25 Claims, No Drawings
Primary Examiner-G. Ozaki
Attorney, Agent, or Firm-Sheridan, Ross & Fields
Copper is recovered from chalcopyrite by means of a
pollution-free hydrometallurgical process which entails
leaching and converting the chalcopyrite with
copper sulfate in order to produce an insoluble copper
sulfide, a soluble iron sulfate and sulfuric acid. A secondary
leach is then conducted in order to react the
copper sulfide with oxygen in the presence of a jarosite-
forming cation to produce a soluble copper sulfate
and an insoluble iron bearing jarosite. This copper sulfate
is separated from the jarosite and sent to a copper
recovery process and/or recycled. Alternatively, the
copper sulfide from the initial leach may be separated
from the iron sulfate solution immediately after the
initial leach, and this copper sulfide can be treated
with other processes to produce elemental copper and
sulfur.
United States Patent [19]
Johnson et al.
[54] RECOVERY OF COPPER FROM
CHALCOPYRITE UTILIZING COPPER
SULFATE LEACH
[75] Inventors: Robert K. Johnson, Denver; Enzo L.
Coltrinari, Arvada, both of Colo.
[73] Assignee: Cyprus Metallurgical Processes
Corporation, Los Angeles, Calif.
[22] Filed: July 24, 1974
[21] App!. No.: 491,275
[52] U.S. CI. 204/106; 204/107;
204/108; 423/27; 423/36; 423/37; 423/32;
423/46; 75/101 R; 75/115; 75/117; 75/121
[51] Int. CJ.2 C22B 3/00; C22B 15/08
[58] Field of Search 204/108, 106, 107;
75/117,115,101 R, 121; 423/36, 37, 27, 32,
46
[56] References Cited
UNITED STATES PATENTS
3,798,304 3/1974 Weston 75/117 X
3,816,105 6/1974 McKay et at. 75/117 X
3,891,522
[57]
[II] 3,957,602
[45] May 18, 1976
1/1974 McKayetal. 75/117 X
ABSTRACT
3,957,602
Cu,S, + 3FeSO, +
DESCRIPTION OF THE PREFERRED
EMBODIMENTS
3CuFeS2 + 6CuSO, + 4H20
4H2SO.
The basic chemical reaction with which this process
is concerned is as follows:
2
residual insoluble iron constituents along with any
other insoluble impurities. The copper may then be
conventionally recovered from the isolated copper
sulfate solution, and if desired a portion of the copper
5 sulfate solution may be recycled for reaction and conversion
with fresh chalcopyrite feed.
10
1
SUMMARY OF THE INVENTION
A pollution-free hydrometallurgical copper recovery
process results from the leaching of chalcopyrite with
copper sulfate in order to form insoluble copper sulfides,
a soluble iron sulfate solution and sulfuric acid.
The copper sulfides can then be separated from the
product mixture and further treated in order to recover
the copper values. Also, the products from the initial
leach may be immediately subjected to a secondary
oxidation leach reaction wherein the copper sulfides
are converted to a soluble copper sulfate solution and
the iron is converted to an insoluble state such that the
copper sulfate solution is easily separated from the
RECOVERY OF COPPER FROM CHALCOPYRITE
UTILIZING COPPER SULFATE LEACH
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the hydroinetallurgical recovery
of copper from chalcopyrite by means of a copper
sulfate leaching process.
