URBAN MINING
How to Recycle Precious Metals Gold and Silver from Electronic Waste
By:
AA.Sandy,ST
Published by
AA.Sandy,ST at Smashwords.com
Smashwords Edition, License notes
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Content
Chapter 1 Precious Metals in Industrial Application
Chapter 2 Important Issues For Consideration in Recycling
Chapter 3 Building The Project
Chapter 4 Operational Stages
Chapter 5 Precious Metals in Electronic Waste
Step by Step How to Recycle Precious Metals Gold and Silver from Electronic Waste
Chapter 1
Precious Metals in Industrial Application
Gold plays an increasingly important role in industrial applications, particularly in electronics, despite its larger use in jewellery and investment products. As the annual statistics show (Gold Survey 2010, GFMS Ltd, London), some 300t or more of gold are used annually in electronic components such as ICs,contacts and circuitry, the latter notably as gold bonding wire.
Sales growth of electronic devices continues to boom and their in-built features continue to become ‘smarter and quicker’ each year, which has led to a substantial net increase in gold demand over recent years, even though specific gold content is being driven down due to thrifting and miniaturisation.
At the end of their use, electronic and other electrical product scrap offer an important recycling potential for the secondary supply of gold into the market. With gold concentrations reaching 300-350 g/t for mobile phone handsets and 200-250 g/t for computer circuit boards, this scrap is an ‘urban mine’ that is significantly richer in gold than the sources of the primary ores today. However, as a forthcoming paper points out, the ‘mineralology’of such scrap products is very different to those of primary ores. Such scrap contains up to 60 different chemical elements that are intimately interlinked in complex assemblies and sub-assemblies.
They are usually associated with organic materials that often incorporate halogenated flame retardants. Thus, specialised metallurgical processes with extensive offgas treatments are required to recover the gold and a wide range of other valuable metals in a cost-effective and environmentally sound way. Equally importantly, the collection of such scrap from millions of households and businesses requires organised logistics to collect and bring the scrap to the recovery and refining facilities; this is undoubtedly a bigger challenge than the primary ore supply chain.
Gold’s Importance to The Economics of Recovery
Recovery of gold and other valuable metals from such scrap involves a complex metallurgical flowsheet and requires state-of-the-art recovery technologies that are available in large-scale, integrated smelter-refinery operations. At the Umicore plant in Belgium,for example, pure gold and 16 other metals are recovered with high yields. Perhaps what is not adequately appreciated is that the recovery of gold is important to the economics of recycling electronic scrap. It is the gold that makes the recovery of all the valuable metals economically worthwhile.
Thus a ‘design for recycling’ approach to the use of gold in electronic equipment assumes an importance when material choices are being made by OEMs; simply seeking use of cheaper alternative materials as substitutes for gold can damage the economics of recycling devices at the end of their life. One needs to take the complete life cycle costs into account at the design stage.
The European Directive on Waste Electronic and Electrical Equipment (WEEE) aims to provide a ‘closed loop’ economy, that is, to foster environmentally sound reuse and recycling, and to preserve natural resources. This is about sustainability of resources.
However, in Europe and elsewhere, there are currently severe deficits in the recycling chain that hinder the achievement of a high overall recovery rate of gold and other metals. This is due in part to substandard processing of scrap in many ‘backyard’ recycling operations, often through the illegal and dubious export of end-of-life electronics to many developing/transition countries around the world. There is also an environmental impact, as discussed below. We should also note that recycling of WEEE in the EU and elsewhere has become a legal requirement.