Hydrometallurgical Recovery and Process Optimization of Rare Earth Fluorides from Recycled Magnets

Magnets containing substantial quantities of rare earth elements are currently one of the most sought-after commodities because of their strategic importance. Recycling these rare earth magnets after their life span has been identified to be a unique approach for mitigating environmental issues that originate from mining and also for sustaining natural resources. The approach is hydrometallurgical, with leaching and precipitation followed by separation and recovery of neodymium (Nd), praseodymium (Pr) and dysprosium (Dy) in the form of rare earth fluorides (REF) as the final product. The methodology is specifically comprised of sulfuric acid (H2SO4) leaching and ammonium hydroxide (NH4OH) precipitation followed by reacting the filtrate with ammonium bifluoride (NH4F·HF) to yield the REF. Additional filtering also produces ammonium sulfate ((NH4)2SO4) as a byproduct fertilizer. Quantitative and qualitative evaluations by means of XRD, ICP and TGA-DSC to determine decomposition of ammonium jarosite, which is an impurity in the recovery process were performed. Additionally, conditional and response variables were used in a surface-response model to optimize REF production from end-of-life magnets. A REF recovery of 56.2% with a REF purity of 62.4% was found to be optimal.

Low-temperature route to prepare rare earth fluorides in a molten NH4NO3 system: a systematic study on the effects of NaF/Ln ratio and the reaction temperature and time

A low-temperature strategy has been applied to synthesize a host of rare earth fluorides including NaLnF4 and LnF3 (Ln = rare earth) with NaF and rare earth nitrates as initial raw materials in NH4NO3 flux.

A general strategy for the synthesis of rare earth fluoride nano(micro)crystals

A simple, and environmentally friendly method to synthesize rare earth fluorides of REF3 (RE = La, Y), and AREF4 (A = Li, Na, K; RE = La, Gd, Y) nano(micro)crystals via a solvothermal route.