Note: Descriptions are shown in the official language in which they were submitted.
1~3~Z~
This invention relates generally to an improved
hydrometallurgical process for the production of metallic
copper from copper-containing materials. In particular,
this improvement is concerned with the metal chloride pro-
cessing of copper sulfide ore concentrates.
In our prior Canadian Patent No. 1,015,691,
a copper hydrometallurgical process was described for pro-
cessing copper sulfide ore concentrates, especially those
containing chalcopyrite. This process has four basic
stages:
(1) an oxidation stage in which materials containing
copper-sulfide ore concentrates are oxidized in a solution
containing ferric chloride and cupric chloride until there is
substantial solubilization of the copper content of said
materials in the form of cupric chloride, and removing solids
from the solution;
(2) a reduction stage separate from the oxidation
stage in which cupric chloride in the solution from the oxidation
stage is substantially reduced to cuprous chloride;
(3) an electrolysis stage in which metallic copper
is recovered and cupric chloride is regenera~ed by electrolysis
of the cuprous chloride solution from the reduction stage; and
(4) a regeneration-purge stage separate from the
reduction and electrolysis stages in which the ferrous chloride
in the solution from the electrolysis stage is reacted with
oxygen in the presence of the regenerated cupric chloride
to regenerate the ferric chloride required in the oxidation
stage and to precipitate, by hydrolysis, compounds including
those having the iron-sulfate ratios of jarosite to thereby
remove excess iron as well as sulfate ions and other impurities
present in the solution.
~ '.
~ .
~1- .
~L0835Z4
The continuing innovative development of the
process of this invention has resulted in the discovery of
additional information together with alternative operating
procedures and conditions which enhance the advantages pro-
vided by the basic process disclosed in the aforesaid
Canadian ~
The present invention provides a hydrometallurgical
process for the production of metallic copper in which there
is provided a cyclic system capable of steady state operation,
comprising an oxidation stage in which materials containing
copper sulfide ore concentrates are oxidized in a solution
containing ferric chloride and cupric chloride until there is
substantial solubilization of the copper content of said
materials in the form of cupric chloride, a reduction stage
separate from the oxidation stage in which at least a substan-
tial portion of the cupric chloride in the solution from the
oxidation stage is reduced to cuprous chloride, an electroly-
sis stage in which metallic copper is recovered and cupric
chloride is regenerated by electrolysis of the cuprous chloride . ~:
solution from the reduction stage, and a regeneration-purge : ~ .
stage separate from the reduction and electrolysis stages in
which the ferrous chloride in the solution from the electroly- :
sis stage is reacted with oxygen in the presence of the
regeneràted cupric chloride to regenerate the ferric chloride
to provide regenerated ferric chloride and cupric chloride ;
required in the oxidation stage and to precipitate, by
hydrolysis,~compounds including those having the iron-sulfate
ratios of jarosite to thereby remove excess iron as well as
sulfate ions and other impurities present in the solution
wherein in said process the total chloride ion concentration is
maintained at a level in the solution throughout the process
by the addition of a saline metal chloride compound selected
from potassium chloride, magnesium chloride, a mixture of mag-
nesium chloride and potassium chloride, or a mixture of any of the
foregoing with sodium chloride, to maximize the the degree of
--2--
'`"` 1(~33S~
reduction of cupric chloride to cuprous chloride in the
reduction stage with minimal loss of copper from solutlon.
This invention further provides ~or a hydrometallurgi-
cal process for the produc~ion of metallic copper from copper
sulfide ore concentrates containing a substantial proportion
of chalcopyrite, comprising a reduction stage in which the
ore concentrates are introduced into an aqueous chloride solu~
tion containing cupric chloride to solubilize part of the
copper and associated iron in said materials and reduce sub-
stantially all of the cupric chloride to cuprous chloride, acopper recovery stage in which metallic copper is recovered by
electrolyzing in electrolytic cells the cuprous chloride in the
solution from the reduction stage to produce metallic copper in
the cathode compartment and to regenerate the cupric chloride in
the anode compartment; wherein in said process the total chloride
ion concentration of said chloride solution relative to the water
content thereof is maintained by the addition of a saline metal
chloride compound selected from potassium chloride, magnesium
chloride, a mixture of magnesium chloride and potassium chloride,
or a mixture of any of the foregoing with sodium chloride,
in an amount near the maximum permitted by the solubility of
the saline metal chlorides in said chloride solution; and
further wherein in said process there is provided an oxidation
stage combined with a regeneration-purge stage to retard
scaling of equipment in which the solution from the copper
recovery stage containing ferrous chloride and regenerated
cupric chloride is reacted with oxygen to form a solution contain-
ing ferric chloride and cupric chloride, and concurrently to
oxidize in said solution the unreacted ore concentrates from the
reduction stage to solubilize substantially all the remainingcopper in said concentrates, thereby forming a solution contain-
ing cupric chloride and minimal residual ferric chloride asdetermined by the controlled available reactive chloride content
of the process liquor, with the concurrent precipitation by
hydrolysis, of iron compounds including those having the iron-
sulfate ratios of jarosite, to thereby remove the excess iron
as well as excess sufate ions and other~impurities
.~ . .
