United States Patent [19]
Peters et al.
[11]
[45]
4,124,379
Nov. 7, 1978
[54] RECOVERY OF SILVER FROM CUPROUS
CHLORIDE SOLUTIONS BY
AMALGAMATION
Primary Examiner-M. J. Andrews
Attorney, Agent, or Firm-Sheridan, Ross, Fields &
McIntosh
21 Claims, 2 Drawing Figures
A process for recovering silver from chloride solutions
comprising contacting the solution with amalgams of
various metals from Groups 2b, 4a, 5a, or 8b of the
periodic table or copper to replace the metal with silver
and recovering silver from the formed silver amalgam.
The process provides an improvement in the process for
recovering copper from its ores in which the copper in
the ore is solubilized as cuprous copper in a leach liquor
and the copper recovered from the leach liquor as cuprous
chloride by crystallization, the improvement
being the removal of silver from the leach liquor prior
to crystallization by use of the amalgam to produce
substantially silver-free cuprous chloride crystals.
[75] Inventors: Mark A. Peters; William G. Kazel,
both of Arvada, Colo.
[73] Assignee: Cyprus Metallurgical Processes
Corporation, Los Angeles, Calif.
[21] Appl. No.: 760,082
[22] Filed: Jan. 17, 1977
[51] Int. Cl.2 C22B 11/00
[52] U.S. Cl 75/118 R; 75/109
[58] Field of Search 75/109, 117, 118, 83
[56] References Cited·
U.S. PATENT DOCUMENTS
1,429,131 9/1922 Field 75/109
3,972,711 8/1976 Goens et a1. 75/117
CUCI
CRYSTALS
[57] ABSTRACf
Cu
CuCI
CRYSTALLIZATION
(COOLING)
MOTHER LIQUOR
BLEEO
CuC!
PRODUCT
U.s. Patent Nov. 7, 1978 Sheet 1 of 2 4,124,379
FLOWSHEET OF Ag RECOVERY BY AMALGAMATION
CuCI
CRYSTALS
NoCI
Cu
(OPTIONAL) ~ t
Cu+2 r1 n REDUCTION
01 SSOLUTION II ( 90°C)
MERCURY
t I
Ag REMOVAL
SILVER
RECOVERY
I LOADED +
MERCURY
Hg ADSORPTION SILVER
(95° C)
CuCI
CRYSTALLIZATION
(COOLING)
MOTHER LIQUOR LIQUID SOLIDS
SEPARATION
BLEED
CuCI
PRODUCT
u.s. Patent Nov. 7, 1978
COPPER SULFIDE
FEED
Sheet 2 of 2 4,124,379
~
Fe CI3 LEACH
CuCI
AND
Cu ++ REDUCTION
CRYSTALLIZATION
TAILS LIQUID SOLIDS
SEPARATION
cub
CRYSTALS
~I
t
SILVER I RECOVERY II----NOCI
MOTHER
LIQUOR
BLEED
CuCI
RECRYSTALLIZATION
H2 t
CuCI
REDUCTION
°2 Cu
I HYDROLYSIS II
I II
IRON
PRECIPITATE
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a flow diagram of the silver recovery process
per se of the invention, and
FIG. 2 is a schematic flow diagram illustrating where
the silver recovery process would be introduced into
the flowsheet of a prior art process for the recovery of
copper from its sulfides described in U.S. Pat. No.
3,972,711.
DESCRIPTION OF THE PREFERRED
EMBODIMENT
2
provement in the process for recovering copper from its
ores in which the copper in the ore is solubilized as
cuprous copper in a leach·and the copper recovered
from the leach liquor.as cuprous chloride by crystalliza-
5 tion, the improvement being the removal of silver from
the leach liquor prior to crystallization by use of the
amalgam to produce substantially silver-free cuprous
chloride crystals.
4,124,379
1
SUMMARY OF THE INVENTION
RECOVERY OF SILVER FROM CUPROUS
CHLOIDDE SOLUTIONS BY AMALGAMATION
BACKGROUND OF THE INVENTION
A process for recovering silver frOin solutions comprising
contacting the solution with amalgams of various
metals from groups 2b, 40, Sa, or 8b of the periodic
table or copper to replace the metal in the amalgam 60
with silver and recovering silver from.the formed silver
amalgam. Silver is eventually recovered from the amalgam
by distillation. A variety of techniques may be
employed to pre-concentrate the silver before distillation.
