XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 293
sites. Evaluating the efficiency and security of the
sequestration process would require this data.
4. Diversifying CO2 utilization sources: Work is
required to develop alternative CO2 utilization
technologies to shift the focus from exclusive
CO2 sequestration in subsurface reservoirs for
enhanced oil recovery to nickel extraction — a
critical mineral that would assist in achieving net
zero emissions.
5. Government Institutions for Auditing: Establish
government agencies with subject matter experts
(SMEs) to audit and provide guidance on CCS
projects and ensure that CO2 capture and seques-
tration project development follows environmen-
tal and safety regulations.
Our study shows potential routes for incorporating CO2
sequestration in nickel processing, an alternative to CO2
sequestration in subsurface reservoirs. This is demonstrated
by CO2 sequestration and utilization opportunities in dif-
ferent mining process flowsheets such as nickel sulfide ore
processing, nickel laterite processing, nickel serpentine
tailings carbonation, etc. Additionally, our study shows
that the same CO2 can be utilized to improve the exist-
ing processes by creating value addition for these processes-
either through enhanced nickel recovery or by the sale of
by-products. Such value addition is an important factor for
industries to adopt CO2 sequestration technology in their
existing process.
ROUTES FOR UTILIZING CO2 IN NICKEL
PROCESSING
Below are some CO2 sequestration and utilization oppor-
tunities explored in different nickel processing flowsheets,
such as ultramafic nickel sulfide ore processing, nickel lat-
erite processing, nickel serpentine tailings carbonation, and
the use of CO2 as a flotation gas. Nickel ores have a mafic
geology that contains divalent ions, mainly Mg2+, which
are an essential source for CO2 sequestration.
Ultramafic Nickel Sulfides
Incorporating CO2 mineralization into ultramafic nickel
sulfide ores before flotation appears beneficial. It boosts
early-stage nickel extraction by introducing a carbonation
process unit. The latter demonstrates superior nickel recov-
ery and grade when comparing mineral mix models rep-
licating uncarbonated and carbonated systems. Serpentine
mineral (unwanted) slimes are positively charged, whereas
the Ni-bearing pentlandite (valuable) mineral is negatively
charged at flotation pH (Khan et al., 2023b). During froth
flotation of an ore containing both minerals, the oppositely
charged serpentine coats the pentlandite surface, negatively
impacting the nickel recovery and grade during separation.
Carbonization leads to serpentine conversion to magnesite,
which avoids the effect of slime coatings on covering the
surface of value minerals and improves the nickel flota-
tion performance. These models indicate that the carbon-
ated system’s minerals don’t experience the slime coating
caused by electrostatic attraction. This insight underscores
carbonation as a valuable method to enhance nickel sulfide
beneficiation. A serpentine ore study showed that carbon-
ation at 185°C, 15 MPa, and with salts increased serpentine
recovery and grade by 29 wt.% and 0.15 wt.%, respectively.
The carbon absorption of this sample reached about 50 t
CO2/t Ni at its best (Khan et al., 2023). A block flow dia-
gram of this combined method is depicted in Figure 1, with
carbonation reactions provided in Equations 1–6 (Khan et
al., 2021).
However, the high temperature and pressure conditions
necessitate equipment costs (CAPEX) and raise operational
expenses (OPEX), compromising the process’s commercial
viability. This is particularly true unless renewable sources
of electricity power the process entirely. Transitioning to an
ambient carbonation reaction could considerably cut costs
and make the tandem process more viable. Exploring the
reaction parameters of ore feed carbonation is essential to
achieve more ambient conditions. This ore carbonation has
a dual significance: CO2 storage and aiding nickel extrac-
tion. While tailings carbonation provides a swift CO2
storage method, ongoing studies aim to retrieve metals
economically, spotlighting the potential in low-grade ore
carbonation.
g CO CO2
2 "^^aqh h (1)
aqh CO H O H CO
2 2 2 3 "+^^lh ^aqh (2)
aq H CO H HCO
2 3 3 "+-^^aq ^aqh h h+ (3)
aq HCO H CO
3 3
2- "-+^^aq ^aqh h h+ (4)
3
1 2H
3
2
3
2
Mg Si O
Mg SiO H O
3 2 5
2+
2 2
"+
+
+^OH
^aqh+
h4
(5)
sh+ Mg HCO MgCO H 2+
3 3 "+-+^(6)
A block diagram (Figure 1) depicts re-utilizing the CO2 in
the tandem carbonation-flotation setup for nickel sulfide
ores. An integrated CO2 mineralization either completely
utilizes CO2 in a single pass or sends back the excess CO2
sites. Evaluating the efficiency and security of the
sequestration process would require this data.
