Waste ITO target recycling for efficient indium recovery through a closed-loop process

Abstract

In this study, an efficient process for waste ITO target recycling has been proposed on the purpose of individual recovery of indium and tin. In2O3 in waste ITO target was selectively dissolved through H2SO4 leaching in the presence of H2O2 under the conditions of H2SO4 concentration of 2.0 mol/L, liquid to solid ratio (L/S) of 4.0 mL/g, reaction temperature of 80 ºC and time of 5.0 h. In the meantime, most of tin was remained in the leach residue in the form of H2SO4-stable SnO2, achieving the efficient separation of indium and tin. The indium-rich leach solution was further processed with oxalic acid under the conditions of C2O42-/In3+ mole ratio of 1.8, reaction temperature of 30 °C and time of 1.0 h to selectively precipitate indium in the form of indium oxalate. The obtained Sn-free indium oxalate precipitates were further subjected to a calcination process for its complete thermal decomposition. Indium was finally recovered in the form of In2O3 powder, which is an ideal raw material for indium metal recovery or fabrication of new ITO targets. XRD, SEM, TG-DSC and XPS analysis were utilized to clarified the reaction mechanisms of the recycling process.