Indium recovery from waste liquid crystal displays by polyvinyl chloride waste

Abstract

Indium (In), a rare element existing only in a few natural minerals, is mainly used to produce indium tin oxide (ITO) thin films for applications including liquid crystal displays (LCDs). Therefore, developing an effective method to recover In from waste LCDs is of great significance. In the present study, In was extracted from indium oxide (In₂O₃) and LCD powder after alkali dissolution via a chloride volatilization process using polyvinyl chloride (PVC) as the chlorination precursor. High purity In₂O₃ was investigated firstly in a nitrogen atmosphere. The results indicated that high purity In₂O₃ could have a high recovery ratio of indium using polyvinyl chloride (PVC) as the chlorination agent. The recovery ratio of indium could reach 99.36%. The product was analyzed by X-ray diffraction (XRD), and the results indicated that the condensed products were InCl₃ and InCl. Real LCD powder after alkali dissolution was also examined. The recovery ratio of indium was 97.50% and the utilization of hydrogen chloride was 53.91% under the conditions of a molar Cl/In ratio of 11, a degradation temperature of PVC of 400 °C, a chlorination temperature of 500 °C, carrier gas flow rate at 0.1 L min⁻¹, and a reaction time of 30 min. The condensed products were also mainly InCl₃ and InCl. It is an effective method to recover In from LCD panels.