676 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
expected, there was 74.8% Fe recovery and a grade of 19.1
wt.% in FS-DI conditions compared to 89.7% Fe recov-
ery and a grade of 13.6 wt.% for the Cer-DI condition.
At pH 10, where less Fe dissolution is expected, the grade
dropped to 15.7% with a 78.9% Fe recovery for FS_DI,
compared to a decrease in Fe recovery and grade to 83.1%
and 11.6 wt.% respectively for Cer-DI. Thus, it is clear that
the presence of dissolved Fe species emanating from the FS
media either aids with gangue depression or promotes Py
flotation. This correlation is consistent with observed lower
solids and water recoveries for the FS cases in Figure 2.
Dissolved SPW ions, on the other hand, do not show any
significant changes when either the pH or the media type
is changed. Hence, it can be submitted that SPW does not
play a major role in Py flotation performance.
As discussed above, pH has a significant effect on flo-
tation performance when using FS due to the dissolution
of Fe from the media. Higher grades were obtained at the
lower pH of 4, which could be through the greater abun-
dance of dissolved Fe ions, which subsequently activate the
surface of Py and, thus, improve its amenability to flotation
with the xanthate collector. This is supported by Eh-pH
stability diagrams [4], [18] showing that at pH 4, FeX2 and
FeX3 are the stable species in the Eh range –400 to +100
mV, FeX3 being found species in the upper 200 mV region
of that range. Depending on Eh, at pH 10, any dissolved Fe
ions are predicted to precipitate out of solution as Fe(OH)2
or Fe(OH)3, hence the complexes formed with xanthate at
pH 4 do not occur.
An interesting point to note in the FS-DI and
FS-5SPW data in Figure 3 is the low recovery and reduced
grade region observed under natural conditions (pH 6–8),
which cannot be observed in experiments with Cer media.
This region may be due, depending on Eh, to the forma-
tion of poorly hydrophobic Fe(OH)X2 or Fe(OH)X [18].
Furthermore, other studies have identified the formation
of -FeS–-Fe(OH)X complexes which eliminates the adsorp-
tion of some hydrophobic xanthate species onto the Py sur-
face [4], [19], [20].
At higher xanthate concentrations, the low-recovery
region in the neutral pH range has been observed to dis-
appear in some studies [21]. In other words, Py depres-
sion was observed to decrease when xanthate was added in
excess of the typical requirement. Thus, Figure 3 shows that
dissolved Fe ions have a significant depressing effect on Py
when the xanthate collector is used at pH 6–8.
Given the presence of dissolved Pb in the mixed-min-
eral system, it may be assumed that Py depression could
have been more successful than was observed in Figure 3.
This assumption is based on other studies showing that Pb
ions have been found to enhance Py floatability by activat-
ing the mineral surface [5].
pH 4
pH
6-8
pH
10
pH 4
pH
6-8
pH
10
pH 4
pH
6-8
pH
10
pH 4
pH
6-8
pH
10
FS -DI FS -5SPW Cer -DI Cer -5SPW
Fe Grade 19,1 11,6 15,7 15,8 13,3 16,0 13,6 12,1 11,6 13,5 10,8 13,2
Fe Recovery 74,8 59,5 78,9 78,2 55,6 79,8 89,7 84,5 83,1 86,4 82,8 83,5
0
10
20
30
40
50
60
70
80
90
100
Figure 3. Effect of pH, milling media, and water composition on Fe grade and recovery
Fe
Grade/Recovery(%)
expected, there was 74.8% Fe recovery and a grade of 19.1
wt.% in FS-DI conditions compared to 89.7% Fe recov-
ery and a grade of 13.6 wt.% for the Cer-DI condition.
At pH 10, where less Fe dissolution is expected, the grade
dropped to 15.7% with a 78.9% Fe recovery for FS_DI,
compared to a decrease in Fe recovery and grade to 83.1%
and 11.6 wt.% respectively for Cer-DI. Thus, it is clear that
the presence of dissolved Fe species emanating from the FS
media either aids with gangue depression or promotes Py
flotation. This correlation is consistent with observed lower
solids and water recoveries for the FS cases in Figure 2.
Dissolved SPW ions, on the other hand, do not show any
significant changes when either the pH or the media type
is changed. Hence, it can be submitted that SPW does not
play a major role in Py flotation performance.
As discussed above, pH has a significant effect on flo-
tation performance when using FS due to the dissolution
of Fe from the media. Higher grades were obtained at the
lower pH of 4, which could be through the greater abun-
dance of dissolved Fe ions, which subsequently activate the
surface of Py and, thus, improve its amenability to flotation
with the xanthate collector. This is supported by Eh-pH
stability diagrams [4], [18] showing that at pH 4, FeX2 and
FeX3 are the stable species in the Eh range –400 to +100
mV, FeX3 being found species in the upper 200 mV region
of that range. Depending on Eh, at pH 10, any dissolved Fe
ions are predicted to precipitate out of solution as Fe(OH)2
or Fe(OH)3, hence the complexes formed with xanthate at
pH 4 do not occur.
An interesting point to note in the FS-DI and
FS-5SPW data in Figure 3 is the low recovery and reduced
grade region observed under natural conditions (pH 6–8),
which cannot be observed in experiments with Cer media.
This region may be due, depending on Eh, to the forma-
tion of poorly hydrophobic Fe(OH)X2 or Fe(OH)X [18].
Furthermore, other studies have identified the formation
of -FeS–-Fe(OH)X complexes which eliminates the adsorp-
tion of some hydrophobic xanthate species onto the Py sur-
face [4], [19], [20].
At higher xanthate concentrations, the low-recovery
region in the neutral pH range has been observed to dis-
appear in some studies [21]. In other words, Py depres-
sion was observed to decrease when xanthate was added in
excess of the typical requirement. Thus, Figure 3 shows that
dissolved Fe ions have a significant depressing effect on Py
when the xanthate collector is used at pH 6–8.
Given the presence of dissolved Pb in the mixed-min-
eral system, it may be assumed that Py depression could
have been more successful than was observed in Figure 3.
This assumption is based on other studies showing that Pb
ions have been found to enhance Py floatability by activat-
ing the mineral surface [5].
pH 4
pH
6-8
pH
10
pH 4
pH
6-8
pH
10
pH 4
pH
6-8
pH
10
pH 4
pH
6-8
pH
10
FS -DI FS -5SPW Cer -DI Cer -5SPW
Fe Grade 19,1 11,6 15,7 15,8 13,3 16,0 13,6 12,1 11,6 13,5 10,8 13,2
Fe Recovery 74,8 59,5 78,9 78,2 55,6 79,8 89,7 84,5 83,1 86,4 82,8 83,5
0
10
20
30
40
50
60
70
80
90
100
Figure 3. Effect of pH, milling media, and water composition on Fe grade and recovery
Fe
Grade/Recovery(%)