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New technique developed to recycle indium from waste LCD screens

June 3, 2016

New technique developed to recycle indium from waste LCD screens

The EU has identified 20 critical raw materials, including indium, with economic importance and a high supply risk. Indium is mainly used for the production of LCD screens and is predominantly sourced from Chinese mines. This study, funded by the European Commission, details the development of a process to recycle indium from waste LCD panels, where indium is found as indium tin oxide (ITO). The study is one of the first to describe how to recover indium from a leaching solution of waste LCD panels. Developing methods to recover materials from waste equipment is an important way of saving resources and reducing primary production of materials.

The researchers recovered indium from waste LCD panels through cementation: the process by which a solid is created from a solution. The panels were first shredded into small pieces and sieved to remove glass and plastic fragments, then indium was dissolved in a strong acid solution. Zinc metal powder was used in the solution to collect the indium, which becomes solid by reacting with zinc during the cementation process.

The study was undertaken in order to identify the best operating conditions under which to recover indium from a solution that contains other metals; 16 experimental treatments were used to investigate the effect of variations in zinc concentration, pH of the acid solution and the duration of the recovery process. An important goal of the process is to ensure that the maximum possible yield of high-purity indium can be obtained from ITO.

The environmental impact of the indium recovery process was also assessed through life-cycle assessment (LCA). The LCA was undertaken to identify the environmental benefits and impacts of recovering indium using this method, in terms of the loss of (non-living) natural resources and global-warming impacts. Indium recovery from waste LCD panels was compared with incineration and use of landfills, which are the current methods of LCD waste disposal.

Read more at "Science for Environment Policy": European Commission DG Environment News Alert Service, edited by SCU, The University of the West of England, Bristol.

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