2204 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
respectively. Flotation was initiated by inducing 3 L/min of
air, and four concentrates were collected for 1, 2, 3 and 4
min. After flotation, flotation products were filtered, dried
and weighed, and then assayed for Cu and Fe at Australian
Laboratory Services (ALS).
Electrochemical Studies
A three-electrode configuration was employed to perform
the electrochemical measurements, and the electrical sig-
nal was measured by CHI 920D Scanning Electrochemical
Microscope (SECM) workstation. In the electrochemical
measurements, chalcopyrite and pyrite electrodes were
used as the working electrode, a platinum (Pt) electrode
was used as the auxiliary electrode, and a Ag/AgCl (3M
KCl) electrode was used as the reference electrode. All the
potential values presented in this work were converted to
standard hydrogen electrode (SHE).
Cyclic voltammetry (CV) analysis was performed to
investigate the reactions on mineral surfaces under different
test conditions. Prior to each test, the sulfide electrode was
wet-ground with 800-grit silicon carbide paper to create
a fresh surface by removing surface contamination. After
placing the chalcopyrite or pyrite electrode in the electro-
lyte, there was a waiting time of 300 s, allowing the elec-
trode to reach a steady open circuit potential (OCP) before
the commencement of CV measurement. Each CV curve
was acquired between –0.6 and 0.8 V, and the measure-
ment started from the OCP, sweeping in a positive direc-
tion to 0.8 V, followed by a negative direction from 0.8
to –0.6 V, and lastly, a positive direction back to the ini-
tial OCP to finish a complete cycle. The scan rate for CV
measurements was 20 mV/s, and for each measurement, at
least three cycles were obtained, and only the last cycle was
presented in this study.
The sulfide electrode was first placed in a solution
containing Cu ions, Fe ions, PMS, or their combinations
before the electrochemical test to simulate the grinding and
flotation environment with the conditioning time of 10, 5
and 5 min, respectively. The reagent addition followed the
order of Cu ions, Fe ions and PMS. The dosage of Cu ions
was 0.5 mM, which was previously employed by Mu and
Peng (2021) to simulate the copper activation on the pyrite
surface. The dosage of Fe ions and PMS was the same, 0.5
mM, and the one-to-one ratio was determined to maximize
the radical production (Ghanbari and Moradi, 2017). After
the conditioning, the sulfide electrode was then placed into
a fresh Borax solution for the CV measurement.
RESULTS AND DISCUSSIONS
Flotation Tests
Grinding and flotation tests were performed with PMS
added in the grinding mill or the flotation cell. The results
are shown in Figure 1.
From Figure 1 (a), it can be found that in the absence
of PMS, the flotation produced a chalcopyrite and pyrite
recovery of 81.5 and 36.6%, respectively. As 500 g/t of
PMS was added in the mill, chalcopyrite recovery increased
to 90.2%, and at the same time, pyrite recovery rose to
52.9%. Interestingly, the addition of 500 g/t PMS showed
no ability to depress pyrite when added in the mill. As
the PMS addition point moved to the flotation cell, the
chalcopyrite recovery improved from 81.5 to 88.0%, and
more importantly, pyrite recovery decreased from 36.6 to
22.9%. This indicates that PMS promoted the chalcopyrite
60 70 80 90 100
0
20
40
60
Chalcopyrite recovery (%)
Baseline (0 g/t PMS)
500 g/t PMS in mill
500 g/t PMS in cell
60 70 80 90 100
4
6
8
10
12
14
Cu recovery (%)
Baseline (0 g/t PMS)
500 g/t PMS in mill
500 g/t PMS in cell
(a) (b)
Figure 1. Flotation performance of Cpy-Py-Q mineral mixture upon the addition of PMS in the mill and flotation cell
expressed in (a) pyrite recovery as a function of chalcopyrite recovery and (b) Cu grade as a function of Cu recovery
Pyrite
r
over
(%)
Cu
grade
(%)
respectively. Flotation was initiated by inducing 3 L/min of
air, and four concentrates were collected for 1, 2, 3 and 4
min. After flotation, flotation products were filtered, dried
and weighed, and then assayed for Cu and Fe at Australian
Laboratory Services (ALS).
