Novel mechanical pre-treatment methods for effective indium recovery from end-of-life liquid-crystal display panels

Abstract

This study investigated the suitability of mechanical pre-treatment methods (mechanical abrasion and treatments of heat, laser, and plasma) together with a hydrometallurgical process comprising leaching and cementation for recovering indium from used LCD screens. With mechanical abrasion pre-treatment, 96.2% of indium was recovered and black mass with an indium content of 15.6 wt percent was obtained. Following the mechanical recovery, sulfuric acid leaching was used to produce leachates with an indium purity ranging from 86.3 to 98.0% with an 88.7–100% yield for indium. Indium was recovered from the leachate by cementation with zinc powder, but also the impurity metals were cemented. The suggested mechanical pre-treatment involving the indium recovery process was seen as a viable option since it dramatically reduces the mass fed to the hydrometallurgical purification process (by roughly a factor of 1000), and up to 97.1% pure indium product can be obtained with a simplified process. The purity of the indium product can be further increased by additional purification steps.