U.S. patent application number 10/706276 was filed with the patent office on 2004-07-29 for process for refining raw copper material containing copper sulfide mineral.
Invention is credited to Ando, Koji, Imamura, Masaki, Kudo, Keiji, Nagase, Noriyuki, Takeda, Kenji.
Application Number | 20040144208 10/706276 |
Document ID | / |
Family ID | 32738839 |
Filed Date | 2004-07-29 |
United States Patent
Application |
20040144208 |
Kind Code |
A1 |
Ando, Koji ; et al. |
July 29, 2004 |
Process for refining raw copper material containing copper sulfide
mineral
Abstract
A process for refining a raw copper material containing a copper
sulfide mineral, e.g., chalcopyrite, by the hydrometallurgical
process which can leach copper out of the raw material at a high
extraction while suppressing oxidation of sulfur, recover it in the
monovalent state by electrolysis and, at the same time, recover a
concomitant valuable metal while minimizing production of wastes,
e.g., leaching residue, as far as possible. The process for
refining a raw copper material containing a copper sulfide mineral,
comprising a chlorine-aided leaching step for leaching the raw
copper material in the presence of chlorine to produce the leaching
product liquor containing the copper ion, copper ion reduction step
for reducing the leaching product liquor in the presence of a
reductant to produce the reduction product liquor containing the
cuprous ion, solvent extraction step for treating the reduction
product liquor to produce the stripping product liquor containing
the copper and raffinate, copper electrowinning step for
electrolyzing the stripping product liquor to produce the
electrolytic copper, solution purification step for treating the
raffinate to produce the purified solution and iron recovery step
for treating the purified solution to recover the iron-containing
solid therefrom.
Inventors: |
Ando, Koji; (Niihama-shi,
JP) ; Takeda, Kenji; (Niihama-shi, JP) ; Kudo,
Keiji; (Niihama-shi, JP) ; Nagase, Noriyuki;
(Niihama-shi, JP) ; Imamura, Masaki; (Niihama-shi,
JP) |
Correspondence
Address: |
ARMSTRONG, KRATZ, QUINTOS, HANSON & BROOKS, LLP
1725 K STREET, NW
SUITE 1000
WASHINGTON
DC
20006
US
|
Family ID: |
32738839 |
Appl. No.: |
10/706276 |
Filed: |
November 13, 2003 |
Current U.S.
Class: |
205/580 ;
205/581; 205/582; 205/584; 205/590; 205/593 |
Current CPC
Class: |
C22B 15/0089 20130101;
Y02P 10/236 20151101; C22B 15/0069 20130101; Y02P 10/20 20151101;
C22B 15/0097 20130101 |
Class at
Publication: |
075/743 |
International
Class: |
C22B 015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 18, 2002 |
JP |
2002-333557 |
Dec 17, 2002 |
JP |
2002-365156 |
Jul 30, 2003 |
JP |
2003-282248 |
Sep 8, 2003 |
JP |
2003-315124 |
Claims
What is claimed is:
1. A process for refining raw copper material containing copper
sulfide mineral characterized by a hydrometallurgical process for
recovering copper and a concomitant valuable metal from a raw
copper material containing a copper sulfide mineral, comprising:
(1) a chlorine-aided leaching step for leaching the raw copper
material in the presence of chlorine in an acidic, aqueous chloride
solution to produce the leaching product liquor containing the
copper ion and residue containing elemental sulfur by leaching
copper in the acidic solution, (2) a copper ion reduction step for
reducing the leaching product liquor in the presence of a reductant
to produce the reduction product liquor containing the cuprous ion,
(3) a solvent extraction step for extracting copper with the aid of
solvent from the reduction product liquor, and stripping loaded
solvent to produce the stripping product liquor containing the
cuprous ion and raffinate containing the ferrous ion, (4) a copper
electrowinning step for electrolyzing the stripping product liquor
to produce the electrolytic copper and spent electrolyte, and (5)
an iron electrowinning step for electrolyzing the raffinate to
produce the electrolytic iron and iron spent electrolyte composed
of the aqueous iron chloride solution.
2. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein said
chlorine-aided leaching step is effected by blowing chlorine gas
into said acidic, aqueous chloride solution.
3. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein said
chlorine-aided leaching step is effected at a slurry concentration
of 100 to 400 g/L, leaching temperature of 100 to 110.degree. C.
and oxidation-reduction potential of 500 to 600 mV (based on an
Ag/AgCl electrode).
4. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein said
chlorine-aided leaching step is controlled in such a way to have a
final chloride ion concentration of 250 to 400 g/L in the acidic,
aqueous chloride solution.
5. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein said copper
ion reduction step uses the copper sulfide mineral as the
reductant.
6. The process according to claim 5 for refining a raw copper
material containing a copper sulfide mineral, wherein said copper
sulfide mineral is treated under heating at the atmospheric
pressure in the leaching product liquor to produce the reduction
product liquor and residue containing elemental sulfur.
7. The process according to claim 6 for refining a raw copper
material containing a copper sulfide mineral, wherein said copper
sulfide mineral is a copper concentrate mainly composed of
chalcopyrite, prepared to have an average particle diameter (D50)
of 0.5 to 60 .mu.m, and temperature at which the leaching product
liquor is reduced is 90 to 110.degree. C. and, at the same time, is
at least the temperature level (A) given by the following formula
1:A(.degree. C.)=6.79.times.Ln(B)+81.5 Formula 1(wherein, B is an
average particle diameter (D50, .mu.m), determined by the Microtrac
analyzer, at a volumetric cumulative frequency of 50% of the copper
concentrate).
8. The process according to claim 6 for refining a raw copper
material containing a copper sulfide mineral, wherein said copper
sulfide mineral is a copper concentrate mainly composed of
chalcopyrite, prepared to have an average particle diameter (D50)
of 0.5 to 60 .mu.m, and temperature at which the leaching product
liquor is reduced is 90 to 110.degree. C. and, at the same time, is
at least the temperature level (A) given by the following formula
2:A(.degree. C.)=7.04.times.Ln(B)+95.2 Formula 2(wherein, B is an
average particle diameter (D50, .mu.m), determined by the Microtrac
analyzer, at a volumetric cumulative frequency of 50% of the copper
concentrate).
9. The process according to claim 6 for refining a raw copper
material containing a copper sulfide mineral, wherein said residue
is recycled back as a raw copper material to the chlorine-aided
leaching step.
10. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein said solvent
extraction step uses an organic solvent containing a solvating
extractant for solvent extraction.
11. The process according to claim 10 for refining a raw copper
material containing a copper sulfide mineral, wherein said organic
solvent contains said solvating extractant at 40% by volume or
more.
12. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein an aqueous
solution for stripping in said solvent extraction step contains
copper at 70 g/L or less and chlorine ion at 50 to 350 g/L.
13. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein said
stripping is effected at 40 to 90.degree. C. in said solvent
extraction step.
14. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein said copper
electrowinning step is effected in an electrolysis tank composed of
a cathode chamber and anode chamber separated from each other by a
diaphragm, characterized in that said stripping product liquor
containing the cuprous ion, discharged from said solvent extraction
step, is supplied to the cathode chamber to electrowin copper on
the cathode, said iron spent electrolyte composed of an aqueous
iron chloride solution, discharged from said iron electrowinning
step, is supplied to the anode chamber for anodic oxidation, and
the solution being supplied to the anode chamber is prevented from
flowing into the cathode chamber through the diaphragm.
15. The process according to claim 14 for refining a raw copper
material containing a copper sulfide mineral, wherein water
permeates through said diaphragm at 0.04 to 0.15
L/m.sup.2.multidot.s.
16. The process according to claim 14 for refining a raw copper
material containing a copper sulfide mineral, wherein said cathode
and anode chambers in said electrolysis tank are structured in such
a way that a solution is charged and discharged separately in each
chamber, and the solution level is kept higher in said cathode
chamber than in said anode chamber.
17. The process according to claim 14 for refining a raw copper
material containing a copper sulfide mineral, wherein the spent
catholyte is recycled back as the aqueous solution for stripping to
said solvent extraction step, and the spent anolyte is recycled
back as the leachate to said chlorine-aided leaching step.
18. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein said iron
electrowinning step is effected in an electrolysis tank composed of
an anode chamber and cathode chamber separated from each other by a
filter cloth, characterized in that the iron ion is supplied to the
anode chamber at a rate at least twice as high as that for the iron
ion deposited on the cathode in order to decrease cell voltage.
19. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein a solution
purification step is included upstream of said iron electrowinning
step to purify said raffinate from said solvent extraction step,
which produces the purified solution and precipitate product.
20. The process according to claim 19 for refining a raw copper
material containing a copper sulfide mineral, wherein said
raffinate from said solvent extraction step is purified in said
solution purification step by a treatment method selected from the
group consisting of sulfidation, cementation and
neutralization.
21. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein said residue
containing elemental sulfur, discharged from said chlorine-aided
leaching step, is distilled in an inert atmosphere to be separated
into the condensed sulfur and residue containing a concomitant
precious metal, after evaporating sulfur.
22. The process according to claim 1 for refining a raw copper
material containing a copper sulfide mineral, wherein said
electrolytic copper produced in said copper electrowinning step is
used as the anode to be refined by electrolysis and separated into
the high-purity, electrolytic copper and silver-containing slime.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a process for refining a
raw copper material containing a copper sulfide mineral, more
particularly a hydrometallurgical refining process for a raw copper
material containing a copper sulfide mineral, e.g., chalcopyrite,
which can leach copper out of the raw material at a high extraction
while suppressing oxidation of sulfur, recover it in the monovalent
state by electrolysis and, at the same time, recover a concomitant
valuable metal while minimizing production of wastes, e.g.,
leaching residue, as far as possible.
[0003] 2. Description of the Prior Art
[0004] At present, copper has been produced mostly by a
pyrometallurgical process worldwide, which treats a copper
concentrate as the starting material. The copper concentrate is
produced from a copper sulfide mineral, e.g., chalcopyrite
(CuFeS.sub.2), chalcocite (CU.sub.2S) or bornite
(Cu.sub.5FeS.sub.4), by a physical separation process, e.g.,
floatation, which concentrates the copper sulfide mineral. The
copper concentrate composition, depending mostly on the site in
which the ore is occurring, contains, in addition to a copper
sulfide mineral, an iron sulfide mineral (e.g., iron pyrite,
pyrrhotite or the like) and oxide mineral (e.g., silicate mineral
as gangue). Moreover, it also contains zinc, lead, a mineral of
Group 5 element in the periodic table (e.g., arsenic, antimony,
bismuth or the like), mineral of Group 6 element in the periodic
table (e.g., selenium, tellurium or the like) and noble metal,
present mostly in the sulfide mineral.
