Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.9/2138
Título: Liquid crystal displays as secondary resources for Indium recovery: characterization and physical processing
Autor: Margarido, F.
Jeremias, J. F.
Nogueira, C. A.
Palavras-chave: Indium
Electronic Waste
Liquid Crystal
Data: 2013
Citação: Margarido, F.; Jeremias, J.F.; Nogueira, C.A. Liquid crystal displays as secondary resources for Indium recovery: characterization and physical processing. In: Materiais 2013 International Conference, Book of Abstracts, Coimbra, Portugal, 25-27 Março, 2013, p. 86
Resumo: End-of-life liquid crystal display (LCD) monitors represent an important emerging flow in electric and electronics waste, which require urgently appropriate technologies for its management. These devices have environmental issues that discourage its treatment trough incineration or disposal. Moreover, the LCD-glass component has in its composition an important and strategic metal, indium, whose recycling is essential in order to assure the continuity of its supply for manufacturing new LCD’s and other thin-film products. The characterization of LCD’s, as well as the study of physical processing by shredding of the LCDglass component, was the main objective of the research work carried out and herein presented. Several LCD monitors were dismantled and the constituting parts were separated in order to perform the mass balance by components and materials. Structural components, mainly metallic and polymeric, are the main constituents of monitors, accounting about 40wt% of ferrous materials and 37wt% of polymers. Once separated, they can be valorized through established recycling circuits. Printed circuit boards (about 7wt%) are also important, valuable and recyclable components. Non-ferrous metals contribute about to 8wt%. Fluorescent lamps (0.5wt%) are used as backlight devices and contain traces of mercury. Its removal without breaking is hardly achieved and constitutes one of the most important problems to solve on the dismantling process. Finally the mass balance is completed by the LCD-glass component which contains the indium-tin oxide (ITO) transparent conductive film and accounts to about 8wt%. The physical processing of the LCD-glass by shredding was performed as the first step of the recycling diagram to be developed. The proposed scheme was a two-stage cutting process, using a grab shredder and a cutting mill, aiming at to reduce efficiently the particle size and to evaluate the potential liberation of particles from the indium-tin oxide conductive film. The process was found appropriate for treating the LCD-glass component, allowing obtaining average particle diameters of 0.48 or 0.64 mm, depending on the discharge grid used (1 mm or 2 mm), with size reduction ratios of 304 or 226, respectively. The chemical analysis of indium showed that this metal is distributed by all the granulometric classes analyzed, being more concentrated in the fines, which demonstrates that during shredding some abrasion of the glass surface occurred, liberating some ITO particles.
URI: http://hdl.handle.net/10400.9/2138
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