A hitchhiker’s guide to critical metals

Materials World magazine
,
7 May 2012

Dr Laura Talens Peiró, a Marie Curie IEF Fellow at the INSEAD Social Innovation Centre in France discusses a recovery solution for metals scarcity that could ease supply for the electronics industry.

In 2010, the People’s Republic of China (PRC) temporarily suspended the export of rare earth metals to Japan because of the territorial conflict over Diaoyu, an island in the East China Sea historically disputed between Japan, PRC and Taiwan. This conflict, together with the publication of several reports from the US National Academy of Science, UNEP and European Commission, prompted global discussions about the availability and supply of minerals and metal resources.

Recycling of scarce metals is presently almost non-existent, except for gallium, germanium, platinum and palladium, mainly due to their dissipative applications and low concentrations in electronic wastes. Scarce metals generally end up in the slag of smelter plants or landfills. However, there is one other option and that is to increase the efficiency of by-product recovery of rare ‘hitchhiker’ metals which are distributed as contaminants or trace elements within mineral ores. To increase the output of one of the ‘hitchhiker’ metals it is necessary either to increase the output of the ‘attractor’ metal or to increase the rate of recovery from the attractor’s ore. This situation is particularly critical in regard to the future potential for thin film photovoltaic modules (e.g. copper-indium-diselenide, cadmium-telluride, galliumarsenide or thin film silicon), virtually all of which require one or more hitchhikers.

Improving the recovery from existing mines is an option applicable to all metals, but especially to metals that are produced from ores mined for their content of the attractor metal. It may involve a significant re-engineering of extraction and refining processes that have originally been designed to concentrate and recover ‘attractor’ metals.

Increasing the recycling of hitchhikers from end-products is an attractive option but it requires a detailed study estimating the amount contained in end-products, the time to reach waste management and developing technologies for the recycling of complex products.

Hitchhiker metals provide specific functions that are key for different purposes, from catalysts for petroleum refining to electrical storage materials in batteries and capacitors and additives for glass, ceramics and abrasives.

Electrical and electronic equipment (EEE) contain the highest number of metal products such as printed circuit boards, phosphors, batteries, capacitors, metal alloys and magnets. In emerging EEE, traditional metals such as steel, lead, zinc, copper and nickel are now partially replaced by hitchhiker metals such as rare earths, platinum, gallium and tantalum among others. The starting of the mass production of EEE has increased the demand for traditional metals and no doubt will boost that of hitchhikers.

Recycling critical metals from EEE is attracting attention because although their concentration is low, it is still higher than in mineral ores. For instance, a printed circuit board and a mobile phone contain 40 times more palladium than mineral ores as cooperite. But recycling also poses many challenges. First, and probably the most important, is that the collection rates of EEE remain low. For instance, only 3% of multifunctional mobile phones in Europe are currently collected for recycling.

There are certain types of EEE containing significant amounts of critical metals, for instance laptops or notebooks that never reach legal collection points at their end-of-life, and are illegally exported to developing countries. Tracing the type and the amount of these devices is in order. Collection and recycling rates could improve by making consumers more conscious of the importance of recycling complex products containing hitchhikers and their importance in our economies. From a technological point of view, recycling hitchhikers is difficult because they are disaggregated in different components and impractical, if not impossible, to disassemble – a good example is the printed circuit board.

The recovery of hitchhikers requires advanced technologies that can cope with this limitation, and a design for disassembly and recycling of those products. There is great potential for improving the current efficiency of the whole recycling chain of EEE but only if it is truly considered a real option for the future.