All fluorescent lights contain small amounts of mercury and rare earth metals. There is a need to safely remove and recycle mercury and rare earth elements from used fluorescent lamps in order to keep the valuable and potentially poisonous metals out of the environment and aid the domestic recovery of critical materials.
Conventional processes include heating and distillation to volatilize the mercury and do not include an adequate process to refine the individual rare earth components. In order to optimize the recyclability of fluorescent lights, a process is needed that doesn't incorporate the volatilization of mercury and a process to refine and separate the various rare earth elements contained within the phosphor composition.
An integrated method was developed to more safely separate and remove mercury and rare earth elements from fluorescent light bulbs without the need for volatilizing the mercury. Process steps include:
Separation of the phosphor powder from glass via ultrasonics
Separation of mercury from phosphor powder
Separation of rare earths from phosphor matrix via oxidation/reduction and acid/base mechanisms
Novel online method to refine rare earths
Rare earths are extracted from the phosphor matrix using a supercritical fluid extraction process with carbon dioxide, mineral acids, acid adducts, and metal complexing agents. Additional refining to separate dissolved rare earths into individual fractions is used to provide rare earth products. Each step in the process is integrated and can be run in batch, semi-batch, or continuous-flow mode for the recovery of mercury and rare earths.