4,816,234 Utilization of oxygen in leaching and/or recovery procedures employing carbon

Patent Number/Link:

United States Patent [19]

Brison et ale

[11] Patent Number:

[45] Date of Patent:

4,816,234

Mar. 28, 1989

[54] UTILIZATION OF OXYGEN IN LEACHING

AND/OR RECOVERY PROCEDURES

EMPLOYING CARBON

U.S. PATENT DOCUMENTS

4,173,519 11/1979 Parker et al ; 75/105

4,174,997 0/1979 Richter.

4,251,352 211981 Shoemaker 209/45

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

4,416,774 1111983 Taylor 210/236

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

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

4,502,952 3/1985 Naden et al 210/86

4,510,721 211985 Sherman et al 423/27

4,557,905 1211985 Sherman et al 423/27

FOREIGN PATENT DOCUMENTS

85559/82 6/1983 Australia.

18928/83 9/1983 Australia.

3126234 111983 Fed. Rep. of Germany.

76/6476 1011976 South Africa.

77/1778 3/1977 South Africa.

78/1184 311978 South Africa.

8111215 211981 South Africa.

987406 3/1965 United Kingdom.

OTHER PUBLICATIONS

Headley, N. and Tabachnick, H. "Chemistry of Cyan-

References Cited

Related U.S. Application Data

Continuation of Ser. No. 732,637, May 10, 1985, abandoned.

20 Claims, 3 Drawing Sheets

dation. Mineral Dressing Notes", American Cyanamid

Co., Jun. 1958, No. 23.

Davidson R. Brown, G. A. Schmidt, C. G. et al "The

Inventive Cyanidation of Gold-Plant Gravity Concentrates",

J. S. Afr. Inst. Min. Metall. 1978, pp. 146-165.

"On the Dissolution of Precious Metals ... ," Tronev et

al., Comptes Rendus (Doklady) de l'Academie des Sciences

(1937), vol. 16, No.5, pp. 281-284.

"The Kamyr Process for Leaching Gold and Silver

Ores," Elmore et al., First International Symposium on

Precious Metals Recovery, Reno, Nev., Jun. 1984.

"The Chemistry of the Extraction of Gold ... ," Gold

Metallurgy in South Africa, Finkelstein, Chapter 10, p.

309 (1972).

"Research on Pressure Leaching of Ores ... ," Pietsch

et al., Erzmetall, Jun. 1983, pp. 261-265.

"The Treatment of Refractory Gold-Bearing ... ,"

Muir et al., Precious Metals: Mining Extraction and

Processing, 1984, pp. 309-322.

"Solubilities of Inorganic and Metal-Organic Compounds

(Seidel)", Linke, 4th Ed., 1958, vol. 1, p. 250,

vol. 2, pp. 1228-1230.

(List continued on next page.)

Primary Examiner-Gary P. Straub

Attorney, Agent, or Firm-Nixon & Vanderhye

[57] 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-leach (CIL) processes and

related processes using resins. Deaeration of the ore

slurry can be practiced prior to the introduction of the

oxygen.

Robert J. Brison, Golden, Colo.; Carl

L. Elmore; Phillip Mitchell, both of

Glens Falls, N.Y.

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

102,742

Sep. 23, 1987

Inventors:

Int. Cl.4 BOlD 11/00; C22B 3/00

U.S. Cl 423/29; 423/27;

75/105; 75/108; 75/118 R

Field of Search 423/27,29,30, 31;

75/105, 101 R, 108, 118 R

Assignee:

Appl. No.:

Filed:

[75]

[73]

[21]

[22]

[63]

[51]

[52]

[58]

[56]

4,816,234

Page 2

OTHER PUBLICATIONS

No. 72/3211, Extract from South Africa Patent Journal.

No. 72/6051, Extract from South Africa Patent Journal.

No. 72/8222, Extract from South Africa Patent Journal.

No. 73/1753, Extract from South Africa Patent Journal.