2. The prior Art
Processes have long been disclosed describing the
recovery of copper from its sulfide and mixed sulfide
forms. Most of the economic copper recovery processes
are classified as pyrometallurgical, with the ore
being smelted to oxidize the sulfide to sulfur dioxide. 15
This sulfur dioxide is now of course recognized as a Along with the digenite (CugSs) some chalcocite
major air pollutant, and means must be used in con- (CU2S) and covellite (CuS) in minor amounts may also
junction with pyrometallurgical plants to eliminate this be produced.
contaminant. As a result considerable development is In addition to chalcopyrite the starting materials may
now being undertaken to formulate hydrometallurgical 20 contain other copper sulfides, such as chalcocite and
processes in order to circumvent the production of the coveIIite, and also may contain sulfides of other metals.
byproduct sulfur dioxide. Much of the hydrometallurgi- For example, copper may be recovered from mixed
cal development centers around chloride and ammoni- sulfides containing chalcopyrite and zinc sulfide acacal
leaching processes, some of which may prove to cording to the above set forth reaction since the zinc
ultimately be beneficial. 25 will go into solution as zinc sulfate, permitting the insol-
Copper sulfate leaching agents have been proposed uble digenite to be easily separated from the solution
to be used in conjunction with a number of metal sul- containing zinc sulfate, iron sulfate and sulfuric acid.
fides, including zinc sulfide. U.S. Pat. No. 3,655,538 to Examples of other metal sulfides which would similarly
Renken discloses such a process whereby the zinc sul- react in the presence of chalcopyrite include nickel and
fide is leached with copper sulfate in order to produce 30 cobalt.
copper sulfide and a zinc sulfate solution, the zinc sul- This initial leach reaction may be operated in accorfate
solution being easily separated for the ultimate dance with conventional leaching techniques, with a
recovery of zinc. Another similar process discloses the reaction temperature preferably maintained at greater
utilization of a copper sulfate leach to recover nickel than about 100°C, more preferably from about 150° to
from a nickel-copper matte, this process being set forth 35 about 250°C, and most preferably from about 180° to
by Llanos et al in a paper presented at the Third An- about 200°C. As is common in leaching operations the
nual Meeting of the Hydrometallurgical Section of the raw feed material is crushed and ground to a suffi-
Metallurgical Society of C.I.N., Edmonton, Oct. 19, ciently small particle size in order to conveniently per~
1973. form concentration operations such as flotation. When
Heretofore the value of leaching chalcopyrite with 40 leaching mixed. sulfides containing chalcopyrite the
copper sulfate has not been recognized, and it has com- copper sulfate concentration is preferably maintained
monly been believed that chalcopyrite does not react from about I gram per liter of copper to saturation
with copper sulfate. This is borne out by the Renken concentration, more preferably from about 30 to about
patent, cited above, which specifically sets forth at 100, and most preferably from about 40 to about 80
column 3 that chalcopyrite does not react with copper 45 grams per liter. When processing chalcopyrite alone,
sulfate. this concentration preferably approaches the copper
It has now been recognized that under the proper sulfate saturation concentration. The mole ratio of
processing conditions, as hereinafter set forth, copper copper sulfate to chalcopyrite is as shown in the above
sulfate can be used as a beneficial leaching agent for set forth reaction, i.e., two moles of copper sulfate per
chalcopyrite, and such a process results in a number of 50 mole of chalcopyrite. This is of course the stoichiometadvantages
including providing an effective means for ric amount required, and an excess amount of copper
separating copper sulfide from many other metal sul- sulfate may be maintained.
fides and other impurities, as well as greatly facilitating The reaction time is inversely proportional to temany
secondary leaching of the copper sulfides. perature, the amount of time decreasing with increased
55 temperatures.
As is conventional in chemical leaching, this initial
leach reaction may be performed in more than one
stage in order to expeditiously carry out the reaction,
and may be conducted cocurrently or countercur-
60 rently.
Following the initial leach reaction the copper sulfide
product may be immediately separated from the soluble
sulfates and sulfuric acid. Such a separation is accomplished
by conventional means in the art, as for
65 example by thickening and filtration. A separation at
this stage of the process may be preferred in some
instances, however, a further separation will be necessitated
at. a later stage of the process since the gangue
3,957,602
3
material will also be separated with the copper sulfides.
