Extraction of metal values from manganese nodules

This invention provides a two-stage leaching procedure for manganese nodules for obtaining directly in one leaching stage the metal values other than manganese in one ammoniacal aqueous solution. The manganese nodules are reduced and then leached initially utilizing a solution of an ammonium salt, e.g., ammonium sulfate, to selectively leach out the manganese value, followed by a second stage leaching with an ammoniacal solution, to leach out the nickel, cobalt and copper values. The nickel, cobalt and copper values can then be individually separated from the second leach solution by liquid ion exchange extraction.

It is not a common situation to obtain a relatively valuable non-ferrous 
metal such as nickel, cobalt, copper and zinc together with a relatively 
large proportion of manganese and a significant quantity of iron. A 
relatively untapped source of high-quality manganiferous ore, however, is 
a material which is found on the ocean floor and has come to be known as 
ocean floor nodule ore, or manganese nodule ore. 
With the increased awareness on the part of both the public and the metals 
industry of the ecological dangers that can arise from continued surface 
mining of minerals required for most ores mined from the land, as well as 
the recent diminution in the availability of valuable industrial ores, the 
mining industry has become interested within the last several years in the 
mining of minerals from the sea. This has been an extremely elusive target 
up to the present. One method of obtaining such minerals has been the 
dredging of the deep ocean floor to obtain an ore which has variously 
become known as ocean floor nodule ores, manganese nodules or merely 
nodules. Such minerals can be merely scooped up from the top surface of 
the ocean floor without requiring a rending of the earth's surface. 
The nodule ore was first collected during the first part of the 1870's. 
Deposits of this ore are found as nodules, lying on the surface of the 
soft sea floor, as large slabs on the ocean floor, or as replacement 
fillings in calcareous debris and other animal remains. They have been 
studied by many workers in an attempt to determine their precise 
composition, and then to decipher ways to wrest from their peculiar 
structure the valuable metals contained therein. It is presently believed 
that these nodules are actually creations of the sea; they are somehow 
grown, generally in the form of the metal oxides, from metal values which 
are dissolved in sea water. 
The metal values of the nodules are almost exclusively in the form of 
oxides and moreover are present in extremely peculiar physical 
configuration. The physical and chemical structure of the nodules are 
believed to be a direct result of the conditions under which they were 
created and to which they have been exposed since their creation. First, 
nodule ore has never been exposed to temperatures other than those at the 
bottom of the ocean at the location at which they were formed. The nodule 
ores have an extremely large surface area, a porosity often greater than 
50%, and are relatively chemically reactive ores. The solid structure of 
the nodules is extremely complex, seemingly formed of many crystalites, 
but without any recognizable overall crystalline pattern or structure. The 
nodules are formed basically of what appears to be an extremely complex 
arrangement, or matrix, of iron and manganese oxides: tiny grains of each 
oxide of a size and type which are substantially impossible to separate by 
presently available physical means. These iron and manganese oxides form 
the basic structure within which other metal values are retained, in what 
is believed to be at least partially a result of a substitution mechanism. 
These other metal values include, as the major ingredient, nickel, copper 
and cobalt, and in addition, chromium, zinc, tin, vanadium and other 
metals, including the rare metals, silver and gold. 
In addition to the metal oxides, described above, there is also present a 
large quantity of silt, or gangue material, intimately admixed with the 
nodule ore. This silt, or gangue, is sand and clay, and includes the usual 
oxides of silicon and aluminum and varying proportions of some carbonates, 
especially calcium carbonate. 
The precise chemical composition, as well as the physical structure, of the 
nodules vary somewhat depending upon their location in the ocean. 
Variation is perhaps caused by differences in temperature in various 
places, and at different depths, differences in the solute composition of 
sea water, perhaps caused by the pressure variations at different depths 
and the composition of adjacent land areas, variations in the amount of 
oxygen which is present in the water in different locations, and perhaps 
other variables not readily apparent to observers. Generally, however, in 
almost all cases, the metals which are present in primary proportions are 
manganese and iron, and the predominant secondary metals are generally 
nickel, copper and cobalt. A detailed analysis of a variety of different 
nodule ores can be found in an article entitled "The Geochemistry of 
Manganese Nodules and Associated Deposits From the Pacific and Indian 
Oceans" by Croonan and Tooms, in Deepsea Research (1969), Volume 16, pages 
335-359, Pergamon Press (Great Britain). 
As a general rule, the nodule ores can be considered as containing the 
following metal content ranges, derived on a fully dry basis. 
______________________________________ 
Percent 
______________________________________ 
Copper 0.8 - 1.8 
Nickel 1.0 - 2.0 
Cobalt 0.1 - 0.5 
Manganese 10.0 - 40.0 
Iron 4.0 - 25.0 
______________________________________ 
Because of the peculiar and intricate crystal structure of the ocean floor 
nodules, many of the common refining techniques used for the refining of 
land ores are not generally suited for the nodules. Most especially, 
because of the great value attached to the nickel and copper values in the 
manganese nodules, and the relatively large amounts of manganese found in 
these ores, special procedures are needed, which are not relevant to 
terrestrial ores, for the refining of these materials. 
