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ESCUELA POLITÉCNICA NACIONAL Quito - Ecuador Faculty of Chemical Engineering and Agroindustry Department of Extractive Metallurgy
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Pb Co Ni Cd Cr
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Au, Ag, Pd, Nb, Rh Epoxy Resins Glass fiber Cu, Pb, Co, Ni, Fe, Cd, Cr Flame Retardant PVC/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] -, d p, t Cyanicide (Cu) Cyanidation
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The elements from the group of Platinum (Pd, Rh) are soluble in mineral acids Pd + 2HNO 3 → Pd(NO 3 ) 2 + 2H - Pd + H 2 SO 4 → Pd(SO 4 ) + 2H - With HNO 3 and H 2 SO 4 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 ºC 1h 0,5 g 30 ml Aqua Regia T a – 850ºC 3 h 0,72 atm 21% O 2 960 ºC 1h Samples Characterization
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Electronic Microscope MEB-EDX
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MetalConcentrationAverage Au244 - 857 g/t421 g/t Ag520 - 2901 g/t1355 g/t Pd68 - 80 g/t74 g/t Rh44 - 54 g/t49 g/t Nb5 – 40 g/t15 g/t Cu10 - 43 %29% Chemical Characterization
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muestra 72 Fecha:7/27/2010 6:21:10 PM Tamaño de imagen:384 x 384 Aum:500x HV:20.0kV
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Cyanidation Preliminary Treatments Parameter Definition ([NaCN], t)Parameter Definition ([NaCN], t) Size reduction Size reduction Roasting Leaching NH 3 / HNO 3 Leaching NH 3 / HNO 3 Acid Leaching Preliminary Treatments Parameter Definition (Concentration, t)Parameter Definition (Concentration, t) Size reduction Size reduction Roasting
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[NaCN]2 g/L Time24 h pH10,5 % Solids2,5-5% Stirring500 rpm 4x4 cm 1x1 cm 7x7 mm 5x5 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
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Influence of the concentration of cyanide in gold and silver recovery Roasted sample; d 80 136 m; solids 2,5-5%, time 24 hours
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Influence of cyanidation time in the gold and silver recovery Roasted sample; d 80 136 m; solids 2,5-5%, [NaCN] 4 g/L
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NH 3 (v/v)HNO 3 (v/v) 9,7 %19,5 % 16,7 %33,3 % 14 % Solids 2 h 500 rpm Preliminary treantments: Leaching NH 3 / HNO 3
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Influence of pretreatments with NH 3 and HNO 3 Roasted sample d 80 136 m; Pretreatment time 2h
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Concentration HNO 3 35 g/L Concentration H 2 SO 4 35 g/L Time1 a 6 h % Solids2,5 - 5 Stirring speed.500 rpm Acid Leaching Concentration NaCl 0,1 M Concentration H 2 SO 4 60% w/w Time1 a 6 h % Solids8 Stirring speed500 rpm
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Kinetics of paladium leaching Roasted sample; d 80 136 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 Roasted sample; d 80 136 m
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Leaching HNO 3 Filtering Electrowinning Elution Scrubber Dismantling Roasting Milling Leachinf NH 3 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 Capacity195 kg/month InvestmentUSD 63400 VANUSD 12 679 TIR18% Investment recovery 5 years C/B1.5
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ESCUELA POLITÉCNICA NACIONAL Quito - Ecuador Faculty of Chemical Engineering and Agroindustry Department of Extractive Metallurgy
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