The recycling of materials from waste electric and electronic equipment (WEEE) poses many challenges. Electronic and electrical equipment contains many valuable materials and some harmful substances. The valuable materials include common metals, critical metals and some organics such as plastics.
The valuable elements are those that are only present at low concentrations in minerals or have a profoundly limited supply. These include elements such as gold and platinum group metals. Some of these valuable elements have been listed as critical elements which are needed for key technologies in today´s society. These include the “rare earths” (Lanthanides) needed for the development of environmentally friendly energy systems, such as the neodymium magnets used in electric vehicle motors and wind mill turbines.
Another challenging substance is the cobalt and other metals which are used in many types of batteries. While cobalt might be only a “base metal”, the metals required for use in batteries and some electrical / electronic systems must have a very high purity. For example, the electrical conductivity of copper is very sensitive to the presence of impurity metals. For the efficient electrical power distribution system needed by modern railways and by the rest of society a large amount of high quality copper wire is required since a large fraction of the power distribution system uses copper wire.
Even the recycling of base metals requires care since the presence of impurities can compromise the functionality of the material the metals are used in. One example is the presence of copper in recycled steel which has a harmful effect on the mechanical properties of the steel. During the recycling of WEEE it is very easy for components containing both copper wire and ferromagnetic materials to cause contamination of the steel with copper. These components include motors, transformers, electromagnets and many transducers. Within IMR we have the pyrometallurgical and hydrometallurgical skills which allow us to develop methods that avoid such problems.
The research on recycling methods for materials in WEEE at the group Industrial Materials Recycling (IMR) covers the materials mentioned above but also many more. Hydrometallurgical methods give the opportunity to extract important metals with high purity from mixtures of materials. The development of hydrometallurgical methods is a central area in the research. These methods are based on a leaching with for example an acid solution followed by extraction of the target elements using specially designed molecules (extractants). Our research covers the whole chain from synthesis of extractants with the desired properties to optimization of industrial separation processes based on commercially available extraction chemicals.
The group has also a significant experience on pyrometallurgical processes and their applications on recycling technologies. The high-temperature processes are used as the main recycling method as well as pre-treatment method before hydrometallurgical processing. The high temperature research in the group focuses on developing direct metal recovery from various waste, pretreatment methods and combustion/pyrolyzing of organics from waste streams.
Our research includes also the development of reagents, conditions and methods for the future recycling methods. One example is the development of selective dissolution and separation using supercritical CO2 where the IMR group is unique in the Nordic countries using this method for dissolution and recycling of batteries and WEEE-fractions. We work to obtain a deep understanding of the behavior and form of atoms and molecules in both waste and at each stage of the separation processes which are needed in recycling. We are also working towards a greater understanding of greener solvents (ionic liquids and deep eutectic solvents) and their possible utilization in recycling processes with lower carbon footprint that those used today.
We also investigate possible methods to produce new technical materials directly from the recycled material fractions. One method that is used for doing this is spray pyrolysis where a dissolved material is used to produce small particles of a metal or a metal compound.
Examples of research on special materials in waste electronics:
The most effective, modern, permanent magnets are based on the rare earth elements Neodymium, Praseodymium and others. These magnets are used in modern technology applications, like in hard discs, motors in electric vehicles and in wind mill turbine generators. Recycling methods based on leaching and metal separation has been shown to give good results. The rare earth elements and other metals can be recovered from the magnets in fractions that are pure enough to be reused in new magnets.
The results have been published in two PhD theses and several journal papers.
Marino Gergoric’s PhD.
Mikhail Tyumentsev’s PhD.
Leaching and recovery of rare-earth elements from neodymium magnet waste using organic acids
Separation of Heavy Rare-Earth Elements from Light Rare-Earth Elements Via Solvent Extraction from a Neodymium Magnet Leachate and the Effects of Diluents
Characterization and Leaching of Neodymium Magnet Waste and Solvent Extraction of the Rare-Earth Elements Using TODGA
Reclaiming rare earth elements from end-of-life products: A review of the perspectives for urban mining using hydrometallurgical unit operations
This research can have impacts outside WEEE recycling. The work of Mikhail Tyumentsev offers a new insight into the separation of f block elements (lanthanides and actinides) by solvent extraction using the greener European malonamide based processes. The European DIAMEX process competes with the American TRUEX and the Chinese TRPO processes. However, the secondary waste from the DIAMEX process will pose a smaller burden than either of the TRUEX or TRPO processes.
A net of metallic conductors on the surfaces of solar panels is needed in order to reduce their resistance. Silver particles in a paste is commonly used and applied by screen printing to produce these conductors. The cost of the silver is a significant part of the cost of the entire module. The possibility to replace silver with another metal is being investigated but there are challenges to be handled before a new technology is in place. Until then the availability of silver, and the reserves of silver in the earths crust is an important factor that can hinder the expansion of the photovoltaic energy production. Recycling of the silver from end-of-use solar panels and from production waste is necessary to make sure that solar power can be an important part of the energy system.
The IMR group has developed a method that makes it possible to recover silver from waste solar panels and to re-create silver particles that can be used in new silver paste for screen printing. The work has been funded by SIP Re:Source.
The IMR group is continuing the work on recycling methods for different types of solar modules in collaboration with Prof. Meng Tao at School of Electrical, Computer and Energy Engineering, Arizona State University.
LCD screens and fluorescent lamps
LCD screens contain indium in the transparent electrode film on the LCD glass and rare earth elements in the fluorescent lamps included in the screens. Both indium and rare earths are valuable elements and recycling methods are needed. Alternative recycling methods based on hydrometallurgy were studied in a PhD project. A process for recovery of indium and rare earth elements was developed in laboratory scale and published in a thesis.
Fluorescent lamps are in common use since they are efficient and energy saving. The technology is based on the use of rare earth elements, yttrium, lantanum, cerium, europium, gadolinium and terbium. Mixes of these metals and their oxides are used in the fluorescence powder that gives red, green and blue color to the light. Recycling methods for these metals from waste fluorescent lamps have been developed and published in a PhD thesis.
The traditional technology for refrigeration is based on the reversable evaporation and condensation of a gas. This technology has been associated with health, safety and environmental issues. As a safer alternative the freons such as (Freon-12 dichlorodifluoromethane) were developed and these were widely used in refrigeration and other applications until it was recognized that they cause serious damage to the ozone layer. The later generation (ozone friendly freons) of halogenated refrigerants such as freon-134a (1,2,2,2-tetrafluoroethane) were used in food preservation, air conditioning and asthma inhalers. Now even these ozone friendly freons are being phased out as they have great global warming potentials so there is a need to move to a totally different heat pumping system.
The magnetocaloric effect offers means of creating a fluid free refrigerator. It gives better cooling effect which means that the devices can be made smaller and, in addition, it gives less emissions of carbon dioxide than the present technology. Magnetocaloric materials based on rare earth metals among others are presently being developed. Since the availability of these elements is critical, recycling methods for these new magnetocaloric materials need to be developed to make sure that their use can be sustainable.
The IMR group has developed hydrometallurgical methods to recover the components in a magnetocaloric material, i.e. an alloy consisting of cerium, iron, lantanum, manganese and silicon. The results have been published in Journal of Cleaner Production.
Professor Christian Ekberg
Professor Britt-Marie Steenari
Professor Teodora Retegan
Docent Martina Petranikova
Researcher Burcak Ebin
Docent Mark Foreman