4,276,084 Hydrometallurgical process for the recovery of lead

Patent Number/Link:

United States Patent [19]

Reynolds et all

[11]

[45]

4,276,084

Jun. 30, 1981

[54] HYDROMETALLURGICAL PROCESS FOR

THE RECOVERY OF LEAD

OTHER PUBLICAnONS

Mellor, "Comprehensive Treatise on Inorganic & Theoretical

Chemistry", vol. 7, 1927, Longmans, Green &

Co., N.Y., pp. 712 and 713.

Wong et al., World Mining and Metals Technology, Sep.

1976, pp. 603-622.

704,639

1,346,642

3,981,962

3,998,628

4,135,993

References Cited

U.S. PATENT DOCUMENTS

[57] ABSTRACT

Scheiner et al., 1978 Mining Yearbook, Colo., pp.

133-138.

Murphy et al., Bureau ofMines, RI (1976) 7913 pp. 1-8.

Haver, Bureau ofMines, RI 8105 (1976) pp. 1-17.

Muir et al., J. Australasian Inst. of Mining and Metallurgy,

No. 259 (Sep. 1976), pp. 23-35.

Bagdasarian, Trans. of Am. Electrochem. Soc., vol. 51,

1927, pp. 449-494.

Primary Examiner-G. Ozaki

Attorney, Agent, or Firm-Sheridan, Ross, Fields &

McIntosh

21 Claims, 1 Drawing Figure

A hydrometallurgical process is used to recover lead

from a lead-bearing ore concentrate. The lead-bearing

ore concentrate is leached with a solution of cupric

chloride in order to precipitate lead as lead chloride,

produce elemental sulfur and substantially leave the

balance of the ore concentrate sulfides in unreacted

form. The residue of the cupric chloride leach is

leached with a brine solution in order to solubilize the

lead chloride to the exclusion of the balance of the

residue. Thereafter, the lead chloride is crystallized

from the brine solution. Elemental lead may be obtained

by the reduction of the lead chloride crystals.

The present process avoids air pollution problems inherent

to smelting processes, allows for a high recOvery

of lead of 97% or greater and allows for the direct

production of a high purity lead.

Hoepfner 75/120 X

Elmore 423/94 X

Smyres et al. 423/94 X

Gandon et al. 423/98 X

Urn 423/98 X

7/1902

7/1920

9/1976

12/1976

1/1979

Inventors: James E. Reynolds, Golden; Alan R.

Williams, Denver, both of Colo.

Assignee: Hazen Research, Inc., Golden, Colo.

Appl. No.: 80,444

Filed: Oct. 1, 1979

Int. CI.3 ............................•................. C22B 13/04

U.S. CI 75/101 R; 75/114;

75/120; 423/94; 423/98; 423/494

Field of Search 75/101 R, 114, 120;

423/94, 98, 494

[75]

[73]

[21J

[22]

[51]

[52J

[58]

[56J

AIR1PbS ORE

IFe,CtZnlS

CuCI

Cu Clz !

LEACH IMPURITIES + Zn,Fe

LIQUID I SOLID REMOVAL

SEPARATION J.Cu VALUES

CuClz

S' HCI

PbClz

UNREACTED

STr

SULFIDE

GANGUE

BRINE PbClz1BRINE SOLUTION

PRESSURE PbClz PbClz

LEACH CRYSTALLIZATION CRYSTALS

+ +

LIQUID / SOLID SEPARATION

SEPARATION

AIR

1UNREACTED

CUPRIC

REGENERATION

HCI

PbClz

VAPOR

REDUCTION

UNREACTED

SULFIDES

GANGUE

1Pb'

f----+s'

RECOVERY

UNREACTED

f----+SULFIDES

'--__---' GANGUE

U.S. Patent

AIR

Jun. 30, 1981 4,276,084

AIR

PbS ORE

(Fe,Cu,ln)S ,.. i CuCI ,.

UNREACTED

PbCll

UNREACTED

SULFIDE

GANGUE

Cu Cil

LEACH

lIQUlO / SOLID

SEPARATION

STEAM

,p •

BRINE

PRESSURE

LEACH

LIQUID / SOLID

SEPARATION

PbCll/BRINE

SOLUTION

IMPURITIES ......Zn, Fe

RENOVAL

!CU VALUES

CuClz

HCI

.. PbCll PbCll

CRYSTALLIZATION CRYSTALS ~

SEPARATION

CUPRIC

REGENERATION

HCI

PbCI2

VAPOR

REDUCTION

UNREACTED

SULFIDES

GANGUE

Pbo

RECOVERY

UNREACTED

I--~- SULFIDES

GANGUE

Fig_l

4,276,084

Disclosure of the Invention

Lead-bearing ore concentrates are leached with cupric

chloride under reaction conditions controlled in

such a manner so as to extract and precipitate lead as

lead chloride, produce sulfur ill elemental form, and

substantially leave the balance of the concentrate sulfides,

particularly zinc, iron and copper, in unreacted

form. Leach liquor is continuously sparged with air in

order to regenerate the cupric chloride leaching agent

in solution.

The residue from the cupric chloride leach is then

preferably leached with a brine solution in order to

solubilize the lead chloride to the exclusion of the balance

of the residue. This brine leach is preferably conducted

under pressure and at an elevated temperature in

order to enhance the dissolution of the lead chloride.

The lead chloride solution is then separated from the

residue, and the lead chloride is crystallized from the

solution. The crystallized lead chloride may then be

reduced to elemental lead, preferably by means of hydrogen

reduction.

The residue from the brine leach step can be further

treated in order to recover the elemental sulfur.

BRIEF DESCRIPTION OF THE DRAWINGS

The FIGURE represents a generalized flow diagram

showing one preferred lead recovery technique.

BEST MODE FOR CARRYING OUT THE

INVENTION

The process ofthe present invention is suitable for the

separation of lead values from metal sulfide ores. The

metal sulfides may be any of those commonly associated

with lead sulfide, and the process is particularly adaptable

to the separation of lead values from metal sulfides

selected from the group consisting of zinc, iron and

copper. The concentrations of the various sulfide starting

materials is not important to the proper conduct of

the process, and hence lead sulfide may exist in an

amount as low as deemed desirable for separation to an

upper limit of nearby pure lead sulfide. Hence lead may

be considered the primary product of the process, or

may be deemed as an impurity in conjunction with, for

example, a relatively high content zinc concentrate.