- . ~ . ........
108352~
from the chloride solution and recycling the chloride solu-
tion containing cupric chloride and minimal ferric chloride
to the reduction stage.
The process of the present invention also
provides a hydrometallurgical process for the production
of metallic copper comprising the steps of: (1) reacting
at about 107C. materials containing principally fresh chalco-
pyrite ore concentrates with a cupric chloride solution con-
taining a limited residual amount of ferric chloride, to thereby .
reduce a substantial portion of the cupric chloride to cuprous
chloride and to produce ferrous chloride; (2) contacting the
solution from step (1) with metal reducing agents selected :
from the group consisting of metallic copper, metallic iron
and mixtures thereof as required to reduce essentially all .
of the remaining cupric chloride to cuprous chloride; (3~ electro-
lyzing in electrolytic cells the cuprous chloride in the
solution from step (2) to produce metallic copper in the
cathode compartment and to regenerate the cupric chloride in
the anode compartment; (4) reacting with oxygen at a tempera- ~ ;
ture between 107C. and 159C. and at a pressure between :
atmospheric pressure and about 60 psig the ferrous chloride in
the spent electrolyte solution in the presence of regenerated :
cupric chloride to regenerate ferric chloride and cupric chloride
and concurrently oxidize in said solution the unreacted ore ~ .
concentrates from step (1) to solubilize substantially all the
remaining copper in the ore concentrates, and (5) recycling the
cupric chloride solution containing a limited residual amount of
the ferric chloride from step (4) to step (1); wherein in said :~
process the cupric chloride solution of said step (1) contains
sufficient sodium chloride and potassium chloride to maintain
the total chloride concentration, related to water, near the
maximum permitted by the solubility of the sodium and potassium
chlorides in the process solution, and further wherein
in step (4) a solution containing cupric chloride
--4--
10~3SZ4
and limited residual ~erric chloride is formed as determined
by the contro].led available reactive chloride content of the
process liquor, with the concurrent precipitation, by hydrolysis,
of iron compounds including potassium jarosite, to thereby remove
excess iron and excess sulfate ions as well as other impurities
from the cupric chloride solution.
The present invention provides still further a
hydrometallurgical process for the production of metallic copper
comprising an oxidation stage in which materials containing
copper-iron sulfide ore concentrates are oxidized in a solution
containing ferric chloride and cupric chloride until there is a
substantial solubilization of the copper content of said materials
in the form of cupric chloride, a reduction stage separate from the
oxidation stage in which at least a substantial portion of the
cupric chloride in the solution from the oxidation stage is reduced
to cuprous chloride, an electrolysis stage in which metallic
copper is recovered and cupric chloride is regenerated by :
electrolysis of the cuprous chloride solution from the reduction
stage, a regeneration-purge stage separate from the reduction
and electrolysis stages in which the ferrous chloride in the
solution from the electrolysis stage is reacted with oxygen in
the presence of the regenerated cupric chloride to regenerate the
ferric chloride required in the oxidation stage, wherein the
controlled total chloride ion includes controlled reactive
chloride and controlled potassium chloride required to be present
in the solution in the regeneration-purge stage in order to
precipitate, by hydrolysis, iron compounds including potassium
jarosite to thereby control the concentration in the solution of
iron as well as sulfate ions and remove other impurities from
3~ the solution. ~
The present invention therefore is directed to ~:
maintaining the total chloride ion concentration at such a level
--5--
- . . . ,, . . . . . ~ ~
1~D83S;~
in the solution throughout the aforesaid basic process by the
a~dition o~ a saline metal chloride compound selected from
potassium chloride, magnesium chloride, a mixture of mag-
nesium chloride and potassium chloride, or a mixture of any
of the foregoing with sodium chloride, so as to maximize the degree
of reduction of cupric chloride to cuprous chloride in the
reduction stage with minimal loss of copper from solution and for
other beneficial effects on the process.
The advantages of the present invention therefore
include the following:
A. Required control of total chloride ion con-
centration in the process liquor.
B. Required control of the inventory of available
reactive chloride ion in the process liquor.
C. Required inclusion of potassium chloride in the
process liquor to reduce and limit the sulfate ion
concentration therein by its precipitation from
solution in the regeneration-purge stage.
D. Advantageous combined operation of the oxidation
and regeneration-purge stages to:
1. Permit the reduction of the iron concen-
tration in the reacted liquor for ultimate
beneficial effects on electrolysis.
2. Retard and limit the scaling of process equipment.
Other advantages of the present invention will appear
from the following description, examples and claims.
In the accompanying drawings, Figure 1 presents a
simplified flow diagram of the process of this invention
wherein the oxidation and regeneration-purge stages are combined.
Figure 2 diagrammatically presents a stoichiometric
molar balance to illustrate the basic chemistry of the process
of Figure 1 applied to chalcopyrite.
_ 6
8352~
Figure 3 presents a flow diagram of one embodiment of
the process according to this invention wherein the oxidation
and regeneration-purge stages are combined.