No. 73/2941, Extract from South Africa Patent Journal.

No. 68/2047, Extract from South Africa Patent Journal.

No. 68/6142, Extract from South Africa Patent Journal.

McDougall et al, "Activated Carbons and Go1d-A

Literature Survey", Minerals Sci. Engng. vol. 12, No.2,

Apr. 1980 pp. 85-99.

Laxen et al, "The Carbon-in-Pulp Gold Recovery

Process-A Major Breakthrough", S. A. Mining &Engineering

Journal, Jul. 1979, vol. 90.

Tsuchida et al, "Studies on the Mechanism of Gold

Absorption on Carbon", Mineral Chemistry Research

Unit, Murdoch University, Perth, W. Australia, 1984.

Newrick et al, "Carbon-in-Pu1p Versus Carbon-

in-Leach", World Mining, Jun. 1983, pp. 48-51.

Laxen et al, "A Review of Pilot-Plant TestworkConducted

on the Carbon-in-Pu1p Process for the Recovery

of Gold", Proceedings, 12th CMMI Congress, 1982,

pp. 551-561.

"Principles of Extractive Metallurgy," Fatha Habashi,

vol. 2, pp. 15-16, 24-30.

Lehrbuch der Metallhiittenkunde, Dr. Ing. Victor Tafel

et al., pp. 17, 31-34.

"Some Studies on the Gold-Dissolution rate in Cyanide

Solutions," Engineering and Mining Journal, pp. 44-47,

vol. 140, No.1, Jan. 1939.

"Unit Operations", G. G. Brown & Associates, John

Wiley & Sons, Inc. (1956), p. 290.

(D a

rJ1 •

foo+. g

l"""fo.

~ --..

--0.. \

i •

.58 I

LOADED

CARBON

TO GOLD

RECOVERY

III

r=----rn 49

I~/

CARBON

ADDITION

COARSE PARTICLES+30

MESH

~./

WASTE

ORE FEED

. FROM

THICKENER

50% SOLIDS

-/50 MESH

u.s. Patent

ORE,

CYANIDE

SLURRY

Mar. 28, 1989

DEAERATE

Sheet 2 of 3

INJECTION

4,816,234

'1 SLFULRORWY

DIRECTION

1CARBON

GRANULE

DIRECTION

LOADED CARBON

TO STRIPPING,

ACID WASHING,

THERMAL

REGENERATION

AND REUSE

~e 70

RESIDUE ~

~~:l---------.GJ CYANIDE DESTRUCTION

a DISPOSAL

t'D a

... ....

0'\

~...

fJ1 •

~a~

CARBON

LOADED

CARBON

TO GOLD

RECOVERY

",010

~ TAILING I~

7..r

FLOCCULANT

.25 ;- ITON

250lD

MILL WATER

169 GPM

OVERSIZE RETURN

TO REGRIND

FIBER

15 'It I TON

7.5 TID

NaCN IT/D

ORE FEED

FROM CLASSIFIER

1000

TID 35%

SOLIDS

~-l

J 02 14001£ /0 ~ IIH:kI I

According to the present invention, it has been found

that the combination of (1) the use of oxygen or oxygenenriched

air and (2) a leach-adsorption system employing

activated carbon results in an extremely efficient

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

like.

It has been found that not only does oxygen increase

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

overall efficiency. of processes employing carbon ad10

sorption in gold and/or silver recovery is significantly

increased by the use of a gas containing a signiftcantly

higher proportion of oxygen than is found in air. .

Although activated carbon is well known to be a

catalyst in decomposition of cyanide' ion 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 as a higher proportion of oxygen

than natural air, it will also have a signiftcantly 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 (as well as causing

other problems), 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-ftfth 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-ftfth 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 signiftcantly decreased.

