Rare Earths and the Balance Problem: How to Deal with Changing Markets?

The balance between the market demand and the natural abundance of the rare-earth elements (REEs) in ores, often referred to as the Balance Problem (or the Balancing Problem), is a major issue for REE suppliers. The ideal situation is a perfect match between the market demand for and the production of REEs, so that there are no surpluses of any of the REEs. This means that the rare-earth industry must find new uses for REEs that are available in excess and search for substitutes for REEs that have either limited availability or are high in demand. We present an overview of the trends in the applications for the different REEs and show that the demand for REEs for use in magnets, catalysts, and alloys is still increasing, while the application of REEs in polishing agents, glass, and ceramics are stable. On the other hand, the use of REEs in nickel–metal-hydride (NiMH) batteries and lamp phosphors is decreasing. These changes in the REE market have an influence on the Balance Problem, because the REEs that can be recycled from fluorescent lamps, cathode-ray tubes (CRTs), and NiMH batteries have to be at least partly reused in other applications. Magnesium and aluminum alloys offer an opportunity to mitigate the Balance Problem caused by these changes in the REE market. This is illustrated for REEs that can be recycled from fluorescent-lamp phosphor waste, CRT phosphors, and NiMH batteries. At present, five REEs (Nd, Eu, Tb, Dy, and Y) are being considered as very critical by Europe, the United States, and Japan, but we forecast that in the medium term, only neodymium will remain a critical REE. This paper discusses the relationship between criticality and the Balance Problem and shows how this relationship influences the market for specific REEs.This work has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No 680629 (REMAGHIC: New Recovery Processes to produce Rare Earth-Magnesium Alloys of High Performance and Low Cost) (project website: http://www.remaghic-project. eu). KB and PTJ acknowledge funding from the European Community’s Seventh Framework Programme ([FP7/2007–2013]) under Grant Agreement No. 607411 (MC-ITN EREAN: European Rare Earth Magnet Recycling Network) (project website of EREAN: http:// www.erean.eu). Paul McGuiness (Sciencewriter.si, Slovenia) is acknowledged for the drawing of the figures

Metal Recovery from Nickel Metal Hydride Batteries Using Cyanex 923 in Tricaprylylmethylammonium Nitrate from Chloride Aqueous Media

Abstract A flow sheet has been developed for recovery of metals from nickel metal hydride batteries using the neutral extractant Cyanex 923 dissolved in the ionic liquid tricaprylylmethylammonium nitrate, [A336][NO 3 ], and a synthetic chloride-based aqueous leach solution. The process allows purification of nickel in a single step by extracting chloride and nitrate complexes of the extractable transition metals and rare earths. Three selective strip operations utilizing first nitrate, stripping cobalt and manganese, and then chloride complexation, stripping the rare earths, followed by stripping of iron and zinc. Cobalt in the nitrate strip solution was separated from manganese by extraction with the ionic liquid tricaprylylmethylammonium thiocyanate, [A336] [SCN]

Selective ion-exchange separation of scandium(III) over iron(III) by crystalline alpha-zirconium phosphate platelets under acidic conditions

A continuous worldwide increase in scandium (Sc) criticality leads to a quest for secondary scandium resources. Among them, bauxite residue (BR) – a waste product from alumina refineries – often contains substantial amounts of scandium. However, the complexity in BR composition drives the need for developing a selective, efficient and cost-effective process to achieve the separation and purification of scandium. Insoluble salts of tetravalent metal ions are inorganic, acid-resistant ion exchangers with well-established preparation procedures, but their potential use in rare-earth recovery and purification has not been extensively explored yet. Zirconium and titanium phosphates, both in amorphous and α-layered crystalline forms, were screened for Sc(III)/Fe(III) separation, as Fe(III) is one of the base elements in BR that is the most challenging to separate from Sc(III). The studied α-zirconium phosphate (α-ZrP, Zr(HPO4)2·H2O) exhibited the highest Sc(III)/Fe(III) separation factors (up to approximately 23) from HCl solutions. The metal selectivity of α-ZrP was considered to be affected by the solution pH, and the size and hydration enthalpy of the metal cations. Breakthrough curves for a binary Sc(III)/Fe(III) solution, composed of metal concentrations realistic to a typical BR leachate, revealed the selectivity of α-ZrP for Sc(III). Furthermore, chromatographic separation of Sc(III) from a real HCl leachate of BR was successfully achieved on an α-ZrP column. After a two-step elution with HCl about 60 % of Sc(III) was collected in fractions without measurable Fe(III), Al(III) or other rare-earth impurities. Overall, this study highlights the possibility for direct and simplified separation of Sc(III) from a much higher concentration of Fe(III) in BR, without the need of using reducing agents.Peer reviewe