1768 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
the pH. This is in addition to the Ca(OH)2 added during
preconditioning.
Gold Recovery
Results from these experiments show that after a leaching
period of 24 hours, the sono-leaching performance shown
for different ultrasonic pre-treatment time (UPT), was far
above that of the other two leaching methods. Figure 2 is
showing that gold grade in the tailings was reduced to less
than 0.10g/t with ultrasonic leaching whilst normal leach-
ing reached only about 0.35g/t. Figure 3 is showing that
gold recoveries of 39.66% and 50.01% were obtained with
the bottle roll and normal leaching methods (leaching in an
agitated vessel), respectively whilst 82.8% gold recovery was
obtained with the ultrasound pre-treatment process. On
the same sample, the bottle roll and the normal leaching
method with the use of activated carbon (to counter preg-
robbing) obtained gold recoveries of 43.1% and 56.9%,
respectively. The CIL setup was however, not used with the
ultrasonic leaching system as the carbon underwent high
attrition during the leaching process. The best recovery of
82.8% was found at 250 W ultrasonic power and a fre-
quency excitation of 24.13 kHz, 5hrs pre-treatment time,
4.7kg/t Ca(OH)2, (double what is needed under conven-
tional methods) 5kg/t NaCN, 37% slurry density after
12hrs of sonoleaching.
However, the fluctuations observed in gold recovery
after 1hr (Figure 2) is associated with the preg-robbing
nature of the ore due to existence of silicates and carbona-
ceous material. There is general gold tailings assay increase
as the time increases because of the mechano-chemical acti-
vation of the preg-robbing sites within the silicates.
Figure 1. Changes in solution pH
Figure 2. Gold in tailings after ultrasound leaching
the pH. This is in addition to the Ca(OH)2 added during
preconditioning.
Gold Recovery
Results from these experiments show that after a leaching
period of 24 hours, the sono-leaching performance shown
for different ultrasonic pre-treatment time (UPT), was far
above that of the other two leaching methods. Figure 2 is
showing that gold grade in the tailings was reduced to less
than 0.10g/t with ultrasonic leaching whilst normal leach-
ing reached only about 0.35g/t. Figure 3 is showing that
gold recoveries of 39.66% and 50.01% were obtained with
the bottle roll and normal leaching methods (leaching in an
agitated vessel), respectively whilst 82.8% gold recovery was
obtained with the ultrasound pre-treatment process. On
the same sample, the bottle roll and the normal leaching
method with the use of activated carbon (to counter preg-
robbing) obtained gold recoveries of 43.1% and 56.9%,
respectively. The CIL setup was however, not used with the
ultrasonic leaching system as the carbon underwent high
attrition during the leaching process. The best recovery of
82.8% was found at 250 W ultrasonic power and a fre-
quency excitation of 24.13 kHz, 5hrs pre-treatment time,
4.7kg/t Ca(OH)2, (double what is needed under conven-
tional methods) 5kg/t NaCN, 37% slurry density after
12hrs of sonoleaching.
However, the fluctuations observed in gold recovery
after 1hr (Figure 2) is associated with the preg-robbing
nature of the ore due to existence of silicates and carbona-
ceous material. There is general gold tailings assay increase
as the time increases because of the mechano-chemical acti-
vation of the preg-robbing sites within the silicates.
Figure 1. Changes in solution pH
Figure 2. Gold in tailings after ultrasound leaching