The optimization of process parameters will, of course,

vary depending upon the precise constituents of the

with hydrochloric acid, ferric chloride, cupric chloride,

oxygen, oxygen and chlorine, chlorine alone, and chlorine

with cupric chloride. The cupric chloride leach

reported was conducted at 95° C. under carbon dioxide

5 pressure with aIM hydrochloric acid concentration.

Zinc extraction was about 95% after 2 hours, and the

cupric leach was not recommended because of high

ferric and cupric concentrations along with the zinc

chloride in the leach solution. A further disclosure in

10 this article describes the use of cupric chloride as a

catalyst with a hydrochloric acid leach (1 to 5M HCI).

Oxygen pressure is used with this process.

A. B. Bagdasarian discloses "Reduction of Metallic

Chlorides by Hydrogen" in 51 Transactions ofthe American

Electrochemical Society, pp 449-494 (1927). The

basic reduction reaction is discussed as well as the theoretical

aspects of the process. The author discloses hydrogen

reduction of lead chloride in closed tubes, with

and without bubbling the hydrogen through the lead

chloride.

BACKGROUND ART

HYDROMETALLURGICAL PROCESS FOR THE

RECOVERY OF LEAD

DESCRIPTION

Technical Field

The process of the invention relates to the hydrometallurgical

recovery of lead from lead concentrates,

and is particularly applicable to separating lead from

zinc, iron and copper.

Prior Art Statement

A leach-electrolysis method for producing lead from 15

galena is disclosed by M. M. Wong and H. P. Haver of

the U.S. Bureau ofMines in Chapter 37 of World Mining

and Metals Technology: Proceedings of thf! Joint MMIPAIME

Meeting, Denver, Colo., USA, Sept. 1-3, 1976,

A. Weiss, Ed. (MMIJ-AIME, 1976). In this process, 20

high grade lead concentrates (about 68 weight percent

lead) are leached with ferric chloride and sodium chloride

for 15 minutes at 100° C. Lead chloride is crystallized

from solution at room temperature and the ferric

chloride leachant is regenerated with chlorine. The lead 25

chloride is then reduced by fused salt electrolysis to

elemental lead.

B. J. Scheiner and R. E. Lindstrom disclose a chlorine-

oxygen leaching technique in "Leaching Complex

Sulfide Concentrates Using Aqueous Chloride Oxida- 30

tion Systems" in the 1978 Mining Yearbook ofthe Colorado

Mining Association, pp 133-38. Lead concentrates

bearing about 50% lead are leached in a two-step procedure

carried out in a pressure reactor with continuous

addition of chlorine and oxygen. The ferric and cupric 35

chlorides extracted from the concentrate by the chlorine

and oxygen then react to extract lead and other

metals as their chlorides. Lead chloride is dissolved

from the leach residue by means of hot brine leach at

90' C., crystallized at room temperature, and the lead is 40

reduced by fused salt electrolysis.

A method for leaching galena with ferric chloride is

disclosed by J. E. Murphy, F. P. Haver and M. M.

Wong in "Recovery of Lead from Galena by a Leach

Electrolysis Procedure", Bureau of Mines Report of 45

Investigations No. RI 7913 (1974). This disclosure concerns

itself primarily with the electrolytic reduction of

lead from lead chloride, and discloses ferric chloride

leaching of the galena ore and dissolution of the formed

lead chloride in 25% brine solution at 100° C. Chlorine 50

is used to regenerate the leachant.

A further disclosure by F. P. Haver and M. M. Wong

entitled "Ferric Chloride-Brine Leaching of Galena

Concentrate" is published in Bureau ofMines Report of

Investigations No. RI 8105 (1976). Hot brine (100° C.) 55

and ferric chloride are used to leach the lead chloride

from the 68% lead-bearing ore, dissolving the lead chloride

as it is formed. Chlorine is used to regenerate the

leachant. This is an improvement over the process disclosed

in Bureau of Mines Report Number RI 7913, 60

described above, wherein the ferric and brine leaches

are not combined.

David M. Muir, Donald C. Gale, A. James Parker,

and Dion E. Giles, in "Leaching ofthe McArthur River

Zinc-Lead Sulphide Concentrate in Aqueous Chloride 65

and Chlorine Systems", J. Australasian Institute ofMining

and Metallurgy, No. 259 (September, 1976), disclose

a number of leaching techniques including leaching

4,276,084

starting material, consistent with the discussion of the

process conditions as hereinafter set forth.

The starting materials are generally concentrated by

techniques known to the art in order to separate the

metal sulfide values from a substantial portion of the 5

gangue material. The concentrated values are then preferably

crushed to a sufficiently small particle size in

order to facilitate the leach reaction: The preferred

concentrate particle size introduced to the leach step is

about -100 mesh, more preferably about -200 mesh, 10

and most preferably about - 325 mesh.

The ore concentrate is then leached with cupric chloride

under reaction conditions selected so as to extract

most of the lead values as lead chloride, while leaving a

substantial portion of the remaining metal sulfides, in- 15

cluding sulfides of zinc, iron and copper, in their unreacted

sulfide form. The lead chloride product is insoluble

in the solution, while the small portions of zinc,

copper and iron sulfides which are extracted as their

corresponding chlorides are dissolved in the solution. 20

The lead chloride product, along with the elemental

sulfur and unreacted residue, is separated following the

leach from the leach solution containing the relatively

small amounts of solubilized metal chlorides.

The required agent for the leach reaction is cupric 25

chloride, with the leach reaction generally being as

follows:

2CuC1Z+PbS---+2CuCI+PbClz+so

The total copper concentration during the leach reac- 30

tion is preferably maintained as low as possible in order

to enhance the selectivity of the separation. The cupric

chloride concentration is therefore selected for a given

feed concentrate and other leach variables so as to maximize

lead extraction from the sulfides, while minimizing 35

the amount of extraction of the remaining metal sulfides.

The cupric chloride concentration is primarily a

function of total copper in solution and solution emf,

and solution emf is primarily a function of the ratio of 40

cupric chloride to cuprous chloride. The total copper

concentration in solution is preferably maintained

within the range of from about 3 to about 100 grams per

liter, more preferably from about 5 to about 50 grams

per liter, and most preferably from about 8 to about 25 45

grams per liter.

As the leach reaction continuously reduces the cupric

chloride to cuprous chloride, a preferred technique for

regera.rating the cupric chloride leaching agent is to

continuously introduce oxygen and/or air into the leach 50

solution during the leach reaction, thereby oxidizing

cuprous chloride to cupric chloride. This oxidation

reaction occurs at the relatively low leach temperatures

preferred for this leach reaction.

