Printed Circuit Boards Recycling: Characterization of Granulometric Fractions from Shredding Process

Abstract

In electronic appliances, printed circuit boards (PCB) represent an important component, containing high grade of valuable metals, besides organic resins and some ceramic materials. Copper is the major metal in PBC’s composition (normally higher than 20% w/w) but many other secondary and minor metal elements, including precious metals, are found in PCB’s. Recycling of PCB´s involves firstly the shredding operation, which is crucial in order to liberate particles from different materials, allowing its further processing by other mechanical, physical and chemical technologies. An efficient shredding operation is difficult to achieve due to the high heterogeneity of these wastes involving materials with different mechanical properties and complex assemblies. This paper presents results from laboratorial studies of shredding of PCB’s and the evaluation of size reduction efficiency as well as the chemical characterization of the obtained shredded fractions. Results showed that an efficient size reduction (characteristic average diameter d50=1.0mm) is obtained using two shredding stages of PCB’s, the first one with a grab shredder and the second one with a cutting mill. Chemical analysis of shredded PCB’s indicated that copper is the principal metal present (28%) followed by Sn, Zn, Pb and Al (3-5%) and many other minor elements. The fine fractions were rich in plastic materials while the metals were essentially present in the intermediate fractions (0.3-1.5 mm). These results can lead to guidelines regarding further design of the physical separation steps in the recycling processes.

Characterization of Printed Circuit Boards for Metal and Energy Recovery after Milling and Mechanical Separation

“… (a) Feldman (1993) [ 13 ]; (b) Menetti et al (1995) [ 14 ]; (c) Iji et al (1997) [ 15 ]; (d) Veit et al (2002) [ 16 ]; (e) Zhao et al (2004) [ 17 ]; (f) Kim et al (2004) [ 18 ]; (g) Wang et al (2005) [ 19 ]; (h) Creamer et al (2006) [ 20 ]; (i) Marco et al (2008) [ 21 ]; (j) Hino et al (2009) [ 2 ]; (k) Das et al (2009) [ 22 ]; (l) Yoo et al (2009) [ 23 ]; (m) Oliveira et al (2010) [ 4 ]. …”

“…In Europe, 7 million tons of electronic waste is generated annually, and this figure is estimated to be increasing at 3%–5% a year [ 4 ].…”

Study and optimisation of copper bioleaching process for electronic waste valorisation

“…Chapter 9: Column bioleaching to recover copper from e-waste found that the higher the particle size, the lower the copper concentration, but they performed the experiments until 3 mm. Therefore, the results found in this work are in accordance to Oliveira et al (2010) in this range size but this work demonstrated that this affirmation was not correct when higher particle size are analysed. For this reason, it is important to analyse the copper content of the particle size used in each experiments for non-erroneous conclusions.…”

“…Chapter 9: Column bioleaching to recover copper from e-waste Despite the heterogeneity of the PCBs mentioned above, Oliveira et al (2010) demonstrated that the metal distribution also depends on the particle size fraction. In particular, they concluded that the major elements such as copper, tin and lead had higher concentrations in the particle size range of 0.3 and 1.5 mm and they substantially decrease in lower fractions.…”

Waste electrical and electronic equipments as urban mines in Burkina Faso: Characterization and release of metal particles

“…However, Pd was very concentrated in the [1.4-1.0] mm class with up to 70 % for this metal. Oliveira et al (2010) showed that gold (Au) distribution in granulometric fractions of ground PCBs did not depend on the size portions while silver (Ag) concentration increased when the size of particle portions decreased.…”