Selective flotation of cubanite and chalcopyrite from copper/nickel mineralized rock

A process for beneficiating a finely ground ore containing sulfide minerals of copper and nickel by selective flotation to produce a copper concentrate and a copper-nickel concentrate comprises pulping the ore with water to form a slurry, conditioning the slurry with an aqueous solution of SO.sub.2 (H.sub.2 SO.sub.3) equivalent to from about 2 to about 4.5 pounds of SO.sub.2 per ton of dry ore for a time sufficiently long to maximize depression of the nickel minerals while maximizing activation of the copper minerals, wherein the conditioned slurry contains about 30 wt. % to about 35 wt. % solids, adding a collector and a frother to the conditioned slurry, subjecting the conditioned material to a rougher flotation stage to produce a rougher copper concentrate and a rougher tailings, conditioning the rougher tailings with additional collector and with Ca(OH).sub.2 to activate unfloated nickel and copper minerals and subjecting the conditioned rougher tailings to froth flotation to produce a rougher copper-nickel concentrate. After regrinding, the rougher copper concentrate is conditioned with H.sub.2 SO.sub.3, and subjected to one or more cleaner flotation stages to recover a final concentrate containing at least about 80% of the copper and less than about 5% of the nickel in the feed material.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to the beneficiation of sulfide ores of copper and 
nickel. More specifically, it relates to the selective flotation of copper 
and nickel minerals. A process has been discovered which permits the 
separate recovery of copper and nickel concentrates from such ores. Thus, 
the invention is useful where it is sought to process nickel- and 
copper-containing ore to recover separately a copper concentrate and a 
nickel concentrate. 
The invention is particularly useful, for instance, in beneficiating ore 
that is found in the copper-nickel mineralization of the Duluth Complex 
orebody in northeastern Minnesota. This copper-nickel ore has resisted 
previous attempts to design a flotation process to recover a copper 
concentrate low in nickel. 
2. Description of the Prior Art 
A brief discussion of the Duluth Complex copper-nickel mineralization 
appears in Engineering & Mining Journal, Vol. 177, April 1976, at pages 
80-83, together with a flowsheet for bulk treatment of the ore to achieve 
a rough separation of the copper and nickel minerals from gangue material. 
The discussion of the flowsheet does not suggest the selective flotation 
of the copper and nickel minerals using the sulfurous acid conditioning 
stage of the process in accordance with the present invention. Treatment 
of ore samples with the process from the disclosed flowsheet (with one 
rougher flotation stage and three cleaner flotation stages) produced bulk 
concentrates having copper contents of about 12%, corresponding to copper 
recoveries on the order of 85%, and nickel contents of about 2.5%, 
corresponding to nickel recoveries of about 68%. 
The Duluth gabbro is also discussed in Transactions, Soc. of Mining 
Engineers, AIME, Vol. 241, December, 1968, at pages 421-431. This article 
discloses a flowsheet for bulk sulfide flotation followed by separation of 
copper minerals from nickel minerals, using traditional conditioning 
agents such as lime/cyanide and lime/British gum. In some runs the pH is 
optionally adjusted to about 6 with sulfuric acid. There is no disclosure 
or suggestion of conditioning the ore in aqueous sulfurous acid, as is 
evident from the results reported which show only mediocre recovery of 
copper in the final copper concentrate. 
There are earlier processes in which mixtures of sulfidic copper and iron 
minerals are conditioned prior to flotation with sulfite derivatives, to 
promote the copper sulfides and depress the iron sulfides. Specifically, 
U.S. Pat. No. 1,397,703 discloses using a "non-alkaline electrolyte", such 
as a solution of sodium sulfite, and U.S. Pat. No. 1,678,259 discloses 
using an acid sulfite or sulfurous acid. Neither patent discloses whether 
nickel minerals were possibly included with the minerals under treatment, 
and the patents thus do not indicate or suggest the effect, if any, of the 
disclosed processes on nickel minerals. In addition, the statement on page 
2, lines 41-44 of U.S. Pat. No. 1,678,259 that solutions of sulfur dioxide 
in water (i.e. sulfurous acid) are unstable and difficult to handle 
suggests to one skilled in this art not to include a sulfurous acid 
conditioning step in a continuous process for the separation of nickel 
sulfide minerals from mixtures with copper sulfide minerals. 
Published South African Patent Application No. 71/1887, filed Mar. 23, 
1971, relates to the froth flotation of copper sulfide minerals from ore 
that also contains carbonates, such as Ca(Mg)CO.sub.3, and magnetite, 
Fe.sub.3 O.sub.4. The application discloses that sulfurous acid added to 
the copper flotation circuit underflow, which is rich in the carbonate 
minerals and contains minor residual amounts of unfloated copper sulfide 
minerals, reacts with the carbonates to form bisulfite compounds such as 
Ca(Mg)(HSO.sub.3).sub.2 which activate the residual copper sulfides for 
recovery in a subsequent flotation stage. The sulfurous acid can also lead 
to precipitation of calcium and magnesium compounds. There is no 
disclosure of what, if any, nickel minerals are present in the ore under 
treatment or in the underflow which is treated with the sulfurous aicd, 
and thus there is no suggestion of the presently claimed discovery that 
conditioning a pulped copper-nickel ore in sulfurous acid can selectively 
activate the copper minerals and depress the nickel minerals. In addition, 
the Duluth gabbro orebody with which the present invention has been found 
to be effective does not contain the large amounts of carbonate minerals 
present in the ore discussed in the South African application; indeed, the 
Duluth gabbro contains no carbonates, or no more than trace amounts which 
do not affect the activation of the copper minerals by the sulfurous acid, 
and the South African application does not suggest that sulfurous acid is 
an effective conditioning medium for ores that are substantially free from 
carbonates. 