The reduction of cupric chloride by means of the 55

primary leach reaction and the oxidation of cuprous ion

by means of the air sparging are preferably controlled

so as to maintain a cupric ion to cuprous ion ratio in

solution offrom about 1:20 to about 16:1, more preferably

from about 1:9 to about 4:1 and most preferably 60

from about 1:5 to about 3:1. Consistent with the preferred

cupric ion to cuprous ion ratio, the solution emf,

which is oxidizing, is preferably maintained during the

leach reaction from about 200 to about 500 millivolts,

. more preferably from about 250 to about 450 millivolts, 65

and most preferably from about 350 to about 400 millivolts,

as measured by saturated calomel/platinum electrodes.

A primary feature of the invention is the libera-

tion of the sulfide sulfur in elemental form. Solution

emf's below about 100 millivolts tend to produce hydrogen

sulfide .as opposed to solid elemental sulfur.

The total chloride ion concentration maintained during

the leach reaction is important for the proper conduct

of the reaction, and to solubilize those minor

amounts of metal sulfides which are extracted during

the leach. The chloride ion concentration is preferably

maintained at a level not substantially exceeding that

amount sufficient to keep the copper in solution. Chloride

ion in excess of this requirement detracts from the

selectivity of the process. The chloride ion concentration

is maintained primarily by the addition of sodium

chloride, although calcium chloride, lithium chloride

and potassium chloride may also be used as sources of

chloride ion. Preferably the leach· solution contains

from about 50 to about 300 grams of sodium chloride

per liter, and more preferably from about 100 to about

250 grams of sodium chloride per liter.

The acidity of the solution is significant from the

standpoint of selectively extracting the lead values to

the substantial exclusion of the other metal values. The

pH is preferably maintained from about 0.5 to about 4,

and more preferably from about 0.5 to about 2. The pH

is preferably maintained by the addition of hydrochloric

acid so as to result in a solution concentration of hydrochloric

acid up to about 20 grams per liter, more preferably

from about 1 to about 16 grams per liter, and most

preferably from about 3 to about 7 grams per liter. The

selectivity of the process is greatly diminished with

excessive hydrochloric acid concentrations, and it is

therefore preferable to use as small an amount as possible.

The temperature of the solution is preferably maintained

as low as possible, consistent with suitable lead

chloride extractions. The solution temperature may be

permitted to go as high as the boiling temperature under

atmospheric conditions by properly controlling the

other process variables, but generally speaking such

high temperatures result in greater extractions of other

metal sulfides in the concentrate. Hence the solution

temperature is preferably maintained at less than about

95° C., more preferably at less than about 75° C. and

most preferably at about 60° C. and less. The lower

limitation is primarily dependent upon suitable reaction

times, and at less than about 30° C. the extraction oflead

becomes too slow to be practical.

The reaction time is maintained so as to obtain sufficient

lead recovery while avoiding extraction of the

other metal sulfides. Hence the reaction time is preferably

kept to a minimum consistent with the desired lead

recoveries. Generally speaking, reaction times of from

about 10 minutes to about 4 hours are preferred, with

reaction times of from about 30 minutes to about 2 hours

being more preferred.

Following the leach reaction, the resulting solid

phase, containing unreacted sulfides, elemental sulfur

and lead chloride are separated from the leach solution.

The separated leach solution is then preferably treated

for additional regeneration of the cupric chloride leaching

agent, and a portion of the liquid phase is treated for

the remov!!l of impurities as necessary. The leach solution

regeneration is preferably conducted by air oxidation,

preferably within a temperature range of from

about 40° C. to about 60° C. Hydrochloric acid is preferably

added as the chloride ion source for the necessary

oxidation of cuprous chloride to cupric chloride.

PbC1z+Hz--+HCI+PbO

The furnace operates at between about 600· C. and

about 900· C., and it is generally preferred to employ

excess hydrogen in order to facilitate the reaction. The

lead chloride reduction with hydrogen produces hydrochloric

acid, which as discussed earlier, may be scrubbed

with spent leach liquor from the cupric chloride

leach stage in order to remove the hydrochloric acid

and any unreduced lead chloride from the gas and provide

a source of chloride ions for the oxidation of cuprous

chloride to cupric chloride.

EXAMPLES

Example 1

Concentrates of compositions as hereinafter presented

were leached with various agents as set forth in

Table 1. Various feed materials were used, designated

concentrates A, B and C. Concentrate A comprised 73.9

percent lead, 0.954 percent zinc, 0.559 percent copper,

and 3.14 percent iron. Concentrate B comprised 25.1

percent lead, 9.57 percent zinc, 0.36 percent copper,

16.3 percent iron. Concentrate C comprised 12.4 percent

lead, 7.53 percent zinc, 2.9 percent copper and 30.4

percent iron. In Test 1, Concentrate A was leached with

hydrochloric acid alone. In Test 2 Concentrate A was

subjected to a ferrous leach with hydrochloric acid,

with oxygen continuously sparged into the slurry to

oxidize the ferrous to ferric ions. Test 3 involved a

cuprous leach, with gradual addition of the feed and

continuous oxygen sparging to oxidize the cuprous to

cupric and prevent the slurry oxidizing emf from dropping

below about +100 millivolts. Test 4 involved the

direct addition of 20 percent excess cupric ion with

clones, which permit the pressure to be reduced to

atmospheric pressure while employing the pressure

drop and hydroclone mechanism to effect the liquidsolid

separation. Hydroclone techniques such as those

discussed in The Hydroclone, D. Bradley, Pergamon

Press, Ltd. 1965 may be utilized in this context.

The solid phase resulting from the hydroclone separation

may be further processed, as desired, for the

recovery ofelemental sulfur and for the further processing

of the residue to recover any desired metal values

therefrom. The elemental sulfur can be recovered by

well known processes, such as solvent extraction, flotation,

and autoclave size enlargement. The hot brine

leach treatment, when conducted above the melting

15 point of sulfur, leaves the sulfur in a form more amenable

to physical separation techniques.

The liquid phase from this brine leach, containing the

lead chloride, is further processed for the removal of

the lead chloride. Preferably the lead chloride is crystallized

from the solution. When the pressure brine leach

technique is eMployed, substantial crystallization occurs

as a result of the reduction of the system pressure

to atmospheric pressure, and further crystallization

occurs by means ofreducing the solution temperature

and/or evaporating the solvent. The solution is preferably

vacuum cooled to about 40· ,C., which reduces the

lead chloride concentration in solution to about 15

grams per liter.