[0005] The pyrometallurgical process for copper refining
electrolytically refines crude copper produced by a series of
pyrometallurgical refining steps which use a smelting furnace,
converter, refining furnace or the like to treat a copper
concentrate. It is suitable for efficient treatment of large
quantities of copper ore. However, it involves several problems.
For example, it needs a huge investment for large-size facilities
because of insufficient reaction efficiency by small-size
facilities, and must be provided with a system for recovering
massively produced SO.sub.2 gas.
[0006] Under these circumstances, hydrometallurgical processes have
been studied recently for copper refining. The conventional
hydrometallurgical copper refining process widely used on an
industrial scale involves spraying sulfuric acid onto a piled
copper ore containing a copper oxide mineral to leach out copper,
solvent extraction to increase copper concentration of the leaching
product liquor, and electrolysis to recover copper. However, this
process involves problems, when applied to refining a sulfide ore,
which accounts for the greater part of copper ore. Taking
chalcopyrite, which is occurring more massively than any other
copper sulfide, as an example, it is leached by sulfuric acid at a
slow rate, resulting in low copper extraction. It is therefore
difficult for the hydrometallurgical process to secure productivity
comparable with that of the pyrometallurgical process for refining
a raw copper material containing chalcopyrite.
[0007] Processes adopting conditions under which chalcopyrite
leaching is promoted have been proposed to solve the above
problems. One of the more representative processes involves
oxidation of a copper ore or concentrate under pressure in a
halide-containing sulfuric acid solution, leaching of the treated
ore or concentrate, solvent extraction of the leaching product
liquor, and electrolysis to recover copper from the stripping
solution containing cupric ion (disclosed by, e.g., Patent Document
1). Another representative process involves leaching of a copper
concentrate with a leachate capable of forming a halide complex,
e.g., BrCl.sub.2--, and electrolysis of the leaching product liquor
containing cuprous ion which has undergone leaching at a low
oxidation-reduction potential to recover copper (disclosed by,
e.g., Patent Document 2).
[0008] The hydrometallurgical refining process has several
advantages over the pyrometallurgical process, e.g., relatively
simple process and hence reduced investment, because it operates at
a lower reaction temperature and can be cyclically started and
stopped in a shorter time, which makes production schedule
adjustment more flexible. However, the hydrometallurgical refining
process still involves the following problems to be solved to
further improve efficiency.
[0009] (1) Higher Copper Extraction with Chalcopyrite, and
Suppressed Oxidation of Sulfur
[0010] The hydrometallurgical process preferably recovers sulfur
from a sulfide mineral in the form of elemental sulfur, which can
be stored more easily than sulfuric acid. However, sulfur tends to
be oxidized in the leaching step, when chalcopyrite, which is
difficult to extract, is leached under a strongly oxidative
atmosphere to attain a high copper extraction, and cannot be
efficiently recovered in the form of elemental sulfur, because it
is eluted out as the sulfate ion in the leaching solution.
Therefore, there are demands for leaching processes which treat
chalcopyrite at a high extraction and, at the same time, realize
suppressed oxidation of sulfur.
[0011] (2) Efficient Reduction of Copper
[0012] The hydrometallurgical process preferably recovers copper by
electrolysis from an aqueous chloride solution containing cuprous
ion. More specifically, copper is present only in the divalent
state in a sulfuric acid solution, whereas it may be monovalent or
divalent in a chloride solution. The electrolysis of cuprous ion
(i.e., monovalent copper) is more economical than that of divalent
copper, because its power consumption is halved. It should be
noted, however, that the copper ion is present in the form of
divalent state in the leach solution from the leaching step which
uses chlorine gas, because of high oxidation-reduction potential of
the solution. It is known that divalent copper has been reduced
into monovalent one by blowing SO.sub.2 gas as a reductant into the
system or recycling part of the copper powder recovered by
electrolysis. However, SO.sub.2 gas increases concentration of the
sulfate ion in the leaching product liquor, to push up the solution
treatment cost. On the other hand, use of the copper powder
directly decreases the product yield by the quantity it is
recycled, which also pushes up the cost. Therefore, development of
efficient processes for reducing the copper ion has been demanded
for electrolysis of monovalent copper.
[0013] (3) Reduction of Residue Wastes and Efficient Recovery of
Iron
[0014] The residue exhausted from the hydrometallurgical leaching
process is generally more chemically unstable than slag from the
pyrometallurgical refining process, and concerns of the
residue-containing impurities eluted into the ambient environments
have been pointed out. It is desirable to improve extraction of
iron as the major ingredient of the leaching residue and recover
the iron in the utilizable form as the countermeasures to decrease
residue wastes.
[0015] Under these situations, there are demands for
hydrometallurgical refining processes which can solve the problems
involved in the conventional processes to efficiently treat a raw
copper material containing a copper sulfide mineral.
[0016] The average particle size (D50) described in this
specification was determined by a Microtrac particle size
distribution analyzer (Nikkiso Co., 9320HRA (X-100)).
[0017] [Patent Document 1]
[0018] Japanese Patent Laid-open Publication No.2001-515145 (Pages
1 and 2)
[0019] [Patent Document 2]
[0020] Japanese Patent No.2,857,930 (Pages 1 to 4)
SUMMARY OF THE INVENTION
[0021] It is an object of the present invention to provide a
hydrometallurgical process for refining a raw copper material
containing a copper sulfide mineral, e.g., chalcopyrite, which can
leach copper out of the raw material at a high extraction while
suppressing oxidation of sulfur, recover it in the monovalent state
by electrolysis and, at the same time, recover a concomitant
valuable metal while minimizing production of wastes, e.g.,
leaching residue, as far as possible, in consideration of the
problems involved in the conventional processes.
[0022] The inventors of the present invention have found, after
having extensively studied processes for refining a raw copper
material containing a copper sulfide mineral, that a process can
efficiently separate and recover copper, iron and a concomitant
valuable metal when it comprises a series of steps for leaching a
raw copper material containing a copper sulfide mineral in the
presence of chlorine in an acidic, aqueous chloride solution,
reduction of the copper ion in the leaching product liquor,
extraction of copper from the reduction product liquor with the aid
of solvent followed by stripping of the extract with the aid of a
solvent, electrolysis for recovering copper, and electrolysis for
recovering iron, achieving the present invention.
[0023] The first aspect of the present invention is a process for
refining raw copper material containing copper sulfide mineral
characterized by a hydrometallurgical process for recovering copper
and a concomitant valuable metal from a raw copper material
containing a copper sulfide mineral, comprising:
[0024] (1) a chlorine-aided leaching step for leaching the raw
copper material in the presence of chlorine in an acidic, aqueous
chloride solution to produce the leaching product liquor containing
the copper ion and residue containing elemental sulfur by leaching
copper in the acidic solution,
[0025] (2) a copper ion reduction step for reducing the leaching
product liquor in the presence of a reductant to produce the
reduction product liquor containing the cuprous ion,
[0026] (3) a solvent extraction step for extracting copper with the
aid of solvent from the reduction product liquor, and stripping
loaded solvent to produce the stripping product liquor containing
the cuprous ion and raffinate containing the ferrous ion,
[0027] (4) a copper electrowinning step for electrolyzing the
stripping product liquor to produce the electrolytic copper and
spent electrolyte, and
[0028] (5) an iron electrowinning step for electrolyzing the
raffinate to produce the electrolytic iron and iron spent
electrolyte composed of the aqueous iron chloride solution.
[0029] The second aspect of the present invention is the process of
the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the chlorine-aided leaching step is
effected by blowing chlorine gas into the acidic, aqueous chloride
solution.
[0030] The third aspect of the present invention is the process of
the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the chlorine-aided leaching step is
effected at a slurry concentration of 100 to 400 g/L, leaching
temperature of 100 to 110.degree. C. and oxidation-reduction
potential of 500 to 600 mV (based on an Ag/AgCl electrode).
[0031] The fourth aspect of the present invention is the process of
the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the chlorine-aided leaching step is
controlled in such a way to have a final chloride ion concentration
of 250 to 400 g/L in the acidic, aqueous chloride solution.
[0032] The fifth aspect of the present invention is the process of
the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the copper ion reduction step uses
the copper sulfide mineral as the reductant.
[0033] The sixth aspect of the present invention is the process of
the fifth aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the copper sulfide mineral is
treated under heating at the atmospheric pressure in the leaching
product liquor to produce the reduction product liquor and residue
containing elemental sulfur.
[0034] The seventh aspect of the present invention is the process
of the sixth aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the copper sulfide mineral is a
copper concentrate mainly composed of chalcopyrite, prepared to
have an average particle diameter (D50) of 0.5 to 60 .mu.m, and
temperature at which the leaching product liquor is reduced is 90
to 110.degree. C. and, at the same time, is at least the
temperature level (A) given by the following formula 1:
A(.degree. C.)=6.79.times.Ln(B)+81.5 Formula 1
[0035] (wherein, B is an average particle diameter (D50, .mu.m),
determined by the Microtrac analyzer, at a volumetric cumulative
frequency of 50% of the copper concentrate).
[0036] The eighth aspect of the present invention is the process of
the sixth aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the copper sulfide mineral is a
copper concentrate mainly composed of chalcopyrite, prepared to
have an average particle diameter (D50) of 0.5 to 60 .mu.m, and
temperature at which the leaching product liquor is reduced is 90
to 110.degree. C. and, at the same time, is at least the
temperature level (A) given by the following formula 2:
A(.degree. C.)=7.04.times.Ln(B)+95.2 Formula 2
[0037] (wherein, B is an average particle diameter (D50, .mu.m),
determined by the Microtrac analyzer, at a volumetric cumulative
frequency of 50% of the copper concentrate).
[0038] The ninth aspect of the present invention is the process of
the sixth aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the residue is recycled back as a
raw copper material to the chlorine-aided leaching step.
[0039] The tenth aspect of the present invention is the process of
the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the solvent extraction step uses an
organic solvent containing a solvating extractant for solvent
extraction.
[0040] The 11.sup.th aspect of the present invention is the process
of the tenth aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the organic solvent contains the
solvating extractant at 40% by volume or more.
[0041] The 12.sup.th aspect of the present invention is the process
of the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein an aqueous solution for stripping
in the solvent extraction step contains copper at 70 g/L or less
and chlorine ion at 50 to 350 g/L.
[0042] The 13.sup.th aspect of the present invention is the process
of the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the stripping is effected at 40 to
90.degree. C. in the solvent extraction step.
