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The rare earth elements (REEs) are a group of 17 elements from the lanthanide series including scandium and yttrium that share similar physical and chemical properties. They are progressively important for transition to a green, low-carbon economy due to their vital role in electric cars, permanent magnets, fluorescent lamps, rechargeable NiMH batteries, catalysts and other applications. In reality, the term “rare” is misleading as these elements are widely present in the earth’s crust. However, even if not rare, REEs have a high supply risk due to the geopolitical situation e.g. resulting from limited Chinese exports. This, along with their importance in various clean and high-tech applications, has led the EU and the U.S. to label certain REEs, especially europium, terbium and yttrium as critical elements. Recycling is often considered as one of the ways to reduce REEs criticality, especially the import dependency.
A recycling strategy for REE requires reliable analytical data of different types of waste streams. The REE bearing waste matrices can be completely different depending on its origin. Digestion methods prior to ICP-OES / -MS analysis must be optimized for the different matrices to guarantee reliable results. We present two examples of different REE bearing waste streams - fluorescence lamp shredder waste and red mud - and show how the analytical procedures were optimized.
Leaching tests are fundamental tools for the assessment of long-term impact of contaminated waste materials on the soil-groundwater pathway. Experiments were carried out in the framework of standardization and validation of column percolation and batch test procedures, in particular concerning the stipulation of the experimental setup. The colloid release of column and batch experiments was compared and the influence of different column filling heights (12.5–50 cm) on the release of polycyclic aromatic hydrocarbons (PAH) from soil was studied, as well as the effect of varying contact times (2.5–16 h) on the release of chromium from construction and demolition (C&D) waste and municipal solid waste incineration (MSWI) bottom ash. The results indicate that filtration of the eluate, which is required for batch tests, does not always allow the simulation of the actual colloid amount in soil pore water. Medium column heights four times the inner diameter of the column seemed to provide reasonable equilibrium adjustment conditions and avoid major biodegradation. The release of chromium was only marginally affected by the contact time, varied between 0.115 and 0.150 mg/kg for demolition waste eluate at a liquid-to-solid ratio of approximately 5 L/kg.