4. Diversifying CO2 utilization sources: Work is
required to develop alternative CO2 utilization
technologies to shift the focus from exclusive
CO2 sequestration in subsurface reservoirs for
enhanced oil recovery to nickel extraction — a
critical mineral that would assist in achieving net
zero emissions.
5. Government Institutions for Auditing: Establish
government agencies with subject matter experts
(SMEs) to audit and provide guidance on CCS
projects and ensure that CO2 capture and seques-
tration project development follows environmen-
tal and safety regulations.
Our study shows potential routes for incorporating CO2
sequestration in nickel processing, an alternative to CO2
sequestration in subsurface reservoirs. This is demonstrated
by CO2 sequestration and utilization opportunities in dif-
ferent mining process flowsheets such as nickel sulfide ore
processing, nickel laterite processing, nickel serpentine
tailings carbonation, etc. Additionally, our study shows
that the same CO2 can be utilized to improve the exist-
ing processes by creating value addition for these processes-
either through enhanced nickel recovery or by the sale of
by-products. Such value addition is an important factor for
industries to adopt CO2 sequestration technology in their
existing process.
ROUTES FOR UTILIZING CO2 IN NICKEL
PROCESSING
Below are some CO2 sequestration and utilization oppor-
tunities explored in different nickel processing flowsheets,
such as ultramafic nickel sulfide ore processing, nickel lat-
erite processing, nickel serpentine tailings carbonation, and
the use of CO2 as a flotation gas. Nickel ores have a mafic
geology that contains divalent ions, mainly Mg2+, which
are an essential source for CO2 sequestration.
Ultramafic Nickel Sulfides
Incorporating CO2 mineralization into ultramafic nickel
sulfide ores before flotation appears beneficial. It boosts
early-stage nickel extraction by introducing a carbonation
process unit. The latter demonstrates superior nickel recov-
ery and grade when comparing mineral mix models rep-
licating uncarbonated and carbonated systems. Serpentine
mineral (unwanted) slimes are positively charged, whereas
the Ni-bearing pentlandite (valuable) mineral is negatively
charged at flotation pH (Khan et al., 2023b). During froth
flotation of an ore containing both minerals, the oppositely
charged serpentine coats the pentlandite surface, negatively
impacting the nickel recovery and grade during separation.
Carbonization leads to serpentine conversion to magnesite,
which avoids the effect of slime coatings on covering the
surface of value minerals and improves the nickel flota-
tion performance. These models indicate that the carbon-
ated system’s minerals don’t experience the slime coating
caused by electrostatic attraction. This insight underscores
carbonation as a valuable method to enhance nickel sulfide
beneficiation. A serpentine ore study showed that carbon-
ation at 185°C, 15 MPa, and with salts increased serpentine
recovery and grade by 29 wt.% and 0.15 wt.%, respectively.
The carbon absorption of this sample reached about 50 t
CO2/t Ni at its best (Khan et al., 2023). A block flow dia-
gram of this combined method is depicted in Figure 1, with
carbonation reactions provided in Equations 1–6 (Khan et
al., 2021).
However, the high temperature and pressure conditions
necessitate equipment costs (CAPEX) and raise operational
expenses (OPEX), compromising the process’s commercial
viability. This is particularly true unless renewable sources
of electricity power the process entirely. Transitioning to an
ambient carbonation reaction could considerably cut costs
and make the tandem process more viable. Exploring the
reaction parameters of ore feed carbonation is essential to
achieve more ambient conditions. This ore carbonation has
a dual significance: CO2 storage and aiding nickel extrac-
tion. While tailings carbonation provides a swift CO2
storage method, ongoing studies aim to retrieve metals
economically, spotlighting the potential in low-grade ore
carbonation.
g CO CO2
2 "^^aqh h (1)
aqh CO H O H CO
2 2 2 3 "+^^lh ^aqh (2)
aq H CO H HCO
2 3 3 "+-^^aq ^aqh h h+ (3)
aq HCO H CO
3 3
2- "-+^^aq ^aqh h h+ (4)
3
1 2H
3
2
3
2
Mg Si O
Mg SiO H O
3 2 5
2+
2 2
"+
+
+^OH
^aqh+
h4
(5)
sh+ Mg HCO MgCO H 2+
3 3 "+-+^(6)
A block diagram (Figure 1) depicts re-utilizing the CO2 in
the tandem carbonation-flotation setup for nickel sulfide
ores. An integrated CO2 mineralization either completely
utilizes CO2 in a single pass or sends back the excess CO2