Compared to conventional CIL processes, the process

according to the invention would reduce the agitated

tank size by a factor of about ftve 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

process according to the invention, and the utilization

4,816,234

UTILIZATION OF OXYGEN IN LEACHING

AND/OR RECOVERY PROCEDURES

EMPLOYING CARBON

This is a continuation of application Ser. No. 732,637

ftled 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

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 15

the gold and/or silver from the ore.

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

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 20

largely dissolved from the pulp. After leaching, the

pulp moves to the CIP adsorption system, which typically

contains about six vessels each having a retention

time of about one hour. The pulp is agitated in each of 25

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

gold and silver from the solution. The inventory of

carbon granules is continuously or periodically trans- 30

ferred from one vessel to the next in the opposite direction

of the flow of the pulp, with carbon discharged

from the ftrst vessel in the series ultimately being passed

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

discharged from the last vessel in the series is leach 35

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

place of carbon granules. Such processes have not yet

received commercial acceptance for Au/Ag leaching. 40

Conventional CIL processes are similar to CIP processes

except that the dissolution and the adsorption of

the gold and silver are practiced essentially simultaneously.

In a typical CIL procedure, the ground and

thickened ore slurry typically passes to a series of about 45

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 countercurrent

paths in basically the same manner as in the CIP

process, with the loaded carbon passed to a recovery 50

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

other preliminary processing steps, such as thickening.

Although the proportion of the total metal dissolved in 55

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

golc;l and/or silver recovery.

It has been known for many years that, under certain 60

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 dissolution

can be signiftcantly increased if generally pure

oxygen gas (e.g. gas having an oxygen content of about 65

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

oxidation during the cyanidation process. However this

fact has not been taken advantage of commercially.

ing about 99 percent or more oxygen). However the

desired results according to the invention, of increased

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

usually inherently (merely by the increase in the proportion

of oxygen), has a determined proportion of

10 carbon dioxid 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

wliich 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 of FIG. I, 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 effects

some agitation of the solution, facilitating efficient

dissolution of the oxygen.

4,816,234

DETAILED DESCRIPTION

BRIEF DESCRIPTION OF THE DRAWINGS

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 5

objects of the invention will become clear from an inspection

of the detailed description ofthe invention, and

from the appended claims.

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;

FIG. 2 is a schematic view of exemplary apparatus 15

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 precede

the adsorption tanks of the enhanced CIP process 20

according to the invention.

The invention will be herein described with respect

to the recovery of gold and/or silver from gold and/or 25

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

and silver ores, and other materials such as tailings,

from which gold and/or silver may be recovered. Also, 30

the invention has applicability to the recovery of other

metals.

In the preferred embodiment according to the present

invention, activated charcoal (also known as activated

carbon, carbon, and the like) is used as the material for 35

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 particles,

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

exchange resins (i.e. a resin-in-pulp process, as de- 40

scribed 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 invention,

the ore is milled in the presence of lime and possibly

cyanide, and ultimately fed through the flow con- 45

trol 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

be thickened by conventional means to remove part of

the solution, which may be treated separately for gold 50

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.

If desired, the ore slurry can be deaerated as by any type

of conventional deaeration means (such as a vacuum 55

system) 16.

After the ore slurry passes through pump 15, a conventional

basic cyanide solution (such as NaCN) is

added to the ore from source 17, additionalHme may be

added as needed, and oxygen containing gas from 60

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

slurry utilizing mixers, although since significant mixing

will take place in subsequent vessels a separate mixer at 65

this point is not essential.

The oxygen containing gas from source 18 preferably

comprises generally pure oxygen (that is a gas contain8.36

4.14

0.2

0.079

98.10

1.8

23.1

Nitrogen

8.97

4.14

0.041

0.2

Air

23.1

99.01

1.8

Atmosphere

8.77

4.14

0.2

0.032

23.4

99.23

1.8

100

Oxygen

Approx. % 02

in atmosphere

Leach solution

assay. Au, mg/l

Final solution assay.

Au, mg/l

Final carbon assay,

Au, oz/ton

Au adsorption. %1

Leach solution assay,

Ag, mg/l

Final solution

assay. Ag, mg/l

Finill carbon assay.

