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

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 (d(2)& BULL;chi)(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.

Automated summary

This study investigates the separation of phosphors from end-of-life compact fluorescent lamps using high-gradient magnetic separation, presenting a fast and reliable quantification method. It also demonstrates the efficient removal and recovery of phosphors through the high-gradient magnetic separator process.