XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 651
and has implications for treating ores with very high pyrite
content.
Bıçak et al. (2012) reported that for water contain-
ing higher concentrations of thiosulphate (approximately
1,200 ppm) and sulphate (approximately 1,700 ppm)
ions, the true flotation of pyrite decreased. This indicates
the depressive effect of the sulphoxy species in the pulp. It
was believed that the thiosulphate and sulphate ions can
counteract the activation of pyrite with dissolved copper
ions when seawater is used. Lehmann et al. (2000), on per-
forming a study on pure pyrite, suggested that the pres-
ence of chloride ion, which is abundant in seawater, can
reduce the flotation of pyrite by promoting the oxidation of
an absorbed intermediate, believed to be the thiosulphate
ion, producing from the reaction between sulphite ions and
elemental sulphur, to soluble tetrathionate ion.
NaHSO3 has been used as a flotation depressant for
pyrite (Ikumapayi, 2010). However, the use of sulphoxy
type depressants, such as sulphite, bisulphite, metabisul-
phite (MBS) and sulphur dioxide, to control the unwanted
flotation of sulphide minerals in mildly alkaline environ-
ments is generally considered to be as the result of the sul-
phite SO32–, or thiosulphate ions, S2O32– (Khmeleva et
al., 2003). Ikumapayi (2010) suggested that the reduced
sulphoxy anions will be much stronger bound to the sul-
phide surface compared with the sulphate anions that are
directly adsorbed through ion exchange/outer-sphere com-
plexation, thus competing more efficiently with collectors
for adsorption sites on sulphides, which may strengthen the
depressing effect of sulphite. This effect, once understood,
can open a new cost effective approach to selectively regu-
late surface properties of sulphides for more effective selec-
tive flotation of valuable sulphide minerals over sulphide
gangue minerals.
The Mechanism for Copper Flotation with
Sulphoxy Compounds
It was believed that under the conditions of pH 7 and air
purging, while sodium bisulphite can depress pyrite by
enhancing the formation of oxide and hydroxide species, it
has very limited impact on the surface chemistry or float-
ability of chalcopyrite (Khmeleva et al., 2003). Ross and
Van Deventer (1985) suggested that the sulphite ion also
has a cleaning effect on chalcopyrite to increase chalcopy-
rite recovery, although this was not proved in their study.
However, they noted that under the conditions studied in
their experiments, milling in a steel mill followed by pre-aer-
ation greatly improved the copper grades and copper-lead
selectivity when sulphurous acid was used as pH regulator
compared to milling in a ceramic mill. It was found (Houot
&Duhamet, 1993) that the depressing effect of sulphite
ions on chalcopyrite-pyrite flotation depends on the pres-
ence of Fe3+ ions released from grinding media.
Grano (1997) also studied the behaviour of sulphite
ions the flotation of pure chalcopyrite and tended to agree
with Houot &Duhamet (1985) suggestion that the effect of
sulphite on chalcopyrite flotation strongly depends on the
oxidation state of the chalcopyrite surface prior to sulphite
addition. If the chalcopyrite has significant surface concen-
trations of adsorbed iron oxyhydroxide species, sulphite
may increase its flotation due to removal of the interfering
iron oxyhydroxide via a mechanism involving reduction of
surface ferric oxyhydroxide to more soluble ferrous species.
However, if excess sulphite is added to the system, sulphite
may decompose the sulphur-rich sub-layer resulting in low
chalcopyrite flotation recovery. Grano also suggested that
the cleaning action of sulphite could be reduced at pH
7.5. He also proposed an Eh value of approximately +
170 mV which Fe(II) species would be more stable. Bulut
et al. (2011) confirmed in their study that pyrite depression
is more effective when metabisulphite was used at pH 6.5
compared to pH 10. This confirms the findings from the
FLOT-ART development work on various ores that pyrite
could be effectively depressed at a much lower pH that nor-
mally used in the conventional lime based process.
Raw seawater is ranked as the most economic source
of water but its use in flotation requires in in-depth under-
standing of the various mechanisms involved such as the
effect and interaction of sulphoxy compounds, aeration
and dissolved ions in the seawater with respect to the
mineralogy of the ore, pH and pulp potential (Barrera &
Cerna, 2009). Once understood, this can open a new cost
effective approach to selectively regulate surface properties
of sulphides for more optimum flotation performance in
saline water. The FLOT-ART process leverages the findings
emanated from various research work carried out in this
area as discussed above.
DEVELOPMENT OF THE LOW ALKALINE
FLOT-ART COPPER FLOTATION
PROCESS
The development of the FLOT-ART stems from addressing
the challenges that were encountered for a challenging large
copper-gold project where the aim was to replace the cya-
nide and lime based scheme due to concerns with the use
of cyanide onsite in an environmentally sensitive location.
An extensive flotation work using conventional lime based
process showed that the site water had a detrimental effect
on flotation performance. The head assays and the locked
cycle results from the conventional flotation process tested
and has implications for treating ores with very high pyrite
content.