The resulting solid lead chloride cake can then be

reduced to elemental lead by various techniques. A

particularly preferred technique is to employ hydrogen

.reduction according to the general reaction:

4,276,084

When the final elemental lead product is produced by

meaas of hydrogen reduction, hydrochloric acid is a

necessary by-product. This hydrochloric acid serves as

a convenient source for the oxidation regeneration reaction,

and can be obtained by means of scrubbing the 5

hydrogen reduction furnace off-gas. The regenerated

cupric chloride leach solution is then recycled to the

leach phase of the process.

A portion ofthe separated.leach liquor from the leach

stage may be treated in order to remove impurities as 10

necessary in order to prevent excessive solution concentrations

of these values. Techniques known to the art,

such as cementation, electrolysis, chemical treatment,

pH adjustment, and others can be employed, as appropriate,

to remove the impurities.

The solids from the cupric chloride leach reaction,

compnsing lead chloride, elemental sulfur, unreacted

metal sulfides and gangue, are then preferably treated

for the separation of lead chloride. The lead chloride is

preferably solubilized from the residue, and a particu- 20

larly preferred technique in this respect is the use of a

brine leach mechanism. This brine leach is preferably

conducted with a brine solution having a sodium chloride

concentration offrom about 200 to about 300 grams

per liter, and more preferably from about 210 to about 25

250 grams per liter. In addition to or in place of sodium

chloride other chlorides such as calcium chloride, magnesium

chloride, lithium chloride and potassium chloride

may be employed in the solution.

The brine leach is preferably conducted at a tempera- 30

ture in excess of the solution boiling temperature,

which, of course, requires a pressurized system. The

temperature is preferably maintained from about 100·

C. to about 170· C., and more preferably from about

120· C. to about ISO· c., and the system pressure is 35

preferably selected so as to accommodate the solution

temperature while preventing solution boiling. Pressures

from about 30 to about ISO psig are suitable to

accomplish this purpose, and the pressure is preferably

maintained from about 40 to about 60 psig. 40

This brine leach, conducted under the described temperatures

and pressures, accomplishes a relatively high

solubility of lead chloride in a relatively short period of

time, while leaving the elemental sulfur and unreacted

metal sulfides in the residue phase. Retention times of 45

from about 30 seconds to about 5 minutes are generally

adequate to dissolve lead chloride to solution concentrations

of at least about 130 grams per liter of lead.

Increased lead concentrations as a result of the high

temperature and pressure brine leach significantly facili- 50

tate further separation processing.

The brine leach may be conducted at lower pressures,

including atmospheric pressure, and lower temperatures.

However, pressures and temperatures lower than

those recited for the preferred range of the brine leach 55

will require more of tlte brine solution per pound lead

chloride and a longer retention time in order to solubilize

the leach .;hloride.

Following the brine leach, the pregnant lead chloride

solution is separated from the remaining residue. Con- 60

ventional separation techniques may be employed, unless

the preferred brine leaching technique of high temperature

and pressure are utilized during the leach. In

such cases, the solid-liquid separation must remain

under pressure in order to prevent flash crystallization 65

of the lead chloride from the solution. One preferable

technique to accomplish the separation while avoiding

flash crystallization is to employ small diameter hydro4,276,084

sufficient hydrochloric acid to maintain the pH at about

1.0. Test 5 involved the same conditions as Test 4 except

that the pH was allowed to remain from about 2 to

suIting solids were brine leached in accordance with the

procedure set forth in Example 1, and Table 2 presents

the resulting extractions.

TABLE 2

COMPARISON OF LEAD CONCENTRATE LEACHES,

CUPRIC AND FERRIC CHLORIDE SYSTEMS

Lead Concentrate Analysis, % Type of Time Temp. Extraction, %

Pb Zn Cu Fe S Leach (hr.) ('C) Pb Zn Cu Fe

72.8 1.16 0.61 3.2 14.0 Fe+3 1 60 96.7 5.5 2.9 ND

72.8 1.16 0.61 3.2 14.0 Fe+3 4 60 99.4 22.4 21.7 21

72.8 1.16 0.61 3.2 14.0 Cu+2 I 60 99.0 4.3 -304 1.8

25.1 9.57 0.36 16.3 28.7 Fe+3 4 60 99.6 10.9 23.4 ND

25.1 9.57 0.36 16.3 28.7 Cu+z 3 60 99.4 1.6 -121 0.7

12.4 7.53 2.9 30.4 41.5 Fe+3 4 60 99.3 18.4 14.0 ND

12.4 7.53 2.9 30.4 41.5 Cu+z 3 60 99.6, 4.6 -39.8 1.0

NO = Not Determined

about 2.5 during the leach. Test 6 was conducted the

same as Test 4, except that the temperature was lowered 20

to 60° C. In Test 7, the Test 4 conditions were followed

except that the leach time was increased to three hours.

Tests 8 and 9 employed the same conditions as Test 7

except that in Test 8 concentrate B was leached and in

Test 9 concentrate C was leached. 25

Following each of the leaches the remaining solids

were leached in a brine solution at 85° C. and about

atmospheric pressure for 30 minutes, and the results of

this extraction are set forth in Table 1 as "Leach Results-

Extraction Percent", the percentage being based 30

upon initial concentrate weights. The negative copper

percentages reported are due to a portion of the cupric

chloride of the leach solution being precipitated as copper

sulfide.

EXAMPLE 3

Different 100 gram samples of a lead concentrate

having a composition of 18 percent lead, 26.2 percent

zinc, 0.54 percent copper, 5.1 troy ounces of silver per

ton of concentrate,' 0.029 percent antimony and 14.4

percent iron were treated with 250 milliliters of a cupric

chloride leach solution comprising about 50 grams of

copper per liter as cupric chloride and 200 grams of

sodium chloride per liter. The pH of the leach solution

was maintained at about 1 through the addition of hydrochloric

acid. After 3 hours, a total of 4.08 and 4.80

grams of hydrochloric acid were added to Sample 1and

Sample 2, respectively. The cupric chloride leach of

Sample I was conducted at a temperature of 60° C. and

the cupric chloride leach of Sample 2 was conducted at

TABLE I

3.3 4.3 5.4

1.6 0.7 45.6

4.6 1.0 134.0

3.3 3.9 19.7

Brine

Leach Results Leach

Extraction, % Residue

Pb Cu Zn Fe (grams)

