Effect of mechanical activation on terbium dissolution from waste fluorescent powders. (15th June 2021)

• Record Type: Journal Article
• Authors: Ippolito, Nicolò Maria; Ferella, Francesco; Innocenzi, Valentina; Trapasso, Francesca; Passeri, Daniele; Belardi, Gianmaria; Vegliò, Francesco
• Is Part Of: Minerals engineering. Volume 167(2021)
• Publication Date: 2021-06-15
• Subjects: Terbium -- Rare earths -- Fluorescent lamps -- Mechanical activation -- Hydrometallurgical treatment -- Waste recycling; Mines and mineral resources -- Periodicals; Ressources minérales -- Périodiques; Mines and mineral resources; Periodicals; Electronic journals; 622
• DOI: 10.1016/j.mineng.2021.106906
• Languages: English
• ISSNs: 0892-6875

Abstract

Highlights: Terbium dissolution from waste fluorescent lamps was studied by factorial plan. Preliminary mechanical activation allows to increase terbium dissolution of 35%. The final product has a purity of 98.3% as rare earth oxides. Technical comparison between mechanical and thermal pretreatment was presented. Thermal treatment allowed a higher dissolution of terbium over the mechanical one. Abstract: Rare earth elements (REEs), independently by the economic value, have a strategic importance and are involved, as critical materials, in the competition for their supply. An innovative process with the introduction of a preliminary physicochemical treatment was proposed. The mechanical activation of waste of fluorescent powders was performed by a vibratory disc mill at different experimental conditions to optimize the process. The mechanical forces induced to the powders cause crystal structure defects with a consequent increase of rare earths leachability. Factorial experimentations and analysis of variance were studied to determine the significant effects of the investigated factors (mechanical activation time, sulfuric acid concentration, pulp density and leaching temperature), especially for terbium dissolution. The preliminary activation allows to increase terbium dissolution of 35%. Then, according to the best conditions the subsequent operations of precipitation and calcination were performed obtaining a purity of 98.3% as rare earth oxides. Based on the experimental results, the flowsheet for rare earths recovery has been proposed and implemented by SuperPro Designer, a simulation software for process analysis and mass-energy balances. Finally, this paper reports a comparison between the present process with the mechanical pre-treatment and the alternative method based on thermal pre-treatment.