The invention includes the use of various sources 6S
ofchloride ion, such as sodium chloride or ferrous chloride
to keep the silver chloride and cuprous chloride in
solution. An application of the invention is as an im-
1. Field of the Invention
The invention lies in the field of recovering silver
from cuprous chloride by amalgamation techniques.
2. Description of the Prior Art
In the recovery of copper from its ores, particularly 10
sulfide ores, it is well known, as disclosed in U.S. Pat.
Nos. 3,785,944 and 3,972,711, in order to avoid the
disadvantages of recovering copper electrolytically,
pyrometallurgically, and by other methods, to solubilize
the copper in the ore as cuprous chloride in a leach 15
followed by cooling the slurry to crystallize the cuprous
chloride and recover copper from the cuprous
chloride crystals. A major disadvantage of wet recovery
like this technique, is that impurities like silver, iron
and others are carried over during the crystallization 20
into the cuprous chloride crystals and end up as impuri- The invention has application in processes for recovties
in the fmal copper product. Some of these impuri- ering copper from its ores containing iron and silver as
ties are deleterious to the properties of copper and re- impurities and in which process the copper sulfide ore is
duce its sale value. While the latter may not be necessar- leached with ferric chloride and the soluble cupric chloily
true of silver, the failure to recover the high priced 25 ride reduced to the cuprous form, followed by recoversilver
so that it is not sold along with the copper at the ing cuprous chloride from the leach liquor by crystaIIiprice
of copper, detracts from the economic feasibility zation and recovery of copper from the crystallized
of the overall process. cuprous chloride. It is difficult in this process to prevent
In accordance with prior art, silver is removed from silver from being carried over into the cuprous chloride
high chloride solution by cementation on copper metal. 30 crystals from which product copper is recovered by
It was found that the presence of cuprous copper in the teduction with hydrogen.
solution however renders this technique inoperative. The invention can be adapted to the above process
For example, it was found that silver was efficiently for the recovery of silver either as shown in FIG. 2, or
removed by cementation with copper metal down to after the cuprous chloride crystallization from sodium
<0.001 gil Ag from 200 gil NACI or 182 gil Fe+ + 35 chloride solution, or earlier in the flowsheet after the
from solutions containing no Cu+. Also that the pres- initial leach. Whichever option is used, any cupric ions
ence of 11, 23, or 30 gil C:u+ in these solutions only in the cuprous chloride solution must be reduced by
permitted the Ag concentration to be lowered to 0.009, copper metal to the cuprous state. The reduced cuprous
0.016, and 0.026 gil Ag, respectively. These data illus- chloride solution is then contacted with an amalgam to
trate the deleterous effect ofCu+ and therefore demon- 40 replace the metal in the amalgam with silver thus restrate
the Ileedfor a reductant which can cement Ag but moving silver from the solution. Obviously, the prenot
cement Cu+ from the solution. ferred metal for replacing silver is copper because the
Accordingly, it is an object of this invention to pro- use of copper does not introduce any additional impurivide
an effective process for recovering silver. from ties which could co-precipitate with cuprous chloride.
cuprous chloride and additionally produce a silver and 45 After the amalgamation step, the mother liquor is
iron-free cuprous chloride. cooled to produce cuprous chloride crystals which are
It is another object of this invention to provide an substantially free of silver and iron. Copper is then
improvement fu the process for recovering copper from recovered from the cuprous chloride crystals, preferraits
ores in which the copper is solubilized as cuprous bly by reduction with hydrogen.
chloride, the cuprous chloride crystallized and the cop- 50 The invention is not restricted in its application to
per produced from the cuprous chloride crystals, the processes for recovering copper from its ore, but applies
improvement being a procedure for recovering silver broadly to the recovery of silver from silver chloride
frOID the cuprous chloride crystals before. copper is solutions and from solutions containing both silver chloproduced.
from them. ride and cuprous chloride, irrespective of the origins of
55 these solutions.
