Copper and zinc extraction from automobile shredder residues via an integrated electrodeposition and crystallization process

Automobile shredder residues (ASR) are produced during recycling processes from used cars and contain valuable metals such as copper and zinc. They constitute the fastest-growing industrial waste around the globe. Most of the produced ASR is thermally converted or ends up landfilled. With the increasing demand for valuable metals, the recovery of metals from ASR may serve as an alternative source for primary mining. Here we introduce an integrated metal recovery system combining leaching of metals from the target ASR waste using an ammonia lixiviant with electrodeposition, ammonia stripping, and crystallization to selectively recover copper and zinc as well as ammonia from ASR waste. The metals were first leached from the target ASR waste with an ammonia lixiviant. The obtained alkaline leachate (pH 9.6) was subsequently treated by electrodeposition, reaching a removal efficiency of 95.2 % for copper at a coulombic efficiency of 19.2 % and energy input of 12.4 kWh kg −1 Cu over 183 h. The further alkalization allowed for ammonia stripping, recovering 66.1 % of the ammonium as lixiviant at a temperature of 60°C. Final crystallization of zinc from the stripper effluent by continuous flushing of CO 2 resulted in the recovery of 43.2 % as solid ZnCO 3 at a neutral pH. Lixiviation was also performed using the treated effluent and recovered ammonia, and the same amount of copper was leached out from the residues showing full circularity of the lixiviant. This integrated system combining lixiviation, electrodeposition, ammonium stripping, and crystallization units is driven by electricity, with minimal input of chemicals and water.