4,124,379 Recovery of silver from cuprous chloride solutions by amalgamation

Patent Number/Link:

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

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

(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

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

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

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.

4,124,379

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.

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

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

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

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:

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.

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

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

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

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

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

21. The process of claim 20 'in which the bottom

phase of Cu-Hg amalgam is recycled to step (a).

* * * * *

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