Kinetics of Indium Extraction from Mechanically Activated ITO Scrap

The indium tin oxide scrap (ITOS) was mechanically activated by a stirring ball mill and subsequently studied for the leaching behavior and kinetics of extracting indium from ITOS in hydrochloric acid solution. The X-ray diffraction (XRD) analysis showed that MA caused the decrease in crystalline phase and increase in lattice distortion. The effects of reaction temperature and hydrochloric acid concentration on the leaching rate of indium were also investigated, which showed that the indium extraction from ITOS had significant dependency on temperature and HCl concentration. The equal-recovery method was used for kinetics analysis. When ITOS was mechanically activated for 15 and 30 min, the apparent activation energy decreased from 90.6 kJ/mol to 70.3 and 53.0 kJ/mol, respectively, which indicated that MA could enhance the reactivity of ITOS and accelerated the reaction. The reaction orders of extracting indium from the nonactivated, milled for 15 and 30 min ITOS with respect to HCl concentration were 2.30, 1.44, and 1.31, respectively.