24 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
THE CONCERTED MINERAL
CARBONATION AND SELECTIVE
LEACHING (CMCSL) PROCESS
The carbonation of basic silicate minerals has been well
studied. A typical condition applied in laboratory studies is
to carbonate a mineral slurry in a background of sodium bi-
carbonate solution using an over pressure of carbon dioxide
gas. Depending on the mineral form in the basic silicate,
the carbonation reaction can be written as follows.
(Mg, Fe, Ca, Ni, Co)2SiO4 +2CO2(g) =
2(Mg, Fe, Ca, Ni, Co)CO3 +SiO2(s)
This reaction can sequester carbon in proportion to
the original mineral composition and the extent of reaction
with respect to each basic silicate present.
The Concerted Mineral Carbonation and Selective
Leaching (CMCSL) process uses the same reaction chem-
istry as the carbonation process but instead of having the
value or battery metals reporting to the carbonate product
solid, the nickel and cobalt can be extracted into solution.
Nitrilotriacetic (NTA) acid trisodium salt is dissolved
in the sodium carbonate solution during carbonation and
selectively complexes nickel and cobalt while allowing the
large proportion of the other metals to form carbonates.
Table 2 shows the relative stability coefficients (LogK) for
the carbonates and the NTA complexes. The NTA com-
plexes of nickel and cobalt are stronger than the respective
carbonate precipitates and hence as a first approximation, it
would be expected that nickel and cobalt could be retained
in solution as NTA complexes during carbonation.
Wang and Dreisinger (2023) demonstrated the prin-
ciple of CMCSL on a range of raw materials including oliv-
ine, saprolite and limonite nickel laterites (Table 3).
The mineralogy of each of the three samples is shown
in Figure 1. The Olivine sample is mainly comprised of the
mineral olivine, followed by some enstatite (MgSiO3) and
hydrated serpentine. The Olivine sample contains 0.22%
nickel and 0.0055% cobalt. The theoretical mineral carbon-
ation capacity is 0.55 t CO2/t Olivine based on total mag-
nesium, iron, and calcium content where each mole of the
divalent metals can stabilize 1 mol CO2 gas carbonates. The
Saprolite sample is mainly comprised of serpentine, mont-
morillonite ((Na,Ca)0.3(Al, Mg)2Si4O10(OH)2⋅nH2O),
quartz (SiO2), followed by olivine, enstatite, and goe-
thite, and contains 2.28% nickel and 0.063% cobalt.
Table 1. Process Options for Primary Nickel and Cobalt Recovery. CO2 Emissions are for Ore to MHP or Nickel Matte.
(Perrenin and Benotmane (Hatch) 2023)
Process High Pressure Acid Leach (HPAL) Laterite matte Flash smelting
Process description Limonite to MHP Saprolite to matte Sulfide Conc to matte
Primary nickel product Mixed Hydroxide Precipitate (MHP) Nickel matte Nickel matte
Maximum T
(Ni production step)
240–260 °C 1600 °C 1300 °C
Maximum P
(Ni production step)
30–50 × atmospheric pressure Atmospheric Atmospheric
CO2 (scope 1 and 2)
t CO2e per t contained Ni
19 (SE Asia) 44 (SE Asia) 13 (Australia)
Gaseous emissions CO2 CO2 CO2 and fugitive SO2
Solid emissions Leach/ neut residue
39 t residue (dry basis) per t Ni
Furnace/converter slags
50 t per t contained Ni
50–200 t flotation tails per t
contained Ni
5.5 t smelter slag per t contained Ni
Table 2. Stability of metal carbonate and metal-NTA complex ions (Kolodynska)
Cations Carbonates LogK NTA Complexes LogK
Mg2+ MgCO
3 5.1 Mg-EDTA 5.5
Ca2+ CaCO
3 8.3 Ca-NTA 6.4
Fe2+ FeCO3 8.3 Fe(II)-NTA 8.3
Co2+ CoCO3 9.3 Co-NTA 10.4
Ni2+ NiCO
3 11.0 Ni-NTA 11.5
a Data are from HSC Chemistry 7.1.
b Data are based on metal:NTA =1:1 complexes
THE CONCERTED MINERAL
CARBONATION AND SELECTIVE
LEACHING (CMCSL) PROCESS
The carbonation of basic silicate minerals has been well
studied. A typical condition applied in laboratory studies is
to carbonate a mineral slurry in a background of sodium bi-
carbonate solution using an over pressure of carbon dioxide
gas. Depending on the mineral form in the basic silicate,
the carbonation reaction can be written as follows.