[0043] The 14.sup.th aspect of the present invention is the process
of the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the copper electrowinning step is
effected in an electrolysis tank composed of a cathode chamber and
anode chamber separated from each other by a diaphragm,
characterized in that the stripping product liquor containing the
cuprous ion, discharged from the solvent extraction step, is
supplied to the cathode chamber to electrowin copper on the
cathode, the iron spent electrolyte composed of an aqueous iron
chloride solution, discharged from the iron electrowinning step, is
supplied to the anode chamber for anodic oxidation, and the
solution being supplied to the anode chamber is prevented from
flowing into the cathode chamber through the diaphragm.
[0044] The 15.sup.th aspect of the present invention is the process
of the 14.sup.th aspect for refining a raw copper material
containing a copper sulfide mineral, wherein water permeates
through the diaphragm at 0.04 to 0.15 L/m.sup.2.multidot.s.
[0045] The 16.sup.th aspect of the present invention is the process
of the 14.sup.th aspect for refining a raw copper material
containing a copper sulfide mineral, wherein the cathode and anode
chambers in the electrolysis tank are structured in such a way that
a solution is charged and discharged separately in each chamber,
and the solution level is kept higher in the cathode chamber than
in the anode chamber.
[0046] The 17.sup.th aspect of the present invention is the process
of the 14.sup.th aspect for refining a raw copper material
containing a copper sulfide mineral, wherein the solution
discharged from the cathode chamber is recycled back as the
stripping solution to the solvent extraction step, and the solution
discharged from the anode chamber is recycled back as the leachate
to the chlorine-aided leaching step.
[0047] The 18.sup.th aspect of the present invention is the process
of the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the iron electrowinning step is
effected in an electrolysis tank composed of an anode chamber and
cathode chamber separated from each other by a filter cloth,
characterized in that the iron ion is supplied to the anode chamber
at a rate at least twice as high as that for the iron ion deposited
on the cathode in order to decrease cell voltage.
[0048] The 19.sup.th aspect of the present invention is the process
of the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein a solution purification step is
included upstream of the iron electrowinning step to purify the
raffinate from the solvent extraction step, which produces the
purified solution and precipitate product.
[0049] The 20.sup.th aspect of the present invention is the process
of the 19.sup.th aspect for refining a raw copper material
containing a copper sulfide mineral, wherein the raffinate from the
solvent extraction step is purified in the solution purification
step by a treatment method selected from the group consisting of
sulfidation, cementation and neutralization.
[0050] The 21.sup.st aspect of the present invention is the process
of the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the residue containing elemental
sulfur, discharged from the chlorine-aided leaching step, is
distilled in an inert atmosphere to be separated into the condensed
sulfur and residue containing a concomitant metal, after
evaporating sulfur.
[0051] The 22.sup.nd aspect of the present invention is the process
of the first aspect for refining a raw copper material containing a
copper sulfide mineral, wherein the electrolytic copper produced in
the copper electrowinning step is used as the anode to be refined
by electrolysis and separated into the high-purity, electrolytic
copper and silver-containing slime.
[0052] The process of the present invention as a hydrometallurgical
process for refining a raw copper material containing a copper
sulfide mineral, e.g., chalcopyrite, can leach copper out of the
raw material at a high extraction while suppressing oxidation of
sulfur, recover it in the monovalent state by electrolysis and, at
the same time, recover a concomitant valuable metal while
minimizing production of wastes, e.g., leaching residue, as far as
possible, and hence is of high industrial value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] FIG. 1 shows one embodiment of the refining process scheme
of the present invention.
[0054] FIG. 2 shows the relationship between the copper ion state
(cuprous/cupric concentration ratio, Cu(1)/Cu(2)) and ORP (based on
an Ag/AgCl electrode), where the chloride solution was incorporated
with a varying concentration of ferrous ion at 90.degree. C.
[0055] FIG. 3 shows the relationships among reduction temperature,
particle size and ORP level (based on an Ag/AgCl electrode), where
the reduction was effected under varying reduction temperature and
particle size.
[0056] FIG. 4 shows the relationship (obtained by the regression
analysis) between temperature and particle size (D50) at a target
ORP level (based on an Ag/AgCl electrode) of 400 mV.
[0057] FIG. 5 shows the relationship (obtained by the regression
analysis) between temperature and particle size (D50) at a target
ORP level (based on an Ag/AgCl electrode) of 380 mV.
[0058] FIG. 6 illustrates one structural embodiment of the
electrolysis tank for the present invention.
[0059] FIG. 7 shows the effects of slurry concentration in the
chlorine-aided leaching step on copper and iron extraction, and
sulfur oxidation.
[0060] FIG. 8 shows the effects of the final chlorine ion
concentration in the chlorine-aided leaching step on copper and
iron extraction, and sulfur oxidation.
[0061] FIG. 9 shows the effects of tributyl phosphate concentration
in the solvent extraction step on copper and iron extraction.
[0062] FIG. 10 shows the effects of tributyl phosphate
concentration in the solvent extraction step on copper/iron
separation coefficient.
[0063] FIG. 11 shows the effects of solution temperature in the
solvent extraction on stripping rate of copper.
NOTATION
[0064] 1 Chlorine-aided leaching step
[0065] 2 Copper ion reduction step
[0066] 3 Solvent extraction step
[0067] 4 Copper electrowinning step
[0068] 5 Solution purification step
[0069] 6 Iron electrowinning step
[0070] 7 leaching residue treatment step
[0071] 8 Raw copper material
[0072] 9 Electrolytic copper
[0073] 10 Electrolytic iron
[0074] 11 Cathode chamber
[0075] 12 Anode chamber
[0076] 13 Diaphragm
[0077] 14 Cathode
[0078] 15 Anode
[0079] 16 Overflow port in the cathode chamber
[0080] 17 Overflow port in the anode chamber
[0081] 18 Cathode supply solution
[0082] 19 Anode supply solution
[0083] 20 Catholyte
[0084] 21 Anolyte
[0085] 22 Spent catholyte
[0086] 23 Spent anolyte
DETAILED DESCRIPTION OF THE INVENTION
[0087] The process of the present invention for refining a raw
copper material containing a copper sulfide mineral is described in
detail.
[0088] First, the process of the present invention for refining a
raw copper material containing a copper sulfide mineral is outlined
by referring to the attached drawings. FIG. 1 shows one embodiment
of the flow of the refining process of the present invention.
[0089] In FIG. 1, the raw copper material 8 containing a copper
sulfide mineral is first sent to the chlorine-aided leaching step
1, where it is separated into the leaching product liquor
containing copper, iron and the like, and sulfur-containing
residue. The product liquor is then sent to the copper ion
reduction step 2, where copper in the solution is reduced to
produce the reduction product liquor containing the cuprous ion.
When the raw copper material containing a copper sulfide mineral is
used as a reductant in this step, the residue from this step is
recycled back to the chlorine-aided leaching step 1. The reduction
product liquor is sent to the solvent extraction step 3, where it
is separated into the stripping product liquor containing the
cuprous ion and raffinate by the solvent extraction and stripping.
The stripping product liquor is sent to the copper electrowinning
step 4, where copper is recovered as the electrolytic copper 9.
[0090] Copper ores containing a copper sulfide mineral generally
contain iron at a concentration comparable to that of copper,
although varying depending on type of raw material for refining
processes. This means that the raffinate from the solvent
extraction step 3 contains a high concentration of iron ion.
Therefore, the raffinate from the solvent extraction step 3 is sent
to the solution purification step 5, as required, to be separated
into the purified solution containing the iron ion and solid
containing one or more types of valuable metals except iron. The
purified solution containing the iron ion is sent to the iron
electrowinning step 6, where iron is recovered as the electrolytic
iron 10.
[0091] The sulfur-containing residue separated in the
chlorine-aided leaching step 1 is sent to the leaching residue
treatment step 7, where elemental sulfur is recovered. The spent
electrolytes separated in the copper electrowinning step 4 are
recycled; the catholyte back to the solvent extraction step 3 as
the solution for the stripping, and anolyte back to the
chlorine-aided leaching step 1 as the leachate. The spent
electrolyte from the iron electrowinning step 6 is recycled back to
the copper electrowinning step 4 as the solution for the anode.
[0092] 1. Raw Copper Material Containing a Copper Sulfide Mineral,
and Concomitant Valuable Metal
[0093] The raw copper materials containing a copper sulfide
mineral, useful for the refining process of the present invention,
include copper ores containing a copper sulfide mineral, e.g.,
chalcopyrite (CuFeS.sub.2), chalcocite (Cu.sub.2S) or bornite
(Cu.sub.5FeS.sub.4); copper concentrate in which a copper sulfide
mineral is concentrated by treating the copper ore by floatation or
the like; copper sulfide mineral; ores containing a varying copper
mineral, e.g., copper oxide, copper arsenide or copper antimonide,
and copper concentrate from the ore; copper matte, including
high-quality copper matte, produced from a copper concentrate or
the like by a pyrometallurgical refining process; and various raw
copper materials, which are sulfide-like, oxide-like or metallic,
when they are available to be treated together with the above.
[0094] The concomitant valuable metals include iron, nickel,
cobalt, manganese, sulfur, zinc, cadmium, tin, lead, zinc, a Group
5 element in the periodic table (e.g., arsenic, antimony, bismuth
or the like), Group 6 element in the periodic table (e.g.,
selenium, tellurium or the like), and noble metal.
[0095] 2. Chlorine-Aided Leaching Step
[0096] The chlorine-aided leaching step for the refining process of
the present invention mainly leaches copper, iron and the like, in
the presence of chlorine, out of a raw copper material containing a
copper sulfide mineral, suspended in an acidic, aqueous chloride
solution containing copper chloride, iron chloride or the like to
produce the leaching product liquor containing the copper and iron
ion and residue containing elemental sulfur by leaching copper,
iron or the like. When the raw copper material is used as a
reductant for the subsequent copper ion reduction step, it is
preferable to use the residue from this step as the raw material
for the leaching step. For example, the raw copper material may be
totally treated in the copper ion reduction step to produce the raw
copper material for the chlorine-aided leaching step.
[0097] Chlorine as the leaching solution for the above step is not
limited, and a chlorine compound capable of oxidizing copper
chloride, iron chloride or the like in the acidic, aqueous chloride
solution is used. However, it is preferable to blow chlorine gas
into the acidic, aqueous chloride solution, because of its high
oxidative power, in particular viewed from reaction efficiency.