Among the procedures is included the reduction of pellets prepared from 
manganese deepsea nodules, to form metallic copper, nickel and cobalt, 
within the pellets, followed by leaching with an ammoniacal ammonium salt 
solution to obtain the copper, nickel and cobalt salts in solution without 
dissolving any manganese or iron. The leaching is carried out in the 
presence of aeration, see U.S. Pat. Nos. 3,788,841 and 3,741,554. 
Nodule ores have also been treated by two-phase leaching utilizing 
ammoniated ammonium salt solutions, wherein the temperatures vary, to 
initially extract copper under milder, room temperature conditions, and 
subsequently to extract nickel under higher temperatures (U.S. Pat. No. 
3,736,125). A selective reduction of the manganese nodules permits the 
selective leaching of copper, nickel, cobalt and molybdenum, without the 
leaching of manganese, according to U.S. Pat. No. 3,734,715, while the 
partial reduction of a nodule ore charge, when utilizing an ammonia 
solution also containing manganous ions, permits the leaching of copper, 
nickel, cobalt and molybdenum (U.S. Pat. No. 3,723,095). 
In a somewhat different direction, manganese has been extracted from 
terrestrial manganiferous ores, which have not contained cobalt, copper 
and nickel, utilizing acidic ammonium salts, such as ammonium sulfate, see 
"Review of Proposed Processes for Recovering Manganese From United States 
Resources, Part 2-Chloride and Fixed Nitrogen Processes", Bureau of Mines, 
Information Circular No. 8160 (1963, U.S. Dept. of Interior), pages 26-28. 
A problem with the previously carried out procedures for separating the 
manganese metal value from the other metal values in the ocean floor 
nodule ore is the problem of extracting at least a minor proportion of the 
manganese together with the other metal values, when the metal values are 
initially extracted. Because of the order of magnitude difference between 
the amount of manganese and the amount of, e.g., nickel and copper, 
present in the ocean floor nodule ores, even a minor extraction of 
manganese results in a significant dilution of the nickel/copper 
concentration in the solution. It is, accordingly, an object of the 
present invention to avoid this problem and enable the art to obtain a 
relatively pure leach solution containing the valuable nickel and copper 
values, as well as the desirable cobalt value, and a separate leach 
solution containing the manganese metal value. It is further an object of 
this invention to provide a continuous process for individually obtaining 
the metal values wherein each leaching solution can be recovered and 
recycled for further use. 
In accordance with the present invention, there is provided a process for 
selectively removing metal values from a manganese nodule ore, the ore 
comprising primary proportions of manganese and iron and secondary 
proportions of nickel, copper and cobalt. Most preferably, the ore 
contains a manganese : iron ratio of at least about 5:1 and optimally at 
least about 6:1, and a total proportion of copper, nickel and cobalt of at 
least about 1.5% by weight. The process comprises the steps of: (a) 
reducing the manganese nodule ore; (b) leaching the reduced ore with an 
aqueous solution of an acidic ammonium salt, to selectively dissolve out 
the manganese value from the ore so as to obtain an initial aqueous leach 
solution comprising dissolved manganese salt, and a solid leached ore; and 
(c) releaching the solid leached ore with an ammoniated aqueous solution 
of an ammonium salt to dissolve out the copper, cobalt and nickel values 
from the ore, so as to form an aqueous releach solution comprising 
dissolved nickel, cobalt and copper salts, and a solid final residue, 
wherein the reduced or leached ore is permitted to be oxidized prior to 
completion of the releaching so that the cobalt, nickel and copper values 
are in a soluble condition. 
In a preferred embodiment of this process, the pregnant releach solution is 
then further treated to separate the individual metal values by treating 
the remaining aqueous solution with a liquid ion exchange agent so as to 
separate the cobalt, nickel and copper values into separate streams 
thereof, by selective extraction. 
In accordance with this process, the nodule ore is preferably initially 
dried and the reduction carried out under anhydrous conditions. The drying 
can be carried out in the same or a separate stage, at temperatures 
substantially below the reduction temperatures. The drying temperatures 
are preferably no greater than about 250.degree. C. and most preferably at 
temperatures in the range of from about 150.degree. C. to about 
250.degree. C. 
In order to increase the rates of drying and subsequent reduction and 
leaching of the nodule ore, the ore is preferably initially comminuted, as 
by grinding and crushing to a particle size of not greater than about 20 
mesh, U.S. Sieve Scale, most preferably not greater than about 50 mesh and 
optimally not greater than about 100 mesh. 
The dried and comminuted nodule ore is next reduced preferably at a 
temperature of at least about 300.degree. C. The reduction is most easily 
and economically carried out by reacting the nodule ore with a 
carbonaceous or hydrogen-containing reducing agent, which is itself 
oxidized to either carbon dioxide or water vapor when the metal values are 
reduced. 
