Content evaluation of different waste PCBs to enhance basic metals recycling

Abstract

This research aims to expand the body of information that researchers require before starting electronic waste (E-waste) recovery experiments. With this purpose, the basic metal contents, alkalinity, polymer components, iron magnetic separation, metal recovery priority and economic values of different types of waste printed circuit boards (PCBs) were investigated. The selected wastes were computer PCBs (CPCBs), CPCBs with wires, mobile phone PCBs (MPPCBs), television PCBs (TVPCBs), fax machine PCBs (FPCBs), copy machine PCBs (COPCBs) and central processing units (CPUs). These E-wastes were prepared in the three fraction sizes of F1<1 mm, 1 < F2<3 mm, and 3 < F3<8 mm to evaluate the metal contents of different PCB fractions. The plastics of some samples were separated through the shaking table method. Magnetic separation of the iron particles attributed the highest amounts of separated iron to the CPCBs (84%) and MPPCBs (76%). Among the investigated E-wastes, the TVPCBs and CPCBs had the highest percentages of plastic (68 and 57%, respectively). Fourier transform infrared (FTIR) spectroscopy declared the presence of polyphenylene oxide (PPO) and polycarbonate (PC) in all evaluated PCBs. The highest quantities of Cu, Ag, Ni and Ti corresponded to the F1 fraction for all E-waste samples while the economic values of the E-wastes were as follows: CPU > FPCBs > MPPCBs > COPCBs > TVPCBs > CPCBs. Accordingly, FPCBs and COPCBs were determined as the high value E-wastes for metal recovery. In addition, Cu, Ag and Sn respectively were found to be the most economic basic metals that should be recovered from most PCBs. Finally, pH analysis of the samples demonstrated that E-waste alkalinity is due to the presence of alkaline metals not plastics.