[0098] When chalcopyrite, which is leached with chlorine more
slowly than chalcocite, bornite or high-quality copper matte, is
the main copper sulfide to be leached out, suppressing oxidation of
sulfur while securing high copper extraction is an important
problem. It is preferable to adequately control oxidative power
during the leaching step, in order to control sulfur oxidation. The
oxidative power can be suppressed by optimizing the conditions,
e.g., oxidation-reduction potential of the leaching solution,
leaching temperature, slurry concentration and chlorine
concentration of the leaching solution.
[0099] Oxidation-reduction potential (sometimes referred to as ORP,
based on an Ag/AgCl electrode) of the leaching solution for the
chlorine-aided leaching step, although not limited, is preferably
500 to 600 mV, more preferably 500 to 520 mV. At below 500 mV,
copper extraction tends to be insufficient, because of insufficient
oxidative power for the leaching step. At above 600 mV, on the
other hand, sulfur tends to be excessively oxidized. It should be
noted that sulfur is little oxidized at an ORP of 500 to 520 mV.
When the raw copper material is mainly composed of chalcopyrite,
the leaching is effected particularly preferably at an ORP of 500
to 520 mV.
[0100] Leaching temperature, although not limited, is preferably
100 to 110.degree. C., more preferably 105 to 110.degree. C. At
lower than 100.degree. C., copper and iron can be leached at an
insufficient rate, while sulfur is oxidized. At higher than
110.degree. C., on the other hand, the leaching step needs a system
operating at an elevated pressure.
[0101] The initial slurry concentration (concentration of the raw
copper material in the slurry) for the above step, although not
limited, is preferably 100 to 400 g/L, more preferably 250 to 400
g/L. At below 100 g/L, copper and iron can be leached at an
insufficient rate, while sulfur is oxidized. At above 400 g/L, on
the other hand, the system investment tends to be higher while the
system operability tends to be lower.
[0102] The chlorine ion concentration in the leaching solution at
the end of the leaching step, although not limited, is preferably
200 to 400 g/L, more preferably 250 to 400 g/L. At below 200 g/L,
copper and iron can be leached at an insufficient rate, while
sulfur is oxidized. On the other hand, the concentration has little
effect for accelerating the reaction, when it is increased to above
400 g/L. It is preferable to control the rate at which chlorine is
blown into the acidic, aqueous chloride solution, in order to keep
the chlorine-ion concentration at 200 to 400 g/L in the final
leaching solution.
[0103] The refining process of the present invention can leach
copper and iron at a rate of 95% or more and 90% or more out of a
raw copper material composed mainly of chalcopyrite while keeping
oxidation of sulfur in the chalcopyrite at a rate of 5% or less,
when the chlorine-aided leaching step is effected under the above
conditions. Therefore, it can achieve high copper extraction for
chalcopyrite while suppressing oxidation of sulfur, which is one of
the objects for developing hydrometallurgical copper refining
processes.
[0104] The leaching product liquor containing the cupric and ferric
ion, and residue containing elemental sulfur may be treated by the
ordinary process for solid/liquid separation.
[0105] 3. Copper Ion Reduction Step
[0106] The copper ion reduction step for the refining process of
the present invention treats, in the presence of a reductant, the
leaching product liquor containing copper ion, iron ion and the
like, discharged from the chlorine-aided leaching step to reduce
these ions, the cupric ion to the cuprous ion and, at the same
time, ferric ion to the ferrous ion. This allows the copper ion to
be extracted selectively by an organic solvent in the subsequent
solvent extraction step from the reduction product liquor in which
the cuprous ion is present at a high proportion.
[0107] In the above step, the reduction product liquor is kept at
an ORP (based on an Ag/AgCl electrode) at which the cupric ion
present in the aqueous chloride solution containing copper and iron
can be reduced into the cuprous ion. The ORP level is preferably 0
to 400 mV, more preferably 0 to 380 mV. At an ORP (based on an
Ag/AgCl electrode) above 400 mV, the copper ion partly becomes the
divalent ion, which can work as an oxidant to partly oxidize the
iron ion into the trivalent one, preventing formation of the
reduction product liquor in which the cuprous ion is present at a
high proportion. At an ORP (based on an Ag/AgCl electrode) below 0
mV, on the other hand, the iron or copper ion may be reduced to the
metallic state and precipitated.
[0108] Although it is difficult to accurately analyze the cuprous
and cupric ion state in the leaching product liquor also containing
the iron ion and the like, the relationship between the copper
modality and ORP is estimated using FIG. 2.
[0109] FIG. 2 shows the relationship between the copper ion state
(cuprous/cupric concentration ratio, Cu(1)/Cu(2)) and ORP (based on
an Ag/AgCl electrode), where the chloride solution was incorporated
with a varying quantity of reagent to change its ferrous ion
concentration. The relationship indicates that the ORP level (based
on an Ag/AgCl electrode) should be 400 mV or less for the copper
and iron ion to be present mostly as the cuprous and ferrous ion,
respectively, and 380 mV or less for these ions to be cuprous and
ferrous. Therefore, in the case of a leaching product liquor which
contains Cu at around 50 g/L and Fe at 50 to 100 g/L, the target
ORP level for the reduction step is around 380 to 400 mV.
[0110] The reductant for the above step, although not limited, can
be at least one type selected from the group consisting of metallic
copper, metals baser than copper, and copper sulfide and copper
sulfide mineral. Of these, copper sulfide and copper sulfide
mineral are particularly preferable, because they can also
accelerate copper leaching. The copper and iron ion can be reduced
to the monovalent and divalent state, respectively, while leaching
part of the copper in a raw copper material beforehand by bringing,
prior to the leaching step, the raw material containing a copper
sulfide mineral into contact with the leach solution from the
chlorine-aided leaching step. The resulting residue containing
elemental sulfur is preferably sent to the chlorine-aided leaching
step as a raw copper material to be leached therein.
[0111] When a copper sulfide mineral is chalcopyrite, the reduction
reactions for converting the cupric and ferric ion into the cuprous
and ferrous ion, respectively, and also for producing elemental
sulfur are represented by the following chemical equations 1 and
2:
Cu.sup.2++1/3CuFeS.sub.2.fwdarw.4/3Cu.sup.++1/3Fe.sup.2++2/3S
Chemical equation 1
Fe.sup.3++1/3CuFeS.sub.2.fwdarw.1/3Cu.sup.++4/3Fe.sup.2++2/3S
Chemical equation 2
[0112] The chemical equations 1 and 2 represent the leaching
reactions of chalcopyrite in the presence of the cupric and ferric
ion, respectively. As shown, leaching of chalcopyrite proceeds with
reduction of the cupric and ferric ion.
[0113] In the above step, the reduction condition is not limited,
when a copper sulfide mineral serves as the reductant. It may be
effected at the atmospheric pressure or an elevated pressure. The
reduction effected at the atmospheric pressure is more preferable,
because it needs no facility to be operated at an elevated
pressure. It is therefore preferable that a copper sulfide mineral
is heated at the atmospheric pressure in the leaching product
liquor to produce the reduced product liquor and residue containing
elemental sulfur.
[0114] The reduction treatment process effected at the atmospheric
pressure is not limited. For example, the reduced state in which
the cuprous ion is present at a high proportion may be produced by
one of the following 2 processes.
[0115] One of these processes treats a copper concentrate mainly
composed of chalcopyrite as the copper sulfide mineral, prepared to
have an average particle diameter (D50) of 0.5 to 60 .mu.m while
keeping reduction temperature of the leaching product liquor at 90
to 110.degree. C. and, at the same time, at least at the level (A)
given by the following formula 1:
A(.degree. C.)=6.79.times.Ln(B)+81.5 Formula 1
[0116] (wherein, B is an average particle diameter (D50, .mu.m),
determined by the Microtrac analyzer, at a volumetric cumulative
frequency of 50% of the copper concentrate). This can keep the
reduction product liquor at an ORP (based on an Ag/AgCl electrode)
of 400 mV or less.
[0117] The other process treats a copper concentrate mainly
composed of chalcopyrite as the copper sulfide mineral, prepared to
have an average particle diameter (D50) of 0.5 to 60 .mu.m while
keeping reduction temperature of the leaching product liquor at 90
to 110.degree. C. and, at the same time, at least at the level (A)
given by the following formula 2:
A(.degree. C.)=7.04.times.Ln(B)+95.2 Formula 2
[0118] (wherein, B is an average particle diameter (D50, .mu.m),
determined by the Microtrac analyzer, at a volumetric cumulative
frequency of 50% of the copper concentrate). This can keep the
reduction product liquor at an ORP (based on an Ag/AgCl electrode)
of 380 mV or less.
[0119] Reactivity of the cupric and ferric ion in the leaching
product liquor with chalcopyrite is important for decreasing
oxidation-reduction potential of the reduction product liquor, and
hence extent of the reduction reaction proceeding in each of the
above processes. Therefore, the essential conditions for the
leaching step are use of a copper concentrate mainly composed of
chalcopyrite, prepared to have a specific average particle diameter
(D50), and selection of an adequate reduction temperature level
based on the formula 1 or 2, which is a function of D50 of the
copper concentrate.
[0120] Use of a copper concentrate whose average particle size is
controlled at a given level can keep the reduction product liquor
at an ORP (based on an Ag/AgCl electrode) of 400 mV or less,
preferably 380 mV or less, at which the cuprous ion prevails over
the cupric ion, when the leaching product liquor is heated at a
given reduction temperature level and the atmospheric pressure.
This means that the cupric ion can be efficiently reduced into the
cuprous ion by the treatment effected at the atmospheric
pressure.
[0121] The copper concentrate for the reduction process has an
average particle size (D50) of 0.5 to 60 .mu.m, preferably 1 to 10
.mu.m, more preferably 3.5 to 8.2 .mu.m. A concentrate having a D50
level below 0.5 .mu.m may cause problems, e.g., leak or
deteriorated precipitation in separation of the reduction product
liquor from the residue. On the other hand, a concentrate having a
D50 level above 60 .mu.m may decrease its reactivity, needing to
hold the leaching product liquor for a longer time at a higher
temperature closer to its boiling point, in order to secure the
target ORP level. This should decrease productivity and energy
efficiency.
[0122] The method for adjusting particle size of the copper
concentrate for the reduction step is not limited. The particle
size can be adjusted by various commercial crushers, e.g.,
agitation/crushing machine using a medium (commonly referred to as
bead mill, e.g., Nano grain Mill NM-G5M supplied by Asada Iron
Works or NVM-2 supplied by Aimex), and planetary ball mill (e.g.,
Planetary Mill SKF-04 supplied by Seishin Enterprise).