The intent of this reducing step is to convert the metal values in the 
nodule ore into forms which are readily leachable by the ammonium salt 
solutions described herein. It has been found that the nodule ore as 
obtained from the ocean floor, and even after drying, is not readily 
susceptible to leaching utilizing the ammonium salt solutions of the 
present invention. After reduction, however, it has been found that the 
metal values can be readily dissolved into an ammonium salt solution, the 
need for free additional ammonia being dependent upon the particular metal 
to be dissolved. The reduction to be carried out in accordance with the 
present step of the process of this invention should result in 
substantially all of the manganese originally present in the ore in the 
tetravalent state to be reduced to the divalent state. Concurrently with 
the reduction of the manganese, there must, almost of necessity, be a 
reduction of the nickel, cobalt and copper values present in the ore. 
Although it is not clear to exactly what valence state the nickel, cobalt 
and copper are reduced, it is generally believed that they are reduced to 
a state below that at which they are found in the ore. Without being 
limited thereto, it is believed that the copper is reduced to the 
elemental state and the nickel and cobalt are reduced to some other state, 
perhaps one intermediate the common divalent and elemental states. 
It has been found that any iron value will also generally be reduced to a 
state below that in which it is normally found, and that at least part of 
the iron is reduced to a state where it is not leached out together with 
the manganese value in accordance with the first leaching step of the 
present invention. This, what is in effect, limited reduction of the iron 
is desirable to decrease the iron dissolved in the initial leach solution 
so as to minimize the problems of subsequent separation of iron from 
manganese in the first leach solution. Generally, the relative proportion 
of manganese and iron in the nodule ore is somewhat too rich in iron to 
obtain a valuable commercial product if all the iron were to be leached 
out in the same proportion as the manganese. 
The nickel, cobalt and copper are generally believed to be suitably 
re-oxidized, if necessary, to a soluble state by simple aeration (or even 
mere exposure to the atmosphere). The exact mechanism by which the various 
metal values are reduced or oxidized, and even the valence states to which 
they are reduced or oxidized, have not been precisely determined, but need 
not be known for the satisfactory carrying out or regulation of the 
process of the present invention. 
Although the scope of this invention should not be limited thereto, it is 
believed that generally any reducing agent which has sufficient reducing 
strength to reduce tetravalent manganese to divalent manganese and to 
reduce the other metal values in the ore can be utilized for the reducing 
stage of this invention. It should, of course, be noted that the reducing 
agent need not be a pure compound or element and that a combination of two 
or more reducing agents can be utilized. For example, many natural 
products, such as hydrogen, natural gas or coal, or manufactured gas, 
e.g., producer gas, contains a combination of compounds or elements at 
least some of which provide at least some reducing action with regard to 
the metal values in the nodule ore. Generally, elemental carbon in any 
physical state, including amorphous or graphitic carbon, or natural or 
semi-manufactured solid carbonaceous materials, such as coal, peat, 
charcoal, and coke, can be used. Oil or other organic sources can be 
utilized as a source for the reducing action of carbon, and any 
hydrocarbon can be used: aromatic, aliphatic or cycloaliphatic, or 
compounds having combinations of these groups, without interfering with 
the reducing action. Solid hydrocarbon compounds, especially the higher 
condensed ring aromatic materials, including most especially those derived 
from petroleum or other natural mineral products which are often available 
as by-product tars from the refining of these materials, have the highest 
proportion of carbon among the hydrocarbons, and, therefore, provide a 
desirable unit weight effectiveness as a solid reducing agent. Gaseous 
materials, such as carbon monoxide, alone or admixed with hydrogen, as in 
reformer gas, can also be readily utilized as reducing agents. As stated 
earlier, hydrogen itself is a strong and effective reducing agent, and, if 
available cheaply enough, can be used commercially. 
Generally, the most efficient temperature, or temperature range, for the 
reduction reaction is dependent upon the reducing agent utilized. The 
reducing agents, which are most effective in reducing tetravalent 
manganese to the divalent state, and which also can reduce the other metal 
values present, at temperatures as low as about 300.degree. C. in 
accordance with this procedure, include normally gaseous materials such as 
hydrogen and carbon monoxide, and synthetic mixtures thereof. Other fluid 
reducing agents, such as, for example, the lower, gaseous or liquid, 
hydrocarbons, which are somewhat less effective in reducing manganese and 
the other metal values, should be used at somewhat higher temperatures of 
at least about 500.degree. C. Generally, the solid reducing agents, such 
as elemental carbon, e.g., coal, or the higher solid hydrocarbons, would 
be utilized at higher temperatures of at least about 550.degree. C. 
Generally, for a given reducing agent, the higher the temperature of 
reaction, the shorter should be the reaction time, in order to avoid 
over-reduction of the ore. In any event, generally, a temperature greater 
than about 850.degree. C. is unnecessary and introduces difficulties in 
the subsequent leaching steps, so that preferably temperatures in the 
range of from about 350.degree. C. to about 800.degree. C. are preferred, 
but optimally, temperatures not greater than about 750.degree. C. are 
utilized. 
The reduction of the nodule ore can be carried out on a batch or a 
continuous basis. The time of reaction is substantially the same and is 
measured as "residence time," for either basis. The reduction reaction 
time, or residence time, is generally maintained at from about 0.5 to 
about 3 hours, and preferably 0.75 to about 1.75 hours. 
