Gold Extraction Methods and Characteristics Explained
Extraction
of
Gold
By
Dr.
A
hmed
Ameed
1
Characteristics and uses
of
gold
Densi
t
y
:
19.3
g/c
m
3
,
T
m
:
1064
Shinny
:
for Jewelry
o
C
Durable
:
does not tarnish or corrode easily, sometimes
used in dentistry to make the crowns for teeth.
Mallea
b
le
and
duc
ti
l
e
:
can
be
bent &
f
l
attened
.
For
reas
o
n
it
is
used
to
make
fine
w
i
res
and
thin,
f
l
at
sheets
Good conductor for heat & electricity
:
used
in transistors, computer circuits & firefighting cloths.
this
2
Types of ores
Gold
usually
occurs
alloyed
principally
as
a
(as
Na
t
ive
me
t
a
l
,
Electrum
),
with
silver
or
an
Amalgam
).
with
mercury
(as
Native gold can occur
as
sizeable
nuggets, flakes,
grains
or
micr
o
s
c
opic
particles embedded in other rocks.
Ores
with
in
which
g
o
ld
oc
c
urs
in
chemical
compositi
o
n
other
el
e
ments
are
comparatively
rar
e
.
They
include
calaverite,
sylvanite,
nagyagite
,
petzite
and
kren
nerite
3
Gold extraction
Gold mining
•
Hard
rock
mining
–
used
to extract gold encased in
rock.
mining
mining.
Either
open
pit
or
underground
•
Panning
)لصفلا(
– sand and gravel
(
ىصح
)
containing
gold
i
n a
th
a
n
the
is
shaken
around with water
pan. Gold
is
much
denser
rock,
bottom
so
of
quickly
the pan.
settles
to
4
Gold extraction
Gold mining
•
Sluicing
–
water
is
channelled
to
flow through
riffles
)تاجومت(
a
at
sluice-box
with
the bottom which
create dead-zones
in
the
water
current
which
allows gold
to
drop
out of suspension.
•
Sluicing and panning results in the
direct
recovery
of
small gold nuggets
)بهذلا تاماخ(
and flakes.
5
Gold extraction
Gold ore processing
G
o
l
d
c
y
a
n
i
d
a
t
i
o
n
:
•
The most commonly used process for gold
extraction.
•
Used to extract gold from low-grade ore.
•
Gold is oxidised to a water-soluble aurocyanide
metallic complex
Au(CN)
2
.
In this dissolution process, the milled ore is agitated
with dilute alkaline cyanide solution, and air is
introduced:
•
4Au + 8NaCN + O
2
+ 2H
2
O
4NaAu(CN)
2
+ 4NaOH
6
Gold extraction
Gold ore processing
G
o
l
d
c
y
a
n
i
d
a
t
i
o
n
:
•
At a slurry concentration of around 50% solids, the
s
l
u
r
ry
p
a
s
s
es
t
h
r
o
u
g
h
a
s
e
r
i
e
s
of
a
g
i
ta
t
ed
mi
x
i
n
g
t
a
n
ks
with
a
r
e
s
i
d
e
n
c
e
t
ime
of
2
4
hrs.
•
The gold-bearing liquid is then separated from the
leached solids in thickener tanks or vacuum filters &
the tailings
)ةجلاعملا تافلخم(
are
and CN
-
prior to disposal.
washed
to
remove
Au
7
Gold extraction
Gold ore processing
H
e
a
p
L
e
a
c
h
i
n
g
•
•
Is an alternative to the agitated leaching
process.
Drastically reduced gold recovery costs of low
ore.
grade
•
Ore grades as low as 0.3 g
per ton can be
economically
processed
by
heap
leaching.
8
Gold
Gold ore processing
extraction
H
e
a
p
L
e
a
c
h
i
n
g
•
Generally
requires
60
to
90
days for
processing
ore
that
could
be
leached
in
24
hrs
in
a
conventional
agitated leach process.
Au recovery is around 70% as
an agitated leach plant.
•
compared with 90% in
•
BUT
,
has
gained wide
favour
due to
vastly reduced
processing costs.
Frequently, mines will use agitated leaching for high-
•
grade ore
&
heap leaching
for
low grade
ores
that
would otherwise be considered waste rock.
9
Gold extraction
Gold ore processing
G
o
l
d
c
y
a
n
i
d
a
t
i
o
n
:
M
e
r
r
i
l
l
-
C
r
o
w
e
p
r
o
c
e
s
s
•
Traditional method for
cyanide solutions.
Au recovery from pregnant
•
Once dissolution of Au is complete, the remaining
rock
pulp if filtered off through various filters to produce a
sparkling )عملا( clear solution.
•
O
2
is removed from the clarified solution by passing
the solution through a vacuum deaeration column.
