726 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
showed an increase in froth stability with an increase in
frother dosage for all investigated conditions. One of the
conclusions from this study was that an increase in frother
dosage could potentially have an effect downstream and
hence the subject of this study.
It is known that mineral flotation is water intensive,
in flotation slurries, water makes between 60% to 85% of
the pulp volume (Muzenda, 2010). In combating water
shortages, recycled water has been used in flotation circuits,
this however results in increased ionic strength of the pro-
cess water, thus significantly altering interactions between
reagents and mineral particles (Manono et al., 2018 Slatter
et al., 2009). This process relies quite heavily on water.
Due to water usage restrictions mining companies almost
have no choice but to resort to recycling and reusing pro-
cess water that is high in ionic strength compared to fresh
or portable water from municipal water resources or even
worse, use treated sewage water. Some reagent species are
also ionic, such as CMCs, these therefore results in ionic
interactions in the pulp phase. Studies performed by Parolis
et al. (2008) showed that divalent ions were much more
efficient in enabling the depression of gangue in the pres-
ence of CMC as opposed to monovalent ions in solution.
After flotation, dewatering of concentrates and tail-
ings follows. The two streams are separately thickened and
filtered. Flocculants and coagulants as dewatering aids are
added to effect the dewatering of concentrates and tailings.
The interaction of dewatering aids with mineral particles
in the concentrate may very well be driven by ionic inter-
actions The dewatering of concentrates is important for
further processing steps, however not much literature is
available concerning how dewatering aids affect the dewa-
tering of flotation concentrates. It is acknowledged that
there may well be residual reagents such as frothers, depres-
sants and xanthates carried into the concentrate and their
interactions with mineral particles in the thickener would
also be important to consider. It is on this premise that, in
this paper, we argue that residual reagents from froth flota-
tion have not been investigated for their influence on the
flocculation and coagulation of product concentrate. There
is currently little to no information on this subject and
its understanding would help in dewatering concentrates
efficiently. Given the status quo, the aim of this study was
therefore to understand the impact of residual reagents post
flotation on dewatering processes filtration, agglomeration
and flocculation. It was hypothesised that as process water
is recycled, there is an increase in ionic species in solution
which may influence the concentrate dewatering process as
dewatering agents are ionic in nature and would in turn
compete with process water ions for the mineral surface.
Coagulation, flocculation and dewatering of flotation con-
centrates are vital in the preparation of concentrates for
further processing downstream. This study therefore, con-
siders the effects of flotation reagents such as depressants on
concentrates post flotation. All other possible influences on
concentrates are not considered in this study, these include
but not limited to pulp density, feed rate, agitation and flo-
tation cell design.
MATERIALS &METHODS
Ore Sample Preparation
A sample of a Merensky ore was acquired from the
Pilanesberg Platinum Mine (PPM) located in the North
West province of South Africa. The bulk sample was firstly
crushed and homogenised. A rotary splitter was used in
splitting the ore into 1 kg sample portions, sealed in plastic
bags. The samples were subsequently sent to the Centre for
Minerals Research (CMR) at the University of Cape Town
(UCT).
Synthetic Plant Water Preparation
Plant water was synthesised in the CMR laboratories
to mimic industrial process water. Deionised water was
modified through the addition of different chemical salts
to achieve ionic concentrations typical of the plant water
in the PPM. Guidelines for the synthesis were obtained
from Smith et al. (2002) and these were followed in con-
junction with the use of the MINTEQA2 software. The
chemical salts used with their concentrations are shown in
Table 1. The plant water was prepared in batches of 40 L
in a container. This was sufficient for 8–10 flotation experi-
ments at a time.
Flotation Reagents and Dewatering Aids
The batch flotation reagents that formed part of this study
were the collector, depressant and frother. These were var-
ied together with the synthesised plant water. Post flotation,
the flocculant and coagulant reagents were added to each
concentrate. The interactive effects of both the residual and
post flotation reagents were of interest in line with the main
aim of this research.
1% solutions of both the liquid collector (namely
sodium isobutyl xanthate (SIBX)) and dry depressant
(namely carboxy methyl cellulose (CMC)) were prepared
fresh each day using deionised water. The depressant was
stirred in deionised water for two hours using a magnetic
stirrer to ensure it dissolves fully, avoiding lumps forma-
tion. The frother used, Flotanol 200, was supplied by
Chemquest (Pty) Ltd. Table 2 summarises the reagent types
and the dosages used.
showed an increase in froth stability with an increase in
frother dosage for all investigated conditions. One of the
conclusions from this study was that an increase in frother
dosage could potentially have an effect downstream and
hence the subject of this study.
