Microwave-Mediated Recovery of Critical Metals from LED E-Waste

In this study, we present a microwave-assisted method for recycling and recovering critical minerals from LED e-waste. This new approach uses microwave irradiation to convert first the plastic lens of LED into a brittle charred residue that encapsulates the LED chip. This residue is then mechanically separated from the metallic pins (Fe, Ni, Ag), which remain intact. Further calcination of the charred residue in air exposes the materials making up the LED chip, which contain critical metals (e.g., Ga, As, In, Y, Au). A follow up two-step acid treatment using aqua regia and hot concentrated HCl, selectively leaches out the other metals ultimately resulting in gallium enrichment. The proposed combination of microwave heating with acid treatment improves significantly the recovery of Ga and provides a practical approach to remediate LED e-waste.