Adsorption and Recovery of Neodymium and Praseodymium from Magnet Waste NdFeB Using a Novel Pyridine Schiff Base Compound

Abstract

This study presents a novel approach for synthesizing (pyridine‐2,5‐diylbis(azaneylylidene) bis(ethan‐1‐yl‐2‐ylidene))bis(benzene‐5,1,3‐triyl) tetrakis(4‐formylbenzoate) to address the growing demand and limited supply of Nd(III) and Pr(III) metal ions. The material, created through Schiff base formation and esterification, aims to enhance the recovery and utilization efficiency of Nd(III) and Pr(III) from solutions. The PYBE adsorbent selectively adsorbs these ions, and its properties were confirmed using FTIR, SEM, TGA, ¹H NMR, ¹³C NMR, and mass spectrometry. Adsorption efficiency was tested under varying conditions, including pH, adsorbent dosage, contact time, solution concentration, and the presence of coexisting ions. The results followed a pseudo‐second‐order kinetic model, with equilibrium isotherms well described by Langmuir, Temkin, and Dubinin–Radushkevich models. The PYBE adsorbent demonstrated high sorption capacities—384.62 mg/g for Nd(III) and 357.14 mg/g for Pr(III) at pH 6. Thermodynamic analysis revealed that the adsorption process was spontaneous and endothermic. The material also successfully recovered Nd(III) and Pr(III) from waste Neodymium‐Iron‐Boron (NdFeB) magnets, yielding high‐purity Nd₂O₃ and Pr₆O₁₁. The adsorption mechanism, driven by chemisorption, aligned with the Langmuir and D–R isotherm models. This innovative PYBE material demonstrates significant potential for efficient rare earth metal recovery, addressing a critical need for sustainable resource management.