Recycling of electronic waste for the recovery of value-added materials

Electronic waste (e-waste) is one of the fastest increasing waste streams worldwide due to unprecedented growth of the electronics industry, rapid obsolescence and subsequent disposal of electronic devices. Printed circuit boards (PCBs), the central component of electronic devices, are highly complex. PCBs are an important resource of metals, and contain substantial amounts of copper, tin, lead and precious metals in concentrations considerably higher than in their ores. The high value and limited reserves of minerals containing these metals makes their urban mining from waste PCBs very attractive. However, these also contained significant quantities of hazardous and toxic materials, which can result in high levels of pollution when such waste is landfilled or processed inappropriately. Research presented in this thesis is focused on developing a novel approach to recover metals and other valuable resources from waste PCBs. High temperature pyrolysis was carried out on waste PCBs in a horizontal tube furnace in the temperature range 750°C–1350°C under Argon atmosphere. Samples were placed in the cold zone of the furnace for 10 minutes to avoid thermal shock, then exposed to high temperatures for up to 20 minutes, and were quenched. This process resulted in the phase separation of solid products into a carbonaceous fraction (NMF) and a metallic phase, composed of copper rich sheets/droplets and tin-lead rich droplets and some wires. Significant proportions of Ag, Au, Pd and Pt were found to be concentrated within the metallic phases; very limited quantities of precious metals were observed in carbons and oxides in NMFs. Inert atmosphere prevented the re-oxidation of metals and loss of carbon in the gaseous fraction. High temperature pyrolysis was successful in recovering copper based alloys and carbon resources, and concentrated precious metals from e-waste. This approach also reduced the volume of material for further processing and management; minimal amounts of secondary wastes were produced. Recycling e-waste is expected to lead to enhance metal recovery, conserve natural resources and provide an environmentally sustainable solution to waste management