Refined bifunctional deep eutectic solvent for one-step selective indium and tin recovery from spent LCDs

Area of Science:

• Materials Science
• Green Chemistry
• Chemical Engineering

Background:

• Electronic waste, particularly discarded liquid crystal displays (LCDs), contains valuable materials like indium.
• Traditional methods for indium recovery can be inefficient and environmentally harmful.
• Developing sustainable and selective methods for recovering indium from LCDs is crucial for resource circularity.

Purpose of the Study:

• To introduce a novel, bifunctional deep eutectic solvent (DES) for efficient and eco-friendly indium recovery from indium tin oxide (ITO)-coated glass.
• To demonstrate a one-step in-situ separation process for indium recovery.
• To optimize the DES-based separation process and analyze its reaction mechanism.

Main Methods:

• Utilized a deep eutectic solvent composed of choline chloride (ChCl) and oxalic acid dihydrate (OAD).
• Employed Response Surface Methodology (RSM) to optimize leaching conditions: temperature, duration, solvent ratio (ChCl:OAD), and solid-to-liquid ratio.
• Investigated the cyclic stability and reaction pathway of the DES for indium recovery.

Main Results:

• Achieved a remarkable 95.6% indium recovery efficiency under optimized conditions (80°C, 8h, 2.6:1 M ChCl:OAD, 10 g/L solid-to-liquid ratio).
• Successfully retained tin as tin oxide (SnO2), demonstrating high selectivity.
• The DES (2.6ChCl:1OAD) exhibited excellent cyclic stability, maintaining ~75% recovery efficiency after six cycles.

Conclusions:

• The bifunctional DES offers a highly efficient and selective method for indium recovery from waste LCDs.
• The developed one-step process is suitable for real-world applications, promoting the valorization of electronic waste.
• This study presents a sustainable and green approach to critical metal recovery from secondary resources.