5,229,085 Utilization of oxygen in leaching and/or recovery procedures employing carbon

Patent Number/Link:

5,229,085

* JuI. 20, 1993'

[11]

[45]

111111111111111111111111111111111111111111111111111111111111111111111111111

US005229085A

Patent Number:

Date of Patent:

United States Patent [19]

Brison et aI.

[73] Assignee:

[*] Notice:

22 Claims, 3 Drawing Sheets

Primary Examiner-Michael Lewis

Assistant Examiner-Steven Bos

Attorney, Agent, or Firm-Nixon & Vanderhye

Carbon", Tsuchida et al., pp. 647-656, Mineral Chern.

Res. Unit, Murdoch Univ., Perth, W. Australia, 1"984.

"Aspects of Laboratory and Pilot Plant Evaluation of

CIP with Relation to Gold Recovery", Davidson et aI.,

XIV Inter. Mining Processing Congress, Oct. 17-23,

1982. .

"Recovery of Gold from Carbonaceous Ores at Carlin,

Nevada", Guay et aI., Society of Mining Engineers,

AIME, Transactions-vol. 254, Mar. 1973.

"The Treatment of Refractory Gold-Bearing Flotation

Concentrates Using Pressure Leaching Techniques",

Muir et aI., Proc. AIME Meeting, Los Angeles, Calif.,

Feb. 1984.

ABSTRACT

In gold and/or silver cyanide leaching-adsorption processes

employing solid adsorbents such as activated

charcoal, the overall efficiency in the recovery of gold

and/or silver from ores or the like is greatly increased

by contacting the cyanide slurry containing the gold

and/or silver, with oxygen gas instead of normal air. A

generally pure oxygen gas can be bubbled into a vessel

containing the slurry, and a cover (e.g. a floating cover)

may be provided on the vessel to reduce the oxygen

transfer out of the solution and to facilitate pressurization

of the system with an oxygen atmosphere. The

procedures of the invention are applicable to carbon-inpulp

(CIP), and carbon-in-Ieach (CIL) processes and

related processes using resins. Deaeration of the ore

slurry can be practiced prior to the introduction of the

oxygen.

[57]

OTHER PUBLICAnONS

"Studies on the Mechanism of Gold Adsorption on

Kamyr, Inc., Glens Falls, N.Y.

The portion of the term of this patent

subsequent to luI. 5, 2005 has been

disclaimed.

[21] Appl. No.: 247,521

[22] Filed: Sep. 22, 1988

Related U.S. Application Data

[60] Division of Ser. No. 102.742, Sep. 23, 1987, Pat. No.

4,816,234, which is a continuation of Ser. No. 732,637,

May 10, 1985, abandoned.

[51] Int. CI.5 C22B 11/00

[52] U.S. Cl. 423/29; 423/30;

423/31

[58] Field of Search 423/27, 29, 30, 31;

75/101 R, 105, 118 R; 204/109

[56] References Cited

U.S. PATENT DOCUMENTS

1,734,306 1111929 Schraps 423/31

4,289,532 9/1981 Matson et al. 75/105

4,438,076 3/1984 Pietsch et al. 423/30

4,501,721 2/1985 Sherman et al. 423/27

4,552,589 11/1985 Mason et al. 75/118 R

4,754,953 7/1988 Brison et al. 423/27

4,816,234 3/1989 Brison et al. 423/29

[54] UTILIZATION OF OXYGEN IN LEACHING

AND/OR RECOVERY PROCEDURES

EMPLOYING CARBON

[75] Inventors: Robert J. Brison, Golden, Colo.; Carl

L. Elmore; Phillip Mitchell, both of

Glens Falls, N.Y.

LOADED

CARBON

TO GOLD

RECOVERY

III

I~~=I

CARBON

ADDITION

COARSE PARTICLES+30

flESH

ORE FEED //

FROM

THICKENER

~O" SOUDS

-ISO MESH

IOXYGEN ,~I ~-=- ----..!tl't-L-.....:~=-__---:=-....J \ 1 /8

----------r----...J

ORE FEED

FROM

THICKENER

50%SOUDS

-150 MESH

t=1t3. 1

CARBON

ADDITION

COARSE PARTICLES+30

MESH

I 49

I~./

LOADED

CARBON

TO GOLD

RECOVERY

•

""d =f"ttD

=f"t-

~=-'-<

~o ....

00=

~..... ....

o.....

..(..II

..\.0

(.II

u.s. Patent July 20, 1993 .Sheet 2 of 3 5,229,085

ORE,

CYANIDE

SLURRY

DEAERATE

INJECTION

tSLURRY

FLOW

DIRECTION

ICARBON

GRANULE

DIRECTION

LOADED CARBON

TO STRIPPING,

ACID WASHING,

THERMAL

REGENERATION

AND REUSE

68 70

RESIDUE ~

~~::J-------_---.JW CYANIDE DESTRUCTION

8 DISPOSAL

..t.il

..\. 0

til

•

fJ1 •

f"1'.

