Synthesis of Rare Earth Compounds from Phosphor Coating of Spent Fluorescent Lamps

ABSTRACT Ultraviolet (UV) rays are produced during operation of fluorescent lamps (FLs). Fluorescent coating, also known as phosphor, converts UV rays to visible light. Various chemical compounds, individually or mixed in certain weight ratio, are used as phosphor. Phosphor prepared from rare earth (RE) compounds is energy-efficient. Various components including phosphor are meant to be recycled from FLs once they cease to operate. Review of literatures related to recycling of phosphor suggested that few papers were published prior to 2009. However, there was avalanche of relevant research articles in the next decade. Although RE phosphors were developed in 70s, their use in FLs gained market only after 2009 when energy protection agency passed a resolution to increase the efficiency of the lamps. In the last decade, researchers have done massive work on recycling of phosphor. In the mean time, they switched from one extractive technique to another to overcome the limitations of the former process. In this review, we have investigated the need of switching from one technique to another. We discovered the gaps in these literatures and proposed what needs to be done to fill these gaps. Flow-sheets prepared by compiling the most efficient techniques have been proposed at the end.