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 - PhysicalIncomplete 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

oMore than 10% of worldwide reserve of Au is used in the

manufacturing of electronic devices.

oDepending 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

analysis1 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 componentsMilling 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

of 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

ParameterUnit 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

of COD% 74 9494

SO4-2 g/L 54 45.72 18.62

Abatement

of SO4-2

% 40.7240.72

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