('D=f"1'.

B.s-

• • CARBON 7

~=-'< TAILING I N

5=' ....

\0 7.r I I LOADED I w\0

CARBON

83 ~ I TO GOLD

RECOVERY •

00 ::r

(!)

(!) t1t11 -w

0 t=1t3. :I .....

FLOCCULANT

.25 - /TON

250~/D

MILL WATER

169 GPM

OVERSiZE RETlmN

TO REGRIND

FIBER

1511-/ TON

7.5 T/D

NaCN IT/D

ORE FEED

FROM CLASSIFIER

1000

T/D 35%

SOLIDS

~-1

J 02 1400# /D ~ 'IH::l<1 I

oxidation during the cyanidation process. However this

fact has not been taken advantage of commercially.

According to the present invention, it has been found

that the combination of (I) the use of oxygen or oxygen-

5 enriched air and (2) a leach-adsorption system employing

actuated carbon results in an extremely efficient

process for treatment of gold and/or silver ores, or the

like.

It has been found that not only does oxygen increase

10 the rate of dissolution of gold and/or silver, but that the

overall efficiency of processes employing carbon adsorption

in gold and/or silver recovery is significantly

increased by the use of a gas containing a significantly

higher proportion of oxygen than is found in air.

Although activated carbon is well known to be a

catalyst in decomposition of cyanideion by oxygen,

surprisingly, it has been found that the use of oxygen

rather than air in CIP or CIL systems does not result in

unacceptable cyanide consumption, the cyanide consumption

being unexpectedly low.

It has been, found that the increased efficiency that

results from the' practice of the present invention has a

number of contributing factors. In CIL and CIP processes,

the oxygen increases the dissolution rate, which

therefore makes the gold and/or silver more readily

available for adsorption by the carbon. Also, since the

gas that is introduced has a higher proportion of oxygen

than natural air, it will also have a significantly lower

proportion of carbon dioxide than normal air. Reduced

carbon dioxide also increases carbon adsorption efficiency

since carbon dioxide reacts with lime in the

cyanide solution to form CaC03, which deposits on the

carbon granules.

Practicing the invention one can either get a higher

percentage of gold and/or silver extraction, or get the

same percentage extraction as in conventional facilities

only using much less, and/or smaller, equipment, or a

combination of these advantages. For instance in a conventional

CIL plant, all of the CIL tanks could be reduced

to about one-fifth their normal size if oxygen

were utilized instead of air to contact the solution. Further,

if oxygen is utilized in a leaching process followed

by CIP the large agitated leach tanks can each be reduced

to about one-fifth their usual size (with commensurate

reduction in the residence time in each).

Compared to conventional CIP processes, according

to the invention since the gold would be adsorbed almost

as soon as it was leached, the driving force for

leaching of the gold would be increased, and the "preg"

robbing effects in the case of carbonaceous ores would

be minimized. Also the tie-up of gold in the in-process

inventory would be sign.ificantly decreased.

Compared to conventional CIL processes, the process

according to the invention would reduce the agitated

tank size by a factor of about five or more, reduce

the carbon and gold loss due to abrasion of the carbon,

reduce the tie-up of gold in the in-process inventory,

and reduce the carbon inventory.

The process according to the invention also has the

potential for optimizing the leach time for differences in

the types of ore utilized. For instance for slow leaching

ores, a pressurized leach-adsorption system could be

utilized to obtain higher oxygen concentration in the

solution. For fast leaching ores, oxygen enriched air

could be utilized to provide only a moderate increase in

leach rate since little is gained by reducing the leach

time below the' time required for carbon adsorption

(about 4-6 hours). In any event, the practice of the'

5,229,085

UTILIZATION OF OXYGEN IN LEACHING

AND/OR RECOVERY PROCEDURES

EMPLOYING CARBON

The present application is a division of application

Ser. No. 07/102,742, filed Sept. 23,1987, now U.S. Pat.

No. 4,816,234, issued Mar. 28, 1989, which, in turn, is a

continuation of application Ser. No. 06/732,637, filed

May 10, 1985, now abandoned.

BACKGROUND AND SUMMARY OF THE

INVENTION

Procedures that have been gaining increasing acceptance

and widespread usage for the recovery of gold 15

and/or silver from ores, and the like, are the carbon-inpulp

(CIP), and carbon-in-Ieach (CIL) processes. These

procedures are versatile, and effect efficient recovery of

the gold and/or silver from the ore.

