Vol.:(0123456789) 1 3 Waste and Biomass Valorization https://doi.org/10.1007/s12649-019-00780-0 ORIGINAL PAPER An Alkaline Glycine‑Based Leach Process of Base and Precious Metals from Powdered Waste Printed Circuit Boards Elsayed A. Oraby 1,2  · Huan Li 1  · Jacobus J. Eksteen 1 Received: 2 April 2019 / Accepted: 6 August 2019 © Springer Nature B.V. 2019 Abstract Electronic waste (E-waste) is accumulating rapidly globally and pose a signifcant environmental challenge. One of the ways to cover the cost of waste processing (in addition to reducing the costs associated with landfll) is through recovery of metals. In addition, toxic and dangerous metals can and must be removed prior to repurposing, incineration or pyrolysis of the plastic substrates. E-waste is usually either transported to landflls or processed by pyrometallurgical and hydrometal- lurgical processes. Recently, a number of hydrometallurgical approaches have been considered in metals recovery from dif- ferent electronic components. In this study, glycine (amino acetic acid) or its salts is considered as a lixiviant in an alkaline environment for base and precious metals recovery from shredded and ground printed circuit boards (PCBs). It was found that alkaline glycine solutions selectively dissolve copper, zinc, and lead over precious metals. Gold and silver were then recovered in a subsequent leaching step using glycine and small amounts of cyanide (at starvation levels, implying no free cyanide is present). The leach system remains alkaline throughout both stages of processing. In the two-stage glycine leach- ing system, gold, silver, zinc, lead and copper recoveries were 92.1%, 85.3%, 98.5%, 89.8%, and 99.1% respectively. The recoveries of precious and base metals by direct cyanidation, single stage glycine–cyanide leaching, and ammonia leaching were lower than the recoveries of these metals using the two-stage glycine and glycine–cyanide systems. Graphic Abstract Flowsheet of a two-stage glycine leaching method for metal extractions from waste PCBs proposed in this study Keywords Glycine · E-waste · Printed circuit boards · Leaching · Metal recovery Statement of Novelty An alkaline glycine leaching system has been evaluated to extract and remove base and precious metals derived from waste printed circuit boards. This leach system has the ben- eft over other alkaline systems such as pure cyanide-based * Jacobus J. Eksteen jacques.eksteen@curtin.edu.au 1 Western Australian School of Mines: Minerals, Energy and Chemical Engineering, Curtin University, GPO Box U1987, Perth, WA 6845, Australia 2 Mining and Metallurgical Engineering, Faculty of Engineering, Assiut University, Assiut, Egypt