Hydrometallurgical processing of waste printed circuit boards for - - PDF document

Hydrometallurgical processing of waste printed circuit boards for Cu, Au and Ag recovery

Ionela Birloaga - University of L’Aquila, Italy Ida De Michelis - EcoRecycling Bernd Kopacek - Austrian Society for Systems Engineering and Automation, Austria Francesco Vegliò - University of L’Aquila, Italy

HIGH TECH RECYCLING INTER-UNIVERSITY RESEARCH CENTER

Outline

Introduction Waste Printed Circuit Boards (WPCBs) Hydrometallurgical process Block diagram Cu recovery Au and Ag recovery Waste water treatment Next steps

Introduction

The WEEE Directive 2002/96/EC was revised by the European Commission and, as result, the new Directive 2012/19/EU was

• introduced. By this the following collection targets have been

introduced: 45% of the sold electronic equipments (starting with 2016); 65% of the sold electronic equipments or 85% of e-wastes generated(starting with 2019). Most of all electronic components present in their structure printed circuit boards (PCB)

Current recycling technologies

Mechanical - Physical

Incomplete separation of elements - pretreatment

Pyrometallurgy Hydrometallurgy Biometallurgy Ionometallurgy

High capital cost; loss of byproducts in slags and residues Presents more flexibility during the upscaling and control processes In the incipient phase In early stage and relatively high cost of reagents

WPCBs Characterization for recycling

• More than 10% of worldwide reserve of Au is used in the

manufacturing of electronic devices.

• Depending on their gold content, the WPCBs are divided into

three categories, namely:

• high grade (>200 mg/kg)
• medium grade (100<200 mg/kg)
• low grade (<100 mg/kg)

Economic drivers in WPCBs treatment (Wang and Gaustad, Waste Management, 32 (2012))

WPCBs Structure and their electronic components analysis

1 Al electrolytic capacitors 2 Heat sink- Al 3 Black panel - Steel, plastic and pins (Cu, Au, Al) 4 Inductors - Cu and ferrite 5 Quartz resonators 6 Battery 7 Multi-layer ceramic capacitors (MLCC) (Ag- 9.5 g/kg; Pd - 1.02g/kg; Nb – 13.29%; Ta – 0.49%) 8 Tantalum ceramic capacitors (Ag – 1 %; Ta – 20%) 9 IC chips (Ag – 1 g/kg; Au – 890 mg/kg; Pd – 15 mg/kg)

Hydrometallurgical process Block diagram

Motherboard with mounted components Removal of a part of Al base components Milling to a particle size of <1mm Cu Zn Al Fe Sn Pb Ni Ag Au Pd % (wt./wt.) mg/kg 20.84 2.79 4.57 2.39 5.11 2.78 0.22 689 306 42 Chemical analysis of WPCBs sample

Preparation and characterization

• f the WPCBs sample

Recovery of Cu

Oxidative leaching process

Cu + H2SO4 + H2O2 = CuSO4 + 2H2O

Cu recovery >98% are observed at lab scale

Cementation with Zn metal powder

Au and Ag recovery

Thioureation process

2Au + Fe2(SO4)3 + 4SC (NH2)2 = [Au (SC (NH2)2)2]2SO4 + 2FeSO4 2Ag + Fe2(SO4)3 + 6SC (NH2)2 + SO2-

4 = [Ag (SC (NH2)2)3]2SO4 + 2FeSO4

Neutralization with sodium hydroxide and cementation with Zn metal powder

[Au(SC(NH2)2)2]2SO4 + Zn → 2Au + 4CS(NH2)2 + ZnSO4 [Ag(SC(NH2)2)3]2SO4 + Zn → 2Ag + 6CS(NH2)2 + ZnSO4 Gold and silver complete precipitation with NaOH at pH 2 and cementation with Zn

Waste water treatment

Parameter Unit of measure Initial conditions After Fenton treatment Final treatment with Ca(OH)2

• Leg. It.

pH 2.5 1.9 10 5.5-9.5 TDS g/L 51 28.82 SST g/L 2.6 COD mg/L 11600 2057 520 500 Abatement

• f COD

% 74 94 94 SO4

• 2

g/L 54 45.72 18.62 Abatement

• f SO4
• 2

% 40.72 40.72

Fenton process

Fe2+ + H2O2 → Fe3+ + OH• + OH OH• + Fe2+ → OH− + Fe3+

Next steps

Recovery of other valuable elements (on progress) for a better sustainability of the process Improve of purity level of the outputs Mobile plant tests