725
Flotation Reagents on the Coagulation and Dewatering of
Flotation Concentrates from a Cu-Ni-PGM Ore
Malibongwe S. Manono, Matimba Mabonda, Lisa O. October, Kirsten C. Corin
Centre for Minerals Research, Department of Chemical Engineering, University of Cape Town, South Africa
ABSTRACT: Chemical reagents such as collectors, depressants and frothers are used during PGM ore flotation
to effect the recovery of desired minerals and ensure their purity. Species such as depressants and ions in
solution, depress the gangue minerals. However, recent studies suggest that the ionic strength of process water
and depressant dosages may influence the dewatering of flotation products. It is therefore hypothesised that
the effectiveness of the dewatering process post-flotation depends on the residual flotation reagents carried
over to the dewatering stages because some flotation reagents can act in the same manner as coagulants and
flocculants. This study further hypothesised that the dewatering of flotation concentrates is enhanced in the
presence of dewatering aids owing to the way coagulants and flocculants interact with particles rendering them
easier to settle. This study aims to understand the impact of residual flotation reagents on dewatering processes
as well as the influence of dewatering aids on the sedimentation of flotation concentrates from a PGM ore
flotation process.
Keywords: Coagulants, Concentrates, Depressants, Dewatering, Flocculants, Flotation
INTRODUCTION
Froth flotation is a separation technique used worldwide for
treating sulfide ores (Wills and Napier-Munn, 2006). This
technique has been used for many years in ore treatment.
The method is based on recovering valuable minerals upon
imparting hydrophobicity on their surfaces. This process
occurs in a flotation cell that can be visualised as having two
phases, namely the froth and pulp zones. Unwanted min-
erals such as gangue that find their way to the froth phase
are depressed back to the pulp using depressants. Chemical
reagents play a vital role during froth flotation. They enable
the process of froth flotation to occur successfully. Most
notable reagents discussed are collectors, depressants and
frothers. Chemical reagents are used in the flotation cell to
affect the recovery of desired minerals from gangue material
including in scenarios where water quality has been altered.
Collectors impart hydrophobicity on desired surface min-
erals, making it easy for them to ascend to the froth zone.
Frothers adsorb at the air-liquid interface, thus affecting
the interfacial properties, resulting in a stable froth. Species
such as carboxy methyl cellulose (CMC), ionic in solution,
depress undesired minerals from the froth zone to the pulp
phase. Unavoidable reagent interactions largely influence
the effectiveness of the process. A good example would be
studies performed by Bradshaw et al. (2005), where highly
concentrated collectors yielded low mineral recoveries.
This could be counteracted through the manipulation of
other reagents such as increasing frother dosage or reduc-
ing depressant concentration. Another study performed by
Wiese and Harris (2012) on the effects of frother type and
dosage in the presence of high depressant concentrations,
Flotation Reagents on the Coagulation and Dewatering of
Flotation Concentrates from a Cu-Ni-PGM Ore
Malibongwe S. Manono, Matimba Mabonda, Lisa O. October, Kirsten C. Corin
Centre for Minerals Research, Department of Chemical Engineering, University of Cape Town, South Africa
ABSTRACT: Chemical reagents such as collectors, depressants and frothers are used during PGM ore flotation
to effect the recovery of desired minerals and ensure their purity. Species such as depressants and ions in
solution, depress the gangue minerals. However, recent studies suggest that the ionic strength of process water
and depressant dosages may influence the dewatering of flotation products. It is therefore hypothesised that
the effectiveness of the dewatering process post-flotation depends on the residual flotation reagents carried
over to the dewatering stages because some flotation reagents can act in the same manner as coagulants and
flocculants. This study further hypothesised that the dewatering of flotation concentrates is enhanced in the
presence of dewatering aids owing to the way coagulants and flocculants interact with particles rendering them
easier to settle. This study aims to understand the impact of residual flotation reagents on dewatering processes
as well as the influence of dewatering aids on the sedimentation of flotation concentrates from a PGM ore
flotation process.
Keywords: Coagulants, Concentrates, Depressants, Dewatering, Flocculants, Flotation
INTRODUCTION
Froth flotation is a separation technique used worldwide for
treating sulfide ores (Wills and Napier-Munn, 2006). This
technique has been used for many years in ore treatment.
The method is based on recovering valuable minerals upon
imparting hydrophobicity on their surfaces. This process
occurs in a flotation cell that can be visualised as having two
phases, namely the froth and pulp zones. Unwanted min-
erals such as gangue that find their way to the froth phase
are depressed back to the pulp using depressants. Chemical
reagents play a vital role during froth flotation. They enable
the process of froth flotation to occur successfully. Most
notable reagents discussed are collectors, depressants and
frothers. Chemical reagents are used in the flotation cell to
affect the recovery of desired minerals from gangue material
including in scenarios where water quality has been altered.
Collectors impart hydrophobicity on desired surface min-
erals, making it easy for them to ascend to the froth zone.
Frothers adsorb at the air-liquid interface, thus affecting
the interfacial properties, resulting in a stable froth. Species
such as carboxy methyl cellulose (CMC), ionic in solution,
depress undesired minerals from the froth zone to the pulp
phase. Unavoidable reagent interactions largely influence
the effectiveness of the process. A good example would be
studies performed by Bradshaw et al. (2005), where highly
concentrated collectors yielded low mineral recoveries.
This could be counteracted through the manipulation of
other reagents such as increasing frother dosage or reduc-
ing depressant concentration. Another study performed by
Wiese and Harris (2012) on the effects of frother type and
dosage in the presence of high depressant concentrations,