Electrochemical Studies
A three-electrode configuration was employed to perform
the electrochemical measurements, and the electrical sig-
nal was measured by CHI 920D Scanning Electrochemical
Microscope (SECM) workstation. In the electrochemical
measurements, chalcopyrite and pyrite electrodes were
used as the working electrode, a platinum (Pt) electrode
was used as the auxiliary electrode, and a Ag/AgCl (3M
KCl) electrode was used as the reference electrode. All the
potential values presented in this work were converted to
standard hydrogen electrode (SHE).
Cyclic voltammetry (CV) analysis was performed to
investigate the reactions on mineral surfaces under different
test conditions. Prior to each test, the sulfide electrode was
wet-ground with 800-grit silicon carbide paper to create
a fresh surface by removing surface contamination. After
placing the chalcopyrite or pyrite electrode in the electro-
lyte, there was a waiting time of 300 s, allowing the elec-
trode to reach a steady open circuit potential (OCP) before
the commencement of CV measurement. Each CV curve
was acquired between –0.6 and 0.8 V, and the measure-
ment started from the OCP, sweeping in a positive direc-
tion to 0.8 V, followed by a negative direction from 0.8
to –0.6 V, and lastly, a positive direction back to the ini-
tial OCP to finish a complete cycle. The scan rate for CV
measurements was 20 mV/s, and for each measurement, at
least three cycles were obtained, and only the last cycle was
presented in this study.
The sulfide electrode was first placed in a solution
containing Cu ions, Fe ions, PMS, or their combinations
before the electrochemical test to simulate the grinding and
flotation environment with the conditioning time of 10, 5
and 5 min, respectively. The reagent addition followed the
order of Cu ions, Fe ions and PMS. The dosage of Cu ions
was 0.5 mM, which was previously employed by Mu and
Peng (2021) to simulate the copper activation on the pyrite
surface. The dosage of Fe ions and PMS was the same, 0.5
mM, and the one-to-one ratio was determined to maximize
the radical production (Ghanbari and Moradi, 2017). After
the conditioning, the sulfide electrode was then placed into
a fresh Borax solution for the CV measurement.
RESULTS AND DISCUSSIONS
Flotation Tests
Grinding and flotation tests were performed with PMS
added in the grinding mill or the flotation cell. The results
are shown in Figure 1.
From Figure 1 (a), it can be found that in the absence
of PMS, the flotation produced a chalcopyrite and pyrite
recovery of 81.5 and 36.6%, respectively. As 500 g/t of
PMS was added in the mill, chalcopyrite recovery increased
to 90.2%, and at the same time, pyrite recovery rose to
52.9%. Interestingly, the addition of 500 g/t PMS showed
no ability to depress pyrite when added in the mill. As
the PMS addition point moved to the flotation cell, the
chalcopyrite recovery improved from 81.5 to 88.0%, and
more importantly, pyrite recovery decreased from 36.6 to
22.9%. This indicates that PMS promoted the chalcopyrite
60 70 80 90 100
0
20
40
60
Chalcopyrite recovery (%)
Baseline (0 g/t PMS)
500 g/t PMS in mill
500 g/t PMS in cell
60 70 80 90 100
4
6
8
10
12
14
Cu recovery (%)
Baseline (0 g/t PMS)
500 g/t PMS in mill
500 g/t PMS in cell
(a) (b)
Figure 1. Flotation performance of Cpy-Py-Q mineral mixture upon the addition of PMS in the mill and flotation cell
expressed in (a) pyrite recovery as a function of chalcopyrite recovery and (b) Cu grade as a function of Cu recovery
Pyrite
r
over
(%)
Cu
grade
(%)