In a typical CIP process, milled ore is leached in a 20

series of agitated vessels (typically approximately six

vessels each having a retention time of about four

hours). In the leach vessels the gold and/or silver is

largely dissolved from the pulp. After leaching, the

pulp moves to the CIP adsorption system, which typi- 25

cally contains about six vessels each having a retention

time of about one hour. The pulp is agitated in each of

these vessels, which are open to the atmosphere, and in

each vessel the pulp is contacted by activated charcoal

particles (i.e. carbon granules) that preferentially adsorb 30

gold and silver from the solution. The inventory of

carbon granules is continuously or periodically transferred

from one vessel to the next in the opposite direction

of the flow of the pulp, with carbon discharged

from the first vessel in the series ultimately being passed 35

to a gold and/or silver recovery station, while the pulp

c.ischarged from the last vessel in the series is leach

residue, which can be disposed of.

Resin-in-pulp processes are similar to carbon-in-pulp

processes except that an ion exchange resin is used in 40

place of carbon granules. Such processes have not yet

received commercial acceptance for Au/Ag leaching.

Conventional CIL processes are similar to CIP processes

except that the dissolution and the adsorption of

the gold and silver are practiced essentially simulta- 45

neously. In a typical CIL procedure, the ground and

thickened ore slurry typically passes to a series of about

six agitated leach-adsorption vessels, each having a

retention time of about four hours. In the agitated leachadsorption

vessels the carbon and ore flow in counter- 50

current paths in basically the same manner as in the CIP

process, with the loaded carbon passed to a recovery

stage and the discharged leach residue is disposed of. As

in most cyanidation operations, part of the gold and/or

silver is typically dissolved in the grinding circuit and in 55

other preliminary processing steps, such as thickening.

Although the proportion of the total metal dissolved in

these steps is often substantial, subsequent treatment in a

series of leach vessels, or leach-adsorption vessels, is

typically practiced in order to obtain more complete 60

gold and,/or silver recovery.

It has been known for many years that, under certain

limiting conditions, the rate of gold dissolution in a

cyanide solution is approximately proportional to the

partial pressure of oxygen, and that the rate of dissolu- 65

tion can be significantly increased if generally pure

oxygen gas (e.g. gas having an oxygen content of about

99 percent or greater) is used instead of air to effect

5,229,085

The oxygen containing gas from source 18 preferably

comprises generally pure oxygen (that is a gas containing

about 99 percent or more oxygen). However the

desired results according to the invention, of increased

5 carbon adsorption efficiency, and the like, can sometimes

be achieved even when generally pure oxygen is

not utilized, but rather merely a gas having a significantly

increased proportion of oxygen compared to

normal air. The gas from source 18 also desirably, and

10 usually inherently (merely by the increase in the proportion

of oxygen), has a decreased proportion of carbon

dioxide compared to normal air, which also results

in decreased cyanide consumption and reduced formation

of CaC03.

In the embodiment actually illustrated in FIG. 1, a

single leach (or pre-leach) tank 22 is illustrated. In the

'tank 22 no carbon is present, but rather only leaching

takes place. As described above, however, the presence

of the oxygen containing gas in the leach tank 22 also

increases the efficiency of the dissolution of the gold

and/or silver into the cyanide solution.

The tank 22 is preferably an agitated tank, having a

conventional mechanical agitator including blades 23

and shaft 24, powered by a powering device 25 or the

like. The slurry within the tank 22 will achieve a certain

level, and in accordance with the present invention it is

desirable to provide a cover for the solution to minimize

the transfer of oxygen from the slurry to the air, and

also to minimize the transfer of nitrogen from the air to

the slurry. A conventional stationary cover tank may be

provided, or, a floating cover is provided, such as the

disc-shaped cover 26 which has a generally flat top

surface 27, and a generally concave bottom surface 28

which is actually in contact with the slurry, and which

has an aperture 29 therein through which the shaft 24

passes. If desired, a permanent lid 30 may also be placed

on the tank 22, and the entire tank provided with an

oxygen atmosphere at about one atmosphere pressure,

or provided with an oxygen atmosphere at significantly

greater than one atmosphere pressure.

Only one leach tank 22 is shown. Typically there

would be about 4 to 6 more such tanks in series to minimize

short-circuiting of the slurry particles.

After the desired retention time in the leach tank 22,

the slurry overflows from tank 22, or through cut-out

31 in the cover 26, and through the conduit 32 into the

first carbon adsorption tank 34 of a series of such tanks.

Three tanks are shown in series in FIG. 1, however any

desired number of tanks may be provided.

