1902 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
RESULTS AND DISCUSSION
Concentrate Characterization
The flotation concentrate contains 12.988 ppm gold and
4541 ppm molybdenum with P80 of 125 microns. It is
composed of 18.764 wt% sulfur indicating that the flota-
tion concentrate is sulfidic with major phase of pyrite as con-
firmed by the concentrate X-ray diffraction pattern shown
in Figure 1. The concentrate also contains 24.55 wt% Si,
6.58 wt% Al, and 9.03 wt% K as gangue minerals. These
results confirm that the concentrate is a refractory gold-
molybdenum concentrate.
Gold occurrence test shows that concentrate contains
9.75% free gold, 44.18% gold that is exposed and associ-
ated that can be recovered by cyanide. However, 40.03% of
gold is present as locked in sulfides that confirms presence
of refractory gold which may not be efficiently recoverable
through conventional cyanidation. Balance of 6.69% of
gold is locked in silicates which is difficult to recover.
Two-Stage Hypochlorite Leaching
The two-stage hypochlorite leaching yielded 93.51% gold
dissolution and 88.54% molybdenum dissolution. Gold
dissolution of around 40% is observed at start of leaching
and stabilized at around 55% throughout the 1st stage as
shown in Figure 2. Gold dissolved during this stage may
be free, exposed, and associated gold (total of 54% from
gold occurrence test) which are easily accessible to react
with hypochlorite. In the first stage, solution pH is at 13.5
indicating hypochlorite ions as dominant oxidizing species.
Table 1. Parameters for two-stage hypochlorite leaching
Stage
Time,
hrs Temp L:S Ratio Agitation, rpm NaCl, g/L Ca(OCl)
2 ,g/L OCl–1, M
NaOH,
%wt /pH
1st Stage 6 Ambient 13 500 30 — 1.89 10 wt%
2nd Stage 2 Ambient — 500 200 200 — 6
Figure 1. XRD pattern of concentrate
Figure 2. Gold dissolution of two-stage hypochlorite leaching
RESULTS AND DISCUSSION
Concentrate Characterization
The flotation concentrate contains 12.988 ppm gold and
4541 ppm molybdenum with P80 of 125 microns. It is
composed of 18.764 wt% sulfur indicating that the flota-
tion concentrate is sulfidic with major phase of pyrite as con-
firmed by the concentrate X-ray diffraction pattern shown
in Figure 1. The concentrate also contains 24.55 wt% Si,
6.58 wt% Al, and 9.03 wt% K as gangue minerals. These
results confirm that the concentrate is a refractory gold-
molybdenum concentrate.
Gold occurrence test shows that concentrate contains
9.75% free gold, 44.18% gold that is exposed and associ-
ated that can be recovered by cyanide. However, 40.03% of
gold is present as locked in sulfides that confirms presence
of refractory gold which may not be efficiently recoverable
through conventional cyanidation. Balance of 6.69% of
gold is locked in silicates which is difficult to recover.
Two-Stage Hypochlorite Leaching
The two-stage hypochlorite leaching yielded 93.51% gold
dissolution and 88.54% molybdenum dissolution. Gold
dissolution of around 40% is observed at start of leaching
and stabilized at around 55% throughout the 1st stage as
shown in Figure 2. Gold dissolved during this stage may
be free, exposed, and associated gold (total of 54% from
gold occurrence test) which are easily accessible to react
with hypochlorite. In the first stage, solution pH is at 13.5
indicating hypochlorite ions as dominant oxidizing species.
Table 1. Parameters for two-stage hypochlorite leaching
Stage
Time,
hrs Temp L:S Ratio Agitation, rpm NaCl, g/L Ca(OCl)
2 ,g/L OCl–1, M
NaOH,
%wt /pH
1st Stage 6 Ambient 13 500 30 — 1.89 10 wt%
2nd Stage 2 Ambient — 500 200 200 — 6
Figure 1. XRD pattern of concentrate
Figure 2. Gold dissolution of two-stage hypochlorite leaching