SUMMARY OF THE INVENTION 
Stated generally, the invention comprises a process for selectively 
recovering a copper concentrate and a copper-nickel concentrate from 
finely ground ore containing sulfide minerals of copper and nickel and 
substantially free from carbonate minerals which comprises pulping the ore 
with water to provide a slurry, adding sulfurous acid to the slurry in an 
amount equivalent to between about 2 pounds and about 4.5 pounds of sulfur 
dioxide per ton of dry ore, wherein the slurry after the addition of the 
sulfurous acid has a solids content between about 25% and about 35% by 
weight, conditioning the slurry with the sulfurous acid sufficiently long 
to maximize depression of the nickel sulfide minerals while maximizing 
activation of the copper sulfide minerals, adding a collector and a 
frother to the conditioned slurry, subjecting the conditioned slurry to 
froth flotation to produce a froth containing a copper rougher concentrate 
and an underflow copper rougher tailing, conditioning the copper rougher 
tailing to activate unfloated copper and nickel minerals, adding 
additional frother and collector to the copper rougher tailing, and then 
subjecting the copper rougher tailing to froth flotation to produce a 
froth containing a copper-nickel rougher concentrate.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to FIG. 1, finely ground ore 1 including nickel and copper 
sulfides is slurried with water 2 at 3, and the slurry is conditioned at 4 
in aqueous sulfurous acid under conditions to be described below in 
greater detail. Appropriate amounts 5 of collector and frother are added, 
and the conditioned slurry is subjected to a copper rougher flotation 
stage 6 which produces a froth 7 containing a rougher copper concentrate, 
and an underflow stream 8. The rougher concentrate is classified at 9 to 
recover a stream 10 of finely divided material, and a stream 11 of 
oversize material which is reground at 12 and then recycled to the 
classifier 9. The resultant stream 10 is conditioned at 13 with additional 
sulfurous acid, and subjected to cleaner froth flotation stages with 
additions 14 as necessary of collector and frother. Two to four cleaning 
stages will normally be used, and three stages have been found preferable 
and are shown in FIG. 1 at 15-17. Underflow from the first two cleaner 
stages is recycled in stream 18 to conditioning stage 3. Underflow stream 
19 from the third cleaning stage 17 is recycled to conditioning stage 13. 
The froth 20 from third cleaning stage 17 is processed for recovery of 
metallic copper. 
Underflow stream 8 from copper rougher stage 6 is conditioned at 21 with 
lime, appropriate amounts 22 of collector and frother are added, and the 
stream is subjected to a copper-nickel rougher froth flotation stage 23. 
This stage produces a froth 24, containing nickel and copper values, which 
is classified at 25 to produce a stream 26 of finely divided copper-nickel 
concentrate and a stream 27 of oversize material which is reground at 28 
and then reclassified. The stream 26 is subjected to several cleaner 
flotation stages, preferably four in number as shown in FIG. 1 at 29-32. 
Additions 33 as needed of collector and frother are made to the 
copper-nickel cleaner stages. The underflow streams 34 and 35 from 
copper-nickel cleaner stages 29 and 30, respectively, are recycled to 
thickener 36 and the thickened stream is fed to nickel rougher 23. 
Underflow streams 37 and 38 from, respectively, third and fourth 
copper-nickel cleaning stages 31 and 32 are recycled to the feed to first 
cleaner stage 29. The froth 39 from the final copper-nickel cleaning stage 
is processed for recovery of metallic copper and nickel. 
The copper-nickel rougher stage 23 also produces an underflow stream which 
is subjected to a scavenger flotation stage 40, producing a froth 41 which 
is thickened in thickener 34 and recycled to the copper-nickel rougher 
stage 23, and a tailings stream 42 which is disposed of. 
The treatment of copper-nickel ore by selective flotation, including the 
sulfurous acid conditioning step described herein, has been found to be 
preferable to bulk flotation of such ore because the concentrates obtained 
through selective flotation are more amenable for proven subsequent 
smelting and refining techniques to produce pure metallic copper and 
nickel. 
The term "flotation" used herein will be understood to mean froth 
flotation. 
As indicated, the present invention is adapted to beneficiating ores 
containing sulfidic copper and nickel minerals, such as minerals of the 
type found in the Duluth Complex. The Duluth Complex orebody is a 
well-defined mineral zone in northeastern Minnesota. 
Feed material which may be beneficiated by the present invention possesses 
several characteristics which are believed to avoid the inefficacy of 
prior art techniques for separating the copper and nickel mineral values. 
Copper is present as cubanite (nominally, Cu.sub.2 S.Fe.sub.4 S.sub.5) and 
chalcopyrite (nominally, CuFeS.sub.2). Nickel is present as fine 
inclusions of pentlandite ((Ni,Fe)S) in pyrrhotite and in the host rock. 
The inclusions of pentlandite are so fine that some of the pentlandite may 
not be liberated from the pyrrhotite and the host rock even when the feed 
material is ground to the smallest sizes that could normally be treated by 
froth flotation. The pyrrhotite has a nominal composition of Fe.sub.n 
S.sub.(n+1), wherein n is between about 5 and about 16. The copper grade 
is typically from about 0.25% to about 3%; the nickel grade is typically 
from about 0.07% to about 0.55%. The present invention may advantageously 
be practiced to achieve high selectivity between copper and nickel in ores 
that are free from carbonate mineralization. 
Initially, in carrying out the invention the mineral-bearing material 
should be crushed and ground to a particle size sufficient to liberate 
most of the sulfide minerals from the host rock. Typically, the material 
should be brought to a size range of at least about 50% minus 200 mesh 
Tyler Screen Size (TSS). Reduction in particle size can be achieved 
through means quite familiar to those skilled in this art, e.g. staged 
crushing and grinding, and should be carried out to a degree which 
maximizes sulfide mineral liberation while minimizing sliming. 
The ground ore is then pulped with sufficient water to provide a slurry, 
containing from about 25% up to about 35% solids by weight, and preferably 
between about 30% and about 35% solids by weight, in order to minimize 
materials handling while maximizing sulfide mineral recovery. 
The slurried ore is then subjected to a conditioning step which constitutes 
one novel and important feature of the invention. The conditioning medium 
is an aqueous solution formed by dissolving sulfur dioxide in water, 
forming sulfurous acid (H.sub.2 SO.sub.3). It has been found that when 
sulfurous acid is added to the slurry to provide a selected ratio of 
sulfur dioxide to dry feed material, the copper minerals (cubanite and 
chalcopyrite) are promoted and the nickel minerals and gangue are suitably 
depressed to permit recovery in subsequent treatment stages of a product 
that represents a surprisingly high recovery of copper values and a 
surprisingly low retention of nickel values. This discovery permits the 
treatment of the copper-nickel ore to recover a concentrate having a 
surprisingly high copper:nickel ratio, together with a copper-nickel 
concentrate having similar amounts of copper and nickel. 
Conditioning the pulped ore in accordance with the present invention 
achieves superior copper recovery and nickel rejection compared to other 
conditioning steps, including those which involve adding sulfuric acid to 
a mineral pulp or which involve the bubbling or sparging of gaseous sulfur 
dioxide directly into a mineral pulp. 
The effectiveness of the conditioning step in achieving a high degree of 
separation between copper and nickel minerals is particularly unexpected 
because one skilled in this art would expect the sulfurous acid to promote 
the nickel sulfide-containing minerals together with the copper 
sulfide-containing minerals. To the contrary, though, it has been found 
that this conditioning step results in promotion of the copper sulfides 
and rejection of the nickel sulfidic material in subsequent flotation 
stages. This effect is observed throughout the range of particle sizes to 
which the feed material is reduced before it is subjected to flotation. 
