Indium Recycling from Waste Liquid Crystal Displays: Is It Possible?

Abstract

The utilization of valuable properties of waste and their reuse as raw materials is an imperative of the circular economy. Waste electrical and electronic equipment (WEEE) is a significant source of valuable raw materials, certain metals, and rare earth elements that are the basis for highly sophisticated IT equipment production. It is estimated that the production of WEEE in Europe in 2019 was 16.20 kg/inhabitant, while quantities continue to grow at a rate of 3–4% per year. Waste liquid crystal displays used in televisions, laptops, desktops, and other devices represent a significant share of WEEE and contain 0.12–0.14% of liquid crystals whose main ingredient is indium—tin oxide. In order to investigate and determine the methods and conditions of indium recycling from waste LCDs, laboratory research was conducted. The influence of temperature, particle size, and retention time in different media with and without ultrasound treatment was monitored to provide the efficiency of indium leaching. The analysis of the results showed that 98% indium leaching was achieved with granulation samples of 10 × 10 mm at a temperature 40 °C/40 min in solution H2O:HCl: HNO3 = 6:2:1 under ultrasound conditions, while aqueous and alkaline media under the same conditions did not show significant efficiency. This study can be used as a practical reference for the recycling of indium from LCD panels.