Comprehensive process for the recovery of value and critical materials from electronic waste

Abstract

The development of technologies that contribute to the proper disposal and treatment of electronic waste is not just an environmental need, but an opportunity for the recovery and recycle of valuable metals and critical materials. Value elements in electronic waste include gold, palladium, silver, copper, nickel, and rare earth elements. This paper presents a technical assessment of the steps involved in a scheme that enables efficient recovery of value and critical materials from scrap mobile electronics. An electrochemical recovery process, based on the regeneration of ferric ion as a weak oxidizer, is studied for the selective recovery of base metals while leaving precious metals for separate extraction at reduced chemical demand. A separate process recovers rare earth oxides from magnets in electronics. Recovery and extraction efficiencies ca. 90% were obtained for the extraction of base metals from the non-ferromagnetic fraction in the two different solution matrices tested (sulfuric and hydrochloric acid). The effect of the pre-extraction of base metals in the increase of precious metals extraction efficiency was verified. On the other hand, the extraction of rare earths from the ferromagnetic fraction, performed by means of anaerobic extraction in acid media, was assessed for the selective recovery of rare earths. A comprehensive flow sheet was developed to process electronic waste to value products.