The effectiveness of this conditioning step is also unexpected because it 
allows recovery of a concentrate having very satisfactory copper content, 
with relatively low nickel retention, as mentioned above, without 
requiring introduction of lime, cyanide, or other conditioning agents to 
the flotation circuit. Omitting these other conditioning agents offers 
relief from both the additional costs and the environmental and safety 
risks that these agents present. As will be seen below, the invention 
including the sulfurous acid conditioning step possesses the additional 
feature that it utilizes smaller amounts of collector in the rougher and 
cleaner flotation stages than would customarily be expected. This feature 
presents additional economical advantages in operation. 
The pulped ore solids are placed in a conditioning tank. The sulfurous acid 
solution is then added to the pulp at a ratio which should correspond to 
from about 2 to about 4.5 pounds of sulfur dioxide per ton of dry feed 
material. A preferred ratio is from about 2 to about 3.5 pounds of sulfur 
dioxide per ton of dry feed. Examples of particular ratios of SO.sub.2 to 
feed material are given below. The slurry after addition of the sulfurous 
acid should have a pulp density between about 30% and about 35% solids by 
weight, and preferably between about 33% and about 35% solids, to permit 
satisfactory conditioning of the pulp and be amenable to the subsequent 
rougher and cleaner flotation stages. The density can be adjusted by 
suitable additions of water or feed material to a satisfactory value which 
one skilled in the art can readily ascertain. 
Conditioning is achieved by agitating the pulp in a tank equipped with 
suitable agitator, such as motor-driven impeller, to provide good 
solid-liquid contact between the finely divided ore and the sulfurous 
acid. The pulp is conditioned sufficiently long to maximize depression of 
the nickel minerals while maximizing activation of the copper minerals. 
Conditioning time will vary from ore to ore but it has been found that for 
the ores tested conditioning times between about 5 minutes and about 10 
minutes, preferably about 6 to about 8 minutes, will provide maximum 
depression of the nickel minerals. The pH of the conditioned slurry should 
be between about 5 and about 6.5, and preferably between about 5.5 and 
about 6. 
It is important to minimize aeration of the pulp during conditioning. 
Excess air will cause unwanted oxidation of the mineral surfaces, 
destroying the selectivity between copper and nickel minerals that is 
afforded by conditioning the ore in sulfurous acid. 
Following the conditioning, the pulp is subjected to a copper rougher 
flotation stage, to recover most of the copper values in the froth 
(concentrate) while rejecting significant quantities of nickel and iron 
values and gangue in the underflow. A collector and a frother are added to 
the conditioned pulp for this flotation. The particular compounds to be 
used as collector and frother can be readily selected by one familiar with 
the flotation separation of copper from nickel minerals. In general, 
dithiophosphate collectors may be used, such as sodium dithiophosphate, or 
proprietary dithiophosphates such as Reagent R-208, sold by American 
Cyanamid Co. Another suitable collector is Reagent Z-200, sold by Dow 
Chemical Co., which has a proprietary formula but is known not to be a 
dithiophosphate. Examples of suitable frothers include methyl isobutyl 
carbinol (MIBC), triethoxy-butane (TEB), and cresylic acid. 
Satisfactory separation between copper and nickel minerals can be achieved 
in the copper rougher stage when the amount of collector used is between 
about 0.01 and about 0.1 pound per ton of dry ore fed. The amount of 
collector used is important in that amounts higher than this range can 
carry too much nickel into the concentrate and impair the separation. The 
preferred range of collector additions is between about 0.040 and about 
0.055 pounds per ton of dry ore. The collector is added to the conditioned 
pulp prior to flotation. 
The amount of frother added to the pulp for the copper rougher flotation is 
dependent on the desired froth characteristics, and can be selected with 
ease by one skilled in this art. A typical range of frother addition is 
about 0.04 to about 0.1 pound of MIBC per ton of dry ore. Incorporation of 
the conditioning stage in accordance with the present invention in place 
of other conditioning methods improves froth characteristics. 
The recoveries and separation in the copper rougher flotation are also 
sensitive to the length of time for which the flotation is carried out. 
Too short a run lowers the copper recovery, while too long a run can bring 
excessive nickel and iron minerals into the copper rougher concentrate. 
Rougher flotation times required to provide the selective flotation of the 
copper minerals from the nickel minerals are dependent upon the nature of 
the ore being treated, but rougher flotation times between about 5 minutes 
and 30 minutes generally provide acceptable levels of selectivity. 
Preferred flotation times are in the range of about 12 to about 18 
minutes; one skilled in this art can readily determine the length of time 
needed to achieve a particular recovery from a given quantity of feed 
material. 
If a mineral pulp of the type described previously is subjected to 
conditioning and rougher flotation under the conditions given herein, the 
copper rougher concentrate produced will have a copper content of at least 
about 7%, and a copper recovery of at least about 80% to about 95%. 
Preferably, the copper content of the rougher concentrate will be at least 
about 8.5%, and the recovery will fall above about 85%, and more 
preferably at least about 90%. 
At the same time, the nickel content of the copper rougher concentrate will 
be typically less than about 1%, and represent a nickel retention of less 
than about 40% and typically under about 30%. It is preferred that the 
nickel content be under about 0.50%, and that the nickel content represent 
a retention of less than about 30%. 
The copper and nickel contents of the froth and underflow streams from the 
copper rougher will, of course, depend on the grade of the feed ore. For a 
feed grade assaying 0.53% Cu and 0.13% Ni, for instance, the copper 
rougher flotation stage produces an underflow stream which has a nickel 
content of at least about 0.10%, and preferably at least about 0.12%. The 
copper content is between about 0.09% and about 0.12%, and advantageously 
is between about 0.10% and about 0.11%. The corresponding rejection of 
nickel to the underflow from the copper rougher stage is at least about 
60%, and preferably at least about 70%. The copper rejection, i.e. the 
copper values that are not carried into the froth of the copper rougher, 
should be from about 5% to about 20%, and advantageously are between about 
10% and about 15%. Typically, about 8% to about 25% of the solids fed to 
the copper rougher leave it in the froth, while about 75% to about 92% are 
carried in the underflow. The subsequent treatment of the underflow stream 
will be discussed below. 
The copper rougher concentrate should be processed further, to improve the 
copper grade and reduce the nickel content of the concentrate. Several 
cleaner flotation stages can be employed to improve the copper grade to a 
very satisfactory level without unduly reducing the overall copper 
recovery of the system, while rejecting additional amounts of nickel. 
