Recovery of rare earth elements (Nd, Dy) from discarded hard disk magnets using EDTA functionalised chitosan

Abstract

Rare earth elements (REEs) are crucial for advanced green technologies and other critical applications, including defence, medical devices, electronics, and catalysts. However, traditional methods of extracting REEs from electronic waste (e-waste) are energy-intensive, generating large amounts of hazardous waste. This study proposes an environmentally conscientious approach to recovering rare earth elements (Nd, Dy) from e-waste using chitosan, a biopolymer. Chitosan has exhibited excellent metal ion adsorption properties, which can be improved by immobilising its functional groups to target specific metal ions. EDTA has been used to functionalize chitosan, allowing it to chelate and recover REEs from discarded hard disk magnets. The proposed route was optimised for maximum yield of REE recovery by adjusting critical process parameters (pH, adsorption time, and temperature). The maximum adsorption was achieved for Nd and Dy, reaching 85.3% and 76.9%, respectively, from discarded computer hard disks. The efficiency of the proposed route was also evaluated based on the adsorption recovery of other impurities (Fe from Nd–Fe–B magnets). It was observed that in comparison to the high efficiency of recovery for Nd and Dy, the proposed route controls the amount of Fe recovered as an impurity with an average maximum yield of 58.73%. In summary, the proposed recovery route provides a promising alternative to conventional metallurgical methods for REE recovery, which can be environmentally intrusive.