It was found that very little silver can be cemented
with the amalgam in the presence of cupric ions. It was
also found that the invention is much more efficient in
the absence of cupric and other ions which have a more
oxidizing emf than silver. Accordingly, in the preferred
modification, a reduction step is performed on the cuprous
chloride solution or leach liquor prior to amalgamation
to reduce any cupric and ferric ions present.
Although the description of the invention and the
flowsheet illustrating it are based on the application of
the invention to a process for recovering copper from
its ores, the invention is not limited to this application as
it includes the recovery of silver from solution broadly.
3
4,124,379
4
Recovery of Ag from CuCI-NaCI Solutions
Free-flowing Amalgam
Table 1
(Upflow)
CuCI = 100-185 gil
NaCI = 200 gil
Ag+ = 0.03-0.05 gil
Temperature = 75-85" C
I" ID X 9" long
Porcelain berl saddles, 6 mm (41% void vol)
75-85" C
Residence Time of
Feed Solution
Test in the Column, %Ag
No. Amalgam min Removed
I Cu,3% 9.3 89
2 Cu,3% 13.1 94
3 Fe, 3% 13 83
4 Fe, 3% 14.4 75
5 Fe, 3% 14.9 94
6 Fe, 3% 4 89
7 Fe, 0.5% 15.8
8 Fe, 0.5% 7.7
9 Zn,0.5% 15 82
10 Zn,0.5% 13.7 91
11 Zn,O.5% 9S
Feed solution:
The data of Table 1 show that copper, iron or zinc
amalgams effectively remove silver from sodium chloride
solutions.
The rationale for utilizing the amalgams is as follows.
Both zinc and iron metal are strong reductants and will
completely cement Cu+ as well as silver from a sodium
chloride solution making them unsuitable as reductants.
If, however, they are amalgamated with mercury metal
and then utilized, little Cu+ is cemented while silver is
still rapidly and completely cemented.
Copper metal will not cement silver from this system
in the presence ofCu+. Ifthe copper metal is amalgamated
with mercury, this Cu-Hg amalgam will then cement
silver from the solution but not Cu+.
Copper is the most desirable amalgam as it is more
compatable with the system and, therefore, additional
tests were completed using copper amalgams and the
data are shown in Tables 2, 3 and 4.
Two types of copper-Hg mixtures, which are referred
to herein as amalgams were tested, a free-flowing
copper (::::::0.1-0.5% Cu) amalgam and a high percent
Cu (::::::90% Cu) amalgam which was essentially copper
shot coated with mercury. It was found that contact of
the feed solution· with the amalgam can be effected
batchwise, but is most conveniently accomplished in a
column configuration. In one series of tests (Table 2) a
low copper free-flowing amalgam was contacted with
the hot CuCI-NaCI feed solution by flowing each counter-
currently through a column packed with bed porcelain
saddles.
In a second series of tests (Tables 3 and 4), essentially
the same type of apparatus was used for the amalgamated
copper shot, similar to an ion exchange column,
and the feed solution upflowed through the shot. No
mercury was pumped into the column.
Column:Dimensions:
10 Packing:
Temperature:
Furthermore, even though the process is described and
illustrated in the flowsheet as starting with cuprous
chloride crystals produced in a process for recovering
copper from its ores in which the copper is recovered as 5
cuprous chloride crystals, it is not limited to this modification
as the feed material can be a solution containing
cuprous chloride.
The invention will now be described with reference
to the accompanying drawings. Referring specifically
to FIG. 1 of the drawing, the feed material is shown as
cuprous chloride crystals which is the crystallization
product of the process illustrated in FIG. 2, that is, a 15
process for recovering copper from a sulfide ore in -------''-----------------
which the copper is recovered as cuprous chloride
crystals.
The cuprous chloride crystals are dissolved in a dissolutl.
On step to produce a cuprous chol'nde soIut'lOD. The 20
cuprous chloride solution is then contacted with copper
to reduce any cupric copper to cuprous copper. A nonoxidizing
atmosphere is maintained to prevent reoxidation
of cuprous ion. 25
From the reduction step the cuprous chloride solu- -------'----------------
tion goes to the silver removal column where it is contacted
with the amalgam to replace the metal in the
amalgam with silver. The silver is then recovered in the 30
silver recovery circuit by distilling the mercury.
