Low-Temperature Reduction-Selective Volatilization for Indium Recovery from Waste Liquid Crystal Displays

Waste liquid crystal displays (LCDs) were a significant secondary source of indium. This study introduced a low-temperature reduction roasting method for selectively volatilizing and recovering indium from waste LCDs. Suitable conditions and thermodynamic feasibility were verified via thermodynamic calculations. The process of volatilization and separation was elucidated by studying the phase behavior in CO-CO₂ and H₂-H₂O atmospheres. The key to the procedure was controlling the indium to produce indium(I) oxide (In₂O), while retaining the nonvolatile tin. CO reduction failed to achieve effective separation even at high temperatures. In contrast, roasting at 875 °C for 2 h under a 50% H₂ atmosphere attained an In/Sn separation coefficient of 11,761 and an indium recovery of 98.5%. Lowering the temperature via H₂ preserved the intact glass structure. The recovered product was a mixture of metallic indium (In) and indium(III) oxide (In₂O₃) nanoparticles with a purity of over 99.5% and an average size of approximately 262.9 nm. Density functional theory (DFT) calculations elucidated the advantages of H₂ for molecular adsorption. This study provided a viable strategy for the clean, effective recycling of waste LCDs.