Rare Metal Recycling - Applications and Problems with Urban Mines
Metallic resources are roughly divided into either the category of base metals, including iron, aluminum and copper, which are used in great quantities, or noble metals, including gold, silver and platinum. Forty-seven rare metals are present between them.
Problems that metallic resources have in common are that the resources are concentrated at specific locations. Rare metals are extremely prominent. As an example, seventeen metals in the rare earth category are concentrated in China. Likewise, other rare earth metals excluding nickel are concentrated in different regions. Also, a surge in resource prices began around the Lehman Shock. Recycling of rare metals has attracted more attention because of export controls by China in addition to wild ups and downs in prices, particularly rare metals.
Potential applications for rare metals such as nickel and chrome are almost as vast as for base metals. However, this is not actually the case. The amount that is usually used is lower.
Rare metals are rarely used independently in a quantitative sense. In many cases they are used as components in structural alloys, not as a principle material or as another complex compound. They are used for high performance applications, e.g. in high-performance parts to achieve miniaturization and weight savings. They are used in most types of small appliances as well as in automobiles and cameras. Additionally, industrial electronic end products cannot be produced without rare metals.
Although rare metals provide high performance, the quantities used in final products are small. Furthermore, since rare metals are compound materials, the amount used in metallic simple substances is even lower. The concentration of rare metals in waste materials is reduced because various rare metals are accumulated when disposed of. Waste materials including these rare metals are called urban mines.
With a background like this, “The Act on Promotion of Recycling Small Waste Electrical and Electronic Equipment” a.k.a. “the Small House Appliance Recycling Law” (co-managed by the Ministry of the Environment and the Ministry of Economy, Trade and Industry) was enacted. Regarding rare metals, management of toxic substances is crucial, together with recycling. Environmental control concerning the disposal process in extracting rare metals for recycling takes top priority to reduce exposure, leakage and dispersion of toxic substances.
With regards to technological development of rare metal recycling, there is technology based on bio-mineralization of indium, gallium and dysprosium using bio-technology. This technological development takes noble metals into consideration. In addition, to recycle neodymium from a neodymium magnet, there are three technologies at work: dry way, wet way, and molten salt electrolysis. According to the technical reports on these technologies, indium is imperative for liquid crystal television film and neodymium for high performance magnets. They had few uses before these applications. Even today, rare metals like cerium have few applications. However, future technological development will potentially require metals such as these for high-performance parts.
Recycling of rare metals seems to have just started, both legally and technologically. We expect future research development to yield practical recycling applications. Furthermore, regarding the recycling of rare metals, metals without abundant applications are also studied and comprehensive utilization of rare metals and the establishment of a recycling framework are required.