Separation and concentration of valuable and critical materials from wasted LEDs by physical processes

Abstract

The generation of wasted LEDs is expected to grow in the coming years, raising the challenge of recycling and recovering their valuable and critical materials. Due to the low concentration of these materials, the current recycling processes available for LEDs have a significant recovery limitation. This study proposes an innovative, clean and effective physical method to segregate the valuable and critical materials into different fractions while enhancing their concentration: particle size separation followed by electrostatic separation. After the determination of the best electrostatic separation conditions (varying tension and rotation) for each particle size, the final fractions were characterized by acid digestion and ICP-OES analysis. The analysis revealed that the economically valuable elements gold, silver, copper and tin became concentrated in the conductive fractions (80.18%, 94.22%, 96.55% and 93.29% of their total recovered mass, respectively), while the strategic critical elements, gallium, cerium and yttrium became concentrated in the non-conductive fractions (96.15%, 100% and 95.20% of their total recovered mass, respectively). Despite some limitations imposed by the mass losses, this novel route may be important to uncover new recycling alternatives, mainly for critical elements, and to improve the economic viability of the recycling routes.