineralization and selective leaching was carried
out at 175 °C, CO2 pressure (PCO2) =34.5 bar, 1.5 m
NaHCO3, and 5% solids for the Olivine and 0.5% solids
for the Saprolite and Limonite. A 600 mL stainless steel
autoclave (Model 5103, Parr Instrument) with 400 mL
solution volume and 21 g Olivine sample (or 2.01 g the
laterite sample) was used for each CO2 mineralization and
leaching test. The P80 of the Olivine, the Saprolite and the
Limonite samples was 30 ± 3 µm. NTA was also added as
a complexing reagent into the CO2 mineralization step at
the molar ratio of NTA versus total nickel (NTA/Ni) in the
natural samples. Since the raw Saprolite and Limonite may
not be reactive for CO2 mineralization due to the high con-
tent of serpentine and goethite, the laterites were calcined
as a pre-treatment in a rotary electric furnace (Nabertherm
RSRB 80–750/11, Germany) at 700 °C, 300 mL/min gas
mixture flow containing 5% CO and 95% N2 for 1 h.
The pre-treatment converts all hydrated silicate minerals
(including serpentine) and ferric oxide to olivine and fer-
rous oxide so that the treated laterites can be suitable for
the CO2 mineralization step. The mineral analysis (XRD)
after calcination is shown in Figure 2. The P80 of the lat-
erites after pre-treatment sightly increased to 35 ± 3 µm.
The elemental analysis of the laterites also increased due to
the loss of –OH as loss on ignition (L.O.I.). After the CO2
mineralization, the slurry was filtered to obtain an aqueous
solution for analysis by inductively coupled plasma atomic
Table 3. Raw Material Analysis
Sample SiO
2 MgO Fe
2 O
3 Al
2 O
3 Cr
2 O
3 Ni Co MnO CaO TiO
2 LOI
Olivine 44.4 45.5 10.1 0.17 0.31 0.22 0.0055 0.1 0.15 0.01 0.18
Saprolite 38.3 24.2 17.3 1.8 1.9 2.28 0.063 0.35 0.28 0.02 12.97
Limonite 43.9 13.4 22.9 3.8 1.2 1.16 0.041 0.37 2.4 0.1 10.48
Figure 1. X-Ray Diffraction Analysis of Olivine, Saprolite and Limonite Samples