Efficient recovery of indium from waste indium tin oxide (ITO) targets by pressure leaching with sulfuric acid

Abstract

As a high indium content material, resourceful recycling of waste ITO targets plays an important role in dealing with the increasing depletion of indium resources. This paper proposes to use dilute sulfuric acid to leach and recover indium under pressure. A leaching rate of indium of up to 96.50% was achieved, using 2 mol L⁻¹ sulfuric acid for 2 hours at 408 K on waste ITO targets. The leaching kinetics and behavior of indium under pressure acid leaching systems were investigated. The analysis of leaching kinetics indicated that the indium leaching process was controlled by a surface chemical reaction, and the activation energy was 41.5 kJ mol⁻¹ (>40 kJ mol⁻¹). The reaction orders of sulfuric acid concentration and particle size were 0.66 and −1.21, respectively. The analysis of the leaching residue showed that the indium tin oxide released In³⁺ into the solution under the attack of sulfuric acid and SnO₂ phase was exposed. The leaching process has the advantages of a high leaching rate, light corrosion on equipment and no waste gas generation, providing an approach for clean recycling and sustainable reuse of indium resources.