Separation immediately following the initial leach reaction
is therefore dictated by the particular copper sulfide
reaction employed to recover the elemental copper
values and also the composition of the initial feed 5
material.
One preferable technique is therefore to subject the
products of the initial leach and conversion reaction
directly to a secondary leach reaction in conjunction
with a jarosite forming cation to convert the copper 10
sulfides to a copper sulfate solution while precipitating
the iron sulfate as jarosite. Due to the nature of this
reaction it is apparent that this secondary leach will
immediately follow the initial leach in those cases when
the sulfides initially fed to the reaction are basically 15
copper or iron sulfides with only relatively small proportions
of other metal sulfides. If the products of the
initial leach include substantial amounts of metal sulfates
other than iron sulfates, it will then be preferable 20
to separate the copper sulfides prior to the initiation of
this secondary leach.
A preferable secondary leach reaction is an oxygen
leach in an acid media in the presence of a jarosite
forming cation. As mentioned the products of this 25
leach reaction are copper sulfate and jarosite. This
oxygen leach is operated in accordance with known
techniques, as for example set forth in U.S. Pat. No.
3,642,435. Partial oxygen pressures for such a reaction
are well below the comparable necessary values re- 30
quired in the absence of the initial copper sulfate leach.
In performing the secondary oxygen leach in the
presence of iron sulfates it is preferred to add a sufficient
amount of a jarosite-forming cation in order that
the iron may be precipitated from the solution. These 35
jarosite-forming cations are discussed in U.S. Pat. No.
3,684,490 and are preferably potassium, sodium and
ammonium. The amount added need only be sufficient
to precipitate the iron from solution.
Other secondary techniques may also be employed to 40
recover the copper values from the copper sulfide
products of the primary leach reaction. For example,
chloride leaching techniques as described in U.S. Pat.
No. 3,767,543 may be utilized. Preferable chloride
leaching agents include ferric chloride and cupric 45
chloride. Also the copper sulfides may be modified by
techniques known in the art in order to employ electrolytic
dissolution processes, as set forth for example in
U.S. Pat. Nos. 3,673,061 and 3,736,238. Other suitable
secondary leach operations include ammoniacal leach- 50
ing and cyanide leaching. It is therefore understood
that while the following discussion assumes the utilization
of a secondary oxygen leach in an acid media, the
artisan can determine from the present state of the art
the necessary modifications to be made should one of 55
these alternative processes be employed.
Following the secondary oxidation leach it is necessary
to separate the copper sulfate from the remaining
solids, including the jarosite and the gangue material.
This separation is conveniently made by thickening and 60
filtration or other means known in the art.
Once the copper sulfate is isolated the copper may be
recovered. This recovery is conveniently made by
means known in the art, preferably by electrolysis or
cementation. A portion of the copper sulfate can also 65
be recycled in order to treat new chalcopyrite feed
material. The amount of copper sulfate recycled is
dependent upon the fresh sulfide feed characteristics.
4
The following examples are illustrative of some of the
aspeCts encompassed by this process.
EXAMPLE NO. 1
A commercial copper concentrate assaying 34.5%
copper, 22.9% iron, 32% total sulfur, 4.9% silica, 1.7
ounces per ton silver, 0.0 I ounces per ton gold, 0.12%
calcium, 0.27% molybdenum, 0.01% lead and 0.02%
nickel and being comprised of the approximate mineral
percentages of 40% chalcopyrite, 23% chalcocite, 23%
pyrite, 3% covellite, I% bornite, less than I% hematite
and 9% gangue was ground to a mesh size of -270 and
reacted with copper sulfate in a ratio of 0.84 pounds of
copper as copper sulfate per pound of copper initially
in the concentrate. The temperature was maintained at
180°C and the reaction was permitted to take place
under normal agitation for 3 hours. The initial pulp
density was 192 grams of solids per liter of solution and
the copper sulfate concentration was 55 grams per liter
of copper. The product analysis indicated that 0.74
pounds of copper was precipitated, mostly as digenite,
per pound of copper initially in the concentrate, representing
a substantial conversion of chalcopyrite copper
to digenite copper. Iron sulfate and sulfuric acid were
also produced.
