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Stellan Holgersson, Britt M Steenari, Max Björkman, and Klas Cullbrand (2018)

Analysis of the metal content of small-size Waste Electric and Electronic Equipment (WEEE) printed circuit boards—part 1: Internet routers, mobile phones and smartphones

Resources, Conservation and Recycling, 133:300-308.

The metal content of printed circuit boards from three types of Waste Electric and Electronic Equipment (WEEE) products were analysed. The products disassembled to retrieve the printed circuit boards (PCBs) were 10 Internet routers, modems and hubs; 30 mobile phones; and 30 smartphones. The collected boards of each product type were milled to 2–3 mm fractions, cryo-milled further and then leached with aqua regia. Leaching solutions were analysed for Ag, Al, As, Au, Be, Bi, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Pd, Pt, Rh, Sb, Sn and Zn. The leaching residues were pyrolysed, fused with LiBO2 and analysed for Al, Ba, Be, Ca, Co, Cr, Fe, K, Mg, Mn, Mo, Na, Nb, P, Sc, Si, Sr, Ti, V, W, Y, Zr and Zn. The results gave a PCB weight of the total product weight of 43% for the routers and 21% for the two phone types. The main constituents of the PCBs were carbon polymers with a concentration of 34%, 30% and 25% for routers, mobile phones and smartphones, respectively and Cu, with a concentration of 22%, 34% and 40% for routers, mobile phones and smartphones, respectively. The concentrations of precious metals, Ag, Au and Pd, in PCBs were found to be 1213 ppm, 199 ppm and 20 ppm for the routers; 2640 ppm, 1051 ppm and 119 ppm for mobile phones; and 2773 ppm, 1083 ppm and 55 ppm for the smartphones, respectively. The concentrations of toxic metals, As, Be, Cr and Pb, in the PCBs were <70 ppm, 0.3 ppm, 506 ppm and 3413 ppm for routers; 93 ppm, 99 ppm, 953 ppm and 3747 ppm for mobile phones; and 141 ppm, 115 ppm, 1306 ppm and 260 ppm for smartphones, respectively. The results demonstrate that for toxic metals, the Pb content is lower in more modern smartphones compared with older mobile phones while the content of other toxic metals are fairly constant. For the routers, the Pb content was similar to the mobile phones, despite the later production year span (2004–2010) compared with the mobile phones (1999–2010). Regarding precious metals the contents of Ag and Au remain at same level when comparing older mobile phones with newer smartphones. Internet routers, modems and hubs are shown to also be a potential source for precious metals, with comparable concentrations to the two phone types if the total product weight is considered.

Aqua regia leaching, Metal concentration, Printed circuit boards, Waste Electric and Electronic Equipment

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