4,816,234

5 6

Another non-conventional component of the tank 34 the apparatus of FIG. 3, the slurried ore in conduit 76 is

comprises the top 47. The top 47, as does the top 30, can mixed with cyanide from conduit 77, and ultimately

seal the tank so that an oxygen atmosphere (either at mixed with oxygen from conduit 78 in a mixer 79. The

one atmosphere pressure, or significantly greater than mixer may be any suitable mixer capable of mixing

one atmosphere pressure) may be maintained in the 5 components of a medium consistency slurry, such as an

tank. MC ® mixer sold by Kamyr, Inc. of Glens Falls, N.Y.

The further tanks 48,49, etc. in the adsorption system Also, as generally disclosed in U.S. Pat. No. 4,501,721,

are each substantially identical to the tank 34 except flocculent and/or fiber can be added to the slurry to

that in the last tank 49 in the series the cover 44' has facilitate locking of the particulized ore in a stable netdisposed

therein a valved opening 50 which allows the 10 work in the slurry. For instance cellulosic fibers, fiberaddition

of activated charcoal particles, which are glass fibers, or the like are mixed with liquid in tank 80

coarser than the ore particles in the slurry [the differ- and then metered to the inlet to mixer 79, while floccuence

in coarseness allowing effective screening]. lents, such as syntheti~ poly~ers o! anionic".cationic, or

The slurry discharged through outlet 38' of the tank nonionic types are 1l1lXed With mill water m tanks 81,

49 goes to tank 52, and from tank 52to withdrawn by 15 and then ultimately passed to conduit 82 prior to intropump

53 and ultimately passed to a disposal site 54 for duction into upflow 83. The leached slurry that is disthe

ore tailings (which is what the pulp has been re- charged from the top 84 of vessel 83 will then pass to

duced to). The carbon particles outlet 42 from the first the CIP recovery station 75, which can be as illustrated

tank 34 pas~ through flow control valve 55 to chute in FIG.l (without the tank 22). The vessel 83 can also

56, and ultimately to the carbon screen 57, with sepa- 20 be pressurized, as by utilizing pressure control valve 85,

rated loaded carbon being passed to the gold and/or and a one atmosphere, or super-atmospheric, oxygen

silver recovery station 58, and separated slurry in con- atmosphere maintained therein, or the vessel can be

duit 59 being recirculated. completely slurry filled.

The apparatus of FIG. 1 can also be utilized for a Utilizing the apparatus heretofore described, accordcarbon-

in-leach process merely by elimination of the 25 ing to the present invention a process of gold and/or

tank 22. Such an arrangement is especially advanta- silver recovery from ore and the like may be practiced.

geous, and the size and/or number of tanks 34, 48, 49 The process comprises the steps of: leaching gold andwould

be less than for conventional CIL processes. lor silver from the ore or the like, to dissolve the gold

FIG. 2 schematically illustrates another form the and/or silver, utilizing a basic cyanide solution; and (b)

apparatus according to the invention can take for the 30 recovering the leached gold and/or silver in solution by

practice of a CIL process. The ore slurry, mixed with contacting the solution with solid material for adsorboxygen,

passes into the top of vertical vessel 60, and ing the gold and/or silver from the solution; wherein

flows continuously downwardly therein. Typical con- step (b) is practiced by providing oxygen gas in the

ditions of the ore slurry would be 50 percent solids solution in an amount significantly greater than can be

(minus 100 mesh), 0.3 gil NaCN, solids specific gravity 35 obtained by contacting the solution with air so as to

of 2.7, and a slurry specific gravity of 1.46. The acti- greatly increase the solution rate of the gold and/or'

vated charcoal granules would be introduced from silver,and by minimizing the amount of carbon dioxide

source 61 into the bottom of the vessel 60 at point 62, in the solution so that it is significantly .less than would

and would flow· upwardly in the vessel. Typically the be obtained by contacting the solution with air, so as to

carbon granules would be relatively large, about 6-16 40 possibly increase the gold and/or silver adsorption effimesh,

and would have a lower specific gravity than the ciency of the adsorbing material, and certainly toreslurry