Conventional components of the tank 34 include the

mechanical agitator including blades 35 and shaft 36,

the slurry inlet 37, the slurry outlet 38 covered by a

carbon screen 39 (e.g. see U.S. Pat. No. 4,416,774),

carbon inlet 40 connected up to carbon pump 41, and

carbon outlet 42. The pumps 41, 41' may be placed near

the top of the tank. The tank 34 may be a conventional

covered tank, or may include a non-conventional floating

cover 44 which is substantially identical to the cover

26 (except there is no necessity for the cut-out 31),

which floats on the top of the slurry within the tank 34.

The floating cover can be a plurality of floating balls.

Non-conventional components of the tank 34 also

include the sparger 46 located adjacent the bottom of

the tank for sparging oxygen into the tank from the

source 18. The sparger 46, in addition to introducing the

oxygen into the solution that is necessary for the increased

efficiency according to the invention, also ef-

FIG. 1 is a schematic view, with parts of some components

shown in cross-section, of exemplary apparatus

for practicing a CIP process according to the present

invention; 15

FIG. 2 is a schematic view of exemplary apparatus

for practicing a CIL process according to the invention;

and

FIG. 3 is a schematic view of exemplary apparatus

for increased efficiency of ore leaching which can pre- 20

cede the adsorption tanks of the enhanced CIP process

according to the invention.

process according to the invention, and the utilization

of the apparatus according to the present invention, is

extremely advantageous.

It is the primary object of the present invention to

provide for the increased efficiency of the recovery of

gold and/or silver from ores or the like. This and other

objects of the invention will become clear from an inspection

of the detailed description of the invention, and

from the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

DETAILED DESCRIPTION

The invention will be herein described with respect 25

to the recovery of gold and/or silver from gold and/or

silver containing ores or the like. The term "ore or the

like" as used in the present specification and claims

means all materials conventionally considered as gold 30

and silver ores, and other materials such as tailings,

from which gold and/or silver may be recovered. Also,

the invention has applicability to the recovery of other

metals.

In the preferred embodiment according to the present 35

invention, activated charcoal (also known as activated

carbon, carbon, and the like) is used as the material for

adsorbing the gold and/or silver from the solution.

However it is to be understood that other materials can

be utilized, besides activated charcoal granules or parti- 40

cles, for adsorbing the gold and/or silver, such as ion

exchange resins (i.e. a resin-in-pulp process, as described

in U.S. Pat. No. 4,502,952).

In the utilization of the apparatus illustrated in FIG. 1

for the practice of a CIP process according to the inven- 45

tion, the ore is milled in the presence of lime and possibly

cyanide, and ultimately fed through the flow control

valve 11 to a separating screen assembly 12 which

screens out the particles that are too large, and is

dumped in discharge 13. If desired, the ore slurry may 50

be thickened by conventional means to remove part of

the solution, which may be treated separately for gold

and/or silver recovery. The ore slurry that passes

through the screen 12 passes to the level control tank

14, and is withdrawn from the tank 14 by the pump 15. 55

Ifdesired, the ore slurry can be deaerated as by any type

of conventional deaeration means (such as a vacuum

system) 16.

After the ore slurry passes through pump 15, a conventional

basic cyanide solution (such as NaCN) is 60

added to the ore from source 17, additional lime may be

added as needed, and oxygen containing gas from

source 18 is added through the flow control valve 19,

and oxygen injector 20. If desired the cyanide solution

and the oxygen containing gas can be added to the 65

slurry utilizing mixers, although since significant mixing

will take place in subsequent vessels a separate mixer at

this point is not essential.

Atmosphere

Oxygen Air Nitrogen

Approx. % 02 100 21 0

in atmosphere

Leach solution assay, 4.14 4.14 4.14

Au, mg/l

Final solution assay, 0.032 0.041 0.079

Au, mgll

Final carbon assay, 23.4 23.1 23.1

Au,oz/ton

Au adsorption, %1 99.23 99.01 98.10

Leach solution assay. 1.8 1.8 1.8

Ag, mg/l

Final solution assay. 0.2 0.2 0.2

ciently dissolving the gold and/or silver in the leaching

stage prior to CIP recovery in station 75. Utilizing the

apparatus of FIG. 3, the slurried ore in conduit 76 is

mixed with cyanide from conduit 77, and ultimately

mixed with oxygen from conduit 78 in a mixer 79. The

mixer may be any suitable mixer capable of mixing

components of a medium consistency slurry, such as an

MC ® mixer sold by Kamyr, Inc. of Glens Falls, New

York. Also, as generally disclosed in U.S. Pat. No.

