Indium extraction from indium tin oxide (Ito) scraps using subcritical water

Abstract

Indium (In) extraction from indium tin oxide scraps was investigated using dilute acid solutions under subcritical condition. Three types of acids, including HCl, H 2 SO 4 , and HNO 3 , were used and HCl yielded the highest extraction efficiency. The pronounced complex formation between In 3+ and Cl – was proposed to be involved in determining extraction efficiency. The extraction efficiency of In increased with HCl concentration and reached 95.41% ± 0.01% within 30 min at 0.75 M of HCl, 150°C, and final pressure of 20 bar. Pressure did not affect the efficiency as it varied from 10 to 60 bar. Efficiency as high as 94% was found at 100°C, implying that subcritical water extraction (SWE) was very effective in the range of 100°C–150°C. The present work demonstrates that SWE is an efficient, simple, and effective extraction technique for In extraction.