XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 327
• Manganese Carbonate by flotation from leach residue
• Copper by solvent extraction and electrowinning
• Nickel by solvent extraction and electrowinning
• Cobalt hydroxide by steam stripping and pH
adjustment
An additional potential product (or products) would be
rare earth elements, to be extracted from the manganese
carbonate flotation tailings as the final residue.
Confirmatory and Scale-Up Testing at ALS
In 2022 Moana Minerals commenced a testing project with
ALS Global at their Perth, Western Australia process test-
ing laboratory. The project was intended to show that the
BGRIMM test results could be reproduced at a larger scale
as well as further investigate the possibility of leaching at
higher slurry densities (%Solids). Larger scale tests would
produce larger volumes of both leach solution and leach
residue and allow some testing of proposed downstream
processing steps. For this test program Moana Minerals
provided ALS with approximately 57 kg of nodules from
the 2020 sampling expedition.
Reproducing BGRIMM Results
The first goal of the ALS bench test program was to repro-
duce the test results achieved at BGRIMM, but on a larger
scale. This was intended to allow ALS to become familiar
with Cuprion Sulfate leaching and to compare results at
a larger scale. ALS chose to use larger samples of Nodule
material and therefore ran tests at larger leach volumes. For
example, BGRIMM’s successful tests at 2.5% solids used
10g of nodules in 400ml whereas the standard ALS test at
2.5% solids used 50 g of nodules in 2 liters of solution.
ALS did successfully reproduce BGRIMM results
when leaching at 2.5% Solids (note all successful testing
by BGRIMM was at 2.5% Solids) and 5× scaleup. A key
requirement for successful testing was shown to be pre-
conditioning of the leach liquor to reduce the Oxidation/
Reduction Potential (ORP) to near –400mV for at least
30 minutes before adding nodule solids. Achieving com-
parable cobalt extraction was the measure of success in this
portion of the program. Comparable cobalt extractions
were achieved: 90.5% by ALS as compared to 90.6% by
BGRIMM.
While the head grades of the samples tested at ALS
were slightly lower than those tested at BGRIMM, the
closely matching results achieved in both sets of tests shows
that minor differences in head grade have little effect on
cobalt and other target metal extractions.
Calculation of performance for Cu extractions was
complicated by the fact that the concentration of copper
added to the initial leach solution for any test (to facilitate
the reduction of Mn) was much greater than the amount
of copper contained in or leached from the nodules during
any test. Hence small amounts of precipitation of copper
or ineffective residue sample washing resulted in high cal-
culated copper extraction variability.
Testing at Higher Slurry Densities
As previously noted, the few tests attempted by BGRIMM
at 5% solids did not achieve acceptable cobalt extractions.
It was suspected that “reagent starvation” was the limiting
factor in BGRIMM’s tests at higher solid/liquid ratios. In
particular, it was thought that additional cuprous copper
might be needed for leaching at the higher solids contents.
After testing at ALS had achieved success at 2.5% sol-
ids, testing commenced at 5% solids by weight. These tests
were conducted using 100 grams of solids in 2 liters of
slurry, 10 times the mass of solids as the BGRIMM tests.
A set of adjustments were made to achieve success at
the higher slurry densities, and included:
• The concentration of copper in the input leach liquor
was increased (Cuprous ion is a “catalytic intermedi-
ate” for Carbon Monoxide reduction of Manganese
Oxy-Hydroxides).
• The flowrate of Carbon Monoxide through the leach
slurry was increased.
• The leach tests were run for longer leach periods.
RESULTS
The series of the 5% solids tests showed that increas-
ing both the copper concentration and carbon monoxide
flowrate were necessary for best results. Three tests at 5%
solids achieved cobalt extractions in the 82–87% range.
Post-leach sample handling was also found to be criti-
cal. Proper filtration techniques were developed to ensure
that extracted cobalt remained in solution. Finally, further
confirmation was obtained that an Oxidation/Reduction
potential of near or below –400 for the last portion of the
leach test was also found to be critical. As 10% solids was
the ultimate target, results of testing at 5% were sufficiently
promising to justify proceeding directly to higher density
solids testing for the next round of tests.
Leaching at 10% Solids by Weight
Having demonstrated that higher solids densities could be
successfully leached, the next round of test were conducted
at 10% solids, by weight, in the slurry. These tests used 200
grams of nodules with 2 liters of leach solution.