4,501,721, flocculent and/or fiber can be added to the

slurry to facilitate locking of the particulized ore in a

stable network in the slurry. For instance cellulosic

fibers, fiberglass fibers, or the like are mixed with liquid

in tank 80 and then metered to the inlet to mixer 79,

15 while flocculents, such as synthetic polymers ofanionic,

cationic, or nonionic types are mixed with mill water in

tanks 81, and then ultimately passed to conduit 82 prior

to introduction into upflow 83. The leached slurry that

is discharged from the top 84 of vessel 83 will then pass

to the CIP recovery station 75, which can be as illustrated

in FIG. 1 (without the tank 22). The vessel 83 can

also be pressurized, as by utilizing pressure control

valve 85, and a one atmosphere, or super-atmospheric,

oxygen atmosphere maintained therein, or the vessel

can be completely slurry filled.

Utilizing the apparatus heretofore described, according

to the present invention a process of gold and/or

silver recovery from ore and the like may be practiced.

The process comprises the steps of: leaching gold and/

or silver from the ore or the like, to dissolve the gold

and/or silver, utilizing a basic cyanide solution; and (b)

recovering the leached gold and/or silver in solution by

contacting the solution with solid material for adsorbing

the gold and/or silver from the solution; wherein

step (b) is practiced by providing oxygen gas in the

solution in an amount significantly greater than can be

obtained by contacting the solution with air so as to

greatly increase the solution rate of the gold and/or

silver, and by minimizing the amount of carbon dioxide

in the solution so that it is significantly less than would

be obtained by contacting the solution with air, so as to

possibly increase the gold and/or silver adsorption efficiency

of the adsorbing material, and certainly to reduce

the production of CaC03. Preferably step (b) is

practiced by substantially saturating the solution with

oxygen, and preferably by utilizing generally pure oxygen.

The following table I indicates the results achieved

by preparing a gold cyanide solution by leaching a

common gold ore sample (the gold ore sample, as is

typical, also contained a small amount of silver), and

then exposing the solution to carbon adsorption in a

rotating bottle for six hours, with atmospheres of air,

oxygen, and nitrogen, respectively.

TABLE I

5,229,085

fects some agitation of the solution, facilitating efficient

dissolution of the oxygen.

Another non-conventional component of the tank 34

comprises the top 47. The top 47, as does the top 30, can

seal the tank so that an oxygen atmosphere (either at 5

one atmosphere pressure, or significantly greater than

one atmosphere pressure) may be maintained in the

tank.

The further tanks 48, 49, etc. in the adsorption system

are each substantially identical to the tank 34 except 10

that in the last tank 49 in the series the cover 44' has

disposed therein a valved opening 50 which allows the

addition of activated charcoal particles, which are

coarser than the ore particles in the slurry (the difference

in coarseness allowing effective screening).

The slurry discharged through outlet 38' of the tank

49 goes to tank 52, and from tank 52 is withdrawn by

pump 53 and ultimately passed to a disposal site 54 for

the ore tailings (which is what the pulp has been reduced

to). The carbon particles outlet 42 from the first 20

tank 34 passes through flow control valve 55 to chute

56, and ultimately to the carbon screen 57, with separated

loaded carbon being passed to the gold and/or

silver recovery station 58, and separated slurry in conduit

59 being recirculated. 25

The apparatus of FIG. 1 can also be utilized for a

carbon-in-leach process merely by elimination of the

tank 22. Such an arrangement is especially advantageous,

and the size and/or number of tanks 34, 48, 49

would be less than for conventional CIL processes. 30

FIG. 2 schematically illustrates another form the

apparatus according to the invention can take for the

practice of a CIL process. The ore slurry, mixed with

oxygen, passes into the top of vertical vessel 60, and

flows continuously downwardly therein. Typical con- 35

ditions of the ore slurry would be 50 percent solids

(minus 100 mesh), 0.3 gil NaCN. solids specific gravity

of 2.7, and a slurry specific gravity of 1.46. The activated

charcoal granules would be introduced from

source 61 into the bottom of the vessel 60 at point 62, 40

and would flow upwardly in the vessel. Typically the

carbon granules would be relatively large, about 6-16

mesh, and would have a lower specific gravity than the

slurry (e.g. 1.2). The slurry density, carbon density and

size, and other factors (such as the addition of flocculent 45

or fibers to the slurry) could be adjusted to optimize the

carbon upflow rate relative to the slurry downflow rate.

The loaded carbon, with some entrained slurry, would

be withdrawn from adjacent the top of the vessel 60 at

point 63, and passed to a carbon screen 64, with the 50

loaded carbon stripped and regenerated for reuse in the

carbon injection system 61, and with separated slurry in

conduit 65 returning to the top of the vessel 60. The

residue withdrawn at the bottom 66 of the vessel 60 by

the pump 67 would either pass into conduit 68 to be

used as part of the liquid for carrying the recycled carbon

into the column within the vessel 60, or would pass

to conduit 69 and ultimately to cyanide destruction and

disposal site 70.