Figure 4 presents a simplified flow diagram of the
process o~ this invention wherein the oxidation and regeneration-
purge stages are separate.
Figure 5 is a tabulation of data showing the effect
of chloride ion concentration upon the reduction of cupric
chloride to cuprous chloride in the embodiment with separate
oxidation and regeneration-purge stages.
Figure 6 is a tabulation of data showing the effect of
chloride ion concentration upon the reduction of cupric chloride
to cuprous chloride in the embodiment with combined oxidation
and regeneration-purge stages.
Figure 7 is a graph showing the effect of chloride ion
concentration upon the reduction of cupric chloride to cuprous
chloride in the reduction stage.
Figure 8 presents a graph of pilot plant data com-
paring concentrations of sulfate ions in liquors entering and ;
leaving the combined oxidation~regeneration stage with onlysodium chloride added to the process liquor, and with potas-
sium chloride added in addition to sodium chloride to the ~`
process liquor.
In Canadian Patent No. 1,015,691, disclosure ismade of the option to operate the Regeneration-Purge Stage and
the Oxidation Stage either separately or combined. The com-
bined operation procedure provides for the oxidation stage
reaction to be conducted in the presence of oxygen, which is an
estab-
1~83~52~
lished requirement ~or the regeneration-purge stageO Under
this procedure the reaction of chalcopyriteg in contact with
the raffinate liquor ~rom the electrolysis state9 in the pres~
ence of oxygen9 involves the continuing oxidation o~ the reac-
tion liquor, speci~ically: the oxidation o~ cuprous chloride
to cupric chloride and ~errous chloride to ferric chloride as
the available reactive chloride ion inventory in the react~on
soiution permits. Tp ~the extent that the inventory o~ reac-
~s~f7~c~e"f
? ~ tive chloride ions is ~e~e~e~ to accommodate the conversion
o~ all the iron to ~erric chloride, ferric hydrate will be
precipitated.
This is illustr~ted by the following chemical reac~
tions.
Reduction Stage~
2CuFeS2 + 3CùCl2--~4CuCl + FeC12 + 2S + CuFeS2
To Electrolysis To Combined
OxidO-R$~n,'Purge
Electrolysis Stage:
4CuCl + FeC12 ~ 2Cu + 2CUC12 + F~C12
Product To Combined
Oxid.-Regen.~Purge
Combined Oxidation, Regenerati~n-Purge Sta~eo
CuFeS2 + 2S + 2CUC12 ~ FeC12 + 3 2 + 3H2~~3C~Cl2 + 2Fe(O )3~4S t~
Reduction Residue -
Thus, the availability of oxygen to the final dissolution re-
action~ as provided in thé combined oxidation and regeneration=
purge procedure, of~ers~in addition to~cupric chlorlde the ben-
efit of the higher reactability of ferric chloride and lts
higher oxidizing power during the course o~ the re~ctlon to
assure the desired maximum possible solubillzation of the
chalcopyrite. The residue is shown in the slmpll~ied equation
g' .,
~)83S2~
as ferric hydroxid~, but in the preferred embodiment it can
be in the form of jarosite.
At the same -time, through the control of the reactive
chloride ion inventory in the process liquor the ultimate iron
concentration in the reacted liquor can be allowed to approach
zero for the benefit of the electrolysis stage. However, it
is preferred to provide for some minimal residual iron to re-
main present in the fully reacted liquor as ferric chloride in
order to assure that all the reacted copper is present in
solution as cupric chloride. This provision for additional
reactive chloride ion in the process liquor is illustrated by
the addition of the following reaction equations to the process
equations previously presented:
Reduction Stage.
2CuFeS2 + 3CuC12 ~ 4CuCl + FeC12 + 2S + CuFeS2
O.lCuFeS2 + O.3FeC13 ~ O.lCuCl + O.4FeC12 + Oo2S
2.1 CuFeS2 + 3CuC12 + O.3FeC13 --~ 4.lCuCl + 1.4FeC12 + 2.2S
+ cuFes2
Electrolysis Stage:
4CuCl + FeC12 J 2Cu + 2 CuC12 + FeC12
O.lCuC1 + 0.4FeC12----~0.1Cu + 0.3FeC12 + O.lFeC13
4.lCuCl + 1.4FeC12----~2.1Cu + 2CuC12 + 1.3FeC12 + O.lFeC13
Combined Oxidatioll, Regeneration-Purge Stage:
CuFeS2 ~ 2S + 2CuC12 + FeC12 + - 2 + 3 H2O
3CuC12 + 2Fe(O~)3 + 4S
O.2S + O.lFeC13 + 0.3FeC12 + 15 2 + 0.15 H20
0~1FeC13 + 0-2FeC13 + o~lFe(oH?3 + 0-2S
CuFeS2 + 2.2S + 2CuC12 + 1.3FeC12 + 0.1FeC13 + 3 15 2
+ 3.15 H2O ~ 3CuC12 + 0.3FeC13 + 2.1Fe(OH)3 + 4.2S
It should be observed that the provision for minimal residual
iron content in the finally reacted combined oxidation regener-
.
. . .
