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~~=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
/4
//
t=1t3. 1
CARBON
ADDITION
COARSE PARTICLES+30
MESH
1
I
I 49
I~./
I'
y8
LOADED
CARBON
TO GOLD
RECOVERY
~
•
00
•
""d =f"ttD
=f"t-
~=-'-<
N
~o ....
\C
\C
CN
00=
~
~..... ....
o.....
CN
..(..II
~~
..\.0
o
00
(.II
u.s. Patent July 20, 1993 .Sheet 2 of 3 5,229,085
ORE,
CYANIDE
SLURRY
DEAERATE
02
INJECTION
60
tSLURRY
FLOW
DIRECTION
ICARBON
GRANULE
DIRECTION
LOADED CARBON
TO STRIPPING,
ACID WASHING,
THERMAL
REGENERATION
AND REUSE
6/
68 70
RESIDUE ~
~~::J-------_---.JW CYANIDE DESTRUCTION
8 DISPOSAL
..t.il
N
N
..\. 0
o
00
til
~
•
fJ1 •
~
~
f"1'.
('D=f"1'.
I
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 .....
w
76
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
I
J 02 1400# /D ~ 'IH::l<1 I
2
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
1
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
4
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.
3
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
6
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.
55
TABLE I
5,229,085
5
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
8
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
5
20
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.
45
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
pH
Filtrate, total
Volume, ml
Au, ~gll
Residue
Weight, g
AU,oz/ton
7
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
9
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
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
11
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-
30
35
40
45
50
55
60
65
12
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 %. • • • • •