Following the amalgamation step the .cuprous chloride
solution goes to a mercury absorption column for
removal of any dissolved mercury and after this step the 35
cuprous chloride solution goes to the recrystallizer
where it is cooled to produce cuprous chloride crystals,
and the crystals flltered to provide a product of cuprous
chloride which is substantially free from silver. Part of 40
the mother liquor from the cuprous chloride crystallization
step is returned to the dissolution step and part of it
is bled off to the main circuit of a copper process for
recovering copper from its ore as illustrated in FIG. 2
for removal of some iron before its return to the ferric 45
chloride leach.
The flowsheet of FIG. 2 depicts a prior art process
for the recovery of copper from a copper sulfide ore in
which the ore is leached with ferric chloride to provide 50
a leach liquor, cuprous chloride crystallized from the
leach liquor followed by a liquid solids separation to
recover the cuprous chloride crystals which are reduced
with hydrogen to provide the final copper prod- 55
uct. In order to insure that this product is substantially
free of silver, iron and other impurities, the silver recovery
process of the invention is introduced before the
cuprous chloride crystals are recovered by cooling, 60
followed by recovery of copper from the cuprous chloride
crystals.
To illustrate the operation of the invention, tests were
made by dissolving the feed material, cuprous chloride, 65
as shown in FIGS. 1 and 2, in sodium chloride solutions
and removing the silver with various amalgams as
shown in Table 1 below.
5~
Table 2
4,124,379
Dimensions: 15" long X 1.8" ID (0,022ft3)
Packing: Porcelain bed saddles, 6mm
(60% void vol)
Temperature: 85-90' C
;;:;0,5% Cu (downflow); flow rate =
23-35 ml./min.
(Upflow); flowrate = 19-36 ml./min.
CuCI = 169 gil
NaCI = 200-220 gil
Ag+ = 0.022-0.040 gil
Temperature' = 80-90' C
Free HCI = ::::: 2 gil (pH = 0.0)
Recovery or.Ag from CuCI-NaCI Solution.
" Free-flowing Cu Amalgam
Amalgam:
Feed
liquor:
Column:
Residence Time
of Feed Solution in Ag Concentration
Test the Column FeedlEmuent %Ag
No. (min) (gil) Removed
I 16.0 0.028/0.005 82
2 19.0 0.040/0.005 88
3 10.0 0.040/0.006 85
4 17.5 0.022/ <0.001 >95
Table 3
Recovery of Ag from CuCl-NaCl Solutions Amalgamated
Cu-Shot Column
Recovery of Ag from CuCI-NaCI Solutions ,.
Amalgamated Cu Shot Column
Column:
Feed liquor:
Temperature:
Table 5
Recovery of Ag from CuCI-NaCI Solutions
Recovery of Ag from Loaded Hg'
Skimming
Assay Distribution
40 Test Weight Ag Cu Ag
No. Sample Description % (%) (%) (%)
Feed Hg 100 0.37 2.2 100
Top Hg phase 17.7 1.54 11.8 74.4
"2
Bottom Hg phase 82.3 0.Q7 0.19 25/6
Feed Hg 100 0.37 100
45 Top Hg phase 20.7 1.50 12.6 82
Bottom Hg phase 79.3 0.08 0.68 18
Feed Hg 100 0.38 1.0 100
Top Hg phase 6.5 3.5 61
Bottom Hg phase 93.5 0.15 39
Emuent Assays
Ag CuCI Hg %Ag
gil gil ppm Removed
0.D38 172:8 0.20
<0.001 172.5 2.74 >97
<0.001 175.0 2.82 >97
0.002 173.4 2.36 95
<0.001 171.2 >95
0.022
0.001 181 2.34 95
0.026 177.2 0.11
0.010 181.9 1.38 62
0.010 182.2 1.75 62
Dimensions 15" long X 1.8" ID
Packing Hi; coated Cu Shot
(3272 g; 9.8% Hg' ).
Void volume 37.2%
85-90' C
Given below
85-90' C
Temperature
Table 4
Feed Liquor
Residence
Time,
min
O-feed
1 20.5
2 14.5
3 10.5
4 4.75
O-feed.
5 11.O
ll'feed
6 12.0·
7 6.9
Test
No.