10
Gold
Gold ore processing
extraction
G
o
l
d
c
y
a
n
i
d
a
t
i
o
n
:
M
e
r
r
i
l
l
-
C
r
o
w
e
p
r
o
c
e
s
s
Zinc dust is then added to the cyanide solution
chemically reduce the gold to the metal.
•
to
2
A
u
(
C
N
)
2
+
Z
n
2
A
u
+
Z
n
(
C
N
)
4
•
The metallic gold is then filtered out & refined.
Smelting
of resultant powder (rich Au) into steel
molds
and the slug is remove from the top furnace.
Electrolysis
purity.
is done to get high gold grade 99.999%
11
Cy
a
nide
process
of
gold
production
12
Gold extraction involves various methods such as hard rock mining, panning, sluicing, and cyanidation. Gold is known for its density, malleability, conductivity, and durability, making it ideal for jewelry, dentistry, and technology. Different types of gold ores exist, including native gold and ores alloyed with elements like silver. The extraction processes aim to separate gold from rocks or low-grade ores through chemical reactions and physical techniques like sluicing and heap leaching.
Download Presentation
Please find below an Image/Link to download the presentation.
The content on the website is provided AS IS for your information and personal use only. It may not be sold, licensed, or shared on other websites without obtaining consent from the author. Download presentation by click this link. If you encounter any issues during the download, it is possible that the publisher has removed the file from their server.
E N D
Presentation Transcript
ExtractionofGold ByDr. AhmedAmeed 1
Characteristics and uses of gold Density :19.3g/cm3, Tm:1064 Shinny: for Jewelry used in dentistry to make the crowns for teeth. Malleable and ductile:canbe bent &flattened . For reasonit isusedto make finewires and thin,flatsheets Good conductor for heat & electricity: used in transistors, computer circuits & firefighting cloths. oC Durable: does not tarnish or corrode easily, sometimes this 2
Types of ores Native metal, Electrum), Gold usually with mercury(as as sizeable nuggets, flakes, grains or microscopic particles embedded in other rocks. Ores with other elements are comparatively rare. They include calaverite,sylvanite,nagyagite, petziteand kren nerite occurs alloyed principally with silver an Amalgam). as a (as Native gold can occur or in which gold occurs in chemical composition 3
Gold extraction Gold mining Hard rock mining used to extract gold encased in rock. mining mining. Either or open pit underground Panning ) ( sand and gravel ( ) containing gold around with water is much denser quickly the pan. is shaken pan. Gold rock, bottom in a than the so of settles to 4
Gold extraction Gold mining Sluicing water is channelled to flow through riffles ) ( at create dead-zones in the water current which allows gold to drop out of suspension. a sluice-box with the bottom which Sluicing and panning results in the direct recovery of small gold nuggets ) (and flakes. 5
Gold extraction Gold ore processing Gold cyanidation: The most commonly used process for gold extraction. Used to extract gold from low-grade ore. Gold is oxidised to a water-soluble aurocyanide metallic complex Au(CN)2. In this dissolution process, the milled ore is agitated with dilute alkaline cyanide solution, and air is introduced: 4Au + 8NaCN + O2 + 2H2O 4NaAu(CN)2 + 4NaOH 6
Gold extraction Gold ore processing Gold cyanidation: At a slurry concentration of around 50% solids, the slurry passes through a series of agitated mixing tanks with a residence time of 24 hrs. The gold-bearing liquid is then separated from the leached solids in thickener tanks or vacuum filters & the tailings ) ( are and CN-prior to disposal. washed to remove Au 7
Gold extraction Gold ore processing Heap Leaching Is an alternative to the agitated leaching process. Drastically reduced gold recovery costs of low ore. grade Ore grades as low as 0.3 g per ton can be economically processed by heap leaching. 8
Gold extraction Gold ore processing Heap Leaching Generally requires 60 to 90 days for processing ore that could be leached in 24 hrs in a conventional agitated leach process. compared with 90% in Au recovery is around 70% as an agitated leach plant. BUT, has gained wide favour due to vastly reduced processing costs. Frequently, mines will use agitated leaching for high- grade ore & heap leaching for low grade ores that would otherwise be considered waste rock. 9
Gold extraction Gold ore processing Gold cyanidation: Merrill-Crowe process Traditional method for cyanide solutions. Au recovery from pregnant Once dissolution of Au is complete, the remaining rock pulp if filtered off through various filters to produce a sparkling ) ( clear solution. O2 is removed from the clarified solution by passing the solution through a vacuum deaeration column. 10
Gold extraction Gold ore processing Gold cyanidation: Merrill-Crowe process Zinc dust is then added to the cyanide solution chemically reduce the gold to the metal. 2Au(CN)2 + Zn The metallic gold is then filtered out & refined. to 2Au+ Zn(CN)4 Smelting of resultant powder (rich Au) into steel molds and the slug is remove from the top furnace. Electrolysis purity. is done to get high gold grade 99.999% 11