EXAMPLE NO.2
The process of Example No. I was followed in all
respects except that the reaction temperature was
maintained at 21 O°C and the total time of the reaction
was I hour. The results showed 0.8 pounds of copper
precipitated as digenite per pound of copper in the
initial concentrate.
EXAMPLE NO.3
Two identical acid pressure leaches were performed
on copper concentrates of identical composition as that
set forth in Example I, one pressure leach being performed
directly on the concentrates while the other
pressure leach was performed subsequent to a copper
sulfate leach reaction. The concentrate was ground to
-325 mesh and a pulp density of 4.7% solids was
formed. The leached solution contained 13 grams per
liter of copper, 33 grams per liter of sulfuric acid, and
II grams per liter of sodium sulfate. In both cases the
reaction temperature was maintained at 95°C, the
vapor and oxygen total pressure at 125 psig and the
solution was agitated at a turbine tip speed of 525 feet
per minute. After an elapsed time of 3 lh hours, the
results showed 82% of the copper was extracted from
the sample that was not treated with copper sulfate,
while 4 grams per liter of iron remained in solution. On
the other hand, the sample that was initially treated
with the copper sulfate leach reaction yielded a 95%
copper extraction, with only 1.3 grams of iron in each
liter of solution, the remaining iron being precipitated
as sodium jarosite.
EXAMPLE NO.4
Another comparative test similar to Example No.3
was performed with two samples of a commercial concentrate
of identical composition as that set forth in
Example No.1. One sample was directly leached under
ammoniacal conditions while the other sample was
initially leached with copper sulfate followed by the
ammoniacal leach reaction. The leach solution had a
concentration of 80 grams per liter of ammonium sulfate
and 75 grams per liter of ammonia as ammonium
3,9.57,602
10
EXAMPLE NO.5
5
hydroxide. The temperature wasrilainta.inedlit 81°C
for both tests, and the oxygen and ammonia total pressure
was kept at 20 psig. After an elapsed time of 2
hours, the sample which had not been treated with the
copper sulfate solution showed a 93% copper recovery,
while the sample which had initially been treated
showed a 98% copper extraction. In both Examples 3
and 4 the copper sulfate leach reaction was performed
in similar fashion to that described in Example 1.
6
8~ The process of claim 6 wherein the temperature of
the copper sulfate reaction is maintained from about
180°C to 200°C.
9. A process for hydrometallurgically recovering
5 copper from chalcopyrite comprising:
leaching and converting the chalcopyrite with a copper
sulfate solution at a temperature and mole ratio
sufficient to concurrently form a mixture of an
insoluble copper sulfide consisting essentially of
digenite, a soluble iron sulfate and sulfuric acid;
subjecting said concurrently formed mixture to a
A commercial copper concentrate consisting of secondary treatment including leaching with oxyabout
75% chalcopyrite and assaying 26.1% copper, gen and addition of a jarosite-forming cation, to
27.5% iron and 31.4% total sulfur was reacted with 2.2 15 produce from said concurrently formed mixture a
moles of copper as copper sulfate per mole of copper in soluble copper sulfate solution and an insoluble
the chalcopyrite concentrate at 18QoC for 3 hours. The jarosite;
product analysis indicated that two moles of copper as separating the soluble copper sulfate solution from
copper sulfate reacted with one mole of copper in the the insoluble jarosite; and
chalcopyrite concentrate to yield three moles of copper 20 recovering elemental copper from the copper sulfate
in the form of digenite, (Ih of a mole of digenite) this solution.
analysis being verified by X-ray diffraction. Essentially 10. The process of claim 9 wherein a portion of the
all of the iron from the chalcopyrite entered into solu- copper sulfate solution produced from the secondary
tion as ferrous sulfate. leaching operation is recycled to treat fresh chalcopy-
What is claimed is: 25 rite feed material.