[0123] The reduction step is effected at 90 to 110.degree. C. The
leaching solution preferably contains the chloride ion at 200 to
400 g/L in the chlorine-aided leaching step, which means that
boiling point of the leaching product liquor increases to near
110.degree. C. At above 110.degree. C., the reduction step is not
operable at the atmospheric pressure. At below 90.degree. C., on
the other hand, leaching efficiency is insufficient, because the
reaction proceeds only slowly, even when the copper concentrate is
divided finely, and the treatment needs a long time to secure the
target ORP level.
[0124] The initial copper concentrate slurry concentration for the
reduction step is not limited. Increasing the concentration
accelerates the reduction reaction on one hand, but the optimum
concentration tends to be limited by other considerations, e.g.,
process mass balance, and solubility of copper chloride and iron
chloride. As a net, it is preferably 50 to 250 g/L, at which
operable limitations are minimized, more preferably around 100 g/L.
Practical problems are not anticipated, when the initial slurry
concentration is set at around 100 g/L.
[0125] In the above reduction process, the relationship between
average particle size (D50) of the copper concentrate and adequate
reduction temperature is established by finding the temperature
level (A) given by the following formula 1 or 2 using the (D50)
level(B) of the concentrate, and setting the leaching product
liquor reduction temperature at 90 to 110.degree. C. and, at the
same time, at least at the temperature level (A):
A(.degree. C.)=6.79.times.Ln(B)+81.5 Formula 1
A(.degree. C.)=7.04.times.Ln(B)+95.2 Formula 2
[0126] (wherein, B is an average particle diameter (D50, .mu.m),
determined by the Microtrac analyzer, at a volumetric cumulative
frequency of 50% of the copper concentrate).
[0127] This can keep the reduction product liquor at the target ORP
level (based on an Ag/AgCl electrode) of 400 mV or less (based on
the formula 1) or 380 mV or less (based on the formula 2), at which
the reduction product liquor containing the cuprous ion at a high
proportion can be obtained.
[0128] The formula 1 or 2 represents the relationship between the
D50 level of a copper concentrate and reduction temperature for
securing the target ORP level (based on an Ag/AgCl electrode) of
400 mV or less or 380 mV or less at the initial copper concentrate
slurry concentration of 100 g/L. The relationship is established by
the following procedure. FIG. 3 shows the relationships among
reduction temperature, particle size and ORP level (based on an
Ag/AgCl electrode), where the reduction treatment was effected
under varying reduction temperature and particle size. The
approximated lines at 90, 104 and 107.degree. C. are drawn in FIG.
3. The relationships among the target ORP, temperature and D50,
obtained by the above procedure, are given in Table 1 and FIGS. 4
and 5. The approximated lines, obtained by the regression analysis,
represent the formula 1 and 2, respectively.
1 TABLE 1 Target ORP (mV) 380 400 D50 (.mu.m) 0.5 2 3 6 4 12 45 60
Temperature (.degree. C.) 90 100 104 107 90 100 107 109
[0129] As discussed above, it is apparent that the reduction
product liquor containing the cuprous ion at a high proportion can
be produced by reducing the cupric ion to the cuprous ion by using
a copper concentrate mainly composed of inexpensive
chalcopyrite.
[0130] As discussed above, the copper ion reduction step for the
refining process of the present invention efficiently reduces the
cupric and ferric ion in an aqueous chloride solution to the
cuprous and ferrous ion while suppressing oxidation of sulfur in a
copper sulfide mineral, to produce the reduction product liquor
containing the cuprous and ferrous ion, and residue containing
elemental sulfur. Therefore, it can achieve efficient reduction of
copper, which is one of the objects for developing
hydrometallurgical copper refining processes.
[0131] 4. Solvent Extraction Step
[0132] The solvent extraction step for the refining process of the
present invention comprises two steps; one is for contacting and
mixing the reduction product liquor containing the cuprous ion,
discharged from the copper ion reduction step, with the aid of an
organic solvent containing an organic extractant to selectively
extract the cuprous ion in the organic solvent, and the other is
for contacting and mixing the organic solvent which has extracted
the cuprous ion with an aqueous solution to strip the ion in the
aqueous solution, to produce the aqueous solution containing the
copper ion and raffinate containing the iron ion and concomitant
valuable metal ion. The reduction product liquor is kept at an ORP
(based on an Ag/AgCl electrode) of 0 to 400 mV.
[0133] The organic extractant for the above step is not limited, so
long as it can extract the cuprous ion and thereby to separate it
from iron and a concomitant valuable metal. However, a solvating
extractant, e.g., tributyl phosphate, is particularly preferable.
Tributyl phosphate as an extractant selectively extracts the
cuprous ion in the organic solvent phase by the solvent extraction
effected at an optimum oxidation-reduction potential, leaving the
ferrous ion, silver ion or the like in the raffinate.
[0134] Concentration of a solvating extractant (e.g., tributyl
phosphate) in the organic solvent phase, although not limited, is
preferably 40 to 100% by volume, more preferably 50 to 100%. At
below 40% by volume, it may not secure a copper extraction
industrially expected. Tributyl phosphate is used normally after
being diluted with a diluent, e.g., kerosene, to keep it fluid.
However, the dilution should be avoided as far as possible to
improve copper ion extraction rate, which depends on concentration
of the chloride ion and that of tributyl phosphate in the reduction
product liquor.
[0135] Concentration of copper in the aqueous solution for the
stripping step, although not limited, is preferably 70 g/L or less.
Increasing the concentration beyond 70 g/L may cause a phenomenon
in which copper conversely moves into the organic solvent
phase.
[0136] Concentration of chlorine in the aqueous solution for the
stripping step, although not limited, is preferably 50 to 350 g/L.
At below 50 g/L, the stripped cuprous ion may not be kept soluble
in the solution, because of its low solubility in water. The
stripped cuprous ion is normally kept soluble in the solution by
sufficiently increasing chlorine ion concentration of the solution
for the stripping in consideration of concentration of the copper
ion to be stripped. However, the chlorine ion concentration is
limited to 350 g/L, which is the practical upper limit.
[0137] Stripping temperature for the above step, although not
limited, is preferably 40 to 90.degree. C., more preferably 50 to
90.degree. C. At below 40.degree. C., movement of the copper ion in
tributyl phosphate towards the aqueous phase may be retarded to
decrease its stripping rate. At above 90.degree. C., on the other
hand, heat radiation from the solution and evaporation of the
solvent tend to be excessive, making it difficult to keep system
temperature at a given level, and also keep the organic solvent and
aqueous phase stable.
[0138] As discussed above, the solvent extraction step for the
refining process of the present invention can efficiently produce
the aqueous solution containing the cuprous ion and raffinate
containing the iron ion and a concomitant valuable metal from the
reduction product liquor, discharged from the copper ion reduction
step.
[0139] 5. Copper Electrowinning Step
[0140] The copper electrowinning step for the refining process of
the present invention recovers copper by electrolyzing the
stripping product liquor containing the cuprous ion, discharged
from the solvent extraction step, to produce the electrolytic
copper on the cathode and spent electrolyte.
[0141] The copper electrowinning method for the above step is not
limited, and may be selected from the various methods which recover
a metal by electrolysis from its chloride. Of these, the
particularly preferable one is diaphragm-aided electrolysis which
uses an electrolysis tank composed of a cathode chamber and anode
chamber separated from each other by a diaphragm, characterized in
that the stripping product liquor (aqueous solution of cuprous
chloride), discharged from the solvent extraction step, is supplied
to the cathode chamber to electrowin copper on the cathode, the
iron spent electrolyte (aqueous solution of iron chloride) composed
of an aqueous iron chloride solution, discharged from the iron
electrowinning step, is supplied to the anode chamber for anodic
oxidation, and the solution being supplied to the anode chamber is
prevented from flowing into the cathode chamber through the
diaphragm. More preferably, the solution discharged from the
cathode chamber is recycled back as the stripping solution to the
solvent extraction step, and the solution discharged from the anode
chamber is recycled back as the leachate to the chlorine-aided
leaching step.
[0142] How copper is electrolyzed and recovered is described by
referring to FIG. 6, which illustrates one structural embodiment of
the electrolysis tank for the copper electrowinning step.
[0143] The electrolysis tank shown in FIG. 6 is composed of the
cathode chamber 11 and anode chamber 12 separated from each other
by the diaphragm 13, each chamber being equipped with the
corresponding electrode. The cathode 14 is not limited, and may be
of metallic copper, titanium or stainless steel. The anode 15 is
also not limited, and may be of an insoluble electrode (e.g.,
DSE.RTM. supplied by Permelec Electrode Ltd.) which has been used
for generating chlorine gas from an aqueous chloride solution in
saline electrolysis or the like.
[0144] The electrolysis tank is structured in such a way to prevent
the solution 19 being supplied to the anode chamber 12 from flowing
into the cathode chamber 11 through the diaphragm 13. The cathode
chamber solution 20 and anode chamber solution 21 are separated
from each other, but not strictly, because the diaphragm 13 should
pass the ions and electricity. In other words, the structure is
acceptable when it prevents free movement of the oxidized anode
chamber solution 21 into the cathode chamber 11, and not necessary
to completely prevent flow of the ions and water.
[0145] The diaphragm for realizing the structural feature of the
electrolysis tank is not limited, and may be of filter cloth or
solid electrolyte membrane. Of these, filter cloth finely woven to
have a low water permeability is more preferable, because a solid
electrolyte membrane is more costly and sensitive to impurities
than cloth.
[0146] Water permeability of the diaphragm, although not limited,
is preferably 0.04 to 0.15 L/m.sup.2.multidot.s. A diaphragm having
a water permeability below 0.04 L/m.sup.2.multidot.s tends to
increase tank voltage and filter cloth cost, because of limited
liquid flow. A diaphragm having a permeability above 0.15
L/m.sup.2.multidot.s, on the other hand, tends to decrease copper
yield, because of excessive solution movement.
[0147] When contamination of the anode chamber solution 21 with a
small quantity of the cathode chamber solution 20 flowing into the
anode chamber 12 has little operational influence, it is preferable
keep head of the cathode chamber solution 20 higher than that of
the anode chamber solution 21 to prevent flow of the anode chamber
solution 21 towards the cathode chamber 11 side. More specifically,
for example, the overflow level is kept slightly higher in the
cathode chamber 11 than in the anode chamber 12, to prevent flow of
chlorine gas and the solution containing chlorine gas in the anode
chamber 12 into the cathode chamber 11 by the solution level
difference.
[0148] It is necessary to equilibrate electrolysis reactions
comprising reduction on the cathode and oxidation on the anode
(anodic oxidation) for smoother copper electrowinning.