~835'~
ation-purge stage liquor, as FeCl39 for the sake of assurance
that all copper in ~he solukion is cupric chloride, has a com~
pensating e~ect on electrolysiso the cDpper dissolved by this
residual ~erric chloride ~rom the process feed solids to the
reduction stage when precipitated at the cathode in the elec~
trolysis stage will occasion the regeneration of the stoichio-
metrically equlvalent ferric chloride in the anolyte~ It w~ll
be noted that this amounts to one-third of the ferric chloride
originally present in the aforesaid combined oxidation regener~
ation-purge stage reacted liquor~
The means is thus revealed whereby the "combined"
procedure o~fers the opportunity to provide the leaching power
of ferric chloride (to assure the maximum solubilization o~ -
chalcopyrite) and at the same time achieve the desirable
limitation o~ the iron content o~ the electrolyte through con-
trol of the available reactive chloride ion inventory in the
process liquor.
It should be noted that the combined oxidation re- :.
generation-purge procedure remains consistent with the basic
-Ca~ n 1,~ /5~9/
premise of the Duval Corporation ~ . Patent NoO ~T~ 4
which provides for an oxidation stage~ in which the higher ~:
oxidizing power o~ ferric chloride is made available in addi-
tion to cupric chloride to assure maximum dissolution power
for chalcopyrite, to function in con~unction with the reduc-
tion stage, in which the reacted liquor from the oxidation
stage is contacted with raw process feed solids, (in stoic~io~
metric excess) whereby the cupric chloride is substantially -~
rèduced to cuprous chloride in preparatlon for electrolyslsO
The teaching of thi~ "combined" procedure includes the revela~ :
tion that the simultaneous oxidation regeneratiDn-purge reac~
tion provides for the controlled reductlon of the iron content
."~.
~ .,
. . . .
35Z4
of the reacted liquor to approach zero. sy this means the
iron content of the feed solution to electrolysis can be
limited essentially to that dissolved in the reduction stage
only, which contributes favorably toward the quality of the
electrolytic copper product.
Additionally, the combined oxidation regeneration-
purge procedure offers the advantage of precipitating the
jarositic iron hydrate and other compounds associated with the
regeneration-purge reaction in the presence of the residual
undissolved solids, which tends to reduce and limit the ten-
dency for scaling process equipment;
a) The irregular surface area of the solids particles,
grossly larger in aggregate as compared with the con-
tacted smooth surfaces of the equipment, offers pref-
erentially attractive sites for crystallization of the
precipitated compounds.
b) The presence of solids in the system provides abrasive
action tending to remove scale from equipment surfaces.
The combining of the oxidation and regeneration-
purge stages offers the additional advantages for production
operations of further simplifying the process and reducing the j~
equipment requirements.
In Canadian Patent No. 1,C15,691 disclosure is made of
the extraordinarily beneficial effects of maintaining a desir-
able total chloride ion concentration in the process liquor by
augmenting the reactive chloride ion inventory of the process
liquor through the addition thereto of a "suitable saline
metal chloride such as sodium chloride, potassium chloride,
magnesium chloride or any mixture thereof". These beneficial
effects which were discussed in Canadian Patent No. 1,015,691 with
respect to sodium chloride, are summarized as follows:
-11-
~0835Z4
1) Increases the solubility of cuprous chloride.
2) Retards the secondary reaction which results in the
loss of copper from solution in the reduction stage,
(step A), thus permitting an increased reduction
achievement.
3) Enhances the solubilization of copper in the oxidation
stage.
4) Retards the oxidation of sulfur to sulfate ions.
5) Protects against the atmospheric reoxidation of cu-
prous chloride during the handling of the process solu-
tion from the reduction stage through the metal re-
covery stage.
6) Provides a favorable influence on the quality of the
electrolytic copper product.
It has been previously noted that associated with
the combined oxidation regeneration-purge operating procedure
a significant reduction in the iron also reduces the total
chloride ion concentration of the process liquor. In accord-
ance with the teaching of Canadian Patent No. 1,015,691, the total
chloride concentration should be maintained at the desired level
by the addition of a suitable saline metal chloride such as
`'sodium chloride, potassium chloride, magnesium chloride and
mixtures thereof".
Laboratory and pilot plant operating experience with
the oxidation and regeneration-purge stages conducted separate-
ly, together with the associated iron concentration in the
process liquor, as illustrated in Figure 2 of Canadian Patent No.
1,015,691, established that the desirable total chloride ion
concentration in the process liquor cou]d be achieved under
these conditions by the addition of the saline metal chloride,
sodium chloride, alone, at near saturation. This was consider-
-12-
.... - : : .