It is known that mineral flotation is water intensive,
in flotation slurries, water makes between 60% to 85% of
the pulp volume (Muzenda, 2010). In combating water
shortages, recycled water has been used in flotation circuits,
this however results in increased ionic strength of the pro-
cess water, thus significantly altering interactions between
reagents and mineral particles (Manono et al., 2018 Slatter
et al., 2009). This process relies quite heavily on water.
Due to water usage restrictions mining companies almost
have no choice but to resort to recycling and reusing pro-
cess water that is high in ionic strength compared to fresh
or portable water from municipal water resources or even
worse, use treated sewage water. Some reagent species are
also ionic, such as CMCs, these therefore results in ionic
interactions in the pulp phase. Studies performed by Parolis
et al. (2008) showed that divalent ions were much more
efficient in enabling the depression of gangue in the pres-
ence of CMC as opposed to monovalent ions in solution.
After flotation, dewatering of concentrates and tail-
ings follows. The two streams are separately thickened and
filtered. Flocculants and coagulants as dewatering aids are
added to effect the dewatering of concentrates and tailings.
The interaction of dewatering aids with mineral particles
in the concentrate may very well be driven by ionic inter-
actions The dewatering of concentrates is important for
further processing steps, however not much literature is
available concerning how dewatering aids affect the dewa-
tering of flotation concentrates. It is acknowledged that
there may well be residual reagents such as frothers, depres-
sants and xanthates carried into the concentrate and their
interactions with mineral particles in the thickener would
also be important to consider. It is on this premise that, in
this paper, we argue that residual reagents from froth flota-
tion have not been investigated for their influence on the
flocculation and coagulation of product concentrate. There
is currently little to no information on this subject and
its understanding would help in dewatering concentrates
efficiently. Given the status quo, the aim of this study was
therefore to understand the impact of residual reagents post
flotation on dewatering processes filtration, agglomeration
and flocculation. It was hypothesised that as process water
is recycled, there is an increase in ionic species in solution
which may influence the concentrate dewatering process as
dewatering agents are ionic in nature and would in turn
compete with process water ions for the mineral surface.
Coagulation, flocculation and dewatering of flotation con-
centrates are vital in the preparation of concentrates for
further processing downstream. This study therefore, con-
siders the effects of flotation reagents such as depressants on
concentrates post flotation. All other possible influences on
concentrates are not considered in this study, these include
but not limited to pulp density, feed rate, agitation and flo-
tation cell design.
MATERIALS &METHODS
Ore Sample Preparation
A sample of a Merensky ore was acquired from the
Pilanesberg Platinum Mine (PPM) located in the North
West province of South Africa. The bulk sample was firstly
crushed and homogenised. A rotary splitter was used in
splitting the ore into 1 kg sample portions, sealed in plastic
bags. The samples were subsequently sent to the Centre for
Minerals Research (CMR) at the University of Cape Town
(UCT).
Synthetic Plant Water Preparation
Plant water was synthesised in the CMR laboratories
to mimic industrial process water. Deionised water was
modified through the addition of different chemical salts
to achieve ionic concentrations typical of the plant water
in the PPM. Guidelines for the synthesis were obtained
from Smith et al. (2002) and these were followed in con-
junction with the use of the MINTEQA2 software. The
chemical salts used with their concentrations are shown in
Table 1. The plant water was prepared in batches of 40 L
in a container. This was sufficient for 8–10 flotation experi-
ments at a time.
Flotation Reagents and Dewatering Aids
The batch flotation reagents that formed part of this study
were the collector, depressant and frother. These were var-
ied together with the synthesised plant water. Post flotation,
the flocculant and coagulant reagents were added to each
concentrate. The interactive effects of both the residual and
post flotation reagents were of interest in line with the main
aim of this research.
1% solutions of both the liquid collector (namely
sodium isobutyl xanthate (SIBX)) and dry depressant
(namely carboxy methyl cellulose (CMC)) were prepared
fresh each day using deionised water. The depressant was
stirred in deionised water for two hours using a magnetic
stirrer to ensure it dissolves fully, avoiding lumps forma-
tion. The frother used, Flotanol 200, was supplied by
Chemquest (Pty) Ltd. Table 2 summarises the reagent types
and the dosages used.