3654 XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3
power consumption. The longer operating time of the
traditional method translated to a higher manpower cost.
Consumables accounted for all the materials and reagents
used for each process. In this aspect, the traditional method
posted lower costs as compared to the alternative method.
Considering all the expenses during operations, the alterna-
tive method resulted in a lower overall cost per gram of gold
recovered.
WASTE TREATMENT
The final effluent from the traditional method’s cyanidation
stage, with an approximate volume of 9.5 cubic meters at
40% solids, was discharged into a nearby temporary tail-
ings dam without any form of detoxification. Upon analysis
of the water discharge, it was found to still contain 0.08%
or 800 ppm cyanide. The Philippines’ allowable limit for
cyanide discharge for class A-D water bodies is 0.05 ppm
CN (DENR AO NO. 2016-08). This greatly exceeds envi-
ronmental regulation limits. While cyanide photodegrada-
tion would eventually reduce cyanide concentrations in
the effluent, it would still take quite some time before the
wastewater reach the appropriate quality for discharge.
As for the alternative process, there are two (2) effluents
generated from the plant. The first one is the flotation tail-
ings which were composed mainly of ore and water that
was directed into a settling pond. The settling pond sepa-
rates the solids from clear water before disposal or recycling.
The second effluent results from the barren solution
after the precipitation stage of the hypochlorite- leach-
ing stage. Lime was added to neutralize the barren solu-
tion to pH 7 before it was made to pass through a series of
chambers containing coco-peat, a co-product of coconut
fiber extraction, and zeolite. At this stage, the residual chlo-
rine and heavy metals can be removed yielding an effluent
ready for disposal.
CONCLUSIONS
The non-mercury, non-cyanide processing plant alternative
was able to effectively recover 79% of the total gold using
gravity concentration whereas the traditional process using
sluices and panning only recovered around 58%. The tra-
ditional gold extraction method had to utilize leaching by
cyanidation to cover the difference in recoveries. Using the
hypochlorite leaching circuit of the alternative process, gold
recovery can further be increased to 86.11%.
As for the operating time, the alternative method only
took 1.2 days for an entire cycle to recover 86.11% of the
gold from the ore compared to almost 6 days for the tradi-
tional small-scale process that only recovered 82.8%.
Operating expenses for both plants resulted in compa-
rable costs, with both power costs being almost the same.
The traditional method has lower costs for consumables but
posted higher labor costs while the alternative method has
lower labor costs and higher expenses in terms of consum-
ables. A summary of the data obtained from running the
two plants is presented in Table 3.
Lastly, a further advantage from the alternative process
is that the overall cost per gram of gold recovered is lower
than that of the traditional small-scale method. The cost
also incorporates tailings treatment that ensures the plant
effluent adheres to the local water quality standards that the
traditional method lacks.
Table 2. Operating expenses (OPEX) for the traditional and alternative process, values are in PhP
Traditional Alternative
Power Cost 2,797.22 2,705.63
Consumables CIL Flotation +Hypochlorite
5,536.75 8,658.15
Labor Cost 4,900.00 2,100.00
Total OPEX 13,233.97 13,463.78
Cost per MT 2,802.92 2,851.59
Cost per gram of gold recovered 717.20 701.60
Table 3. Summary of data from the parallel test
Traditional Points of Comparison Alternative
82.80% Gold Overall Recovery 86.11%
143.45 hrs (6 days) Operating Time 29 hrs (1.2 days)
2,802.92 Total Operating Cost (PhP per MT) 2,851.59
717.20 Cost per gram Gold, PhP 701.60
power consumption. The longer operating time of the
traditional method translated to a higher manpower cost.
Consumables accounted for all the materials and reagents
used for each process. In this aspect, the traditional method
posted lower costs as compared to the alternative method.
Considering all the expenses during operations, the alterna-
tive method resulted in a lower overall cost per gram of gold
recovered.
WASTE TREATMENT
The final effluent from the traditional method’s cyanidation
stage, with an approximate volume of 9.5 cubic meters at
40% solids, was discharged into a nearby temporary tail-
ings dam without any form of detoxification. Upon analysis
of the water discharge, it was found to still contain 0.08%
or 800 ppm cyanide. The Philippines’ allowable limit for
cyanide discharge for class A-D water bodies is 0.05 ppm
CN (DENR AO NO. 2016-08). This greatly exceeds envi-
ronmental regulation limits. While cyanide photodegrada-
tion would eventually reduce cyanide concentrations in
the effluent, it would still take quite some time before the
wastewater reach the appropriate quality for discharge.
As for the alternative process, there are two (2) effluents
generated from the plant. The first one is the flotation tail-
ings which were composed mainly of ore and water that
was directed into a settling pond. The settling pond sepa-
rates the solids from clear water before disposal or recycling.
The second effluent results from the barren solution
after the precipitation stage of the hypochlorite- leach-
ing stage. Lime was added to neutralize the barren solu-
tion to pH 7 before it was made to pass through a series of
chambers containing coco-peat, a co-product of coconut
fiber extraction, and zeolite. At this stage, the residual chlo-
rine and heavy metals can be removed yielding an effluent
ready for disposal.
CONCLUSIONS
The non-mercury, non-cyanide processing plant alternative
was able to effectively recover 79% of the total gold using
gravity concentration whereas the traditional process using
sluices and panning only recovered around 58%. The tra-
ditional gold extraction method had to utilize leaching by
cyanidation to cover the difference in recoveries. Using the
hypochlorite leaching circuit of the alternative process, gold
recovery can further be increased to 86.11%.
As for the operating time, the alternative method only
took 1.2 days for an entire cycle to recover 86.11% of the
gold from the ore compared to almost 6 days for the tradi-
tional small-scale process that only recovered 82.8%.
Operating expenses for both plants resulted in compa-
rable costs, with both power costs being almost the same.
The traditional method has lower costs for consumables but
posted higher labor costs while the alternative method has
lower labor costs and higher expenses in terms of consum-
ables. A summary of the data obtained from running the
two plants is presented in Table 3.
Lastly, a further advantage from the alternative process
is that the overall cost per gram of gold recovered is lower
than that of the traditional small-scale method. The cost
also incorporates tailings treatment that ensures the plant
effluent adheres to the local water quality standards that the
traditional method lacks.
Table 2. Operating expenses (OPEX) for the traditional and alternative process, values are in PhP
Traditional Alternative
Power Cost 2,797.22 2,705.63
Consumables CIL Flotation +Hypochlorite
5,536.75 8,658.15
Labor Cost 4,900.00 2,100.00
Total OPEX 13,233.97 13,463.78
Cost per MT 2,802.92 2,851.59
Cost per gram of gold recovered 717.20 701.60
Table 3. Summary of data from the parallel test
Traditional Points of Comparison Alternative
82.80% Gold Overall Recovery 86.11%
143.45 hrs (6 days) Operating Time 29 hrs (1.2 days)
2,802.92 Total Operating Cost (PhP per MT) 2,851.59
717.20 Cost per gram Gold, PhP 701.60