- ~083S~4
ed an acceptable practice and was presented in the ~preferred
C~ n /,~5~91
embodiment" of U.~0 Patent NoO 3J785g~4~, s~nce sodium chl~ride
is normally the most economically available of the saline metal
chloridesO
The continuing laboratory and pllot plants operating
experience, in which the oxidation and regeneration-purge
stages were combined and conducted simultaneously, in accord-
ance with the pre~erred procedures illustrated by the chemical
reactions presented earlier in this specification, have estab-
lished that the desirable total chloride ion concentration can-
not be satisfactorily achieved by the addition of the saline
metal chloride, sodium chloride9 alone, at near saturationO
However, thè addltional chloride ion required to offset the
reductlon in chloride ion associated with the lower iron con~
centration ln the process liquor can be achieved by the substi~
tution of magnesium chloride for sodium chldride as the saline
metal chloride additive, or prë~erably by the ~ddition of po~ :
tassium chloride in the process liquor, already near satura~
tion with sodium chloride,.to a concentration representing :
near saturation ~or the comblnation of these two saline metal
chloride salts in the process liquo~0
The use of potassium chloride in combination with
sodium chloride as the saline metal chloride additive to the ~
process liquor is preferredJ ba~ed on the di~covery that to :~:
the extent potassium ion (together with iron) is available in
the process liquor practically all sulfate ion is precipitated
therefrom as potassium iron ~arosite in the regeneration~pùrge
reaction This is an important benefit in the control of
scaling of the process equipmentO
The chemistry of the process liqubr with respect to
chloride ion concentration in relation to the optional operat~
'
s
.. . i
1~835Z~
ing modes is illustrated in the accompanying Figures 5 and 6
The tabulations set forth the pertinent chemistry of
the Reduction Stage reaction for the process operating mode in
which the Oxidation and Regeneration~Purge stages are maintain-
~ d~J~
ed separate, (in accordance with Figure 2 in ~, Patent NoO
1, D~5,~ql
~ 5~4)~ for comparison with the combined operating modeg
which is the subject ~or further examination and development in
this application.
The chemical structure for the reaction system is
indicated in mols per 1000 mols o~ water, as well as in weight
percentO
The reaction time was held constant at one hour at
constant temperature, 107~Co~ in an agitated closed vessel
equipped with reflux condenserO
It will be noted that data are presented for progres-
sively varying levels of total chloride ion, (Cl ), in the
feed liquor to the Reduction Stage for each operating mode for
the process:
1, Separated Oxidation Regeneration-Purge Stages
a. 175 mols Cl- as established by maintaining the
sodium chloride concentration at 71 ~olsO
b. 155 mols Cl- resulting from a reduction in the
sodium chloride concentr~tion to 51 molsg for
e~fect.
cO 140 mols Cl resulting ~rom a reduction in the
sodium chloride concentrations to 36 mols, ~or ~`
effect.
do 125 mols Cl- resulting from a reduction in the
sodium chloride concentration to 21 mols, ~or
effect
2. Combined Oxidation Regen ~ tion~Purge Stages
.:
`
335Z4
aO 122 mols Cl resulting ~rom the reductlon o~ the
iron ~hloride c~ncentration ~rom 32.5 mols FeC12
t~ 400 mols FeCl30
bo 140 mols Cl~ resulting ~rom increasing the sodium
chloride concentration from 71,0 mols to 8005,
(very near saturation), and introducing 8.5 mols
of potassium chlorideO
c. 155 mols Cl resulting frorn increasing the sodium -
chloride concentration ~rom 7100 mols to 8005,
(very near saturation), and introducing 2305 mols
of potassium chloride.
d~ 175 mols Cl- resulting ~rom increasing the sodium
chloride concentration ~rom 710 0 mols to 80059
(very near saturation), and lntroducing 4305 mols
of potassium chlorideO ~ `
e. 175 mols Cl established by introducing magnesium
chloride, alone, as the saline metal chloride at
62 0 mols per 1000 mols water.
It will be observed that with the reductlon in ~otal
Cl concentration under the above outlined conditions the re
duction ~rom 100% cupric ions in the feed liquor to cuprous
ions in the reacted liquor varied at the extremes ~rom 9703 -
99.7% at 175 mols Cl- to 7500 - 7609% at 122 - 125 mols Cl~o
. .
No loss of copper from solution by secondary reaction was Ob=r
served even at the very high level o~ reduction to cuprou~
ion that was achieved.
Summarizing, the selected data presented in the ac~
company~ng tables shown in Figures 5 and 6 illustrate the im~
portant in~luence of total chloride ion concentration on the
Reduction Stage, (step A), reactlon o~ raw copper sul~ide con~
centrates for the reduction o~ cupric chloride to cuprous
'.
1~83~iZ9~
chloride~ For the operating mode in wh~ch the Oxidation and
Regeneration Purge Stages are maintained separate the total
chloride ion concentration was varied by ad~usting the sodium
chloride, NaCl, concentration. For the combined operatlng
mode in which the iron concentration was lowered the compen-
sating addition of chloride ion was achieved, as indicated, by
substitution of magnesium chloride, MgC12, for NaCl, and alter-
natively by the introduction of potassium chloride, KClg as
required to establish the desired total chloride ion concen-
tration above that achievable with NaCl, alone, due to the
limitation of the solubility of ~aC10
The in~ormation of the tables shown in Figures 5 and
6 is also presented graphically in the accompanying Figure 7.