The copper rougher concentrate should first be treated to reduce the 
particle size to at least about 50%, and preferably at least about 85%, 
minus 400 mesh TSS. Although the entire copper rougher concentrate can be 
comminuted to the required particle size, the overall efficiency of the 
cleaning operation is enhanced by classifying the copper rougher 
concentrate and comminuting only the oversized material to the requisite 
particle size. The copper rougher concentrate can be classified by 
well-known means, such as hydrocyclones. The particles larger than desired 
are reground to the proper size, and are recombined with the remaining 
fraction. The copper rougher concentrate is then fed to a second sulfurous 
acid cleaner conditioning stage. 
This conditioning step is similar to the conditioning step that precedes 
the rougher flotation. A pulp is formed by adding the copper rougher 
concentrate to an aqueous solution of sulfur dioxide (i.e. H.sub.2 
SO.sub.3), at a ratio equivalent to about 1 pound of sulfur dioxide per 
ton of dry feed material introduced to the rougher circuit. The density of 
this pulp is adjusted to between about 10% and 25% solids by weight, 
preferably between about 18% and about 24% solids by weight, and the pulp 
is preferably conditioned for about 3 up to about 10 minutes, preferably 
about 8 to about 10 minutes. 
The conditioned pulp, containing the copper rougher concentrate and 
recycled tailings from subsequent cleaning steps as described below, is 
then subjected to copper cleaner flotation stages. As is the case for the 
copper rougher flotation, the amounts of frother and collector added to 
the pulp, and the duration of the cleaner flotation stage, are determined 
with a view to the degree of separation required or desired, and these 
factors are readily identified by one skilled in this art. One may find 
that additions of collector and/or frother are not necessary, if 
sufficient quantities of the reagents have been carried along with the 
concentrate from the preceding copper rougher flotation. Thus, the 
appropriate amounts to add to the first copper cleaner stage are 0 to 
about 0.005 pounds of collector, and 0 to about 0.025 pounds of frother, 
per ton of new dry copper rougher circuit feed. The duration of the first 
copper cleaner flotation is about 10 to about 12 minutes. The pH is 
between about 5 and about 6.5, and preferably about 5.4 to about 5.7. 
The concentrate produced in the first copper cleaner flotation stage 
typically has a copper content of at least about 13%. The corresponding 
copper recovery from the cleaner feed (including recycled tails) is at 
about 60%. The cleaner concentrate also contains nickel, but the nickel 
content has been reduced to below about 1%, and preferably less than about 
0.5%. This corresponds to a nickel rejection of about 75%, based on the 
feed to the rougher circuit. The tailings from the first copper cleaner 
flotation are recycled to the conditioning step that precedes the copper 
rougher flotation. 
The concentrate from the first copper cleaner flotation is subjected to one 
and, more preferably, two additional copper cleaner flotation stages. In 
each, the requirements for collector and frother can be readily 
determined; also, the length of time during which the flotation is carried 
out to obtain a highly satisfactory copper content and recovery can be 
identified without great effort. Of course, the concentrate from the 
second copper cleaner flotation is fed to the third copper cleaner 
flotation stage. The tailings from the second copper cleaner should be 
recycled to the conditioning stage which precedes the copper rougher 
flotation stage. The tailings from the third copper cleaner may be 
recycled to the feed to the first copper cleaner flotation stage. 
From 0 to about 0.014 pounds of collector, and 0 to about 0.065 pounds of 
frother, per ton of new dry copper rougher feed, should be added to the 
second copper cleaner stage, and flotation should last from about 9 to 11 
minutes. In the third copper cleaner stage reagent additions are generally 
not required, but, if needed, additions will be of the same order of 
magnitude as additions to the second cleaner. Flotation in the third 
cleaner is carried out for between about 8 and about 10 minutes. The pH in 
the second copper cleaner stage should be between about 5 and about 6.6, 
preferably about 5.6 to about 5.8, and the pH in the third copper cleaner 
stage should be about 5.5 to about 7.0. 
In the concentrate from the third copper cleaner stage, the overall copper 
recovery from the new rougher feed is typically at least about 75%, 
preferably above about 80%, and can exceed about 85%. In this product, the 
nickel rejection is typically at least about 90%, and can be over about 
95%. 
The content of copper and nickel in the second copper concentrate is 
typically about 15% to about 19% copper, and from about 0.45% to about 
0.3% nickel, preferably from about 0.35% to about 0.34%. Typical copper 
content of the third copper cleaner concentrate will be from about 17% to 
about 25%. The nickel content of the third copper cleaner concentrate will 
be about 0.8% or under, typically less than about 0.32% to under about 
0.25%. Recovery of the metals into this concentrate is about 75-85% of the 
copper present in the crude ore and about 3% to about 6% of the nickel 
present in the crude ore. 
The product, concentrated in copper, which results from the copper cleaner 
stages is suitable for treatment by known methods to recover metallic 
copper. 
The underflow stream from the copper rougher flotation stage is also 
conditioned and subjected to additional flotation stages, to produce a 
copper-nickel concentrate from which metallic copper and nickel may be 
refined by known methods. As indicated above, it is desirable that most of 
the copper contained in the ground ore be recovered in the copper rougher 
froth, but copper values remaining in the underflow from the copper 
rougher can be concentrated and recovered. 
The underflow stream is first fed to a conditioning stage, in which a 
conditioner such as lime is added to activate the nickel values in the 
stream. Optionally, copper sulfate (CuSO.sub.4) may be added. This 
conditioning activates the remaining copper minerals as well as the nickel 
minerals. The conditioning raises the pH of the stream to between about 8 
and about 9, preferably between about 8.2 and about 8.4. Conditioning may 
be carried out by adding the conditioning agent to the underflow stream in 
a tank under agitation by e.g. an impeller, to afford good solid-liquid 
contact. Agitation should be maintained for sufficiently long to maximize 
activation of the nickel minerals, preferably for about 2 to about 4 
minutes. 
The conditioned stream, which has a solids content of about 30% to about 
35% solids by weight, is then subjected to a copper-nickel rougher 
flotation stage, to recover most of the metal values in the stream. Most 
of the copper values that were not recovered in the froth in the copper 
rougher stage will also report to the copper-nickel rougher froth. A 
collector and a frother should be added to the conditioned stream prior to 
the copper-nickel rougher flotation. Compounds that can be used as 
collector and as frother, and the appropriate amounts thereof to use, can 
be readily determined by those skilled in the art. For instance, suitable 
collectors include higher xanthathes, e.g. potassium amyl xanthate and 
suitable frothers include MIBC, triethoxybutane (TEB), and cresylic acid. 
