J. Clean. Prod. 230, 580–591 (2019)

Short-lived electronic devices have become a significant waste stream. This waste is a potential source of valuable metals, but only a small portion is currently recycled. A common electronic waste is the liquid-crystal display (LCD) screen used in computers and televisions. LCDs contain two glass plates sandwiching a liquid-crystal mixture. The outer plate surfaces are covered with polarizer films, but the inner plate surfaces contain a functional indium tin oxide film. Indium is a critical raw material with limited supplies and high costs. Several possible recycling methods have been developed to recover indium but purity remains low.

Credit: Tom Uhlman / Alamy Stock Photo

Ville Lahtela and colleagues from LUT University in Finland compared several pre-treatment methods to produce high-purity indium. First, LCD panels were split, and liquid crystals were removed. Then, combinations of mechanical abrasion, plasma, heat, and laser pre-treatment methods were tested. Using brushing with sand abrasion, the authors recovered 96.2% of the indium, and this pre-treatment made indium recovery economically feasible by significantly reducing the mass needing further treatment. Next, sulfuric acid leaching was used to increase the purity up to 97.1%. This is another step towards recycling more electronics waste and recovering indium.