The progressive relationship between the total chlo-
ride ion (Cl ) concentration and the accompanying reduction of
cuprlc to cuprous chloride in the reacted liquor is depicted
for the range of totàl chloride ion concentration expressed as
122 to 175 mols Cl per 1000 mols H20, and alternatively ex~
pressed as 16 to 21% Cl-o
It will be observed that in the combined oxidation
and regeneration-purge mode the chloride system~ low in iron,
and augmented with sodium and potassium chloride, delin~ated
on the graph by the solid lines displays a more ~avorable en
vironment for the reduction of cupric to cuprous than that in
the separate oxidation and re~eneration~purge mode which is a
high lron chloride system augmented by sodium chlorlde, a~one,
(delineated on the graph by the dotted lines)O This revelation
is- a further basis o~ the expressed preference for the inclu- :
sion of potassium chloride ~n the addition of saline metal
chloride to the systemO
The basic chemistry for the preferred embodiment of
~\b
~ . . .
". ~,. ~ . . . -, . . . .
... . .. . ..
z~
the process operating mode in which the Oxidation and Regener-
ation-Purge Stages are combined is illustrated by the stoichio
metric molar balance o~ Figure 2g as applied to chalcopyrite.
The impo-tant discovery, previously described hereing
that to the extent potassium ion (together with iron) is avail7
able in the process liquor practically all sul~ate ion is pre-
cipitated therefrom as potassium iron ~arosite in the regener-
ation-purge reaction is illustrated by the selected pilot
plant operating data presented graphically in Figure 80 It
will be observed that the level o~ sulfate ion in the post
oxidation liquor in the presence o~ sodium chlorideg alone, :
as the saline metal chloride additive, drops precipitously to
near zero upon the introduction o~ potassium chloride to the
process liquor in the system~
The simplified basic process ~or the treatment o~
copper-containing materials wher.ein the o~idation and regener-
ation-purge stages are combined will readily be understood ~.
~rom the diagram o~ Figure 1, and the ~asic chemistry is il~
lustrated by the stoichiometric molar balance of ~igure 2, as
applied to chalcopyriteO For a more complete description of a
preferred embodiment, however, re~erence should be made to
Figure 3 and the following illustrative descriptionO
In the treatment o~ copper sul~ide ore concentrates
containing principally chalcopyrite, the ~resh ore concen-
trates are added to reduction stage 1, step ~, through line 2
(~igure 3)0 As used herein, "~resh" or "raw" re~ers to cop-
per-containing materials not previously reacted with any re~
agent in the process. Cupric chloride, sodium chlorlde and -~
potassium chloride are introduced into reduction stage 1, step
30 A, through line 3. Makeup o~ sodium chloride and potassium .. .:
chloride is introduced into ll.ne 3 through line 3~0
r~
.. . . ~ , ... . . , .. . . .. ...
. .... ~ . I. I . ..
3524
In the reducti~n stage ly ~tep ~, which is essential~
ly closed to the atmosphere, the cupric chloride in the solu-
tion is ~ubstantially reduced to cuprous chloride b~ reaction
with the sulfide ore concentrates at near atmospheric boiling
temperature, about 107C, The partially reacted sulfide ore
concentrates as well as the solution containing some unreduced
cupric chloride, the cuprous chloride3 ferrous chloride, so-
dium chloride and potassium chloride are passed through line 4
to separation device 5, where the solids are separated ~rom
the solution by gravity sedimentationO
The solution ~rom separator 5 containing cupric
chloride, cuprous chloride, ferrous chloride, sodium chloride
and potassium chloride is then passed through line 6 to reduc- -~
tion stage 7, step B, into which is also passed cement copper
through line 80 The cement copper is used to reduce substan~
tially all the remaining cupric chloride to cuprous chloride
at near atmospheric boiling temperature, about 107aC~ Concur
rently, the cement copper is solubilized in the ~orm o~ cuprous
chloride.
- The solution ~rom reduction stage 7, step Bg con-
taining cuprous chloride, ferrous chloride, sodium chloride
and potassium chloride is removed therefrom through line 9 and
Anters a suitable filter 12, such as a sand filter, for the re~
moval of any suspended solids. ~:
If a calcium sul~ate salt accumulates in the process
liquor it can be controlled to an acceptable level by providing
a crystallization step ~or its removal ~rom the systemO The
filtered electrolyte solution then passes through line 13 and
enters into electrolytic cells 140 In these cells ~uprous
chloride is electrolyzed to deposit metallic copper at the
cathodes and to regenerate cupr ~ chlpride at the anodesO The
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1~33~iZ~I
metallic copper together with any silver deposited therewith
is removed from electrolytic cells 14 at 15.
