Condition evaluation and 3R guidelines for reuse of rare-earth phosphor from used fluorescent lamps in Japan

Abstract

ABSTRACT Fluorescent lamps in common use utilise rare earths as key constituent elements for light emission, and these involve resource risk and are difficult to replace with other components. In Japan, the recycling of fluorescent lamps began because of environmental concerns, but is now also pursued because of resource risk, with the 3 Rs (reduce, reuse and recycle) being equally important in the case of the rare earths used in such lamps. In order to reduce costs and environmental load, it is effective to directly reuse the phosphor in such lamps as part of lamp manufacturing, rather than refining the rare-earth element component in the phosphor. Therefore, the present study conducted a performance evaluation of the deterioration condition of used phosphor from fluorescent lamps. Although the brightness of the phosphor decreased with use, the main reason was considered to be the absorption of light by coloured staining on the surface. This staining showed variation in density, depending on its positional relationship to the emitter, and the distribution of the stain was correlated to the emission intensity of the phosphor. Therefore, the proposed 3 R guidelines for the treatment of used phosphor from such lamps are designed to reflect the degree of staining.