Discarded fluorescent light bulbs represent a source of rare Earth metals, if only a feasible recovery and recycling route can be developed. Fortunately, a bright idea for capturing the rare-Earth-based phosphors that coat the inner surfaces of these bulbs and contribute to the color of light has been advanced by researchers from Karlsruhe Institute of Technology, Germany.

The magnetized chromatography method uses a wire coil to externally administer a magnetic field to a glass chromatography column containing stacked stainless-steel mesh disks. The process was applied to a demonstration sample composed of weakly magnetic rare-Earth phosphors that were mixed in a liquid solution with nonmagnetic silica oxide and strongly magnetic iron oxide nanoparticles to represent glass and metal components in the bulbs, respectively.

The phosphors and iron oxide nanoparticles adhered to the magnetized stainless-steel mesh as liquid was injected into the chromatography column. Gradually reducing the external magnetic field strength while rinsing the column with liquid facilitated release of the strongly magnetic iron oxide nanoparticles.

The procedure detailed in ACS Sustainable Chemistry & Engineering retrieved 93% of the rare-Earth phosphors from the initial mixture that simulated lamp components.