| Abstract Scope |
With promoted use of fluorescent lamps and the increasing amount of fluorescent lamp waste, its phosphors have become an ideal secondary source for critical materials, such as yttrium, europium and terbium. Conventional recycling processes based on hydrometallurgy rely on large volume of acids and organic solvents and generate large volumes of hazardous waste. Here, a novel environmentally friendly process based on supercritical fluid was developed to recycle the critical rare earth elements from waste fluorescent lamp. The proposed process uses supercritical CO¬2 as the solvent, which is inert, safe and abundant, along with tributyl-phosphate nitric acid (TBP-HNO3¬) chelating agent. An extraction efficiency of 50% was achieved without sample pretreatment. Pretreating samples with mechanical activation (ball milling) for 1 h resulted in 20% improvement in extraction efficiency. High resolution transmittance electron microscopy showed that during mechanical activation the sample becomes polycrystalline with nano-sized crystallite size, resulting in enhanced leaching efficiency. |