Indium Recovery from the Acid Elute of Waste Indium Tin Oxide Glass by Bipolar Membrane Electrodialysis with Ethylenediaminetetraacetic Acid as a Chelating Agent

• Published in: Industrial & engineering chemistry research 2021-06, Vol.60 (25), p.9151-9158
• Main Authors: Takemura, Yuki, Abe, Masahiro, Noguchi, Miyuki, Yamasaki, Akihiro
• Format: Article
• Language: English
• Subjects: Separations
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.1c01047

We propose a method to recover indium from an acid leaching solution of waste liquid crystal display (LCD) containing indium tin oxide by bipolar membrane electrodialysis (BPED) using ethylenediaminetetraacetic acid (EDTA) as a chelating agent. The model solution was a mixture solution of indium ions and aluminum ions with a given amount of EDTA added. Aluminum is a major coexisting component after precipitation of tin hydroxide from a leaching solution of waste LCD panels. Due to the difference in the chelate stability, indium ions would preferably be chelated with fully dissociated EDTA (Y4–) to form anionic chelates, [In–Y]−, while aluminum ions would exist as Al3+ cations. The BPED system is composed of five three-cell type units with electrode cells: the feed cell is the space between a cation-exchange membrane (CEM) and an anion-exchange membrane (AEM), the indium recovery cell is the space between a bipolar membrane (BPM) and an AEM, and the aluminum recovery cell is the space between a CEM and a BPM. BPED was applied to the model solutions, and indium ions were transported through the AEM to the indium recovery cell, while aluminum ions were transported through the CEM to the aluminum recovery cell. The effect of the initial pH, additive EDTA concentration in the feed solution, and the applied voltage on the separation performances of indium was studied. The selectivity of indium in the indium recovery cell was 95.3%, and the recovery ratio of indium in the indium recovery cell was 91.8% under the conditions of initial pH = 4.0, applied voltage of 30.0 V, and operation time of 60 min, where the power consumption for the recovery of indium was in the range of 24.7 kW h/kg-In.