Indium recovery from In-Sn-Cu-Al mixed system of waste liquid crystal display panels via acid leaching and two-step electrodeposition

Since indium (In) was the most valuable resource in waste liquid crystal panels (LCDs), most researches only focused on preliminary recovery of In, while those coexisting metal elements (Cu, Sn, Al) raised little concern. This could lead to waste of resources, potential risk of heavy metal pollution, and also complexation of following In purification procedures. Besides, current hydrometallurgy processes for In purification are complicated, consume more reagents and generate more wastewater. Therefore, this research applied simple acid leaching and two-step electrodeposition for In-Sn and In-Cu-Al separation with minimum waste generation and input. Considering the special doping structure of indium-tin oxide (ITO), feasibility for concurrent In leaching and Sn precipitation was explored based on the unique Sn species' dissolution and precipitation behavior during acid leaching. Since the behavior of Sn was more sensitive to acidity and temperature, 97.07% of Sn removal and 99.25% of In recovery could be achieved using 1 mol/L H₂SO₄ at 70 ℃ for 1 h. A specific kinetic model depicting In leaching in thin ITO film situation was developed referring to avrami equation. Then, the application of two-step electrodeposition enabled 95.32% extraction of Cu and deposition of In with a purity over 99 wt% at respective potential.