Behavior and Mechanism of Indium Extraction from Waste Liquid-Crystal Display Panels by Microwave-Assisted Chlorination Metallurgy

Abstract

Using ammonium chloride as a chlorination agent, indium in waste liquid-crystal display panels was successfully extracted by microwave-assisted chloride metallurgy under vacuum pressure. The optimal conditions for indium extraction from pure indium oxide were explored through single-factor and orthogonal experiments, achieving an indium extraction ratio of 98.91% when the temperature was 500°C, the Cl/In molar ratio was 8, and the heating duration was 3 min for pure In2O3. The Cl/In molar ratio exhibited the most important effect on the indium extraction ratio, followed by the heating temperature and duration. When extracting indium from waste liquid-crystal display panel powder (–13 µm) after ball milling, the indium extraction ratio was nearly 79.46% when using an ammonium chloride mass ratio of 0.6 wt.%, temperature of 500°C, and heating duration of 3 min. Excess gaseous hydrogen chloride reacts with ammonia to form ammonium chloride during the condensation, thereby avoiding emission of hydrogen chloride into the environment. The results of this work indicate that this technology represents a promising option for the extraction of indium from waste liquid-crystal display panels with a very short heating duration and relatively low chlorination agent loss, as well as no harmful gas emissions.