Bıçak et al. (2012) reported that for water contain-
ing higher concentrations of thiosulphate (approximately
1,200 ppm) and sulphate (approximately 1,700 ppm)
ions, the true flotation of pyrite decreased. This indicates
the depressive effect of the sulphoxy species in the pulp. It
was believed that the thiosulphate and sulphate ions can
counteract the activation of pyrite with dissolved copper
ions when seawater is used. Lehmann et al. (2000), on per-
forming a study on pure pyrite, suggested that the pres-
ence of chloride ion, which is abundant in seawater, can
reduce the flotation of pyrite by promoting the oxidation of
an absorbed intermediate, believed to be the thiosulphate
ion, producing from the reaction between sulphite ions and
elemental sulphur, to soluble tetrathionate ion.
NaHSO3 has been used as a flotation depressant for
pyrite (Ikumapayi, 2010). However, the use of sulphoxy
type depressants, such as sulphite, bisulphite, metabisul-
phite (MBS) and sulphur dioxide, to control the unwanted
flotation of sulphide minerals in mildly alkaline environ-
ments is generally considered to be as the result of the sul-
phite SO32–, or thiosulphate ions, S2O32– (Khmeleva et
al., 2003). Ikumapayi (2010) suggested that the reduced
sulphoxy anions will be much stronger bound to the sul-
phide surface compared with the sulphate anions that are
directly adsorbed through ion exchange/outer-sphere com-
plexation, thus competing more efficiently with collectors
for adsorption sites on sulphides, which may strengthen the
depressing effect of sulphite. This effect, once understood,
can open a new cost effective approach to selectively regu-
late surface properties of sulphides for more effective selec-
tive flotation of valuable sulphide minerals over sulphide
gangue minerals.
The Mechanism for Copper Flotation with
Sulphoxy Compounds
It was believed that under the conditions of pH 7 and air
purging, while sodium bisulphite can depress pyrite by
enhancing the formation of oxide and hydroxide species, it
has very limited impact on the surface chemistry or float-
ability of chalcopyrite (Khmeleva et al., 2003). Ross and
Van Deventer (1985) suggested that the sulphite ion also
has a cleaning effect on chalcopyrite to increase chalcopy-
rite recovery, although this was not proved in their study.
However, they noted that under the conditions studied in
their experiments, milling in a steel mill followed by pre-aer-
ation greatly improved the copper grades and copper-lead
selectivity when sulphurous acid was used as pH regulator
compared to milling in a ceramic mill. It was found (Houot
&Duhamet, 1993) that the depressing effect of sulphite
ions on chalcopyrite-pyrite flotation depends on the pres-
ence of Fe3+ ions released from grinding media.
Grano (1997) also studied the behaviour of sulphite
ions the flotation of pure chalcopyrite and tended to agree
with Houot &Duhamet (1985) suggestion that the effect of
sulphite on chalcopyrite flotation strongly depends on the
oxidation state of the chalcopyrite surface prior to sulphite
addition. If the chalcopyrite has significant surface concen-
trations of adsorbed iron oxyhydroxide species, sulphite
may increase its flotation due to removal of the interfering
iron oxyhydroxide via a mechanism involving reduction of
surface ferric oxyhydroxide to more soluble ferrous species.
However, if excess sulphite is added to the system, sulphite
may decompose the sulphur-rich sub-layer resulting in low
chalcopyrite flotation recovery. Grano also suggested that
the cleaning action of sulphite could be reduced at pH
7.5. He also proposed an Eh value of approximately +
170 mV which Fe(II) species would be more stable. Bulut
et al. (2011) confirmed in their study that pyrite depression
is more effective when metabisulphite was used at pH 6.5
compared to pH 10. This confirms the findings from the
FLOT-ART development work on various ores that pyrite
could be effectively depressed at a much lower pH that nor-
mally used in the conventional lime based process.
Raw seawater is ranked as the most economic source
of water but its use in flotation requires in in-depth under-
standing of the various mechanisms involved such as the
effect and interaction of sulphoxy compounds, aeration
and dissolved ions in the seawater with respect to the
mineralogy of the ore, pH and pulp potential (Barrera &
Cerna, 2009). Once understood, this can open a new cost
effective approach to selectively regulate surface properties
of sulphides for more optimum flotation performance in
saline water. The FLOT-ART process leverages the findings
emanated from various research work carried out in this
area as discussed above.
DEVELOPMENT OF THE LOW ALKALINE
FLOT-ART COPPER FLOTATION
PROCESS
The development of the FLOT-ART stems from addressing
the challenges that were encountered for a challenging large
copper-gold project where the aim was to replace the cya-
nide and lime based scheme due to concerns with the use
of cyanide onsite in an environmentally sensitive location.
An extensive flotation work using conventional lime based
process showed that the site water had a detrimental effect
on flotation performance. The head assays and the locked
cycle results from the conventional flotation process tested