60.8 0.0 8.7 3.2 43.6

93.9 6.7 16 0.0 40.5

76.8 99.8 19.2 7.3 69.2

99.0 -304 4.3 3.8 6.1

94.6 -107 4.2 2.5 4.7

60 88.4 -135

180 98.0 -312

180 99.4 -121

180 98.9 -39.8

200

200 60 60

200

200 90-95 145

200 85-90 60

137 85-90 60

133 90 220

47.5 30

with 02

48 ::::4.5

pH 1.0

47 ::::3.8

pH 2-

2.25

47 ::::4.8

pH 1.0

60 ::::5.2

47 ::::3.4

47 ::::5.4

Test Feed Fe+z

I. A

2. A 100

withOz

3. A

4. A

5. A

6. A

7. A

8. B

9. C

Leach Solution

___---'L~i~xi-"vi""an~t...::S~p:::ec""ie~s,wg:;:;m"'II_'__ Temp. Time

Cu+1 Cu+2 HCI NaCI ('C.) (min.)

EXAMPLE 2

Metal extraction percentages are presented for both

ferric chloride and cupric chloride leaches using three 60

different feed materials. The ferric chloride leach maintained

a ferric to ferrous ratio in grams per liter of about

9: 1. The leach was conducted with 20 percent solids and

a pH of less than 0.5. The cupric leaches were carried

out with a solution of about 50 grams of copper per liter 65

as cupric chloride, 10 percent solids, 5 grams hydrochloric

acid per liter and 230 grams sodium chloride per

liter, and the pH was maintained at about 1.0. The rea

temperature of 80° C. The residue of the cupric chloride

leach of each of the samples was separately brine

leached in a brine solution containing about 250 grams

of sodium chloride per liter at a temperature of 80°-85°

C. and about one atmosphere for one-half hour. Each

brine leach slurry was filtered while hot and the residue

was washed first with hot brine solution and then with

water. The analyses of the brine leach residue and the

results of this extraction are set forth in Table 3. The

negative extracted copper percentages are due to a

portion of the cupric chloride of the leach solution

being precipitated to copper sulfide.

4,276,084

TABLE 3

Cupric

Leach Brine Leach Residue Assay, % Extraction, %

Time Weight Ag

(Hours) Product (gm) Pb Zn Cu Fe (oz/ton) Sb Pb Zn Cu Fe Ag Sb

Sample I:

1.0 1 hr. 4.32 0.49 36.1 0.78 20.8 1.4 0.013 98.3 11.8 7.9 7.6 82.4 71

residue

3.0 Final 50.7 0.11 36.1 0.96 20.0 1.8 0.014 99.6 18.7 -4.5 18.1 79.2 72

residue

Sample 2:

1.0 1 hr. 4.43 0.10 37.4 0.98 19.8 1.2 0.018 99.6 7.2 -17.5 10.6 84.7 60

residue

2.0 2 hr. 4.52 0.08 36.7 1.00 19.2 1.1 0.011 99.7 17.4 -8.9 21.3 87.3 78

residue

3.0 Final 48.3 0.06 36.2 1.44 19.8 1.2 0.015 99.8 22.6 -49 23.0 86.8 71

residue

Example 10

A 100 gram sample of a lead concentrate having the

same composition as the sample of Example 5 was

TABLE 4

Cu Zn

0.805

0.21

from the feed are given below in Table 5. The negative

Example 4 extracted copper values of Examples 5-13 are due to a

A 125 gram sample of a lead concentrate having a 20 portion of the cupric chloride of the leach solution

composition of25.1 percent lead, 9.57 percent zinc, 0.36 being precipitated to copper sulfide.

percent copper and 16.3 percent iron was treated with

500 milliliters of a cupric chloride leach solution com- Example 6

prising about 50 grams of copper per liter as cupric A 100 gram sample of a lead concentrate having the'

chloride, 200 grams of sodium chloride per liter and 25 same composition as the sample of Example 5 was

sufficient hydrochloric acid to maintain a pH of about 1. milled for one-half hour in a ceramic pebble mill. The

The cupric chloride leach was conducted at a tempera- milled concentrate was then treated the same as the

ture of 60° C. for 2 hours. The residue of the cupric concentrate in Example 5. The assay of the brine leach

chloride leach was subjected to a 900 milliliter brine residue and percent metals extracted from the concenleach

at a temperature of 80°-90. C. and about atmo- 30 trate are given below in Table 5.

sphe~c pressure for one-half ho~r. The br:me solu~ion E 1 7

contamed about 250 grams of sodium chlonde per lIter. xamp e

The analysis of the brine leach residue, which weighed A 100 gram sample of a lead concentrate having the

83 grams, and the results of the extraction are set forth same composition as the sample of Example 5 was

in Table 4. 35 treated with 250 milliliters of a cupric chloride leach

The extraction resulted in 19.0 grams oflead chloride containing about 50 grams of copper per liter as cupric

being produced. This lead chloride was reduced to lead chloride and 200 grams of sodium chloride per liter at a

in an atmosphere of 175 cubic centimeters per minute of temperature of 90.-95° C. for 1 hour. The pH of the

hydrogen, 75 cubic centimeters per minute of carbon leach was maintained at about Iby the addition of hymonoxide,

75 cubic centimeters per minute of carbon 40 drochloric acid. The assay of the brine leach residue

dioxide at a temperature of 800° C. for 35 minutes. The and the percentage of metals extracted from the lead

lead metal was assayed by emission spectroscopy. The concentrate are given in Table 5.

lead metal was 99.98 percent pure. It contained impurities

of 0.01 percent silicon, 0.005 percent iron, 0.001

percent copper and 0.001 percent bismuth with no other 45

elements being detected.

Example 5

A 100 gram sample of a lead concentrate was treated

with 250 milliliters of a cupric chloride leach solution 60

comprising about 50 grams of copper per liter as cupric

chloride and 200 grams of sodium chloride per liter.

The cupric chloride leach was conducted at a temperature

of 40· C. for 4 hours with the pH of the leach being

maintained at about 1by the addition of about 4.1 grams 65

of hydrochloric acid throughout the leaching period.

The initial composition of the feed, assay of the brine

leach residue and the percentage of metals extracted

Example 8

A 100 gram sample of a lead concentrate having the

same composition as the sample of Example 5 was

milled for one-half hour in a ceramic pebble mill and

then treated exactly the same as the sample of Example

Brine Leach Residue Assay, % 7. The results are given in Table 5.