The results presented in Table 5 show that 80% of the
Ag can be skimmed off in the top phase which is 20.7%
of the total weight of the feed amalgam. A 61% Ag
recovery can be realized if only a 6.5 wt% fraction is
skimmed off. The bottom phase which can be recycled
55 contained 0.2-0.68% Cu and 0.07~O.15% Ag. The feed
amalgam contained 1-2.2% Cu and 0.37% Ag. In order
to apply the skimming technique, the feed amalgam
must contain at least 1% Cu by weight or no Ag-Hg
phase will float to the top of the amalgam.
Silver was recovered from the loaded amalgamated
copper shot by elution with mercury. The loaded shot
was placed in a glass column along with the Hg and
some HCl solution (pH 0-1). The mixture was inverted
periodically during the contact time. The free mercury
was then drained from the column. Tests showed that
85-91% of silver can be removed from the loaded Cu
shot (0.35.- 0.79% Ag) by contacting with free Hg. The
Hg effluent contains 0.25 - 0.38% Ag and the stripped
Hg '%Ag
ppm Removed
0.11
92
1.14 85
1.34 92
1.90 93
0.11
1.74 69
176.9
175.5
Emuent Assays
Ag CuCI
gil gil
Feed Liquor
Residence
Test Time,
No. min
O-feed
I 8
2 4.4
3 12.0
ll'feed
4 8.8
o-feed
5 8.3
The data of Tables 2, 3 and 4 shows that effecient
silver recoveries were achieved with both types of copper
amalgams.
The free-flowing copper amalgam was prepared by 65
shaking the pure mercury \\lith .150-mes~ copper powder
under a pH 0;5Hp sohitioil; 'the copper entered iIie
mercury phase within one half minute of hand shaking.
0.026 177.2
0.002
0.004
0.002
0.176
0.012 172.2
0.026 177.2
_________0_.00_8__1_70_.8 60
Recovery of Ag from CuCI-NaCI Solutions
Investigation of Various Amalgams
4,124,379
7
shot contained 0.05% Ag. This stripping procedure also
re-amalgamates any Cu shot that; may have· become
depleted in Hg and, therefore, rejuvenates the column
for its next service cycle. A series of tests were made .
using the elution procedure and the results are 'pres- 5
ented in the following Table 6.'
Table 6
Temperature:
Feed
solution:
Amalgam:
8
Table 7
25· C
0.055 g~Ag, 176 gil CuCl, 300 gil NaCl, 0.9-3.7
gil Fe'+- , pH = 0.0, 100 m!.
60g
Recovery of Ag from CuCl-NaCl Solutions '"
Recovery of Ag from Loaded Amalgamated Cu Shot
Elution with Hg·
Procedure: Mix free·flowing Hg with the loaded amalgamated Cu
shot and drain off free-flowing Hg·
Temperature: 25· C
Test
No.
2
3
Assay
Sample Wt Ag Cu Hg Ag
Description (g) (%) (%) (%) Recovery
Loaded Cu shot 80 0.024 93.4 ::::6.6
Free Hg·, before elution 229 0.002 0.34 99.66
Free Hg·, emuent 0.01 0.10 99.9 ::::53%
Stripped Cu shot 0.010
Loaded Cu shot 74 0.79 85.9 13-3
Free Hg, before elution 200 0.002 99:9
Free Hg, emuent 200 0.25 99.75 ::::91%
Stripped Cu shot 69.5 0.051
Loaded Cu shot 77 0.35 89.9 9.8
Free Hg, before elution 66 0.002 99.9 ,
Free Hg, emuent 61.5 0.38 ::::85%
Stripped Cu shot 81 0.49
Procedure: Mix amalgam and solution batchwise
Reaction % Removed
Test Feed Amalgam Time From Solution
No. Metal % (hr) Ag Cu
I Bi 0.64 2.5 98 3
2 Pb 1.6 2.5 >98
3 Cd 3.1 2.5 >98 13.1
4 Ni 0.38 >98
Zn 0.46 2.5 >98
5 Zn 0.5 0.5 >95
6 Fe 0.5 0.5 >95
7 Cu 0.1 2.5 98
The results show that up to 98% ofsilver is removed
from the cuprous chloride-sodiiun chloride solution and
that the bismuth, lead, cadmium, nickel, zinc and iron
amalgams are as effective as the copper amalgam for
silver removal. These other amalgams were prepared
by a method similar to that used for preparing the copper
amalgam as described above.
