Recovery of rare earth elements from end of life fluorescent lamp

Abstract

Fluorescent lamp is a gas-discharge lamp that uses electricity to excite mercury vapor. However, the United States Environmental Protection Agency classifies fluorescent lamps as hazardous waste, and recommends that they are segregated from general waste for recycling or safe disposal. In addition, main components of fluorescent lamp are rare earth phosphor including La (Lanthanum), Tb (Terbium), Ce (Cerium), Eu (Europium) and Y (Yttrium), the price of which has become increasing. Therefore, the used fluorescent lamps are considered as an important secondary resource for rare earth element. In this study, ultrasonic dry sieving as well as wet vibration sieving has been used for separation of rare earth elements from the ground used lamp. Sample characterization then separation, tests were conducted. Ultrasonic dry sieving in 5, 8, 10 and 12.5 µm for 2 minutes each was performed to determine the optimum sieve size, and then wet vibration sieving 5 µm was conducted in different times to compare wet and dry sieving. In the recovery of rare earth elements process, influences of sieving size and time were investigated in order to identify the optimum condition for the separation process. In term of the air classification which is an instrument to verify the separation performance of dry separation process, the optimum condition was obtained when the feed rate is 10 kg/h with rotation speed of 2000, 3000, 4000, 5000, 6000 and 7000 rpm by with and without compressed air.