Ag SO

(oz/ton) Sb Example 9

13.9 22.8 2.0 0.33 A 100 gram sample of a lead concentrate having the

Extraction, %

Pb Cu Zn Fe Sb same composition as the sample of Example 5 was

Ag treated with 250 milliliters of a cupric chloride leach

--9-94'---~_-4-8-.5=.:.:36':..-_.:7.:..1:......_-=..:8.1:.:6.....__-=32=-_ 55 solution containing about 10 grams of copper per liter as

cupric chloride and 200 grams of sodium chloride per

liter at a temperature of 60° C. for 3 hours. The leach

solution was subjected to an air sparge of 1 liter per

minute to regenerate cupric ions from cuprous ions. The

pH of the leach solution was maintained at about 1.0 to

1.2. The lead concentrate was gradually added to the

leach solution in order to maintain an oxidizing emf of

the slurry at greater than 350 millivolts.

Results are given below in Table 5.

4,276,084

11 12

milled for one-half hour in a ceramic pebble mill and due and the percentage of metals extracted from the

then treated with 250 milliliters of a cupric chloride lead concentrate are given below in Table 5.

leach solution containing about 50 grams of copper per

liter as cupric chloride and 200 grams of sodium chlo- Example 13

ride per liter at a temperature of 40° C. for 4 hours. The 5 A 50 gram sample of a lead concentrate having the

pH of the leach solution was maintained at about 1.6 by same composition as the sample of Example 5 was

the addition of hydrochloric acid. The assay of the brine milled for one-half hour in a ceramic pebble mill and

leach residue and the percent metals extracted from the then treated with 125 milliliters of a cupric chloride

lead concentrate are given below in Table 5. leach solution containing about 10 grams of copper per

Example 11

10 liter as cupric chloride and 200 grams of sodium chloride

per liter at 50° C. for 4.5 hours. Throughout the

A 50 gram sample of a lead concentrate having the course of the leach, the leach solution was subjected to

same composition as the sample of Example 5 was an air sparge of 1 liter per minute and the pH of the

milled for one-half hour in a ceramic pebble mill and solution was maintained at about 1.6 by the addition of

then treated with 125 milliliters of a cupric chloride 15 hydrochloric acid. The final emfof the slurry was +360

leach solution comprising about 10 grams of copper per millivolts. The assay of the brine .leach residue and

liter as cupric chloride and 200 grams of sodium chlo- percentage of metals extracted from the lead concenride

per liter at a temperature of 40° C. for 4 hours. The trate are given below in Table 5.

TABLE 5

Assay, %

Time Weight Ag Extraction, %

Ex. (Hrs.) Product (gm) Pb Zn Cu (oz/ton) Sb Fe Pb Zn Cu Ag Sb Fe

0 Feed 18.0 26.2 0.54 5.1 0.029 14.4

1 Residue 4.97 2.06 37.5 0.86 2.3 19.4 92 1.2 -9.9 69 7.0

2 Residue 4.68 1.85 36.3 0.83 2.3 20.0 93 9.9 0.1 71 9.7

4 Residue 53.0 1.36 36.5 0.89 2.3 0.010 20.2 95 15 -0.5 72 79 14

6 1 Residue 5.31 1.17 37.9 1.05 3.0 19.7 96 0.2 -34 59 5.6

2 Residue 4.89 0.47 38.0 1.45 1.6 19.4 98 4.3 -77 79 11

4 Residue 55.3 0.86 37.3 0.94' 2.3 0.070 20.6 97 8.9 -11 71 8.4

7 0.08 Residue 5.28 1.68 36.6 0.95 2.0 19.2 94 11 -12 75 15

0.16 Residue 3.89 1.16 34.3 1.02 2.2 20.6 96 20 -15 74 13

0.25 Residue 4.28 0.68 35.4 1.09 2.0 20.5 98 20 -19 77 16

1 Residue 44.6 0.065 36.1 1.49 1.3 0.080 19.7 99.8 21 -57 85 22

8 0.08 Residue 4.38 0.52 36.0 1.02 1.5 19.9 98 15 -17 82 14

0.16 Residue 4.13 0.16 35.3 0.91 1.2 20.0 99.5 19 -1.1 86 17

0.28 Residue 4.42 0.075 36.9 1.10 1.2 19.3 99.8 18 -18 86 22

1 Residue 46.3 0.043 35.8 1.64 1.3 0.038 19.7 99.9 21 -76 85 24 21

9 3 Residue 62.2 2.40 31.4 0.96 1.8 0.018 19.9 91.7 26 -11 78 14

10 1 Residue 5.59 1.36 38.4 0.86 2.5 20.4 95 0.3 -8.3 67 3.7

2 Residue 5.38 1.11 39.2 0.88 2.4 20.9 96 1.2 -7.6 69 4.2

4 Residue 55.1 1.06 39.4 0.91 2.1 0.024 21.4 96 2.2 -9.5 73 46 3.4

11 4 Residue 33.3 1.30 39.8 0.83 2.4 0.029 21.5 95 0.0 0.0 69 33 0.6

12 4.5 Residue 37.0 4.74 35.4 0.81 5.0 0.027 20.1 80 0.0 -11 27 31 0.0

13 4.5 Residue 32.7 1.84 35.6 0.89 2.2 0.023 21.0 93 11.1 -7.8 72 48 4.6

leach solution was subjected to an air sparge of 1 liter

per minute throughout the leaching process. The pH of 45

the leach solution was maintained at about 1.6 by the

addition of hydrochloric acid. The lead concentrate

feed was added to the leach solution over the course of

the leach in order to maintain an oxidizing emf of the

slurry at greater than or equal to 350 millivolts. 50

The assay of the brine leach residue and the percent

metals extracted from the lead concentrate are given

below in Table 5.

Example 12. 55

A 50 gram sample of a lead concentrate having the

same composition as the sample of Example 5 was

milled for one-half hour in a ceramic pebble mill and

then treated with 125 milliliters of a cupric chloride

leach solution containing about 10 grams of copper per 60

liter as cupric chloride and 20 grams of sodium chloride

per liter at a temperature of 40° C. for 4.5 hours.

