Challenges for the recovery of critical metals from waste electronic equipment - A case study of indium in LCD panels

One of the resilient strategies to assure a long term supply of critical metals is the implementation of closed loop management systems, in which the of end-of-life (EoL) recycling plays a central role. Since the major application of primary indium is liquid crystal displays (LCD), strategy development has to focus on their recycling and their use as secondary raw material. A literature survey, own experiments, and company interviews were conducted to identify indium potential, assembly of LCD and material composition. Recycling and recovery restrains for Indium from LCD has been identified and technical requirements for future processes were concluded. Additionally, available re-use, recycling and recovery approaches have been reviewed and their potential for indium recovery from LCD scrap evaluated. Indium content in obsolete LCDs lies apparently in a range of 100 - 200 ppm and several studies suggest i.a. acid leaching for its separation from the other materials. However, this procedure addresses only a small part of the whole recycling and recovery chain. Suggestions for the implementation of available indium recovery approaches in an overall concept are presented and further need for research is pointed out.