1. A process for hydrometallurgically recovering 11. The process of claim 9 wherein the leaching of
elemental copper from chalcopyrite comprising: the chalcopyrite with copper sulfate is performed at a
reacting the chalcopyrite with a copper sulfate solu- temperature of from about 180°C to about 200°C.
tion at a temperature and mole ratio sufficient to 12. The process of claim 9 wherein elemental copper
form an insoluble copper sulfide consisting essen- 30 is recovered by means of electrolysis.
tially of digenite, a soluble iron sulfate and sulfuric 13. The process of claim 9 wherein the jarosite-formacid;
ing cation is sodium.
separating the copper sulfide from the iron sulfate; 14. The process of claim 9 wherein the jarosite-formand
ing cation is potassium.
recovering the elemental copper from the copper 35 15. The process of claim 9 wherein the jarosite-formsulfide.
ing cation is an ammonium ion.
16. The process of claim 9 wherein the chalcopyrite
2. The process of claim 1 wherein the concentration
f th If I ·· f b 30 b initially treated with the copper sulfate solution is in the
o e copper suo ate so utlOn IS rom a out to a out resence of other mixed sulfides. .
100 grams per hter of c~pper.. . 40 P 17. The process of claim 9 wherein the mole ratio of
3. !he ~rocess of claim 1 wherein the ochalcopYrlte copper sulfate to chalcopyrite reactants is at least
reaction IS conducted from about 180 C to about about two to one
200°C .
. .. . 18. The process of claim 9 wherein the temperature
4. The process of claim 1 wherein the mole ratio of of the copper sulfate reaction is maintained from about
copper sulfate to chalcopyrite reactants is at least 45 180°C to 2000C.
about two toone... 19. A process for hydrometallurgically recovering
5. The process of clalll~ 4 ~herel? th~ temperature of elemental copper from chalcopyrite comprising:
the ocopper sulfate roeactlOn IS maintained from about reacting the chalcopyrite with a copper sulfate solu-
180 C to about 200 C. . . tion at a temperature and mole ratio sufficient to
6. A process for h~drometa~l~rglcally recovering 50 form an insoluble copper sulfide consisting essencopper
from chalcopyrite comprising: tially of digenite a soluble iron sulfate and sulfuric
initially leaching the chalcopyrite with a copper sul- acid' '
f~te solution ~t a temper~tur~ and ~ole ratio suffi- separ;ting the copper sulfide from the iron sulfate;
clent to form Insoluble dlgemte, minor amounts of leaching the separated copper sulfide with a chloride
other insoluble copper sulfides and a soluble iron 55 selected from the group consisting of ferric chlorsulfat.
e; . ide and cupric chloride in order to produce a soluseparating
the Insoluble copper sulfides from the tion comprising cuprous chloride, cupric chloride
soluble iron sulfate;' and ferrous chloride; and
secondarily leaching the copper sulfides with oxygen reducing at least a portion of the cuprous chloride to
in an acid medium and in the presence of a jarosite 60 elemental copper.
forming cation to form a soluble copper sulfate 20. The process of claim 19 wherein the chalcopyrite
solution and an insoluble jarosite; and reaction is conducted from about 180°C to about
recovering a portion <:>f the copper from the copper 200°C.
sulfate solution and recycling the remainder of the 21. The process of claim 20 wherein the mole ratio of
copper sulfate solution to the initial leach reaction. 65 copper sulfate to chalcopyrite reactants is at least
7. The process of claim 6 wherein the mole ratio of about two to one.
copper sulfate to chalcopyrite reactants is at least 22. The process of claim 19 wherein the solution
about two to one. comprising cuprous chloride, cupric chloride and fer3,957,602
* * * * *
7
rous chloride is subjected to electrolysis to produce
elemental copper.