Throughout the course of the leach, the leach solution

was subjected to an air sparge of 1 liter per minute. The

pH of the leach solution was maintained at about 1.6 65

and the feed was added over the course of the leach in

order to maintain an oxidizing emf of the slurry at 350

millivolts or greater. The assay of the brine leach resi-

What is claimed is:

1. A process for obtaining lead chloride from sulfide

ores containing lead sulfide comprising:

(a) leaching the ore with an aqueous solution containing

cupric chloride under reaction conditions of

temperature, time, pH, an oxidizing emf, total copper

concentration and total chloride ion concentration

selected so as to convert a substantial portion

of the lead sulfide to lead chloride while leaving

the remainder of the ore substantially unreacted

and wherein the cupric chloride leach solution

does not solubilize all of the lead chloride so that a

portion of the lead chloride precipitates from the

leach solution; and

(b) separating solids comprising lead chloride, unreacted

ore, sulfur and gangue from the leach solution.

2. A process for separating lead chloride formed from

sulfide ores containing lead sulfide comprising:

(a) leaching the ore with an aqueous solution containing

cupric chloride under reaction conditions of

temperature, time, pH, an oxidizing emf, total copper

concentration and total chloride ion concentration

selected so as to convert a substantial portion

of the lead sulfide to lead chloride while leaving

the remainder of the ore substantially unreacted

4,276,084

and wherein the cupric chloride leach solution

does not solubilize all of the lead chloride formed

so that a portion of the lead chloride precipitates

from the leach solution;

(b) separating solids comprising lead chloride, unre- 5

acted ore, sulfur and gangue from the leach solution;

a temperature of from about 100° C. to about 170°

C. and a pressure of from about 30 p.s.i.g. to about 10

150 p.s.i.g. in order to substantially solubilize the

lead chloride to the exclusion of the other solids;

(d) separating the brine leach solution containing the

solubilized lead chloride from the solids; and

(e) separating the lead chloride from the brine leach 15

solution separated in step (d).

3. The process of claim 1 or ciaim 2 wherein the

cupric chloride leach solution solubilies less than about

10 percent of the lead chloride formed.

4. The process of claim 1 or claim 2 wherein the 20

cupric chloride of the leach solution ofstep (a) is regenerated

by sparging the leach solution with a source of

oxygen.

5. The process of claim 4 wherein the cupric chloride

leach solution separated in step (b) is recycled back to 25

step (a).

6. The process ofclaim 1 or claim 2 wherein a portion

of the cupric chloride leach solution of step (a) is removed,

treated to remove the dissolved metal chlorides

contained therein and thereafter the treated cupric chlo- 30

ride leach solution is returned to step (a).

7. The process of claim 1 or claim 2 wherein the

cupric chloride leach of the ore is conducted at a temperature

of from about 30° to about 95° C. and a pH

between about 0.5 and 4, wherein the cupric chloride 35

leach solution contains from about 3 to about 100 grams

of copper in solution per liter of the leach solution and

wherein the cupric ion to cuprous ion ratio of the leach

solution is maintained within a range of from about 1:20

to about 16:1. 40

8. The process of claim 7 wherein the leach solution

emfis maintained from about 200 to about 500 millivolts

so as to cause the formation of elemental sulfur from the

sulfide sulfur contained within the ore.

9. The process of claim 7 wherein the chloride ion 45

concentration of the cupric chloride leach solution does

not substantially exceed the amount needed to keep the

copper in solution and wherein the chloride ion concentration

is maintained by the addition of a monovalent,

water soluble, chloride salt in an amount containing 50

from about 0.85 moles to about 5 moles of chloride.

10. A process of forming lead chloride from sulfide

ores containing lead sulfide comprising:

(a) leaching the ore with an aqueous solution containing

cupric chloride and saturated with lead chlo- 55

ride at a temperature of from about 30° C. to about

95° C. and a pH of from about 0.5 to about 4,

wherein the cupric chloride leach solution contains

from about 3 to about 100 grams of copper in solution

per liter of leach solution, and less than about 60

20 grams of hydrochloric acid per liter of leach

solution, and wherein the cupric chloride leach

solution has a chloride ion concentration not substantially

exceeding the amount of chloride ion

needed to keep the copper in solution with the 65

chloride ion concentration being maintained by the

addition of a monovalent, water soluble, chloride

salt in an amount containing from about 0.85 moles

to about 5 moles of chloride per liter of leach solution,

has a cupric ion to cuprous ion ratio maintained

in the range of about 1:20 to about 16:1 and

has an oxidizing emf, so as to convert a substantial

portion of the lead sulfide to lead chloride while

leaving the remainder of the ore substantially unreacted;

(b) separating solids comprising lead chloride, unreacted

ore, sulfur and gangue from the leach solution.

11. A process for separating lead chloride formed

from sulfide ores containing lead sulfide comprising:

(a) leaching the ore with an aqueous solution containing

cupric chloride and saturated with lead chloride

at a temperature of from about 30° C. to about

95° C. and a pH of from about 0.5 to about 4,

wherein the cupric chloride leach solution contains

from about 3 to about 100 grams of copper in solution

per liter of leach solution and less than about

20 grams of hydrochloric acid per liter of leach

solution, and wherein the cupric chloride leach

solution has a chloride ion concentration not substantially

exceeding the amount of chloride ion

needed to keep the copper in solution with the

chloride ion concentration being maintained by the

addition of a monovalent, water soluble, chloride

salt in an amount containing-from about 0.85 moles

to about 5 moles of chloride per liter of leach solution,

has a cupric ion to cuprous ion ratio maintained

in the range of about 1:20 to about 16:1 and

has an oxidizing emf, so as to convert a substantial

portion of the lead sulfide to lead chloride while

leaving the remainder of the ore substantially

ureacted;

(b) separating solids comprising lead chloride, unreacted

ore, sulfur and gangue from the leach solution;

a temperature from about 100° C. to about 170° C.

and a pressure of from about 30 p.s.i.g. to about 150

p.s.i.g. in order to substantially solubilize the lead

chloride to the exclusion of the other solids;

(d) separating the brine leach solution containing the

solubilized lead chloride from the solids; and

(e) separating the lead chloride from the brine leach

solution separated in step (d).

12. The process ofclaim 11 wherein the brine leach of

step (c) contains from about 200 to about 300 grams of

sodium chloride per liter.

13. The process of claim 10 or claim 11 wherein the

cupic chloride contained in the leach solution of step (a)

is regenerated by sparging the leach solution with a

source of oxygen.

14. The process of claim 13 wherein a bleed stream is

taken from the leach solution of step (a), treated to

remove dissolved metal chlorides contained therein and

then returned to leach step (a).

