XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 101
There is a theoretical limit to the grade and recovery
achievable for a particular flotation circuit, which is a func-
tion of liberation. An example of a theoretical grade versus
recovery curve is shown in Figure 2 for a galena flotation
concentrator. This curve denotes the change in concentrate
grade that results from the addition of particles of decreas-
ing grade to the concentrate. It demonstrates how it is
impossible to recover all the galena particles without fall-
ing below the concentrate grade target, which, in this case,
is 40%.
The selectivity shown in Figure 2 is for a theoretical
perfect separation. In reality, selectivity achieved in a flo-
tation circuit is poorer than this theoretical limit due to
unselective entrainment recovery and the general probabi-
listic nature of flotation. This theoretical limit also assumes
that all the gangue in the feed is non-floatable, but this
is not always true. Some gangue can be naturally floatable
(e.g., talc), and some gangue minerals can be rendered
floatable by the reagents added to the process (e.g., pyrite).
Xanthates, the most common reagent used in sulfide flota-
tion, are notoriously poor at achieving selectivity between
valuable and gangue sulfide minerals. Large proportions
of floatable gangue in the flotation feed will thus result in
poorer selectivity and poor overall flotation performance.
The mining industry is currently undergoing a trans-
formation, and many new technologies are being developed
that have the potential to improve flotation. New flotation
machines are emerging that can recover coarser and finer
particles, traditionally not recovered well during flotation.
Flotation reagents with increased specificity have the
potential to enable selective separation of minerals of simi-
lar chemical structures. New comminution methods are
improving the liberation and thus the selectivity achievable
in flotation. In addition, a range of new diagnostic tools
have been developed that provide an opportunity to better
diagnose and overcome circuit bottlenecks. Process control
methods are also emerging that have the potential to enable
circuits to be operated at more optimal conditions.
This paper aims to provide an overview of these emerg-
ing new technologies that can transform and improve flota-
tion and outline the challenges that must be overcome to
enable fast adoption by a traditionally conservative min-
ing industry. Where applicable, the potential benefits these
technologies can have on the overall sustainability of the
mining process will also be discussed. Flotation is intrin-
sically energy intensive, with the comminution processes
used to produce the fine particle sizes required for flotation
estimated to account for 0.4% of the world’s energy use,
for base metal production alone (Napier-Munn, 2015).
Flotation uses a large quantity of water therefore, dewater-
ing and recycling are imperative, especially in arid regions
where water supply is scarce. Flotation produces large
quantities of fine tailings that need to be stored stably to
safeguard surrounding communities. Changes in flotation,
which can result in less energy use, improved dewatering
efficacy, or more stable tailings storage, can be as important
as those that result in improved selectivity and recovery.
Figure 2. Theoretical relationship between grade and recovery obtained by adding
particles of decreasing lead grade to a concentrate calculated using MLA analysis of the
feed (Runge et al, 2024)
There is a theoretical limit to the grade and recovery
achievable for a particular flotation circuit, which is a func-
tion of liberation. An example of a theoretical grade versus
recovery curve is shown in Figure 2 for a galena flotation
concentrator. This curve denotes the change in concentrate
grade that results from the addition of particles of decreas-
ing grade to the concentrate. It demonstrates how it is
impossible to recover all the galena particles without fall-
ing below the concentrate grade target, which, in this case,
is 40%.
The selectivity shown in Figure 2 is for a theoretical
perfect separation. In reality, selectivity achieved in a flo-
tation circuit is poorer than this theoretical limit due to
unselective entrainment recovery and the general probabi-
listic nature of flotation. This theoretical limit also assumes
that all the gangue in the feed is non-floatable, but this
is not always true. Some gangue can be naturally floatable
(e.g., talc), and some gangue minerals can be rendered
floatable by the reagents added to the process (e.g., pyrite).
Xanthates, the most common reagent used in sulfide flota-
tion, are notoriously poor at achieving selectivity between
valuable and gangue sulfide minerals. Large proportions
of floatable gangue in the flotation feed will thus result in
poorer selectivity and poor overall flotation performance.
The mining industry is currently undergoing a trans-
formation, and many new technologies are being developed
that have the potential to improve flotation. New flotation
machines are emerging that can recover coarser and finer
particles, traditionally not recovered well during flotation.
Flotation reagents with increased specificity have the
potential to enable selective separation of minerals of simi-
lar chemical structures. New comminution methods are
improving the liberation and thus the selectivity achievable
in flotation. In addition, a range of new diagnostic tools
have been developed that provide an opportunity to better
diagnose and overcome circuit bottlenecks. Process control
methods are also emerging that have the potential to enable
circuits to be operated at more optimal conditions.
This paper aims to provide an overview of these emerg-
ing new technologies that can transform and improve flota-
tion and outline the challenges that must be overcome to
enable fast adoption by a traditionally conservative min-
ing industry. Where applicable, the potential benefits these
technologies can have on the overall sustainability of the
mining process will also be discussed. Flotation is intrin-
sically energy intensive, with the comminution processes
used to produce the fine particle sizes required for flotation
estimated to account for 0.4% of the world’s energy use,
for base metal production alone (Napier-Munn, 2015).
Flotation uses a large quantity of water therefore, dewater-
ing and recycling are imperative, especially in arid regions
where water supply is scarce. Flotation produces large
quantities of fine tailings that need to be stored stably to
safeguard surrounding communities. Changes in flotation,
which can result in less energy use, improved dewatering
efficacy, or more stable tailings storage, can be as important
as those that result in improved selectivity and recovery.
Figure 2. Theoretical relationship between grade and recovery obtained by adding
particles of decreasing lead grade to a concentrate calculated using MLA analysis of the
feed (Runge et al, 2024)