The solution from the electrolytic cells containing
ferrous chloride, sodium chloride and potassium chloride and
regenerated cupric chloride is then passed through line 16 to
oxidation and regeneration-purge stage l9o Also added to
stage 19 through line 17 are the solids, including the partial-
ly reacted ore concentrates, from separation device 50 With
the reaction temperature maintained~at about 140Co and the
pressure at about 60 psig., air or oxygen is passed through
line 18 into stage 19 wherein the ferrous chloride is oxidized
to ferric chloride, with the cupric chloride in the solutlon
acting as a catalystO Concurrently, the ~erric chloride and
cupric chloride react with the solids so as to essentially
completely dissolve the copper there~rom. The excess iron
dissolved into the process solution, sulfate ions and other
contaminants present in the system are concurrently precipi-
tated in the form of basic iron oxide and potassium ~arositeO
This combined stage is advantageously conducted at
elevated temperatures to lower the reaction time required ~or
the oxidation and regeneration-purge reactions. It is be-
lieved that at a temperature above the melking point of sulfur
but below the temperature a~ which the viscosity of sulfur
rises abruptly, i.e. 3 within the range ~rom abouk 115C. to
about 159C., the superheated aqueous solution displace~ the
molten sulfur from the mineral surfaces, thus pre~enting
"blinding" and exposing the minerals to contact by the oxid~z-
in~ solution. The preferred temperature range is about 140C.
to about 150C. For example laboratory tests conducted in ac
cordance with the above procedure at 140C, and 60 psig.3 us-
ing oxygen, with 60 minutes reaction time, yielded 9905~ dis
,~ ,
0
~r~
- . . ~ . , .
~4D8~3S2~
solution o~ the copper ~rom copper sulfide ore concentrates,
consisting principally of chalcopyrite, and having a typical
particle size range.
After cooling to a temperàture below atmospheric
boiling to prevent uncontrolled flashing7 at which temperature
the elemental sulfur exists in the solid form, the resultant
slurry containing the sulfurg insoluble residue, potassium
jarosite precipitate, cupric chlorideg ferric chloride, so
dium chloride and potassi~m chloride is passed through llne 20
into separation device 210 In this device gravity sedimenta-
tion is used to separate the insoluble residue, sulfur and
potassium jarosite precipitate from the solution containing
cupric chloride, ferric chloride, sodium chloride and potas
sium chloride. This solution is then recycled through line 3
to reducing stage 1, step A. The solids are removed from de~
vice 21 through line 22 to a washing filter 23 where substan-
tially all remaining process liquor is displacedO The fil~
tered solids (sulfur, insoluble residue and potassium jarosite
precipitate) are removed at 24 and the recovered liquid is
added to the solution in line 3 through line 250 The solids
can be further treated by conventional methods to remove ele-
mental sulfur, the potassium ~arosite precipitate ~d any in
soluble precious metals.
It has been found that conducting the combined stage
at atmospheric boiling temperature requires extension o~ the
mea~ reaction time to 10 or 12 hours to obtain the desired 99%
d~ssolution o~ copper from typically sized chalcopyrite con~
centrates. Thus~ from an operating standpointg the mechanical
advantage of atmospheric pressure can be obtained at the ex~
pense of extending the reaction time~
Through control of the chloride lnventory ~n the
~1 :
~Y~,
~083~
process liquor the ultimate iron concentration in the reacted
liquor can be allowed to approach zerog to thereby minimize
iron in the process liquor and thereby to lmprove the quallty
of copper product in the electrolysis stage. However~ it is
pre~erred to provide for some residual iron to remain present
in the reacted liquor (as ferric chloride)g in order to assure
that all the reacted copper is present in solution as cupric
chloride.
Although one embodiment of this invention has been
described in relation to the treatment of copper sulfide ore
concentrates comprised principally o~ chalcopyrite, it has
also been found that a mixture of such sul~ide ore concentrates
and non-sul~ide materials, such as native copper and copper
oxides, carbonates, and silicates, can likewise be effective-
ly treated in accordance with the present inventionO Accord
ingly, since substantially all copper ores contain chalcopy-
rite, and most other copper-containing materials in such ores
are more easily solubilized, the process of our invention has
the important advantage that practically any copper ore con~
centrate or any mixture of copper concentrates can be leached
on a commercial basis ~t
In another emb~diment o~ the present invention as
illustrated in the ~low diagram o~ Figure 4 the use o~ potas~
sium chloride alone or with sodium chloride has been -found ad~
vantageous in the process in which the steps o~ the regenera~
tion-purge stage and the oxidati.on stage are per~ormed separate
ly. The addition o~ potassium chloride makes available potas-
sium ion in the process liquor whereby practically all sul~ate
~ion can be preclpitated therefrom as potassium ~aroslte in the
-30 regeneration-purge reaction~ This is important in the control
~ ~.of scaling in the process equipment~
~ ,~7 . .
~t
'''
11~835Z~
In reacting cupric chloride ~rom the oxidation stage
with fresh chalcopyrite in the reduction stage, ~e ha~e dis-
covered that the degree of reduction achievable can be limited
by a secondary reaction resulting in the 1GSS 0~ copper from
solution~ We believe on the basis o~ evidence c~rrentlY avail-
able that a stable form o~ copper sulfide is precipitated~ It
has ~urther been discovered that the reaction is temperature
sensitive, and that by limiting the temperature to atmospheric
boiling, about 107Co ~ the reduction of cupric chloride that
is possible with minimal or no loss of copper ~rom solution
can be obtained in about four hours' mean reaction timeO Thus
it will be understood that limiting the temperatures of the
reduction reaction can limit the reaction rate to an extent
that permits practical control bf the reactionO
Further reduction of the cupric chlor~de from the
first step of the reduction stage can be achieved with appro-
priate reducing agents such as sulfur dioxide, sodium sulfite9
meta-iic ironJ and material containing metallic copperO To
the extent that scrap copper or cement copper is available
economically, its use, obviously, would be advantageous in
that this copper is upgraded to electrolytic grade copper in
the electrolysis stageO In fact, the entire reduction o~
cupric chloride to cuprous chloride can be accomplished by any
o~ these reducing agents.