15. The process of claim 10 or claim 11 wherein the

cupric chloride leach solution has a pH of from about

0.5 to about 2 and the cupric chloride leach is conducted

at a temperature of from about 30' C. to about

75° C., wherein the cupric chloride leach solution contains

from about 5 to about 50 grams of copper in solution

per liter ofleach solution and from about 1 to about

10 grams of hydrochloric acid per liter ofleach solution

and wherein the cupric chloride leach solution has a

chloride ion concentration not substantially exceeding

the amount of chloride ion needed to keep the copper in

* * * * >I<

60° C. and a pH of from about 0.5 to about 2,

wherein the cupric chloride leach solution contains

from about 8 grams to about 25 grams of copper in

solution per liter of leach solution and from about 3

grams to about 7 grams of hydrochloric acid per

liter of leach solution and wherein the cupric chloride

leach solution has a cupric ion to cuprous ion

ratio of from about 1:5 to about 3:1, has an emf of

from about 350 to about 400 millivolts and has a

chloride ion concentration not substantially exceeding

the amount of chloride ion needed to keep

the cooper in solution with the chloride ion concentration

being maintained by the addition of

sodium chloride in an amount of from about 100

grams to about 250 grams of sodium chloride per

liter of leach solution, so as to convert a substantial

portion of the lead sulfide to lead chloride while

leaving the remainder of the ore substantially unreacted;

and

(b) separating the solids comprising lead chloride,

unreacted ore, sulfur and gangue from the leach

solution;

leach containing from about 210 to about 250

grams of sodium chloride per liter of leach at a

temperature offrom about 120° C. to about 150° C.

and a pressure of from about 40 p.s.i.g. to about 60

p.s.i.g. in order to substantially solubilize the lead

chloride to the exclusion of the other solids;

(d) separating the brine leach solution containing the

solubilized lead chloride from the solids; and

(e) crystallizing the lead chloride from the separated

brine leach solution of step (d).

20. The process of claim 18 or claim 19 wherein the

cupric chloride contained in the leach solution of step

(a) is regenerated by sparging the leach solution with a

source of oxygen, wherein a bleed stream is taken from

the leach solution of step (a), treated to remove dissolved

metal chlorides contained therein and then returned

to leach step (a) and wherein at least a portion of

cupric chloride leach solution is comprised of the separated

leach solution of step (b).

21. The process of claim 20 wherein the crystallized

lead chloride of step (e) is reduced to obtain elemental

lead.

4,276,084

solution with the chloride ion concentration being

maintained by the addition of a monovalent, water soluble,

chloride salt in an amount containing from about

1.7 moles to about 4.3 moles of chloride per liter of

leach solution, has a cupric ion to cuprous ion ratio of 5

from about 1:9 to about 4:1 and has an emf of from about

250 to about 450 millivolts. .

16. The process of claim 15 wherein the chloride ion

concentration is maintained by the addition of from

about 100 grams to about 250 grams of sodium chloride 10

per liter of cupric chloride leach solution.

17. The process of claim 10 or claim 11 wherein at

least a portion of the cupric chloride leach solution

saturated with lead chloride is supplied from the separated

leach solution of step (b).

18. A process of forming lead chloride from sulfide

ores containing lead sulfide comprising:

(a) leaching the ore with an aqueous solution containing

cupric chloride and saturated with lead chloride

at a temperature of from about 30° C. to about 20

60° and a pH of from about 0.5 to about 2, wherein

the cupric chloride leach solution contains from

about 8 grams to about 25 grams of copper in solution

per liter of leach solution and from about 3

grams to about 7 grams of hydrochloric acid per 25

liter of leach solution and wherein the cupric chloride

leach solution has a cupric ion to cuprous ion

ratio of from about 1:5 to about 3:1, has an emf of

from about 350 to about 400 millivolts and has a

chloride ion concentration not substantially ex- 30

ceeding the amount of chloride ion needed to keep

the copper in solution with the chloride ion concentration

being maintained by the addition of

sodium chloride in an amount of from about 100

grams to about 250 grams of sodium chloride per 35

liter of leach solution, so as to convert a substantial

portion of the lead sulfide to lead chloride while

leaving the remainder of the ore substantially unreacted;

and

(b) separating the solids comprising lead chloride, 40

unreacted ore, sulfur and gangue from the leach

solution.

19. A process of separating leach chloride formed

from sulfide ores containing lead sulfide comprising:

(a) leaching the ore with an aqueous solution contain- 45

ing cupric chloride and saturated with lead chloride

at a temperature of from about 30° C. to about

tX��op@s� >smaltite.

48. The process of claim 38 wherein the sulfide ore is 65

tetrahedrite.

49. The process of claim 30 wherein the gas is nitrogen

and the ore is galena.

• • • • •

cite, chalcopyrite, orpiment, pentlandite, stibnite and

tetrahedrite.

67. The process of claim 66 wherein the sulfide ore is

galena.

68. The process of claim 66 wherein the sulfide ore is

stibnite.

69. The process of claim 66 wherein the sulfide ore is

bornite.

70. The process of claim 66 wherein the sulfide ore is

chalcocite.

71. The process of claim 66 wherein the sulfide ore is

orpiment.

72. The process of claim 66 wherein the sulfide ore is

15 pentlandite.

73. The process of claim 66 wherein the sulfide ore is

cinnabar.

74. The process of claim 66 wherein the sulfide ore is

arsenopyrite.

75. The process of claim 66 wherein the sulfide ore is

smaltite.

76. The process of claim 66 wherein the sulfide ore is

tetrahedrite.

4,276,081

62. The process of claim 16 wherein the iron containing

compound is employed in an amount of from about

1 to about 50 kilograms per metric ton of ore and the

selective magnetic enhancement reaction is carried out

at a temperature within a range of 50' C. less than the 5

general decomposition temperature of the iron containing

compound in a specific system for the ore being

treated for a period of time from about 0.15 to about 2

hours.

63. The process ofclaim 62 wherein the iron contain- 10

ing compound is an iron carbonyl and the treatment

process is carried out at a temperature within a range of

15' C. less than the general decomposition temperature

of the iron carbonyl in the specific system for the ore

being treated.

64. The process of claim 62 wherein the mineral values

are physically separated from the gangue by a magnetic

separation process.

65. The process of claim 62 wherein the mineral values

are physically separated from the gangue by an 20

electrostatic technique.

66. The process of claim 35 wherein the sulfide ore is

selected from the group consisting of galena, molybdenite,

bornite, cinnabar, arsenopyrite, smaltite, chalco-