26 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
emission spectroscopy (ICP-AES) and a solid residue for
LECO total carbon analysis, X-ray diffraction (XRD), and
scanning electron microscopy with energy dispersive X-ray
spectroscopy (SEM-EDX) analysis. In this step, nickel
and cobalt from the Olivine, Saprolite, and Limonite are
stabilized in solution by NTA as (Ni,Co)NTA–complex
ions in aqueous solution and the magnesium and iron are
stabilized after reaction with CO2 as mineral carbonates
(Mg,Fe) CO3.
The selective extraction of nickel and cobalt were dem-
onstrated (Figure 3). The leach solutions containing nickel
and cobalt were filtered and recovered and the precipitated
with hydrogen sulfide gas to form mixed sulfide precipitate.
The mixed sulfide precipitate was removed and the residual
sulfide oxidized and the solution recycled. The recycle solu-
tion (Wang and Dreisinger, 2023) showed similar extrac-
tions over three recycles. A flowsheet has been developed
for further evaluation of the process (Figure 4). The process
simultaneously sequesters carbon while recovering nickel
and cobalt as a mixed sulfide for further refining. The car-
bonated residue represents permanent storage of carbon
dioxide by carbonate mineralization. The process is actively
under development with a focus on (1) increased %solids
in the primary carbonation process and (2) confirmation of
the recyclability of NTA at the higher %solids levels.
THE PRESSURE OXIDATION OF NICKEL
SULFIDE CONCENTRATES
Nickel sulfide concentrates often contain iron sulfide min-
erals such as pyrrhotite or pyrite, and copper sulfide min-
erals such as chalcopyrite. The conventional treatment of
nickel concentrates is via smelting, converting, and refin-
ing. This process produces a slag containing iron oxide,
an off-gas containing sulfur dioxide that can be used to
manufacture sulfuric acid for sale, nickel metal, a cobalt
product, and a copper product. If precious metals (gold,
platinum, palladium, rhodium, silver, etc.) are present, the
smelting, converting and refining process will also recover
these metals for value. These elements are separated in a
PGM refinery.
The conventional process is advantageous for the
production of nickel metal of high quality. However, the
conventional process has environmental challenges due to
fugitive gas and dust emissions from the smelting operation,
the volatilization of deleterious impurities during smelting
and high capital and operating costs. If the concentrate is
Figure 2. X-ray diffraction analysis of calcined olivine, saprolite and limonite samples
emission spectroscopy (ICP-AES) and a solid residue for
LECO total carbon analysis, X-ray diffraction (XRD), and
scanning electron microscopy with energy dispersive X-ray
spectroscopy (SEM-EDX) analysis. In this step, nickel
and cobalt from the Olivine, Saprolite, and Limonite are
stabilized in solution by NTA as (Ni,Co)NTA–complex
ions in aqueous solution and the magnesium and iron are
stabilized after reaction with CO2 as mineral carbonates
(Mg,Fe) CO3.
The selective extraction of nickel and cobalt were dem-
onstrated (Figure 3). The leach solutions containing nickel
and cobalt were filtered and recovered and the precipitated
with hydrogen sulfide gas to form mixed sulfide precipitate.
The mixed sulfide precipitate was removed and the residual
sulfide oxidized and the solution recycled. The recycle solu-
tion (Wang and Dreisinger, 2023) showed similar extrac-
tions over three recycles. A flowsheet has been developed
for further evaluation of the process (Figure 4). The process
simultaneously sequesters carbon while recovering nickel
and cobalt as a mixed sulfide for further refining. The car-
bonated residue represents permanent storage of carbon
dioxide by carbonate mineralization. The process is actively
under development with a focus on (1) increased %solids
in the primary carbonation process and (2) confirmation of
the recyclability of NTA at the higher %solids levels.
THE PRESSURE OXIDATION OF NICKEL
SULFIDE CONCENTRATES
Nickel sulfide concentrates often contain iron sulfide min-
erals such as pyrrhotite or pyrite, and copper sulfide min-
erals such as chalcopyrite. The conventional treatment of
nickel concentrates is via smelting, converting, and refin-
ing. This process produces a slag containing iron oxide,
an off-gas containing sulfur dioxide that can be used to
manufacture sulfuric acid for sale, nickel metal, a cobalt
product, and a copper product. If precious metals (gold,
platinum, palladium, rhodium, silver, etc.) are present, the
smelting, converting and refining process will also recover
these metals for value. These elements are separated in a
PGM refinery.
The conventional process is advantageous for the
production of nickel metal of high quality. However, the
conventional process has environmental challenges due to
fugitive gas and dust emissions from the smelting operation,
the volatilization of deleterious impurities during smelting
and high capital and operating costs. If the concentrate is
Figure 2. X-ray diffraction analysis of calcined olivine, saprolite and limonite samples