The reduced ore is next subjected to an aqueous leaching, utilizing an 
aqueous solution of an acidic ammonium salt. The divalent manganese value 
present in the reduced ore has been found to be selectively leached by 
this ammonium salt, substantially without leaching of the other metal 
values, specifically nickel, copper and cobalt. The ammonium salt in the 
leaching solution, it is believed, reacts with the divalent manganese 
oxide in the reduced ore to form the corresponding soluble salt of 
manganese and dissolved ammonia, or ammonium hydroxide. Although the scope 
of this invention is not to be limited thereto, it is believed that the 
leaching reaction proceeds in accordance with reaction equation 1, below, 
which utilizes ammonium sulfate as the example of the leaching ammonium 
salt: 
EQU MnO + H.sub.2 O + 2NH.sub.4.sup.+ + SO.sub.4.sup.= .fwdarw. Mn.sup.++ + 
SO.sub.4.sup.= + 2NH.sub.4 OH I. 
it has been found, surprisingly, that the reaction will proceed rapidly 
towards dissolution of the manganese metal value, even without the 
continuous evolution of free ammonia from the liquid. Although the 
leaching reaction does occur at substantially ambient temperatures, the 
first leaching step is preferably carried out at a temperature of at least 
about 75.degree. C., most preferably about 85.degree. C. up to just below 
the boiling point, and optimally in the range of from about 85.degree. C. 
to about 95.degree. C. It has been found that free ammonia is not evolved 
in any substantial quantities from the leach liquid unless the liquid is 
actually boiling, under the usual conditions of leaching. 
The leaching liquid should contain a substantially stoichiometric amount of 
the ammonium salt to react with the manganese oxide in accordance with the 
above equation. Though it is recognized that a stoichiometric quantity is 
optimum, it is also recognized that maintaining a precise stiochiometric 
relationship between the leaching liquid and the ore is difficult if not 
impossible on a practical basis. Accordingly, it has been found that 
preferably the leaching liquid contain plus or minus 20% by weight of the 
stoichiometric amount of the ammonium salt and optimally plus or minus 10% 
of the stoichiometric amount. By maintaining the ratio of the leaching 
ammonium salt and the manganese ore as close as possible to the 
stoichiometric proportions, the dissolution of the nickel, cobalt and 
copper values into this first leach solution is held down. By maintaining 
the proportion of the ammonium salt and the ore within at least 20% of the 
precise stoichiometric ratio, the solution of the other metal values is 
substantially avoided, and it is for this reason that the closer the ratio 
is to the stoichiometric quantities the more selective is the leaching in 
accordance with the present process for manganese value. The concentration 
of the ammonium salt in the leach liquid is not critical, though it is 
preferred that a too-low concentration be avoided in order to avoid the 
high cost of treating a relatively large volume of liquid in order to 
obtain a given amount of manganese solute and a too-high concentration of 
the ammonium salt would interfere with the leaching of the manganese 
value. 
The leaching liquid can be an aqueous solution of an ammonium salt which 
can react with manganese to form a soluble manganese salt. Generally 
useful such salts the the ammonium salts of anions selected from the group 
consisting of the halides, especially chloride, bromide and iodide, 
nitrate, and sulfate. The anions can be present alone or in combination, 
and other anions can be present as long as they do not form insoluble 
manganese salts. 
The leach solution containing the dissolved manganese salt is separated 
from the leached ore. The manganese salt solution can then be further 
treated so as to obtain the desired manganese metal. The leach liquid can 
contain in addition to the dissolved manganese most of that portion of the 
iron in the reduced ore which was reduced to a leachable state. The 
solution can be substantially free from nickel, cobalt and copper values, 
especially when the leaching was carried out under near stoichiometric 
conditions, as defined above. As pointed out above, however, the 
proportion of iron present in the leach solution, relative to the 
proportion of manganese, is sufficiently low such that a mixture of iron 
and manganese ultimately to be obtained from the leach liquid does provide 
a commercially valuable ferromanganese product. 
A solid manganese salt, generally admixed with an iron salt, can be 
obtained from the leach liquid by a variety of methods, including 
precipitation and crystalization. Manganese value can be caused to 
precipitate by merely oxidizing the manganese value in the solution or by 
sparging of the ammonia; for example, by merely aerating the solution, 
preferably at a temperature not greater than about 75.degree. C., and as 
low as room temperature, manganese and iron are oxidized and the ammonia 
sparged, resulting in a precipitate of the desired manganese and iron 
oxides, or hydroxides. The oxidation results in the formation of an 
insoluble, higher valence manganese compound and ferric hydroxide, or the 
oxyhydroxides. This method of recovering the manganese and iron values 
also results in a regeneration of the leaching liquid to form the 
corresponding ammonium salt; following separation of the manganese and 
iron precipitate from the aqueous solution, the aqueous solution can then 
be recycled for further use as a leaching liquid on fresh ore. 
Alternatively, the manganese and iron values can be precipitated 
utilizing, for example, an ammonium salt of an anion which forms a 
water-insoluble salt of manganese, for example, ammonium carbonate or 
ammonium phosphate. Salts other than the ammonium salts of these 
insolublizing anions can be utilized, such as, for example, the sodium 
salts. However, the ammonium salts are preferred as it avoids the 
introduction of undesirable additional cations. 
