Download - TMS - June 2003 Chloride Altern
1Lakefield Research
C.J. Ferron, C.A. Fleming, SGS Lakefield Research Limited
D. Dreisinger, University of British Columbia
T. O’Kane, O’Kane Consultants Inc.
Chloride as an Alternative toCyanide for the Extraction of
Gold - Going Full Circle?
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Outline
Introduction : A brief look at history
Chloride Process for Gold Extraction chloride and preg-robbers
PLATSOL for Cu-Ni-Au-PGM’s ores
treatment of Cu-Au concentrates
treatment of refractory Au concentrates (non-preg-robbers)
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Outline - continued
Gold Recovery from PLATSOL Liquor: - NaHS, Carbon, IX
Silver Recovery with PLATSOL
Gold Recovery from Preg-Robbing Ores
Engineering Implications
Conclusions
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Introduction - Flash-Back
Before cyanidation, chlorination was used Cl2 (gas), bleach + H2SO4, KMnO4 + NaCl + H2SO4
Cl2/HCl to dissolve Au (+PGM’s) in refineries
Putnam (1947)
Chloride roasting
Au-Sb slag in RSA
McGill University - Pressure chloride leaching with [Cl]
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PLATSOL DiscoveryAu, Chloride, Preg-Robbers
LIHIR
Santa Fe Pacific Gold Corporation
Con Mine
PLATSOL : add small amount of chloride to HTPOX (225oC) to dissolve Au + PGM’s
First Application : Northmet Project
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Eh - pH Diagram for the Au-Cl-H2O Systemat 25oC: [Au] = 0.00001M; [Cl] = 0.2M
14121086420
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
Eh (Volts)
pH
Au
Au(OH)3
AuCl4(-a)
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Effect of Chloride Additionson Metal Extractions
(225oC, 2 hours)
Effect of Temperature onMetal Dissolutions
(5g/L NaCl, 2 hours)
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20
g/L NaCl
% E
xtra
cti
on
Au
Pt
Pd
70
80
90
100
190 200 210 220 230 240
Temperature °C
% E
xtra
cti
on
Cu
Au
Pt
Pd
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Analyses of Various Cu-Ni Concentrates TestedElements Concentrate Type
% A B C D E F G H I _______________________________________________________Cu 2.1 12.0
Ni 0.9 9.9
Fe 12.6 35.9
S 7.3 34.1
Au g/t 2.5 3.6 4.0 12.4 5.0 0.9 0.5 3.0 2.1
Pt g/t 0.8 490
Pd g/t 2.0 294
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Results(10-20g/L NaCl; 220oC; 50g/L H2SO4 Initial; 100psi O2 overpressure)
% Concentrate TypeRec’y A B C D E F G H
Cu 99.9 98 99.9 99.9 99.9 99.3 99.0 99.3
Ni 99.9 99 99.9 99 99 93.8 99.6 98.7
Au 93 83 96 99 83 97.1 84.3 96.0
Pt 72 80 76 95 51 97.4 98.2 99.0
Pd 97 93 94 94 80 98.1 93.9 98.4
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PLATSOL forChalcopyrite-Au Concentrates
Origin Chile Canada Australia
Assays% Cu 28.9 32.0 26.1% S2- 29.6 28.5 29.3g/t Au 5.8 2.5 12
PLATSOL ConditionsT(ºC) 225 225 225g/L NaCl 10 10 10P80 (µm) 15 20 15Duration (h) 2 2 2
PLATSOL Results% Cu extracted 99.7 99.8 99.9% Au extracted 95.9 93.1 88.3
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PLATSOL for Refractory Gold Concentrates
Concentrate Origin South Africa South America Greece RomaniaType Au
encapsulatedin Fe2O3
Auencapsulated
in pyrite
Auencapsulated
in arsenopyrite
Auencapsulated
in arsenopyriteChemical Analysis
g/t Au 17.7 50.9 19.9 11.2g/t Ag 6.8 350 19.4 146
PLATSOL® Conditions
Temperature (ºC) 225 225 225 225Duration (h) 6 4 3 3
g/L NaCl 10 20 20 20P80 (µm) 25 16 15 16
PLATSOL® Results
Au extraction (%) 90 96 96 92Ag extraction (%) 41 5 99.5 7