The vessel 60 may be operated at atmospheric pres- 60

sure, or at super-atmospheric pressure, and an oxygen

atmosphere may be provided at the top thereof in either

case. Also, the system could be operated so that the

slurry flowed upwardly and the carbon granules flowed

downwardly, if denser carbon were utilized, and/or if 65

the slurry solids had a lower specific gravity.

FIG. 3 schematically illustrates other exemplary apparatus

that can be utilized for effectively and effi5,229,085

TABLE III-continued

Test #1 Test #2

% Solids 27 27

pH: initial/adj. 8.7/10.9 8.7/10.9

NaCN, initial gil 0.3 0.3

Time, hr 61 62

Feed

Weight, g 399.9 399.9

AU,oz/ton 0.217 0.217

Reagents added, total

Cao,g 0.12 0.12

NaCN, g 0.25 0.25

Carbon

Mesh size, Tyler 6 X 14 6 X 14

Initial wt. g 22.00 22.00

Final wt, g 22.26 22.07

Au,oz/ton 2.684 2.695

Sol'n, end of test'

pH 10.5 10.6

Filtrate, total

Volume, ml 1412.67 1417.76

NaCN, gil 0.24 0.22

Residue

Weight, g 298.24 298.48

Au,oz/ton 0.019 0.018

Reagents consumed 0.37 0.47

NaCN, Ib/ton

Extraction, % Au 91.3 91.7

Calculated heads 0.219 0.217

Au,oz/ton

Ipre.saturated with 02 at ambo press. for 16 hours previous to leach.

20uring 6 hr CIP leach. purge with 02 at T = 0 hr and T = I hr. Also add II g

30 carbon at each of these times.

In conclusion, according to the present invention, a

method and apparatus are provided for the extremely

efficient and effective recovery of gold and/or silver

35 from ore or the like. While the invention has been

herein shown and described in what is presently conceived

to be the most practical and preferred embodiment

thereof, it will be apparent to those of ordinary

skill in the art that many modifications may be made

40 thereof within the scope of the invention, which scope

is to be accorded the broadest interpretation of the

appended claims 'So as to encompass all equivalent process

and apparatus.

What is claimed is:

1. In the recovery of gold or silver from an ore slurry,

an adsorbent-in-leach process comprising the steps of

simultaneously, in the same vessel: (a) leaching gold or

silver from the ore slurry, to dissolve the gold or silver,

utilizing a basic cyanide solution; and (b) recovering the

50 leached gold or silver in solution by contacting the

slurry with an adsorbing material selected from the

group consisting essentially of activated charcoal granules

and ion-exchange resins for adsorbing the gold or

silver from the solution; wherein

steps (a) and (b) are practiced by providing a dissolved

oxygen concentration in the slurry that is

significantly greater than a dissolved oxygen con

·centration in the slurry if the slurry is contacted

with air under identical pressure conditions such

that increased gold or solver extraction per unit

time occurs as compared with contacting the slurry

with air; and

wherein steps (a) and (b) are practiced in a covered

vented vessel so as to decrease the transfer of oxygen

out of solution and decrease the transfer of

nitrogen or carbon dioxide into the slurry.

2. In the recovery of gold or silver from an ore slurry,

an adsorbent-in-leach process comprising the steps of

8.36

88.1

Test #2

77.9% ·200

8.97

88.6

Test #1

77.9%·200

300.0 300.0 300.0

0.217 0.110 0.186

0.12 0.12 0.12

0.25 0.25 0.25

6 X 14 6 X 14 6 X 14

22.00 22.00 22.00

22.05 22.11 22.09

2.631 0.966 1.779

0.276 0.245 0.264

10.6 10.6 10.4

1414 1453 1399

0.004 0.002 0.003

298.7 298.6 298.6

0.017 0.004 O.oJ5

O.oJ5

rerun

0.16 0.33 0.26

92.0 94.7 89.8

Test #1 Test #2 Test #3

77.9% • 200 80% ·200 80% - 200

27 27 27 25

8.7/10.9 9.0/10/8 9.0/10.7

0.3 0.3 0.3

10 10 10

Oxygen Air Nitrogen

Ag, mgll

Final carbon assay, 8.77

Ag,oz/ton

Ag adsorption. o/c t 88.6

Conditions

Grind

IBased on final carbon and final solution.

The following table II indicates the results from a 10

carbon-in-pulp cyanidation test utilizing three different

types of Gencor ore samples from, respectively, Buffeisfontein

(No.1), Leslie (No.2), and St. Helena (No.3).

The tests indicate high gold extractions (in the range of

90-95 %), and, surprisingly, low cyanide consumption. 15

All tests were performed in rotated bottles with oxygen

atmosphere at the local atmospheric pressure of 12.1

psia. The time in each case (total of 10 hours) was a six

hour cyanide leach plus a four hour CIP process.