The manganese, as well as the iron, precipitate can be separated from the 
regenerated ammonium leach solution by any conventional methods, 
including, for example, filtration. The separated precipitate can then be 
dried and preferably decomposed to the oxides at elevated temperatures by 
known means. 
Oxidation of the manganese and iron can be carried out in addition to the 
simple aeration methods by utilizing a halogen, for example, elemental 
chlorine or bromine, as well as other strong oxidizing agents, for 
example, a permanganate. 
The solid leached ore from the first leaching step can then be releached in 
accordance with the present invention utilizing as the releaching solution 
an ammoniated ammonium salt solution. It has been found, when carrying out 
this procedure, that the leached ore should be permitted to be at least 
partially reoxidized in order to improve the dissolution of the metal 
values of nickel, copper and cobalt. It has been found to be sufficient to 
merely permit the leached ore to contact the atmosphere and, further, to 
aerate the releach solution before separation from the remaining solid 
residue to ensure that all of the metal values have been reoxidized to 
their soluble state. 
The releaching solution can be an aqueous solution of ammonium hydroxide 
and an ammonium salt. The mechanism for the leaching of the nickel, copper 
and cobalt is believed to be similar in each case and to result in the 
formation of a soluble ammoniated metal complex of each of the aforesaid 
metal values in the solution. The ammonium salt can contain any anion 
which forms a water-soluble compound with the ammoniated metal complex. 
Suitable ammonium salts include the halides, especially chloride, bromide 
and iodide, nitrate, sulfate, and, preferably, the carbonate. The 
ammoniated metal carbonate salts are water-soluble, although the 
corresponding simple carbonate salts may not be water-soluble. Without 
limiting the scope of this invention, it is believed that the leaching 
reaction proceeds in accordance with the mechanism set forth in the 
reaction equation II, utilizing nickel and ammonium carbonate as examples: 
EQU NiO + H.sub.2 O +2NH.sub.4.sup.+ + CO.sub.3.sup.= + yNH.sub.3 
.fwdarw.Ni(NH.sub.3).sub.y.sup.++ + CO.sub.3.sup.= + 2NH.sub.4 OH II 
preferably, the ammonium salt is present in at least a substantially 
stoichiometric amount to react with and dissolve all of the remaining 
metal values in the ore. Generally, the ore contains small amounts of 
metal values other than nickel, cobalt, and copper, as described above, 
including, for example, molybdenum, which would also be dissolved in 
accordance with the present leaching reaction. However, the amounts of 
such materials are relatively small, and a small excess of the 
stoichiometric amount required to dissolve the nickel, copper and cobalt 
is sufficient to dissolve all those materials. The concentration of the 
ammonium salt in the releaching solution is preferably not less than about 
0.25 Normal. 
The quantity of ammonia dissolved in the releaching solution is limited by 
that amount needed to cause the solution of the desired metal values, and 
especially nickel, copper and cobalt. The precise ammonia/metal complex 
which is formed with each of the metal values is not definitely known. 
Without seeking to limit the scope of this invention, the mols of ammonia 
per gram-atom of metal dissolved in the releaching solution is believed to 
be in the range of from about 3 to about 5. It has been found that the 
concentration of the releaching liquid should be at least about 0.5 molar 
ammonia and generally greater than about 10 molar has been found to be 
unnecessary, and may even be undesirable in resulting in dissolution of 
unwanted manganese in the solution. Similarly, the maximum amount of the 
ammonium salt is not critical, but generally greater than about 3.3 
mols/liter of the ammonium salt has been found to be unnecessary and 
therefore undesirable. 
The releach solution is a relatively pure solution of the three valuable 
metal values from the ore i.e., nickel, cobalt and copper, together with a 
relatively smaller proportion of other valuable metal values, including 
for example, chromium, vanadium and molybdenum. The relatively pure 
solution of the nickel, cobalt and copper salts can then be treated in a 
variety of ways to obtain the individual metal values in a pure state. 
One preferred method of separating the individual nickel, cobalt and copper 
values from the solution is by liquidion exchange procedures. One such 
liquidion exchange procedure for separating nickel from cobalt, is shown, 
for example, in U.S. Pat. No. 3,276,863. This procedure is especially 
effective when the ammonium salt is the carbonate. 
In one example of such a procedure, an ammoniacal solution of nickel, 
cobalt and copper is initially aerated to ensure that all of the cobalt 
has been oxidized to the trivalent state. This can generally be 
accomplished for example, by passing air through the solution, especially 
at elevated temperatures. The solution is then contacted with a 
water-insoluble organic solution of a liquid ion exchange agent, such as 
an alpha-hydroxy oxime, or a 7-hydrocarbon-substituted-8-hydroxyquinoline. 
The copper values are first selectively extracted into the organic 
solution so that when the organic and aqueous solutions are separated, the 
first aqueous raffinate comprises a solution of nickel and cobalt salt, 
substantially free of copper salt, and the organic solution contains 
copper, substantially free of nickel and cobalt value. The cobalt and 
nickel can be subsequently separated by extracting the nickel from the 
first raffinate, using the same extraction agent to form a second aqueous 
raffinate containing the cobalt value, substantially free from copper 
value, and an organic phase comprising the nickel value. The two organic 
phases can be stripped utilizing a weak acid solution. A more complete 
exposition of the various extraction agents utilized for separating the 
copper and nickel from cobalt is shown, for example, in U.S. Pat. No. 