In the second step of the reduction stage (also re~
~erred tQ as step B), the temperature at which the reaction is
advantageously conducted wilI vary according to the spec~fic
redùcing agent used. Fbr example, in using cement copper or
metallic iron, a reaction temperature near atmospherlc boi~ing
~about 107Co ) has been ~ound satis~actoryO
9~
In both the oxidation and regeneration~purge ~*ge~ :
, .
3S'~k
,?~ e 7~ef 0 ~e
- and the reducti3n stage~ it has been ~ound ~ to con-
duct the reactions out of contact with the atmosphere to min-
imize vapor 10ssg and in the reduction stage to avoid oxida
tion of cuprous chloride to cupric chlorideO
It has been found advantageous to control the temper-
ature of the electrolysis~ Increasing temperature increases
the electrical conductivity of the electrolyte, and enhances
the solubility of the dissolved salts, both of which ef~ects
are advantageous; however, the vapor pressure o~ hydrochlorlc
10 acid in the electrolyte also increases~ which is disadvantage-
ous. Laboratory experimentation and also experimental pilot
plant operations have t~n indicated that a temperature range
of about 30C. to about ~0C0 is acceptable ~or electrolysls;
however, a temperature of about 55C. is preferred~
It has also been found preferable to clarify the
pregnant solution before it is passed into the electrolytic
cells. This i8 done to remove any small partlcles still re~
maining in the solution which could adversely a~fect the .
quality of the metallic copper produced at the cathodes in the
electrolytic cells. Thls can be accomplished by any suitable
apparatus, such as a.sand filter
The electrolysis of the pregnant (feed) solution9
which contains cuprous chloride and ferrous chloride9 results .
; in the transfer of copper ions to the cathode for the produc-
tion of metalllc copper and the simultaneous transfer of chlo
ride ions to the anode to be released in the presence of the
anolyte solution, thereby oxidizing the cuprous.chloride
therein to cupric chlorlde. In the aeparate oxidation and
regeneration-purge mode the process is pre~érably controlled
so that the copper electrolyticall~ preclpitated amounts to no
more than about one half the cuprous copper content of the
' .
: ~ . . : .. . . .
- . . . , - . ..
: . .~ . ;
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83524
pregnant solution feed to electrolysis.
However, as previously noted, in the combined oxida-
tion and regeneration purge mode, it is desirable t~at a small
amount of ferric chloride be introduced into the reduction
stage with the cupric chloride from the oxidation stage. In
this case, the amount of copper removed in the electrolytic
cell should exceed one-half of the cuprous content of the
pregnant liquor by the amount solubilized by ferric chloride
in the reduction stage. Also an amount of ferric chloride
stoichiometrically equivalent to the copper electrolyzed and
equal to one-third of the amount reduced to ferrous chloride
in the reduction stage will be oxidized to ferric chloride in
the anode compartment of the cell.
The desirable characteristics of diaphragms that can
be used in the electrolytic cells are that they be substantially
inert to the solution and have maximal resistance to hydraulic
flow of the solution and minimal electrical resistance. Available
materials to meet these requirements include Teflon, (Teflon is
a registered trademark) polypropylene, polyethylene, and
polyacrylate, all of suitable texture, including felted, woven,
needled, or gas-expanded, processed as required to establish
desirable limited permeability to solution flow, together with
minimal electrical resistance. Other available materials include
membranes used in the electrical de-salination of water, such as
chlorosulfonated polyethylene sheets.
The relative levels of solution in the catholyte
compartment and anolyte compartment of the electrolytic cell
are controlled by weir-type arrangements to maintain a hydraulic
gradient from the catholyte compartment to the anolyte compartment
in order to preclude the counterflow through the diaphragms
of anolyte solution into the catholyte compartment.
-24-
- ~
1~835;~
The anolyte solution contains cupric chlorideO If this solu-
tion were permitted to back ~low into the catholyte compart
ment, it would tend to re~dissol.ve.copper ~rom the cathode
which would impair electrical ef~iciencyO
The practice o~ this invention is not l~mited to the
use of any special equipmentO The stages and process steps
described herein may be conducted on a batch or continuous
basis and in any appropriate conventional equipment, including
for example, reactors, containers and vessels which may be
made open or closed to the atmosphere by conventional meansO
Moreover, each stage or step as described herein may be con~
ducted in one or more reactors, vessels or containersO Fur-
ther, the use of available compartmented, divided or segmented
units of equipment is within the conte~plation o~ this inven~ .
tion. .
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