TABLE II

Reagents consumed

NaCN, Ib/ton

Extraction, % Au

Atmosphere

Conditions

Grind

% Solids

pH: initial/adj.

NaCN, initial gil

Time, hr.

Feed

Weight, g

AU,oz/ton

Reagents added. total

CaO, g

NaCN, g

Carbon

Mesh size Tyler

Initial wI. g

Final wt. g

Au.oz/ton

Sorn. end of test

NaCN, gil

Filtrate, total

Volume, ml

Au, ~gll

Residue

Weight, g

AU,oz/ton

TABLE I-continued

In the following table III, further bottle-type tests

were conducted for a carbon-in-leach cyanidation, confirming

that simultaneous leaching and carbon adsorption

in an oxygenated slurry results in rapid high gold

extraction with low cyanide consumption. The ore 55

tested in each of the two tests in table III was Gencor's

Buffelsfontein ore. With gold extractions of about 91-92

%, in six hours, cyanide consumption was only

0.37-0.47 lbs. per ton. If the pulp density and carbon

concentration was closer to expected plant conditions, 60

cyanide consumption is expected to be as little as

0.19-0.27 lbs. per ton. The low cyanide consumption is

very unexpected and advantageous.

______---=T..::..;A:,:B;.:L:,:E::..;I::I:..I 65

5,229,085

simultaneously, in the same vessel: (a) leaching gold or

silver from the ore slurry, to dissolve the gold or silver,

utilizing a basic cyanide solution; and (b) recovering the

leached gold or silver in solution by contacting the

slurry with an adsorbing material selected from the 5

group consisting essentially of activated charcoal granules

and ion-exchange resins for adsorbing the gold or

silver from the solution; wherein

steps (a) and (b) are practiced by providing a dissolved

oxygen concentration in the slurry that is 10

significantly greater than a dissolved oxygen concentration

in the slurry if the slurry is contacted

with air under identical pressure conditions such

that increased gold or silver extraction per unit

time occurs as compared with contacting the slurry 15

with air; and

wherein steps (a) and (b) are further practiced by

providing the slurry and adsorbing material in a

~;:St~~ ~~dth~a~~~~~~~ng an oxygen atmosphere in 20

3. A process as recited in claim 2 comprising the

further step of degassing the slurry before practicing

steps (a) and (b).

4. A process as recited in claim 2 wherein the pressure 25

in the vessel is maintained at a pressure greater than one

atmosphere so as to increase the concentration of oxygen

in the solution.

5. A process as recited in claim 2 wherein steps (a)

and (b) are practiced by directing the flow of the ore 30

slurry in a first direction, and directing a flow of adsorbing

material in a second direction, opposite the first

direction.

6. A process as recited in claim 2 wherein steps (a)

and (b) are further practiced by agitating the slurry and 35

7. A process as recited in claim 6 wherein said agitating

step is practiced by mechanically agitating the

slurry and adsorbing material.

8. In the recovery of gold or silver from an ore slurry,

an adsorbent-in-leach process comprising the steps of 40

simultaneously, in the same vessel: (a) leaching gold or

silver from the ore slurry, to dissolve the gold or silver,

utilizing a basic cyanide solution; and (b) recovering the

leached gold or silver in solution by contacting the

slurry with an adsorbing material selected from the 45

group consisting essentially of activated charcoal granules

and ion-exchange resins for adsorbing the gold or

silver from the solution; wherein

steps (a) and (b) are practiced by providing a dissolved

oxygen concentration in the slurry that is 50

significantly greater than a dissolved oxygen concentration

in the slurry if the slurry is contacted

with air under identical pressure conditions such

that increased gold or silver extraction per unit

time occurs as compared with contacting the slurry 55

with air; and

wherein steps (a) and (b) are further practiced by

agitating the slurry and adsorbing material and the

agitating step is practiced by introducing oxygen

gas under pressure into the bottom of a vessel con- 60

taining the slurry and the adsorbing material.

9. A process as recited in claim 8 such that the consumption

of the cyanide is decreased by using said

greater dissolved oxygen concentration in the slurry as

compared with using the dissolved oxygen concentra~ 65

tion in the slurry ifthe slurry is contacted with air under

identical pressure conditions for the same amount of

gold or silver extracted from the ore.

10. A process as recited in claim 8 wherein steps (a)

and (b) are carried out in each of a plurality of serially.

connected vessels and including the further steps of

directing the flow of the ore slurry in a first direction

serially through said vessels and directing a flow of

adsorbing material in a second direction serially

through said vessels opposite the first direction.

11. A process according to claim 10 such that the

consumption of the cyanide is decreased by using said

greater dissolved oxy·gen concentration in the slurry as

compared with using the dissolved oxygen concentration

in the slurry ifthe slurry is contacted with air under

identical pressure conditions for the same amount of

gold or silver extracted from the ore.

