Analysis of Indium and Tin in Different Scrap Liquid Crystal Display Glass by Heavy Metal Digestion Method

Disposing of liquid crystal display (LCD) waste has significant effects on the environment, human and animal health, and metal resources by extension if inappropriately treated. In this study, we have developed a process for the separation of indium–tin oxide (ITO) glass from the LCD panel and evaluated the best digestion process for the analysis of In and Sn from ITO glass. The digestion process of scrap LCD in this work involves the separation of the polarizing film from ITO glass by environmentally friendly cold thermal shock method with liquid nitrogen, the removal of liquid crystals between the ITO glass substrates by ultrasonic cleaning, and the analysis of In and Sn from ITO glass by acid digestion method with a suitable reagent. Various brands of scrap LCDs were treated with six different digestion methods to determine In and Sn concentrations. The result of this study indicates that aqua-regia digestion procedure was the best method for the analysis of In and Sn. The concentrations of In and Sn in various brands of LCDs were in the range of 233–332 mg/kg and 43–421.5 mg/kg, respectively. Further, the analysis of In and Sn metals at different locations of the same scrap LCD was also carried out and it was observed that the concentrations of these metals (In—0.0278–0.0369% and Sn—0.0033–0.0078%) were significantly similar, with slight variations in their percentages.