706 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
have found that salts can hinder bubble coalescence due
to the electrical repulsive forces present when bubbles are
brought into contact by the motion of the liquid (Lessard
and Zieminski, 1971 Manono et al., 2013 Marrucci and
Nicodemo, 1967). Lessard and Zieminski, (1971) found
that an increase in the concentration of sodium chloride
increased the gas holdup, indicating the salt could decrease
the bubble size. This decrease in bubble size also explains
the increase in the solids recovered as a decrease in bubble
size leads to an increase in the surface area available for bub-
bleparticle attachment, leading to more particles attach-
ing to the bubbles (Hewitt et al., 1994). Bubble-particle
attachment may also be increased when the electrical dou-
ble layers undergo ion-induced compression, leading to an
increase in the recovery of solids (Kurniawan et al., 2011
Li et al., 2017). Despite the increase in the recoveries of
solids with an increase in ionic strength, copper and nickel
recoveries were not affected by changes to the ionic strength
of the water, collector dosage and collector type. The inde-
pendence of chalcopyrite recovery on ionic strength has
also been noted by Corin et al. (2011). Pentlandite (rep-
resented by nickel recovery) is partially affected by the
changes in flotation conditions. A decrease in the presence
of calcium and magnesium ions in the water at low depres-
sant dosages would increase the recovery of nickel (Ikotun
et al., 2017). This is because the calcium and magnesium
ions cause surface passivation on pentlandite (Bremmell et
al., 2005 Hirajima et al., 2016). Conversely, an increase
in sodium ions, known to activate mineral surfaces, could
enhance their recovery (Li et al., 2017). It was expected
that an increase in the ionic strength would lead to higher
froth stability, higher water recovery and therefore, more
entrainment resulting in a decrease in the grade of the valu-
able minerals (Corin et al., 2011 Corin et al., 2022 Wiese,
2009). Studies have found these unexpected results may
point towards interactive effects that exist between collector
type, dosage and ionic strength that may have stabilised the
grades despite the increase in water recovery (McFadzean
et al., 2016).
COLLECTOR CHAIN-LENGTH
Contrary to expectations based on earlier studies, this study
found that SIBX, despite having a longer hydrophobic
hydrocarbon chain, resulted in lower solids and water recov-
eries compared to SEX, particularly at low ionic strengths.
This finding contradicts the hypothesis that increased
hydrophobicity, indicated by larger contact angles, would
enhance recovery efficiency. The observed trend aligns with
previous observations by Wiese et al. (2010) and Dippenaar
(1978), where SIBX consistently achieved lower recoveries
than SEX, attributed to froth destabilisation caused by
larger contact angles and bubble rupture. Park et al. (2018)
supported the idea that froth stability increases with the
contact angle up to a critical point, beyond which stabil-
ity diminishes. The natural hydrophobicity of base metal
sulfides, which can destabilise froths, seems less impactful
at the particle size used in this study (60% passing 75 µm),
yet it may have contributed to the observed lower recover-
ies in combination with the longer chain length of SIBX.
Interestingly, despite the lower water recoveries associated
with SIBX, this study recorded higher grades of nickel
and copper under certain conditions (50 g/t of SIBX in 0
SPW). This suggests that lower water recoveries, typically
indicative of lower entrainment, can lead to higher min-
eral grades. However, SEX, with higher solids and water
recoveries, did not show a consistent decrease in grades. The
findings suggest that SEX’s ability to form metal complexes
with mineral surfaces, as noted by Ikotun et al. (2017),
might enhance its selectivity towards nickel.
COLLECTOR DOSAGE
Studies have shown an increase in collector dosage can
lead to an increase in mineral recovery (Langa et al., 2014
Mpongo and Siame, 2010). Ostadrahimi et al. (2021)
found that an increase in collector dosage resulted in higher
froth recoveries, indicating a more stable froth (Farrokhpay,
2011). This increase in froth stability was due to the increase
in the number of hydrophobic particles in the froth.
Therefore, it would be expected that an increase in collector
dosage would result in higher solids and water recoveries
due to the increase in hydrophobic particles reporting to
the froth and the subsequent froth stability. However, there
was no clear trend in the solids and water recoveries for
either collector when the dosage was increased, implying
collector dosage had little or no effect on the froth stability
under the conditions used within this study.
CONCLUSIONS
This study aimed to determine the effects of changing the
ionic strength of plant water, collector chain length and col-
lector dosage on the flotation response of a Merensky ore.
