XXXI International Mineral Processing Congress 2024 Proceedings/Washington, DC/Sep 29–Oct 3 323
PROCESSING POLYMETALLIC NODULES
A necessary step to recover the desired metals, such as
cobalt, copper and nickel, from ocean nodules is to chemi-
cally break down the manganese matrix. (Mechanical deg-
radation of the manganese oxy-hydroxide will not achieve
liberation of the desired metals). This is accomplished
by the reduction of manganese from a +4 oxidation state
(Mn+4) to a +2 oxidation state (Mn+2) in the oxide matrix.
Several different processing schemes have been proposed
and tested to accomplish this basic task.
In 1977 the consulting firm of Dames and Moore
produced the report “Description of Manganese Nodule
Processing Activities for Environmental Studies” for the
U.S. National Oceanic and Atmospheric Administration
(NOAA) (Dames &Moore 1977). The report evaluated the
input requirements, land use and outputs (including waste
materials) for five potential treatment systems for ocean
nodules. The treatment systems evaluated were:
• Reduction Roast/Ammoniacal Leach Process (a
modified Caron process)
• Cuprion/Ammonia Leach Process (generally called
the Cuprion process)
• High Temperature and Pressure Sulfuric Acid Leach
Process (HPAL)
• Reduction/Hydrochloric Acid Leach Process
• Smelting (Electric Furnace)
From this original list of reviewed processes, it is worth not-
ing that the Caron process has been used commercially for
nickel recovery, and that HPAL process plants are currently
processing lateritic ores to recover nickel as are Rotary Kiln-
Electric Furnace (RKEF) plants. More recently, nitric acid
leaching has been developed for treating nickel laterites
and proposed for treating some polymetallic nodules, and
the treatment of manganiferous ores with sulfurous acid to
release trapped precious metals has also been tested. At the
start of Moana Minerals’ nodule processing development
program, NO process for treating polymetallic nodules had
been demonstrated beyond the pilot plant stage of develop-
ment. More specifically, no process had been tested at even
laboratory scale using the nodules of the Cook Islands.
Processing Nodules with the Cuprion Process
The Cuprion process (Cuprion/Ammonia carbonate leach)
was developed by the Kennecott Copper Company, in
the 1970 and early 1980s, as the leader of a consortium
intending to develop Clarion-Clipperton zone nodules as
a copper-nickel resource. Figure 3 shows a simplified flow
chart of the Cuprion process. This hydrometallurgical pro-
cess uses the cuprous copper ion (Cu+1) in aqueous solution
as the reductant for the Mn+4 to Mn+2 reaction. In that
reaction the cuprous ion is converted to the cupric (Cu+2)
ion which remains in solution. Copper and nickel are very
soluble in the ammonium carbonate-based solution of
the Cuprion process. Carbon monoxide (CO) is bubbled
through the solution to convert the cupric ions back into
cuprous ions to reduce additional manganese.
The Cuprion leaching process operates at relatively
low temperature (50°C) and at atmospheric pressure.
Figure 2. Imagery from August 2023 ROV Transect in Moana Minerals’ EL-3 License Area
(spacing laser dots 35mm)
PROCESSING POLYMETALLIC NODULES
A necessary step to recover the desired metals, such as
cobalt, copper and nickel, from ocean nodules is to chemi-
cally break down the manganese matrix. (Mechanical deg-
radation of the manganese oxy-hydroxide will not achieve
liberation of the desired metals). This is accomplished
by the reduction of manganese from a +4 oxidation state
(Mn+4) to a +2 oxidation state (Mn+2) in the oxide matrix.
Several different processing schemes have been proposed
and tested to accomplish this basic task.
In 1977 the consulting firm of Dames and Moore
produced the report “Description of Manganese Nodule
Processing Activities for Environmental Studies” for the
U.S. National Oceanic and Atmospheric Administration
(NOAA) (Dames &Moore 1977). The report evaluated the
input requirements, land use and outputs (including waste
materials) for five potential treatment systems for ocean
nodules. The treatment systems evaluated were:
• Reduction Roast/Ammoniacal Leach Process (a
modified Caron process)
• Cuprion/Ammonia Leach Process (generally called
the Cuprion process)
• High Temperature and Pressure Sulfuric Acid Leach
Process (HPAL)
• Reduction/Hydrochloric Acid Leach Process
• Smelting (Electric Furnace)
From this original list of reviewed processes, it is worth not-
ing that the Caron process has been used commercially for
nickel recovery, and that HPAL process plants are currently
processing lateritic ores to recover nickel as are Rotary Kiln-
Electric Furnace (RKEF) plants. More recently, nitric acid
leaching has been developed for treating nickel laterites
and proposed for treating some polymetallic nodules, and
the treatment of manganiferous ores with sulfurous acid to
release trapped precious metals has also been tested. At the
start of Moana Minerals’ nodule processing development
program, NO process for treating polymetallic nodules had
been demonstrated beyond the pilot plant stage of develop-
ment. More specifically, no process had been tested at even
laboratory scale using the nodules of the Cook Islands.
Processing Nodules with the Cuprion Process
The Cuprion process (Cuprion/Ammonia carbonate leach)
was developed by the Kennecott Copper Company, in
the 1970 and early 1980s, as the leader of a consortium
intending to develop Clarion-Clipperton zone nodules as
a copper-nickel resource. Figure 3 shows a simplified flow
chart of the Cuprion process. This hydrometallurgical pro-
cess uses the cuprous copper ion (Cu+1) in aqueous solution
as the reductant for the Mn+4 to Mn+2 reaction. In that
reaction the cuprous ion is converted to the cupric (Cu+2)
ion which remains in solution. Copper and nickel are very
soluble in the ammonium carbonate-based solution of
the Cuprion process. Carbon monoxide (CO) is bubbled
through the solution to convert the cupric ions back into
cuprous ions to reduce additional manganese.
The Cuprion leaching process operates at relatively
low temperature (50°C) and at atmospheric pressure.
Figure 2. Imagery from August 2023 ROV Transect in Moana Minerals’ EL-3 License Area
(spacing laser dots 35mm)