12. A process according to claim 11 comprising the

further step of degassing the slurry before practicing

steps (a) and (b), and wherein the step of recovering the

leached gold or silver in solution includes contacting

the slurry with activated carbon granules for adsorbing

the gold or silver from the solution.

13. A process according to claim 12 wherein the

activated carbon granules are non-deoxygenated prior

to contact with the slurry.

14. In the recovery of gold or silver from an ore

slurry, an adsorbent-in-leach process comprising the

steps of simultaneously, in the same vessel: (a) leaching

gold or silver from the ore slurry, to dissolve the gold

or silver, utilizing a basic cyanide solution; and (b) recovering

the leached gold or silver in solution by contacting

the slurry with an adsorbing material selected

from the group consisting essentially of activated charcoal

granules and ion-exchange resins for adsorbing the

gold or silver from the solution; wherein

steps (a) and (b) are practiced by providing a dissolved

oxygen concentration in the slurry that is

significantly greater than a dissolved oxygen concentration

in the slurry if the slurry is contacted

with air under identical pressure conditions such

that increased gold or silver extraction per unit

time occurs as compared with contacting the slurry

with air; and

wherein steps (a) and (b) are practiced by directing

the flow of the ore slurry in a first direction, and

directing a flow of adsorbing material in a second

direction, opposite the first direction and such that

the consumption of the cyanide is decreased by

using said greater dissolved oxygen concentration

in the slurry as compared with using the dissolved

oxygen concentration in the slurry if the slurry is

contacted with air under identical pressure conditions

for the same amount of gold or silver extracted

from the ore; and

wherein the steps (a) and (b) are praCticed in a covered

vessel so as to decrease the transfer of oxygen

out of solution and decrease the transfer of nitrogen

or carbon dioxide into the slurry.

15. A process according to claim 14 wherein steps (a)

and (b) are further practiced by providing the slurry

and adsorbing material in a vessel, and maintaining an

oxygen atmosphere in the top of the vessel.

16. A process according to claim 15 wherein the

dissolved oxygen concentration is provided by introducing

oxygen gas under pressure into the bottom of

the vessel containing the slurry and the adsorbing material.

17. A process according to claim 16 comprising the

further step of degassing the slurry before practicing

steps (a) and (b).

5,229,085

18. In the recovery of gold or silver from an ore

slurry, an adsorbent-in-leach process comprising the

steps of simultaneously, in the same vessel: (a) leaching

gold or silver from the ore slurry, to dissolve the gold

or silver, utilizing a basic cyanide solution; and (b) re- 5

covering the leached gold or silver in solution by contacting

the slurry with an adsorbing material selected

from the group consisting essentially of activated charcoal

granules and ion-exchange resins for adsorbing the

gold or silver from the solution; wherein 10

steps (a) and (b) are practiced by providing a dissolved

oxygen concentration in the slurry that is

significantly greater than a dissolved oxygen concentration

in the slurry if the slurry is contacted

with air under identical pressure conditions such 15

that increased gold or silver extraction per unit

time occurs as compared with contacting the slurry

with air; and

introducing oxygen gas under pressure into the bottom

of the vessel containing the slurry and the 20

adsorbing material.

19. In the recovery of gold or silver from an ore

slurry, an adsorbent-in-leach process comprising the

steps of simultaneously, in the same vessel: (a) leaching

gold or silver from the ore slurry, to dissolve the gold 25

or silver, utilizing a basic cyanide solution; and (b) recovering

the leached gold or silver in solution by contacting

the slurry with an adsorbing material selected

from the group consisting essentially of activated char-

coal granules and ion-exchange resins for adsorbing the

gold or silver from the solution; wherein

steps (a) and (b) are practiced by providing a dissolved

oxygen concentration in the slurry that is

significantly greater than a dissolved oxygen concentration

in the slurry if the slurry is contacted

with air under identical pressure conditions such

that increased gold or silver extraction per unit

time occurs as compared with contacting the slurry

with air; and

introducing generally pure oxygen into the slurry in

contact with the adsorbing material.

20. A process according to claim 19 wherein steps (a)

and (b) are practiced by directing the flow of the ore

slurry in a first direction, and directing a flow of adsorbing

material in a second direction, opposite the first

direction and such that the consumption of the cyanide

is decreased by using said greater dissolved oxygen

concentration in the slurry as compared with using the

dissolved oxygen concentration in the slurry if the

slurry is contacted with air under identical pressure

conditions for the same amount of gold or silver extracted

from the ore.

21. A process according to claim 19 wherein steps (a)

and (b) are practiced at about atmospheric pressure.

22. A process according to claim 19 wherein said

generally pure oxyge~ has an oxygen content of about

99 %. • • • • •