Recycling and Sustainable Utilization of Precious and Specialty Metals

Abstract

There is urgent need for more effective recycling of Earth's technology metal supply. Precious and specialty metals that constitute this supply are essential components of clean tech applications, high-tech electronic devices, and other products that are vital to the global economy. These metals form integral parts of a wide variety of products making recycling a complex process. Collection of end-of-life (EoL) products and pre-conditioning them for recovery of target metals are important first steps in the recycling process, followed by metallurgical and chemical processes indispensable for generating pure metals fit for reuse in another product cycle. Successful achievements have been made in precious metal recovery using integrated smelter and advanced refining technologies. Recycling of metals is very efficient for industrial applications in closed cycles, such as recovery of platinum group metals from process catalysts used in the chemical industry. Recovery of precious metals in open cycles typical in most consumer applications is more challenging. Although at the metallurgical refining stage very efficient recovery processes with high metal yields are well established, the complex structures and procedures used to collect and precondition EoL consumer products currently lead to significant losses. Recycling works relatively well for autocatalytic converters, while recovery of precious and specialty metals from electronic waste, such as computers, cell phones, or TVs still offers a huge improvement potential. Collection rates are low, and a significant share of EoL electronics from North America and other industrialized countries finally ends up, often illegally, in inefficient and environmentally harmful informal recycling operations in non-Organization for Economic Cooperation and Development (OECD) nations. The amount of e-waste generated globally is estimated to be 30-50 million tons annually, but it needs to be understood that only a fraction of this is relevant for the recycling of precious and specialty metals, namely electronics such as information and communication technology (ICT)-equipment and audio and video devices. White goods as well as electric household products, such as vacuum cleaners, toasters or electric tools are of importance for the recycling of steel, base metals (e.g., Cu) and plastics but contain very small amounts of precious and specialty metals. Only a fraction of the total e-waste is currently properly recycled. Globally, most e-waste is discarded into landfill or open dumps, incinerated, or stored. Even formal recycling in industrialized countries often bears large improvement potential, especially in the sorting and preconditioning steps. Recycling of technology metals holds many benefits for society including conservation of a valuable resource; reduction of the environmental burden of mining that, otherwise, would be required to replace the lost metal; and metal supply security. E-waste products, when collected, contain appreciable amounts of technology metals. Recovery of these metals from such an urban mine is appealing because some metals occur usually in much higher concentrations than in virgin ore bodies. However, the elemental composition of electronic devices can be very complex, comprising over 40 chemical elements in combinations not existing in geological deposits, and also including many organic substances (plastics, halogenated flame retardants, resins). It is impossible to recover all metals from such complex mixes, and hence choices need to be made and the rules of thermodynamics determine the limits of even the most advanced processes. The principal challenge is to recover as much of the valuable substances as is technically and economically feasible while ensuring that toxic elements are well controlled and no harmful emissions into air, effluents, or soil result from the recycling process itself. It is essential that various stakeholders become aware of the importance of technology metals to global society and of the challenges linked to their proper recycling. These stakeholders need to become partners in preserving these metals, which are essential to the continuation of domestic, commercial, industrial, and military activities world-wide.