Recovery of aluminium, nickel–copper alloys and salts from spent fluorescent lamps

Abstract

This study explores a combined pyro-hydrometallurgical method to recover pure aluminium, nickel–copper alloy(s), and some valuable salts from spent fluorescent lamps (SFLs). It also examines the safe recycling of clean glass tubes for the fluorescent lamp industry. Spent lamps were decapped under water containing 35% acetone to achieve safe capture of mercury vapour. Cleaned glass tubes, if broken, were cut using a rotating diamond disc to a standard shorter length. Aluminium and copper–nickel alloys in the separated metallic parts were recovered using suitable flux to decrease metal losses going to slag. Operation variables affecting the quality of the products and the extent of recovery with the suggested method were investigated. Results revealed that total loss in the glass tube recycling operation was 2% of the SFLs. Pure aluminium meeting standard specification DIN 1712 was recovered by melting at 800 °C under sodium chloride/carbon flux for 20 min. Standard nickel–copper alloys with less than 0.1% tin were prepared by melting at 1250 °C using a sodium borate/carbon flux. De-tinning of the molten nickel–copper alloy was carried out using oxygen gas. Tin in the slag as oxide was recovered by reduction using carbon or hydrogen gas at 650–700 °C. Different valuable chloride salts were also obtained in good quality. Further research is recommended on the thermodynamics of nickel–copper recovery, yttrium and europium recovery, and process economics.