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

Abstract

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.

Sulfuric Acid Leaching of Altered Ilmenite Using Thermal, Mechanical and Chemical Activation

“…There are two main groups of methods for processing ores using fluorine compounds such as the thermal and hydrometallurgical methods [40,41]. The latter is becoming widely used since this method is very prospective due to the possibility of recycling the main components [7,[42][43][44]. Nowadays, hydrometallurgical methods for the processing of various concentrates are at the initial stage of their development [5,6,[45][46][47].…”

Effect of Copolymer Structure on Rare‐Earth‐Element Chelation Thermodynamics

“…can be accomplished using ionic solvents or materials. [6][7][8] One approach for extracting and purifying REEs is to employ polymeric chelators-polymers containing ligands that can selectivity bind REEs in solution-in conjunction with polymer enhanced ultrafiltration (PEUF). [9,10] In PEUF, water-soluble, high-molecular-weight polymer chelators bind to the desired metal ion in solution.…”

Sustainability applications of rare earths from metallurgy, magnetism, catalysis, luminescence to future electrochemical pseudocapacitance energy storage

“…Sarfo et al used a novel hydrometallurgical process to recover rare earth magnet scrap, which consisted of H 2 SO 4 leaching, NH 4 OH precipitation and NH 4 F·HF reaction. 89 The magnet scrap was converted into rare earth fluoride, which was then converted into rare earth metals by high-temperature calcination. The process of this work not only avoids the use of hydrofluoric acid, but also optimizes the process through statistics and modeling to achieve high-purity rare earth resource recovery, which lays a solid foundation for the sustainable development of rare earth magnetic materials.…”