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PLATSOL and Silver Concentrates
PRINCIPLE: PLATSOL
Silver Mineral AgCl in residue(and not Ag-Jarosite)
AgCl can be recovered from residuecyanidation flotationNaTS leaching
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PLATSOL and Silver Concentrates - continued
EXAMPLE 1: Ag-tetrahedrite, USA16% Cu, 30% Pb, 9.8% Sb, 3.5% AgPLATSOL = 99% Cu in solution, ~0% Ag
Cyanidation:95.4% (96 hours)NaTS: 87.5% (6 hours, RT)
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PLATSOL and Silver Concentrates - continued
EXAMPLE 2: Cu-Ag-Au-As concentrate from Peru
1.4% Ag, 21 g/t Au, 7% As
PLATSOL = Cu, Au (92.5%) in solution, ~0% Ag
ATS dissolved 88% Ag (one test)
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PLATSOL & Preg-RobbersFlotation of Graphitic Carbon
from PLATSOL Residue
AuFraction Wgt(%)
g/t % Recovery
Rougher 1 26.6 1132 75.4
Rougher 2 19.7 290 14.2
Total Rougher 46.3 774 89.6
Rougher Tail 53.7 77 10.4
PLATSOL®
Residue 100 399 100
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Gold Recovery fromPLATSOL Liquors
Various methods:
carbon
NaHS precipitation
ion exchange
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Extraction Isotherms at 45oC for Au, Pd from PLATSOL NorthMet Pulps.
AuRix 100 Resin
10
100
1000
10000
0.01 0.1 1
Concentration in Barren (mg/L)
Res
in L
oad
ing
(g
/t)
Au
Pd
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Engineering Implications1) Refractory gold autoclaves
(225oC, 100 psi O2, 20 - 40 g/L H2SO4)
2) Presence of 5 -10 g/L Cl Polymeric membrane
- Macraes- Laterites- Phelps Dodge
3) Rest of the circuit must handle acidic chloride solutions
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Engineering Implications- cont’d
But…
1) No cyanide circuit
2) Real potential for RIP, CIP
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CONCLUSIONS
Results indicate that the PLATSOL is a
viable non-cyanide alternative for:
copper-gold concentrates (i.e. Phelps Dodge) enargite-gold concentrates refractory non-preg robber ores/concentrates high silver concentrates (modified) especially
with Sb, As
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Adsorption of Metals from Autoclave Pregnant Leach Solution on Activated Carbon
Conditions Solution Assays (mg/L) Carbon Assays (g/t, %)Temp
ºC
Time
h
Carbon
g/LStream Au Pt Pd Au Pt Pd Cu Ni Fe
20 24 5 Preg 0.21 0.19 1.08Barren <0.01 0.03 0.07 14 31 197 0.72 0.54 0.18
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Elution of Activated Carbon-Zadra Method
ProductCarbon Analyses (g/t, %)
Au Pt Pd Cu Fe
Loaded carbon 16 118 732 0.15 0.20Eluted carbon 0.6 1.8 7 0.002 0.20
Elution efficiency % 96 98 99 99 ~0
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Extraction Isotherms at 45oC forAu, Pd from PLATSOL NorthMet Pulp
on Activated Carbon
10
100
1000
10000
0.01 0.1 1
Concentration in Barren (mg/L)
Car
bo
n L
oad
ing
(g
/t)
Au
Pd
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Kinetics of Gold CIP Adsorptionfrom NorthMet PLATSOL Pulp
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
0 10 20 30
Time (h)
Res
idu
al A
u (
mg
/L)
85ºC
40ºC
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CIC Feed and Discharge Au Concentrations
Gold (mg/L)
Feed CIC-6 DischargePP5-1 0.10 0.01PP5-2 0.12 0.02PP5-3 0.08 <0.01PP5-4 0.09 0.01PP5-5 0.12 0.01PP5-6 0.14 <0.01PP5-7 0.11 <0.01PP5-8 0.08 0.01PP5-9 0.12 <0.01PP5-10 0.14 0.01PP5-11 0.10 <0.01PP5-12 0.13 <0.01PP5-13 0.11 <0.01
Average 0.11 <0.01