(Mg, Fe, Ca, Ni, Co)2SiO4 +2CO2(g) =
2(Mg, Fe, Ca, Ni, Co)CO3 +SiO2(s)
This reaction can sequester carbon in proportion to
the original mineral composition and the extent of reaction
with respect to each basic silicate present.
The Concerted Mineral Carbonation and Selective
Leaching (CMCSL) process uses the same reaction chem-
istry as the carbonation process but instead of having the
value or battery metals reporting to the carbonate product
solid, the nickel and cobalt can be extracted into solution.
Nitrilotriacetic (NTA) acid trisodium salt is dissolved
in the sodium carbonate solution during carbonation and
selectively complexes nickel and cobalt while allowing the
large proportion of the other metals to form carbonates.
Table 2 shows the relative stability coefficients (LogK) for
the carbonates and the NTA complexes. The NTA com-
plexes of nickel and cobalt are stronger than the respective
carbonate precipitates and hence as a first approximation, it
would be expected that nickel and cobalt could be retained
in solution as NTA complexes during carbonation.
Wang and Dreisinger (2023) demonstrated the prin-
ciple of CMCSL on a range of raw materials including oliv-
ine, saprolite and limonite nickel laterites (Table 3).
The mineralogy of each of the three samples is shown
in Figure 1. The Olivine sample is mainly comprised of the
mineral olivine, followed by some enstatite (MgSiO3) and
hydrated serpentine. The Olivine sample contains 0.22%
nickel and 0.0055% cobalt. The theoretical mineral carbon-
ation capacity is 0.55 t CO2/t Olivine based on total mag-
nesium, iron, and calcium content where each mole of the
divalent metals can stabilize 1 mol CO2 gas carbonates. The
Saprolite sample is mainly comprised of serpentine, mont-
morillonite ((Na,Ca)0.3(Al, Mg)2Si4O10(OH)2⋅nH2O),
quartz (SiO2), followed by olivine, enstatite, and goe-
thite, and contains 2.28% nickel and 0.063% cobalt.
Table 1. Process Options for Primary Nickel and Cobalt Recovery. CO2 Emissions are for Ore to MHP or Nickel Matte.
(Perrenin and Benotmane (Hatch) 2023)
Process High Pressure Acid Leach (HPAL) Laterite matte Flash smelting
Process description Limonite to MHP Saprolite to matte Sulfide Conc to matte
Primary nickel product Mixed Hydroxide Precipitate (MHP) Nickel matte Nickel matte
Maximum T
(Ni production step)
240–260 °C 1600 °C 1300 °C
Maximum P
(Ni production step)
30–50 × atmospheric pressure Atmospheric Atmospheric
CO2 (scope 1 and 2)
t CO2e per t contained Ni
19 (SE Asia) 44 (SE Asia) 13 (Australia)
Gaseous emissions CO2 CO2 CO2 and fugitive SO2
Solid emissions Leach/ neut residue
39 t residue (dry basis) per t Ni
Furnace/converter slags
50 t per t contained Ni
50–200 t flotation tails per t
contained Ni
5.5 t smelter slag per t contained Ni
Table 2. Stability of metal carbonate and metal-NTA complex ions (Kolodynska)
Cations Carbonates LogK NTA Complexes LogK
Mg2+ MgCO
3 5.1 Mg-EDTA 5.5
Ca2+ CaCO
3 8.3 Ca-NTA 6.4
Fe2+ FeCO3 8.3 Fe(II)-NTA 8.3
Co2+ CoCO3 9.3 Co-NTA 10.4
Ni2+ NiCO
3 11.0 Ni-NTA 11.5
a Data are from HSC Chemistry 7.1.
b Data are based on metal:NTA =1:1 complexes