[0149] Therefore, the electrolysis tank is structured in such a way
to send the stripping product liquor (aqueous solution of cuprous
chloride), discharged from the solvent extraction step, as the
cathode supply solution 18 to the cathode chamber 11 to reduce the
cuprous ion on the cathode 14 and electrodeposit the metallic
copper thereon, and, on completion of the reaction, to directly
discharge the cathode chamber solution 20 from the cathode chamber
11 for recovery.
[0150] The electrolysis tank is also structured in such a way to
send the iron spent electrolyte (aqueous solution of iron chloride)
discharged from the iron electrowinning step as the anode supply
solution 19 to the anode chamber 12 for anodic oxidation on the
anode 15, and, on completion of the reaction, to directly discharge
the anode chamber solution 21 from the anode chamber 12 for
recovery. The aqueous solution of iron chloride, discharged from
the iron electrowinning step, contains the ion which can be
oxidized on the anode to release the electron, and hence can
establish the electrolysis reaction. For example, when the reaction
to oxidize ferrous chloride to ferric chloride is effected as the
anodic reaction to reduce cell voltage, the solution leaving the
anode in the iron electrowinning step is suitable as the anode
supply solution 19 for copper electrowinning, because it is a
solution of ferric chloride containing a sufficient quantity of the
chlorine ion. The anodic oxidation of the aqueous solution of
ferric chloride in the iron electrowinning step releases chlorine
gas.
[0151] The anode chamber solution 21 is discharged after being
contaminated with part of the cathode chamber solution 20, because
the solution 21 is not strictly separated from the solution 20 by
the diaphragm 13. However, most of the cathode chamber solution 20
is directly discharged as the spent catholyte 22. As a result, the
cuprous ion not extracted and remaining in the cathode chamber
solution 20 can be recovered without being oxidized by the
oxidative anode chamber solution 21. Therefore, it is suitable as
the stripping solution for the solvent extraction step, because it
causes no reaction-related problem.
[0152] The spent anolyte 23, which is recycled back to the
chlorine-aided leaching step, causes no problem related to the
liquid balance, because there is essentially no fluctuation in the
solution volume in the copper electrowinning step. Moreover, ferric
chloride serving as an oxidant is transformed into more oxidative
chlorine gas, which is preferable for further improving efficiency
of the leaching step.
[0153] The method for discharging the spent catholyte 22 or spent
anolyte 23 is not limited, so long as the solution level in each
chamber is kept constant. These solutions can be automatically
discharged in a simple manner when the chambers are provided with
an overflow port 16 and 17 matching the liquid level in each
chamber.
[0154] The copper electrowinning step for the refining process of
the present invention achieves high current efficiency, because of
the electrowinning of the cuprous ion in the step. The cathode
chamber solution produced by the step is reductive, which is a
reactionally stable and suitable feature as the stripping solution
for the solvent extraction step. On the other hand, the anode
chamber solution is strongly oxidative, which is a suitable feature
as the leaching solution for the chlorine-aided leaching step.
Recycling these solutions back to the respective step achieves the
overall liquid balance for the whole process including these
steps.
[0155] 6. Iron Electrowinning Step
[0156] The iron electrowinning step for the refining process of the
present invention electrolyzes the raffinate discharged from the
solvent extraction step and recovers iron from the residue, to
produce the electrolytic iron on the cathode and anode supply
solution suitable for the copper electrowinning step. The iron
electrowinning step is preferable, because it provides the site for
treating the residue and effective resource utilization since the
electrolytic iron can be reused as pure or scrap iron.
[0157] How iron is electrolyzed and recovered in the above step is
not limited. For example, it is preferable to adopt diaphragm-aided
electrolysis in which the raffinate is used as the anode supply
solution to produce the solution from the anode chamber. The spent
anolyte is an aqueous solution of iron chloride, and can be
recycled back to the chlorine-aided leaching step as the leaching
solution for newly leach copper. However, it is preferably recycled
back to the copper electrowinning step as the anode supply
solution. In other words, it is particularly preferable, viewed
from over all efficiency of the hydrometallurgical copper refining
process, that the spent anolyte is supplied to the anode chamber
via the copper electrowinning step and then recycled back to the
chlorine-aided leaching step.
[0158] The diaphragm-aided electrolysis method is not limited.
However, the one treating a specific supply solution under specific
electrolysis conditions is preferable to control generation of
chlorine gas and decrease cell voltage. In such a system,
electrowinning of iron is controlled to an extent less than
one-thirds of that for the divalent iron ion supplied to the anode
chamber, because the divalent iron is oxidized into the trivalent
iron on the anode at a rate twice as high as that for the iron ion
deposited on the cathode. The electrolysis sufficiently proceeds
when the divalent iron is merely oxidized into the trivalent iron
on the anode, and hence generation of chlorine gas is controlled.
In other words, generation of chlorine gas is controlled and cell
voltage is decreased in the diaphragm-aided electrolysis step by
supplying the iron ion to the anode chamber at a rate at least
twice as high as that for the iron deposited on the cathode.
[0159] Oxidation of the divalent iron into the trivalent one in the
solvent extraction step or subsequent step, when occurs, decreases
current efficiency in the iron electrowinning step to increase the
power cost. Therefore, iron powder, iron plate or the like is
preferably provided at the supply port for the iron electrowinning
step to reduce the trivalent ion in the solution into the divalent
one.
[0160] As discussed above, the diaphragm-aided electrolysis which
treats a specific supply solution under specific electrolysis
conditions in the iron electrowinning step forms the anode supply
solution suitable for the electrolytic iron and copper
electrowinning step, and, at the same time, controls generation of
chlorine gas and decreases cell voltage. Therefore, it can achieve
efficient recovery of iron while reducing residue wastes, which is
one of the objects for developing hydrometallurgical copper
refining processes.
[0161] 7. Solution Purification Step
[0162] The refining process of the present invention can include,
as required, the solution purification step upstream of the iron
electrowinning step to treat the raffinate containing iron,
discharged from the solvent extraction step. This step is to
separate the raffinate containing iron, discharged from the solvent
extraction step, into the solid containing a concomitant valuable
metal and purified solution containing iron by precipitating the
valuable metal.
[0163] In general, iron potentially tends to form an eutectoid with
another impurity in the iron electrowinning step. It is therefore
necessary to remove the impurity, in order to obtain iron reusable
as a resource. The solution purification step can be included to
recover a concomitant valuable metal from the raffinate discharged
from the solvent extraction step and obtain iron reusable as a
resource.
[0164] The method for the solution purification step can be
selected from known ones. Of these, at least one selected from the
group consisting of sulfidation, cementation and neutralization is
preferable. It can be adequately selected according to type and
content of the concomitant valuable metal, which vary depending on
how it is contained in the raw material and solvent extraction
conditions, and cannot be specified.
[0165] The solid containing the concomitant valuable metal and
purified solution containing iron, discharged from the solution
purification step, are separated from each other by the ordinary
solid/liquid separation method.
[0166] 8. Leaching Residue Treatment Step
[0167] The refining process of the present invention may include,
as required, the leaching residue treatment step, as required, to
treat the residue containing elemental sulfur, discharged from the
chlorine-aided leaching step. The leaching residue treatment step
distills the residue containing elemental sulfur under heating in
an inert atmosphere to separate the residue into the condensed
sulfur and residue containing a concomitant noble metal or the
like, after evaporating sulfur.
[0168] Distillation temperature, although not limited, is
preferably 250 to 350.degree. C., more preferably 330 to
350.degree. C. At below 250.degree. C., sulfur is evaporated
insufficiently.
[0169] Sulfur condensed at the cooling section in the distillation
unit in the distillation treatment may be further refined, as
required, to produce a sulfur product. On the other hand, the noble
metal concentrated in the residue can be recovered by a noble metal
recovery system which has been adopted in the conventional refining
and purification method. The residue is treated to be completely
free of elemental sulfur and the noble metal contained therein can
be efficiently recovered.
[0170] 9. Copper Electrolysis/Purification Step
[0171] The refining process of the present invention may include,
as required, the copper electrolysis/purification step which treats
extracted copper produced by the copper electrowinning step, which
is used as the anode to be electrolyzed and purified. This step
separates the electrolytic copper into the high-purity,
electrolytic copper and silver-containing slime. It is adopted, as
required, when the electrolytic copper produced by the copper
electrowinning step contains an impurity at a high proportion. For
example, the electrolytic copper is molten and cast into the anode,
which is treated by the common electrolysis/purification system to
distribute the impurity and noble metal into the slime or
electrolytic solution, thereby it can produce the high-purity
electrolytic copper on the cathode. The electrolytic copper may be
also cast into the anode by a converter or refining furnace
provided in the latter stage of an existing pyrometallurgical
refining process. The anode can be treated in an existing copper
electrolysis refining process.
[0172] The structure of the process scheme for the present
invention, described above in detail, may be selected from the
adequate ones in consideration of raw copper material composition
(type and content of copper sulfide, content of iron, noble metal
content and another valuable substance), quality of the recovered
product, plant site, and so on. For example, when iron is present
at a low content in the raw material and discharged from the system
mostly in the leaching residue, in particular when the raw material
is chalcocite (Cu.sub.2S) or high-quality copper matte, the solvent
extraction, solution purification and iron recovery steps may be
saved.
EXAMPLES
[0173] The present invention is described in detail by EXAMPLES
which by no means limit the present invention. The following
analytical procedures and measurement procedure of average particle
size (D50) were used in EXAMPLES.
[0174] (1) Analysis of metals: ICP emission spectrometry was used,
with the liquid sample analyzed directly and solid sample analyzed
after it was dissolved in an acid.
[0175] (2) Analysis of chlorine concentration: Hydrochloric acid
concentration was determined by potentiometric titration with
silver nitrate, and concentrations of the chlorine ion accompanying
the copper, iron and sodium ions, determined by ICP emission
spectrometry, were calculated, to sum up these values.
[0176] (3) Analysis of mineral species composition and sulfur
modality: These were estimated from the chemical analysis results
after the mineral species was microscopically identified.
[0177] (4) Measurement of average particle size (D50): Average
particle size (D50) was determined by a Microtrac particle size
distribution analyzer (Nikkiso, 9320HRA (X-100)).
Example 1
[0178] (1) Chlorine-Aided Leaching Step
[0179] A raw copper material was leached with the aid of chlorine
in an acidic, aqueous solution of chloride to elute out copper in
the solution to produce the leaching product liquor containing the
copper ion and reside containing elemental sulfur, which were
evaluated.