Between about 0.01 and about 0.07 pounds of collector, and between about 
0.04 and about 0.11 pounds of frother, per ton of new dry solids fed to 
the copper rougher, should be used. 
Flotation should be carried out long enough so as to maximize recovery of 
the metal values; the flotation time will depend on the nature of the 
minerals in the stream being treated, but times between about 14 and about 
16 minutes will generally provide satisfactory recoveries. 
The copper-nickel rougher flotation carried out under the foregoing 
conditions should produce a froth having a nickel content of at least 
about 1.4%, and preferably higher, i.e. above about 2.5%. The nickel 
recovery, based on the ground ore fed to the copper rougher stage, is at 
least about 65% and preferably at least about 75%. The copper content of 
the froth will be about 1.5%. The corresponding copper recovery in the 
copper-nickel rougher froth is less than about 20%, preferably about 10%. 
The underflow from the copper-nickel rougher flotation is subjected to a 
scavenger flotation, employing about 0.04 to about 0.07 pounds of 
collector and about 0.005 to about 0.010 pounds of frother per ton of 
solids fed to the copper rougher circuit. Suitable collector and frother 
compounds are the same as those usable in the copper-nickel rougher stage. 
The scavenger froth typically contains about 0.5% to about 1.0% nickel, 
and about 0.5% to about 1.0% copper. Relatively long retention times are 
required for the copper-nickel rougher and scavenger flotation stages, 
e.g. times on the order of about 15 and 25 minutes, respectively. The 
scavenger froth is thickened and recycled to the nickel rougher. The 
scavenger underflow, typically containing less than about 0.04% nickel and 
less than about 0.04% copper, is disposed of as tailings. 
The froth from the copper-nickel rougher and scavenger stages should be 
processed further, to improve the grade of the nickel concentrate. The 
froth should first be reground to a particle size such that at least about 
85% is minus 400 TSS. The froth is advantageously classified so that only 
oversize particles are reground; the classification is carried out in 
equipment such as a hydrocyclone. 
There follow several, preferably four, nickel cleaning flotation stages. 
Appropriate amounts of collector and frother are added, as needed; 
appropriate reagents are those identified above for use in the 
copper-nickel rougher. The amounts, as needed, can be readily determined 
by one skilled in this art. 
Advantageously, the underflow streams from the first two cleaner stages are 
thickened and recycled to the nickel rougher, and the underflow streams 
from the subsequent cleaner stages are recycled to the feed to the first 
copper-nickel cleaner. 
The concentrate produced by the last copper-nickel cleaner stage typically 
contains at least about 4% nickel, and preferably at least about 5.5%. The 
nickel recovery based on the nickel fed to the copper rougher corresponds 
to at least about 60%, and preferably at least about 70%. The copper 
content of the final copper-nickel cleaner concentrate is between about 3% 
and about 6%, with a recovery of about 10% to about 20% of the copper fed 
to the copper rougher. 
The concentrate produced by the copper-nickel cleaner stages can be treated 
by known methods to recover metallic nickel and copper. 
The improved selectivity that can be obtained between the copper and nickel 
minerals of the orebody under investigation by conditioning the pulped ore 
in sulfurous acid in accordance with the present invention can be 
demonstrated by comparison to ore treatment techniques employing other 
approaches to conditioning the ore. Accordingly, the following Examples 
1-3 report the results obtained by subjecting the pulped ore to copper 
rougher flotation without conditioning of the ore (Example 1), with 
conditioning of the pulped ore by sparging gaseous sulfur dioxide into the 
pulp (Example 2), and with conditioning of the pulped ore by adding an 
aqueous solution of sulfuric acid (H.sub.2 SO.sub.4) (Example 3). 
In all the following Examples 1-8, amounts of reagents added are expressed 
as pounds "per ton of dry ore fed", by which is meant pounds per ton of 
fresh dry ore which is ground, slurried, and fed to the copper rougher 
circuit. All of the tests reported herein except Example 3 were performed 
in a continuously operated pilot plant at a nominal feed rate of 1000 
pounds/hour, in which the first and second copper cleaner underflows were 
recycled to the conditioning stage upstream from the copper rougher. 
Example 3 was performed in the laboratory. 
EXAMPLE 1 
Ore assaying 0.74% Cu and 0.17% Ni was ground to 51.8% minus 200 mesh TSS, 
and then slurried in water to 43% solids by weight. The pH of the slurry 
was 8.7. 
The slurry was prepared for the copper rougher flotation by adding to it 
collector, Cyanamid R-208, at 0.045 pounds per ton of dry ore fed and 
frother, MIBC, at 0.099 pounds per ton of dry ore fed. This mixture was 
subjected to froth flotation for about 15 minutes. A froth was obtained 
which contained 7.5 wt.% solids, comprising 8.4% Cu and 1.5% Ni. The 
corresponding recoveries in the froth were 85% Cu and 69% Ni. 
EXAMPLE 2 
Ore assaying 0.83% Cu and 0.18% was ground to 62.2% minus 200 mesh TSS and 
then slurried with water to 33% solids by weight. Sulfur dioxide 
(SO.sub.2) was bubbled through a submerged pipe into the ore slurry at a 
rate of 3.5 pounds of SO.sub.2 per ton of dry ore fed. The pH was 6.3. The 
slurry was agitated, during and following addition of the SO.sub.2, for 10 
minutes; agitation was carried out in a manner which minimized aeration of 
the ore. 
Flotation reagents were then added to the conditioned slurry, at rates of 
0.037 pounds of Cyanamid R-208 (collector) and 0.062 pounds of MIBC 
(frother) per ton of dry ore fed. This mixture was subjected to froth 
flotation for about 14 minutes. A froth was obtained containing 8.9% 
solids by weight, and having a Cu content of 8.2% and a Ni content of 
1.1%. The corresponding recoveries in the froth were 88% Cu and 55% Ni. 
EXAMPLE 3 
Ore assaying 0.80% Cu and 0.17% Ni was ground to about 65% minus 200 mesh 
TSS, and then slurried with water to about 30% by weight. Sulfuric acid 
(H.sub.2 SO.sub.4) at the rate of 6.36 pounds of acid per ton of ore was 
added to the ore slurry. The pH was 5.4. The acid-ore slurry was agitated 
for 10 minutes. 
The thus conditioned pulp was prepared for copper rougher flotation by 
adding to it 0.030 pounds of Cyanamid R-208 (collector) per ton of dry ore 
fed, and 0.024 pounds of MIBC (frother) per ton of dry ore fed. This 
mixture was then subjected to froth flotation for 8 minutes. A froth was 
obtained having a solids content of 9.76 wt.% and having a Cu content of 
7.8% and a Ni content of 1.33%. The corresponding recoveries in the froth 
were 96% Cu and 76% Ni. 
