High-Gradient Magnetic Separation of Compact Fluorescent Lamp Phosphors: Elucidation of the Removal Dynamics in a Rotary Permanent Magnet Separator

Abstract

In an ongoing effort towards a more sustainable rare-earth element market, there is a high potential for an efficient recycling of rare-earth elements from end-of-life compact fluorescent lamps by physical separation of the individual phosphors. In this study, we investigate the separation of five fluorescent lamp particles by high-gradient magnetic separation in a rotary permanent magnet separator. We thoroughly characterize the phosphors by ICP-MS, laser diffraction analysis, gas displacement pycnometry, surface area analysis, SQUID-VSM, and Time-Resolved Laser-Induced Fluorescence Spectroscopy. We present a fast and reliable quantification method for mixtures of the investigated phosphors, based on a combination of Time-Resolved Laser-Induced Fluorescence Spectroscopy and parallel factor analysis. With this method, we were able to monitor each phosphors’ removal dynamics in the high-gradient magnetic separator and we estimate that the particles’ removal efficiencies are proportional to (d2·χ)1/3. Finally, we have found that the removed phosphors can readily be recovered easily from the separation cell by backwashing with an intermittent air–water flow. This work should contribute to a better understanding of the phosphors’ separability by high-gradient magnetic separation and can simultaneously be considered to be an important preparation for an upscalable separation process with (bio)functionalized superparamagnetic carriers.

Design of a Magnetic Field-Controlled Chromatography Process for Efficient and Selective Fractionation of Rare Earth Phosphors from End-of-Life Fluorescent Lamps

“…Recent investigations have shown that the removal dynamics of paramagnetic phosphors in an HGMS system are dependent on the intrinsic magnetic susceptibilities of the materials. − To investigate the retardation behavior of the phosphors within the magnetic field-controlled chromatography column employed in this work, proof-of-concept experiments were conducted using pure suspended phosphors. Three different chromatography operation modes (isocratic, elution, and step gradient, refer to Section ) were compared with each other.…”

“…In a recent study, Boelens et al intensively investigated the removal dynamics of multiple fluorescent lamp phosphors in a rotary permanent magnet HGMS system with a horizontal field gradient at a background field of 0.32 T. They observed significant differences in the removal dynamics depending on the phosphor’s intrinsic magnetic susceptibilities. Despite this, they concluded that the system was not suitable for phosphor separation in its current configuration, because they found that the removal efficiency declined over time as a result of a shift in the particle size distribution …”

“…In this paper, we present an approach based on this technique for the purification of paramagnetic RE-containing phosphors used in EOL fluorescent lamps. Differences in the phosphor’s intrinsic susceptibilities , lead to varying particle affinities towards a magnetizable chromatography matrix. We selectively separated the particle species from each other and from other pollutants within a single processing step by leveraging these affinity differences.…”

Identification of yttrium oxide‐specific peptides for future recycling of rare earth elements from electronic scrap

“…Also, further characterization is needed to quantify process conditions, reusability, and scale-up possibilities. Furthermore, the peptides identified in this work may be used in the selective separation of Y 2 O 3 , using superparamagnetic particles (such as Dynabeads) functionalized with surface-binding peptides that can bind to the particles of the target material, facilitating their separation (Boelens et al, 2021(Boelens et al, , 2022.…”

A Novel Approach for Quantifying Magnetic Susceptibility of Aqueous and Organic Solutions

“…Holmium ion solutions, as an ion with strong paramagnetic properties, as well as organic extractants used for the extraction of rare earth metals, were selected for the study of their magnetic properties. This metal was chosen for experimental work due to one of the highest values of the magnetic moment among the rare earth metals. , Rare earth metal ions are characterized by different magnetic properties, , which can potentially be used in the separation of these metals in hydrometallurgical processes. − So far, research works on the analysis of the transport of rare earth metal ions under the influence of a heterogeneous magnetic field in both static, , two-phase and dynamic systems have been developed. Works related to the analysis of the transport of metal ions such as dysprosium, yttrium, europium − and other rare earth metals ions have appeared in the literature so far.…”