Additional tests were completed (Table 8), illustrating
the applicability of the invention to the removal of
silver from ferrous containing leach liquors.
Table 8
It will be noted from the results that up to about 91%
silver was recovered using the elution procedure.
A detailed incorporation of the above procedure as
shown in FIG. 1 is presented below. ..30 _:--_ __::;:----=--;-;----::-::---~::-__:___:__,__
The CuCI crystals (150 ppm Ag, 200 ppm Fe) were
dissolved in the Ag circuit mother liquor (:::::200 gil
NaCI, ::::: 140 gil CuCl, 0.001 gil Ag+, 0.0003 gil Hg) at
:::::90· C. After reduction of any soluble Cu++ with
metallic copper, this hot solution (200 gil NaCI, 205 gil 35
CuCI, 0.011 gil Ag+, 90° C) was passed through the Ag
removal column. The column effiuent (200 gil NaCI,
0.001 gil Ag, :::::0.0025' gil Hg) was passed through a
column packed with Cu metal to reduce the soluble Hg
level to 0.0004 gil Hg before cooling to 35° C. The 40
resulting CuCI crystals (65 gil CuCl crop) contained
<20 ppm Ag, :::::1.2 ppm Hg, and <20 ppm Fe. The
mother liquor from crystallization was recycled. The
Ag can be periodically recovered from the loaded Cu
amalgam by the techniques described above.. 45
A series of tests were conducted utilizing amalgams
of other metals and the procedure outlined above. The
Amalgam Description Feed Solution Product Filtrate Reaction
Test . g Metal Fe+2 Cu+! Ag Fe+2 Cu+! Ag Zn Hg Time Ag Removal
No. Metal gHg (gil) (gil) (gil) (gil) (gil) (gil) (gil) (gil) (hr) %
I Hg coated
Zn 5 gil. coating 166 67 0.034 50.7 0.008 3.4 0.02 I 76
2 Zn 5 gil. coating 126 70 0.34 126.8 69 0.018 1.04 0.002 I 95
3 Zn 5 gil. coating 143 60 0.24 141 56 0.05 1.70 0.024 4 79
4 Hg only 77 0.56 77 0.50 0.006 18 11
5 Zn.Hg 0.3/13.8 155 78 0.032 154 76 0.015 1.68 0.0034 2 53
6 Zn-Hg 1.8/14 155 78 0.032 162 76 0.022 0.6 0.006 2 31
7 Zn-Hg 1.4/14 164 103 0.050 172 84 0.014 0.002 4 72
8 Zn-Hg 1.91/191 167 89 O.~ - 84 <0.001 5.3 0.01 0.5 100
9 Hg coated
Cu 5 glcoating 77 0.56 80 0.34 0.128 18 39
10 Fe-Hg 1.9/190' 167 89 0.044 177 73 <0.001 0.003 1.0 100
[Note:Cu+ 2 = 02 gil in all tests]
The solution· COntained ferrous, ferric, cuprousartd
cupric ions along with silver. The types of amalgams
employed were Zn-Hg, Hg pool, Cu-Hg and Fe-Hg.
A.U tests were ~n at 65°--'15° C with feed liquors which
contained 126-176 gil Fe++ ata pH of 0.5. Various
weight ratios of zinc to merc\lry amalgams were used
4,124,379
5
35
9
and, in addition, various ratios of processed liquor to
amalgams were tried.
The results show that Zn, Cu and Fe amalgams effectively
remove silver from these leach liquors. Mercury
alone was ineffective in removing silver.
n is seen from the above description and results that
a process has been provided for the effective recovery
of silver from cuprous chloride solutions. The process is
seen to be particularly effective for use in combination
with processes for the recovery of copper from its sul- 10
fide ores in which the copper is sOlubilized as the cuprous
ion and recovered by cuprous chloride crystallization.
The process results in a successful recovery of
substantially all of the valuable silver in the ore with a
consequent result that a salable copper product is pro- 15
duced which is substantially free from silver.
