escuela politÉcnica nacional quito - ecuador faculty of chemical engineering and agroindustry...
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RECOVERY OF PRECIOUS METALS FROM DISCARDED
CELLPHONESE. de la Torre , S. Espinoza, A. Guevara
ESCUELA POLITÉCNICA NACIONALQuito - Ecuador
Faculty of Chemical Engineering and Agroindustry
Department of Extractive Metallurgy
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• Pb• C
o• Ni• C
d• Cr
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Au, Ag, Pd, Nb, Rh
• Epoxy Resins• Glass fiber• Cu, Pb, Co, Ni, Fe, Cd, Cr• Flame RetardantPVC/PC/ABS
ceramics
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• Low cost and effectiveness to dissolve noble metals.
4Au + 8(CN)- → 4Au(CN)2-
• Au > Ag > Pd > Rh
• [CN]-, dp, t
• Cyanicide (Cu)
Cyanidation
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• The elements from the group of Platinum (Pd, Rh) are soluble in mineral acids
Pd + 2HNO3 → Pd(NO3)2 + 2H-
Pd + H2SO4 → Pd(SO4) + 2H-
• With HNO3 and H2SO4 the
dissolution is slow.
• Nd y Rh are dissolved with difficulty
• Presence of Cl- ion benefits the dissolution ofPd
Acid Leaching
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1000 ºC1h
0,5 g30 ml Aqua Regia
Ta – 850ºC
3 h 0,72 atm 21% O2
960 ºC 1h
Samples Characterization
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Electronic Microscope MEB-EDX
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Metal Concentration Average
Au 244 - 857 g/t 421 g/t
Ag 520 - 2901 g/t 1355 g/t
Pd 68 - 80 g/t 74 g/t
Rh 44 - 54 g/t 49 g/t
Nb 5 – 40 g/t 15 g/t
Cu 10 - 43 % 29%
Chemical Characterization
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muestra 72Fecha:7/27/2010 6:21:10 PMTamaño de imagen:384 x 384Aum:500xHV:20.0kV
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1 2 3 4 5 6 7 8 9keV
0
2
4
6
8
10
12
14
cps/eV
Ag Ag Ag Au Au Au Au
Nb Nb
Nb
dore 1 Fecha:7/27/2010 6:10:37 PM HV:20.0kV D. imp.:8.17kcps El AN Series unn. C norm. C Atom. C Error [wt.%] [wt.%] [at.%] [wt.%] -------------------------------------------- Ag 47 L-series 57.74 67.14 77.49 1.8 Au 79 M-series 26.14 30.40 19.21 1.0 Nb 41 L-series 2.11 2.46 3.30 0.1 -------------------------------------------- Total: 85.99 100.00 100.00
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Cyanidation
• Preliminary Treatments
• Parameter Definition ([NaCN], t)
• Size reduction
• Roasting
• Leaching NH3 / HNO3
Acid Leaching
• Preliminary Treatments
• Parameter Definition (Concentration, t)
• Size reduction
• Roasting
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[NaCN] 2 g/L
Time 24 h
pH 10,5
% Solids 2,5-5%
Stirring 500 rpm
4x4 cm1x1 cm7x7 mm5x5 mm
1000 m
136 m
Size reduction, roasting and cyanidation
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Influence of roasting and size reduction in the gold and silver cyanidation
[NaCN] 2 g/L; solids 2,5-5%, time24 hours
0
20
40
60
80
100
100 1 000 10 000 100 000
Recovery o
f m
eta
ls i
n s
olu
tion
(%
)
Particle size (µm)
Au Roasted Sample Ag Roasted Sample
Au Not Roasted Sample Ag Not Roasted Sample
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0 1 2 3 4 5 6 7 8 90
20
40
60
80
100
Au Ag
Concentration of NaCN (g/L)
Me
tal
Re
co
ve
ry i
n s
olu
tio
n
(%)
Influence of the concentration of cyanide in gold and silver recovery
Roasted sample; d80 136 m; solids 2,5-5%, time 24 hours
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Influence of cyanidation time in the gold and silver recovery
0 5 10 15 20 25 30 35 40 45 500
20
40
60
80
100
Au Ag
Cyanidation time(h)
Me
tal
Re
co
ve
ry i
n s
olu
tio
n
(%)
Roasted sample; d80 136 m; solids 2,5-5%, [NaCN] 4 g/L
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NH3 (v/v) HNO3 (v/v)
9,7 % 19,5 %16,7 % 33,3 %
14 % Solids
2 h
500 rpm
Preliminary treantments: Leaching NH3 / HNO3
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Influence of pretreatments with NH3
and HNO3
NH3 (16,7%) HNO3 (33,3%)0
20
40
60
80
100
Cu Disuelto (%)Au Recuperado por cianuración (%)Ag Recuperada por cianuración (%)
Roasted sample d80 136 m; Pretreatment time 2h
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Concentration HNO3
35 g/L
ConcentrationH2SO4
35 g/L
Time 1 a 6 h
% Solids 2,5 - 5
Stirring speed. 500 rpm
Acid Leaching
Concentration NaCl 0,1 M
Concentration H2SO4
60% w/w
Time 1 a 6 h
% Solids 8
Stirring speed 500 rpm
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Kinetics of paladium leaching
0 1 2 3 4 5 6 70
20
40
60
80
100
Pd con H2SO4 Pd con HNO3
Time (h)
Me
tal
Re
co
ve
ry i
n s
olu
tio
n (
%)
Roasted sample; d80 136 m; solids 2,5-5%, [acid] 50 g/L
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Effects of chloride ions in the leaching of paladium with sulfuric acid
0 1 2 3 4 5 6 70
20
40
60
80
100
H2SO4 (60% v/v) y NaCl (0,1M)H2SO4 50[g/L]
Time (h)Rec
ove
ry o
f P
d i
n s
olu
tio
n (
%)
Roasted sample; d80 136 m
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Leaching HNO3
Filtering Electrowinning
Electrowinning
Elution
Scrubber
Dismantling
Roasting
Milling
Leachinf NH3
Filtering
Cyanidation
CIP
Filering
Discarded Cellphones
Printed circuit board
Solid Waste
Gases to atmosphere
Ammonia liquor
Cyanide liquor
Cases, keyboards, Screens
Charged Carbon
Au, Ag Ag, Pd
Acid liquor
Gases
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• It is factible to recover 85% Au , 80% Ag, 80% Pd y 80% Cu by installing a treatment plant of 195 kg/month for the printed circuit boards of discarted cellphones
• Nb y Rh couldn`t be recovered
Conclusions
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Economic criteria
Capacity 195 kg/month
Investment USD 63400
VAN USD 12 679
TIR 18%
Investment recovery
5 years
C/B 1.5
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RECOVERY OF PRECIOUS METALS FROM DESCARTED
CELLPHONESE. de la Torre , S. Espinosa, A. Guevara
ESCUELA POLITÉCNICA NACIONALQuito - Ecuador
Faculty of Chemical Engineering and Agroindustry
Department of Extractive Metallurgy