By contrast with Examples 1-3, it can be shown that conditioning a pulped 
ore with sulfurous acid in accordance with the foregoing description leads 
to much better selectivity between copper and nickel minerals in the 
copper rougher flotation stage. This selectivity in turn improves the 
copper-to-nickel ratio of the concentrates produced in the copper cleaning 
stages. Thus, the invention is described and illustrated in the following 
non-limiting Examples 4-8. 
EXAMPLE 4 
Ore assaying 0.91% Cu and 0.20% Ni was ground to 57% minus 200 mesh TSS. 
The ground ore was slurried with water to 33% solids by weight. An aqueous 
solution of 2.2 wt.% H.sub.2 SO.sub.3 was prepared continuously by 
dissolving sulfur dioxide in water, and this solution was added to the 
slurried ore to from a pulp having a ratio of acid to ore equivalent to 
3.5 pounds of sulfur dioxide per ton of dry ore fed to the circuit. The 
pulp density was 33 wt.% solids. The pH was 6.0. The pulp was agitated for 
about 8 minutes. 
The conditioned pulp was prepared for the copper rougher flotation by 
adding to it, per ton of dry ore fed, 0.044 pounds of American Cyanamid 
Co. Reagent R-208 (a dithiophosphate collector) and 0.078 pounds of MIBC 
(frother). This mixture was subjected to copper rougher flotation for 14 
minutes. A froth was obtained containing 10.8 wt.% solids, and an 
underflow stream was obtained containing 89.2 wt.% solids. The grades and 
recoveries of copper and nickel in the two product streams are given below 
in Table 1. 
The copper rougher concentrate was classified and reground so that 90% was 
minus 400 mesh TSS. This reground concentrate was not subjected to further 
conditioning in H.sub.2 SO.sub.3. The reground concentrate, as a pulp 
which contained 10% solids by weight, was agitated for 3 minutes. It was 
then subjected to a first copper cleaner flotation stage, using no 
additional collector and 0.023 pounds of MIBC (frother) per ton of dry ore 
fed. Flotation lasted for 10 minutes at a pH of 6.2. The resultant cleaner 
concentrate was subjected to second and third copper cleaner flotation 
stages, during which no additional collector and frother were required. 
Second cleaner flotation lasted for 10 minutes, at a pH of 6.6. Third 
cleaner flotation lasted for 8 minutes, at a pH of 7.1. Underflows from 
the first and second cleaner stages were recycled to the first 
conditioning stage (upstream from the copper rougher), and the underflow 
from the third copper cleaner was recycled to the feed to the first copper 
cleaner. 
The copper and nickel contents and recoveries in the concentrates from the 
copper cleaner flotation stages are given in Table 1. 
Table 2 shows the solids content, and copper and nickel recovery data, for 
the underflow stream from the copper rougher flotation. 1.97 pounds of 
lime per ton of dry ore fed was added to the underflow stream to activate 
the nickel and residual copper, raising the pH of the stream to 7.9. The 
stream, containing the conditioner, was agitated for about 3 minutes. Then 
0.049 pounds of sodium isopropyl xanthate (collector) and 0.059 pounds of 
MIBC (frother) (each, per ton of dry ore fed) were added to the 
conditioned stream, and the stream was subjected to a copper-nickel 
rougher flotation for about 30 minutes. The copper-nickel rougher 
concentrate was reground to about 85 wt.% minus 400 mesh TSS, and then 
subjected to three stages of cleaning. Underflows from the copper cleaning 
stages were recycled to the copper first cleaner. 
The solids content, copper and nickel contents, and copper and nickel 
recoveries from the copper-nickel cleaning circuit are given in Table 2. 
EXAMPLE 5 
Ore assaying 0.73% Cu and 0.16% Ni was ground to 60% minus 200 mesh TSS. 
The ground ore was slurried with water to 27% solids by weight. An aqueous 
solution of 2.2 wt.% H.sub.2 SO.sub.3 was prepared continuously by 
dissolving sulfur dioxide in water, and this solution was added to the 
slurried ore to form a pulp having a ratio of acid to ore equivalent to 
3.5 pounds of sulfur dioxide per ton of ore. Th pulp density was 27 wt.% 
solids. The pH was 5.7. The pulp was agitated for about 8 minutes. 
The conditioned pulp was prepared for the copper rougher flotation by 
adding to it, per ton of dry ore fed, 0.046 pounds of American Cyanamid 
Co. Reagent R-208 (collector) and 0.083 pounds of MIBC (frother). This 
mixture was subjected to copper rougher flotation for 14 minutes. A froth 
was obtained containing 8.5 wt.% solids, and an underflow stream was 
obtained containing 91.5 wt.% solids. The grades and recoveries of copper 
and nickel in the two product streams are given below in Table 1. 
The copper rougher concentrate was classified and reground so that 90% was 
minus 400 mesh TSS, and then it was conditioned by adding to it an amount 
of H.sub.2 SO.sub.3 in solution equivalent to adding 1.0 pound of SO.sub.2 
per ton of dry ore fed. The resultant pulp, which had a density of 14% 
solids by weight, was agitated for 3 minutes. It was then subjected to a 
first copper cleaner flotation stage using, per ton of dry ore fed, 0.005 
pounds of Reagent R-208 (collector) and no additional frother. Flotation 
lasted for 10 minutes at a pH of 5.2. The resultant cleaner concentrate 
was itself subjected to a second copper cleaner flotation stage, for which 
0.011 pound of MIBC (frother) per ton of dry ore fed and no additional 
collector were added. Flotation lasted for 10 minutes, at a pH of 5.5. The 
concentrate from this stage was fed to a third copper cleaner flotation 
stage, with no additional reagents. Flotation lasted for 8 minutes, at a 
pH of 5.6. Underflows from the first and second cleaner stages were 
recycled to the first conditioning stage, and the underflow from the third 
copper cleaner was recycled to the second conditioning stage. 
The copper and nickel contents and recoveries in the concentrates from the 
copper cleaner flotation stages are given in Table 1. 