(e.g. 1.2). The slurry density, carbon density and duce the production of CaC03. Preferably step (b) is

size, and other factors (such as the addition of flocculent practiced by substantially saturating the solution with

or fibers to the slurry) could be adjusted to optimize the oxygen, and preferably by utilizing generally pure oxycarbon

upflow rate relativ to the slurry downflow rate. 45

The loaded carbon, with some entrained slurry, would ge~e following table I indicates the results achieved

be .withdrawn from adjacent the top of the vess:l 60 at by preparing a gold cyanide solution by leaching a

pomt 63, and p~d to a carbon screen 64, Wlt~ the common gold ore sample (the gold ore sample, as is

loaded carbon stopped and regenerated for reuse m the typo al al contained a small amount of silver) and

carbo~ injection s~stem 61, and with separated slurry in 50 the~c e~po:~g the solution to carbon adsorption' in a

co~dwt 6~ returnmg to the top of the vessel 60. The rotatin bottle for six hours, with atmospheres of air,

reSidue Withdrawn at t.he bottom.66 of the v~ssel 60 by x e: and nitrogen respectively.

the pump 67 would eIther pass mto condwt 68 to be 0 yg , ,

used as part of the liquid for carrying the recycled car- TABLE I

bon into the column within the vessel 60, or would pass 55

to conduit 69 and ultimately to cyanide destruction and

disposal site 70.

The vessel 60 may be operated at atmospheric pressure,

or at super-atmospheric pressure, and an oxygen

atmosphere may be provided at the top thereof in either 60

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

the slurry solids had a lower specific gravity.

FIG. 3 schematically illustrates other exemplary ap- 65

paratus that can be utilized for effectively and efficiently

dissolving the gold and/or silver in the leaching

stage prior to the CIP recovery in station 75. Utilizing

TABLE I-continued

4,816,234

TABLE III-continued

Atmosphere Test #1 Test #2

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

2During 6-hr elP leach, purge with 02 at T = 0 hr and T= 1 hr. Also add II g

30 carbon at each of these times.

8.7/10.9

0.3

399.9

0.217

6 X 14

22.00

22.07

2.695

10.6

0.12

0.25

91.7

1417.76

0.22

298.48

0.018

0.47

8.7/10.9

0.3

399.9

0.217

10.5

0.12

0.25

6 X 14

22.00

22.26

2.684

298.24

0.019

91.3

1412.67

0.24

0.37

pH: initial/adj.

NaCN, initial gil

Time, hr

Feed

Weight, g

Au, oz/ton

Reagents added, lotal

Cao, g

NaCN, g

Mesh size Tyler

Initial wi, g

Final wt, g

Au, oz/ton

Sol'n, end of lest

Filtrate, total

Volume, ml

NaCN, gil

Weight, g

Au, oz/ton

Reagents consumed

NaCN, 1b/ton

Extraction, %

Calculated heads

Au, oz/ton 0.219 0.217

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

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 at about atmospheric

pressure by providing a dissolved oxygen concentration

in the slurry that is significantly greater

thana 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, wherein steps

(a) and (b) are further practiced by introducing

generally pure oxygen into the slurry in contact

with the adsorbing material.

2. A process as recited in claim 1 comprising the

further step of degassing the slurry before practicing

steps (a) and (b).

88.1

Air Nitrogen

88.6

Ag,ozlton

Ag adsorption, %1 88.6

Oxygen

Test #1 Test #2 65

Conditions

Grind 77.9% ·200 77.9% - 200

% Solids 27 27

IBased on fmal carbon and fmal solution.