• Manganese Carbonate by flotation from leach residue
• Copper by solvent extraction and electrowinning
• Nickel by solvent extraction and electrowinning
• Cobalt hydroxide by steam stripping and pH
adjustment
An additional potential product (or products) would be
rare earth elements, to be extracted from the manganese
carbonate flotation tailings as the final residue.
Confirmatory and Scale-Up Testing at ALS
In 2022 Moana Minerals commenced a testing project with
ALS Global at their Perth, Western Australia process test-
ing laboratory. The project was intended to show that the
BGRIMM test results could be reproduced at a larger scale
as well as further investigate the possibility of leaching at
higher slurry densities (%Solids). Larger scale tests would
produce larger volumes of both leach solution and leach
residue and allow some testing of proposed downstream
processing steps. For this test program Moana Minerals
provided ALS with approximately 57 kg of nodules from
the 2020 sampling expedition.
Reproducing BGRIMM Results
The first goal of the ALS bench test program was to repro-
duce the test results achieved at BGRIMM, but on a larger
scale. This was intended to allow ALS to become familiar
with Cuprion Sulfate leaching and to compare results at
a larger scale. ALS chose to use larger samples of Nodule
material and therefore ran tests at larger leach volumes. For
example, BGRIMM’s successful tests at 2.5% solids used
10g of nodules in 400ml whereas the standard ALS test at
2.5% solids used 50 g of nodules in 2 liters of solution.
ALS did successfully reproduce BGRIMM results
when leaching at 2.5% Solids (note all successful testing
by BGRIMM was at 2.5% Solids) and 5× scaleup. A key
requirement for successful testing was shown to be pre-
conditioning of the leach liquor to reduce the Oxidation/
Reduction Potential (ORP) to near –400mV for at least
30 minutes before adding nodule solids. Achieving com-
parable cobalt extraction was the measure of success in this
portion of the program. Comparable cobalt extractions
were achieved: 90.5% by ALS as compared to 90.6% by
BGRIMM.
While the head grades of the samples tested at ALS
were slightly lower than those tested at BGRIMM, the
closely matching results achieved in both sets of tests shows
that minor differences in head grade have little effect on
cobalt and other target metal extractions.
Calculation of performance for Cu extractions was
complicated by the fact that the concentration of copper
added to the initial leach solution for any test (to facilitate
the reduction of Mn) was much greater than the amount
of copper contained in or leached from the nodules during
any test. Hence small amounts of precipitation of copper
or ineffective residue sample washing resulted in high cal-
culated copper extraction variability.
Testing at Higher Slurry Densities
As previously noted, the few tests attempted by BGRIMM
at 5% solids did not achieve acceptable cobalt extractions.
It was suspected that “reagent starvation” was the limiting
factor in BGRIMM’s tests at higher solid/liquid ratios. In
particular, it was thought that additional cuprous copper
might be needed for leaching at the higher solids contents.
After testing at ALS had achieved success at 2.5% sol-
ids, testing commenced at 5% solids by weight. These tests
were conducted using 100 grams of solids in 2 liters of
slurry, 10 times the mass of solids as the BGRIMM tests.
A set of adjustments were made to achieve success at
the higher slurry densities, and included:
• The concentration of copper in the input leach liquor
was increased (Cuprous ion is a “catalytic intermedi-
ate” for Carbon Monoxide reduction of Manganese
Oxy-Hydroxides).
• The flowrate of Carbon Monoxide through the leach
slurry was increased.
• The leach tests were run for longer leach periods.
RESULTS
The series of the 5% solids tests showed that increas-
ing both the copper concentration and carbon monoxide
flowrate were necessary for best results. Three tests at 5%
solids achieved cobalt extractions in the 82–87% range.
Post-leach sample handling was also found to be criti-
cal. Proper filtration techniques were developed to ensure
that extracted cobalt remained in solution. Finally, further
confirmation was obtained that an Oxidation/Reduction
potential of near or below –400 for the last portion of the
leach test was also found to be critical. As 10% solids was
the ultimate target, results of testing at 5% were sufficiently
promising to justify proceeding directly to higher density
solids testing for the next round of tests.
Leaching at 10% Solids by Weight
Having demonstrated that higher solids densities could be
successfully leached, the next round of test were conducted
at 10% solids, by weight, in the slurry. These tests used 200
grams of nodules with 2 liters of leach solution.