It was hypothesised that the simultaneous usage of a lon-
ger chained collector, higher collector dosage and increased
ionic strength would lead to higher solids recovery and a
lower grade of concentrate. The study found increases in
the ionic strength led to the strongest responses in terms
of solids and water recoveries. Ionic strength also had an
effect on the performance of the collectors as an increase
in the ionic strength of SPW improved the solids and
water recoveries of the longer chained collector. Therefore,
have found that salts can hinder bubble coalescence due
to the electrical repulsive forces present when bubbles are
brought into contact by the motion of the liquid (Lessard
and Zieminski, 1971 Manono et al., 2013 Marrucci and
Nicodemo, 1967). Lessard and Zieminski, (1971) found
that an increase in the concentration of sodium chloride
increased the gas holdup, indicating the salt could decrease
the bubble size. This decrease in bubble size also explains
the increase in the solids recovered as a decrease in bubble
size leads to an increase in the surface area available for bub-
bleparticle attachment, leading to more particles attach-
ing to the bubbles (Hewitt et al., 1994). Bubble-particle
attachment may also be increased when the electrical dou-
ble layers undergo ion-induced compression, leading to an
increase in the recovery of solids (Kurniawan et al., 2011
Li et al., 2017). Despite the increase in the recoveries of
solids with an increase in ionic strength, copper and nickel
recoveries were not affected by changes to the ionic strength
of the water, collector dosage and collector type. The inde-
pendence of chalcopyrite recovery on ionic strength has
also been noted by Corin et al. (2011). Pentlandite (rep-
resented by nickel recovery) is partially affected by the
changes in flotation conditions. A decrease in the presence
of calcium and magnesium ions in the water at low depres-
sant dosages would increase the recovery of nickel (Ikotun
et al., 2017). This is because the calcium and magnesium
ions cause surface passivation on pentlandite (Bremmell et
al., 2005 Hirajima et al., 2016). Conversely, an increase
in sodium ions, known to activate mineral surfaces, could
enhance their recovery (Li et al., 2017). It was expected
that an increase in the ionic strength would lead to higher
froth stability, higher water recovery and therefore, more
entrainment resulting in a decrease in the grade of the valu-
able minerals (Corin et al., 2011 Corin et al., 2022 Wiese,
2009). Studies have found these unexpected results may
point towards interactive effects that exist between collector
type, dosage and ionic strength that may have stabilised the
grades despite the increase in water recovery (McFadzean
et al., 2016).
COLLECTOR CHAIN-LENGTH
Contrary to expectations based on earlier studies, this study
found that SIBX, despite having a longer hydrophobic
hydrocarbon chain, resulted in lower solids and water recov-
eries compared to SEX, particularly at low ionic strengths.
This finding contradicts the hypothesis that increased
hydrophobicity, indicated by larger contact angles, would
enhance recovery efficiency. The observed trend aligns with
previous observations by Wiese et al. (2010) and Dippenaar
(1978), where SIBX consistently achieved lower recoveries
than SEX, attributed to froth destabilisation caused by
larger contact angles and bubble rupture. Park et al. (2018)
supported the idea that froth stability increases with the
contact angle up to a critical point, beyond which stabil-
ity diminishes. The natural hydrophobicity of base metal
sulfides, which can destabilise froths, seems less impactful
at the particle size used in this study (60% passing 75 µm),
yet it may have contributed to the observed lower recover-
ies in combination with the longer chain length of SIBX.
Interestingly, despite the lower water recoveries associated
with SIBX, this study recorded higher grades of nickel
and copper under certain conditions (50 g/t of SIBX in 0
SPW). This suggests that lower water recoveries, typically
indicative of lower entrainment, can lead to higher min-
eral grades. However, SEX, with higher solids and water
recoveries, did not show a consistent decrease in grades. The
findings suggest that SEX’s ability to form metal complexes
with mineral surfaces, as noted by Ikotun et al. (2017),
might enhance its selectivity towards nickel.
COLLECTOR DOSAGE
Studies have shown an increase in collector dosage can
lead to an increase in mineral recovery (Langa et al., 2014
Mpongo and Siame, 2010). Ostadrahimi et al. (2021)
found that an increase in collector dosage resulted in higher
froth recoveries, indicating a more stable froth (Farrokhpay,
2011). This increase in froth stability was due to the increase
in the number of hydrophobic particles in the froth.
Therefore, it would be expected that an increase in collector
dosage would result in higher solids and water recoveries
due to the increase in hydrophobic particles reporting to
the froth and the subsequent froth stability. However, there
was no clear trend in the solids and water recoveries for
either collector when the dosage was increased, implying
collector dosage had little or no effect on the froth stability
under the conditions used within this study.
CONCLUSIONS
This study aimed to determine the effects of changing the
ionic strength of plant water, collector chain length and col-
lector dosage on the flotation response of a Merensky ore.
It was hypothesised that the simultaneous usage of a lon-
ger chained collector, higher collector dosage and increased
ionic strength would lead to higher solids recovery and a
lower grade of concentrate. The study found increases in
the ionic strength led to the strongest responses in terms
of solids and water recoveries. Ionic strength also had an
effect on the performance of the collectors as an increase
in the ionic strength of SPW improved the solids and
water recoveries of the longer chained collector. Therefore,