The following table II indicates the results from a

carbon-in-pulp cyanidation test utilizing three different 10

types of Gencor ore samples from, respectively, Buffeisfontein

(No. I), 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.

All tests were performed in rotated bottles with oxygen 15

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 eIP process.

TABLE II

-------~;;.;;;;;..;;;;;~;....-------20

In the following table III, further bottle-type tests 50

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

that simultaneous leaching and carbon adsorption

in an oxygenated slurry results in rapid higli gold

extraction with low cyanide consumption. The ore

tested in each of the two tests in table III was Gencor's 55

Buffiesfontein ore. With gold extractions of about

91-92%, in six hours, cyanide consumption was only

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

concentration was closer to expected plant conditions,

cyanide consumption is expected to be as little as 60

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

very unexpected and advantageous.

TABLE III

Test #1 Test #2 Test #3

Conditions

Grind 77.9% - 200 80%·200 80% - 200

% Solids 27 27 27

pH: initial/adj. 8.7/10.9 9.0/10/8 9.0/10.7

NaCN, initial gil 0.3 0.3 0.3

Time, hr. 10 10 10

Feed

Weight, g 300.0 300.0 300.0

AU,oz/ton 0.217 0.110 0.186

Reagents added, total

Cao,g 0.12 0.12 0.12

NaCN, g 0.25 0.25 0.25

Carbon

Mesh size Tyler 6 X 14 6 X 14 6 X 14

Initial wt, g 22.00 22.00 22.00

Final wt, g 22.05 22.11 22.09

Au,oz/ton 2.631 0.966 1.779

. Sol'n, end of test

NaCN, gil 0.276 0.245 0.264

pH 10.6 10.6 10.4

Filtrate, total

Volume, ml 1414 1453 1399

Au, mgll 0.004 0.002 0.003

Residue

Weight, g 298.7 298.6 298.6

Au, oz/ton 0.017 0.004 0.015

0.015 rerun

Reagents consumed

NaCN, 1b/ton 0.16 0.33 0.26

Extraction, %

Au 92.0 94.7 89.8

4,816,234

3. A process according to claim 1 wherein said generally

pure oxygen has an oxygen content of about 99%.

4. A process as recited in claim 1 wherein steps (a)

and (b) are practiced in a covered vented vessel so as to

decrease the transfer of oxygen out of solution and 5

decrease the transfer of nitrogen or carbon dioxide into

the slurry.

5. A process as recited in claim 1 wherein steps (a)

and (b) are further practiced by providing the slurry

and adsorbing material in a vessel, and maintaining an 10

oxygen atmosphere in the top of the vessel.

6. A process as recited in claim 1 wherein steps (a)

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

slurry in a fIrst direction, and directing a flow ofadsorbing

material in a second direction, opposite the fIrst 15

direction.

7. A process as recited in claim 1 wherein steps (a)

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

adsorbing material.

8. A process as recited in claim 7 wherein said agitat- 20

ing step is practiced by mechanically agitating the

slurry and adsorbing material.

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

step is practiced by introducing oxygen gas under

pressure into the bottom of a vessel containing the 25

slurry and the adsorbing material.

10. A process as recited in claim 1 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- 30

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.

11. A process as recited in claim 1 wherein steps (a)

and (b) are carried out in each of a plurality of serially 35

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. 40

12. A process according to claim 11 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 ifthe slurry is contacted with air under 45

identical pressure conditions for the same amount of

gold or silver extracted from the ore.

13. A process according to claim 12 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.

14. A process according to claim 13 wherein the

activated carbon granules are non-deoxygenated prior

to contact with the slurry.

15. A process according to claim 1 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.

16. A process according to claim 15 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.

17. A propess according to claim 15 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.

18. A process according to claim 17 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.

19. A process according to claim 18 comprising the

further step of degassing the slurry before practicing

steps (a) and (b).

20. A process according to claim 1 including introducing

oxygen gas under pressure into the bottom of

the vessel containing the slurry and the adsorbing material.

* * * * *