An Experimental Investigation of the Liquid–Liquid Extraction of Neodymium from Aqueous Solutions Using bis(2-Ethylhexyl) Phosphoric Acid

Rare earth elements (REEs) are indispensable to clean energy and advanced technologies, with neodymium (Nd) being critical for permanent magnets and high-performance devices. Therefore, efficient, and sustainable recovery of Nd(III) is essential. This study investigates the liquid-liquid extraction (LLE) of Nd(III) from aqueous chloride solutions using bis(2-ethylhexyl) phosphoric acid (D2EHPA) in toluene under batch conditions. Four parameters, aqueous pH (1.0–3.0), extractant concentration (0.15–0.60 mol L–1), agitation rate (250–450 rpm) and residence time (5–20 min) were taken and varied in this study. The study used UV-Vis spectroscopy at 583 nm to quantify Nd(III), and FTIR confirmed the metal-extractant complex. The findings show that extraction efficiency increased sharply with pH, achieving around 55% at pH 2.0 and reaching equilibrium near 58% at pH 3.0. An extractant concentration of 0.45 mol L–1 and agitation at 400 rpm for 15 min yielded optimal recovery while minimizing reagent use and processing time. Triplicate experiments demonstrated reproducibility with a mean relative standard deviation of around 3%. These findings establish a clear mechanistic and parametric understanding of Nd(III) transfer, contributing to conscious solvent extraction and a foundation for intensified processes.