What is claimed is:
1. A process for recovering silver from a cuprous
chloride solution which comprises:
(a) contacting the solution with a mercury amalgam 20
of a metal selected from the group consisting of
metals of groups 4a, Sa, 2b, and 8 of the periodic
table and copper to replace said metal in the amalgam
with silver, and
(b) recovering the silver by separating it from the 25
formed silver amalgam. .
2. The process of claim 1 in which the metal is a
member selected from the group consisting of lead,
bismuth, copper, zinc, cadmium, iron and nickel.
3. The process of claim 2 in which the metal is cop- 30
per.
4. The process of claim 2 in which the metal is iron.
5. The process of claim 2 in which the metal is zinc.
6. The process of claim 2 in which the metal is bismuth.
7. The process of claim 2 in which the metal is lead.
8. The process of claim 2 in which the metal is cadmium.
9. The process of claim 2 in which the metal is nickel.
10. The process of claim 2 in which any cupric ions in 40
the solution are reduced to cuprous ions prior to contact
of the solution with the amalgam.
11. The process of claim 2 in which the silver is recovered
from the silver amalgam by distilling the mer-
~~ ~
12. The process of claim 2 in which the cuprous chloride
is maintained in solution by the addition of sodium
chloride or ferrous chloride to the solution prior to
contacting the solution with the amalgam.
13. In the process for the recovery of copper from its 50
ores in which the copper in a leach solution is reduced
10
to the cuprous form and recovered as cuprous chloride
by crystallization, the improvement for recovering silver
from the leach solution which comprises:
(a) contacting the cuprous chloride solution prior to
crystallization with a mercury amalgam of a metal
selected from the group consisting of groups 40, Sa,
2b, and 8 of the periodic table and copper to replace
said metal or alloy in the amalgam with silver;
(b) recovering the silver by separating it from the
formed silver amalgam; and
(c) recovering copper from the crystallized cuprous
chloride.
14. The process of claim 13 in which said metal is a
member selected from metals of the group consisting of
lead, bismuth, copper, zinc, cadmium, iron and nickel.
15. The process of claim 13 in which the ore is a
sulfide ore.
16. The process of claim 15 in which the ore is chalcopyrite.
17. A process for recovering silver from a silver chloride
solution which comprises:
(a) contacting the solution with a mercury coated
substrate of a metal selected from the group consisting
of metals of groups 40, Sa, 2b and 8 of the
periodic table and copper which absorbs the silver
from solution on -the substrate;
(b) contacting the mercury coated substrate loaded in
silver with pure free-flowing mercury to remove
the silver from the substrate so that it dissolves in
the free-flowing mercury and therby regenerate
the mercury coated substrate, and
(c) recovering silver from the mercury.
18. The process of claim 17 in which is selected from
the group consisting of lead, bismuth, copper, zinc,
cadmium, iron and nickel.
19. The process of claim 18 in which the metal is
copper.
20. A process for recovering silver from a cuprous
chloride solution which comprises:
(a) contacting the solution with a copper - mercury
amalgam for a period to replace not more than 99
percent by weight copper in the amalgam so that
the lighter Cu-Hg and Ag-Hg amalgam phase
floats on the Cu-Hg amalgam;
(b) skimming off the floating top phase, and
(c) recovering silver from said skimming product.
21. The process of claim 20 'in which the bottom
phase of Cu-Hg amalgam is recycled to step (a).
* * * * *
55
60
65
UNITED STATES PATENT AND TRADEMARK OFFICE
CERTIFICATE OF CORRECTION
PATENT NO. : 4,124,379
DATED November 7, 1978
INVENTOR(S): Mark A. Peters, William G. Kazel
It is certified that error appears in the above-identified patent and that said Letters Patent
are hereby corrected as shown below:
Amend Table 8, the line corresponding to Test 1, by leaving
the space under Product Filtrate, Fe+2 blank, and moving the
data thereunder one column to the right, and thus moving all
subsequent data one column to the right, as follows:
Product Filtrate
Fe+2 cu+l Reaction
Ag Zn Hg Time Ag Removal
(gil) (gil) (gil) (gil) (gil) (hr) %
50.7 0.008 3.4 0.02 1 76
[SEAL)
Anest:
RUTH C. MASON
Anes,;", Offu:er
~igncd and ~calcd this
Te.t" Day of April1979
DONALD W. BANNER