Impact of Ferric and Ferrous Iron on the Crystallization of Rare Earth Sulphate Hydrates
Nitin Pawar, Alexandre Chagnes, Marie Christine Boiron, Michel Cathelineau, Michael Svärd, Kerstin Forsberg
TL;DR
This study explores how iron affects the crystallization of rare earth elements from magnet waste, aiming to improve recovery purity and efficiency.
Contribution
The novel contribution is the investigation of how ferric and ferrous iron influence the crystallization of rare earth sulphate hydrates during recycling.
Findings
Higher crystal purity (above 99%) is achieved with seeding and lower antisolvent dosing rates.
Fe(III) is incorporated into the pure neodymium phase but not the mixed neodymium-dysprosium phase.
Fe(II) forms a separate phase and does not interfere with the rare earth crystal phases.
Abstract
Rare earth elements (REEs) are important for permanent magnets used in for example wind turbines and motors. There is an imbalance in supply and demand of this commodity and the REE have been identified as critical raw materials by the European Union. This study focuses on recovery of REEs from sulfuric acid solutions using antisolvent crystallization in recycling of magnet waste. Ethanol is used as an antisolvent to crystallize Nd2(SO4)3·8H2O and (Nd/Dy)2(SO4)3·8H2O. The impact of the presence of Fe in ferrous and ferric states, and of different seeding strategies, on the quality of the crystal product in terms of purity, crystal size, morphology and agglomeration has been investigated. Higher purity (above 99%) is obtained for seeded experiments and the purity is higher for higher seed loading and lower antisolvent dosing rate. Furthermore, Fe(III) has a higher tendency to be…
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Taxonomy
TopicsExtraction and Separation Processes · Geochemistry and Elemental Analysis · Radioactive element chemistry and processing