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.
Highlights
In a global effort towards a low-carbon and green economy, rare-earth elements (REEs) are becoming increasingly important, due to their essential role in permanent magnets, lamp phosphors, rechargeable batteries, and catalysts [1]
We investigate the removal dynamics of Compact Fluorescent Lamps (CFLs) phosphors, using a rotary permanent magnet high-gradient magnetic separator (HGMS) device that had been previously designed by Hoffmann et al for biotechnological applications which incorporate superparamagnetic beads
We have characterized five CFL phosphors in terms of their chemical compositions and physical properties that are most relevant for a magnetic separation (i.e., particle size distributions (PSDs), ρ, Sm, ψ and χ)
Summary
In a global effort towards a low-carbon and green economy, rare-earth elements (REEs) are becoming increasingly important, due to their essential role in permanent magnets, lamp phosphors, rechargeable batteries, and catalysts [1]. Surface-binding peptides are a promising tool for highly selective bioseparation processes They can be employed for the functionalization of superparamagnetic beads or nanoparticles to facilitate a rapid removal of target particles from a mixed suspension under the influence of a magnetic field [17]. We give a mathematical elucidation of the empirically observed removal dynamics The goal of this investigation is two-fold: to obtain a better understanding of the phosphors’ separability by HGMS and to prepare future bioseparation experiments, demonstrating the upscalability of particle separation based on superparamagnetic beads functionalized with selectively surface-binding peptides such as the ones identified by Lederer et al.. The samples were cooled down to room temperature, diluted to 25 mL and measured by ICP-MS
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