Table 2 shows the solids content, and copper and nickel recovery data, for 
the underflow stream from the copper rougher flotation. 2.11 pounds of 
lime and 0.27 pounds of CuSO.sub.4, per ton of dry ore fed, were added to 
the underflow stream to activate the nickel and residual copper, raising 
the pH of the stream to 8.6. The stream, containing these conditioners, 
was agitated for about 3 minutes. Then 0.030 pound of sodium isopropyl 
xanthate (collector) and 0.104 pound of a MIBC-cresylic acid mixture 
(frother) (each, per ton of dry ore fed) were added to the conditioned 
stream, and the stream was subjected to copper-nickel rougher flotation 
for about 30 minutes. The solids content, nickel content and recovery, and 
copper content and recovery, of the nickel rougher concentrate are shown 
in Table 2. The copper-nickel rougher concentrate was reground to about 86 
wt.% minus 400 mesh TSS, and then subjected to three stages of cleaner 
flotation. Underflows from the first and second cleaner stages were 
recycled to the Cu-Ni rougher. 
The solids content, copper and nickel contents, and copper and nickel 
recoveries from the copper-nickel cleaning circuit are given in Table 2. 
EXAMPLE 6 
Ore assaying 0.51% Cu and 0.11% Ni was ground to 57.2% minus 200 mesh TSS. 
The ground ore was slurried with water to 35% solids by weight. An aqueous 
solution of 2.2 wt.% H.sub.2 SO.sub.3 was prepared by dissolving sulfur 
dioxide in water, and this solution was added to the slurried ore to form 
a pulp having a ratio of acid to ore equivalent to 3.47 pounds of sulfur 
dioxide per ton of ore. The pulp density was 34 wt.% solids. The pH was 
5.9. The pulp was agitated for about 8 minutes. 
The conditioned pulp was prepared for the copper rougher flotation by 
adding to it, per ton of dry ore fed, 0.012 pounds of American Cyanamid 
Co. Reagent R-208 (collector) and 0.047 pounds of MIBC (frother). The 
circuit was using continuously recycled water containing some reagents. 
This mixture was subjected to copper rougher flotation for 14 minutes. A 
froth was obtained containing 12.1 wt.% solids, and an underflow stream 
was obtained containing 87.9 wt.% solids. The grades and recoveries of 
copper and nickel in the two product streams are given below in Table 1. 
The copper rougher concentrate was classified and reground so that 88% was 
minus 400 mesh TSS, and then it was conditioned by adding to it an amount 
of H.sub.2 SO.sub.3 in solution equivalent to adding 0.99 pound of 
SO.sub.2 per ton of dry ore fed. The resultant pulp, which had a density 
of 15% solids by weight, was agitated for 10 minutes. It was then 
subjected to a first copper cleaner flotation stage, using no additional 
collector and 0.012 pounds of MIBC (frother) per ton of dry ore fed. 
Flotation lasted for 11 minutes at a pH of 5.6. The resultant cleaner 
concentrate was itself subjected to a second copper cleaner floatation 
stage, for which no additional collector and 0.006 pounds of MIBC 
(frother) per ton of dry ore fed were added. Flotation lasted for 10 
minutes, at a pH of 5.7. The concentrate from this stage was fed to a 
third copper cleaner flotation stage, with no additional reagents. 
Flotation lasted for 9 minutes, at a pH of 6.0. Underflows from the first 
and second cleaner stages were recycled to the first conditioning stage, 
and the underflow from the third copper cleaner was recycled to the second 
conditioning stage. 
The copper and nickel contents and recoveries in the concentrate from the 
copper cleaner flotation stages are given in Table 1. 
Table 2 shows the solids content, and copper and nickel recovery data, for 
the underflow stream from the copper rougher flotation. The stream was 
conditioned with lime, and subjected to copper-nickel rougher flotation 
under conditions similar to those of Example 5. The resulting rougher 
concentrate was reground and upgraded by cleaner flotation in the manner 
described in Example 5 but employing four flotation stages. The solids 
content, copper and nickel contents, and copper and nickel recoveries from 
the copper-nickel cleaning circuit are given in Table 2. 
EXAMPLE 7 
Ore assaying 0.50% Cu and 0.11% Ni was ground to 56.4% minus 200 mesh TSS. 
The ground ore was slurried with water to 32% solids by weight. An aqueous 
solution of 2.2wt.% H.sub.2 SO.sub.3 was prepared by dissolving sulfur 
dioxide in water, and this solution was added to the slurried ore to form 
a pulp having a ratio of acid to ore equivalent to 3.5 pounds of sulfur 
dioxide per ton of ore. The pulp density was 32 wt.% solids. The pH was 
6.2. The pulp was agitated for about 6 minutes. 
The conditioned pulp was prepared for the copper rougher flotation by 
adding to it, per ton of dry ore fed, 0.052 pound of American Cyanamid Co. 
Reagent R-208 (collector) and 0.088 pound of MIBC (frother). This mixture 
was subjected to copper rougher flotation for 15 minutes. A froth was 
obtained containing 10.8 wt.% solids, and an underflow stream was obtained 
containing 89.2 wt.% solids. The grades and recoveries of copper and 
nickel in the two product streams are given below in Table 1. 
The copper rougher concentrate was classified and reground so that 91.2% 
was minus 400 mesh TSS, and then it was conditioned by adding to it an 
amount of H.sub.2 SO.sub.3 in solution equivalent to adding 1. pound of 
SO.sub.2 per ton of dry ore fed. The resultant pulp, which had a density 
of 16% solids by weight, was agitated for 10 minutes. It was then 
subjected to a first copper cleaner flotation stage, using no additional 
collector and 0.022 pound of MIBC (frother) per ton of dry ore fed. 
Flotation lasted for 10 minutes at a pH of 5.7. The resultant cleaner 
concentrate was itself subjected to a second copper cleaner flotation 
stage, for which no additional collector and 0.018 pound of MIBC (frother) 
per ton of dry ore fed were added. Flotation lasted for 10 minutes, at a 
pH of 6.0. The concentrate from this stage was fed to a third copper 
cleaner flotation stage, with no additional reagents added. Flotation 
lasted for 9 minutes, at a pH of 6.4. Underflows from the first and second 
cleaner stages were recycled to the first conditioning stage, and the 
underflow from the third cleaner was recycled to the second conditioning 
stage. 
The copper and nickel contents and recoveries in the concentrate from the 
copper cleaner flotation stages are given in Table 1. 
Table 2 shows the solids content, and copper and nickel recovery data, for 
the underflow stream from the copper rougher flotation. This stream was 
conditioned with lime, and subjected to copper-nickel rougher flotation 
under conditions similar to thoseof Example 5. The resulting rougher 
concentrate was reground and upgraded by cleaner flotation in the manner 
described in Example 5 but employing four flotation stages. The solids 
content, copper and nickel contents, and copper and nickel recoveries from 
the copper-nickel cleaning circuit are given in Table 2. 
EXAMPLE 8 
Ore assaying 2.89% Cu and 0.53% Ni was ground to 63.1% minus 200 mesh TSS. 
