Simultaneous leaching and extraction of indium from waste LCDs with acidic ionic liquids

Abstract

The fragile indium supply inspired the development of recycling programs for end-of-life electronics products, especially liquid crystal displays (LCDs). LCDs consume 70% of the total indium resources used in the world today. In this study, a novel fusion of leaching and extraction processes was proposed to recycle indium from waste LCDs using the functionalized ionic liquid betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]). Under the optimum conditions of 10 mL 50% (v/v) ionic liquid/ascorbic acid, 20 g/L of solid/liquid ratio, and 90 °C operation temperature within 24 h, the indium leaching rate could reach as high as 99.75% and the indium extraction rate could be enriched by 98.63% in the ionic liquid phase after cooling and stratifying. Introducing ascorbic acid into the process in place of deionized water decreased the distribution rate of iron from 59.87% to 8.84% and promoted the separation of indium and iron. Indium in the ionic liquid phase could then be transferred into an indium-rich solution using oxalic acid and retrieve the ionic liquid. The characteristics of the regenerated ionic liquid remained relatively stable for reutilization. Therefore, the proposed fusion of leaching and extraction processes by [Hbet][Tf2N] provides an efficient alternative to recycle indium from waste LCDs.