Process optimization for acidic leaching of rare earth elements (REE) from waste electrical and electronic equipment (WEEE)

E-waste (EW) from discarded electrical and electronic devices is a potential source of rare earth elements (REEs) that might be recovered from urban and industrial wastes. REEs are essential raw materials for emerging and high technologies. China currently dominates global REE production with a proportion of 97%. To increase the independence of REE supply and eliminate the environmental impacts related to REE mining, methods for an efficient REE recovery from secondary sources like EW are needed. In this work, we examine improvements in pre-treatment and acidic leaching processes to recover REEs and other valuable metals. EW was crushed and ground prior to the sieving. The materials obtained were then subjected to acid leaching. The parameters used to optimize the conditions for leaching were as follows: acid type (HCl, HNO3, and aqua regia), particle size, and waste-to-acid ratio. The maximum leaching efficiency was obtained from the ground, sieved, and undersized part of e-waste by using HCl with a W:A of 12.5 mg/mL. The total REE concentration was 435 mg/kg. Several treatment scenarios are identified with promise for improving REE recovery at full scale in EW recovery plants and thereby advancing goals for a sustainable, circular economy.