The ground ore was slurried with water to 29% solids by weight. An aqueous 
solution of 2.2 wt.% H.sub.2 SO.sub.3 was prepared continuously by 
dissolving sulfur dioxide in water, and this solution was added to the 
slurried ore to form a pulp having a ratio of acid to ore equivalent to 
2.5 pounds of sulfur dioxide per ton of dry ore. The pH was 5.9. The pulp 
was agitated for about 8 minutes. 
The conditioned pulp was prepared for the copper rougher flotation by 
adding to it, per ton of dry ore fed, 0.087 pound of American Cyanamid Co. 
Reagent R-208 (collector) and 0.095 pound of MIBC (frother). This mixture 
was subjected to copper rougher flotation for 14 minutes. A froth was 
obtained containing 22.75 wt.% solids, and an underflow stream was 
obtained containing 77.25 wt.% solids. The grades and recoveries of copper 
and nickel in the two product streams are given below in Table 1. 
The copper rougher concentrate was classified and reground so that 52% was 
minus 400 mesh TSS, and then it was conditioned by adding to it an amount 
of H.sub.2 SO.sub.3 in solution equivalent to adding 1 pound of SO.sub.2 
per ton of dry ore fed. The resultant pulp, which had a density of 10.5% 
solids by weight, was agitated for 3 minutes. It was then subjected to a 
first copper cleaner flotation stage using no additional collector and 
0.045 pounds of MIBC (frother) per ton of dry ore fed. Flotation lasted 
for 10 minutes at a pH of 5.9. The resultant cleaner concentrate was 
itself subjected to second and third copper cleaner flotation stages, for 
which 0.014 pound of American Cyanamid Co. Reagent R-208 (collector) and 
0.065 pound of MIBC (frother) were required per ton of dry ore fed in each 
cleaner stage. Second cleaner flotation lasted for 10 minutes, at a pH of 
5.9. Third cleaner flotation lasted for 8 minutes, at a pH of 6.0. 
Underflows from the first and second copper cleaner stages were recycled 
to the first conditioning stage, and the underflow from the third cleaner 
stage was recycled to the second conditioning stage. 
The copper and nickel contents and recoveries in the concentrate from the 
copper cleaner flotation stages are given in Table 1. 
Table 2 shows the solids content, and copper and nickel recovery data, for 
the underflow stream from the copper rougher flotation. 3.23 pounds of 
lime per ton of dry ore fed was added to the underflow stream to activate 
the nickel and residual copper, raising the pH of the stream to 8.6. The 
stream containing the conditioner was agitated for about 3 minutes. Then 
0.10 pound of sodium isopropyl xanthate (collector) and 0.10 pound of MIBC 
(frother), each per ton of dry ore fed, were added to the conditioned 
stream and the pulp was subjected to copper-nickel rougher flotation, 
followed by three stages of cleaning. The solids content, and copper and 
nickel contents and recoveries, from the copper-nickel cleaning circuit 
are given in Table 2. 
TABLE 1 
______________________________________ 
Example No. 
4 5 6 7 8 
______________________________________ 
Feed grade, % Cu 
0.91 0.82 0.51 0.50 2.89 
% Ni 0.20 0.18 0.11 0.11 0.53 
Cu Rougher conc. 
solids, % of 
circuit feed 10.8 8.5 12.1 10.8 22.75 
grade, % Cu 7.78 8.93 8.63 7.17 12.5 
% Ni 0.72 1.00 0.70 0.42 0.75 
First Cu cleaner con. 
grade, % Cu 15.4 14.1 13.9 13.4 16.1 
% Ni 0.88 0.68 0.48 0.38 0.59 
Second Cu cleaner con. 
solids, % of 
circuit feed 4.6 -- -- -- -- 
grade, % Cu 16.4 15.4 17.1 16.8 16.9 
% Ni 0.86 0.40 0.42 0.34 0.34 
Third Cu cleaner con. 
solids, % of 
circuit feed 4.1 3.36 1.87 1.86 12.1 
grade, % Cu 17.7 19.2 22.7 20.6 19.9 
% Ni 0.80 0.27 0.23 0.22 0.23 
recovery, % Cu 
80.0 88.4 83.3 76.6 83.6 
% Ni 16.8 5.2 3.9 3.7 5.7 
______________________________________ 
TABLE 2 
______________________________________ 
Example No. 
4 5 6 7 8 
______________________________________ 
Cu rougher underflow 
solids, % of 
circuit feed 89.2 96.6 98.2 98.1 87.9 
grade, % Cu 0.076 0.088 0.093 0.12 0.72 
% Ni 0.13 0.17 0.11 0.11 0.66 
recovery, % Cu 7.4 11.6 18.1 23.4 16.4 
% Ni 59.8 94.8 96.2 96.3 94.3 
Cu--Ni rougher con. 
solids, % of 
circuit feed -- 4.17 9.34 10.1 27.7 
grade, % Cu -- 1.61 1.51 1.49 2.69 
% Ni -- 3.59 1.48 1.41 2.51 
First Cu--Ni cleaner con. 
grade, % Cu -- 2.90 2.85 3.32 5.71 
% Ni -- 6.75 3.11 3.00 4.87 
Second Cu--Ni cleaner con. 
grade, % Cu -- 3.49 2.90 4.57 6.29 
% Ni -- 9.75 3.78 4.34 5.47 
Third Cu--Ni cleaner con. 
solids, % of 
circuit feed 2.0 1.14 -- -- -- 
grade, % Cu 6.29 3.78 3.05 4.60 6.88 
% Ni 4.56 10.3 4.14 4.66 5.96 
recovery, % Cu 14.0 5.9 -- -- 13.0 
% Ni 43.6 67.0 -- -- 68.9 
Fourth Cu--Ni cleaner con. 
solids, % of 
circuit feed -- -- 1.72 1.62 -- 
grade, % Cu -- -- 3.15 5.42 -- 
% Ni -- -- 4.81 5.03 -- 
recovery, % Cu -- -- 10.8 17.5 -- 
% Ni -- -- 69.6 68.7 -- 
______________________________________ 
It will be recognized that the copper grade of the cleaner concentrates may 
depend on, among other factors, the copper grade of the feed material. The 
copper grade of the feed material, in turn, depends on the relative 
proportions of chalcopyrite and cubanite in the feed material, since a 
given quantity of chalcopyrite contains more copper than the same quantity 
of cubanite. We have found, though, that the copper concentrate grade is 
relatively independent of the feed grade in our process. The recovery data 
given herein are, moreover, obtainable over a wide range of copper grades 
in the feed material.