3,894,139, which can be utilized in the present procedure.

In the drawings, and in the following description of the processes, the 
elements of the apparatus and the general features of the procedure are 
shown and described in highly simplified form, and generally in an 
essentially symbolic manner. Appropriate structural details and parameters 
for actual operation are readily known and understood by those skilled in 
the art and are not set forth in the description or the drawings, but are 
included in the specific examples set forth below. Generally, all process 
vessels and fluid conduits can be of conventional construction and 
materials suitable for the particular reagents and products to be 
contained in accordance with the present process. 
Referring to FIG. 1, manganese nodule ore is crushed and dried, then ground 
to a particle size preferably not greater than about 20 mesh and optimally 
not greater than about 50 mesh, U.S. sieve sizes. The dried ore particles 
are then treated with a reducing agent, for example a solid 
carbon-containing material, such as coke or coal, or a gaseous material, 
such as carbon monoxide, hydrogen, or a mixture thereof, at a temperature 
of at least about 350.degree. C., in order to reduce the tetravalent 
manganese to divalent manganese and to reduce the cobalt, copper and 
nickel values present in the ore. The reduction is carried out until the 
ore is in a state at which substantially all of the aforesaid four metal 
values can be leached from the reduced ore utilizing first an ammonium 
salt solution followed by an ammoniated ammonium salt solution. The 
reduced nodules are removed from the reduction reactor and permitted to 
cool to below 100.degree. C., and then admixed with a first releaching 
solution comprising an aqueous solution of an ammonium salt. The leaching 
can be carried out in a single large tank reactor or in a plurality of 
smaller reactors. Both of these situations as well as any other method for 
contacting the leaching liquid with reduced nodule ore are encompassed 
within the portion indicated by the numeral 12. The solid, separated from 
the pregnant leach liquid, is passed via conduit means 13 to the releach 
stage 16. The pregnant leach liquid passes via conduit 15 to a manganese 
recovery system 18, where oxygen is passed through the liquid, for example 
by the bubbling of air through the solution in a tank, so as to form an 
oxidic precipitate of the manganese and iron values. 
The oxidic manganese and iron precipitate is separated, as by filtration, 
from the liquid and is removed via conduit means 19. The leach liquid, 
which is regenerated by the precipitation of the manganese to 
substantially its original concentration of ammonium salt, is recycled via 
conduit 21 back to the leach stage 12. 
It has been recognized that the manganese nodule ore contains a variety of 
soluble metal values, especially including the alkali and alkaline earth 
metals, such as sodium, potassium, and magnesium. In order to prevent the 
build-up of such materials in the leaching liquid, a minor portion of the 
leaching liquid passing through the recycle conduit 21 is bled-off through 
bleed stream 23 and passed to a salt removal stage 20, wherein the bleed 
stream is evaporated and the salts therein crystalized. The crystalized 
salts are continued to be heated until the ammonium salt is decomposed and 
passes off overhead through an ammonium salt conduit 25 from which it is 
condensed and remixed into the recycle conduit 21. As needed, additional 
makeup ammonium salt can be fed into the recycle stream 21. 
The leached reduced ore residue passing through conduit means 13 into 
releach stage 16 is contacted with the releach solution comprising the 
ammoniated aqueous solution of the ammonium salt. The contact between the 
ore solids and the releaching solution can be in a single tank stage or 
can be countercurrently in a series of contact stages. In any event, air, 
or other oxygen-containing oxidizing gas is passed through the releaching 
solution while it is in contact with the ore solids in order to ensure 
that substantially all of the nickel, cobalt and copper in the ore solids 
have been oxidized to the soluble valence level. In a multistage contact 
procedure, the air can be passed into the solution only in the last or the 
last several stages, if desired. The ore residue is again separated from 
the releach solution and can be discarded. The releach solution is passed 
from the releaching stage through conduit 29. 
The releach liquid in the nickel, cobalt, copper recovery stage 32 is then 
treated, for example, by liquid ion exchange extraction, so as to remove 
the nickel, copper and cobalt values from the releach liquid, thus 
regenerating the ammonium salt which is passed through recycle stream 35 
and re-used in the releaching stage 16. As required, make-up ammonia 37 
and make-up CO.sub.2 39 can be added to the recycle stream 35, as 
required. 
The nickel, copper and cobalt can be separated from the releach liquid in 
their recovery stage 32, by the liquid ion exchange extraction procedures 
described above, wherein the nickel and copper are selectively extracted 
utilizing one of the aforesaid liquid ion exchange reagents, leaving the 
releach liquid containing the cobalt value, which can then be removed by, 
for example, sulfide precipitation, regenerating the substantially pure 
ammonium salt/ammonia releaching liquid. The separated nickel salts, 
copper salts and cobalt salts can then be further treated as desired, to, 
for example, form the pure metals. 
In the example shown, the initial leach stage 12 utilizes an ammonium 
chloride leaching solution and the releaching stage 16 utilizes an 
ammonium carbonate/ammonia releaching solution. 