[0180] The chemical composition of the raw copper material is given
in Table 2, and that of the copper concentrate as a mineral species
composition is given in Table 3.
2 TABLE 2 Composition (% by weight) Content (g/t) Cu Fe S SiO.sub.2
Au Ag 27.9 26.0 30.5 5.1 9 95
[0181]
3TABLE 3 Mineral species (% by weight) Chalcocite Chalcopyrite Iron
pyrite (Cu.sub.2S) (CuFeS.sub.2) (FeS.sub.2) Others <0.1 85.7
4.1 10.2
[0182] A 500 mL reactor of titanium was charged with a given
quantity (30 to 120 g) of the copper concentrate and 300 mL of an
acidic, aqueous solution of chloride containing copper at 60 g/L
and chlorine ion at 200 g/L, where the slurry concentration was set
at 100 to 400 g/L.
[0183] The concentrate, kept at 105 to 110.degree. C. by an oil
bath, was treated in the chlorine-aided leaching step with chlorine
gas blown to keep the system at a constant ORP (based on an Ag/AgCl
electrode) of 450 to 750 mV. The samples were collected 1, 3 and 6
hours after the treatment was started, to measure quantity of the
leaching residue, and concentrations of copper ion, iron ion and
sulfur in the leaching product liquor, thereby determining rates at
which copper and iron were leached out of the copper concentrate
and sulfur oxidation rate.
[0184] The leaching step was conducted with the initial leaching
solution, prepared in such a way to have a chlorine ion
concentration at 22 to 419 g/L with copper chloride, iron chloride
and sodium chloride, at an ORP (based on an Ag/AgCl electrode) of
520 mV and 100 to 110.degree. C.
[0185] Table 4 gives the effects of oxidation-reduction potential
(ORP) on copper and iron extraction and sulfur oxidation, FIG. 7
the effects of slurry concentration on copper and iron extraction,
and FIG. 8 the effects of the final chlorine ion concentration and
copper and iron extraction and sulfur
4 TABLE 4 ORP Extraction (%) Sulfur (mV) Cu Fe oxidation (%) 450
63.2 61.2 5.8 475 72.9 68.4 4.6 500 97.1 91.0 5.3 520 98.1 92.1 3.4
560 92.6 83.0 3.8 640 93.2 86.9 6.2 750 91.0 91.5 42
[0186] High copper and iron extraction and low sulfur oxidation can
be realized by keeping the chlorine-aided leaching solution
preferably at an ORP (based on an Ag/AgCl electrode) of 500 to 600
mV, more preferably 500 to 520 mV (Table 4), by keeping the initial
slurry concentration of the leaching solution preferably at 100 to
400 g/L, more preferably 250 to 400 mg/L (FIG. 7), and by keeping
the final chlorine ion concentration, i.e., concentration of
chlorine ion in the final leaching solution, preferably at 200 to
400 g/L, more preferably 250 to 400 g/L (FIG. 8).
[0187] (2) Copper Ion Reduction Step
[0188] The copper ion reduction step was carried out with Leaching
Product Liquors A, B, C, D, E, F, G and H, and Copper Concentrates
A, B, C, D, E and F at a given reduction temperature of 89 to
109.degree. C. following the procedure, described below, for
reducing the leaching product liquor, to measure the final ORP
level (based on an Ag/AgCl electrode). The results are given in
Table 5. The starting ORP level (based on an Ag/AgCl electrode,
90.degree. C.) of the leaching product liquor is also given for
reference.
[0189] [Leaching Product Liquor]
[0190] (1) Composition: Each of Leaching Product Liquors contained
copper, iron and chloride ion at 30, 100 and 220 g/L,
respectively.
[0191] (2) Initial ORP (based on an Ag/AgCl electrode, 90.degree.
C.) A: 508 mV, B: 490 mV, C: 481 mV, D: 482 mV, E: 490 mV, F: 491
mV, G: 495 mV and H: 498 mV
[0192] [Copper Concentrate]
[0193] A: Copper Concentrate A (D50: 60 .mu.m, Chemical
composition: 26% of copper, 29% of iron, 28% of sulfur and 17% of
others, all percentages being by weight)
[0194] B: Copper Concentrate A dry-crushed by a planetary ball mill
(Planetary Mill SKF-04 supplied by Seishin Enterprise) to have a
D50 value of 3.77 .mu.m, where Copper Concentrate A was ball-milled
in a vessel filled with 8 mm-diameter steel balls to 50% of the
volume at 150 rpm for 1 hour.
[0195] C: Copper Concentrate A wet-crushed by a beads mill (Nano
mill NM-G5M supplied by Asada Iron Works) to have a D50 value of
1.08 .mu.m, where Copper Concentrate A was slurried with water to
have a concentration of 100 g/L and passed 3 times through the
crushing chamber of the beads mill.
[0196] D: Copper Concentrate A wet-crushed by a beads mill (Nano
mill NM-G5M supplied by Asada Iron Works) to have a D50 value of
1.33 .mu.m, where Copper Concentrate A was slurried with water to
have a concentration of 100 g/L and passed 2 times through the
crushing chamber of the beads mill.
[0197] E: Copper Concentrate A wet-crushed by a beads mill (Nano
mill NM-G5M supplied by Asada Iron Works) to have a D50 value of
2.21 .mu.m, where Copper Concentrate A was slurried with water to
have a concentration of 100 g/L and passed once through the
crushing chamber of the beads mill.
[0198] F: Copper Concentrate A wet-crushed by a beads mill (Nano
mill NM-G5M supplied by Asada Iron Works) to have a D50 value of
0.76 .mu.m, where Copper Concentrate A was slurried with water to
have a concentration of 100 g/L and circulated in the crushing
chamber of the beads mill for 1 hour.
[0199] [Procedure for Reducing the Leaching Product Liquor]
[0200] The leaching product liquor of given composition was mixed
with 50 g of the copper concentrate prepared to have a given
average particle size (D50) in a 500 mL glass beaker in such a way
to have an initial slurry concentration of 100 g/L, and heated with
stirring to a given reduction temperature, at which the mixture was
held for 3 hours.
5 TABLE 5 Copper ORP Leaching concentrate Reduction (mV) product
D50 temperature Initial Final No. liquor case case (.mu.m)
(.degree. C.) solution solution 1 A B 3.77 107 508 375 2 B B 3.77
104 490 382 3 C A 60 109 481 395 4 C C 1.08 92 481 388 5 C D 1.33
91 481 392 6 C E 2.21 90 481 400 7 C F 0.76 92 481 383 8 D A 60 89
482 430 9 E A 60 98 490 413 10 F A 60 101 491 413 11 G A 60 104 495
409 12 H A 60 106.5 498 404
[0201] As shown in Table 5, an ORP level (based on an Ag/AgCl
electrode) of 400 or less can be attained, when reduction
temperature is controlled for the leaching product liquor at 90 to
110.degree. C. and at least (A) which satisfies the formula 1 as a
function of D50 of the copper concentrate used, as shown in Table 5
(Run No.1 to 7). Particularly noted is that the level of 380 mV or
less can be attained, when the temperature is controlled at least
at (A) which satisfies the formula 2 (run No.1). By contrast, it is
noted that an ORP level (based on an Ag/AgCl electrode) of 400 mV
or less cannot be attained, when the reduction temperature fails to
satisfy the formula 1 or 2, which represents the relationship
between D50 of the copper concentrate and reduction temperature
(Run No.8 to 12). It is therefore preferable to control reduction
temperature at least at the level (A) given by the formula 1 or
2.
[0202] (3) Solvent Extraction Step
[0203] Leaching Product Liquors A, B, C and D were treated by the
solvent extraction step to extract copper, which was then treated
by the stripping step to produce the stripping product liquor
containing the cuprous ion and raffinate containing the ferrous
ion. These stripping product streams were evaluated.
[0204] The reduction product liquor containing Cu and Fe at 75 and
51 g/L, prepared in the above step was used as Reduction Product
Liquor A, where 500 mL of the solution was incorporated with
powdered copper to have an ORP (based on an Ag/AgCl electrode) of
300 mV, to completely reduce the copper ion in the solution into
the monovalent state. The resulting solution was used as the
initial solution for the solvent extraction step, where the
solution was incorporated with 500 mL of tributyl phosphate
(Daihachi Chemical Industry, TBP.RTM.) diluted with an diluent
(Showa-Shell, SHELLSOL A) to have a concentration of 40% by volume,
and the mixture was shaked at 50.degree. C. for 10 minutes for the
solvent extraction to produce the organic solvent phase and aqueous
phase. Then, the organic phase was stripped with 250 mL of water,
controlled at pH 1 with hydrochloric acid, with shaking for 10
minutes.
[0205] Table 6 gives the compositions of the stripping product
liquor, initial solution for the solvent extraction step and
raffinate.
6 TABLE 6 Cu and Fe concentrations (g/L) Solvent extraction Cu Fe
Initial solution 75 51 Raffinate 13 48 Stripping product 31 4
liquor
[0206] Use of tributyl phosphate as the extractant efficiently
separates copper selectively over iron, as shown in Table 6.
[0207] The solvent extraction step was carried out for the
synthetic aqueous solution containing cupric chloride and ferric
chloride at 80 and 50 g/L as Cu and Fe (Reduction Product Liquor
B), where the solution was incorporated with sodium chloride to
have a chlorine ion concentration of 200 g/L, and further
incorporated with powdered iron at 60.degree. C. to have an ORP
(based on an Ag/AgCl electrode) of 300 mV. The resulting solution
was brought into contact at room temperature with an organic
solvent diluted with kerosene to have a given tributyl phosphate
concentration of 40 to 100% by volume, to extract the metallic ions
into the tributyl phosphate, in an inert atmosphere of nitrogen to
prevent oxidation at the gas/liquid interface. The copper and iron
extraction were determined. The results are given in FIGS. 9 and
10.
[0208] Increasing tributyl phosphate concentration increases copper
extraction, but changes iron extraction to only a limited extent,
as shown in FIG. 9. Increasing tributyl phosphate concentration
also improves copper/iron separation coefficient, as shown in FIG.
10.
[0209] The solvent extraction step was carried out for the solution
containing cupric chloride, ferric chloride and silver chloride at
118 g/L, 90 g/L and 9 mg/L as Cu, Fe and Ag (Reduction Product
Liquor C), where the solution was incorporated with powdered iron
at 60.degree. C. to have an ORP (based on an Ag/AgCl electrode) of
300 mV. The resulting solution was brought into contact at room
temperature with tributyl phosphate to extract the metallic ions
thereinto, in an inert atmosphere of nitrogen to prevent oxidation
at the gas/liquid interface. Then, the resulting solution was
stripped with a stripping solution controlled at pH 1.0 with
hydrochloric acid and a chlorine ion concentration at 50 g/L with
sodium chloride, to strip the copper ion in the tributyl phosphate
at 50.degree. C. The raffinate and stripping product liquor were
analyzed for their Cu, Fe and Ag concentrations.
