Recovery of Indium and Gallium from Spent IGZO Targets by Leaching and Solvent Extraction

Abstract

Indium, gallium, and zinc oxide (IGZO) is a semiconducting material that is widely used in the manufacturing of semiconductors, touch panels, displays, etc. This work aims to shed some light on the recovery and separation of indium, gallium, and zinc from spent IGZO targets by solvent extraction (SX). The process involved leaching, SX in high acidity, stripping, re-extraction in low acidity, and re-stripping, followed by the cementation of the gallium and indium with zinc dust. Triisobutyl phosphate (T-iso-BP) was employed as the extractant to separate the majority of zinc from indium and gallium in the leaching solution. The leaching solution was utilized directly without further adjustment, to avoid consuming an enormous amount of water. The loaded organic (LO) solution was then stripped with HCl solution at pH 2, moving the majority of indium and gallium from LO phase to aqueous phase. The extraction and stripping process enabled the transfer of indium and gallium from the leaching solution (8–8.5 mol/L HCl solution) to HCl solution at pH 2, without diluting the leaching solution with an enormous amount of water. The stripped solution was then extracted with di-(2-ethylhexyl) phosphoric acid to separate indium from gallium. The optimum extraction conditions and stripping conditions were studied. From the actual spent IGZO target, 97.8% of indium with a purity of 98.3% and 96.2% of gallium with a purity of 99.6% were separated and recovered.