Referring to FIG. 2, a system is described therein wherein the same 
ammonium salt is recycled throughout the entire system and utilized for 
both the leaching solution and the releaching solution. 
The nodule ore is ground, dried, and reduced in the same manner as 
described with regard to FIG. 1, before being placed into contact with the 
leaching solution in leaching stage 112, wherein the leaching solution 
comprises ammonium sulfate. After completion of the leaching, the pregnant 
leach solution is separated from the first reduced ore leach residue, the 
solution being passed through the manganese recovery conduit 115 to the 
manganese recovery system 118 where it is aerated to cause the 
precipitation of manganese and iron hydroxides which are then separated 
and the reconstituted ammonium salt solution passed out through the 
releaching liquid line 117. The ammonium salt solution is passed through 
the releaching line 117 to the releaching stage 116, where it is admixed 
once again with the leached reduced ore solid residue and ammonia. 
Alternatively, the ammonium sulfate solution can be premixed with ammonia 
prior to introduction into the releaching stage 116. 
Upon completion of the releaching, the pregnant releach liquid is separated 
from the solid ore residue which can then be discarded via residue line 
109 and the releach liquid passed through the releach conduit 129 to the 
nickel, copper, cobalt recovery stage 132 where it is treated, for 
example, in the manner set forth above with regard to FIG. 1 to remove the 
nickel, copper and cobalt values in the form of salts and the thus 
regenerated ammonium salt/ammonia solution is then passed through the 
recovery conduit 133 to an ammonia recovery stage 136 where it is boiled 
to remove substantially all of the ammonia through overhead ammonia 
recycle conduit 131. The ammonia overhead from the NH.sub.3 removal stage 
136, as well as any additionally needed make-up ammonia, is passed into 
the ammonia recycle line 131 and then to the releaching stage 116 for 
remixture with the releaching solution. The deammoniated ammonium salt 
solution is passed from the ammonia recovery stage 136 and recycled to the 
leaching stage 112 via recycle conduit 137. Additional make-up ammonium 
salt can be added to the recycle conduit 137 as needed to replenish the 
ammonium salt prior to leaching. 
As explained above, with regard to FIG. 1, a bleed-stream 123 removes a 
minor proportion of the reconstituted ammonium salt solution from the 
manganese recovery stage 118. The bleed stream is evaporated and any 
ammonium salt present therein decomposed and passed overhead back to the 
recycle stream 137 through overhead conduit 121. 
Now, referring to FIG. 3, an alternative manganese recovery system is shown 
wherein the manganese value is precipitated as manganese carbonate. Carbon 
dioxide is passed into the manganese-rich pregnant leach solution in the 
manganese recovery stage 218 so as to cause the precipitation of 
substantially all of the manganese value as manganese carbonate. The 
reconstituted ammonium salt solution, e.g., ammonium sulfate, is separated 
from the precipitate and recycled to the leaching stage, as in FIG. 1, or 
passed to the releaching stage, as in FIG. 2. The solid manganese 
carbonate is decomposed in a kiln 201 to manganese oxide and carbon 
dioxide, which is then recycled back to the manganese recovery stage 218. 
The manganese carbonate precipitate is generally initially dehydrated to 
form the anhydrous salt which is then decomposed in a manner well known to 
the art to form manganese oxide dioxide. 
The following examples include preferred embodiments of the procedures 
carried out in accordance with the process of the present invention. The 
various process steps set forth in the following working examples, and in 
the aforedescribed drawings, are intended to be merely exemplary of the 
present invention and do not limit the scope thereof, which encompasses 
procedures as broadly defined above and all equivalents thereof. 
EXAMPLE 1 
A sample of an ocean floor nodule ore (containing 15.2% manganese, 10.2% 
iron, 0.54% nickel, 0.28% cobalt, and 0.09% copper, having been ground to 
a particle size of not greater than about 100 mesh U.S. sieve scale, i.e. 
50 grams of the ore, is placed into a 2.5" Vycor tube and placed into a 
furnace. The tube and the contents are initially purged with nitrogen at a 
rate of 150cc/minute while the furnace is being heated to a temperature of 
about 450.degree. C. When the operating temperature is reached, the 
nitrogen purge is closed off and the kiln was manually rotated 180.degree. 
and back every five minutes while 300ml/minute of a dilute carbon monoxide 
(50 volume % CO and 50 volume % N.sub.2) were injected into the kiln for a 
total time of 75 minutes. 
Following completion of the reduction reaction, the reduced ore was cooled 
and discharged into a 200 milliliter centrifuge bottle containing 175ml 
ammonium carbamate solution (260 grams/liter NH.sub.3 - 150 grams/liter 
CO.sub.2), stoppered and rotated for 1 hour at 25.degree. C. Following 
subsequent centrifugation, the supernatant liquid was quickly decanted 
into a sample bottle which was then capped. The remaining solids were then 
admixed with 150 milliliters of additional fresh ammonium carbamate 
solution, rotated for an additional hour at 25.degree. C., centrifuged and 
the supernatant liquid decanted. The two supernatant liquids were combined 
and the combined solution analyzed for dissolved metal values. 
