Novel resource-efficient recovery of high purity indium products: Unlocking value from end-of-life mobile phone liquid crystal display screens

Abstract

Liquid crystal display (LCD) screens found in most electrical and electronic equipment consume approximately 75% of the total indium produced globally. Due to indium’s unique properties and applications, the escalation in demand for the metal and the threat to supply of the metal, mined primarily as a by-product of zinc production, are critical. To mitigate these challenges the need to recover indium from end-of-life (EoL) products is becoming an imperative. In this work, EoL mobile phones (EoL-MPs), which represent a resource-rich stream for critical metals in general, and, specifically indium from LCDs, are used as a feedstock. Using a simulated Model Test System, with the task-specific ionic liquid, Cyphos 101, the optimal conditions for recovery of indium are determined before application to real samples. A complete hydrometallurgical process was developed for the recovery of indium from as-received EoL-MP LCDs as a four-step process involving pre-treatment, liquid-liquid extraction, elution and reduction, using the task-specific IL, Cyphos 101, as extractant. This novel hydrometallurgical process developed can achieve overall efficiencies of ≥ 90% for indium recovery in the form of two high-purity (≥ 99%) indium products of commercial value and offers a promising approach for recovery from any e-waste stream rich in indium. Moreover, this low energy process permits the reuse of the IL up to five consecutive times and has the potential to unlock value as polymeric films, glass substrate and liquid crystal for recycle and reuse within the circular economy.