2388
Enhanced Flotation of Ultramafic Nickel Ores Using CO
2
as a Flotation Gas and Sodium Tripolyphosphate (STPP) as
Serpentine Depressant
Nzubechukwu C. Ezeonyi, Erin R. Bobicki
Department of Chemical and Materials Engineering, University of Alberta, Canada
Omar B. Wani
Department of Applied Chemistry and Chemical Engineering, University of Toronto, Canada
Farzaneh Sadri
Department of Chemical and Materials Engineering, University of Alberta, Canada
The Robert M. Buchan Department of Mining Engineering, Canada
ABSTRACT: Low-grade ores like the ultramafic ores contain large amounts of gangue minerals which impacts
recovery of the valuable pentlandite minerals. In ultramafic nickel ores, serpentine (MgO-bearing mineral)
slime-coats and decreases the recovery of the nickel-bearing pentlandite. To improve the recovery of pentlandite
and subsequently suppress serpentine in ultramafic nickel ores, CO2 gas (either as a depressant or a flotation gas)
and sodium tripolyphosphate (STPP) as a reagent for serpentine depression are used in this study. Phosphate
groups in STPP chelate magnesium ions and can facilitate serpentine depression in flotation systems. CO2
can also precipitate divalent cations like magnesium cations, and due to the high solubility of CO2 gas, it
can form fine bubbles on hydrophobic valuable minerals to improve their recovery. The surface charge on the
serpentine samples were completely reversed upon either the introduction of STPP at above 10 mg/L or by
conditioning the suspension with CO2 gas during zeta potential measurements. The resulting negative charge
of the serpentine mineral indicates that the heterogeneous agglomeration with pentlandite surface is weakened,
which should allow for a more pentlandite floatability. Subsequently, an optimum concentration of 50 mg/L
was obtained which was then used to perform flotation tests and XPS analysis. Flotation benefits were achieved
as serpentine suppression and enhanced pentlandite recovery was observed for both STPP and CO2 cases.
STPP was more effective in suppressing serpentine by 5%, while the highest pentlandite recovery of 88% was
obtained when CO2 was used as a flotation gas, which is a 20% increase in recovery from the baseline case. The
more effective STPP suppressing ability was validated by XPS results and provides an opportunity to explore the
combination of STPP and CO2 in future studies. Results from this study open up the opportunity of mineral
carbonation as a decarbonization strategy and will serve as a guide for researchers to perform more experiments
in the direction of CO2-assisted flotation.
Enhanced Flotation of Ultramafic Nickel Ores Using CO
2
as a Flotation Gas and Sodium Tripolyphosphate (STPP) as
Serpentine Depressant
Nzubechukwu C. Ezeonyi, Erin R. Bobicki
Department of Chemical and Materials Engineering, University of Alberta, Canada
Omar B. Wani
Department of Applied Chemistry and Chemical Engineering, University of Toronto, Canada
Farzaneh Sadri
Department of Chemical and Materials Engineering, University of Alberta, Canada
The Robert M. Buchan Department of Mining Engineering, Canada
ABSTRACT: Low-grade ores like the ultramafic ores contain large amounts of gangue minerals which impacts
recovery of the valuable pentlandite minerals. In ultramafic nickel ores, serpentine (MgO-bearing mineral)
slime-coats and decreases the recovery of the nickel-bearing pentlandite. To improve the recovery of pentlandite
and subsequently suppress serpentine in ultramafic nickel ores, CO2 gas (either as a depressant or a flotation gas)
and sodium tripolyphosphate (STPP) as a reagent for serpentine depression are used in this study. Phosphate
groups in STPP chelate magnesium ions and can facilitate serpentine depression in flotation systems. CO2
can also precipitate divalent cations like magnesium cations, and due to the high solubility of CO2 gas, it
can form fine bubbles on hydrophobic valuable minerals to improve their recovery. The surface charge on the
serpentine samples were completely reversed upon either the introduction of STPP at above 10 mg/L or by
conditioning the suspension with CO2 gas during zeta potential measurements. The resulting negative charge
of the serpentine mineral indicates that the heterogeneous agglomeration with pentlandite surface is weakened,
which should allow for a more pentlandite floatability. Subsequently, an optimum concentration of 50 mg/L
was obtained which was then used to perform flotation tests and XPS analysis. Flotation benefits were achieved
as serpentine suppression and enhanced pentlandite recovery was observed for both STPP and CO2 cases.
STPP was more effective in suppressing serpentine by 5%, while the highest pentlandite recovery of 88% was
obtained when CO2 was used as a flotation gas, which is a 20% increase in recovery from the baseline case. The
more effective STPP suppressing ability was validated by XPS results and provides an opportunity to explore the
combination of STPP and CO2 in future studies. Results from this study open up the opportunity of mineral
carbonation as a decarbonization strategy and will serve as a guide for researchers to perform more experiments
in the direction of CO2-assisted flotation.