A second sample of the dried and ground ore, but without reduction, is 
treated with the ammonium carbamate solutions in the same manner as 
described above. The ammonium carbamate solutions are combined and 
analyzed for dissolved metal values. 
The combined liquid solution obtained from the reduced ore material 
contained the following percentages of the metal values present in the 
leached ore: manganese - 78.3% by weight, iron - 78% by weight, nickel - 
92.2% by weight, and cobalt - 81% by weight. The supernatant leached 
liquid obtained from the non-reduced ore was found to contain 
substantially no metal values, other than the undesirable alkali and 
alkaline earth metals. Accordingly, it has been shown that the reduction 
of the ore is necessary before any substantial leaching of the metal 
values can be obtained utilizing an ammoniated leach solution. 
EXAMPLE 2 
A further sample, 50 grams, of the ground ore of Example 1 was reduced in a 
hydrogen gas atmosphere for a period of sixty minutes at 560.degree. C. 
The reduced ground ore was cooled and admixed with 250 milliliters of an 
ammonium sulfate solution (215 g/liter) in a centrifuge bottle which was 
then rotated for one hour at a temperature of between 86 and 90.degree. C. 
The solution was then centrifuged and the supernatant liquid quickly 
decanted into a sample bottle and capped. The decanted liquid was then 
analyzed for metal values, and it was found that the following percentages 
of the total metal values present in the nodule ore were leached into the 
ammonium sulfate solution: 70% manganese, 17% nickel, 8% cobalt, less than 
5% copper, and 4% iron. A second leaching of the leached ore residue with 
fresh ammonium sulfate solution results in the extraction of substantially 
the remaining quantity of manganese without any substantial further 
leaching, or extraction, of the remaining metal values. 
Upon passing air through the leach solution, at substantially room 
temperature, an oxidic precipitate of substantially all of the manganese 
value, as manganese oxide, was formed, which can be readily separated from 
the remaining aqueous solution. Upon reanalysis of the remaining aqueous 
solution, it was found that substantially all of the dissolved iron was 
precipitated out, together with the manganese and separated from the 
aqueous solution, probably as ferric hydroxide. 
The leached ore subsequent to the leaching with ammonium sulfate, was next 
contacted with 250 milliliters of releaching solution solution containing 
267 grams per liter of ammonia and 163 grams per liter of CO.sub.2 
(ammonium carbamate and hydroxide), at from 25 - 30.degree. C. The contact 
was again made in a single stage centrifuge bottle and the bottle rotated 
for 60 minutes. The mixture of reduced ore and aqueous leach solution was 
then centrifuged and the supernatant liquid decanted into a sample bottle. 
The releach solution is analyzed for the remaining metal values and the 
following percentages of the metal values in the reduced ore were found to 
have been dissolved into the pregnant releach solution: 50% nickel, 40% 
cobalt, and 60% iron. 
EXAMPLE 3 
An ammoniacal carbonate solution, of the type obtained by the leaching of a 
reduced manganese nodule ore, was prepared by forming a leaching solution 
by admixing 150 ml. concentrated NH.sub.4 OH to give a total volume of 250 
ml. This dilute ammonium hydroxide solution was mixed with 250 grams of 
ammonium carbonate, and the resulting solution contacted with a mixture of 
copper, nickel and cobalt metals to give a solution containing 7500ppm 
copper, 6250ppm nickel and 600ppm cobalt. The solution after the leaching 
had a pH of 9.4. The solution was next subjected to liquid ion exchange in 
accordance with this process to obtain a separation of the three metal 
values. 
The liquid ion exchange solution was an organic, water-insoluble solution 
comprising 5% by volume of a 7-hydrocarbon-substituted-8-hydroxyquinoline 
(Kelex 100), 5% isodecanol and 90% aromatic hydrocarbon solvent (Napoleum 
470). 
The leach solution prepared above was contacted with an equal volume of the 
above-described organic liquid ion exchange solution in a mixing vessel. 
The mixed liquids were then permitted to settle and the upper, organic 
layer decanted. The lower aqueous solution, raffinate, was then contacted 
with a second equal volume of fresh liquid ion exchange solution according 
to the same procedure as above and again the organic and aqueous layers 
were separated. A third contact, with fresh, organic, liquid ion exchange 
solution, was made with the aqueous raffinate from the second contact. The 
aqueous raffinate after each of the three contacts were analyzed and the 
amounts of copper, nickel and cobalt values remaining therein were 
determined and are set forth in the following table: 
Table 1 
______________________________________ 
Copper Nickel Cobalt 
(ppm) (ppm) (ppm) 
______________________________________ 
Feed solution 7,500 6,250 600 
After 1st Contact 
4,000 6,000 600 
After 2nd Contact 
900 5,850 600 
After 3rd Contact 
0 3,250 600 
______________________________________ 
As shown from the above table, the copper can first be readily separated 
from the nickel and cobalt, and in a subsequent series of contacts nickel 
can be readily separated from the cobalt leaving the cobalt substantially 
undisturbed in the aqueous final raffinate. The nickel can be stripped 
from the organic liquid ion exchange solution by a weak acid solution, for 
example having a pH of about 2.