Environmentally friendly approach for the recovery of metallic fraction from waste printed circuit boards using pyrolysis and ultrasonication

Abstract

Electronic waste (e-waste) with an annual growth rate of 3–5% is one of the fastest-growing waste streams. The unregulated accumulation and improper recycling can cause grave hazards to human beings and the environment. On the contrary, e-waste can be considered as a secondary source of metals and energy due to its high metal content and polymeric material. Thus, the present study demonstrates technology for the metallic fraction recovery and the production of valuable gases from e-waste. The process involves pyrolysis at a temperature range of 200 °C–600 °C in a fixed bed setup for 10–60 min. Under optimized operating conditions, 35 wt% combustible gases and 60 wt% solid product were obtained at a pyrolysis temperature of 400 °C in 20 min. The gaseous product consisted of CH4, H2, CO and CO2, having the heating value 28 MJ/kg whereas, the solid product is a mixture of metals and other solid residue material. Treatment of the solid product using an ultrasonication process resulted in around 90 wt% recovery of metallic fraction, thereby leaving behind solid residue. Moreover, the transfer of precious metals (Au, Ag, Pd and Pt) was nearly 100% to the metallic fraction. This process combines mild temperature pyrolysis and ultrasonication process to provide a solution for efficient management of e-waste, metallic fraction recovery and valuable gases production.