674 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
For all the experimental variations in the milling envi-
ronment, FS-DI (using FS milling media and DI water),
FS-5SPW, Cer-DI, and Cer-SPW, the pH range of 4 to
10 was investigated. For FS-DI this increase in pH led to
a decrease in Eh for all cases shown in Figure 1, indicat-
ing the formation of a more reducing environment. As a
result, the efficiency of the xanthate collector was expected
to decline in terms of dixanthogen at pH 10, as the final Eh
value was noted to be –71 mV. Similarly, in the FS-5SPW
experiments, the presence of dissolved salts in the plant
water led to a decrease in Eh, resulting in a reduction in
collector efficiency in terms of dixanthogen formation at
natural pH (+59.2 mV). A similar trend was observed in
the case of Cer-DI and Cer-5SPW experiments, further
suggesting that only under FS-DI conditions can sulfide
minerals be effectively recovered under natural conditions
if dixanthogen formation is required to promote flotation.
These hypotheses are tested in the results shown in
the following section in which the recoveries and grades
obtained from the flotation experiments are presented.
Solids-Water Recovery Analysis
The flotation behaviour of a mineral sample was evaluated
by analysing the solids and water recovery data, which can
be further correlated with the variations in the milling envi-
ronment and their impact on the Eh. The resulting data for
the solid vs water recoveries, obtained from all tests at pH 4
and 6–8, are presented in Figure 2. At pH 10, there was no
significant variation in the individual trends for different
milling media and water types used, with solids recoveries
ranging between 140–160 g, and water recoveries in the
range 900–1000 g hence, the graph has not been included.
The overall analysis provides valuable insights into froth
stability and the mechanisms by which the minerals report
to the froth phase.
The experimental findings indicate that when Cer
media was used, higher solids and water recoveries were
obtained at both pH levels. However, it is noteworthy
that the water recovery for the Cer-5SPW is significantly
higher than that of the Cer-DI at natural pH (6–8) by
250 g, despite the absence of dissolved media contribut-
ing Fe ions. This observation suggests that the presence of
dissolved salts in the plant water promotes water recovery,
thereby increasing the likelihood of minerals, including
gangue, being entrained into the froth phase. This is based
on the well-known fact that there is a strong linear relation-
ship between solids and water recovery when entrainment
occurs.
pH4 pH6-8 pH 10 pH4 pH6-8 pH 10 pH4 pH6-8 pH 10 pH4 pH6-8 pH 10
FS-DI FS-5SPW CER-DI CER-5SPW
Midpoint Eh 272 ,0 148 ,1 45,8 231 ,4 14,5 66,4 226,7 81,6 60,9 246 ,9 89,0 72,4
Final Eh 405 ,3 302 ,8 -71,4 300 ,8 59,2 -98,8 394 ,0 65,0 -60,7 394 ,2 70,8 -4,8
-100,0
0,0
100,0
200,0
300,0
400,0
500,0
600,0
Key: FS – Forged Steel Media, Cer – Ceramic Media, DI- Deionised Water, 5SPW – Synthetic Plant Water at an ionic strength of 5
(0.1205 M).
Figure 1. Eh variation during the milling process for different milling media compositions, water types, and pHs
Eh
(mV)
For all the experimental variations in the milling envi-
ronment, FS-DI (using FS milling media and DI water),
FS-5SPW, Cer-DI, and Cer-SPW, the pH range of 4 to
10 was investigated. For FS-DI this increase in pH led to
a decrease in Eh for all cases shown in Figure 1, indicat-
ing the formation of a more reducing environment. As a
result, the efficiency of the xanthate collector was expected
to decline in terms of dixanthogen at pH 10, as the final Eh
value was noted to be –71 mV. Similarly, in the FS-5SPW
experiments, the presence of dissolved salts in the plant
water led to a decrease in Eh, resulting in a reduction in
collector efficiency in terms of dixanthogen formation at
natural pH (+59.2 mV). A similar trend was observed in
the case of Cer-DI and Cer-5SPW experiments, further
suggesting that only under FS-DI conditions can sulfide
minerals be effectively recovered under natural conditions
if dixanthogen formation is required to promote flotation.
These hypotheses are tested in the results shown in
the following section in which the recoveries and grades
obtained from the flotation experiments are presented.
Solids-Water Recovery Analysis
The flotation behaviour of a mineral sample was evaluated
by analysing the solids and water recovery data, which can
be further correlated with the variations in the milling envi-
ronment and their impact on the Eh. The resulting data for
the solid vs water recoveries, obtained from all tests at pH 4
and 6–8, are presented in Figure 2. At pH 10, there was no
significant variation in the individual trends for different
milling media and water types used, with solids recoveries
ranging between 140–160 g, and water recoveries in the
range 900–1000 g hence, the graph has not been included.
The overall analysis provides valuable insights into froth
stability and the mechanisms by which the minerals report
to the froth phase.
The experimental findings indicate that when Cer
media was used, higher solids and water recoveries were
obtained at both pH levels. However, it is noteworthy
that the water recovery for the Cer-5SPW is significantly
higher than that of the Cer-DI at natural pH (6–8) by
250 g, despite the absence of dissolved media contribut-
ing Fe ions. This observation suggests that the presence of
dissolved salts in the plant water promotes water recovery,
thereby increasing the likelihood of minerals, including
gangue, being entrained into the froth phase. This is based
on the well-known fact that there is a strong linear relation-
ship between solids and water recovery when entrainment
occurs.
pH4 pH6-8 pH 10 pH4 pH6-8 pH 10 pH4 pH6-8 pH 10 pH4 pH6-8 pH 10
FS-DI FS-5SPW CER-DI CER-5SPW
Midpoint Eh 272 ,0 148 ,1 45,8 231 ,4 14,5 66,4 226,7 81,6 60,9 246 ,9 89,0 72,4
Final Eh 405 ,3 302 ,8 -71,4 300 ,8 59,2 -98,8 394 ,0 65,0 -60,7 394 ,2 70,8 -4,8
-100,0
0,0
100,0
200,0
300,0
400,0
500,0
600,0
Key: FS – Forged Steel Media, Cer – Ceramic Media, DI- Deionised Water, 5SPW – Synthetic Plant Water at an ionic strength of 5
(0.1205 M).
Figure 1. Eh variation during the milling process for different milling media compositions, water types, and pHs
Eh
(mV)