[0210] The raffinate contained Cu, Fe and Ag at 60 g/L, 90 g/L and
8 mg/L, and the stripping product liquor contained Cu, Fe and Ag at
28 g/L, 5 g/L and 1 mg/L or less, by which was meant that silver
was not extracted into tributyl phosphate but left in the
raffinate, and copper and silver were separated almost
completely.
[0211] The solvent extraction step was carried out for the
synthetic aqueous solution containing cupric chloride and ferric
chloride at 50 and 70 g/L as Cu and Fe (Reduction Product Liquor
D), where the solution was incorporated with sodium chloride to
have a chlorine ion concentration of 200 g/L, and further
incorporated with powdered iron at 60.degree. C. to have an ORP
(based on an Ag/AgCl electrode) of 275 mV. The resulting solution
was brought into contact at room temperature with tributyl
phosphate, to extract the metallic ions into the tributyl
phosphate, in an inert atmosphere of nitrogen to prevent oxidation
at the gas/liquid interface. Then, the resulting solution was
stripped with a stripping solution controlled at pH 0.5 with
hydrochloric acid and a chlorine ion concentration at 100 g/L with
sodium chloride, to strip the copper ion in the tributyl phosphate
at 30, 40, 60 and 75.degree. C. The Cu was analyzed to find
stripping rate for each run. The results are given in FIG. 11.
[0212] Increasing stripping temperature increases stripping rate,
preferably to 50.degree. C. or higher to strip copper present in
tributyl phosphate at 50% or more.
[0213] (4) Copper Electrowinning Step
[0214] The copper electrowinning step was carried out for the
stripping product liquor by the following diaphragm-aided
electrolysis tank to produce the electrolytic copper and spent
electrolyte, which were evaluated.
[0215] FIG. 6 illustrates the diaphragm-aided electrolysis tank
structure, where the anode was a 70 by 70 mm insoluble electrode
(DSE.RTM. supplied by Permelec Electrode) and cathode was a 60 by
65 mm pure copper plate. The cathode and anode chambers were
separated by a filter cloth of TETRON.RTM. with fine texture and
low water permeability (water permeability: 0.06
L/m.sup.2.multidot.s) as the diaphragm. Each of these chambers was
provided with an overflow type discharge port to independently
discharge the solution, where the overflow level was kept slightly
higher in the cathode chamber than in the anode chamber, to prevent
flow of chlorine gas and the solution containing chlorine gas in
the anode chamber into the cathode chamber by the solution level
difference.
[0216] The cathode chamber in the electrolysis tank was supplied
with an aqueous solution of cuprous chloride containing copper at
80 g/L at a rate of 2.5 mL/minute, while the anode chamber with an
aqueous solution of ferric chloride containing iron at 80 g/L,
where the aqueous solution of cuprous chloride was kept at an ORP
(based on an Ag/AgCl electrode) of 309 mV.
[0217] The copper electrowinning step was carried out at a current
density of 308 A/m.sup.2 by passing current of around 1.2 A. A
current efficiency from the electrolytic copper was 93%, which is
equivalent to that associated with the common electrolysis of
cuprous chloride (85 to 95%). A total of 25.5 mL of the solution
was supplied to the cathode chamber for 10 minutes, and 25.2 mL of
the solution was discharged from the chamber, a cathode chamber
solution recovery rate of 99%. In other words, only a small
quantity of the solution flowed from the cathode chamber into the
anode chamber, whereas it is judged that no flow occurred in the
opposite direction. The solution discharged from the cathode
chamber was at an ORP (based on an Ag/AgCl electrode) of 307 mV,
and the cathode chamber solution had essentially unchanged
properties, except for consumption of the copper ion. This means
that the solution supplied to the cathode chamber can be recovered
essentially totally except for decreased copper ion content, and
that the solution discharged from the chamber is suitable as the
stripping solution for the solvent extraction step.
[0218] The aqueous solution of ferric chloride having an ORP (based
on an Ag/AgCl electrode) of 600 mV was supplied to the anode
chamber, where it was strongly oxidized on the anode to produce
chlorine gas and, at the same time, increase ORP (based on an
Ag/AgCl electrode) of the discharged solution to 900 mV or more.
Therefore, recycling the solution discharged from the anode chamber
and chlorine gas back to the chlorine-aided leaching step produces
a high oxidation power.
[0219] The analysis results of the electrolytic copper produced by
the copper electrowinning step are given in Table 7. As shown, the
step produced 99.99% pure (by weight) electrolytic copper
containing trace quantities of impurities.
7TABLE 7 Cu purity Impurity contents (ppm) (% by weight) Fe Ag As
Sb Pb Zn Ni 99.99 <10 <10 10 <10 <10 <50 <50
[0220] (5) Solution Purification Step
[0221] The raffinate discharged from the solvent extraction step
contains copper at 2 to 5 g/L, and a number of concomitant valuable
metals, e.g., arsenic, antimony, nickel, zinc, lead and cadmium at
around 0.5 g/L, and silver at around 0.1 g/L, in addition to iron.
These concomitant metals are impurities for the recovery of
iron.
[0222] The raffinate was cleaned by sulfidation, cementation and
neutralization at 50.degree. C. for 1 hour for each method. It was
neutralized with slaked lime to have a pH level of 3 for the
neutralization; incorporated with an aqueous solution of sodium
hydrosulfide in a quantity 2 to 5 times of the equivalent needed
for sulfidation of the impurities at pH 0.5 for the sulfidation;
and incorporated with powdered iron to control its ORP level (based
on an Ag/AgCl electrode), and treated at pH 1.4 and ORP of -71 mV
or pH 1.1 and ORP of -250 mV for the cementation. The element
removal rates by the purification step are given in Table 8.
8TABLE 8 Treatment Removal rates (%) method Conditions Cu Fe As Sb
Ni Ag Zn Ph Cd Neutralization pH3 0 6 100 100 1 24 0 11 0
Cementation pH1.4 45 0 13 82 2 100 0 0 0 ORP-71 mV pH1.1 92 0 61
100 2 100 0 1 0 ORP-250 mV Sulfidation pH0.5 100 1 -- 100 64 100 21
97 99 Twice the equivalent pH0.5 100 4 -- 100 94 100 42 100 100 5
times of the equivalent (--: Not analyzed)
[0223] These impurities can be efficiently removed by each solution
purification method, as shown in Table 8. For example, the
neutralization can remove arsenic or antimony, sulfidation is
suitable for removal of lead or nickel, and cementation or
sulfidation is effective for recovering silver. The solution
purification step may use a method adequately selected depending on
impurities present in the copper concentrate, and does not always
need all of these methods.
[0224] The impurity can be selectively separated and recovered in
compound suitable for effective utilization or treatment by
adequately selecting one or more of these methods.
[0225] (6) Iron Electrowinning Step
[0226] The iron electrowinning step was carried out for the
iron-containing purified solution treated by the solution
purification step, to evaluate the solution.
[0227] The electrolysis tank, 500 mL in inner volume, was provided
with an insoluble anode electrode (e.g., DSE.RTM. supplied by
Permelec Electrode) having an electrode area of 60 by 60 mm and
cathode (titanium plate) masked to have the same electrode area, 60
mm apart from each other.
[0228] The electrowinning step was carried out by passing current
through the supply solution, pumped to the cathode partitioned by a
filter cloth at 1 or 5 mL/minute, to have a current density of 200
A/m.sup.2. The discharged electrolytic solution was not reused but
directly stored in a spare tank. Iron was theoretically extracted
at 1.5 g/hour. The iron ion was carried by the solution at 1.5
g/hour when the solution was supplied at 1 mL/minute, and at 7.5
g/hour when the solution was supplied at 5 mL/minute. These rates
corresponded to the same as, and 5 times higher than, the rate at
which copper is theoretically extracted.
[0229] The deposited cathode was cleaned after electrowinning for 5
hours, to determine deposited amount and current efficiency. The
treatment was found to be carried out at a current density of
97%.
[0230] Cell voltage was 2.9V when the solution was supplied at 1
mL/minute, and generation of chlorine gas from the anode was
visually observed. When it was supplied at 5 mL/minute, on the
other hand, no chlorine gas generation from the anode was observed,
while cell voltage was decreased to 2.3V. As discussed above, it is
demonstrated that the electrolysis step of the present invention
can decrease power cost.
[0231] (7) Leaching Residue Treatment Step
[0232] The leaching residue treatment step was carried out by
distilling the residue from the chlorine-aided leaching step to
separate elemental sulfur and recover the residue containing a
noble metal, where 150 g of the residue put in a quartz boat was
heated in a tubular furnace at 320.degree. C. in a flow of
nitrogen. The gaseous stream was air-cooled by a cooling tube
provided at the gas discharge port. The heating was continued for 4
hours, and the system was allowed to cool in a flow of nitrogen.
Then, the residue and sulfur were withdrawn when furnace inside
temperature was decreased to 70.degree. C. or lower. Table 9 gives
chemical analysis results of the leaching residue before and after
the sulfur removal treatment, and sulfur modality analysis
results.
9 TABLE 9 Chemical composition Sulfur modality Leaching (% by
weight) (g/t) (% by weight) residue Cu Fe S SiO.sub.2 Au Ag
CuFeS.sub.2 FeS.sub.2 So Before 4.2 13.5 54.9 -- 47 -- 12.8 20.4
47.4 sulfur removal treatment After 6.3 19.2 30.2 27.8 63 34 18.3
28.8 8.3 sulfur removal treatment (--: Not analyzed)
[0233] The leaching residue treatment step removed sulfur from the
feed stream, to concentrate the gold present in the residue by that
extent, as shown in Table 9.
[0234] Advantage of the Invention
[0235] As discussed above, the process of the present invention for
refining a raw copper material containing a copper sulfide mineral
can be used as a hydrometallurgical refining process for a raw
copper material containing a copper sulfide mineral, is useful as a
process for leaching copper to recover it by the monovalent copper
electrolysis while suppressing oxidation of sulfur in the raw
material, as a process for recovering and effectively utilizing a
concomitant valuable metal and as a process for minimizing
production of wastes, e.g., leaching residue, as far as possible,
and particularly suitable for refining chalcopyrite, which is known
as a compound difficult to leach.
* * * * *