23. A process for hydrometallurgically recovering
elemental copper from chalcopyrite comprising:
reacting the chalcopyrite with copper sulfate solution
at a temperature and mole ratio sufficient to form
an insoluble copper sulfide consisting essentially of
digenite, a soluble iron sulfate and sulfuric acid;
separating the copper sulfide form the iron sulfate;
8
leaching the separated copper sulfide with an ammoniacal
leach solution; and
recovering copper from the ammoniacal leached
solution.
5 24. The process of claim 23 wherein the chalcopyrite
reaction is conducted from about 180°C to about
200°C.
25. The process of claim 24 wherein the mole ratio of
copper sulfate to chalcopyrite reactants is at least
10 about two to one.
15
20
25
30
35
40
45
50
55
60
65
Roman",g�Ni"0�(D�ast-font-family: HiddenHorzOCR'>Yield (per
cent) 48.0 6.8 25.0
HCI solution and repulped and refiltered. This operation
was continued until the wash water checked below
45 acceptable levels of detrimental metals.
The solids were then repulped to 30 to 40 percent
solids, utilizing about 20 Ibs. of NaOH per ton of dry
feed to give a pH slurry reading of I I or 30 Ibs./ton for
a pH of 13 and charged into the autoclave. The autoclave
was sealed, the agitator started, and steam was
injected into the jacket for the heating cycle. The speed
of the agitator is that at which the particles are kept in
suspension and a homogeneous slurry is maintained. At
This example shows the process is effective for zinc
concentrates and shows the deleterious effect of zinc
and iron ions on yield.
EXAMPLE VII (See Example III)
About 270 grams of a concentrate produced by the
oxidation of chalcopyrite-containing sulfur 48%,chalcopyrite
12%, pyrite and other minerals 40%, was 50
washed, slurried in I liter of water and held at 135°C ±
5° for the times shown. The slurry was cooled and
screened on a 100 mesh U.S. Standard screen.
Test I Test 2 Test 3
Additive 2 gm NaOH 2 gm NaOH 2 gm NaOH
(.74 gm/lOO gm of (.74 gm/lOO gm of (.74 gm/lOO gm
feed) feed) of feed)
Time 30 min. 60 min. 235 min.
Product
(o/c sulfur) 88.5 90.9 86.7
Yield (%) 23.0 19.0 59.0
This example shows that while a ,small amount of 65
coalescence occurs very quickly that times in excess of
I hour are necessary to obtain a high degree of coale~cence.
the end of the heating cycle, steam was shut off, cooling
water was admitted to the jacket, the autoclave cooled
down, and when the temperature dropped below 80°C
the' agitator was slowed down, the bottom valve opened
and the autoclave 'dischargedtoa screen. The sulfur
3,939,256
9
product was removed as the oversize + 65 .mesh, and
the fine materials or the tailings proceeded on to a
thickener. The sulfur product averaged around 96%
elemental sulfur with a recovery of over 85%. The
particles were greenish-yellow in color and irregularly 5
shaped.
What is claimed is:
l. A process for the recovery of elemental sulfur
from mixtures in which it is present with soluble calcium
compound impurities which comprises: 10
a. contacting the mixture with water to solubilize
calcium ions;
b. separating the solids content of the treated mixture
from the liquid content and washing the solids
15
20
25
30
35
40
45
50
55
60
65
10
content to remove said solubilized calcium ions
from the solids content;
c. forming a water slurry of said solids content;
d. adding to the slurry a surface modifying additive
selected from the group consisting of alkali metal
hydroxides, alkali metal carbonates, and mixtures
thereof to produce an alkaline slurry pH of at least
about 9;
e. heating the slurry to at least the melting point of
sulfur for a period sufficient to coalesce substantially
all of the sulfur particles, and
f. recovering the coalesced sulfur from the slurry.
* * * * *