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Leaching of Rare Earth Metals from Phosphor Coating of Waste Fluorescent Lamps
摘要： Phosphors made from compounds of rare earth metals (REMs) are very efficient. This material needs to be recycled for recovery of REMs after the fluorescent lamps (FLs) reach end of life. This work focuses on the leaching studies of REMs from phosphor. The phosphor was recovered from the spent linear FLs by end cut-push method. After detailed characterization of phosphor, effects of parameters viz. leachant, concentration, temperature, and pulp density were studied to determine the optimum leaching conditions. By using 9% (v/v) H2SO4, 98.6% (w/w) yttrium and 96.2% (w/w) europium could be leached out from phosphor at temperature, 70 °C, time, 4 h, and pulp density, 10% (w/v). The residue generated was treated with 54% (v/v) HCl to leach out 98.9% (w/w) lanthanum, 98.2% (w/w) cerium and 96.5% (w/w) terbium at temperature, 90 °C, time, 2 h, and pulp density, 10% (w/v). Kinetic studies of leaching reactions were also carried out.
关键词： Phosphor,Leaching,Waste recycling,Rare earth metals,Fluorescent lamps
更新于2025-09-09 09:28:46
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Surface potential and thin film quality of low work function metals on epitaxial graphene
摘要： Metal films deposited on graphene are known to influence its electronic properties, but little is known about graphene’s interactions with very low work function rare earth metals. Here we report on the work functions of a wide range of metals deposited on n-type epitaxial graphene (EG) as measured by Kelvin Probe Force Microscopy (KPFM). We compare the behaviors of rare earth metals (Pr, Eu, Er, Yb, and Y) with commonly used noble metals (Cr, Cu, Rh, Ni, Au, and Pt). The rare earth films oxidize rapidly, and exhibit unique behaviors when on graphene. We find that the measured work function of the low work function group is consistently higher than predicted, unlike the noble metals, which is likely due to rapid oxidation during measurement. Some of the low work function metals interact with graphene; for example, Eu exhibits bonding anomalies along the metal-graphene perimeter. We observe no correlation between metal work function and photovoltage, implying the metal-graphene interface properties are a more determinant factor. Yb emerges as the best choice for future applications requiring a low-work function electrical contact on graphene. Yb films have the strongest photovoltage response and maintains a relatively low surface roughness, ~5 nm, despite sensitivity to oxidation.
关键词： work function,Kelvin Probe Force Microscopy,photovoltage,rare earth metals,graphene
更新于2025-09-09 09:28:46